Matching control method and control equipment of network-forming type photovoltaic inverter and photovoltaic system

Abstract

The invention provides a matching control method and control equipment of a network-forming photovoltaic inverter and a photovoltaic system, and belongs to the photovoltaic field. The method comprises the following steps: acquiring a reference voltage and an actual voltage of a bus of a photovoltaic system; determining a difference value between the reference voltage of the bus and the actual voltage of the bus; according to the difference value, inertia control is carried out, and the frequency adjustment amount is determined; and determining a reference phase angle based on the frequency adjustment amount, and performing network construction type control on the photovoltaic inverter according to the reference phase angle. Charge and discharge characteristics of the bus capacitor can be utilized to simulate characteristics of the generator, the inertia control problem of the grid-forming type photovoltaic inverter is solved, grid-forming type control of the photovoltaic inverter is further realized, the photovoltaic inverter is equivalent to a voltage source, a power grid can be supported, and the stability of the power grid is improved.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, and in particular to a matching control method, control equipment, and photovoltaic system for a grid-connected photovoltaic inverter. Background Technology

[0002] The penetration rate of photovoltaic (PV) systems in the power system continues to increase, gradually forming a "dual-high" power grid configuration characterized by a high proportion of renewable energy and a high proportion of power electronic equipment. Against this backdrop, large-scale centralized integration of PV power generation can easily lead to a decrease in grid strength, triggering weak grid operation conditions and posing a severe challenge to system stability.

[0003] In related technologies, photovoltaic inverters typically employ a grid-following control strategy, where the inverter can be considered equivalent to a controlled current source, with the phase and amplitude of its output current tracking the grid voltage. However, this control method struggles to provide the inertial response capability of a synchronous generator, and cannot effectively support system frequency and voltage when grid disturbances occur. This exacerbates operational risks under high-voltage and high-frequency grid conditions, and is particularly prone to oscillation and instability problems under weak grid conditions.

[0004] To enhance grid stability, grid-based control technology is gaining increasing attention. Under this control method, the photovoltaic inverter can be considered an equivalent voltage source, possessing the ability to actively adjust its output voltage and frequency. It can provide inertia and voltage support to the grid, helping to improve dynamic performance under weak grid conditions. However, in photovoltaic power generation systems, effectively achieving a reliable transition from grid-following control to grid-based control for photovoltaic inverters, and ensuring their stable operation in weak grid environments, remains a key technical challenge that urgently needs to be overcome. Summary of the Invention

[0005] This invention provides a matching control method, control device, and photovoltaic system for a grid-connected photovoltaic inverter, thereby solving the problem that existing technologies cannot achieve grid-connected control of photovoltaic inverters.

[0006] In a first aspect, embodiments of the present invention provide a matching control method for a grid-connected photovoltaic inverter, comprising: Obtain the reference voltage and actual voltage of the photovoltaic system's busbar; Determine the difference between the reference voltage and the actual voltage of the busbar; Based on the difference, inertia control is performed to determine the frequency adjustment amount; The reference phase angle is determined based on the frequency adjustment, and the grid configuration control of the photovoltaic inverter is performed based on the reference phase angle.

[0007] In one possible implementation, obtaining the reference voltage of the photovoltaic system's bus includes: Obtain the actual voltage and actual current of the photovoltaic array in the photovoltaic system; The reference voltage of the busbar is determined based on the actual voltage and actual current of the photovoltaic array.

[0008] In one possible implementation, the reference voltage of the bus is determined based on the actual voltage and actual current of the photovoltaic array, including: Based on the preset maximum power point tracking algorithm, the reference voltage of the bus is determined according to the actual voltage and actual current of the photovoltaic array.

[0009] In one possible implementation, based on a preset maximum power point tracking algorithm, the reference voltage of the bus is determined according to the actual voltage and actual current of the photovoltaic array, including: The actual voltage and actual current of the photovoltaic array are used as inputs to the preset maximum power point tracking algorithm to obtain the candidate bus reference voltage output by the preset maximum power point tracking algorithm. The candidate bus reference voltage is subjected to amplitude limiting to obtain the bus reference voltage, which limits the bus reference voltage to between the maximum power point tracking voltage and the open circuit voltage of the photovoltaic array.

[0010] In one possible implementation, inertia control is performed based on the difference to determine the frequency adjustment amount, including: Obtain the inertia coefficient; Inertia control is performed based on the difference, inertia coefficient, and integral processing to determine the frequency change.

