Two-stage photovoltaic grid-connected system double-layer low-voltage ride-through control method and system

Abstract

The application provides a two-stage photovoltaic grid-connected system double-layer low-voltage ride-through control method and system, and the scheme comprises the following steps: detecting the grid-connected point voltage in real time, and judging whether the grid-connected point voltage is qualified; when the grid-connected point voltage is unqualified, taking the improvement of the grid-connected point positive sequence voltage and the reduction of the grid-connected point negative sequence voltage as the target, generating a current instruction, and realizing the control of the inverter voltage and current through the positive and negative sequence current inner loop and the phase-locked loop; after the positive and negative sequence voltage support of the alternating current layer is realized, judging whether there is remaining capacity of the rear-stage inverter based on the generated current instruction, if there is the remaining capacity, calculating the remaining capacity and generating an active power instruction to be sent to the direct current layer; after the rear-stage inverter obtains the output active power instruction, the instruction is shared to the front-stage inverter, and the front-stage inverter compensates the current reference value of the direct current side during the low ride-through period according to the photovoltaic output characteristic curve.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power systems, and particularly relates to a two-stage photovoltaic grid-connected system double-layer low-voltage ride-through control method and system. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute the prior art.

[0003] With the increasing penetration of new energy, the number of power electronic inverters connected to the grid is increasing. The control system of power electronic devices is susceptible to voltage sag, which leads to grid disconnection of the grid-connected system and reduces the safety and reliability of the system. Therefore, the grid-connected inverter should have low-voltage ride-through capability to provide voltage support for the grid during faults. Voltage sag in power systems is mostly caused by asymmetric faults, so it is of great significance to study the low-voltage ride-through control technology of grid-connected inverters under asymmetric fault conditions for the safe and reliable operation of power systems.

[0004] The inventors have found that the following problems exist in the current low-voltage ride-through control method of grid-connected inverters under asymmetric faults:

[0005] When the grid-side voltage drops, the active power output by the rear-stage inverter instantaneously decreases. If the control system of the Boost circuit is still in the maximum power point tracking (MPPT) mode, the power output by the front-stage and rear-stage inverters will not match, which easily causes overvoltage at the DC side. Therefore, the control loop of the front-stage inverter should ensure the stability of the DC side voltage during low-voltage ride-through. In the existing research, the front-stage inverter passively adjusts the active power output by the photovoltaic power according to the change of the DC bus voltage, which leads to a longer transient process for the DC side voltage to reach stability during low-voltage ride-through. SUMMARY

[0006] Embodiments of the present application provide a two-stage photovoltaic grid-connected system double-layer low-voltage ride-through control method and system to solve the problem that in the traditional scheme, the front-stage inverter passively adjusts the active power output by the photovoltaic power according to the change of the DC bus voltage, which leads to a longer transient process for the DC side voltage to reach stability during low-voltage ride-through.

[0007] According to a first aspect of embodiments of the present application, a two-stage photovoltaic grid-connected system double-layer low-voltage ride-through control method is provided, comprising:

[0008] real-time detection of the grid-connected point voltage and determination of whether the grid-connected point voltage is qualified;

[0009] When the grid-connected point voltage is unqualified, current instructions are generated by taking the goal of improving the positive sequence voltage of the grid-connected point and reducing the negative sequence voltage of the grid-connected point, and the control of the inverter voltage and current is realized through the positive and negative sequence current inner loop and the phase-locked loop;

[0010] After the AC layer realizes the positive and negative sequence voltage support, based on the generated current instructions, it is judged whether there is remaining capacity for the rear-stage inverter, if there is remaining capacity, the remaining capacity is calculated and active power instructions are generated and sent to the DC layer;

[0011] After the rear-stage inverter obtains the output active power instructions, the instructions are shared to the front-stage inverter, and the front-stage inverter compensates the current reference value on the DC side during the low penetration period according to the photovoltaic output characteristic curve.

[0012] Further, the current instructions generated by taking the goal of improving the positive sequence voltage of the grid-connected point and reducing the negative sequence voltage of the grid-connected point, and the control of the inverter voltage and current realized through the positive and negative sequence current inner loop and the phase-locked loop are specifically: when the asymmetric fault occurs, the maximum and minimum limits of the grid-connected point phase voltage are determined based on a preset strategy, so that the maximum and minimum limits of the grid-connected point phase voltage are relatively close, wherein the preset strategy is specifically expressed by the following formula:

[0013]

[0014] Wherein, V max and V min are the maximum and minimum values of the specified grid-connected point voltage; γ max and γ min are the maximum and minimum values of the cosine of the phase angle difference of the three-phase positive and negative sequence voltage, V + is the amplitude of the positive sequence component of the grid-connected point voltage, V - is the amplitude of the negative sequence component of the grid-connected point voltage, is the phase angle of the positive and negative sequence voltage.

