Matching control-based network construction type photovoltaic grid-connected pre-synchronization control method and system

Abstract

According to the matching control-based grid construction type photovoltaic grid-connected pre-synchronization control method and system provided by the invention, the initial state of each switch is preset and the electrical parameters are collected, so that the error grid-connected impact in the pre-synchronization stage is avoided; inputting the three-phase voltage into a phase-locked loop, and outputting a power grid voltage phase angle through coordinate transformation and PI regulation; introducing the phase angle difference between the power grid voltage phase angle and the output phase angle of the network construction type photovoltaic inverter into a network construction type photovoltaic control strategy based on matching control; when the phase angle difference exceeds the threshold value, the direct current voltage is corrected through the phase amplitude correction module, the inversion phase is driven to approach the power grid phase, impact generated by large phase difference in traditional grid connection is eliminated, and the problem that in the prior art, current impact is caused to a power grid when a grid-forming photovoltaic system is connected to the power grid is solved.

Description

Technical Field

[0001] This invention relates to the field of grid-connected inverter control technology, and in particular to a grid-connected photovoltaic pre-synchronization control method and system based on matched control. Background Technology

[0002] As one of the most promising renewable energy sources, photovoltaics is developing rapidly, with its installed capacity continuously increasing. However, with the integration of a high proportion of renewable energy sources, the power system dominated by traditional grid-connected inverters faces severe challenges.

[0003] Traditional photovoltaic (PV) power plants connect to the grid via grid-connected inverters, relying on the voltage and frequency support provided by the grid. When grid faults or disturbances occur, grid-connected inverters may fail to provide effective support and may even disconnect from the grid due to protection mechanisms, exacerbating system instability. Secondly, with the large-scale integration of PV systems, the pressure on the grid to regulate voltage and frequency increases. Grid-connected inverters lack proactive regulation capabilities, making it difficult to meet the grid's real-time demands for voltage, frequency, and power balance.

[0004] For inverters, direct grid connection may result in huge inrush currents due to large voltage, frequency, or phase angle differences, which can damage the equipment and the power grid, or even trigger protection actions and cause grid connection failure. Summary of the Invention

[0005] This invention provides a pre-synchronization control method and system for grid-connected photovoltaic systems based on matched control, which solves the problem of current surges to the power grid when grid-connected photovoltaic systems are connected to the grid in the prior art.

[0006] On one hand, this invention provides a pre-synchronization control method for grid-connected photovoltaic systems based on matched control, applicable to grid-connected photovoltaic systems. The grid-connected photovoltaic system includes a phase-locked loop, a grid-connected photovoltaic inverter, a DC / DC converter, a phase amplitude correction module, a DC voltage switching switch, a grid-connection switch, and a photovoltaic panel switch. The initial states of the DC voltage switching switch, the grid connection switch, and the photovoltaic panel switch are set according to the preset procedure, and the three-phase voltage and DC voltage measurement values ​​of the grid-type photovoltaic power grid are collected. The three-phase voltage is input to the phase-locked loop to obtain the grid voltage phase angle; Unlock the grid-connected photovoltaic inverter, input the DC voltage measurement value to the grid-connected photovoltaic control strategy based on matching control, and output the inverter phase angle of the grid-connected photovoltaic inverter; Calculate the phase angle difference between the grid voltage phase angle and the inverter phase angle; If the phase angle difference is greater than a preset threshold, the phase angle difference is introduced into the phase amplitude correction module, a corrected DC voltage constant value is output, and the phase angle difference is recalculated until the phase angle difference is less than the preset threshold. If the phase angle difference is less than the preset threshold, then close the grid-connected switch, close the photovoltaic panel switch, switch the DC voltage switching switch to the DC voltage measurement range, and unlock the DC / DC converter.

[0007] Optionally, the step of setting the initial states of the DC voltage switching switch, the grid-connected switch, and the photovoltaic panel switch according to a preset procedure, and collecting the three-phase voltage of the grid-type photovoltaic power grid, includes: Confirm that the grid-connected switch and the photovoltaic panel switch are in the off state, switch the DC voltage switching switch to the DC voltage constant value position, and lock the DC / DC converter and the grid-type photovoltaic inverter; the DC voltage constant value position matches the DC voltage constant value. Close the photovoltaic panel switch, unlock the DC / DC converter, raise the DC capacitor of the locked grid-type photovoltaic inverter to the rated value through the DC / DC converter, then lock the DC / DC converter and disconnect the photovoltaic panel switch; Collect the three-phase voltage and DC voltage measurements of the grid-type photovoltaic power grid.

[0008] Optionally, the three-phase voltage is input to the phase-locked loop to obtain the grid voltage phase angle, including: The three-phase voltage is input into the coordinate transformation module of the phase-locked loop to perform coordinate transformation on the three-phase voltage, so that the three-phase voltage is transformed from the abc stationary coordinate system to the dq rotating coordinate system, and the q-axis voltage component in the dp rotating coordinate system is obtained. The q-axis voltage component is input into a PI controller consisting of a proportional coefficient and an integral coefficient, and the output frequency adjustment is achieved. The actual tracking angular frequency is obtained by superimposing the frequency adjustment amount with the rated angular frequency of the power grid. The actual tracking angular frequency is integrated to obtain the grid voltage phase angle, and the grid voltage phase angle is fed back to the coordinate transformation module.

[0009] Optionally, the grid-connected photovoltaic inverter is unlocked, the DC voltage measurement value is input to the grid-connected photovoltaic control strategy based on matched control, and the inverter phase angle of the grid-connected photovoltaic inverter is output, including: Send an unlock command to the grid-connected photovoltaic inverter to release the locked state of the grid-connected photovoltaic inverter; The DC voltage measurement value of the DC side of the grid-type photovoltaic inverter is collected, and the DC voltage measurement value is input into the proportional circuit for gain adjustment, and then processed by the integral circuit to output the inverter phase angle.

[0010] Optionally, it also includes: Obtain the reactive power setpoint and the reactive power measured value, and calculate the deviation value between the reactive power setpoint and the reactive power measured value; The deviation value is input into a PI controller consisting of a proportional coefficient and an integral coefficient, and the q-axis duty cycle component is output. Set a reference value for the d-axis voltage as the d-axis duty cycle component; The coordinate transformation module converts the inverter phase angle, the d-axis duty cycle component, and the q-axis duty cycle component into a modulation signal for the abc stationary coordinates. The modulation signal is pulse-width modulated to generate drive information for controlling the output of the grid-type photovoltaic inverter.