[0011] In one possible implementation, the reference phase angle is determined based on the frequency adjustment amount, including: Obtain the rated frequency; Determine the reference frequency based on the rated frequency and the frequency adjustment amount; The reference phase angle is obtained by integrating the reference frequency.

[0012] In one possible implementation, grid-type control of the photovoltaic inverter is performed based on a reference phase angle, including: Obtain the reference voltage amplitude; The reference voltage is determined based on the reference voltage amplitude and the reference phase angle; Grid-based control of the photovoltaic inverter is performed based on the reference voltage.

[0013] In one possible implementation, the photovoltaic system is a centralized photovoltaic system.

[0014] Secondly, embodiments of the present invention provide a matching control device for a grid-connected photovoltaic inverter, comprising: The acquisition module is used to acquire the reference voltage and actual voltage of the photovoltaic system's bus. The difference determination module is used to determine the difference between the reference voltage and the actual voltage of the bus. The inertia control module is used to perform inertia control based on the difference and determine the frequency adjustment amount. The grid control module is used to determine the reference phase angle based on the frequency adjustment amount and to perform grid-type control of the photovoltaic inverter according to the reference phase angle.

[0015] Thirdly, embodiments of the present invention provide a control device, including a processor and a memory, wherein the memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory to execute the matching control method for a grid-connected photovoltaic inverter as described in the first aspect or any possible implementation thereof.

[0016] Fourthly, embodiments of the present invention provide a photovoltaic system, including a photovoltaic array, a bus, a photovoltaic inverter, and a control device as described in the third aspect; The busbars are connected to the photovoltaic array and the photovoltaic inverter respectively; the photovoltaic inverter is controlled by the control equipment.

[0017] Fifthly, embodiments of the present invention provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the matching control method for a grid-connected photovoltaic inverter as described in the first aspect or any possible implementation thereof.

[0018] This invention provides a matching control method, control device, and photovoltaic system for a grid-connected photovoltaic inverter. The method uses the difference between the reference voltage and the actual voltage of the bus to perform inertia control, determine the frequency adjustment amount, and determine the reference phase angle based on the frequency adjustment amount. Grid-connected control of the photovoltaic inverter is then performed according to the reference phase angle. This allows the charging and discharging characteristics of the bus capacitor to simulate the characteristics of a generator, solving the inertia control problem of the grid-connected photovoltaic inverter and achieving grid-connected control of the photovoltaic inverter. This makes the photovoltaic inverter equivalent to a voltage source, providing support to the power grid and improving grid stability. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of a photovoltaic system provided in an embodiment of the present invention; Figure 2This is a flowchart illustrating the implementation of a matching control method for a grid-connected photovoltaic inverter according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the control loop of a photovoltaic inverter provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the control loop of a photovoltaic inverter provided in another embodiment of the present invention; Figure 5 This is a schematic diagram of a matching control device for a grid-type photovoltaic inverter provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of a control device provided in an embodiment of the present invention. Detailed Implementation

[0021] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described below in conjunction with the accompanying drawings.

[0023] See Figure 1 This diagram illustrates the structure of a photovoltaic system according to an embodiment of the present invention. The photovoltaic system may include a photovoltaic array 11, a bus, a photovoltaic inverter 12, and a control device; the bus connects the photovoltaic array 11 and the photovoltaic inverter 12 respectively; the photovoltaic inverter 12 is controlled by the control device. The control device is used to execute the matching control method for grid-connected photovoltaic inverters in subsequent embodiments.

[0024] See Figure 1 The busbar is a DC busbar, which may include a positive DC bus BUS+ and a negative DC bus BUS-. A busbar capacitor may be connected between the positive DC bus BUS+ and the negative DC bus BUS-. Figure 1 (Not shown in the image).

[0025] The photovoltaic array 11 may include multiple photovoltaic strings connected in parallel, and each photovoltaic string may include multiple photovoltaic modules connected in series. The number of photovoltaic modules in each photovoltaic string may be the same or different, depending on actual needs. The photovoltaic modules can convert solar energy into direct current (DC), and the photovoltaic array 11 can aggregate the conversion capabilities of numerous photovoltaic modules to output the DC power required by the subsequent photovoltaic inverter 12.

[0026] The positive output terminal of photovoltaic array 11 is connected to the positive DC bus BUS+, and the negative output terminal of photovoltaic array 11 is connected to the negative DC bus BUS-. The positive DC bus BUS+ is connected to the positive input terminal of photovoltaic inverter 12, and the negative DC bus BUS- is connected to the negative input terminal of photovoltaic inverter 12.

