JP2022108885A - multilevel inverter - Google Patents

Abstract

To perform voltage boosting using an inverter circuit.SOLUTION: A multilevel inverter includes: a battery; a first capacitor connected between middle point wiring and low potential input wiring; a second capacitor connected between high potential input wiring and the middle point wiring; a charging circuit; and a control circuit. The charging circuit includes: a DC charging port; charging positive electrode wiring that connects a positive electrode of the DC charging port with a cathode of a first middle point side intermediate diode; and charging negative electrode wiring that connects a negative electrode of the DC charging port with an anode of a second middle point side intermediate diode. When a charger is connected to the DC charging port, the control circuit executes voltage boosting control of alternately repeating a first operation of turning on a first middle point side intermediate switching element to charge the first capacitor with power of the charger and a second operation of turning on a second middle point side intermediate switching element to charge the second capacitor with power of the charger.SELECTED DRAWING: Figure 1

Description

The technology disclosed in this specification relates to multilevel inverters.

Patent Document 1 discloses a multi-level inverter. The multi-level inverter converts DC power input from the battery into AC power. A multi-level inverter can control the voltage of each output wiring in multiple levels. A multi-level inverter allows for more precise control of the output current.

Japanese Patent Application Laid-Open No. 2011-109801

A voltage may be applied to the battery by an external charger to charge the battery. At this time, if the supply voltage of the charger is lower than the output voltage of the battery, it is necessary to boost the supply voltage of the charger and apply the boosted voltage to the battery. In such a case, conventionally, a boost converter circuit is provided in the multi-level inverter, and the voltage supplied to the charger is boosted by the boost converter circuit. This configuration has a problem of increasing the size of the entire multilevel inverter. This specification proposes a technique for boosting the supply voltage of the charger using an inverter circuit inside the multi-level inverter.

The multi-level inverter disclosed in this specification includes a battery, a high potential input wiring connected to the positive terminal of the battery, a low potential input wiring connected to the negative terminal of the battery, a midpoint wiring, and the midpoint a first capacitor connected between the wiring and the low potential input wiring; a second capacitor connected between the high potential input wiring and the midpoint wiring; a first output wiring; and a second output wiring. , a third output wiring, a first switching circuit, a second switching circuit, a third switching circuit, a charging circuit, and a control circuit. The first switching circuit is connected to the high potential input wiring, the midpoint wiring, the low potential input wiring, and the first output wiring. The second switching circuit is connected to the high potential input wiring, the midpoint wiring, the low potential input wiring, and the second output wiring. The third switching circuit is connected to the high potential input wiring, the midpoint wiring, the low potential input wiring, and the third output wiring. The first switching circuit includes a first upper arm switching element connected between the high potential input wiring and the first output wiring, and a first upper arm switching element connected between the first output wiring and the low potential input wiring. 1 lower arm switching element, a first middle point side intermediate diode having an anode connected to the middle point wiring, a cathode connected to the cathode of the first middle point side middle diode and an anode connected to the first A first output-side intermediate diode connected to the output wiring, a first intermediate-point-side switching element connected in parallel to the first intermediate-point-side intermediate diode, and the first output-side intermediate diode. a first output intermediate switching element connected in parallel to the output side. The second switching circuit includes a second upper arm switching element connected between the high potential input wiring and the second output wiring, and a second switching element connected between the second output wiring and the low potential input wiring. 2 a lower arm switching element, a second intermediate diode whose cathode is connected to the intermediate point wiring, and an anode which is connected to the anode of the second intermediate intermediate diode and whose cathode is the second a second output-side intermediate diode connected to the output wiring, a second intermediate-point-side switching element connected in parallel to the second intermediate-point-side intermediate diode, and the second output-side intermediate diode. a second output-side intermediate switching element connected in parallel to the output-side intermediate switching element. The charging circuit includes a DC charging port, a charging positive electrode wiring connecting the positive electrode of the DC charging port and the cathode of the first intermediate diode, and the negative electrode of the DC charging port and the second intermediate diode. a charging negative electrode line connecting with the anode of the diode. a first operation in which the control circuit turns on the first midpoint side intermediate switching element to charge the first capacitor with power of the charger when the charger is connected to the DC charging port; A voltage step-up control is executed in which a second operation of turning on the second intermediate point side intermediate switching element and charging the second capacitor with the electric power of the charger is alternately repeated.

In this multilevel inverter, an inverter circuit that converts DC power into AC power is configured by a first switching circuit, a second switching circuit, a third switching circuit, and the like. In the first operation, the positive electrode of the DC charging port is connected to the midpoint wiring by turning on the first midpoint side intermediate switching element. Therefore, in the first operation, the first capacitor can be charged by connecting the negative electrode of the DC charging port to the low potential input wiring. In the second operation, the second midpoint-side intermediate switching element is turned on to connect the negative electrode of the DC charging port to the midpoint wiring. Therefore, the second capacitor can be charged by connecting the positive terminal of the DC charging port to the high potential input wiring. Thus, the first action charges the first capacitor and the second action charges the second capacitor. The control circuit alternately repeats the first operation and the second operation in boost control. Therefore, the first capacitor and the second capacitor are charged. When the first capacitor is charged, the potential on the low potential input wire of the midpoint wire rises to a potential close to the supply voltage of the charger. As the second capacitor charges, the potential for the midpoint wire of the high potential input wire rises to a potential close to the supply voltage of the charger. Therefore, the potential of the high potential input wire with respect to the low potential input wire rises to a potential higher than the supply voltage of the charger. Thus, the battery is charged with a voltage higher than the supply voltage of the charger. Thus, in this multi-level inverter, the inverter circuit can be used to boost the supply voltage of the charger to a higher voltage and apply the boosted voltage to the battery. Therefore, the battery can be charged without providing a dedicated boost converter circuit.

FIG. 2 is a circuit diagram of the multilevel inverter of Example 1; 4 is a graph showing low-voltage charging control in Example 1; FIG. 2 is a circuit diagram of the multilevel inverter of Example 1; FIG. 2 is a circuit diagram of the multilevel inverter of Example 1; A circuit diagram of a multi-level inverter without input switching elements. FIG. 2 is a circuit diagram of the multilevel inverter of Example 1; FIG. 4 is a circuit diagram of a multi-level inverter as a modification of the first embodiment; 9 is a graph showing low-voltage charging control in Example 2; The circuit diagram of the multi-level inverter of Example 2. FIG. The circuit diagram of the multi-level inverter of Example 3. FIG. 10 is a graph showing low-voltage charging control in Example 3; The circuit diagram of the multi-level inverter of Example 3. FIG. The circuit diagram of the multi-level inverter of Example 3. FIG. 4 is a circuit diagram of a multi-level inverter of Modification 1. FIG. FIG. 10 is a circuit diagram of a multi-level inverter of Modification 2; FIG. 11 is a circuit diagram of a multi-level inverter of Modification 3;

In one example of the multi-level inverter disclosed in this specification, when one of the positive charging wiring and the negative charging wiring is a specific charging wiring and the other is a non-specific charging wiring, the specific charging wiring is interposed. It may further comprise an inductor.

According to this configuration, it is possible to prevent a surge from being input from the charging port to the first switching circuit and the second switching circuit.

An example multi-level inverter disclosed in this specification includes a positive-side diode having an anode connected to the charging positive line and a cathode connected to the high-potential input line, and an anode connected to the low-potential input line. and a negative electrode side diode having a cathode connected to the charging negative electrode wiring. The specific charging wiring may be the positive charging wiring, and the anode of the positive diode may be connected to the positive charging wiring on a side closer to the first midpoint-side intermediate diode than the inductor, or The specific charging wiring may be the charging negative wiring, and the cathode of the negative diode may be connected to the charging negative wiring on a side closer to the second intermediate diode than the inductor.

In this configuration, in the first operation, the negative electrode of the charging port is connected to the low-potential input wiring through the negative diode, so that the first capacitor can be appropriately charged. Further, in this configuration, in the second operation, the positive electrode of the charging port is connected to the high-potential input wiring via the positive-side diode, so that the second capacitor can be appropriately charged.

In one example of the multi-level inverter disclosed in this specification, in the first operation, the first output-side intermediate switching element, the second intermediate-point-side intermediate switching element, and the second output-side intermediate switching element are turned off. You may Further, in the second operation, the first intermediate point side intermediate switching element, the first output side intermediate switching element, and the second output side intermediate switching element may be turned off.

According to this configuration, it is possible to prevent the supply voltage applied to the charging port from the external charger from being applied to the first output wiring and the second output wiring. As a result, malfunction of devices connected to each output wiring can be prevented.

In one example of the multi-level inverter disclosed in this specification, in the first operation, the first upper arm switching element, the first lower arm switching element, the second upper arm switching element, and the second lower arm switching element A switching element may be turned off. In the second operation, the first upper arm switching element, the first lower arm switching element, the second upper arm switching element, and the second lower arm switching element may be turned off.

According to this configuration, it is possible to more reliably prevent malfunction of devices connected to each output wiring.

