Charging control method and charging control system

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

[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. Summary of the Invention

[0003] In the above-mentioned conventional technology, switching is required to convert the DC voltage according 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, the current change will be large, resulting in large inverter loss and motor loss.

[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 to a battery from the external power supply.

[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 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 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. This 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 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 charging control system. Fig. 2 is a diagram showing an example of setting a position at which a motor rotor is stopped. Fig. 3 is a diagram showing characteristics of an input current value to a stator and magnetic flux of each phase of the stator. Fig. 4 is a flowchart showing an example of charging processing.

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

[0008] 1 is a block diagram showing an example of the configuration of a charge control system 100. Specifically, the charge 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 a three-phase AC motor such as an interior permanent magnet synchronous motor (IPMSM) 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.

[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 power modules for driving a motor.

[0022] 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 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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. 4 .

[0030] 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.

[0031] 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.

[0032] [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.

[0033] 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.

[0034] 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.

[0035] [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.

[0036] 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.

[0037] Specifically, as shown in the following equation 1, the larger the inductance L of the motor, the more magnetic flux φ can be generated with a smaller current i. And, as shown in the following equation 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

[0038] Therefore, in this embodiment, when the voltage of the external power supply is boosted via the motor and inverter and the battery is charged from the external power supply, the position of the motor rotor is set so that the motor inductance L is at or near its maximum value, thereby making it possible to reduce losses that occur when the voltage of the external power supply is boosted via the motor and inverter and the battery is charged from the external power supply.

[0039] [Example of rotor position setting during charging] First, a position for increasing the inductance of the motor 3 will be described. The position for increasing the inductance of the motor 3 is a position that satisfies both of the following (1) and (2). The d-axis of the rotor magnet means the central axis of the winding side of the rotor. (1) A position where the circumferential center of any phase of the stator coil coincides with the d-axis of the rotor magnet. (2) A position where the magnetic flux generated by the current flowing through the stator coil is oriented opposite to the magnetic flux generated by the magnet.

[0040] Of 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 FIGS. 2 and 3. FIG.

[0041] FIG. 2 is a diagram showing an example of setting a position at which the rotor of the motor 3 is stopped when the battery 1 of the electric vehicle C1 is charged from the external power supply 5. In FIG.

[0042] FIG. 2A 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. 2B 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. 2A and 2B indicates the rotor position of motor 3. The vertical axis of the graph shown in FIG. 2A indicates the value of inductance generated in the stator of motor 3. The vertical axis of the graph shown in FIG. 2B indicates the value of magnetic flux of each phase generated in the stator of motor 3. Note that FIGS. 2A and 2B show simplified inductance that changes depending on the rotor position when charging battery 1.

[0043] As shown in Figure 2 (A), the inductance value of the motor 3 changes depending on the rotor position when the electric vehicle C1 is stopped. The inductance value, which changes depending on the stopped position of the rotor of the motor 3, has an upwardly convex characteristic. The relationship between the magnetic flux φ generated in the stator of the motor 3, the inductance L of the motor 3, and the input current value Idc to the motor 3 is expressed by the above-mentioned formula 1. The relationship between the output voltage value V from the motor 3, the frequency f, and the magnetic flux φ is expressed by the above-mentioned formula 2.

[0044] Therefore, the rotor position where the inductance L of the motor 3 is at its maximum is the rotor position where the output voltage value V from the motor 3 is at its maximum. In other words, the rotor position where the inductance L of the motor 3 is at its maximum is the position where voltage can be efficiently boosted. Specifically, positions E1 to E3 (shown by dotted lines) where the inductance L of the motor 3 reaches its extreme values ​​are the rotor positions where the inductance is at its maximum. As such, there are localized rotor positions where charging efficiency can be improved. Therefore, it is possible to confirm in advance the rotor position where the inductance L of the motor 3 is at its maximum based on experiments or simulations, and then retain that position in advance. For example, it is possible to perform magnetic field analysis to determine the rotor position where the inductance L of the motor 3 is at its maximum. It is also possible to determine the rotor position where the inductance L of the motor 3 is at its maximum by calculation, for example. Alternatively, it is possible to change the rotor position through preliminary experiments or simulations, and obtain the current waveforms and charging efficiency of each phase, thereby determining the optimal rotor position for each input power.

