Power conversion device and method of controlling the same

Abstract

The present application provides a kind of power conversion device and its control method.Power conversion device (10) has: converter (12), including switching element (34Uu, 34Vu, 34Wu, 34Ud, 34Vd, 34Wd), AC voltage supplied from AC power supply (14) via switch (16) is converted into DC voltage;Filter (24) is arranged between switch and converter, including reactor (46U, 46V, 46W, 48U, 48V, 48W) and capacitor (54U, 54V, 54W), for removing noise;And control unit (64), after making switch to open state, make switching element to on state, so that the charge stored in capacitor is discharged.

Description

TECHNICAL FIELD

[0001] The present application relates to a power conversion device and a control method thereof. BACKGROUND

[0002] In Japanese Patent Application Publication No. 2016-027774, a power conversion device is disclosed that stops a switch of a converter when an input voltage or an input current of the converter is equal to or greater than a set value. According to Japanese Patent Application Publication No. 2016-027774, it is possible to contribute to preventing damage to an electrical component. SUMMARY

[0003] However, in the technology described in Japanese Patent Application Publication No. 2016-027774, it is not necessarily possible to sufficiently prevent damage to a switching element or the like provided in a converter.

[0004] An object of the present application is to provide a power conversion device and a control method thereof that can sufficiently prevent damage to a switching element or the like.

[0005] One aspect of the present application provides a power conversion device including: a converter including a switching element that converts an alternating-current voltage supplied from an alternating-current power source via an on-off device into a direct-current voltage; a filter including an inductor and a capacitor that is provided between the on-off device and the converter and removes noise; and a control unit that causes the switching element to be in an on state after causing the on-off device to be in an on state, thereby causing electric charges accumulated in the capacitor to be discharged.

[0006] Another aspect of the present application provides a control method of a power conversion device including: a converter including a switching element that converts an alternating-current voltage supplied from an alternating-current power source via an on-off device into a direct-current voltage; a filter including an inductor and a capacitor that is provided between the on-off device and the converter and removes noise; and a control unit that controls the on-off device and the switching element, the control method including: a step of causing the on-off device to be in an on state; and a step of causing the switching element to be in an on state, thereby causing electric charges accumulated in the capacitor to be discharged.

[0007] According to the present application, it is possible to provide a power conversion device and a control method thereof that can sufficiently prevent damage to a switching element or the like.

[0008] The above objects, features, and advantages will be apparent from the following description of the embodiments, given with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 FIG. 1 is a diagram showing the configuration of a power conversion device according to a first embodiment.

[0010] Figure 2 A diagram for showing an example of a discharge path when the upper branch side switch elements of the respective power element sections are simultaneously brought to the on state.

[0011] Figure 3 A diagram for showing an example of a discharge path when the lower branch side switch elements of the respective power element sections are simultaneously brought to the on state.

[0012] Figure 4 A flowchart for showing an example of the operation of the power conversion device of the first embodiment.

[0013] Figure 5 A flowchart for showing another example of the operation of the power conversion device of the first embodiment.

[0014] Figure 6 A flowchart for showing still another example of the operation of the power conversion device of the first embodiment.

[0015] Figure 7 A flowchart for showing still another example of the operation of the power conversion device of the first embodiment.

[0016] Figure 8 A diagram for showing the configuration of the power conversion device of the second embodiment.

[0017] Figure 9 A diagram for showing an example of a current path when the shutters are brought to the closed state.

[0018] Figure 10 A diagram for showing another example of a current path when the shutters are brought to the closed state.

[0019] Figure 11 A diagram for showing a discharge path when the upper branch side switch element corresponding to U is brought to the on state.

[0020] Figure 12 A diagram for showing a discharge path when the upper branch side switch element corresponding to V is brought to the on state.

[0021] Figure 13 A diagram for showing a discharge path when the upper branch side switch element corresponding to W is brought to the on state.

[0022] Figure 14 A diagram for showing a discharge path when the lower branch side switch element corresponding to U is brought to the on state.

[0023] Figure 15 A diagram for showing a discharge path when the lower branch side switch element corresponding to V is brought to the on state.

[0024] Figure 16 1 is a diagram showing a discharge path when the switching element on the lower arm side corresponding to W is turned on.

[0025] Figure 17 This is a flowchart showing an example of the operation of the power conversion device according to the second embodiment.

[0026] Figure 18 This is a flowchart showing another example of the operation of the power conversion device according to the second embodiment. DETAILED DESCRIPTION

[0027] The power conversion device and the control method thereof according to the present invention will be described in detail below with reference to the accompanying drawings, using preferred embodiments thereof.

[0028] [First embodiment]

[0029] use Figures 1-7 , a power conversion device and a control method thereof according to a first embodiment will be described. Figure 1 It is a diagram showing the configuration of the power conversion device according to this embodiment.

[0030] like Figure 1 As shown, the power conversion device 10 of this embodiment includes a converter 12. The converter 12 converts an AC voltage supplied from an AC power source 14 via a switch 16 into a DC voltage. The converter 12 is, for example, a well-known pulse width modulation (PWM) converter, but is not limited thereto.

[0031] The AC power supply 14 is, for example, a multi-phase AC power supply that supplies multi-phase voltages, more specifically a three-phase AC power supply, but is not limited thereto. The AC power supply 14 can supply, for example, U-phase, V-phase, and W-phase voltages each shifted by 120 degrees.

[0032] The switch 16 is used to turn on and off the supply of the AC voltage from the AC power source 14 to the power conversion device 10. As the switch 16, for example, an electromagnetic contactor, a circuit breaker, etc. can be used, but the present invention is not limited thereto.

[0033] The power conversion device 10 is further provided with a filter 24. The filter 24 is provided between the switch 16 and the converter 12. The filter 24 can remove noise transmitted from the converter 12 side to the AC power supply 14 side, and can remove noise transmitted from the AC power supply 14 side to the converter 12 side.

[0034] The converter 12 includes a rectifier circuit 30. The rectifier circuit 30 rectifies the AC voltage supplied from the AC power source 14 via the switch 16 into a DC voltage.

[0035] In the rectifier circuit 30, power element sections 32U, 32V, 32W are provided corresponding to each phase of the alternating-current power supply 14.

[0036] The power element section 32U corresponding to U is provided with a diode 36Uu on the upper branch side, a diode 36Ud on the lower branch side, a switching element (semiconductor switching element) 34Uu on the upper branch side, and a switching element 34Ud on the lower branch side.

[0037] The power element section 32V corresponding to V is provided with a diode 36Vu on the upper branch side, a diode 36Vd on the lower branch side, a switching element 34Vu on the upper branch side, and a switching element 34Vd on the lower branch side.

[0038] The power element section 32W corresponding to W is provided with a diode 36Wu on the upper branch side, a diode 36Wd on the lower branch side, a switching element 34Wu on the upper branch side, and a switching element 34Wd on the lower branch side.

