[go: up one dir, main page]

WO2019049009A1 - Bidirectional energy-conversion apparatus of a dc-dc type operating between a low-voltage system and a high-voltage system of a vehicle comprising an energy-recovery stage, and corresponding method - Google Patents

Bidirectional energy-conversion apparatus of a dc-dc type operating between a low-voltage system and a high-voltage system of a vehicle comprising an energy-recovery stage, and corresponding method Download PDF

Info

Publication number
WO2019049009A1
WO2019049009A1 PCT/IB2018/056674 IB2018056674W WO2019049009A1 WO 2019049009 A1 WO2019049009 A1 WO 2019049009A1 IB 2018056674 W IB2018056674 W IB 2018056674W WO 2019049009 A1 WO2019049009 A1 WO 2019049009A1
Authority
WO
WIPO (PCT)
Prior art keywords
voltage
converter
buck
bus
low
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/IB2018/056674
Other languages
French (fr)
Inventor
Andrea Nepote
Giordano Greco
Piero Antonio CONTI
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Marelli Europe SpA
Marelli Suspension Systems Italy SpA
Original Assignee
Magneti Marelli SpA
Sistemi Sospensioni SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Magneti Marelli SpA, Sistemi Sospensioni SpA filed Critical Magneti Marelli SpA
Publication of WO2019049009A1 publication Critical patent/WO2019049009A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of DC power input into DC power output
    • H02M3/02—Conversion of DC power input into DC power output without intermediate conversion into AC
    • H02M3/04—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters
    • H02M3/10—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1582—Buck-boost converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load

