WO2025032792A1 - Charging control method and charging control system - Google Patents

Abstract

This charging control method is for controlling an electric vehicle charging control system that is provided with: a first terminal and a second terminal that are connected to an external power source; a capacitor that is connected between the first terminal and the second terminal; a neutral point where output lines of an electric motor are gathered and that is connected to the first terminal; and a switch that is disposed between the neutral point and the first terminal. The charging control system is capable of charging a battery from the external power source by raising the voltage of the external power source via the electric motor and a power conversion device. The charging control method includes: detection processing to detect charging of the battery from the external power source while an electric vehicle is stopped; and control processing to execute control to rotate a rotor of the electric motor to a prescribed position and stop the rotor there if charging of the battery from the external power source has been detected.

Description

Charging control method and charging control system

The present invention relates to a charging control method and charging control system for an electric vehicle that is capable of charging a battery from an external power source by boosting the voltage of the external power source via an electric motor and a power conversion device.

JP2021-175363A discloses a technology that uses an inverter to boost the charging voltage received at the neutral point of a motor from an external power source to a high voltage and charge the battery.

Summary of the Invention

In the conventional technology described above, switching is required to convert the voltage into a DC voltage that corresponds to the battery voltage level. In this case, the motor inductance also serves as the converter function, so if the motor inductance is small, the current change will be large, resulting in large inverter losses and motor losses.

The purpose of the present invention is to reduce losses that occur when charging a battery from an external power source by boosting the voltage of the external power source via an electric motor and a power conversion device.

One aspect of the present invention is a charging control method for controlling a charging control system in an electric vehicle that includes a first terminal and a second terminal connected to an external power source, a capacitor connected between the first and second terminals, a neutral point where each output line of an electric motor is gathered and is connected to the first terminal, and a switch provided between the neutral point and the first terminal, and that is capable of charging a battery from the external power source by boosting the voltage of the external power source via the electric motor and a power conversion device. This charging control method includes a detection process that detects that the battery is being charged from the external power source while the electric vehicle is stopped, and a control process that executes control to rotate the rotor of the electric motor to a predetermined position and stop it when it is detected that the battery is being charged from the external power source.

FIG. 1 is a block diagram showing an example of the configuration of a charging control system. FIG. 2 is a diagram showing an example of setting the position at which the rotor of the motor is stopped. FIG. 3 is a diagram showing the characteristics of the input current value to the stator and the magnetic flux of each phase of the stator. FIG. 4 is a flowchart showing an example of the charging process.

Below, an embodiment of the present invention will be described with reference to the attached drawings.

[Charging control system configuration]
1 is a block diagram showing an example of the configuration of a charging control system 100. Specifically, the charging control system 100 includes a battery 1, an inverter 2, a motor 3, a controller 4, an external power supply terminal 6, a current sensor 7, capacitors 8 and 11, voltage sensors 9 and 12, a first relay R1, a second relay R2, and a third relay R3.

In other words, the charging control system 100 of this embodiment is configured using elements of an electric vehicle drive system that uses a battery 1 as a power source and drives a motor 3 via an inverter 2. In particular, the charging control system 100 is a control system that boosts the voltage of an external power source 5 via the motor 3 and the inverter 2 to charge the battery 1. The charging control system 100 is mounted, for example, on an electric vehicle (EV) or a plug-in hybrid vehicle (PHEV). In the following description, each of these vehicles will be referred to as an electric vehicle C1.

Battery 1 is a DC power source that functions as a driving power source for motor 3. For example, battery 1 is configured as an on-board high-voltage battery such as a lithium-ion secondary battery.

The inverter 2 is a power conversion device that converts the DC power output by the battery 1 into AC power and supplies it to the motor 3 when driving the motor 3. The configuration of the inverter 2 will be described in detail later.

Motor 3 is a three-phase AC motor such as an interior permanent magnet synchronous motor (IPMSM) and functions as a drive source for electric vehicle C1. A rotor position signal indicating the position of the rotor of motor 3 is detected by a resolver (not shown) and output to controller 4.

The charging control system 100 not only drives the motor 3, but also functions as a charging control system that uses the inverter 2 as a power factor correction circuit (PFC) when charging the battery 1 with an external power source 5. For this reason, the charging control system 100 includes an external power source terminal 6, which is a connection terminal for connecting the external power source 5 (such as a direct current power source of a direct current type).

The external power source 5 is, for example, a charging device that supplies DC power, such as a DC charger installed in a charging station. The external power source 5 is, for example, a charging device capable of supplying DC power of about 400 volts.

The external power supply terminal 6 is a terminal for connecting the external power supply 5 to the battery 1 via the inverter 2 when charging the battery 1 with the external power supply 5. The external power supply terminal 6 also includes a first terminal 6a and a second terminal 6b.

The current sensor 7 is a sensor for measuring the current value at three of the four terminals, and outputs the measured current value to the controller 4.

Capacitor 8 is a capacitor connected in parallel to the external power supply 5 to stabilize the potential of the neutral point N1 of the motor 3. By providing capacitor 8 in parallel to the external power supply 5 in this way, the LC circuit consisting of the zero-phase inductance of the motor 3 and capacitor 8 can reduce noise generated by the operation of each switching element Tr1 to Tr6 during charging.

The voltage sensor 9 detects the voltage across the capacitor 8 as a DC voltage V_DC that corresponds to the output voltage of the external power source 5, and outputs it to the controller 4.

Capacitor 11 is a capacitor that smoothes the DC power obtained by rectifying the DC power input from the external power source 5 using the power modules 10u to 10w. Capacitor 11 is connected in parallel between the power modules 10u to 10w and the battery 1.

