Solar power generation and energy storage system

Abstract

This prevents the mixing of electricity sold at a fixed price (surplus electricity) from batteries with electricity sold at a free price (excess electricity). [Solution] The solar power generation and energy storage system of the present invention is connected to a commercial power source and comprises a first PCS, a second PCS, a third PCS, a first solar cell panel connected only to the first PCS, a switching device capable of switching the connection between the first PCS and the second PCS, a second solar cell panel 36 connected to the switching device, a storage battery connected to the first PCS, a third solar cell panel connected only to the third PCS, and a control unit that controls the first PCS, the second PCS, the third PCS, and the switching device, wherein the control unit implements control to provide a predetermined blank period after sunset during which no electricity is sold to the commercial power source and no electricity is stored in the storage battery.

Description

Technical Field

[0001] The present invention relates to a photovoltaic power storage system that efficiently distributes electric power generated by photovoltaic power generation for self-consumption, power storage, and selling electricity to a power company.

Background Art

[0002] The feed-in tariff (FIT) system for renewable energy is a system in which the country promises that a power company will purchase electricity generated from renewable energy at a fixed price for a certain period. A part of the cost for the power company to purchase is collected from the public in the form of a levy, and this mechanism promotes the stable purchase of renewable energy by the power company and promotes the spread of renewable energy. Although the total amount of generated electricity is subject to purchase, in the case of a solar cell panel with a power generation capacity of less than 10 kW installed on the roof of a house or a solar cell panel with a power generation capacity of 10 to 50 kW installed on the roof of a building or factory, the surplus power exceeding self-consumption is subject to purchase.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, FIT rates are decreasing year by year. For systems under 10kW, the FIT rates for solar power generation in fiscal year 2025 are 15 yen per kWh for the April-September period, and 24 yen per kWh (up to 4 years) and 8.3 yen per kWh (5-10 years) for the October-March period. In contrast, electricity purchase prices are rising year by year. For example, the electricity rate (1kWh) for Tokyo Electric Power Company's Standard S plan in fiscal year 2025 is 29.80 yen (up to 120kWh), meaning that electricity purchase prices are higher than electricity sales prices. For renewable energy power generators, it is more profitable to consume the generated electricity themselves than to sell it under a FIT contract (fixed-price electricity sales). As a result, there is a growing demand to either consume the generated electricity themselves or to store it. Furthermore, when installing a solar power generation and storage system as a renewable energy source, solar panels are required to generate electricity, and a power conditioner (PCS, Power Conditioning System) is needed to convert the DC current generated by the solar panels into AC current. Generally, solar panels are cheaper than PCS, so there is a tendency to install many solar panels to increase the efficiency of selling electricity, and sometimes the number of solar panels installed exceeds the processing capacity of the PCS. However, under the FIT (Feed-in Tariff) system, electricity exceeding the processing capacity of the PCS (Power Conditioning System) is considered excess electricity (excess electricity) and is not eligible for FIT sales. Therefore, if excess electricity is stored, measures must be taken to prevent this stored electricity from being mixed with the electricity sold under the FIT system.

[0005] The present invention has been made in view of the above problems, and its purpose is to provide a solar power generation and energy storage system comprising solar panels, a PCS, and a storage battery that stores excess power when excess power occurs, and prevents the mixing of electricity sold at a free price from the storage battery (excess power) with electricity sold at a fixed price to the commercial power supply (surplus power). [Means for solving the problem]

[0006] The solar power generation and energy storage system according to claim 1 is connected to a commercial power source and comprises a first PCS, a second PCS, a third PCS, a first solar cell panel connected only to the first PCS, a switching device capable of switching the connection between the first PCS and the second PCS, a second solar cell panel 36 connected to the switching device, a storage battery connected to the first PCS, a third solar cell panel connected only to the third PCS, and a control unit that controls the first PCS, the second PCS, the third PCS, and the switching device, wherein the control unit implements control to provide a predetermined blank period after sunset during which no electricity is sold to the commercial power source and no electricity is stored in the storage battery.

[0007] The solar power generation and energy storage system according to claim 2 is characterized in that, when the control unit detects excess power exceeding the surplus power generated by the first solar panel and the second solar panel, it controls the switching device from a state in which the second solar panel and the second PCS are connected to a state in which the second solar panel and the first PCS are connected, and performs control to store the power generated by the first solar panel and the second solar panel in the energy storage battery.

[0008] The solar power generation and energy storage system according to claim 3 includes a control unit which controls the battery to stop storing energy in the battery when the amount of energy stored in the battery reaches the upper limit of the battery's energy storage capacity, and controls the switching device from a state in which the second solar panel and the first PCS are connected to a state in which the second solar panel and the second PCS are connected.