[0011] Optionally, calculating the phase angle difference between the grid voltage phase angle and the inverter phase angle includes: Perform a periodic consistency check on the grid voltage phase angle to obtain the first phase angle; Hysteresis compensation is performed on the inverter phase angle to obtain the second phase angle; Substituting the first phase angle and the second phase angle into the phase deviation quantization model, the phase angle difference is obtained.

[0012] Optionally, after substituting the first phase angle and the second phase angle into the phase deviation quantization model to obtain the phase angle difference, the method further includes: Monitor the changing trend of the phase angle difference and the harmonic distortion rate of the output voltage of the grid-type photovoltaic inverter; If the phase angle difference shows a divergent trend and the harmonic distortion rate is lower than the preset allowable upper limit, then increase the correction gain of the phase amplitude correction module; If the phase angle difference shows a converging trend but the harmonic distortion rate exceeds the preset allowable upper limit, then reduce the correction gain of the phase amplitude correction module; If the phase angle difference fluctuation amplitude is less than the preset steady-state fluctuation threshold and the harmonic distortion rate is within the preset range, then the correction gain of the phase amplitude correction module is maintained.

[0013] Optionally, it also includes: Monitor the deviation between the measured DC voltage value and the rated DC voltage value. If the absolute value of the deviation is greater than a first preset percentage of the rated value for a preset number of control cycles, then lock the grid-type photovoltaic inverter, disconnect the photovoltaic panel switch, and record the abnormal state. The fluctuation of reactive power measurement value is monitored. If the fluctuation exceeds the second preset percentage of the reactive power set value within the power grid cycle, the adjustment of the phase amplitude correction module is suspended, and the current DC voltage is maintained at a constant value until the fluctuation is less than the set value and then the correction is started. The phase angle jump of the grid voltage output by the phase-locked loop is monitored. If the absolute value of a single jump is greater than the preset value, the grid voltage is determined to be abnormal, and a grid abnormality signal is output.

[0014] Optionally, it also includes: Harmonic content, frequency fluctuation rate, and short-circuit capacity parameters of the power grid voltage are collected to construct a power grid strength assessment index. The power grid strength assessment index is obtained by weighted calculation of harmonic distortion rate, frequency change rate, and short-circuit ratio, and the weighting coefficients are generated based on historical power grid operation data. If the power grid strength assessment index is higher than the preset strong grid threshold, the correction coefficient gain of the phase amplitude correction module is reduced to decrease the DC voltage adjustment amplitude. If the power grid strength assessment index is lower than the preset weak grid threshold, the correction coefficient gain of the phase amplitude correction module is increased, and a virtual inertia compensation link is introduced to expand the DC voltage phase dynamic response bandwidth.

[0015] On the other hand, the present invention also provides a grid-connected photovoltaic pre-synchronization control system based on matched control, comprising: The state initialization unit is used to set the initial state of the DC voltage switching switch, grid connection switch and photovoltaic panel switch according to the preset process, and to collect the three-phase voltage and DC voltage measurement values ​​of the grid-type photovoltaic power grid. A phase acquisition unit is used to input the three-phase voltage into the phase-locked loop to obtain the grid voltage phase angle; Unlock the grid-connected photovoltaic inverter, input the DC voltage measurement value to the grid-connected photovoltaic control strategy based on matching control, and output the inverter phase angle of the grid-connected photovoltaic inverter; A phase angle difference calculation and correction unit is used to calculate the phase angle difference between the grid voltage phase angle and the inverter phase angle; If the phase angle difference is greater than a preset threshold, the phase angle difference is introduced into the phase amplitude correction module, a corrected DC voltage constant value is output, and the phase angle difference is recalculated until the phase angle difference is less than the preset threshold. The grid-connected execution unit is used to close the grid-connected switch and the photovoltaic panel switch if the phase angle difference is less than the preset threshold, switch the DC voltage switching switch to the DC voltage measurement range, and send an unlocking command to the DC / DC converter.

[0016] On the other hand, the present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the grid-connected photovoltaic pre-synchronization control method based on matching control as described above.

[0017] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the grid-connected pre-synchronization control method for grid-connected photovoltaic systems based on matching control as described above.

[0018] On the other hand, the present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the pre-synchronization control method for grid-connected photovoltaic systems based on matching control as described above.

[0019] This invention provides a pre-synchronization control method and system for grid-connected photovoltaic (PV) systems based on matched control. The method avoids grid-connection erroneous impacts during the pre-synchronization stage by pre-setting the initial states of each switch and collecting electrical parameters. The three-phase voltage is input into a phase-locked loop (PLL), and after coordinate transformation and PI regulation, the output grid voltage phase angle is determined. The phase angle difference between the grid voltage phase angle and the output phase angle of the grid-connected PV inverter is incorporated into the matched control-based PV control strategy. When the phase angle difference exceeds a threshold, the DC voltage is corrected through a phase amplitude correction module, driving the inverter phase to approximate the grid phase, eliminating the impact caused by large phase differences in traditional grid connection, and solving the problem of current surges to the grid caused by grid-connected PV systems when connected to the grid in existing technologies. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a grid-type photovoltaic structure provided in an embodiment of the present invention; Figure 2 This is a flowchart illustrating the pre-synchronization control method for grid-connected photovoltaic systems based on matched control provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the phase-locked loop structure provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the control structure of the grid-type photovoltaic control strategy based on matched control provided in an embodiment of the present invention; Figure 5This is a schematic diagram of the phase amplitude correction module structure provided in an embodiment of the present invention; Figure 6 This is a diagram showing the grid connection point voltage and output current of a grid-connected photovoltaic system in direct grid connection, provided in an embodiment of the present invention. Figure 7 This is a diagram showing the grid connection point voltage and output current of a grid-connected photovoltaic system when connected to the grid after the pre-synchronization control method provided in this embodiment of the invention. Figure 8 This is a schematic diagram of the grid-connected photovoltaic pre-synchronization control system based on matched control provided in an embodiment of the present invention; Figure 9 This is a schematic diagram of the structure of the electronic device provided in an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] Figure 1 This is a schematic diagram of a grid-type photovoltaic structure provided in an embodiment of the present invention. The grid-type photovoltaic system includes a phase-locked loop, a grid-type photovoltaic inverter, a DC / DC converter, a phase amplitude correction module, a DC voltage switching switch, a grid-connected switch, and a photovoltaic panel switch.

