Power converter and control method for power converter

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 the 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 system (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 that generates power using natural energy. When the power generation device and the PCS are disconnected from the power system, a part of the operation mode of the PCS is set to a voltage control mode in which the output voltage is controlled to the target voltage, and the remaining part of the operation mode of the PCS is set to a current control mode in which the output current is controlled to the 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 failure to start charging 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 charge and discharge 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

[0005] Conventional technologies typically employ a control system that, in order to stabilize the load during sudden changes in power generation from solar cells, etc., supplies power from the battery to the load when power generation decreases sharply, and charges the battery with surplus power when power generation increases sharply.

[0006] In the prior art disclosed in Patent Document 1, each PCS controls the charging and discharging amount of the battery based on commands from a management device. In this system, when power generation from natural energy sources such as solar cells changes suddenly, the process proceeds as follows: measurement by a measuring device, calculation processing by a management device, transmission to an evaluation function setting unit, transmission to a command value distribution unit, and then each PCS performs battery control. In such a configuration, there is a problem that the responsiveness of the battery control deteriorates due to the time required for communication and the time required for processing in the management device.

[0007] Furthermore, in the prior art disclosed in Patent Document 2, when power generation from natural energy sources such as solar cells changes suddenly, each power converter performs charging and discharging of the storage battery according to the information. Therefore, communication between the management device and the power converter is omitted, and faster control of the storage battery becomes possible. However, in order to stably control the energy control and voltage vdc of the system, it is necessary for the two power converters to cooperate in their control, and a control device that can simultaneously manage the first converter circuit and the second converter circuit is required. [Means for solving the problem]

[0008] One aspect of the present invention is a power converter equipped with three input / output ports, characterized in that it 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.

[0009] The system includes a first controller that receives a voltage command value and outputs a current control value corresponding to the difference between the measured voltage value and the voltage command value, and a second controller that receives a current command value and the current control value and outputs a control signal corresponding to the difference between the sum of the current command value and the current control value and the measured current value. 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] Furthermore, the system includes a first controller that receives a voltage command value and outputs a current control value corresponding to the difference between the measured voltage value and the voltage command value, and a second controller that receives a current command value and the current control value and outputs a control signal corresponding to the difference between the sum of the current command value and the current control value and the measured current value. 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 to output the current control.

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

[0012] Furthermore, it is preferable that the DC power supply is a power source that utilizes renewable energy.

[0013] Furthermore, it is preferable that at least one of the first switching control and the second switching control is performed in response to at least one of the changes in the voltage of the DC port to which the DC power supply is connected and the changes in the State of Charge (SOC) of the energy storage device.

[0014] Another aspect of the present invention is a control method for a power converter having three input / output ports, including DC ports and AC ports, characterized in that it 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. [Effects of the Invention]

[0015] According to the present invention, it is possible to switch between voltage control and current control at any timing, and to provide a power conversion device and control method thereof that can operate the system stably even when there is a sudden change in power generation using natural energy. [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows the configuration of a power system in an embodiment of the present invention. [Figure 2] This figure shows the configuration of a power conversion circuit in an embodiment of the present invention. [Figure 3] This figure shows the configuration of a power conversion circuit in an embodiment of the present invention. [Figure 4] This figure shows the configuration of the control circuit of a power conversion circuit in an embodiment of the present invention. [Figure 5] This figure illustrates the switching control between voltage control and current control in an embodiment of the present invention. [Figure 6] This figure illustrates the switching control between voltage control and current control in an embodiment of the present invention. [Figure 7] This figure shows a timing chart illustrating the switching process from voltage control to current control in an embodiment of the present invention. [Figure 8] This figure shows a timing chart illustrating the switching process from current control to voltage control in an embodiment of the present invention. [Figure 9] This figure shows another example of the configuration of a power conversion circuit in an embodiment of the present invention. [Figure 10] It is a diagram showing another example of the configuration of the power conversion circuit in the embodiment of the present invention. [Figure 11] It is a diagram showing the result of operation confirmation of the power conversion circuit in the embodiment of the present invention. [Figure 12] It is a diagram showing the result of operation confirmation of the power conversion circuit in the embodiment of the present invention. [Figure 13] It is a diagram showing a comparison between the prior art and the power conversion circuit in the embodiment of the present invention.

