A power grid power reverse flow prevention optical storage system and a control method thereof

Abstract

This invention provides a photovoltaic-storage system and its control method for preventing grid power backflow, relating to the field of photovoltaic-storage power generation system control technology. The system includes photovoltaic modules, a DC bus, an inverter, a battery, a grid-connected power monitoring module, and an anti-backflow module. The photovoltaic modules are connected to the DC side of the inverter via the DC bus, the AC side of the inverter is connected to the grid and the load, and the battery is connected in parallel to the DC bus. The grid-connected power monitoring module is used to acquire the grid-connected power. The anti-backflow module is used to reduce the inverter output current through current feedforward control and control the battery charging to absorb excess photovoltaic power when the grid-connected power indicates that the inverter output power is greater than the load power, causing the DC side voltage to rise. This maintains the grid-connected power in a non-backflow state. The beneficial effects are real-time monitoring of the grid-connected power, rapid suppression of backflow through current feedforward, avoidance of grid operation risks, improvement of photovoltaic absorption rate and system stability, achievement of dynamic energy balance, and strong engineering practicality.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic power generation system control technology, and in particular to a photovoltaic power generation system and control method for preventing grid power backflow. Background Technology

[0002] With the large-scale application and increasing penetration of photovoltaic (PV) power generation technology, PV systems have brought new challenges to the safe, stable, and economical operation of power distribution networks. In a typical integrated PV-storage system, the PV array converts direct current (DC) into alternating current (AC) synchronized with the grid via an inverter to supply power to the load, with the grid bearing the portion of the power required by the load. However, when the PV power generation exceeds the load consumption, the excess power flows back into the grid. This reverse power flow can trigger a series of technical problems, such as local voltage exceeding limits, line overload, protection malfunctions, and power quality degradation, significantly pressuring the grid's planned operation and safety control. The reverse flow problem is particularly prominent in weak grid areas with limited distribution transformer capacity or high-penetration PV integration, limiting the effective absorption of PV power generation.

[0003] Traditional control methods have limitations in terms of real-time performance, accuracy, energy efficiency, and system coordination. There is an urgent need for a more efficient, faster, more reliable, and easier-to-implement coordinated control method for photovoltaic-storage system inverters, capable of real-time and precise scheduling of photovoltaic power generation and energy storage charging and discharging. This method would maximize the utilization of photovoltaic energy while ensuring no backflow at the grid connection point, thereby enhancing the regulation value of the energy storage system and the economic efficiency of system operation. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a photovoltaic-storage system for preventing grid power backflow, comprising photovoltaic modules, a DC bus, an inverter, and a battery; the photovoltaic modules are connected to the DC side of the inverter via the DC bus, the AC side of the inverter is connected to the grid and the electrical load, and the battery is connected in parallel to the DC bus; The grid-connected power monitoring module is used to obtain the grid-connected power at the connection point between the AC side of the inverter and the grid. The anti-reverse current module is used to reduce the output current of the inverter by current feedforward when the output power of the inverter is greater than the load power of the electrical load, causing the DC voltage to rise. This reduces the difference between the output power and the load power. At the same time, it controls the battery to enter the charging state to absorb the excess photovoltaic power of the photovoltaic module, thereby maintaining the grid connection point power in a non-reverse current state.

[0005] Preferably, the anti-backflow module includes: The inverter control submodule is used to generate a DC voltage compensation amount and a current feedforward command value based on the grid connection point power when the output power of the inverter is greater than the load power of the electrical load, resulting in a rise in the DC side voltage. The DC voltage compensation amount is then superimposed with an initial setpoint to adjust the voltage reference of the DC bus. Subsequently, the current setpoint value generated based on the voltage reference and the actual voltage of the DC bus is reduced by the current feedforward command value to obtain a final setpoint current command value to control the inverter to reduce the output current. The energy storage side control submodule, connected to the inverter control submodule, is used to adjust the battery's charging state to absorb the excess photovoltaic power of the photovoltaic module based on the deviation between the actual voltage of the DC bus and the set final voltage value.

[0006] Preferably, the inverter control submodule includes: A power outer loop control unit is used to generate the DC voltage compensation amount based on the grid connection point power. The voltage outer loop control unit is used to superimpose the DC voltage compensation amount with the initial given value to generate the voltage reference reference. The current inner loop control unit is used to input the difference between the voltage reference and the actual voltage of the DC bus to the voltage controller to obtain the current setpoint.

