Energy storage system
The power storage system addresses PID issues in hybrid systems by applying a DC voltage to the negative terminal of solar cells when power output is low, effectively preventing PID without increasing system size or cost.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- NICHICON CORP
- Filing Date
- 2022-10-17
- Publication Date
- 2026-06-02
Smart Images
Figure 0007868943000001 
Figure 0007868943000002 
Figure 0007868943000003
Abstract
Description
Technical Field
[0001] The present invention relates to a power storage system, and more particularly to a power storage system equipped with a solar power generation function.
Background Art
[0002] In a transformerless (non-insulated) type solar power generation system aimed at higher efficiency, when the power conditioner of the solar power generation system performs grid-connected operation during the day, a large potential difference (the voltage of the negative electrode of the solar cell is negative with respect to FG) occurs between the internal circuit of the solar cell and the frame ground (hereinafter referred to as FG) of the solar cell. If this large potential difference continues for a long time, there are solar cells in which a PID (Potential Induced Degradation) phenomenon occurs in which the power generation ability deteriorates rapidly. However, by disconnecting the solar cell from the commercial power grid (hereinafter referred to as the grid) at night when the solar cell is not generating power, the potential difference between the internal circuit of the solar cell and FG is eliminated, and the occurrence of the PID phenomenon is suppressed.
[0003] On the other hand, in a hybrid type power storage system, that is, a power storage system equipped with a solar power generation function, since the solar cell is not disconnected from the grid at night (the solar cell is connected to the grid for 24 hours), the occurrence of the PID phenomenon cannot be suppressed. In addition, since there are also solar cells in which the PID phenomenon is unlikely to occur, PID countermeasures are not always necessary.
[0004] Therefore, in the hybrid type power storage system 1D shown in FIG. 5, when using solar cells PV1 and PV2 in which the PID phenomenon may occur, the solar cells PV1 and PV2 and the power conditioner 3 are connected via a connection box 2 for PID countermeasures.
[0005] The junction box 2 includes relays RL11 and RL12, a control circuit 2a, a control power supply 2b, a voltage detection unit 2c, and bridge diodes D11 and D12 for preventing reverse current. The power conditioner 3 includes a DC / DC converter 4 (4-1) connected to solar cell PV1 via the junction box 2, and a DC / DC converter 4 (4-2) connected to solar cell PV2 via the junction box 2.
[0006] The control circuit 2a is activated by the power supply voltage supplied from the control power supply 2b, and controls the on / off state of relays RL11 and RL12 according to the voltage value detected by the voltage detection unit 2c (the voltage value of the generated voltage input from solar cells PV1 and PV2). For example, the control circuit 2a turns off relays RL11 and RL12 when solar cells PV1 and PV2 are not generating power (for example, at night).
[0007] When relays RL11 and RL12 are in the off state, even if the power conditioner 3 is operating in grid connection mode, no potential difference is generated between the internal circuits of solar cells PV1 and PV2 and FG, thus suppressing the occurrence of PID phenomena. This configuration, in which a junction box is used to disconnect the solar cells from the grid when they are not generating power, is disclosed in, for example, Patent Documents 1 to 3.
[0008] However, using a junction box as a PID countermeasure leads to the problem of increasing the overall size and cost of the system. [Prior art documents] [Patent Documents]
[0009] [Patent Document 1] Japanese Patent Publication No. 2017-169436 [Patent Document 2] Japanese Patent Publication No. 2017-169434 [Patent Document 3] Japanese Patent Publication No. 2019-103209 [Overview of the Initiative] [Problems that the invention aims to solve]
[0010] The present invention has been made in view of the above circumstances, and its objective is to provide an energy storage system that can suppress the occurrence of PID phenomena without using a junction box. [Means for solving the problem]
[0011] To solve the above problems, the energy storage system according to the present invention is A grid connection terminal that connects to the power grid, The DC / DC converter section receives DC power generated from the power generation section, A bidirectional DC / DC converter to which a power storage device is connected, A bidirectional DC / AC inverter, in which the DC side is connected to the DC / DC converter section and the bidirectional DC / DC converter, and the AC side is connected to the grid connection terminal, A power storage system equipped with, A rectifier and smoothing circuit whose input terminal is electrically connected to the grid connection terminal without going through the bidirectional DC / AC inverter, The system comprises a voltage application circuit connected to the output terminal of the rectifier and smoothing circuit and electrically connected to the negative terminal of the power generation unit, The rectifier-smoothing circuit outputs a first DC voltage obtained by rectifying and smoothing the system voltage of the power system. The voltage application circuit is characterized by applying the first DC voltage to the negative terminal of the power generation unit, and increasing the voltage to ground of the negative terminal of the power generation unit when the amount of power output from the power generation unit is less than or equal to a predetermined value.
