Photovoltaic inverter all-limit networking control method considering output characteristics of photovoltaic panel

Abstract

The invention provides a photovoltaic inverter out-of-limit networking control method considering output characteristics of a photovoltaic panel. When the system power instruction is lower than the maximum power capable of being generated by the photovoltaic array, the photovoltaic array and the DC / DC converter stabilize the direct current bus voltage through coordination control, the whole DC / DC converter has the constant voltage source characteristic, and at the moment, the DC / AC converter operates as a standard network-forming unit; and when the power instruction exceeds the complete response interval of the photovoltaic array, the system is smoothly switched to a maximum power point tracking mode, the DC / AC converter is converted into a self-synchronizing voltage source, the DC bus voltage is kept stable through power adjustment, and maximum energy capture is realized. And between the two operation modes, the system judges the switching opportunity based on the change trend of the output power of the photovoltaic array and the terminal voltage polarity, and introduces a seamless switching strategy to ensure that the transition process is smooth and rapid. According to the scheme, the grid construction operation potential of the photovoltaic inverter can be excavated as far as possible, a sensor or a peripheral circuit does not need to be additionally arranged, and the method is suitable for research and development of novel photovoltaic inverters and transformation and upgrading of existing equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new energy grid-connected technology, and can realize full-range controllability and rapid regulation within the reachable range of photovoltaic power supply power, in particular to a photovoltaic inverter limit network construction control method considering photovoltaic panel output characteristics. BACKGROUND

[0002] With the continuous increase of intermittent and strong fluctuation new energy installed capacity such as photovoltaic, the power grid energy structure has undergone profound changes. The proportion of synchronous generators in the system is gradually reduced, the system frequency change rate is increased, the transient frequency deviation is increased, the voltage support ability is insufficient during fault, and the stability problems such as oscillation risk are increasingly prominent, which threatens the safe operation of power grid.

[0003] The photovoltaic inverter is the core equipment of new energy grid-connected, and its traditional control strategy mainly adopts maximum power point tracking technology, aiming at maximizing power generation, and implements grid-following control. Under this control mode, the inverter behaves as a controlled current source, only responding to the phase and amplitude changes of the grid voltage, lacking inertia and damping support capability, and difficult to meet the dynamic regulation demand of the grid.

[0004] To cope with the above challenges, the existing technology usually relies on the configuration of external energy storage equipment to provide short-time power support. Although this method improves the dynamic response of the system to a certain extent, it also leads to problems such as rising investment cost, complicating the control system, and difficulty in coordinating the operation of multiple devices, and does not essentially improve the active support capability of new energy power generation equipment to the grid. How to implement grid-constructing transformation on existing photovoltaic systems, or ensure that new photovoltaic runs in grid-constructing mode, and promote the transformation of new energy equipment with power electronic interface from passive following grid to active supporting grid, is a technical difficulty to be overcome. SUMMARY

[0005] The present application aims at the deficiencies of the prior art, and proposes a photovoltaic inverter limit network control method considering photovoltaic panel output characteristics. When the system power instruction is lower than the maximum available power of the photovoltaic array, through the coordinated control of the photovoltaic array and the DC / AC converter, the inverter is released from the requirement of stabilizing the DC side, and operates as a standard network type unit to provide inertia and voltage support for the system; when the operating point exceeds the complete response interval, the system is smoothly switched to the maximum power point tracking mode, and the DC / AC converter operates as a self-synchronous voltage source to maintain the stability of the DC voltage and realize the maximum energy capture. Between the two operating modes, the system dynamically determines the switching time based on the output power and the voltage change trend of the photovoltaic array, and introduces a seamless switching mechanism to ensure the rapidity and smoothness of the transition of the operating state. The control scheme can fully tap the potential of the photovoltaic inverter in network operation, and does not need to additionally add sensors or peripheral auxiliary circuits, and is suitable for the research and development of new photovoltaic inverters and the upgrading and modification of existing photovoltaic power generation systems.