[0007] Preferably, the power outer loop control unit includes a first PI controller, the output of which is connected to a first limiter. The first PI controller is used to generate an initial voltage command value based on the grid connection point power, and the first limiter is used to limit the initial voltage command value to obtain the DC voltage compensation amount. The limiting range of the first limiter is [0, ... U dc * ],in U dc * This is the maximum DC voltage compensation amount set. When the grid connection point power is negative, the first limiter is used to limit the DC voltage compensation amount to 0, and when the grid connection point power is positive, the first limiter is used to limit the DC voltage compensation amount to no more than the maximum DC voltage compensation amount.

[0008] Preferably, the inverter control submodule further includes a current feedforward unit connected to the current inner loop control unit, which is used to multiply the grid connection point power by a positive gain coefficient, process it through a second limiter to generate the current feedforward command value, and then subtract it from the current setpoint to quickly reduce the final given current command, thereby controlling the output current of the inverter to decrease.

[0009] Preferably, the limiting range of the second limiter is [0, ... i dmax * ],in i dmax * This is the maximum d-axis current feedforward command value set. When the grid connection point power is negative, the second limiter is used to limit the current feedforward command value to 0, and when the grid connection point power is positive, the second limiter is used to limit the current feedforward command value to no higher than the maximum d-axis current feedforward command value.

[0010] Preferably, an inductor is connected in series on each path between the AC side of the inverter and the power grid, and the energy storage side control submodule includes: The energy storage voltage outer loop control unit is used to calculate the deviation between the final voltage setpoint and the actual voltage of the DC bus when the output power of the inverter at the grid connection point is greater than the load power of the electrical load, resulting in a rise in the DC side voltage, and generate an outer loop output current command value. The energy storage current inner loop control unit is used to control the battery to enter the charging state according to the outer loop output current command value and the current feedback value of the inductor, so as to absorb the excess photovoltaic power of the photovoltaic module.

[0011] Preferably, the outer loop control unit for energy storage voltage includes a second PI controller. The second PI controller is used to process the deviation between the final voltage setpoint and the actual voltage of the DC bus to obtain the outer loop output current command value. The output terminal of the second PI controller is connected to a third limiter, and the limiting range of the third limiter is [-]. i Lmax * [,0], where i Lmax * The maximum charging current command value is set. When the grid connection point power is negative, the third limiter is used to limit the outer loop output current command value to 0, and when the grid connection point power is positive, the second limiter is used to limit the current feedforward command value to a negative value not less than the maximum charging current command value.

[0012] The present invention also provides a control method for preventing grid power reverse current in a photovoltaic-storage system, characterized in that it is applied to the above-mentioned photovoltaic-storage system and includes: Step S1: The photovoltaic-storage system continuously acquires the grid connection point power at the connection between the AC side of the inverter and the grid. In step S2, when the output power of the inverter at the grid connection point is greater than the load power of the electrical load, causing the DC voltage to rise, the photovoltaic storage system controls the output current of the inverter to decrease through current feedforward, thereby reducing the difference between the output power and the load power. At the same time, it controls the battery to enter the charging state to absorb the excess photovoltaic power of the photovoltaic module, thereby maintaining the grid connection point power in a non-reverse state.

[0013] Preferably, step S2 includes: Step S21: When the grid connection point power indicates that the output power of the inverter is greater than the load power of the electrical load, causing the DC side voltage to rise, the photovoltaic energy storage system generates a DC voltage compensation amount and a current feedforward command value based on the grid connection point power. The DC voltage compensation amount is superimposed with the initial given value to adjust the voltage reference of the DC bus. Then, the current given value generated based on the voltage reference and the actual voltage of the DC bus is reduced by the current feedforward command value to obtain the final given current command value to control the inverter to reduce the output current. In step S22, the photovoltaic energy storage system adjusts the battery to enter the charging state to absorb the excess photovoltaic power of the photovoltaic module based on the deviation between the actual voltage of the DC bus and the set final voltage value.