[0015] Further, the generated current instructions are specifically expressed as follows:

[0016]

[0017] Wherein, and are the positive and negative sequence voltage reference values of the grid-connected point; is the amplitude of the positive sequence component of the grid-side voltage; V + is the amplitude of the positive sequence component of the grid-connected point voltage; ω is the angular frequency under the power grid frequency; are the active and reactive positive sequence current instructions output by the inverter; is the amplitude of the positive sequence component of the grid-side voltage; V - is the amplitude of the negative sequence component of the grid-connected point voltage; X g and Rg is the ratio of the reactance value to the resistance value in the line; is the oscillation limit value of the DC side voltage; V dc is the DC side voltage value; ε max is the maximum cosine value of the positive sequence and negative sequence current angle; respectively, are the active and reactive negative sequence current commands of the inverter output.

[0018] Further, the pre-stage inverter compensates the current reference value of the DC side during the low voltage ride through according to the photovoltaic output characteristic curve, specifically: according to the power difference before and after the voltage drop and the power-voltage characteristic curve of the photovoltaic, the voltage difference of the photovoltaic before and after the voltage drop is obtained; based on the voltage difference and the voltage-current characteristic curve of the photovoltaic, the current difference of the photovoltaic output before and after the fault is obtained, and the current difference value is compensated to the current reference value of the DC side.

[0019] Further, the current difference value is specifically represented as:

[0020]

[0021] wherein, ΔP is the power difference, C1 and C2 are the inherent gain coefficients of the photovoltaic panel, V MPPT is the photovoltaic panel voltage at the maximum power tracking, V oc is the open circuit voltage of the photovoltaic panel, I sc is the reverse saturation current.

[0022] Further, the power difference before and after the voltage drop is specifically the difference between the active power reference value shared by the alternating current layer and the power at the maximum power point.

[0023] Further, the voltage at the grid-connected point is detected in real time, and whether the voltage at the grid-connected point is qualified is judged, specifically, the positive and negative sequence voltages at the grid-connected point are collected by using a decoupled double synchronous reference frame phase-locked loop, and when the positive sequence voltage drop depth at the grid-connected point reaches below a preset threshold, it is determined that the voltage at the grid-connected point is unqualified.

[0024] According to a second aspect of the embodiment of the present application, a two-stage photovoltaic grid-connected system double-layer low voltage ride through control system is provided, comprising:

[0025] a grid-connected point voltage real-time monitoring module, configured to detect the voltage at the grid-connected point in real time and judge whether the voltage at the grid-connected point is qualified;

[0026] an alternating current layer low voltage ride through module, configured to, when the voltage at the grid-connected point is unqualified, generate a current command with the target of improving the positive sequence voltage at the grid-connected point and reducing the negative sequence voltage at the grid-connected point, and realize the control of the inverter voltage and current through the positive and negative sequence current inner loop and the phase-locked loop;

[0027] A residual capacity detection module is used to judge whether there is residual capacity for the post-stage inverter based on the generated current instruction after the positive and negative sequence voltage support of the alternating current layer is realized, and if there is residual capacity, the residual capacity is calculated and active power instruction is generated and sent to the direct current layer;

[0028] An information sharing and direct current side voltage stabilization module is used to share the output active power instruction to the front-stage inverter after the post-stage inverter obtains the output active power instruction, and the front-stage inverter compensates the current reference value of the direct current side during the low voltage penetration period according to the photovoltaic output characteristic curve.

[0029] According to a third aspect of the embodiments of the present application, an electronic device is provided, comprising a memory, a processor and a computer program stored in the memory and run on the memory, and the processor implements the two-stage photovoltaic grid-connected system double-layer low voltage penetration control method when executing the program.