[0006] The object of the present application is achieved by the following technical solutions: Real-time acquisition of the output voltage of the photovoltaic array and the output current , and calculating the instantaneous output power thereof ; delay recording and difference operation are performed on the sampling signals to obtain the instantaneous change amount of the output voltage and the instantaneous change amount of the output power ; based on the change trend and amplitude characteristics of and , the current operating area of the photovoltaic array is determined; Based on the photovoltaic operating area, a mode switching flag signal is generated Flag . When the discrimination algorithm identifies that the photovoltaic operating point deviates from the complete response interval, immediately update Flag from high level indicating fast power control to low level indicating maximum power tracking, to ensure smooth and rapid switching process; Flag After switching, a preset delay period will be maintained, and after the operating state returns to the controllable interval, it will be automatically switched back to high level to ensure the transient stability of the system in the whole working condition range; The system executes the corresponding DC side control strategy according to Flag . Within the complete response interval, the photovoltaic power supply and the DC / DC converter cooperatively maintain the constant voltage source characteristic, and jointly maintain the stability of the DC bus voltage. By collecting the DC bus voltage of the photovoltaic inverter, the input voltage reference signal of the DC / DC converter is generated through double-loop regulation; after exceeding the controllable interval, the and , the input voltage reference signal of the DC / DC converter is generated by a maximum power tracking algorithm ; after obtaining the voltage reference signal, the system further calculates the duty cycle and generates a corresponding modulation signal ; The system executes a corresponding AC side control strategy. Flag In the fast power control mode, the active power reference instruction of the inverter is given by the system scheduling instruction, which improves the control accuracy of the photovoltaic power source as much as possible and fully utilizes the advantages of grid-forming control in frequency regulation and voltage regulation and system support; in the maximum power tracking mode, the DC / AC converter operates in a self-synchronous power supply mode, and by constructing a DC voltage closed-loop control loop, the obtained in step 3 and the voltage reference value are used to generate an active reference , so as to realize accurate and stable control of the DC side voltage and ensure that the photovoltaic inverter has both dynamic response rapidity and complete grid support integrity in the full operating range. The voltage , output current and grid-connected current of the photovoltaic inverter grid-connected point are collected, and the active power reference instruction generated in step 4 is combined to generate a reference value of the inverter output current by the system based on the grid-forming control strategy; the deviation between the reference value and the actual output current is closed-loop adjusted by a proportional-integral controller to generate a modulation signal of the subsequent converter; the modulation signal is further converted into a driving signal of the power switching device through a sine pulse width modulation technology, so as to realize the maximum grid-connected control of the two-stage grid-forming photovoltaic inverter.

[0007] Compared with the prior art, the technical scheme of the present application has the following advantages: 1. The technical scheme of the present application can realize full-range controllability of the photovoltaic power source from zero output to maximum power. Without adding hardware, the photovoltaic power source can be upgraded to a micro-grid controllable grid-forming unit with maximum operating and active support capability, and the frequency regulation and voltage regulation capability and inertia damping support advantage of the grid-forming control can be fully utilized.

[0008] 2. The technical scheme of the present application can effectively improve the regulation speed and control accuracy of the active output of the photovoltaic power source. In the full response range of the photovoltaic array, the method can avoid the tracking process of the maximum available power in the classical control, and guarantee the fast power response capability of the system in the power fluctuation.

[0009] 3. The application can realize self-stabilization control of DC bus without external energy storage. Based on the power interaction and dynamic balance mechanism between two-stage converters, the system can adaptively maintain the stability of DC bus voltage, overcoming the limitation of traditional photovoltaic systems that need to rely on energy storage to balance voltage and schedule demand, and providing a high-reliability voltage support solution for microgrids with no or weak energy storage.