Definitions

  • the present invention relates to a bidirectional energy-conversion apparatus of a DC-DC type operating between a low-voltage system and a high-voltage system0 of a vehicle comprising an energy-recovery stage,
  • said low-voltage system which operates at a first voltage, comprising a battery that supplies said first voltage on a low-voltage bus,
  • said high-voltage system which operates at a5 second voltage higher than said first voltage, comprising said energy-recovery stage of the vehicle that supplies said second voltage,
  • said second voltage being supplied through an intermediate energy-storage system to a DC-DC0 conversion module, which converts said second voltage into said first voltage for said low-voltage bus.
  • energy-recovery systems In the automotive field, energy-recovery systems are known. In particular, energy-recovery systems are known that use regenerative shock absorbers, which5 convert movements of the shock absorber into electrical energy .
  • regenerative shock absorbers that0 envisage a conversion of the linear motion of the stem into a rotary motion of the shaft of an electric generator from which it is hence possible to recover in the form of electricity the energy that would otherwise be dissipated in heat. It is known to carry out this5 conversion using mechanical or hydraulic means in such a way that the rotation of the shaft of the electric generator will occur always in the same direction of rotation, irrespective of the direction of the velocity of the stem. This enables a higher efficiency of energy conversion, from kinetic to electrical energy.
  • the electric generator is usually a DC generator which supplies a DC voltage at output. If, instead, a synchronous generator is used, an inverter is employed. In either case, it is anyway necessary to use a DC-DC converter to match the output voltage of the electric generator to the battery of the vehicle, in particular a motor vehicle.
  • FIG. 1 Illustrated in Figure 1 is a diagram representing an electro-mechanical model of a known energy-recovery apparatus, designated as a whole by the reference number 10.
  • Designated by 11 is a shaft of an electric generator 12, associated to which are an angular velocity (fi and a torque ⁇ .
  • R og denotes the output resistance of the electric generator 12, for example a DC generator
  • R e denotes the equivalent resistance of the circuits of the portion of apparatus downstream of the electric generator 12, i.e., the resistance seen by the electric generator 12, the equivalent resistance Re being regulated, for example, by the aforementioned inverter.
  • V og is the loadless voltage of the electric generator 12
  • I g is the current of the generator 12
  • V inDC Dc is the voltage that is set up on the equivalent resistance R e .
  • FIG. 2 Illustrated in Figure 2 is a conversion apparatus designated as a whole by the reference number 90.
  • the above conversion apparatus 90 comprises an energy-recovery stage 30, which includes a plurality of regenerative shock absorbers 12, in particular four regenerative shock absorbers, associated to respective DC-DC converters in the form of inverters 13, the outputs of which are gathered in a single output node of the energy-recovery stage 30.
  • the output node of the energy-recovery stage 30 basically corresponds to a high-voltage bus HV, set up on which are a voltage V inDC Dc / which is the voltage on the DC side of the inverter 13 and an output current from the inverter which is the sum of the four currents at output from the inverters 13.
  • the voltage Vin DCD c of the high-voltage bus HV is sent to the input of a high-voltage-to-low-voltage conversion stage 50, which in the example comprises a DC-DC converter 23, set in parallel on the input of which is a storage element, i.e., a capacitance, C DC .
  • the storage element may be a battery.
  • the DC-DC converter 23 Entering the DC-DC converter 23 is an input current linDCDc that is equal to the current at output from the inverter IoutiNv minus the current that flows in the storage element C DC .
  • the voltage on the bus HV is defined high with respect to the voltage on the other end of the DC-DC converter 23, on the low-voltage bus LV, which is, instead, of a lower value and in general corresponds to the voltage of the electrical systems of the vehicle, usually 12 V.
  • the bus on the DC side of the inverter which is also the high-voltage side HV, is in what follows referred to as "DC-link bus", and the storage element C DC is referred to as "DC-link capacitance".
  • the DC- link capacitance corresponds in general to the capacitor connected to the input of the DC-DC converter 23, where the DC voltage to be converted to a lower voltage arrives.
  • the DC-link capacitance is usually obtained via an electrolytic or film capacitor that decouples the input of the DC-DC converter.
  • the aforesaid DC-link capacitance C DC in the example described, provides an intermediate energy- storage stage 40 at the input of the DC-DC converter 23.
  • the voltage of the DC-link bus has, for example, a value of 48 V.
  • the bidirectional DC-DC converter 23 which converts the high voltage of the high-voltage bus HV into a low voltage on the low-voltage bus LV, for charging the battery 14, but, if need be, can operate in the other direction to convert the low voltage on the low-voltage bus LV into high voltage on the high- voltage bus HV.
  • This bidirectionality is frequently required in hybrid or electric vehicles.
  • the battery 14 is also connected to an alternator 60, which applies thereto a charging voltage V A LT -
  • a drawback of the aforesaid systems is the management of any excess energy produced, for example, by the energy-recovery system 30.
  • the object of the present invention is to provide an improved apparatus and an improved method that will enable the drawbacks mentioned above to be overcome.
  • FIG. 3 illustrates a principle diagram of a preferred embodiment of the apparatus described herein;
  • Figure 4A shows a converter used by the apparatus described herein in a preferred embodiment
  • FIG. 4B shows a converter used by the apparatus described herein in another embodiment
  • FIG. 5A illustrates a regulation circuit for the preferred embodiment of the apparatus of Figure 4A
  • FIG. 5B illustrates a regulation circuit for the preferred embodiment of the apparatus of Figure 4B
  • - Figures 6, 7, and 8 illustrate implementations of the converter of Figure 4 ;
  • FIG. 9 Figures 9, 10, and 11 illustrate control signals and signals that are set up in the apparatus of Figure 3 in different configurations of operation of the apparatus .
  • the solution according to the invention regards a bidirectional energy-conversion apparatus of a DC-DC type operating between a low-voltage system and a high-voltage system of a vehicle comprising an energy-recovery stage,
  • said low-voltage system which operates at a first voltage, comprising a battery that supplies said first voltage on a low-voltage bus,
  • said high-voltage system which operates at a second voltage higher than said first voltage, comprising said energy-recovery stage of the vehicle that supplies said second voltage
  • said second voltage being supplied through an intermediate energy-storage system to a DC-DC conversion module, which converts said second voltage into said first voltage (for said low-voltage bus),
  • said DC-DC conversion module comprises a bidirectional DC-DC converter connected between the intermediate energy-storage stage and the vehicle battery
  • said apparatus is configured for selecting a direction of conversion of said bidirectional converter, from high voltage to low voltage or from low voltage to high voltage, via a control circuit as a function of the value of the voltage on the high- voltage bus.
  • the first bidirectional converter comprises a buck converter for conversion from high voltage to low voltage and a boost converter, the converters being selectable by said control circuit for operating, respectively, conversion from high voltage to low voltage or from low voltage to high voltage.
  • the control circuit comprises a comparator with hysteresis with an upper hysteresis threshold and a lower hysteresis threshold configured for comparing the voltage on the bus with a reference voltage, and, if the voltage on the bus exceeds the upper threshold, a status signal is generated for enabling the operation of conversion from high voltage to low voltage, or buck mode, and, if the voltage on the bus drops below the lower threshold, a status signal is generated for enabling the operation of conversion from low voltage to high voltage, or boost mode.
  • Figure 3 illustrates a bidirectional energy-conversion apparatus of a DC-DC type, designated by the reference 190, which comprises a bidirectional DC-DC conversion module 123, which comprises a first bidirectional DC-DC converter 124 connected between the intermediate energy-storage stage 40 and the vehicle battery 14 and a second auxiliary DC-DC converter 125 connected between the intermediate energy-storage stage 40 and an auxiliary load R aU x-
  • the apparatus corresponds to the one described in the figure, where the energy- recovery system 30 is represented via a current generator, which generates the current at output from the inverter I ou tiNv- Represented connected in parallel to the battery 14, on which a battery voltage drop V bat is present, is a generic electrical load 19, representing the electrical loads of the vehicle that are connected to the low-voltage bus LV (e.g., the heated rear window) .
  • FIG. 4A illustrates, instead, a possible topology for providing the converter module 123.
  • This topology which is one of the simplest topologies for obtaining a bidirectional conversion and to which reference will be made in what follows for illustrating the solution described herein, comprises the bidirectional DC-DC converter 124 configured with buck topology, i.e., comprising a switch that connects (and disconnects) a series inductor to (from) the input, i.e., the voltage V DC ii nk that is the energy source, so that the inductor charges with magnetic energy and then discharges into the battery, in this circumstance a diode connected with its anode to ground enabling a path for the current from ground to the battery.
