Power converter

Abstract

To provide a power conversion device that can consume the energy of a load in a relatively short time during a power outage. [Solution] A power conversion device 1 that converts an AC input current into a DC output current and supplies the output current to an inductive load L comprises a switching unit 2, a rectifier unit 3, a capacitor unit 4, a chopper unit 5 including switching elements U~Y, a smoothing unit 6, and a control unit 7. The control unit 7 is characterized in that, in the event of a power outage, the switching control unit 10 opens the switching unit 2, the switching control unit 9 continues the switching control, and the current setting unit 8 controls the current setting value to attenuate the current, thereby causing the energy of the capacitor unit 4 to be consumed by the load L, and then the energy of the load L is regenerated back into the capacitor unit 4.

Description

Technical Field

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

Background Art

[0002] Conventionally, a power conversion device that converts an alternating current input current into a direct current output current and supplies it to an inductive load (for example, an electromagnet) has been known (for example, see Patent Document 1). A conventional power conversion device includes a main circuit section and a control section that controls the main circuit section. The main circuit section includes a rectifier section, a capacitor section, and a chopper section.

[0003] In a conventional power conversion device, when the power supply voltage is not supplied to the control section due to a power outage, the operations of a PLC, FPGA, microcomputer, etc. that constitute the control section are not guaranteed. Therefore, it is necessary to stop the output of the main circuit section as quickly as possible. Specifically, it is necessary to quickly consume the energy (power) remaining in the load and make the output current of the main circuit section zero.

[0004] In a conventional power conversion device, during a power outage, the energy of the load is refluxed and consumed by the chopper section, or the energy of the load is regenerated to the capacitor section, and the amount that cannot be regenerated is refluxed and consumed by the chopper section. In either case, the time until the energy of the load is completely consumed depends on the time constant of the load. That is, a conventional power conversion device has a problem that it takes time to completely consume the energy of the load.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] This invention has been made in view of the above circumstances, and its objective is to provide a power conversion device that can consume the energy of a load in a relatively short time during a power outage. [Means for solving the problem]

[0007] To solve the above problems, the power conversion device according to the present invention is A power conversion device that converts an AC input current into a DC output current and supplies the output current to an inductive load, A main circuit section that converts the input current into the output current, A switching unit that, when in the open state, interrupts the input of the input current to the main circuit section, The system includes a control unit that controls the main circuit section, The main circuit section is, A rectifier unit that rectifies the input current input via the switching unit, A capacitor section that smooths the output of the rectifier section, A chopper section including a switching element is provided downstream of the capacitor section, The system includes a smoothing unit that smooths the output of the chopper unit to generate the output current, The control unit, An opening / closing control unit that controls the opening / closing section, A current setting unit for setting the current setting value of the output current, The system includes a switching control unit that performs switching control to turn the switching element on and off so that the current value of the output current approaches the current set value, In the event of a power outage, the opening / closing control unit opens the opening / closing unit, the switching control unit continues the switching control, and the current setting unit reduces the current setting value, thereby causing the energy of the capacitor unit to be consumed by the load, and then the energy of the load to be regenerated into the capacitor unit.

[0008] In this configuration, during a power outage, the current setting value is attenuated while continuing switching control, allowing the capacitor's energy to be consumed by the load, and then the load's energy to be regenerated back into the capacitor. This makes it possible to consume the load's energy in a relatively short time. Note that the power outage in this invention includes not only a state in which the input current is stopped for a predetermined period of time or longer, but also a state in which the input current is lower than normal, or a state in which the input current is stopped momentarily (for less than a predetermined period of time).

[0009] In the aforementioned power converter, The current setting unit can be configured to maintain the current setting value at a constant value for a predetermined time during a power outage, and then to decrease the current setting value from the constant value.

[0010] In the aforementioned power converter, The switching control unit, During the first period in which the energy of the capacitor section is consumed by the load, the switching control is continued so that the chopper section alternately switches between a powering state in which it outputs a positive voltage and a recirculation state in which it does not output a voltage. During the second period in which the energy of the load is regenerated in the capacitor section, the switching control can be continued so that the chopper section alternately switches between a regenerative state in which it outputs a negative voltage and the recirculation state.

