Charging device and power conversion device

Abstract

This charging device comprises: an inverter that has a plurality of switching elements connected to a power storage device; a rotary electric machine that has a plurality of windings; at least one relay; and a capacitor. By selecting, as a voltage-boost switching element, a switching element among the plurality of switching elements that does not have a connection part provided between said switching element and a corresponding winding or that is connected via a connection part to the relay, with the relay being switched to an off state, and causing the voltage-boost switching element to perform switching, the inverter can perform a voltage-boosting operation in which the winding is used to boost the voltage of DC power and the DC power is supplied to the power storage device. The relay, if connected via the connection part to a switching element other than the voltage-boost switching element, is switched to an on state when the inverter performs the voltage-boosting operation.

Description

Charging devices, power conversion devices

[0001] The present invention relates to a charging device and a power conversion device.

[0002] In recent years, as part of efforts to protect the environment and combat global warming, the use of electrically powered vehicles such as electric vehicles and plug-in hybrid vehicles has become increasingly common. These vehicles charge their onboard batteries with power provided by external charging equipment, and the electric motor is driven using the electrical energy stored in the onboard battery to run the vehicle. Generally, there are two types of charging methods for onboard batteries in electrically powered vehicles: normal charging, in which a commercial household power source is converted into direct current (DC) power for charging, and rapid charging, in which high-power DC power supplied from a dedicated charging facility is used to rapidly charge the battery.

[0003] In recent years, the voltage of onboard batteries has been increasing in order to improve the driving performance of electric vehicles and increase the efficiency of power conversion. As a result, the voltage of DC power (e.g., 400 V) that can be supplied from a charging facility for rapid charging may be lower than the charging voltage (e.g., 800 V) of the onboard battery. To enable charging of the onboard battery even in such cases, a boost circuit for boosting the voltage of the DC power supplied from the charging facility may be installed in the vehicle. However, the large-capacity boost circuits that can achieve this tend to be large and heavy, making them unsuitable for installation in a vehicle. Furthermore, this increases the cost of the vehicle.

[0004] One technique proposed to solve the above problem is that described in, for example, Patent Document 1. Patent Document 1 describes a charging system that has a first relay having one end connected to a DC connection end and the other end connected to a charging power input end, and a second relay having one end connected to a neutral point of a motor and the other end connected to the charging power input end, and that controls the states of these relays and also controls the on / off states of each switching element of an inverter, thereby enabling charging power provided from a charging facility to be boosted by a motor coil and provided to a battery.

[0005] Japanese Patent Application Publication No. 2021-175363

[0006] In the charging system of Patent Document 1, the neutral point of the motor is connected to one end of the second relay, and a structure is required in which the neutral point of the motor is drawn outside the motor so that the neutral point can be connected to the charging power input terminal via this second relay. In other words, in order to apply the charging system of Patent Document 1, a special structure different from that of a normal motor must be adopted, which still results in increased costs.

[0007] The present invention has been made in view of the above-mentioned problems, and a main object of the present invention is to realize a charging power boost function at low cost.

[0008] The charging device according to the present invention includes an inverter having a plurality of switching elements connected to a power storage device, a rotating electric machine having a plurality of windings each corresponding to a different phase of AC power output from the inverter, with one end of each winding connected to the switching element and the other end of each winding connected to each other, at least one relay having one end connected to a connection portion provided between the winding and the switching element corresponding to at least one phase of the AC power and the other end connected to a connection point with an external DC power source that supplies DC power for charging the power storage device, and which is switched between an ON state and an OFF state to establish or break conduction between the connection portion and the DC power source, and a relay between the relay and the connection point. and a capacitor having one end connected to the negative electrode of the power storage device and the other end connected to the negative electrode of the power storage device, wherein the inverter selects, as a boost switching element, a switching element that does not have the connection part between itself and the winding or that is connected via the connection part to the relay that is switched to the OFF state, and by switching the boost switching element, it is possible to perform a boost operation in which the voltage of the DC power is boosted using the winding and supplied to the power storage device, and the relay that is connected via the connection part to a switching element other than the boost switching element is switched to the ON state when the inverter performs the boost operation.The power conversion device according to the present invention includes a plurality of switching elements that perform a switching operation to convert first DC power supplied from a power storage device into AC power and output the AC power to a rotating electric machine; at least one relay having one end connected to a connection portion provided between the switching element corresponding to at least one phase of the AC power and a winding of the rotating electric machine and having the other end connected to a connection point with an external DC power source that supplies second DC power for charging the power storage device, and being switched ON or OFF to establish or break conduction between the connection portion and the DC power source; and at least one relay having one end connected between the relay and the connection point and the other end connected to a negative electrode of the power storage device. and a capacitor to which the relay is connected, and among the plurality of switching elements, a switching element that does not have the connection portion between itself and the winding or is connected via the connection portion to the relay switched to the OFF state is selected as a boost switching element, and by switching the boost switching element, it is possible to perform a boost operation of boosting the voltage of the second DC power using the winding and supplying it to the power storage device, and the relay that is connected via the connection portion to a switching element other than the boost switching element is switched to the ON state when performing the boost operation.

[0009] According to the present invention, the charging power boost function can be realized at low cost.

