Power conversion system and power storage system

Abstract

To provide a power conversion system and a power storage system that can easily synchronize a switching operation of a distribution board and a power supply operation from a storage battery during autonomous operation.SOLUTION: A power conversion system includes a power converter, a switching switch, and a control circuit for controlling the power converter and the switching switch, and the switching switch receives an input of a control signal from the control circuit and connects the power converter and a commercial power system or opens the connection between the power converter and the commercial power system.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power conversion system and a power storage system. [Background technology]

[0002] There is a known power storage system that is connected to a commercial power grid, operates autonomously during a power grid outage, and supplies power stored in a storage battery to a specific load via a power conversion device. There is also a known power storage system that is connected to a solar power generation system and stores in a storage battery the power generated in excess of the power supplied to the load (i.e., surplus power). A power storage system connected to a solar power generation system can be interconnected to the grid, for example, by supplying the generated power to the commercial power grid depending on the power generation status of the solar power generation system.

[0003] The energy storage system is connected to a distribution board, and supplies power to loads (i.e., standalone operation, etc.) and receives and transmits power to and from the commercial power grid (i.e., grid interconnection) via the distribution board. For example, Patent Document 1 discloses a full-load distribution board that can be easily and safely separated from the energy storage unit during maintenance, etc. This full-load distribution board includes a control unit separate from the power conditioner that controls the energy storage unit, and controls a changeover switch that switches the connection relationship when the commercial power grid experiences a power outage, independently of the power conditioner. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-198204 Summary of the Invention [Problem to be solved by the invention]

[0005] In the configuration disclosed in Patent Document 1, the distribution board operates independently from the power conditioner, making it difficult to synchronize them during a power outage in the commercial power grid (i.e., during stand-alone operation). That is, when the distribution board and the power conditioner each independently detect a power outage in the commercial power grid using a measuring device such as a current transformer, it is difficult to coordinate the timing of switching the distribution board's selector switch (i.e., relay, etc.) and the timing of starting power supply from the storage battery under the control of the power conditioner. If synchronization is insufficient, for example, the power conditioner may start outputting stand-alone power before the selector switch is properly switched. Another problem is the cost involved in providing multiple systems that detect power outages and control their operation.

[0006] Therefore, an object of the present disclosure is to provide a power conversion system and a power storage system that can easily synchronize the switching operation of a distribution board with the power supply operation from a storage battery during autonomous operation. [Means for solving the problem]

[0007] A power conversion system according to an aspect of the present disclosure includes a power converter, a changeover switch, and a control circuit that controls the power converter and the changeover switch, and the changeover switch connects the power converter to a commercial power system or disconnects the power converter from the commercial power system upon receiving a control signal from the control circuit.

[0008] A power storage system according to another aspect of the present disclosure includes the above-described power conversion system and a storage battery, wherein the power converter converts output power of the storage battery into AC power and outputs the AC power. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a power conversion system and a power storage system that can easily synchronize the switching operation of a distribution board with the power supply operation from a storage battery during autonomous operation. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is a block diagram showing the configuration of a power storage system according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a block diagram showing the configuration of a control circuit of the power storage system shown in FIG. [Figure 3] FIG. 3 is a block diagram showing the configuration of the switch control unit shown in FIG. [Figure 4] FIG. 4 is a block diagram showing a path of noise in the power storage system shown in FIG. [Figure 5] FIG. 5 is a block diagram showing the configuration of a power storage system according to the second embodiment of the present disclosure. [Figure 6] FIG. 6 is a circuit diagram showing an example of a noise filter circuit of the power storage system shown in FIG. [Figure 7] FIG. 7 is a circuit diagram different from that of FIG. 6, showing an example of a noise filter circuit of the power storage system shown in FIG. [Figure 8] FIG. 8 is a circuit diagram different from FIGS. 6 and 7, showing an example of a noise filter circuit of the power storage system shown in FIG. [Figure 9] FIG. 9 is a circuit diagram different from those in FIGS. 6 to 8, showing an example of a noise filter circuit in the power storage system shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Description of the embodiments of the present disclosure] First, the contents of the embodiments of the present disclosure will be listed and described. At least some of the embodiments described below may be combined in any manner.