[0014] The above technical solution has the following advantages or beneficial effects: By monitoring the grid-connected power in real time, when a reverse current trend is detected, current feedforward control is used to quickly reduce the inverter output current, and the battery charging is simultaneously controlled to absorb excess power. This solution effectively avoids grid operation risks caused by reverse current, significantly improves photovoltaic absorption rate and system operation stability, and simultaneously achieves dynamic energy balance and efficient utilization of energy storage equipment, thus possessing strong engineering practical value. Attached Figure Description

[0015] Figure 1 A schematic diagram of the electrical connection structure of the photovoltaic energy storage system is shown in a preferred embodiment of the present invention. Figure 2 A schematic diagram of the functional module structure of a photovoltaic energy storage system for preventing grid power backflow is provided in an embodiment of the present invention. Figure 3 This is a control logic block diagram of the inverter control submodule in an embodiment of the present invention; Figure 4This is a control logic block diagram of the energy storage side control submodule in an embodiment of the present invention; Figure 5(a) is a schematic diagram of the simulated waveform of photovoltaic module power generation when grid power anti-reverse current is achieved in an embodiment of the present invention; Figure 5(b) is a schematic diagram of the simulation waveform of the actual DC bus voltage when the grid power anti-reverse current is realized in an embodiment of the present invention; Figure 5(c) is a schematic diagram of the simulated waveform of the grid power when implementing grid power anti-reverse flow in an embodiment of the present invention; Figure 5(d) is a schematic diagram of the simulated waveform of the battery power on the energy storage side when the grid power anti-reverse current is realized in an embodiment of the present invention. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment; other embodiments that conform to the spirit of the present invention may also fall within the scope of the present invention.

[0017] In a preferred embodiment of the present invention, based on the above-mentioned problems existing in the prior art, a photovoltaic energy storage system for preventing grid power backflow is provided.

[0018] Example 1 This embodiment provides a photovoltaic-storage system that prevents grid power backflow, and its overall structure is as follows: Figure 1 , Figure 2 As shown. Figure 1 As shown, the system includes a photovoltaic module 100, a DC bus 200, an inverter 300, and a battery 400. The photovoltaic module 100 is connected to the DC side of the inverter 300 through the DC bus 200. The AC side of the inverter 300 is connected to the power grid 500 and the electrical load 600. The battery 400 is connected in parallel to the DC bus 200.

[0019] like Figure 2 As shown, the system also includes: Grid-connected power monitoring module 1: Used to acquire the grid-connected power at the connection point between the inverter's AC side and the grid. ; The anti-reverse current module 2, connected to the grid-connected power monitoring module 1, is used to reduce the output current of the inverter by current feedforward when the output power of the inverter is greater than the load power of the electrical load, causing the DC voltage to rise. This reduces the difference between the output power and the load power. At the same time, it controls the battery to enter the charging state to absorb the excess photovoltaic power of the photovoltaic module, thereby maintaining the grid-connected power in a non-reverse current state.

[0020] The core of this embodiment lies in real-time monitoring of the grid connection point power, coordinating the inverter's output current and the battery's charging status. When a reverse current trend is detected (i.e., the inverter's output power is greater than the load power of the electrical load; those skilled in the art should know that the inverter converts the DC power generated by the photovoltaic modules into AC current for the grid, so the inverter's output power reflects the photovoltaic power generation; the reverse current trend here means that the photovoltaic power generation is too high, causing the inverter's output power to be too high and higher than the load power of the electrical load, resulting in reverse current to the grid), causing the DC bus voltage to rise, the inverter's output current is reduced through current feedforward control, thereby reducing the difference between the output power and the load power. At the same time, the battery is controlled to enter the charging state to absorb the excess photovoltaic power of the photovoltaic modules, thereby maintaining the grid connection point power in a non-reverse current state.

[0021] To address the issues of poor real-time performance, insufficient control precision, and low energy utilization efficiency in existing photovoltaic-storage systems when dealing with grid power reverse current, this embodiment provides a photovoltaic-storage system for preventing grid power reverse current. This system introduces a grid-connected power monitoring module and an anti-reverse current module to achieve real-time monitoring and rapid response to grid-connected power. When a reverse current trend is detected, indicating that the inverter output power exceeds load demand and the DC-side voltage is rising, the system rapidly reduces the inverter output current through a current feedforward control mechanism, effectively suppressing the power difference. Simultaneously, it coordinates the battery to enter a charging state to absorb excess photovoltaic power. This solution not only solves the problems of slow response and low control precision in the reverse current suppression process of traditional control methods but also avoids safety hazards such as grid voltage exceeding limits and line overload caused by reverse current, significantly improving the photovoltaic power absorption capacity and system operational stability. Furthermore, through the collaborative participation of the energy storage system, dynamic energy balance and optimized scheduling are achieved, improving the utilization efficiency of energy storage devices and the overall economic efficiency of the system, demonstrating strong engineering practical value and promising prospects for widespread application.

