Photovoltaic inverter low voltage ride through control method and device, electronic equipment and storage medium

Abstract

The embodiment of the invention discloses a photovoltaic inverter low-voltage ride-through control method and device, electronic equipment and a storage medium. The method comprises the following steps: acquiring a grid-connected point voltage and a direct-current side voltage of a photovoltaic inverter; judging whether the grid-connected point voltage is greater than a first threshold value or not; if the grid-connected point voltage is greater than the first threshold value, controlling the photovoltaic inverter to adopt constant direct current voltage control and constant reactive power control; if the grid-connected point voltage is not greater than the first threshold value, judging whether the photovoltaic inverter enters a low-voltage ride-through state or not according to the size of the direct-current side voltage so as to perform control switching; according to the low-voltage ride-through strategy of the photovoltaic inverter, a direct-current voltage criterion is added, so that the direct-current voltage can be recovered to a normal value under a low-voltage condition.

Description

Technical Field

[0001] The present invention relates to the technical field of low voltage ride through control, and in particular to a low voltage ride through control method for a photovoltaic inverter. Background Art

[0002] The transmission of large-scale new energy in deserts, Gobi, wasteland, deep sea, etc. through flexible direct current is one of the main ways to transmit large-scale new energy. At this time, the new energy grid and the flexible direct current system form a 100% power electronic system, which is a grid form that has not yet appeared. Due to the concentrated development of new energy in deserts, Gobi, and wasteland areas, especially the development of photovoltaic resources in Tibetan pastoral areas and uninhabited areas, compared with existing new energy bases, the transmission distance is longer, the conventional power supply is less, and the grid strength is weaker. When a short-circuit fault occurs in the sending-end AC system, it will seriously affect the stable operation of the photovoltaic collection system and the flexible direct current system, and the photovoltaic inverter will also enter the low voltage ride-through state, injecting reactive power into the system.

[0003] When the PV inverter is operating normally, positive sequence double closed-loop control with DC voltage and reactive power as control targets is usually adopted, and the DC voltage reference value is obtained by maximum power tracking control. When the PV inverter enters low voltage ride-through, its control switches to constant current control, and the dq axis current set value is determined by its low voltage ride-through strategy. At this time, the DC voltage control will lose its function, which may further lead to the loss of control of the DC voltage. The DC voltage may continue to be at a value lower than the value before the fault after the fault is cleared, affecting the voltage stability of the PV inverter. Summary of the invention

[0004] The main purpose of the present invention is to provide a photovoltaic inverter low voltage ride-through control method, device, electronic equipment and storage medium, which can restore the DC voltage to a normal value under low voltage conditions when the photovoltaic inverter enters low voltage ride-through.

[0005] To achieve the above-mentioned object, the first aspect of the present application provides a photovoltaic inverter low voltage ride-through control method, the method comprising:

[0006] Obtain the grid connection point voltage and DC side voltage of the photovoltaic inverter;

[0007] Determining whether the grid connection point voltage is greater than a first threshold;

[0008] If the grid connection point voltage is greater than the first threshold, controlling the photovoltaic inverter to adopt constant DC voltage control and constant reactive power control;

[0009] If the grid connection point voltage is not greater than the first threshold, it is determined whether the photovoltaic inverter enters a low voltage ride-through state according to the magnitude of the DC side voltage, so as to perform control switching.

[0010] Optionally, determining whether to control the PV inverter to enter the low-voltage ride-through state for control switching according to the magnitude of the DC-side voltage includes:

[0011] Determining whether the DC-side voltage is greater than a second threshold;

[0012] If the DC-side voltage is greater than the second threshold, the PV inverter enters the low-voltage ride-through state, and its control is switched to constant-current control.

[0013] Optionally, the method further includes:

[0014] If the DC-side voltage is not greater than the second threshold, the PV inverter does not enter the low-voltage ride-through state and maintains the constant DC voltage control and the constant reactive power control.

[0015] Optionally, the first threshold is N times the rated value, and N is a positive number less than 1.

[0016] Optionally, the second threshold is M times the rated value, and M is a positive number less than 1.

[0017] Optionally, N is 0.9; M is 0.8.

[0018] Optionally, the method further includes:

[0019] During the low-voltage ride-through process, controlling the PV inverter to switch from single-inner-loop direct current control to double-loop control.