[0039] In describing the diodes as a whole, the symbol 36 is used, and in describing each diode, the symbols 36Uu, 36Ud, 36Vu, 36Vd, 36Wu, 36Wd are used. Also, in describing the diodes on the upper branch side as a whole, the symbol 36u is used, and in describing each diode on the upper branch side, the symbols 36Uu, 36Vu, 36Wu are used. Also, in describing the diodes on the lower branch side as a whole, the symbol 36d is used, and in describing each diode on the lower branch side, the symbols 36Ud, 36Vd, 36Wd are used.

[0040] In describing the switching elements as a whole, the symbol 34 is used, and in describing each switching element, the symbols 34Uu, 34Ud, 34Vu, 34Vd, 34Wu, 34Wd are used. Also, in describing the switching elements on the upper branch side as a whole, the symbol 34u is used, and in describing each switching element on the upper branch side, the symbols 34Uu, 34Vu, 34Wu are used. Also, in describing the switching elements on the lower branch side as a whole, the symbol 34d is used, and in describing each switching element on the lower branch side, the symbols 34Ud, 34Vd, 34Wd are used. The switching element 34 can use, for example, an insulated gate bipolar transistor (IGBT: Insulated Gate Bipolar Transistor), but is not limited thereto. A FET (Field Effect Transistor) can also be used as the switching element 34.

[0041] The diode 36u on the upper branch side is connected in series with the diode 36d on the lower branch side. The cathode of the diode 36u on the upper branch side is connected to one of the output lines 42u. The anode of the diode 36u on the upper branch side is connected to the cathode of the diode 36d on the lower branch side. The anode of the diode 36d on the lower branch side is connected to the other of the output lines 42d.

[0042] The switch element 34u on the upper branch side is connected in series with the switch element 34d on the lower branch side. The first terminal of the switch element 34u on the upper branch side is connected to the cathode of the diode 36u on the upper branch side. In the case where the switch element 34 is an IGBT, for example, the first terminal is the collector, and in the case where the switch element 34 is an FET, for example, the first terminal is one of the source / drain. The second terminal of the switch element 34u on the upper branch side is connected to the anode of the diode 36u on the upper branch side. In the case where the switch element 34 is an IGBT, for example, the second terminal is the emitter, and in the case where the switch element 34 is an FET, for example, the second terminal is the other of the source / drain. The first terminal of the switch element 34d on the lower branch side is connected to the cathode of the diode 36d on the lower branch side. The second terminal of the switch element 34d on the lower branch side is connected to the anode of the diode 36d on the lower branch side.

[0043] The node 38U connected to the anode of the diode 36Uu on the upper branch side, the second terminal of the switch element 34Uu on the upper branch side, the cathode of the diode 36Ud on the lower branch side, and the first terminal of the switch element 34Ud on the lower branch side is supplied with the voltage of the U phase.

[0044] The node 38V connected to the anode of the diode 36Vu on the upper branch side, the second terminal of the switch element 34Vu on the upper branch side, the cathode of the diode 36Vd on the lower branch side, and the first terminal of the switch element 34Vd on the lower branch side is supplied with the voltage of the V phase.

[0045] The node 38W connected to the anode of the diode 36Wu on the upper branch side, the second terminal of the switch element 34Wu on the upper branch side, the cathode of the diode 36Wd on the lower branch side, and the first terminal of the switch element 34Wd on the lower branch side is supplied with the voltage of the W phase.

[0046] The power conversion device 10 is further equipped with a smoothing capacitor 18. The smoothing capacitor 18 is equipped at the rear stage of the converter 12. One end of the smoothing capacitor 18 is connected to one of the output lines 42u. The other end of the smoothing capacitor 18 is connected to the other of the output lines 42d. The smoothing capacitor 18 smoothes the direct-current voltage output from the converter 12, that is, the direct-current voltage rectified by the rectifier circuit 30.

[0047] The filter 24 is provided with reactors 46U, 46V, 46W. One ends of the reactors 46U, 46V, 46W are connected to the input / output terminals 44U, 44V, 44W of one side of the filter 24, respectively. The alternating voltage from the alternating current power supply 14 is supplied to the input / output terminals 44U, 44V, 44W of one side of the filter 24 via the switch 16, respectively.

[0048] The filter 24 is further provided with reactors 48U, 48V, 48W. The other ends of the reactors 46U, 46V, 46W are connected to one ends of the reactors 48U, 48V, 48W, respectively. The other ends of the reactors 48U, 48V, 48W are connected to the input / output terminals 50U, 50V, 50W of the other side of the filter 24, respectively. The nodes 38U, 38V, 38W are connected to the input / output terminals 50U, 50V, 50W of the other side of the filter 24, respectively.

[0049] The filter 24 is further provided with resistors 52U, 52V, 52W. The resistors 52U, 52V, 52W are damping resistors as resistors for suppressing resonance phenomenon. Nodes 53U, 53V, 53W connected to the other ends of the reactors 46U, 46V, 46W and the one ends of the reactors 48U, 48V, 48W are connected to one ends of the resistors 52U, 52V, 52W, respectively.

[0050] The filter 24 is further provided with capacitors 54U, 54V, 54W. When the capacitors as a whole are described, the symbol 54 is used, and when each of the capacitors is described, the symbols 54U, 54V, 54W are used. The other ends of the capacitors 54U, 54V, 54W are connected to the other ends of the resistors 52U, 52V, 52W, respectively.

[0051] The filter 24 is further provided with resistors 56U, 56V, 56W. The resistors 56U, 56V, 56W are connected in parallel with respect to the capacitors 54U, 54V, 54W, respectively. The resistors 56U, 56V, 56W are used to discharge the electric charges accumulated in the capacitors 54U, 54V, 54W.

[0052] The other ends of the capacitors 54U, 54V, 54W are connected to each other.

[0053] The input / output terminals 44U, 44V, 44W of one side of the filter 24 are connected to the input / output terminals 66U, 66V, 66W of one side of the switch 16. The input / output terminals 68U, 68V, 68W of the other side of the switch 16 are connected to the alternating current power supply 14 via the power supply line (electric power distribution line) 70U of the U phase, the power supply line 70V of the V phase, and the power supply line 70W of the W phase, respectively. When the power supply lines as a whole are described, the symbol 70 is used, and when each of the power supply lines is described, the symbols 70U, 70V, 70W are used.

[0054] The power conversion device 10 is further equipped with a control circuit 29. The control circuit 29 functions to control the converter 12. Specifically, the control circuit 29 applies a voltage to the 3rd terminal (gate) of the switching element 34 based on a signal (command) supplied from a control section 64, thereby appropriately switching the switching element 34. The control circuit 29 is able to perform adjustment of the output voltage, i.e., adjustment of the voltage across the smoothing capacitor 18, and the like, by appropriately switching the switching element 34.

[0055] The power conversion device 10 is further equipped with a control device 26. The control device 26 governs control of the entire power conversion device 10. The control device 26 is equipped with an arithmetic section 58 and a storage section 60. The arithmetic section 58 can be constituted by, for example, a CPU (Central Processing Unit), but is not limited thereto. In the storage section 60, for example, a non-illustrated volatile memory and a non-illustrated non-volatile memory are equipped. As the volatile memory, for example, a RAM (Random Access Memory) or the like can be cited. As the non-volatile memory, for example, a ROM (Read Only Memory), a flash memory, or the like can be cited. Programs, data, tables, and the like can be stored in the storage section 60.