  • buck topology i.e., comprising a switch that connects (and disconnects) a series inductor to (from) the input, i.e., the voltage V DC ii nk that is the energy source, so that the inductor charges with magnetic energy and
  • the buck topology of the bidirectional converter 124 comprises in this case two switches, designated by Q Bu c k and Qsoost in Figure 4A, obtained for example via MOSFET transistors, for providing the characteristic of bidirectionality, in such a way one implements, seen from the high-voltage terminals HV, the buck behaviour, and the other implements, seen from the low-voltage terminals LV, the boost behaviour.
  • Each of the switches Q Bu ck and Q Boos t is represented with a diode in parallel connected so as to enable flow, when the switch Q Bu ck or Q Bo ost is open, of a current in a direction opposite to that in which the switch Q Buc k or Q B oost causes flow of the current when it is closed. This may, for example, be obtained via the reverse diode between the source and the drain that is normally present in the MOSFET. This diode completes in the case of the buck switch the boost scheme and in the case of the boost switch the buck scheme.
  • the bidirectional DC-DC converter 124 comprises an input capacitance Ci n connected from the DC-link node to ground and a first switch Q buc k connected to the node of the DC-link bus, with a reverse diode D Boost in parallel with its cathode connected to the DC-link node, which separates the latter from a series inductor L in which an inductor current I L flows.
  • the series inductor L is connected to an output node, which presents towards ground an output capacitor C out , to which the battery 14 is connected in parallel.
  • the boost switch Q B oost- Seen from the terminals of the battery 14
  • said second switch Q B0 ost with the series inductor L provides, in the direction of conversion from the low-voltage bus HV to the high-voltage bus LV, a converter with boost topology.
  • the unidirectional auxiliary DC-DC converter 125 Likewise connected to the DC-link node is the input of the unidirectional auxiliary converter 125, which also envisages, as has been said, a buck topology.
  • the unidirectional auxiliary DC-DC converter 125 comprises an auxiliary switch Q aU x / connected to the DC-link node, which separates the latter from an auxiliary series inductor L aux in which an auxiliary-inductor current lLaux flows.
  • the auxiliary series inductor L aux is connected to an output node, which presents towards ground an auxiliary output capacitor C aux , to which the auxiliary load R aux is connected in parallel.
  • a diode D aux with its anode connected to ground and its cathode connected between the auxiliary switch Q aux and the auxiliary series inductor L aux completes the buck- converter scheme of the converter 125.
  • the two converters 124 and 125 are controlled in closed loop in such a way that the controlled quantity is the DC-link voltage V DC ii nk / hence, the input voltage in the case of the first bidirectional DC-DC converter 124 in forward mode and of the second auxiliary DC-DC converter 125, and the output voltage in the case of the first bidirectional DC-DC converter 124 in reverse mode.
  • the regulation guarantees an extremely low voltage ripple and continuity of operation .
  • the second auxiliary DC-DC converter 125 enables dissipation of the excess energy in a load at a higher voltage (up to that of the DC-link bus) with respect to the voltage of the battery 14, hence with lower currents, in addition to the advantage of not burdening the low-voltage system with a further load. Moreover, also for this converter closed-loop (non-hysteretic) operation enables a better aspect ratio of the dissipated power.
  • the first bidirectional DC-DC converter 124 and the auxiliary DC-DC converter 125 are driven according to different modes on the basis of the operating conditions of the system, in particular of the voltage on the bus V DC ii n k, and, possibly of a reference voltage V ref , as described more fully hereinafter.
  • the bidirectional DC-DC converter 124 can be activated in forward or reverse mode, according to the type of conversion required by the vehicle, whereas the second auxiliary DC-DC converter 125 is activated only in the condition in which there becomes necessary dissipation of excess energy in conversion from the energy-recovery system 30 to the battery 14 (from the high-voltage bus HV to the low-voltage bus LV) .
  • the bidirectional DC-DC converter 124 In order to determine the direction of operation of the bidirectional DC-DC converter 124, as has been said, it is envisaged to carry out substantially only reading of the voltage on the bus V DC ii n k with consequent determination of the direction of operation of the first bidirectional DC-DC converter 124 and possible activation of the second auxiliary converter 125.
  • a comparator with hysteresis designated by 141 in Figure 5, where represented in detail is a regulation module 140, which as a function of the voltage on the bus V DC ii n k / is configured for generating PWM (Pulse-Width Modulation) driving signals PWM Buck , PWM Boost , and PWM Aux to control the switches Q Bu ck / and Q A ux / respectively.
  • the comparator with hysteresis 141 is configured with an upper hysteresis threshold V TH and a lower hysteresis threshold V TL .
  • This DC-link voltage V DC ii n k is compared with a reference voltage V ref , the value of which is intermediate between the value of the two hysteresis thresholds V TH and V TL and corresponds to a nominal voltage value of the high-voltage bus HV or, in any case, to a target voltage value.
  • the nominal voltage value of the high-voltage bus HV may be 48 V
  • the upper hysteresis threshold V TH and the lower hysteresis threshold V TL may be 46V and 50V, respectively
  • the reference voltage V ref may be 48 V.
  • a (status) signal is generated for enabling operation in buck mode Buck_mode, so that the flow of energy will go from the DC-link bus to the battery 14 in order to cause a reduction of the DC-link voltage V D ciin k on the DC-link bus.
  • a (status) signal is generated for enabling the operation in boost mode Boost_mode, so that the flow of energy will go from the battery 14 to the DC-link bus in order to cause a rise of the DC-link voltage V DC ii nk on the DC-link bus.
  • the bidirectional DC-DC converter 124 seeks to set the nominal voltage (or in any case the target voltage) whether it is in buck mode or in boost mode.
  • auxiliary converter 125 of a buck type is subordinate to the presence of the signal for enabling operation in buck mode Buck_mode to prevent operation thereof during the boost operation of the bidirectional DC-DC converter 124 (this would amount to a transfer from the battery 14 to the high-voltage bus HV, with useless dissipation of energy) .
  • the reference voltages of the two converters 124 and 125 must be set so as to guarantee precedence of operation for the bidirectional DC-DC converter 124, which is the main converter and generates recovery of energy, over operation of the auxiliary converter 125, which, instead, determines dissipation of energy.
  • the first is the reference voltage V ref , which is used for regulating the bidirectional DC-DC converter 124
  • the second is a maximum overvoltage V max , which is higher than the reference voltage V ref and corresponds to the value of overvoltage accepted in conditions of excess regenerated energy, which is used for regulating the auxiliary DC-DC converter 125.
  • Figure 5A illustrates an implementation of the regulation module 140 that comprises the voltage comparator with hysteresis 141, which receives on its inputs the bus voltage V DC ii nk and the reference voltage V ref and generates at output a comparison logic signal HC, which is picked up to obtain a buck-mode-enable signal Buck_mode, and is in parallel picked up and inverted via an inverter 145 to obtain a boost-mode- enable signal Boost_mode.
  • the regulation module 140 comprises the voltage comparator with hysteresis 141, which receives on its inputs the bus voltage V DC ii nk and the reference voltage V ref and generates at output a comparison logic signal HC, which is picked up to obtain a buck-mode-enable signal Buck_mode, and is in parallel picked up and inverted via an inverter 145 to obtain a boost-mode- enable signal Boost_mode.
  • the boost-mode-enable signal Boost_mode is sent to an AND logic gate 146 together with a boost PWM signal PWM Boost originated by a boost regulation circuit 142, which regulates the pulse-width modulation that is used for controlling the boost switch Q Boost so as to obtain the desired voltage regulation V DC ii n k, in a way in itself known to the person skilled in the branch, in particular by controlling the inductor current I L , i.e., the input current, on the low-voltage vehicle side, i.e., on the battery, of the converter 124 when it operates in the above boost mode.
  • the regulation circuit 142 also receives the reference voltage value V ref , as control quantity of a voltage control loop, as described in greater detail in what follows.
  • boost-mode-enable signal Boost_mode is active, i.e., in the case illustrated has the value of a logic one, at output from the AND logic gate 146 there is the boost PWM signal PWM Boost , which can be sent to the switch QBoost of the bidirectional DC-DC converter 124, as represented in greater detail in Figure 6.
  • the buck-mode-enable signal Buck_mode at output from the inverter 145 is sent to an AND logic gate 147 together with a buck PWM signal PWM Buck originated by a buck regulation circuit 143, which regulates the pulse- width modulation so as to obtain the desired voltage regulation V DC ii n k / in a way in itself known to the person skilled in the branch, in particular by controlling the inductor current I L , i.e., the output current of the converter 124 operating in forward mode (buck mode) .