[0012] (1) A power conversion system according to a first aspect of the present disclosure includes a power converter, a changeover switch, and a control circuit that controls the power converter and the changeover switch. The changeover switch connects or disconnects the power converter from the commercial power grid in response to a control signal input from the control circuit. This makes it easy to synchronize the changeover switch's switching operation with the power converter's power supply operation during a power outage in the commercial power grid in a system that supplies battery power from the power converter. The system is also less expensive than systems that separately control the power converter and the changeover switch.

[0013] (2) In the above (1), the power conversion system may further include a noise filter circuit disposed between the changeover switch and the control circuit, and the control signal output from the control circuit may be input to the changeover switch via the noise filter circuit, thereby reducing noise generated in conjunction with the operation of the power converter and output to the outside via the changeover switch.

[0014] (3) In the above (2), the control circuit may include a photocoupler, and the control signal may be input to the noise filter circuit via the photocoupler, thereby further reducing noise generated during operation of the power converter and output to the outside via the changeover switch.

[0015] (4) In the above (2) or (3), the noise filter circuit may include an LC filter circuit, which allows the cutoff frequency band to be appropriately set and inexpensively realizes the function of reducing noise generated by the operation of the power converter and output to the outside via the changeover switch.

[0016] (5) In the above (2) or (3), the noise filter circuit may include a low-pass filter circuit, which can effectively reduce noise that occurs during operation of the power converter and is output to the outside via the changeover switch.

[0017] (6) In the above (5), the cutoff frequency of the low-pass filter circuit is 150 kHz or more and 250 kHz or less. This makes it possible to more effectively reduce noise that is generated during operation of the power converter and output to the outside via the changeover switch.

[0018] (7) In any one of (1) to (6) above, the power conversion system can further include a housing that houses the changeover switch and the control circuit. This allows the power conversion system to be formed as an integrated unit, making it easier to handle and reducing installation space. Furthermore, by housing the changeover switch and the control circuit in a single housing, it is possible to prevent, for example, noise contained in the control signal output from the control circuit from being output outside the housing and affecting the surroundings of the power conversion system.

[0019] (8) In any one of (1) to (7) above, the power converter includes a DC / DC conversion unit and a DC / AC conversion unit, and the changeover switch connects the DC / AC conversion unit to the commercial power grid or disconnects the DC / AC conversion unit from the commercial power grid in response to a control signal. This allows power to be supplied to the load when the commercial power grid experiences a power outage.

[0020] (9) A power storage system according to a second aspect of the present disclosure includes any one of the power conversion systems (1) to (8) above and a storage battery, and the power converter converts the output power of the storage battery into AC power and outputs it. This allows power from the storage battery to be supplied to a load during a power outage in the commercial power grid, and makes it easy to synchronize the switching operation of the changeover switch with the power supply operation of the power converter. Furthermore, this system is less expensive than a system that separately controls the power converter and the changeover switch.

[0021] [Details of the embodiments of the present disclosure] In the following embodiments, the same components are denoted by the same reference numerals, and have the same names and functions. Therefore, detailed description thereof will not be repeated.

[0022] [First embodiment] (Overall composition) 1, a power storage system 100 according to the first embodiment of the present disclosure includes a power conversion unit 102, a distribution board unit 104, a storage battery 106, and a switch 108. The storage battery 106 is a rechargeable storage battery such as a lithium-ion secondary battery. The switch 108 is for connecting a power generation device (not shown) such as a solar power generation system (e.g., a solar power generation panel) to the power storage system 100. When the switch 108 is closed, power supplied from the power generation device is supplied to the power storage system 100 (i.e., the power conversion unit 102). When the switch 108 is opened, the power generation device is disconnected from the power storage system 100.

[0023] The power conversion unit 102 includes an input filter 120, DC / DC converters (i.e., DC / DC conversion units) 122 and 124, a capacitor 126, a DC / AC converter 128, an output filter 130, and a control circuit 132. The input filter 120 reduces noise superimposed on the power (i.e., DC power) supplied from the storage battery 106 and the switch 108, and outputs the power to the DC / DC converters 122 and 124, respectively. Each of the DC / DC converters 122 and 124 converts an input DC voltage into a predetermined DC voltage and outputs the converted voltage. Specifically, the DC / DC converters 122 and 124 convert the input DC voltage into a voltage according to the input power specifications of the DC / AC converter (i.e., DC / AC conversion unit) 128, which will be described later, and outputs the converted voltage.