[0056] The arithmetic section 58 is equipped with the control section 64. The control section 64 can be realized by execution of a program stored in the storage section 60 by the arithmetic section 58.

[0057] The control section 64 is able to control opening and closing of the shutter 16. When the shutter 16 is closed, a state is brought about in which the alternating-current voltage supplied from the alternating-current power supply 14 is supplied to the converter 12 via the shutter 16 and the filter 24. When the shutter 16 is opened, a state is brought about in which the alternating-current voltage is not supplied to the filter 24 and the converter 12.

[0058] The control section 64 is able to generate a signal (command) supplied to the control circuit 29, for example, based on information and the like acquired by a non-illustrated voltage sensor, a current sensor, or the like. The control section 64 is able to perform adjustment of the output voltage, i.e., adjustment of the voltage across the smoothing capacitor 18, and the like, by using the control circuit 29 to appropriately switch the switching element 34. In addition, as will be described later, the control section 64 is able to cause the charge accumulated in the capacitor 54 equipped in the filter 24 to be discharged by using the control circuit 29 to appropriately switch the switching element 34.

[0059] A voltage corresponding to the line-to-line voltage of phase 3 is applied across the capacitor 54. Electric charge corresponding to the applied voltage is accumulated in the capacitor 54. When the shutter 16 is changed from the closed state to the open state, the electric charge accumulated in the capacitor 54 at that time starts to be discharged through the resistor 56. In a period in which the elapsed time from the time when the shutter 16 is changed from the closed state to the open state is short, the electric charge accumulated in the capacitor 54 is not completely discharged, and the voltage across the capacitor 54 is still in a state in which it is large. When the shutter 16 is changed from the open state to the closed state, a resonance voltage can be generated in the filter 24. In a case in which the period until the shutter 16 that is changed to the open state is again returned to the closed state is short, and the phase of the line-to-line voltage at the time when the shutter 16 is changed to the open state is opposite to the phase of the line-to-line voltage at the time when the shutter 16 is returned to the closed state, the peak value of the resonance voltage can be significantly large. In a case in which the resonance voltage in which the peak value is significantly large is applied to the switching element 34, there is a risk that the switching element 34 is damaged. Thus, in the present embodiment, the switching element 34 is brought to the on state after the shutter 16 is brought to the open state. Therefore, in the present embodiment, the electric charge accumulated in the capacitor 54 is rapidly discharged. Thus, according to the present embodiment, it is possible to prevent the peak value of the resonance voltage from being significantly large, and further, it is possible to well prevent the switching element 34 and the like from being damaged.

[0060] The control section 64 can simultaneously bring the switching elements 34u on the upper branch side of the respective power element sections 32 to the on state after the shutter 16 is brought to the open state. Figure 2 A diagram for illustrating an example of a discharge path when the switching elements on the upper branch side of the respective power element sections are simultaneously brought to the on state. In Figure 2 , an example in which the shutter 16 is in the open state, and the capacitor 54 in which the voltage across both terminals is the lowest is the capacitor 54U corresponding to U is illustrated. The voltage of the capacitor 54V corresponding to V is higher than the voltage of the capacitor 54U corresponding to U. In addition, the voltage of the capacitor 54W corresponding to W is higher than the voltage of the capacitor 54U corresponding to U. Thus, as illustrated in Figure 2 , the electric charge accumulated in the capacitor 54V corresponding to V flows through the diode 36Vu, and the electric charge accumulated in the capacitor 54W corresponding to W flows through the diode 36Wu. The electric charges that flow through the diodes 36Vu, 36Wu flow through the switching element 34Uu corresponding to U, and flow into the capacitor 54U corresponding to U. In a case in which the switching elements 34u on the upper branch side of the respective power element sections 32 are simultaneously brought to the on state, in this way, the electric charges accumulated in the capacitors 54 are discharged.

[0061] The control section 64 can cause the switch elements 34d on the lower branch side of each of the plurality of power element sections 32 to be in the on state simultaneously after causing the shutter 16 to be in the open state. Figure 3 A diagram for illustrating an example of a discharge path when the switch elements on the lower branch side of each of the plurality of power element sections are caused to be in the on state simultaneously. In Figure 3 , an example is illustrated in which the shutter 16 is in the open state, and the capacitor 54 with the highest voltage across both terminals is the capacitor 54U corresponding to U. The voltage of the capacitor 54V corresponding to V is lower than the voltage of the capacitor 54U corresponding to U. Also, the voltage of the capacitor 54W corresponding to W is lower than the voltage of the capacitor 54U corresponding to U. Therefore, as illustrated in Figure 3 , the charge accumulated in the capacitor 54U corresponding to U flows via the switch element 34Ud. The charge that has flowed via the switch element 34Ud flows via the diode 36Vd corresponding to V and the diode 36Wd corresponding to W, and flows into the capacitor 54V corresponding to V and the capacitor 54W corresponding to W. In the case where the switch elements 34d on the lower branch side of each of the plurality of power element sections 32 are caused to be in the on state simultaneously, in this way, the charge accumulated in the capacitor 54 is discharged.

[0062] The control section 64 can cause any one of the switch elements 34u on the upper branch side of each of the plurality of power element sections 32 to be in the on state after causing the shutter 16 to be in the open state, and switch the switch elements 34u that are in the on state in order. For example, in the case where the capacitor 54 with the lowest voltage across both terminals is the capacitor 54U corresponding to U, when the switch element 34Uu corresponding to U is in the on state, discharge is performed along the path as illustrated in Figure 2 . Also, in the case where the capacitor 54 with the lowest voltage across both terminals is the capacitor 54U corresponding to U, whether the switch element 34Vu corresponding to V is in the on state or the switch element 34Wu corresponding to W is in the on state, discharge is not performed along the path as illustrated in Figure 2 .

[0063] The control section 64 can cause any one of the switch elements 34d on the lower branch side of each of the plurality of power element sections 32 to be in the on state after causing the shutter 16 to be in the open state, and switch the switch elements 34d that are in the on state in order. For example, in the case where the capacitor 54 with the highest voltage across both terminals is the capacitor 54U corresponding to U, when the switch element 34Ud corresponding to U is in the on state, discharge is performed along the path as illustrated in Figure 3the path shown is discharged. Further, in a case where the capacitor 54 with the highest voltage at both ends is the capacitor 54U corresponding to U, the discharge as shown is not performed regardless of whether the switching element 34Vd corresponding to V is in the on state or the switching element 34Wd corresponding to W is in the on state. Figure 3 the discharge as shown is performed.

[0064] Using Figure 4 An example of the operation of the power conversion device 10 of the present embodiment will be described. Figure 4 A flowchart for showing an example of the operation of the power conversion device of the present embodiment.

[0065] In step S1, the control section 64 determines whether the shutter 16 has shifted from the closed state to the open state. In a case where the shutter 16 has shifted from the closed state to the open state (YES in step S1), the process proceeds to step S2. In a case where the shutter 16 has not shifted from the closed state to the open state (NO in step S1), the process returns to step S1. Figure 4 the process as shown is completed.