[0022] Example 2 This embodiment is a further refinement of the inverter control module in Embodiment 1.

[0023] The anti-backflow module 2 in this embodiment includes: The inverter control submodule 21 is used to generate a DC voltage compensation amount and a current feedforward command value based on the grid connection point power when the output power of the inverter is greater than the load power of the electrical load, resulting in a rise in the DC side voltage. The DC voltage compensation amount is then superimposed with an initial setpoint to adjust the voltage reference of the DC bus. Subsequently, the current setpoint generated based on the voltage reference and the actual voltage of the DC bus is reduced by the current feedforward command value to obtain a final setpoint current command value to control the inverter to reduce the output current. The energy storage side control submodule 22 is connected to the inverter control submodule 21 and is used to adjust the battery to enter the charging state to absorb the excess photovoltaic power of the photovoltaic module based on the deviation between the actual voltage of the DC bus and the set final voltage value.

[0024] like Figure 2 As shown, Figure 2 As shown, the inverter control submodule 21 includes: The power outer loop control unit 211 is used to determine the power at the grid connection point. Generate DC voltage compensation amount DC voltage compensation Depend on After being clipped, the following was obtained: Depend on (obtained after PI control processing) The voltage outer loop control unit 212 is used to adjust the DC voltage compensation amount. With the initial given value Superimposed to generate a DC bus voltage reference; The current inner loop control unit 213 is used to compare the voltage reference with the actual voltage of the DC bus. The difference is then input to the voltage controller PI to obtain the current setpoint. .

[0025] Ultimately, the inverter control submodule 21 determines the current based on the given current value. and current feedforward command The process is performed (e.g., subtraction) to obtain the final set current command value used to control the inverter. and order =0, will As the d-axis control current As the q-axis control current, based on the d-axis control current and q-axis control current The output pulse width modulation signal controls the inverter to reduce the output current.

[0026] Example 3 This embodiment is based on embodiment 2, and refers to... Figure 3 A limiting mechanism is introduced for the output of the power outer loop control unit 211. Specifically, the power outer loop control unit 211 includes a first PI controller, the output of which is connected to a first limiter. The first PI controller is used to generate an initial voltage command value based on the grid connection point power. The first limiter is used to limit the initial voltage command value. The DC voltage compensation amount is obtained by limiting the amplitude. The limiting range of the first limiter is [0, ... U dc * ],in U dc * This is the maximum DC voltage compensation amount set. When the grid connection point power is negative, the first limiter is used to limit the DC voltage compensation amount to 0, and when the grid connection point power is positive, the first limiter is used to limit the DC voltage compensation amount to no more than the maximum DC voltage compensation amount.

[0027] Its working logic is as follows: the power outer loop control unit according to... Calculated initial voltage command The actual output DC voltage compensation amount is obtained after processing by the first limiter. According to the system definition, the direction of power flow from the inverter to the grid is defined as the positive direction. Therefore: When the photovoltaic power is less than the load power <0, the power grid supplies power to the load, and there is no reverse current. At this time, the power outer loop control unit 211 is in reverse saturation, and its output... It is limited to 0 by the first limiter.

[0028] When the photovoltaic power is greater than the load power <0, indicating a reverse flow trend. The power outer loop control unit 211 exits saturation and begins positive integration, making... >0, thus providing an additional boost command for the DC bus voltage.

[0029] The first limiter ensures that, under normal power supply mode, the power outer loop does not interfere with the voltage regulation function of the voltage outer loop; it only operates at the safe upper limit when reverse current protection is required. Internal voltage compensation enhances the system's reliability and stability. The size can be freely adjusted according to the actual system requirements.

[0030] Example 4 This embodiment further supplements the inverter control module in Embodiment 2 or 3 by introducing a current feedforward unit 214 to improve dynamic response speed. For example... Figure 2 As shown, the inverter control submodule 21 also includes a current feedforward unit 214.