[0020] Optionally, the method further includes:

[0021] If it is determined that the PV inverter enters the low-voltage ride-through state, based on the grid connection point voltage and the DC-side voltage of the PV inverter, the output of the PV inverter is predicted and controlled through a model.

[0022] A second aspect of the present application provides a low-voltage ride-through control device for a PV inverter, including:

[0023] An acquisition module for acquiring the grid connection point voltage and the DC-side voltage of the PV inverter;

[0024] A judgment module for judging whether the grid connection point voltage is greater than a first threshold;

[0025] A control module for, if the grid connection point voltage is greater than the first threshold, controlling the PV inverter to adopt constant DC voltage control and constant reactive power control;

[0026] The determination module is further configured to, if the grid connection point voltage is not greater than the first threshold, determine whether the PV inverter enters the low voltage ride-through state according to the magnitude of the DC side voltage, so as to perform control switching.

[0027] A third aspect of the present application provides an electronic device, including a memory and a processor. The memory stores a computer program. When the computer program is executed by the processor, the processor is caused to execute the steps of the first aspect and any possible implementation manner thereof.

[0028] A fourth aspect of the present application provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor is caused to execute the respective steps in the method described in the first aspect.

[0029] The present application provides a low voltage ride-through control method for a PV inverter. By obtaining the grid connection point voltage and the DC side voltage of the PV inverter; determining whether the grid connection point voltage is greater than a first threshold; if the grid connection point voltage is greater than the first threshold, controlling the PV inverter to adopt constant DC voltage control and constant reactive power control; if the grid connection point voltage is not greater than the first threshold, determining whether the PV inverter enters the low voltage ride-through state according to the magnitude of the DC side voltage, so as to perform control switching; this low voltage ride-through strategy for the PV inverter ensures that the DC voltage can be restored to the normal value under low voltage conditions by adding a DC voltage criterion. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Among them:

[0032] Figure 1 is a schematic flowchart of a low voltage ride-through control method for a PV inverter provided by an embodiment of the present application;

[0033] Figure 2 is a schematic diagram of the topology of a photovoltaic power generation unit provided by an embodiment of the present application;

[0034] Figure 3 is a schematic flowchart of another low voltage ride-through control method for a PV inverter provided by an embodiment of the present application;

[0035] Figure 4Schematic diagram of a low-voltage ride-through control device for a photovoltaic inverter provided by an embodiment of the present application;

[0036] Figure 5 Schematic diagram of an electronic device provided by an embodiment of the present application. Detailed implementation manners

[0037] In order to enable those skilled in the art to better understand the solution of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0038] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0039] Referring to "embodiment" herein means that a specific feature, structure or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0040] The low-voltage ride-through (LVRT) of the photovoltaic inverter mentioned in the embodiments of the present application refers to the ability of the inverter to maintain grid-connected operation and provide reactive power to support the recovery of the grid voltage when the grid voltage drops. This is an important function for the photovoltaic grid-connected system to maintain stable operation during grid faults.

[0041] The embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application.

[0042] First, the current low-voltage ride-through strategy of the photovoltaic inverter will be introduced.

[0043] Generally, the corresponding dq-axis reference current is usually given according to the degree of voltage drop at the inverter grid connection point, as follows:

[0044] For I qref , its calculation formula is as shown in (1):

[0045]

[0046] In the formula, U T is the grid connection point voltage of the photovoltaic power station, and I N is the rated current of the photovoltaic power station.

[0047] Limited by the overcurrent capacity of the equipment, the given value of I dref needs to first calculate the active current limit value according to the maximum current allowable value of the equipment and the magnitude of I qref , and the calculation formula is as shown in (2):

[0048]

[0049] When the AC voltage dip is not deep, I qref is small, and the active current limit value is greater than the active current reference value before the fault. At this time, the active current reference value during the fault remains unchanged at the value before the fault; when the AC voltage dip is deep and I qref is large, the active current limit value is less than the active current reference value before the fault, and the active current reference value during the fault is based on the limit value shown in the above formula (2).

[0050] However, before and after the fault disappears, the AC voltage may drop below the threshold (such as 0.9 p.u.). At this time, if the DC voltage also drops below the normal value, due to the existence of the low voltage ride-through strategy, the DC voltage may get out of control, and then the DC side voltage may be in a low voltage for a long time, affecting the power transmission of the photovoltaic inverter.