[0009] The solar power generation and energy storage system according to claim 4 comprises a first power conditioner, a second power conditioner, a storage battery, a first solar cell panel, a second solar cell panel, a switching device, and a control device for controlling these, wherein the first solar cell panel is connected only to the first PCS, the second solar cell panel is connected to the switching device, the storage battery is connected only to the first PCS, and the switching device is connected to both the first and second PCS and is configured to be switchable between the first and second PCS, thereby enabling the switching of the connection between the second solar cell panel and either the first or second PCS.

[0010] The photovoltaic energy storage system according to claim 5 further comprises a third PCS and a third solar cell panel connected only to the third PCS. [Effects of the Invention]

[0011] Thus, the solar power generation and energy storage system of the present invention comprises solar panels, a PCS (Power Conditioning System), and a storage battery. When excess power is generated, it stores the excess power, and by implementing a control that provides a predetermined gap period after sunset during which neither power is sold nor stored, it is possible to prevent the stored excess power from being mixed with power sold under the FIT (Feed-in Tariff) system. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a connection diagram showing an example of a schematic configuration of a solar power generation and energy storage system according to an embodiment of the present invention. [Figure 2] Figure 2 shows an example of a schematic configuration of a Home Energy Management System (HEMS). [Figure 3] Figure 3 shows an example of a schematic configuration of the control unit of a HEMS (Home Energy Management System). [Figure 4] Figure 4 shows an example of changes in power generation, self-consumption, power sold, power purchased, surplus power, and excess power. [Figure 5]Figure 5 is a flowchart showing an example of the processing steps in a solar power generation and storage system. [Figure 6] Figure 6 is a flowchart illustrating an example of the processing steps in a solar power generation and storage system, showing the processing flow that follows the flowchart shown in Figure 5. [Modes for carrying out the invention]

[0013] An embodiment of the present invention, a solar power generation and energy storage system, will be described with reference to Figures 1 to 6.

[0014] As shown in Figure 1, the solar power generation and storage system 1 according to this embodiment includes a HEMS 16, a first PCS 20, a second PCS 22, a third PCS 24, a first switching device 26, a second switching device 28, a third switching device 30, a storage battery 32, and first to sixth solar panels 34 to 44. The solar power generation and storage system 1 is connected to a commercial power supply 10, and a first power meter 12 and a second power meter 14 are interposed between the solar power generation and storage system 1 to measure forward and reverse power flow. In addition, household electrical appliances 18 are connected to the solar power generation and storage system 1. Household electrical appliances 18 include, for example, a television, an electric refrigerator, a washing machine, an automatic rice cooker, lighting, an air conditioner, a microwave oven, an EcoCute (heat pump water heater), and other electrical equipment.

[0015] The commercial power supply 10 supplies power to the solar power generation and storage system 1, for example, at an AC voltage of 100V, which becomes the electricity purchased by the solar power generation and storage system 1. The commercial power supply 10 also receives electricity sold by the solar power generation and storage system 1. The electricity purchased and sold to and from the commercial power supply 10 is measured by the first power meter 12 and the second power meter 14. The first power meter 12 measures the exchange of electricity between the commercial power supply 10 and the solar power generation and storage system 1. The forward power flow, that is, the amount of electricity supplied from the commercial power supply 10 to the solar power generation and storage system 1 (purchased electricity), is measured by the first power meter 12 and the second power meter 14. The electricity purchased from the commercial power supply 10 becomes either self-consumption by household electrical appliances 18 or electricity stored in the storage battery 32.

[0016] The reverse power flow, that is, the amount of electricity supplied from the solar power generation and storage system 1 to the commercial power supply 10 (the amount of electricity sold), is measured by the first power meter 12 and the second power meter 14. The first power meters 12 and 14 measure forward and reverse power flow and transmit the measured power data wirelessly to the HEMS 16 and the power company.

[0017] The electricity generated by solar panels that exceeds the amount consumed by the user (surplus electricity) is sold at a fixed price, and the amount of electricity sold is measured as reverse power flow electricity by the first power meter 12. When electricity stored in the battery 32 is sold, it does not fall under fixed-price electricity sales, but is sold under a contract other than the FIT contract (free-market electricity sales). The amount of electricity sold at free market prices is measured as reverse power flow electricity by the second power meter 14. The amount of forward power flow and reverse power flow is measured, for example, by the 30-minute demand value.