[0010] 4. The technical solution of the application is not only suitable for network-type photovoltaic inverters, but also compatible with traditional network-following photovoltaic inverters, and suitable for various inverter topologies such as two-level, three-level, and modular multi-level. Based on existing photovoltaic power stations, the flexibility and controllability of photovoltaic power sources can be effectively enhanced by upgrading the control strategy. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 A full-process control block diagram of a photovoltaic inverter limit network construction control method considering the output characteristics of a photovoltaic panel is provided for the embodiments of the application. Figure 2 A constant voltage source characteristic diagram of an inverter DC side in a fast power control mode of the limit network construction control method is provided for the embodiments of the application. Figure 3 A full-process implementation flowchart of the photovoltaic inverter limit network construction control method is provided for the embodiments of the application. Figure 4 A generation algorithm flowchart of the photovoltaic inverter limit network construction control method is provided for the embodiments of the application. Flag A generation algorithm flowchart of the photovoltaic inverter limit network construction control method is provided for the embodiments of the application. Figure 5 A photovoltaic power operating point change trajectory diagram of the photovoltaic inverter limit network construction control method under four basic working conditions is provided for the embodiments of the application. Figure 6 A simulation running effect diagram of the photovoltaic inverter limit network construction control method under four basic working conditions is provided for the embodiments of the application. Figure 7 A simulation running effect diagram of the photovoltaic inverter limit network construction control method under a composite working condition is provided for the embodiments of the application. Figure 8 A flowchart of a specific example of a small-sized photovoltaic grid-connected experimental system integrated with the limit network construction control is provided for the embodiments of the application. Figure 9 A composition diagram of a specific example of a computer device is provided for the embodiments of the application. DETAILED DESCRIPTION

[0012] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings. The specific operation methods in the method embodiments can also be applied to the device embodiments or system embodiments. It should be noted that, in the description of the present application, "at least one" means one or more, wherein more means two or more than two. In view of this, "more" in the embodiments of the present application can also be understood as "at least two". "And / or", which describes the association relationship of the associated objects, means that there can be three kinds of relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. In addition, the character " / ", if not specially stated, generally represents that the front and rear associated objects are in an "or" relationship. In addition, it should be understood that, in the description of the present application, "first", "second", etc. are used only for the purpose of distinguishing the description, and cannot be understood as indicating or implying relative importance. The present application will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0013] Embodiment 1: A photovoltaic inverter limit network forming control method considering photovoltaic panel output characteristics is provided, including the following basic steps: Please refer to Figure 1 , the control structure of the photovoltaic inverter limit network forming control method considering photovoltaic panel output characteristics, including: a flag signal generation controller for monitoring the operation state of the photovoltaic system in real time and generating an operation state flag signal Flag ; a DC / DC controller for realizing DC side voltage stability based on a fast power control and maximum power tracking dual-mode cooperative working mechanism; and a DC / AC network forming controller for generating an active reference instruction through a self-synchronization mechanism in a maximum power tracking mode, realizing stable operation of the photovoltaic inverter through network forming type control. The controllers operate in coordination, completely simulate the operation characteristics of a synchronous generator within the photovoltaic output range, realize frequency and voltage regulation, inertia response and damping support functions, and the mode switching process is smooth and has no impact.

[0014] Please refer to Figure 2 , after using the photovoltaic inverter limit network forming control method, in a fast power control mode, a constant voltage source characteristic diagram of the inverter DC side. When the system power instruction is lower than the maximum available power of the photovoltaic array, the photovoltaic array and the DC / DC converter maintain the DC bus voltage stability through coordinated control, and the whole presents a constant voltage source characteristic. At this time, the DC / AC converter is released from the requirement of DC side voltage stabilization, and turns to execute a standard network forming type control strategy, which has inertia damping support, frequency and voltage regulation capability.

[0015] Please refer to Figure 3A schematic diagram of the entire implementation process of the photovoltaic inverter grid-connected control scheme, including: Step S301: Use a voltage sensor to detect the real-time output voltage of the photovoltaic array. Using a current sensor to monitor the real-time output current of the photovoltaic array ; Step S302: Please refer to Figure 4 The photovoltaic inverter grid-limited control method provided in this embodiment of the invention Flag A flowchart of the generation algorithm is shown, including: Calculate the instantaneous output power of the photovoltaic panel based on the sampled data. By recording data with a delay and performing difference calculations, the instantaneous changes in output voltage and output power can be obtained. and The details are as follows: (9) in, This represents the sampling period.

[0016] Calculate the product of the voltage and power changes of the photovoltaic array to determine the position of the photovoltaic system's operating point relative to the maximum power point. At that time, if If the condition is met, the photovoltaic array is determined to be operating in the region to the left of the maximum power point; otherwise, the photovoltaic array is determined to be operating in the region to the right of the maximum power point. At that time, if If the condition is met, the photovoltaic array is determined to be operating in the region to the left of the maximum power point; otherwise, the photovoltaic array is determined to be operating in the region to the right of the maximum power point.

