Charging control method and charging control system

Abstract

Provided is a charging control method for controlling a charging control system in an electric vehicle, the charging 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 at which respective output lines of a winding field type electric motor are collected and that is connected to the first terminal; and a switch provided between the neutral point and the first terminal, wherein a battery can be charged from the external power supply by boosting the voltage of the external power supply via the electric motor and a power conversion device. This charging control method includes: detection processing for detecting charging of a battery from an external power supply while an electric vehicle is stopped; and control processing for, when charging of the battery from the external power supply is detected, rotating a rotor of an electric motor to a predetermined position and stopping the rotor, and executing control for causing a predetermined field current to flow to winding of the rotor.

Description

Charging control method and charging control system

[0001] The present invention relates to a charging control method and a charging control system for an electric vehicle that is capable of charging a battery from an external power supply by boosting the voltage of the external power supply via an electric motor and a power conversion device.

[0002] JP2021-175363A discloses a technology for boosting the charging voltage received at the neutral point of a motor from an external power source to a high voltage using an inverter and charging the battery.

[0003] The above-mentioned conventional technology requires switching when converting to a DC voltage corresponding to the battery voltage level. In this case, the motor inductance also functions as a converter, so if the motor inductance is small, current fluctuations become large, resulting in large inverter and motor losses. In particular, if the current input to the motor is increased beyond a certain level to increase charging power, magnetic saturation within the motor reduces inductance, further increasing these losses.

[0004] An object of the present invention is to reduce losses that occur when the voltage of an external power supply is boosted via an electric motor and a power conversion device and then charged into a battery.

[0005] One aspect of the present invention is a charge control method for controlling a charge control system in an electric vehicle that includes first and second terminals connected to an external power supply, a capacitor connected between the first and second terminals, a neutral point where output lines of a wound-field type electric motor are gathered together and 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 supply by boosting the voltage of the external power supply via the electric motor and a power conversion device. The charge control method includes a detection process for detecting, while the electric vehicle is stopped, that the battery is being charged from the external power supply, and a control process for rotating the rotor of the electric motor to a predetermined position and stopping it, and flowing a predetermined field current through the rotor winding, when it is detected that the battery is being charged from the external power supply.

[0006] FIG. 1 is a block diagram showing an example of the configuration of a charge control system of a first embodiment. FIG. 2 is a cross-sectional view showing an example of the configuration of a motor. FIG. 3 is a diagram showing an example of the distribution of stator magnetic flux on teeth. FIG. 4 is a diagram showing the relationship between the current flowing in the stator winding and the inductance of the motor during charging. FIG. 5 is a diagram showing the relationship between the current flowing in the stator winding and the phase magnetic flux during charging. FIG. 6 is a diagram showing the relationship between the inductance of the motor, the field current, and the number of turns of the rotor winding. FIG. 7 is a flowchart showing an example of charging processing. FIG. 8 is a block diagram showing an example of the configuration of a charge control system of a second embodiment. FIG. 9 is a diagram explaining the effects of the charge control method of the second embodiment.

[0007] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0008] [First embodiment] [Configuration of charging control system] Fig. 1 is a block diagram showing an example 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.

[0009] That is, the charge 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 charge control system 100 is a control system that boosts the voltage of an external power supply 5 via the motor 3 and the inverter 2 to charge the battery 1. The charge control system 100 is mounted on, for example, 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.

[0010] The battery 1 is a DC power supply that functions as a drive power source for the motor 3. For example, the battery 1 is configured as an in-vehicle high-voltage battery such as a lithium-ion secondary battery.

[0011] The inverter 2 is a power conversion device that converts DC power output from the battery 1 into AC power and supplies the AC power to the motor 3 when driving the motor 3. The configuration of the inverter 2 will be described in detail later.

[0012] The motor 3 is configured as an electrically excited synchronous motor (EESM) or the like, and functions as a drive source for the electric vehicle C1. A rotor position signal indicating the position of the rotor of the motor 3 is detected by a resolver (not shown) and output to the controller 4. The motor 3 is an example of a wound field type electric motor.

[0013] In addition to driving the motor 3, the charge control system 100 also functions as a charge control system that uses the inverter 2 as a power factor correction circuit (PFC) when charging the battery 1 from an external power supply 5. For this reason, the charge control system 100 includes an external power supply terminal 6, which is a connection terminal for connecting the external power supply 5 (such as a DC power supply of a direct current type).

[0014] The external power supply 5 is, for example, a charging facility that supplies DC power, such as a DC charger disposed in a charging station, and is capable of supplying DC power of, for example, about 400 volts.

[0015] 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.

[0016] The current sensor 7 is a sensor for measuring the current values ​​at three of the four terminals, and outputs the measured current values ​​to the controller 4 .

[0017] Capacitor 8 is a capacitor connected in parallel to the external power supply 5 in order to stabilize the potential of the neutral point N1 of the motor 3. By providing capacitor 8 in parallel with 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 of the switching elements Tr1 to Tr6 during charging.

[0018] The voltage sensor 9 detects the voltage across the capacitor 8 as a DC voltage V_DC corresponding to the output voltage of the external power supply 5 and outputs it to the controller 4 .

[0019] The capacitor 11 is a capacitor that smoothes the DC power obtained by rectifying the DC power input from the external power supply 5 using the power modules 10u to 10w. The capacitor 11 is connected between the power modules 10u to 10w and the battery 1 in parallel with them.