[0012] In this configuration, the rectifier-smoothing circuit outputs a first DC voltage obtained by rectifying and smoothing the power system voltage, and the voltage application circuit applies this first DC voltage to the negative terminal of the power generator. When the amount of power generated by the power generator is below a predetermined value, the voltage to ground of the negative terminal of the power generator, which was negative relative to the frame ground (FG), rises. As a result, the negative potential difference between the internal circuit of the power generator and FG decreases or disappears. Therefore, with this configuration, the occurrence of PID phenomena can be suppressed without using a junction box.
[0013] In the aforementioned energy storage system, The rectifier and smoothing circuit described above is A rectifier means interposed in the power line connecting the grid connection terminal and the voltage application circuit without going through the bidirectional DC / AC inverter, The system can be configured to include a smoothing means to which a positive terminal is connected at the connection point between the rectifier means and the voltage application circuit.
[0014] In the aforementioned energy storage system, The voltage application circuit includes a first switching element interposed in the power line connecting the output terminal of the rectifier and smoothing circuit and the negative terminal of the power generation unit. The first switching element can be configured to turn on when the amount of power generated is less than or equal to the predetermined value, and to turn off when the amount of power generated exceeds the predetermined value.
[0015] In the aforementioned energy storage system, The power generation unit comprises N power generation means (where N is an integer of 2 or more), The DC / DC converter section comprises N DC / DC converters, one end of which is connected to the N power generation means, and N first diodes, the other end of which is connected to the negative terminal. The voltage application circuit can be configured to include a first switching element, one end of which is connected to the output terminal of the rectifier-smoothing circuit, and N second diodes provided between the other end of the current path of the first switching element and the negative terminal of each of the N power generation means.
[0016] In the aforementioned energy storage system, The power generation unit comprises N power generation means (where N is an integer of 2 or more), The DC / DC converter section includes N DC / DC converters with one end connected to the N power generation means, and a first diode interposed in a power line connecting the connection point of the negative terminals on the other end side of the N DC / DC converters and the negative terminal on the DC side of the bidirectional DC / AC inverter. The voltage application circuit includes a first switching element having one end of a current path connected to the output end of the rectifying and smoothing circuit and the other end of the current path connected to the negative pole of each of the N power generation means without passing through a diode. A second switching element can be configured to be connected in parallel to the first diode.
[0017] In the power storage system, The power generation section includes N power generation means (N is an integer of 2 or more). The DC / DC converter section includes N DC / DC converters with one end connected to the N power generation means, and N first diodes connected to the negative terminals on the other end side of the N DC / DC converters. The voltage application circuit includes a first resistor with one end connected to the output end of the rectifying and smoothing circuit, and N second diodes provided between the other end of the first resistor and the negative pole of each of the N power generation means. A second resistor can be configured to be connected in parallel to the first diode.
Advantages of the Invention
[0018] According to the present invention, it is possible to provide a power storage system capable of suppressing the occurrence of the PID phenomenon without using a connection box.
Brief Description of the Drawings
[0019] [Figure 1] It is a diagram showing a power storage system according to the first embodiment of the present invention, and is a diagram when the bidirectional DC / AC inverter is on standby. [Figure 2] It is a diagram showing a power storage system according to the first embodiment of the present invention, and is a diagram when the bidirectional DC / AC inverter is operating. [Figure 3] This figure shows an energy storage system according to a second embodiment of the present invention. [Figure 4] This figure shows an energy storage system according to a third embodiment of the present invention. [Figure 5] This diagram shows a conventional energy storage system. [Modes for carrying out the invention]
[0020] Hereinafter, embodiments of the energy storage system according to the present invention will be described with reference to the attached drawings.
[0021] [First Embodiment] Figure 1 shows a power storage system 1A according to the first embodiment of the present invention. The power storage system 1A is a hybrid power storage system equipped with a battery charging / discharging function and a solar power generation function. It is connected to solar cells PV1 and PV2 (each corresponding to a "power generation means") which correspond to the "power generation unit" of the present invention, and to a battery BT which corresponds to the "power storage means" of the present invention. It is also connected to the commercial power grid (hereinafter referred to as the grid) via terminals T1 to T3 which correspond to the "grid connection terminals" of the present invention, and to an independent load via T4 and T5.