[0017] When the operating point is to the left of the maximum power point, if Flag If the initial state is not low, it remains high, corresponding to the fast power control mode, ensuring instantaneous power balance between the photovoltaic array and the inverter, and maintaining DC bus voltage stability; if Flag It is initially at a low level, and then switches to a high level after a fixed delay.

[0018] When the operating point is to the right of the maximum power point Flag Immediately set to low level and start timer to record duration. At this time, the system is running in maximum power point tracking mode. The photovoltaic power supply simulates generator characteristics to the extent possible through self-synchronization. The system still has frequency and voltage regulation and inertial damping support capabilities.

[0019] Step S303: Determine Flag Whether the signal is high determines the corresponding operating mode. Flag When the signal is high, the system executes fast power control mode; when Flag When the signal is low, the system executes maximum power point tracking mode.

[0020] Step S304: In fast power control mode, the control system acquires the bus voltage on the DC side of the photovoltaic inverter. The power reference value is generated after processing by the voltage outer loop controller. This reference value is then used to generate the input voltage reference signal for the DC / DC converter through power loop regulation. The details are as follows: When initially starting in fast power control mode, the basic logic of the control loop is as follows: (10) in, This is the power reference value for the photovoltaic array. , This is the transfer function for the control loop.

[0021] During system operation, in order to achieve a smooth switch from maximum power point tracking mode to fast power control mode, the control loop is adjusted accordingly: (11) in, T The time constant of a first-order inertial element is given by [the time constant during the switching transient]. Flag The signal serves as the trigger condition, assigning an external reset value to the voltage loop PI controller. The power loop PI controller is externally reset and assigned a value. .

[0022] Step S305: In maximum power point tracking mode, the system uses the real-time output voltage of the photovoltaic array obtained in step 1. With current The input voltage reference signal of the DC / DC converter is calculated and generated using the maximum power point tracking algorithm. As shown in the following formula: (12) in, Adjust the increment for the preset voltage reference signal.

[0023] Step S306: In fast power control mode, the expected active power adjustment signal is incremented. Given, and during the instruction update cycle Update the given By accumulating all historical cycles Generate cumulative active power reference value As a basic scheduling instruction; during system operation, in order to achieve a smooth switch from maximum power point tracking mode to fast power control mode, a mode switching compensation amount is superimposed in the control loop. This leads to the final active power scheduling instruction. If the set value exceeds the photovoltaic array's full response range defined by the protective switching algorithm in step 2, the system will immediately switch to maximum power point tracking mode to maintain stable operation; when the system switches back to fast power control mode, the... The sampled compensation value will be reassigned through mode switching, and automatically corrected to within the safe operating range.

[0024] Step S307: In maximum power point tracking mode, based on the DC bus voltage of the photovoltaic inverter obtained in step 3... Compare it with the given voltage reference value The resulting deviation signal is compared and then regulated by the voltage loop to generate the inverter's active power reference value. The specific generation method is shown in the following formula: If the system is initially started in maximum power point tracking mode, the basic logic of the control loop is as follows: (13) in, It is a proportional-integral controller.

[0025] During system operation, in order to achieve a smooth switch from fast power control mode to maximum power point tracking mode, the control loop is adjusted accordingly: (14) Where is the time constant of the first-order inertial element, and during the switching transient process, is... Flag The signal serves as the trigger condition, assigning an external reset value to the voltage loop PI controller. .

[0026] Step S308: Use voltage and current sensors to measure the voltage at the grid connection point PCC of the three-phase photovoltaic inverter. Output current Grid-connected current Sampling is performed, and the collected electrical physical quantities are transformed using the Park transform to obtain the coordinates. d-q Components in rotating coordinate system , , ; Based on the system state variables obtained from the transformation, the instantaneous active power of the photovoltaic inverter is calculated. reactive power The calculation formula is as follows: (15) Next, a low-pass filter is used to filter the instantaneous power to obtain the filtered output power. , : (16) in, This is the cutoff frequency of the low-pass filter.

[0027] Then, the output power is compared with the power reference value. , By comparison, a reference phase is generated using a grid-type power outer loop control based on the simulated synchronous droop characteristics. , As shown in the following formula: (17) in, The inverter's grid-connected voltage angular frequency, For grid-connected voltage phase, , These are the rated angular frequency and the rated voltage amplitude, respectively. The preset reactive power reference value, , The output power is extracted after filtering, and the calculated photovoltaic inverter power is... d Shaft voltage reference value.

