Control method and system for dynamic power balance compensation of photovoltaic energy storage power station

Abstract

The application discloses a control method and system for dynamic power balance compensation of a photovoltaic energy storage power station, relates to the technical field of photovoltaic energy storage, and comprises the following steps: performing multi-source state parameter detection, introducing a deployed linear quadratic regulator, performing active damping control analysis, determining energy storage charging and discharging instructions, and performing basic scheduling management; by calculating the SOC range, a transformer array connected in the energy storage system is optionally triggered, target equalization current is calculated by taking the energy storage charging and discharging instructions as a power constraint, corresponding PWM duty cycle signals are generated to drive the switching tubes of corresponding bidirectional buck-boost auxiliary transformers; and by dividing a target power grid region into three-source power supply branches, low-voltage ride-through event decision and power supply branch switching management are performed according to a voltage drop detector. The application solves the technical problem of the response lag of the dynamic power balance compensation of the photovoltaic energy storage power station in the prior art, and achieves the technical effect of improving the response speed and control stability of the dynamic power balance compensation.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic energy storage technology, and more specifically to a control method and system for dynamic power balance compensation in photovoltaic energy storage power stations. Background Technology

[0002] During the operation of a photovoltaic energy storage power station, photovoltaic output fluctuates significantly due to the influence of sunlight intensity and environmental conditions, while load-side demand and grid conditions also change constantly, requiring frequent dynamic adjustments to the system's power balance. Traditional power compensation often relies on passive response mechanisms, which have a certain time delay in detection, decision-making, and execution. This makes it difficult for the energy storage system to quickly adjust to power changes, leading to problems such as untimely compensation, increased bus voltage fluctuations, and decreased system stability under conditions of large or sudden power fluctuations. Summary of the Invention

[0003] This application provides a control method and system for dynamic power balance compensation in photovoltaic energy storage power stations, which is used to address the technical problem of lag in the response of dynamic power balance compensation in existing photovoltaic energy storage power stations.

[0004] In view of the above problems, this application provides a control method and system for dynamic power balance compensation of photovoltaic energy storage power stations.

[0005] A first aspect of this application provides a control method for dynamic power balance compensation in a photovoltaic energy storage power station, the method comprising: Multi-source state parameter detection is performed on the target power grid area, and the deployed linear quadratic regulator is imported to perform active damping control analysis based on energy storage-photovoltaic coupling. The energy storage charging and discharging command is determined, and basic scheduling and control are performed. By calculating the SOC range of each energy storage unit, the converter array connected to the energy storage system can be selectively triggered. The target equalization current is calculated with the energy storage charging and discharging command as the power constraint, and the corresponding PWM duty cycle signal is generated to drive the switching transistor of the corresponding bidirectional buck-boost auxiliary converter. In this process, the target power grid area is divided into three power supply branches, and low voltage ride-through event decision-making and power supply branch switching management are performed based on the built-in voltage drop detector.

[0006] A second aspect of this application provides a control system for dynamic power balance compensation in a photovoltaic energy storage power station, the system comprising: The parameter detection module is used to detect multi-source state parameters of the target power grid area, import them into the deployed linear quadratic regulator, perform active damping control analysis based on energy storage-photovoltaic coupling, determine energy storage charging and discharging commands, and perform basic scheduling and control. The calculation module is used to calculate the SOC range of each energy storage unit, optionally trigger the converter array connected to the energy storage system, calculate the target equalization current with the energy storage charging and discharging commands as power constraints, and generate the corresponding PWM duty cycle signal to drive the switching transistors of the corresponding bidirectional buck-boost auxiliary converter. The decision management module is used to divide the target power grid area into three power supply branches, and perform low voltage ride-through event decision-making and power supply branch switching management based on the built-in voltage drop detector.

[0007] One or more technical solutions provided in this application have at least the following technical effects or advantages: This application performs multi-source state parameter detection on the target power grid area, imports the data into a deployed linear quadratic regulator, executes active damping control analysis based on energy storage-photovoltaic coupling, determines energy storage charging and discharging commands, and performs basic scheduling and control. By calculating the SOC range of each energy storage unit, the converter array connected to the energy storage system can be selectively triggered. The target equalization current is calculated using the energy storage charging and discharging commands as power constraints, and a corresponding PWM duty cycle signal is generated to drive the switching transistors of the corresponding bidirectional buck-boost auxiliary converter. The target power grid area is divided into three power supply branches, and low-voltage ride-through event decision-making and power supply branch switching management are performed based on a built-in voltage drop detector. This invention solves the technical problem of lag in dynamic power balance compensation response in existing photovoltaic energy storage power stations. By determining energy storage charging and discharging commands through active damping control based on energy storage-photovoltaic coupling, it achieves the technical effect of improving the dynamic power balance compensation response speed and control stability. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 This is a schematic flowchart of a control method for dynamic power balance compensation in a photovoltaic energy storage power station, provided in an embodiment of this application. Figure 2 This is a schematic diagram of the control system structure for dynamic power balance compensation of a photovoltaic energy storage power station, provided in an embodiment of this application.

[0010] Explanation of reference numerals in the attached diagram: Parameter detection module 11, Calculation module 12, Decision management module 13. Detailed Implementation

[0011] This application provides a control method and system for dynamic power balance compensation in photovoltaic energy storage power stations. It addresses the technical problem of lag in the response of dynamic power balance compensation in existing technologies by using active damping control based on energy storage-photovoltaic coupling to determine energy storage charging and discharging commands, thereby improving the response speed and control stability of dynamic power balance compensation.

[0012] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0013] It should be noted that any variation of the terms "comprising" and "having" is intended to cover non-exclusive inclusion, for example, a process, method, system, product, or server that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or modules that are not explicitly listed or that are inherent to such processes, methods, products, or devices.

[0014] Example 1, as Figure 1 As shown, this application provides a control method for dynamic power balance compensation in photovoltaic energy storage power stations, the method comprising: Step S100: Perform multi-source state parameter detection on the target power grid area, import the deployed linear quadratic regulator, perform active damping control analysis based on energy storage-photovoltaic coupling, determine energy storage charging and discharging commands, and perform basic dispatch and control.

[0015] In this embodiment, multi-source state parameter detection is performed on the target power grid area. First, the operating parameters of the photovoltaic array, energy storage system, and DC bus are simultaneously collected. Specifically, the output state of the photovoltaic array is detected to obtain the photovoltaic power, the operating state of the energy storage system is detected to obtain the energy storage power, the voltage state of the DC bus is detected to obtain the bus voltage, and the state of charge (SOC) of each energy storage unit is acquired. The photovoltaic power, energy storage power, bus voltage, and SOC of each energy storage unit are then aggregated to form state variables reflecting the current operating conditions of the target power grid area. Subsequently, the power output characteristics of the photovoltaic array are modeled as a nonlinear source, and the energy storage system is modeled as a variable impedance load. Based on the second-order dynamic architecture formed by the coupling of the nonlinear source and the variable impedance load through the DC bus, a deployed linear quadratic regulator is introduced, incorporating the aforementioned state variables and the charging and discharging current driving parameters of each energy storage converter into the control solution process.

[0016] During the operation of the linear quadratic regulator, active damping control analysis is performed on the dynamic process between photovoltaic power variation, energy storage power regulation, and bus voltage fluctuation based on the energy storage-photovoltaic coupling relationship. Comprehensive optimization is then implemented focusing on minimizing bus voltage fluctuation, smoothing energy storage power, and achieving SOC balance, resulting in the solution of the corresponding state feedback gain matrix. After completing the state feedback solution, the control result corresponding to the current operating condition is output, thereby obtaining the energy storage charging and discharging command. Subsequently, the charging and discharging currents of each energy storage converter are adjusted according to the energy storage charging and discharging command, and the adjustment results are used for basic dispatch and control, enabling the energy storage system to participate in the dynamic power balance compensation of the target grid area according to the generated charging or discharging power.