[0022] The energy storage system 1A includes a DC / DC converter unit 10A, a bidirectional DC / DC converter 20, a capacitor C1, a bidirectional DC / AC inverter 30, a relay circuit 40, a rectifier and smoothing circuit (diodes 50, 51 and capacitor 52), a voltage application circuit (first switching element 53 and diodes 54, 55), and a control unit (not shown).
[0023] The DC / DC converter unit 10A has one end connected to solar cells PV1 and PV2, and the other end connected to the bidirectional DC / DC converter 20 and the bidirectional DC / AC inverter 30 via capacitor C1. The DC / DC converter unit 10A comprises a DC / DC converter 10 (10-1, 10-2) and diodes D1 and D2 corresponding to the "first diode" of the present invention, and boosts the generated voltage input from solar cells PV1 and PV2 and outputs it to the bidirectional DC / DC converter 20 and / or the bidirectional DC / AC inverter 30.
[0024] The DC / DC converter 10-1 includes a voltage detection unit 11 that detects the DC generated voltage input from the solar cell PV1, a current detection unit 12 (e.g., a DCCT) that detects the DC generated current input from the solar cell PV1, and a boost chopper circuit including a capacitor 13, a coil 14, a switching element 15, a diode 16, and a capacitor 17. The voltage detection signal from the voltage detection unit 11 and the current detection signal from the current detection unit 12 are transmitted to the control unit.
[0025] The DC / DC converter 10-2 includes a voltage detection unit 11 that detects the DC generated voltage input from the solar cell PV2, a current detection unit 12 (e.g., a DCCT) that detects the DC generated current input from the solar cell PV2, and a boost chopper circuit including a capacitor 13, a coil 14, a switching element 15, a diode 16, and a capacitor 17. The voltage detection signal from the voltage detection unit 11 and the current detection signal from the current detection unit 12 are transmitted to the control unit. Thus, the DC / DC converter 10-1 and the DC / DC converter 10-2 have the same configuration.
[0026] Diode D1 has its anode connected to the negative terminal of capacitor C1, and its cathode connected to the negative terminal of the output side (other end) of DC / DC converter 10-1 (the negative terminal of capacitor 17). Diode D2 has its anode connected to the negative terminal of capacitor C1, and its cathode connected to the negative terminal of the output side (other end) of DC / DC converter 10-2 (the negative terminal of capacitor 17). The connection point X1 between the anodes of diode D1 and D2 is connected to the negative terminal of capacitor C1.
[0027] The bidirectional DC / DC converter 20 has one end connected to the battery BT and the other end connected to both ends of the capacitor C1. The bidirectional DC / DC converter 20 includes a voltage detection unit 21, a current detection unit 22 (e.g., DCCT), and a bidirectional chopper circuit including a capacitor 23, a coil 24, and switching elements 25, 26, and performs charging and discharging operations on the battery BT. For example, a lithium-ion battery can be used as the battery BT. The voltage detection signal from the voltage detection unit 21 and the current detection signal from the current detection unit 22 are transmitted to the control unit.
[0028] The bidirectional DC / AC inverter 30 includes DC terminals (positive terminal T11 and negative terminal T12) connected to both ends of capacitor C1 and AC terminals connected to relay circuit 40. Although not shown in the figure, the bidirectional DC / AC inverter 30 includes a bridge circuit formed by bridging multiple switching elements and an LC filter circuit consisting of a coil and a capacitor, and converts the AC voltage applied to the AC terminals to DC and outputs it to the bidirectional DC / DC converter 20, or converts the DC voltage applied to the DC terminals (positive terminal T11 and negative terminal T12) to AC and outputs it to relay circuit 40.
[0029] The relay circuit 40 includes relays S1 to S6. Relays S1, S2, S5, and S6 are interposed in the power lines connecting the bidirectional DC / AC inverter 30 to terminals T1 to T5, specifically in the power lines connecting the bidirectional DC / AC inverter 30 to terminals T1, T3, T4, and T5. Terminals T2 and T5 are connected by a power line interposed with relay S3. Terminals T3 and T4 are connected by a power line interposed with relay S4.
[0030] Terminals T1 to T3 are connected to the U, O, and W phases of the grid, while terminals T4 and T5 are connected to the voltage and neutral lines of a single-phase two-wire system. An independent load (household load such as electrical appliances that you want to continue operating even during a grid outage) is connected between the voltage and neutral lines of the single-phase two-wire system.
