A photovoltaic string control system

Abstract

The present application relates to the field of photovoltaic power generation control, in order to improve the overall power generation efficiency of photovoltaic string, a photovoltaic string control system is provided, an independent photovoltaic module optimizer is configured for each photovoltaic module, the maximum power point tracking at the module level is realized, the influence of shadow shielding and module attenuation is avoided, the power generation efficiency of the string is significantly improved, the photovoltaic module optimizer collects real-time voltage, current and temperature state data, cooperates with the abnormality judgment and shutdown mechanism of the power station centralized controller, can quickly isolate the faulty module and trigger the power reduction of the string inverter, avoids the chain failure caused by abnormality, and improves the operation safety; The string inverter adopts the lowest maximum power point voltage unified matching strategy, realizes the accurate voltage coordination at the string level, guarantees the stable and efficient operation of the whole string module, the power station centralized controller integrates power generation prediction, automatic power generation and automatic voltage control functions, can realize global power optimization scheduling combined with the grid instruction, and improves the power generation utilization rate and grid adaptability.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic power generation control, specifically a photovoltaic string control system. Background Technology

[0002] With the rapid development of the photovoltaic industry and the continuous expansion of photovoltaic power plant scale, the power generation efficiency and operational stability of photovoltaic strings have become the core focus of the industry.

[0003] Existing photovoltaic string control systems mostly employ string-level maximum power point tracking, which cannot independently control individual photovoltaic modules. This makes them susceptible to factors such as shading and module degradation, leading to a significant decrease in the overall string's power generation efficiency. Furthermore, existing systems lack effective module status monitoring and anomaly handling mechanisms. When parameters of a single module become abnormal, a rapid response is difficult, easily triggering a chain reaction of failures.

[0004] Furthermore, existing string inverters lack targeted voltage coordination strategies, making it difficult to achieve precise matching of string-level voltages. Some systems also lack PID effect suppression functions, leading to PID decay in components during long-term operation, which affects their lifespan. Communication stability between control units at all levels is insufficient, making communication interruptions likely, and there is a lack of comprehensive safety emergency mechanisms. At the same time, global power dispatch lacks accurate prediction and control methods, making it difficult to match grid demand and resulting in low power generation utilization. Summary of the Invention

[0005] In order to improve the overall power generation efficiency of photovoltaic strings, this application provides a photovoltaic string control system.

[0006] The technical solution adopted by the present invention to solve the above problems is: A photovoltaic string control system includes: multiple photovoltaic modules, multiple photovoltaic module optimizers, at least one string inverter, and a power station central controller, wherein the photovoltaic module optimizers are electrically connected to the photovoltaic modules one by one. A photovoltaic module optimizer is used to track the maximum power point of a corresponding photovoltaic module and collect the status data of the photovoltaic module in real time; multiple photovoltaic module optimizers are connected in series to form a photovoltaic string; The DC input terminal of the string inverter is electrically connected to the photovoltaic string. The string inverter establishes a bidirectional communication connection with each photovoltaic module optimizer to receive status data, and performs string-level voltage coordination and islanding protection operations based on the received status data. It also inverts the received DC power into AC power for output. The power plant central controller establishes a bidirectional communication connection with at least one string inverter. The string inverter uploads all received status data to the power plant central controller, which then performs the following control operations based on the status data: When it is determined that the status data of any photovoltaic module exceeds the preset normal threshold, a shutdown command is sent to the photovoltaic module optimizer corresponding to the photovoltaic module, and a power reduction operation command is sent to the string inverter to which the photovoltaic module optimizer belongs. Based on the status data of all photovoltaic modules, a global power dispatch command is generated and sent to each string inverter.

[0007] Furthermore, the status data includes voltage, current, and temperature.