In one example of the multi-level inverter disclosed in this specification, in the boost control, the control circuit may repeat the first operation, the second operation, and the pause operation. In the pause operation, the first middle point side intermediate switching element, the first output side middle switching element, the second middle point side middle switching element, and the second output side middle switching element may be turned off. .

By executing the resting operation in this way, the current flowing through the inductor (that is, the current charging the first capacitor and the second capacitor) during the resting operation can be reduced. Therefore, a voltage lower than the supply voltage of the external charger can be applied to the first capacitor and the second capacitor. This allows the voltage applied to the battery to be controlled to less than twice the supply voltage of the external charger.

In one example of the multi-level inverter disclosed in this specification, in the boost control, the control circuit may repeat the first operation, the second operation, and the current increasing operation. In the current increasing operation, the first middle point side intermediate switching element and the second middle point side intermediate switching element may be turned on.

In the current increasing operation, current flows from the positive terminal of the charging port to the negative terminal of the charging port through the first middle point side intermediate switching element and the second middle point side intermediate switching element. This current passes through the inductor. As the current flows through the inductor in this manner, the current flowing through the inductor increases. After that, when the first operation and the second operation are performed, a voltage higher than the supply voltage of the external charger can be applied to the first capacitor and the second capacitor by the induced electromotive force generated in the inductor. This allows the voltage applied to the battery to be controlled to a voltage higher than twice the supply voltage of the external charger.

In one example of the multi-level inverter disclosed in this specification, the first operation may turn on the second output-side intermediate switching element. The second operation may turn on the first output-side intermediate switching element.

In this configuration, in the first operation, the negative electrode of the charging port is connected to the low potential input wiring via the second output-side intermediate switching element, so that the first capacitor can be charged. Also, in this configuration, in the second operation, the positive terminal of the charging port is connected to the positive terminal of the battery through the first output-side intermediate switching element, so that the second capacitor can be charged.

In one example of the multi-level inverter disclosed in this specification, in the boost control, the control circuit may repeat the first operation, the second operation, and the current increasing operation. In the current increasing operation, the first middle point side intermediate switching element and the second middle point side intermediate switching element may be turned on.

In the current increasing operation, current flows from the positive terminal of the charging port to the negative terminal of the charging port through the first middle point side intermediate switching element and the second middle point side intermediate switching element. This current passes through the inductor. As the current flows through the inductor in this manner, the current flowing through the inductor increases. After that, when the first operation and the second operation are performed, a voltage higher than the supply voltage of the external charger can be applied to the first capacitor and the second capacitor by the induced electromotive force generated in the inductor. This allows the voltage applied to the battery to be controlled to a voltage higher than twice the supply voltage of the external charger.

An example of the multi-level inverter disclosed in this specification may further include a switch connected to the specific charging line in series with the inductor.

A multi-level inverter or an external charger may be provided with an input capacitor that connects the positive and negative terminals of the charging port. When the multi-level inverter performs an inverter operation (that is, an operation of outputting AC power to the output wiring) with the first switching circuit and the second switching circuit connected to the input capacitor, part of the current flows into the input capacitor. flow, and the waveform of AC power collapses. On the other hand, if a switch is provided in the specific charging wiring as described above, the waveform of the AC power can be prevented from collapsing by turning off the switch during the inverter operation.

In one example of the multi-level inverter disclosed in the present specification, the switch includes a semiconductor switching element interposed in the specific charging line and the semiconductor switching element so that the current flowing through the specific charging line is in the forward direction. A diode may be interposed in the specific charging wiring in series with the element.

With this configuration, the size of the switch can be reduced.

An example of the multi-level inverter disclosed in this specification further includes an input capacitor connecting the non-specific charging wiring and the specific charging wiring closer to the DC charging port than the inductor and the switch. good too.

According to this configuration, by keeping the switch off during the inverter operation, it is possible to prevent the waveform of the AC power from collapsing.

An example multi-level inverter disclosed in this specification may further include a relay that turns on and off the charging negative wire.

With this configuration, the charging port can be electrically isolated from each switching circuit when the charging port is not in use.

In one example of the multi-level inverter disclosed in this specification, the specific charging wiring may be the positive charging wiring. In this case, the multi-level inverter may further include a charging diode having an anode connected to the charging positive wire between the inductor and the relay and a cathode connected to the positive electrode of the battery.

According to this configuration, the charging port can receive two levels of voltage as the supply voltage. When a low voltage is supplied as the supply voltage, the battery can be charged by boost control. Also, when a high voltage is supplied as the supply voltage, the high voltage can be applied to the positive electrode of the battery via the charging diode. This allows the battery to be charged.

In one example of the multi-level inverter disclosed in this specification, the specific charging wiring may be the charging negative wiring. In this case, the multi-level inverter may further include a charging diode having a cathode connected to the charging negative wire between the inductor and the relay and an anode connected to the negative electrode of the battery.

According to this configuration, the charging port can receive two levels of voltage as the supply voltage. When a low voltage is supplied as the supply voltage, the battery can be charged by boost control. Also, when a high voltage is supplied as the supply voltage, the high voltage can be applied to the negative electrode of the battery via the charging diode. This allows the battery to be charged.

FIG. 1 shows a circuit diagram of a multi-level inverter 10a of Example 1. As shown in FIG. The multilevel inverter 10a is mounted on the vehicle. The vehicle is also equipped with a running motor 60 . The traveling motor 60 is a three-phase motor. The multilevel inverter 10a has a battery 18. As shown in FIG. The multilevel inverter 10 a converts the DC power output by the battery 18 into three-phase AC power, and supplies the three-phase AC power to the motor 60 for traveling. As a result, the running motor 60 is driven and the vehicle runs.

The multilevel inverter 10 a has an inverter circuit 30 and a charging circuit 70 . The inverter circuit 30 converts the DC power applied by the battery 18 into three-phase AC power. A charging circuit 70 charges the battery 18 .

The inverter circuit 30 has a high potential input wiring 12 , a midpoint wiring 14 , a low potential input wiring 16 , a first capacitor 31 and a second capacitor 32 . The high potential input wiring 12 is connected to the positive terminal of the battery 18 . The low potential input wiring 16 is connected to the negative electrode of the battery 18 . An output voltage Vb (that is, a DC voltage) of the battery 18 is applied between the high potential input wiring 12 and the low potential input wiring 16 . The potential VH of the high potential input wiring 12 is higher than the potential VL of the low potential input wiring 16 . The first capacitor 31 is connected between the midpoint wiring 14 and the low potential input wiring 16 . The second capacitor 32 is connected between the high potential input wiring 12 and the midpoint wiring 14 . Therefore, the potential VM of the midpoint wiring 14 is higher than the potential VL of the low potential input wiring 16 and lower than the potential VH of the high potential input wiring 12 . In inverter operation for supplying three-phase AC power to running motor 60, voltage VHL between high potential input wiring 12 and low potential input wiring 16 (that is, the difference between potential VH and potential VL) is the output of battery 18. equal to voltage Vb. Further, in the inverter operation, the potential VM of the midpoint wire 14 is about 1/2 of the potential VH. In the charging operation for charging battery 18, a voltage higher than output voltage Vb of battery 18 is applied as voltage VHL.

The inverter circuit 30 has three output wirings 50u, 50v, and 50w. The output wirings 50u, 50v, and 50w are connected to the running motor 60 . The inverter circuit 30 also has a U-phase switching circuit 41 , a V-phase switching circuit 42 , and a W-phase switching circuit 43 . The U-phase switching circuit 41 is connected to the high potential input wiring 12, the low potential input wiring 16, the midpoint wiring 14, and the output wiring 50u. The V-phase switching circuit 42 is connected to the high potential input wiring 12, the low potential input wiring 16, the midpoint wiring 14, and the output wiring 50v. The W-phase switching circuit 43 is connected to the high potential input wiring 12, the low potential input wiring 16, the midpoint wiring 14, and the output wiring 50w.

The U-phase switching circuit 41 has switching elements 41US, 41MMS, 41OMS, and 41LS. The switching elements 41US, 41MMS, 41OMS, and 41LS are composed of MOSFETs (metal oxide semiconductor field effect transistors). Furthermore, the U-phase switching circuit 41 has diodes 41UD, 41MMD, 41OMD, and 41LD. A cathode of the diode 41UD is connected to the high potential input wiring 12 . The anode of the diode 41UD is connected to the output wiring 50u. The switching element 41US is connected in parallel with the diode 41UD. A drain of the switching element 41 US is connected to the high potential input wiring 12 . The source of the switching element 41US is connected to the output wiring 50u. A cathode of the diode 41LD is connected to the output wiring 50u. The anode of the diode 41LD is connected to the low potential input wiring 16. FIG. The switching element 41LS is connected in parallel with the diode 41LD. The drain of the switching element 41LS is connected to the output wiring 50u. A source of the switching element 41LS is connected to the low potential input wiring 16 . The anode of the diode 41MMD is connected to the midpoint wiring 14 . The cathode of diode 41MMD is connected to the cathode of diode 41OMD. The anode of the diode 41OMD is connected to the output wiring 50u. The switching element 41MMS is connected in parallel with the diode 41MMD. The source of the switching element 41MMS is connected to the anode of the diode 41MMD. The drain of the switching element 41MMS is connected to the cathode of the diode 41MMD. The switching element 41OMS is connected in parallel with the diode 41OMD. The drain of switching element 41OMS is connected to the cathode of diode 41OMD. The source of switching element 41OMS is connected to the anode of diode 41OMD.