[0031] The rectifier-smoothing circuit comprises diodes 50 and 51 corresponding to the "rectifier means" of the present invention, and a capacitor 52 corresponding to the "smoothing means" of the present invention. The input terminal of the rectifier-smoothing circuit is electrically connected to terminals T1 and T3 via a relay circuit 40 without going through a bidirectional DC / AC inverter 30, and the output terminal is electrically connected to a voltage application circuit.
[0032] Diode 50 has its anode connected to a power line connected to terminal T1 between the bidirectional DC / AC inverter 30 and the relay circuit 40, and its cathode is electrically connected to the first switching element 53 of the voltage application circuit. Diode 51 has its anode connected to a power line connected to terminal T3 between the bidirectional DC / AC inverter 30 and the relay circuit 40, and its cathode is electrically connected to the cathode of diode 50. The anodes of diode 50 and diode 51 become the input terminals of the rectifier and smoothing circuit.
[0033] Capacitor 52 has its positive terminal connected to the cathodes of diode 50 and diode 51, and its negative terminal connected to the negative terminal T12 of the bidirectional DC / AC inverter 30 and the negative terminal of capacitor C1. The positive terminal of capacitor 52 is the output terminal of the rectifier and smoothing circuit.
[0034] The voltage application circuit comprises a first switching element 53 (for example, an FET) and diodes 54 and 55 corresponding to the "second diode" of the present invention. One end of the current path of the first switching element 53 is connected to the positive terminal of the capacitor 52, and the other end of the current path is connected to the anode of diode 54 and the anode of diode 55. The cathode of diode 54 is connected to the connection point between the negative terminal of solar cell PV1 and the negative terminal of capacitor 13 of DC / DC converter 10-1, and the cathode of diode 55 is connected to the connection point between the negative terminal of solar cell PV2 and the negative terminal of capacitor 13 of DC / DC converter 10-2.
[0035] The control unit is composed of, for example, a microcontroller or a control IC such as an FPGA (Field-Programmable Gate Array). The control unit controls the on / off state of the switching elements 15 of the DC / DC converters 10-1 and 10-2, the switching elements 25 and 26 of the bidirectional DC / DC converter 20, the switching elements of the bidirectional DC / AC inverter 30, and the relays S1 to S6 of the relay circuit 40.
[0036] The control unit further controls the on / off state of the first switching element 53. When the power generation amount (power generation or voltage generation) of both solar cells PV1 and PV2 is below a predetermined value, the control unit stops the switching elements 15 of the DC / DC converters 10-1 and 10-2 and turns on the first switching element 53. On the other hand, when the power generation amount (voltage generation) of at least one of the solar cells PV1 and PV2 exceeds a predetermined value, the control unit turns off the first switching element 53 and switches the switching element 15 of the exceeding solar cell. The control unit calculates the power generation of solar cells PV1 and PV2 based, for example, on the voltage detection signal from the voltage detection unit 11 and the current detection signal from the current detection unit 12. The predetermined value is set, for example, to the lower limit of the power generation amount (power generation or voltage generation) at which the DC / DC converters 10-1 and 10-2 can perform boost operation.
[0037] In this embodiment, it is assumed that solar cell PV1 and solar cell PV2 have the same configuration and that their power generation (power generation or voltage generation) is the same under the same conditions, and the above predetermined value is set as a single threshold. If solar cell PV1 and solar cell PV2 have different configurations, it is preferable to set a predetermined value for each solar cell PV1 and PV2.
[0038] Next, the PID phenomenon suppression effect of the energy storage system 1A will be explained separately for the case where the bidirectional DC / AC inverter 30 is in standby mode (Figure 1) and the case where the bidirectional DC / AC inverter 30 is in operation (Figure 2).
[0039] (When the bidirectional DC / AC inverter 30 is in standby mode) Figure 1 shows the energy storage system 1A in a situation where the power generation amount (generated power or generated voltage) of solar cells PV1 and PV2 falls below a predetermined value during nighttime or bad weather, the DC / DC converters 10-1 and 10-2 cannot perform boost operation, and the bidirectional DC / AC inverter 30 is in standby mode.
[0040] In this case, a system voltage of AC101[V] is applied between terminals T1 and T2, and also between terminals T2 and T3. The total system voltage of AC202[V] is full-wave rectified by the diodes of the switching elements included in the bridge circuit of the bidirectional DC / AC inverter 30, and then smoothed by capacitor C1.