[0027] The photovoltaic inverter 12 can also be connected to the power grid 13. The photovoltaic inverter 12 may include an inverter circuit for converting direct current to alternating current, providing support to the power grid 13 and improving the stability of the power grid 13.

[0028] This application does not limit the specific composition of the photovoltaic array 11 or the specific topology of the photovoltaic inverter 12; any feasible composition or structure is acceptable.

[0029] The following is based on Figure 1 , combined Figure 2 The matching control method for grid-type photovoltaic inverters provided in the embodiments of this application will be described.

[0030] See Figure 2 The diagram illustrates the implementation flowchart of the matching control method for a grid-connected photovoltaic inverter provided in this embodiment of the invention. The execution subject of the matching control method for the grid-connected photovoltaic inverter is a control device, which can be a controller, such as a DSP (Digital Signal Processor), etc.

[0031] See Figure 2 The matching control method for this grid-connected photovoltaic inverter is described in detail below: In S201, the reference voltage and actual voltage of the photovoltaic system's bus are obtained.

[0032] The reference voltage of the busbar can also be called the given voltage or target voltage of the busbar, which can be understood as the voltage that the busbar needs to achieve. The reference voltage of the busbar can be a pre-set reference voltage or a reference voltage determined by other means; no specific restrictions are made here.

[0033] The actual voltage of the busbar is the current voltage of the busbar, which can be obtained through a voltage acquisition device or other means.

[0034] In this embodiment of the application, it is necessary to use a certain control method to make the actual voltage of the bus reach or approach the reference voltage of the bus.

[0035] This application does not impose specific restrictions on the method of obtaining the reference voltage and actual voltage of the photovoltaic system bus; any feasible method is acceptable.

[0036] In S202, the difference between the reference voltage of the bus and the actual voltage of the bus is determined.

[0037] In the embodiments of this application, see Figure 3 The reference voltage U of the busbar bus_ref Subtract the actual voltage U of the bus bus_fdb The above difference was obtained.

[0038] In S203, inertia control is performed based on the difference to determine the frequency adjustment amount.

[0039] See Figure 3 Reference voltage U based on the bus bus_ref and the actual voltage U of the bus bus_fdb The difference is used for inertia control, which generates a frequency adjustment amount W1. The frequency adjustment amount W1 is used to adjust the rated frequency of the photovoltaic inverter so that the actual voltage U of the bus is adjusted accordingly. bus_fdb The reference voltage U near the bus bus_ref The direction adjustment. The frequency adjustment amount W1 is the frequency adjustment amount of the photovoltaic inverter.

[0040] In S204, the reference phase angle is determined based on the frequency adjustment amount, and the grid configuration control of the photovoltaic inverter is performed according to the reference phase angle.

[0041] In the embodiments of this application, see Figure 3 After determining the frequency adjustment amount W1 of the photovoltaic inverter, the reference phase angle θ of the photovoltaic inverter can be further determined based on the frequency adjustment amount W1. Then, grid-type control of the photovoltaic inverter can be performed based on the reference phase angle θ to ensure that the actual voltage U of the aforementioned bus is... bus_fdb Reaching the reference voltage U of the bus bus_ref .

[0042] The reference phase angle θ, also known as the given phase angle or target phase angle, is the reference phase angle for the output voltage of the photovoltaic inverter.

[0043] For example, when the grid frequency decreases, the photovoltaic inverter needs to provide more power to support the grid. The inverter draws more energy from the bus to increase power output and counteract the frequency drop, effectively adding electronic inertia to the grid. This increased energy draw from the bus causes the bus capacitors to discharge, leading to a decrease in the actual bus voltage. The method provided in this application adjusts the actual bus voltage to reach the bus's reference voltage. Conversely, when the grid frequency increases, the photovoltaic inverter reduces its output power, and the actual bus voltage increases accordingly. The method provided in this application adjusts the actual bus voltage to reach the bus's reference voltage.

[0044] This application embodiment uses the difference between the reference voltage and the actual voltage of the busbar to perform inertia control, determine the frequency adjustment amount, and determine the reference phase angle based on the frequency adjustment amount. Grid-type control of the photovoltaic inverter is then performed based on the reference phase angle. This allows the charging and discharging characteristics of the busbar capacitor to simulate the characteristics of a generator, solving the inertia control problem of grid-type photovoltaic inverters. This enables grid-type control of the photovoltaic inverter, making it equivalent to a voltage source, providing support to the power grid and improving grid stability.