[0017] Furthermore, in the method provided in the application embodiments, the linear quadratic regulator further includes: The power output characteristics of the photovoltaic array are modeled as a nonlinear source, and the energy storage system is modeled as a variable impedance load. The nonlinear source is affected by light intensity, temperature, and load. The nonlinear source and the variable impedance load are coupled through a DC bus to form a second-order dynamic architecture. Based on the second-order dynamic architecture, state variables and control variables are introduced to execute a deployment based on the optimal control law, thus forming the linear quadratic regulator.

[0018] In this embodiment, when modeling the power output characteristics of the photovoltaic array as a nonlinear source, the following steps are taken: First, the illuminance, module temperature, output voltage, output current, and DC bus-side load power demand are simultaneously collected at the output end of the photovoltaic array, and the data at each sampling moment are continuously recorded at a preset sampling period. Then, at each sampling moment, the output power of the photovoltaic array is calculated based on the output voltage and output current, and the illuminance, module temperature, load power demand, output voltage, output current, and output power are grouped into corresponding operating condition data sets. After obtaining multiple sets of operating condition data, the operating condition data are sorted and stored according to illuminance range, temperature range, and load range. When the illuminance, module temperature, and load power demand collected in the current control cycle correspond to a stored operating condition data set, that data set is directly read. The output current and output power corresponding to the operating condition data group are calculated by interpolation when the light intensity, module temperature and load power demand collected in the current control cycle are between adjacent operating condition data groups. The output current and output power under the current control cycle are then written as real-time output parameters of the photovoltaic side into the subsequent control calculation process. The acquisition, matching or interpolation and power update are re-executed in the next control cycle, so that the output parameters of the photovoltaic array change synchronously with the changes in light intensity, temperature and load during the continuous control process. Thus, the power output characteristics of the photovoltaic array are modeled as a nonlinear source, in which the nonlinear source is affected by light intensity, temperature and load.

[0019] When modeling the energy storage system as a variable impedance load, the terminal voltage, terminal current, charging / discharging power, and SOC of each energy storage unit are first collected in each control cycle. Simultaneously, the driving parameters of the charging / discharging current and the current charging or discharging state of each energy storage converter are read. Then, based on the current conversion direction and conversion ratio of each energy storage converter, the terminal voltage and terminal current on the energy storage battery side are converted into the equivalent voltage and equivalent current on the DC bus side. The power exchange amount for the current control cycle is then calculated based on the equivalent voltage and equivalent current. After obtaining the equivalent voltage, equivalent current, and power exchange amount on the DC bus side, the ratio of the current DC bus voltage to the equivalent current is used to calculate... The equivalent impedance value is calculated either by the ratio of the square of the DC bus voltage to the power exchange, and then corrected by combining the SOC of each energy storage unit, the charging and discharging power, and the driving parameters of the charging and discharging current of each energy storage converter. When the energy storage system switches from charging to discharging, or from discharging to charging, or when the SOC, charging and discharging power, and driving parameters of the charging and discharging current of each energy storage unit change, the voltage and current conversion, power exchange calculation, and equivalent impedance value correction are re-executed. This ensures that the energy storage system participates in subsequent calculations with real-time updated impedance characteristics in each control cycle, thereby modeling the energy storage system as a variable impedance load.

[0020] After obtaining the nonlinear source and the variable impedance load, the nonlinear source is connected to the photovoltaic side branch of the DC bus, and the variable impedance load is connected to the energy storage side branch of the DC bus. In each control cycle, the output voltage, output current, and output power of the nonlinear source, as well as the equivalent voltage, equivalent current, power exchange, and equivalent impedance value of the variable impedance load, are read. Subsequently, the net current for the current control cycle is calculated based on the current inflow and outflow at the DC bus nodes. The nonlinear source output current is used as the inflow term, and the equivalent current on the energy storage side and the load side current are used as the outflow terms, combined with the DC bus... The capacitance value is used to calculate the bus voltage change in the current control cycle. Simultaneously, the energy storage power in the current control cycle is calculated based on the equivalent voltage and equivalent current of the energy storage side. The energy storage power in the current control cycle is compared with the energy storage power in the previous control cycle to obtain the energy storage power change. The bus voltage change and the energy storage power change are then jointly updated as two main dynamic quantities, so that the nonlinear source output change, the variable impedance load impedance change, and the DC bus voltage change are described in the same continuous update process. This allows the nonlinear source and the variable impedance load to form a second-order dynamic architecture through DC bus coupling.

[0021] Based on a second-order dynamic architecture, when implementing deployment based on optimal control laws by introducing state variables and control variables, the following steps are taken: First, in each control cycle, photovoltaic power, energy storage power, bus voltage, and the SOC of each energy storage unit are read and arranged into state variables in a fixed order. Simultaneously, the driving parameters of the charging and discharging currents of each energy storage converter are arranged into control variables in a fixed order. Then, the bus voltage deviation is calculated based on the current bus voltage and the target bus voltage; the change in energy storage power is calculated based on the current energy storage power and the energy storage power of the previous control cycle or a smoothed reference value; and the SOC deviation of each energy storage unit is calculated based on the SOC of each unit and the average SOC of all energy storage units. After obtaining the bus voltage deviation, the change in energy storage power, and the SOC deviation of each energy storage unit, these deviations are weighted according to preset weights. The system performs weighted calculations on the control quantities corresponding to the driving parameters of the charging and discharging currents of each energy storage converter. The weighted results of the deviation and the control quantities are then combined to form the comprehensive evaluation quantity for the current control cycle. Next, based on the state relationship, control relationship, and weighted relationship of the comprehensive evaluation quantity at the current operating point of the second-order dynamic architecture, the state feedback gain matrix is ​​solved. This matrix is ​​then multiplied with the state variables of the current control cycle to obtain the charging and discharging current regulation quantity for each energy storage converter within the current control cycle. Finally, the charging and discharging current regulation quantity for each energy storage converter is written into the control output. In the next control cycle, the processes of state variable reading, deviation calculation, comprehensive evaluation quantity update, state feedback gain matrix solution, and control output update are repeated, forming a linear quadratic regulator.

[0022] Furthermore, the method provided in the application embodiments also includes: The state variables include photovoltaic power, energy storage power, bus voltage, and SOC of each energy storage unit; the control variables are the driving parameters of the charging and discharging current of each energy storage converter; the setting of the optimal control law includes: taking the minimization of bus voltage fluctuation, the smoothing of energy storage power, and the balance of SOC as joint optimization objectives, solving the state feedback gain matrix, and taking the energy storage charging and discharging command as the output.

[0023] In this embodiment, when performing deployment based on the optimal control law using a second-order dynamic architecture as a reference, the output voltage and current of the photovoltaic array are first read in each control cycle, and the output voltage and current are multiplied to obtain the photovoltaic power; the terminal voltage and current of the energy storage system are read, and the current charging or discharging state is determined according to the direction of the terminal current. After determining the power direction, the terminal voltage and current are multiplied to obtain the energy storage power; the real-time voltage of the DC bus is collected synchronously to obtain the bus voltage; the current of each energy storage unit in the current control cycle is integrated over time to obtain the change in charging and discharging capacity in the control cycle, and then the change in charging and discharging capacity is divided by the rated capacity of the corresponding energy storage unit, and updated by adding or subtracting from the SOC value of the previous control cycle to obtain the SOC of each energy storage unit. After completing the above calculations, the photovoltaic power, energy storage power, bus voltage, and SOC of each energy storage unit are arranged in a fixed order to form state variables, which include photovoltaic power, energy storage power, bus voltage, and SOC of each energy storage unit. At the same time, the driving parameters of the charging and discharging current of each energy storage converter are read and arranged in the order corresponding to each energy storage unit to form control variables, which are the driving parameters of the charging and discharging current of each energy storage converter.