[0041] The voltage across capacitor C1 is 286[V] (=202[V] × √2). Therefore, a voltage of 143[V] (half of 286[V]) is applied between the positive terminal of capacitor C1 and the frame ground (hereinafter referred to as FG), and a voltage of -143[V] is applied between the negative terminal of capacitor C1 and FG.
[0042] Furthermore, the AC202[V] system voltage applied between terminals T1-T3 is rectified by diodes 50 and 51 of the rectifier-smoothing circuit and smoothed by capacitor 52 of the rectifier-smoothing circuit. The voltage across capacitor 52 becomes 286[V] (=202[V] × √2). Therefore, a voltage of 143[V], which is half of 286[V], is applied between the positive terminal of capacitor 52 and FG, similar to capacitor C1. This 143[V] voltage corresponds to the "first DC voltage" of the present invention.
[0043] In this state, when the first switching element 53 is turned on, a voltage of 143[V] (the voltage drop generated by the first switching element 53 and diodes 54, 55 is negligible and therefore ignored) is applied between the negative electrodes of solar cells PV1 and PV2 and FG. As a result, the voltage to ground of the negative electrodes of solar cells PV1 and PV2 rises to zero or higher, thus suppressing the occurrence of PID phenomena.
[0044] (When the bidirectional DC / AC inverter 30 is in operation) Figure 2 shows the power generation (power or voltage) of solar panels PV1 and PV2 at night or in bad weather. This shows energy storage system 1A in a case where the voltage drops below a predetermined value, preventing DC / DC converters 10-1 and 10-2 from performing boost operation, while the bidirectional DC / AC inverter 30 is performing boost operation.
[0045] In this case, the AC202[V] system voltage applied between terminals T1-T3 is boosted by the bidirectional DC / AC inverter 30 so that the voltage after smoothing by capacitor C1 becomes 320[V].
[0046] When the voltage across capacitor C1 reaches 320[V], a voltage of 160[V] (half of 320[V]) is applied between the positive terminal of capacitor C1 and FG, and a voltage of -160[V] is applied between the negative terminal of capacitor C1 and FG.
[0047] Furthermore, the AC202[V] system voltage applied between terminals T1-T3 is rectified by diodes 50 and 51 of the rectifier-smoothing circuit and smoothed by capacitor 52 of the rectifier-smoothing circuit. The voltage across capacitor 52 is not boosted by the bidirectional DC / AC inverter 30, so it becomes 286[V] (=202[V] × √2). Therefore, a voltage of 143[V], which is half of 286[V], is applied between the positive terminal of capacitor 52 and FG. This voltage of 143[V] corresponds to the "first DC voltage" of the present invention.
[0048] In this state, when the first switching element 53 is turned on, a voltage of 143[V] (the voltage drop generated by the first switching element 53 and diodes 54, 55 is negligible and therefore ignored) is applied between the negative electrodes of solar cells PV1 and PV2 and FG. As a result, the voltage to ground of the negative electrodes of solar cells PV1 and PV2 rises to zero or higher, thus suppressing the occurrence of PID phenomena.
[0049] As described above, in the energy storage system 1A according to this embodiment, the voltage application circuit applies a voltage rectified and smoothed by the rectifier and smoothing circuit to the negative electrodes of solar cells PV1 and PV2. When the amount of power generated (power or voltage) output from solar cells PV1 and PV2 is below a predetermined value, the voltage to ground of the negative electrodes of solar cells PV1 and PV2 is raised to zero or above. Since the voltage to ground of the negative electrodes of solar cells PV1 and PV2, which was negative relative to FG, rises to zero or above, the negative potential difference between the internal circuits of solar cells PV1 and PV2 and FG is eliminated. Therefore, according to the energy storage system 1A according to this embodiment, the occurrence of PID phenomena can be suppressed without using a junction box.
[0050] Furthermore, in the energy storage system 1A according to this embodiment, since the rectifier-smoothing circuit and the voltage application circuit do not pass through the bidirectional DC / AC inverter 30, the same voltage (143[V] in the above example) can be applied to the negative electrodes of the solar cells PV1 and PV2 regardless of the operating state of the bidirectional DC / AC inverter 30.
