Power conversion device and method for controlling power conversion device

Abstract

To provide a power conversion device and a control method thereof that are capable of switching between voltage control and current control at any timing and that enable stable operation of the system even when power generation using natural energy changes suddenly.SOLUTION: A power conversion circuit 100 has three input / output ports, and switches between voltage control and current control using a first switching control that switches to current control using a control command value during voltage control, and a second switching control that switches to voltage control using a control command value during current control.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a power conversion device and a control method for a power conversion device.

Background Art

[0002] There is disclosed a battery control device that can operate a power generation device even when a disconnection occurs in an associated power grid (Patent Document 1). It is a battery control device that controls charging and discharging of a battery capable of temporarily storing electric power generated by a power generation device using natural energy. When the power generation device and the PCS are disconnected from the power grid, a part of the operation mode of the PCS is set to a voltage control mode in which the output voltage is controlled to a target voltage, and the remaining operation mode of the PCS is set to a current control mode in which the output current is controlled to a target current. Then, based on the measured value of the output of the PCS in the voltage control mode, the charge and discharge amount of the PCS in the current control mode is determined so as to absorb the output.

[0003] Also, there is disclosed a power control device that suppresses a poor start of charging of surplus power and enables effective use of the generated power of a distributed power source (Patent Document 2). In a microgrid including a distributed power source (solar cell) and a power storage device, it includes a first adjustment unit that adjusts the output of the distributed power source, a second adjustment unit that adjusts the charging and discharging of the power storage device, an inverter circuit that converts the power supplied from the distributed power source and the power storage device from DC to AC and outputs it to a load, and a control device. The control device controls the output of the distributed power source by the first adjustment unit so that the received power of the microgrid becomes a first target value, and performs control to charge the surplus power of the distributed power source to the power storage device via the second adjustment unit so that the received power of the microgrid becomes a second target value.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the prior art, in order to stabilize the load during sudden changes in power generation such as solar power generation, it is common to control the power supply from the storage battery to the load during sudden decreases in power generation and charge the surplus power generation into the storage battery during sudden increases in power generation.

[0006] In the prior art disclosed in Patent Document 1, each PCS controls the charge and discharge amount of the storage battery according to a command from a management device. In this system, when the power generation from natural energy such as solar power generation suddenly changes, the process is carried out in the following flow: measurement by a measurement device, arithmetic processing by a management device, transmission to an evaluation function setting unit, transmission to a command value distribution unit, and each PCS performs battery control. In such a configuration, there is a problem that the responsiveness of the control of the storage battery deteriorates due to the time related to communication and the time related to processing in the management device.

[0007] Also, in the prior art disclosed in Patent Document 2, when the power generation from natural energy such as solar power generation suddenly changes, each power converter performs charge and discharge of the storage battery according to information. Therefore, communication between the management device and the power converter is omitted, and the control of the storage battery can be performed at a higher speed. However, in order to stably control the energy control and the voltage vdc of the system, it is necessary for two power converters to perform control in cooperation with each other, and a control device that can simultaneously manage the first converter circuit and the second converter circuit is required.

Means for Solving the Problems

[0008] One aspect of the present invention is a power conversion device having three input / output ports, which mutually switches voltage control and current control by using a first switching control for switching to current control using a control command value during voltage control and a second switching control for switching to voltage control using a control command value during current control.

[0009] Here, a first controller that receives an input of a voltage command value and outputs a current control value according to a difference between the measured voltage value and the voltage command value, and a second controller that receives an input of a current command value and the current control value and outputs a control signal according to a difference between a sum of the current command value and the current control value and the measured current value are provided. In the first switching control, it is preferable to hold the current control value generated from the voltage command value by the first controller during voltage control and input it as the current command value, and then switch to current control by fixing the current control value.

[0010] Also, a first controller that receives an input of a voltage command value and outputs a current control value according to a difference between the measured voltage value and the voltage command value, and a second controller that receives an input of a current command value and the current control value and outputs a control signal according to a difference between a sum of the current command value and the current control value and the measured current value are provided. In the second switching control, it is preferable to release the fixed current control value, and then switch to voltage control by inputting an arbitrary voltage command value to the first controller and outputting the current control.

[0011] Also, it is preferable that a DC power supply is connected to at least one DC port among the input / output ports, and a power storage device is connected to at least one DC port among the input / output ports.