The voltage sensor 12 detects the voltage across the capacitor 11 as a DC voltage V_BAT equivalent to the voltage of the battery 1, and outputs it to the controller 4.

[Inverter configuration example]
The inverter 2 is a power conversion device that includes power modules 10u to 10w as power modules for driving a motor.

In a drive mode in which the power modules 10u to 10w drive the motor 3, they convert the DC power input from the battery 1 into three-phase AC power and input it to each phase (U phase, V phase, and W phase) of the motor 3. On the other hand, in a charge mode, the power modules 10u to 10w boost the DC power input from the external power source 5 at a desired boost ratio and input it to the battery 1.

The power modules 10u to 10w each include a plurality of legs each consisting of a pair of arms provided corresponding to each phase of the motor 3. More specifically, the U-phase power module 10u is connected to the U-phase of the motor 3, and includes an upper arm consisting of a U-phase switching element Tr1 and a U-phase freewheel diode D1, and a lower arm consisting of a U-phase switching element Tr2 and a U-phase freewheel diode D2. Similarly, the V-phase power module 10v is connected to the V-phase of the motor 3, and includes an upper arm consisting of a V-phase switching element Tr3 and a V-phase freewheel diode D3, and a lower arm consisting of a V-phase switching element Tr4 and a V-phase freewheel diode D4. Furthermore, the V-phase power module 10v is connected to the W-phase of the motor 3, and includes an upper arm consisting of a W-phase switching element Tr5 and a W-phase freewheel diode D5, and a lower arm consisting of a W-phase switching element Tr6 and a W-phase freewheel diode D6. Each switching element Tr1 to Tr6 is composed of a power semiconductor element, for example, an IGBT (Insulated Gate Bipolar Transistor) or a MOS-FET. In principle, the upper arm and lower arm that make up one leg are turned on and the other is turned off depending on the polarity of the AC power.

The inverter 2 also performs pulse width modulation (PWM) control of each of the switching elements Tr1 to Tr6 based on a power command value determined according to the desired motor torque (torque command value). In this way, the energy for driving the motor 3 flows from the battery 1 to the motor 3.

In addition, when power is fed from the neutral point N1 of the motor 3 to the DC connection terminals 2a and 2b of the inverter 2, two switching elements (e.g., switching elements Tr1 and Tr2) included in one leg of the inverter 2 and a coil in the motor 3, one end of which is connected to the connection node 2c of these two switching elements Tr1 and Tr2, constitute one DC converter circuit that can boost the voltage of the neutral point N1 of the motor 3 and provide it to the DC connection terminals 2a and 2b of the inverter 2. The DC connection terminals 2a and 2b are the positive terminal (2a) and negative terminal (2b) respectively connected to both ends of the battery 1. The connection node 2c of the two switching elements Tr1 and Tr2 becomes the motor connection terminal 2f that is connected to one phase of the motor 3. The same applies to the other two switching elements Tr3 and Tr4, Tr5 and Tr6, the other two connection nodes 2d and 2e, and the other two motor connection terminals 2g and 2h.

The connection structure of the coils in the inverter 2 and the motor 3 is therefore equivalent to a total of three converter circuits connected in parallel, and by controlling each of the switching elements Tr1 to Tr6 to operate these multiple parallel-connected DC converters simultaneously, selectively, or in an interleaved manner, the voltage at the neutral point N1 of the motor 3 can be boosted and provided to the battery 1.

In this embodiment, it is possible to set a first charging mode in which the external charging power is provided directly to the battery 1 (without going through the neutral point N1) based on the magnitude of the maximum voltage of the external charging power provided from the external power source 5 to the external power source terminal 6 and the voltage detection value of the battery 1, and a second charging mode in which the external charging power is provided to the neutral point N1 of the motor 3, and then boosted by controlling each of the switching elements Tr1 to Tr6 of the inverter 2 before being provided to the battery 1. However, the following mainly describes the setting of the second charging mode.

The controller 4 controls each part of the charging control system 100 based on various programs stored in a memory unit (not shown). The controller 4 is realized by a processing device such as a CPU (Central Processing Unit). The vehicle ECU (Electronic Control Unit) of the electric vehicle C1 may also be used as the controller 4, or a processing device different from the vehicle ECU may be provided as the controller 4.

In this way, the controller 4 is a computer for comprehensively controlling the operation of the electric vehicle C1 and the operation of the charging control system 100. For example, the controller 4 determines a torque command value for the motor 3 according to the accelerator opening degree of the electric vehicle C1 and controls the inverter 2 and the like. The controller 4 also acquires various information from various sensors installed in the electric vehicle C1 and external devices (e.g., a server) of the electric vehicle C1, and based on this information, detects that the electric vehicle C1 will stop while traveling in order to charge the battery 1 from the external power source 5. Based on this information, the controller 4 also detects that the battery 1 will be charged from the external power source 5 while the electric vehicle C1 is stopped. These detection processes will be described in detail with reference to FIG. 4.

When the motor is driven, the controller 4 generates a PWM signal based on the torque command value of the motor 3, the currents (hereinafter referred to as phase currents) iu, iv, and iw flowing through each phase of the motor 3, the DC voltage V_BAT, and a rotor position signal indicating the position of the rotor of the motor 3. The controller 4 then outputs the generated PWM signal to the inverter 2. By driving each switching element Tr1 to Tr6 based on this PWM signal, the output torque of the motor 3 can be adjusted to a value corresponding to the torque command value. The phase currents iu, iv, and iw are detected (sampled) by current sensors 7 provided in each phase. The rotor position signal indicating the position of the rotor of the motor 3 is detected by a resolver.