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 has 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 may be used as long as the control described later in the power conversion circuit 100 is switched.

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

[0020] The power conversion circuit 100 is a three-port power converter equipped with three input / output ports. The power conversion circuit 100 comprises 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. Each switching element can be an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). When IGBTs are used as switching elements, two IGBTs are connected in series, meaning the collector terminal of one IGBT is connected to the emitter terminal of the other IGBT. When MOSFETs are used as switching elements, two MOSFETs are connected in series, meaning the drain terminal of the other MOSFET is connected to the source terminal of the other MOSFET. Each switching element also includes a diode. When IGBTs are used as switching elements, the anode terminal is connected to the emitter terminal and the cathode terminal is connected to the collector terminal. When MOSFETs are used as switching elements, the anode terminal is connected to the source terminal and the cathode terminal is connected to the drain terminal.

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

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

[0025] The same applies to the following switching elements, including the use of IGBTs, MOSFETs, etc., in each switching element, the inclusion of diodes in each switching element, the definition of series connection of switching elements, and the definition of parallel connection of switching arms.

[0026] The capacitor-split power conversion circuit 20 comprises 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 comprises switching elements S1 and S2 (first switching element and second switching element) connected in series. The V-phase switching arm 26V comprises switching elements S3 and S4 (third switching element and fourth switching element) connected in series. The capacitor arm C comprises an upper capacitor Cu and a lower capacitor Cd (first capacitor and 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 and lower parallel connection points 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 points of switching elements S1 and S2 and the connection points of switching elements S3 and S4. The secondary winding 22 is magnetically coupled to the primary winding 18 and together with the primary winding 18 constitutes a transformer. A reactor L is connected between a tap located at an intermediate point in the conductor constituting the secondary winding 22 and the connection points of the upper capacitor Cu and the lower capacitor Cd. The tap may be a center tap located 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 points of switching arm 12X, switching arm 12Y, and capacitor C0 are connected to the negative terminal 14n as well as the second port negative terminal 16n. One end of reactor L1 is connected to the tap of primary winding 18, and the other end of reactor L1 is connected to the second port positive terminal 16p. The second port capacitor C2 is connected between the second port positive terminal 16p and the second port negative terminal 16n.

[0031] In the power supply system configuration shown in Figure 1, a power generation device such as a photovoltaic power generation device 102 and a generator 104 is 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. A power load such as a power grid system 108 and a load 110 is connected between the positive terminal 24p and the negative terminal 24n.

[0032] Figure 3 shows another example of the power conversion circuit 100. This example shows a 3-port / 2-port type power conversion circuit 100. The power conversion circuit 100 comprises power converters 20a to 20c and a 3-phase power converter 30. Each of the power converters 20a to 20c has the same configuration as the capacitor-split type power conversion circuit 20 shown in Figure 2 and performs the same switching operation.

[0033] The three-phase power converter 30 comprises 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. Switching arm 32A comprises switching elements Sap and San connected in series. Switching arm 32B comprises switching elements Sbp and Sbn connected in series. Switching arm 32C comprises switching elements SCP and Scn connected in series.

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

[0035] One end of reactor La is connected to the tap of primary winding 18a. One end of reactor Lb and one end of reactor Lc are connected to the taps of primary winding 18b and primary winding 18c, respectively. The other ends of reactors La to Lc are connected to positive terminal 38p. The lower parallel connection point of switching arms 32A to 32C and capacitor C3 is connected to negative terminal 36n as well as negative terminal 38n. Capacitor C4 is connected between positive terminal 38p and negative terminal 38n.

[0036] In the power supply system configuration shown in Figure 1, a power generation device such as a photovoltaic power generation device 102 and a generator 104 is 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. A power load such as a three-phase power grid system 108 and a three-phase load 110 is connected between the positive terminal 24p and the negative terminal 24n.

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

[0038] Figure 4 shows the configuration of the control circuit 200 that controls the operation of the power conversion circuit 100. The control circuit 200 comprises 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: voltage control and current control.