[0045] Traditional photovoltaic (PV) inverters employ a grid-connected control method, relying on the grid to provide stable voltage and frequency for operation. When grid disturbances occur, they may shut down, further exacerbating grid instability. In contrast, the grid-connected PV inverter of this application functions like a miniature generator, capable of autonomously establishing and maintaining grid frequency stability. Specifically, when the grid frequency changes (manifested as fluctuations in the actual voltage of the bus), the grid-connected PV inverter can rapidly absorb or release energy (manifested as charging and discharging of the bus capacitors) to generate power inversely to the rate of frequency change, actively suppressing frequency fluctuations and thus significantly improving grid stability. Furthermore, the grid-connected PV inverter is capable of remaining grid-connected and not disconnecting when grid anomalies occur (e.g., frequency changes).

[0046] In addition, the embodiments of this application cleverly combine bus voltage control and inertia control. It does not rely on complex communication and central dispatch. It can support the grid frequency simply by measuring the actual voltage of the local bus. It is a distributed, autonomous intelligent control that is very reliable and easy to expand.

[0047] The embodiments of this application determine the reference phase angle by adjusting the frequency, so that the photovoltaic inverter can smoothly adjust the phase of the output voltage, enabling it to be seamlessly synchronized with the grid and avoiding grid connection shocks.

[0048] In some embodiments, in S201, obtaining the reference voltage of the photovoltaic system bus includes: Obtain the actual voltage and actual current of the photovoltaic array in the photovoltaic system; The reference voltage of the busbar is determined based on the actual voltage and actual current of the photovoltaic array.

[0049] Among them, see Figure 4 The actual voltage U of the photovoltaic array pv The actual output voltage of the photovoltaic array, and the actual current I of the photovoltaic array. pv The actual output current of the photovoltaic array can be determined using methods found in related technologies, and no specific limitations are imposed here.

[0050] This application embodiment can be based on the actual voltage U of the photovoltaic array. pvand the actual current I of the photovoltaic array pv Determine an optimal bus reference voltage U for the photovoltaic system. bus_ref The reference voltage U of the busbar bus_ref It can change with the actual voltage U of the photovoltaic array pv and actual current I pv It changes with the changes, and is no longer a fixed value, so it can be combined with photovoltaic characteristics.

[0051] This application embodiment is based on the actual voltage U of the photovoltaic array. pv and the actual current I of the photovoltaic array pv Determine the reference voltage U of the bus. bus_ref There are no specific restrictions on the specific means of implementation; any feasible means are acceptable.

[0052] In this embodiment, the reference voltage of the bus is no longer a fixed value or simply specified by a host computer, but is related to the actual working state of the photovoltaic array. This allows for dynamic and adaptive adjustment of the reference voltage of the bus, enhancing the stability and robustness of the photovoltaic system.

[0053] Specifically, if the reference voltage of the bus is a fixed value, when the irradiance changes drastically, the output power of the photovoltaic array will suddenly change, causing the actual voltage of the bus to fluctuate drastically. This may trigger the overvoltage or undervoltage protection of the photovoltaic system, leading to grid disconnection. However, the embodiments of this application combine the reference voltage of the bus with the actual output of the photovoltaic array, making the reference voltage of the bus a reasonable value that matches the current power generation capacity. When the irradiance changes, the reference voltage of the bus will automatically adapt and adjust, thereby improving the operational stability and robustness of the photovoltaic system in variable environments.

[0054] In some embodiments, see Figure 4 The reference voltage of the busbar is determined based on the actual voltage and actual current of the photovoltaic array, including: Based on the preset Maximum Power Point Tracking (MPPT) algorithm, according to the actual voltage U of the photovoltaic array pv and the actual current I of the photovoltaic array pv Determine the reference voltage U of the bus. bus_ref .

[0055] The preset maximum power point tracking algorithm can be a pre-defined MPPT algorithm, or any MPPT algorithm, without specific limitations. For example, it can be the perturbation observation method, the incremental conductance method, or the current scanning method, etc.

[0056] This application embodiment uses a preset MPPT algorithm and the actual voltage U of the photovoltaic array.pv and the actual current I of the photovoltaic array pv The reference voltage U of the bus can be determined. bus_ref .

[0057] In some possible implementations, the actual voltage U of the photovoltaic array pv and the actual current I of the photovoltaic array pv It can be used as input to a preset MPPT algorithm, which will output a current optimal operating voltage for the photovoltaic array. This current optimal operating voltage can be used as the reference voltage U for the bus. bus_ref Alternatively, a certain voltage value can be subtracted from or added to the current optimal operating voltage to serve as the reference voltage U for the bus. bus_ref The current optimal operating voltage is the voltage corresponding to the current maximum power point of the photovoltaic array, as determined by the preset MPPT algorithm.