[0024] in, This is the grid voltage. For grid current, , These are the equivalent inductance and equivalent resistance of the power grid, respectively. , , These are the filter capacitor, filter inductor, and filter parasitic resistance of the grid-connected converter, respectively. The voltage at the grid connection point. The output current is for grid-connected photovoltaic systems; the DC / AC inverter is a grid-connected photovoltaic inverter.

[0025] Figure 2 This is a schematic flowchart of the pre-synchronization control method for grid-connected photovoltaic systems based on matched control provided in an embodiment of the present invention.

[0026] Figure 3 This is a flowchart of the predictive synchronization control method for grid-connected photovoltaic systems based on matched control, provided in an embodiment of the present invention. For three-phase grid voltage input; For DC voltage measurement; This is the reactive power setpoint. This represents the measured reactive power value; dq / abc is the coordinate transformation module. The phase angle of the grid voltage; The inverter phase angle; Phase angle difference; To correct the constant value of DC voltage; and These are the d-axis duty cycle components and the q-axis duty cycle components, respectively.

[0027] like Figure 2 and Figure 3 As shown in the figure, the pre-synchronization control method for grid-connected photovoltaic systems based on matched control provided in this embodiment of the invention mainly includes the following steps: 101. Set the initial state of the DC voltage switching switch, grid connection switch, and photovoltaic panel switch according to the preset procedure, and collect the three-phase voltage and DC voltage measurement values ​​of the grid-type photovoltaic power grid.

[0028] The preset procedure involves placing the DC voltage switching switch, grid connection switch, and photovoltaic panel switch all in the off state to ensure safety during startup. The collected three-phase voltage and DC voltage measurements are used for subsequent control and status assessment, ensuring the grid-connected photovoltaic system is in a correct and safe initial state before grid connection.

[0029] Specifically, the initial states of the DC voltage switching switch, grid connection switch, and photovoltaic panel switch are set according to a preset procedure, and the three-phase voltage of the grid-type photovoltaic power grid is collected, including: Confirm that the grid-connected switch and the photovoltaic panel switch are in the off state, switch the DC voltage transfer switch to the DC voltage constant value position, and lock the DC / DC converter and the grid-type photovoltaic inverter; the DC voltage constant value position is matched with the DC voltage constant value. Close the photovoltaic panel switch, unlock the DC / DC converter, raise the DC capacitor of the locked grid-type photovoltaic inverter to the rated value through the DC / DC converter, then lock the DC / DC converter and disconnect the photovoltaic panel switch; Collect the three-phase voltage and DC voltage measurements of the grid-type photovoltaic power grid.

[0030] In the initial stage of the grid-connected pre-synchronization control process for grid-connected photovoltaic systems, the initial configuration of equipment status and the acquisition of electrical parameters must be completed in sequence.

[0031] First, confirm that the grid-connected switch and photovoltaic panel switch are in the open state, cutting off any unintended connections between the photovoltaic system and the grid, and between the photovoltaic panels and subsequent circuits. Simultaneously, switch the DC voltage transfer switch to a position compatible with a constant DC voltage value, providing an initial reference for DC-side voltage control, and perform a lockout operation on the DC / DC converter and grid-connected photovoltaic inverter to prevent equipment malfunction. Next, close the photovoltaic panel switch and unlock the DC / DC converter. Utilizing the power regulation capability of the DC / DC converter, smoothly raise the DC-side capacitor voltage of the grid-connected photovoltaic inverter to its rated value. After the voltage boost is complete, lock the DC / DC converter again and disconnect the photovoltaic panel switch to maintain a stable energy state on the DC side. Finally, using a voltage acquisition device, synchronously acquire the three-phase voltage of the grid-connected photovoltaic system and the DC voltage measurement value of the grid-connected photovoltaic inverter. The DC voltage measurement value and the three-phase voltage provide the basic electrical signals for subsequent phase-locked loop phase tracking and grid-connected control strategy calculations, ensuring the accuracy of pre-synchronization control.

[0032] 102. Input the three-phase voltage into the phase-locked loop to obtain the grid voltage phase angle.

[0033] Among them, phase-locked loops such as Figure 4 As shown, the phase-locked loop consists of a coordinate transformation module, a PI controller, and an integral controller. By inputting the three-phase voltage into the phase-locked loop, the phase angle of the grid voltage can be obtained.

[0034] Specifically, the three-phase voltage is input into the phase-locked loop to obtain the grid voltage phase angle, including: The three-phase voltage is input to the coordinate transformation module of the phase-locked loop to perform coordinate transformation, converting the three-phase voltage from the abc stationary coordinate system to the dq rotating coordinate system, obtaining the q-axis voltage component in the dp rotating coordinate system. This represents the q-axis voltage component.

[0035] The q-axis voltage component is input into a PI controller consisting of proportional and integral coefficients, and the output frequency adjustment is achieved.

[0036] The actual tracking angular frequency is obtained by superimposing the frequency adjustment amount with the rated angular frequency of the power grid.

[0037] The actual tracking angular frequency is integrated to obtain the grid voltage phase angle, and the grid voltage phase angle is fed back to the coordinate transformation module.

[0038] In the phase-locked loop (PLL) process, the acquired three-phase grid voltages are first input to the coordinate transformation module. These three-phase grid voltages are instantaneous values ​​in the abc stationary coordinate system. The coordinate transformation module, based on the synchronous rotating coordinate system theory, uses the phase angle of the grid voltage output from the PLL as the rotation reference to construct a dq rotating coordinate system. Through cascaded Clark and Park transformations, the three-phase voltages are first projected onto... The stationary coordinate system is then rotated and projected onto a dq coordinate system that rotates synchronously with the grid voltage, ultimately extracting the q-axis voltage component. The q-axis voltage component directly reflects the deviation between the grid voltage phase and the phase-locked loop tracking phase.

[0039] After obtaining the q-axis voltage component, the q-axis voltage is input to a PI controller consisting of proportional and integral coefficients. The proportional component can quickly respond to phase deviations and immediately output the frequency compensation; the integral component continuously accumulates the deviation to eliminate steady-state errors. The two components are superimposed to output the frequency regulation, which enables the phase-locked loop to track the phase and synchronize with the grid phase, achieving dynamic adaptation to grid frequency fluctuations or initial phase deviations.