Gates of the switching elements 41 US, 41 MMS, 41 OMS, and 41 LS are connected to the control circuit 90 . Therefore, the switching elements 41US, 41MMS, 41OMS, 41LS are controlled by the control circuit 90. FIG. When the switching element 41US is turned on, the high potential input wiring 12 is electrically connected to the output wiring 50u, and the potential VH of the high potential input wiring 12 is applied to the output wiring 50u. When the switching element 41MMS and the switching element 41OMS are turned on, the middle point wiring 14 is electrically connected to the output wiring 50u, and the potential VM of the middle point wiring 14 is applied to the output wiring 50u. When the switching element 41LS is turned on, the low potential input wiring 16 is electrically connected to the output wiring 50u, and the potential VL of the low potential input wiring 16 is applied to the output wiring 50u. Thus, the U-phase switching circuit 41 changes the potential of the output wiring 50u between the potential VH, the potential VM, and the potential VL.

The V-phase switching circuit 42 has switching elements 42US, 42MMS, 42OMS, and 42LS. The switching elements 42US, 42MMS, 42OMS, and 42LS are composed of MOSFETs. Furthermore, the V-phase switching circuit 42 has diodes 42UD, 42MMD, 42OMD and 42LD. A cathode of the diode 42UD is connected to the high potential input wiring 12 . The anode of the diode 42UD is connected to the output wiring 50v. The switching element 42US is connected in parallel with the diode 42UD. A drain of the switching element 42 US is connected to the high potential input wiring 12 . The source of the switching element 42US is connected to the output wiring 50v. A cathode of the diode 42LD is connected to the output wiring 50v. The anode of the diode 42LD is connected to the low potential input wiring 16. FIG. The switching element 42LS is connected in parallel with the diode 42LD. The drain of the switching element 42LS is connected to the output wiring 50v. A source of the switching element 42LS is connected to the low potential input wiring 16 . A cathode of the diode 42MMD is connected to the midpoint wiring 14 . The anode of diode 42MMD is connected to the anode of diode 42OMD. A cathode of the diode 42OMD is connected to the output wiring 50v. The switching element 42MMS is connected in parallel with the diode 42MMD. The source of switching element 42MMS is connected to the anode of diode 42MMD. The drain of switching element 42MMS is connected to the cathode of diode 42MMD. The switching element 42OMS is connected in parallel with the diode 42OMD. The drain of switching element 42OMS is connected to the cathode of diode 42OMD. The source of switching element 42OMS is connected to the anode of diode 42OMD.

Gates of the switching elements 42 US, 42 MMS, 42 OMS, and 42 LS are connected to the control circuit 90 . Therefore, the switching elements 42 US, 42 MMS, 42 OMS, 42 LS are controlled by the control circuit 90 . When the switching element 42US is turned on, the high potential input wiring 12 is electrically connected to the output wiring 50v, and the potential VH of the high potential input wiring 12 is applied to the output wiring 50v. When the switching element 42MMS and the switching element 42OMS are turned on, the midpoint wire 14 is electrically connected to the output wire 50v, and the potential VM of the midpoint wire 14 is applied to the output wire 50v. When the switching element 42LS is turned on, the low potential input wiring 16 is electrically connected to the output wiring 50v, and the potential VL of the low potential input wiring 16 is applied to the output wiring 50v. Thus, the V-phase switching circuit 42 changes the potential of the output wiring 50v between the potential VH, the potential VM, and the potential VL.

The W-phase switching circuit 43 has switching elements 43US, 43MMS, 43OMS, and 43LS. The switching elements 43US, 43MMS, 43OMS, and 43LS are composed of MOSFETs. Furthermore, the W-phase switching circuit 43 has diodes 43UD, 43MMD, 43OMD and 43LD. A cathode of the diode 43UD is connected to the high potential input wiring 12 . The anode of the diode 43UD is connected to the output wiring 50w. The switching element 43US is connected in parallel with the diode 43UD. A drain of the switching element 43 US is connected to the high potential input wiring 12 . The source of the switching element 43US is connected to the output wiring 50w. A cathode of the diode 43LD is connected to the output wiring 50w. The anode of the diode 43LD is connected to the low potential input wiring 16. FIG. The switching element 43LS is connected in parallel with the diode 43LD. A drain of the switching element 43LS is connected to the output wiring 50w. A source of the switching element 43LS is connected to the low potential input wiring 16 . A cathode of the diode 43MMD is connected to the midpoint wiring 14 . The anode of diode 43MMD is connected to the anode of diode 43OMD. A cathode of the diode 43OMD is connected to the output wiring 50w. The switching element 43MMS is connected in parallel with the diode 43MMD. The source of switching element 43MMS is connected to the anode of diode 43MMD. The drain of the switching element 43MMS is connected to the cathode of the diode 43MMD. The switching element 43OMS is connected in parallel with the diode 43OMD. The drain of switching element 43OMS is connected to the cathode of diode 43OMD. The source of switching element 43OMS is connected to the anode of diode 43OMD.

Gates of the switching elements 43 US, 43 MMS, 43 OMS, and 43 LS are connected to the control circuit 90 . Therefore, the switching elements 43US, 43MMS, 43OMS, 43LS are controlled by the control circuit 90. FIG. When the switching element 43US is turned on, the high potential input wiring 12 is electrically connected to the output wiring 50w, and the potential VH of the high potential input wiring 12 is applied to the output wiring 50w. When the switching element 43MMS and the switching element 43OMS are turned on, the midpoint wire 14 is electrically connected to the output wire 50w, and the potential VM of the midpoint wire 14 is applied to the output wire 50w. When the switching element 43LS is turned on, the low potential input wiring 16 is electrically connected to the output wiring 50w. Therefore, the potential VL of the low potential input wiring 16 is applied to the output wiring 50w. Thus, the W-phase switching circuit 43 changes the potential of the output wiring 50w between the potential VH, the potential VM, and the potential VL.

Diodes 41UD, 41LD, 41MMD, 41OMD, 42UD, 42LD, 42MMD, 42OMD, 43UD, 43LD, 43MMD, and 43OMD are body diodes of MOSFETs connected in parallel (that is, parasitically formed inside the MOSFETs). diode).

Also, the switching elements 41US, 41MMS, 41OMS, 41LS, 42US, 42MMS, 42OMS, 42LS, 43US, 43MMS, 43OMS, and 43LS may be composed of elements other than MOSFETs (eg, IGBTs (insulated gate bipolar transistors)). good. In that case, the emitter of the IGBT can be connected to the anode of the diodes connected in parallel, and the collector of the IGBT can be connected to the cathode of the diodes connected in parallel.

In inverter operation, the U-phase switching circuit 41, the V-phase switching circuit 42, and the W-phase switching circuit 43 change the potentials of the output wirings 50u, 50v, and 50w between the potential VL, the potential VM, and the potential VL. As a result, three-phase AC power is generated between the output wirings 50u, 50v, and 50w, and the three-phase AC power is supplied to the motor 60 for traveling.

The charging circuit 70 has a positive charging wire 22 , a negative charging wire 24 , a charging port 72 , a relay module 74 , an input capacitor 76 , an inductor 77 , an input switching element 78 and an input diode 79 .

An external charger 92 is connected to the charging port 72 . The charging port 72 has a positive electrode 72a and a negative electrode 72b. When the charger 92 is connected to the charging port 72, the charger 92 applies a voltage Vs (hereinafter referred to as supply voltage Vs) between the positive electrode 72a and the negative electrode 72b so that the positive electrode 72a has a higher potential than the negative electrode 72b. be done. A low voltage charger 92a and a high voltage charger 92b can be connected to the charging port 72 . The low voltage charger 92a supplies a low voltage VsL (eg, 400V) as the supply voltage Vs. The high voltage charger 92b supplies a high voltage VsH (eg, 800V) as the supply voltage Vs. The low voltage VsL is lower than the battery 18 output voltage Vb, and the high voltage VsH is higher than the battery 18 output voltage Vb.

One end of the charging positive wire 22 is connected to the positive electrode 72 a of the charging port 72 . The other end of the charging positive line 22 is connected to the cathode of the diode 41MMD, the cathode of the diode 41OMD, the drain of the switching element 41MMS, and the drain of the switching element 41OMS. One end of the charging negative electrode wiring 24 is connected to the negative electrode 72 b of the charging port 72 . The other end of the charging negative line 24 is connected to the anode of the diode 42MMD, the anode of the diode 42OMD, the source of the switching element 42MMS, and the source of the switching element 42OMS.