[0024] After the state variables and control variables are determined, the second-order dynamic architecture at the current operating point is organized into state and control relationships under discrete control cycles, establishing a correspondence between the changes in state variables and control variables in the current control cycle. Subsequently, the quantities in the joint optimization objective are calculated. Specifically, the bus voltage fluctuation is obtained by subtracting the bus voltage of the previous control cycle from the bus voltage of the current control cycle; the energy storage power change is obtained by subtracting the energy storage power of the previous control cycle from the energy storage power of the current control cycle; the SOC of all energy storage units is summed and divided by the total number of energy storage units to obtain the average SOC; and the SOC deviation of each energy storage unit is obtained by subtracting the average SOC from the SOC of each energy storage unit. Finally, the driving parameters of the charging and discharging currents of each energy storage converter in the current control cycle are subtracted from the driving parameters of the corresponding charging and discharging currents in the previous control cycle to obtain the changes in control variables. After completing the above calculations, the bus voltage fluctuation, energy storage power change, SOC deviation of each energy storage unit, and control variable change are squared respectively, and written into the corresponding positions according to the order of the state variables in the state vector and the order of the control variables in the control vector, forming state evaluation items and control evaluation items to reflect the minimization of bus voltage fluctuation, smoothing of energy storage power, and SOC balance. Specifically, when the bus voltage fluctuation, energy storage power change, SOC deviation of each energy storage unit, and control variable change are written into the state evaluation items and control evaluation items, they correspond to voltage weight coefficient, power weight coefficient, SOC weight coefficient, and control weight coefficient, respectively. The voltage weight coefficient, power weight coefficient, SOC weight coefficient, and control weight coefficient are determined according to the allowable variation range of the corresponding quantities. Specifically, the allowable fluctuation range of bus voltage, the allowable variation range of energy storage power, the allowable deviation range of SOC of each energy storage unit, and the allowable variation range of the driving parameters of the charging and discharging current of each energy storage converter are obtained, and the reciprocal square of each allowable variation range is used as the corresponding coefficient and written into the state evaluation items and control evaluation items.

[0025] After the state evaluation terms and control evaluation terms are formed, the state feedback gain matrix is ​​solved based on the state and control relationships. Specifically, the state evaluation terms are first organized into a state evaluation matrix, and the control evaluation terms are organized into a control evaluation matrix. The state evaluation matrix is ​​then used as the initial value of the intermediate matrix. Subsequently, the intermediate matrix from the previous round is multiplied on the left and right by the state relationship to obtain the state propagation term. The intermediate matrix from the previous round is then multiplied on the left and right by the control relationship, and combined with the control evaluation matrix, and inverted to obtain the control correction term. The control correction term is then combined with the state propagation term and added to the state evaluation matrix to obtain a new intermediate matrix. The calculation of the state propagation term, the calculation of the control correction term, and the update of the intermediate matrix are repeated until the intermediate matrix no longer changes between the previous and current rounds. After the intermediate matrix stabilizes, the transpose of the control relationship, the intermediate matrix, the control relationship, and the control evaluation matrix are combined sequentially to obtain the control solution matrix. The control solution matrix is ​​then inverted and multiplied sequentially with the transpose of the control relationship, the intermediate matrix, and the state relationship to obtain the state feedback gain matrix. This completes the setting of the optimal control law, which includes solving the state feedback gain matrix with the joint optimization objectives of minimizing bus voltage fluctuations, smoothing energy storage power, and achieving SOC balance.

[0026] After obtaining the state feedback gain matrix, the state feedback gain matrix is ​​multiplied with the state variables of the current control cycle to obtain the charging and discharging current regulation amount corresponding to each energy storage converter. Then, the charging and discharging current regulation amount corresponding to each energy storage converter is superimposed and updated with the driving parameters of the charging and discharging current of the current control cycle to obtain the updated driving parameters of the charging and discharging current of each energy storage converter. Subsequently, the updated driving parameters of the charging and discharging current of each energy storage converter are multiplied with the corresponding energy storage unit terminal voltage to obtain the charging power or discharging power of each energy storage unit in the current control cycle. Energy storage charging and discharging commands are generated according to the direction and magnitude of the charging or discharging power, and the energy storage charging and discharging commands are output.

[0027] Step S200: By calculating the SOC range of each energy storage unit, the converter array connected to the energy storage system can be selectively triggered. The target equalization current is calculated with the energy storage charging and discharging command as the power constraint, and the corresponding PWM duty cycle signal is generated to drive the switching transistor of the corresponding bidirectional buck-boost auxiliary converter.

[0028] In this embodiment, the SOC value of each energy storage unit is first collected in real time, and the maximum and minimum SOC values ​​of each energy storage unit are compared to calculate the SOC range of each energy storage unit. After obtaining the SOC range, the SOC range is compared with a judgment threshold set in the first judge. When the SOC range meets the triggering condition, a current balancing command is output, thereby optionally triggering the converter array connected to the energy storage system to participate in the balancing adjustment. The converter array consists of bidirectional buck-boost auxiliary converters connected in parallel with each energy storage unit. The common terminal of each bidirectional buck-boost auxiliary converter is connected to the balancing bus, thereby establishing a controlled energy transmission path between each energy storage unit and the balancing bus.

[0029] After the converter array is triggered, the energy storage charging and discharging commands of each energy storage unit output from the preceding control process are read, and these commands are written into the target equalization current calculation process as power constraints. Subsequently, combining the current charging or discharging power of each energy storage unit with its maximum charging or discharging power, the remaining usable power of each unit in the current control cycle is calculated. For energy storage units in a high SOC state, the remaining discharge power is calculated by subtracting the current discharge power from the maximum discharge power; for energy storage units in a low SOC state, the remaining charging power is calculated by subtracting the current charging power from the maximum charging power. After obtaining the remaining usable power, the terminal voltage of the corresponding energy storage unit in the current control cycle is read, and then... Based on the correspondence that power equals the product of voltage and current, the remaining available power is divided by the corresponding energy storage unit terminal voltage to obtain the allowable equalization current. Specifically, for energy storage units in a high SOC state, the allowable output equalization current is obtained by dividing the remaining discharge power by the corresponding energy storage unit terminal voltage, while for energy storage units in a low SOC state, the allowable absorption equalization current is obtained by dividing the remaining charging power by the corresponding energy storage unit terminal voltage. Then, the equalization current requirement is calculated based on the deviation of each energy storage unit's SOC from the equalization state, and the equalization current requirement is compared with the allowable equalization current. The smaller of the two values ​​is taken to obtain the target equalization current for each energy storage unit, so that the target equalization current is always limited by the remaining power boundary corresponding to the energy storage charging and discharging command.

[0030] After the target equalization current is determined, the PWM duty cycle signal is calculated based on the target equalization current and the transformation relationship between the input and output voltages of the corresponding bidirectional buck-boost auxiliary converter. The PWM duty cycle signal is then sent to the switching transistor of the corresponding bidirectional buck-boost auxiliary converter to adjust the on-time and off-time of the switching transistor in the current control cycle. Subsequently, the corresponding bidirectional buck-boost auxiliary converter outputs or absorbs the target equalization current under the action of the PWM duty cycle signal, so that the high SOC unit outputs the target equalization current through the equalization bus, and the low SOC unit absorbs the target equalization current through the equalization bus. This completes the continuous control process of calculating the SOC range of each energy storage unit, selectively triggering the converter array connected to the energy storage system, calculating the target equalization current with the energy storage charging and discharging command as the power constraint, and generating the corresponding PWM duty cycle signal to drive the switching transistor of the corresponding bidirectional buck-boost auxiliary converter.

