Power conversion system

Abstract

This facilitates system modifications for power conversion systems that can be equipped with batteries. [Solution] The power conversion system includes a D / A circuit 4 that converts DC power to AC power, a first function that enables the D / A circuit 4 to convert DC power generated by solar cells 2a to 2d into AC power when DC power generated by solar cells 2a to 2d is supplied to the D / A circuit 4, a second function that enables the D / A circuit 4 to convert at least one of the DC power generated by solar cells 2a to 2d or the DC power output from storage batteries 13a to 13d into AC power when DC power output from storage batteries 13a to 13d is supplied to the D / A circuit 4, and a third function that selects either the first function or the second function based on the presence or absence of a storage battery.

Description

Technical Field

[0001] The present invention relates to a power conversion system including a power conversion circuit that converts DC power generated by a solar cell into AC power, and particularly to a power conversion system that changes an operation mode based on the presence or absence of connection of a storage battery.

Background Art

[0002] In recent years, systems that convert DC power generated by solar cells into AC power for self-consumption by loads in a building and sell surplus power during this process to the grid, or systems that sell all of this AC power to the grid, have come to be used. Since these systems rely on the power generation of solar cells, they could not be substantially utilized at night or in dark conditions. In particular, during a power outage in the grid, surplus power could not be sold, and it was also impossible to reuse it at night.

[0003] For this reason, as described in Patent Document 1, a power conversion system has been proposed that uses a storage battery to temporarily store surplus power and reuse it as needed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] What is described in Patent Document 1 is a system premised on connecting a storage battery so that the control power supply of this power conversion system can be ensured from the storage battery. However, securing sufficient energy storage capacity requires a large proportion of the installation space for the battery, which has hindered its widespread use in homes and other residential buildings. Furthermore, if a system utilizing battery storage is requested later, the entire system must be replaced with a new battery-based system. This has hindered replacement and widespread adoption of systems with a lifespan of only about 10 years once installed. Furthermore, while there are electronic devices that simply allow the removal of a battery (or storage battery), these devices do not convert DC power to AC power regardless of whether a battery (or storage battery) is present or not. In other words, they cannot supply AC power to loads inside a building during a power outage. Furthermore, there is a system that allows a battery installed in an electric vehicle to be connected to a power converter that converts DC power generated by solar cells into AC power. However, this system itself is large and requires securing a place to install it together with the electric vehicle. [Means for solving the problem]

[0006] The power conversion system of the present invention is characterized by comprising: a power conversion circuit that converts DC power to AC power; a first function that enables the power conversion circuit to convert DC power generated by a solar cell into AC power when DC power generated by a solar cell is supplied to the power conversion circuit; a second function that enables the power conversion circuit to convert at least one of the DC power generated by the solar cell or the DC power output from the storage battery into AC power when DC power output from a storage battery is supplied to the power conversion circuit; and a third function that selects either the first function or the second function based on the presence or absence of a storage battery. [Effects of the Invention]

[0007] The power conversion system of the present invention, by having such a configuration, can operate by switching between operating modes, specifically between a state with a battery and a state without a battery, using a single power conversion system. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is an explanatory diagram including a power conversion system according to one embodiment of the present invention. [Figure 2] Figure 2 is an explanatory diagram showing an example of a D / D circuit. [Figure 3] Figure 3 is an explanatory diagram showing an example of a D / A circuit. [Figure 4] Figure 4 is an explanatory diagram of a chopper-type bidirectional D / D circuit. [Figure 5] Figure 5 is an explanatory diagram showing the operation of a part of the control unit. [Modes for carrying out the invention]

[0009] The power conversion system of the present invention comprises: a power conversion circuit that converts DC power to AC power; a first function that enables the power conversion circuit to convert DC power generated by a solar cell to AC power when DC power generated by a solar cell is supplied to the power conversion circuit; a second function that enables the power conversion circuit to convert at least one of the DC power generated by a solar cell or the DC power output from a storage battery to AC power when DC power output from a storage battery is supplied to the power conversion circuit; and a third function that selects either the first function or the second function based on the presence or absence of a storage battery.