[0008] Furthermore, the photovoltaic module optimizer specifically includes: a data acquisition module and a maximum power point tracking controller. The data acquisition module is used to collect voltage, current and temperature data, including a voltage sampling unit, a current sampling unit and a temperature sampling unit; The maximum power point tracking controller is configured to independently perform maximum power point tracking operations based on the real-time voltage and current parameters of the corresponding photovoltaic module. The maximum power point tracking controller has a built-in shut-off switch for disconnecting the circuit. The shut-off switch is connected in series in the output circuit of the photovoltaic module optimizer and is used to disconnect its own output circuit in response to the shut-off command issued by the power plant central controller.

[0009] Furthermore, a model-free adaptive control strategy or a perturbation-observation method is employed when performing maximum power point tracking.

[0010] Furthermore, the photovoltaic module optimizer also includes a communication detection module, which is used to detect the communication connection status between the photovoltaic module optimizer and the corresponding string inverter in real time. When a communication interruption is detected, the photovoltaic module optimizer automatically enters an autonomous safety mode: while continuing to perform maximum power point tracking operation, it limits its own output power to below a preset safety threshold; if the communication interruption continues for more than a preset time threshold, it actively shuts down its own output.

[0011] Furthermore, the string inverter integrates a PID effect suppression module, which is configured to apply a reverse repair voltage to the corresponding photovoltaic string when the photovoltaic string needs to suppress and repair the PID attenuation effect.

[0012] Furthermore, when a string inverter performs string-level voltage coordination operation based on the received status data, it specifically includes the following steps: Extract the maximum power point voltage calculated by each photovoltaic module optimizer in its respective photovoltaic string from the status data uploaded by each photovoltaic module optimizer. The maximum power point voltage of all extracted photovoltaic modules is screened to determine the lowest value; The lowest value is used as the unified DC bus voltage reference value for the photovoltaic string, and the operating point of the string inverter is adjusted based on the unified DC bus voltage reference value.

[0013] Furthermore, the power dispatch instructions include active power dispatch instructions and reactive power dispatch instructions; The power plant centralized controller specifically includes: The automatic power generation control module is used to receive grid dispatch instructions and generate active power dispatch instructions by combining the status data of all photovoltaic modules, so as to achieve the matching of system active power with grid demand. The automatic voltage control module is used to collect the grid connection point voltage in real time, generate reactive power dispatching instructions based on the grid connection point voltage deviation, and achieve stable control of the grid connection point voltage by adjusting the system reactive power output.

[0014] Furthermore, the power plant centralized controller also includes a power generation prediction module, which uses a time-series prediction model to predict the power generation of each photovoltaic module based on historical status data and real-time meteorological data, and generates power dispatch instructions based on the prediction results.

[0015] Furthermore, the power plant central controller and the string inverter communicate bidirectionally via RS485 bus or wireless communication network; the string inverter and each photovoltaic module optimizer communicate bidirectionally via power line carrier communication or wireless communication.

[0016] The advantages of this invention compared to the prior art are: Each photovoltaic module is equipped with an independent photovoltaic module optimizer to achieve module-level maximum power point tracking, unaffected by shading or module degradation, significantly improving string power generation efficiency.

[0017] The photovoltaic module optimizer collects real-time data on voltage, current, and temperature, and, in conjunction with the power station's centralized controller's anomaly detection and shutdown mechanism, can quickly isolate faulty modules and trigger the string inverter to reduce power, preventing cascading failures caused by anomalies and improving operational safety. It also features an autonomous safety protection mechanism for communication interruptions, enhancing system reliability.

[0018] The string inverter adopts a unified matching strategy of minimum and maximum power point voltage to achieve precise voltage coordination at the string level, ensuring stable and efficient operation of the entire string of modules. The string inverter has a built-in PID effect suppression module, which can apply reverse repair voltage to suppress and repair PID degradation of the modules and extend the service life of the photovoltaic modules.

