JP2019009856A - Battery charging device - Google Patents

Abstract

To reduce the number of components, the cost, and the device capacity of a battery charging device.SOLUTION: N (N≥3) inverters INV1, INV2 and INV3 are connected in parallel with a battery 17. The inverters INV1, INV2 and INV3 each perform an inverter operation of inverting DC power from the battery 17 to AC power and outputting the AC power, and a converter operation of converting the AC power to DC power and outputting the DC power to the battery 17. Motors M1, M2 and M3 are connected to respective three-phase AC sides of the inverters INV1, INV2 and INV3. A secondary winding of a transformer 13 is connected to any one phase of the three-phase AC sides of the three inverters INV1, INV2 and INV3 among the N inverters INV1, INV2 and INV3. A switch 12 is connected between the primary winding of the transformer 13 and a three-phase AC power source 11.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a battery charging device.

  An electric vehicle needs to be charged in advance with a battery mounted in order to secure traveling power. FIG. 7 shows a charging circuit using the transformer 13 and the rectifier 18. In this circuit, the battery 17 is charged by applying a constant voltage, so that a large current flows at the initial stage of charging when the battery voltage is low, and a large burden is generated on the battery 17.

  As a method for reducing the burden on the battery 17, there is a method in which the rectifier 18 in FIG. 7 is replaced with a converter. By controlling this converter, AC power is converted to DC power and the battery 17 is charged. By performing current control with the converter, the battery 17 can be charged with a constant current, and the burden on the battery 17 can be suppressed and charged at high speed.

  However, it is necessary to separately add a switching element, and a circuit for driving the added switching element, a control circuit for supplying a drive signal, a current detector for performing control, and the like are required. As a result, an increase in the number of parts, an accompanying increase in cost and device volume, and an increase in the failure rate of the device become problems.

  Patent Documents 1 to 6 are disclosed as methods for solving the above problems.

JP-A-8-126122 JP-A-8-126121 JP 2011-211889 A JP2013-243868A Special table 2014-524731 gazette Japanese Patent No. 5979253

  In the configuration of Patent Document 1 shown in FIG. 8, a diode rectifier is not required as compared with the conventional circuit shown in FIG. 7, but a filter 19 for switching ripple removal must be added separately. In order to ensure safety, it is necessary to insulate between AC input UVW and filter 19 with a transformer. Further, the disconnect connector 20 is inserted between the motor M and the inverter INV. If a contact failure occurs in the disconnecting connector 20, the motor M cannot be driven, and there is a concern about an abnormal stop during traveling.

  In Patent Document 2 shown in FIG. 9, a single-phase converter is constituted by two motor-driven inverters INV1 and INV2. Since windings 30-1 to 3 and 31-1 to 3 of motors M1 and M2 are used as a filter, it is not necessary to add a filter reactor. A connector between the motors M1, M2 and the inverters INV1, INV2 is also unnecessary. However, the motors M1 and M2 are limited to star connection, and further, neutral point terminals 32 and 33 need to be provided. Even in this configuration, it is necessary to insulate the single-phase AC power supply 11 and the motors M1 and M2 with a transformer. Moreover, since it is a single phase alternating current power supply, there exists a problem that a big pulsation of the frequency twice as high as the single phase alternating current power supply 11 is superimposed on a battery charging current.

  The configuration of Patent Document 3 shown in FIG. 10 can be applied even when the motors M1 and M2 are Δ-connected. However, a diode rectifier 18 is required separately. Further, since a specially wound transformer called the Scott transformer 34 is used, there are problems in terms of transformer cost and delivery time.

  In Patent Document 4 shown in FIG. 11, a three-phase converter is configured by two motor-driven inverters INV1 and INV2. Unlike Patent Document 2, the motors M1 and M2 can be applied to either star connection or Δ connection. However, the motors M1 and M2 must be open windings in which terminals at both ends of the windings of each of the three phases are output to the outside.

  Patent Document 5 shown in FIG. 12 can be applied whether the motor M is a star connection or a Δ connection. However, a separate step-down converter CNV is required in the configuration of one motor M, and the number of parts is greatly increased. In addition, there is a mechanical switch 35 between the motor M and the inverter INV, and there is a risk of abnormal stop during traveling due to poor contact as in Patent Document 1.