[0010] Figure 1 is an explanatory diagram including a power conversion system according to one embodiment of the present invention. 1 is a power conditioner, which includes DC / DC conversion circuits 3a to 3d (hereinafter referred to as "D / D circuits 3a to 3d") that boost the DC power generated by solar cells 2a to 2d (hereinafter referred to as "solar cells 2a to 2d"), and a power conversion circuit 4 (hereinafter referred to as "D / A circuit") that converts the DC power output from the D / D circuits 3a to 3d into AC power. Each of the solar cells 2a to 2d is electrically connected to its respective D / D circuit 3a to 3d via its respective terminal (indicated by a circle in the figure). The DC power generated by each of the solar cells 2a to 2d is supplied to its respective D / D circuit 3a to 3d. Note that a switch to interrupt the supply of DC power is provided between each of the D / D circuits 3a to 3d and its corresponding terminal, but this is omitted from the illustration in Figure 1.

[0011] The D / D circuit 3a changes the boost ratio so that the DC power output from the solar cell 2a reaches its maximum value or a target value. The boost circuit method is not limited; for example, there is a non-isolated chopping method mainly using a reactor, switching element, diode, and smoothing capacitor, and an isolated forward type mainly using a switching element, isolation transformer, rectifier circuit, and capacitor. Furthermore, charge pump type, flyback type, and resonant type can also be used. The boost ratio is controlled by the control unit 5. Note that D / D circuits 3b to 3d have a similar configuration, so their explanation is omitted.

[0012] D / A circuit 4 is a power conversion circuit that converts DC power into AC power at a predetermined frequency (for example, a frequency synchronized with system 6 when operating in grid-connected mode, or either 50Hz or 60Hz when operating independently). For example, based on the PWM (Pulse Width Modulation) method, it generates a pseudo-sine wave by repeatedly switching multiple switching elements (such as semiconductors) on and off, and then removes or attenuates high-frequency components with a filter circuit to obtain AC power. In Figure 1, D / A circuit 4 is shown including this filter circuit, but it may also be shown separately. Furthermore, the configuration of the conversion circuit is not limited to such a PWM method; it can also be an NPC (Neutral Point Clamped) inverter, a gradation control type inverter, or the output of an inverter bridge circuit. The DC / AC conversion method is not limited to clamping the side or input side.

[0013] The D / A circuit 4 only needs to be able to output AC power and control the frequency, peak voltage (effective value is also acceptable), and phase difference between voltage and current of this AC power. The D / A circuit 4 is controlled by the control unit 5, similar to the D / D circuits 3a to 3d. The configuration of the control unit 5 is not limited and can be one or more microprocessors (general-purpose microcontrollers), or one centered around a DSP (Digital Signal Processor).

[0014] 7 is a switching circuit (for example, a relay circuit or a circuit using a semiconductor switch) that switches between the output of AC power during grid-connected operation with grid 6 and the output of AC power during standalone operation. During grid-connected operation with grid 6, the AC power output from the D / A circuit 4 is supplied to grid 6 via the switching circuit 7 and the grid-connected relay 8. In other words, the DC power generated by the solar cells 2a to 2d is converted into AC power that can be synchronized with grid 6 using the D / D circuits 3a to 3d and the D / A circuit 4, and the operation of converting the DC power generated by the solar cells into AC power using the power conversion circuit corresponds to the first function. This first function may include controls necessary for grid-connected operation, such as detection of power outages in grid 6, output suppression control to grid 6, and operation of the switching circuit 7. Furthermore, the power supplied to grid 6 is controlled by controlling the peak voltage of this AC power to be higher than the peak voltage of grid 6. In addition, by controlling the phase difference between the voltage and current of this AC power and injecting reactive power into grid 6, it is possible to use this for detecting islanding operation of power conditioner 1.

