RU2849575C2 - Power factor corrector - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: in power factor corrector containing connected to device negative and positive potential input terminals series circuit of first (1), second (2) and third (3) diodes, anode of first diode (1) is connected to terminal of negative potential, and cathode of third diode (3) is connected to terminal of positive potential, common connection point of first (1) and second (2) diodes is connected to positive potential terminal through first capacitor (4), and second (2) and third (3) diodes common connection point is connected to second capacitor (5) first terminal, series circuit is shunted according to the second series circuit from fourth (6), fifth (7) and sixth (8) diodes, the second terminal of second capacitor 5 is connected to the common connection point of fourth (6) and fifth (7) diodes, and common connection point of fifth (7) and sixth (8) diodes is connected to negative potential terminal through third capacitor (9).

EFFECT: increasing power coefficient and efficiency of power supply units with power coefficient corrector, as well as improving coefficient of form, reducing coefficient of harmonics of current consumed from the mains and multiplicity of their start-up current.

1 cl, 1 dwg

Description

This invention relates to electrical engineering and can be used in the design of new energy-efficient power supplies for gas-discharge and LED lamps, as well as other types of power supply devices for various consumers with capacitive filters and capacitive loads from an AC network. The invention aims to increase the power factors and efficiency of power supplies, as well as improve the form factor, reduce the harmonic distortion factor of the current drawn from the network, and reduce the frequency of their starting current.

A power factor corrector is known that contains a capacitor connected to the input terminals of the negative and positive potential of the device and a resistor shunting it (P. 162915 RF, IKI H01L 33/00. Integrated source of optical radiation / Silkin E.M. - Stated 12.08.2015, published 27.06.2016, Bulletin No. 18).

This connection of elements is used for voltage filtering, for example, at the output of a single-phase rectifier in various designs of modern power supply systems of relatively low power and represents a nonlinear capacitive load for the network.

The disadvantages of conventional power factor correctors include low efficiency and a low performance factor, which in the designs used can reach values of no more than 50-70%. The device is typically characterized by extremely high achievable harmonic distortion factors (THDs) of the current drawn from the grid and inrush current ratios. In fact, such a corrector has a negative (reverse) effect—it reduces the power factor to 0.5–0.6, and the inrush current ratio without the use of additional components is limited only by the internal resistances of the rectifier circuits and the impedance of the capacitor. However, as noted above, the technical solution discussed is widely used to smooth out voltage pulsations in the DC link of low-power and, less commonly, medium-power power supplies. Reducing the AC component of the rectified voltage (reducing the ripple factor) by increasing the capacitor capacitance leads to a further reduction in the power factor, an increase in the harmonic distortion factor and the inrush current, and an increase in the effective input current of the power supply in operating modes. All this significantly increases the overall losses in the device and leads to a further reduction in efficiency.

A power factor corrector is known that contains a series circuit of a capacitor and a dinistor connected to the input terminals of the negative and positive potential of the device, the cathode of which is connected to the positive potential terminal and shunted by a counter diode (P. 185192 RF, IKI H02M 7/06. Power factor corrector / Soldatkin V.S., Ivanov A.N., Olisovets A.Yu., Tuev V.I., Khabarov M.V. - Claim 06.07.2018, published 26.11.2018, Bulletin No. 33).

A disadvantage of the known power factor corrector is its comparatively low achievable efficiency and the low performance factor of devices based on it, which can be as low as 65%. The power factor achieved by the device does not exceed 0.7, the inrush current ratio cannot be lower than when using filter capacitors, and the harmonic distortion factor is at least 135%. The device is characterized by a wide range of achieved parameters and non-repeatability of operating modes, as well as low reliability of the correction process itself due to the specific characteristics of the typical dinistor and, to a certain extent, the circuit complexity.

A power factor corrector is known that comprises a series circuit of first and second diodes, a choke, and third and fourth diodes connected to the input terminals of the negative and positive potential of the device, the anode of the first diode being connected to the terminal of the negative potential, and the cathode of the fourth diode being connected to the terminal of the positive potential, the common connection point of the first and second diodes being connected to the terminal of the positive potential through the first capacitor, and the common connection point of the third and fourth diodes being connected to the terminal of the negative potential through the second capacitor (P. 158331 RF, IPC H01L 33/00. Optical radiation source / Silkin E.M. - Cl. 21.05.2015, published 27.12.2015, Bulletin No. 36).