[0028] Then, a reference modulation voltage is generated through dual closed-loop control of voltage and current. Then, after the anti-Parker transformation, we get As shown in the following formula: (18) in, , , For the voltage, output current, and grid-connected current of the photovoltaic inverter at the grid connection point dq Quantity, , It is a proportional-integral controller. This is the modulation signal for the photovoltaic inverter.

[0029] Finally, the power transistor switching signal is obtained through SPWM modulation technology, realizing the maximum grid control of the two-stage grid-type photovoltaic inverter.

[0030] Please refer to Figure 5 The photovoltaic power operating point change trajectory diagram of the photovoltaic inverter grid-connected control method provided in this embodiment of the invention under four basic operating conditions; please refer to... Figure 6 The simulation operation effect diagram of the photovoltaic inverter grid-limited control method provided in the embodiments of the present invention under four basic operating conditions.

[0031] As shown in subfigures (a) and (b), when the irradiance changes but the power command remains constant and does not exceed the limit, the photovoltaic array operates in fast power control mode, capable of autonomously and rapidly adjusting its power output and quickly converging to the steady-state operating point on the corresponding photovoltaic characteristic curve. As shown in subfigures (c) and (d), when the power command exceeds the limit, the photovoltaic array performs limit tracking in fast power control mode; once the detection algorithm determines that the system operating point exceeds the full response range, Flag The system switches from high to low level, enters maximum power point tracking mode, and stabilizes at the maximum power point under the current irradiance; after a preset delay period, Flag The system switches back to fast power control mode after the low-level signal changes to a high-level signal, and corrects any over-limit active power commands. Simulation results verify that the limit-based network control method proposed in this embodiment can effectively achieve the expected control objectives.

[0032] Please refer to Figure 7 The simulation operation effect diagram of the photovoltaic inverter grid-connected control method provided in this embodiment of the invention under combined operating conditions is shown. In this embodiment, the active power setpoint changes stepwise with a period of 1 second, and the reactive power setpoint is constantly set to 40kW; starting from 8 seconds, the irradiance received by the photovoltaic array also changes stepwise with a period of 1 second. Figure 7 The waveforms of the indicator signal, irradiance, active power output of the photovoltaic array, and active and reactive power output of the photovoltaic inverter are presented from top to bottom.

[0033] Simulation results show that when irradiance changes abruptly, the photovoltaic array and inverter can achieve rapid coordination and dynamic tracking of active power commands using the limit grid control method of this invention, with a response time of less than 150ms. Especially when irradiance drops sharply at 8s and 10s, the controller can quickly detect the operating status and autonomously switch modes to maintain stable power output as a self-synchronizing power source.

[0034] In summary, the method provided by this invention achieves fully controllable and rapid adjustment of output within the feasible power domain of the photovoltaic array, driving a significant transformation in the role of photovoltaic power sources in microgrids. This elevates them from traditional energy supply units to active control units with rapid power response capabilities. Based on a DC-side power dynamic balance mechanism, this method achieves rapid and precise control of photovoltaic output power without relying on external energy storage. Within the photovoltaic output range, the system can fully simulate the operating characteristics of a synchronous generator; even when exceeding the photovoltaic output limit, it still operates stably in a self-synchronizing manner. The mode switching process is autonomous, smooth, and shock-free. Under complex operating conditions such as microgrid islanding or high-proportion renewable energy integration, it can effectively improve system stability and dynamic response accuracy, providing reliable technical support for building new power systems with high-proportion renewable energy integration.

[0035] Example 2: Please refer to Figure 8 The miniaturized photovoltaic grid-connected experimental system with integrated limitless grid control provided in this embodiment of the invention includes: DC unit module 1 includes a current source, diodes, series resistors and parallel resistors, and is used to simulate the time-varying output characteristics of a photovoltaic array; this module performs the method described in embodiment 1, which will not be repeated here.

[0036] DC / DC conversion circuit module 2 is used to convert the unstable DC voltage output by the DC power generation unit module into the target DC voltage to achieve optimized power regulation; this module performs the method described in embodiment 1, which will not be repeated here.

