Photovoltaic energy storage system based on electricity price signal and collaborative control method thereof

Abstract

This invention discloses a photovoltaic energy storage system and its coordinated control method based on electricity price signals, belonging to the field of photovoltaic power generation and energy storage technology. It adds a DC charging branch between the existing photovoltaic array and the photovoltaic inverter. This branch includes a DC-DC charging module and a battery pack controlled by a time relay or intelligent controller, and also features an independent energy storage inverter. The system controller performs intelligent scheduling based on electricity price signals. During low-price periods, it prioritizes charging the battery pack with photovoltaic DC power, and after charging is complete, it restores the photovoltaic system to normal grid connection. During high-price periods, it controls the energy storage inverter to discharge and performs real-time power coordination with the photovoltaic inverter to ensure that the total output power of both does not exceed the maximum allowable limit at the grid connection point. This invention achieves efficient direct storage of photovoltaic DC power, avoiding the double energy conversion losses of traditional solutions; it significantly improves the system's economic efficiency through "low-price storage and high-power generation"; the power coordination control is reliable and easy to retrofit into existing photovoltaic systems, showing broad engineering application prospects.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic power generation and energy storage technology, specifically, to a photovoltaic energy storage system based on electricity price signals and its collaborative control method. Background Technology

[0002] With the widespread adoption of photovoltaic (PV) power generation, the mismatch between its power generation capacity and electricity load over time has become increasingly prominent. Under the mainstream application model of "self-consumption with surplus power fed into the grid," user-side electricity prices generally exhibit peak-valley price differences: PV output is at its peak during midday, but this period usually corresponds to a price trough, making direct grid connection or self-consumption of PV power less economical; while peak consumption periods such as the evening often correspond to peak prices, during which PV output significantly decreases or even disappears completely, requiring users to purchase electricity from the grid, resulting in persistently high electricity costs.

[0003] In existing technologies, a common solution to the above problems is to connect an independent energy storage system (such as a conventional energy storage inverter with a battery pack) in parallel on the AC grid-connected side of the photovoltaic system. This solution has the following inherent drawbacks: 1) Long and inefficient energy conversion links: Photovoltaic power needs to be converted into AC power by a photovoltaic inverter, and the AC power needs to be rectified into DC power when the energy storage system is charging. There are two power conversions, DC-AC and AC-DC, and the superimposed conversion losses lead to low overall energy utilization efficiency; 2) Complex coordinated control and poor operational stability: The photovoltaic inverter and the energy storage inverter operate in parallel on the AC side. The coordinated regulation of their output power relies on a high-speed communication link, the control strategy is complex, and it is prone to problems such as circulating current and voltage fluctuations due to power mismatch, which affect the stable operation of the system; 3) Difficult and costly system modification: This solution requires a major modification to the original photovoltaic system's AC lines, including adding parallel interfaces and expanding the lines. The modification process is cumbersome and uneconomical.

[0004] Therefore, there is a need to provide a photovoltaic energy storage system based on electricity price signals and its collaborative control method to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a photovoltaic energy storage system based on electricity price signals and its collaborative control method, which can directly and efficiently utilize photovoltaic DC power, has a compact structure, simple control logic, and can be smoothly integrated with existing photovoltaic systems, in order to solve the problems of low efficiency, difficult control, and high retrofit cost in the existing technology.