[0012] Also, it is preferable that the DC power supply is a power generation source using renewable energy.

[0013] Also, it is preferable that at least one of the first switching control and the second switching control is executed according to at least one of a change in voltage of the DC port to which the DC power supply is connected and a change in the SOC of the power storage device.

[0014] Another aspect of the present invention is a control method for a power conversion device having three input / output ports including a DC port and an AC port, which uses a first switching control for switching to current control using a control command value during voltage control, and a second switching control for switching to voltage control using a control command value during current control, and mutually switches between voltage control and current control.

Advantages of the Invention

[0015] According to the present invention, it is possible to switch between voltage control and current control at an arbitrary timing, and to provide a power conversion device and a control method thereof that can stably operate the system even when power generation using natural energy suddenly changes.

Brief Description of the Drawings

[0016]

Figure 1

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Embodiments for Carrying Out the Invention

[0017] As shown in FIG. 1, the power conversion system in the embodiment of the present invention includes a power conversion circuit 100, a photovoltaic power generation device 102, a generator 104, a power storage device 106, a power system 108, a load 110, and a control circuit 200.

[0018] The power conversion circuit 100 includes at least three input / output ports. One of the three input / output ports is connected to power generation devices such as the photovoltaic power generation device 102 and the generator 104 via a DC grid, another one is connected to a power storage device 106 capable of storing power, and another one is connected to power loads such as the power system 108 and the load 110. The control circuit 200 controls the power conversion circuit 100. However, the connection configuration for the power conversion circuit 100 is not limited to this, and any configuration that switches and uses the control described later in the power conversion circuit 100 may be used.

[0019] FIG. 2 shows a configuration example of the power conversion circuit 100. The same components shown in multiple drawings are denoted by the same reference numerals to simplify the description. Terms indicating directions such as "up", "down", "left", and "right" in this specification indicate the directions in the circuit diagram and do not limit the postures when arranging each member.

[0020] The power conversion circuit 100 is a three-port power conversion device having three input / output ports. The power conversion circuit 100 includes a power conversion circuit 10 and a capacitor-split type power conversion circuit 20.

[0021] The power conversion circuit 10 includes an X-phase switching arm 12X, a Y-phase switching arm 12Y, a capacitor C0, a primary winding 18, a positive terminal 14p, and a negative terminal 14n.

[0022] The X-phase switching arm 12X includes switching elements S5 and S6 connected in series. The switching arm 12Y includes switching elements S7 and S8 connected in series. For each switching element, an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) can be used. When an IGBT is used as the switching element, the series connection of two IGBTs means that the collector terminal of one IGBT is connected to the emitter terminal of the other IGBT. When a MOSFET is used as the switching element, the series connection of two MOSFETs means that the drain terminal of one MOSFET is connected to the source terminal of the other MOSFET. Also, each switching element includes a diode. When an IGBT is used as the switching element, the anode terminal is connected to the emitter terminal, and the cathode terminal is connected to the collector terminal. When a MOSFET is used as the switching element, the anode terminal is connected to the source terminal, and the cathode terminal is connected to the drain terminal.

[0023] In the following description, the X-phase switching arm 12X and the Y-phase switching arm 12Y are referred to as the switching arms 12X and 12Y, respectively. The switching arms 12X and 12Y are connected in parallel. That is, the terminal on the side opposite to the switching element S6 of the switching element S5 (the upper terminal) and the terminal on the side opposite to the switching element S8 of the switching element S7 (the upper terminal) are connected. Also, the terminal on the side opposite to the switching element S5 of the switching element S6 (the lower terminal) and the terminal on the side opposite to the switching element S7 of the switching element S8 (the lower terminal) are connected.

[0024] A capacitor C0 is connected in parallel to the switching arms 12X and 12Y. That is, the capacitor C0 is connected between the two parallel connection points of the switching arms 12X and 12Y. The upper parallel connection point of the switching arms 12X, 12Y, and the capacitor C0 is connected to the positive terminal 14p, and the lower parallel connection point of the switching arms 12X, 12Y, and the capacitor C0 is connected to the negative terminal 14n. A primary winding 18 is connected between the connection point of the switching elements S5 and S6 and the connection point of the switching elements S7 and S8.