[0045] 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 rotor position (or within a predetermined range close to that position) where the inductance L of the motor 3 is at its maximum, 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. Therefore, in such cases, 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. This makes it possible to improve charging efficiency and suppress the occurrence of motor loss and inverter loss.

[0046] Here, the relationship between the inductance L of the motor 3 and the iron loss within the motor 3 will be explained. As described above, switching of the inverter 2 is required when charging by boosting the voltage of the battery 1 according to its voltage level. That is, the switching of the inverter 2 fluctuates the current to generate magnetic flux for the motor 3. In this case, the inductance L of the motor 3 also functions as a converter, so if the inductance L of the motor 3 is small, it is necessary to generate harmonic current with an amplitude above a certain level. That is, if the inductance L of the motor 3 is small, the current pulsation of each phase of the motor 3 increases, and therefore the iron loss within the motor 3 increases.

[0047] In contrast, in this embodiment, the inductance L of the motor 3 is set to a maximum value or a value close to this maximum 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 significantly changing the current due to switching of the inverter 2. For example, when looking at the current waveforms of each phase of the motor 3 generated by switching of the inverter 2, the amplitude of current harmonics generated by current changes varies 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 harmonic currents with an amplitude above a certain level are generated. In other words, when the inductance L of the motor 3 is small, the current changes are large, and switching losses, i.e., inverter losses and motor losses, become large.

[0048] In contrast, if the inductance L of the motor 3 is set to a maximum value or a value close to this maximum value, 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 per amplitude of the harmonic in 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 becomes 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 becomes 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.

[0049] Next, saturation of magnetic flux due to correlation of magnetic fields between the rotor and stator in the motor 3 will be described.

[0050] For example, as the input current value Idc to the motor 3 increases, the magnetic flux of the stator of the motor 3 increases. Then, as the input current value Idc to the motor 3 is further increased, the magnetic flux of the stator of the motor 3 reaches saturation. 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 the motor 3 is prevented from reaching saturation, and the inductance of the motor 3 is increased.

[0051] Fig. 3 is a diagram showing the characteristics of the input current value Idc to the stator of the motor 3 and the magnetic flux φ of each phase generated in the stator of the motor 3. Specifically, the horizontal axis of the graph shown in Fig. 3 represents the input current value Idc to the stator of the motor 3, and the vertical axis represents the value of the magnetic flux generated in the stator of the motor 3. Fig. 3 also shows an example of the transition of the magnetic flux in the stator when the rotor of the motor 3 is stopped at position E1 shown in Fig. 2.

[0052] 2A and 2B, the graphs show how the magnetic flux of each phase changes in response to an increase in the input current Idc to the stator of the motor 3 when the rotor position of the motor 3 is changed. Specifically, in the graphs shown in FIGS. 2A and 2B, when the rotor position of the motor 3 is 30 degrees (dotted line E1) and the input current Idc to the stator of the motor 3 is 0, the starting positions of the magnetic fluxes φu, φv, and φw of each phase are the leftmost positions shown in FIG. 3. When the input current 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 greatest represents the optimum state for the inductance L.

[0053] In the graph shown in FIG. 3 , φv and φw are the same, and therefore 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 more likely to occur. That is, 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 maximized with respect to an increase in the input current value Idc to the stator.

[0054] As a comparative example, consider the case where the rotor of the motor 3 is stopped at 90 degrees (dotted line E4) in the graphs shown in FIGS. 2A and 2B. In this case, the w-phase magnetic flux φw is relatively high and therefore prone to saturation. On the other hand, the u- and v-phase magnetic fluxes φv and φu start from negative values ​​and are therefore less likely to saturate. However, these u- and v-phase magnetic fluxes φv and φu are lower than the v- and w-phase magnetic fluxes φv and φw shown in FIG. 3 but higher than the u-phase magnetic flux φu. Therefore, the u- and v-phase magnetic fluxes φv and φu are considered to be more prone to saturation than the u-phase magnetic flux φu shown in FIG. 3. In this case, the total increase in the magnetic fluxes φv, φu, and φw of the phases is smaller than when the rotor of the motor 3 is stopped at 30 degrees (dotted line E1), resulting in a smaller inductance L. In other words, the rotor stop position where any of the magnetic fluxes φv, φu, and φw of each phase is at its minimum (local minimum) is likely to have a high inductance L. That is, by setting the rotor stop position at any of the dotted lines E1 to E3 shown in FIG. 2, it is possible to increase the inductance L. As such, the inductance L is periodic depending on the rotor position of the motor 3, and this periodicity can be used to set the rotor stop position. Note that such periodicity exists in interior permanent magnet (IPM) and surface permanent magnet (SPM).