  As described above, it is a problem to reduce the number of parts, cost, and device volume in the battery charging device.

  The present invention has been devised in view of the conventional problems, and one aspect thereof is a battery and N (N ≧ 3) units connected in parallel to the battery, and the DC power of the battery is converted to AC power. An inverter operation for converting to and outputting, a three-phase inverter for performing a converter operation for converting AC power to DC power and outputting to the battery, a motor connected to the three-phase AC side of each inverter, and A transformer in which a secondary winding is connected to any phase on the three-phase AC side of three inverters of the N inverters, and a primary winding is connected to a three-phase AC power source; the inverter and the transformer Or between the primary winding of the transformer and the three-phase AC power source, or between the inverter and the secondary winding of the transformer, and the primary winding of the transformer. Three-phase AC A switch connected between the source, characterized by comprising a.

  Further, as another aspect, a battery and an inverter operation in which N (N ≧ 2) units are connected in parallel to the battery, and the DC power of the battery is converted into AC power and output, and the AC power is converted into DC power. A three-phase inverter that performs converter operation for conversion and output to the battery, a motor connected to the three-phase AC side of each inverter, and a secondary winding of two inverters out of the N inverters A transformer connected to any phase on the three-phase AC side and having a primary winding connected to a single-phase AC power source, and between the inverter and the secondary winding of the transformer, or the primary winding of the transformer And a switch connected between the inverter and the secondary winding of the transformer, and between the primary winding of the transformer and the single-phase AC power supply. Special To.

  As one aspect thereof, the motor is a delta connection.

  As another aspect, the motor is a star connection.

  Further, as one aspect thereof, the inverter has a switching element on the upper and lower arms of each phase, and the charging current control unit of each inverter to which the secondary winding of the transformer is connected during battery charging operation Turns off the switching elements of the upper and lower arms of the phase to which the secondary winding of the transformer is connected, and detects the converter output current command value and the two-phase converter input current that is not connected to the secondary winding of the transformer A converter voltage command value is calculated based on the deviation of the converter output current detection value obtained by adding the value and the converter voltage detection value, PWM control is performed based on the converter voltage command value, and the secondary of the transformer A gate command value for a switching element of a two-phase upper and lower arm to which no winding is connected is generated.

  Further, as one aspect thereof, the PWM control is carried out by performing PWM control based on a carrier triangular wave in one of the two phases to which the secondary winding of the transformer is not connected, and the other phase being the carrier triangular wave. PWM control is performed based on a signal obtained by inverting the signal.

  According to the present invention, it is possible to reduce the number of parts, cost, and device volume in a battery charging device.

FIG. 3 is a diagram illustrating a battery charging device according to the first embodiment. The block diagram which shows the charging current control part in Embodiment 1-3. The block diagram which shows the parallel control part and PWM control part at the time of applying the interleave control in Embodiment 1-3. The figure which shows the equivalent circuit of the battery charging device at the time of battery charging operation in Embodiment 1,2. FIG. 6 is a diagram illustrating a battery charging device according to a second embodiment. FIG. 6 is a diagram illustrating a battery charging device according to a third embodiment. The figure which shows an example of the conventional battery charging device. The figure which shows the battery charging device of patent document 1. FIG. The figure which shows the battery charging device of patent document 2. FIG. The figure which shows the battery charging device of patent document 3. FIG. The figure which shows the battery charging device of patent document 4. FIG. The figure which shows the battery charging device of patent document 5. FIG.

  Hereinafter, Embodiments 1 to 3 of the battery charger according to the present invention will be described in detail with reference to FIGS.

[Embodiment 1]
FIG. 1 shows a battery charger according to the first embodiment. The battery charging device according to the first embodiment includes a battery 17, N (N ≧ 3) units (three units in the first embodiment) connected in parallel to the battery 17, and three-phase inverters INV1, INV2, INV3, The motor M1, M2, M3 connected to the three-phase AC side of the inverters INV1, INV2, INV3, and any phase on the three-phase AC side of the three inverters INV1, INV2, INV3 among the inverters INV1, INV2, INV3 A transformer 13 having a secondary winding connected to (phase W in the first embodiment), a switch 12 having one end connected to the primary winding of the transformer 13 and the other end connected to the three-phase AC power source 11, Is provided.