[0024] DC / DC converters 122 and 124 are connected in parallel to capacitor 126. In Fig. 1, the wiring for transmitting power between each unit is represented by a single solid line, but in reality there are two wirings. That is, of the two output wirings of DC / DC converter 122, one wiring is connected to one terminal of capacitor 126, and the other wiring is connected to the other terminal. The two output wirings of DC / DC converter 124 are similarly connected to both terminals of capacitor 126.

[0025] Both DC / DC converters 122 and 124 can convert and output power in both directions. Therefore, if a solar power generation system is connected to switch 108, the power generated by the solar power generation system is supplied to storage battery 106 via DC / DC converters 124 and 122 and stored in storage battery 106.

[0026] Of the two input wirings of the DC / AC converter 128, one wiring is connected to one terminal of the capacitor 126, and the other wiring is connected to the other terminal. The DC / AC converter 128 converts input DC power (i.e., DC voltage) into AC power (i.e., AC voltage) and outputs it to the output filter 130. The DC / AC converter 128 includes a switching element. The DC / AC converter 128 is realized by a bridge circuit configured with semiconductor switching elements such as FETs (Field Effect Transistors). High-frequency noise is generated with the operation of the DC / AC converter 128, i.e., the on / off operation of the switching elements, and is superimposed on the output power (i.e., first output voltage V1) of the DC / AC converter 128. If the output power of the DC / AC converter 128 is supplied to the outside as is, it will affect the load to which the power is supplied. The output filter 130 removes noise superimposed on the input AC voltage (i.e., the first output voltage V1) and outputs it to the distribution board unit 104 as the second output voltage V2 without changing the AC voltage level (e.g., peak voltage).

[0027] The control circuit 132 outputs a first control signal S1 to the DC / AC converter 128 via a first control line 134, and controls the power conversion operation of the DC / AC converter 128 (for example, the on / off operation of a switching element included in the DC / AC converter 128). The control circuit 132 also outputs a second control signal S2 to the changeover switch 150 via a second control line 136, and controls the changeover operation of the changeover switch 150, which will be described later.

[0028] The distribution board unit 104 includes a changeover switch 150, a first terminal block 152, and a second terminal block 154. The changeover switch 150 is realized by, for example, a relay (e.g., an electromagnetic relay with a relatively large current capacity). The first terminal block 152 connects the output section of the output filter 130 to a load 900 at the installation location (e.g., a home) of the power storage system 100. Note that a changeover switch such as a relay may be included between the output filter 130 and the first terminal block 152. The second terminal block 154 connects the changeover switch 150 to the commercial power system 902. Of the two terminals of the changeover switch 150, the first terminal 156 is connected to the connection node between the output filter 130 and the first terminal block 152, and the second terminal 158 is connected to the second terminal block 154. The changeover switch 150 is controlled by the control circuit 132. That is, the second control signal S2 is received from the control circuit 132 via the second control line 136, and in response to the second control signal S2, the first terminal 156 and the second terminal 158 are connected (i.e., closed), or the connected first terminal 156 and the second terminal 158 are opened (i.e., opened).

[0029] 1, the power conversion unit 102, the distribution board unit 104, and the storage battery 106 are housed in, for example, a single housing. This allows the power storage system 100 to be formed as an integrated unit, making it easier to handle and reducing the installation space. Furthermore, housing them in a single housing prevents noise generated inside the power conversion unit 102 (for example, noise contained in a control signal output from the control circuit 132) from being output outside the housing and affecting the surrounding area.

[0030] 2, the control circuit 132 includes a main control unit 170, a PWM (Pulse Width Modulation) control unit 172, a switch control unit 174, and an instrumentation unit 176. The main control unit 170 includes a CPU (Central Processing Unit), a microcomputer, or the like. The main control unit 170 outputs a signal to the PWM control unit 172 via a first internal control line 138 to control the operation of the DC / AC converter 128. The main control unit 170 also outputs a signal to the switch control unit 174 via a second internal control line 140 to control the operation of the changeover switch 150.

[0031] The PWM control unit 172 outputs a control signal for controlling the switching elements that constitute the DC / AC converter 128. Here, it is assumed that the DC / AC converter 128 is a bridge circuit that is configured with a plurality of semiconductor switching elements (for example, FETs, etc.). The PWM control unit 172 outputs a PWM control signal for controlling the on / off of each switching element.