[0025] Regarding the points that IGBTs, MOSFETs, etc. are used for each switching element, the points that each switching element includes a diode, the definition of the series connection of the switching elements, and the definition of the parallel connection of the switching arms, the same applies to the following switching elements.

[0026] The capacitor-split type power conversion circuit 20 includes a U-phase switching arm 26U, a V-phase switching arm 26V, a capacitor arm C, a secondary winding 22, a reactor L, a positive terminal 24p, and a negative terminal 24n.

[0027] The U-phase switching arm 26U includes switching elements S1 and S2 (the first switching element and the second switching element) connected in series. The V-phase switching arm 26V includes switching elements S3 and S4 (the third switching element and the fourth switching element) connected in series. The capacitor arm C includes an upper capacitor Cu and a lower capacitor Cd (the first capacitor and the second capacitor) connected in series. The U-phase switching arm 26U, the V-phase switching arm 26V, and the capacitor arm C are connected in parallel. The upper parallel connection point and the lower parallel connection point of the U-phase switching arm 26U, the V-phase switching arm 26V, and the capacitor arm C are connected to the positive terminal 24p and the negative terminal 24n, respectively.

[0028] A secondary winding 22 is connected between the connection point of the switching elements S1 and S2 and the connection point of the switching elements S3 and S4. The secondary winding 22 is magnetically coupled to the primary winding 18 and constitutes a transformer together with the primary winding 18. A reactor L is connected between a tap at an intermediate point of the conductor constituting the secondary winding 22 and the connection point of the upper capacitor Cu and the lower capacitor Cd. The tap may be a center tap at the midpoint of the conductor constituting the secondary winding 22.

[0029] The power conversion circuit 100 further includes a reactor L1, a second port capacitor C2, a second port positive terminal 16p, and a second port negative terminal 16n.

[0030] The lower parallel connection point of the switching arm 12X, the switching arm 12Y, and the capacitor C0 is connected to the second port negative terminal 16n in addition to the negative terminal 14n. One end of the reactor L1 is connected to the tap of the primary winding 18, and the other end of the reactor L1 is connected to the second port positive terminal 16p. A second port capacitor C2 is connected between the second port positive terminal 16p and the second port negative terminal 16n.

[0031] In the case of the configuration of the power supply system shown in FIG. 1, power generation devices such as the photovoltaic power generation device 102 and the generator 104 are connected between the positive terminal 14p and the negative terminal 14n of the power conversion circuit 100 via a DC grid. A power storage device 106 is connected between the second port positive terminal 16p and the second port negative terminal 16n. Power loads such as the power system 108 and the load 110 are connected between the positive terminal 24p and the negative terminal 24n.

[0032] FIG. 3 shows another example of the power conversion circuit 100. In this example, an example of a 3-port / 2-port type power conversion circuit 100 is shown. The power conversion circuit 100 includes power converters 20a to 20c and a three-phase power conversion device 30. Each of the power converters 20a to 20c has the same configuration as the capacitor-split type power conversion circuit 20 shown in FIG. 2 and performs the same switching operation.

[0033] The three-phase power conversion device 30 includes switching arms 32A to 32C, primary windings 18a to 18c, reactors La to Lc, capacitors C3 and C4, positive terminals 36p and 38p, and negative terminals 36n and 38n. The switching arm 32A includes switching elements Sap and San connected in series. The switching arm 32B includes switching elements Sbp and Sbn connected in series. The switching arm 32C includes switching elements Scp and Scn connected in series.

[0034] The switching arms 32A to 32C and the capacitor C3 are connected in parallel. The upper parallel connection points of the switching arms 32A to 32C and the capacitor C3 are connected to the positive terminal 36p, and the lower parallel connection points of the switching arms 32A to 32C and the capacitor C3 are connected to the negative terminal 36n. A primary winding 18a is connected between the connection points of the switching elements Sap and San and the connection points of the switching elements Sbp and Sbn. A primary winding 18b is connected between the connection points of the switching elements Sbp and Sbn and the connection points of the switching elements Scp and Scn. A primary winding 18c is connected between the connection points of the switching elements Scp and Scn and the connection points of the switching elements Sap and San.