  The switch 12 may be configured to be provided on the secondary winding side of the transformer 13 or may be configured to be provided on both the primary winding side and the secondary winding side of the transformer 13. Further, the inverters INV1, INV2, and INV3 are configured to include one switching element on the upper and lower arms of each phase as shown in FIG.

  The first embodiment is different from the battery charger of FIG. 7 in the following points. A rectifier between the transformer 13 and the battery 17 is not used. The secondary winding of the transformer 13 is connected to the W phase on the three-phase AC side of the three inverters INV1, INV2, and INV3 for driving the motor. In FIG. 1, the secondary winding of the transformer 13 is connected to the W phase, but may be connected to the U phase and the V phase.

  The inverters INV1, INV2, and INV3 convert the DC power of the battery 17 into AC power and output it to the motors M1, M2, and M3, and convert AC power fed from the three-phase AC power source 11 into DC power. Then, a converter operation for outputting to the battery 17 is performed.

  Current detectors 14u, 14v, 15u, 15v, 16u, 16v are provided on the three-phase AC side of each inverter INV1, INV2, INV3. This current detector is provided in a phase to which the secondary winding of the transformer 13 is not connected, and may be two phases out of the three phases. Current detectors 14u, 14v, 15u, 15v, 16u, and 16v detect converter input current detection values Iinv1U, Iinv1V, Iinv2U, Iinv2V, Iinv3U, and Iinv3V. Although FIG. 1 shows a configuration without a current detector in the W phase, if the phase to which the secondary winding of the transformer 13 is not connected is the U phase, the U phase has no current detector. If the phase to which the secondary winding of the transformer 13 is not connected is the V phase, the V phase has no current detector. The windings of the motors M1, M2, and M3 are Δ-connected and have no neutral point.

  In the first embodiment, a three-phase converter is configured using three drive inverters INV1, INV2, and INV3 of motors M1, M2, and M3. With this three-phase converter, AC power output from the AC power supply 11 is converted into DC power, and the battery 17 is charged. The winding inductances of the motors M1, M2, and M3 and the leakage inductance of the transformer 13 are used as a filter for removing the switching ripple.

  A method of driving the inverters INV1, INV2, and INV3 when the battery 17 is charged will be described. By considering the inverter INV1 as the converter U phase, the inverter INV2 as the converter V phase, and the inverter INV3 as the converter W phase, the three inverters INV1, INV2, and INV3 can be handled as one three-phase grid-connected converter.

  However, the W phase in the inverters INV1, INV2, and INV3 turns off both the upper and lower arm switching elements during the charging operation and performs switching only in the U phase and the V phase. As a result, the battery charging current passes only through the U phase and the V phase.

  As a U-phase converter output current command value (current command value on the DC side of the inverter INV1) IcnvU *, a sine wave having the same phase and constant amplitude as the U-phase converter voltage detection value Vu is given, and the positive Icharge direction shown in FIG. If current control is performed so as to give active power, the battery 17 can be charged. Unlike the single-phase converter of Patent Document 2, no voltage pulsation having a frequency twice that of the fundamental wave is generated in the DC bus (both ends of the battery 17), so the burden on the battery 17 can be reduced.

  FIG. 2 shows an example of a block diagram of a charging current control unit per inverter INV (converter 1 phase). FIG. 2 shows a block diagram of INV1 (converter U phase). First, the adder 1 adds a U-phase inverter input current detection value Iinv1U and a V-phase inverter input current detection value Iinv1V, which are two-phase current detection values to which the secondary winding of the transformer 13 is not connected. Is the U-phase converter output current detection value (current detection value on the AC side of the inverter INV1) IcnvU. The filter 2 removes noise from the U-phase converter output current detection value IcnvU.

  In the subtracter 3, the deviation is calculated by subtracting the U-phase converter output current detection value IcnvU from the U-phase converter output current command value IcnvU *. This deviation is amplified by the proportional amplifier P.