[0040] The frequency adjustment amount is compared with the rated angular frequency of the power grid, such as the power frequency of 50Hz. By superimposing the values, the actual tracking angular frequency is obtained, where, The actual tracking angular frequency determines the basic anchor point of the phase-locked loop (PLL) tracking frequency. Dynamically correcting the tracking frequency ensures that the PLL output phase not only matches the actual frequency of the power grid but also responds quickly to phase deviations.

[0041] Finally, the actual tracking angular frequency is integrated, and the transfer function of the integrator is: The phase angle of the grid voltage is obtained, where, Figure 4 middle, The grid voltage phase angle serves two purposes: firstly, it acts as the output of the phase-locked loop (PLL), providing a grid phase reference for the pre-synchronization control of the grid-connected photovoltaic inverter; secondly, it feeds the grid voltage phase angle back to the coordinate transformation module, enabling the rotation reference of the dq rotating coordinate system to be correlated with the output phase angle in real time. This forms a closed-loop control system encompassing coordinate transformation, error adjustment, frequency synthesis, phase output, and feedback correction, ensuring that the PLL continuously and accurately tracks the grid voltage phase. Even when there are harmonics or frequency fluctuations in the grid voltage, it can still stably output a reliable phase reference.

[0042] 103. Unlock the grid-connected photovoltaic inverter, input the DC voltage measurement value to the grid-connected photovoltaic control strategy based on matching control, and output the inverter phase angle of the grid-connected photovoltaic inverter.

[0043] Among them, the grid-type photovoltaic control strategy is an algorithm adapted to the grid-type photovoltaic inverter to autonomously construct voltage phase and support the grid. The logic of the grid-type photovoltaic control strategy is to associate the DC side energy state with the AC side phase output by simulating the rotor dynamic characteristics of a synchronous generator.

[0044] For details, see again. Figure 3 Unlock the grid-connected photovoltaic inverter, input the DC voltage measurement value to the grid-connected photovoltaic control strategy based on matching control, and output the inverter phase angle of the grid-connected photovoltaic inverter, including: Send an unlock command to the grid-connected photovoltaic inverter to release its locked state.

[0045] The DC voltage measurement value of the DC side of the grid-type photovoltaic inverter is collected, and the voltage measurement value is input into the proportional loop for gain adjustment. Then, after the integral loop is used for calculation, the inverter phase angle is output.

[0046] During the pre-synchronization control process, in order to enable the grid-connected photovoltaic inverter to transition from the ready state to the operational state, an unlocking command needs to be sent to the grid-connected photovoltaic inverter. This unlocking command acts on the internal lockout control loop of the grid-connected photovoltaic inverter, releasing the lockout state and enabling the inverter to output power according to subsequent control strategies and participate in pre-synchronization regulation. This creates the hardware operating conditions for subsequent phase generation based on matching control, ensuring that the grid-connected photovoltaic inverter can respond to DC voltage measurements and control strategies, and achieve dynamic adjustment of the inverter phase angle.

[0047] When generating the inverter phase angle, it is necessary to use data acquisition devices such as voltage sensors to obtain the DC voltage measurement value on the DC side of the grid-connected photovoltaic inverter. The DC voltage measurement value reflects the DC side energy state. Next, the DC voltage measurement value is input into a proportional loop. Based on the correspondence between the dynamic DC voltage and the dynamic synchronous generator rotor in the matching control, the gain of the DC voltage measurement value is adjusted through a set proportional coefficient, converting the DC side voltage information into an intermediate signal suitable for phase adjustment requirements. Then, the intermediate signal is input into an integrator. Integral operations are used to simulate the inertial dynamic characteristics of the synchronous generator rotor, converting the voltage-related instantaneous information into a phase quantity that accumulates over time. Finally, the inverter phase angle is output. The inverter phase angle is related to the DC side energy and is a key parameter for grid-connected photovoltaic systems to autonomously construct voltage phase and participate in pre-synchronization control.

[0048] In some embodiments, see again Figure 3 The grid-connected pre-synchronization method and system for grid-connected photovoltaic systems based on matched control also includes: Obtain the reactive power setpoint and reactive power measurement value, and calculate the deviation value of the reactive power setpoint and reactive power measurement value.

[0049] Specifically, based on grid voltage regulation requirements or operational strategies, a preset reactive power setpoint and real-time reactive power measurements from the grid-connected photovoltaic inverter are obtained. The reactive power deviation is calculated by subtracting the reactive power setpoint from the measured reactive power. The reactive power deviation reflects the gap between the current reactive power output and the target value.

[0050] The deviation value is input into a PI controller consisting of a proportional coefficient and an integral coefficient, and the q-axis duty cycle component is output.

[0051] The calculated reactive power deviation is input into a PI controller composed of preset proportional and integral coefficients. The PI controller amplifies and adjusts the instantaneous deviation through the proportional element and continuously corrects the cumulative deviation through the integral element. The two work together to output the q-axis duty cycle component. The q-axis duty cycle component is directly related to the reactive power output of the grid-connected photovoltaic inverter.

[0052] Set the d-axis voltage reference value as the d-axis duty cycle component.

[0053] The coordinate transformation module converts the inverter phase angle, d-axis duty cycle component, and q-axis duty cycle component into a modulated signal of abc stationary coordinates.

[0054] Specifically, based on the amplitude requirements of the output voltage of the grid-connected photovoltaic inverter, a d-axis voltage reference value is preset and directly used as the d-axis duty cycle component. The d-axis duty cycle component mainly affects the amplitude of the output voltage of the grid-connected photovoltaic inverter, and together with the q-axis duty cycle component, they constitute the control quantity in the synchronous rotating dq coordinate system.

[0055] The modulation signal is pulse-width modulated to generate drive information for controlling the output of the grid-type photovoltaic inverter.

[0056] The converted abc stationary coordinate system modulation signal undergoes pulse width modulation (PWM) processing. Based on the amplitude and frequency of the modulation signal, a pulse signal with a specific duty cycle is generated by comparing it with a triangular carrier wave through a comparator. This pulse signal serves as the driving information for the power switching devices of the grid-connected photovoltaic (PV) inverter. By controlling the on and off times of the switching devices, the amplitude, frequency, and phase of the output voltage of the grid-connected PV inverter track the modulation signal, ultimately achieving control over the output characteristics of the grid-connected PV inverter and meeting the pre-synchronization and post-grid connection operation requirements.