  • the regulation circuit 143 also receives the reference voltage value V ref , as control quantity of a voltage control loop, as described in greater detail in what follows.
  • Buck_mode If the buck-mode-enable signal, Buck_mode, is active, i.e., in the case illustrated is a logic one, at output there is has the buck PWM signal PWM Buck , which can be sent to the switch Q Bu ck of the bidirectional DC-DC converter 124.
  • the buck-mode-enable signal Buck_mode is also sent to an AND logic gate 148 together with a auxiliary PWM signal PWM aux originated by an auxiliary regulation circuit 144, which regulates the pulse-width modulation so as to obtain the desired voltage drop V DC ii n k , in particular by controlling the auxiliary-inductor current I L , i.e., the output current of the converter 125.
  • the regulation circuit 144 also receives the maximum overvoltage value V max , as control quantity of a voltage control loop, as described in greater detail in what follows.
  • Figure 4B illustrates a bidirectional DC-DC energy-conversion apparatus 123' , which comprises the first bidirectional DC-DC converter 124 connected between the intermediate energy-storage stage 40 and the vehicle battery 14, but not the second auxiliary DC-DC converter 125 connected between the intermediate energy-storage stage 40 and an auxiliary load R aux .
  • Figure 5B accordingly illustrates an embodiment of the control circuit 140' for the converter 123' , which comprises just the bidirectional converter 124. Consequently, as compared to the circuit illustrated in Figure 5A, it does not comprise the AND logic gate 148 nor the auxiliary regulation circuit 143.
  • the solution described herein refers in general to an apparatus for bidirectional conversion of energy between high and low voltage, which does not necessarily comprise circuits for dissipating energy overshooting by the high-voltage bus like the auxiliary converter of Figure 5A; i.e., it refers in general to a bidirectional energy-conversion apparatus of a DC-DC type operating between a low- voltage system LV and a high-voltage system HV of a vehicle comprising an energy-recovery stage 30,
  • said low-voltage system LV which operates at a first voltage V bat , comprising a battery 14 that supplies said first voltage V bat on a low-voltage bus LV said high-voltage system HV, which operates at a second voltage V inDCD c/ V DC ii n k higher than said first voltage V bat , comprising said energy-recovery stage 30 of the vehicle that supplies said second voltage V inDCD c / said second voltage V inDCD c/ V DC ii n k being supplied through an intermediate energy-storage system 40 to a DC-DC conversion module 23; 123, which converts said second voltage V inDCD c/ V DC ii n k into said first voltage V bat for said low-voltage bus LV, wherein said DC-DC conversion module 123 comprises a bidirectional DC-DC converter 124 connected between the intermediate energy-storage stage 40 and the vehicle battery 14, and said apparatus is configured for selecting a direction of conversion of said bidirectional converter 124, from high voltage HV to low voltage
  • the auxiliary load R aux must be sized so as to guarantee the entire dissipation of the excess energy; i.e., it must have a resistive value not higher than, i.e., lower than or equal to, the value that would cause a voltage drop across it equal to the voltage on the bus V DC iink in the presence of the maximum current deriving from the auxiliary DC-DC converter 125 of a buck type.
  • Each regulation circuit 142, 143, 144 envisages a respective voltage control loop on the bus V DC ii n k and a pulse-width modulator, where this is understood as being a circuit that generates a PWM signal with a pulse-width modulation determined by one or more control signals, which regulates an internal inductor-current loop (for example, a loop operating in Peak-Current Mode) .
  • the outputs of the three pulse-width modulators are enabled by the boost-mode-enable signal Boost_mode or buck- mode-enable signal Buck_mode described above and directed to the switches Qsoost / QA UX (or to their drivers) for operating in the required configuration.
  • the control loop comprises an adder 143a, which receives as control quantity, or setpoint, the reference voltage V ref , which it compares with the bus voltage DC ii n k picked up on the input of the converter 123, to obtain an error signal that drives, through a compensation circuit 143b, an internal current loop 143c, which, for example, carries out a current limitation.
  • the output of the current loop is supplied as control signal to a pulse-width modulator 143d, which also receives also the current value I L of the inductor L for controlling the pulse-width-modulation value and, as illustrated in Figure 5, supplies a signal PWM Buck to the logic gate 147, which also receives the buck-mode-enable signal Buck_mode.
  • the signal PWM buck At output from the logic gate 147 is the signal PWM buck , which controls, preferably through drivers, opening and closing of the buck switch Q Bu ck-
  • the boost switch Q B0 ost is kept open.
  • the boost regulation circuit 142 is similar, with an internal current loop 142c that carries out a current limitation of its own at a limit current value.
  • auxiliary regulation circuit 144 is similar, with an internal current loop 144c that carries out a current limitation of its own, and moreover the maximum overvoltage V max is given as reference or setpoint value for limiting the voltage value .
  • Figure 9 illustrates diagrams that plot as a function of time the waveforms of signals of the apparatus described herein in a condition of turning-on and successive entry of excess energy on the bus.
  • the auxiliary DC-DC converter 125 is enabled if the voltage on the bus V D ciink has exceeded the maximum overvoltage V max and the bidirectional converter 124 is in buck mode (the driving signal PWM aux is issued) .
  • the auxiliary converter 125 is disabled when the voltage on the bus D C iink has dropped below the maximum overvoltage V max .
  • the apparatus returns into boost mode.
  • the control circuit 140' comprises the comparator with hysteresis 141 with an upper hysteresis threshold V T H and a lower hysteresis threshold V T L configured for comparing the voltage on the bus V DC iink with a reference voltage V re f, and, if the voltage on the bus V DC ii n k exceeds the upper threshold V TH , a status signal is generated for enabling the operation of conversion from high voltage to low voltage, or buck mode Buck_mode, and if the voltage on the bus V DC iink drops below the lower threshold V TL , a status signal is generated for enabling the operation of conversion from low voltage to high voltage, or boost mode Boost_mode.
  • the control circuit 140 only comprises the respective regulation circuits 142, 143 for the buck mode and the boost mode, which generate respective PWM driving signals PWM Buck , PWM Boost for driving respective switches Q Buc k / QBoost of said buck converter Q Bu ck, L, D Buck and boost converter Q Boost , L, D B oost / and just the logic circuits 147, 148 for selectively supplying at output from said regulation circuit 140 said PWM driving signals PWM Buck , PWM Boost to said respective switches Q Buc k / QBoost / under the control of said status signal for enabling the operation of conversion from high voltage to low voltage, Buck_mode, and said status signal for enabling the operation of conversion from low voltage to high voltage, Boost_mode .
  • Figure 10 illustrates diagrams that plot as a function of time the waveforms of signals of the apparatus in a condition in which the input energy, coming from the energy-recovery system 30 is in excess with respect to the energy that can be transferred into the battery 14.
  • the converter 123 is in buck mode; when the voltage on the bus V DC ii n k exceeds the maximum overvoltage V max the auxiliary converter 125 is enabled (the driving signal PWM aux is issued) .
  • Figure 11 illustrates diagrams that plot as a function of time the waveforms of signals of the apparatus in an additional condition that represents the case where the maximum overvoltage V max is set at a value higher than that of the other thresholds.
  • V max the maximum overvoltage
  • the voltage ripple increases, but a better mean energy transfer is obtained, in so far as dissipation of the excess energy is limited by storing it temporarily in the storage element.
  • the converter 123 initially in buck mode with the bidirectional DC-DC converter 124 activated in buck mode to convert the high voltage into low voltage, activates the auxiliary DC-DC converter 125 when the voltage on the bus DC ii nk exceeds the maximum overvoltage V max and de-activates it, instead, when the voltage on the bus V DC ii nk subsequently drops below the maximum overvoltage V max .
  • the solution proposed may be applied also in the case in which is energy-management strategies are to be implemented by varying the voltage of the high-voltage bus (for example, in the presence of an energy-storage element such as supercapacitors or a Li-ion battery) .
  • the reference voltages V ref , the threshold hysteresis voltages V TH , V TL , and the maximum overvoltage V max must be rendered settable in time.
  • the apparatus and method described enable regulation of the flow of power in an automatic way without requiring reading of the currents.
  • Known solutions for determining the direction of operation of a bidirectional DC-DC converter envisage acquisition of the sign of the currents at input and output and consequent setting of the control.
  • the devices connected to the bus are numerous (at least four controllers for the shock absorbers) this approach may be complex.
  • the solution proposed envisages, instead, just reading of the voltage on the high- voltage bus with consequent determination of the direction of operation of the first converter and possible activation of the second converter.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