[0037] DC / AC conversion circuit module 3 includes a main power conversion circuit and an LCL-type filter circuit. The main power conversion circuit realizes DC / AC power conversion, and the LCL-type filter circuit consists of a filter inductor on the inverter side. Filter capacitor and grid-side filter inductor The composition, and its topological connection relationship, are as follows: the AC terminals of the main power conversion circuit are connected sequentially. , , It is then connected to the power grid; this module performs the method described in Example 1, which will not be repeated here.

[0038] System control module 4 adopts a hierarchical control architecture and mainly consists of a high-precision sampling module, an instantaneous power calculation module, a dynamic flag signal generation module, a power conversion circuit control module, and a modulation module. Among them, the dynamic flag signal generation module generates a working mode flag signal based on the real-time identified photovoltaic array operating status, and the power conversion circuit control module executes the corresponding working mode based on the flag signal. This module executes the method described in embodiment 1, which will not be repeated here.

[0039] AC unit module 5 is used to simulate the actual main power grid and provide voltage and frequency support for the system; this module performs the method described in Example 1, which will not be repeated here.

[0040] Example 3: Please refer to Figure 9This invention provides a computer device, including: at least one processor 901, such as a central processing unit (CPU), at least one communication interface 903, a memory 904, and at least one communication bus 902 connecting the components to enable communication. The communication interface 903 is equipped with a display screen and a keyboard, and can be expanded with standard wired or wireless interfaces. The memory 904 is implemented using high-speed random access memory (RAM) or non-volatile memory (NVM), including but not limited to disk storage, and can be configured as an independent storage device remote from the processor 901. The processor 901 is configured to execute the photovoltaic inverter grid-connected control method described in Embodiment 1, and implements the method operation by calling program code stored in the memory 904.

[0041] The processor 901 can be implemented in hardware as a central processing unit, a network processor (NP), or a combination of a CPU and an NP. It can also be further integrated with an application-specific integrated circuit (ASIC), a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a generic array logic (GAL), or any combination thereof. When the program instructions stored in the memory 904 are called by the processor 901, the photovoltaic inverter grid-limited control method described in Embodiment 1 will be executed.

[0042] The communication bus 902 can be selected from either the Peripheral Component Interconnect (PCI) bus or the Extended Industry Standard Architecture (EISA) bus, including address bus, data bus, and control bus functions. It should be noted that... Figure 9 The single bus diagram is for simplification only and does not limit the number or type of buses.

[0043] The memory 904 includes at least one of volatile memory and non-volatile memory, wherein the volatile memory is random access memory, and the non-volatile memory includes flash memory, hard disk drive (HDD) or solid-state drive (SSD), and also supports a combination architecture of the above storage media.

[0044] This invention also provides a computer-readable storage medium storing computer-executable instructions. When these instructions are executed, they implement the photovoltaic inverter grid-limited control method of Embodiment 1. The storage medium is selected from magnetic disks, optical disks, read-only memory (ROM), random access memory, flash memory, hard disk drives, solid-state drives, or combinations thereof.

[0045] This invention is not limited to the embodiments described above. The above description of specific embodiments is intended to illustrate and explain the technical solutions of this invention. The specific embodiments described above are merely illustrative and not restrictive. Without departing from the spirit and scope of the claims, those skilled in the art can make many specific modifications based on the teachings of this invention, and these modifications all fall within the scope of protection of this invention.