[0055] In this way, the magnetic fluxes φv, φu, and φw of the phases of the motor 3 increase as the input current Idc to the stator increases, so a low initial value is less susceptible to saturation even when the current increases. In other words, even when the input current Idc to the stator is increased, the inductance L of the motor 3 can be increased.

[0056] In this way, the magnetic fluxes φv, φu, and φw of each phase of the motor 3 also saturate due to the correlation between the magnetic fields between the rotor and the stator. Therefore, when the input current value Idc to the stator is set to 0, stopping the rotor at a position where the magnetic flux of one of the phases is at its minimum makes the magnetic flux density of each phase less likely to saturate, allowing the inductance of the motor 3 to be effectively utilized. Note that in this embodiment, the control based on the relationship between the inductance L and the rotor position has been mainly described, assuming that approximately the same level of current flows through each phase of the motor 3. On the other hand, even if the current levels of each phase of the motor 3 vary from one another, the above-described control can be performed using the same logic by appropriately correcting the relationship between the inductance L and the rotor position based on the variation.

[0057] [Example of Operation of Charge Control System] Figure 4 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 3.

[0058] 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.

[0059] In step S502, the controller 4 determines whether or not a charging command for the electric vehicle C1 has been issued. For example, the controller 4 can detect 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 as a charging command. In particular, when the controller 4 detects the insertion of a charging cable, the controller 4 in this embodiment uses the insertion as a trigger to adjust the rotor position of the motor 3, as described below, and then starts charging. If it is determined in step S502 that charging of the electric vehicle C1 is to be executed, the process proceeds to step S503. On the other hand, if it is not determined that charging of the electric vehicle C1 is to be executed, the charging process ends.

[0060] In step S503, the controller 4 rotates the rotor of the motor 3 within a range that does not affect the behavior of the stopped electric vehicle C1, and stops the rotor at a predetermined position. In this embodiment, this predetermined position is the position (30 degrees, 150 degrees, or 270 degrees) shown in Figures 2 and 3. The controller 4 can also stop the rotor at the predetermined position by rotating the rotor of the motor 3 within a predetermined range of tooth flank distance (backlash) in a gearbox to which the rotor shaft of the motor 3 is connected. In other words, it is possible to rotate the rotor using backlash in the gearbox.

[0061] Furthermore, the controller 4 can stop the rotor of the motor 3 at a predetermined position by rotating the rotor of the motor 3 within a range determined based on a predetermined backlash (variation) of the motor 3. For example, when the rotation amount of the rotor of the motor 3 increases, it is possible to eliminate both backlash in the gearbox and backlash in the motor 3. Furthermore, even in a situation where it is impossible to move the gears in the gearbox, 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.

[0062] 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 of the motor 3 in the direction opposite to the traveling direction when the electric vehicle C1 is stopped. That is, the controller 4 can stop the rotor at a predetermined position by rotating the rotor of the motor 3 in the direction opposite to the vehicle state (forward or reverse) before the electric vehicle C1 is stopped. In this way, by specifying the predetermined position where the rotor of the motor 3 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 of the motor 3 is rotated within a range that does not affect the behavior of the electric vehicle C1.

[0063] In step S504, the controller 4 executes a charging process to charge 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.

[0064] 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 charging. If it has detected that the electric vehicle C1 is stopping for charging, the process proceeds to step S506. On the other hand, if it has not detected that the electric vehicle C1 is stopping for charging, the charging process ends.