[0039] Figure 5 shows the control method by the control circuit 200. Figure 5(a) shows the control method when the power generation of the solar power generation device 102 decreases, and Figure 5(b) shows the control method when the power generation of the solar power generation device 102 increases. As shown in Figure 5(a), when the power generation of the solar power generation device 102 decreases, the control switches from current control where the solar power generation device 102 generates voltage to voltage control where the energy storage device 106 generates voltage. Also, as shown in Figure 5(b), when the power generation of the solar power generation device 102 increases, the control switches from voltage control where the energy storage device 106 generates voltage to current control where the solar power generation device 102 generates voltage.

[0040] When the amount of power generated by the solar power generation system 102 changes rapidly, the voltage Vdc2 of the DC grid fluctuates. Therefore, the system uses the fluctuation of the voltage Vdc2 to switch between voltage control and current control based on the value of the voltage Vdc2. If the power generation by the solar power generation system 102 decreases rapidly, the voltage Vdc2 decreases, so the system switches to voltage control using the energy of the energy storage device 106 to generate the voltage Vdc2. This allows power to be supplied from the energy storage device 106 to the load. On the other hand, if the power generation by the solar power generation system 102 increases rapidly, the solar power generation system 102 can generate the voltage Vdc2, so current control is applied. If there is a surplus of power generated by the solar power generation system 102, the energy storage device 106 can be charged by current control.

[0041] Furthermore, as shown in Figure 6, control may be performed according to the State of Charge (SOC) of the energy storage device 106. If charging continues when the SOC of the energy storage device 106 is high, it will result in overcharging, which can cause deterioration of the energy storage device 106 and lead to fire. Therefore, when the SOC of the energy storage device 106 is above the switching SOC reference value, it is necessary to actively discharge the energy stored in the energy storage device 106, so the control is switched from current control to voltage control. When the SOC of the energy storage device 106 is below the switching SOC reference value, it is necessary to charge and discharge the energy storage device 106, so the control is switched from voltage control to current control. In this way, the battery can be safely charged and discharged.

[0042] During voltage control, the first PI controller 40 and the second PI controller 42 are combined to make the control circuit 200 function 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 this input value. The difference between the first control signal and the current Icd1 flowing through the reactor L1, and the sum of this difference and the current command value Idc1_ref for the current 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 this input value. The second control signal becomes the duty cycle that controls the on / off state of the switching elements included in the power conversion circuit 10 and the capacitor-split type power conversion circuit 20, or the three-phase power converter 30 and the capacitor-split type power conversion circuit 20. The second control signal controls the power conversion circuit 10 and the capacitor-split type power conversion circuit 20, or the three-phase power converter 30 and the capacitor-split type power conversion circuit 20, to operate under voltage control.

[0043] During current control, the control circuit 200 functions as a current control circuit 202 via 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 reactor L1 and the current Icd1 flowing through reactor L1 is input to the second PI controller 42. The second PI controller 42 outputs a second control signal according to this input value. The second control signal becomes the duty cycle that controls the on / off state of the switching elements included in the power conversion circuit 10 and the capacitor-split type power conversion circuit 20, or the three-phase power converter 30 and the capacitor-split type power conversion circuit 20. The second control signal controls the power conversion circuit 10 and the capacitor-split type power conversion circuit 20, or the three-phase power converter 30 and the capacitor-split type power conversion circuit 20, so that they are in current control mode.

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

[0045] In step S10, the switching signal is changed from a value indicating voltage control (0) to a value indicating current control (1), 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 held value of the 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, which is now in 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] Figure 8 is a timing chart showing the process of switching the power conversion circuit 100 from current control to voltage control. Before this switching process, the control circuit 200 is assumed to be in a current control state 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 in which the output of the first PI controller 40 was fixed 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, as a result of the above control, the control circuit 200 switches to voltage control using the first PI controller 40 and the second PI controller 42. This allows the power conversion circuit 100 to be continuously switched from current control to voltage control without fluctuations in the second control signal (duty2).

[0048] This control method, which continuously switches 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] In the first scenario, in the configuration example shown in Figure 1, if the output of the solar power generation device 102 and the generator 104 drops significantly or stops, the power conversion circuit 100 is controlled to switch from current control to voltage control. When the output of the solar power generation device 102 and the generator 104 drops significantly or stops, the voltage Vdc2 of the power conversion circuit 100 drops. When the voltage Vdc2 drops, the energy storage device 106 can no longer supply sufficient power to the power grid system 108 and the load 110. As a result, the utilization rate of the energy 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 power conversion circuit 100 can be controlled to generate a voltage Vdc2 and prevent the power supply from the energy storage device 106 from being interrupted.