[0057] 104. Calculate the phase angle difference between the grid voltage phase angle and the inverter phase angle.

[0058] Specifically, calculating the phase angle difference between the grid voltage phase angle and the inverter phase angle includes: Perform a periodic consistency check on the grid voltage phase angle to obtain the first phase angle.

[0059] The grid voltage phase angle is output in real time by a phase-locked loop (PLL), but its phase angle is subject to periodic drift due to grid frequency fluctuations, harmonic interference, or transient responses of the PLL. A period consistency check compares the grid voltage phase angle with the grid's rated period: if the rate of change of the phase angle over time matches the rated period without abrupt changes, it is determined to be periodically consistent; if a deviation exists, anomalies are corrected through linear interpolation or sliding window filtering to ensure the phase angle is continuous and periodically stable on the time axis, ultimately yielding the verified first phase angle.

[0060] The inverter phase angle is compensated for by hysteresis to obtain the second phase angle.

[0061] The inverter phase angle is generated by the grid-type control strategy. However, the generation path of the inverter phase angle can cause the actual output phase to lag behind the theoretically calculated value. Especially during dynamic adjustment, the lag can affect the accuracy of the phase angle difference. Lag compensation corrects the inverter phase angle in advance by using a pre-calibrated lag time constant. For example, a compensation amount related to the lag time and angular frequency is superimposed on the current inverter phase angle to offset the phase lag caused by the propagation delay, resulting in a corrected second phase angle. This ensures that the phase of the grid-type photovoltaic inverter can truly reflect the actual output state.

[0062] Substituting the first phase angle and the second phase angle into the phase deviation quantization model, the phase angle difference is obtained.

[0063] The phase deviation quantization model, based on trigonometric functions, converts the processed first and second phase angles into phase quantities in a unified reference frame. For example, it calculates the difference between the two. The calculation is performed using periodic normalization to eliminate calculation ambiguities caused by the periodicity of the phase angle. The final output phase angle difference reflects the degree of phase matching between the power grid and the grid-connected photovoltaic inverter output.

[0064] In some embodiments, after substituting the first phase angle and the second phase angle into the phase deviation quantization model to obtain the phase angle difference, the method further includes: Monitor the changing trend of phase angle difference and the harmonic distortion rate of the output voltage of the grid-type photovoltaic inverter; If the phase difference shows a divergent trend and the harmonic distortion rate is lower than the preset allowable upper limit, then increase the correction gain of the phase amplitude correction module. If the phase difference shows a converging trend but the harmonic distortion rate exceeds the preset allowable upper limit, then reduce the correction gain of the phase amplitude correction module. If the phase angle difference fluctuation amplitude is less than the preset steady-state fluctuation threshold and the harmonic distortion rate is within the preset range, the correction gain of the phase amplitude correction module is maintained.

[0065] After obtaining the phase angle difference between the first and second phase angles, it is necessary to continuously collect real-time data of the phase angle difference, calculate the change in the phase angle difference within adjacent sampling periods, and determine whether the overall phase angle difference is divergent, convergent, or fluctuating. In addition, it is also necessary to perform spectral decomposition on the output voltage of the grid-type photovoltaic inverter and calculate the harmonic distortion rate, which reflects the power quality of the output voltage of the grid-type photovoltaic inverter.

[0066] When a diverging trend in the phase angle difference is detected, it indicates that the phase deviation between the grid and the grid-connected photovoltaic inverter is continuously widening. Without intervention, this could lead to pre-synchronization failure. Furthermore, when the harmonic distortion rate of the grid-connected photovoltaic inverter's output voltage is lower than the preset allowable upper limit, the correction gain increase logic is triggered. By increasing the correction gain of the phase amplitude correction module, the module's response sensitivity to the phase angle difference is enhanced, accelerating the speed at which the inverter phase angle approaches the grid phase angle, rapidly curbing the diverging trend of the phase angle difference, and promoting the phase synchronization process.

[0067] If the phase angle difference shows an overall converging trend, it indicates that the adjustment direction is correct and the phase deviation is gradually decreasing. However, if the harmonic distortion rate of the output voltage of the grid-connected photovoltaic inverter exceeds the preset allowable upper limit, then the correction gain reduction operation will be executed. Reducing the correction gain can slow down the adjustment amplitude of the phase angle difference by the phase amplitude correction module, making the change in the inverter phase angle smoother. This avoids exacerbating harmonic problems due to adjustment overshoot and maintains the convergence trend of the phase angle difference while ensuring that the power quality meets the requirements.

[0068] When the fluctuation amplitude of the phase angle difference is less than the preset steady-state fluctuation threshold and the harmonic distortion rate of the output voltage of the grid-type photovoltaic inverter is within the preset qualified range, the correction gain of the phase amplitude correction module remains unchanged. This can avoid unnecessary gain adjustments that could cause secondary fluctuations in the phase angle difference or abnormal harmonic distortion rate, thus ensuring the stable progress of the pre-synchronization process.

[0069] 105. If the phase angle difference is greater than the preset threshold, the phase angle difference is introduced into the phase amplitude correction module, the corrected DC voltage constant value is output, and the phase angle difference is recalculated until the phase angle difference is less than the preset threshold.

[0070] Among them, the phase amplitude correction module is as follows Figure 5 As shown, the phase amplitude correction module is mainly responsible for dynamically adjusting the constant value of the DC voltage output by the grid-type photovoltaic inverter based on the real-time monitored phase angle difference, thereby controlling the output phase of the grid-type photovoltaic inverter. When the phase angle difference is large, the phase amplitude correction module will output a large DC voltage correction value to quickly reduce the phase angle difference; while when the phase angle difference approaches the preset threshold, the phase amplitude correction module will gradually reduce the correction amplitude.

[0071] Specifically, when the calculated phase angle difference exceeds a preset threshold, the adjustment process of the phase amplitude correction module is triggered. The phase amplitude correction module, based on its internal calculation logic, adjusts the input phase angle difference... As shown in Figure XX, the phase angle difference is calculated by correlating the DC voltage reference value. It participates in the input stage of the phase amplitude correction module, and works together with the DC voltage reference value to output a corrected constant DC voltage value.