[0006] The present invention achieves the above objectives through the following technical solutions: One of the technical solutions: A photovoltaic energy storage system based on electricity price signals, which works in conjunction with existing photovoltaic arrays, photovoltaic inverters, and grid-connected cabinets; including a DC charging branch, battery pack, energy storage inverter, and system controller: DC charging branch: This includes a time relay or intelligent controller, a DC-DC charging module, and a battery pack connected in sequence. The input terminal of the time relay or intelligent controller is connected to the DC output terminal of the photovoltaic array. Its core function is to selectively switch the DC output path of the photovoltaic array on and off according to a preset time period signal or a received external electricity price signal. During the charging period, the DC power from the photovoltaic array is directed to the DC-DC charging module to charge the battery pack; during non-charging periods, the charging branch is disconnected to ensure that the photovoltaic power is normally delivered to the photovoltaic inverter. Battery pack: As the core unit of energy storage, it is used to store the electrical energy generated by the photovoltaic array during periods of low electricity price and release it during periods of high electricity price, so as to achieve the economic goal of "low-price storage and high-generation"; the battery pack is equipped with a battery management system (BMS) to monitor the battery's state of charge (SOC), voltage, temperature and other parameters in real time, and feed the monitoring data back to the system controller. Energy storage inverter: The DC input terminal is connected to the output terminal of the battery pack, and the AC output terminal is connected to the grid-connected cabinet. Its core function is to invert the DC power stored in the battery pack into AC power that meets the grid connection standards, and feed it into the grid or directly supply the load according to the system controller's instructions; The system controller, which establishes communication connections with the time relay or intelligent controller, DC-DC charging module, energy storage inverter, and photovoltaic inverter via wired or wireless communication, is the core control unit of the system. The system controller is configured to implement the following control logic: By receiving external electricity price signals or relying on the built-in real-time clock, the "electricity price valley period" and "electricity price peak period" can be accurately defined. The external electricity price signals include the peak and valley electricity price signals issued by the power grid dispatch. The "electricity price valley period" is used as the charging period and the "electricity price peak period" is used as the discharging period. During off-peak electricity prices, an action command is sent to the time relay or intelligent controller to switch the DC output of the photovoltaic array to the DC charging branch and start the DC-DC charging module to charge the battery pack. The SOC data fed back by the battery pack BMS is received in real time. When the battery pack SOC reaches the preset full charge value or target value, a switching command is immediately sent to make the time relay or intelligent controller switch the DC output of the photovoltaic array back to the original path and directly transmit it to the photovoltaic inverter to restore the conventional photovoltaic power generation grid connection mode. During peak electricity price periods, a start-up command is sent to the energy storage inverter to control it to enter discharge mode; simultaneously, the real-time output power P of the photovoltaic inverter is collected in real time via the communication link. 光 and the real-time output power P of the energy storage inverter 储 ; Execute power coordinated constraint control: based on the maximum allowable output power P preset at the grid connection point. 允 Ensure P 光 + P 储 ≤P 允 When P 光 When the level rises, P decreases simultaneously. 储 When P 光 When decreased, P can be adaptively upregulated. 储 The total output power is always kept within the limit.

[0007] Furthermore, the time relay can be replaced by an intelligent controller with logic judgment function, which can directly receive the command signal from the system controller and execute the switching of the DC output path of the photovoltaic array, thereby improving the response speed and control accuracy of the path switching.

[0008] Furthermore, the DC-DC charging module adopts a bidirectional DC-DC converter, which enables the system controller to control the battery pack for controlled discharge under special operating conditions, including battery pack equalization maintenance and emergency power replenishment, thereby expanding the system's functional flexibility.