[0010] FIG. 1 is a diagram showing the configuration of a charging device according to a first embodiment of the present invention; FIG. 2 is a diagram showing the time variation of currents Iv and Iw flowing through a V-phase winding and a W-phase winding, respectively, when a boost operation is performed with a V-phase switching element being switched and a W-phase switching element being kept in an OFF state; FIG. 3 is a diagram showing the time variation of currents Iv and Iw flowing through a V-phase winding and a W-phase winding, respectively, when a boost operation is performed with a V-phase switching element and a W-phase switching element being switched; FIG. 4 is a diagram showing an example in which the switching period of a V-phase switching element and a W-phase switching element are partially shifted; FIG. 5 is a diagram showing an example in which the switching period of a V-phase switching element and a W-phase switching element are completely shifted; FIG. 6 is a diagram showing the configuration of a charging device according to a second embodiment of the present invention; FIG. 7 is a diagram showing an example of relay switching timing in the second embodiment of the present invention; FIG. 8 is a diagram showing the change in line inductance depending on rotor position; and FIG. 9 is a diagram showing an example of a fixed position of a rotor when a V-phase switching element is switched as a boost switching element. 1A and 1B are diagrams illustrating an example of a fixed position of a rotor when a V-phase switching element and a W-phase switching element are switched as boost switching elements, respectively, and are diagrams illustrating an example of line-to-line inductance when the rotor is fixed at a 50° position at the start of boost operation, and are diagrams illustrating an example of line-to-line inductance when the rotor is fixed at a 120° position at the start of boost operation, respectively.

[0011] (First embodiment) Fig. 1 is a diagram showing the configuration of a charging device according to a first embodiment of the present invention. The charging device 2 shown in Fig. 1 is mounted on and used in an electrically powered vehicle such as an electric vehicle or a plug-in hybrid vehicle, and is connected to a vehicle system 1 including an electricity storage device 11. The charging device 2 has an inverter 20 and a rotating electric machine 30.

[0012] The inverter 20 has switching elements 21a and 21b constituting the upper and lower arms of the U phase, respectively, switching elements 22a and 22b constituting the upper and lower arms of the V phase, respectively, and switching elements 23a and 23b constituting the upper and lower arms of the W phase, respectively. These switching elements 21a to 23b are switched on and off in response to gate signals output from a gate drive circuit (not shown), thereby converting DC power supplied from the power storage device 11 into AC power and outputting it to the rotating electric machine 30. This generates a rotational driving force in the rotating electric machine 30, and this rotational driving force can be used to run an electric vehicle.

[0013] The gate drive circuit receives gate commands from a control device (not shown) configured by a microcomputer or the like, and outputs gate signals to each switching element in response to these gate commands. The control device can generate gate commands in response to external torque commands by performing well-known PWM control, for example, and output the gate commands to the gate drive circuit, but detailed description thereof will be omitted.

[0014] Although FIG. 1 shows an example in which each switching element of the inverter 20 is configured with a MOSFET, the switching elements 21a to 23b may be configured using other semiconductor elements such as an IGBT.

[0015] The inverter 20 also has, between the switching elements 21a to 23b and the power storage device 11, a smoothing capacitor 26 for suppressing voltage fluctuations in the DC power supplied from the power storage device 11, and Y capacitors 27a, 27b for suppressing noise.

[0016] The rotating electric machine 30 has a U-phase winding 31, a V-phase winding 32, and a W-phase winding 33, which respectively correspond to the U-phase, V-phase, and W-phase of the three-phase AC power output from the inverter 20. One end of the U-phase winding 31 is connected to the U-phase switching elements 21 a and 21 b of the inverter 20, one end of the V-phase winding 32 is connected to the V-phase switching elements 22 a and 22 b of the inverter 20, and one end of the W-phase winding 33 is connected to the W-phase switching elements 23 a and 23 b of the inverter 20. The other ends of the U-phase winding 31, the V-phase winding 32, and the W-phase winding 33 are connected to each other and form a neutral point of the rotating electric machine 30.

[0017] Between the inverter 20 and the rotating electric machine 30, a connection portion 41u to which a wiring 40u is connected is provided between the U-phase switching elements 21a, 21b and the U-phase winding 31. A relay 42u is provided on the wiring 40u, with one end of the relay 42u connected to the connection portion 41u and the other end of the relay 42u connected to a connection point 44. When the charging terminals 12a, 12b provided on the vehicle system 1 are connected to the external DC power source 4, the connection point 44 is a point at which the charging device 2 is electrically connected to the positive electrode of the DC power source 4 via the charging terminal 12a and a wiring 13a within the vehicle system 1. The connection point 44 corresponds to a connector terminal or contact (not shown) provided on the charging device 2. Note that the wiring 40u and the wiring 13a may be integrated, and any point on this wiring may be used as the connection point 44.

[0018] When charging terminals 12a, 12b are connected to DC power supply 4 and relay 42u is switched to the ON state, connection portion 41u is electrically connected to the positive electrode of DC power supply 4 via wiring 40u and connection point 44. As a result, one end of U-phase winding 31 is electrically connected to the positive electrode of DC power supply 4.