Claims

1. A method for grid-connected control of photovoltaic inverters taking into account the output characteristics of photovoltaic panels, characterized in that, Includes the following steps: Step 1: Real-time acquisition of photovoltaic array output voltage With output current Calculate its instantaneous output power. The sampled signal is delayed and recorded, and the difference is calculated to obtain the instantaneous change in the output voltage of the photovoltaic array. With the instantaneous change in output power ;according to , Based on the changing trend and amplitude characteristics, determine the current operating area of ​​the photovoltaic array; Step 2: Generate mode switching flag signal based on photovoltaic operating area Flag When the discrimination algorithm detects that the photovoltaic operating point deviates from the full response range, it immediately... Flag The high level indicating fast power control is updated to a low level indicating maximum power tracking to ensure a smooth and rapid switching process; Flag After the signal goes low, the system starts a preset delay timer. If the delay period is exceeded... Furthermore, once the operating state returns to a controllable range, it automatically switches back to a high level to ensure the transient stability of the system across all operating conditions. Step 3, the system according to Flag The corresponding DC-side control strategy is executed. Within the full response range, the photovoltaic power source and the DC / DC converter work together to maintain constant voltage source characteristics and jointly maintain the stability of the DC bus voltage. This is achieved by acquiring the DC-side bus voltage of the photovoltaic inverter. The input voltage reference signal of the DC / DC converter is generated through dual-loop regulation. After exceeding the controllable range, based on the information obtained in step 1... and The input voltage reference signal of the DC / DC converter is generated using the maximum power point tracking algorithm. After acquiring the voltage reference signal, the duty cycle is further calculated to generate a modulation signal for the DC / DC converter. ; Step 4, the system according to Flag The corresponding AC-side control strategy is executed. In fast power control mode, the inverter's active power reference command... Given system scheduling commands, the control accuracy of the photovoltaic power supply is maximized to fully leverage the advantages of grid-based control in frequency and voltage regulation and system support. In maximum power point tracking mode, the DC / AC converter operates as a self-synchronizing power supply. By constructing a DC voltage closed-loop control loop, based on the data obtained in step 3... With voltage reference value Generate active reference This enables precise and stable control of the DC-side voltage, ensuring that the photovoltaic inverter maintains both rapid dynamic response and grid support integrity throughout its entire operating range. Step 5: Collect the voltage at the grid connection point of the photovoltaic inverter. Output current and grid-connected current Combined with the active power reference command generated in step 4 The inverter output current reference value is generated through a grid-based control strategy. The proportional-integral controller is used to control the output current. Closed-loop regulation is performed to generate the modulation signal for the subsequent converter, and then the drive signal for the power switching device is generated through sinusoidal pulse width modulation technology. In dual mode, the frequency and voltage regulation and inertial damping support capabilities of the grid controller are fully utilized, ultimately realizing the maximum grid control of the two-stage photovoltaic inverter in the entire operating range.

2. The grid-connected control method for photovoltaic inverters according to claim 1, characterized in that, The specific process of step 1 is as follows: Photovoltaic array output voltage With output current Calculate instantaneous output power The sampled signal is delayed and recorded, and the difference is calculated to obtain the instantaneous change in the output voltage of the photovoltaic array. With the instantaneous change in output power : （1） in, Represents the sampling period; according to , Based on the changing trend and amplitude characteristics, determine the current operating area of ​​the photovoltaic array. At that time, if If the condition is met, the photovoltaic array is determined to be operating in the region to the left of the maximum power point; otherwise, the photovoltaic array is determined to be operating in the region to the right of the maximum power point. At that time, if If the condition is met, the photovoltaic array is determined to be operating in the region to the left of the maximum power point; otherwise, the photovoltaic array is determined to be operating in the region to the right of the maximum power point.

3. The grid-connected control method for photovoltaic inverters according to claim 1, characterized in that, The reference flag signal described in step 2 Flag The generation logic is as follows: When the photovoltaic array is operating in the region to the left of the maximum power point and the time exceeds At this time, the controller generates a high-level flag signal. Flag This corresponds to the fast power control mode, which maintains the DC bus voltage stability based on the instantaneous power balance mechanism between the photovoltaic array and the inverter, drives the photovoltaic power supply to autonomously follow the command to adjust the output, and achieves complete controllability and fast adjustment within the corresponding range. When the photovoltaic array is operating in the region to the right of the maximum power point or the time has not exceeded At that time, a low-level flag signal is generated. Flag This corresponds to the maximum power point tracking mode. In this mode, the photovoltaic inverter operates as a self-synchronizing power source, continuously tracking and maintaining the photovoltaic array to maximize output power, thereby ensuring stable operation of the system during transient processes.

4. The grid-connected control method for photovoltaic inverters according to claim 1, characterized in that, The specific process of step 3 is as follows: The system according to Flag The corresponding DC-side control strategy is executed. The basic logic of the control loop during initial startup in fast power control mode is as follows: （2） in, This is the power reference value for the photovoltaic array. The voltage loop transfer function. The power loop transfer function; During system operation, in order to achieve a smooth switch from maximum power point tracking mode to fast power control mode, the control loop is adjusted accordingly: （3） in, T The time constant of a first-order inertial element is given by [the time constant during the switching transient]. Flag The signal serves as the trigger condition, assigning an external reset value to the voltage loop PI controller. The power loop PI controller is externally reset and assigned a value. ; In maximum power point tracking mode, the DC / DC converter input voltage reference signal The generation method is as follows: （4） in, Adjust the increment for the preset voltage reference signal.