[0051] [Second Embodiment] Figure 3 shows a power storage system 1B according to a second embodiment of the present invention. Except for the DC / DC converter unit 10B and the voltage application circuit (first switching element 53), the power storage system 1B has the same configuration as the power storage system 1A of the first embodiment.
[0052] The DC / DC converter section 10B comprises a DC / DC converter 10 (10-1, 10-2), a diode D1 corresponding to the "first diode" of the present invention, and a switching element SW1 corresponding to the "second switching element" of the present invention. The DC / DC converters 10-1 and 10-2 have the same configuration as in the first embodiment.
[0053] Diode D1 has its anode connected to the negative terminal of capacitor C1, and its cathode connected to the connection point X2 between the negative terminal of the output side (other end) of DC / DC converter 10-1 (the negative terminal of capacitor 17) and the negative terminal of the output side (other end) of DC / DC converter 10-2 (the negative terminal of capacitor 17).
[0054] Switching element SW1 is connected in parallel to diode D1. Switching element SW1 may be composed of a semiconductor switch such as an FET, or it may be composed of a relay. Under the control of the control unit, switching element SW1 is in the off state when the first switching element 53 is in the on state, and in the on state when the first switching element 53 is in the off state. When the DC / DC converters 10-1 and 10-2 perform boost operation, switching element SW1 short-circuits both ends of diode D1, preventing a large current from flowing through diode D1.
[0055] The voltage application circuit includes a first switching element 53 (for example, a FET). One end of the current path of the first switching element 53 is connected to the positive terminal of the capacitor 52. The other end of the current path of the first switching element 53 is connected without a diode to the connection point between the negative terminal of solar cell PV1 and the negative terminal of capacitor 13 of DC / DC converter 10-1, and also to the connection point between the negative terminal of solar cell PV2 and the negative terminal of capacitor 13 of DC / DC converter 10-2.
[0056] In the energy storage system 1B according to this embodiment, similar to the first embodiment, the voltage application circuit (first switching element 53) applies a voltage rectified and smoothed by the rectifier and smoothing circuit (diodes 50, 51 and capacitor 52) to the negative poles of solar cells PV1 and PV2. When the amount of power generated (power generated or voltage generated) output from solar cells PV1 and PV2 is below a predetermined value, the voltage to ground of the negative poles of solar cells PV1 and PV2 is raised to zero or higher. This suppresses the occurrence of PID phenomena without using a junction box.
[0057] Furthermore, in the energy storage system 1B according to this embodiment, the number of components (diodes D2, 54, 55) can be reduced compared to the first embodiment.
[0058] [Third Embodiment] Figure 4 shows a power storage system 1C according to a third embodiment of the present invention. The power storage system 1C has the same configuration as the power storage system 1A of the first embodiment, except for the DC / DC converter section 10C and the voltage application circuit (first resistor 56 and diodes 54, 55).
[0059] The DC / DC converter section 10C comprises DC / DC converters 10 (10-1, 10-2), diodes D1, D2, and resistors R1, R2. The DC / DC converters 10-1, 10-2 and diodes D1, D2 have the same configuration as in the first embodiment.
[0060] Resistor R1 corresponds to the "second resistor" of the present invention and is connected in parallel with diode D1. Resistor R2 corresponds to the "second resistor" of the present invention and is connected in parallel with diode D2.
[0061] The voltage application circuit comprises a first resistor 56 and diodes 54 and 55 corresponding to the "second diode" of the present invention. One end of the first resistor 56 is connected to the positive terminal of capacitor 52, and the other end is connected to the anode of diode 54 and the anode of diode 55. The cathode of diode 54 is connected to the connection point between the negative terminal of solar cell PV1 and the negative terminal of capacitor 13 of DC / DC converter 10-1, and the cathode of diode 55 is connected to the connection point between the negative terminal of solar cell PV2 and the negative terminal of capacitor 13 of DC / DC converter 10-2. It is preferable that resistors R1 and R2 have higher resistance values than the first resistor 56.
[0062] In the energy storage system 1C according to this embodiment, similar to the first embodiment, the voltage application circuit (first resistor 56 and diodes 54, 55) applies a voltage rectified and smoothed by the rectifier and smoothing circuit (diodes 50, 51 and capacitor 52) to the negative poles of solar cells PV1 and PV2. When the amount of power generated (power generated or voltage generated) output from solar cells PV1 and PV2 is below a predetermined value, the voltage to ground of the negative poles of solar cells PV1 and PV2 is raised to zero or higher, thereby suppressing the occurrence of PID phenomena without using a junction box.