[0058] This application embodiment is based on a preset MPPT algorithm. According to the actual voltage and actual current of the photovoltaic array, the reference voltage of the bus is determined. Subsequently, the actual voltage of the bus is controlled to reach the reference voltage of the bus. This can make the photovoltaic array work at or near its maximum power point as much as possible, and improve the power generation efficiency of the photovoltaic system while meeting the grid demand.

[0059] In some embodiments, see Figure 4 The above is based on a preset maximum power point tracking algorithm, according to the actual voltage U of the photovoltaic array. pv and the actual current I of the photovoltaic array pv Determine the reference voltage U of the bus. bus_ref ,include: The actual voltage U of the photovoltaic array pv and the actual current I of the photovoltaic array pv As input to the preset maximum power point tracking algorithm, the candidate bus reference voltage output by the preset maximum power point tracking algorithm is obtained; The candidate bus reference voltage is limited to obtain the bus reference voltage U. bus_ref This makes the reference voltage U of the busbar bus_ref The voltage is limited to between the maximum power point tracking voltage and the open-circuit voltage of the photovoltaic array.

[0060] The P (power)-V (voltage) curve of a photovoltaic (PV) array initially shows that power increases with increasing voltage. Then, at the maximum power point tracking (MPPT) voltage, the power reaches its maximum value. Afterward, the power decreases with increasing voltage until it reaches the open-circuit voltage, at which point the power becomes zero. The MPPT voltage and the open-circuit voltage of the PV array have a certain proportional relationship. In this embodiment, the MPPT voltage is obtained by multiplying the open-circuit voltage by a preset proportionality coefficient. This preset coefficient can be in the range of 0.75-0.85, for example, it could be 0.78, 0.8, or 0.82, etc. The open-circuit voltage of the PV array can be determined by consulting product parameters or by actual measurement; no specific limitation is made here.

[0061] See Figure 4 In this application embodiment, the actual voltage U of the photovoltaic array is first... pv and the actual current I of the photovoltaic array pv As input to the preset maximum power point tracking algorithm, the candidate bus reference voltage output by the preset MPPT algorithm is obtained. This candidate bus reference voltage can be the current optimal operating voltage as determined by the preset MPPT algorithm, or the voltage value obtained by subtracting or adding a certain voltage value to the current optimal operating voltage. Then, the candidate bus reference voltage is subjected to amplitude limiting processing to obtain the bus reference voltage U. bus_ref The purpose of the limiting process is to ensure that the reference voltage U of the bus is within acceptable limits. bus_ref The reference voltage is limited to between the maximum power point tracking voltage (inclusive) and the open-circuit voltage (exclusive) of the photovoltaic array. Specifically, if the candidate bus reference voltage is within the above range, then the bus reference voltage U... bus_ref The candidate bus reference voltage is used. If the candidate bus reference voltage is not within the above range, then the bus reference voltage U... bus_ref The critical value that is closest to the candidate bus reference voltage.

[0062] This embodiment limits the reference voltage of the busbar to between the maximum power point tracking voltage (MPPT) and the open-circuit voltage of the photovoltaic (PV) array. This is equivalent to adjusting the actual voltage of the busbar to between these two voltages. Since the busbar is connected to the PV array, the actual voltage of the PV array is limited to this range, meaning it's confined to a region where power decreases as voltage increases. Specifically, if the actual voltage of the PV array rises, its actual power decreases; conversely, if the actual voltage decreases, its actual power increases. If a disturbance causes the actual voltage of the busbar to rise (i.e., the actual voltage of the PV array also rises), its actual power will naturally decrease. This power reduction will prevent the PV array from supporting higher voltages, causing the actual voltage of the busbar to be pulled back to its original value, and vice versa. This effectively creates a negative feedback mechanism, making the operating point more stable.

[0063] Zooming out to the photovoltaic system and the power grid, when the grid needs more power, the photovoltaic inverter increases its output power, causing a decrease in the actual voltage of the bus, i.e., a decrease in the actual voltage of the photovoltaic array. This results in an increase in the actual power of the photovoltaic array, which in turn compensates for the energy consumed by the photovoltaic inverter, helping the photovoltaic system restore balance. Conversely, when the grid needs less power, the photovoltaic inverter decreases its output power, causing an increase in the actual voltage of the bus, i.e., an increase in the actual voltage of the photovoltaic array. This results in a decrease in the actual power of the photovoltaic array, which in turn reduces the energy supplied to the photovoltaic inverter, helping the photovoltaic system restore balance.