[0020] The voltage sensor 12 detects the voltage across the capacitor 11 as a DC voltage V_BAT corresponding to the voltage of the battery 1 and outputs it to the controller 4 .

[0021] [Configuration Example of Inverter] The inverter 2 is a power conversion device including power modules 10u to 10w as motor drive power modules, switching elements Tr7 and Tr8, and diodes D11 and D12.

[0022] Specifically, in a drive mode in which the power modules 10u to 10w drive the motor 3, the power modules 10u to 10w convert 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 supply 5 at a desired boost ratio and input it to the battery 1.

[0023] The power modules 10u to 10w each include a plurality of legs, each consisting of a pair of arms, 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 of the switching elements Tr1 to Tr6 is formed of a power semiconductor element, such as an IGBT (Insulated Gate Bipolar Transistor) or a MOS-FET. In principle, one of the upper arm and the lower arm that make up one leg is turned on and the other is turned off depending on the polarity of the AC power.

[0024] The inverter 2 also connects a pair of switching elements Tr7 and Tr8 and diodes D11 and D12 to both ends of a winding (hereinafter referred to as the "rotor winding WDR") arranged on the rotor RT1 for rotor current control, and by turning on / off the switching elements Tr7 and Tr8 in response to a drive signal, a desired current (hereinafter referred to as the "field current I ｆ In the first embodiment, the field current I ｆ The example shows the case where the direction of the field current I is one direction (forward direction). ｆ An example in which the direction is bidirectional (forward and reverse) will be described in a second embodiment.

[0025] The inverter 2 also performs pulse width modulation (PWM) control of the switching elements Tr1 to Tr6 based on a power command value determined according to a desired motor torque (torque command value). In this way, energy for driving the motor 3 flows from the battery 1 to the motor 3.

[0026] When power is supplied 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 a connection node 2c of these two switching elements Tr1 and Tr2, constitute a DC converter circuit that boosts the voltage at the neutral point N1 of the motor 3 and provides 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 the negative terminal 2b, respectively, connected to both ends of the battery 1. The connection node 2c of the two switching elements Tr1 and Tr2 is a 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.

[0027] Therefore, the connection structure of the inverter 2 and the coils in the motor 3 corresponds 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.

[0028] In this embodiment, it is possible to set a first charging mode in which the external charging power is supplied directly to the battery 1 (without passing through the neutral point N1) based on the magnitude of the maximum voltage of the external charging power supplied 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 supplied to the neutral point N1 of the motor 3, and then boosted by controlling the switching elements Tr1 to Tr6 of the inverter 2 before being supplied to the battery 1. However, the following mainly describes the time when the second charging mode is set.

[0029] The controller 4 controls each part of the charging control system 100 based on various programs stored in a storage 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.

[0030] As described above, the controller 4 is a computer for comprehensively controlling the operation of the electric vehicle C1 and the operation of the charge 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, etc. The controller 4 also acquires various information from sensors installed in the electric vehicle C1 and external devices (e.g., a server) of the electric vehicle C1, and detects, based on this information, that the electric vehicle C1 will stop while traveling to charge the battery 1 from the external power source 5. The controller 4 also detects, based on this information, 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. 7 .

[0031] During motor driving, the controller 4 generates a PWM signal based on a torque command value for the motor 3, currents iu, iv, and iw flowing through each phase of the motor 3 (hereinafter referred to as phase currents), 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 of the switching elements 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.

[0032] 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 a control signal (PWM signal) generated by the controller 4 in accordance with the duty ratio (switching pattern) determined by the PWM signal.

[0033] [Example of Charging Process from External Power Source] Here, a charging method using the charge control system 100 will be described. The charging process starts when the external power source 5 is electrically connected to the external power source terminal 6. 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 source 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.

[0034] 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 directly supply DC charging power from the external power supply 5 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, thereby enabling the charging power provided to the external power supply terminal 6 to be directly supplied to the battery 1 without passing through the neutral point N1 of the motor 3, thereby charging the battery 1.

[0035] 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 supply 5 is converted by switching the switching elements of the boost converter circuit realized by the motor 3 and the inverter 2, and the DC charging power from the external power supply 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, thereby making it possible to provide the charging power provided to the external power supply terminal 6 to the battery 1 via the neutral point N1 of the motor 3 and the switching elements. The third relay R3 is a switch provided for inputting to the neutral point N1 of the motor 3.

[0036] [Regarding Losses During Charging] In recent years, there has been a demand for higher output in electric vehicles. To this end, electric vehicles equipped with high-voltage batteries of, for example, about 800V have begun 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 conceivable to extensively modify charging facilities installed in various locations to enable the supply of power of, for example, about 800V. However, extensive modifications to such charging facilities require significant costs. Therefore, it is conceivable to boost the voltage on the vehicle side before charging. For example, to charge an 800V battery from a 400V charging facility, it is conceivable to install a new DC-DC converter in the electric vehicle and use the DC-DC converter to boost the power from the charging facility before charging the battery. However, this requires a new circuit for boosting the voltage, which increases the manufacturing cost of the electric vehicle. Therefore, in order to effectively utilize each charging facility and suppress increases in manufacturing costs of electric vehicles, it is conceivable to boost the voltage using the motor and inverter already installed in the electric vehicle and charge the 800V battery from the 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.