The input capacitor 76 is connected between the positive charging line 22 and the negative charging line 24 . Input capacitor 76 smoothes the voltage applied between positive charging line 22 and negative charging line 24 .

A relay module 74 is positioned between the input capacitor 76 and the charging port 72 . The relay module 74 has a relay 74a and a relay 74b. The relay 74a is interposed in the charging positive electrode wiring 22 on the side closer to the charging port 72 than the input capacitor 76 is. The relay 74b is interposed in the charging negative electrode wiring 24 on the side closer to the charging port 72 than the input capacitor 76 is. When the relays 74a and 74b are turned off, the charging port 72 is electrically disconnected from the input capacitor 76, the inverter circuit 30, and the like. Relays 74 a and 74 b are controlled by control circuit 90 .

The inductor 77 is interposed in the charging positive electrode wiring 22 on the side closer to the inverter circuit 30 than the input capacitor 76 is.

The input switching element 78 is interposed in the charging positive electrode wiring 22 on the side closer to the inverter circuit 30 than the inductor 77 is. Input switching element 78 is an IGBT. The collector of input switching element 78 is connected to inductor 77 . Input switching element 78 is controlled by control circuit 90 . The input diode 79 is interposed in the charging positive line 22 on the side closer to the inverter circuit 30 than the input switching element 78 is. The anode of input diode 79 is connected to the emitter of input switching element 78 . The cathode of input diode 79 is connected to the cathode of diode 41MMD.

The multilevel inverter 10 a further has a positive diode 82 and a negative diode 84 . The anode of the positive diode 82 is connected to the charging positive line 22 between the inductor 77 and the input switching element 78 . A cathode of the positive diode 82 is connected to the high potential input wiring 12 . The anode of the negative diode 84 is connected to the low potential input wiring 16 . A cathode of the negative diode 84 is connected to the charging negative wiring 24 .

The multilevel inverter 10a can implement charge control. Charging control is performed when the inverter operation is not performed. When the vehicle is stopped, the relays 74a and 74b are off and the input switching element 78 is off. When the external charger 92 is connected to the charging port 72 while the vehicle is stopped, the control circuit 90 detects the supply voltage Vs with a voltmeter (not shown). The control circuit 90 performs low voltage charging control when the supply voltage Vs is the low voltage VsL, and performs high voltage charging control when the supply voltage Vs is the high voltage VsH.

(low voltage charging control)
When the control circuit 90 detects that the supply voltage Vs is the low voltage VsL, it controls the relays 74a and 74b to ON, and controls the input switching element 78 to ON. As a result, the supply voltage Vs (that is, the low voltage VsL) is applied between the positive charging wire 22 and the negative charging wire 24 .

In low voltage charging control, the control circuit 90 keeps the switching elements 41US, 41OMS, 41LS, 42US, 42OMS, 42LS, 43US, 43MMS, 43OMS, 43LS in the off state. Further, the control circuit 90 alternately turns on the switching element 41MMS and the switching element 42MMS, as shown in FIG. More specifically, the control circuit 90 controls the ON period Ton1 during which the switching element 41MMS is ON and the switching element 42MMS is OFF, the OFF period Toff1 during which both the switching elements 41MMS and 42MMS are OFF, and the switching element 42MMS is OFF. The switching elements 41MMS and 42MMS are controlled such that an ON period Ton2 in which the switching element 41MMS is turned off and an OFF period Toff2 in which both the switching elements 41MMS and 42MMS are turned off repeat in this order.

In the on period Ton1, the switching element 41MMS is turned on, so that a current flows as indicated by an arrow 100 in FIG. That is, current flows from the positive electrode 72a to the negative electrode 72b via the inductor 77, the input switching element 78, the input diode 79, the switching element 41MMS, the first capacitor 31, and the negative electrode diode 84. The current thus flowing charges the first capacitor 31 . A current IL indicates the current flowing through the inductor 77 . In the ON period Ton1, the induced electromotive force of inductor 77 is generated in the direction opposite to the direction in which current IL flows (that is, arrow 100). The induced electromotive force gradually decreases over time. Therefore, as shown in FIG. 2, the current IL gradually increases during the ON period Ton1.

In the off period Toff1, both the switching element 41MMS and the switching element 42MMS are off, so current flows as indicated by arrow 102 in FIG. That is, in the OFF period Toff1, the induced electromotive force of the inductor 77 is generated in the same direction as the current IL flows (that is, the arrow 102). Therefore, the potential of the anode of the positive diode 82 becomes higher than the potential of the cathode of the positive diode 82 (that is, the potential of the high potential input wiring 12). Therefore, as indicated by arrow 102, current flows from positive electrode 72a through inductor 77, positive diode 82, battery 18, and negative diode 84 to negative electrode 72b. In the off period Toff1, the induced electromotive force of the inductor 77 decreases over time. Therefore, as shown in FIG. 2, the current IL decreases during the off period Toff1.

In the on period Ton2, the switching element 42MMS is turned on, so that a current flows as indicated by an arrow 104 in FIG. That is, current flows from the positive electrode 72a to the negative electrode 72b via the inductor 77, the positive diode 82, the second capacitor 32, and the switching element 42MMS. The current thus flowing charges the second capacitor 32 . In the ON period Ton2, the induced electromotive force of inductor 77 is generated in the direction opposite to the direction in which current IL flows (that is, arrow 104). The induced electromotive force gradually decreases over time. Therefore, as shown in FIG. 2, the current IL gradually increases during the ON period Ton2.

During the off-period Toff2, both the switching element 41MMS and the switching element 42MMS are turned off, so a current flows as indicated by the arrow 102 in FIG. 3, similarly to the off-period Toff1. Therefore, as shown in FIG. 2, the current IL decreases during the off period Toff2.

In this manner, in the low-voltage charging control, the first capacitor 31 and the second capacitor 32 are charged alternately by alternately repeating the ON period Ton1 and the ON period Ton2. The voltage VHL between the high-potential input wiring 12 and the low-potential input wiring 16 is the sum of the voltage VC1 across the first capacitor 31 and the voltage VC2 across the second capacitor 32 . By charging the first capacitor 31, the voltage VC1 across the first capacitor 31 rises up to the low voltage VsL. Due to the charging of the second capacitor 32, the voltage VC2 across the second capacitor 32 rises up to the low voltage VsL. When the voltage VC1 rises to the low voltage VsL and the voltage VC2 rises to the low voltage VsL, the voltage VHL between the high potential input wiring 12 and the low potential input wiring 16 rises to double the low voltage VsL. Thus, according to the low voltage charging control, the voltage VHL between the high potential input wiring 12 and the low potential input wiring 16 can be raised to a voltage higher than the low voltage VsL supplied by the charger 92 . Therefore, even if low voltage VsL is lower than output voltage Vb of battery 18, voltage VHL can be raised to a voltage higher than output voltage Vb of battery 18. FIG. Therefore, the battery 18 can be charged. As described above, according to the multi-level inverter 10a of the first embodiment, the inverter circuit 30 can be used to boost the low voltage VsL and charge the battery 18 with the boosted voltage. Thus, the battery 18 can be charged using the low voltage VsL without providing a dedicated boost converter circuit. Therefore, the multilevel inverter 10a can be miniaturized.

Further, as shown in FIG. 2, the current IL increases during the ON periods Ton1 and Ton2 and decreases during the OFF periods Toff1 and Toff2. By controlling the ratio between the ON periods Ton1, Ton2 and the OFF periods Toff1, Toff2, the magnitude of the current IL can be controlled. Thereby, the voltage VC1 of the first capacitor 31 and the voltage VC2 of the second capacitor 32 can be controlled. For example, if the on-periods Ton1 and Ton2 are sufficiently longer than the off-periods Toff1 and Toff2 as shown in FIG. VC2 can be raised to the low voltage VsL. Also, if the ratio of the off periods Toff1 and Toff2 is made larger than in FIG. 2, the current IL becomes smaller and the voltages VC1 and VC2 can be controlled to smaller values. For example, the voltage VC1 can be controlled to be 0.8 times the low voltage VsL, and the voltage VC2 can be controlled to be 0.8 times the low voltage VsL. In this case, the voltage VHL is 1.6 times the low voltage VsL. Even in this case, a voltage higher than the low voltage VsL can be applied as the voltage VHL, and the battery 18 can be charged.

Note that in the first embodiment, either or both of the off periods Toff1 and Toff2 may not exist. In this case, the current IL tends to become high.

In addition, in the multilevel inverter 10a of the first embodiment, the control circuit 90 keeps the switching elements 41OMS, 42MMS, 42OMS, 43MMS, and 43OMS off during the ON periods Ton1 and Ton2 of the low voltage charging control. Therefore, it is possible to prevent the potential of the positive charging wire 22 and the potential of the negative charging wire 24 from being applied to the output wires 50u, 50v and 50w. Also, during the ON periods Ton1 and Ton2 of the low-voltage charging control, the control circuit 90 keeps the switching elements 41US, 41LS, 42US, 42LS, 43US, and 43LS off. Therefore, it is possible to prevent the potential of the high-potential input wiring 12 and the potential of the low-potential input wiring 16 from being applied to the output wirings 50u, 50v, and 50w. Therefore, it is possible to prevent vibrations or the like from occurring in the running motor 60 during the low voltage charging control.