[0064] In some embodiments, see Figure 3 and Figure 4 Based on the difference, inertia control is performed to determine the frequency adjustment amount, including: Obtain the inertia coefficient J; Based on the difference, inertia coefficient J, and integral processing, inertia control is performed to determine the frequency change W1.

[0065] See Figure 3 and Figure 4 Multiplying the above difference by 1 / (Js) yields the frequency change W1. Here, J is the inertia coefficient, the value of which can be set according to actual needs; 1 / s is the integral operation, and s is the Laplace operator.

[0066] The embodiments of this application can set the sensitivity and resistance of the photovoltaic system to frequency changes through the inertia coefficient. Based on the difference, inertia coefficient and integral processing, inertia control is performed to determine the frequency change. In essence, it simulates the rotor motion of a generator. It can be understood as creating a virtual rotor that connects the DC bus energy and the AC grid frequency, so that the photovoltaic inverter can sense the frequency change of the grid like a generator and provide dynamic frequency support for the grid.

[0067] In some embodiments, see Figure 3 and Figure 4 Determining the reference phase angle based on the frequency adjustment includes: Obtain the rated frequency W n ; According to the rated frequency W n And the frequency adjustment amount W1, determine the reference frequency; The reference phase angle θ is obtained by integrating the reference frequency.

[0068] The reference frequency can also be called the given frequency or the target frequency.

[0069] In this embodiment of the application, the rated frequency W n The rated frequency of the photovoltaic inverter is usually equal to the rated frequency of the power grid, for example, 50Hz. The rated frequency W... n The sum of the frequency adjustment amount W1 and the frequency adjustment amount W1 is used as the reference frequency of the photovoltaic inverter. Integrating the reference frequency of the photovoltaic inverter, the reference phase angle θ of the photovoltaic inverter is obtained.

[0070] The fundamental difference between a grid-connected inverter and a grid-linked inverter lies in the fact that the latter does not rely on the voltage and phase angle of the existing power grid, but instead generates its own reference voltage and reference frequency. The embodiments of this application determine the reference phase, and then determine the reference voltage based on the reference phase, autonomously constructing the voltage to achieve true grid-connected photovoltaic inverter functionality.

[0071] The active power transmission between the photovoltaic system and the power grid is mainly determined by the voltage phase angle difference between the two. In this embodiment, the rated frequency is adjusted by a frequency adjustment amount to determine the reference frequency. The integrated reference phase angle will produce a difference with the phase angle of the power grid. The phase angle difference will automatically and without additional control realize the flow of active power, thereby balancing the power deficit. Moreover, the reference phase angle is the integral of the reference frequency, which means that the phase angle cannot change abruptly. Any instantaneous change in frequency requires time to accumulate into a significant change in phase angle. This physical process directly simulates the mechanical inertia of the huge rotor of a synchronous generator, making the power output response of the photovoltaic inverter smooth rather than instantaneous step. This provides stable inertia for the power grid and effectively dampens power oscillations.

[0072] In some embodiments, grid-type control of the photovoltaic inverter is performed based on a reference phase angle, including: Obtain the reference voltage amplitude; The reference voltage is determined based on the reference voltage amplitude and the reference phase angle; Grid-based control of the photovoltaic inverter is performed based on the reference voltage.

[0073] The method for obtaining the reference voltage amplitude is a mature technology in the relevant field and will not be elaborated further.

[0074] Based on the reference voltage amplitude and reference phase angle of the photovoltaic inverter, a reference voltage for the photovoltaic inverter, i.e., the reference output voltage of the photovoltaic inverter, can be generated, which may include the A-phase reference voltage, B-phase reference voltage, and C-phase reference voltage. This reference voltage is used as the voltage setpoint for the voltage control loop of the photovoltaic inverter, thereby obtaining the reference current of the photovoltaic inverter. This reference current is then used as the current setpoint for the current control loop of the photovoltaic inverter, thereby obtaining the control quantity of the photovoltaic inverter. Finally, based on this control quantity, corresponding control is performed on the photovoltaic inverter to achieve grid-type control of the photovoltaic inverter.

[0075] This application embodiment enables the regulation of active power and grid frequency by referencing the phase angle, and the regulation of reactive power and grid voltage by referencing the voltage amplitude. This decoupled control allows the system to simultaneously and independently address grid frequency and voltage issues. This application embodiment can realize a grid-connected photovoltaic inverter that exhibits ideal voltage source characteristics, allowing its output voltage to be determined by its own control and unaffected by external disturbances.