[0011] In the aforementioned power converter, The current setting unit can be configured to attenuate the current setting value such that the slope of the attenuation of the current setting value is constant. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a power conversion device that can consume the energy of a load in a relatively short time during a power outage. [Brief explanation of the drawing]

[0013] [Figure 1]It is a circuit diagram of a power conversion device according to the present invention. [Figure 2] It is a waveform diagram showing the charging voltage of the capacitor unit of the present invention, the output current of the present invention, and the output current of the comparative example. [Figure 3] It is a diagram showing the states of the switching elements U to Y, the output voltage of the chopper unit, and the state of the chopper unit during the period from time t0 to t1 in FIG. 2. [Figure 4] It is a diagram showing the current path of the chopper unit, where (A) is the diagram at state 1, (B) is the diagram at state 2, (C) is the diagram at state 3, and (D) is the diagram at state 4. [Figure 5] It is a diagram showing the states of the switching elements U to Y, the output voltage of the chopper unit, and the state of the chopper unit at a minute time including time t1 in FIG. 2. [Figure 6] It is a diagram showing the states of the switching elements U to Y, the output voltage of the chopper unit, and the state of the chopper unit during the period from time t1 to t2 in FIG. 2. [Figure 7] It is a diagram showing the current path of the chopper unit, where (A) is the diagram at state 1', (B) is the diagram at state 2, (C) is the diagram at state 3', and (D) is the diagram at state 4. [Figure 8] It is a waveform diagram showing the charging voltage of the capacitor unit of the modified example, the output current of the modified example, and the output current of the comparative example.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of a power conversion device according to the present invention will be described with reference to the accompanying drawings.

[0015] FIG. 1 shows a circuit diagram of a power conversion device 1 according to an embodiment of the present invention. The power conversion device 1 includes input terminals T1 to T3 and output terminals T4, T5, a switching unit 2, a main circuit unit M (a rectifying unit 3, a capacitor unit 4, a chopper unit 5, and a smoothing unit 6), and a control unit 7.

[0016] Input terminals T1 to T3 are connected to a commercial AC power supply, and AC input current is supplied from the commercial AC power supply. Output terminals T4 and T5 are connected to an inductive load L (an electromagnet in this embodiment), and supply DC output current to the inductive load L.

[0017] The switching unit 2 is provided on the power line connecting the input terminals T1 to T3 and the rectifier unit 3. The switching unit 2 is normally closed, but opens during a power outage (including momentary dips and momentary interruptions). When the switching unit 2 is open, it interrupts the input current. The switching unit 2 remains open at least until the power outage is resolved. For example, an electromagnetic contactor can be used as the switching unit 2.

[0018] The rectifier section 3 comprises a filter circuit 3a and a three-phase bridge diode 3b. The filter circuit 3a comprises capacitors C1 to C3 and inductors L1 to L3. The three-phase bridge diode 3b comprises six bridge-connected diodes D1 to D6. The rectifier section 3 removes noise from the input current input via the switching section 2 and rectifies the input current from which the noise has been removed.

[0019] The capacitor section 4 is connected downstream of the rectifier section 3. The capacitor section 4 comprises at least one capacitor and smooths the output of the rectifier section 3. The capacitor section 4 also stores at least a portion of the energy (electricity) output from the rectifier section 3.

[0020] The chopper section 5 comprises four switching elements U to Y. Switching element U constitutes the upper arm of the first leg, switching element X constitutes the lower arm of the first leg, switching element V constitutes the upper arm of the second leg, and switching element Y constitutes the lower arm of the second leg. Switching elements U to Y can be, for example, IGBTs (isolated gate bipolar transistors), MOSFETs (metal-oxide-semiconductor field-effect transistors), etc. A freewheeling diode is connected in parallel to the current path of switching elements U to Y. The connection point P1 between switching element U and switching element X and the connection point P2 between switching element V and switching element Y are connected to the smoothing section 6.

[0021] The smoothing section 6 comprises coils L4 to L6, capacitors C4 and C5, and a resistor R. The smoothing section 6 smooths the output of the chopper section 5 to generate an output current. The smoothing section 6 also functions as a filter circuit. The output current output from the smoothing section 6 is supplied to the load L connected to the output terminals T4 and T5.

[0022] The control unit 7 includes a current setting unit 8, a switching control unit 9, and a switching control unit 10. The control unit 7 may be composed of a digital circuit such as a PLC, FPGA, or microcontroller, or it may be composed of a circuit that combines a digital circuit and an analog circuit.