[0031] Furthermore, in the method provided in the application embodiments, the optional triggering of the converter array connected to the energy storage system further includes: In the energy storage system, a converter array is connected. A bidirectional buck-boost auxiliary converter is connected in parallel to each energy storage unit, and the common terminal of the converter is connected to the balancing bus as the access method. The SOC value of each energy storage unit is collected in real time, and the threshold judgment and current balancing control based on the SOC value are triggered according to the first judgment unit.

[0032] In this embodiment, when connecting a converter array to an energy storage system, a corresponding number of bidirectional buck-boost auxiliary converters are first configured according to the number of energy storage units, and each bidirectional buck-boost auxiliary converter is connected in parallel with one energy storage unit. During the parallel connection process, the power terminal of the corresponding bidirectional buck-boost auxiliary converter is connected to the positive and negative terminals of the corresponding energy storage unit, so that the bidirectional buck-boost auxiliary converter can directly obtain the terminal voltage of the corresponding energy storage unit and exchange energy bidirectionally with the corresponding energy storage unit. After completing the parallel connection of each energy storage unit with the bidirectional buck-boost auxiliary converter, the common converter terminals of all bidirectional buck-boost auxiliary converters are connected to the same equalization bus, so that each energy storage unit establishes a controlled connection relationship with the equalization bus through its corresponding bidirectional buck-boost auxiliary converter. This forms a converter array composed of multiple bidirectional buck-boost auxiliary converters, and an independent and controllable current transmission branch is established between each energy storage unit and the equalization bus.

[0033] After the converter array is connected, the SOC value of each energy storage unit is acquired in real time. During the acquisition process, the terminal voltage and terminal current of each energy storage unit are read in each control cycle, and the terminal current of each energy storage unit in the current control cycle is integrated to obtain the energy change value of each energy storage unit in the current control cycle. The energy change value is then converted with the rated capacity of the corresponding energy storage unit, and the SOC value of the current control cycle is updated in combination with the SOC value of the corresponding energy storage unit in the previous control cycle. After the SOC value of each energy storage unit is updated, the SOC values ​​of all energy storage units are written into the SOC data sequence according to the energy storage unit number, and the SOC data sequence is input into the first judge, thereby completing the real-time acquisition and subsequent judgment input of the SOC value of each energy storage unit.

[0034] After receiving the SOC data sequence, the first judge performs a threshold judgment on the SOC value of each energy storage unit. Specifically, it first compares all SOC values ​​in the SOC data sequence one by one, extracts the maximum and minimum SOC values, and then subtracts the minimum SOC value from the maximum SOC value to obtain the SOC range between each energy storage unit. After obtaining the SOC range, it compares the SOC range with the threshold set in the first judge. When the SOC range reaches the threshold judgment condition, the first judge outputs a trigger signal and identifies the energy storage unit with the higher current SOC value as the high SOC-side adjustment target and the energy storage unit with the lower current SOC value as the low SOC-side adjustment target. This completes the threshold judgment process based on the SOC value.

[0035] After the first judgment unit outputs a trigger signal, current balancing control is triggered. During this process, the trigger signal is sent to the control terminal of the converter array, causing the bidirectional buck-boost auxiliary converters connected in parallel with each energy storage unit to switch from standby state to balancing regulation state, and enabling each bidirectional buck-boost auxiliary converter to participate in current exchange on the balancing bus in subsequent control cycles. Since the common terminal of each bidirectional buck-boost auxiliary converter is uniformly connected to the balancing bus, and each bidirectional buck-boost auxiliary converter is connected in parallel with its corresponding energy storage unit, after the threshold judgment is triggered, the high SOC side regulation object can output balancing current to the balancing bus through the corresponding bidirectional buck-boost auxiliary converter, and the low SOC side regulation object can absorb balancing current from the balancing bus through the corresponding bidirectional buck-boost auxiliary converter. This forms a continuous execution process consisting of connecting the converter array to the energy storage system, real-time acquisition of the SOC value of each energy storage unit, threshold judgment based on the first judgment unit, and triggering current balancing control.

[0036] Furthermore, the method provided in the application embodiments also includes: Based on the set threshold embedded in the first judge, the SOC range between each energy storage unit is calculated. When it exceeds the set threshold, a current balancing command is triggered. Based on the current balancing command, the charging and discharging commands of each energy storage unit are read and used as power constraints to calculate the target balancing current of each energy storage unit. Based on the target balancing current, a PWM duty cycle signal is generated and sent to the corresponding bidirectional buck-boost converter for switching control.

[0037] In this embodiment, the first judgment unit embeds a set threshold and receives the SOC value of each energy storage unit in each control cycle. The SOC value is obtained by integrating the terminal current of the corresponding energy storage unit in the current control cycle and updating it by combining the SOC value of the previous control cycle and the rated capacity of the corresponding energy storage unit. The first judgment unit compares the SOC values ​​of all energy storage units, extracts the maximum and minimum SOC values, and subtracts the minimum SOC value from the maximum SOC value to obtain the SOC range. The SOC range is used to characterize the dispersion of the state of charge among the energy storage units. After obtaining the SOC range, the SOC range is compared with the set threshold embedded in the first judgment unit. The set threshold is used to limit whether to enter the equalization adjustment process. The set threshold can be 5%. When the SOC range is greater than the set threshold, it is determined that the difference in the state of charge among the energy storage units has reached the equalization trigger condition. The first judgment unit outputs a current equalization command, so that the control process enters the target equalization current calculation stage from the SOC state judgment stage.

[0038] After the current balancing command is triggered, the controller reads the charge and discharge commands currently being executed by each energy storage unit and writes these commands as power constraints into the target balancing current calculation process. The charge and discharge commands are the energy storage charge and discharge commands output by the front-end active damping control analysis. The power constraints are used to limit the remaining regulation capacity that the corresponding energy storage unit can still allocate to the SOC balancing task while undertaking the main power compensation task. Subsequently, the controller reads the maximum charging power and maximum discharging power of each energy storage unit and calculates the remaining available power of each energy storage unit in combination with the currently executed charging and discharging commands. The remaining discharge capacity of high SOC units is calculated by subtracting the current discharging command from the maximum discharge power, and the remaining charging capacity of low SOC units is calculated by subtracting the current charging command from the maximum charging power. After obtaining the remaining available power, the corresponding energy storage unit terminal voltage is read, and the remaining available power is divided by the corresponding energy storage unit terminal voltage to obtain the allowable balancing current. Simultaneously, the average SOC value of all energy storage units is calculated to obtain the average SOC value. Then, the difference between the SOC value of each energy storage unit and the average SOC value is used to obtain the SOC deviation. The current SOC deviation is matched with the pre-stored SOC deviation-balancing current demand correspondence in the controller to obtain the balancing current demand corresponding to the current SOC deviation. Then, the allowable balancing current is compared with the balancing current demand, and the smaller value of the two is taken as the target balancing current of the corresponding energy storage unit. This ensures that the target balancing current reflects the degree of SOC difference and meets the constraint that the sum of the power of the main power compensation task and the SOC balancing task does not exceed the maximum charging and discharging capacity of the corresponding energy storage unit.