[0065] 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.

[0066] 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.

[0067] 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 the 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 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 of the motor 3 to stop at a 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 perform control similar to the control executed during 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.

[0068] In this embodiment, an example is shown in which the DC current from the external power supply 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 to each phase from the neutral point of the motor of an electric vehicle, boosted, and charged to the battery.

[0069] [Configuration and Effects of the Present Embodiment] A charge control method according to the present embodiment is a charge control method for controlling a charge control system 100 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 motor 3 (an example of an electric motor) are gathered together and 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 charge control method includes, while the electric vehicle C1 is stopped, a detection process (step S502) that detects that the battery 1 is being charged from the external power supply 5, and a control process (step S503) that, when it is detected that the battery 1 is being charged from the external power supply 5, rotates the rotor of the motor 3 to a predetermined position and stops the rotor. The program according to the present embodiment is a program that causes 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 of the functions that can be executed by the charging control system 100.

[0070] 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, 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 supply 5 is boosted via the motor 3 and the inverter 2 and the battery 1 is charged from the external power supply 5.

[0071] Furthermore, 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 within the gearbox to which the rotor shaft of motor 3 is connected.

[0072] With this configuration, it is possible to determine the predetermined position at which the rotor of the motor 3 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 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.

[0073] Furthermore, 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.

[0074] According to this configuration, it is possible to determine the predetermined position at which the rotor 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 of the motor 3 within a range that does not affect the behavior of the electric vehicle C1.

[0075] Furthermore, 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.

[0076] According to this configuration, by determining the predetermined position at which the rotor of the motor 3 is stopped based on the vehicle state before the electric vehicle C1 is stopped, it is 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.

[0077] Furthermore, in the charge control method according to this embodiment, the predetermined position can be set to a 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.

[0078] This configuration makes it possible to reduce the loss that occurs when the voltage of the external power supply 5 is boosted via the motor 3 and the inverter 2 and the battery 1 is charged from the external power supply 5 .

[0079] Furthermore, the charge control method according to this embodiment is a charge control method for controlling a charge 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 together and that is connected to the first terminal 6a, and a third relay (an example of a switch) that is 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 a battery 1 from the external power source 5. This charge control method includes a detection process (step S505) for detecting that the electric vehicle C1 will stop 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 will stop to charge the battery 1 from the external power source 5. Furthermore, 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 charge control system 100.

[0080] According to this configuration, when it is detected that the electric vehicle C1 is stopping while traveling to charge the battery 1 from the external power supply 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 supply 5 is boosted via the motor 3 and the inverter 2 to charge the battery 1 from the external power supply 5.

[0081] 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 supply 5, a capacitor 8 connected between the first terminal 6a and the second terminal 6b, a neutral point N1 where output lines of a 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 is capable of boosting the voltage of the external power supply 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 supply 5. 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 supply 5 while the electric vehicle C1 is stopped, and that, when it is detected that the battery 1 is being charged from the external power supply 5, controls the rotor of the motor 3 to rotate to a predetermined position and stop it.

[0082] 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, 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 supply 5 is boosted via the motor 3 and the inverter 2 and the battery 1 is charged from the external power supply 5.

[0083] Note that each processing procedure shown in this embodiment is an example for realizing this embodiment, and the order of some of the processing procedures may be changed within the scope that makes it possible to realize this embodiment, and some of the processing procedures may be omitted or other processing procedures may be added.

[0084] Each process described in this embodiment is executed based on a program that causes 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 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 described in this embodiment.

[0085] 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 an 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 executing 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.

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 a position where the inductance of the motor is at a maximum value or a position within a predetermined range based on that position.

6. A charging control method for controlling a charging control system in 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 an 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 method including: a detection process for detecting that the electric vehicle will stop to charge the battery from the external power source while the electric vehicle is traveling; and a control process for executing control to stop the rotor of the electric motor at a predetermined position while the electric vehicle is performing a stopping operation when it is detected that the vehicle will stop to charge the battery from the external power source.

7. 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 each output line of an 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 supply by boosting the voltage of the external power supply 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 supply while the electric vehicle is stopped, and 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 supply.

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