[0050] In the second scenario, in the configuration example shown in Figure 1, if the State of Charge (SOC) of the energy storage device 106 becomes high, the power conversion circuit 100 is switched from current control to voltage control. If the SOC of the energy storage device 106 becomes high, continuing to charge the energy storage device 106 will result in overcharging, which can cause deterioration of the energy storage device 106 or lead to malfunctions in the energy storage device 106. When the SOC of the energy storage device 106 is high, it is desirable to actively discharge the energy from the energy storage device 106. By applying control to switch the power conversion circuit 100 from current control to voltage control, it is possible to reliably change to voltage control that discharges from the energy storage device 106.

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

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

[0053] Figures 9 and 10 show power conversion circuits 300 and 302, which apply the power conversion circuit 100 in this embodiment as a circuit capable of generating three-phase alternating current.

[0054] The power conversion circuit 300 shown in Figure 9 is configured in the same way as shown in Figure 3, with inverters 50a, 50b, and 50c further connected to power converters 20a, 20b, and 20c, respectively. The power conversion circuit 302 shown in Figure 10 is configured by providing switching elements between the phases of the secondary winding 22 of the three-phase power converter 30 shown in Figure 3 to form a converter 304, and further connecting an inverter 306 to the converter 304 by providing switching elements.

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

[0056] The operation of the power conversion circuit 100 was verified using the configuration shown in Figure 1. For the verification, a first DC power supply simulating a battery was connected in place of the energy storage device 106, and a second DC power supply simulating solar power generation was connected in place 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] Figure 11 shows the experimental results when a control mechanism that switches the power conversion circuit 100 from voltage control to current control is applied. The timing of the switch from voltage control to current control corresponds to the timing when the DC grid voltage changes (370V → 360V). At that time, none of the other voltages and currents became unstable, and the switch from voltage control to current control was performed stably and continuously.

[0058] Figure 12 shows the experimental results when a control mechanism is applied that switches the power conversion circuit 100 from current control to voltage control. Similar to Figure 11, the timing of the switch from current control to voltage control corresponds to the timing when the DC grid voltage changes (360V → 370V). At that time, none of the other voltages or currents became unstable, and the switch from voltage control to current control was stable and continuous.

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

[0060] Figure 13 shows a comparison of the power conversion circuit 100 in the prior art and in this embodiment. Prior art 1 is shown in Japanese Patent Application Publication No. 2022-21371, and prior art 2 is shown in Japanese Patent Application Publication No. 2022-133626.

[0061] In Conventional Technology 1, battery control is performed using communication with a management device, so when the power output of solar cells or other sources changes suddenly, it takes time for the battery control to respond. The response time depends on the communication environment and is thought to take several seconds to several minutes. Next, in Conventional Technology 2, since the battery control decision can be made by detecting the voltage vdc, a management device is not required, and the response time of the battery control can be increased to several milliseconds. However, in Conventional Technology 2, since there are two circuits to be controlled, a control device is required to manage the two circuits. In contrast to these, in the configuration according to this embodiment, a management device is not required, similar to Conventional Technology 2, and furthermore, since there is only one circuit to be controlled, battery control can be achieved at an even faster speed of several microseconds.

[0062] [Structure of the present invention] [Configuration 1] A power converter equipped with three input / output ports, A power conversion device characterized by mutually switching 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. [Configuration 2] The power conversion device described in Configuration 1, A first controller that receives a voltage command value input and outputs a current control value corresponding to the difference between the measured voltage value and the voltage command value, A second controller receives a current command value and the current control value as inputs and outputs a control signal corresponding to the difference between the sum of the current command value and the current control value and the measured current value. Equipped with, In the first switching control, the power converter is characterized in that, 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 device switches to current control by fixing the current control value. [Configuration 3] A power conversion device according to configuration 1 or 2, A first controller that receives a voltage command value input and outputs a current control value corresponding to the difference between the measured voltage value and the voltage command value, A second controller receives a current command value and the current control value as inputs and outputs a control signal corresponding to the difference between the sum of the current command value and the current control value and the measured current value. Equipped with, The power conversion device is characterized in that, in the second switching control, the fixed current control value is released, and then an arbitrary voltage command value is input to the first controller to output the current control, thereby switching to voltage control. [Structure 4] A power conversion device according to any one of items 1 to 3, A DC power supply is connected to at least one of the aforementioned 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. [Composition 5] The power conversion device described in configuration 4, The DC power supply is a power source that utilizes renewable energy, and is a power conversion device characterized by this. [Composition 6] A power conversion device according to configuration 4 or 5, A power conversion device characterized in that at least one of the first switching control and the second switching control is performed in response to at least one of the change in voltage of the DC port to which the DC power supply is connected and the change in the state of charge (SOC) of the energy storage device. [Composition 7] A control method for a power converter having three input / output ports, including a DC port and an AC port, A control method for a power converter, characterized by mutually switching 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. [Explanation of symbols]