[0037] In this way, when the voltage of an external power supply is boosted via a motor and an inverter and then charged from the external power supply to a battery, switching is required to convert the voltage into a DC voltage that corresponds to the battery voltage level. In this case, the inductance of the motor also functions as a converter, so if the inductance of the motor is small, current changes become large, and switching losses, i.e., inverter losses and motor losses, become large, resulting in poor charging efficiency during voltage boost. Therefore, in this embodiment, switching losses are reduced by adjusting the inductance L (L component) of the motor.

[0038] Specifically, the current i (hereinafter referred to as the "stator input current I") flowing through the winding arranged in the stator of the motor (hereinafter referred to as the "stator winding WDT") is ｄｃ ") and the generated magnetic flux φ (hereinafter referred to as "stator magnetic flux φ Ｓ The relationship between the inductance L and the stator input current I is shown in the following equation 1. Therefore, the larger the inductance L, the smaller the stator input current I ｄｃ The desired magnitude of stator flux φ Ｓ As shown in the following equation 2, the stator magnetic flux φ Ｓ If the inductance L can be increased, the voltage V can be increased. Ｓ By increasing the stator input current I required for the target voltage V, ｄｃ In other words, the efficiency during charging accompanied by the voltage boost can be increased.

[0039] φ=Li...Formula 1 V=2πfφ...Formula 2

[0040] Furthermore, when the inductance L is small, the current pulsation becomes large, and iron loss in the motor increases. Therefore, the smaller the inductance L, the greater the inverter loss and motor loss. For this reason, when the voltage of an external power supply is boosted via the motor and inverter to charge the battery from the external power supply, it is desirable to maintain the inductance L of the motor as large as possible.

[0041] On the other hand, the stator input current I ｄｃ When this magnetic saturation occurs, the stator input current I ｄｃ Even if the desired stator flux φ Ｓ It becomes difficult to generate the inductance L.

[0042] Therefore, the stator input current I ｄｃ In situations where a large amount of charging power is required (such as in rapid charging), there is a concern that inverter loss and motor loss will increase further.

[0043] Therefore, in this embodiment, when the battery 1 is charged using the external power supply 5, in order to suppress an increase in loss due to the magnetic saturation, the position of the rotor RT1 when the electric vehicle C1 is stopped for charging (rotor stop position) is adjusted to a predetermined target position. Furthermore, in a state where the rotor RT1 is stopped at this target position, a desired field current I is supplied to the rotor winding WDR. ｆ Flush.

[0044] More specifically, when the rotor RT1 is stopped at the target position, a field current I ｆ The field current I ｆ The magnetic flux generated by the rotor (hereinafter referred to as the rotor magnetic flux φ ｆ ") is used to generate the stator magnetic flux φ Ｓ The magnetic saturation is suppressed by canceling (alleviating) the above. The details are explained below.

[0045] [Example of Rotor Position Setting During Charging] Fig. 2 is a cross-sectional view showing an example of the configuration of the motor 3. Specifically, it shows an example of the configuration of the rotor RT1 and the stator ST1. Note that in Fig. 2, for ease of explanation, only a portion of the rotor RT1 and the stator ST1 is shown in a simplified form.

[0046] The stator ST1 has teeth TS (seven teeth in the figure) and a stator winding WDT wound around each tooth of the teeth TS. The rotor RT1 also has a rotor winding WDR.

[0047] FIG. 3 shows the stator magnetic flux φ on the teeth TS. Ｓ 3 is a diagram showing an example of the distribution of . Note that in Fig. 3, thin arrows U, V, and W indicate the directions of currents flowing through the U-phase winding, the V-phase winding, and the W-phase winding, respectively.

[0048] Stator magnetic flux φ Ｓ is the U-phase magnetic flux φ generated by the U-phase winding, the V-phase winding, and the W-phase winding, respectively. ｕ , V-phase magnetic flux φ ｖ , and W-phase magnetic flux φ ｗ3, the manner in which the magnetic fluxes of each phase are combined varies depending on the position on the tooth TS, and therefore the magnitude and direction of the magnetic flux varies depending on the position. More specifically, at positions P1 to P4 on the tooth TS, the U-phase magnetic flux φ ｕ , V-phase magnetic flux φ ｖ , and W-phase magnetic flux φ ｗ These are combined to form a composite phase magnetic flux φ ｕｖｗ In particular, at positions P1 and P4, an inward composite phase magnetic flux φ ｕｖｗ At positions P1 and P4, an outward composite phase magnetic flux φ ｕｖｗ On the other hand, at other positions (such as the intermediate position between positions P1 and P2), only two-phase magnetic fluxes in opposite directions are generated, resulting in a composite phase magnetic flux φ ｕｖｗ becomes smaller.

[0049] Therefore, positions P1 to P4 on the teeth TS can be said to be the portions that generate the magnetic flux to be mitigated (suppressed). Note that, in the case of a 48-slot, 8-pole motor, positions P1 to P4 exist at intervals of 60° electrical angle (15° mechanical angle).