[0023] The current setting unit 8 sets the current setting value for the output current under normal conditions and during a power outage. In this embodiment, the current setting unit 8 attenuates the current setting value at a constant slope during a power outage. The slope of the current setting value during a power outage is preset to a value that prevents the capacitor unit 4 from becoming overcharged, based on the parameters of the coil and resistance components of the load L and the capacitance of the capacitor unit 4.

[0024] The switching control unit 9 performs switching control by turning the switching elements U~Y on and off so that the output current value approaches the current set value. During switching control, the switching control unit 9 approaches the output current value approaches the current set value by changing the on-duty cycle of the switching elements U~Y, for example, by PWM control. Details of this switching control will be described later. The switching control unit 9 also includes a detection unit. The detection unit includes, for example, detection circuits such as current sensors and / or voltage sensors that detect the current value and / or voltage value necessary for switching control, and peripheral circuits therefor.

[0025] The switching control unit 10 detects power outages and, if a power outage is detected, opens the switching unit 2 to cut off the input current. Known methods can be used for power outage detection. For example, the switching control unit 10 can detect the presence or absence of a power outage by detecting the power received by the control unit 7 (a voltage generated based on the voltage of the commercial AC power supply) using a voltage sensor.

[0026] Figure 2 shows the waveforms of the charging voltage of the capacitor section 4 of the power converter 1, the output current of the power converter 1, and the output current of the power converter in the comparative example during a power outage.

[0027] The power converter according to the comparative example has the same configuration as power converter 1, but differs from power converter 1 in that it does not perform the above-mentioned switching control during a power outage. The power converter according to the comparative example consumes the energy of the load by recirculating it in the chopper section during a power outage, similar to the power converter described in Patent Document 1.

[0028] Immediately before time t0 shown in Figure 2 (under normal conditions), the switching control unit 9 performs switching control so that the output current value matches the current setting value set by the current setting unit 8. At this time, a positive voltage is applied to the load L, and a positive output current of current value A1 [A] is supplied.

[0029] When a power outage occurs at time t0, the switching control unit 10 opens the switching unit 2, electrically disconnecting the main circuit unit M from the input terminals T1 to T3. The switching control unit 9 continues switching control. At time t0, energy (power) is stored in the capacitor unit 4, and the charging voltage (terminal voltage) of the capacitor unit 4 is V2 [V] (where V2 > 0). Also, energy (power) remains in the load L.

[0030] During the period from time t0 to t1 (strictly speaking, until the start of a very short time including time t1, which corresponds to the "first period" of the present invention), the current setting unit 8 attenuates the current setting value at a constant slope. The switching control unit 9 performs switching control so that the current value of the output current matches the current setting value. As a result, the energy of the capacitor unit 4 and the energy of the load L are consumed by the load L. The charging voltage of the capacitor unit 4 decreases from V2 [V] to V1 [V] (where V1 < V2).

[0031] Fig. 3 shows an example of the states of the switching elements U to Y, the output voltage of the chopper unit 5, and the state of the chopper unit 5 during the period from time t0 to t1. Fig. 4 shows the current paths in each state of the chopper unit 5 during the period from time t0 to t1. The switching control unit 9 performs switching control with states 1, 2, 3, and 4 as one cycle.

[0032] In state 1, the switching elements U, X, V, and Y are on, off, off, and on, respectively, and the output voltage of the chopper unit 5 becomes positive. The chopper unit 5 in state 1 is in the power running state, and the current path of the chopper unit 5 is as shown in Fig. 4(A).

[0033] In state 2, the switching elements U, X, V, and Y are off, on, off, and on, respectively, and the output voltage of the chopper unit 5 becomes zero. The chopper unit 5 in state 2 is in the reflux state, and the current path of the chopper unit 5 is as shown in Fig. 4(B).

[0034] In state 3, the switching elements U, X, V, and Y are on, off, off, and on, respectively, and the output voltage of the chopper unit 5 becomes positive. The chopper unit 5 in state 3 is in the power running state, and the current path of the chopper unit 5 is as shown in Fig. 4(C). State 3 is the same state as state 1.

[0035] In state 4, the switching elements U, X, V, and Y are on, off, on, and off, respectively, and the output voltage of the chopper unit 5 becomes zero. The chopper unit 5 in state 4 is in the reflux state, and the current path of the chopper unit 5 is as shown in Fig. 4(D).