5. The grid-connected control method for photovoltaic inverters according to claim 1, characterized in that, The specific process of step 4 is as follows: The system according to Flag The corresponding AC-side control strategy is executed. In fast power control mode, the expected active power adjustment signal is expressed incrementally. Given, and in the period Update the given By accumulating all historical cycles Generate basic scheduling instructions To achieve smooth switching during system operation, mode switching compensation is superimposed on the control loop. Ultimately, active power scheduling instructions are obtained. ; If the scheduling command exceeds the full response range of the photovoltaic array defined by the protective switching algorithm in step 2, the system will immediately switch to maximum power point tracking mode to maintain stable operation; When the system switches back to fast power control mode, the The sampled compensation value will be reassigned through mode switching and automatically corrected to within the safe operating range; If the system is initially started in maximum power point tracking mode, the basic logic of the control loop is as follows: （5） in, It is a proportional-integral controller; During system operation, in order to achieve a smooth switch from fast power control mode to maximum power point tracking mode, the control loop is adjusted accordingly: （6） in, T The time constant of a first-order inertial element is given by [the time constant during the switching transient]. Flag The signal serves as the trigger condition, assigning an external reset value to the voltage loop PI controller. .

6. The grid-connected control method for photovoltaic inverters according to claim 1, characterized in that, The specific process of step 5 is as follows: Collect grid-connected voltage of photovoltaic inverter Output current and grid-connected current Combined with the active power reference command generated in step 4 A reference modulation signal is generated through a network-based control strategy. The process of generating the voltage loop reference signal in the network-based power outer loop is as follows: （7） in, The inverter's grid-connected voltage angular frequency, For grid-connected voltage phase, , These are the rated angular frequency and the rated voltage amplitude, respectively. The preset reactive power reference value, , The output power is extracted after filtering. For the calculated photovoltaic inverter d Shaft voltage reference value; The process of generating and modulating the voltage and current dual closed-loop signal in the network configuration is shown in the following equation: （8） in, , , For the voltage, output current, and grid-connected current of the photovoltaic inverter at the grid connection point dq Quantity, , It is a proportional-integral controller. This is the modulation signal for the photovoltaic inverter.

7. A miniaturized photovoltaic grid-connected experimental system integrating limitless grid control, characterized in that, include: The DC unit module uses an equivalent circuit model that includes a current source, diodes, series resistors, and parallel resistors to dynamically simulate the time-varying output characteristics of the photovoltaic array. The parameters need to be set according to the characteristics of the photovoltaic panel. The DC / DC conversion circuit module is used to convert the unstable DC voltage output from the DC power generation unit module into the target DC voltage, thereby achieving optimized power regulation. The DC / AC conversion circuit module performs the power conversion from DC to AC, and consists of a main power conversion unit and an LCL filter. The main power conversion unit performs the DC / AC conversion function, and the LCL filter includes a filter inductor on the converter side. Filter capacitor and grid-side filter inductor Its topological configuration is characterized by the AC output terminal of the main power conversion unit being connected via... , , Connect to the power grid after sequential connection; The system control module implements the grid-connection control strategy described in claims 1-6, and outputs drive signals to control the switching on and off of power semiconductor devices in the DC / DC conversion circuit module and the DC / AC conversion circuit module; it mainly includes a high-precision electrical quantity sampling unit, an instantaneous power calculation unit, a flag signal dynamic generation unit, a power conversion circuit control unit, and a modulation unit; wherein, the flag signal dynamic generation unit generates a working mode flag signal based on the real-time identified photovoltaic array operating status, and the power conversion circuit control unit executes the corresponding working mode based on the flag signal; The AC unit module provides the voltage and frequency support environment for the actual power grid.

8. A computer device, characterized in that, include: At least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to cause the at least one processor to perform the grid-limited control method for a photovoltaic inverter according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to execute the grid-limited control method for the photovoltaic inverter according to any one of claims 1-6.

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