In addition, the drive circuit (not shown) of the inverter 2 drives each of the switching elements Tr1 to Tr6 (i.e. turns them on or off) based on the control signal (PWM signal) generated by the controller 4 and in accordance with the duty ratio (switching pattern) determined by the PWM signal.

[Example of charging from an external power source]
Here, a charging method using the charge control system 100 will be described. When the external power supply 5 is electrically connected to the external power supply terminal 6, the charging process starts. Specifically, when the charging process starts, the controller 4 acquires the voltage of the battery 1 (detected value V_BAT) and the maximum charging voltage V_EE_max of the charging power provided by the external power supply 5. Then, the controller 4 compares the detected value V_BAT of the voltage of the battery 1 with the maximum charging voltage V_EE_max.

When the detected voltage value V_BAT of the battery 1 is smaller than the maximum charging voltage V_EE_max, it is possible to provide DC charging power from the external power source 5 directly to the battery 1 without a conversion process. In this case, the controller 4 closes the first relay R1 and the second relay R2 and opens the third relay R3, so that the charging power provided to the external power source terminal 6 can be provided directly to the battery 1 without passing through the neutral point N1 of the motor 3, thereby charging the battery.

On the other hand, when the detected voltage value V_BAT of the battery 1 is greater than the maximum charging voltage V_EE_max, the magnitude of the voltage of the DC charging power from the external power source 5 is converted by switching the switching element of the boost converter circuit realized by the motor 3 and the inverter 2, and the DC charging power from the external power source 5 is provided to the battery 1. In this case, the controller 4 opens the first relay R1 and closes the second relay R2 and the third relay R3, making it possible to provide the charging power provided to the external power source terminal 6 to the battery 1 via the neutral point N1 of the motor 3 and the switching element. The third relay R3 is a switch provided for input to the neutral point N1 of the motor 3.

[Losses during charging]
Here, in recent years, there is a demand for higher output in electric vehicles. For this reason, electric vehicles equipped with high-voltage batteries of, for example, about 800V are beginning to become popular. However, many existing charging facilities are capable of supplying power of, for example, about 400V. Therefore, in order to charge electric vehicles equipped with high-voltage batteries of about 800V, it is considered to renovate the charging facilities installed in various places on a large scale so that they can supply power of, for example, about 800V. However, a large amount of money is required to renovate each of these charging facilities on a large scale. Therefore, it is considered to charge by boosting the voltage on the vehicle side. For example, in order to charge an 800V battery from a 400V charging facility, it is considered to newly install a DC-DC converter in the electric vehicle, boost the power from the charging facility with the DC-DC converter, and then charge the battery. However, in this case, a new circuit for boosting the voltage is required, which increases the manufacturing cost of the electric vehicle. Therefore, in order to effectively utilize each charging facility and suppress increases in the manufacturing costs of the electric vehicle, it is conceivable to boost the voltage using the motor and inverter already installed in the electric vehicle and charge the 800V battery from a 400V charging facility. In this case, the output voltage (400V) of the charging facility is applied to the neutral point of the motor installed in the electric vehicle to flow a direct current, thereby realizing a line voltage of 800V and charging the battery.

In this way, when the voltage of an external power supply is boosted via a motor and inverter to charge a battery from the external power supply, switching is required to convert it into a DC voltage that corresponds to the battery voltage level. In this case, the inductance of the motor also serves as a converter, so if the inductance of the motor is small, the current change becomes large and the switching loss, i.e., inverter loss and motor loss, becomes large, resulting in poor charging efficiency during boosting. Therefore, in this embodiment, the switching loss is reduced by adjusting the inductance L (L component) of the motor.

Specifically, as shown in the following formula 1, the larger the inductance L of the motor, the more likely it is that a smaller current i will generate magnetic flux φ. And, as shown in the following formula 2, if the magnetic flux φ can be increased, the voltage V can be increased. Therefore, by increasing the inductance L of the motor, the magnetic flux φ can be increased and the current i required for the target voltage V can be reduced. Furthermore, when the inductance L of the motor is small, the current pulsation becomes large and the iron loss in the motor increases. Therefore, the smaller the inductance L of the motor, the greater the inverter loss and motor loss.
φ=Li ... Equation 1
V = 2πfφ ... Equation 2

In this embodiment, when the voltage of an external power supply is boosted via a motor and an inverter to charge a battery from the external power supply, the position of the motor rotor is set so that the inductance L of the motor is at or near its maximum value. This makes it possible to reduce losses that occur when the voltage of an external power supply is boosted via a motor and an inverter to charge a battery from the external power supply.

[Example of rotor position setting during charging]
First, a description will be given of a position for increasing the inductance of the motor 3. The position for increasing the inductance of the motor 3 is a position that satisfies both of (1) and (2) below. Note that the magnet d-axis of the rotor refers to the central axis of the rotor on the winding side.
(1) The position where the circumferential center of any phase of the stator coil coincides with the d-axis of the rotor magnet. (2) The position where the magnetic flux generated by the current flowing through the stator coil faces the magnetic flux generated by the magnet.

Among the positions that satisfy both (1) and (2) above, the position that maximizes the inductance of the motor 3 will be described with reference to Figures 2 and 3.

FIG. 2 shows an example of how to set the position at which the rotor of the motor 3 is stopped when the battery 1 of the electric vehicle C1 is charged from an external power source 5.