[0015] Figure 2 is an explanatory diagram showing an example of D / D circuit 3a. It consists of a reactor, switching elements, diodes, and capacitors connected to form a chopper-type boost circuit. Figure 3 is an explanatory diagram showing an example of D / A circuit 4. It consists of four (six in the case of three-phase AC power) switching elements connected in a single-phase bridge configuration (or a three-phase bridge configuration in the case of three-phase AC power), and the output side consists of a filter circuit consisting of a reactor and a capacitor, and an output clamp circuit using two switching elements in series to short-circuit the regenerative current from the reactor.

[0016] 9 is a power detector that detects, for example, the power supplied to or from system 6 and outputs it to the control unit 5. The power detection method is not limited to direct power detection, voltage and current detection and calculation, or integration from the voltage waveform.

[0017] In the case shown in FIG. 1, the breaker 10 for the switchboard is connected to the power wiring between the system interlocking relay 8 and the power detector 9 and is configured to be able to obtain AC power from both the system 6 and the power conditioner 1. For example, sub - breakers 10a and 10b are connected to the breaker 10 for the switchboard. The sub - breaker 10b supplies AC power to general loads in the building, and the sub - breaker 10a supplies power to a specific load via the switch 11. The specific load is a load with a high priority of supplying AC power even when the system 6 has an abnormality such as a power outage and power is not supplied, and includes an emergency notification system, a refrigerator, etc., and electrical equipment designated by the user.

[0018] When the control unit 5 determines that the power conditioner 1 is in the single - operation state due to a power outage of the system 6 or the like and switches the switching circuit 7 to the self - operation side to output AC power, the switch 11 detects that AC power is being supplied from the switching circuit 7 of the power conditioner 1 and supplies the AC power from the power conditioner 1 to the specific load. When no AC power is supplied from the power conditioner 1, the switch 11 supplies the AC power from the sub - breaker 10a to the specific load.

[0019] 12 is a monitor, which is configured to be able to transmit and receive control signals and data with the control unit 5 via a signal line. The monitor 12 is configured to be able to perform signal communication regardless of whether it is wired - connected or wireless - connected to the control unit 5. A personal computer, a mobile communication device, a mobile terminal, a dedicated terminal, etc. connected via a communication network can also be used for this monitor 12. The monitor 12 displays the power generation amount of the solar cell, the power selling amount to the system 6, the power buying amount from the system 6, etc., and receives a control signal and a signal for determining the upper limit of the power supplied to the system 6 from an external server via the communication network, operates in conjunction with the control unit 5, and can also transmit data such as the power generation amount to a server or other monitors.

[0020] 13a to 13d are storage batteries, and each may have functions such as at least charge-discharge control (constant voltage charging, constant current charging, control of discharge amount, etc.), display (transmission) of the charge rate (SOC), and protection operations against overcharging and overdischarging, and the type of battery is not limited. 14a and 14b are converters, and each降压 the DC voltage supplied from the power conditioner 1 to the voltage at which the charge control of the storage battery (for example, the storage battery 13a, and the same applies to the other storage batteries 13b to 13d) functions, and升压 the discharge voltage of the storage battery to the voltage at which the D / A circuit 4 functions, and includes bidirectional D / D circuits 15a, 15b (bidirectional D / D circuits 15c, 15d) and converter control units 16a (converter control units 16b).

[0021] FIG. 4 is an explanatory diagram of a chopper-type bidirectional D / D circuit showing an example of the bidirectional D / D circuit 15a (the same applies to the bidirectional D / D circuits 15b to 15d and the explanation is omitted). This circuit is obtained by adding a降压 circuit composed of a switching element and a capacitor to the chopper-type升压 circuit shown in FIG. 2. When升压 the DC voltage on the low voltage side, the reactor 18a, the switching element 18b, the diode 18c, and the capacitor 18d form a chopper-type升压 circuit, and the ON duty of the switching element 18b is variably controlled so that a target voltage is obtained on the high voltage side based on the feedback value. When降压 the DC voltage on the high voltage side, the switching element 18e, the reactor 18a, and the capacitor 18f form a chopper-type降压 circuit, and the ON duty of the switching element 18e is variably controlled so that a target voltage is obtained on the low voltage side based on the feedback value.