A disadvantage of the conventional power factor corrector is its relatively low achievable efficiency (0.89...0.91) and the low efficiency of devices based on it, which can be as low as 75% due to significant losses in the inductor and diodes. The harmonic distortion factor (HDF) of the current drawn from the grid in systems based on it typically does not exceed 30%. Power supply devices are also characterized by relatively low reliability due to the neutral wire being loaded with multiple harmonics of the current. Moreover, the starting current of devices using conventional power factor correctors is significantly reduced compared to systems using filter capacitors, but remains insufficiently low.

The closest in technical essence to the invention is a power factor corrector, comprising a series circuit of first, second and third diodes connected to the input terminals of the negative and positive potential of the device, the anode of the first diode is connected to the terminal of the negative potential, and the cathode of the third diode is connected to the terminal of the positive potential, the common connection point of the first and second diodes is connected to the terminal of the positive potential through the first capacitor, and the common connection point of the second and third diodes is connected to the terminal of the negative potential through the second capacitor (P. 160311 RF, IPC H01L 33/00. Integrated source of optical radiation / Silkin E.M. - Cl. 25.06.2015, published 10.03.2016, Bulletin No. 7).

A well-known power factor corrector is selected as a prototype of the invention.

This technical solution provides efficiency up to 0.88...0.90, a reduction in harmonic distortion of 30...37%, and a fourfold reduction in starting current (compared to devices using capacitive filtering). The voltage across the capacitors is halved, significantly increasing the reliability of the corresponding devices.

The disadvantage of the prototype remains the low efficiency factor (about 80%) due to the relatively high harmonic distortion factor of the current consumed from the network, the limited maximum efficiency value (>0.9), the relatively high starting current factor for critical applications and the rather significant level of the operating effective current, which reduce the reliability of the power supply and electrical power systems.

The invention is aimed at improving the efficiency (average power factor of power supply and electrical power systems), the maximum efficiency, and the reliability of devices, which is the objective of the invention. The technical result consists of increasing the power factor and efficiency, reducing the harmonic distortion factor of the current drawn from the network, optimizing the shape factor of the current drawn by devices, reducing the inrush current ratio and the effective operating current, and increasing the operational reliability of power supply and electrical power systems with the claimed (passive) power factor corrector.

The said objective and technical result are achieved by the fact that in a power factor corrector containing a series circuit of the first, second and third diodes connected to the input terminals of the negative and positive potential of the device, the anode of the first diode is connected to the terminal of the negative potential, and the cathode of the third diode is connected to the terminal of the positive potential, the common connection point of the first and second diodes is connected to the terminal of the positive potential through the first capacitor, and the common connection point of the second and third diodes is connected to the first terminal of the second capacitor, the series circuit is shunted accordingly by a second series circuit of the fourth, fifth and sixth diodes, the second terminal of the second capacitor is connected to the common connection point of the fourth and fifth diodes, and the common connection point of the fifth and sixth diodes is connected to the terminal of the negative potential through the third capacitor.

A significant distinguishing feature of the invention is the increase in the power factor to 0.96...0.97, and the efficiency of devices with a power factor corrector to 90...93% due to a change in the operating principle, improved technical characteristics of the power factor corrector, and possible design options. Devices with the claimed passive corrector exhibit low levels of radio interference and emissions, have a comparatively low harmonic distortion factor of the current consumed from the network (>14%) and an improved form factor, ensuring small surges (multiples) of the inrush current (during switch-on, they are virtually absent, taking into account the impedances of the capacitors). Inrush current multiples are reduced (under the same, comparable parameters and conditions) by at least nine times compared to, for example, systems using filter capacitors, and the amplitudes of the input operating current are also limited. The device's effective current consumption from the mains (when operating at the specified power level) and switching losses in components, particularly in the bridge diodes used in rectifier assemblies, have been reduced by 50-60%. Maximum capacitor voltages can be reduced by a factor of three, improving operational reliability.