[0035] One end of the reactor La is connected to a tap of the primary winding 18a. One ends of the reactor Lb and the reactor Lc are connected to a tap of the primary winding 18b and a tap of the primary winding 18c, respectively. The other ends of the reactors La to Lc are connected to the positive terminal 38p. The lower parallel connection point of the switching arms 32A to 32C and the capacitor C3 is connected not only to the negative terminal 36n but also to the negative terminal 38n. A capacitor C4 is connected between the positive terminal 38p and the negative terminal 38n.

[0036] In the case of the configuration of the power supply system shown in FIG. 1, power generation devices such as a solar power generation device 102 and a generator 104 are connected between the positive terminal 36p and the negative terminal 36n of the power conversion circuit 100 via a DC grid. A power storage device 106 is connected between the positive terminal 38p and the negative terminal 38n. Power loads such as a three-phase power system 108 and a three-phase load 110 are connected between the positive terminal 24p and the negative terminal 24n.

[0037] In this embodiment, the solar power generation device 102 is used, but other types of power generation devices that utilize renewable energy such as natural energy may also be used.

[0038] FIG. 4 shows the configuration of a control circuit 200 that controls the operation of the power conversion circuit 100. The control circuit 200 includes a first PI controller 40 and a second PI controller 42. The control circuit 200 controls the power conversion circuit 100 by switching between two states of voltage control and current control.

[0039] FIG. 5 shows a control method by the control circuit 200. FIG. 5(a) shows a control method when the power generation amount of the photovoltaic power generation device 102 decreases, and FIG. 5(b) shows a control method when the power generation amount of the photovoltaic power generation device 102 increases. As shown in FIG. 5(a), when the power generation amount of the photovoltaic power generation device 102 decreases, the photovoltaic power generation device 102 switches from current control for generating voltage to voltage control for the energy storage device 106 to generate voltage. Also, as shown in FIG. 5(b), when the power generation amount of the photovoltaic power generation device 102 increases, the energy storage device 106 switches from voltage control for generating voltage to current control for the photovoltaic power generation device 102 to generate voltage.

[0040] When the power generation amount of the photovoltaic power generation device 102 changes suddenly, the voltage Vdc2 of the DC grid fluctuates. Therefore, by using the fluctuation of the voltage Vdc2, the voltage control and the current control are switched based on the value of the voltage Vdc2. When the power generation by the photovoltaic power generation device 102 suddenly decreases, the voltage Vdc2 decreases, so the voltage control is switched to use the energy of the energy storage device 106 to generate the voltage Vdc2. Thereby, power can be provided from the energy storage device 106 to the load. On the other hand, when the power generation by the photovoltaic power generation device 102 suddenly increases, since the photovoltaic power generation device 102 can generate the voltage Vdc2, the current control is applied. When there is an excess in the generated power of the photovoltaic power generation device 102, the energy storage device 106 can be charged by the current control.

[0041] Also, as shown in FIG. 6, control may be performed according to the SOC of the power storage device 106. If charging continues when the SOC of the power storage device 106 is high, overcharging occurs, which causes deterioration of the power storage device 106 and ignition. Therefore, when the SOC of the power storage device 106 is equal to or higher than the switching SOC reference value, it is necessary to actively discharge the energy stored in the power storage device 106, so the control is switched from current control to voltage control. When the SOC of the power storage device 106 is less than the switching SOC reference value, since it is necessary to charge and discharge the power storage device 106, the control is switched from voltage control to current control. By doing so, the storage battery can be charged and discharged safely.

[0042] During voltage control, the first PI controller 40 and the second PI controller 42 are combined, and the control circuit 200 functions as a voltage control circuit 204. The difference between the voltage command value Vdc2_ref for the DC grid and the measured voltage value Vdc2 of the DC grid is input to the first PI controller 40. The first PI controller 40 outputs a first control signal according to the input value. The difference between the first control signal and the current Icd1 flowing through the reactor L1, and further the sum of the difference and the current command value Idc1_ref for the current flowing through the reactor L1 are input to the second PI controller 42. The second PI controller 42 outputs a second control signal according to the input value. The second control signal becomes the duty ratio for controlling the on / off of the switching elements included in the power conversion circuit 10 and the capacitor-divided power conversion circuit 20, or the three-phase power conversion device 30 and the capacitor-divided power conversion circuit 20. By the second control signal, the power conversion circuit 10 and the capacitor-divided power conversion circuit 20, or the three-phase power conversion device 30 and the capacitor-divided power conversion circuit 20 are controlled to perform voltage control.