A bidirectional energy-conversion apparatus of a DC-DC type operating between a low-voltage system (LV) and a high-voltage system (HV) of a vehicle comprising an energy-recovery stage (30), said low-voltage system (LV), which operates at a first voltage (Vbat), comprising a battery (14) that supplies said first voltage (Vbat) on a low-voltage bus (LV), said high-voltage system (HV), which operates at a second voltage (VinDCDC, VDClink) higher than said first voltage (Vbat), comprising said energy-recovery stage (30) of the vehicle that supplies said second voltage (VinDCDC; VDClink), said second voltage (VinDCDC, VDClink) being supplied through an intermediate energy-storage system (40) to a DC-DC conversion module (23; 123), which converts said second voltage (VinDCDC, VDClink) into said first voltage (Vbat) for said low-voltage bus (LV). The aforesaid DC-DC conversion module (123) comprises a bidirectional DC-DC converter (124) connected between the intermediate energy-storage stage (40) and the vehicle battery (14). Said apparatus is configured for selecting a direction of conversion of said bidirectional converter (124), from high voltage (HV) to low voltage (LV) or from low voltage (LV) to high voltage (HV) via a control circuit (140) as a function of the value of the voltage (VDClink) on the high-voltage bus (HV).

Description

BIDIRECTIONAL ENERGY-CONVERSION APPARATUS OF A DC-DC TYPE OPERATING BETWEEN A LOW-VOLTAGE SYSTEM AND A HIGH-VOLTAGE SYSTEM OF A VEHICLE COMPRISING AN ENERGY-RECOVERY STAGE, AND CORRESPONDING METHOD
5 * * *
TEXT OF THE DESCRIPTION
The present invention relates to a bidirectional energy-conversion apparatus of a DC-DC type operating between a low-voltage system and a high-voltage system0 of a vehicle comprising an energy-recovery stage,
said low-voltage system, which operates at a first voltage, comprising a battery that supplies said first voltage on a low-voltage bus,
said high-voltage system, which operates at a5 second voltage higher than said first voltage, comprising said energy-recovery stage of the vehicle that supplies said second voltage,
said second voltage being supplied through an intermediate energy-storage system to a DC-DC0 conversion module, which converts said second voltage into said first voltage for said low-voltage bus.
In the automotive field, energy-recovery systems are known. In particular, energy-recovery systems are known that use regenerative shock absorbers, which5 convert movements of the shock absorber into electrical energy .
In this context, for example, of particular interest from the standpoint of efficiency of conversion are regenerative shock absorbers that0 envisage a conversion of the linear motion of the stem into a rotary motion of the shaft of an electric generator from which it is hence possible to recover in the form of electricity the energy that would otherwise be dissipated in heat. It is known to carry out this5 conversion using mechanical or hydraulic means in such a way that the rotation of the shaft of the electric generator will occur always in the same direction of rotation, irrespective of the direction of the velocity of the stem. This enables a higher efficiency of energy conversion, from kinetic to electrical energy. The electric generator is usually a DC generator which supplies a DC voltage at output. If, instead, a synchronous generator is used, an inverter is employed. In either case, it is anyway necessary to use a DC-DC converter to match the output voltage of the electric generator to the battery of the vehicle, in particular a motor vehicle.
It is likewise known to use a stage for conversion from high voltage to low voltage, specifically a DC-DC converter that is controlled in output voltage, to be matched to the battery voltage, in a way similar to the regulator of an alternator.
Illustrated in Figure 1 is a diagram representing an electro-mechanical model of a known energy-recovery apparatus, designated as a whole by the reference number 10. Designated by 11 is a shaft of an electric generator 12, associated to which are an angular velocity (fi and a torque τ . Rog denotes the output resistance of the electric generator 12, for example a DC generator, whereas Re denotes the equivalent resistance of the circuits of the portion of apparatus downstream of the electric generator 12, i.e., the resistance seen by the electric generator 12, the equivalent resistance Re being regulated, for example, by the aforementioned inverter. Denoted by Vog is the loadless voltage of the electric generator 12, denoted by Ig is the current of the generator 12, and denoted by VinDCDc is the voltage that is set up on the equivalent resistance Re.
Consequently, from what has been discussed so far, it follows that it is possible to control damping of the shock absorber by acting on the equivalent resistance Re seen by the electric generator 12, but the fact of having to act on the equivalent resistance Re to control damping renders it, however, impossible to operate, as in other energy-harvesting systems, by matching the impedance seen by the generator, which, in particular, depends upon the inverter, to the output impedance of the electric generator 12 in order to maximize power transfer.
Illustrated in Figure 2 is a conversion apparatus designated as a whole by the reference number 90.
The above conversion apparatus 90 comprises an energy-recovery stage 30, which includes a plurality of regenerative shock absorbers 12, in particular four regenerative shock absorbers, associated to respective DC-DC converters in the form of inverters 13, the outputs of which are gathered in a single output node of the energy-recovery stage 30.
The output node of the energy-recovery stage 30 basically corresponds to a high-voltage bus HV, set up on which are a voltage VinDCDc/ which is the voltage on the DC side of the inverter 13 and an output current from the inverter
Figure imgf000005_0001
which is the sum of the four currents at output from the inverters 13. The voltage VinDCDc of the high-voltage bus HV is sent to the input of a high-voltage-to-low-voltage conversion stage 50, which in the example comprises a DC-DC converter 23, set in parallel on the input of which is a storage element, i.e., a capacitance, CDC. In variant embodiments, the storage element may be a battery. Entering the DC-DC converter 23 is an input current linDCDc that is equal to the current at output from the inverter IoutiNv minus the current that flows in the storage element CDC. Of course, in the present context, the voltage on the bus HV is defined high with respect to the voltage on the other end of the DC-DC converter 23, on the low-voltage bus LV, which is, instead, of a lower value and in general corresponds to the voltage of the electrical systems of the vehicle, usually 12 V.
In the systems as the one described in which a system at a higher voltage is connected, by means of a converter, to a system at lower voltage, in particular to the electrical systems connected to the vehicle battery, the bus on the DC side of the inverter, which is also the high-voltage side HV, is in what follows referred to as "DC-link bus", and the storage element CDC is referred to as "DC-link capacitance". The DC- link capacitance corresponds in general to the capacitor connected to the input of the DC-DC converter 23, where the DC voltage to be converted to a lower voltage arrives. The DC-link capacitance is usually obtained via an electrolytic or film capacitor that decouples the input of the DC-DC converter.
The aforesaid DC-link capacitance CDC, in the example described, provides an intermediate energy- storage stage 40 at the input of the DC-DC converter 23. The voltage of the DC-link bus has, for example, a value of 48 V.
Set between the intermediate energy-storage stage
40 and the low-voltage bus LV, on which the battery 14 is connected, is the bidirectional DC-DC converter 23, which converts the high voltage of the high-voltage bus HV into a low voltage on the low-voltage bus LV, for charging the battery 14, but, if need be, can operate in the other direction to convert the low voltage on the low-voltage bus LV into high voltage on the high- voltage bus HV. This bidirectionality is frequently required in hybrid or electric vehicles.
The battery 14 is also connected to an alternator 60, which applies thereto a charging voltage VALT -
A drawback of the aforesaid systems is the management of any excess energy produced, for example, by the energy-recovery system 30.
Known from the U.S. patent No. US8723490B2 is an apparatus for automatic regulation of the flow of power, which envisages, in order to determine the direction of operation of a bidirectional DC-DC converter, acquisition of the sign of the currents at input and at output and consequent setting of the control. In the case where the devices connected to the bus are numerous (at least four controllers for the shock absorbers), this approach may be complex.
The object of the present invention is to provide an improved apparatus and an improved method that will enable the drawbacks mentioned above to be overcome.
According to the present invention, the above object is achieved thanks to an apparatus, as well as to a corresponding method, having the characteristics referred to specifically in the ensuing claims.
The invention will now be described with reference to the annexed drawings, which are provided purely by way of non-limiting example and in which:
Figure 1 and 2 have already been described previously;
- Figure 3 illustrates a principle diagram of a preferred embodiment of the apparatus described herein;
Figure 4A shows a converter used by the apparatus described herein in a preferred embodiment;
- Figure 4B shows a converter used by the apparatus described herein in another embodiment;
- Figure 5A illustrates a regulation circuit for the preferred embodiment of the apparatus of Figure 4A;
- Figure 5B illustrates a regulation circuit for the preferred embodiment of the apparatus of Figure 4B; - Figures 6, 7, and 8 illustrate implementations of the converter of Figure 4 ;
- Figures 9, 10, and 11 illustrate control signals and signals that are set up in the apparatus of Figure 3 in different configurations of operation of the apparatus .
In brief, the solution according to the invention regards a bidirectional energy-conversion apparatus of a DC-DC type operating between a low-voltage system and a high-voltage system of a vehicle comprising an energy-recovery stage,
said low-voltage system, which operates at a first voltage, comprising a battery that supplies said first voltage on a low-voltage bus,
said high-voltage system, which operates at a second voltage higher than said first voltage, comprising said energy-recovery stage of the vehicle that supplies said second voltage,
said second voltage being supplied through an intermediate energy-storage system to a DC-DC conversion module, which converts said second voltage into said first voltage (for said low-voltage bus),
According a main aspect of the solution described herein,
said DC-DC conversion module comprises a bidirectional DC-DC converter connected between the intermediate energy-storage stage and the vehicle battery
said apparatus is configured for selecting a direction of conversion of said bidirectional converter, from high voltage to low voltage or from low voltage to high voltage, via a control circuit as a function of the value of the voltage on the high- voltage bus.
In particular the first bidirectional converter comprises a buck converter for conversion from high voltage to low voltage and a boost converter, the converters being selectable by said control circuit for operating, respectively, conversion from high voltage to low voltage or from low voltage to high voltage. The control circuit comprises a comparator with hysteresis with an upper hysteresis threshold and a lower hysteresis threshold configured for comparing the voltage on the bus with a reference voltage, and, if the voltage on the bus exceeds the upper threshold, a status signal is generated for enabling the operation of conversion from high voltage to low voltage, or buck mode, and, if the voltage on the bus drops below the lower threshold, a status signal is generated for enabling the operation of conversion from low voltage to high voltage, or boost mode.