[0019] In vehicle system 1, wiring 13b is provided between charging terminal 12b and the negative electrode of power storage device 11. As a result, when charging terminal 12b is connected to DC power supply 4, the negative electrode of power storage device 11 is electrically connected to the negative electrode of DC power supply 4 via charging terminal 12b and wiring 13b.

[0020] The DC power supply 4 is, for example, a power supply for rapid charging. In this embodiment, the voltage of the DC power that the DC power supply 4 can supply (for example, about 400 Vdc) is lower than the charging voltage of the power storage device 11 (for example, about 800 Vdc).

[0021] The relay 42u is switched between an ON state and an OFF state by a control device (not shown), thereby establishing or interrupting conduction between the connection portion 41u and the DC power supply 4. Details of the switching control of the relay 42u will be described later.

[0022] Furthermore, a capacitor 43 is provided between the inverter 20 and the connection point 44. One end of the capacitor 43 is connected between the relay 42u and the connection point 44, and the other end of the capacitor 43 is connected to the negative electrode of the power storage device 11. As a result, when the charging terminal 12a is connected to the DC power supply 4, the capacitor 43 is electrically inserted between the negative electrode of the power storage device 11 and the positive electrode of the DC power supply 4.

[0023] 1 shows an example in which wiring 40u, relay 42u, and capacitor 43 are arranged outside inverter 20, but they may also be arranged inside inverter 20. That is, inverter 20, which is a power conversion device, may be configured to include at least one of wiring 40u, relay 42u, and capacitor 43 in addition to switching elements 21a-23b, smoothing capacitor 26, and Y capacitors 27a and 27b. Furthermore, vehicle system 1 and charging device 2 may include any parts or devices other than those shown in FIG. 1, such as various relays and other components.

[0024] Next, the operation of the charging device 2 when the DC power supply 4 is connected to the vehicle system 1 to charge the power storage device 11 will be described below. At this time, the electric vehicle including the vehicle system 1 is stopped, and the position of the rotor of the rotating electric machine 30 is fixed (locked), and the positive and negative electrodes of the DC power supply 4 are connected to the charging terminals 12a and 12b, respectively.

[0025] As described above, the voltage of the DC power that can be supplied from the DC power supply 4 is lower than the charging voltage of the power storage device 11. Therefore, in the charging device 2, the inverter 20 performs a boost operation described below to boost the DC power supplied from the DC power supply 4 and supply it to the power storage device 11. This makes it possible to charge the power storage device 11 using the DC power supply 4.

[0026] When starting the voltage boosting operation of the inverter 20, first, all switching elements are turned OFF and the relay 42u is switched ON, thereby electrically connecting the inverter 20 and the rotating electrical machine 30 to the DC power supply 4.

[0027] Next, among the switching elements 21a to 23b included in the inverter 20, V-phase switching elements 22a, 22b that do not have a connection to the DC power supply 4 between them and the corresponding V-phase winding 32 are alternately turned ON / OFF to perform a boost operation by the inverter 20. Specifically, first, the upper arm switching element 22a is turned OFF and the lower arm switching element 22b is turned ON, thereby causing an excitation current to flow from the DC power supply 4 to the U-phase winding 31 and the V-phase winding 32. Thereafter, the lower arm switching element 22b is turned OFF and the upper arm switching element 22a is turned ON, thereby passing a boost current, which is the boosted voltage of the DC power supply 4, through the capacitor 43 and the power storage device 11. In inverter 20, by repeating the switching operation of V-phase switching elements 22a, 22b, a boost operation can be performed in which U-phase winding 31 and V-phase winding 32 are used to boost the DC voltage supplied from DC power supply 4 and supply the boosted voltage to power storage device 11. In the following description, the switching elements that are switched on and off in inverter 20 during the boost operation are also referred to as "boost switching elements."

[0028] The switching control of the boost switching elements 22a, 22b may be performed by a control device that outputs the above-mentioned gate command to the gate drive circuit when the inverter 20 converts the DC power supplied from the power storage device 11 into AC power. Alternatively, a circuit that generates a gate command for boost operation may be provided separately from the control device, and the switching control of the boost switching elements 22a, 22b may be performed by using this circuit.

[0029] Furthermore, while the V-phase switching elements 22 a, 22 b are used to perform the voltage step-up operation as described above, the W-phase switching elements 23 a, 23 b may be left in the OFF state. Alternatively, similar to the V-phase, the W-phase switching elements 23 a, 23 b may also be switched repeatedly to energize the U-phase winding 31 and the W-phase winding 33 to perform the voltage step-up operation.

[0030] 2 shows the time variations in the currents Iv and Iw flowing through the V-phase winding 32 and the W-phase winding 33, respectively, when the V-phase switching elements 22a and 22b are switched and the W-phase switching elements 23a and 23b are kept OFF to perform a voltage boost operation. In this case, as shown in FIG. 2, the current Iv through the V-phase winding 32 fluctuates up and down as the switching elements 22a and 22b repeatedly switch, while the current Iw through the W-phase winding 33 remains unchanged at zero.