[0022] Therefore, for example, when charging the storage battery 13a, the DC power supplied from the power conditioner 1 is降压 to the charging voltage by the bidirectional D / D circuit 15a, and when the storage battery 13a discharges, the DC power升压 by the bidirectional D / D circuit 15a is supplied to the power conditioner 1.

[0023] The bidirectional D / D circuit 13a is not limited to the chopper type shown in Figure 4; it can also use a push-pull type bidirectional DC / DC converter using an isolation transformer, a full-bridge type bidirectional DC / DC converter, a DAB (Dual Active Bridge) type bidirectional DC / DC converter, a bidirectional DC / DC converter using an LLC resonant converter, and is not limited to these types.

[0024] The converter control unit 16a controls the boost and buck operations of the bidirectional D / D circuits 13a and 13b, and acquires the status and state of charge (SOC) of the batteries 13a and 13b via signal lines (indicated by dashed lines) connected to the batteries 13a and 13b. Furthermore, the converter control unit 16a is connected to the control unit 5 of the power conditioner 1 via signal lines (indicated by dashed lines), and is configured to send and receive control signals and SOC data to and from each other.

[0025] Converter 14a is connected to two batteries 13a and 13b, but the number of connected batteries is not limited to these and may be increased or decreased. In this case, a bidirectional D / D circuit may be provided for each connected battery, or multiple batteries may be connected to a bidirectional D / D circuit with a large output capacity. Converter 14b can be configured in the same way as converter 14a, so its explanation is omitted.

[0026] One of the bidirectional D / D circuits of converters 14a and 14b is connected via a switch 17 to a DC line 19 through which DC power flows, connecting the D / D circuits 3a to 3d and the D / A circuit 4 of the power conditioner 1. Therefore, this DC line 19 is connected to the high-voltage side of the bidirectional D / D circuit, enabling the DC power discharged from the battery to be converted into AC power by the D / A circuit 4. The switch 17 has an auxiliary contact 17a for signaling, which is linked to the switching operation, and the open / closed state of the auxiliary contact 17a is scanned by the control unit 5 and used for control. Note that the switch 17 is a switch that can be manually switched between open and closed states. That is, when a battery is connected (when a battery is present), the operator manually closes the switch 17.

[0027] When the switch 17 is closed and at least one of the D / D circuits of converter 14a or converter 14b is connected to the DC line 19 of the power conditioner 1, it becomes possible to control the charging and discharging of the storage battery in addition to the operation based on the first function (the function of converting DC power generated by the solar cell into AC power). By boosting the DC power output from this storage battery in the D / D circuit and supplying it to the D / A circuit 4 via the DC line 19, it becomes possible to convert the DC power from the storage battery into AC power. Therefore, it becomes possible to convert at least one of the DC power generated by the solar cell or the DC power output from the storage battery into AC power using the D / A circuit 4. (Second function)

[0028] The discharge control of converter 14a (and similarly for converter 14b) is performed by the converter control unit 16a based on the control signal transmitted from the control unit 5 (the state of charge (SOC) used to terminate the discharge and the amount of discharge per unit time). When the combined charge rate (SOC) of the storage batteries 13a and 13b connected to the converter 14a drops below, for example, 10%, the process of ending the discharge is performed and a signal indicating the end of discharge (SOC = 10%) is transmitted to the control unit 5. Note that the charge rate (SOC) for determining the end of discharge is not limited to 10% and can be set arbitrarily. When it is desired to always ensure a charge rate (SOC) of a certain level or higher in preparation for disasters, power outages, etc., a larger value such as 50%, 60% (90% is also possible) can be used. When it is desired to efficiently utilize the storage batteries, a smaller value such as 0%, 10% can be set. This value of the charge rate (SOC) may be set in advance according to the operating mode set in the control unit 5.

[0029] Also, when the discharge amount per unit time of the bidirectional D / D circuit 15a (the same applies to the bidirectional D / D circuit 15b) is set to, for example, AA "W" (a value not exceeding the allowable discharge amount of the storage battery), the boost ratio of the bidirectional D / D circuit 15a is controlled so that the power on the low-voltage side of the bidirectional D / D circuit 15a (the product of the voltage and current of the storage battery) becomes AA "W". Note that when two storage batteries are connected, the respective discharge amounts are distributively controlled so that the total discharge amount of the two storage batteries becomes AA "W".