[0072] The corrected DC voltage constant value is fed back to the DC-side control loop, affecting the voltage state on the DC side of the grid-connected photovoltaic inverter, and thus changing the basis for generating the inverter phase angle. Subsequently, based on the updated DC voltage state, parameters are re-acquired, and the phase angle difference between the grid voltage phase angle and the inverter phase angle is calculated. This adjustment process continues until the phase angle difference is reduced to less than a preset threshold, ensuring that the risk of inrush current due to excessive phase difference during grid connection is effectively avoided.

[0073] 106. If the phase angle difference is less than the preset threshold, close the grid connection switch, close the photovoltaic panel switch, switch the DC voltage switching switch to the DC voltage measurement range, and unlock the DC / DC converter.

[0074] When the detected phase angle difference is less than a preset threshold, it indicates that the output voltage of the grid-connected photovoltaic inverter and the grid voltage have met the safe grid connection requirements in terms of phase. At this time, the grid connection switch is closed sequentially according to the procedure to establish a physical connection path between the grid-connected photovoltaic system and the grid; the photovoltaic panel switch is closed simultaneously to allow the photovoltaic panels to resume supplying power to the grid-connected photovoltaic system; then, the DC voltage switching switch is switched to the DC voltage measurement range to prepare for unlocking and power regulation of the DC / DC converter. Finally, the DC / DC converter is unlocked, allowing it to transition from a locked state to an operational state. Based on the maximum power point tracking control strategy, it can dynamically adjust the energy interaction between the photovoltaic panels and the DC side, achieving efficient conversion and stable grid connection of photovoltaic power, completing the transition of the grid-connected photovoltaic system from pre-synchronization to formal grid-connected operation.

[0075] Furthermore, if a grid-connected photovoltaic system based on matched control is directly connected to the grid from an off-grid state within 1 second, then the grid connection point voltage and output current of the grid-connected photovoltaic system will be as follows: Figure 6 As shown, grid-connected photovoltaic systems cannot operate stably when directly connected to the grid, and they transmit large-amplitude inrush currents to the grid, affecting the grid's stability.

[0076] After adopting the pre-synchronization control method provided by this invention, when a grid-connected photovoltaic system based on matched control is set to connect to the grid from an off-grid state, the grid connection point voltage and output current of the grid-connected photovoltaic system are as follows: Figure 7 As shown, after adopting the pre-synchronization control method, the grid-connected photovoltaic system can be smoothly connected to the grid without causing a strong current surge to the grid.

[0077] In some embodiments, the grid-connected pre-synchronization method for photovoltaic systems based on matching control further includes: Monitor the deviation between the measured DC voltage value and the rated DC voltage value. If the absolute value of the deviation is greater than the first preset percentage of the rated value for a preset number of control cycles, then lock the grid-type photovoltaic inverter, disconnect the photovoltaic panel switch, and record the abnormal status. Monitor the fluctuation of reactive power measurement value. If the fluctuation exceeds the second preset percentage of the reactive power set value within the power grid cycle, the adjustment of the phase amplitude correction module is suspended, and the current DC voltage is maintained at a constant value until the fluctuation is less than the set value and then the correction is started. The phase angle jump of the grid voltage output by the phase-locked loop is monitored. If the absolute value of a single jump is greater than the preset value, the grid voltage is determined to be abnormal, and a grid abnormality signal is output.

[0078] Specifically, the deviation between the measured DC voltage value and the rated DC voltage value of the grid-connected photovoltaic inverter is monitored in real time. When the absolute value of the deviation exceeds a first preset percentage of the rated value for a consecutive preset number of control cycles, a continuous voltage anomaly is determined to have occurred on the DC side. At this time, the protection mechanism is triggered, locking the grid-connected photovoltaic inverter to cut off the output and prevent the abnormal voltage from affecting the subsequent circuits; simultaneously, the photovoltaic panel switch is disconnected to block the energy input source; and the continuous voltage anomaly on the DC side is recorded.

[0079] When continuously monitoring the real-time fluctuations of reactive power measurements, if the fluctuation exceeds the second preset percentage of the reactive power setpoint within a single grid cycle, it indicates insufficient reactive power output stability. To prevent fluctuations from affecting phase synchronization accuracy, the adjustment action of the phase amplitude correction module will be paused, maintaining the current DC voltage constant to temporarily stabilize the inverter phase angle. Once the reactive power fluctuation drops below the set value and the output returns to stability, the correction module will be restarted to ensure phase adjustment is performed on a stable reactive power output basis.

[0080] Finally, the phase angle of the grid voltage output by the phase-locked loop is tracked in real time. If the absolute value of a single jump is detected to be greater than the preset threshold, it indicates that the grid voltage may experience a sudden rise, sudden drop, short circuit, or other faults. The grid voltage is determined to be abnormal, and a grid abnormality signal is output to prevent forced grid connection under grid fault conditions and avoid the spread of faults or damage to equipment due to grid abnormalities.

[0081] In some embodiments, the grid-connected pre-synchronization method for photovoltaic systems based on matching control further includes: Harmonic content, frequency fluctuation rate, and short-circuit capacity parameters of the power grid voltage are collected to construct power grid strength assessment indicators. The power grid strength assessment indicators are obtained by weighted calculation of harmonic distortion rate, frequency change rate, and short-circuit ratio, with weighting coefficients generated based on historical power grid operation data. If the power grid strength assessment index is higher than the preset strong grid threshold, the correction coefficient gain of the phase amplitude correction module will be reduced to decrease the DC voltage adjustment amplitude. If the power grid strength assessment index is lower than the preset weak grid threshold, the correction coefficient gain of the phase amplitude correction module is increased, and a virtual inertia compensation link is introduced to expand the DC voltage phase dynamic response bandwidth.

[0082] To adapt to pre-synchronization control under different power grid operating conditions, it is necessary to first obtain the harmonic content of the power grid voltage through harmonic detection, capture the frequency fluctuation rate, and calculate the short-circuit capacity in combination with the power grid topology and parameters. Subsequently, based on historical power grid operating data, a weighted calculation method is used to construct a power grid strength assessment index: with harmonic distortion rate, frequency change rate, and short-circuit ratio as the basic variables, the weight coefficients of each variable are determined through regression analysis. For example, the short-circuit ratio has a higher weight in strong grid scenarios, while the frequency change rate has a higher weight in weak grid scenarios. Finally, an assessment index that comprehensively reflects the power grid's anti-disturbance capability and power quality is output.