[0032] Referring to FIG. 3, the switch control unit 174 includes a photocoupler 180. The photocoupler 180 is a device configured with a light-emitting element (i.e., an LED) and a light-receiving element (i.e., a phototransistor). The light-emitting element is connected between the main control unit 170 and ground. Light emission is controlled by a control signal Sc input from the main control unit 170 via the second internal control line 140. The light-emitting element emits light when the control signal Sc is equal to or higher than a predetermined voltage, and does not emit light when the control signal Sc is lower than the predetermined voltage. The light-receiving element is connected between a DC voltage Vd and ground via a resistor R. When the light-emitting element is not emitting light, the second control signal S2 is the DC voltage Vd. When the light-emitting element emits light, the light-receiving element is turned on, causing the second control signal S2 to drop to the ground voltage level. For example, if the changeover switch 150 is an electromagnetic relay, when the second control signal S2 is a DC voltage Vd, power is supplied to close the changeover switch 150, and when the second control signal S2 is a ground voltage level, power is not supplied to close the changeover switch 150, and the changeover switch 150 is opened.

[0033] The light-emitting element of the photocoupler 180 is connected to the same ground as the main control unit 170, and the ground to which the light-receiving element is connected is electrically separated from the ground to which the light-emitting element is connected. This allows the circuit portion on the main control unit 170 side (i.e., the circuit portion including the second control line 136) to be electrically separated from the circuit portion on the first control line 134 side. Therefore, it is possible to prevent noise present in the circuit portion on the first control line 134 side (i.e., the DC / AC converter 128 and the control circuit 132, etc.) from being transmitted to the circuit on the second control line 136 side (i.e., the changeover switch 150, etc.).

[0034] The instrumentation unit 176 receives detection signals from sensors (i.e., voltage sensors, current sensors, etc.) arranged in various parts of the power storage system 100, adjusts the signals to an input level for the main control unit 170, and outputs the adjusted signals to the main control unit 170. For example, the instrumentation unit 176 receives a measured value of the voltage of the commercial power system 902, and outputs a signal corresponding to the measured value to the main control unit 170. This enables the main control unit 170 to determine whether power is being supplied normally from the commercial power system 902, and to detect the occurrence of a power outage in the commercial power system 902.

[0035] (Control action) The power storage system 100 monitors the power supply state of the commercial power system 902 based on a signal input from the instrumentation unit 176. If the commercial power system 902 is normal, the changeover switch 150 is closed, and the power storage system 100 is grid-connected. That is, power is supplied from the commercial power system 902 to the load 900 via the second terminal block 154, the changeover switch 150, and the first terminal block 152. Furthermore, if a photovoltaic power generation system is connected to the switch 108, the generated power is supplied to the DC / AC converter 128 via the DC / DC converter 124, converted into AC power by the DC / AC converter 128, and supplied to the load 900 from the first terminal block 152. If the power generated by the photovoltaic power generation system is greater than the power consumed by the load 900, the surplus power is stored in the storage battery 106 as described above. The surplus power may be supplied (ie, sold) to the commercial power grid 902 via the changeover switch 150 and the second terminal block 154.

[0036] When a power outage occurs in the commercial power grid 902, the power storage system 100 performs independent operation. That is, the control circuit 132 outputs a second control signal S2 at a level that opens the changeover switch 150 (that is, disconnects the power storage system 100 from the commercial power grid 902). This disconnects the power storage system 100 from the commercial power grid 902. In synchronization with this, the control circuit 132 converts the output power of the storage battery 106 into AC power (for example, AC 100V or 200V, etc.) using the DC / DC converter 122 and the DC / AC converter 128, and supplies the AC power to the load 900 via the first terminal block 152.

[0037] As a result, in the event of a power outage in the commercial power grid 902, the power storage system 100 (i.e., the power conversion unit 102) can operate autonomously and supply power from the storage battery 106 to the load 900. At this time, the control circuit 132 (i.e., the main control unit 170) controls both the operation of the DC / AC converter 128 and the opening and closing operation of the changeover switch 150, so that it is possible to easily synchronize the switching operation of the changeover switch 150 with the power supply operation from the power conversion unit 102. Furthermore, the power storage system 100 can be realized at a lower cost than when a control unit separate from the control circuit 132 is provided in the distribution board unit 104.