Further, as described above, the switching element 41MMS is turned off when the ON period Ton1 is switched to the OFF period Toff1. Similarly, when switching from the ON period Ton2 to the OFF period Toff2, the switching element 42MMS is turned off. If a high surge voltage is applied to the switching elements 41MMS and 42MMS by the induced electromotive force of the inductor 77 when the switching elements 41MMS and 42MMS are turned off, a high load is applied to the switching elements 41MMS and 42MMS. However, in the multilevel inverter 10a of the first embodiment, the positive diode 82 and the negative diode 84 form a bypass path that bypasses the switching elements 41MMS and 42MMS. This bypass path suppresses the surge voltage applied to the switching elements 41MMS and 42MMS. That is, when the switching elements 41MMS and 42MMS are turned off, the positive diode 82 and the negative diode 84 are turned on during the off periods Toff1 and Toff2, as described above. As a result, current flows around the switching elements 41MMS and 42MMS, as indicated by arrows 102 in FIG. Therefore, the surge voltage applied to the switching elements 41MMS and 42MMS is suppressed. In addition, during the low-voltage charging control, there is a possibility that at least one of the switching element 41MMS, the switching element 42MMS, and the input switching element 78 will be interrupted due to some abnormality. Even in the event of such an instantaneous interruption of the switching elements, current flows bypassing the switching elements 41MMS, 42MMS, and the input switching element 78 as indicated by arrow 102 in FIG. Thereby, the surge voltage applied to the switching element 41MMS, the switching element 42MMS, and the input switching element 78 is suppressed.

Also, during low-voltage charging control, a surge voltage generated within the charger 92 may be applied between the positive electrode 72a and the negative electrode 72b. When a rush current flows through any switching element due to such a surge voltage, a high load is applied to that switching element. However, in the multi-level inverter 10a of Example 1, when a surge voltage is applied between the positive electrode 72a and the negative electrode 72b, the inductor 77 suppresses the rise of the current IL. This suppresses the inrush current. Therefore, the inrush current is suppressed from flowing through the switching elements in the multi-level inverter 10a.

(high voltage charging control)
When the control circuit 90 detects that the supply voltage Vs is the high voltage VsH, it performs high voltage charging control. In high voltage charging control, the control circuit 90 controls the relays 74a, 74b to ON and the input switching element 78 to OFF. Also, the control circuit 90 turns off the switching elements 41US, 41LS, 41MMS, 41OMS, 42US, 42LS, 42MMS, 42OMS, 43US, 43LS, 43MMS, and 43OMS. When each part is controlled in this way, the high voltage VsH is higher than the output voltage Vb of the battery 18, so current flows as indicated by the arrow 102 in FIG. That is, current flows from the positive electrode 72a to the negative electrode 72b via the inductor 77, the positive electrode diode 82, the battery 18, and the negative electrode diode 84. Current always flows as indicated by arrow 102 during high voltage charging control. The battery 18 is thereby charged.

Thus, the multi-level inverter 10a can select and execute low voltage charging control and high voltage charging control. According to this configuration, the common charge port 72 can receive the supply of the low voltage VsL and the supply of the high voltage VsH. Since there is no need to separately provide charging ports for the low voltage VsL and the high voltage VsH, the multilevel inverter 10a can be miniaturized. Also, if the relay module 74 is turned off, the charging port 72 can be cut off from both the high voltage charging circuit and the low voltage charging circuit. Since there is no need to provide separate relay modules for the circuit for high-voltage charging and the circuit for low-voltage charging, the multilevel inverter 10a can be miniaturized.

Next, functions of the input switching element 78 and the input diode 79 will be described. As described above, the multilevel inverter 10a supplies three-phase AC power to the traveling motor 60 through inverter operation. Without input switching element 78 and input diode 79, current would flow between U-phase switching circuit 41 and V-phase switching circuit 42 via input capacitor 76 during inverter operation, as indicated by arrow 106 in FIG. When the current flows in this manner, the waveform of the alternating current flowing through the output wirings 50u, 50v, and 50w is broken, and the driving efficiency of the running motor 60 is lowered. On the other hand, in the multi-level inverter 10a of the first embodiment, an input switching element 78 and an input diode 79 are interposed in the charging positive line 22 between the input capacitor 76 and the U-phase switching circuit 41. FIG. Control circuit 90 keeps input switching element 78 off during inverter operation. Therefore, no current flows as indicated by arrow 106 in FIG. 5 during inverter operation. Therefore, in the multi-level inverter 10a, it is possible to prevent the waveforms of alternating currents flowing through the output wirings 50u, 50v, and 50w from collapsing.

Although the charging circuit 70 has the input capacitor 76 in the first embodiment, the charging circuit 70 may not have the input capacitor 76 as shown in FIG. Even in this case, if the charger 92 has an input capacitor 94 connected between the positive electrode 72a and the negative electrode 72b as shown in FIG. 6, current will flow through the input capacitor 94 during inverter operation. , the waveform of the alternating current may be distorted. In such a case, by keeping the input switching element 78 off during the inverter operation, it is possible to prevent the waveform of the alternating current from collapsing.

Further, in the first embodiment described above, the inductor 77 is interposed in the charging positive electrode wiring 22 , but the inductor 77 may be interposed in the charging negative electrode wiring 24 . Even with this configuration, the induced electromotive force of the inductor 77 can be used to perform the low-voltage charging control in substantially the same manner as in the first embodiment described above. For example, an inductor 77 can be interposed in the charging negative electrode wiring 24 as shown in FIG. In FIG. 7, the inductor 77 is interposed in the charging negative electrode wiring 24 closer to the inverter circuit 30 than the input capacitor 76 is. Also, the cathode of the negative diode 84 is connected to the charging negative wire 24 closer to the inverter circuit 30 than the inductor 77 is.

Further, in the first embodiment described above, the input switching element 78 and the input diode 79 are interposed in the charging positive electrode wiring 22 , but they may be interposed in the charging negative electrode wiring 24 . Even in this configuration, by keeping the input switching element 78 off during inverter operation, it is possible to prevent the waveform of the alternating current from collapsing. In this case, the input switching element 78 and the input diode 79 are installed along the direction in which the current of the charging negative wire 24 flows. For example, as shown in FIG. 7 , when the inductor 77 is interposed in the negative charge line 24 , the input switching element 78 and the input diode 79 may also be interposed in the negative charge line 24 . In FIG. 7 , the input switching element 78 and the input diode 79 are interposed in the charging negative electrode wiring 24 closer to the inverter circuit 30 than the connection point between the charging negative electrode wiring 24 and the negative electrode diode 84 .

The multilevel inverter of the second embodiment differs from the first embodiment in the control method of the switching elements 41MMS and 42MMS in the low voltage charging control. Other configurations of the multi-level inverter of the second embodiment are the same as those of the first embodiment.

In the low voltage charging control in the multi-level inverter of Example 2, the control circuit 90 keeps the switching elements 41US, 41OMS, 41LS, 42US, 42OMS, 42LS, 43US, 43MMS, 43OMS, 43LS in the off state. Further, the control circuit 90 alternately turns on the switching element 41MMS and the switching element 42MMS as shown in FIG. More specifically, the control circuit 90 controls an ON period Ton1 during which the switching element 41MMS is ON and the switching element 42MMS is OFF, a current increasing period Tac1 during which both the switching elements 41MMS and 42MMS are ON, and a switching element 42MMS. is turned on and the switching element 41MMS is turned off, and the current increase period Tac2 during which both the switching elements 41MMS and 42MMS are turned on repeats in this order. .

In the current increasing period Tac2, both the switching elements 41MMS and 42MMS are turned on, so that a current flows as indicated by an arrow 110 in FIG. That is, the current flows from the positive electrode 72a to the negative electrode 72b via the inductor 77, the input switching element 78, the input diode 79, the switching element 41MMS, and the switching element 42MMS. Thus, no current flows through the load other than inductor 77 . Therefore, in the current increasing period Tac2, the induced electromotive force of the inductor 77 is generated in the direction opposite to the direction in which the current IL flows. Also, in the current increasing period Tac2, the induced electromotive force of the inductor 77 decreases over time. Therefore, as shown in FIG. 8, the current IL increases during the current increasing period Tac2.