[0050] From the above, the target position of the rotor RT1 when it is stopped is set to a position of the rotor RT1 that faces at least one of positions P1 to P4 on the teeth TS. In particular, in this embodiment, the target position is set to the rotor position (position P11 on the drawing) when the central axis of the rotor winding WDR (the d-axis of the motor 3) overlaps with position P1 on the teeth TS, and the rotor position (position P14 on the drawing) when the central axis of the rotor winding WDR overlaps with position P4 on the teeth TS. Here, in this embodiment, the forward field current I ｆ By passing the rotor magnetic flux φ from the rotor winding WDR toward the stator ST1 (outward in the figure), ｆ Therefore, when the rotor RT1 is stopped at the position P11 or the position P14, the field current I ｆ By passing the current, an inward composite phase magnetic flux φ is generated at position P1 or P1 on the teeth TS. ｕｖｗThe outward rotor magnetic flux φ ｆ This can reduce the magnetic flux generated in the teeth TS and prevent magnetic saturation.

[0051] FIG. 4 shows the stator input current I ｄｃ 4 is a diagram showing an example of the relationship between the stator input current I and the inductance L. In particular, FIG. 4 shows the relationship between the stator input current I and the inductance L when the rotor RT1 is stopped at the target position. ｄｃ and inductance L. The solid line LT1 and dotted line LT2 respectively represent the field current I ｆ 5 shows an example of the transition when the stator input current I flows and when it does not flow. ｄｃ 5 is a diagram showing the relationship between the phase magnetic flux at a position P1 on the tooth TS and the rotor RT1 when the rotor RT1 is stopped at the target position and the field current I ｆ When no current flows, the stator input current I ｄｃ and phase flux.

[0052] As can be seen from FIG. 4, the field current I ｆ When no current flows, the stator input current I ｄｃ In the current region where the inductance L is equal to or greater than a certain value A1, the inductance L decreases. ｄｃ As the stator input current I ｄｃ In the region where is larger than a certain value, the stator input current I ｄｃ The range of change in phase magnetic flux is small relative to the change in

[0053] On the other hand, the field current I ｆ When the stator input current I ｄｃ In the region where A2 is larger than A1, the inductance L is maintained without decreasing. Therefore, when the rotor RT1 is stopped at the target position determined as described above, the field current I ｆ By passing a larger stator input current I, the current region in which the inductance L can be maintained can be expanded.ｄｃ Even in a situation where charging is performed by setting the (charging current), the inductance L can be maintained without decreasing, and an increase in loss can be prevented.

[0054] [Example of setting the field current applied to the rotor winding] FIG. 6 shows the relationship between the inductance L and the field current I ｆ and the number of turns Tr of the rotor winding WDR. The number of turns Tr means the number of turns of the coil for one pole in the rotor winding WDR. In the following, the number of turns of one turn of the coil in the stator winding WDT will be referred to as the "number of turns Ts."

[0055] In particular, in FIG. 6, the stator input current I ｄｃ The thick lines LT11 to LT13 show the inductance characteristics when the stator input current I (input current to one turn of the coil) is changed. More specifically, the inductance characteristics LT11, LT12, and LT13 are ｄｃ and the number of turns Ts respectively take different values ​​A, B, and C. Note that the inductance characteristics LT11, LT12, and LT13 are simplified representations of data obtained by analysis based on experiments or simulations, etc.

[0056] As shown in FIG. 6, the field current I ｆ In particular, as can be seen from FIG. 6, the inductance characteristics LT11, LT12, and LT13 change when the field current I ｆ When is a variable, it becomes a curve with an upward convex extreme value.

[0057] Here, the field current I ｆ the multiplication value of the number of turns Tr (first multiplication value), and the rotor magnetic flux φ ｆ It is considered that there is a certain correlation between the stator input current I and the stator input current I. For example, they are almost equal. ｄｃ and the number of turns Ts (second multiplication value), and the stator magnetic flux φ Ｓ It is thought that there is a certain degree of correlation between these two. For example, they are approximately equal.

[0058] In addition, the above-mentioned stator magnetic flux φ ＳRotor flux φ suitable for mitigating ｆ From the viewpoint of generating a field current I that satisfies the relationship shown in the following equation 3: ｆ It is preferable to adjust I ｆ ×Tr ∝ I ｄｃ ×Ts...Formula 3

[0059] That is, the field current I is adjusted so that a proportional relationship is established between the first multiplied value and the second multiplied value. ｆ It is preferable to adjust

[0060] Furthermore, the field current I is set so that the relationship shown in the following equation 4 holds between the first multiplication value and the second multiplication value. ｆ It is preferable to adjust I ｆ ×Tr / 2<I ｄｃ ×Ts<I ｆ ×Tr×1.5 …Formula 4

[0061] The dotted rectangles H11, H12, and H13 shown in FIG. 6 represent the second multiplication value (I ｄｃ ×Ts) respectively take different values ​​A, B, and C, the region (I ｆ , L). ｆ , L) are the different stator input currents I ｄｃ A field current I that can maintain a relatively high inductance L for each ｆ Therefore, the required stator input current I ｄｃ (charging current) to satisfy Equation 4. ｆ By adjusting the value of the inductance L, the decrease in the inductance L can be suppressed.

[0062] [Example of Operation of Charge Control System] Figure 7 is a flowchart showing an example of the charging process in the charge control system 100. This charging process is executed by the controller 4 (see Figure 1) based on a program stored in a memory (not shown). This charging process is also executed continuously for each control period. This charging process will be explained with appropriate reference to Figures 1 to 6.

[0063] 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 S506.

[0064] In step S502, the controller 4 determines whether or not there is a charge command for the electric vehicle C1. For example, the controller 4 can detect as a charge command a detection signal indicating that a cover for a 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 adjusts the rotor position of the motor 3, which will be described later, using the insertion as a trigger, and also supplies a predetermined field current I to the rotor winding WDR. ｆ If it is determined in 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 determined that the electric vehicle C1 is to be charged, the charging process ends.