  As shown in FIG. 1, the voltage detector PT converts the line voltage into a phase voltage, and outputs it as a U-phase converter voltage detection value Vu, a V-phase converter voltage Vv, and a W-phase converter voltage Vw. The filter 4 removes noise from the U-phase converter voltage detection value Vu. In the adder 5, the U-phase converter voltage detection value Vu after passing through the filter 4 is added to the output of the proportional amplifier P to perform feedback control to obtain a U-phase converter voltage command value Vu *.

  Although FIG. 2 shows an example of the configuration of the charging current control unit, the charging current control unit may have another configuration. For example, in the first embodiment, an example in which the amplifier processing is performed on the fixed coordinates without performing the three-phase two-phase conversion or the dq conversion is shown, but the three-phase two-phase conversion or the dq conversion may be performed. The reason why the three-phase two-phase conversion and the dq conversion are not performed in the first embodiment is to reduce the communication load between the three motors M1, M2, and M3. In the first embodiment, an example in which an integration amplifier is not used is shown. However, an integration amplifier may be used. The reason why the integrating amplifier is not used in the first embodiment is that the gain of the integrating amplifier is finite and the deviation does not become zero for the fundamental wave of 50 Hz or 60 Hz.

  As shown in FIG. 3, parallel controller 6 multiplies U-phase converter output current command value IcnvU * by ½ in multiplier 21. Filters 23a and 23b remove noise from U-phase converter input current detection value Iinv1U and V-phase converter input current detection value Iinv1V. Subtractors 22a and 22b subtract U-phase converter input current detection value Iinv1U and V-phase converter input current detection value Iinv1V after passing through filters 23a and 23b, respectively, from the output of multiplier 21. The multipliers 24a and 24b multiply the outputs of the subtractors 22a and 22b by a gain G. Adders 25a and 25b add the U-phase converter voltage command value Vu * to the outputs of multipliers 24a and 24b, respectively.

  In the subtractor 26a, the PWM controller 7 subtracts the carrier triangular wave from the output of the adder 25a. The multiplier 27 multiplies the carrier triangular wave by −1 and inverts the carrier triangular wave. The subtractor 26b subtracts the inverted carrier triangular wave from the output of the adder 25b.

  The comparators 28a and 28b compare whether or not the outputs of the subtractors 26a and 26b are greater than 0, that is, the output of the adder 25a and the magnitude of the carrier triangular wave, and the output of the adder 25b and the magnitude of the inverted carrier triangular wave. 1 is output when it is greater than 0, and 0 is output when 0 or less. The dead time processors 29a and 29b add a dead time to the outputs of the comparators 28a and 28b, and output them as gate commands (on / off commands) for the respective switching elements.

Thereby, the ripple of the U-phase current of the inverter INV1 and the ripple of the V-phase current of the inverter INV1 cancel each other, and the ripple of the U-phase converter current can be reduced. (If the reduction in the converter current ripple is not important, the multiplier 27 in FIG. 3 may not be provided.)
When it is necessary to more effectively remove the ripple of the converter current, a method of adding a filter capacitor between the transformer 13 and the motors M1, M2, and M3 can be considered.

  The U-phase / V-phase arms of the inverters INV1 to INV3 are connected in parallel via the winding inductances of the motors M1, M2, and M3. If the winding inductance is sufficiently large, the switching elements are grouped into two upper arms and two lower arms, and each is switched at the same timing, so that the passing current can be equally shared. Therefore, charging with a large current is also possible. By omitting the multiplier 27 in FIG. 3, the switching elements of the two upper arms and the two lower arms can be switched at the same timing. Even when the winding inductance is very small, the current sharing can be made uniform by applying the technique of Patent Document 6. Thereby, the loss of the switching elements (two in total) of two upper arms and two lower arms can be equalized. Moreover, the loss which generate | occur | produces in the winding between UW / VW of a motor can also be equalized.

  In the configuration shown in FIG. 3 where the carrier triangular wave input to the subtractor 26b is inverted by the multiplier 27, the switching timing of the U-phase switching element is exactly the same as the switching timing of the V-phase switching element. Don't be. However, the effective value per cycle of the current passing through each switching element, that is, the loss of each switching element can be equalized by the control block of FIG.