The improvement in power factor and efficiency, reduction in the harmonic distortion factor of the current drawn from the grid, optimization of the current shape factor of the devices, reduction in the inrush current ratio, and reduction in the amplitude and effective operating current, as well as increased reliability of power supply systems and power supplies with the claimed passive power factor corrector, are due to new design principles and a new corrector design, a new electrical circuit, implementation of the input circuit, new components and connections—that is, the distinctive features of the invention. Thus, the distinctive features of the claimed power factor corrector are significant.

The figure shows a typical electrical circuit of a power factor corrector.

The power factor corrector comprises a series circuit of the first (1), second (2) and third (3) diodes connected to the input terminals of the negative and positive potential of the device, the anode of the first diode 1 is connected to the terminal of the negative potential, and the cathode of the third diode 3 is connected to the terminal of the positive potential, the common connection point of the first 1 and second 2 diodes is connected to the terminal of the positive potential through the first capacitor (4), and the common connection point of the second 2 and third 3 diodes is connected to the first terminal of the second capacitor (5), the series circuit is shunted accordingly by a second series circuit of the fourth (6), fifth (7) and sixth (8) diodes, the second terminal of the second capacitor 5 is connected to the common connection point of the fourth 6 and fifth 7 diodes, and the common connection point of the fifth 7 and sixth 8 diodes is connected to the terminal of the negative potential through the third capacitor (9).

The power factor corrector operates in steady-state mode as follows. Assume the corrector and load are connected to the output of a single-phase rectifier bridge with diodes or thyristors (transistors). The capacitance values of capacitors 4, 5, and 9 in the device may be equal to each other or different (in various combinations of values). When implementing the device, it is preferable to have equal capacitances for capacitors 4, 5, and 9. In this case, capacitors 4, 5, and 9 are rated for the same maximum voltage and, during operation, charge to the same voltage values, approximately equal to one-third (1/3) of the maximum voltage between the input terminals of the negative (-) and positive (+) potential. The single-phase bridge can be implemented using discrete elements or have an integrated design (e.g., MBS10F or KC407). The operating principle of the device remains unchanged. A single-phase bridge rectifies (converts) the alternating supply (line) voltage into direct voltage with a pulsation frequency of 100 Hz (at a line voltage frequency of 50 Hz). That is, the voltage at the output of the single-phase rectifier bridge is a pulsating voltage with a frequency equal to twice the frequency of the power supply network (at the input of the rectifier bridge) and an amplitude equal to the amplitude of the power supply network voltage, reduced by the voltage drop across the diodes (thyristors) of the bridge and the connecting buses (the winding of the power transformer, if any). If the instantaneous voltage at the input of the device (corrector and load) exceeds the sum of the voltages on capacitors 4, 5, 9, they begin to charge. The charging of capacitors 4, 5, 9 occurs through diodes 2, 7 (see figure) along the circuit: "+" - 4 - 2 - 5 - 7 - 9 - "-". When the capacitances of capacitors 4, 5, and 9 are equal, they are charged, as noted, to approximately equal voltages of one-third (1/3) of the supply voltage amplitude. Charging occurs in a series circuit of capacitors 4, 5, and 9. If the capacitances of capacitors 4, 5, and 9 are different, the voltages across them are inversely proportional to the values of the aforementioned capacitances. The equivalent capacitance in the charging circuit corresponds to the capacitance of the series connection (which is, at most, three times less than the capacitance of a single capacitor if the capacitances are equal). When the instantaneous voltage at the input of the power factor corrector (at the output of the bridge) decreases to a value of 1/3 of the amplitude of the supply network voltage (approximately, when the capacitances of capacitors 4, 5, 9 are equal), diodes 1 and 8 are turned on, and capacitors 4, 9 begin to discharge in parallel onto the load connected between the input terminals of the negative (-) and positive (+) potential of the corrector (discharge circuits: "-" - 1 - 4 - "+" and "-" - 9 - 8 - "+"). The capacitance in the discharge circuit is equal to the sum of the capacitances of capacitors 4 and 9. With a further decrease in voltage (minimum by the value of the voltage drop on one diode, when the capacitances of capacitors 4, 5, 9 are equal), diodes 3 and 6 are turned on and the discharge of capacitor 5 onto the load begins along the circuit: "-" - 6 - 5 - 3 - "+". If the corrector is made with different capacities of capacitors 4, 5, 9, it is possible to separate the moments of switching on each of the capacitors 4, 5, 9. In this case, all three capacitors 4, 5, 9 are switched on at the final discharge interval and operate in parallel on the load (with equal capacitor capacities, the equivalent capacitance is nine times greater than the equivalent capacitance when charging capacitors 4, 5, 9, which allows, in particular, to reduce the amplitude of the surge or the current multiple when switching on the device by nine times and to significantly improve the form factor of the consumed current).