[0051] The p.u. mentioned in the embodiments of this application is an abbreviation of per unit, which is a dimensionless relative unit system used in power system analysis and engineering calculations. The per unit value represents the relative values of various physical quantities and parameters, and is the ratio of the actual value to a selected reference value with the same unit. The advantage of this unit system is that it can eliminate the proportional coefficient in the formula, simplify the calculation, and make the component parameters of the power system closer, facilitating calculation and analysis and comparison. The calculation formula for the per unit value is: per unit value = actual value / reference value. The selection of the reference value must have the same dimension as its actual value, and the reference value is usually denoted by the subscript B, and the per unit value is denoted by the subscript *. For example, if the actual value of a voltage is 38.5 kV, when 35 kV is selected as the reference value, its per unit value is 1.1; when 110 kV is selected as the reference value, its per unit value is 0.35.

[0052] In the low-voltage ride-through (LVRT) strategy of a photovoltaic inverter, per-unit values may be used to quantify the degree of grid voltage dip and the inverter's response to the grid. By using per-unit values, it is easier to compare the performance under different grid conditions and simplify the design of control algorithms. For example, if the grid voltage drops to 0.9 times its rated value (0.9 p.u.), the inverter may need to take specific control measures to maintain grid stability.

[0053] Please refer to Figure 1 , which is a schematic flowchart of a low-voltage ride-through control method for a photovoltaic inverter provided by an embodiment of this application. As Figure 1 shown, the method includes:

[0054] 101. Obtain the grid connection point voltage and DC side voltage of the photovoltaic inverter.

[0055] First, refer to Figure 2 , Figure 2 , which is a schematic diagram of the topology of a photovoltaic power generation unit provided by an embodiment of this application.

[0056] As Figure 2 shown, this schematic diagram of the topology shows the basic components of the photovoltaic power generation system and the power flow path from the photovoltaic cells to the grid. Through this system, the direct current generated by the photovoltaic cells can be converted into alternating current suitable for grid connection. The explanations of each part are as follows:

[0057] 1. Photovoltaic cells (Solar Panel): The square array on the left side of the figure represents the photovoltaic cells, which convert solar energy into direct current, and the output voltage is marked as u dc .

[0058] 2. Boost converter: The photovoltaic cells are connected to a boost converter, which is used to boost the relatively low DC voltage generated by the photovoltaic cells to a higher DC voltage level for grid connection or further processing. The output voltage of the boost converter is marked as u g .

[0059] 3. Filter: At the output of the boost converter, there is usually a filter circuit to smooth the output voltage and reduce voltage fluctuations. The filter may include an inductor L f and a capacitor C f .

[0060] 4. Point of common coupling (PCC): This is the point where the photovoltaic system is connected to the grid. Figure 2 The PCC in

[0061] 5. Grid voltage: denoted as u s The part marked as u represents the grid voltage.

[0062] 6. Impedance (R f and L f ): R f and L f represent the resistance and inductance of the filter respectively. Together with the capacitor C f , they form an LC filter to suppress current harmonics and improve power quality.

[0063] The method in the embodiment of this application can be directed to Figure 2 the photovoltaic power generation unit shown in the figure, and improve the criterion for it to enter low voltage ride through. The grid connection point voltage u pcc of the photovoltaic inverter and the DC side voltage u dc can be detected and then judged.

[0064] 102. Judge whether the above grid connection point voltage is greater than the first threshold.

[0065] Specifically, the above first threshold can be set to judge the grid connection point voltage. When the grid connection point voltage is greater than the first threshold, step 103 can be executed; when the grid connection point voltage is not greater than the first threshold, step 104 can be executed.

[0066] Among them, the above first threshold can be determined by the rated value (p.u.).

[0067] In an optional implementation manner, the above first threshold is N times the rated value, and N is a positive number less than 1. For example, N = 0.9.

[0068] 103. If the above grid connection point voltage is greater than the above first threshold, control the above photovoltaic inverter to adopt constant DC voltage control and constant reactive power control.

[0069] The constant DC voltage control and constant reactive power control mentioned in the embodiment of this application are two important control strategies of the photovoltaic inverter during grid-connected operation, and they play a key role in low voltage ride through (LVRT).