[0043] During current control, the control circuit 200 functions as a current control circuit 202 by the second PI controller 42. The first control signal is set to 0, and the difference between the current command value Idc1_ref for the current flowing through the reactor L1 and the current Icd1 flowing through the reactor L1 is input to the second PI controller 42. The second PI controller 42 outputs a second control signal according to the input value. The second control signal becomes the duty ratio for controlling the on / off of the switching elements included in the power conversion circuit 10 and the capacitor-divided power conversion circuit 20, or the three-phase power conversion device 30 and the capacitor-divided power conversion circuit 20. By the second control signal, the power conversion circuit 10 and the capacitor-divided power conversion circuit 20, or the three-phase power conversion device 30 and the capacitor-divided power conversion circuit 20 are controlled to perform current control.

[0044] Figure 7 is a timing chart showing the process of switching the power conversion circuit 100 from voltage control to current control. Before performing the switching process, it is assumed that the control circuit 200 is in a state of voltage control using the first PI controller 40 and the second PI controller 42.

[0045] In step S10, the switching signal is changed from a value (0) indicating voltage control to a value (1) indicating current control, and the first control signal (duty1), which is the output of the first PI controller 40 in the control circuit 200, is held. Next, in step S12, the first control signal (duty1), which is the output of the first PI controller 40, is fixed to 0. In step S14, the value of the held first control signal (duty1) is input as the current command value Idc1_ref of the second PI controller 42 in the control circuit 200. As a result, the control circuit 200 switches to current control using only the second PI controller 42. In step S16, an arbitrary current command value Idc1_ref is input to the control circuit 200 that has entered the current control state. As a result, there is no fluctuation in the second control signal (duty2), and the power conversion circuit 100 can be continuously switched from voltage control to current control.

[0046] FIG. 8 is a timing chart showing a process of switching the power conversion circuit 100 from current control to voltage control. Before performing the switching process, it is assumed that the control circuit 200 is in a state of current control using only the second PI controller 42.

[0047] In step S20, the switching signal is changed from a value (1) indicating current control to a value (0) indicating voltage control. Next, in step S22, the state of fixing the output of the first PI controller 40 to 0 is released. In step S24, an arbitrary voltage command value Vdc2_ref is input to the first PI controller 40. In step S26, by the above control, the control circuit 200 switches to voltage control using the first PI controller 40 and the second PI controller 42. As a result, there is no fluctuation in the second control signal (duty2), and the power conversion circuit 100 can be continuously switched from current control to voltage control.

[0048] The control for continuously switching the power conversion circuit 100 from current control to voltage control, or from voltage control to current control, can be applied in the following situations.

[0049] As a first situation, in the configuration example of FIG. 1, when the outputs of the photovoltaic power generation device 102 and the generator 104 are significantly reduced or stopped, the control for switching the power conversion circuit 100 from current control to voltage control is performed. When the outputs of the photovoltaic power generation device 102 and the generator 104 are significantly reduced or stopped, the voltage Vdc2 of the power conversion circuit 100 decreases. When the voltage Vdc2 decreases, it becomes impossible to sufficiently supply power from the power storage device 106 to the power system 108 and the load 110. As a result, the utilization rate of the power storage device 106 decreases, and its power cannot be fully utilized. Therefore, by switching the power conversion circuit 100 from current control to voltage control, the voltage Vdc2 of the power conversion circuit 100 can be generated, and the power conversion circuit 100 can be controlled so that the power supply from the power storage device 106 is not interrupted.

[0050] As a second situation, in the configuration example of FIG. 1, when the SOC (State of Charge) of the power storage device 106 becomes high, control is performed to switch the power conversion circuit 100 from current control to voltage control. When the SOC of the power storage device 106 becomes high, if charging of the power storage device 106 is continued, overcharging will occur, which may cause deterioration of the power storage device 106 or cause an abnormality in the power storage device 106. When the SOC of the power storage device 106 is high, since it is desired to actively discharge the energy of the power storage device 106, by applying control to switch the power conversion circuit 100 from current control to voltage control, it is possible to surely change to voltage control in which power is discharged from the power storage device 106.