[0030] According to a fourth aspect of the embodiments of the present application, a non-transitory computer readable storage medium is provided, and the computer readable storage medium stores a computer program, and the program is executed by a processor to implement the two-stage photovoltaic grid-connected system double-layer low voltage penetration control method.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] The present application provides a two-stage photovoltaic grid-connected system double-layer low voltage penetration control method and system, and the active power instruction output by the alternating current layer is shared with the direct current layer converter, so that the photovoltaic device actively adjusts the output active power according to the instruction, and the direct current side voltage is stabilized; meanwhile, the characteristic curve of the photovoltaic output is used to compensate the direct current side current reference value during the low voltage penetration period, the transient process of the direct current side during the low voltage penetration period is shortened, and the time for the direct current side voltage to reach stability is reduced.

[0033] The advantages of the additional aspects of the present application will be partially given in the following description, partially will become obvious from the following description, or will be understood through the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0034] The drawings accompanying the specification of the present application form a part thereof, serve to provide further understanding of the present application, and together with the description of the exemplary embodiments of the present application and the explanation thereof serve to explain the present application, and do not constitute an improper limitation of the present application.

[0035] Figure 1 A flow chart of a two-stage photovoltaic grid-connected system double-layer low voltage penetration control method described in the embodiments of the present application;

[0036] Figure 2 A direct current side boost inverter control structure described in the embodiments of the present application;

[0037] Figure 3A result graph of the fast stabilization of the DC side voltage described in the embodiments of the present application. DETAILED DESCRIPTION

[0038] The present application is further described below in conjunction with the accompanying drawings and embodiments.

[0039] It should be noted that the following detailed description is illustrative only, and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0040] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0041] In the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0042] In one or more embodiments, as shown in the scheme described in the embodiments, the scheme described in the embodiments provides Figure 1

[0043] Step 1: Real-time detection is performed on the grid-connected point voltage, and it is determined whether the grid-connected point voltage is qualified;

[0044] In a specific implementation, the step 1 specifically performs the following processing process:

[0045] A decoupled double synchronous reference frame phase-locked loop (DDSRF-PLL) is applied to collect the positive and negative sequence voltages of the grid-connected point, and it is monitored in real time whether the grid-connected point voltage drops. If the positive sequence voltage of the grid-connected point drops to below 0.9 p.u., the photovoltaic grid-connected system enters a low-voltage ride-through control mode.

[0046] Step 2: When the grid-connected point voltage is unqualified, current instructions are generated by taking the positive sequence voltage of the grid-connected point and the negative sequence voltage of the grid-connected point as targets, and the control of the inverter voltage and current is realized through the positive and negative sequence current inner loops and the phase-locked loop;

[0047] In a specific implementation, the step 2 specifically performs the following processing process:

[0048] ​When the system determines that the grid-connected point voltage is unqualified, the photovoltaic grid-connected system automatically enters the low-voltage ride-through control mode. Based on the positive and negative sequence transformation under the DDSRF, when the asymmetric fault occurs, the positive sequence relationship between the grid-side voltage, the grid-connected point voltage and the output current of the inverter in the rear stage can be described as:

[0049]

[0050] Wherein, v + represents the positive sequence component of the grid-connected point voltage; i + represents the positive sequence component of the inverter output current; is the positive sequence component of the grid-side voltage; L g and R g are the inductance and resistance values in the line; t represents the time.

[0051] Similarly, the negative sequence relationship can be written as:

[0052]

[0053] Wherein, v - represents the negative sequence component of the grid-connected point voltage; i - represents the negative sequence component of the inverter output current; is the negative sequence component of the grid-side voltage.

[0054] The above formula can be transformed as:

[0055]

[0056] Wherein, is the amplitude of the positive sequence component of the grid-side voltage; V + is the amplitude of the positive sequence component of the grid-connected point voltage; ω is the angular frequency under the power grid frequency; is the active and reactive positive sequence current command of the inverter output.

[0057]

[0058] Wherein, is the amplitude of the negative sequence component of the grid-side voltage; V - is the amplitude of the negative sequence component of the grid-connected point voltage; is the active and reactive negative sequence current command of the inverter output.

[0059] At this time, the three-phase voltage at the grid-connected point can be described as:

[0060]

[0061] Wherein, V a , V b , V c are the amplitudes of the a, b and c three-phase voltages at the grid-connected point; is the phase angle of positive and negative sequence voltage.