2(A) shows the relationship between the stop position of the rotor of motor 3 and the inductance generated in the stator of motor 3 when the value of the current flowing through the stator winding of motor 3 (hereinafter referred to as the "input current value Idc") is zero. FIG. 2(B) shows the relationship between the stop position of the rotor of motor 3 and the magnetic flux generated in the stator of motor 3 when the input current value Idc to motor 3 is zero. Specifically, the horizontal axis of the graphs shown in FIGS. 2(A) and (B) shows the position of the rotor of motor 3. The vertical axis of the graph shown in FIG. 2(A) shows the value of inductance generated in the stator of motor 3. The vertical axis of the graph shown in FIG. 2(B) shows the value of magnetic flux of each phase generated in the stator of motor 3. Note that FIGS. 2(A) and (B) show a simplified representation of the inductance that changes depending on the rotor position when charging battery 1.

As shown in Figure 2 (A), the inductance value of motor 3 changes depending on the rotor position when electric vehicle C1 is stopped. The inductance value, which changes depending on the stopping position of motor 3's rotor, has an upwardly convex characteristic. The relationship between the magnetic flux φ generated in the stator of motor 3, the inductance L of motor 3, and the input current value Idc to motor 3 is shown in the above-mentioned formula 1. The relationship between the output voltage value V from motor 3, the frequency f, and the magnetic flux φ is shown in the above-mentioned formula 2.

Therefore, the rotor position where the inductance L of the motor 3 is at its maximum value is the rotor position where the output voltage value V from the motor 3 is at its maximum value. In other words, the rotor position where the inductance L of the motor 3 is at its maximum value is the position where the voltage can be efficiently boosted. Specifically, the positions E1 to E3 (shown by dotted lines) where the inductance L of the motor 3 is at its extreme value are the rotor positions where the inductance is at its maximum value. In this way, there are rotor positions locally where it is possible to improve the charging efficiency. For this reason, it is possible to confirm in advance the rotor position where the inductance L of the motor 3 is at its maximum value based on an experiment or a simulation, and to hold that position in advance. For example, it is possible to perform a magnetic field analysis to find the rotor position where the inductance L of the motor 3 is at its maximum value. It is also possible to find the rotor position where the inductance L of the motor 3 is at its maximum value by calculation, for example. Alternatively, it is possible to change the rotor position by a prior experiment or a simulation, and obtain the current waveform of each phase and the charging efficiency, thereby detecting the optimal rotor position according to each input power.

In this embodiment, when it is determined that the electric vehicle C1 is to be stopped for the purpose of charging, or when it is determined that charging will be performed after the electric vehicle C1 is stopped, the rotor is rotated to a position (or within a predetermined range close to that position) where the inductance L of the motor 3 is at its maximum value, and the rotor is stopped at that position. Note that it may be difficult to pinpoint and stop the rotor at the position where the inductance L of the motor 3 is at its maximum value. In such a case, therefore, a more appropriate voltage boost can be obtained by stopping the rotor close to the position where the inductance L of the motor 3 is at its maximum value. This makes it possible to increase charging efficiency and suppress the occurrence of motor loss and inverter loss.

Here, the relationship between the inductance L of the motor 3 and the iron loss in the motor 3 will be explained. As mentioned above, switching of the inverter 2 is required when charging the battery 1 by boosting the voltage according to its voltage level. That is, the current is varied by switching of the inverter 2 to generate magnetic flux in the motor 3. In this case, since the inductance L of the motor 3 also functions as a converter, if the inductance L of the motor 3 is small, it is necessary to generate a harmonic current with an amplitude of a certain level or more. That is, if the inductance L of the motor 3 is small, the current pulsation of each phase of the motor 3 increases, and the iron loss in the motor 3 increases.

In contrast, in this embodiment, the inductance L of the motor 3 is set to a maximum value or a value close to this value, making it possible to generate magnetic flux with a small current value. This makes it possible to generate magnetic flux in the motor 3 without moving the current significantly by switching the inverter 2. For example, when looking at the current waveforms of each phase of the motor 3 generated by switching the inverter 2, the amplitude of the current harmonics generated by the change in current differs depending on the magnitude of the inductance L of the motor 3. For example, when the inductance L of the motor 3 is small, charging is not possible unless a harmonic current is generated with an amplitude above a certain level. In other words, when the inductance L of the motor 3 is small, the current change becomes large, and the switching loss, i.e., the inverter loss and motor loss, become large.

In contrast, if the inductance L of the motor 3 is set to the maximum value or a value close to it, it becomes possible to generate harmonic currents with smaller amplitudes. This makes it possible to reduce the amplitude of the current harmonics, and to reduce the loss for each amplitude of the harmonic of the current of each phase of the motor 3. In this way, by reducing the harmonic components of the current of each phase of the motor 3, it is possible to reduce the iron loss generated in the motor 3. In other words, the higher the inductance L of the motor 3, the more it is possible to reduce the current pulsation of each phase of the motor 3, and the more it becomes possible to reduce the iron loss generated in the motor 3.

Next, we will explain magnetic flux saturation due to the correlation of the magnetic fields between the rotor and stator in motor 3.

For example, as the input current value Idc to motor 3 is increased, the magnetic flux of the stator of motor 3 increases. Then, as the input current value Idc to motor 3 is further increased, the magnetic flux of the stator of motor 3 becomes saturated. In this saturated state, the magnetic flux does not increase even if the input current value Idc is increased. Therefore, in this embodiment, the magnetic flux density of the stator of motor 3 is prevented from becoming saturated, and the inductance of motor 3 is increased.

FIG. 3 is a diagram showing the characteristics of the input current value Idc to the stator of motor 3 and the magnetic flux φ of each phase generated in the stator of motor 3. Specifically, the horizontal axis of the graph shown in FIG. 3 indicates the input current value Idc to the stator of motor 3, and the vertical axis indicates the value of the magnetic flux generated in the stator of motor 3. FIG. 3 also shows an example of the transition of the magnetic flux of the stator when the rotor of motor 3 is stopped at position E1 shown in FIG. 2.