[0076] In some embodiments, the photovoltaic system is a centralized photovoltaic system.

[0077] The method provided in this application embodiment can be applied to centralized photovoltaic systems, such as... Figure 1 The photovoltaic system shown is a centralized photovoltaic system where the photovoltaic inverter does not include a boost circuit.

[0078] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0079] Figure 5 A schematic diagram of the matching control device for a grid-connected photovoltaic inverter provided in an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below: like Figure 5 As shown, the matching control device 30 for a grid-connected photovoltaic inverter includes: an acquisition module 31, a difference determination module 32, an inertia control module 33, and a grid-connected control module 34.

[0080] The acquisition module 31 is used to acquire the reference voltage and actual voltage of the bus of the photovoltaic system; The difference determination module 32 is used to determine the difference between the reference voltage of the bus and the actual voltage of the bus; The inertia control module 33 is used to perform inertia control based on the difference and determine the frequency adjustment amount. The grid control module 34 is used to determine the reference phase angle based on the frequency adjustment amount and to perform grid-type control on the photovoltaic inverter according to the reference phase angle.

[0081] In one possible implementation, the acquisition module 31 acquires the reference voltage of the photovoltaic system's bus, including: Obtain the actual voltage and actual current of the photovoltaic array in the photovoltaic system; The reference voltage of the busbar is determined based on the actual voltage and actual current of the photovoltaic array.

[0082] In one possible implementation, in the acquisition module 31, the reference voltage of the bus is determined based on the actual voltage and actual current of the photovoltaic array, including: Based on the preset maximum power point tracking algorithm, the reference voltage of the bus is determined according to the actual voltage and actual current of the photovoltaic array.

[0083] In one possible implementation, in the acquisition module 31, based on a preset maximum power point tracking algorithm, the reference voltage of the bus is determined according to the actual voltage and actual current of the photovoltaic array, including: The actual voltage and actual current of the photovoltaic array are used as inputs to the preset maximum power point tracking algorithm to obtain the candidate bus reference voltage output by the preset maximum power point tracking algorithm. The candidate bus reference voltage is subjected to amplitude limiting to obtain the bus reference voltage, which limits the bus reference voltage to between the maximum power point tracking voltage and the open circuit voltage of the photovoltaic array.

[0084] In one possible implementation, in the inertia control module 33, inertia control is performed based on the difference to determine the frequency adjustment amount, including: Obtain the inertia coefficient; Inertia control is performed based on the difference, inertia coefficient, and integral processing to determine the frequency change.

[0085] In one possible implementation, the reference phase angle is determined in the network control module 34 based on the frequency adjustment amount, including: Obtain the rated frequency; Determine the reference frequency based on the rated frequency and the frequency adjustment amount; The reference phase angle is obtained by integrating the reference frequency.

[0086] In one possible implementation, the grid control module 34 performs grid-type control of the photovoltaic inverter based on a reference phase angle, including: Obtain the reference voltage amplitude; The reference voltage is determined based on the reference voltage amplitude and the reference phase angle; Grid-based control of the photovoltaic inverter is performed based on the reference voltage.

[0087] In one possible implementation, the photovoltaic system is a centralized photovoltaic system.

[0088] Figure 6 This is a schematic diagram of the control device provided in an embodiment of the present invention. Figure 6 As shown, the control device 4 in this embodiment includes a processor 40 and a memory 41. The memory 41 stores a computer program 42, and the processor 40 calls and runs the computer program 42 stored in the memory 41 to execute the steps in the matching control method embodiments of the various grid-type photovoltaic inverters described above. Alternatively, the processor 40 calls and runs the computer program 42 stored in the memory 41 to implement the functions of each module / unit in the various device embodiments described above.

[0089] For example, the computer program 42 may be divided into one or more modules / units, which are stored in the memory 41 and executed by the processor 40 to complete the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program 42 in the control device 4.

[0090] The control device 4 may include, but is not limited to, a processor 40 and a memory 41. Those skilled in the art will understand that... Figure 6 This is merely an example of control device 4 and does not constitute a limitation on control device 4. It may include more or fewer components than shown, or combine certain components, or different components. For example, the control device may also include input / output devices, network access devices, buses, etc.

[0091] The processor 40 can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor.

[0092] The memory 41 can be an internal storage unit of the control device 4, such as a hard disk or memory of the control device 4. The memory 41 can also be an external storage device of the control device 4, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the control device 4. Furthermore, the memory 41 can include both internal storage units and external storage devices of the control device 4. The memory 41 is used to store the computer program and other programs and data required by the control device. The memory 41 can also be used to temporarily store data that has been output or will be output.