[0018] HEMS16 is a control device that coordinates with equipment such as solar power generation energy storage systems, storage batteries, and electric vehicles (EVs), and optimizes the energy management of an entire house. HEMS16 communicates with the first PCS 20, the second PCS 22, the third PCS 24, and the first switching device 26, the second switching device 28, and the third switching device 30 via wireless communication, controls the first PCS 20, the second PCS 22, the third PCS 24, and the first switching device 26, the second switching device 28, and the third switching device 30, and exchanges various data with them.

[0019] PCSs 20, 22, 24 are inverters that convert the DC power generated by solar panels into AC power that can be used in homes, factories, etc., and have functions to adjust output voltage, frequency, etc. PCSs 20, 22, 24 measure the power generated by solar panels. PCSs 20, 22, 24 perform voltage control for forward or reverse power flow. The total power generation of the entire solar power generation energy storage system 1 is the sum of the power measured by PCSs 20, 22, 24, and is grasped by HEMS16 that has received the transmission of power measurement data from PCSs 20, 22, 24.

[0020] Each of the switching devices 26, 28, 30 is connected to the first PCS 20 and the second PCS 22 via the first PCS side wirings 50, 54, 58 and the second PCS side wirings 52, 56, 60. The switching devices 26, 28, 30 are configured to be able to switch between the first PCS side wirings 50, 54, 58 connected to the first PCS 20 and the second PCS side wirings 52, 56, 60 connected to the second PCS 22. HEMS16 performs switching control of the switching devices 26, 28, 30.

[0021] HEMS16 controls the entire solar power generation and energy storage system 1 by acquiring data such as forward and reverse power flow measured by power meters 12 and 14, power generation acquired by PCS 20, 22, and 24, discharge and storage amounts of battery 32, power consumption (self-consumption) of household electrical appliances 18, and weather forecast data (precipitation probability data), as well as wireless control of PCS 20, 22, 24 and switching devices 26, 28, and 30. Wired communication control may be used instead of wireless communication control.

[0022] The battery 32 charges (stores) and discharges electricity. The battery 32 charges with excess power or electricity purchased from the commercial power supply 10.

[0023] Solar panels 34-44 are devices that convert sunlight energy into electrical energy, and are also called solar panels or solar cell modules. They are installed on the roofs of houses and have the function of generating electricity.

[0024] The battery 32 and the first solar panel 34 are connected only to the first PCS 20. The second solar panel 36 is connected to the first switching device 26. The third solar panel 38 is connected to the second switching device 28. The fourth solar panel 40 is connected to the third switching device 30. The fifth solar panel 42 and the sixth solar panel 44 are connected to the third PCS 24.

[0025] As shown in Figure 2, the HEMS 16 comprises a control unit 100, a ROM (Read Only Memory) 101, a memory 102, a communication unit 103, and a storage unit 104, which are connected by a data bus 105. The control unit 100 is a CPU (Central Processing Unit) and performs various calculations such as judgment and generation of control instructions in the solar power generation and storage system 1. The ROM 101 includes, for example, a mask ROM, an EPROM (Eraseable Programmable Read-Only Memory), or flash memory, and stores various software and parameters for driving the control unit 100. The memory 102 is, for example, a DRAM (Dynamic Random Access Memory) or an SRAM (Static Random Access Memory) and functions as the main memory or cache memory of the control unit 100. The communication unit 103 is wirelessly connected to the power meters 12 and 14, PCS 20, 22, and 24, switching devices 26, 28, and 30, and the Internet, and exchanges various data and control commands. The storage unit 104 stores the calculation results of the control unit 100 and weather forecast data acquired via the Internet.

[0026] As shown in Figure 3, the control unit 100 includes a power generation amount determination unit 110, a precipitation probability determination unit 111, a sunrise / sunset time determination unit 112, a surplus power control unit 113, an excess power control unit 114, a power storage control unit 115, a power purchase / sale control unit 116, and a blank time determination unit 117. The power generation amount determination unit 110 determines power generation, surplus power, and excess power from power data acquired from PCS 20, 22, and 24. The precipitation probability determination unit 111 determines the probability of precipitation extracted from acquired weather forecast data. The sunrise / sunset time determination unit 112 determines that the current time is sunrise time and sunset time from the sunrise time and sunset time for the day acquired via the Internet. The surplus power control unit 113 controls the sale of surplus power. The excess power control unit 114 controls the storage and sale (free price sale) of excess power. The energy storage control unit 115 controls the charging and discharging of the battery 32. The electricity purchase / sale control unit 116 controls the purchase of electricity from the commercial power supply 10 and the sale of electricity to the commercial power supply 10. The blank time determination unit 117 determines the elapsed of a predetermined blank time after sunset. These control units and determination units are virtually implemented by software driven in the control unit 100.