[0039] After the target equalization current for each energy storage unit is determined, the controller reads the input voltage, output voltage, and switching cycle of the corresponding bidirectional buck-boost converter. The input voltage is the voltage at the corresponding energy storage unit, the output voltage is the equalization bus voltage, and the switching cycle is a preset single PWM cycle for the bidirectional buck-boost converter. Then, the operating direction of the bidirectional buck-boost converter is determined based on the energy transfer direction corresponding to the target equalization current. When a high-SOC unit outputs the target equalization current to the equalization bus, if the voltage at the corresponding energy storage unit is less than the equalization bus voltage, the bidirectional buck-boost converter operates in boost mode, and the basic on-time ratio is calculated based on the ratio of the input voltage to the output voltage. Specifically, the basic on-time ratio is obtained by subtracting the ratio of the input voltage to the output voltage from 1. If the voltage at the corresponding energy storage unit is greater than the equalization bus voltage, the bidirectional buck-boost converter operates in buck mode, and the basic on-time ratio is obtained by the ratio of the output voltage to the input voltage. When the balancing bus inputs the target balancing current to the low SOC unit, if the balancing bus voltage is greater than the corresponding energy storage unit terminal voltage, the bidirectional buck-boost converter operates in buck mode, and the basic conduction time ratio is obtained by the ratio of the output voltage to the input voltage. If the balancing bus voltage is less than the corresponding energy storage unit terminal voltage, the bidirectional buck-boost converter operates in boost mode, and the basic conduction time ratio is obtained by subtracting the ratio of the input voltage to the output voltage from 1. After obtaining the basic conduction time ratio, it is multiplied by the switching cycle to obtain the basic conduction time. Then, the target balancing current is compared with the actual current of the current balancing branch; the actual current of the balancing branch is obtained through the sampling value of the corresponding branch current. When the target balancing current is greater than the actual current of the current balancing branch, the conduction time ratio is increased in the next control cycle; when the target balancing current is less than the actual current of the current balancing branch, the conduction time ratio is decreased in the next control cycle; when the target balancing current is the same as the actual current of the current balancing branch, the current conduction time ratio remains unchanged. After updating the on-time ratio of the current control cycle, the PWM duty cycle signal is obtained and sent to the corresponding bidirectional buck-boost converter for switching control. This enables the high SOC unit to output the target equalization current to the equalization bus through the corresponding bidirectional buck-boost converter, and the low SOC unit to absorb the target equalization current from the equalization bus through the corresponding bidirectional buck-boost converter. This forms a continuous control process in which SOC range calculation, threshold comparison, current equalization command triggering, target equalization current calculation under power constraints, PWM duty cycle signal generation, and switching control are sequentially connected.

[0040] Furthermore, the method provided in the application embodiments also includes: The switching transistor control mode includes a first equalization mode and a second equalization mode. Each energy storage unit is divided into a high SOC unit and a low SOC unit according to a preset division standard. The high SOC unit responds to the corresponding PWM duty cycle signal and outputs the corresponding target equalization current to the equalization bus. The low SOC unit responds to the corresponding PWM duty cycle signal and absorbs the corresponding target equalization current from the equalization bus.

[0041] In this embodiment, the switching transistor control mode includes a first equalization mode and a second equalization mode. Before entering the switching transistor control process, each energy storage unit is divided according to a preset division standard. Specifically, the SOC value of all energy storage units is read in the current control cycle. The sum of all SOC values ​​is divided by the total number of energy storage units to obtain the average SOC value. Then, the SOC value of each energy storage unit is compared with the average SOC value. Energy storage units with SOC values ​​greater than the average SOC value are classified as high SOC units, and energy storage units with SOC values ​​less than the average SOC value are classified as low SOC units. After the division is completed, the target equalization current corresponding to each energy storage unit is read, and a correspondence is established between each target equalization current and the PWM duty cycle signal of the corresponding bidirectional buck-boost auxiliary converter. The target equalization current is the current command value obtained from the previous equalization current calculation process, and the PWM duty cycle signal is used to characterize the proportion of the conduction time of the corresponding switching transistor in one switching cycle to the entire switching cycle. Specifically, first read the switching frequency of the corresponding bidirectional buck-boost auxiliary converter, and calculate the current switching cycle based on the switching frequency, where the current switching cycle is equal to the reciprocal of the switching frequency; then multiply the duty cycle value corresponding to the PWM duty cycle signal by the current switching cycle to obtain the on-time of the switch in the current switching cycle, and subtract the on-time from the current switching cycle to obtain the off-time of the switch in the current switching cycle.

[0042] In the first equalization mode, the controller calls the bidirectional buck-boost auxiliary converter corresponding to the high SOC unit and writes the corresponding PWM duty cycle signal into the switching transistor drive process. Then, based on the PWM duty cycle signal, the on-time and off-time of the switching transistor within the current switching cycle are determined, enabling the corresponding bidirectional buck-boost auxiliary converter to establish a current transmission path along the direction from the energy storage unit to the equalization bus. After the current transmission path is established, the high SOC unit outputs current to the equalization bus according to the corresponding target equalization current. The equalization bus is the common node for equalization current exchange among the energy storage units. As the bidirectional buck-boost auxiliary converters corresponding to each high SOC unit continuously perform switching transistor control, the target equalization current from each high SOC unit is collected and fed to the equalization bus.

[0043] In the second equalization mode, the controller calls the bidirectional buck-boost auxiliary converter corresponding to the low SOC unit and writes the corresponding PWM duty cycle signal into the switching transistor drive process. Then, based on the PWM duty cycle signal, it determines the on-time and off-time of the switching transistor within the current switching cycle, enabling the corresponding bidirectional buck-boost auxiliary converter to establish a current transmission path along the direction from the equalization bus to the energy storage unit. After the current transmission path is established, the low SOC unit absorbs current from the equalization bus according to the corresponding target equalization current, transferring the target equalization current output from the high SOC unit to the low SOC unit. This achieves equalization current transmission between the energy storage units through the cooperation of the first and second equalization modes. Specifically, at the beginning of the current switching cycle, the controller outputs an on-control signal, causing the corresponding switching transistor to enter the on state and maintaining it until the on-time ends. When the on-time is reached, the controller outputs a off-control signal, causing the corresponding switching transistor to enter the off state and maintaining it until the end of the current switching cycle. The corresponding bidirectional buck-boost auxiliary converter establishes an energy transmission path from the equalization bus to the low SOC unit during the switching transistor's conduction period and completes current freewheeling during the switching transistor's turn-off period, thereby enabling the low SOC unit to absorb current from the equalization bus according to the target equalization current in the current switching cycle.

[0044] Step S300: The target power grid area is divided into three power supply branches, and low voltage ride-through event decision-making and power supply branch switching management are performed based on the built-in voltage drop detector.

[0045] In this embodiment, the target power grid area is first divided into three power supply branches, which are then connected in parallel to the power bus of the control center via ideal diodes. The main branch supplies power to the control center via AC-DC conversion after drawing power from the grid; the backup branch supplies power to the control center via DC-DC conversion after the energy storage system; and the emergency branch supplies power to the control center via step-down conversion after the DC bus. By connecting the main branch, backup branch, and emergency branch to the same power bus of the control center, a three-way parallel system supplying power to the control center is formed, providing the control center with a basis for switching between different power sources.

[0046] After the three-source power supply branch is established, the built-in voltage sag detector continuously monitors the grid-side voltage. During the monitoring process, the voltage sag detector samples the grid-side voltage and calculates the effective value of the current grid-side voltage based on the continuous sampling results. The effective value is then compared with the rated voltage to obtain a voltage ratio characterizing the current grid voltage state. Subsequently, based on whether the voltage ratio is lower than the corresponding judgment condition and whether the duration meets the set cycle requirement, a decision is made as to whether the current operating condition constitutes a low-voltage ride-through event. The low-voltage ride-through event characterizes an operating state where the grid-side voltage drops but the control center still needs to maintain power supply.