[0065] In step S503, the controller 4 rotates the rotor RT1 within a range that does not affect the behavior of the stopped electric vehicle C1, and stops the rotor RT1 at the target position described above. In particular, in this embodiment, the controller 4 stops the rotor RT1 at a target position that exists within a predetermined range of tooth surface distance (backlash) within the gearbox to which the rotor shaft of the motor 3 is connected. This makes it possible to rotate the rotor RT1 using backlash within the gearbox.

[0066] Furthermore, the controller 4 rotates the rotor RT1 aiming at a target position within a range determined based on a predetermined backlash (variation) of the motor 3. In particular, when the rotation amount of the rotor RT1 of the motor 3 increases, a target position can be determined within a range that eliminates both the backlash in the gearbox and the backlash of the motor 3. Note that 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 determine a target position within the range of that backlash. In this way, the target position at which the rotor RT1 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 RT1 within a range that does not affect the behavior of the electric vehicle C1.

[0067] Here, the portion where backlash occurs in the gearbox and the portion where backlash occurs in the motor 3 are determined by the behavior of the electric vehicle C1 immediately before the electric vehicle C1 is stopped. That is, when the electric vehicle C1 is stopped while moving forward, backlash in the forward direction is eliminated. On the other hand, when the electric vehicle C1 is stopped while moving backward, backlash in the reverse direction is eliminated. Therefore, it is preferable to rotate the rotor RT1 of the motor 3 in a direction opposite to the traveling direction when the electric vehicle C1 is stopped. That is, the controller 4 can stop the rotor RT1 at a target position by rotating the rotor RT1 in a direction opposite to the vehicle state (forward or reverse) before the electric vehicle C1 is stopped. In this way, by specifying the target position at which the rotor RT1 of the motor 3 is stopped based on the vehicle state before the electric vehicle C1 is stopped, it is possible to determine a target position that can alleviate magnetic flux saturation within a range that does not affect the behavior of the electric vehicle C1.

[0068] In step S504, the controller 4 calculates the field current I ｆ In particular, in this embodiment, the field current I ｆ is the area shown in FIG. ｆ , L). This predetermined current is supplied from the battery 1. In this manner, in this embodiment, the field current I ｆHowever, the decrease in the inductance L is suppressed, so that the field current I ｆ It is possible to achieve a loss suppression effect that exceeds the corresponding power reduction amount.

[0069] In step S505, the controller 4 executes a charging process for charging the battery 1 from the external power supply 5. This charging process is similar to a known charging process, and therefore a detailed description thereof will be omitted here.

[0070] On the other hand, if the determination result in step S501 is negative (the electric vehicle C1 is traveling), in step S506, 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 S507. 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.

[0071] For example, the locations of external power sources 5 installed in various locations are stored in map information. Furthermore, the current location of the electric vehicle C1 can be obtained based on location information obtained by a location information acquisition unit, such as a GPS device, installed in the electric vehicle C1. Therefore, it is possible to determine whether the electric vehicle C1 is approaching the external power source 5 based on the location of the external power source 5 stored in the map information and the location information acquired by the location 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. Furthermore, for example, when the external power source 5 is set as a destination in a navigation device, it is possible to determine that the electric vehicle C1 will stop for charging when the electric vehicle C1 arrives at the external power source 5.

[0072] The determination may also be made using remaining charge information of the battery 1. For example, when the SOC (State of Charge) of the battery 1 is less than a predetermined value, for example, when the battery 1 is nearly empty, it is possible to determine that the electric vehicle C1 will stop for charging at the timing when the electric vehicle C1 stops. Alternatively, 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 at the timing when the electric vehicle C1 stops at the external power source 5 when the battery 1 is nearly empty. Furthermore, for example, when an 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. In other words, it is possible to determine that the electric vehicle C1 will stop for charging based on speech information from the driver. Alternatively, it is possible to charge the electric vehicle C1 using the external power source 5 at home. Therefore, when the electric vehicle C1 approaches the home, it can be determined that the electric vehicle C1 will stop for charging. Furthermore, if schedule information related to charging is set for the electric vehicle C1, the determination may be made based on the schedule information. For example, if a charging time is set in the schedule information, it can be determined that the electric vehicle C1 will stop for charging at a 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 based on the criteria.

[0073] In step S507, the controller 4 controls the rotor RT1 to stop at the target position when the electric vehicle C1 stops. Specifically, the rotation of the rotor RT1 is adjusted within a range that does not affect the behavior of the electric vehicle C1 during the stopping operation, and the rotor RT1 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 RT1 at the target position so as not to cause discomfort to the driver who is pressing the brake pedal. However, it is also expected that it may be difficult to control the rotor RT1 to stop at the predetermined position so as not to cause discomfort to the driver who is pressing the brake pedal during the stopping operation. In this case, it is possible to execute control similar to the control executed during stopping shown in step S503 immediately after the electric vehicle C1 stops, and stop the rotor RT1 at the target position.