  In the first embodiment, the reason why the motors M1, M2, M3 do not rotate when the battery 17 is charged will be described. Currents of the same amplitude and phase flow through the windings between UW and VW of the motors M1, M2, and M3. A magnetic field is generated in the motors M1, M2, and M3, and the magnitude and sign of the magnetic field change. However, since the phase is fixed, no rotating magnetic field is generated. Therefore, if the motors M1, M2, M3 are stopped by the induction machine, no starting torque is generated and the motors M1, M2, M3 do not rotate. Therefore, if the motors M1, M2, and M3 are induction machines, charging can be performed safely without preparing an additional mechanism such as fixing or removing a shaft or a tire.

  In the first embodiment, the reason why no current flows in the W phase of each of the inverters INV1, INV2, and INV3 when the battery 17 is charged will be described. FIG. 4 is a simplified diagram of FIG. 1 during the battery 17 charging operation. The left reactor Tr represents the leakage inductance of the transformer, and the right reactor represents the winding inductance of the motors M1, M2, and M3.

  As shown in FIG. 4, the W-phase voltages of the inverters INV1, INV2, and INV3 are determined by the partial pressures of the two reactors. If the DC voltage (battery 17 voltage) is larger than the line voltage peak of the AC power supply 11, the W-phase voltages of the inverters INV1, INV2, and INV3 are smaller than the inverter U-phase voltage and V-phase voltage, that is, the DC voltage. The diode does not conduct and no current flows in the W phase. When charging the battery 17 with a constant current, the voltage of the AC power source 11, the transformation ratio of the transformer 13, and the minimum voltage (DC voltage) of the battery 17 are designed so as to satisfy this condition. Thus, no current flows in the W phase of the inverters INV1, INV2, and INV3.

  Unlike the patent document 5, the first embodiment does not require a switch for disconnecting the W phase of the inverters INV1, INV2, and INV3, so that the number of components can be reduced. Further, there is no possibility that the motor contacts M1, M2 and M3 will stop abnormally during running because the switch contact causes a contact failure.

  Since the inverters INV1, INV2, and INV3 for driving the motors M1, M2, and M3 are used as a battery charging converter and the motor winding is used as a filter reactor for removing a switching ripple, the first embodiment is compared with FIG. The rectifier diode for charging the battery and its cooling mechanism are not required, and the number of parts, cost, and device volume can be reduced.

  Further, since the harmonic current flowing out to the AC power supply 11 is smaller than that of the rectifier diode, the iron loss of the motors M1, M2, M3 and the transformer 13 is reduced when the battery 17 is charged, the passive elements connected to the AC power supply 11 are Burnout and malfunction of the device can be prevented. This effect can be greatly obtained by the configuration in which the carrier triangular wave input to the U-phase subtractor 26a and the carrier triangular wave input to the V-phase subtractor 26a shown in FIG. 3 are inverted.

  Further, the inverters INV1, INV2, and INV3 can be operated by the current detectors 14u, 14v, 15u, 15v, 16u, and 16v for two phases not only in the driving operation of the motors M1, M2, and M3 but also in the charging operation. Since the current detector used for the driving operation and the charging operation can be used together, the number of parts of the current detector does not increase. The charging current flows through two phases including current detectors 14u, 14v, 15u, 15v, 16u, and 16v.

  Further, if the technology of Patent Document 6 is applied, the current duty and the heat duty of the switching element can be made uniform, battery charging with a large current, long life of the element, iron loss of the motors M1, M2, M3 during charging. Can be reduced. Further, as shown in FIG. 3, when the switching element is interleaved during battery charging, the ripple current flowing out to the AC power supply 11 can be further reduced, and the harmonic current flowing out to the AC power supply 11 can be reduced.

  If induction machines are used as the motors M1, M2, and M3, the motors M1, M2, and M3 do not start rotating while the battery 17 is being charged. Therefore, there are mechanisms such as separating the motor shaft from the tires and fixing the tires. It is unnecessary.

  Compared with Patent Document 1, the disconnecting connector (reference numeral 20 in FIG. 8) between the motors M1, M2, and M3 and the inverters INV1, INV2, and INV3 becomes unnecessary, so that the number of parts can be reduced and the battery charging device can be downsized. , It is possible to reduce the cost. Further, since no mechanical switch is connected between the inverters INV1, INV2, and INV3 and the motors M1, M2, and M3, it is possible to prevent an abnormal motor stop due to a contact failure.