[0070] The constant DC voltage control strategy aims to maintain the stability of the DC side voltage of the inverter. When a low voltage ride through event occurs in the power grid, by controlling the switching actions of the inverter, its output current is adjusted to keep the DC side voltage near the set value. This control method helps to reduce the fluctuation of the DC side voltage, thereby protecting the inverter from voltage dips.

[0071] During a grid voltage dip, the constant reactive power control strategy allows the inverter to inject reactive power into the grid to support the recovery of the grid voltage. This control method can improve the stability of the grid, especially when the grid voltage is low, by providing reactive power to help maintain the grid voltage and prevent further voltage drops.

[0072] Specifically, under low voltage ride-through conditions, these two control strategies can be combined to achieve the stable operation of the inverter and support the stability of the grid. For example, when the grid voltage drops, the inverter can first stabilize the DC side voltage through constant DC voltage control, and then provide the necessary reactive power to the grid through constant reactive power control to help the grid voltage recover. This comprehensive control strategy helps improve the reliability of the photovoltaic power generation system during grid faults and its support ability for the grid.

[0073] For example, if N = 0.9, then when the grid connection point voltage u pcc > 0.9 p.u., the photovoltaic inverter adopts constant DC voltage control and constant reactive power control, and the calculation formula for the given value of the d-axis current can be shown as in (3)(4):

[0074]

[0075] I qref = 0 (4)

[0076] Where, V mppt is the DC voltage reference value obtained by maximum power point tracking control, and k p and k i are the proportional coefficient and integral coefficient of the PI controller of the DC voltage outer loop respectively.

[0077] 104. If the grid connection point voltage is not greater than the first threshold, determine whether the above photovoltaic inverter enters the low voltage ride-through state according to the magnitude of the above DC side voltage to perform control switching.

[0078] If the grid connection point voltage is not greater than the first threshold, the DC side voltage can be used as a criterion.

[0079] In an optional implementation manner, the above determining whether to control the above photovoltaic inverter to enter the low voltage ride-through state according to the magnitude of the above DC side voltage to perform control switching includes:

[0080] Determine whether the above DC side voltage is greater than the second threshold;

[0081] If the above DC side voltage is greater than the second threshold, the above photovoltaic inverter enters the low voltage ride-through state, and its control is switched to constant current control.

[0082] Further optionally, the above method further includes:

[0083] If the DC-side voltage is not greater than the second threshold, the PV inverter does not enter the low-voltage ride-through state and continues to adopt the fixed DC voltage control and the fixed reactive power control.

[0084] Specifically, the second threshold can be set to judge the DC-side voltage. When the grid connection point voltage is not greater than the first threshold and the DC-side voltage is greater than the second threshold, the PV inverter enters the low-voltage ride-through state, and its control switches to the fixed current control. The dq-axis current reference is determined by its low-voltage ride-through strategy, and the calculation formulas can be as shown in (1) and (2).

[0085] Among them, the second threshold can be determined by the rated value (p.u.), and the second threshold is usually less than the first threshold.

[0086] In an alternative embodiment, the second threshold is M times the rated value, where M is a positive number less than 1. For example, M = 0.8.

[0087] For example, if N = 0.9 and M = 0.8, then when the grid connection point voltage u pcc is less than 0.9 p.u. and the DC-side voltage u dc is greater than 0.8 p.u., the PV inverter enters the low-voltage ride-through state, and its control switches to the fixed current control. The dq-axis current reference is determined by its low-voltage ride-through strategy.

[0088] If the DC-side voltage is not greater than 0.8 p.u., the PV inverter can still adopt the fixed DC voltage control and the fixed reactive power control. The dq-axis current reference values are as shown in (3) and (4), which will not be elaborated here.

[0089] In an alternative embodiment, the method further includes:

[0090] During the above low-voltage ride-through process, control the PV inverter to switch from the single-inner-loop direct current control to the double-loop control.

[0091] During the low-voltage ride-through process, the control strategy of the PV inverter can be switched from the single-inner-loop direct current control to the double-loop control to maximize the active power output of the inverter. In addition, when the DC bus voltage first drops to its rated value, setting the output of the integral link in the DC bus voltage outer-loop PI control to 0 helps to stabilize the DC bus voltage as soon as possible and enables the PV power generation system to resume stable operation as soon as possible.