[0036] During the period from time t0 to t1, the switching control unit 9 gradually decreases the powering time for states 1 and 3 per cycle, while gradually increasing the recirculation time for states 2 and 4 per cycle, in order to attenuate the output current value at a constant slope according to the current setting value. The switching control unit 9 fixes the time of one cycle and increases the recirculation time by the amount by which the powering time has been reduced.

[0037] Incidentally, the load L has both a resistive component and an inductive component. The voltage generated by the resistive component is calculated as output current × resistance value and decreases as the output current decays. In this embodiment, since the slope of the output current decay is constant, the voltage generated by the resistive component decays at a constant slope. On the other hand, the voltage generated by the inductive component is calculated as inductance value × (discharge current of load L / discharge time), and in this embodiment, since the slope of (discharge current of load L / discharge time), i.e., the discharge current, is constant, it becomes a constant negative voltage. The voltage applied to the load L is the sum of the voltage generated by the resistive component and the voltage generated by the inductive component, and is positive during the period from time t0 to t1, zero at time t1 (strictly speaking, a small time including time t1), and negative during the period from time t1 to t2, changing at a constant ratio during the period from time t0 to t2.

[0038] Figure 5 shows an example of the states of switching elements U~Y, the output voltage of the chopper section 5, and the state of the chopper section 5 during a small time interval including time t1. During this small time interval including time t1, the powering time for states 1 and 3 per cycle becomes zero, and one cycle consists only of the return time for states 2 and 4. At this time, the output voltage of the chopper section 5 becomes zero.

[0039] As shown in Figure 2, during the period from time t1 (more precisely, from the end of the minute time including time t1) to t2 (corresponding to the "second period" of the present invention), the current setting unit 8 decays the current setting value at a constant slope. The slope of the current setting value during the period from time t1 to t2 is the same as the slope of the current setting value during the period from time t0 to t1. The switching control unit 9 performs switching control to match the current value of the output current to the current setting value. As a result, the energy of the load is regenerated in the capacitor unit 4, and the charging voltage of the capacitor unit 4 rises from V1 [V] to V3 [V] (where V3 > V2).

[0040] Figure 6 shows an example of the states of switching elements U to Y, the output voltage of the chopper unit 5, and the state of the chopper unit 5 during the period from time t1 to t2. Figure 7 shows the current path for each state of the chopper unit 5 during the period from time t1 to t2. The switching control unit 9 performs switching control with states 1', 2, 3', and 4 as one cycle.

[0041] In state 1', the switching elements U, X, V, and Y are off, on, on, and off, and the output voltage of the chopper section 5 becomes negative. In state 1', the chopper section 5 is in a regenerative state, and the current path of the chopper section 5 is as shown in Figure 7(A).

[0042] In state 2, the switching elements U, X, V, and Y are off, on, off, and on, and the output voltage of the chopper section 5 becomes zero. In state 2, the chopper section 5 is in a free-recirculating state, and the current path of the chopper section 5 is as shown in Figure 7(B).

[0043] In state 3', the switching elements U, X, V, and Y are off, on, on, and off, and the output voltage of the chopper section 5 becomes negative. In state 3', the chopper section 5 is in a regenerative state, and the current path of the chopper section 5 is as shown in Figure 7(C). State 3' is the same state as state 1'.

[0044] In state 4, the switching elements U, X, V, and Y are on, off, on, and off, and the output voltage of the chopper section 5 becomes zero. In state 4, the chopper section 5 is in a free-recirculating state, and the current path of the chopper section 5 is as shown in Figure 7(D).

[0045] During the period from time t1 to t2, the switching control unit 9 gradually decreases the recirculation time for states 2 and 4 per cycle, while gradually increasing the regeneration time for states 1' and 3' per cycle, in order to attenuate the output current value at a constant slope according to the current set value. The switching control unit 9 fixes the time of one cycle and increases the regeneration time by the amount by which the recirculation time was reduced. As shown in Figure 2, when the output current becomes zero at time t2, the switching control unit 9 stops the switching control.

[0046] As can be seen from Figure 2, the power converter 1 according to this embodiment can reduce the output current to zero faster than the power converter according to the comparative example, without causing the capacitor section 4 to become overcharged. In other words, the power converter 1 according to this embodiment consumes the energy of the capacitor section 4 and the energy of the load L in the load L, and then recovers the energy of the load to the capacitor section 4, making it possible to consume the energy of the load L in a relatively short time.