[0074] [Second Embodiment] In the first embodiment, a forward field current I ｆ Here, the field current I flows in both the forward and reverse directions in the rotor winding WDR. ｆ By providing a circuit capable of passing a field current I in the forward direction to the rotor winding WDR, it becomes possible to more precisely control the target position of the rotor RT1 when it is stopped. ｆ and the reverse field current I ｆ 1 shows an example of a charging control system 200 including a circuit capable of passing

[0075] [Configuration of charging control system] Fig. 8 is a block diagram showing an example of the configuration of a charging control system 200. Note that the charging control system 200 differs from the charging control system 100 shown in Fig. 1 in that switching elements Tr9 and Tr10 are provided instead of the diodes D11 and D12 in the charging control system 100. That is, the rotor magnetic flux φ ｆThe second embodiment differs from the charge control system 100 in that the circuit that generates the current is a wound-field motor 3 with a Hi / Lo bridge configuration. Therefore, the following will describe the differences from the charge control system 100, and the same reference numerals will be used to designate parts that are common to the charge control system 100, and descriptions of these parts will be omitted. Furthermore, since the second embodiment is a modified example of the first embodiment, only the differences from the first embodiment will be described, and descriptions of parts that are common to the first embodiment will be omitted.

[0076] In addition, in FIG. 8, a field current i flows in the forward direction through the rotor winding WDR. ｆ The flow of current when the field current i flows in the rotor winding WDR in the reverse direction is shown by the dotted arrow EL1. ｆ The flow of current when the field current I flows is shown by the dotted arrow EL2. ｆ The current flowing through the capacitor is controlled by the controller 4.

[0077] In this way, the rotor magnetic flux φ ｆ By configuring the circuit that generates the field current I in both directions in the rotor winding WDR, ｆ This allows the target position when the rotor stops to be doubled, and the amount of movement (amount of rotation) of the rotor RT1 to be reduced. Details of this will be explained below.

[0078] [Example] Figure 9 is a diagram illustrating the effects of a charge control method (example) that assumes a circuit with the Hi / Lo bridge configuration described above. In particular, Figure 9(A) shows a mode in which the rotor RT1 is moved from a predetermined reference position P0 to a target position in the example. On the other hand, Figure 9(B) shows a mode in which the rotor RT1 is moved from the reference position P0 to a target position in a comparative example (control when a circuit with a one-sided diode configuration is adopted). Note that in each figure, the composite phase magnetic flux φ at positions P1 to P4 on the teeth TS described in the first embodiment is ｕｖｗ is indicated by the black arrow.

[0079] As already explained, the inward composite phase magnetic flux φ generated at the position P1 or the position P4 on the tooth TS is ｕｖｗFor the rotor RT1, the rotor RT1 is stopped at position P11 or P14 and the forward field current i ｆ flows, and the outward rotor magnetic flux φ ｆ On the other hand, the outward composite phase magnetic flux φ generated at the position P2 or P3 on the tooth TS can be mitigated. ｕｖｗ To mitigate this, the inward rotor magnetic flux φ ｆ It is necessary to generate

[0080] In this situation, in the control of the comparative example that is based on a circuit with a one-sided diode configuration, the forward field current I ｆ Only the inward rotor magnetic flux φ ｆ 9B ) is set as the target position, and if it is assumed that the rotor RT1 is to be moved (rotated) from the reference position P0 to the position P11, the rotation amount indicated by the arrow AN2 (equivalent to, for example, an electrical angle of 90° (mechanical angle of 22.5°)) is required.

[0081] In such a situation, if the control of the embodiment employing a circuit having a Hi / Lo bridge configuration is used, the field current I ｆ flows to create an inward rotor magnetic flux φ ｆ Therefore, it is possible to set position P12 corresponding to position P2 on the teeth TS and / or position P13 corresponding to position P3 as the target position when the rotor is stopped. For this reason, for example, when position P12 shown in the figure is set as the target position, if it is assumed that the rotor RT1 is to move (rotate) from the reference position P0 to position P12, a smaller rotation amount indicated by arrow AN1 (for example, equivalent to an electrical angle of 30° (mechanical angle of 7.5°)) will be sufficient. Therefore, the forward field current I ｆ Compared to when only the rotor is allowed to flow, the amount of rotation of the rotor can be reduced, thereby reducing the effect on the behavior of the electric vehicle C1.

[0082] In the above embodiments, the charging control method has been described as being based on a system configuration that boosts the DC current from the external power supply 5 and charges the battery 1. However, the system configuration for executing the charging control method is not limited to the above. In particular, the circuit configuration can be appropriately changed within the scope of the function of applying a current from the external power supply to each phase via the neutral point of the motor of the electric vehicle to boost the voltage and charge the battery.

[0083] [Configuration and Effects of the Present Embodiment] The charge control method according to the present embodiment is a charge control method for controlling a charge control system 100, 200 in an electric vehicle C1 that includes a first terminal 6 a and a second terminal 6 b connected to an external power supply 5, a capacitor 8 connected between the first terminal 6 a and the second terminal 6 b, a neutral point N1 where output lines of a wound-field motor 3 (an example of an electric motor) are gathered together and which is connected to the first terminal 6 a, and a third relay (an example of a switch) provided between the neutral point N1 and the first terminal 6 a, and that is capable of boosting the voltage of the external power supply 5 connected to the first terminal 6 a and the second terminal 6 b via the motor 3 and an inverter 2 (an example of a power conversion device) to charge the battery 1 from the external power supply 5. This charging control method includes a detection process (step S502) for detecting that the battery 1 is being charged from the external power supply 5 while the electric vehicle C1 is stopped, and when it is detected that the battery 1 is being charged from the external power supply 5, rotating the rotor RT1 of the motor 3 to a predetermined position (target position) and stopping it, and supplying a predetermined field current I to the rotor winding WDR. ｆ The program according to the present embodiment includes a control process (steps S503 and S504) for controlling the flow of the current. 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 for causing a computer to realize each of the functions that can be executed by the charging control system 100.