[0031] Reference Figure 3 The workflow of this unit is as follows: The grid connection point power... After being multiplied by a positive gain coefficient K, and then processed by a second limiter, a current feedforward command is generated. This instruction is used when a reverse flow trend is detected (i.e., When >0), the current command output by the outer voltage loop. This difference rapidly reduces the final d-axis current command used to control the inverter. .

[0032] Its technical principle lies in: when When >0, current feedforward command It is positive, and it is the same as Subtraction results in This reduces the active current supplied by the inverter to the grid, thereby accelerating the reverse current suppression process at the current loop level. The gain coefficient K is positive and can be freely adjusted according to the actual system's response speed requirements to optimize dynamic performance.

[0033] Example 5 This embodiment specifically defines the parameters of the second limiter in Embodiment 4. The limiting range of the second limiter is [0, ...]. ],in This is the set maximum d-axis current feedforward command value.

[0034] This limiting setting ensures the current feedforward command. Always non-negative (because) (Effective only when >0), and will not exceed the maximum allowable feedforward current value of the system. This ensures that the current feedforward mechanism only functions in the positive direction when preventing reverse current, and also prevents the system from overloading or becoming unstable due to excessive feedforward commands, thus playing a role in safety protection.

[0035] Example 6 This embodiment is a further refinement of the energy storage side control submodule 22 in Embodiment 2, and clarifies its connection relationship with the main circuit. Each path between the AC side of the inverter and the power grid is typically connected in series with a filter inductor L, and the core of the energy storage side control submodule 22 is to control the on / off state of the current path connected between the DC bus 200 and the battery 400.

[0036] The control flow of the energy storage side control submodule 22 is as follows: Figure 4Specifically, it includes: The energy storage voltage outer loop control unit 2211 is used to set the final voltage setpoint when the output power of the inverter at the grid connection point power indicator is greater than the load power of the electrical load, causing the DC side voltage to rise. The actual voltage of the DC bus Perform deviation calculations to generate the outer loop output current command value. ; The inner loop control unit 222 of the energy storage current is used to determine the output current command value of the outer loop. The actual current feedback value of the inductor The difference between the feedback current of the inductor and the current is then processed by the PI controller and the PWM unit to output a pulse width modulation signal, which ultimately controls the battery to turn on and enter the charging state to absorb the excess photovoltaic power of the photovoltaic module.

[0037] This dual-loop control structure enables the energy storage side to accurately respond to changes in the DC bus voltage. When the voltage is boosted by the inverter side, it quickly absorbs current and achieves power transfer.

[0038] Example 7 This embodiment, based on embodiment 6, introduces directional limiting on the output of the energy storage voltage outer loop control unit 221. The energy storage voltage outer loop control unit includes a second PI controller, which processes the deviation between the final voltage setpoint and the actual voltage of the DC bus to obtain the outer loop output current command value. The output terminal of the second PI controller is connected to a third limiter. Figure 4 The limiting range of the third limiter is [ [,0], where This is the maximum charging current command value set.

[0039] This limiting range (from negative to zero) has a clear physical meaning: it limits the outer loop output current command on the energy storage side. It can only be negative or zero. According to the system definition, the direction of power flow from the battery to the DC side is positive. Therefore, a negative value... The command value corresponds to the current flowing from the DC side to the battery, i.e., the battery charging state. A negative limit ensures that the energy storage side is only allowed to charge to absorb excess power, and will not discharge to the DC bus in this anti-reverse current control mode, thus strictly guaranteeing the goal of unidirectional power regulation, and by controlling the maximum charging current... The limitations implemented overload protection.

[0040] In summary, the photovoltaic energy storage system of this invention has two operating modes; First mode (no reverse current / grid power supply mode): When the grid connection point power A value less than 0 indicates that the photovoltaic power generation is less than the power required by the load, and the grid supplies power to the load. In this mode, the photovoltaic-storage system operates in the first mode. In this mode, the power outer loop control unit 211 in the inverter control submodule 21 is suppressed, and its output DC voltage compensation is reduced. =0. The actual voltage of the DC bus is stabilized at the initial setpoint by the voltage outer loop control unit 212 of the inverter control submodule 21. The inverter operates in a standard voltage and current dual closed-loop regulation mode. Simultaneously, since the DC bus voltage stabilizes at the initial setpoint, the energy storage side control submodule 21 adjusts its voltage based on the final setpoint. Actual voltage of DC bus Forward saturation, the outer loop outputs the current command. When the third limiter sets the value to 0, the energy storage side (i.e., the battery) does not operate, and there is no power flow.