[0092] In an alternative embodiment, the method further includes:

[0093] If it is determined that the above photovoltaic inverter enters the above low-voltage ride-through state, based on the grid-connected point voltage and the DC-side voltage of the above photovoltaic inverter, the output of the above photovoltaic inverter is predicted and controlled through a model.

[0094] Under low-voltage ride-through conditions, a photovoltaic inverter can use a model predictive control method to achieve fast current tracking control and leakage current suppression. This method can establish an accurate model under unbalanced grid conditions, while suppressing grid-connected current harmonics and leakage current, and achieving fast current tracking under low-voltage ride-through conditions. First, an accurate model of the photovoltaic inverter can be established under grid unbalance conditions.

[0095] Specifically, under low-voltage ride-through conditions, the above model inputs and outputs can be defined as follows:

[0096] Inputs:

[0097] Grid voltage: including the real-time measured value of the grid-connected point voltage \(u_{pcc}\).

[0098] DC-side voltage: the voltage value on the DC side of the photovoltaic inverter.

[0099] Reference current or power: the current or power reference value set according to grid demand or control strategy.

[0100] System parameters: may include inverter parameters, grid impedance, etc., for the calculation of model predictive control.

[0101] Outputs:

[0102] Inverter switching signals: the inverter switching states calculated according to the model predictive control algorithm, used to control the inverter output current.

[0103] Reactive power command: when needed, output a reactive power command to regulate the grid voltage.

[0104] DC-side voltage control signal: if the DC-side voltage deviates from the set value, output a control signal to adjust the DC-side voltage.

[0105] Leakage current suppression signal: output a signal to reduce the leakage current generated by the inverter and improve system safety.

[0106] The method of using the model is to predict and control the output of the inverter to achieve fast current tracking and leakage current suppression. This method realizes precise control of the inverter by predicting the future current or power output and selecting the optimal control strategy. Under low-voltage ride-through conditions, this method can improve the stability and reliability of the photovoltaic inverter, while reducing the negative impact on the grid.

[0107] In the embodiments of the present application, the judgment and control methods can be selected as needed. For example, the judgment and control can be performed by thresholds, or the judgment and control can be performed by model prediction. After it is determined through the foregoing step 104 that the PV inverter enters the low-voltage ride-through state, the judgment and control can be further combined with a model, and the parameters and functions of the model can be adjusted as needed. The embodiments of the present application do not limit this.

[0108] In the method of the embodiments of the present application, by introducing a DC voltage criterion, when the grid-connected voltage of the PV inverter is lower than the specified threshold and the DC voltage is also lower than the specified threshold, the DC-side voltage can be controlled, and it can be restored to the normal range under control, so that when the PV inverter enters the low-voltage ride-through state, the DC-side voltage remains above the specified threshold.

[0109] To more clearly show the method in the embodiments of the present application, reference can be made to Figure 3 , Figure 3 which is a schematic flowchart of another low-voltage ride-through control method for a PV inverter provided by the embodiments of the present application. As Figure 3 shown, the method mainly includes:

[0110] 1. Detect the grid-connected voltage and DC-side voltage of the PV inverter;

[0111] 2. When the grid-connected voltage u pcc > 0.9 p.u., it does not enter the low-voltage ride-through, and the PV inverter can adopt constant DC voltage control and constant reactive power control;

[0112] 2. When the grid-connected voltage u pcc is less than 0.9 p.u., further judge whether the DC-side voltage u dc is greater than 0.8 p.u.; if the DC-side voltage does not meet this condition, the PV inverter does not enter the low-voltage ride-through state and can still adopt constant DC voltage control and constant reactive power control.

[0113] 3. If the grid-connected voltage u pcc is less than 0.9 p.u. and the DC-side voltage u dc is greater than 0.8 p.u., then the PV inverter enters the low-voltage ride-through state, and its control switches to constant current control.

[0114] Based on the description of the foregoing method embodiments, the embodiments of the present application also provide a low-voltage ride-through control device for a PV inverter.

[0115] Figure 4 which is a schematic structural diagram of a low-voltage ride-through control device for a PV inverter provided by the embodiments of the present application.