[0038] Although the above describes a case where the power conversion unit 102, the distribution board unit 104, and the storage battery 106 are housed in a single housing, the present invention is not limited to this. The power conversion unit 102 and the distribution board unit 104 may be disposed separately. For example, the power conversion unit 102 and the storage battery 106 may be housed in a single housing, and the distribution board unit 104 may be housed in a separate housing. Even in such a case, if the control circuit 132 controls both the operation of the DC / AC converter 128 and the opening and closing operation of the changeover switch 150, synchronization between the switching operation of the changeover switch 150 and the power supply operation from the power conversion unit 102 can be easily achieved.

[0039] 1 illustrates a case where there is one switch 108, but this is not limiting and a plurality of switches 108 may be included. In this case, a DC / DC converter for converting power generated by a power generation device connected to each switch may be connected in parallel with DC / DC converter 122.

[0040] Although the above description has been given of a case where the switch control section 174 includes the photocoupler 180, the present invention is not limited to this. The switch control section 174 may be configured by a circuit that does not include the photocoupler 180.

[0041] [Second embodiment] In the above-described power storage system 100, there is a possibility that the noise superimposed on the power output to the outside cannot be sufficiently reduced because there is a path through which noise can be transmitted to the outside without passing through the output filter 130. That is, referring to Fig. 4, the noise generated from the DC / AC converter 128 as described above reaches the changeover switch 150 via the first control line 134, the control circuit 132, and the second control line 136, as indicated by the dashed arrows. Furthermore, the noise is transmitted to the first terminal block 152 and the second terminal block 154 via the changeover switch 150, and can be output to the outside.

[0042] As described above, noise superimposed on the power output from the DC / AC converter 128 can be reduced by the output filter 130, but noise sneaking in from the changeover switch 150 still superimposes on the power output from the first terminal block 152. Furthermore, when a solar power generation panel is connected to the switch 108, noise sneaking in from the changeover switch 150 is also superimposed on the power output from the second terminal block 154. Even if the control circuit 132 is configured to output the second control signal S2 via the photocoupler 180 as described above, it has been confirmed that in practice it is not possible to sufficiently prevent noise associated with the switching operation of the DC / AC converter 128 from being superimposed on the second control signal S2. The power storage system according to the second embodiment is intended to solve this problem.

[0043] (Overall composition) 5, a power storage system 200 according to the second embodiment of the present disclosure includes a power conversion unit 202, a distribution board unit 104, a storage battery 106, and a switch 108. The power storage system 200 is configured by replacing the power conversion unit 102 in the power storage system 100 shown in FIG. 1 with the power conversion unit 202. In FIG. 5, components denoted with the same reference numerals as those in FIG. 1 have the same functions as those described above. Therefore, hereinafter, redundant description will not be repeated, and differences between the power storage system 200 and the power storage system 100 will be mainly described.

[0044] The power conversion unit 202 is configured by adding a noise filter circuit 204 between the control circuit 132 and a third control line 206 to the power conversion unit 102. The noise filter circuit 204 outputs a signal from which noise components have been removed from an input signal. A second control signal S2 for controlling the changeover switch 150, output from the control circuit 132, is input to the noise filter circuit 204. The control signal S3 output from the noise filter circuit 204 maintains the level of the second control signal S2 for controlling the operation of the changeover switch 150, and is a signal from which noise superimposed on the second control signal S2 has been removed.

[0045] The noise filter circuit 204 can be realized by an LC filter circuit (for example, a low-pass filter circuit). Referring to FIG. 6, the noise filter circuit 204 is configured by a coil (i.e., inductor) L and a capacitor C. The coil L is connected between the second control line 136 and the third control line 206. The capacitor C is connected between the second control line 136 and ground. The circuit shown in FIG. 6 is a low-pass filter circuit, which reduces frequency components higher than a predetermined frequency (i.e., cut-off frequency) for an input signal Sin and outputs an output signal Sout. The cut-off frequency fc of the circuit shown in FIG. 6 is expressed as fc=(2π(LC)) where L and C are the inductance of the coil L and the capacitance of the capacitor C, respectively. -1 It is calculated as follows.