  Further, compared to Patent Document 2, the windings of the motors M1, M2, and M3 can be applied even by Δ connection, and a neutral point terminal is unnecessary, so that a general induction machine can be applied. Further, since the battery 17 can be charged by the three-phase converter, a voltage / current pulsation twice the fundamental wave is not superimposed on the DC bus, and the burden on the battery 17 can be reduced. Thereby, the life of the battery 17 can be extended.

  Further, compared with Patent Document 3, no rectifier diode is required. Further, since a general three-phase transformer can be applied to the transformer 13 instead of a Scott transformer, it is advantageous in terms of cost and delivery date of the transformer 13.

  Further, compared to Patent Document 4, the motors M1, M2, and M3 do not need to be open windings, and a general induction machine in which the windings are Δ connection or star connection can be applied.

  Further, compared with Patent Document 5, since the step-down converter CNV is unnecessary, the number of components can be reduced. Further, the mechanical switch 35 between the inverters INV1, INV2, INV3 and the motors M1, M2, M3 is also unnecessary. Therefore, it is possible to reduce the size and cost of the battery charger.

  In addition, the charging current control unit according to the first embodiment can have the same hardware configuration in each of the inverters INV1, INV2, and INV3 if only the detection value and the command value are replaced.

  Further, it is possible to equalize the current duty during charging by the inverters INV1, INV2, and INV3. Further, in each inverter INV1, INV2, INV3, it is possible to equalize the losses of two switching elements of the upper arm and two switching elements of the lower arm (four in total) that flow during charging. Further, it is possible to equalize the loss generated in the windings between the UWs and the VWs of the motors M1, M2, M3 during charging. As a result, the thermal design of each component is facilitated.

FIG. 1 shows a configuration with three inverters and motors. Even when the number of inverters and motors is four or more, battery charging is performed using three inverters and motors. Therefore, in the configuration of four or more inverters and motors, the secondary winding of the transformer 13 may be connected to the fourth and subsequent inverters.
[Embodiment 2]
FIG. 5 shows a battery charger of the second embodiment. In the second embodiment, the windings of the motors M1, M2, and M3 of the first embodiment are star-connected. The neutral point 32 exists in the motors M1, M2, and M3 due to the star connection. However, the point that the neutral point 32 is not connected to the terminal is the same as that of the first embodiment.

  The second embodiment performs the same operation as the first embodiment except that the motor windings are differently connected, and the same control method can be applied. However, if the inductances of the windings per phase of the Δ connection motor and the star connection motor are the same value, the inductance between the U phase and the V phase of the inverters INV1, INV2, and INV3 is the same as that of the first embodiment. Compared to larger. Therefore, as the operation of the inverter U phase / V phase, the star connection is easier to perform switching at exactly the same timing and to reduce the output current ripple by the control block of FIG. On the other hand, in the Δ connection of the first embodiment, since the inductance between the inverter U phase and the V phase is small, the parallel control according to Patent Document 6 exhibits a high effect.

  In the second embodiment, the reason why the motors M1, M2, M3 do not rotate during battery charging will be described. In the star winding, a current having the same amplitude and phase flows in the U-phase winding and the V-phase winding, and a current whose sign is inverted with a double amplitude flows in the W-phase winding. The magnetic field in the motors M1, M2, and M3 changes in magnitude and sign as in the case of the winding of Δ connection, but the phase is fixed, so no rotating magnetic field is generated. Therefore, as in the first embodiment, if the motors M1, M2, and M3 are stopped by the induction machine, no starting torque is generated and the motors M1, M2, and M3 do not rotate.

  As described above, according to the second embodiment, the same operational effects as those of the first embodiment can be obtained.

[Embodiment 3]
FIG. 6 shows a battery charger according to the third embodiment. The third embodiment is a case where the present invention is applied when the AC power supply 11 for charging is a single phase, and the following points are different.