[0062] When the asymmetric fault occurs, in order to make the system run in the safe range, the maximum and minimum limits of the grid point phase voltage should be specified, and in order to achieve the goal of improving the positive sequence voltage and reducing the negative sequence voltage of the grid point, the maximum and minimum values of the phase voltage should be relatively close. At this time, the maximum and minimum phase voltages can be expressed as:

[0063]

[0064] wherein, V max and V min are the maximum and minimum values of the specified grid point voltage; γ max and γ min are the maximum and minimum values of the cosine of the phase angle difference of the three-phase positive and negative sequence voltage, which can be expressed as:

[0065]

[0066] Solving the above equation, the current command output by the rear-stage inverter for the goal of improving the positive sequence voltage and reducing the negative sequence voltage of the grid point is:

[0067]

[0068] wherein, and are the reference values of the positive and negative sequence voltage of the grid point; is the amplitude of the positive sequence component of the grid-side voltage; V + is the amplitude of the positive sequence component of the grid point voltage; ω is the angular frequency under the power grid frequency; are the active and reactive positive sequence current commands output by the inverter; is the amplitude of the positive sequence component of the grid-side voltage; V - is the amplitude of the negative sequence component of the grid point voltage; X g and R g are the reactance and resistance values in the line; is the oscillation limit value of the DC side voltage; V dc is the DC side voltage value; ε max is the maximum cosine value of the positive and negative sequence current angle; are the active and reactive negative sequence current commands output by the inverter.

[0069] and can be specifically expressed as:

[0070]

[0071] wherein,

[0072] Step 3: After the positive and negative sequence voltage support is realized in the alternating current layer, based on the generated current instruction, it is determined whether there is remaining capacity in the rear-stage inverter. If there is remaining capacity, the remaining capacity is calculated and an active power instruction is generated and sent to the direct current layer;

[0073] In a specific implementation, the step 3 specifically performs the following processing process:

[0074] At this time, the current instruction generated by the rear-stage inverter output. If the output active current instruction is greater than 0, the active power that can be output by the inverter is obtained as an active power reference value and transmitted to the direct current layer:

[0075]

[0076] Step 4: After the rear-stage inverter obtains the output active power instruction, the instruction is shared with the front-stage inverter. The front-stage inverter compensates the current reference value on the direct current side during the low penetration period according to the photovoltaic output characteristic curve.

[0077] In a specific implementation, the step 4 specifically performs the following processing process:

[0078] After the rear-stage inverter obtains the output active power, the instruction is shared with the front-stage inverter. According to the power difference before and after the voltage drop and the P-V characteristic curve of the photovoltaic, the voltage difference of the photovoltaic before and after the voltage drop is obtained. Then, according to the V-I characteristic curve of the photovoltaic, the current difference of the photovoltaic output before and after the fault is obtained. The current difference value is compensated to the current reference value on the direct current side, so that the direct current side voltage can quickly reach stability during the low penetration period.

[0079] Further, in order to quickly stabilize the direct current side voltage under asymmetric fault, the direct current layer will generate a compensation current ΔI according to ΔP, which is the active power reference value P ref at the maximum power point P MPPT . In order to establish the analytical relationship between ΔP and ΔI, an intermediate variable ΔV is needed. According to the P-V characteristic curve of the photovoltaic array, the difference ΔV of the direct current side voltage can be obtained. Then, by substituting ΔV into the V-I characteristic curve of the photovoltaic array, the compensation current ΔI of the boost converter can be derived to realize the quick stabilization of the direct current link voltage. The detailed implementation is as follows:

[0080] Under the fixed light intensity and temperature, the P-V characteristic of the photovoltaic array can be written as:

[0081]

[0082] The second-order Taylor expansion of the above formula can obtain the analytical expression of ΔP and ΔV:

[0083]

[0084] With the AC layer sharing active power instruction, the DC layer can calculate AV through power difference:

[0085]

[0086] The V-I characteristic curve of the photovoltaic panel can also be expanded in the second order Taylor, so as to obtain the relationship expression of AI and AV:

[0087]

[0088] Among them:

[0089]

[0090] The variable AV is brought into the expression of the compensation current, and the complete compensation current injection value can be obtained:

[0091]

[0092] Further, the duty ratio of the boost inverter under asymmetric fault can be expressed as:

[0093]

[0094] As shown in Figure 2 , the DC side boost inverter control structure described in the embodiment is shown; as shown in Figure 3 , the DC side voltage fast stabilization result diagram described in the embodiment is shown.