In other words, FIG. 3 shows how the magnetic flux of each phase changes in response to an increase in the input current value Idc to the stator of the motor 3 when the position of the rotor of the motor 3 is changed in each of the graphs shown in FIGS. 2(A) and (B). Specifically, in each of the graphs shown in FIGS. 2(A) and (B), when the position of the rotor of the motor 3 is 30 degrees (dotted line E1) and the input current value Idc to the stator of the motor 3 is 0, the starting position of the magnetic fluxes φu, φv, and φw of each phase is the leftmost position shown in FIG. 3. Then, when the input current value Idc to the stator of the motor 3 is increased with the rotor position of the motor 3 at 30 degrees (dotted line E1), the magnetic fluxes φu, φv, and φw of each phase increase. The state in which the total increase in the magnetic fluxes φu, φv, and φw of each phase is the largest is the best state for the inductance L.

In the graph shown in FIG. 3, φv and φw are the same, so they are shown by the same line. Also, as shown in FIG. 3, when the input current value Idc to the stator is increased, the magnetic fluxes φv, φu, and φw of each phase increase. Here, when the initial position is high, saturation is likely to occur. In other words, the magnetic fluxes φv and φw are closer to saturation than the magnetic flux φu. Therefore, with respect to an increase in the input current value Idc to the stator, the magnetic fluxes φv and φw increase at a lower rate than the magnetic flux φu. Therefore, in this embodiment, the total increase in the magnetic fluxes φv, φu, and φw of each phase is set to be maximum with respect to an increase in the input current value Idc to the stator.

Here, as a comparative example, in each graph shown in Figures 2 (A) and (B), it is assumed that the rotor position of the motor 3 is stopped at 90 degrees (dotted line E4). In this case, the w-phase magnetic flux φw is a relatively high value, so it is likely to become saturated. On the other hand, the u-phase and v-phase magnetic fluxes φv and φu start from negative values, so they are unlikely to become saturated. However, these u-phase and v-phase magnetic fluxes φv and φu are lower than the v-phase and w-phase magnetic fluxes φv and φw shown in Figure 3, but higher than the u-phase magnetic flux φu. For this reason, it is considered that the u-phase and v-phase magnetic fluxes φv and φu are more likely to become saturated than the u-phase magnetic flux φu shown in Figure 3. In this case, the total increase in the magnetic fluxes φv, φu, and φw of each phase is smaller than when the rotor position of the motor 3 is stopped at 30 degrees (dotted line E1), so the inductance L is also smaller. In other words, the rotor stop position where any of the magnetic fluxes φv, φu, φw of each phase is at a minimum (local minimum) is characterized by the tendency for inductance L to be high. That is, it is possible to increase inductance L by setting the rotor stop position to any of the dotted lines E1 to E3 shown in Figure 2. In this way, since inductance L has periodicity depending on the position of the rotor of motor 3, it is possible to set the rotor stop position by utilizing this periodicity. Note that such periodicity exists in IPM (Interior Permanent Magnet) and SPM (Surface Permanent Magnet).

In this way, the magnetic fluxes φv, φu, and φw of each phase of the motor 3 increase in response to an increase in the input current value Idc to the stator, so a lower initial value is less susceptible to saturation even if the current value increases. In other words, the inductance L of the motor 3 can be increased even if the input current value Idc to the stator is increased.

In this way, the magnetic fluxes φv, φu, and φw of each phase of the motor 3 also saturate due to the correlation of the magnetic fields between the rotor and the stator. For this reason, when the input current value Idc to the stator is set to 0, the magnetic flux density of each phase is less likely to saturate by stopping the rotor at a position where the magnetic flux of any of the phases is at its minimum value, and the inductance of the motor 3 can be effectively utilized. Note that in this embodiment, the control based on the relationship between the inductance L and the rotor position, which is based mainly on the assumption that approximately the same level of current flows through each phase of the motor 3, has been described. On the other hand, even if the current levels of each phase of the motor 3 vary from one another, the above-mentioned control can be executed with the same logic by appropriately correcting the relationship between the inductance L and the rotor position based on the variation.

[Example of charging control system operation]
Fig. 4 is a flowchart showing an example of a charging process in the charging control system 100. This charging process is executed by the controller 4 (see Fig. 1) based on a program stored in a memory (not shown). This charging process is executed continuously for each control period. This charging process will be described with reference to Figs. 1 to 3 as appropriate.

In step S501, the controller 4 determines whether the electric vehicle C1 is stopped. The controller 4 can determine whether the electric vehicle C1 is stopped by using, for example, detection values from wheel speed sensors, the position of the shift lever, and/or a parking lock signal. If the electric vehicle C1 is stopped, the process proceeds to step S502. On the other hand, if the electric vehicle C1 is traveling, the process proceeds to step S505.

In step S502, the controller 4 determines whether or not there is a charging command for the electric vehicle C1. For example, the controller 4 can detect as a charging command a detection signal indicating that the cover of the charging terminal installed on the electric vehicle C1 has been opened, a detection signal indicating that a charging cable has been inserted into the terminal, and/or a charging signal from the external power source 5. In particular, when the controller 4 of this embodiment detects the insertion of a charging cable, the controller 4 uses the insertion as a trigger to adjust the rotor position of the motor 3, which will be described later, and then starts charging. If it is detected in the determination of step S502 that the electric vehicle C1 is to be charged, the process proceeds to step S503. On the other hand, if it is not detected that the electric vehicle C1 is to be charged, the charging process ends.