[0047] Upon detecting a low-voltage ride-through event, the voltage sag detector outputs a switching signal, initiating the power supply branch switching management process. During the switching process, the main branch exits the normal power supply path due to the grid-side voltage sag. The backup branch and emergency branch establish subsequent power supply paths through ideal diodes connected in parallel with the control center power bus, transferring power from the main branch to the backup or emergency branch. After the power supply branch switching is completed, the control center continues to operate using the switched power supply branch, thus enabling low-voltage ride-through event decision-making and power supply branch switching management based on the built-in voltage sag detector.

[0048] Furthermore, the method provided in the application embodiments, which performs low-voltage ride-through event decision-making and power supply branch switching management based on the built-in voltage drop detector, also includes: The target power grid area is divided into three power supply branches, and a voltage drop detector is built in. The voltage on the grid side is sampled by the voltage drop detector, and the voltage ratio between the effective value and the rated value is calculated by a sliding window. If the voltage ratio is lower than a first preset value and the continuous count is greater than a second preset power frequency cycle, it is determined to be a low voltage ride-through event. When the low voltage ride-through event exists, a switching signal is output through the voltage drop detector to perform switching management based on the three power supply branches.

[0049] In this embodiment, the target power grid area is divided into three power supply branches, and a voltage drop detector is built in. The voltage drop detector continuously samples the grid-side voltage according to the sampling period, obtaining a voltage sample value at each sampling moment, and writing the voltage sample value into a sliding window in chronological order. When a new voltage sample value enters the sliding window, the voltage sample value that entered the sliding window earliest is simultaneously moved out, so that the voltage data set corresponding to the current continuous sampling interval is always maintained in the sliding window. After obtaining all the voltage sample values ​​in the current sliding window, each voltage sample value is first squared, and then the squared results are accumulated. The accumulated result is divided by the total number of voltage sample values ​​in the sliding window to obtain the mean square value. Then, the mean square value is squared to obtain the effective value of the grid-side voltage corresponding to the current sliding window. Finally, the effective value of the grid-side voltage is divided by the rated value to obtain the voltage ratio, whereby the voltage ratio is used to characterize the degree of voltage drop of the current grid-side voltage relative to the rated value.

[0050] After obtaining the voltage ratio, the power frequency cycle of the grid-side voltage is identified, and continuous counting is performed in units of power frequency cycles. Specifically, the voltage drop detector performs zero-crossing detection on the continuously sampled voltage waveform. When the voltage waveform changes from a negative value to a positive value, it is recorded as a positive zero-crossing, or when the voltage waveform changes from a positive value to a negative value, it is recorded as a reverse zero-crossing. The time interval between two adjacent zero-crossings in the same direction is selected as one power frequency cycle. For each complete power frequency cycle identified, the corresponding voltage sample value within that power frequency cycle is extracted, and the effective value of the grid-side voltage corresponding to that power frequency cycle is obtained according to the aforementioned sliding window effective value calculation process. Then, the voltage ratio corresponding to that power frequency cycle is calculated. Subsequently, the voltage ratio corresponding to the current power frequency cycle is compared with a first preset value. When the voltage ratio corresponding to the current power frequency cycle is lower than the first preset value, the continuous count is incremented by one power frequency cycle. When the voltage ratio corresponding to subsequent power frequency cycles is still lower than the first preset value, the continuous count continues to accumulate. When the voltage ratio corresponding to any subsequent power frequency cycle recovers to or above the first preset value, the continuous count is reset to zero, and the comparison and counting of subsequent power frequency cycles restarts. When the voltage ratio is lower than the first preset value and the continuous count is greater than the second preset power frequency cycle, it is determined to be a low-voltage ride-through event.

[0051] Upon detecting a low-voltage ride-through event, the voltage sag detector outputs a switching signal and executes switching management based on the three power supply branches. Specifically, after the switching signal is output, the main branch currently powered by the grid is first deactivated, preventing it from serving as a valid power supply path to the control center. Then, the current power supply status of the remaining branches is assessed, allowing subsequent branches that meet the power supply requirements to connect to the control center's power bus. This transfers the control center's power supply from the main branch to a backup or emergency branch. After the switching is complete, the voltage sag detector continues to monitor the power supply status after the switch. When the control center's power bus voltage recovers to a level sufficient to maintain control operation, the currently connected power supply branch remains operational.

[0052] Furthermore, the method provided in the application embodiments also includes: The voltage drop detector outputs a switching signal, driving the AC contactor of the main branch to disconnect and the ideal diode of the backup branch to conduct. When the switching is completed, the voltage drop detector generates an interrupt signal indicating that the auxiliary power supply switching is complete and sends it to the control center. The control center switches the optimal control law from minimizing the bus voltage fluctuation to maximizing the energy storage output power and adjusts the voltage weight coefficient in the state feedback gain matrix in sync.

[0053] In this embodiment, when the voltage drop detector determines that a low-voltage ride-through event exists based on the grid-side voltage sampling results, the voltage drop detector outputs a switching signal, which is then sent to the switching execution terminals of the main branch and the backup branch, respectively. On the main branch side, the switching signal acts on the control terminal of the AC contactor coil of the main branch, causing the AC contactor of the main branch to switch from a closed state to an open state, thereby cutting off the power supply path from the main branch to the control center power bus after AC-DC conversion. On the backup branch side, the switching signal acts on the takeover control terminal of the backup branch, causing the DC-DC converter output of the backup branch to establish power supply conditions to the control center power bus. When the output voltage of the backup branch is higher than the voltage of the control center power bus and meets the forward conduction condition of the ideal diode, the ideal diode of the backup branch enters the conducting state, allowing the backup branch to continue supplying power to the control center power bus via DC-DC conversion. The AC contactor is used to mechanically disconnect the power supply path of the main branch, and the ideal diode is used to establish a unidirectional conduction path and block reverse current when the backup branch has forward power supply conditions.

[0054] After the AC contactor of the main branch is disconnected and the ideal diode of the backup branch is turned on, the voltage drop detector continues to determine the auxiliary power supply switching status. Specifically, it first reads the contact feedback status of the AC contactor of the main branch to confirm that the AC contactor of the main branch is in the disconnected state; then it reads the output status of the DC-DC converter unit of the backup branch to confirm that the backup branch output has been established; subsequently, it reads the power bus voltage of the control center and compares the current power bus voltage with the minimum operating voltage required for the control center to maintain control operation. When the current power bus voltage is not lower than the minimum operating voltage, it is determined that the control center is being powered by the backup branch. When the main branch is disconnected, the backup branch is turned on, and the control center power bus voltage meets the operating conditions simultaneously, the switching is determined to be complete. After the switching is completed, the voltage drop detector generates an interrupt signal indicating that the auxiliary power supply switching is complete and sends the interrupt signal to the control center, so that the control center can obtain the status information that the current auxiliary power supply path has been switched from the main branch to the backup branch.