[0031] 3 is a diagram showing time variations in the currents Iv and Iw flowing through the V-phase winding 32 and the W-phase winding 33, respectively, when the V-phase switching elements 22a and 22b and the W-phase switching elements 23a and 23b are switched to perform a boost operation. In this case, as shown in FIG. 3, the V-phase switching elements 22a and 22b and the W-phase switching elements 23a and 23b each repeatedly switch, causing the current Iv of the V-phase winding 32 and the current Iw of the W-phase winding 33 to fluctuate up and down. In this case, the switching frequencies of the V-phase switching elements 22a and 22b and the W-phase switching elements 23a and 23b may or may not be the same.

[0032] Furthermore, by shifting the phases at which V-phase switching elements 22a, 22b and W-phase switching elements 23a, 23b are switched, it is possible to expect that the ripple current generated in U-phase winding 31 and the ripple voltage generated in capacitor 43 can be leveled and effectively suppressed. Therefore, the phases of the switching operations of the V-phase and W-phase may be shifted as necessary.

[0033] Furthermore, during the boost charging operation period, the period during which the V-phase switching elements 22 a, 22 b are switched and the period during which the W-phase switching elements 23 a, 23 b are switched may be shifted partially or entirely from each other. An example of this will be described below with reference to FIGS. 4 and 5.

[0034] 4 shows an example in which the switching period T22 of the V-phase switching elements 22 a, 22 b and the switching period T23 of the W-phase switching elements 23 a, 23 b are partially shifted from each other. In this example, the V-phase switching period T22 and the W-phase switching period T23 are shifted from each other in each period indicated by hatching in the figure.

[0035] 5 shows an example in which the switching period T22 of the V-phase switching elements 22 a, 22 b and the switching period T23 of the W-phase switching elements 23 a, 23 b are all shifted from each other. In this example, the V-phase switching period T22 and the W-phase switching period T23 are all shifted from each other.

[0036] 4 and 5, by preventing at least a portion of the V-phase switching period T22 and the W-phase switching period T23 from overlapping with each other, the heat generated during switching in the V-phase switching elements 22 a, 22 b and the heat generated during switching in the W-phase switching elements 23 a, 23 b can be dispersed in time, thereby effectively preventing the inverter 20 from becoming overheated.

[0037] When charging of the power storage device 11 is completed, all the switching elements are turned off again, and the relay 42u is switched to the off state. Thereafter, the DC power supply 4 and the vehicle system 1 are disconnected.

[0038] In the charging device 2, by switching the relay 42u and performing the boost operation of the inverter 20 as described above, the DC voltage supplied from the DC power source 4 is boosted and supplied to the storage device 11, thereby charging the storage device 11.

[0039] During the boost operation of inverter 20, the temperatures of windings 31-33 of rotating electric machine 30 and boost switching elements of inverter 20 may be detected, and the output of boost current may be adjusted based on the temperature detection results to prevent overheating. In particular, when both V-phase switching elements 22a, 22b and W-phase switching elements 23a, 23b are operated as boost switching elements, a current Iu, which is the sum of current Iv of V-phase winding 32 and current Iw of W-phase winding 33, is passed through U-phase winding 31, causing a large temperature rise in U-phase winding 31. Therefore, in such cases, it is preferable to monitor the temperature of U-phase winding 31 to reliably prevent overheating.

[0040] Furthermore, in the above embodiment, an example has been described in which the connection portion 41u with the DC power supply 4 is provided between the U-phase switching elements 21a, 21b and the U-phase winding 31, but a connection portion with the DC power supply 4 may be provided between the V-phase switching elements 22a, 22b and the V-phase winding 32, or between the W-phase switching elements 23a, 23b and the W-phase winding 33. Even in such a case, similar to the above, by alternately turning on and off the upper arm and lower arm switching elements of a phase not provided with a connection portion as boost switching elements, it is possible to perform a boost operation by the inverter 20 and charge the power storage device 11.

[0041] Furthermore, in the above embodiment, an example is shown in which the DC power source 4 on the low voltage side is charged at a boost voltage to the storage device 11 on the high voltage side, but conversely, power may be supplied at a reduced voltage from the storage device 11 on the high voltage side to the DC power source 4 on the low voltage side.

[0042] According to the first embodiment of the present invention described above, the following advantageous effects are achieved.

[0043] (1) The charging device 2 includes an inverter 20 having switching elements 21a to 23b connected to the power storage device 11, a rotating electric machine 30 having windings 31 to 33 respectively corresponding to different phases (U phase, V phase, W phase) of AC power output from the inverter 20, one end of each winding being connected to the switching elements 21a to 23b respectively and the other ends of each winding being connected to each other, and switching elements 21a and 21b corresponding to at least one phase (U phase) of the AC power. The inverter 20 includes at least one relay (relay 42u) having one end connected to a connection 41u provided between the U-phase winding 31 and the V-phase winding 32, and the other end connected to a connection point 44 with an external DC power source 4 that supplies DC power for charging the power storage device 11, and being switched ON or OFF to connect or disconnect the connection 41u and the DC power source 4, and a capacitor 43 having one end connected between the relay 42u and the connection point 44 and the other end connected to the negative electrode of the power storage device 11. The inverter 20 selects, as step-up switching elements, V-phase switching elements 22a, 22b and / or W-phase switching elements 23a, 23b that do not have a connection with the windings 32, 33, among the switching elements 21a-23b, and switches the step-up switching elements, thereby performing a step-up operation in which the voltage of the DC power from the DC power source 4 is boosted and supplied to the power storage device 11. Furthermore, relay 42u, which is connected to switching elements 21a and 21b other than the boost switching element via connection portion 41u, is switched to the ON state when inverter 20 performs boost operation. Since this configuration eliminates the need to extract the neutral point of rotating electric machine 30 externally, the boost function for charging power can be realized at low cost.