[0063] Furthermore, in the energy storage system 1C according to this embodiment, the overall cost of the system can be reduced by using a first resistor 56, which is less expensive than a switching element, in the voltage application circuit.
[0064] Although embodiments of the energy storage system according to the present invention have been described above, the present invention is not limited to the above embodiments.
[0065] The energy storage system according to the present invention comprises a grid connection terminal connected to a power grid, a DC / DC converter unit to which DC generated power from a power generation unit is input, a bidirectional DC / DC converter to which energy storage means are connected, and a bidirectional DC / AC inverter whose DC side is connected to the DC / DC converter unit and the bidirectional DC / DC converter, and whose AC side is connected to the grid connection terminal, and further comprises a rectifier and smoothing circuit whose input terminal is electrically connected to the grid connection terminal without going through the bidirectional DC / AC inverter, and a voltage application circuit connected to the output terminal of the rectifier and smoothing circuit and electrically connected to the negative terminal of the power generation unit, wherein the rectifier and smoothing circuit outputs a first DC voltage obtained by rectifying and smoothing the grid voltage of the power grid, and the voltage application circuit applies the first DC voltage to the negative terminal of the power generation unit, and the configuration can be changed as appropriate as long as the amount of power output from the power generation unit is increased to raise the voltage to ground of the negative terminal of the power generation unit when the amount of power output from the power generation unit is less than or equal to a predetermined value.
[0066] For example, the DC / DC converter section may consist of one DC / DC converter 10, or it may consist of three or more DC / DC converters 10. The configuration of the DC / DC converter 10 can be changed as appropriate, as long as it performs a boost operation.
[0067] In the first embodiment, the connection destination of the cathode of diode 54 constituting the voltage application circuit can be changed as appropriate, as long as it is between the negative terminal of solar cell PV1 and the cathode of diode D1. Similarly, the connection destination of the cathode of diode 55 constituting the voltage application circuit can be changed as appropriate, as long as it is between the negative terminal of solar cell PV2 and the cathode of diode D2.
[0068] In the second embodiment, the first resistor 56 of the third embodiment may be used instead of the first switching element 53, or the resistor R1 of the third embodiment may be used instead of the switching element SW1. [Explanation of Symbols]
[0069] 1A~1C Energy Storage System 10A~10C DC / DC Converter Section 10(10-1, 10-2) DC / DC converter 11 Voltage detection unit 12 Current detection unit 13 Capacitors 14 coils 15 Switching elements 16 diodes 17 Capacitors 20 Bidirectional DC / DC Converter 21 Voltage detection unit 22 Current detection unit 23 Capacitors 24 coils 25,26 Switching elements 30 Bidirectional DC / AC Inverter 40 Relay Circuits 50, 51 diodes 52 Capacitors 53 First switching element 54, 55 diodes 56 1st resistor
Claims
1. A grid connection terminal connected to a power grid, The DC / DC converter section receives DC power generated from the power generation section, A bidirectional DC / DC converter to which a power storage device is connected, A bidirectional DC / AC inverter, in which the DC side is connected to the DC / DC converter section and the bidirectional DC / DC converter, and the AC side is connected to the grid connection terminal, A power storage system equipped with, A rectifier and smoothing circuit whose input terminal is electrically connected to the grid connection terminal without going through the bidirectional DC / AC inverter, The system comprises a voltage application circuit connected to the output terminal of the rectifier and smoothing circuit and electrically connected to the negative terminal of the power generation unit, The rectifier and smoothing circuit outputs a first DC voltage obtained by rectifying and smoothing the system voltage of the power system. The voltage application circuit includes a first switching element interposed in the power line connecting the output terminal of the rectifier and smoothing circuit and the negative terminal of the power generation unit, and applies the first DC voltage to the negative terminal of the power generation unit, and raises the voltage to ground of the negative terminal of the power generation unit when the amount of power output from the power generation unit is less than or equal to a predetermined value. The first switching element turns on when the amount of power generated is less than or equal to the predetermined value, and turns off when the amount of power generated exceeds the predetermined value. A power storage system characterized by the following features.