[0093] Corresponding to the control device described above, this embodiment of the invention also provides a photovoltaic system, including a photovoltaic array, a bus, a photovoltaic inverter, and the control device described above; The busbars are connected to the photovoltaic array and the photovoltaic inverter respectively; the photovoltaic inverter is controlled by the control equipment.

[0094] For a description of the photovoltaic system, please refer to the description in the foregoing embodiments, and it will not be repeated here.

[0095] This application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of any of the above-described matching control methods for a grid-connected photovoltaic inverter.

[0096] This application also provides a computer program product, including a computer program that, when executed by a processor, implements any of the above-described matching control methods for a grid-connected photovoltaic inverter.

[0097] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0098] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0099] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0100] In the embodiments provided by this invention, it should be understood that the disclosed apparatus / control devices and methods can be implemented in other ways. For example, the apparatus / control device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0101] 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 units can be selected to achieve the purpose of this embodiment according to actual needs.

[0102] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0103] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the matching control method embodiments for each of the above-described grid-type photovoltaic inverters. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0104] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. 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. Such 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, and should all be included within the protection scope of the present invention.

Claims

1. A matching control method for a grid-connected photovoltaic inverter, characterized in that, include: Obtain the reference voltage and actual voltage of the photovoltaic system's busbar; Determine the difference between the reference voltage of the bus and the actual voltage of the bus; Based on the difference, inertia control is performed to determine the frequency adjustment amount; The reference phase angle is determined based on the frequency adjustment amount, and the grid configuration control of the photovoltaic inverter is performed according to the reference phase angle.

2. The matching control method for a grid-type photovoltaic inverter according to claim 1, characterized in that, Obtain the reference voltage of the photovoltaic system's bus, including: Obtain the actual voltage and actual current of the photovoltaic array in the photovoltaic system; The reference voltage of the busbar is determined based on the actual voltage and actual current of the photovoltaic array.

3. The matching control method for a grid-type photovoltaic inverter according to claim 2, characterized in that, The process of determining the reference voltage of the busbar based on the actual voltage and actual current of the photovoltaic array includes: Based on the preset maximum power point tracking algorithm, the reference voltage of the bus is determined according to the actual voltage and actual current of the photovoltaic array.

4. The matching control method for a grid-type photovoltaic inverter according to claim 3, characterized in that, The method for determining the reference voltage of the bus based on the preset maximum power point tracking algorithm, according to the actual voltage and actual current of the photovoltaic array, includes: The actual voltage and actual current of the photovoltaic array are used as inputs to the preset maximum power point tracking algorithm to obtain the candidate bus reference voltage output by the preset maximum power point tracking algorithm. The candidate bus reference voltage is subjected to amplitude limiting processing to obtain the bus reference voltage, thereby limiting the bus reference voltage between the maximum power point tracking voltage and the open circuit voltage of the photovoltaic array.

5. The matching control method for a grid-type photovoltaic inverter according to claim 1, characterized in that, The step of performing inertia control and determining the frequency adjustment amount based on the difference includes: Obtain the inertia coefficient; Based on the difference, the inertia coefficient, and integral processing, inertia control is performed to determine the frequency change.

6. The matching control method for a grid-connected photovoltaic inverter according to any one of claims 1 to 5, characterized in that, Determining the reference phase angle based on the frequency adjustment amount includes: Obtain the rated frequency; The reference frequency is determined based on the rated frequency and the frequency adjustment amount; The reference frequency is integrated to obtain the reference phase angle.

7. The matching control method for a grid-connected photovoltaic inverter according to any one of claims 1 to 5, characterized in that, The grid configuration control of the photovoltaic inverter based on the reference phase angle includes: Obtain the reference voltage amplitude; The reference voltage is determined based on the reference voltage amplitude and the reference phase angle; The photovoltaic inverter is subjected to grid-type control based on the reference voltage.

8. The matching control method for a grid-connected photovoltaic inverter according to any one of claims 1 to 5, characterized in that, The photovoltaic system is a centralized photovoltaic system.

9. A control device, characterized in that, It includes a memory and a processor, the memory being used to store a computer program, and the processor being used to call and run the computer program stored in the memory to execute the matching control method for a grid-connected photovoltaic inverter as described in any one of claims 1 to 8.

10. A photovoltaic system, characterized in that, Includes a photovoltaic array, a busbar, a photovoltaic inverter, and the control device as described in claim 9; The busbars are connected to the photovoltaic array and the photovoltaic inverter respectively; the photovoltaic inverter is controlled by the control device.

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