[0095] In one or more embodiments, corresponding to the above method, the embodiment provides a two-stage photovoltaic grid-connected system double-layer low-voltage ride-through control system, comprising:

[0096] The grid-connected point voltage real-time monitoring module is used for real-time detection of the grid-connected point voltage and judgment of whether the grid-connected point voltage is qualified;

[0097] The AC layer low-voltage ride-through module is used for generating current instruction when the grid-connected point voltage is unqualified, and realizing control of the inverter voltage and current through the positive and negative sequence current inner loop and the phase-locked loop, with the target of improving the grid-connected point positive sequence voltage and reducing the grid-connected point negative sequence voltage;

[0098] The remaining capacity detection module is used for judging whether there is remaining capacity of the rear-stage inverter based on the generated current instruction after the AC layer realizes positive and negative sequence voltage support, and if there is remaining capacity, calculating the remaining capacity and generating active power instruction to send to the DC layer;

[0099] Information sharing and DC side voltage stabilization module, for the output of the active power command, the command is shared to the front stage inverter, the front stage inverter according to photovoltaic output characteristic curve, the current reference value of DC side during low wear is compensated.

[0100] Further, the related technical details of the system described in the embodiment are described in detail in embodiment one, so here is no longer tedious.

[0101] In more embodiments, also provided are:

[0102] An electronic device, comprising a memory and a processor, and computer instructions stored in the memory and running on the processor, when the computer instructions are run by the processor, the method described in embodiment one is completed. For the sake of brevity, it is not described here.

[0103] It should be understood that in the embodiment, the processor can be a central processing unit CPU, the processor can also be other general-purpose processors, digital signal processors DSP, application specific integrated circuits ASIC, ready programmable gate arrays FPGA or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc.

[0104] The memory can include read-only memory and random access memory, and provide instructions and data to the processor, a part of the memory can also include non-volatile random access memory. For example, the memory can also store device type information.

[0105] A computer readable storage medium for storing computer instructions, when the computer instructions are executed by the processor, the method described in embodiment one is completed.

[0106] The method in embodiment one can be directly embodied as hardware processor execution is completed, or with hardware and software module combination in the processor is executed to complete. The software module can be located in random access memory, flash memory, read-only memory, programmable read-only memory or electrically erasable programmable memory, register, etc. The storage medium in the art is mature. The storage medium is located in the memory, and the processor reads the information in the memory, and combines the hardware to complete the steps of the above method. To avoid repetition, it is not described here in detail.

[0107] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A two-stage low-voltage ride-through control method for a two-level photovoltaic grid-connected system, characterized in that, include: The voltage at the grid connection point is monitored in real time, and it is determined whether the voltage at the grid connection point is qualified. When the grid connection point voltage is not up to standard, the current command is generated with the goal of increasing the positive sequence voltage and decreasing the negative sequence voltage of the grid connection point, and the inverter voltage and current are controlled by the positive and negative sequence current inner loop and the phase-locked loop. After the AC layer implements positive and negative sequence voltage support, it determines whether the downstream inverter has remaining capacity based on the generated current command. If there is remaining capacity, it calculates the remaining capacity and generates an active power command to send to the DC layer. The generated current command is specifically represented as follows: in, and These are the reference values ​​for the positive and negative sequence voltages at the grid connection point, respectively. This represents the magnitude of the positive sequence component of the grid-side voltage. The magnitude of the positive-sequence component of the grid connection point voltage; The angular frequency at the power grid frequency; , These are the active and reactive positive sequence current commands output by the inverter, respectively. This represents the magnitude of the positive sequence component of the grid-side voltage. The magnitude of the negative sequence component of the grid connection point voltage; and These are the reactance and resistance values ​​in the circuit; This is the oscillation limit for the DC-side voltage; This is the DC side voltage value; ε max It is the maximum cosine value of the angle between the positive and negative sequence currents; , These are the active and reactive negative sequence current commands output by the inverter, respectively. After receiving the output active power command, the downstream inverter shares the command with the upstream inverter. The upstream inverter then compensates for the DC current reference value during the low-voltage period based on the photovoltaic output characteristic curve.