In step S503, the controller 4 rotates the rotor of the motor 3 within a range that does not affect the behavior of the parked electric vehicle C1, and stops the rotor at a predetermined position. In this embodiment, the predetermined position is the position shown in Figures 2 and 3 (30 degrees, 150 degrees, or 270 degrees). The controller 4 can also stop the rotor at a predetermined position by rotating the rotor of the motor 3 within a predetermined tooth surface distance (backlash) range in the gearbox to which the rotor shaft of the motor 3 is connected. In other words, it is possible to rotate the rotor using the backlash in the gearbox.

The controller 4 can also rotate the rotor of the motor 3 within a range determined based on the predefined backlash (variation) of the motor 3, thereby stopping the rotor of the motor 3 at a predetermined position. For example, when the amount of rotation of the rotor of the motor 3 increases, it is possible to eliminate both the backlash in the gearbox and the backlash of the motor 3. Also, for example, even in a situation where the gears in the gearbox cannot be moved, if there is backlash in the motor 3, it is possible to rotate the rotor of the motor 3 within the range of that backlash. In this way, the predetermined position at which the rotor of the motor 3 is stopped can be determined using the distance between the tooth surfaces in the gearbox to which the rotor shaft of the motor 3 is connected, or the backlash of the motor 3. As a result, even when the electric vehicle C1 is stopped, it is possible to rotate the rotor of the motor 3 within a range that does not affect the behavior of the electric vehicle C1.

Here, the part where rattle occurs in the gearbox and the part where rattle occurs in the motor 3 are determined by the behavior of the electric vehicle C1 immediately before the electric vehicle C1 stops. That is, when the electric vehicle C1 is stopped while moving forward, rattle in the forward direction is eliminated. On the other hand, when the electric vehicle C1 is stopped while moving backward, rattle in the backward direction is eliminated. Therefore, it is preferable to rotate the rotor of the motor 3 in the direction opposite to the traveling direction when the electric vehicle C1 is stopped. That is, the controller 4 rotates the rotor of the motor 3 in the direction opposite to the vehicle state (forward, backward) before the electric vehicle C1 is stopped, so that the rotor can be stopped at a predetermined position. In this way, by specifying the predetermined position where the rotor of the motor 3 is stopped according to the vehicle state before the electric vehicle C1 is stopped, it is possible to increase the range in which the rotor of the motor 3 is rotated within a range that does not affect the behavior of the electric vehicle C1.

In step S504, the controller 4 executes a charging process to charge the battery 1 from the external power source 5. This charging process is similar to a known charging process, so a detailed description of it will be omitted here.

On the other hand, if the determination result in step S501 is negative (the electric vehicle C1 is traveling), in step S505, the controller 4 determines whether or not it has detected that the electric vehicle C1 is stopping for the purpose of charging. If it has detected that the electric vehicle C1 is stopping for the purpose of charging, the process proceeds to step S506. On the other hand, if it has not detected that the electric vehicle C1 is stopping for the purpose of charging, the charging process ends.

For example, the positions of the external power sources 5 installed in various locations are stored in the map information. In addition, the current location of the electric vehicle C1 can be obtained based on position information obtained by a position information acquisition unit, such as a GPS device, installed in the electric vehicle C1. Therefore, it is possible to determine that the electric vehicle C1 is approaching the external power source 5 based on the position of the external power source 5 stored in the map information and the position information obtained by the position information acquisition unit installed in the electric vehicle C1. For example, when the electric vehicle C1 is approaching the external power source 5 and the distance between the electric vehicle C1 and the external power source 5 is less than a predetermined value, for example, a few meters, it is possible to determine that the electric vehicle C1 will stop for charging purposes. In addition, for example, when the external power source 5 is set as the destination in the navigation device, it is possible to determine that the electric vehicle C1 will stop for charging purposes at the timing when the electric vehicle C1 arrives at the external power source 5.

In addition, the determination may be made using remaining charge information of the battery 1. For example, when the SOC (States Of Charge) of the battery 1 is less than a predetermined value, for example, when the battery 1 is about to be empty, it is possible to determine that the electric vehicle C1 will stop for charging purposes at the timing when the electric vehicle C1 stops. Or, when the SOC of the battery 1 is less than a predetermined value and the electric vehicle C1 approaches the external power source 5, it is possible to determine that the electric vehicle C1 will stop for charging purposes at the timing when the electric vehicle C1 stops at the external power source 5 when the battery 1 is about to be empty. Also, for example, when the information providing device provides the location of the external power source 5 to the driver and the driver responds affirmatively, it is possible to determine that the electric vehicle C1 will stop for charging purposes. In other words, it is possible to determine that the electric vehicle C1 will stop for charging purposes based on speech information of the driver. It is also conceivable that the electric vehicle C1 will be charged at the external power source 5 at home. Therefore, when the electric vehicle C1 approaches the home, it is possible to determine that the electric vehicle C1 will stop for charging purposes. Furthermore, when schedule information regarding charging is set for the electric vehicle C1, the determination may be made based on the schedule information. For example, when a charging time is set in the schedule information, it is possible to determine that the electric vehicle C1 will stop for charging purposes at the timing when the electric vehicle C1 stops at a time close to the charging time. In this way, it is possible to set some kind of criteria (determination standard) and detect that the electric vehicle C1 will stop for charging purposes based on the criteria.