[0009] Technical Solution Two: A control method for a photovoltaic energy storage system based on electricity price signals, comprising the following steps: S1: System initialization configuration: After the photovoltaic energy storage system based on electricity price signals is powered on, it completes self-tests of various components including time relays, DC-DC charging modules, energy storage inverters, and communication links; it obtains information on peak and valley electricity price periods, battery pack charging target SOC of 80%-90%, and the maximum allowable output power P at the grid connection point by means of manual preset or automatic reception of external signals. S2: Time Period Judgment: The system controller determines whether the current period is a preset "electricity price off-peak period", i.e., a charging period, based on the built-in clock or external electricity price signal; S3: Charging Start: During off-peak electricity prices, the system controller sends a charging path switching command to the time relay or smart controller to connect the DC output of the photovoltaic array to the DC-DC charging module and start the battery pack charging process; at the same time, it sends charging parameters to the DC-DC charging module, including constant current and constant voltage charging strategy parameters. S4: Charging Status Monitoring: Receives SOC data from the battery pack BMS in real time to determine whether the battery pack SOC has reached the preset full charge value or target value. S5: Charging Stop and Path Switching: When the battery pack SOC reaches the target value, the system controller sends a reset command to the time relay or intelligent controller to switch the DC output of the photovoltaic array back to the original path and directly connect it to the photovoltaic inverter. The system then resumes the normal photovoltaic power generation grid-connected mode. If the target value is not reached, the charging state continues. S6: Discharge period judgment: The system controller continuously monitors the period information to determine whether the current period has entered the preset "electricity price peak period", i.e., the discharge period; S7: Discharge Start-up: During the peak electricity price period, the system controller sends a start-up command to the energy storage inverter, controlling it to enter the discharge-ready state; at the same time, it obtains the current output power P of the photovoltaic inverter in real time through the communication link. S8: Calculation of discharge power limit: based on the maximum allowable output power P at the grid connection point. 允 and real-time collected P 光 Calculate the maximum allowable discharge power P of the energy storage inverter. 储 The calculation formula is: P 储 = P 允 - P 光 ; S9: Discharge Execution: The system controller sends a discharge command to the energy storage inverter, controlling it to discharge at a power not exceeding P, ensuring that the initial total output power does not exceed the limit; S10: Dynamic Power Coordination: During discharge, the system controller continuously monitors P in real time. 光 Dynamic changes, such as P caused by changes in light intensity 光 Fluctuations, and according to P 光 Dynamically adjust the actual output power P of the energy storage inverter according to changes 储 Always strictly meet P 光 +P 储 ≤ P 允 The constraints.

[0010] Compared with the prior art, the beneficial effects of the present invention are: High energy conversion efficiency: During off-peak electricity price periods, the DC power output from the photovoltaic array is used directly to charge the battery pack, completely avoiding the two conversion losses of DC-AC-AC-DC in the traditional AC-side energy storage scheme, improving charging efficiency by 8%-15%, and significantly improving energy utilization efficiency. Significantly improved economic efficiency: Through the "low-price storage, high-generation" dispatch strategy driven by electricity price signals, the surplus photovoltaic power during low-price periods is stored and released to the grid or used by the user during high-price periods, which greatly improves the overall economic benefits of photovoltaic power generation systems. According to calculations, it can shorten the investment payback period of household photovoltaic systems by 1-3 years. Strong operational stability and grid-friendliness: Real-time power coordination control of photovoltaic inverters and energy storage inverters is achieved through the system controller, strictly ensuring that the total output power at the grid connection point does not exceed the limit, effectively avoiding problems such as grid disconnection and fines caused by power exceeding the limit, reducing the impact on the grid, and improving the system's operational safety and grid-friendliness; Easy to retrofit and low cost: This energy storage device achieves path switching on the DC side through time relays or intelligent controllers, without the need for major modifications to the AC side lines of the original photovoltaic system. It can be directly installed and integrated on the existing photovoltaic system. The retrofit process is simple, the cycle is short, and the retrofit cost is reduced by more than 30%. Reliable structure and simple control: The system adopts a modular design, with each component functioning independently and working in an orderly manner; the control strategy is based on clear electricity price time periods and power arithmetic constraints, eliminating the need for complex communication protocols and high-speed response control chips, thus reducing the system failure rate and improving long-term operational reliability. Attached Figure Description

[0011] Figure 1 This is a structural block diagram of a photovoltaic energy storage system provided in an embodiment of the present invention; Figure 2 A flowchart of the collaborative control method provided in an embodiment of the present invention. Detailed Implementation

[0012] Example:

[0013] See Figure 1-2 This embodiment demonstrates a photovoltaic energy storage system based on electricity price signals, which works in conjunction with existing photovoltaic arrays, photovoltaic inverters, and grid-connected cabinets; it includes a DC charging branch, a battery pack, an energy storage inverter, and a system controller. DC charging branch: This includes a time relay or intelligent controller, a DC-DC charging module, and a battery pack connected in sequence. The input terminal of the time relay or intelligent controller is connected to the DC output terminal of the photovoltaic array. Its core function is to selectively switch the DC output path of the photovoltaic array on and off according to a preset time period signal or a received external electricity price signal. During the charging period, the DC power from the photovoltaic array is directed to the DC-DC charging module to charge the battery pack; during non-charging periods, the charging branch is disconnected to ensure that the photovoltaic power is normally delivered to the photovoltaic inverter. Battery pack: As the core unit of energy storage, it is used to store the electrical energy generated by the photovoltaic array during periods of low electricity price and release it during periods of high electricity price, so as to achieve the economic goal of "low-price storage and high-generation"; the battery pack is equipped with a battery management system (BMS) to monitor the battery's state of charge (SOC), voltage, temperature and other parameters in real time, and feed the monitoring data back to the system controller. Energy storage inverter: The DC input terminal is connected to the output terminal of the battery pack, and the AC output terminal is connected to the grid-connected cabinet. Its core function is to invert the DC power stored in the battery pack into AC power that meets the grid connection standards, and feed it into the grid or directly supply the load according to the system controller's instructions; The system controller, which establishes communication connections with the time relay or intelligent controller, DC-DC charging module, energy storage inverter, and photovoltaic inverter via wired or wireless communication, is the core control unit of the system. The system controller is configured to implement the following control logic: By receiving external electricity price signals or relying on the built-in real-time clock, the "electricity price valley period" and "electricity price peak period" can be accurately defined. The external electricity price signals include the peak and valley electricity price signals issued by the power grid dispatch. The "electricity price valley period" is used as the charging period and the "electricity price peak period" is used as the discharging period. During off-peak electricity prices, an action command is sent to the time relay or intelligent controller to switch the DC output of the photovoltaic array to the DC charging branch and start the DC-DC charging module to charge the battery pack. The SOC data fed back by the battery pack BMS is received in real time. When the battery pack SOC reaches the preset full charge value or target value, a switching command is immediately sent to make the time relay or intelligent controller switch the DC output of the photovoltaic array back to the original path and directly transmit it to the photovoltaic inverter to restore the conventional photovoltaic power generation grid connection mode. During peak electricity price periods, a start-up command is sent to the energy storage inverter to control it to enter discharge mode; simultaneously, the real-time output power P of the photovoltaic inverter is collected in real time via the communication link. 光 and the real-time output power P of the energy storage inverter 储 ; Execute power coordinated constraint control: based on the maximum allowable output power P preset at the grid connection point. 允 Ensure P 光 + P 储 ≤P 允 When P 光 When the level rises, P decreases simultaneously. 储 When P 光 When decreased, P can be adaptively upregulated. 储 The total output power is always kept within the limit.

[0014] Furthermore, the time relay can be replaced by an intelligent controller with logic judgment function, which can directly receive the command signal from the system controller and execute the switching of the DC output path of the photovoltaic array, thereby improving the response speed and control accuracy of the path switching.

[0015] Furthermore, the DC-DC charging module adopts a bidirectional DC-DC converter, which enables the system controller to control the battery pack for controlled discharge under special operating conditions, including battery pack equalization maintenance and emergency power replenishment, thereby expanding the system's functional flexibility.

[0016] This embodiment also provides a control method for a photovoltaic energy storage system based on electricity price signals, the steps of which include: S1: System initialization configuration: After the photovoltaic energy storage system based on electricity price signals is powered on, it completes self-tests of various components including time relays, DC-DC charging modules, energy storage inverters, and communication links; it obtains information on peak and valley electricity price periods, battery pack charging target SOC of 80%-90%, and the maximum allowable output power P at the grid connection point by means of manual preset or automatic reception of external signals. S2: Time Period Judgment: The system controller determines whether the current period is a preset "electricity price off-peak period", i.e., a charging period, based on the built-in clock or external electricity price signal; S3: Charging Start: During off-peak electricity prices, the system controller sends a charging path switching command to the time relay or smart controller to connect the DC output of the photovoltaic array to the DC-DC charging module and start the battery pack charging process; at the same time, it sends charging parameters to the DC-DC charging module, including constant current and constant voltage charging strategy parameters. S4: Charging Status Monitoring: Receives SOC data from the battery pack BMS in real time to determine whether the battery pack SOC has reached the preset full charge value or target value. S5: Charging Stop and Path Switching: When the battery pack SOC reaches the target value, the system controller sends a reset command to the time relay or intelligent controller to switch the DC output of the photovoltaic array back to the original path and directly connect it to the photovoltaic inverter. The system then resumes the normal photovoltaic power generation grid-connected mode. If the target value is not reached, the charging state continues. S6: Discharge period judgment: The system controller continuously monitors the period information to determine whether the current period has entered the preset "electricity price peak period", i.e., the discharge period; S7: Discharge Start-up: During the peak electricity price period, the system controller sends a start-up command to the energy storage inverter, controlling it to enter the discharge-ready state; at the same time, it obtains the current output power P of the photovoltaic inverter in real time through the communication link. S8: Calculation of discharge power limit: based on the maximum allowable output power P at the grid connection point. 允 and real-time collected P 光 Calculate the maximum allowable discharge power P of the energy storage inverter. 储 The calculation formula is: P 储 = P 允 - P 光 ; S9: Discharge Execution: The system controller sends a discharge command to the energy storage inverter, controlling it to discharge at a power not exceeding P, ensuring that the initial total output power does not exceed the limit; S10: Dynamic Power Coordination: During discharge, the system controller continuously monitors P in real time. 光 Dynamic changes, such as P caused by changes in light intensity 光 Fluctuations, and according to P 光Dynamically adjust the actual output power P of the energy storage inverter according to changes 储 Always strictly meet P 光 +P 储 ≤ P 允 The constraints.