[0044] Furthermore, with the above configuration, the charging device 2 and the DC power supply 4 can be connected at a single connection point 44, thereby achieving further cost reduction compared to a conventional circuit configuration that requires separate connection points on the positive and negative sides of the DC power supply 4. Furthermore, during the voltage step-up operation of the inverter 20, an excitation current can be passed through at least two phases of windings (the U-phase winding 31 and the V-phase winding 32 and / or the W-phase winding 33) in the rotating electric machine 30, thereby increasing the inductance and reducing current ripple compared to a conventional circuit configuration in which an excitation current flows through only one phase of windings.

[0045] (2) The inverter 20 performs boost operation by switching the boost switching elements 22a, 22b, 23a, and 23b corresponding to two phases (V and W phases) of AC power as boost switching elements. The boost switching elements for one of the V and W phases are preferably switched during boost operation so that the periods during which the boost switching elements for one phase are switched do not at least partially overlap with the periods during which the boost switching elements for the other phase are switched (see FIGS. 4 and 5). This allows the heat generated during switching in each phase to be dispersed over time, effectively preventing the inverter 20 from overheating.

[0046] Second Embodiment Next, a second embodiment of the present invention will be described.

[0047] Fig. 6 is a diagram showing the configuration of a charging device according to a second embodiment of the present invention. A charging device 2A shown in Fig. 6 differs from the charging device 2 described in the first embodiment in that each of the U, V, and W phases is configured to be connectable to a DC power supply 4. That is, in addition to the U-phase wiring 40u, connection portion 41u, and relay 42u described in the first embodiment, the charging device 2A of this embodiment has a V-phase wiring 40v, connection portion 41v, and relay 42v, and a W-phase wiring 40w, connection portion 41w, and relay 42w.

[0048] The connection 41v is provided between the V-phase switching elements 22a, 22b and the V-phase winding 32, and is connected to the wiring 40v. The wiring 40v is provided with a relay 42v, one end of which is connected to the connection 41v and the other end of which is connected to the connection point 44.

[0049] Connection 41w is provided between W-phase switching elements 23a, 23b and W-phase winding 33, and wiring 40w is connected to connection 41w. Relay 42w is provided on wiring 40w, and one end of relay 42w is connected to connection 41w, and the other end of relay 42w is connected to connection point 44.

[0050] In this embodiment, the relays 42u, 42v, and 42w are alternately switched to the ON state while the charging device 2A is performing boost charging of the power storage device 11. This distributes the energization periods of the U-phase winding 31, the V-phase winding 32, and the W-phase winding 33 over time, thereby averaging out heat generation due to energization.

[0051] 7 is a diagram illustrating an example of the switching timing of the relays 42u, 42v, and 42w in the second embodiment of the present invention. When the charging device 2A starts boost charging, one of the relays 42u, 42v, and 42w, for example, the U-phase relay 42u, is first switched to the ON state for a predetermined period. During this period, in the inverter 20, the V-phase switching elements 22a and 22b and / or the W-phase switching elements 23a and 23b are selected as boost switching elements while the U-phase switching elements 21a and 21b are kept in the OFF state. Then, by switching the boost switching elements, a boost operation similar to that of the first embodiment is performed, and the DC power supplied from the DC power source 4 is boosted to charge the power storage device 11.

[0052] When a predetermined period has elapsed since the U-phase relay 42u was switched to the ON state, the relay 42u is switched to the OFF state, and one of the other relays 42v, 42w, for example, the V-phase relay 42v, is switched to the ON state for a predetermined period. During this period, in the inverter 20, the U-phase switching elements 21a, 21b and / or the W-phase switching elements 23a, 23b are selected as boost switching elements while the V-phase switching elements 22a, 22b are kept in the OFF state. Then, a boost operation is performed by switching the boost switching elements, and the DC power supplied from the DC power supply 4 is boosted to charge the power storage device 11.

[0053] Furthermore, when a predetermined period has elapsed since V-phase relay 42v was switched to the ON state, relay 42v is switched to the OFF state, and the remaining W-phase relay 42w is switched to the ON state for a predetermined period. During this period, in inverter 20, U-phase switching elements 21a, 21b and / or V-phase switching elements 22a, 22b are selected as boost switching elements while W-phase switching elements 23a, 23b are kept in the OFF state. Then, boost operation is performed by switching these boost switching elements, and DC power supplied from DC power supply 4 is boosted to charge power storage device 11.

[0054] Thereafter, the above operation is repeated to alternately switch the relays 42u, 42v, and 42w to the ON state at predetermined intervals and to switch the boost switching elements that are switched on during boost operation, thereby dispersing heat generated in the U-phase winding 31, the V-phase winding 32, and the W-phase winding 33.