[0027] Next, the processing details in the solar power generation and storage system 1 will be explained with reference to Figures 4, 5, and 6. Figure 4 is an example diagram showing an overview of the power changes in the solar power generation and storage system 1 on a sunny day.

[0028] Let's explain this in chronological order. First, as shown in Figure 4, for example at midnight, the precipitation probability determination unit 111 of the HEMS 16 determines the probability of precipitation during the day based on the acquired weather forecast data (precipitation probability data). If rain or cloudy weather is expected, electricity purchased from the commercial power supply 10 is stored in the storage battery 32 and used for the self-consumption of household electrical appliances 18 during the day. In this case, the control of the present invention is not used, and even if the weather forecast is wrong and it becomes sunny, resulting in excess power, the excess power is not stored in the storage battery 32. The weather forecast in the precipitation probability determination unit 111 is determined, for example, by whether or not the probability of precipitation exceeds 20%.

[0029] If clear weather is expected based on the daytime precipitation probability, the control system of the present invention is implemented. For example, at midnight as shown in Figure 4, the charge level of the battery 32 is zero. Switching devices 26, 28, and 30 are connected to the second PCS side wiring 52, 56, and 60, respectively. In this state, the first solar panel 34 is connected to the first PCS 20, solar panels 36-40 are connected to the second PCS 22, and solar panels 42 and 44 are connected to the third PCS 24.

[0030] From midnight until sunrise (time T1), there is no power generation from solar panels 34-44, so self-consumption is covered by electricity purchased from commercial power supply 10. At sunrise (time T1), power generation begins from solar panels 34-44, and when the power generation amount determination unit 110 detects power generation (YES in step S1), the power purchase / sale control unit 116 controls the voltage generated by PCS 20, 22, and 24 to reduce the amount of electricity purchased from commercial power supply 10 (step S2).

[0031] Next, when the amount of power generated by solar panels 34 to 44 increases, and at time T2 the amount of power generated exceeds the amount of self-consumption, and the surplus power control unit 113 detects surplus power (YES in step S3), the power purchase / sale control unit 116 and the surplus power control unit 113 control the voltage generated by PCS 20, 22, and 24 to stop purchasing power (step S4) and start selling power at a fixed price (step S5). In other words, of the power generated by the first solar panel 34 to the sixth solar panel 44, the power that exceeds self-consumption is sold at a fixed price as surplus power. If the surplus power control unit 113 does not detect surplus power (NO in step S3), the system returns to step S3 until sunset (NO in step S21), and when sunset arrives (YES in step S21), the system proceeds to step S14.

[0032] Next, as the amount of electricity generated by solar panels 34-44 increases further, and at time T3 the amount of electricity generated exceeds the upper limit E1 of the fixed-price electricity sales, the excess power control unit 114 detects the excess power (YES in step S6). Next, the excess power control unit 114 controls the first switching device 26, the second switching device 28, and the third switching device 30, and performs control to switch them to connect to the first PCS side wiring 50, 54, 58. As a result, the second solar panel 36, the third solar panel 38, and the fourth solar panel 40 are connected to the first PCS 20. The energy storage control unit 115 controls the first PCS 20 to store the excess power in the battery 32 (step S7). In other words, the electricity generated by the first solar panel 34, the second solar panel 36, the third solar panel 38, and the fourth solar panel 40 is stored in the battery 32 as excess power. The electricity generated by the fifth solar panel 42 and the sixth solar panel 44 will continue to be sold at a fixed price as surplus electricity. If the excess power control unit 114 detects excess power, it will continue to store electricity in the battery 32 until the amount of electricity stored in the battery reaches the upper limit of its storage capacity (NO in step S9).

[0033] If the amount of power generated decreases due to a change in weather to rain or cloudy skies, and excess power is no longer detected (NO in step S8), the excess power control unit 114 controls the first switching device 26, the second switching device 28, and the third switching device 30 to the second PCS side wiring 52, 56, 60, and the energy storage control unit 115 controls the first PCS 20 to stop storing energy in the battery 32 (step S20). After that, until sunset, the system returns to detecting excess power (step S3) (NO in step S21), and when sunset occurs (YES in step S21), the blank time is counted (step S14). Sunrise and sunset are determined by the sunrise / sunset time determination unit 112, and the blank time is counted by the blank time determination unit 117.