In step S506, the controller 4 controls the rotor of the motor 3 to stop at a predetermined position when the electric vehicle C1 stops. Specifically, the rotation of the rotor of the motor 3 is adjusted within a range that does not affect the behavior of the electric vehicle C1 during the stopping operation, and the rotor is stopped at a predetermined position. For example, the electric vehicle C1 basically performs a stopping operation based on the amount of depression of the brake pedal by the driver. During this stopping operation, control is executed to stop the rotor of the motor 3 at a predetermined position so as not to give a sense of discomfort to the driver who is depressing the brake pedal. However, it is expected that it may be difficult to control the rotor of the motor 3 to stop at a predetermined position so as not to give a sense of discomfort to the driver who is depressing the brake pedal during the stopping operation. In this case, it is possible to execute control similar to the control at the time of stopping shown in step S503 immediately after the electric vehicle C1 stops, and to stop the rotor of the motor 3 at a predetermined position.

In this embodiment, an example is shown in which the DC current from the external power source 5 is boosted and charged to the battery 1, but this embodiment can also be applied to other configurations in which a current is applied from the neutral point of the motor of an electric vehicle to each phase, boosted, and charged to the battery.

[Configuration and Effects of the Present Embodiment]
The charging control method according to the present embodiment is a charging control method for controlling a charging control system 100 in an electric vehicle C1 that includes a first terminal 6a and a second terminal 6b connected to an external power source 5, a capacitor 8 connected between the first terminal 6a and the second terminal 6b, a neutral point N1 where each output line of a motor 3 (an example of an electric motor) is gathered and is connected to the first terminal 6a, and a third relay (an example of a switch) provided between the neutral point N1 and the first terminal 6a, and that is capable of charging a battery 1 from the external power source 5 by boosting the voltage of the external power source 5 connected to the first terminal 6a and the second terminal 6b via the motor 3 and an inverter 2 (an example of a power conversion device). This charging control method includes a detection process (step S502) for detecting that the battery 1 is being charged from the external power source 5 while the electric vehicle C1 is stopped, and a control process (step S503) for executing control to rotate the rotor of the motor 3 to a predetermined position and stop the motor 3 when it is detected that the battery 1 is being charged from the external power source 5. The program according to the present embodiment is a program for causing a computer to execute each of these processes. In other words, the program according to the present embodiment is a program that causes a computer to realize each function that can be executed by the charging control system 100 .

With this configuration, when it is detected that the battery 1 is being charged from the external power source 5 while the electric vehicle C1 is stopped, it is possible to set the position of the rotor of the motor 3 so that the inductance L of the motor 3 is at or near its maximum value. This makes it possible to reduce losses that occur when the voltage of the external power source 5 is boosted via the motor 3 and the inverter 2 to charge the battery 1 from the external power source 5.

In addition, in the charging control method according to this embodiment, the control process (step S503) stops the rotor of motor 3 (an example of an electric motor) at a predetermined position by rotating the rotor of motor 3 within the range of the tooth surface distance in the gearbox to which the rotor shaft of motor 3 is connected.

With this configuration, it is possible to determine the predetermined position at which the rotor of the motor 3 is stopped by utilizing the tooth surface distance in the gearbox to which the rotor shaft of the motor 3 is connected. This makes it possible to rotate the rotor of the motor 3 within a range that does not affect the behavior of the electric vehicle C1, even when the electric vehicle C1 is stopped.

In addition, in the charge control method according to this embodiment, the control process (step S503) stops the rotor of motor 3 at a predetermined position by rotating the rotor of motor 3 (an example of an electric motor) within a range determined based on the backlash of the motor 3.

With this configuration, it is possible to determine the predetermined position where the rotor of the motor 3 is stopped by utilizing the backlash of the motor 3. This makes it possible to rotate the rotor of the motor 3 within a range that does not affect the behavior of the electric vehicle C1, even when the electric vehicle C1 is stopped.

In addition, in the charge control method according to this embodiment, the control process (step S503) stops the rotor of the motor 3 at a predetermined position by rotating the rotor of the motor 3 in a direction opposite to the direction of travel of the electric vehicle C1 immediately before the electric vehicle C1 is stopped.

With this configuration, the predetermined position at which the rotor of the motor 3 is stopped is determined based on the vehicle state before the electric vehicle C1 is stopped, making it possible to increase the range over which the rotor position of the motor 3 can be moved without affecting the behavior of the electric vehicle C1.

Furthermore, in the charging control method according to this embodiment, the predetermined position can be the position where the inductance L of the motor 3 (an example of an electric motor) is at its maximum value or a position within a predetermined range based on that position.

This configuration makes it possible to reduce losses that occur when the voltage of the external power source 5 is boosted via the motor 3 and inverter 2 to charge the battery 1 from the external power source 5.

In addition, the charging control method of this embodiment is a charging control method for controlling a charging control system 100 in an electric vehicle C1 which includes a first terminal 6a and a second terminal 6b connected to an external power source 5, a capacitor 8 connected between the first terminal 6a and the second terminal 6b, a neutral point N1 where each output line of a motor 3 (an example of an electric motor) is gathered together and connected to the first terminal 6a, and a third relay (an example of a switch) provided between the neutral point N1 and the first terminal 6a, and which is capable of boosting the voltage of the external power source 5 connected to the first terminal 6a and the second terminal 6b via the motor 3 and an inverter 2 (an example of a power conversion device) to charge the battery 1 from the external power source 5. This charging control method includes a detection process (step S505) for detecting that the electric vehicle C1 is stopping to charge the battery 1 from the external power source 5 while traveling, based on at least one of location information regarding the current location of the electric vehicle C1 and the location where the external power source 5 is installed, remaining charge information of the battery 1, schedule information regarding charging of the battery 1, and speech information of the driver of the electric vehicle C1, and a control process (step S506) for executing control to stop the rotor of the motor 3 at a predetermined position while the electric vehicle C1 is performing a stopping operation when it is detected that the electric vehicle C1 is stopping to charge the battery 1 from the external power source 5. The program according to this embodiment is a program that causes a computer to execute each of these processes. In other words, the program according to this embodiment is a program that causes a computer to realize each function that can be executed by the charging control system 100.