[0030] Also, when the voltage of the DC line 19 of the power conditioner 1 rises above a predetermined protection voltage due to the boost operation of the bidirectional D / D circuit 15a and the bidirectional D / D circuit 15b, the control unit 5 determines this voltage rise and transmits a signal to the converter control unit 16a to reduce the discharge amount to BB "W" (<AA "W"). This discharge amount of AA "W" may be calculated, for example, as a supplement when the power generation amount of the solar cells 2a to 2d is insufficient for the power consumption of the load. Also, this shortage may be calculated as a supplement for the amount exceeding a certain amount of the power purchased from the grid 6. Furthermore, it may be calculated as a supplement for these at a specific time zone within a day, or as equivalent to the power consumption of a specific load during independent operation. It may be set according to the design specifications of the power conversion system. Note that these calculations may be set for each operating mode and configured so that the user can arbitrarily select the operating mode.

[0031] The charge control of converter 14a (and similarly for converter 14b) is performed by the converter control unit 16a based on the control signal transmitted from the control unit 5 (the state of charge (SOC) used to terminate charging and the amount of charge per unit time). When the state of charge (SOC) of the batteries 13a and 13b connected to the converter 14a exceeds, for example, 100%, the charging termination process is performed and a charging termination signal (SOC=100%) is sent to the control unit 5. Note that the SOC at which charging termination is determined is not limited to 100% but can be set arbitrarily. For example, SOC=90% may be used to consider stress on the batteries, or 95% may be used to determine charging termination based on charging characteristics.

[0032] Furthermore, if the amount of charge per unit time in the bidirectional D / D circuit 15a (and similarly in the bidirectional D / D circuit 15b) is set to, for example, CC "W" (a value that satisfies the allowable charging voltage and allowable current of the storage battery), the step-down ratio of the bidirectional D / D circuit 15a is controlled so that the power on the low-voltage side of the bidirectional D / D circuit 15a (the product of the storage battery voltage and current) becomes CC "W".

[0033] When a lithium-ion battery is used as the storage battery, constant current constant voltage charging (CCCV) can be used within CC "W". The current value for constant current charging is 1C "A", which corresponds to 10% of the nominal capacity of the storage battery, and the voltage value for constant voltage charging is 4.2 "V", which corresponds to the cell, but is not limited to this. When the CC "W" value transmitted from the control unit 5 is small, values ​​such as 0.7C or 0.5C may be used.

[0034] The value of the amount of charge per unit time transmitted from the control unit 5 may be calculated, for example, from the surplus amount of power generated by the solar cells 2a to 2d relative to the power consumption of the load. If charging is prioritized, a value that allows charging at 1C may be calculated. Also, when charging at night, a value that allows charging at 1C (or a smaller value such as 0.5C or 0.7C if it is acceptable to extend the charging time) may be calculated.

[0035] The converter 14a has a setting section for manually selecting the type of battery, allowing for settings such as lithium-ion batteries, nickel-metal hydride batteries, and lead-acid batteries. The converter 14a performs appropriate charge / discharge control according to the selected battery type. This setting can also be configured via the monitor 12.

[0036] Monitor 12 can display the amount of electricity generated by the battery and information on electricity sales, and also has various setting functions for power conditioner 1. By operating the operation buttons or the touch panel on the display, it is possible to switch the operating mode of the power conversion system, which includes at least power conditioner 1 and the battery, switch display items, and set the number of converters connected. It can also be connected to a home energy management system in the home, and control signals and data can be exchanged with that system.

[0037] Alternatively, instead of scanning the state of the auxiliary contact piece 17a which is linked to the switch (manual switch) 17 to determine whether the battery is connected or not, the monitor 12 can be operated to electrically store the state of whether the battery is connected or not in the monitor, and then the stored data can be transmitted to the control unit 5 to set the power conditioner 1.