[0055] In the above embodiment, an example has been described in which the U, V, and W phases are connectable to the DC power supply 4 via the wiring 40u, 40v, and 40w connected to the connection portions 41u, 41v, and 41w, respectively, and the relays 42u, 42v, and 42w provided on the wiring 40u, 40v, and 40w, respectively. However, only two of the U, V, and W phases may be connectable to the DC power supply 4. Even in this case, the relays are alternately switched to the ON state, and in the inverter 20, the switching elements other than those connected to the relays switched to the ON state are used as boost switching elements at predetermined intervals, thereby enabling the boost operation.

[0056] According to the second embodiment of the present invention described above, the charging device 2A includes an inverter 20 having switching elements 21a to 23b connected to the power storage device 11, a rotating electric machine 30 having windings 31 to 33 respectively corresponding to different phases (U phase, V phase, W phase) of AC power output from the inverter 20, one end of each winding being connected to the switching elements 21a to 23b respectively and the other ends of each winding being connected to each other, and a rotating electric machine 30 having windings 31 to 33 and switching elements 21a to 23b corresponding to at least one phase (U phase, V phase, W phase) of the AC power. 3, and the other end is connected to a connection point 44 with an external DC power source 4 that supplies DC power for charging the power storage device 11, and the relay 42u, 42v, 42w is switched to an ON state or an OFF state to establish or cut off conduction between the connection points 41u, 41v, 41w and the DC power source 4; and a capacitor 43 having one end connected between the relay 42u, 42v, 42w and the connection point 44 and the other end connected to the negative electrode of the power storage device 11. The inverter 20 selects, as boost switching elements, those of the switching elements 21a to 23b that are connected to the relays 42u, 42v, and 42w switched to the OFF state via the connections 41u, 41v, and 41w, and switches the selected boost switching elements to perform a boost operation in which the inverter 20 boosts the voltage of the DC power from the DC power source 4 using the windings 31 to 33 and supplies the boosted voltage to the power storage device 11. Furthermore, the relays 42u, 42v, and 42w that are connected to the switching elements 21a to 23b other than the boost switching elements via the connections 41u, 41v, and 41w, respectively, are switched to the ON state when the inverter 20 performs the boost operation. This eliminates the need to externally connect the neutral point of the rotating electric machine 30, as in the first embodiment, and therefore the boost function for charging power can be achieved at low cost.

[0057] The charging device 2A also has multiple relays (relays 42u, 42v, and 42w). One end of each of these relays 42u, 42v, and 42w is connected to connection parts 41u, 41v, and 41w, respectively, provided on different phases of AC power. At least one of the relays 42u, 42v, and 42w is switched to the ON state when the inverter 20 performs a boost operation. The inverter 20 performs a boost operation by switching each of the switching elements 21a to 23b, except for the relays 42u, 42v, and 42w that are switched to the ON state and the switching elements connected via connection parts 41u, 41v, or 41w, and by switching the boost switching elements. This configuration allows the heat generated by the current flowing through each winding of the rotating electric machine 30 to be dispersed over time, further effectively suppressing overtemperature.

[0058] Third Embodiment Next, a third embodiment of the present invention will be described. In this embodiment, an example will be described in which the rotor position during voltage boosting operation is determined in consideration of the fact that the line-to-line inductance of each of the windings 31 to 33 of the rotating electrical machine 30 depends on the rotor position.

[0059] The charging device according to this embodiment can have the same configuration as that of the first or second embodiment described above. The charging device according to this embodiment will be described below using the configuration of the charging device 2 described in the first embodiment.

[0060] In the rotating electric machine 30, the magnetic path changes depending on the rotor position. Therefore, the line-to-line inductance of each combination of two of the U-phase winding 31, V-phase winding 32, and W-phase winding 33 changes depending on the rotor position, as shown by curves 81, 82, and 83 in Figure 8. Here, curve 81 represents the U-phase-V phase line-to-line inductance, i.e., the inductance of the U-phase winding 31 and the V-phase winding 32. Curve 82 represents the V-phase-W phase line-to-line inductance, i.e., the inductance of the V-phase winding 32 and the W-phase winding 33, and curve 83 represents the U-phase-W phase line-to-line inductance, i.e., the inductance of the U-phase winding 31 and the W-phase winding 33. In this way, the line-to-line inductance of each of the windings 31 to 33 is dependent on the rotor position, and the line-to-line inductances are shifted from one another.

[0061] Therefore, in this embodiment, by utilizing the rotor position dependency of the line-to-line inductance of each winding 31-33, when switching a switching element of one of the phases as a boost switching element, the rotor is fixed in a position that maximizes the inductance of the winding energized by the switching operation. This suppresses the ripple current flowing through each winding of the rotating electric machine 30 during boost operation, thereby reducing magnetostrictive noise and voltage ripple generated by the rotating electric machine 30. Alternatively, the switching frequency required for boost operation can be reduced, thereby reducing losses in the switching elements. Generally, semiconductor elements capable of driving at a switching frequency of approximately 10 kHz are often used for the switching elements 21a-23b of the inverter 20. Therefore, it is important to ensure a large inductance in each winding of the rotating electric machine 30 so that sufficient boost operation can be performed at this switching frequency.