[0017] See Figure 1 The DC power output from the photovoltaic array is switched via a time relay / intelligent controller. During off-peak hours, the DC-DC charging module charges the battery pack, while during other times, the power is directed to the photovoltaic inverter. The battery pack is connected to the grid-connected cabinet via the energy storage inverter. The system controller achieves centralized control of each component through a communication link, and simultaneously receives electricity price signals / clock signals as the basis for scheduling. The AC outputs of both the photovoltaic inverter and the energy storage inverter are connected to the grid-connected cabinet, ultimately achieving connection with the grid / load.

[0018] See Figure 2 If so, the charging process is executed, and after full charge, it switches back to regular grid connection; if it is not a valley period, it is determined whether it is a peak period. If so, the discharging process is executed, and the upper limit of the discharge power is calculated in real time and dynamically adjusted to ensure that the total power does not exceed the limit; the entire process is executed in a loop to achieve intelligent scheduling based on electricity price signals.

[0019] Application example: This application example is a photovoltaic energy storage system based on electricity price signals, specifically including: a photovoltaic array, a time relay or intelligent controller, a DC-DC charging module, a battery pack with a BMS, an energy storage inverter, a photovoltaic inverter, a grid-connected cabinet, and a system controller. The connection relationships of each component are as follows: The output DC bus of the photovoltaic array is divided into two paths: One path connects to the existing photovoltaic inverter via the normally closed contact of the time relay to form a conventional photovoltaic power generation path; Another path is connected to the input terminal of the DC-DC charging module via the normally open contact of the time relay (forming a charging path).

[0020] The output of the DC-DC charging module is connected to the input of the battery pack; the output of the battery pack is connected to the DC input of the energy storage inverter. The AC outputs of the photovoltaic inverter and the energy storage inverter are connected in parallel and then connected to the grid-connected cabinet, which is ultimately connected to the power grid or load. The system controller establishes bidirectional communication with the time relay, DC-DC charging module, battery pack BMS, energy storage inverter, and photovoltaic inverter via a CAN bus or Ethernet communication link, enabling the issuance of control commands and the acquisition of operational data.

[0021] The specific time depends on the local power grid settings; specific parameters need to be set. The off-peak electricity price period is 12:00-14:00, and the peak electricity price period is 18:00-21:00; the maximum allowable output power P at the grid connection point is 50kW; the target SOC of the battery pack is 90%, and the full charge SOC is 100%; the DC-DC charging module adopts a bidirectional converter with a rated charging power of 20kW.

[0022] The specific work process is as follows: Off-peak charging process, starting at 12:00: At 12:00, the system controller, using its built-in clock, determines that the electricity price is in a low-price period and immediately sends a command to the time relay, causing its normally closed contacts to open and its normally open contacts to close. This switches the DC output path of the photovoltaic array to the DC-DC charging module. The system controller then sends a constant current and constant voltage charging command to the DC-DC charging module, setting the charging current to 5A and the charging voltage to 400V. The DC power output from the photovoltaic array directly charges the battery pack through the DC-DC charging module. At this time, the photovoltaic inverter stops operating due to the lack of DC input. During the charging process, the battery pack BMS feeds back SOC data to the system controller every 100ms.