[0051] As a third situation, when the output of the solar power generation device 102 and the generator 104 decreases or stops at night or during a disaster, and then the solar power generation device 102 or the generator 104 recovers, control is performed to switch the power conversion circuit 100 from voltage control to current control. At night or during a disaster, control is performed so that the voltage Vdc2 of the power conversion circuit 100 is maintained by the power storage device 106 by voltage control in order to supply power to the power system 108 and the load 110. Then, at the timing when the solar power generation device 102 starts generating power or the generator 104 recovers, control to switch the power conversion circuit 100 from voltage control to current control is applied.

[0052] However, these situations are merely examples, and the control by the power conversion circuit 100 and the control circuit 200 is not limited to these.

[0053] FIGS. 9 and 10 show a power conversion circuit 300 and a power conversion circuit 302 to which the power conversion circuit 100 in the present embodiment is applied as a circuit capable of generating three-phase alternating current.

[0054] The power conversion circuit 300 shown in Fig. 9 has a configuration in which inverters 50a, 50b, and 50c are further connected to each of the power converters 20a, 20b, and 20c in the configuration shown in Fig. 3. Also, the power conversion circuit 302 shown in Fig. 10 forms a converter 304 by providing switching elements between the phases of the secondary winding 22 of the three-phase power conversion device 30 shown in Fig. 3, and further connects an inverter 306 by providing switching elements to the converter 304.

[0055] In the configurations of these power conversion circuits 300 and 302 as well, similar to the power conversion circuit 100 shown in Figs. 2 and 3, control for switching between voltage control and current control can be applied.

[0056] The operation of the power conversion circuit 100 was confirmed using the configuration shown in Fig. 1. In the operation confirmation, a first DC power supply simulating a storage battery was connected instead of the energy storage device 106, and a second DC power supply simulating solar power generation was connected instead of the generator 104. The output of the first DC power supply was set to 175V, and the output of the second DC power supply was set to 360V. When the power conversion circuit 100 was voltage-controlled, the command value of the DC grid voltage was set to 370V.

[0057] Fig. 11 shows the experimental results when control for switching the power conversion circuit 100 from voltage control to current control was applied. The timing at which the DC grid voltage changed (370V → 360V) is the timing at which the control switched from voltage control to current control. At that time, none of the other voltages and currents became unstable, and the control switched stably and continuously from voltage control to current control.

[0058] Fig. 12 shows the experimental results when control for switching the power conversion circuit 100 from current control to voltage control was applied. Similar to Fig. 11, the timing at which the DC grid voltage changed (360V → 370V) is the timing at which the control switched from current control to voltage control. At that time, none of the other voltages and currents became unstable, and the control switched stably and continuously from current control to voltage control.

[0059] As described above, it was confirmed that stable control is performed in both the switching from voltage control to current control and the switching from current control to voltage control.

[0060] FIG. 13 shows a comparison of the power conversion circuit 100 in the prior art and the present embodiment. Prior art 1 refers to Japanese Patent Application Laid-Open No. 2022-21371, and prior art 2 refers to Japanese Patent Application Laid-Open No. 2022-133626.

[0061] In prior art 1, since the control of the storage battery is performed using communication with the management device, it takes time for the response of the storage battery control when the power generation output of a solar cell or the like suddenly changes. The responsiveness depends on the communication environment and is considered to take time from several seconds to minutes. Next, in prior art 2, since the control of the storage battery can be determined by detecting the voltage vdc, the management device becomes unnecessary, and the responsiveness of the storage battery control can be increased to the order of several ms. However, in prior art 2, since there are two control target circuits, a control device for managing the two circuits is required. In contrast, in the configuration according to the present embodiment, the management device is unnecessary as in prior art 2, and furthermore, since there is only one control target circuit, the control of the storage battery can be realized at a higher speed up to the order of several μs.