[0083] When the grid strength assessment index is higher than the preset strong grid threshold, it indicates that the grid has strong anti-disturbance capability and good power quality. In scenarios such as large grid main grid access, it is determined that aggressive phase correction is not necessary. At this time, the correction coefficient gain of the phase amplitude correction module is reduced. By reducing the gain value, the DC voltage adjustment amplitude under the same phase angle difference is reduced, avoiding inverter output fluctuations caused by over-correction, and achieving adaptation of the pre-synchronization process to strong grid operating conditions.

[0084] When the grid strength assessment index is lower than the preset weak grid threshold, such as in the end of the distribution network or microgrid scenarios, the grid's anti-disturbance capability is weak and it is easily affected by photovoltaic (PV) grid connection. Therefore, it is necessary to strengthen phase correction capabilities and enhance the inertia support of grid-connected PV systems. On the one hand, the gain of the phase amplitude correction module is increased. By increasing the gain, the convergence speed of the phase angle difference is accelerated, enabling the output phase of the grid-connected PV inverter to track the grid phase more agilely, thus compensating for the insufficient self-regulation capability of the weak grid. On the other hand, a virtual inertia compensation stage is introduced. Based on the dynamic correlation characteristics of DC voltage phase, the dynamic response bandwidth of the DC voltage phase is expanded, simulating the inertia response of a synchronous generator. This provides additional frequency and phase support for the weak grid, enhancing the adaptability of PV grid connection to weak grids.

[0085] Based on the same general inventive concept, this invention also protects a grid-connected photovoltaic pre-synchronization control system based on matched control. The grid-connected photovoltaic pre-synchronization control system based on matched control provided by this invention will be described below. The grid-connected photovoltaic pre-synchronization control system based on matched control described below can be referred to in correspondence with the grid-connected photovoltaic pre-synchronization control method based on matched control described above.

[0086] like Figure 8 As shown, this embodiment of the invention provides a grid-connected photovoltaic pre-synchronization control system based on matched control, comprising: The state initialization unit 810 is used to set the initial state of the DC voltage switching switch, grid connection switch and photovoltaic panel switch according to the preset process, and to collect the three-phase voltage and DC voltage measurement values ​​of the grid-type photovoltaic power grid. The phase acquisition unit 820 is used to input the three-phase voltage into the phase-locked loop to obtain the phase angle of the grid voltage. Unlock the grid-connected photovoltaic inverter, input the DC voltage measurement value to the grid-connected photovoltaic control strategy based on matching control, and output the inverter phase angle of the grid-connected photovoltaic inverter; The phase angle difference calculation and correction unit 830 is used to calculate the phase angle difference between the grid voltage phase angle and the inverter phase angle; If the phase angle difference is greater than the preset threshold, the phase angle difference is introduced into the phase amplitude correction module, the corrected DC voltage constant value is output, and the phase angle difference is recalculated until the phase angle difference is less than the preset threshold. The grid-connected execution unit 840 is used to close the grid-connected switch and the photovoltaic panel switch if the phase angle difference is less than a preset threshold, switch the DC voltage switching switch to the DC voltage measurement range, and send an unlocking command to the DC / DC converter.

[0087] Figure 9 This is a schematic diagram of the structure of the electronic device provided in an embodiment of the present invention.

[0088] like Figure 9 As shown, the electronic device may include a processor 910, a communication interface 920, a memory 930, and a communication bus 940. The processor 910, communication interface 920, and memory 930 communicate with each other via the communication bus 940. The processor 910 can call logic instructions from the memory 930 to execute a grid-connected photovoltaic pre-synchronization control method based on matched control.

[0089] Furthermore, the logical instructions in the aforementioned memory 930 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0090] On the other hand, the present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer is able to execute the grid-connected photovoltaic pre-synchronization control method based on matching control provided by the above methods.

[0091] In another aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to perform the grid-connected pre-synchronization control method for grid-connected photovoltaic systems based on matching control provided by the methods described above.

[0092] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0093] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pre-synchronization control method for grid-connected photovoltaic systems based on matched control, characterized in that, Applied to grid-connected photovoltaic systems, the grid-connected photovoltaic system includes a phase-locked loop, a grid-connected photovoltaic inverter, a DC / DC converter, a phase amplitude correction module, a DC voltage switching switch, a grid-connected switch, and a photovoltaic panel switch, comprising: The initial states of the DC voltage switching switch, the grid connection switch, and the photovoltaic panel switch are set according to the preset procedure, and the three-phase voltage and DC voltage measurement values ​​of the grid-type photovoltaic power grid are collected. The three-phase voltage is input to the phase-locked loop to obtain the grid voltage phase angle; Unlock the grid-connected photovoltaic inverter, input the DC voltage measurement value to the grid-connected photovoltaic control strategy based on matching control, and output the inverter phase angle of the grid-connected photovoltaic inverter; Calculate the phase angle difference between the grid voltage phase angle and the inverter phase angle; If the phase angle difference is greater than a preset threshold, the phase angle difference is introduced into the phase amplitude correction module, a corrected DC voltage constant value is output, and the phase angle difference is recalculated until the phase angle difference is less than the preset threshold. If the phase angle difference is less than the preset threshold, then close the grid-connected switch, close the photovoltaic panel switch, switch the DC voltage switching switch to the DC voltage measurement range, and unlock the DC / DC converter.

2. The pre-synchronization control method for grid-connected photovoltaic systems based on matched control according to claim 1, characterized in that, The initial states of the DC voltage switching switch, the grid-connected switch, and the photovoltaic panel switch are set according to a preset procedure, and the three-phase voltage of the grid-type photovoltaic power grid is collected, including: Confirm that the grid-connected switch and the photovoltaic panel switch are in the off state, switch the DC voltage switching switch to the DC voltage constant value position, and lock the DC / DC converter and the grid-type photovoltaic inverter; the DC voltage constant value position matches the DC voltage constant value. Close the photovoltaic panel switch, unlock the DC / DC converter, raise the DC capacitor of the locked grid-type photovoltaic inverter to the rated value through the DC / DC converter, then lock the DC / DC converter and disconnect the photovoltaic panel switch; Collect the three-phase voltage and DC voltage measurements of the grid-type photovoltaic power grid.