2. The two-stage low-voltage ride-through control method for a two-level photovoltaic grid-connected system as described in claim 1, characterized in that, The goal is to increase the positive-sequence voltage and decrease the negative-sequence voltage at the grid connection point. Current commands are generated, and the inverter voltage and current are controlled through positive and negative sequence current inner loops and phase-locked loops. Specifically, when an asymmetric fault occurs, the maximum and minimum limits of the phase voltage at the grid connection point are determined based on a preset strategy, making the maximum and minimum limits relatively close. The preset strategy is specifically expressed by the following formula: in, and These are the maximum and minimum values ​​of the specified grid connection point voltage, respectively. and The maximum and minimum values ​​of the cosine of the phase angle difference between the three-phase positive and negative sequence voltages. The magnitude of the positive sequence component of the grid connection point voltage. The magnitude of the negative sequence component of the grid connection point voltage. It represents the phase angle between the positive and negative sequence voltages.

3. The two-stage low-voltage ride-through control method for a two-level photovoltaic grid-connected system as described in claim 1, characterized in that, The front-end inverter compensates for the DC-side current reference value during the low-voltage period based on the photovoltaic output characteristic curve. Specifically, it obtains the photovoltaic voltage difference before and after the voltage drop based on the power difference before and after the voltage drop and the photovoltaic power-voltage characteristic curve; it obtains the photovoltaic output current difference before and after the fault based on the voltage difference and the photovoltaic voltage-current characteristic curve, and compensates the DC-side current reference value with the current difference.

4. The two-stage low-voltage ride-through control method for a two-level photovoltaic grid-connected system as described in claim 3, characterized in that, The current difference is specifically expressed as follows: Where ΔP is the power difference, respectively This represents the inherent gain coefficient of the photovoltaic panel. The voltage of the photovoltaic panel during maximum power point tracking. This is the open-circuit voltage of the photovoltaic panel. This is the reverse saturation current.

5. The two-stage low-voltage ride-through control method for a two-level photovoltaic grid-connected system as described in claim 3, characterized in that, The power difference before and after the voltage drop is specifically the power difference between the active power reference value shared by the AC layer and the power at the maximum power point.

6. The two-stage low-voltage ride-through control method for a two-level photovoltaic grid-connected system as described in claim 1, characterized in that, The method involves real-time detection of the grid connection point voltage and determination of whether the grid connection point voltage is qualified. Specifically, a decoupled dual synchronous reference coordinate system phase-locked loop is used to collect the positive and negative sequence voltages of the grid connection point. When the positive sequence voltage drop depth of the grid connection point reaches below a preset threshold, the grid connection point voltage is determined to be unqualified.

7. A two-stage photovoltaic grid-connected system with a double-layer low-voltage ride-through control system, characterized in that, include: The grid connection point voltage real-time monitoring module is used to detect the grid connection point voltage in real time and determine whether the grid connection point voltage is qualified. The AC layer low voltage ride-through module is used to generate current commands to increase the positive sequence voltage and decrease the negative sequence voltage of the grid connection point when the grid connection point voltage is unqualified. It then controls the inverter voltage and current through the positive and negative sequence current inner loop and the phase-locked loop. The generated current command is specifically represented as follows: in, and These are the reference values ​​for the positive and negative sequence voltages at the grid connection point, respectively. This represents the magnitude of the positive sequence component of the grid-side voltage. The magnitude of the positive-sequence component of the grid connection point voltage; The angular frequency at the power grid frequency; , These are the active and reactive positive sequence current commands output by the inverter, respectively. This represents the magnitude of the positive sequence component of the grid-side voltage. The magnitude of the negative sequence component of the grid connection point voltage; and These are the reactance and resistance values ​​in the circuit; This is the oscillation limit for the DC-side voltage; This is the DC side voltage value; ε max It is the maximum cosine value of the angle between the positive and negative sequence currents; , These are the active and reactive negative sequence current commands output by the inverter, respectively. The remaining capacity detection module is used to determine whether the downstream inverter has remaining capacity after the AC layer has implemented positive and negative sequence voltage support, based on the generated current command. If there is remaining capacity, the remaining capacity is calculated and an active power command is generated and sent to the DC layer. The information sharing and DC-side voltage stabilization module is used by the downstream inverter to share the output active power command with the upstream inverter after receiving the command. The upstream inverter then compensates for the DC-side current reference value during the low-voltage period based on the photovoltaic output characteristic curve.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and running thereon, characterized in that, When the processor executes the program, it implements the two-level low-voltage ride-through control method for a two-stage photovoltaic grid-connected system as described in any one of claims 1-6.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by the processor, the program implements the two-level low-voltage ride-through control method for a two-stage photovoltaic grid-connected system as described in any one of claims 1-6.

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