[0047] Although embodiments of the power conversion device according to the present invention have been described above, the present invention is not limited to the above embodiments.

[0048] [Differentiation] In the power converter 1 described above, the current setting unit 8 may maintain the current setting value at a constant value for a predetermined time during a power outage, and then decrease the current setting value from that constant value. In this case, the current setting unit 8 can make the slope of the current setting value decrease greater than in the above embodiment.

[0049] Fig. 8 shows the waveforms of the charging voltage of the capacitor unit 4 of the power conversion device 1, the output current of the power conversion device 1, and the output current of the power conversion device according to the comparative example when the current set value is maintained at a constant value for a predetermined time.

[0050] Immediately before time t0 shown in Fig. 8 (normal time), the switching control unit 9 performs switching control so that the current value of the output current matches the current set value set by the current setting unit 8. At this time, a positive voltage is applied to the load L, and a positive output current with a current value of A1 [A] is supplied.

[0051] When a power outage occurs at time t0, the opening / closing control unit 10 opens the opening / closing unit 2 to electrically disconnect the main circuit unit M from the input terminals T1 to T3. The switching control unit 9 continues the switching control. At time t0, energy is stored in the capacitor unit 4, and the charging voltage (terminal voltage) of the capacitor unit 4 is V2 [V].

[0052] During the period from time t0 to t1', the current setting unit 8 maintains the current set value at a constant value. The switching control unit 9 performs switching control so that the current value of the output current matches the current set value. As a result, the energy of the capacitor unit 4 is consumed by the load L. The charging voltage of the capacitor unit 4 decreases from V2 [V] to V1' [V] (where V1' < V1).

[0053] The energy consumed by the resistance component of the load L is calculated by the square of the output current × resistance value × time and decreases due to the attenuation of the output current. During the period from time t0 to t1', since the output current is maintained at a constant value, the energy consumed by the resistance component is larger than that in the above embodiment. As a result, as shown in Fig. 8, the charging voltage of the capacitor unit 4 decreases more significantly than in the above embodiment.

[0054] During the period from time t0 to t1', the switching control unit 9 increases the powering time for states 1 and 3 per cycle, while decreasing the recirculation time for states 2 and 4 per cycle, in order to maintain the output current value at a constant value according to the current setting value, in accordance with the decrease in the charging voltage of the capacitor unit 4.

[0055] At time t1', the current setting unit 8 begins to decay the current setting value. In this modified example, the current setting unit 8 begins to decay the current setting value at a preset timing (time t1'), but it may also detect the charging voltage of the capacitor unit 4 with a voltage sensor and begin decaying the current setting value when the charging voltage drops to a preset voltage.

[0056] During the period from time t1' to t2', the current setting unit 8 decays the current setting value at a constant rate. The switching control unit 9 performs switching control to match the output current value to the current setting value.

[0057] In this modified example, since the slope of the decay of the current setting value is set to a larger value than in the above embodiment, the voltage of the coil component calculated by inductance value × (discharge current of load L / discharge time) becomes a negative voltage with a larger absolute value than in the above embodiment. As a result, the voltage applied to the load L is negative during the period from time t1' to t2'. The switching control unit 9 performs switching control with states 1', 2, 3', and 4 as one cycle, similar to the above embodiment. As a result, the energy of the load L is regenerated in the capacitor section 4, and the charging voltage of the capacitor section 4 rises from V1'[V] to V3[V].

[0058] During the period from time t1' to t2', the switching control unit 9 gradually decreases the recirculation time for states 2 and 4 per cycle, while gradually increasing the regeneration time for states 1' and 3' per cycle, in order to attenuate the output current value at a constant slope according to the current set value. The switching control unit 9 fixes the time of one cycle and increases the regeneration time by the amount by which the recirculation time was reduced. When the output current becomes zero at time t2', the switching control unit 9 stops the switching control.

[0059] As can be seen from the comparison between Figure 8 and Figure 2, in this modified version, the output current can be reduced to zero in a shorter time than the power converter 1 of the above embodiment. In other words, according to this modified version, it is possible to completely consume the energy of the load L in a shorter time than the power converter 1 of the above embodiment.