[0055] After receiving the interruption signal, the control center maintains the state variable acquisition process unchanged, continuing to read photovoltaic power, energy storage power, bus voltage, and the SOC of each energy storage unit. During the state feedback gain matrix solution process, the optimization objective of the optimal control law is switched. Specifically, before the auxiliary power supply switch is completed, the optimal control law prioritizes minimizing bus voltage fluctuations. The bus voltage fluctuation has a corresponding voltage weighting coefficient during the state feedback gain matrix solution process. This voltage weighting coefficient characterizes the degree of participation of the bus voltage fluctuation in the feedback solution. When the voltage weighting coefficient is large, the influence of the bus voltage fluctuation on the state feedback gain matrix solution result is enhanced; conversely, when the voltage weighting coefficient is small, the influence of the bus voltage fluctuation on the state feedback gain matrix solution result is weakened. After the auxiliary power supply is switched, the control center switches from minimizing the bus voltage fluctuation of the optimal control law to maximizing the energy storage output power. It also adjusts the voltage weighting coefficients in sync with the calculation cycle of the state feedback gain matrix. Specifically, at the beginning of each control cycle, the bus voltage fluctuation, energy storage power change, and SOC deviation of each energy storage unit are read. The voltage weighting coefficients corresponding to the bus voltage fluctuation are then updated from their pre-switch values ​​to their post-switch values. The updated voltage weighting coefficients are written into the state feedback gain matrix solution process of the current control cycle. Subsequently, the state feedback gain matrix of the current control cycle is recalculated based on the updated voltage weighting coefficients and the state and control variables of the current control cycle. The updated state feedback gain matrix is ​​then used to generate the energy storage charging and discharging commands for the current control cycle.

[0056] Furthermore, the method provided in the application embodiments also includes: The three-source power supply branch consists of a main branch, a backup branch, and an emergency branch, and is connected to the power bus of the control center through ideal diodes in parallel. The main branch is powered by the grid through AC-DC conversion, the backup branch is powered by the energy storage system through DC-DC conversion, and the emergency branch is powered by the DC bus through step-down conversion.

[0057] In this embodiment, the three power supply branches consist of a main branch, a backup branch, and an emergency branch, and are connected to the power bus of the control center in parallel via ideal diodes. Each of the three power supply branches corresponds to an independent power supply path, and their outputs are connected to the same power bus of the control center via their respective ideal diodes, thus forming a multi-source parallel connection structure on the control center's power bus. The ideal diodes are used to establish a conduction path when the corresponding power supply branch meets the power supply conditions, and to block reverse current when the power supply conditions are not met, thereby realizing the parallel connection of the main branch, backup branch, and emergency branch on the control center's power bus.

[0058] The main branch is powered by electricity drawn from the power grid and converted to DC power via AC-DC conversion. After AC power is input from the grid, it enters the AC-DC conversion stage, where it is converted into DC power matching the power supply requirements of the control center. This DC power is then fed into the control center's power bus via the corresponding ideal diode in the main branch. The backup branch is powered by an energy storage system via DC-DC conversion. After the energy storage system outputs DC power, it enters the DC-DC conversion stage, where it is adjusted to a DC voltage matching the control center's power bus. This DC voltage is then fed into the control center's power bus via the corresponding ideal diode in the backup branch.

[0059] The emergency branch supplies power to the DC bus via a step-down converter. After the DC bus outputs power, it enters the step-down converter stage, where it is converted into the operating voltage that the control center can maintain. This voltage is then fed into the control center's power bus via the ideal diode corresponding to the emergency branch. Thus, the main branch, backup branch, and emergency branch correspond to the three power sources: the power grid, the energy storage system, and the DC bus, respectively, and are connected to the control center's power bus in parallel via ideal diodes.

[0060] In summary, the embodiments of this application have at least the following technical effects: This application performs multi-source state parameter detection on the target power grid area, imports the data into a deployed linear quadratic regulator, executes active damping control analysis based on energy storage-photovoltaic coupling, determines energy storage charging and discharging commands, and performs basic scheduling and control. By calculating the SOC range of each energy storage unit, the converter array connected to the energy storage system can be selectively triggered. The target equalization current is calculated using the energy storage charging and discharging commands as power constraints, and a corresponding PWM duty cycle signal is generated to drive the switching transistors of the corresponding bidirectional buck-boost auxiliary converter. The target power grid area is divided into three power supply branches, and low-voltage ride-through event decision-making and power supply branch switching management are performed based on a built-in voltage drop detector. This invention solves the technical problem of lag in dynamic power balance compensation response in existing photovoltaic energy storage power stations. By determining energy storage charging and discharging commands through active damping control based on energy storage-photovoltaic coupling, it achieves the technical effect of improving the dynamic power balance compensation response speed and control stability.

[0061] Example 2, based on the same inventive concept as the control method for dynamic power balance compensation of photovoltaic energy storage power stations in the foregoing examples, such as... Figure 2 As shown, this application provides a control system for dynamic power balance compensation in photovoltaic energy storage power stations. The system and method embodiments in this application are based on the same inventive concept. The system includes: The parameter detection module 11 is used to detect multi-source state parameters of the target power grid area, import them into the deployed linear quadratic regulator, perform active damping control analysis based on energy storage-photovoltaic coupling, determine energy storage charging and discharging commands, and perform basic scheduling and control. The calculation module 12 is used to calculate the SOC range of each energy storage unit, optionally trigger the converter array connected to the energy storage system, calculate the target equalization current with the energy storage charging and discharging command as the power constraint, and generate the corresponding PWM duty cycle signal to drive the switching transistor of the corresponding bidirectional buck-boost auxiliary converter. The decision management module 13 is used to divide the target power grid area into three power supply branches, and perform low voltage ride-through event decision-making and power supply branch switching management based on the built-in voltage drop detector.

[0062] Furthermore, the system is also used to implement the following functions: The power output characteristics of the photovoltaic array are modeled as a nonlinear source, and the energy storage system is modeled as a variable impedance load. The nonlinear source is affected by light intensity, temperature, and load. The nonlinear source and the variable impedance load are coupled through a DC bus to form a second-order dynamic architecture. Based on the second-order dynamic architecture, state variables and control variables are introduced to execute a deployment based on the optimal control law, thus forming the linear quadratic regulator.

[0063] Furthermore, the system is also used to implement the following functions: The state variables include photovoltaic power, energy storage power, bus voltage, and SOC of each energy storage unit; the control variables are the driving parameters of the charging and discharging current of each energy storage converter; the setting of the optimal control law includes: taking the minimization of bus voltage fluctuation, the smoothing of energy storage power, and the balance of SOC as joint optimization objectives, solving the state feedback gain matrix, and taking the energy storage charging and discharging command as the output.

[0064] Furthermore, the system is also used to implement the following functions: In the energy storage system, a converter array is connected. A bidirectional buck-boost auxiliary converter is connected in parallel to each energy storage unit, and the common terminal of the converter is connected to the balancing bus as the access method. The SOC value of each energy storage unit is collected in real time, and the threshold judgment and current balancing control based on the SOC value are triggered according to the first judgment unit.

[0065] Furthermore, the system is also used to implement the following functions: Based on the set threshold embedded in the first judge, the SOC range between each energy storage unit is calculated. When it exceeds the set threshold, a current balancing command is triggered. Based on the current balancing command, the charging and discharging commands of each energy storage unit are read and used as power constraints to calculate the target balancing current of each energy storage unit. Based on the target balancing current, a PWM duty cycle signal is generated and sent to the corresponding bidirectional buck-boost converter for switching control.

[0066] Furthermore, the system is also used to implement the following functions: The switching transistor control mode includes a first equalization mode and a second equalization mode. Each energy storage unit is divided into a high SOC unit and a low SOC unit according to a preset division standard. The high SOC unit responds to the corresponding PWM duty cycle signal and outputs the corresponding target equalization current to the equalization bus. The low SOC unit responds to the corresponding PWM duty cycle signal and absorbs the corresponding target equalization current from the equalization bus.

[0067] Furthermore, the system is also used to implement the following functions: The target power grid area is divided into three power supply branches, and a voltage drop detector is built in. The voltage on the grid side is sampled by the voltage drop detector, and the voltage ratio between the effective value and the rated value is calculated by a sliding window. If the voltage ratio is lower than a first preset value and the continuous count is greater than a second preset power frequency cycle, it is determined to be a low voltage ride-through event. When the low voltage ride-through event exists, a switching signal is output through the voltage drop detector to perform switching management based on the three power supply branches.