[0019] The system adopts multiple communication methods, including power line carrier / wireless and RS485 / wireless, to ensure stable data transmission. The power station's centralized controller integrates power generation forecasting, automatic power generation, and automatic voltage control functions. It can combine grid commands to achieve global power optimization scheduling, improve power generation utilization and grid adaptability, and enhance the overall economic benefits and operation and maintenance stability of the photovoltaic power station. Attached Figure Description

[0020] Figure 1 This is a diagram of the photovoltaic string control system architecture. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] like Figure 1 As shown, a photovoltaic string control system includes: multiple photovoltaic modules, multiple photovoltaic module optimizers, at least one string inverter and a power station central controller, wherein the photovoltaic module optimizers are electrically connected to the photovoltaic modules one by one; A photovoltaic module optimizer is used to independently perform maximum power point tracking operation for the corresponding photovoltaic module and collect the voltage, current and temperature parameters of the photovoltaic module in real time to generate status data containing the above parameters; multiple photovoltaic module optimizers are connected in series to form a photovoltaic string.

[0023] The photovoltaic module optimizer specifically includes a data acquisition module and a maximum power point tracking controller. The data acquisition module includes a voltage sampling unit, a current sampling unit, and a temperature sampling unit.

[0024] The maximum power point tracking controller is configured to independently perform maximum power point tracking operation based on the real-time voltage and current parameters of the corresponding photovoltaic module. The tracking operation adopts a model-free adaptive control strategy or a disturbance observation method. The maximum power point tracking controller has a built-in turn-off switch for a fast turn-off path. The turn-off switch is connected in series in the output circuit of the photovoltaic module optimizer to respond to the turn-off command issued by the power plant central controller, disconnect its own output circuit, and thus realize the offline turn-off of the corresponding photovoltaic module.

[0025] Furthermore, the photovoltaic module optimizer is also equipped with a communication detection module. This module monitors the communication connection status between the photovoltaic module optimizer and the corresponding string inverter in real time. When a communication interruption is detected, the photovoltaic module optimizer automatically enters an autonomous safety mode: while continuing to perform maximum power point tracking (MPPT) operations, it limits its own output power to below a preset safety threshold; if the communication interruption continues for more than a preset time threshold, it actively shuts off its own output. This communication detection module implements an autonomous safety protection mechanism for communication interruptions, effectively improving system reliability.

[0026] The DC input terminal of the string inverter is electrically connected to the photovoltaic string. The string inverter establishes a bidirectional communication connection with each photovoltaic module optimizer to receive status data, and performs string-level voltage coordination and islanding protection operations based on the received status data. The received DC power is then inverted into AC power for output.

[0027] When a string inverter performs string-level voltage coordination operation based on status data, the specific steps include: Extract the maximum power point voltage calculated by each photovoltaic module optimizer in its respective photovoltaic string from the status data uploaded by each photovoltaic module optimizer. The maximum power point voltage of all extracted photovoltaic modules is screened to determine the lowest value; The lowest value is used as the unified DC bus voltage reference value for the photovoltaic string. The operating point of the string inverter is adjusted based on the unified DC bus voltage reference value to ensure that the entire string of photovoltaic modules operates stably and achieves optimal power generation efficiency.

[0028] Furthermore, the string inverter also integrates a PID effect suppression module. The PID effect suppression module is configured to apply a reverse repair voltage to a designated photovoltaic string when the system is in standby mode, based on the repair command issued by the power station's central controller, to suppress and repair the PID degradation effect of the photovoltaic modules, thereby extending the service life of the photovoltaic modules.

[0029] The power plant central controller establishes a bidirectional communication connection with at least one string inverter. The string inverter uploads all received status data to the power plant central controller, which then performs the following control operations based on the status data: When it is determined that the status data of any photovoltaic module exceeds the preset normal threshold, a shutdown command is sent to the photovoltaic module optimizer corresponding to the photovoltaic module, and a power reduction operation command is sent to the string inverter to which the photovoltaic module optimizer belongs. Based on the status data of all photovoltaic modules, a global power dispatch command is generated and sent to each string inverter to achieve optimized control of the power generation of the entire system.

[0030] The power plant's centralized controller and string inverters communicate bidirectionally via RS485 bus or wireless communication network; the string inverters and each photovoltaic module optimizer communicate bidirectionally via power line carrier communication or wireless communication, enabling information synchronization and command transmission between control units at all levels.