[0084] According to this configuration, when it is detected that the battery 1 is being charged from the external power supply 5 while the electric vehicle C1 is stopped, the rotor RT1 is stopped at the target position and the field current I is supplied to the rotor winding WDR. ｆ By passing the current, the stator magnetic flux φ ＳThis can reduce magnetic saturation and suppress a decrease in inductance L of the motor 3. As a result, when the neutral point N1 of the motor 3 is used to boost external power and charge the battery 1, an increase in loss due to a decrease in inductance L can be suppressed.

[0085] Furthermore, in the charge control method according to this embodiment, the control process (step S503) stops the rotor RT1 at a target position by rotating the rotor RT1 within the range of the tooth surface distance within the gearbox to which the rotor shaft of the motor 3 (an example of an electric motor) is connected.

[0086] According to this configuration, it is possible to determine the predetermined position at which the rotor RT1 is stopped by utilizing the distance between the tooth surfaces in the gearbox to which the rotor shaft of the motor 3 is connected. This makes it possible to rotate the rotor RT1 within a range that does not affect the behavior of the electric vehicle C1, even when the electric vehicle C1 is stopped.

[0087] Furthermore, in the charge control method according to this embodiment, the control process (step S503) stops the rotor RT1 at a target position by rotating the rotor RT1 within a range determined based on the backlash of the motor 3 (an example of an electric motor).

[0088] According to this configuration, it is possible to determine the target position at which the rotor RT1 of the motor 3 is stopped by utilizing the backlash of the motor 3. As a result, even when the electric vehicle C1 is stopped, it is possible to rotate the rotor RT1 within a range that does not affect the behavior of the electric vehicle C1.

[0089] Furthermore, in the charge control method according to this embodiment, the control process (step S503) stops the rotor RT1 at the target position by rotating the rotor RT1 in a rotation direction opposite to the direction of travel of the electric vehicle C1 immediately before the electric vehicle C1 is stopped.

[0090] According to this configuration, by defining the target position at which the rotor RT1 is stopped based on the vehicle state before the electric vehicle C1 is stopped, it is possible to increase the range in which the rotor position of the motor 3 can be moved without affecting the behavior of the electric vehicle C1.

[0091] Furthermore, in the charge control method according to this embodiment, the target position at which the rotor RT1 of the motor 3 is stopped is determined to be a position (P11 to P14) where the central axis of the rotor winding WDR faces a predetermined position (P1 to P4) on the teeth TS of the stator ST1 of the motor 3 (an example of an electric motor).

[0092] According to this configuration, the position on the tooth TS where the magnetic flux should be relaxed (the composite phase magnetic flux φ ｕｖｗ Depending on the position where the field current I ｆ It is possible to stop the rotor RT1 at an appropriate position where the flow of the air is to be performed.

[0093] Furthermore, in this embodiment, the field current I is calculated based on the positional relationship between the target position and the teeth TS. ｆ Set.

[0094] In particular, the charging control system 200 supplies a forward field current I to the winding of the rotor RT1. ｆ and the reverse field current I ｆ Then, in the control process (step S503), the forward and reverse field currents I are supplied based on the target position at which the rotor RT1 is rotated and stopped. ｆ Switch between.

[0095] According to this configuration, the field current I ｆ to switch the direction of the rotor flux φ required to alleviate the magnetic flux saturation. ｆ can be generated.

[0096] More specifically, the target position is determined by the forward field current I ｆ The magnetic flux generated when the rotor magnetic flux φ ｆ ) flows into the stator ST1 of the motor 3 (an example of an electric motor) as a current (stator input current I ｄｃ ) flows, the magnetic flux (resultant phase magnetic flux φ ｕｖｗ) and a first position (positions P11 and P13) in which the field current I ｆ The rotor magnetic flux φ generated when ｆ is the stator input current I ｄｃ The resultant phase magnetic flux φ generated when ｕｖｗ and a second position (positions P12, P14) in the opposite direction to the first position.

[0097] This effectively increases the target position at which rotor RT1 should be stopped (the position of rotor RT1 at which magnetic flux saturation can be alleviated), reduces the amount of movement (amount of rotation) of rotor RT1, and further reduces the impact on the behavior of electric vehicle C1 when adjusting the rotor position while the vehicle is stopped.

[0098] In the charge control method according to this embodiment, the field current I ｆ The magnitude of the current flowing through the stator winding WDT (stator input current I ｄｃ ), the number of turns Ts of the stator winding WDT, and the number of turns Tr of the rotor winding WDR.

[0099] As a result, the field current i ｆ The magnitude of the required stator input current I ｄｃ It is possible to set the inductance L so as to maintain a high value according to the charging current.

[0100] Furthermore, the charge control method according to this embodiment is a charge control method for controlling charge control systems 100, 200 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 wound-field type motor 3 (an example of an electric motor) is gathered together and which 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 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 charge control method includes a detection process (step S506) for detecting that the electric vehicle C1 is stopping to charge the battery 1 from the external power source 5 while the electric vehicle C1 is running, and when it is detected that the electric vehicle C1 is stopping to charge the battery 1 from the external power source 5, stopping the rotor RT1 of the motor 3 at a predetermined position (target position) while the electric vehicle C1 is performing a stopping operation, and supplying a predetermined field current I to the rotor winding WDR. ｆ The program according to the present embodiment includes a control process (steps S507 and S504) for controlling the flow of the current. 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 for causing a computer to realize each of the functions that can be executed by the charging control system 100.