When switching from the current increasing period Tac2 to the ON period Ton1, the switching element 42MMS is turned off. Therefore, in the on period Ton1, the switching element 41MMS is on and the switching element 42MMS is off. As a result, a current flows as indicated by arrow 100 in FIG. 1, and the first capacitor 31 is charged. In the ON period Ton1, an induced electromotive force is generated in the inductor 77 in the same direction as the current IL flows. Therefore, a voltage obtained by adding the induced electromotive force of the inductor 77 to the low voltage VsL is applied to the first capacitor 31 . Therefore, in the ON period Ton1, the first capacitor 31 can be charged so that the voltage VC1 of the first capacitor 31 becomes higher than the low voltage VsL. During the ON period Ton1, the induced electromotive force gradually decreases over time. Therefore, as shown in FIG. 8, the current IL gradually decreases during the ON period Ton1.

When switching from the ON period Ton1 to the current increasing period Tac1, the switching element 42MMS is turned ON. Therefore, both the switching elements 41MMS and 42MMS are on during the current increasing period Tac1. Therefore, in the current increasing period Tac1, as in the current increasing period Tac2, the current flows as indicated by the arrow 110 in FIG. 9, and the current IL increases.

When switching from the current increasing period Tac1 to the ON period Ton2, the switching element 41MMS is turned off. Therefore, during the ON period Ton2, the switching element 42MMS is on and the switching element 41MMS is off. As a result, a current flows as indicated by arrow 104 in FIG. 4, and the second capacitor 32 is charged. In the ON period Ton2, an induced electromotive force is generated in the inductor 77 in the same direction as the current IL flows. Therefore, the voltage obtained by adding the induced electromotive force of the inductor 77 to the low voltage VsL is applied to the second capacitor 32 . Therefore, in the ON period Ton2, the second capacitor 32 can be charged so that the voltage VC2 of the second capacitor 32 becomes higher than the low voltage VsL. During the ON period Ton2, the induced electromotive force gradually decreases over time. Therefore, as shown in FIG. 8, the current IL gradually decreases during the ON period Ton2.

Thus, in the low-voltage charging control of the second embodiment, the first capacitor 31 is charged so that the voltage VC1 becomes higher than the low voltage VsL during the ON period Ton1, and the voltage VC2 becomes the low voltage VsL during the ON period Ton2. The second capacitor 32 is charged to a voltage higher than . Therefore, the voltage VHL between the high potential input wiring 12 and the low potential input wiring 16 rises to a voltage higher than twice the low voltage VsL. Therefore, the battery 18 can be efficiently charged. Thus, even in the multi-level inverter of the second embodiment, the battery 18 can be charged using the low voltage VsL without providing a dedicated boost converter circuit.

Further, as shown in FIG. 8, the current IL decreases during the ON periods Ton1 and Ton2 and increases during the current increasing periods Tac1 and Tac2. Therefore, the magnitude of the current IL can be controlled by controlling the ratio between the ON periods Ton1 and Ton2 and the current increase periods Tac1 and Tac2. By controlling the magnitude of the current IL in this manner, the voltage VC1 of the first capacitor 31 and the voltage VC2 of the second capacitor 32 can be controlled to the intended voltages.

The multi-level inverter 10b of Example 3 shown in FIG. 10 does not have the positive side diode 82 and the negative side diode 84. Other configurations of the multilevel inverter 10b of the third embodiment are the same as those of the first embodiment. Also, the multi-level inverter 10b of the third embodiment executes low voltage charging control and does not execute high voltage charging control. The third embodiment differs from the first embodiment in the method of controlling each switching element in the low voltage charging control.

In the low voltage charging control of Example 3, the control circuit 90 keeps the input switching element 78 on. Also, the control circuit 90 keeps the switching elements 43MMS and 43OMS off. Also, the control circuit 90 controls the switching elements 41MMS, 42OMS, 42MMS, and 41OMS as shown in FIG. More specifically, the control circuit 90 controls the switching elements 41MMS, 42OMS, 42MMS, and 41OMS such that the ON period Ton1, the current increasing period Tac1, the ON period Ton2, and the current increasing period Tac2 repeat in this order. In the ON period Ton1, the switching elements 41MMS and 42OMS are on and the switching elements 42MMS and 41OMS are off. In the current increasing period Tac1, all of the switching elements 41MMS, 42OMS, 42MMS, and 41OMS are on. In the ON period Ton2, the switching elements 42MMS and 41OMS are on and the switching elements 41MMS and 42OMS are off. In the current increasing period Tac2, all of the switching elements 41MMS, 42OMS, 42MMS, and 41OMS are on.

In the current increasing period Tac2, all of the switching elements 41MMS, 42OMS, 42MMS, and 41OMS are turned on, so that current flows as indicated by arrow 120 in FIG. That is, current flows from positive electrode 72a through inductor 77, input switching element 78, input diode 79, switching element 41MMS, and switching element 42MMS to negative electrode 72b. Thus, no current flows through the load other than inductor 77 . Therefore, in the current increasing period Tac2, the induced electromotive force of the inductor 77 is generated in the direction opposite to the direction in which the current IL flows. Also, in the current increasing period Tac2, the induced electromotive force of the inductor 77 decreases over time. Therefore, as shown in FIG. 11, the current IL increases during the current increasing period Tac2.

When switching from the current increasing period Tac2 to the ON period Ton1, the switching elements 42MMS and 41OMS are turned off. Therefore, in the ON period Ton1, the switching elements 41MMS and 42OMS are on, and the switching elements 42MMS and 41OMS are off. Therefore, current flows as indicated by arrow 122 in FIG. That is, current flows from positive electrode 72a to negative electrode 72b through inductor 77, input switching element 78, input diode 79, switching element 41MMS, first capacitor 31, diode 42LD, and switching element 42OMS. The first capacitor 31 is charged by the current flowing in this way. In the ON period Ton1, an induced electromotive force is generated in the inductor 77 in the same direction as the current IL flows. Therefore, a voltage obtained by adding the induced electromotive force of the inductor 77 to the low voltage VsL is applied to the first capacitor 31 . Therefore, in the ON period Ton1, the first capacitor 31 can be charged so that the voltage VC1 of the first capacitor 31 becomes higher than the low voltage VsL. During the ON period Ton1, the induced electromotive force gradually decreases over time. Therefore, as shown in FIG. 11, the current IL gradually decreases during the ON period Ton1.

When switching from the on period Ton1 to the current increasing period Tac1, the switching elements 42MMS and 41OMS are turned on. Therefore, in the current increasing period Tac1, all the switching elements 41MMS, 42OMS, 42MMS, and 41OMS are on. Therefore, in current increasing period Tac1, as in current increasing period Tac2, current flows as indicated by arrow 120 in FIG. 10, and current IL increases.

When switching from the current increasing period Tac1 to the ON period Ton2, the switching elements 41MMS and 42OMS are turned off. Therefore, during the ON period Ton2, the switching elements 42MMS and 41OMS are on, and the switching elements 41MMS and 42OMS are off. Therefore, current flows as indicated by arrow 124 in FIG. That is, current flows from positive electrode 72a to negative electrode 72b via inductor 77, input switching element 78, input diode 79, switching element 41OMS, diode 41UD, second capacitor 32, and switching element 42MMS. The flow of current in this way charges the second capacitor 32 . In the ON period Ton2, an induced electromotive force is generated in the inductor 77 in the same direction as the current IL flows. Therefore, the voltage obtained by adding the induced electromotive force of the inductor 77 to the low voltage VsL is applied to the second capacitor 32 . Therefore, in the ON period Ton2, the second capacitor 32 can be charged so that the voltage VC2 of the second capacitor 32 becomes higher than the low voltage VsL. During the ON period Ton2, the induced electromotive force gradually decreases over time. Therefore, as shown in FIG. 11, the current IL gradually decreases during the ON period Ton2.

Thus, in the low-voltage charging control of the third embodiment, the first capacitor 31 is charged so that the voltage VC1 becomes higher than the low voltage VsL during the ON period Ton1, and the voltage VC2 becomes the low voltage VsL during the ON period Ton2. The second capacitor 32 is charged to a voltage higher than . Therefore, the voltage VHL between the high potential input wiring 12 and the low potential input wiring 16 rises to a voltage higher than twice the low voltage VsL. Therefore, the battery 18 can be efficiently charged. Thus, even in the multi-level inverter 10b of the third embodiment, the battery 18 can be charged using the low voltage VsL without providing a dedicated boost converter circuit.

Further, as shown in FIG. 11, the current IL decreases during the ON periods Ton1 and Ton2 and increases during the current increasing periods Tac1 and Tac2. Therefore, the magnitude of the current IL can be controlled by controlling the ratio between the ON periods Ton1 and Ton2 and the current increase periods Tac1 and Tac2. By controlling the magnitude of the current IL in this manner, the voltage VC1 of the first capacitor 31 and the voltage VC2 of the second capacitor 32 can be controlled to the intended voltages.