[0031] Specifically, the power plant centralized controller includes: An automatic power generation control module receives grid dispatch instructions and, in conjunction with the status data of all photovoltaic modules, generates active power dispatch instructions to achieve precise matching between the system's active power and grid demand; and... The automatic voltage control module is used to collect the grid connection point voltage in real time, generate reactive power dispatching instructions based on the grid connection point voltage deviation, and achieve stable control of the grid connection point voltage by adjusting the system reactive power output. The power dispatch instructions include active power dispatch instructions and reactive power dispatch instructions.

[0032] The power plant's centralized controller also includes a power generation prediction module. This module uses a time-series forecasting model to predict the power generation of each photovoltaic module based on historical status data and real-time meteorological data, and then optimizes and generates power dispatch instructions based on the prediction results. Using a time-series forecasting model to predict the power generation of each photovoltaic module is existing technology and will not be elaborated upon here.

[0033] When the photovoltaic string control system is in use, after the system is started, multiple photovoltaic modules convert solar energy into direct current. Each photovoltaic module is connected to a photovoltaic module optimizer. The photovoltaic module optimizer has a built-in maximum power point tracking (MPPT) controller. Based on a model-free adaptive control strategy or perturbation observation method, it independently collects the real-time voltage and current parameters of the corresponding photovoltaic module, accurately tracks the maximum power point of the module, and is not affected by the shading, attenuation, or failure of other modules, and outputs the optimal power generation power independently.

[0034] The data acquisition module of the photovoltaic module optimizer is started simultaneously. Through the voltage sampling unit, current sampling unit, and temperature sampling unit, it collects three core parameters of the photovoltaic module in real time: output voltage, output current, and panel temperature. It integrates and generates standardized status data to provide a data foundation for subsequent control.

[0035] The photovoltaic module optimizer uploads status data to the corresponding string inverter in real time via power line carrier communication / wireless communication; the string inverter then aggregates the status data uploaded by all module optimizers and uploads it to the power plant central controller via RS485 bus / wireless communication network, thus completing the bidirectional communication link construction and data synchronization of the three-level units.

[0036] After receiving the status data from all photovoltaic module optimizers within the string, the string inverter performs standardized voltage coordination operations: Extract the maximum power point voltage calculated by each photovoltaic module optimizer in the photovoltaic string from the status data uploaded by all photovoltaic module optimizers. The maximum power point voltage of all extracted photovoltaic modules is screened and compared one by one to determine the lowest voltage value. The lowest selected voltage value is set as the unified DC bus voltage reference value for this photovoltaic string; Based on this unified DC bus voltage reference value, the string inverter precisely adjusts its own DC side operating point to ensure that the entire string of photovoltaic modules operates stably under the unified voltage standard, thereby achieving optimal string-level power generation efficiency.

[0037] When the entire photovoltaic string control system is in standby mode, the power station central controller sends a PID repair command to the string inverter. The PID effect suppression module integrated inside the string inverter responds to the command, applies a reverse repair voltage to the specified photovoltaic string, continuously suppresses the PID degradation effect of the photovoltaic module, and repairs the performance of the photovoltaic module that has already experienced PID degradation, ensuring the long-term operational stability of the photovoltaic module.

[0038] The string inverter continuously monitors the grid operation status based on the status data uploaded by all photovoltaic module optimizers in real time, and automatically performs islanding protection operations. Once an islanding effect is detected, the protection mechanism is immediately activated to ensure the safety of the system and the grid. The string inverter converts the DC power output from the photovoltaic string into AC power that meets the grid access standards through the inverter circuit, and outputs it stably to the grid or load.