[0066] In step S2, the control section 64 simultaneously brings the switching elements 34u on the upper branch side of the plurality of power element sections 32 into the on state. Thereafter, the process proceeds to step S3.

[0067] In step S3, the control section 64 determines whether a prescribed time has elapsed from the time when the switching elements 34u on the upper branch side were brought into the on state. The prescribed time can be counted, for example, by a timer not shown. In a case where the prescribed time has elapsed from the time when the switching elements 34u on the upper branch side were brought into the on state (YES in step S3), the process proceeds to step S4. In a case where the prescribed time has not elapsed from the time when the switching elements 34u on the upper branch side were brought into the on state (NO in step S3), the process returns to step S3.

[0068] In step S4, the control section 64 simultaneously brings the switching elements 34u on the upper branch side of the plurality of power element sections 32 into the off state. Thus, Figure 4 the process as shown is completed.

[0069] Using Figure 5 Another example of the operation of the power conversion device 10 of the present embodiment will be described. Figure 5 A flowchart for showing another example of the operation of the power conversion device of the present embodiment.

[0070] In step S11, the control unit 64 determines whether the switch 16 has changed from the closed state to the open state. If the switch 16 has changed from the closed state to the open state ("Yes" in step S11), the process proceeds to step S12. If the switch 16 has not changed from the closed state to the open state ("No" in step S11), the process proceeds to step S12. Figure 5 The indicated processing is completed.

[0071] In step S12 , the control unit 64 turns on the switching elements 34 d on the lower arm sides of the plurality of power element units 32 at the same time, and then the process proceeds to step S13 .

[0072] In step S13, the control unit 64 determines whether a predetermined time has elapsed since the lower arm switching element 34d was turned on. If the predetermined time has elapsed since the lower arm switching element 34d was turned on ("Yes" in step S13), the process proceeds to step S14. If the predetermined time has not elapsed since the lower arm switching element 34d was turned on ("No" in step S13), step S13 is repeated.

[0073] In step S14, the control unit 64 turns off the switching elements 34d on the lower arm side of each of the plurality of power element units 32 at the same time. Figure 5 The indicated processing is completed.

[0074] use Figure 6 , another example of the operation of the power conversion device 10 according to this embodiment will be described. Figure 6 This is a flowchart showing still another example of the operation of the power conversion device according to this embodiment. Figure 6 This example shows a case where the upper arm switching element 34Uu corresponding to U is turned on, followed by the upper arm switching element 34Vu corresponding to V, and then the upper arm switching element 34Wu corresponding to W. The order in which the upper arm switching elements 34u are turned on is not limited to this.

[0075] In step S21, the control unit 64 determines whether the switch 16 has changed from the closed state to the open state. If the switch 16 has changed from the closed state to the open state ("Yes" in step S21), the process proceeds to step S22. If the switch 16 has not changed from the closed state to the open state ("No" in step S21), the process proceeds to step S23. Figure 6 The indicated processing is completed.

[0076] In step S22, the control section 64 brings the switching element 34Uu on the upper branch side corresponding to U into an on state. Thereafter, the process proceeds to step S23.

[0077] In step S23, the control section 64 determines whether or not a prescribed time has elapsed from the time when the switching element 34Uu on the upper branch side corresponding to U was brought into an on state. In the case where the prescribed time has elapsed from the time when the switching element 34Uu on the upper branch side corresponding to U was brought into an on state (YES in step S23), the process proceeds to step S24. In the case where the prescribed time has not elapsed from the time when the switching element 34Uu on the upper branch side corresponding to U was brought into an on state (NO in step S23), the process of step S23 is repeated.

[0078] In step S24, the control section 64 brings the switching element 34Uu on the upper branch side corresponding to U into an off state. Thereafter, the process proceeds to step S25.

[0079] In step S25, the control section 64 brings the switching element 34Vu on the upper branch side corresponding to V into an on state. Thereafter, the process proceeds to step S26.

[0080] In step S26, the control section 64 determines whether or not a prescribed time has elapsed from the time when the switching element 34Vu on the upper branch side corresponding to V was brought into an on state. In the case where the prescribed time has elapsed from the time when the switching element 34Vu on the upper branch side corresponding to V was brought into an on state (YES in step S26), the process proceeds to step S27. In the case where the prescribed time has not elapsed from the time when the switching element 34Vu on the upper branch side corresponding to V was brought into an on state (NO in step S26), the process of step S26 is repeated.

[0081] In step S27, the control section 64 brings the switching element 34Vu on the upper branch side corresponding to V into an off state. Thereafter, the process proceeds to step S28.

[0082] In step S28, the control section 64 brings the switching element 34Wu on the upper branch side corresponding to W into an on state. Thereafter, the process proceeds to step S29.

[0083] In step S29, the control section 64 determines whether or not a prescribed time has elapsed from the time when the switching element 34Wu on the upper branch side corresponding to W was brought into an on state. In the case where the prescribed time has elapsed from the time when the switching element 34Wu on the upper branch side corresponding to W was brought into an on state (YES in step S29), the process proceeds to step S30. In the case where the prescribed time has not elapsed from the time when the switching element 34Wu on the upper branch side corresponding to W was brought into an on state (NO in step S29), the process of step S29 is repeated.

[0084] In step S30, the control section 64 brings the upper branch side switching element 34Wu corresponding to W into an off state. Thereafter, the processing shifts to step S31.

[0085] In step S31, the control section 64 determines whether further discharging is required, i.e., whether further execution of steps S22 to S30 is required. For example, in a case where the above prescribed time is not long enough, multiple discharges are required in order to sufficiently discharge the charge accumulated in the capacitor 54. In a case where further discharging is required (YES in step S31), the processing after step S22 is executed again. In a case where further discharging is not required (NO in step S31), the processing shifts to step S32. Figure 6 The processing illustrated above is completed.

[0086] Using Figure 7 Another example of the operation of the power conversion device 10 of the present embodiment will be described. Figure 7 A flowchart showing another example of the operation of the power conversion device of the present embodiment. Figure 7 An example in which the lower branch side switching element 34Ud corresponding to U is brought into an on state, and thereafter the lower branch side switching element 34Vd corresponding to V is brought into an on state, and thereafter the lower branch side switching element 34Wd corresponding to W is brought into an on state is shown. Further, the order in which the lower branch side switching elements 34d are brought into an on state is not limited to this.

[0087] In step S41, the control section 64 determines whether the shutter 16 has shifted from the closed state to the open state. In a case where the shutter 16 has shifted from the closed state to the open state (YES in step S41), the processing shifts to step S42. In a case where the shutter 16 has not shifted from the closed state to the open state (NO in step S41), the processing shifts to step S44. Figure 7 The processing illustrated above is completed.

[0088] In step S42, the control section 64 brings the lower branch side switching element 34Ud corresponding to U into an on state. Thereafter, the processing shifts to step S43.

[0089] In step S43, the control section 64 determines whether a prescribed time has elapsed from the time when the lower branch side switching element 34Ud corresponding to U was brought into an on state. In a case where the prescribed time has elapsed from the time when the lower branch side switching element 34Ud corresponding to U was brought into an on state (YES in step S43), the processing shifts to step S44. In a case where the prescribed time has not elapsed from the time when the lower branch side switching element 34Ud corresponding to U was brought into an on state (NO in step S43), step S43 is repeated.