[0063] 10 Power conversion circuit, 12X, 12Y switching arm, 14n negative terminal, 14p positive terminal, 18a~18c primary winding, 20 Capacitor-split power conversion circuit, 20a~20c power converter, 22 secondary winding, 24n negative terminal, 24p positive terminal, 26 switching arm, 30 3-phase power converter, 32A~32C switching arm, 36n, 38n negative terminal, 36p, 38p positive terminal, 50a, 50b inverter, 100 Power conversion circuit, 102 Solar power generation device, 104 Generator, 106 Energy storage device, 108 Power grid 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 comprising three input / output ports: a first input / output port to which a power generation device is connected, a second input / output port to which an energy storage device is connected, and a third input / output port to which a power load is connected, A first controller outputs a first control signal duty1 corresponding to the difference between the voltage command value Vdc2_ref of the first input / output port and the measured voltage value Vdc2, A second controller receives a current command value Idc1_ref and a first control signal duty1 for the current flowing through a reactor connected to the second input / output port, and outputs a second control signal duty2 for controlling power conversion between the first input / output port, the second input / output port, and the third input / output port according to the difference between the sum of the current command value Idc1_ref and the first control signal duty1 and the measured current value Idc1 flowing through the reactor. Equipped with, During voltage control, the first switching control involves holding the first control signal duty1, fixing it to 0, and inputting the value of the held first control signal duty1 as the current command value Idc1_ref to the second controller, thereby switching to current control. A power converter characterized by switching between voltage control and current control using a second switching control that, during current control, releases the first control signal duty 1 which is fixed to 0, and inputs the value of the first control signal duty 1 output by the first controller according to the difference between the voltage command value Vdc2_ref and the voltage value Vdc2 as the current command value Idc1_ref to the second controller, thereby switching to voltage control.

2. A power conversion device according to claim 1, The power generation device is a power conversion device characterized by being a power source that utilizes renewable energy.

3. A power conversion device according to claim 1 or 2, A power conversion device characterized in that at least one of the first switching control and the second switching control is performed in response to at least one of a change in the voltage of the first input / output port to which the power generator is connected and a change in the state of charge (SOC) of the energy storage device.

4. A control method for a power converter having three input / output ports: a first input / output port to which a power generator is connected, a second input / output port to which an energy storage device is connected, and a third input / output port to which a power load is connected, The aforementioned power converter is A first controller outputs a first control signal duty1 corresponding to the difference between the voltage command value Vdc2_ref of the first input / output port and the measured voltage value Vdc2, A second controller receives a current command value Idc1_ref and a first control signal duty1 for the current flowing through a reactor connected to the second input / output port, and outputs a second control signal duty2 for controlling power conversion between the first input / output port, the second input / output port, and the third input / output port according to the difference between the sum of the current command value Idc1_ref and the first control signal duty1 and the measured current value Idc1 flowing through the reactor. Equipped with, During voltage control, the first switching control involves holding the first control signal duty1, fixing it to 0, and inputting the value of the held first control signal duty1 as the current command value Idc1_ref to the second controller, thereby switching to current control. A control method for a power converter, characterized by using a second switching control that, during current control, releases the first control signal duty 1 which is fixed to 0, and switches to voltage control by inputting the value of the first control signal duty 1 output by the first controller according to the difference between the voltage command value Vdc2_ref and the voltage value Vdc2 as the current command value Idc1_ref to the second controller.

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