  The secondary winding of the transformer 13 is connected to the W phase without the current detectors 14u, 14v, 15u, 15v, 16u, and 16v of the two inverters INV1 and INV2. FIG. 6 shows a configuration in which the secondary winding of the transformer 13 is connected to the W phase. However, if there is no current detector in the U phase, the secondary winding of the transformer 13 is connected to the U phase. . If there is no current detector in the V phase, the secondary winding of the transformer 13 is connected to the V phase. Further, the inverter INV3 is not connected to the AC power supply 11.

  The inverters INV1 and INV2 are single-phase grid-connected converters, and can charge the battery 17 by applying current control. 2 and 3 can be applied as they are to the charging current control unit. Patent Document 6 is also applicable.

  The charging current control unit of the inverter INV2 inputs -IcnvU * to the subtractor 3 and the parallel control unit 6 instead of IcnvU * in FIG. Similarly, -Vu is input to the filter 4 instead of Vu in FIG.

  As described above, according to the third embodiment, the present invention can be applied even when the AC power supply 11 is a single-phase AC, and the same operations and effects as those of the first and second embodiments can be obtained.

  FIG. 6 shows a configuration with three inverters and motors. Even when there are four or more inverters and motors, battery charging is performed using two inverters and motors. Therefore, in the configuration of three or more inverters and motors, the secondary winding of the transformer 13 may be connected to the third and subsequent inverters. In the configuration with two inverters and motors, all the two inverters INV1 and INV2 are connected to the secondary winding of the transformer 13, and the inverter INV3 does not exist.

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are naturally within the scope of the claims.

DESCRIPTION OF SYMBOLS 11 ... AC power supply 12 ... Switch 13 ... Transformer 14u, 14v, 15u, 15v, 16u, 16v ... Current detector 17 ... Battery INV1, INV2, INV3 ... Inverter M1, M2, M3 ... Motor

Claims (6)

Battery,
N (N ≧ 3) units connected in parallel to the battery, an inverter operation for converting the DC power of the battery into AC power and outputting it, and a converter operation for converting the AC power into DC power and outputting it to the battery A three-phase inverter,
A motor connected to the three-phase AC side of each inverter;
A transformer in which a secondary winding is connected to any phase on the three-phase AC side of three inverters among the N inverters, and a primary winding is connected to a three-phase AC power source;
Between the inverter and the secondary winding of the transformer, or between the primary winding of the transformer and the three-phase AC power source, or between the inverter and the secondary winding of the transformer, and the transformer. A switch connected between the primary winding and the three-phase AC power source;
A battery charging device comprising: Battery,
N (N ≧ 2) units connected in parallel to the battery, an inverter operation for converting the DC power of the battery into AC power and outputting it, and a converter operation for converting the AC power into DC power and outputting it to the battery A three-phase inverter,
A motor connected to the three-phase AC side of each inverter;
A transformer in which a secondary winding is connected to any phase on the three-phase AC side of two inverters of the N inverters, and a primary winding is connected to a single-phase AC power source;
Between the inverter and the secondary winding of the transformer, or between the primary winding of the transformer and the single-phase AC power source, or between the inverter and the secondary winding of the transformer, and the transformer. A switch connected between the primary winding and the single-phase AC power source;
A battery charging device comprising:   The battery charging device according to claim 1, wherein the motor is a Δ connection.   The battery charging device according to claim 1, wherein the motor is a star connection. The inverter is configured to have a switching element on the upper and lower arms of each phase,
During the battery charging operation, the charging current control unit of each inverter connected to the secondary winding of the transformer is:
Turn off the switching elements of the upper and lower arms of the phase to which the secondary winding of the transformer is connected,
Deviation between the converter output current command value and the converter output current detection value obtained by adding the two-phase converter input current detection value to which the secondary winding of the transformer is not connected,
Converter voltage detection value,
The converter voltage command value is calculated based on the converter voltage, the PWM control is performed based on the converter voltage command value, and the gate command value of the switching element of the two-phase upper and lower arms not connected to the secondary winding of the transformer is generated. The battery charger according to any one of claims 1 to 4, wherein the battery charger is provided. The PWM control is
Of the two phases to which the secondary winding of the transformer is not connected, one phase performs PWM control based on a carrier triangular wave, and the other phase performs PWM control based on a signal obtained by inverting the carrier triangular wave The battery charger according to claim 5.

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