In this connection, Figure 3 illustrates a bidirectional energy-conversion apparatus of a DC-DC type, designated by the reference 190, which comprises a bidirectional DC-DC conversion module 123, which comprises a first bidirectional DC-DC converter 124 connected between the intermediate energy-storage stage 40 and the vehicle battery 14 and a second auxiliary DC-DC converter 125 connected between the intermediate energy-storage stage 40 and an auxiliary load RaUx- As may be noted, for the rest the apparatus corresponds to the one described in the figure, where the energy- recovery system 30 is represented via a current generator, which generates the current at output from the inverter IoutiNv- Represented connected in parallel to the battery 14, on which a battery voltage drop Vbat is present, is a generic electrical load 19, representing the electrical loads of the vehicle that are connected to the low-voltage bus LV (e.g., the heated rear window) . It is emphasized how the solution described herein is not, however, limited to an apparatus such as the apparatus 190 of Figure 3, but also regards a bidirectional energy-conversion apparatus of a DC-DC type 123, which comprises the first bidirectional DC-DC converter 124 connected between the intermediate energy-storage stage 40 and the vehicle battery 14, but not the second auxiliary DC-DC converter 125 connected between the intermediate energy-storage stage 40 and an auxiliary load Raux.
In other words, the solution described herein also applies to a conversion apparatus that only carries out bidirectional conversion between a high voltage and a low voltage. This apparatus is exemplified in Figure 4B, whereas a corresponding regulation circuit is illustrated in Figure 5B.
Figure 4A illustrates, instead, a possible topology for providing the converter module 123. This topology, which is one of the simplest topologies for obtaining a bidirectional conversion and to which reference will be made in what follows for illustrating the solution described herein, comprises the bidirectional DC-DC converter 124 configured with buck topology, i.e., comprising a switch that connects (and disconnects) a series inductor to (from) the input, i.e., the voltage VDCiink that is the energy source, so that the inductor charges with magnetic energy and then discharges into the battery, in this circumstance a diode connected with its anode to ground enabling a path for the current from ground to the battery. The buck topology of the bidirectional converter 124, however, comprises in this case two switches, designated by QBuck and Qsoost in Figure 4A, obtained for example via MOSFET transistors, for providing the characteristic of bidirectionality, in such a way one implements, seen from the high-voltage terminals HV, the buck behaviour, and the other implements, seen from the low-voltage terminals LV, the boost behaviour. Each of the switches QBuck and QBoost is represented with a diode in parallel connected so as to enable flow, when the switch QBuck or QBoost is open, of a current in a direction opposite to that in which the switch QBuck or QBoost causes flow of the current when it is closed. This may, for example, be obtained via the reverse diode between the source and the drain that is normally present in the MOSFET. This diode completes in the case of the buck switch the boost scheme and in the case of the boost switch the buck scheme.
Hence, the bidirectional DC-DC converter 124 comprises an input capacitance Cin connected from the DC-link node to ground and a first switch QBuck connected to the node of the DC-link bus, with a reverse diode DBoost in parallel with its cathode connected to the DC-link node, which separates the latter from a series inductor L in which an inductor current IL flows. The series inductor L is connected to an output node, which presents towards ground an output capacitor Cout, to which the battery 14 is connected in parallel. Connected to ground between the buck switch QBuck and the series inductor L is a second switch, the boost switch QBoost- Seen from the terminals of the battery 14 said second switch QB0ost with the series inductor L provides, in the direction of conversion from the low-voltage bus HV to the high-voltage bus LV, a converter with boost topology.
Likewise connected to the DC-link node is the input of the unidirectional auxiliary converter 125, which also envisages, as has been said, a buck topology. Hence, the unidirectional auxiliary DC-DC converter 125 comprises an auxiliary switch QaUx/ connected to the DC-link node, which separates the latter from an auxiliary series inductor Laux in which an auxiliary-inductor current lLaux flows. The auxiliary series inductor Laux is connected to an output node, which presents towards ground an auxiliary output capacitor Caux, to which the auxiliary load Raux is connected in parallel. In this case, since there is no dual boost switch as in the converter 124, a diode Daux with its anode connected to ground and its cathode connected between the auxiliary switch Qaux and the auxiliary series inductor Laux completes the buck- converter scheme of the converter 125.
According to the solution described herein, the two converters 124 and 125 are controlled in closed loop in such a way that the controlled quantity is the DC-link voltage VDCiink / hence, the input voltage in the case of the first bidirectional DC-DC converter 124 in forward mode and of the second auxiliary DC-DC converter 125, and the output voltage in the case of the first bidirectional DC-DC converter 124 in reverse mode. In this way, the regulation guarantees an extremely low voltage ripple and continuity of operation .
The second auxiliary DC-DC converter 125 enables dissipation of the excess energy in a load at a higher voltage (up to that of the DC-link bus) with respect to the voltage of the battery 14, hence with lower currents, in addition to the advantage of not burdening the low-voltage system with a further load. Moreover, also for this converter closed-loop (non-hysteretic) operation enables a better aspect ratio of the dissipated power.
The first bidirectional DC-DC converter 124 and the auxiliary DC-DC converter 125 are driven according to different modes on the basis of the operating conditions of the system, in particular of the voltage on the bus VDCiink, and, possibly of a reference voltage Vref, as described more fully hereinafter.
The bidirectional DC-DC converter 124 can be activated in forward or reverse mode, according to the type of conversion required by the vehicle, whereas the second auxiliary DC-DC converter 125 is activated only in the condition in which there becomes necessary dissipation of excess energy in conversion from the energy-recovery system 30 to the battery 14 (from the high-voltage bus HV to the low-voltage bus LV) .
In order to determine the direction of operation of the bidirectional DC-DC converter 124, as has been said, it is envisaged to carry out substantially only reading of the voltage on the bus VDCiink with consequent determination of the direction of operation of the first bidirectional DC-DC converter 124 and possible activation of the second auxiliary converter 125.
This is obtained using a comparator with hysteresis, designated by 141 in Figure 5, where represented in detail is a regulation module 140, which as a function of the voltage on the bus VDCiink/ is configured for generating PWM (Pulse-Width Modulation) driving signals PWMBuck, PWMBoost, and PWMAux to control the switches QBuck/
Figure imgf000013_0001
and QAux/ respectively. The comparator with hysteresis 141 is configured with an upper hysteresis threshold VTH and a lower hysteresis threshold VTL. This DC-link voltage VDCiink is compared with a reference voltage Vref, the value of which is intermediate between the value of the two hysteresis thresholds VTH and VTL and corresponds to a nominal voltage value of the high-voltage bus HV or, in any case, to a target voltage value. For example, the nominal voltage value of the high-voltage bus HV may be 48 V, the upper hysteresis threshold VTH and the lower hysteresis threshold VTL may be 46V and 50V, respectively, and the reference voltage Vref may be 48 V.
When the voltage on the bus VDCiink exceeds the upper threshold VTH (for example, on account of an event of generation of energy by the shock absorbers 12) a (status) signal is generated for enabling operation in buck mode Buck_mode, so that the flow of energy will go from the DC-link bus to the battery 14 in order to cause a reduction of the DC-link voltage VDciink on the DC-link bus.
Instead, if the DC-link voltage VDCiink becomes lower than the lower threshold VTL (for example, on account of a demand for actuation) a (status) signal is generated for enabling the operation in boost mode Boost_mode, so that the flow of energy will go from the battery 14 to the DC-link bus in order to cause a rise of the DC-link voltage VDCiink on the DC-link bus.
If the voltage VDCiink remains within the two thresholds VTH and VTL the most recent setting is maintained. The target, or nominal, voltage of the DC- link bus des not change in the various operating modes, so that, within the two thresholds VTH and VTL, the bidirectional DC-DC converter 124 seeks to set the nominal voltage (or in any case the target voltage) whether it is in buck mode or in boost mode. Activation of the auxiliary converter 125 of a buck type is subordinate to the presence of the signal for enabling operation in buck mode Buck_mode to prevent operation thereof during the boost operation of the bidirectional DC-DC converter 124 (this would amount to a transfer from the battery 14 to the high-voltage bus HV, with useless dissipation of energy) . The reference voltages of the two converters 124 and 125 must be set so as to guarantee precedence of operation for the bidirectional DC-DC converter 124, which is the main converter and generates recovery of energy, over operation of the auxiliary converter 125, which, instead, determines dissipation of energy. To guarantee this, two values of reference voltage are considered: the first is the reference voltage Vref, which is used for regulating the bidirectional DC-DC converter 124, the second is a maximum overvoltage Vmax, which is higher than the reference voltage Vref and corresponds to the value of overvoltage accepted in conditions of excess regenerated energy, which is used for regulating the auxiliary DC-DC converter 125. If the bus voltage is lower than both of the values of the voltage references Vref and Vmax, the two converters 124 and 125, which are both in buck configuration, do not work; i.e., their operation is not enabled. With the bus voltage VDCiink comprised between the two voltage references Vref and Vmax operation only of the bidirectional DC-DC converter 124 is enabled. With a voltage higher than both of the voltage references Vref and Vmax both of the converters 124 and 125 are enabled and active.
Hence, Figure 5A illustrates an implementation of the regulation module 140 that comprises the voltage comparator with hysteresis 141, which receives on its inputs the bus voltage VDCiink and the reference voltage Vref and generates at output a comparison logic signal HC, which is picked up to obtain a buck-mode-enable signal Buck_mode, and is in parallel picked up and inverted via an inverter 145 to obtain a boost-mode- enable signal Boost_mode.
The boost-mode-enable signal Boost_mode is sent to an AND logic gate 146 together with a boost PWM signal PWMBoost originated by a boost regulation circuit 142, which regulates the pulse-width modulation that is used for controlling the boost switch QBoost so as to obtain the desired voltage regulation VDCiink, in a way in itself known to the person skilled in the branch, in particular by controlling the inductor current IL, i.e., the input current, on the low-voltage vehicle side, i.e., on the battery, of the converter 124 when it operates in the above boost mode. The regulation circuit 142 also receives the reference voltage value Vref, as control quantity of a voltage control loop, as described in greater detail in what follows. If the boost-mode-enable signal Boost_mode is active, i.e., in the case illustrated has the value of a logic one, at output from the AND logic gate 146 there is the boost PWM signal PWMBoost, which can be sent to the switch QBoost of the bidirectional DC-DC converter 124, as represented in greater detail in Figure 6.