[0039] The power plant's centralized controller receives real-time status data from all photovoltaic module optimizers uploaded by each set of string inverters, and accurately compares each set of status data with preset normal thresholds: When it is determined that the voltage, current, or temperature parameters of any photovoltaic module exceed the preset normal threshold, the power station central controller immediately sends a shutdown command to the photovoltaic module optimizer corresponding to the abnormal photovoltaic module. At the same time, the power plant's central controller sends a power reduction operation command to the string inverter to which the abnormal photovoltaic module optimizer belongs; Upon receiving a shutdown command, the photovoltaic module optimizer immediately activates the shutdown switch connected in series in its output circuit, disconnecting its own output circuit and achieving offline shutdown of the corresponding abnormal photovoltaic module, thus completely isolating the source of the fault.

[0040] The photovoltaic module optimizer's built-in communication detection module continuously monitors the communication status. Once a communication interruption with the corresponding string inverter is detected, the photovoltaic module optimizer immediately and automatically enters an autonomous safety mode: while continuing to maintain the maximum power point tracking controller's normal maximum power point tracking operation, it actively limits its own output power to below a preset safety threshold. If the communication interruption continues for more than a preset time threshold, the photovoltaic module optimizer does not need to wait for external instructions and actively shuts off its own output, completely eliminating safety hazards.

[0041] The power plant's centralized controller integrates an automatic generation control module, an automatic voltage control module, and a power generation prediction module. These three modules work together to complete global power dispatch.

[0042] The power generation prediction module calls up the historical status data stored in the system, combines it with the real-time meteorological data input from the outside, and uses a time series prediction model to accurately predict the short-term power generation of each photovoltaic module and generate power generation prediction results. The automatic power generation control module receives external grid dispatch instructions and combines the real-time status data of all photovoltaic modules with the power generation prediction results to generate active power dispatch instructions, ensuring that the system's active power output is accurately matched with grid demand. The automatic voltage control module collects the grid connection point voltage in real time. Based on the deviation between the actual value and the standard value of the grid connection point voltage, it generates a reactive power dispatch command and achieves stable control of the grid connection point voltage by adjusting the reactive power output of the system. The power plant's centralized controller will uniformly distribute global power dispatch commands, including active power dispatch commands and reactive power dispatch commands, to each string inverter group. Each string inverter group will respond to the commands and adjust its output power to achieve optimized control of the power generation of the entire system.

[0043] This invention equips each photovoltaic module with an independent photovoltaic module optimizer, achieving module-level maximum power point tracking, unaffected by shading or module degradation, significantly improving string power generation efficiency. The photovoltaic module optimizer collects real-time voltage, current, and temperature data across the entire system. Combined with the power station's centralized controller's anomaly detection and shutdown mechanism, it can quickly isolate faulty modules and trigger the string inverter to reduce power, preventing cascading failures and improving operational safety. The string inverter employs a unified minimum maximum power point voltage matching strategy to achieve precise voltage coordination at the string level, ensuring stable and efficient operation of the entire string of modules. The string inverter has a built-in PID effect suppression module that can apply reverse repair voltage to suppress and repair module PID degradation, extending the photovoltaic module's lifespan. The system uses multiple communication methods, including power line carrier / wireless and RS485 / wireless, to ensure stable data transmission. The optimizer has an autonomous security protection mechanism for communication interruptions, improving system reliability. The power station's centralized controller integrates power generation prediction, automatic power generation, and automatic voltage control functions, and can combine grid commands to achieve global power optimization scheduling, improving power generation utilization and grid adaptability, and overall enhancing the economic benefits and operational stability of the photovoltaic power station.