[0023] Assuming the SOC reaches 90% at 13:30, the charging switchover process is complete: At 13:30, the system controller received feedback from the BMS that the SOC reached 90% (target value). It immediately sent a stop charging command to the DC-DC charging module and a reset command to the time relay, causing its normally open contacts to open and its normally closed contacts to close. The DC output path of the photovoltaic array switched back to the photovoltaic inverter. After receiving DC input, the photovoltaic inverter started operating, converting the photovoltaic DC power into AC power and feeding it into the grid. The system then resumed its conventional photovoltaic power generation mode.

[0024] Peak discharge period, starting at 19:00: At 19:00, the system controller determines that the peak electricity price period has begun. It first collects the current output power P of the photovoltaic inverter via the communication link. 光 Since there is no sunlight at this time, the photovoltaic inverter has no power output, P=0kW. The system controller calculates the maximum allowable discharge power of the energy storage inverter, P=50kW - 0kW=50kW, and then sends a discharge command to the energy storage inverter, setting the initial discharge power to 40kW (less than P). 允 After the energy storage inverter starts, it converts the DC power stored in the battery pack into 220V / 50Hz AC power, which is then connected to the power grid through the grid-connected cabinet.

[0025] Assuming a sudden change in illumination at 19:30, the dynamic power coordination process is as follows: At 19:30, the clouds dispersed, allowing for a brief period of sunlight. The photovoltaic inverter started generating electricity, and the system controller collected P data in real time. 光The power output suddenly spiked to 15kW. The system controller immediately recalculated P = 50kW - 15kW = 35kW and issued a power adjustment command within 50ms, reducing the energy storage inverter's output power from 40kW to 35kW. After the adjustment, the total output power was 15kW + 35kW = 50kW, strictly conforming to P... 允 Limit requirements. When the light disappears again, P 光 When the power drops to 0kW, the system controller recalculates P=50kW and increases the discharge power of the energy storage inverter to 40kW to maintain stable discharge.

[0026] The parameters set in this application example, such as electricity price period, P, and charging power, are only examples and can be flexibly adjusted according to specific scenarios in actual applications. At the same time, the selection of time relays, the type of communication link, etc., can also be replaced with equivalent technical means according to engineering requirements. These adjustments and replacements do not depart from the protection scope defined by the claims of this invention.

[0027] Compared with the prior art, the beneficial effects of the present invention are: High energy conversion efficiency: During off-peak electricity price periods, the DC power output from the photovoltaic array is used directly to charge the battery pack, completely avoiding the two conversion losses of DC-AC-AC-DC in the traditional AC-side energy storage scheme, improving charging efficiency by 8%-15%, and significantly improving energy utilization efficiency. Significantly improved economic efficiency: Through the "low-price storage, high-generation" dispatch strategy driven by electricity price signals, the surplus photovoltaic power during low-price periods is stored and released to the grid or used by the user during high-price periods, which greatly improves the overall economic benefits of photovoltaic power generation systems. According to calculations, it can shorten the investment payback period of household photovoltaic systems by 1-3 years. Strong operational stability and grid-friendliness: Real-time power coordination control of photovoltaic inverters and energy storage inverters is achieved through the system controller, strictly ensuring that the total output power at the grid connection point does not exceed the limit, effectively avoiding problems such as grid disconnection and fines caused by power exceeding the limit, reducing the impact on the grid, and improving the system's operational safety and grid-friendliness; Easy to retrofit and low cost: This energy storage device achieves path switching on the DC side through time relays or intelligent controllers, without the need for major modifications to the AC side lines of the original photovoltaic system. It can be directly installed and integrated on the existing photovoltaic system. The retrofit process is simple, the cycle is short, and the retrofit cost is reduced by more than 30%. Reliable structure and simple control: The system adopts a modular design, with each component functioning independently and working in an orderly manner; the control strategy is based on clear electricity price time periods and power arithmetic constraints, eliminating the need for complex communication protocols and high-speed response control chips, thus reducing the system failure rate and improving long-term operational reliability.