The buck-mode-enable signal Buck_mode at output from the inverter 145, is sent to an AND logic gate 147 together with a buck PWM signal PWMBuck originated by a buck regulation circuit 143, which regulates the pulse- width modulation so as to obtain the desired voltage regulation VDCiink/ in a way in itself known to the person skilled in the branch, in particular by controlling the inductor current IL, i.e., the output current of the converter 124 operating in forward mode (buck mode) . The regulation circuit 143 also receives the reference voltage value Vref, as control quantity of a voltage control loop, as described in greater detail in what follows. If the buck-mode-enable signal, Buck_mode, is active, i.e., in the case illustrated is a logic one, at output there is has the buck PWM signal PWMBuck, which can be sent to the switch QBuck of the bidirectional DC-DC converter 124.
The buck-mode-enable signal Buck_mode is also sent to an AND logic gate 148 together with a auxiliary PWM signal PWMaux originated by an auxiliary regulation circuit 144, which regulates the pulse-width modulation so as to obtain the desired voltage drop VDCiink , in particular by controlling the auxiliary-inductor current IL, i.e., the output current of the converter 125. The regulation circuit 144 also receives the maximum overvoltage value Vmax, as control quantity of a voltage control loop, as described in greater detail in what follows. It is clear how with this configuration if the buck-mode-enable signal Buck_mode is de- activated, i.e., it is a logic zero, the output of the logic gate 148 is always at zero, and hence operation of the converter 125 is inhibited, in so far as the auxiliary switch Qaux remains open.
As mentioned, Figure 4B illustrates a bidirectional DC-DC energy-conversion apparatus 123' , which comprises the first bidirectional DC-DC converter 124 connected between the intermediate energy-storage stage 40 and the vehicle battery 14, but not the second auxiliary DC-DC converter 125 connected between the intermediate energy-storage stage 40 and an auxiliary load Raux. Figure 5B accordingly illustrates an embodiment of the control circuit 140' for the converter 123' , which comprises just the bidirectional converter 124. Consequently, as compared to the circuit illustrated in Figure 5A, it does not comprise the AND logic gate 148 nor the auxiliary regulation circuit 143.
It is emphasized in this regard how the solution described herein refers in general to an apparatus for bidirectional conversion of energy between high and low voltage, which does not necessarily comprise circuits for dissipating energy overshooting by the high-voltage bus like the auxiliary converter of Figure 5A; i.e., it refers in general to a bidirectional energy-conversion apparatus of a DC-DC type operating between a low- voltage system LV and a high-voltage system HV of a vehicle comprising an energy-recovery stage 30,
said low-voltage system LV, which operates at a first voltage Vbat, comprising a battery 14 that supplies said first voltage Vbat on a low-voltage bus LV said high-voltage system HV, which operates at a second voltage VinDCDc/ VDCiink higher than said first voltage Vbat, comprising said energy-recovery stage 30 of the vehicle that supplies said second voltage VinDCDc/ said second voltage VinDCDc/ VDCiink being supplied through an intermediate energy-storage system 40 to a DC-DC conversion module 23; 123, which converts said second voltage VinDCDc/ VDCiink into said first voltage Vbat for said low-voltage bus LV, wherein said DC-DC conversion module 123 comprises a bidirectional DC-DC converter 124 connected between the intermediate energy-storage stage 40 and the vehicle battery 14, and said apparatus is configured for selecting a direction of conversion of said bidirectional converter 124, from high voltage HV to low voltage LV or from low voltage LV to high voltage HV via a control circuit 140 as a function of the value of the voltage VDCiink on the high- voltage bus HV.
The auxiliary load Raux must be sized so as to guarantee the entire dissipation of the excess energy; i.e., it must have a resistive value not higher than, i.e., lower than or equal to, the value that would cause a voltage drop across it equal to the voltage on the bus VDCiink in the presence of the maximum current deriving from the auxiliary DC-DC converter 125 of a buck type.
The operation described, in particular for the regulation circuit of Figure 5A, is obtained via the use of the three regulation circuits 142, 143, 144, one for each mode, the boost mode, the buck mode, and the auxiliary mode, the latter mode being enabled only during buck-mode operation. Each regulation circuit 142, 143, 144 envisages a respective voltage control loop on the bus VDCiink and a pulse-width modulator, where this is understood as being a circuit that generates a PWM signal with a pulse-width modulation determined by one or more control signals, which regulates an internal inductor-current loop (for example, a loop operating in Peak-Current Mode) . The outputs of the three pulse-width modulators are enabled by the boost-mode-enable signal Boost_mode or buck- mode-enable signal Buck_mode described above and directed to the switches Qsoost/
Figure imgf000019_0001
QAUX (or to their drivers) for operating in the required configuration.
For example, with reference to Figure 6, the control loop comprises an adder 143a, which receives as control quantity, or setpoint, the reference voltage Vref, which it compares with the bus voltage DCiink picked up on the input of the converter 123, to obtain an error signal that drives, through a compensation circuit 143b, an internal current loop 143c, which, for example, carries out a current limitation. The output of the current loop is supplied as control signal to a pulse-width modulator 143d, which also receives also the current value IL of the inductor L for controlling the pulse-width-modulation value and, as illustrated in Figure 5, supplies a signal PWMBuck to the logic gate 147, which also receives the buck-mode-enable signal Buck_mode. At output from the logic gate 147 is the signal PWMbuck, which controls, preferably through drivers, opening and closing of the buck switch QBuck- The boost switch QB0ost is kept open.
In Figure 7 the boost regulation circuit 142 is similar, with an internal current loop 142c that carries out a current limitation of its own at a limit current value.
In Figure 8 the auxiliary regulation circuit 144 is similar, with an internal current loop 144c that carries out a current limitation of its own, and moreover the maximum overvoltage Vmax is given as reference or setpoint value for limiting the voltage value .
Figure 9 illustrates diagrams that plot as a function of time the waveforms of signals of the apparatus described herein in a condition of turning-on and successive entry of excess energy on the bus.
The voltage on the bus VDCiink upon the turning-on rises, while the converter 23 is operating in boost mode (signal Boost_mode at high level) . When the voltage on the bus VDCiink exceeds the upper hysteresis threshold VTH of the comparator 141, this switches its output, the boost-mode-enable signal Boost_mode drops to the low logic level, and the buck-mode-enable signal Buck-mode goes to high logic level, enabling the bidirectional DC-DC converter 124 to function in buck mode converting the high voltage of the HV side into low voltage on the LV side. The auxiliary DC-DC converter 125 is enabled if the voltage on the bus VDciink has exceeded the maximum overvoltage Vmax and the bidirectional converter 124 is in buck mode (the driving signal PWMaux is issued) . The auxiliary converter 125 is disabled when the voltage on the bus DCiink has dropped below the maximum overvoltage Vmax. When the voltage on the bus VDCiink drops below the lower hysteresis threshold VTL of the comparator 141, the apparatus returns into boost mode.
In the more general case of the solution here described of Figure 5B, the control circuit 140' comprises the comparator with hysteresis 141 with an upper hysteresis threshold VTH and a lower hysteresis threshold VTL configured for comparing the voltage on the bus VDCiink with a reference voltage Vref, and, if the voltage on the bus VDCiink exceeds the upper threshold VTH, a status signal is generated for enabling the operation of conversion from high voltage to low voltage, or buck mode Buck_mode, and if the voltage on the bus VDCiink drops below the lower threshold VTL, a status signal is generated for enabling the operation of conversion from low voltage to high voltage, or boost mode Boost_mode. The control circuit 140 only comprises the respective regulation circuits 142, 143 for the buck mode and the boost mode, which generate respective PWM driving signals PWMBuck, PWMBoost for driving respective switches QBuck/ QBoost of said buck converter QBuck, L, DBuck and boost converter QBoost, L, DBoost/ and just the logic circuits 147, 148 for selectively supplying at output from said regulation circuit 140 said PWM driving signals PWMBuck, PWMBoost to said respective switches QBuck/ QBoost/ under the control of said status signal for enabling the operation of conversion from high voltage to low voltage, Buck_mode, and said status signal for enabling the operation of conversion from low voltage to high voltage, Boost_mode .
Figure 10 illustrates diagrams that plot as a function of time the waveforms of signals of the apparatus in a condition in which the input energy, coming from the energy-recovery system 30 is in excess with respect to the energy that can be transferred into the battery 14.
In this case, the converter 123 is in buck mode; when the voltage on the bus VDCiink exceeds the maximum overvoltage Vmax the auxiliary converter 125 is enabled (the driving signal PWMaux is issued) .
Figure 11 illustrates diagrams that plot as a function of time the waveforms of signals of the apparatus in an additional condition that represents the case where the maximum overvoltage Vmax is set at a value higher than that of the other thresholds. In this mode, the voltage ripple increases, but a better mean energy transfer is obtained, in so far as dissipation of the excess energy is limited by storing it temporarily in the storage element.
Also in this case, the converter 123, initially in buck mode with the bidirectional DC-DC converter 124 activated in buck mode to convert the high voltage into low voltage, activates the auxiliary DC-DC converter 125 when the voltage on the bus DCiink exceeds the maximum overvoltage Vmax and de-activates it, instead, when the voltage on the bus VDCiink subsequently drops below the maximum overvoltage Vmax.
The solution proposed may be applied also in the case in which is energy-management strategies are to be implemented by varying the voltage of the high-voltage bus (for example, in the presence of an energy-storage element such as supercapacitors or a Li-ion battery) . In this case, the reference voltages Vref, the threshold hysteresis voltages VTH, VTL, and the maximum overvoltage Vmax must be rendered settable in time.
Hence, from the foregoing description the advantages of the solution emerge clearly.
Advantageously, the apparatus and method described enable regulation of the flow of power in an automatic way without requiring reading of the currents. Known solutions for determining the direction of operation of a bidirectional DC-DC converter envisage acquisition of the sign of the currents at input and output and consequent setting of the control. In the case where the devices connected to the bus are numerous (at least four controllers for the shock absorbers) this approach may be complex. The solution proposed envisages, instead, just reading of the voltage on the high- voltage bus with consequent determination of the direction of operation of the first converter and possible activation of the second converter.
Of course, without prejudice to the principle of the invention, the details of construction and the embodiments may vary widely with respect to what has been described and illustrated herein purely by way of example, without thereby departing from the scope of the present invention.