[0060] [Other variations] The power conversion device according to the present invention is a power conversion device that converts an AC input current into a DC output current and supplies the output current to an inductive load, and comprises a main circuit section that converts the input current to an output current, a switching section that interrupts the input of the input current to the main circuit section when it is open, and a control section that controls the main circuit section, the main circuit section comprising a rectifier section that rectifies the input current input via the switching section, a capacitor section that smooths the output of the rectifier section, a chopper section provided downstream of the capacitor section and including a switching element, and a smoothing section that smooths the output of the chopper section to generate an output current, the control section comprising a switching control section that controls the switching section, a current setting section that sets a current setting value for the output current, and a switching control section that performs switching control to turn the switching element on and off so that the current value of the output current approaches the current setting value, the configuration can be appropriately changed if, in the event of a power outage, the switching control section opens the switching section, the switching control section continues the switching control, and the current setting section attenuates the current setting value so that the energy of the capacitor section is consumed by the load and then the energy of the load is regenerated to the capacitor section.

[0061] For example, in the above embodiment and its modifications, the current setting value is attenuated so that the slope of the attenuation of the current setting value is constant, but the current setting value may be attenuated while changing the slope of the attenuation.

[0062] In the above modified example, the slope of the decay of the current setting value is set so that the voltage applied to the load L is negative during the period from time t1' to t2'. However, the slope of the decay of the current setting value may also be set so that the voltage applied to the load L changes from positive, zero, and negative after time t1'.

[0063] In the above embodiment, if the power supply state in which the chopper unit 5 outputs a positive voltage and the return state in which the chopper unit 5 does not output a voltage alternate during the first period in which the energy of the capacitor unit 4 and the energy of the load L are consumed by the load L, then the states of the switching elements U, X, V, and Y can be changed as appropriate. For example, one cycle of switching control may consist of a power supply state in which the switching elements U, X, V, and Y are on, off, off, and on, and a return state in which the switching elements U, X, V, and Y are off, on, off, and on.

[0064] Similarly, in the above embodiment, if, during the second period in which the energy of the load L is regenerated to the capacitor section 4, the chopper section 5 alternates between a regenerative state in which it outputs a negative voltage and a recirculation state in which it does not output a voltage, then the states of the switching elements U, X, V, and Y can be changed as appropriate. [Explanation of symbols]

[0065] 1. Power converter 2 Opening and closing section 3 Rectifier 3a Filter circuit 3b Three-phase bridge diode 4 Capacitor section 5 Choppa Club 6. Smooth section 7 Control Unit 8 Current setting section 9 Switching Control Unit 10 Opening / closing control unit

Claims

1. A power conversion device that converts an AC input current into a DC output current and supplies the output current to an inductive load, A main circuit section that converts the input current into the output current, A switching unit that, when in the open state, interrupts the input of the input current to the main circuit section, The system includes a control unit that controls the main circuit section, The main circuit section is, A rectifier unit that rectifies the input current input via the switching unit, A capacitor section that smooths the output of the rectifier section, A chopper section including a switching element is provided downstream of the capacitor section, The system includes a smoothing unit that smooths the output of the chopper unit to generate the output current, The control unit, An opening / closing control unit that controls the opening / closing section, A current setting unit for setting the current setting value of the output current, The system includes a switching control unit that performs switching control to turn the switching element on and off so that the current value of the output current approaches the current set value, During a power outage, the opening / closing control unit opens the opening / closing unit, the switching control unit continues the switching control, and the current setting unit reduces the current setting value, thereby causing the energy of the capacitor unit to be consumed by the load, and then the energy of the load to be regenerated into the capacitor unit. A power conversion device characterized by the following features.

2. The current setting unit maintains the current setting value at a constant value for a predetermined time during a power outage, and then decreases the current setting value from the constant value. The power conversion device according to feature 1.

3. The switching control unit, During the first period in which the energy of the capacitor section is consumed by the load, the switching control is continued so that the chopper section alternately switches between a powering state in which it outputs a positive voltage and a recirculation state in which it does not output a voltage. During the second period in which the energy of the load is regenerated in the capacitor section, the switching control is continued so that the chopper section alternately switches between a regenerative state in which it outputs a negative voltage and the recirculation state. The power conversion device according to feature 1.

4. The current setting unit reduces the current setting value so that the slope of the current setting value's decay becomes constant. The power conversion device according to feature 1.

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