[0116] As Figure 4As shown, the low-voltage ride-through control device 400 of the photovoltaic inverter includes:

[0117] An acquisition module 410, configured to acquire the grid connection point voltage and the DC side voltage of the photovoltaic inverter;

[0118] A judgment module 420, configured to judge whether the grid connection point voltage is greater than a first threshold;

[0119] A control module 430, configured to, if the grid connection point voltage is greater than the first threshold, control the photovoltaic inverter to adopt constant DC voltage control and constant reactive power control;

[0120] The judgment module 420 is further configured to, if the grid connection point voltage is not greater than the first threshold, judge whether the photovoltaic inverter enters the low-voltage ride-through state according to the magnitude of the DC side voltage, so as to perform control switching.

[0121] Wherein, Figure 4 The method steps that the device in the shown embodiment can execute have been described in the foregoing Figure 1 、 Figure 3 shown embodiments, and will not be elaborated here.

[0122] Based on the description of the foregoing method embodiments, in an embodiment of the present application, an electronic device is further proposed. Please refer to Figure 5 , Figure 5 is a schematic structural diagram of an electronic device provided by an embodiment of the present application. As Figure 5 shown, the electronic device 500 includes a processor 501 and a memory 502. The memory 502 stores a computer program. When the computer program is executed by the processor 501, it will execute any step in the method embodiments shown in Figure 1 or Figure 3 shown. The electronic device 500 may further include input / output devices, etc. In a specific implementation manner, the electronic device may be a terminal device, etc.

[0123] In an embodiment, a computer-readable storage medium is further proposed. The computer-readable storage medium stores a computer program. When the computer program is executed by the processor 501, it causes the processor 501 to execute any step in the above method embodiments.

[0124] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, storage, database, or other medium used in the embodiments provided in the present application can include non-volatile and / or volatile memories. Non-volatile memories can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memories can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and Rambus dynamic RAM (RDRAM), etc.

[0125] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0126] The above-described embodiments merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A photovoltaic inverter low voltage ride-through control method, characterized in that: The method comprises: Obtain the grid connection point voltage and DC side voltage of the photovoltaic inverter; Determining whether the grid connection point voltage is greater than a first threshold; If the grid connection point voltage is greater than the first threshold, controlling the photovoltaic inverter to adopt constant DC voltage control and constant reactive power control; If the grid connection point voltage is not greater than the first threshold, it is determined whether the photovoltaic inverter enters a low voltage ride-through state according to the magnitude of the DC side voltage, so as to perform control switching.

2. The photovoltaic inverter low voltage ride through control method according to claim 1, characterized in that: The step of judging whether to control the photovoltaic inverter to enter a low voltage ride-through state according to the magnitude of the DC side voltage to perform control switching includes: Determining whether the DC side voltage is greater than a second threshold; If the DC side voltage is greater than the second threshold, the photovoltaic inverter enters a low voltage ride-through state, and its control is switched to constant current control.

3. The photovoltaic inverter low voltage ride through control method according to claim 2, characterized in that: The method further comprises: If the DC side voltage is not greater than the second threshold, the photovoltaic inverter does not enter the low voltage ride-through state, and the constant DC voltage control and the constant reactive power control are maintained.

4. The photovoltaic inverter low voltage ride through control method according to claim 3, characterized in that: The first threshold is N times the rated value, where N is a positive number less than 1.

5. The photovoltaic inverter low voltage ride through control method according to claim 4, characterized in that: The second threshold is M times the rated value, where M is a positive number less than 1.

6. The photovoltaic inverter low voltage ride through control method according to claim 5, characterized in that: The method further comprises: During the low voltage ride-through process, the photovoltaic inverter is controlled to switch from single inner loop direct current control to dual loop control.

7. The photovoltaic inverter low voltage ride through control method according to claim 6, characterized in that: The method further comprises: If it is determined that the photovoltaic inverter enters the low voltage ride-through state, the output of the photovoltaic inverter is predicted and controlled through a model based on the grid connection point voltage and the DC side voltage of the photovoltaic inverter.

8. A photovoltaic inverter low voltage ride through control device, characterized in that: include: An acquisition module is used to obtain the grid connection point voltage and DC side voltage of the photovoltaic inverter; A judging module, used to judge whether the grid connection point voltage is greater than a first threshold; A control module, configured to control the photovoltaic inverter to adopt constant DC voltage control and constant reactive power control if the grid connection point voltage is greater than the first threshold value; The judgment module is further used to judge whether the photovoltaic inverter enters a low voltage ride-through state according to the magnitude of the DC side voltage if the grid connection point voltage is not greater than the first threshold value, so as to perform control switching.

9. An electronic device, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 7.

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