3. The pre-synchronization control method for grid-connected photovoltaic systems based on matched control according to claim 1, characterized in that, The three-phase voltage is input to the phase-locked loop to obtain the grid voltage phase angle, including: The three-phase voltage is input into the coordinate transformation module of the phase-locked loop to perform coordinate transformation on the three-phase voltage, so that the three-phase voltage is transformed from the abc stationary coordinate system to the dq rotating coordinate system, and the q-axis voltage component in the dp rotating coordinate system is obtained. The q-axis voltage component is input into a PI controller consisting of a proportional coefficient and an integral coefficient, and the output frequency adjustment is achieved. The actual tracking angular frequency is obtained by superimposing the frequency adjustment amount with the rated angular frequency of the power grid. The actual tracking angular frequency is integrated to obtain the grid voltage phase angle, and the grid voltage phase angle is fed back to the coordinate transformation module.

4. The pre-synchronization control method for grid-connected photovoltaic systems based on matched control according to claim 1, characterized in that, Unlock the grid-connected photovoltaic inverter, input the DC voltage measurement value to the grid-connected photovoltaic control strategy based on matched control, and output the inverter phase angle of the grid-connected photovoltaic inverter, including: Send an unlock command to the grid-connected photovoltaic inverter to release the locked state of the grid-connected photovoltaic inverter; The DC voltage measurement value of the DC side of the grid-type photovoltaic inverter is collected, and the DC voltage measurement value is input into the proportional circuit for gain adjustment, and then processed by the integral circuit to output the inverter phase angle.

5. The pre-synchronization control method for grid-connected photovoltaic systems based on matched control according to claim 3, characterized in that, Also includes: Obtain the reactive power setpoint and the reactive power measured value, and calculate the deviation value between the reactive power setpoint and the reactive power measured value; The deviation value is input into a PI controller consisting of a proportional coefficient and an integral coefficient, and the q-axis duty cycle component is output. Set a reference value for the d-axis voltage as the d-axis duty cycle component; The coordinate transformation module converts the inverter phase angle, the d-axis duty cycle component, and the q-axis duty cycle component into a modulation signal for the abc stationary coordinates. The modulation signal is pulse-width modulated to generate drive information for controlling the output of the grid-type photovoltaic inverter.

6. The pre-synchronization control method for grid-connected photovoltaic systems based on matched control according to claim 1, characterized in that, Calculating the phase angle difference between the grid voltage phase angle and the inverter phase angle includes: Perform a periodic consistency check on the grid voltage phase angle to obtain the first phase angle; Hysteresis compensation is performed on the inverter phase angle to obtain the second phase angle; Substituting the first phase angle and the second phase angle into the phase deviation quantization model, the phase angle difference is obtained.

7. The pre-synchronization control method for grid-connected photovoltaic systems based on matched control according to claim 6, characterized in that, Substituting the first phase angle and the second phase angle into the phase deviation quantization model, after obtaining the phase angle difference, the method further includes: Monitor the changing trend of the phase angle difference and the harmonic distortion rate of the output voltage of the grid-type photovoltaic inverter; If the phase angle difference shows a divergent trend and the harmonic distortion rate is lower than the preset allowable upper limit, then increase the correction gain of the phase amplitude correction module; If the phase angle difference shows a converging trend but the harmonic distortion rate exceeds the preset allowable upper limit, then reduce the correction gain of the phase amplitude correction module; If the phase angle difference fluctuation amplitude is less than the preset steady-state fluctuation threshold and the harmonic distortion rate is within the preset range, then the correction gain of the phase amplitude correction module is maintained.

8. The pre-synchronization control method for grid-connected photovoltaic systems based on matched control according to claim 1, characterized in that, Also includes: Monitor the deviation between the measured DC voltage value and the rated DC voltage value. If the absolute value of the deviation is greater than a first preset percentage of the rated value for a preset number of control cycles, then lock the grid-type photovoltaic inverter, disconnect the photovoltaic panel switch, and record the abnormal state. The fluctuation of reactive power measurement value is monitored. If the fluctuation exceeds the second preset percentage of the reactive power set value within the power grid cycle, the adjustment of the phase amplitude correction module is suspended, and the current DC voltage is maintained at a constant value until the fluctuation is less than the set value and then the correction is started. The phase angle jump of the grid voltage output by the phase-locked loop is monitored. If the absolute value of a single jump is greater than the preset value, the grid voltage is determined to be abnormal, and a grid abnormality signal is output.

9. The pre-synchronization control method for grid-connected photovoltaic systems based on matched control according to claim 1, characterized in that, Also includes: Harmonic content, frequency fluctuation rate, and short-circuit capacity parameters of the power grid voltage are collected to construct a power grid strength assessment index. The power grid strength assessment index is obtained by weighted calculation of harmonic distortion rate, frequency change rate, and short-circuit ratio, and the weighting coefficients are generated based on historical power grid operation data. If the power grid strength assessment index is higher than the preset strong grid threshold, the correction coefficient gain of the phase amplitude correction module is reduced to decrease the DC voltage adjustment amplitude. If the power grid strength assessment index is lower than the preset weak grid threshold, the correction coefficient gain of the phase amplitude correction module is increased, and a virtual inertia compensation link is introduced to expand the DC voltage phase dynamic response bandwidth.

10. A grid-connected photovoltaic pre-synchronization control system based on matched control, characterized in that, include: The state initialization unit is used to set the initial state of the DC voltage switching switch, grid connection switch and photovoltaic panel switch according to the preset process, and to collect the three-phase voltage and DC voltage measurement values ​​of the grid-type photovoltaic power grid. The phase acquisition unit is used to input the three-phase voltage into the phase-locked loop to obtain the grid voltage phase angle; Unlock the grid-connected photovoltaic inverter, input the DC voltage measurement value to the grid-connected photovoltaic control strategy based on matching control, and output the inverter phase angle of the grid-connected photovoltaic inverter; A phase angle difference calculation and correction unit is used to calculate the phase angle difference between the grid voltage phase angle and the inverter phase angle; If the phase angle difference is greater than a preset threshold, the phase angle difference is introduced into the phase amplitude correction module, a corrected DC voltage constant value is output, and the phase angle difference is recalculated until the phase angle difference is less than the preset threshold. The grid-connected execution unit is used to close the grid-connected switch and the photovoltaic panel switch if the phase angle difference is less than the preset threshold, switch the DC voltage switching switch to the DC voltage measurement range, and send an unlocking command to the DC / DC converter.

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