[0062] Specifically, for example, as described in the first embodiment, when the relay 42u is switched to the ON state and the V-phase switching elements 22a and 22b are switched as boost switching elements to perform boost operation, the U-phase winding 31 and the V-phase winding 32 are energized and an excitation current flows. Therefore, in this case, the rotor is fixed in a position where the U-phase-V-phase line inductance shown by curve 81 is larger than the other line inductances, as shown by the dashed line 84 in Figure 9.

[0063] Furthermore, for example, as described in the first embodiment, when boost operation is performed by switching the V-phase switching elements 22 a, 22 b and the W-phase switching elements 23 a, 23 b as boost switching elements, the U-phase winding 31 and the V-phase winding 32, and the U-phase winding 31 and the W-phase winding 33, are energized and excitation current flows. Therefore, in this case, the rotor is fixed in a position where the U-phase-V-phase line inductance shown by curve 81 and the U-phase-W-phase line inductance shown by curve 83 become relatively large, as shown in the range indicated by dashed line 85 in Figure 10.

[0064] In this embodiment, the rotor position to be fixed during boost operation is preferably a position where the line-to-line inductance corresponding to the combination of energized windings is maximized, as described above, but it does not necessarily have to be a position where the maximum line-to-line inductance is obtained.The effect of this embodiment can be obtained at least as long as the rotor is at a position other than the position where the inductance of the windings energized in response to switching of the boost switching elements is minimized.

[0065] Any method can be used to fix the rotor position in the rotating electric machine 30. For example, the rotor position can be fixed using an electric parking lock system that operates in an electric vehicle on which the rotating electric machine 30 is mounted, that is, a fixing mechanism that can mechanically fix the rotating shaft of the rotating electric machine 30 to the housing of the reducer.

[0066] Alternatively, the rotor position may not be fixed, and the inverter 20 may start boosting operation at any rotor position. In this case, when current is applied to a winding of any phase, the rotor position at which the magnetic flux of that winding is at its maximum becomes the stable point, and the rotor moves to the optimal position by itself. Note that after the rotor moves to the stable point position, the rotor may or may not be fixed at that position.

[0067] According to the third embodiment of the present invention described above, the charging device 2, 2A has a fixing mechanism that can fix the position of the rotor of the rotating electric machine 30. When the inverter 20 performs a boost operation, this fixing mechanism fixes the rotor to a position other than the position where the inductance of the windings 31 to 33 of the rotating electric machine 30 that are energized in response to switching of the boost switching elements is minimum. This configuration makes it possible to suppress ripple current flowing through the rotating electric machine 30 when the inverter 20 performs a boost operation.

[0068] Next, a fourth embodiment of the present invention will be described. In this embodiment, an example will be described in which switching elements to be switched on and off during voltage step-up operation are selected in consideration of the rotor position dependency of the line inductance described in the third embodiment.

[0069] The charging device according to this embodiment can also have the same configuration as the first or second embodiment. The charging device according to this embodiment will be described below using the configuration of the charging device 2 described in the first embodiment.

[0070] As explained in the third embodiment, in the rotating electrical machine 30, the line inductances of the windings 31 to 33 each have rotor position dependency, and the phases are shifted from one another. In this embodiment, by utilizing this rotor position dependency of the line inductance, boost switching elements are selected so that the winding of the phase with the relatively large inductance at the rotor position during boost operation is energized. This makes it possible to obtain the same effects as in the third embodiment.

[0071] Specifically, for example, if the rotor is fixed at the 50° position at the start of the boost operation, the U-phase-V-phase line inductance indicated by curve 81 will be larger than the other line inductances, as indicated by dashed line 86 in Fig. 11. Therefore, in this case, the boost operation is performed by switching V-phase switching elements 22a and 22b in inverter 20 as boost switching elements so that U-phase winding 31 and V-phase winding 32 are energized and an excitation current flows.

[0072] Furthermore, for example, if the rotor is fixed at the 120° position at the start of the boost operation, the line-to-line inductance between the U phase and the W phase, indicated by curve 83, becomes larger than the other line-to-line inductances, as shown by dashed line 87 in Fig. 12. Therefore, in this case, the boost operation is performed by switching W-phase switching elements 23a and 23b in inverter 20 as boost switching elements so that U-phase winding 31 and W-phase winding 33 are energized and an excitation current flows.

[0073] 1 , only relay 42u corresponding to the U phase is provided, and relays corresponding to the V phase and the W phase are not provided, so that excitation current cannot be passed through V-phase winding 32 and W-phase winding 33. Therefore, in this case, even if the rotor is fixed in a position where the line-to-line inductance between the V phase and the W phase is larger than the other line-to-line inductances, it is preferable to perform a boost operation by switching V-phase switching elements 22a, 22b or W-phase switching elements 23a, 23b in inverter 20 as boost switching elements so that either U-phase winding 31 and V-phase winding 32 or U-phase winding 31 and W-phase winding 33 are energized and an excitation current flows.

[0074] 6, by switching any one of relays 42u, 42v, and 42w to the ON state, it is possible to energize any two combinations of U-phase winding 31, V-phase winding 32, and W-phase winding 33 to pass an excitation current. Therefore, in this case, it is preferable to switch any one of relays 42u, 42v, and 42w to the ON state so that the windings of the two phases having the largest line-to-line inductance according to the rotor position are energized and an excitation current flows, and to switch any one of U-phase switching elements 21a and 21b, V-phase switching elements 22a and 22b, and W-phase switching elements 23a and 23b in inverter 20 as a boost switching element to perform a boost operation.