[0090] In step S44, the control section 64 brings the lower arm side switching element 34Ud corresponding to U into the off state. Thereafter, the process proceeds to step S45.

[0091] In step S45, the control section 64 brings the lower arm side switching element 34Vd corresponding to V into the on state. Thereafter, the process proceeds to step S46.

[0092] In step S46, the control section 64 determines whether or not a prescribed time has elapsed from the time when the lower arm side switching element 34Vd corresponding to V was brought into the on state. In the case where the prescribed time has elapsed from the time when the lower arm side switching element 34Vd corresponding to V was brought into the on state (YES in step S46), the process proceeds to step S47. In the case where the prescribed time has not elapsed from the time when the lower arm side switching element 34Vd corresponding to V was brought into the on state (NO in step S46), the process of step S46 is repeated.

[0093] In step S47, the control section 64 brings the lower arm side switching element 34Vd corresponding to V into the off state. Thereafter, the process proceeds to step S48.

[0094] In step S48, the control section 64 brings the lower arm side switching element 34Wd corresponding to W into the on state. Thereafter, the process proceeds to step S49.

[0095] In step S49, the control section 64 determines whether or not a prescribed time has elapsed from the time when the lower arm side switching element 34Wd corresponding to W was brought into the on state. In the case where the prescribed time has elapsed from the time when the lower arm side switching element 34Wd corresponding to W was brought into the on state (YES in step S49), the process proceeds to step S50. In the case where the prescribed time has not elapsed from the time when the lower arm side switching element 34Wd corresponding to W was brought into the on state (NO in step S49), the process of step S49 is repeated.

[0096] In step S50, the control section 64 brings the lower arm side switching element 34Wd corresponding to W into the off state. Thereafter, the process proceeds to step S51.

[0097] In step S51, the control section 64 determines whether further discharging is required, i.e., whether further execution of steps S42-S50 is required. For example, in a case where the above prescribed time is not long enough, discharging is required a plurality of times in order to sufficiently discharge the electric charge accumulated in the capacitor 54. In a case where further discharging is required (YES in step S51), the processing after step S42 is executed again. In a case where further discharging is not required (NO in step S51), the processing shown in FIG. 6 is completed. Figure 7 The processing shown in FIG. 6 is completed.

[0098] Thus, according to the present embodiment, after the shutter 16 is brought to the open state, the switching element 34 is brought to the on state, so the electric charge accumulated in the capacitor 54 is rapidly discharged via the switching element 34. Therefore, according to the present embodiment, it is possible to prevent the peak value of the resonance voltage from becoming significantly large, and further, it is possible to prevent the switching element 34 and the like from being damaged.

[0099] [2nd Embodiment]

[0100] Use Figures 8-18 The power conversion device of the 2nd embodiment and the control method thereof will be described. Figure 8 A diagram showing the configuration of the power conversion device of the present embodiment. The same components as those of the power conversion device of the 1st embodiment shown in FIG. 1 and the control method thereof will be attached with the same symbols, and the description thereof will be omitted or simplified. Figures 1-7

[0101] The power conversion device 10 of the present embodiment brings the switching element 34u on the upper branch side corresponding to the phase with the highest phase voltage, or the switching element 34d on the lower branch side corresponding to the phase with the lowest phase voltage, to the on state.

[0102] As Figure 8 shown in FIG. 1, the power conversion device 10 of the present embodiment is further equipped with a voltage sensor (detection section) 28. A plurality of input terminals of the voltage sensor 28 are connected to the power supply lines 70U, 70V, 70W, respectively. The voltage sensor 28 is capable of detecting the phase voltage in each phase of the alternating-current power supply 14. More specifically, the voltage sensor 28 is capable of acquiring the instantaneous value of the phase voltage in each phase of the alternating-current power supply 14, i.e., the voltage instantaneous value. The voltage instantaneous value acquired by the voltage sensor 28 is supplied to the control device 26.

[0103] The arithmetic section 58 is further equipped with a determination section 62. The determination section 62 can be realized by the arithmetic section 58 executing the program stored in the storage section 60.

[0104] ​The determination unit 62 can determine the phase with the highest phase voltage or the phase with the lowest phase voltage on the basis of information supplied from the voltage sensor 28, that is, the detection result of the voltage sensor 28. The phase with the highest phase voltage and the phase with the lowest phase voltage change with time because the phase voltage changes with time.

[0105] The control unit 64 can cause the switching element 34u on the upper branch side corresponding to the phase with the highest phase voltage or the switching element 34d on the lower branch side corresponding to the phase with the lowest phase voltage to become in the on state in that order.

[0106] In the present embodiment, causing the switching element 34u on the upper branch side corresponding to the phase with the highest phase voltage or the switching element 34d on the lower branch side corresponding to the phase with the lowest phase voltage to become in the on state in that order is based on the following reasons. That is, in a case where the switching element 34 that becomes in the on state is neither the switching element 34u on the upper branch side corresponding to the phase with the highest phase voltage nor the switching element 34d on the lower branch side corresponding to the phase with the lowest phase voltage, the following occurs. In such a case, when an unexpected transition from the open state to the closed state occurs in the shutter 16, the power supply line 70 becomes in the short-circuit state due to the switching element 34 that becomes in the on state, a large current flows through the switching element 34, and the switching element 34 is damaged. On the other hand, in a case where the switching element 34 that becomes in the on state is the switching element 34u on the upper branch side corresponding to the phase with the highest phase voltage or the switching element 34d on the lower branch side corresponding to the phase with the lowest phase voltage, the following occurs. That is, the switching element 34 that becomes in the on state is the switching element 34 connected in parallel with respect to the diode 36 that is in the on state, so even when an unexpected transition from the open state to the closed state occurs in the shutter 16, no particular problem occurs. Based on such a reason, in the present embodiment, the switching element 34u on the upper branch side corresponding to the phase with the highest phase voltage or the switching element 34d on the lower branch side corresponding to the phase with the lowest phase voltage is caused to become in the on state in that order. Further, the unexpected transition from the open state to the closed state can occur, for example, by the shutter 16 being operated by a user or the like.

[0107] Figure 9 A diagram for illustrating an example of a current path when the shutter becomes in the closed state. In Figure 9 , an example in a case where the phase with the highest phase voltage is the U phase and the phase with the lowest phase voltage is the W phase is illustrated. In a case where the phase with the highest phase voltage is the U phase and the phase with the lowest phase voltage is the W phase, as illustrated in Figure 9As shown, diode 36Uu and diode 36Wd are turned on. In such a case, even if switch element 34Uu connected in parallel with respect to diode 36Uu is brought into an on state, the switch element 34Uu is not damaged. Further, in such a case, even if switch element 34Wd connected in parallel with respect to diode 36Wd is brought into an on state, the switch element 34Wd is not damaged. Thus, in a case where the phase with the highest phase voltage is the U phase and the phase with the lowest phase voltage is the W phase, even if the charge accumulated in capacitor 54 is discharged via switch element 34Uu when shutter 16 is turned into a closed state, the switch element 34Uu is not damaged. Further, in a case where the phase with the highest phase voltage is the U phase and the phase with the lowest phase voltage is the W phase, even if the charge accumulated in capacitor 54 is discharged via switch element 34Wd when shutter 16 is turned into a closed state, the switch element 34Wd is not damaged.