Claims

1. A photovoltaic string control system, characterized in that, include: Multiple photovoltaic modules, multiple photovoltaic module optimizers, at least one string inverter and a power station central controller, with each photovoltaic module optimizer electrically connected to a corresponding photovoltaic module; A photovoltaic module optimizer is used to track the maximum power point of a corresponding photovoltaic module and collect the status data of the photovoltaic module in real time; multiple photovoltaic module optimizers are connected in series to form a photovoltaic string; The DC input terminal of the string inverter is electrically connected to the photovoltaic string. The string inverter establishes a bidirectional communication connection with each photovoltaic module optimizer to receive status data, and performs string-level voltage coordination and islanding protection operations based on the received status data. It also inverts the received DC power into AC power for output. The power plant central controller establishes a bidirectional communication connection with at least one string inverter. The string inverter uploads all received status data to the power plant central controller, which then performs the following control operations based on the status data: When it is determined that the status data of any photovoltaic module exceeds the preset normal threshold, a shutdown command is sent to the photovoltaic module optimizer corresponding to the photovoltaic module, and a power reduction operation command is sent to the string inverter to which the photovoltaic module optimizer belongs. Based on the status data of all photovoltaic modules, a global power dispatch command is generated and sent to each string inverter.

2. The photovoltaic string control system according to claim 1, characterized in that, Status data includes voltage, current, and temperature.

3. A photovoltaic string control system according to claim 2, characterized in that, The photovoltaic module optimizer specifically includes: a data acquisition module and a maximum power point tracking controller. The data acquisition module is used to collect voltage, current and temperature data, including a voltage sampling unit, a current sampling unit and a temperature sampling unit; The maximum power point tracking controller is configured to independently perform maximum power point tracking operations based on the real-time voltage and current parameters of the corresponding photovoltaic module. The maximum power point tracking controller has a built-in shut-off switch for disconnecting the circuit. The shut-off switch is connected in series in the output circuit of the photovoltaic module optimizer and is used to disconnect its own output circuit in response to the shut-off command issued by the power plant central controller.

4. A photovoltaic string control system according to claim 3, characterized in that, When performing maximum power point tracking, a model-free adaptive control strategy or a perturbation-observation method is used.

5. A photovoltaic string control system according to claim 3, characterized in that, The photovoltaic module optimizer also includes a communication detection module, which is used to detect the communication connection status between the photovoltaic module optimizer and the corresponding string inverter in real time. When a communication interruption is detected, the photovoltaic module optimizer automatically enters an autonomous safety mode: while continuing to perform maximum power point tracking operation, it limits its own output power to below a preset safety threshold; if the communication interruption continues for more than a preset time threshold, it actively shuts down its own output.

6. A photovoltaic string control system according to claim 1, characterized in that, The string inverter integrates a PID effect suppression module, which is configured to apply a reverse repair voltage to the corresponding photovoltaic string when the PID attenuation effect needs to be suppressed and repaired.

7. A photovoltaic string control system according to claim 1, characterized in that, When a string inverter performs string-level voltage coordination based on received status data, the specific steps include: Extract the maximum power point voltage calculated by each photovoltaic module optimizer in its respective photovoltaic string from the status data uploaded by each photovoltaic module optimizer. The maximum power point voltage of all extracted photovoltaic modules is screened to determine the lowest value; The lowest value is used as the unified DC bus voltage reference value for the photovoltaic string, and the operating point of the string inverter is adjusted based on the unified DC bus voltage reference value.

8. A photovoltaic string control system according to claim 1, characterized in that, Power dispatch instructions include active power dispatch instructions and reactive power dispatch instructions; The power plant centralized controller specifically includes: The automatic power generation control module is used to receive grid dispatch instructions and generate active power dispatch instructions by combining the status data of all photovoltaic modules, so as to achieve the matching of system active power with grid demand. The automatic voltage control module is used to collect the grid connection point voltage in real time, generate reactive power dispatching instructions based on the grid connection point voltage deviation, and achieve stable control of the grid connection point voltage by adjusting the system reactive power output.

9. A photovoltaic string control system according to claim 8, characterized in that, The power plant centralized controller also includes a power generation prediction module, which uses a time-series prediction model to predict the power generation of each photovoltaic module based on historical status data and real-time meteorological data, and generates power dispatch instructions based on the prediction results.

10. A photovoltaic string control system according to claim 1, characterized in that, The power plant's centralized controller and string inverters communicate bidirectionally via RS485 bus or wireless communication network; the string inverters and each photovoltaic module optimizer communicate bidirectionally via power line carrier communication or wireless communication.

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