Claims

1. A bidirectional energy-conversion apparatus of a DC-DC type operating between a low-voltage system (LV) and a high-voltage system (HV) of a vehicle comprising an energy-recovery stage (30),
said low-voltage system (LV) , which operates at a first voltage (Vbat) , comprising a battery (14) that supplies said first voltage (Vbat) on a low-voltage bus (LV) ,
said high-voltage system (HV) , which operates at a second voltage (VinDCDc, VDCiink) higher than said first voltage (Vbat) , comprising said energy-recovery stage (30) of the vehicle that supplies said second voltage (VinDCDC; Vnclink) ,
said second voltage (VinDCDc, VDCiink) being supplied, through an intermediate energy-storage system (40), to a DC-DC conversion module (23; 123), which converts said second voltage (VinDCDc, VDCiink) into said first voltage (Vbat) for said low-voltage bus (LV) ,
said apparatus being characterized in that:
said DC-DC conversion module (123) comprises a bidirectional DC-DC converter (124), connected between the intermediate energy-storage stage (40) and the vehicle battery (14); and
said apparatus is configured for selecting a direction of conversion of said bidirectional converter (124), from high voltage (HV) to low voltage (LV) or from low voltage (LV) to high voltage (HV) , via a control circuit (140) as a function of the value of the voltage (VDCiink) on the high-voltage bus (HV) .
2. The apparatus according to Claim 1, characterized in that said first bidirectional converter (124) is configured for operating in a buck- conversion mode
Figure imgf000024_0001
L, DBuck) from high voltage to low voltage and a boost-conversion mode (QBoost, L, DBoost) , said modes being selectable by said control circuit (140) for operating, respectively, conversion from high voltage (HV) to low voltage (LV) or from low voltage (LV) to high voltage (HV) .
3. The apparatus according to Claim 2, characterized in that said control circuit (140) comprises a comparator with hysteresis (141) with an upper hysteresis threshold (VTH) and a lower hysteresis threshold (VTL) , which is configured for comparing the voltage on the bus (VDCiink) with a reference voltage Vref, and, if the voltage on the bus (VDCiink) exceeds the upper threshold (VTH) , a status signal is generated for enabling the operation of conversion from high voltage to low voltage, or buck mode (Buck_mode) , and
if the voltage on the bus (VDCiink) drops below the lower threshold (VTL) , a status signal is generated for enabling the operation of conversion from low voltage to high voltage, or boost mode (Boost_mode) .
4. The apparatus according to any one of the preceding claims, characterized in that said control circuit (140) comprises respective regulation circuits (142, 143) for the buck mode and the boost mode, which generate respective PWM (Pulse-Width Modulation) driving signals (PWMBuck, PWMBoost) for driving respective switches (QBuck, QBoost) of said buck converter (QBuck, L, DBuck) and said boost converter (QBoost, L, DBoost) , and logic circuits (147, 148) for selectively supplying at output from said regulation circuit (140) said PWM driving signals (PWMBuck, PWMBoost) to said respective switches (QBuck/ QBoost/ ) under the control of said status signal for enabling the operation of conversion from high voltage to low voltage (Buck_mode) and said status signal for enabling the operation of conversion from low voltage to high voltage (Boost_mode) .
5. The apparatus according to any one of the preceding claims, characterized in that said apparatus (90; 190) comprises an auxiliary load (Raux) , in particular an external load, which can be connected in order to enable dissipation of the excess energy supplied by the energy-recovery system (30),
said DC-DC conversion module (123) further comprising a bidirectional DC-DC converter (124) connected between the intermediate energy-storage stage (40) and the vehicle battery (14), and a second DC-DC converter (125) connected between the intermediate energy-storage stage (40) and said auxiliary load
6. The apparatus according to any one of the preceding claims, characterized in that said apparatus is configured for selecting a direction of conversion of the first bidirectional converter (124), from high voltage (HV) to low voltage (LV) or from low voltage (LV) to high voltage (HV) ) , and activation or deactivation of said second auxiliary converter (124) via a control circuit (140) as a function of the value of the voltage (VDCiink) on the high-voltage bus (HV) .
7. The apparatus according to any one of the preceding claims, characterized in that said first bidirectional converter (124) further comprises an auxiliary buck converter (QAUX J LAUX J Daux) , which can be selected if said one buck converter (QBuck/ L, DBuck) is selected active for conveying the bus voltage (VDCiink) on the auxiliary load (Raux) ·
8. The apparatus according to any one of the preceding claims, characterized in that said control circuit (140) is configured for:
disabling operation of the first converter (124) and of the second converter (125) if the bus voltage is lower both than the reference voltage value (Vref) and than a maximum overvoltage value (Vmax) ,
enabling operation only of the bidirectional DC-DC converter (124) if the bus voltage (VDCiink) is comprised between the reference voltage value (Vref) and the maximum overvoltage value (Vmax) ,
enabling operation of the first converter (124) and of the second converter (125) if the bus voltage (VDCiink) is higher both than a reference voltage value (Vref) and than a maximum overvoltage value (Vmax) .
9. A method for bidirectional energy conversion between a low-voltage system (LV) and a high-voltage system of a vehicle according to any one of Claims 1 to 8, said method comprising selecting a direction of conversion of the first bidirectional converter (124), from high voltage (HV) to low voltage (LV) or from low voltage (LV) to high voltage (HV) ) , as a function of the value of the voltage (VDCiink) on the high-voltage bus (HV) .
10. The method according to Claim 9, characterized in that it comprises executing an operation of comparison with hysteresis (141) with an upper hysteresis threshold (VTH) and a lower hysteresis threshold (VTL) , and, if the voltage on the bus (VDCiink) exceeds the upper threshold (VTH) , a status signal is generated for enabling the operation of conversion from high voltage to low voltage, or buck mode (Buck_mode) , if the voltage on the bus (VDCiink) drops below the lower threshold (VTL) , a status signal is generated for enabling the operation of conversion from low voltage to high voltage, or boost mode (Boost_mode) .
PCT/IB2018/056674 2017-09-08 2018-08-31 Bidirectional energy-conversion apparatus of a dc-dc type operating between a low-voltage system and a high-voltage system of a vehicle comprising an energy-recovery stage, and corresponding method Ceased WO2019049009A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT102017000101028 2017-09-08
IT102017000101028A IT201700101028A1 (en) 2017-09-08 2017-09-08 BIDIRECTIONAL ENERGY CONVERSION SYSTEM OF DC-DC TYPE OPERATING BETWEEN A LOW VOLTAGE SYSTEM AND A HIGH VOLTAGE SYSTEM OF A VEHICLE INCLUDING A STAGE OF ENERGY RECOVERY AND ITS PROCEDURE

Publications (1)

Publication Number Publication Date
WO2019049009A1 true WO2019049009A1 (en) 2019-03-14

Family

ID=61006105

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2018/056674 Ceased WO2019049009A1 (en) 2017-09-08 2018-08-31 Bidirectional energy-conversion apparatus of a dc-dc type operating between a low-voltage system and a high-voltage system of a vehicle comprising an energy-recovery stage, and corresponding method

Country Status (2)

Country Link
IT (1) IT201700101028A1 (en)
WO (1) WO2019049009A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021181273A1 (en) * 2020-03-10 2021-09-16 Khalifa University of Science and Technology Ultra high gain bidirectional dc to dc converter
US20220410725A1 (en) * 2019-12-18 2022-12-29 Sew-Eurodrive Gmbh & Co. Kg Method of operating an electric vehicle and electric vehicle

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5710699A (en) * 1996-05-28 1998-01-20 General Electric Company Power electronic interface circuits for batteries and ultracapacitors in electric vehicles and battery storage systems
EP2193954A1 (en) * 2008-12-02 2010-06-09 General Electric Company Auxiliary drive apparatus and method of manufacturing same
US20140210389A1 (en) * 2013-01-29 2014-07-31 Fanuc Corporation Motor control device including electric storage device and resistance discharge device
WO2014145018A2 (en) * 2013-03-15 2014-09-18 Levant Power Corporation Active vehicle suspension improvements
EP2821265A1 (en) * 2013-07-04 2015-01-07 Magneti Marelli S.p.A. Apparatus for obtaining predetermined damping characteristics and a simultaneous energy recovery in regenerative shock absorbers and corresponding method

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5710699A (en) * 1996-05-28 1998-01-20 General Electric Company Power electronic interface circuits for batteries and ultracapacitors in electric vehicles and battery storage systems
EP2193954A1 (en) * 2008-12-02 2010-06-09 General Electric Company Auxiliary drive apparatus and method of manufacturing same
US20140210389A1 (en) * 2013-01-29 2014-07-31 Fanuc Corporation Motor control device including electric storage device and resistance discharge device
WO2014145018A2 (en) * 2013-03-15 2014-09-18 Levant Power Corporation Active vehicle suspension improvements
EP2821265A1 (en) * 2013-07-04 2015-01-07 Magneti Marelli S.p.A. Apparatus for obtaining predetermined damping characteristics and a simultaneous energy recovery in regenerative shock absorbers and corresponding method

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220410725A1 (en) * 2019-12-18 2022-12-29 Sew-Eurodrive Gmbh & Co. Kg Method of operating an electric vehicle and electric vehicle
US12263739B2 (en) * 2019-12-18 2025-04-01 Sew-Eurodrive Gmbh & Co. Kg Method of operating an electric vehicle and electric vehicle
WO2021181273A1 (en) * 2020-03-10 2021-09-16 Khalifa University of Science and Technology Ultra high gain bidirectional dc to dc converter
US12081111B2 (en) 2020-03-10 2024-09-03 Khalifa University of Science and Technology Ultra high gain bidirectional DC to DC converter

Also Published As

Publication number Publication date
IT201700101028A1 (en) 2019-03-08

Similar Documents

Publication Publication Date Title
US10340810B2 (en) Bidirectional DC converter assembly having cascade of isolated resonant converter and step-up/step-down converter
US9575502B2 (en) Bi-directional DC-DC converter with current reference by comparing the voltage errors of the low and high voltage sides
US9849789B2 (en) Power supply system
US9698684B2 (en) Adaptive soft switching control for power converter
US8994349B2 (en) Synchronous rectifier bi-directional converter
US10164453B2 (en) Apparatus for managing the energy supplied to a low-voltage system of a motor vehicle that comprises an energy-recovery stage, and corresponding method
EP2463995B1 (en) Fault tolerant synchronous rectifier PWM regulator
WO2011084742A2 (en) Bidirectional signal conversion
US10170927B2 (en) Apparatus for managing the energy supplied to a low-voltage system of a motor vehicle that comprises an energy-recovery stage, and corresponding method
US20160261123A1 (en) Charging circuit for an energy storage device and method for charging an energy storage device
CN110739848A (en) High-gain DC-DC converter for electric vehicle
JP5928518B2 (en) Power conversion apparatus and control method thereof
Rigogiannis et al. Experimental investigation of a digitally current controlled synchronous buck DC/DC converter for microgrids applications
Mane et al. Design, modelling and control of bidirectional DC-DC converter (for EV)
WO2019049009A1 (en) Bidirectional energy-conversion apparatus of a dc-dc type operating between a low-voltage system and a high-voltage system of a vehicle comprising an energy-recovery stage, and corresponding method
JP5255094B2 (en) DC-DC converter and DC-DC converter system
WO2019049006A1 (en) Energy-conversion apparatus of a dc-dc type operating between a low-voltage system and a high-voltage system of a vehicle comprising an energy-recovery stage, and corresponding method
EP2501013A2 (en) Electrical accumulator units with safe turn-off
US11689093B2 (en) Current source inverter having hybrid switches
JP4871647B2 (en) DC-DC converter and DC-DC converter system
Vilberger et al. Bidirectional DC-DC Conversion in the Traction Drive
JP2016131428A (en) Power supply device for industrial vehicle

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 18770093

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 18770093

Country of ref document: EP

Kind code of ref document: A1