With this configuration, when it is detected that the electric vehicle C1 is stopping while traveling to charge the battery 1 from the external power source 5, it is possible to set the position of the rotor of the motor 3 so that the inductance L of the motor 3 is at or near its maximum value. This makes it possible to reduce losses that occur when the voltage of the external power source 5 is boosted via the motor 3 and the inverter 2 to charge the battery 1 from the external power source 5.

The charging control system 100 is a charging control system for an electric vehicle C1 that includes a first terminal 6a and a second terminal 6b connected to an external power source 5, a capacitor 8 connected between the first terminal 6a and the second terminal 6b, a neutral point N1 where each output line of a motor 3 (an example of an electric motor) is gathered and is connected to the first terminal 6a, and a third relay (an example of a switch) provided between the neutral point N1 and the first terminal 6a, and that is capable of charging the battery 1 from the external power source 5 by boosting the voltage of the external power source 5 connected to the first terminal 6a and the second terminal 6b via the motor 3 and an inverter 2 (an example of a power conversion device). The charging control system 100 includes a controller 4 (an example of a control unit) that detects that the battery 1 is being charged from the external power source 5 while the electric vehicle C1 is stopped, and executes control to rotate the rotor of the motor 3 to a predetermined position and stop it when it is detected that the battery 1 is being charged from the external power source 5.

With this configuration, when it is detected that the battery 1 is being charged from the external power source 5 while the electric vehicle C1 is stopped, it is possible to set the position of the rotor of the motor 3 so that the inductance L of the motor 3 is at or near its maximum value. This makes it possible to reduce losses that occur when the voltage of the external power source 5 is boosted via the motor 3 and the inverter 2 to charge the battery 1 from the external power source 5.

Note that each processing step shown in this embodiment is an example for realizing this embodiment, and the order of some of the processing steps may be changed within the scope that allows this embodiment to be realized, and some of the processing steps may be omitted or other processing steps may be added.

Note that each process shown in this embodiment is executed based on a program for causing a computer to execute each processing procedure. Therefore, this embodiment can also be understood as an embodiment of a program that realizes the function of executing each of these processes, and a recording medium that stores this program. For example, the program can be stored in the controller's storage device by an update process for adding a new function to the controller. This makes it possible to cause the updated controller to execute each of the processes shown in this embodiment.

　Although the embodiments of the present invention have been described above, the above embodiments merely show some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

Claims (7)

A charge control method for controlling a charge control system in an electric vehicle that is capable of charging a battery from an external power supply by boosting a voltage of the external power supply via the electric motor and a power conversion device, the charge control system comprising: a first terminal and a second terminal connected to an external power supply; a capacitor connected between the first terminal and the second terminal; a neutral point where output lines of an electric motor are gathered together and connected to the first terminal; and a switch provided between the neutral point and the first terminal,
a detection process for detecting that the battery is being charged from the external power supply while the electric vehicle is stopped;
and a control process for executing control for rotating a rotor of the electric motor to a predetermined position and stopping the rotor when it is detected that the battery is being charged from the external power supply.
Charging control method. 2. The charge control method according to claim 1,
In the control process, the rotor is rotated within a range of a tooth surface distance in a gear box to which a rotor shaft of the electric motor is connected, thereby stopping the rotor at the predetermined position.
Charging control method. The charge control method according to claim 2,
the control process rotates the rotor within a range determined based on backlash of the electric motor, thereby stopping the rotor at the predetermined position.
Charging control method. A charge control method according to any one of claims 1 to 3,
In the control process, the rotor is rotated in a rotation direction opposite to a traveling direction of the electric vehicle immediately before the electric vehicle is stopped, thereby stopping the rotor at the predetermined position.
Charging control method. A charge control method according to any one of claims 1 to 3,
The predetermined position is a position where the inductance of the motor is at a maximum value or a position within a predetermined range based on the position.
Charging control method. A charge control method for controlling a charge control system in an electric vehicle that is capable of charging a battery from an external power supply by boosting a voltage of the external power supply via the electric motor and a power conversion device, the charge control system comprising: a first terminal and a second terminal connected to an external power supply; a capacitor connected between the first terminal and the second terminal; a neutral point where output lines of an electric motor are gathered together and connected to the first terminal; and a switch provided between the neutral point and the first terminal,
a detection process for detecting, while the electric vehicle is traveling, that the electric vehicle is stopped in order to charge the battery from the external power supply;
a control process for executing control to stop a rotor of the electric motor at a predetermined position while the electric vehicle is performing a stopping operation when it is detected that the electric vehicle is stopping to charge the battery from the external power supply.
Charging control method. A charging control system for an electric vehicle, comprising: a first terminal and a second terminal connected to an external power supply; a capacitor connected between the first terminal and the second terminal; a neutral point where output lines of an electric motor are gathered together and connected to the first terminal; and a switch provided between the neutral point and the first terminal, and capable of charging a battery from the external power supply by boosting a voltage of the external power supply via the electric motor and a power conversion device,
detecting that the battery is being charged from the external power supply while the electric vehicle is stopped;
a control unit that executes control to rotate a rotor of the electric motor to a predetermined position and stop the rotor when it is detected that the battery is being charged from the external power supply;
Charging control system.

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