[0046] In the power storage system 200, the frequency band (hereinafter referred to as the cutoff frequency band) to be reduced by the noise filter circuit 204 as noise is preferably, for example, 250 kHz or more and 10 MHz or less. More preferably, the cutoff frequency band is 150 kHz or more and 30 MHz or less. Therefore, when a low-pass filter circuit is used for the noise filter circuit 204, it is preferable to determine the combination of the inductance of the coil L and the capacitance of the capacitor C so that the cutoff frequency fc is, for example, approximately 250 kHz. More preferably, the combination of the inductance of the coil L and the capacitance of the capacitor C is determined so that the cutoff frequency is a value of 150 kHz or more and 250 kHz or less.

[0047] It should be noted that since the noise generated by the switching operation of DC / AC converter 128 depends on the switching frequency (for example, the frequency of the PWM control signal), it is preferable to set the cutoff frequency of noise filter circuit 204 according to the switching frequency.

[0048] Furthermore, since an actual coil has a capacitance component and a capacitor has an inductance component, it is preferable to take these into consideration when selecting the elements that make up the noise filter circuit 204 so that the target cutoff frequency fc can be roughly obtained.

[0049] (Control action) The power storage system 200 operates in the same manner as the power storage system 100 shown in FIG. 1. That is, the power storage system 200 monitors the power supply state of the commercial power grid 902 using a signal input from the instrumentation unit 176 (see FIG. 2). If the commercial power grid 902 is normal, the changeover switch 150 is closed, and the power storage system 200 is grid-connected. Power is supplied from the commercial power grid 902 to the load 900 via the second terminal block 154, the changeover switch 150, and the first terminal block 152. If a photovoltaic power generation system is connected to the switch 108, the generated power is supplied to the DC / AC converter 128 via the DC / DC converter 124, converted into AC power by the DC / AC converter 128, and supplied to the load 900 from the first terminal block 152. If the power generated by the photovoltaic power generation system is greater than the power consumed by the load 900, the surplus power is stored in the storage battery 106 as described above. The surplus power may be supplied (ie, sold) to the commercial power grid 902 via the changeover switch 150 and the second terminal block 154.

[0050] When a power outage occurs in the commercial power grid 902, the power storage system 200 performs independent operation. That is, the control circuit 132 outputs a second control signal S2 at a level that opens the changeover switch 150 (that is, disconnects the power storage system 200 from the commercial power grid 902), and the noise filter circuit 204 outputs a control signal S3 at the same level as the second control signal S2. As a result, the power storage system 200 is disconnected from the commercial power grid 902. In synchronization with this, the control circuit 132 converts the output power of the storage battery 106 into AC power (for example, AC 100V or 200V) using the DC / DC converter 122 and the DC / AC converter 128, and supplies the AC power to the load 900 via the first terminal block 152.

[0051] As a result, when a power outage occurs in the commercial power grid 902, the power storage system 200 (i.e., the power conversion unit 202) operates autonomously and can supply power from the storage battery 106 to the load 900. At this time, the control circuit 132 (i.e., the main control unit 170) controls both the operation of the DC / AC converter 128 and the opening and closing operation of the changeover switch 150, so that it is possible to easily achieve synchronization between the switching operation of the changeover switch 150 and the power supply operation from the power conversion unit 102. Furthermore, the power storage system 200 can be realized at a lower cost than when a control unit separate from the control circuit 132 is provided in the distribution board unit 104.

[0052] By including the noise filter circuit 204, the power storage system 200 can reduce noise that is generated in association with the operation of the DC / AC converter 128 and is output to the outside via the changeover switch 150. Even if the control circuit 132 (specifically, the switch control unit 174) does not include the photocoupler 180 shown in Fig. 3, the noise filter circuit 204 can reduce noise that is associated with the switching operation of the DC / AC converter 128 and that is superimposed on the second control signal S2 output from the control circuit 132. If the control circuit 132 includes the photocoupler 180 as shown in Fig. 3, the noise filter circuit 204 can further reduce noise that is associated with the switching operation of the DC / AC converter 128 and that is superimposed on the second control signal S2 output from the control circuit 132.

[0053] 6 is used for the noise filter circuit 204, and by setting the inductance of the coil and the capacitance of the capacitor, a desired cutoff frequency band (for example, the cutoff frequency of a low-pass filter) can be appropriately set. Also, a function of reducing noise that occurs in conjunction with the switching operation of the DC / AC converter 128 and is output to the outside of the power storage system 200 via the changeover switch 150 can be realized at low cost.