[0038] In the operating modes, for example, in the first operating mode, when the DC power generated by the solar cells 2a to 2d is boosted by the D / D circuits 3a to 3d and then supplied to the D / A circuit 4 (when the solar cells are generating power), the DC power generated by the solar cells is converted to AC power in the D / A circuit 4 and supplied to the grid 6 or load. (A function that encompasses the first function).

[0039] In the second operating mode, in addition to the operations of the first operating mode, when the power consumed by the load is less than the power generated by the solar cells 2a to 2d, resulting in surplus power, the batteries 13a to 13d are charged at a rate of CC "W" per unit time according to the amount of this surplus power. If there is still surplus power remaining during this charging, or if it is determined that charging of batteries 13a to 13d has ended, this surplus power (DC power) is converted to AC power and sold to the grid.

[0040] When the power generation from solar cells 2a to 2d is low, when there is no power generation, when the load's power consumption is greater than the power generation, or when the amount of electricity purchased from grid 6 per unit time exceeds a predetermined value, a DC power discharge of AA "W" per unit time is performed to the DC line 19. If the discharge amount is insufficient compared to the load's power consumption, the deficit is compensated for by grid 6. Furthermore, in the event of a power outage, the switching circuit 7 switches, and AC power is supplied only to specific loads. That is, when DC power output from the battery is supplied to the D / A circuit 4 via the DC line 19, at least one of the DC power generated by the solar cells or the DC power output from the battery is converted to AC power by the D / A circuit 4. (Function encompassing the second function) The D / A circuit 4 can convert either the power generated by the solar cell or the power discharged from the storage battery, or the sum of the power generated by the solar cell and the power discharged from the storage battery, into AC power.

[0041] In the third operating mode, in addition to the operation of the first operating mode, the batteries 13a to 13d are charged at night (during specific time periods, such as when off-peak electricity is available), and when the amount of power generated by the solar cells 12a to 12d is less than the power consumption of the load, the deficit is discharged from the batteries 13a to 13d. At this time, similar to the second operating mode, at least one of the DC power generated by the solar cells or the DC power output from the batteries is converted into AC power by the D / A circuit 4. (This corresponds to the second function.)

[0042] If the amount of electricity generated by solar cells 12a to 12d exceeds the power consumption of the load, the surplus will be sold to grid 6. Furthermore, if the total state of charge (SOC) of batteries 13a to 13d is below a predetermined value, the system may be configured to charge batteries 13a to 13d with any amount exceeding the set value of electricity sold per unit time from the batteries.

[0043] In the fourth operating mode, in addition to the third operating mode, the discharge of batteries 13a to 13d is prevented from falling below a state of charge (SOC) of 60% (the SOC may be changed to 70%, 80%, etc., depending on usage). The batteries are charged to 100% SOC overnight, and if there is sufficient power generation capacity from the solar cells 12a to 12d, charging continues during the day to the extent possible. In this case, similar to the second operating mode, at least one of the DC power generated by the solar cells or the DC power output from the batteries is converted to AC power by the D / A circuit 4. (This corresponds to the second function.)

[0044] The operating modes are not limited to these first to fourth operating modes, but only need to include at least the first and second functions, and the specifications of the operating modes can be arbitrarily set according to the expected usage conditions.

[0045] Figure 5 is an explanatory diagram illustrating the general operation of the third function of the control unit 5. In step S1, the presence or absence of the battery is determined. This determination is made by first scanning the open / closed state of the auxiliary contact 17a corresponding to the set state of the switch 17 (manual switch). If the auxiliary contact 17a is closed, it is further determined whether signal communication is possible between the converter control unit 16a and the control unit 5. If this signal communication is possible, it is determined that the converter 14a is connected. In other words, it can be determined that at least one of either the battery 13a or the battery 13b is connected (present). The connection or absence of the converter 14b is determined in the same way. Alternatively, instead of scanning the state of the auxiliary contact 17a, it is also possible to use the electrically set state (data) of the presence or absence of the battery stored in the monitor 12. Furthermore, it is also possible to determine the presence or absence of the battery using at least one of the following: the state of the auxiliary contact 17a, the state in which signal communication with the converter control units 16a and 16b is possible, or the data from the monitor 12. Furthermore, the presence or absence of the battery can be determined by whether or not the potential on the converter 14a side of the switch 17 rises when a signal instructing discharge is sent to the converter control unit 16a. In this case, it can also be determined at the same time whether signal communication is possible between the converter control unit 16a and the control unit 5. After the presence or absence of the battery is determined, that state is maintained and the process proceeds to the step of selecting the operating mode.