[0034] As charging progresses in the battery 32, when the amount of charge in the battery 32 reaches the upper limit of its storage capacity at time T4, the power storage control unit 115 detects the upper limit of the storage capacity (YES in step S9) and performs control to switch the first switching device 26, the second switching device 28, and the third switching device 30 to the connections of the second PCS side wiring 52, 56, and 60. As a result, the second solar cell panel 36, the third solar cell panel 38, and the fourth solar cell panel 40 are connected to the second PCS 22. The power storage control unit 115 controls the first PCS 20 to stop charging the battery 32 (step S10).

[0035] Next, if the surplus power control unit 113 detects surplus power, it continues selling electricity at a fixed price (YES in step S11). If it does not detect surplus power at time T5 (NO in step S11), it stops selling electricity at a fixed price and starts purchasing electricity commercially (step S12).

[0036] Next, when the sunrise / sunset time determination unit 112 determines that it is sunset time T6 (YES in step S13), the blank time determination unit 117 counts the blank time (step S14), and at time T7, it determines that the blank time has elapsed (YES in step S15), and when the energy storage control unit 115 determines that there is energy stored in the battery 32 (YES in step S16), the power purchase / sale control unit 116 controls the battery 32 and the first PCS 20 and starts selling electricity at a free price (step S17). The amount of electricity sold at a free price is counted by the second power meter 14, and the second power meter 14 transmits the amount of electricity sold at a free price to the power company and HEMS 16. The blank time is, for example, 30 minutes.

[0037] Next, at time T8, if the energy storage control unit 115 determines that the amount of energy stored in the battery 32 has become zero (NO in step S18), the power purchase / sale control unit 116 stops selling electricity at a free price (step S19). With this, the control according to the embodiment is completed.

[0038] According to the present invention, by providing a gap period after sunset during which there is no power sales or storage, it is possible to prevent the mixing of power sales at a fixed price (surplus power) from the storage battery 32 with power sales at a fixed price (surplus power) to the commercial power supply 10.

[0039] Although preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the invention, and these modifications are also included within the scope of the present invention. For example, a control device for overall control of the solar power generation and storage system 1 may be provided separately, or the connection location and number of power meters may be changed. [Explanation of symbols]

[0040] 1. Solar power generation and energy storage system 10 Commercial power supply 12. First power meter 14. Second power meter 16. HEMS (Heat Energy Management System) 18 Household electrical appliances 20 1st PCS 22 2nd PCS 24 3rd PCS 26. First switching device 28. Second switching device 30 Third switching device 32 Storage batteries 34. First solar power generation panel 36. Second solar panel 38. Third solar panel 40. Fourth solar panel 42. Fifth solar panel 44. Solar Panel No. 6 100 Control Unit

Claims

1. Connected to commercial power supply, First power conditioner and, The second power conditioner, The third power conditioner, A first solar panel connected only to the first power conditioner, A switching device capable of switching the connection between the first power conditioner and the second power conditioner, A second solar panel connected to the switching device, A battery connected to the first power conditioner, A third solar panel connected only to the third power conditioner, A solar power generation and energy storage system comprising the first power conditioner, the second power conditioner, the third power conditioner, and a control unit for controlling the switching device, The control unit implements control to provide a predetermined gap period after sunset during which no electricity is sold to the commercial power source and no electricity is stored in the battery, in a solar power generation and energy storage system.

2. The solar power generation and energy storage system according to claim 1, wherein the control unit, when it detects excess power exceeding the surplus power from the first solar panel and the second solar panel, controls the switching device from a state in which the second solar panel and the second power conditioner are connected to a state in which the second solar panel and the first power conditioner are connected, and performs control to store the power generated by the first solar panel and the second solar panel in the storage battery.

3. The solar power generation and energy storage system according to claim 2, wherein the control unit controls the battery to stop storing energy when the amount of energy stored in the battery reaches the upper limit of the battery's storage capacity, and controls the switching device from a state in which the second solar panel and the first power conditioner are connected to a state in which the second solar panel and the second power conditioner are connected.

4. It comprises a first power conditioner, a second power conditioner, a storage battery, a first solar panel, a second solar panel, a switching device, and a control device for controlling these. The first solar panel is connected only to the first power conditioner. The second solar cell panel is connected to the switching device, The aforementioned battery is connected only to the first power conditioner. A solar power generation and energy storage system comprising a switching device connected to the first power conditioner and the second power conditioner, and configured to switch the connection between the first power conditioner and the second power conditioner, thereby enabling switching between the connection between the second solar panel and the first power conditioner or the second power conditioner.

5. Furthermore, the solar power generation and energy storage system according to claim 4 further comprises a third power conditioner and a third solar panel connected only to the third power conditioner.

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