[0075] According to the fourth embodiment of the present invention described above, the inverter 20 selects one of the U-phase, V-phase, and W-phase of the AC power in which the line-to-line inductance is relatively large depending on the position of the rotor of the rotating electric machine 30, and performs a boost operation using the switching elements corresponding to that phase as boost switching elements. This makes it possible to suppress the ripple current flowing through the rotating electric machine 30 during the boost operation of the inverter 20.

[0076] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, or the configuration of another embodiment can be added to the configuration of one embodiment. Furthermore, part of the configuration of each embodiment can be added, deleted, or replaced with other configurations. Furthermore, the above-described configurations, functions, processing units, processing means, etc. may be implemented in hardware, in part or in whole, by designing, for example, an integrated circuit. Furthermore, the above-described configurations, functions, etc. may be implemented in software, by a processor interpreting and executing a program that realizes each function. Information such as programs, tables, and files that realize each function can be stored in memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD.

[0077] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0078] 1: vehicle system, 2, 2A: charging device, 4: DC power supply, 11: power storage device, 20: inverter, 21a, 21b, 22a, 22b, 23a, 23b: switching elements, 30: rotating electric machine, 31: U-phase winding, 32: V-phase winding, 33: W-phase winding, 40u, 40v, 40w: wiring, 41u, 41v, 41w: connection portion, 42u, 42v, 42w: relay, 43: capacitor, 44: connection point

Claims

1. A rotating electric machine comprising: an inverter having a plurality of switching elements connected to a power storage device; a rotating electric machine having a plurality of windings each corresponding to a different phase of AC power output from the inverter, one end of each winding being connected to the switching elements and the other ends of the windings being connected to each other; at least one relay having one end connected to a connection portion provided between the windings and the switching element corresponding to at least one phase of the AC power and having the other end connected to a connection point with an external DC power source that supplies DC power for charging the power storage device, the relay being switched between an ON state or an OFF state to establish or break conduction between the connection portion and the DC power source; and a capacitor having one end connected between the relay and the connection point and the other end connected to a negative electrode of the power storage device, The inverter is capable of performing a boost operation of boosting the voltage of the DC power using the winding and supplying it to the power storage device by selecting, from among the plurality of switching elements, a switching element that does not have the connection portion between the winding and the relay that is switched to the OFF state via the connection portion as a boost switching element and switching the boost switching element, and the relay that is connected to a switching element other than the boost switching element via the connection portion is switched to the ON state when the inverter performs the boost operation.

2. The charging device according to claim 1, wherein the inverter performs the boost operation by switching the boost switching elements of one phase and the other phase of the two phases, with the switching elements corresponding to the two phases of the AC power being the boost switching elements.

3. The charging device according to claim 2, wherein the inverter switches each boost switching element in the boost operation so that a period during which the boost switching element of one phase is switched and a period during which the boost switching element of the other phase is switched do not at least partially overlap each other.

4. The charging device according to claim 1, further comprising a plurality of the relays, one end of each of the relays being connected to the connection parts provided on different phases of the AC power, at least one of the plurality of relays being switched to the ON state when the inverter performs the boost operation, and the inverter performs the boost operation by switching each of the switching elements, except for the switching element connected to the relay switched to the ON state via the connection part, as the boost switching element.

5. The charging device according to claim 4, wherein a plurality of the relays are each switched to the ON state or the OFF state.

6. A charging device as claimed in any one of claims 1 to 5, further comprising a fixing mechanism capable of fixing the position of a rotor of the rotating electric machine, the fixing mechanism fixing the rotor to a position other than a position at which the inductance of one of the plurality of windings that is energized in response to switching of the boost switching element is minimum when the inverter performs the boost operation.

7. A charging device as claimed in any one of claims 1 to 5, wherein the inverter selects, from among the multiple phases of the AC power, a phase in which line-to-line inductance is relatively large depending on the position of the rotor of the rotating electric machine, and performs the boost operation by using the switching element corresponding to that phase as the boost switching element.

8. A power storage device comprising: a plurality of switching elements that perform a switching operation for converting a first DC power supplied from a power storage device into AC power and outputting the AC power to a rotating electric machine; at least one relay having one end connected to a connection part provided between the switching element corresponding to at least one phase of the AC power and a winding of the rotating electric machine and the other end connected to a connection point with an external DC power source that supplies second DC power for charging the power storage device, and being switched to an ON state or an OFF state to establish or block conduction between the connection part and the DC power source; and a capacitor having one end connected between the relay and the connection point and the other end connected to a negative electrode of the power storage device; wherein a switching element that does not have the connection part provided between the winding and the relay that is switched to the OFF state is selected as a boost switching element from among the plurality of switching elements, and the boost switching element is switched to perform a boost operation for boosting the voltage of the second DC power using the winding and supplying it to the power storage device; the relay, which is connected to a switching element other than the boost switching element via the connection portion, is switched to the ON state when the boost operation is performed.

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