Note that, as shown in FIG. 11, in the low-voltage charging control of the third embodiment, the switching element 42LS is turned on during a part of the ON period Ton1. When the switching element 42LS is turned on, the current flowing through the diode 42LD (see FIG. 12) branches to flow through the diode 42LD and the switching element 42LS. This suppresses the loss caused by the diode 42LD. As shown in FIG. 11, between the period in which the switching element 42LS is turned on and the period in which the switching element 42MMS is turned on (that is, the current increasing periods Tac1 and Tac2), there is a dead time DT1 (that is, both the switching elements 42LS and 42MMS are turned off). period) is provided. The dead time DT1 prevents both the switching elements 42LS and 42MMS from turning on to short-circuit the middle point wiring 14 and the low potential input wiring 16. FIG. In addition, in the low-voltage charging control of the third embodiment, the switching elements 41LS and 43LS may be controlled in the same manner as the switching element 42LS, or the switching elements 41LS and 43LS may be kept off. Similarly to the switching element 42LS, even if the switching elements 41LS and 43LS are turned on, no current flows through the switching elements 41LS and 43LS, so there is no effect on the low-voltage charging control. Also, if the diode 42LD does not cause a very high loss, the switching element 42LS may be kept off in the low-voltage charging control of the third embodiment.

Further, as shown in FIG. 11, in the low-voltage charging control of the third embodiment, the switching element 41US is turned on during part of the ON period Ton2. When the switching element 41US is turned on, the current flowing through the diode 41UD (see FIG. 13) branches to flow through the diode 41UD and the switching element 41US. This suppresses the loss caused by the diode 41UD. As shown in FIG. 11, between the period in which the switching element 41US is turned on and the period in which the switching element 41MMS is turned on (that is, the current increasing periods Tac1 and Tac2), there is a dead time DT2 (that is, both the switching elements 41US and 41MMS are turned off). period) is provided. The dead time DT2 prevents both the switching elements 41US and 41MMS from turning on to short-circuit the middle point wiring 14 and the high-potential input wiring 12. FIG. In addition, in the low-voltage charging control of the third embodiment, the switching elements 42US and 43US may be controlled in the same manner as the switching element 41US, or the switching elements 42US and 43US may be kept off. As with the switching element 41US, even if the switching elements 42US and 43US are turned on, no current flows through the switching elements 42US and 43US, so there is no effect on the low-voltage charging control. Also, if the diode 41UD does not cause a very high loss, the switching element 41US may be kept off in the low-voltage charging control of the third embodiment.

Also in the third embodiment, the inductor 77 suppresses the inrush current from flowing through the switching elements in the multi-level inverter 10b. Further, in the third embodiment as well, the input switching element 78 is kept off during inverter operation, thereby preventing the waveforms of alternating currents flowing through the output wirings 50u, 50v, and 50w from collapsing. Also in the third embodiment, the charging circuit 70 may not have the input capacitor 76 as shown in FIG. Also in the third embodiment, the inductor 77 may be interposed in the charging negative electrode wiring 24 as shown in FIG. Also in the third embodiment, an input switching element 78 and an input diode 79 may be interposed in the charging negative line 24 as shown in FIG.

In addition, in the low-voltage charging control of the third embodiment, at least one of the current increasing periods Tac1 and Tac2 may not exist. Further, in the low-voltage charging control of the third embodiment, off periods Toff1 and Toff2 in which all the switching elements 41MMS, 42OMS, 42MMS and 41OMS are turned off may be provided instead of the current increasing periods Tac1 and Tac2. In this case, if a bypass path is provided to pass current from the positive electrode 72a to the negative electrode 72b by bypassing the switching elements 41MMS, 42OMS, 42MMS and 41OMS in the off periods Toff1 and Toff2, the current is applied to the switching elements 41MMS, 42OMS, 42MMS and 41OMS. Surge voltage can be suppressed.

Next, multi-level inverters of modifications 1 to 3 obtained by modifying the multi-level inverter 10b of the embodiment 3 will be described. The multi-level inverters of Modifications 1 to 3 are obtained by modifying the multi-level inverter 10b of Embodiment 3 so that high voltage charging control can be performed.

A multi-level inverter 10 c of Modification 1 shown in FIG. 14 has a charging diode 86 . Other configurations of the multilevel inverter 10c of Modification 1 are the same as those of the multilevel inverter 10b of the third embodiment.

The anode of charging diode 86 is connected to charging positive line 22 at a position between inductor 77 and relay 74a. A cathode of the charging diode 86 is connected to the high potential input wiring 12 .

When the high voltage VsH is applied as the supply voltage Vs, the control circuit 90 turns on the relays 74a and 74b, turns off the input switching element 78, and turns on the switching element 42OMS. Also, the control circuit 90 turns off the switching elements 41US, 41LS, 41MMS, 41OMS, 42US, 42LS, 42MMS, 43US, 43LS, 43MMS, and 43OMS. Control circuit 90 maintains this control state during high voltage charging control. When each part is controlled in this way, the high voltage VsH is higher than the output voltage Vb of the battery 18, so current flows as indicated by the arrow 130 in FIG. That is, current flows from the positive electrode 72a to the negative electrode 72b through the charging diode 86, the battery 18, the diode 42LD, and the switching element 42OMS. The battery 18 is charged by the current flowing in this way.

In a multi-level inverter 10d of Modification 2 shown in FIG. 15, an inductor 77, an input switching element 78, and an input diode 79 are interposed in the charging negative electrode wiring 24 in the same manner as in FIG. Also, the multi-level inverter 10 d of Modification 2 has a charging diode 88 . The cathode of charging diode 88 is connected to charging negative electrode line 24 at a position between inductor 77 and relay 74b. The anode of charging diode 88 is connected to low potential input wiring 16 . Other configurations of the multilevel inverter 10d of the fifth embodiment are the same as those of the multilevel inverter 10b of the third embodiment.

When the high voltage VsH is applied as the supply voltage Vs, the control circuit 90 turns on the relays 74a and 74b, turns off the input switching element 78, and turns on the switching element 41OMS. Also, the control circuit 90 turns off the switching elements 41US, 41LS, 41MMS, 42US, 42LS, 42MMS, 42OMS, 43US, 43LS, 43MMS, and 43OMS. Control circuit 90 maintains this control state during high voltage charging control. When each part is controlled in this way, the high voltage VsH is higher than the output voltage Vb of the battery 18, so current flows as indicated by arrow 132 in FIG. That is, current flows from the positive electrode 72a to the negative electrode 72b via the switching element 41OMS, the diode 41UD, the battery 18, and the charging diode 88. The battery 18 is charged by the current flowing in this manner.

A multi-level inverter 10 e of Modification 3 shown in FIG. 16 has charging diodes 86 and 88 . Other configurations of the multilevel inverter 10e of Modification 3 are the same as those of the multilevel inverter 10b of Example 3. FIG. The anode of charging diode 86 is connected to charging positive line 22 at a position between inductor 77 and relay 74a. A cathode of the charging diode 86 is connected to the high potential input wiring 12 . The cathode of charging diode 88 is connected to charging negative electrode wiring 24 at a position between relay 74 b and V-phase switching circuit 42 . The anode of charging diode 88 is connected to low potential input wiring 16 .

The control circuit 90 turns on the relays 74a and 74b and turns off the input switching element 78 when the high voltage VsH is applied as the supply voltage Vs. Also, the control circuit 90 turns off the switching elements 41US, 41LS, 41MMS, 41OMS, 42US, 42LS, 42MMS, 42OMS, 43US, 43LS, 43MMS, and 43OMS. Control circuit 90 maintains this control state during high voltage charging control. When each part is controlled in this manner, the high voltage VsH is higher than the output voltage Vb of the battery 18, so current flows as indicated by arrow 134 in FIG. That is, current flows from the positive electrode 72a to the negative electrode 72b via the charging diode 86, the battery 18, and the charging diode 88. The battery 18 is charged by the current flowing in this manner.

When the low voltage VsL is applied as the supply voltage Vs, the control circuit 90 performs charge control in the same manner as in the fourth embodiment. Therefore, the battery 18 can be charged.

The control circuit 90 turns on the relays 74a and 74b and turns off the input switching element 78 when the high voltage VsH is applied as the supply voltage Vs. Also, the control circuit 90 turns off the switching elements 41US, 41LS, 41MMS, 41OMS, 42US, 42LS, 42MMS, 42OMS, 43US, 43LS, 43MMS, and 43OMS. When each part is controlled in this manner, the high voltage VsH is higher than the output voltage Vb of the battery 18, so current flows as indicated by arrow 134 in FIG. That is, current flows from the positive electrode 72a to the negative electrode 72b via the charging diode 86, the battery 18, and the charging diode 88. The battery 18 is charged by the current flowing in this manner.

As described above, according to the multilevel inverters 10c to 10e of Modifications 1 to 3, high voltage charging control can be executed. Further, according to the multilevel inverters 10c to 10e of the modified examples 1 to 3, like the multilevel inverter 10b of the third embodiment, low voltage charging control can be executed. According to the configurations of Modifications 1 to 3, since the common charging port 72 can receive the supply of the low voltage VsL and the high voltage VsH, the size of the multilevel inverter 10c can be reduced. Further, according to the configurations of Modifications 1 to 3, one relay module 74 can cut off the charging port 72 from both the high-voltage charging circuit and the low-voltage charging circuit. Therefore, the multilevel inverter 10a can be miniaturized.