[0054] The cutoff frequency of the low-pass filter circuit is, for example, 150 kHz or more and 250 kHz or less, which makes it possible to more effectively reduce noise that is generated during operation of the power converter and output to the outside via the changeover switch.

[0055] The noise filter circuit 204 may use, for example, circuits shown in Figures 7 to 9 depending on the impedance of the control circuit 132 and the changeover switch 150 connected to the noise filter circuit 204. The circuit shown in Figure 6 is effective when the impedance on the input signal Sin side is relatively small and the impedance on the output signal Sout side is relatively large.

[0056] In contrast, the circuit of Figure 7 is effective when the impedance on the input signal Sin side and the impedance on the output signal Sout side are both relatively large. The capacitances of capacitors C1 and C2 are set to be equal. The circuit of Figure 8 is effective when the impedance on the input signal Sin side is relatively large and the impedance on the output signal Sout side is relatively small. The circuit of Figure 9 is effective when the impedance on the input signal Sin side and the impedance on the output signal Sout side are both relatively small. The inductances of coils L1 and L2 are set to be equal.

[0057] 6 and 7, the noise filter circuit 204 may be any circuit having a low-pass filter function. The low-pass filter circuit can effectively reduce noise accompanying the switching operation of the DC / AC converter 128 without affecting the switching operation of the changeover switch 150.

[0058] 6 to 9 may be combined and connected in series in multiple stages. The noise filter circuit 204 is not limited to an LC filter circuit configured by a coil L and a capacitor C.

[0059] Although the present invention has been described above by explaining the embodiments, the above-described embodiments are merely examples, and the present invention is not limited to the above-described embodiments. The scope of the present invention is defined by the claims in the appended claims, taking into consideration the detailed description of the invention, and includes all modifications within the meaning and scope equivalent to the wordings described therein. [Explanation of symbols]

[0060] 100, 200 Energy storage system 102, 202 Power conversion unit 104 Distribution board section 106 Storage battery 108 Switch 120 Input Filter 122, 124 DC / DC converters 126, C, C1, C2 capacitors 128 DC / AC converters 130 Output Filter 132 control circuit 134 First Control Line 136 Second Control Line 138 First internal control line 140 Second internal control line 150 Changeover switch 152 1st terminal block 154 2nd terminal block 156 1st terminal 158 2nd terminal 170 Main control unit 172 PWM control unit 174 Switch control unit 176 Instrumentation Department 180 Photocoupler 204 Noise filter circuit 206 Third Control Line 900 load 902 Commercial power system L, L1, L2 coils R resistance S1 First control signal S2 Second control signal S3, Sc control signal Sin input signal Sout output signal V1 First output voltage V2 Second output voltage Vd DC voltage

Claims

1. a power converter; a changeover switch provided in a distribution board to which a commercial power system is connected; a control circuit for controlling the power converter and the changeover switch; a noise filter circuit disposed between the changeover switch and the control circuit; The control signal output from the control circuit is input to the changeover switch via the noise filter circuit, the changeover switch connects the power converter to the commercial power system or disconnects the power converter from the commercial power system in response to a control signal input from the control circuit.

2. the control circuit includes a photocoupler; The power conversion system according to claim 1 , wherein the control signal is input to the noise filter circuit via the photocoupler.

3. The power conversion system according to claim 1 or 2, wherein the noise filter circuit includes an LC filter circuit.

4. The power conversion system according to claim 1 or 2, wherein the noise filter circuit includes a low-pass filter circuit.

5. The power conversion system according to claim 4 , wherein the cutoff frequency of the low-pass filter circuit is equal to or greater than 150 kHz and equal to or less than 250 kHz.

6. The power conversion system according to claim 1 or 2, further comprising a housing that houses the changeover switch and the control circuit.

7. the power converter includes a DC / DC conversion unit and a DC / AC conversion unit, 3. The power conversion system according to claim 1, wherein the changeover switch connects the DC / AC conversion unit to the commercial power system or disconnects the DC / AC conversion unit from the commercial power system in response to input of the control signal.

8. The power conversion system according to claim 1 or 2; a storage battery; The power converter converts the output power of the storage battery into AC power and outputs the AC power.

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