[0041] Second mode (anti-backflow mode): When the grid connection point power A value greater than 0 indicates that the photovoltaic power generation exceeds the load's required power, suggesting a tendency for reverse current to flow into the grid. The system operates in the second mode. At this time, the power outer loop control unit 211 in the inverter control submodule 21 is activated, and the output DC voltage compensation... >0, compared to the initial given value The superposition raises the DC bus voltage reference level, driving the actual voltage of the DC bus. The voltage increases. Simultaneously, the current feedforward unit 214 operates, outputting DC voltage compensation. >0, rapidly reducing the inverter output current. (This is followed by a seemingly unrelated phrase: "as the actual voltage...") As the voltage rises, the outer loop control unit 212 of the energy storage side control submodule 21 detects the final voltage setpoint. Actual voltage of DC bus Exit saturation and integrate in reverse to output a negative outer loop output current command. (Limited to a safe range by the third limiter), the inner loop control unit 222 of the energy storage current is triggered to control the battery to conduct and enter the charging state, absorbing the excess photovoltaic power on the DC side. Ultimately, the system stabilizes at a new equilibrium point, enabling... Returning to 0 achieves operation without backflow.

[0042] Figures 5a to 5d The simulation waveforms verified the aforementioned mode switching and anti-reverse current process. Initially, under initial conditions, grid power flows to the load; at steady state, the actual voltage of the DC bus... =700V, P_grid=-500W, the system is in the first mode; after the photovoltaic power increases, the excess power will flow back into the grid. >0, the system switches to the second mode, the power controller desaturates, and the voltage setpoint... Increase, actual voltage The voltage is increased from 700V to 735V, while the DC-side battery charges to absorb excess photovoltaic power, eventually stabilizing. =735V, P_grid=0.

[0043] The beneficial effects of this application are as follows: It enables the photovoltaic-storage system to adaptively protect against grid power reverse current, thereby improving the security of the distribution network and the photovoltaic absorption rate.

[0044] Through coordinated control of the inverter side and the energy storage side, smooth and rapid power transfer is achieved, with good dynamic response performance.

[0045] By utilizing the limiter mechanism, precise control is achieved while also providing overload protection, resulting in high system reliability.

[0046] The control strategy has a clear hierarchy, is easy to implement on a digital control platform, and has high engineering application value.

[0047] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made using the content of this specification and illustrations should be included within the protection scope of the present invention.

Claims

1. A photovoltaic-storage system for preventing grid power backflow, characterized in that, It includes photovoltaic modules, a DC bus, an inverter, and a battery; the photovoltaic modules are connected to the DC side of the inverter via the DC bus, the AC side of the inverter is connected to the power grid and the electrical load, and the battery is connected in parallel to the DC bus; The grid-connected power monitoring module is used to obtain the grid-connected power at the connection point between the AC side of the inverter and the grid. The anti-reverse current module is used to reduce the output current of the inverter by current feedforward when the output power of the inverter is greater than the load power of the electrical load, causing the DC voltage to rise. This reduces the difference between the output power and the load power. At the same time, it controls the battery to enter the charging state to absorb the excess photovoltaic power of the photovoltaic module, thereby maintaining the grid connection point power in a non-reverse current state.

2. The photovoltaic energy storage system according to claim 1, characterized in that, The anti-backflow module includes: The inverter control submodule is used to generate a DC voltage compensation amount and a current feedforward command value based on the grid connection point power when the output power of the inverter is greater than the load power of the electrical load, resulting in a rise in the DC side voltage. The DC voltage compensation amount is then superimposed with an initial setpoint to adjust the voltage reference of the DC bus. Subsequently, the current setpoint value generated based on the voltage reference and the actual voltage of the DC bus is reduced by the current feedforward command value to obtain a final setpoint current command value to control the inverter to reduce the output current. The energy storage side control submodule, connected to the inverter control submodule, is used to adjust the battery's charging state to absorb the excess photovoltaic power of the photovoltaic module based on the deviation between the actual voltage of the DC bus and the set final voltage value.

3. The coordinated control system according to claim 2, characterized in that, The inverter control submodule includes: A power outer loop control unit is used to generate the DC voltage compensation amount based on the grid connection point power. The voltage outer loop control unit is used to superimpose the DC voltage compensation amount with the initial given value to generate the voltage reference reference. The current inner loop control unit is used to input the difference between the voltage reference and the actual voltage of the DC bus to the voltage controller to obtain the current setpoint.