Since capacitors 4, 5, 9 are charged during operation via diodes 2, 7 to a voltage equal to approximately (maximum) one-third of the amplitude of the bridge output voltage or, equivalently (approximately), one-third of the amplitude of the mains supply (AC) voltage, and capacitors 4, 5, 9 are charged in a series circuit while discharging in a parallel circuit, the amplitudes of the charging currents and the duration of the charge-discharge intervals are reduced, and the operation of the device with a higher power factor is ensured. During discharge (via diodes 1, 8 and 3, 6) to the load ("-" "+"), capacitors 4, 5, 9, as noted, operate in parallel. The charging and discharging intervals are spaced in time. This is energetically advantageous. The harmonic distortion coefficient (distortion) of the current consumed by the device from the mains lies within 14%. The voltage at the output terminals of the bridge does not drop to a value less than 30% of the amplitude value, which ensures the normal operation of the entire device and the load (supplying the load with the discharge current of capacitors 4, 5, 9).

Compared to the prototype, the power factor and efficiency of the devices are significantly increased by changing the operating principle, improving technical characteristics, and possible design options. Indeed, the claimed power factor corrector provides a significantly higher maximum power factor (up to 96-97%) and low levels of radio interference and emissions (not exceeding established standards). Devices based on it have a comparatively low harmonic distortion factor of the current consumed from the network (no more than 14%), ensure small inrush current (when the device is turned on, they are reduced to 30% compared to the prototype), and also a low amplitude of the input operating current. The harmonic distortion factor of the device selected as the prototype reaches 30-37%. Higher harmonics of the consumed current in the prototype are sources of additional electrical losses. The new power supply reduces the effective current consumed from the network (when operating at a specified power) and switching losses in the components, particularly in the bridge diodes, by 6-7%. The efficiency of systems with the claimed power factor corrector can reach 90-93% (exceeding the values achieved with the prototype by up to 13%). As a result (taking into account differences in design), the maximum efficiency of devices with the new power factor corrector increases by approximately 10-13%.

Reliability of devices is increased by reducing high-frequency harmonics, electrical losses, currents, and voltages. Mean time between failures is more than doubled.

The scope of application of the new passive power factor corrector can be further expanded. The proposed power factor corrector meets modern technical specifications for such devices.

The range of power factor corrector designs based on the new design is significantly expanded. Each design offers an optimal design and a highly technologically advanced device, which, in particular, reduces the final price of industrial products based on the proposed passive power factor corrector. The voltage across the device's capacitors is reduced, allowing for a wider range of components used in the corrector, further improving its energy performance, and reducing the cost.

A passive power factor corrector can be fully or partially implemented as an integrated design.

Claims (1)

A power factor corrector comprising a series circuit of a first, second and third diodes connected to the input terminals of the negative and positive potential of the device, the anode of the first diode being connected to the terminal of the negative potential, and the cathode of the third diode being connected to the terminal of the positive potential, the common connection point of the first and second diodes being connected to the terminal of the positive potential through the first capacitor, and the common connection point of the second and third diodes being connected to the first terminal of the second capacitor, characterized in that the series circuit is shunted according to a second series circuit of the fourth, fifth and sixth diodes, the second terminal of the second capacitor being connected to the common connection point of the fourth and fifth diodes, and the common connection point of the fifth and sixth diodes being connected to the terminal of the negative potential through the third capacitor.