[0108] Figure 10 A diagram for showing another example of a discharge path when the switch element on the upper branch side corresponding to the U phase is brought into an on state. In Figure 10 , an example in a case where the phase with the highest phase voltage is the V phase and the phase with the lowest phase voltage is the U phase is shown. In a case where the phase with the highest phase voltage is the V phase and the phase with the lowest phase voltage is the U phase, as shown in Figure 10 , diode 36Vu and diode 36Ud are turned on. In such a case, even if switch element 34Vu connected in parallel with respect to diode 36Vu is brought into an on state, the switch element 34Vu is not damaged. Further, in such a case, even if switch element 34Ud connected in parallel with respect to diode 36Ud is brought into an on state, the switch element 34Ud is not damaged. Thus, in a case where the phase with the highest phase voltage is the V phase and the phase with the lowest phase voltage is the U phase, even if the charge accumulated in capacitor 54 is discharged via switch element 34Vu when shutter 16 is turned into a closed state, the switch element 34Vu is not damaged. Further, in a case where the phase with the highest phase voltage is the V phase and the phase with the lowest phase voltage is the U phase, even if the charge accumulated in capacitor 54 is discharged via switch element 34Ud when shutter 16 is turned into a closed state, the switch element 34Ud is not damaged.

[0109] Further, in the above, an example in a case where the phase with the highest phase voltage is the U phase and the phase with the lowest phase voltage is the W phase, and an example in a case where the phase with the highest phase voltage is the V phase and the phase with the lowest phase voltage is the U phase are shown, but the combination of the phase with the highest phase voltage and the phase with the lowest phase voltage is not limited to the above. In other combinations, it is also possible to consider in the same manner as the above.

[0110] Figure 11 A diagram for showing another example of a discharge path when the switch element on the upper branch side corresponding to the U phase is brought into an on state. InFigure 11 In FIG. 16, an example is shown in which the shutter 16 is in the open state, and the capacitor 54 with the lowest voltage across is the capacitor 54U corresponding to U. The voltage of the capacitor 54V corresponding to V and the voltage of the capacitor 54W corresponding to W are higher than the voltage of the capacitor 54U corresponding to U. Therefore, as shown in FIG. 16, the charge accumulated in the capacitor 54V corresponding to V flows via the diode 36Vu, and the charge accumulated in the capacitor 54W corresponding to W flows via the diode 36Wu. The charges flowing via the diodes 36Vu, 36Wu flow via the switching element 34Uu corresponding to U, and flow into the capacitor 54U corresponding to U. In this way, in the case in which the capacitor 54 with the lowest voltage across is the capacitor 54U corresponding to U, when the switching element 34Uu on the upper branch side corresponding to U is brought to the on state, the charge accumulated in the capacitor 54 is discharged. Figure 11

[0111] Figure 12 A diagram showing the discharge path when the switching element on the upper branch side corresponding to W is brought to the on state. In FIG. 17, an example is shown in which the shutter 16 is in the open state, and the capacitor 54 with the lowest voltage across is the capacitor 54W corresponding to W. The voltage of the capacitor 54U corresponding to U and the voltage of the capacitor 54V corresponding to V are higher than the voltage of the capacitor 54W corresponding to W. Therefore, as shown in FIG. 17, the charge accumulated in the capacitor 54U corresponding to U flows via the diode 36Uu, and the charge accumulated in the capacitor 54V corresponding to V flows via the diode 36Vu. The charges flowing via the diodes 36Uu, 36Vu flow via the switching element 34Wu corresponding to W, and flow into the capacitor 54W corresponding to W. In this way, in the case in which the capacitor 54 with the lowest voltage across is the capacitor 54W corresponding to W, when the switching element 34Wu on the upper branch side corresponding to W is brought to the on state, the charge accumulated in the capacitor 54 is discharged. Figure 12 Figure 12

[0112] Figure 13 A diagram showing the discharge path when the switching element on the upper branch side corresponding to W is brought to the on state. In FIG. 17, an example is shown in which the shutter 16 is in the open state, and the capacitor 54 with the lowest voltage across is the capacitor 54W corresponding to W. The voltage of the capacitor 54U corresponding to U and the voltage of the capacitor 54V corresponding to V are higher than the voltage of the capacitor 54W corresponding to W. Therefore, as shown in FIG. 17, the charge accumulated in the capacitor 54U corresponding to U flows via the diode 36Uu, and the charge accumulated in the capacitor 54V corresponding to V flows via the diode 36Vu. The charges flowing via the diodes 36Uu, 36Vu flow via the switching element 34Wu corresponding to W, and flow into the capacitor 54W corresponding to W. In this way, in the case in which the capacitor 54 with the lowest voltage across is the capacitor 54W corresponding to W, when the switching element 34Wu on the upper branch side corresponding to W is brought to the on state, the charge accumulated in the capacitor 54 is discharged. Figure 13 Figure 13 ​​​​As shown in FIG. 16, the charge accumulated in the capacitor 54U corresponding to U flows via the diode 36Uu. The charge flowing via the diode 36Uu flows via the switch element 34Wu corresponding to W, and flows into the capacitor 54W corresponding to W. Thus, in the case where the capacitor 54 having the lowest voltage across both terminals is the capacitor 54W corresponding to W, when the switch element 34Wu on the upper branch side corresponding to W is brought to the on state, the charge accumulated in the capacitor 54 is discharged.

[0113] Figure 14 FIG. 17 is a diagram for showing a discharge path when the switch element on the lower branch side corresponding to U is brought to the on state. In Figure 14 , an example is shown in which the shutter 16 is in the open state, and the capacitor 54 having the highest voltage across both terminals is the capacitor 54U corresponding to U. The voltage of the capacitor 54U corresponding to U is higher than the voltage of the capacitor 54V corresponding to V and the voltage of the capacitor 54W corresponding to W. Therefore, as shown in FIG. 17, the charge accumulated in the capacitor 54U corresponding to U flows via the switch element 34Ud. The charge flowing via the switch element 34Ud flows via the diode 36Vd corresponding to V and the diode 36Wd corresponding to W. The charge flowing via the diode 36Vd corresponding to V flows into the capacitor 54V, and the charge flowing via the diode 36Wd corresponding to W flows into the capacitor 54W. Thus, in the case where the capacitor 54 having the highest voltage across both terminals is the capacitor 54U corresponding to U, when the switch element 34Ud on the lower branch side corresponding to U is brought to the on state, the charge accumulated in the capacitor 54 is discharged. Figure 14