4. The coordinated control system according to claim 3, characterized in that, The power outer loop control unit includes a first PI controller. The output terminal of the first PI controller is connected to a first limiter. The first PI controller is used to generate an initial voltage command value according to the grid connection point power. The first limiter is used to limit the initial voltage command value to obtain the DC voltage compensation amount. The limiting range of the first limiter is [0, ... U dc * ],in U dc * This is the maximum DC voltage compensation amount set. When the grid connection point power is negative, the first limiter is used to limit the DC voltage compensation amount to 0, and when the grid connection point power is positive, the first limiter is used to limit the DC voltage compensation amount to no more than the maximum DC voltage compensation amount.

5. The coordinated control system according to claim 3, characterized in that, The inverter control submodule also includes a current feedforward unit connected to the current inner loop control unit. This unit multiplies the grid-connected power by a positive gain coefficient, processes it through a second limiter to generate the current feedforward command value, and then subtracts it from the current setpoint to quickly reduce the final given current command, thereby controlling the inverter's output current to decrease.

6. The coordinated control system according to claim 5, characterized in that, The limiting range of the second limiter is [0, i dmax * ], where i dmax * This is the set maximum d-axis current feedforward command value; When the grid connection point power is negative, the second limiter is used to limit the current feedforward command value to 0, and when the grid connection point power is positive, the second limiter is used to limit the current feedforward command value to no higher than the maximum d-axis current feedforward command value.

7. The coordinated control system according to claim 2, characterized in that, An inductor is connected in series on each path between the AC side of the inverter and the power grid. The energy storage side control submodule includes: The energy storage voltage outer loop control unit is used to calculate the deviation between the final voltage setpoint and the actual voltage of the DC bus when the output power of the inverter at the grid connection point is greater than the load power of the electrical load, resulting in a rise in the DC side voltage, and generate an outer loop output current command value. The energy storage current inner loop control unit is used to control the battery to enter the charging state according to the outer loop output current command value and the current feedback value of the inductor, so as to absorb the excess photovoltaic power of the photovoltaic module.

8. The coordinated control system according to claim 7, characterized in that, The energy storage voltage outer loop control unit includes a second PI controller. The second PI controller processes the deviation between the final voltage setpoint and the actual voltage of the DC bus to obtain the outer loop output current command value. The output terminal of the second PI controller is connected to a third limiter, and the limiting range of the third limiter is [-i]. Lmax * [, 0], where i Lmax * The maximum charging current command value is set. When the grid connection point power is negative, the third limiter is used to limit the outer loop output current command value to 0, and when the grid connection point power is positive, the second limiter is used to limit the current feedforward command value to a negative value not less than the maximum charging current command value.

9. A control method for preventing grid power reverse current in a photovoltaic-storage system, characterized in that, Applied to the photovoltaic energy storage system as described in any one of claims 1-8, comprising: Step S1: The photovoltaic-storage system continuously acquires the grid connection point power at the connection between the AC side of the inverter and the grid. In step S2, when the output power of the inverter at the grid connection point is greater than the load power of the electrical load, causing the DC voltage to rise, the photovoltaic storage system controls the output current of the inverter to decrease through current feedforward, thereby reducing the difference between the output power and the load power. At the same time, it controls the battery to enter the charging state to absorb the excess photovoltaic power of the photovoltaic module, thereby maintaining the grid connection point power in a non-reverse state.

10. The control method according to claim 9, characterized in that, Step S2 includes: Step S21: When the grid connection point power indicates that the output power of the inverter is greater than the load power of the electrical load, causing the DC side voltage to rise, the photovoltaic energy storage system generates a DC voltage compensation amount and a current feedforward command value based on the grid connection point power. The DC voltage compensation amount is superimposed with the initial given value to adjust the voltage reference of the DC bus. Then, the current given value generated based on the voltage reference and the actual voltage of the DC bus is reduced by the current feedforward command value to obtain the final given current command value to control the inverter to reduce the output current. In step S22, the photovoltaic energy storage system adjusts the battery to enter the charging state to absorb the excess photovoltaic power of the photovoltaic module based on the deviation between the actual voltage of the DC bus and the set final voltage value.

Images