[0028] The above are merely some embodiments of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of the present invention, and all such modifications and improvements fall within the scope of protection of the present invention.

Claims

1. A photovoltaic energy storage system based on electricity price signals, characterized in that: Works in conjunction with photovoltaic arrays, photovoltaic inverters, and grid-connected cabinets, including: DC charging branch: includes a time relay or intelligent controller, a DC-DC charging module and a battery pack connected in sequence; the input terminal of the time relay or intelligent controller is connected to the DC output terminal of the photovoltaic array to control the path selection of the DC output of the photovoltaic array; Energy storage inverter: The DC input terminal is connected to the battery pack, and the AC output terminal is connected to the grid-connected cabinet; System controller: It is connected to the time relay or intelligent controller, DC-DC charging module, and energy storage inverter respectively. The system controller is configured to: define charging and discharging periods based on electricity price signals or clock signals; during the charging period, control the DC output of the photovoltaic array to charge the battery pack through the DC charging branch, and switch to the photovoltaic inverter after the battery pack is fully charged; During the discharge period, the energy storage inverter is controlled to start, and the output power P of the photovoltaic inverter is monitored in real time. 光 With the output power P of the energy storage inverter 储 Execute power constraint control: P 光 + P 储 ≤ P 允 , where P 允 This represents the maximum allowable output power at the grid connection point.

2. The photovoltaic energy storage system based on electricity price signals according to claim 1, characterized in that: The DC-DC charging module is a bidirectional DC-DC converter.

3. A photovoltaic energy storage system based on electricity price signals according to claim 1, characterized in that: During the discharge period, the system controller dynamically calculates the maximum allowable discharge power P of the energy storage inverter. 储 = P 允 - P 光 And control the output power of the energy storage inverter to not exceed P 储 .

4. A photovoltaic energy storage system based on electricity price signals according to claim 1, characterized in that: The battery pack is equipped with a battery management system (BMS), which communicates with the system controller and is used to provide feedback on the battery pack's state of charge (SOC) to the system controller.

5. A photovoltaic energy storage system based on electricity price signals and its coordinated control method, characterized in that: The collaborative control of the photovoltaic energy storage system based on electricity price signals as described in any one of claims 1-4 includes the following steps: Determine whether the current period has entered the preset charging time; If so, the DC output of the photovoltaic array is switched to the DC charging branch to charge the battery pack until the battery pack reaches the target charging state, and then switched back to the photovoltaic inverter. Determine if the preset discharge period has been entered; if so, start the energy storage inverter to discharge and obtain the current output power P of the photovoltaic inverter. 光 ; Based on the maximum allowable power P at the grid connection point 允 With P 光 Determine the upper limit of the allowable discharge power of the energy storage inverter; The energy storage inverter is controlled to discharge under the condition that the allowable discharge power limit is not exceeded.

6. The photovoltaic energy storage system based on electricity price signals and its coordinated control method according to claim 5, characterized in that: "Determining the upper limit of the allowable discharge power of the energy storage inverter" specifically involves: calculating P... 光 = P 允 - P 储 .

7. A photovoltaic energy storage system based on electricity price signals and its coordinated control method according to claim 5, characterized in that: During the discharge period, P was continuously monitored. 光 The changes in the value of the energy storage inverter are used to dynamically adjust the actual output power P of the inverter. 储 Always maintain P 光 + P 储 ≤ P 允 .

8. The photovoltaic energy storage system based on electricity price signals and its coordinated control method according to claim 5, characterized in that: The discharge period corresponds to the period of high electricity prices.

9. A photovoltaic energy storage system based on electricity price signals and its coordinated control method according to claim 5, characterized in that: Before switching the DC output of the photovoltaic array to the DC charging branch to charge the battery pack, the system also includes an initialization step: completing self-tests of each component and obtaining information on peak and off-peak electricity price periods, the target charging status of the battery pack, and the maximum allowable output power P at the grid connection point. 允 .

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