[0114] Figure 15 FIG. 18 is a diagram for showing a discharge path when the switch element on the lower branch side corresponding to V is brought to the on state. In Figure 15 , an example is shown in which the shutter 16 is in the open state, and the capacitor 54 having the highest voltage across both terminals is the capacitor 54V corresponding to V. The voltage of the capacitor 54V corresponding to V is higher than the voltage of the capacitor 54U corresponding to U and the voltage of the capacitor 54W corresponding to W. Therefore, as shown in FIG. 18, the charge accumulated in the capacitor 54V corresponding to V flows via the switch element 34Vd. The charge flowing via the switch element 34Vd flows via the diode 36Ud corresponding to U and the diode 36Wd corresponding to W. The charge flowing via the diode 36Ud corresponding to U flows into the capacitor 54U, and the charge flowing via the diode 36Wd corresponding to W flows into the capacitor 54W. Thus, in the case where the capacitor 54 having the highest voltage across both terminals is the capacitor 54V corresponding to V, when the switch element 34Vd on the lower branch side corresponding to V is brought to the on state, the charge accumulated in the capacitor 54 is discharged. Figure 15 ​As shown in FIG. 12, the charge accumulated in the capacitor 54V corresponding to V flows via the switching element 34Vd. The charge flowing via the switching element 34Vd flows via the diode 36Ud corresponding to U and the diode 36Wd corresponding to W. The charge flowing via the diode 36Ud corresponding to U flows into the capacitor 54U, and the charge flowing via the diode 36Wd corresponding to W flows into the capacitor 54W. In this way, in the case where the capacitor 54 having the highest voltage across both terminals is the capacitor 54V corresponding to V, when the switching element 34Vd on the lower branch side corresponding to V is brought to the on state, the charge accumulated in the capacitor 54 is discharged.

[0115] Figure 16 A diagram showing the discharge path when the switching element on the lower branch side corresponding to W is brought to the on state. In Figure 16 , an example is shown in which the shutter 16 is in the open state, and the capacitor 54 having the highest voltage across both terminals is the capacitor 54W corresponding to W. The voltage of the capacitor 54W corresponding to W is higher than the voltage of the capacitor 54U corresponding to U and the voltage of the capacitor 54V corresponding to V. Therefore, as shown in Figure 16 , the charge accumulated in the capacitor 54W corresponding to W flows via the switching element 34Wd. The charge flowing via the switching element 34Wd flows via the diode 36Ud corresponding to U and the diode 36Vd corresponding to V. The charge flowing via the diode 36Ud corresponding to U flows into the capacitor 54U, and the charge flowing via the diode 36Vd corresponding to V flows into the capacitor 54V. In this way, in the case where the capacitor 54 having the highest voltage across both terminals is the capacitor 54W corresponding to W, when the switching element 34Wd on the lower branch side corresponding to W is brought to the on state, the charge accumulated in the capacitor 54 is discharged.

[0116] Using Figure 17 , an example of the operation of the power conversion device 10 of the present embodiment will be described. Figure 17 A flowchart showing an example of the operation of the power conversion device of the present embodiment.

[0117] In step S61, the control section 64 determines whether the shutter 16 has been changed from the closed state to the open state. In the case where the shutter 16 has been changed from the closed state to the open state (YES in step S61), the process proceeds to step S62. In the case where the shutter 16 has not been changed from the closed state to the open state (NO in step S61), the process shown in FIG. 13 is completed. Figure 17

[0118] In step S62, the determination section 62 determines the phase having the highest phase voltage on the basis of the detection result of the voltage sensor 28. Thereafter, the process proceeds to step S63.​

[0119] In step S63, the control section 64 brings the upper arm side switching element 34u corresponding to the phase with the highest phase voltage into the on state. Thereafter, the process shifts to step S64.

[0120] In step S64, the control section 64 determines whether the phase with the highest phase voltage has changed. In the case where the phase with the highest phase voltage has not changed (NO in step S64), the process of step S64 is repeated. In the case where the phase with the highest phase voltage has changed (YES in step S64), the process shifts to step S65.

[0121] In step S65, the control section 64 brings the upper arm side switching element 34u in the on state into the off state. Thereafter, the process shifts to step S66.

[0122] In step S66, the control section 64 determines whether the process of bringing the upper arm side switching element 34u into the on state has been completed for all of the upper arm side switching elements 34u. In the case where the process has not been completed for any of the upper arm side switching elements 34u (NO in step S66), the process after step S62 is repeated. In the case where the process has been completed for all of the upper arm side switching elements 34u (YES in step S66), the process shifts to step S67.

[0123] In step S67, the control section 64 determines whether further discharging is required, i.e., whether further execution of the process of steps S62 to S66 is required. For example, in the case where the time from the transition of the switching element 34u to the on state to the transition to the off state is not long enough, multiple discharges are required in order to sufficiently discharge the charge accumulated in the capacitor 54. In the case where further discharging is required (YES in step S67), the process after step S62 is executed again. In the case where further discharging is not required (NO in step S67), Figure 17 the process shown is completed.

[0124] Using Figure 18 Another example of the operation of the power conversion device 10 of the present embodiment will be described. Figure 18 A flowchart showing another example of the operation of the power conversion device of the present embodiment.

[0125] In step S71, the control section 64 determines whether the shutter 16 has transitioned from the closed state to the open state. In the case where the shutter 16 has transitioned from the closed state to the open state (YES in step S71), the process shifts to step S72. In the case where the shutter 16 has not transitioned from the closed state to the open state (NO in step S71), Figure 18The illustrated processing is completed.

[0126] In step S72, the determination section 62 determines the phase in which the phase voltage is the lowest, based on the detection result of the voltage sensor 28. Thereafter, the processing proceeds to step S73.

[0127] In step S73, the control section 64 causes the lower arm side switching element 34d corresponding to the phase in which the phase voltage is the lowest to be in the on state. Thereafter, the processing proceeds to step S74.

[0128] In step S74, the control section 64 determines whether the phase in which the phase voltage is the lowest has changed. In the case where the phase in which the phase voltage is the lowest has not changed (NO in step S74), the processing of step S74 is repeated. In the case where the phase in which the phase voltage is the lowest has changed (YES in step S74), the processing proceeds to step S75.

[0129] In step S75, the control section 64 causes the lower arm side switching element 34d that is in the on state to be in the off state. Thereafter, the processing proceeds to step S76.

[0130] In step S76, the control section 64 determines whether the processing of causing the lower arm side switching element 34d to be in the on state has been completed for all of the lower arm side switching elements 34d. In the case where the processing has not been completed for any of the lower arm side switching elements 34d (NO in step S76), the processing from step S72 is repeated. In the case where the processing has been completed for all of the lower arm side switching elements 34d (YES in step S76), the processing proceeds to step S77.

[0131] In step S77, the control section 64 determines whether further discharging is required, i.e., whether further execution of the processing of steps S72 to S76 is required. For example, in the case where the time from the transition of the switching element 34d to the on state to the transition to the off state is not long enough, multiple discharges are required in order to sufficiently discharge the charge accumulated in the capacitor 54. In the case where further discharging is required (YES in step S77), the processing from step S72 is executed again. In the case where further discharging is not required (NO in step S77), Figure 18 The illustrated processing is completed.