[0101] According to this configuration, when the electric vehicle C1 is stopped to charge the battery 1 using the external power supply 5, the position of the rotor RT1 at the time of stopping is adjusted to the target position, and the field current I ｆ can be streamed.

[0102] The charging control systems 100 and 200 are charging control systems for an electric vehicle C1 that include 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 output lines of a wound-field type motor 3 (an example of an electric motor) are 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 that are 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. The charging control system 100 detects that the battery 1 is being charged from the external power source 5 while the electric vehicle C1 is stopped, and when it has detected that the battery 1 is being charged from the external power source 5, rotates the rotor RT1 of the motor 3 to a predetermined position (target position) and stops it, and supplies a predetermined field current I to the rotor winding WDR. ｆ The device is equipped with a controller 4 (an example of a control unit) that controls the flow of the

[0103] According to this configuration, the charge control systems 100 and 200 suitable for executing the above-described charge control method are realized.

[0104] Note that each processing procedure shown in each embodiment is an example for realizing each embodiment, and the order of some of the processing procedures may be changed within the scope that makes it possible to realize each embodiment, and some of the processing procedures may be omitted or other processing procedures may be added.

[0105] Each process shown in each embodiment is executed based on a program that causes a computer to execute each processing procedure. Therefore, each embodiment can also be understood as an embodiment of a program that realizes the function of executing each process and a recording medium that stores the program. For example, an update process for adding a new function to the controller can store the program in the controller's storage device. This makes it possible to cause the updated controller to execute each process shown in each embodiment.

[0106] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

Claims

1. A charging control method for controlling a charging control system in an electric vehicle which is equipped with a first terminal and a second terminal connected to an external power source, a capacitor connected between the first terminal and the second terminal, a neutral point where each output line of a wound field type electric motor is gathered together and connected to the first terminal, and a switch provided between the neutral point and the first terminal, and which 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, the charging control method including: a detection process for detecting that the battery is being charged from the external power source while the electric vehicle is stopped; and a control process for rotating the rotor of the electric motor to a predetermined position and stopping it, and executing control to flow a predetermined field current through the rotor winding, when it is detected that the battery is being charged from the external power source.

2. A charging control method as claimed in claim 1, wherein the control process stops the rotor at the specified position by rotating the rotor within a range of a tooth flank distance within a gearbox to which the rotor shaft of the electric motor is connected.

3. A charging control method according to claim 2, wherein the control process stops the rotor at the predetermined position by rotating the rotor within a range determined based on backlash of the electric motor.

4. A charging control method according to any one of claims 1 to 3, wherein the control process stops the rotor at the predetermined position by rotating the rotor in a rotation direction opposite to the traveling direction of the electric vehicle immediately before the electric vehicle was stopped.

5. A charging control method according to any one of claims 1 to 3, wherein the predetermined position is determined to be a position where the central axis of the winding of the rotor faces a predetermined position on the teeth of the stator of the electric motor.

6. A charging control method according to claim 5, further comprising the step of setting the field current based on a positional relationship between the predetermined position and the teeth.

7. A charging control method as claimed in claim 6, wherein the charging control system comprises a circuit capable of flowing a forward field current and a reverse field current, and the control process switches between the forward and reverse field currents based on the specified position at which the rotor is rotated and stopped.

8. A charging control method as described in claim 7, wherein the predetermined positions include a first position where the magnetic flux generated when the forward field current is caused to flow is opposite to the magnetic flux generated when a current is caused to flow through the stator of the motor, and a second position where the magnetic flux generated when the reverse field current is caused to flow is opposite to the magnetic flux generated when a current is caused to flow through the stator of the motor.

9. A charging control method according to any one of claims 1 to 3, wherein the magnitude of the field current is set based on the current flowing through a stator winding of the motor, the number of turns of the stator winding, and the number of turns of the rotor winding.

10. A charging control method for controlling a charging control system in an electric vehicle which is equipped with a first terminal and a second terminal connected to an external power source, a capacitor connected between the first terminal and the second terminal, a neutral point where each output line of a wound-field type electric motor is gathered together and connected to the first terminal, and a switch provided between the neutral point and the first terminal, and which 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, the charging control method including: a detection process for detecting, while the electric vehicle is traveling, that the vehicle has stopped to charge the battery from the external power source; and a control process for stopping the rotor of the electric motor at a predetermined position while the electric vehicle is performing a stopping operation and controlling a predetermined field current to flow through a rotor winding when it is detected that the vehicle has stopped to charge the battery from the external power source.

11. A charging control system for an electric vehicle comprising: a first terminal and a second terminal connected to an external power source; a capacitor connected between the first terminal and the second terminal; a neutral point where each output line of a wound field type electric motor is 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 source by boosting the voltage of the external power source via the electric motor and a power conversion device, the charging control system comprising: a control unit that detects that the battery is being charged from the external power source while the electric vehicle is stopped, and when it is detected that the battery is being charged from the external power source, rotates the rotor of the electric motor to a predetermined position and stops it, and executes control to pass a predetermined field current through the rotor winding.

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