[0062] [Configuration of the present invention] [Configuration 1] A power conversion device having three input / output ports, characterized in that voltage control and current control are mutually switched using a first switching control for switching to current control using a control command value during voltage control and a second switching control for switching to voltage control using a control command value during current control. [Configuration 2] The power conversion device according to Configuration 1, comprising a first controller that receives an input of a voltage command value and outputs a current control value according to a difference between the measured voltage value and the voltage command value, and a second controller that receives an input of a current command value and the current control value and outputs a control signal according to a difference between the sum of the current command value and the current control value and the measured current value, and comprising. In the first switching control, during voltage control, the current control value generated from the voltage command value by the first controller is held and input as the current command value, and then the current control is switched by fixing the current control value. A power conversion device characterized by this. [Configuration 3] The power conversion device according to Configuration 1 or 2, A first controller that receives an input of a voltage command value and outputs a current control value corresponding to a difference between the measured voltage value and the voltage command value, A second controller that receives an input of a current command value and the current control value, and outputs a control signal corresponding to a difference between the sum of the current command value and the current control value and the measured current value, Comprising In the second switching control, the fixed current control value is released, and then any voltage command value is input to the first controller to output the current control, thereby switching to voltage control. A power conversion device characterized by this. [Configuration 4] The power conversion device according to any one of Configurations 1 to 3, A DC power supply is connected to at least one DC port among the input / output ports, A power conversion device characterized in that a power storage device is connected to at least one DC port among the input / output ports. [Configuration 5] The power conversion device according to Configuration 4, The DC power supply is a power generation source using renewable energy. A power conversion device characterized by this. [Configuration 6] The power conversion device according to Configuration 4 or 5, At least one of the first switching control and the second switching control is executed in response to at least one of a change in the voltage of the DC port to which the DC power supply is connected and a change in the SOC of the power storage device. A power conversion device characterized by this. [Configuration 7] A control method for a power conversion device including three input / output ports including a DC port and an AC port, A control method for a power conversion device, characterized by mutually switching between voltage control and current control by using a first switching control for switching to current control using a control command value during voltage control and a second switching control for switching to voltage control using a control command value during current control.

Explanation of symbols

[0063] 10 Power conversion circuit, 12X, 12Y Switching arms, 14n Negative terminal, 14p Positive terminal, 18a~18c Primary windings, 20 Capacitor-split type power conversion circuit, 20a~20c Power converters, 22 Secondary winding, 24n Negative terminal, 24p Positive terminal, 26 Switching arm, 30 Three-phase power conversion device, 32A~32C Switching arms, 36n, 38n Negative terminals, 36p, 38p Positive terminals, 50a, 50b Inverters, 100 Power conversion circuit, 102 Solar power generation device, 104 Generator, 106 Energy storage device, 108 Power system, 110 Load, 200 Control device, 200 Control circuit, 202 Current control circuit, 204 Voltage control circuit, 300 Power conversion circuit, 302 Power conversion circuit, 304 Converter, 306 Inverter.

Claims

1. A power conversion device having three input / output ports, characterized in that voltage control and current control are mutually switched using first switching control for switching to current control using a control command value during voltage control and second switching control for switching to voltage control using a control command value during current control.

2. The power conversion device according to claim 1, comprising a first controller that receives an input of a voltage command value and outputs a current control value corresponding to a difference between a measured voltage value and the voltage command value, and a second controller that receives inputs of a current command value and the current control value and outputs a control signal corresponding to a difference between a sum of the current command value and the current control value and a measured current value, wherein in the first switching control, the current control value generated from the voltage command value by the first controller during voltage control is held and input as the current command value, and then switching to current control is performed by fixing the current control value.

3. The power conversion device according to claim 1 or 2, comprising a first controller that receives an input of a voltage command value and outputs a current control value corresponding to a difference between a measured voltage value and the voltage command value, and a second controller that receives inputs of a current command value and the current control value and outputs a control signal corresponding to a difference between a sum of the current command value and the current control value and a measured current value, wherein in the second switching control, the fixed current control value is released, and then any voltage command value is input to the first controller to output the current control, thereby switching to voltage control.

4. The power conversion device according to claim 1, wherein a DC power supply is connected to at least one DC port of the input / output ports, and a power storage device is connected to at least one DC port of the input / output ports.

5. The power conversion device according to claim 4, wherein the DC power supply is a power generation source using renewable energy.

6. The power conversion device according to claim 4 or 5, wherein at least one of the first switching control and the second switching control is executed in response to at least one of a change in voltage of the DC port to which the DC power supply is connected and a change in the SOC of the power storage device.

7. A control method for a power conversion device including three input / output ports including a DC port and an AC port, characterized in that voltage control and current control are mutually switched by using first switching control for switching to current control using a control command value during voltage control and second switching control for switching to voltage control using a control command value during current control.

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