[0132] Thus, according to the present embodiment, the switching element 34 corresponding to the phase with the highest phase voltage or the switching element 34 corresponding to the phase with the lowest phase voltage becomes in the on state in that order. When the switching element 34 becomes in the on state, even if an unexpected transition from the open state to the closed state occurs in the shutter 16, a short circuit of the power supply line 70 via the switching element 34 does not occur. Thus, according to the present embodiment, the power conversion device 10 that can more reliably prevent damage to the switching element 34 and the like can be provided.

[0133] When the above-described embodiments are summarized, the following is obtained.

[0134] The power conversion device (10) includes a converter (12) including switching elements (34Uu, 34Vu, 34Wu, 34Ud, 34Vd, 34Wd) that convert an alternating-current voltage supplied from an alternating-current power supply (14) via a shutter (16) into a direct-current voltage, a filter (24) including reactors (46U, 46V, 46W, 48U, 48V, 48W) and capacitors (54U, 54V, 54W) that are provided between the shutter and the converter and that remove noise, and a control section (64) that causes the switching elements to become in the on state after the shutter becomes in the open state, thereby causing electric charges accumulated in the capacitors to be discharged. According to such a configuration, after the shutter becomes in the open state, the electric charges accumulated in the capacitors are rapidly discharged via the switching elements. Thus, according to such a configuration, it is possible to prevent the peak value of the resonance voltage from becoming significantly large, and it is possible to more reliably prevent the switching elements 34 and the like from being damaged.

[0135] It can also be that the alternating-current power supply is a multiphase alternating-current power supply that supplies a multiphase phase voltage, the converter has a plurality of power element sections (32U, 32V, 32W) corresponding to each phase of the alternating-current power supply, the power element section (32U, 32V, 32W) has the switching element on the upper branch side and the switching element on the lower branch side connected in series with each other, the filter includes the reactor and the capacitor corresponding to each phase of the alternating-current power supply, and the control section causes the switching elements on the upper branch side or the lower branch side of the plurality of power element sections to all become in the on state, thereby causing electric charges accumulated in the capacitors provided corresponding to each phase of the alternating-current power supply to be discharged. According to such a configuration, even if the capacitor with a large voltage across both terminals is arbitrary, it is possible to cause the electric charges accumulated in the capacitor to be discharged via the switching elements.

[0136] The control section can also cause the switching elements of the upper branch side or the lower branch side of each of the plurality of power element sections to simultaneously become in the on state. According to such a configuration, the time required for discharging can be shortened compared to a case in which the switching elements become in the on state in order.

[0137] The control section can also cause any one of the switching elements of the upper branch side or the lower branch side of each of the plurality of power element sections to become in the on state, and sequentially switch the switching elements that become in the on state.

[0138] A detection section (28) that detects the phase voltage in each phase of the alternating-current power source can also be provided. The control section can cause the switching element of the upper branch side corresponding to the phase with the highest phase voltage to become in the on state based on the detection result of the detection section. According to such a configuration, even when an unexpected transition from the open state to the closed state occurs in the contact, the power line can be prevented from being short-circuited via the switching element, and further, the switching element can be prevented from being damaged.

[0139] A detection section that detects the phase voltage in each phase of the alternating-current power source can also be provided. The control section can cause the switching element of the lower branch side corresponding to the phase with the lowest phase voltage to become in the on state based on the detection result of the detection section. According to such a configuration, even when an unexpected transition from the open state to the closed state occurs in the contact, the power line can be prevented from being short-circuited via the switching element, and further, the switching element can be prevented from being damaged.

[0140] The plurality of power element sections can be connected in parallel to each other, and a node (38U, 38V, 38W) at which the switching element of the upper branch side and the switching element of the lower branch side of the power element section are connected can be supplied with the phase voltage of the corresponding phase.

[0141] A control method of a power conversion device including a converter including a switching element that converts an alternating-current voltage supplied from an alternating-current power source via a contact into a direct-current voltage, a filter including an inductor and a capacitor that is provided between the contact and the converter and removes noise, and a control section that controls the contact and the switching element, the control method including a step (S1) of causing the contact to be in an open state, and a step (S2) of causing the switching element to be in an on state, thereby discharging electric charges accumulated in the capacitor.

Claims

1. A power conversion device, comprising: a converter including a switching element for converting an AC voltage supplied from an AC power source via a switch into a DC voltage; a filter provided between the switch and the converter, comprising a reactor and a capacitor, for removing noise; and a control unit that turns the switch on and then turns the switching element on to discharge the charge stored in the capacitor after turning the switch on. The AC power supply is a multi-phase AC power supply that supplies multi-phase voltages. The converter includes a plurality of power element units corresponding to respective phases of the AC power supply, each power element unit including the switching element on the upper arm side and the switching element on the lower arm side connected in series with each other. The filter includes the reactor and the capacitor corresponding to each of the AC power supplies. The control unit turns on all of the switching elements on the upper arm side or the lower arm side of each of the plurality of power element units, thereby discharging the charge accumulated in the capacitors provided corresponding to the respective AC power sources. The control unit turns on the switching element on the upper arm side of any one of the plurality of power element units, and then turns on the switching elements on the upper arm sides of the other power element units in sequence. Alternatively, the control unit turns on the switching element on the lower arm side of any one of the plurality of power element units, and then sequentially turns on the switching elements on the lower arm sides of the other power element units.

2. The power conversion device according to claim 1, wherein: The power conversion device further includes a detection unit that detects the phase voltage in each phase of the AC power supply. The control unit turns on the switching element on the upper arm side corresponding to the highest phase voltage based on the detection result of the detection unit.

3. The power conversion device according to claim 1, wherein: The power conversion device further includes a detection unit that detects the phase voltage in each phase of the AC power supply. The control unit turns on the switching element on the lower arm side corresponding to the phase with the lowest voltage based on the detection result of the detection unit.

4. The power conversion device according to any one of claims 1 to 3, characterized in that: The plurality of power element units are connected in parallel with each other. The phase voltage of the corresponding phase is supplied to a node where the switching element on the upper arm side and the switching element on the lower arm side of the power element unit are connected.

5. A method for controlling a power conversion device, the method comprising: a converter including a switching element for converting an AC voltage supplied from an AC power source via a switch into a DC voltage; a filter provided between the switch and the converter and including a reactor and a capacitor for removing noise; and a control unit for controlling the switch and the switching element, the method comprising: a step of placing the shutter in an open state; and a step of turning on the switching element to discharge the charge stored in the capacitor, The AC power supply is a multi-phase AC power supply that supplies multi-phase voltages. The converter includes a plurality of power element units corresponding to respective phases of the AC power supply, each power element unit including the switching element on the upper arm side and the switching element on the lower arm side connected in series with each other. The filter includes the reactor and the capacitor corresponding to each of the AC power supplies. In the step of discharging, all of the switching elements on the upper arm side or the lower arm side of each of the plurality of power element units are turned on, thereby discharging the charge accumulated in the capacitors provided corresponding to the respective AC power sources. In the step of discharging, the switching element on the upper arm side of any one of the plurality of power element units is turned on, and then the switching elements on the upper arm sides of the other power element units are turned on in sequence. Alternatively, in the discharging step, the switching element on the lower arm side of any one of the plurality of power element units is turned on, and then the switching elements on the lower arm sides of the other power element units are sequentially turned on.

Images