[0068] Furthermore, the system is also used to implement the following functions: The voltage drop detector outputs a switching signal, driving the AC contactor of the main branch to disconnect and the ideal diode of the backup branch to conduct. When the switching is completed, the voltage drop detector generates an interrupt signal indicating that the auxiliary power supply switching is complete and sends it to the control center. The control center switches the optimal control law from minimizing the bus voltage fluctuation to maximizing the energy storage output power and adjusts the voltage weight coefficient in the state feedback gain matrix in sync.

[0069] Furthermore, the system is also used to implement the following functions: The three-source power supply branch consists of a main branch, a backup branch, and an emergency branch, and is connected to the power bus of the control center through ideal diodes in parallel. The main branch is powered by the grid through AC-DC conversion, the backup branch is powered by the energy storage system through DC-DC conversion, and the emergency branch is powered by the DC bus through step-down conversion.

[0070] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, the above description focuses on specific embodiments of this specification. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired results. In some implementations, multitasking and parallel processing are possible or may be advantageous.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A control method for dynamic power balance compensation in photovoltaic energy storage power stations, characterized in that, The method includes: Multi-source state parameter detection is performed on the target power grid area, the deployed linear quadratic regulator is imported, active damping control analysis based on energy storage-photovoltaic coupling is performed, energy storage charging and discharging commands are determined, and basic dispatching and control are performed. By calculating the SOC range of each energy storage unit, the converter array connected to the energy storage system can be selectively triggered. The target equalization current is calculated with the energy storage charging and discharging command as the power constraint, and the corresponding PWM duty cycle signal is generated to drive the switching transistor of the corresponding bidirectional buck-boost auxiliary converter. Among them, by dividing the target power grid area into three power supply branches, low voltage ride-through event decision-making and power supply branch switching management are carried out based on the built-in voltage drop detector. The linear quadratic regulator includes: The power output characteristics of the photovoltaic array are modeled as a nonlinear source, and the energy storage system is modeled as a variable impedance load. The nonlinear source is affected by light intensity, temperature and load. The nonlinear source and the variable impedance load are coupled through a DC bus to form a second-order dynamic architecture. Based on the second-order dynamic architecture, state variables and control variables are introduced to execute deployment based on the optimal control law, thus forming the linear quadratic regulator; The state variables include photovoltaic power, energy storage power, bus voltage, and the state of charge (SOC) of each energy storage unit. The control variables are the driving parameters of the charging and discharging current of each energy storage converter; The optimal control law is set by: taking the minimization of bus voltage fluctuation, the smoothing of energy storage power, and the balance of SOC as joint optimization objectives, solving the state feedback gain matrix, and taking the energy storage charging and discharging command as the output.

2. The control method for dynamic power balance compensation in a photovoltaic energy storage power station as described in claim 1, characterized in that, Optional converter arrays connected to the trigger energy storage system include: In the energy storage system, a converter array is connected. In this case, a bidirectional buck-boost auxiliary converter is connected in parallel to each energy storage unit, and the common terminal of the converter is connected to the equalization bus as the access method. By collecting the SOC value of each energy storage unit in real time, the first judgment device triggers threshold judgment and current balance control based on the SOC value.

3. The control method for dynamic power balance compensation in a photovoltaic energy storage power station as described in claim 2, characterized in that, Based on the set threshold embedded in the first judge, the SOC range between each energy storage unit is calculated. When it exceeds the set threshold, a current balancing command is triggered. Based on the current balancing command, the charging and discharging commands of each energy storage unit are read and used as power constraints to calculate the target balancing current of each energy storage unit. A PWM duty cycle signal is generated based on the target equalization current and sent to the corresponding bidirectional buck-boost converter for switching control.

4. The control method for dynamic power balance compensation in a photovoltaic energy storage power station as described in claim 3, characterized in that, The switching transistor control modes include a first equilibrium mode and a second equilibrium mode; Among them, each energy storage unit is divided into high SOC unit and low SOC unit according to a preset division standard; The high SOC unit responds to the corresponding PWM duty cycle signal and outputs the corresponding target equalization current to the equalization bus. The low SOC unit responds to the corresponding PWM duty cycle signal and absorbs the corresponding target equalization current from the equalization bus.

5. The control method for dynamic power balance compensation in a photovoltaic energy storage power station as described in claim 1, characterized in that, Low-voltage ride-through event decision-making and power supply branch switching management are performed based on the built-in voltage drop detector, including: The target power grid area is divided into three power supply branches, and a voltage drop detector is built in. Based on the voltage drop detector, the grid-side voltage is sampled, and the voltage ratio between the effective value and the rated value is calculated using a sliding window. If the voltage ratio is lower than the first preset value and the continuous count is greater than the second preset power frequency, it is determined to be a low voltage ride-through event. When the low voltage ride-through event occurs, a switching signal is output through the voltage drop detector to perform switching management based on the three power supply branches.

6. The control method for dynamic power balance compensation in a photovoltaic energy storage power station as described in claim 5, characterized in that, The voltage drop detector outputs a switching signal, which drives the AC contactor of the main branch to disconnect and turns on the ideal diode of the backup branch. Once the switching is complete, the voltage drop detector generates an interrupt signal indicating that the auxiliary power supply switching is complete and sends it to the control center. The control center switches the optimal control law from minimizing bus voltage fluctuations to maximizing energy storage output power, and adjusts the voltage weighting coefficients in the state feedback gain matrix in sync.

7. The control method for dynamic power balance compensation in a photovoltaic energy storage power station as described in claim 6, characterized in that, The three-source power supply branch consists of a main branch, a backup branch and an emergency branch, and is connected to the power bus of the control center through ideal diodes in parallel. The main branch line draws power from the power grid and supplies it via AC-DC conversion; the backup branch line supplies power from the energy storage system via DC-DC conversion; and the emergency branch line supplies power from the DC bus via step-down conversion.

8. A control system for dynamic power balance compensation in photovoltaic energy storage power stations, characterized in that, The system is used to execute the control method for dynamic power balance compensation of a photovoltaic energy storage power station as described in any one of claims 1-7, the system comprising: The parameter detection module is used to detect multi-source state parameters of the target power grid area, import them into the deployed linear quadratic regulator, perform active damping control analysis based on energy storage-photovoltaic coupling, determine energy storage charging and discharging commands, and perform basic dispatching and control. The calculation module is used to calculate the SOC range of each energy storage unit, optionally trigger the converter array connected to the energy storage system, calculate the target equalization current with the energy storage charging and discharging command as the power constraint, and generate the corresponding PWM duty cycle signal to drive the switching transistor of the corresponding bidirectional buck-boost auxiliary converter. The decision management module is used to divide the target power grid area into three power supply branches and perform low voltage ride-through event decision-making and power supply branch switching management based on the built-in voltage drop detector. The system is also used for: The power output characteristics of the photovoltaic array are modeled as a nonlinear source, and the energy storage system is modeled as a variable impedance load. The nonlinear source is affected by light intensity, temperature and load. The nonlinear source and the variable impedance load are coupled through a DC bus to form a second-order dynamic architecture. Based on the second-order dynamic architecture, state variables and control variables are introduced to execute deployment based on the optimal control law, thus forming the linear quadratic regulator; The state variables include photovoltaic power, energy storage power, bus voltage, and the state of charge (SOC) of each energy storage unit. The control variables are the driving parameters of the charging and discharging current of each energy storage converter; The optimal control law is set by: taking the minimization of bus voltage fluctuation, the smoothing of energy storage power, and the balance of SOC as joint optimization objectives, solving the state feedback gain matrix, and taking the energy storage charging and discharging command as the output.

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