2. A grid connection terminal connected to a power grid, The DC / DC converter section receives DC power generated from the power generation section, A bidirectional DC / DC converter to which a power storage device is connected, A bidirectional DC / AC inverter, in which the DC side is connected to the DC / DC converter section and the bidirectional DC / DC converter, and the AC side is connected to the grid connection terminal, A power storage system equipped with, A rectifier and smoothing circuit whose input terminal is electrically connected to the grid connection terminal without going through the bidirectional DC / AC inverter, The system comprises a voltage application circuit connected to the output terminal of the rectifier and smoothing circuit and electrically connected to the negative terminal of the power generation unit, The rectifier and smoothing circuit outputs a first DC voltage obtained by rectifying and smoothing the system voltage of the power system. The voltage application circuit applies the first DC voltage to the negative terminal of the power generation unit, and when the amount of power output from the power generation unit is less than or equal to a predetermined value, it increases the voltage to ground of the negative terminal of the power generation unit. The power generation unit comprises N power generation means (where N is an integer of 2 or more), The DC / DC converter section comprises N DC / DC converters, one end of which is connected to the N power generation means, and N first diodes, the other end of which is connected to the negative terminal. The voltage application circuit comprises a first switching element whose current path is connected to the output terminal of the rectifier-smoothing circuit, and N second diodes provided between the other end of the current path of the first switching element and the negative terminal of each of the N power generation means. A power storage system characterized by the following features.
3. A grid connection terminal connected to a power grid, The DC / DC converter section receives DC power generated from the power generation section, A bidirectional DC / DC converter to which a power storage device is connected, A bidirectional DC / AC inverter, in which the DC side is connected to the DC / DC converter section and the bidirectional DC / DC converter, and the AC side is connected to the grid connection terminal, A power storage system equipped with, A rectifier and smoothing circuit whose input terminal is electrically connected to the grid connection terminal without going through the bidirectional DC / AC inverter, The system comprises a voltage application circuit connected to the output terminal of the rectifier and smoothing circuit and electrically connected to the negative terminal of the power generation unit, The rectifier and smoothing circuit outputs a first DC voltage obtained by rectifying and smoothing the system voltage of the power system. The voltage application circuit applies the first DC voltage to the negative terminal of the power generation unit, and when the amount of power output from the power generation unit is less than or equal to a predetermined value, it increases the voltage to ground of the negative terminal of the power generation unit. The power generation unit comprises N power generation means (where N is an integer of 2 or more), The DC / DC converter section comprises N DC / DC converters, one end of which is connected to the N power generation means, and a first diode interposed in a power line connecting the connection point of the negative terminals on the other ends of the N DC / DC converters to the negative terminal on the DC side of the bidirectional DC / AC inverter. The voltage application circuit comprises a first switching element, one end of which is connected to the output terminal of the rectifier and smoothing circuit, and the other end of which is connected to the negative terminal of each of the N power generation means without passing through a diode. The first diode is connected in parallel with a second switching element. A power storage system characterized by the following features.
4. A grid connection terminal connected to a power grid, The DC / DC converter section receives DC power generated from the power generation section, A bidirectional DC / DC converter to which a power storage device is connected, A bidirectional DC / AC inverter, in which the DC side is connected to the DC / DC converter section and the bidirectional DC / DC converter, and the AC side is connected to the grid connection terminal, A power storage system equipped with, A rectifier and smoothing circuit whose input terminal is electrically connected to the grid connection terminal without going through the bidirectional DC / AC inverter, The system comprises a voltage application circuit connected to the output terminal of the rectifier and smoothing circuit and electrically connected to the negative terminal of the power generation unit, The rectifier and smoothing circuit outputs a first DC voltage obtained by rectifying and smoothing the system voltage of the power system. The voltage application circuit applies the first DC voltage to the negative terminal of the power generation unit, and when the amount of power output from the power generation unit is less than or equal to a predetermined value, it increases the voltage to ground of the negative terminal of the power generation unit. The power generation unit comprises N power generation means (where N is an integer of 2 or more), The DC / DC converter section comprises N DC / DC converters, one end of which is connected to the N power generation means, and N first diodes, the other end of which is connected to the negative terminal. The voltage application circuit comprises a first resistor, one end of which is connected to the output terminal of the rectifier-smoothing circuit, and N second diodes provided between the other end of the first resistor and the negative terminals of each of the N power generation means. The first diode is connected in parallel with a second resistor. A power storage system characterized by the following features.
5. The rectifier and smoothing circuit described above is A rectifier means interposed in a power line connecting the grid connection terminal and the voltage application circuit without going through the bidirectional DC / AC inverter, The system includes a smoothing means to which a positive terminal is connected at the connection point between the rectifier means and the voltage application circuit. The energy storage system according to any one of claims 1 to 4.