At least one of the charging diodes 86 and 88 described in Modifications 1 to 3 may be provided in the multilevel inverter of Embodiments 1 or 2. Even in this case, high voltage charging can be performed via at least one of the charging diodes 86 and 88 .

In the above-described embodiment, instead of the input switching element 78 and the input diode 79, a contact type switch such as a relay may be provided. Even in this configuration, by turning off the contact type switch during inverter operation, it is possible to prevent the waveform of the alternating current from collapsing.

Each component of the embodiment described above will be described. The output wiring 50u is an example of a first output wiring. The output wiring 50v is an example of a second output wiring. The output wiring 50w is an example of a third output wiring. U-phase switching circuit 41 is an example of a first switching circuit.
V-phase switching circuit 42 is an example of a second switching circuit. The W-phase switching circuit 43 is an example of a third switching circuit. The switching element 41US is an example of a first upper arm switching element. The switching element 41LS is an example of a first lower arm switching element. Diode 41MMD is an example of a first midpoint-side intermediate diode. Diode 41OMD is an example of a first output-side intermediate diode. The switching element 41MMS is an example of a first midpoint-side intermediate switching element. The switching element 41OMS is an example of a first output-side intermediate switching element. The switching element 42US is an example of a second upper arm switching element. The switching element 42LS is an example of a second lower arm switching element. Diode 42MMD is an example of a second intermediate diode. Diode 42OMD is an example of a second output-side intermediate diode. The switching element 42MMS is an example of a second midpoint-side intermediate switching element. The switching element 42OMS is an example of a second output-side intermediate switching element. Low voltage charge control is an example of boost control. The operation of the multilevel inverter during the ON period Ton1 is an example of the first operation. The operation of the multilevel inverter during the ON period Ton2 is an example of the second operation. The operation of the multilevel inverter during the off periods Toff1 and Toff2 is an example of resting operation. The operation of the multilevel inverter during the current increasing periods Tac1 and Tac2 is an example of the current increasing operation.

Although the embodiments have been described in detail above, they are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the techniques exemplified in this specification or drawings simultaneously achieve a plurality of purposes, and achieving one of them has technical utility in itself.

10a to 10e: multi-level inverter, 12: high potential input wiring, 14: middle point wiring, 16: low potential input wiring, 18: battery, 22: charging positive electrode wiring, 24: charging negative electrode wiring, 30: inverter circuit, 31 : first capacitor, 32: second capacitor, 50u to 50w: output wiring, 60: running motor, 70: charging circuit, 72: charging port, 74: relay module, 76: input capacitor, 77: inductor, 78: input switching element, 79: input diode

Claims (15)

A multi-level inverter,
a battery (18);
a high potential input wire (12) connected to the positive electrode of the battery;
a low potential input wire (16) connected to the negative electrode of said battery;
a midpoint wire (14);
a first capacitor (31) connected between the midpoint wiring and the low potential input wiring;
a second capacitor (32) connected between the high potential input wiring and the midpoint wiring;
a first output wiring (50u);
a second output wiring (50v);
a third output wiring (50w);
a first switching circuit (41) connected to the high potential input wiring, the midpoint wiring, the low potential input wiring, and the first output wiring;
a second switching circuit (42) connected to the high potential input wiring, the midpoint wiring, the low potential input wiring, and the second output wiring;
a third switching circuit (43) connected to the high-potential input wiring, the midpoint wiring, the low-potential input wiring, and the third output wiring;
a charging circuit (70);
a control circuit (90),
has
The first switching circuit is
a first upper arm switching element (41US) connected between the high potential input wiring and the first output wiring;
a first lower arm switching element (41LS) connected between the first output wiring and the low potential input wiring;
a first midpoint-side intermediate diode (41MMD) whose anode is connected to the midpoint wiring;
a first output-side intermediate diode (41OMD) having a cathode connected to the cathode of the first intermediate-point-side intermediate diode and having an anode connected to the first output wiring;
a first midpoint side intermediate switching element (41MMS) connected in parallel to the first midpoint side intermediate diode;
a first output-side intermediate switching element (41OMS) connected in parallel to the first output-side intermediate diode;
has
the second switching circuit,
a second upper arm switching element (42US) connected between the high potential input wiring and the second output wiring;
a second lower arm switching element (42LS) connected between the second output wiring and the low potential input wiring;
a second midpoint-side intermediate diode (42MMD) whose cathode is connected to the midpoint wiring;
a second output-side intermediate diode (42OMD) having an anode connected to the anode of the second intermediate-point-side intermediate diode and a cathode connected to the second output wiring;
a second midpoint side intermediate switching element (42MMS) connected in parallel to the second midpoint side intermediate diode;
a second output-side intermediate switching element (42OMS) connected in parallel to the second output-side intermediate diode;
has
The charging circuit
a DC charging port (72);
a charging positive electrode wiring (22) connecting the positive electrode of the DC charging port and the cathode of the first intermediate diode;
a charging negative electrode wiring (24) connecting the negative electrode of the DC charging port and the anode of the second intermediate diode;
has
a first operation in which the control circuit turns on the first midpoint side intermediate switching element to charge the first capacitor with power of the charger when the charger is connected to the DC charging port; performing step-up control that alternately repeats a second operation of turning on the second intermediate point side intermediate switching element and charging the second capacitor with the electric power of the charger;
multilevel inverter. 2. When one of said positive charging wiring and said negative charging wiring is a specific charging wiring and the other is a non-specific charging wiring, it further comprises an inductor (77) interposed in said specific charging wiring. multi-level inverter as described in . a positive side diode (82) having an anode connected to the charging positive line and a cathode connected to the high potential input line;
a negative diode (84) having an anode connected to the low potential input wiring and a cathode connected to the charging negative wiring;
further having
The specific charging wiring is the positive charging wiring, and the anode of the positive diode is connected to the positive charging wiring on a side closer to the first intermediate diode than the inductor, or the specific charging wiring is connected to the positive charging wiring. The charging wiring is the charging negative electrode wiring, and the cathode of the negative electrode side diode is connected to the charging negative electrode wiring on a side closer to the second midpoint side intermediate diode than the inductor.
3. A multi-level inverter as claimed in claim 2. In the first operation, the first output-side intermediate switching element, the second intermediate-point-side intermediate switching element, and the second output-side intermediate switching element are turned off;
In the second operation, the first intermediate point side intermediate switching element, the first output side intermediate switching element, and the second output side intermediate switching element are turned off.
A multi-level inverter according to claim 3. in the first operation, turning off the first upper arm switching element, the first lower arm switching element, the second upper arm switching element, and the second lower arm switching element;
In the second operation, the first upper arm switching element, the first lower arm switching element, the second upper arm switching element, and the second lower arm switching element are turned off.
A multi-level inverter according to claim 4. In the boost control, the control circuit repeats the first operation, the second operation, and the pause operation,
In the pause operation, the first midpoint side intermediate switching element, the first output side intermediate switching element, the second midpoint side intermediate switching element, and the second output side intermediate switching element are turned off.
A multi-level inverter according to any one of claims 3-5. In the boost control, the control circuit repeats the first operation, the second operation, and the current increasing operation,
In the current increasing operation, the first middle point side intermediate switching element and the second middle point side intermediate switching element are turned on.
A multi-level inverter according to any one of claims 3-5. turning on the second output-side intermediate switching element in the first operation;
In the second operation, the first output-side intermediate switching element is turned on;
3. A multi-level inverter as claimed in claim 2. In the boost control, the control circuit repeats the first operation, the second operation, and the current increasing operation,
In the current increasing operation, the first middle point side intermediate switching element and the second middle point side intermediate switching element are turned on.
A multi-level inverter according to claim 8. The multi-level inverter according to any one of claims 2 to 9, further comprising switches (78, 79) connected to said specific charging line in series with said inductor. the switch
a semiconductor switching element (78) interposed in the specific charging wiring;
a diode (79) interposed in the specific charging line in series with the semiconductor switching element so as to be in the forward direction with respect to the current flowing through the specific charging line;
11. The multi-level inverter of claim 10, having 12. A multi-level inverter according to claim 10 or 11, further comprising an input capacitor (76) connecting said non-specific charging wiring and said specific charging wiring closer to said DC charging port than said inductor and said switch. 13. The multi-level inverter of claim 12, further comprising a relay (74) for turning on and off the positive charging wire and the negative charging wire on a side closer to the DC charging port than the input capacitor. The specific charging wiring is the charging positive electrode wiring,
14. The multi-level inverter of claim 13, further comprising a charging diode (82) having an anode connected to the charging positive line between the inductor and the relay and a cathode connected to the positive terminal of the battery. the specific charging wiring is the charging negative electrode wiring,
14. The multi-level inverter of claim 13, further comprising a charging diode (84) having a cathode connected to the charging negative wire between the inductor and the relay and an anode connected to the negative electrode of the battery.

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