[0046] If it is determined in step S1 that there is no battery (if it is not determined that there is a battery), the process proceeds to step S2 to set the first operating mode, and the power conversion system is operated in step S7. If it is determined in step S1 that there is a battery, the process proceeds to step S3 to enable selection from the second to fourth operating modes, and then it is determined which operating mode is selected. This operating mode selection is set by operating the monitor 12, but it is also possible to select it using a setting switch on the power conditioner 1 or other information equipment connected to the control unit 5 via a signal line. If the second operating mode is selected, the second operating mode is set in step S4, and the power conversion system is operated in step S7. If the third operating mode is selected, the third operating mode is set in step S5, and the power conversion system is operated in step S7. If the fourth operating mode is selected, the fourth operating mode is set in step S6, and the power conversion system is operated in step S7. [Industrial applicability]

[0047] The power conversion system of the present invention is applicable to a power conversion system that enables the conversion of at least one of DC power generated by a solar cell or DC power output from a storage battery into AC power using a power conversion circuit.

[0048] Although one embodiment of the present invention has been described above, this description is intended to facilitate understanding of the present invention and does not limit it. The present invention can be modified and improved without departing from its spirit, and of course, equivalents thereof are included in the present invention. [Explanation of symbols]

[0049] 1 Power Conditioner 2a to 2d solar cells 3a to 3d D / D circuit 4 D / A circuit 5. Control Unit 6 lines 12 monitors 13a to 14d Storage battery 14a, 14b converter 15a to 15d Bidirectional D / D circuit 16a to 16b Converter control unit 17 Switch 17a Auxiliary contact piece 19 DC line

Claims

1. A power conversion circuit that converts the DC power output from the solar cell into AC power and supplies it to the load, A battery can be connected to a terminal that is connected to the DC line, The system comprises the power conversion circuit and a control unit for controlling the charging and discharging of the battery, The control unit performs control based on the operating mode selected from a plurality of operating modes. The aforementioned plurality of operating modes include an operating mode that can be selected when the battery is connected to the terminal and cannot be selected when the battery is not connected to the terminal. The power conversion system is characterized in that the operating mode includes an operating mode in which the battery is charged when the power consumed by the load is less than the power generated by the solar cell, resulting in a surplus of power.

2. The power conversion system according to claim 1, wherein the operating mode charges the storage battery so that the amount of charge per unit time is set to a set value, and if the surplus power is not resolved even after this charging, or if it is determined that the charging of the storage battery has ended, the power conversion circuit converts the surplus power into AC power and supplies it to the grid.

3. A power conversion circuit that converts the DC power output from the solar cell into AC power and supplies it to the load, A battery can be connected to a terminal that is connected to the DC line, The system comprises the power conversion circuit and a control unit for controlling the charging and discharging of the battery, The control unit performs control based on the operating mode selected from a plurality of operating modes. The aforementioned plurality of operating modes include an operating mode that can be selected when the battery is connected to the terminal and cannot be selected when the battery is not connected to the terminal. The operating mode is a power conversion system characterized by charging the storage battery during specific time periods and discharging the deficit from the storage battery when the amount of power generated by the solar cell is less than the power consumption of the load.

4. The power conversion system according to claim 3, characterized in that the aforementioned specific time period is nighttime.

5. The power conversion system according to claim 3, characterized in that the aforementioned specific time period is a time period during which off-peak electricity is available.

6. The power conversion system according to claim 3, characterized in that the plurality of operating modes include an operating mode that prevents the State of Cost (SOC) of the storage battery from falling below a predetermined value when discharging from the storage battery.

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