Double-layer low-voltage ride-through control method and system for two-stage photovoltaic grid-connected system

Abstract

The invention provides a double-layer low-voltage ride-through control method and system for a two-stage photovoltaic grid-connected system, and the method comprises the steps: carrying out the real-time detection of the voltage of a grid-connected point, and judging whether the voltage of the grid-connected point is qualified or not; when the voltage of the grid-connected point is not qualified, a current instruction is generated by taking the improvement of the positive sequence voltage of the grid-connected point and the reduction of the negative sequence voltage of the grid-connected point as targets, and the control of the voltage and the current of the inverter is realized through a positive and negative sequence current inner loop and a phase-locked loop; after the alternating current layer realizes positive and negative sequence voltage support, whether a post-stage inverter has residual capacity is judged based on a generated current instruction, and if yes, the residual capacity is calculated, and an active power instruction is generated and sent to the direct current layer; and after the back-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 in the low-pass period according to the photovoltaic output characteristic curve.

Description

Technical Field

[0001] The invention 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 Technique

[0002] The statements in this part only provide background technical information related to the present invention, and do not necessarily constitute prior art.

[0003] With the continuous increase in the penetration rate of new energy, the number of power electronic inverters connected to the power grid is increasing day by day. The control system of power electronic devices is vulnerable to voltage dips, resulting in the disconnection of the grid - connected system and reducing the safety and reliability of the system. Therefore, grid - connected inverters should have the ability of low - voltage ride - through to provide a certain voltage support for the power grid during faults. Most of the voltage dips in the power system are caused by asymmetric faults. Therefore, studying the low - voltage ride - through control technology of grid - connected inverters under asymmetric fault conditions is of great significance for the safe and reliable operation of the power system.

[0004] The inventor found that there are the following problems in the current low - voltage ride - through control methods of grid - connected inverters under asymmetric faults:

[0005] When the grid - side voltage drops, the active power output by the rear - stage inverter decreases instantaneously. If the Boost circuit control system is still in the maximum power point tracking (MPPT) working mode, the power output by the front and rear stages is mismatched, which is likely to cause over - voltage on 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 existing research, the front - stage inverter passively adjusts the active power output of the photovoltaic according to the change of the DC - bus voltage, resulting in a relatively long transient process for the DC - side voltage to reach stability during low - voltage ride - through. Summary of the Invention

[0006] The embodiments of the present invention 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 of the photovoltaic according to the change of the DC - bus voltage, resulting in a relatively long transient process for the DC - side voltage to reach stability during low - voltage ride - through.

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

[0008] Real - time detection of the grid - connection point voltage and judgment of whether the grid - connection point voltage is qualified;

[0009] When the grid connection point voltage is unqualified, aiming to increase the positive sequence voltage and decrease the negative sequence voltage at the grid connection point, a current command is generated, and the voltage and current of the inverter are controlled through the positive and negative sequence current inner loops and the phase-locked loop;

[0010] After the positive and negative sequence voltage support is achieved at the AC layer, based on the generated current command, it is judged whether there is remaining capacity in the subsequent inverter. If there is remaining capacity, the remaining capacity is calculated and an active power command is generated and sent to the DC layer;

[0011] After receiving the output active power command, the subsequent inverter shares the command with the previous inverter, and the previous inverter compensates the current reference value on the DC side during the low voltage ride through period according to the PV output characteristic curve.

[0012] Further, the process of generating a current command aiming to increase the positive sequence voltage and decrease the negative sequence voltage at the grid connection point, and controlling the voltage and current of the inverter through the positive and negative sequence current inner loops and the phase-locked loop is as follows: When an asymmetric fault occurs, the maximum and minimum limits of the grid connection point phase voltage are determined based on a preset strategy, so that the maximum and minimum limits of the grid connection point phase voltage are relatively close. Among them, the preset strategy is specifically expressed by the following formula:

[0013]

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

[0015] Further, the generated current command is specifically expressed as follows:

[0016]

[0017] where, and are respectively the positive and negative sequence voltage reference values of the grid connection 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 connection point voltage; ω is the angular frequency at the power grid power frequency; are respectively the positive sequence current commands of active and reactive power 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 connection point voltage; X g and Rg is the reactance and resistance values in the circuit; 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 included angles; are the active and reactive negative sequence current commands output by the inverter respectively.

[0018] Further, the front-stage inverter compensates the current reference value on the DC side according to the PV output characteristic curve, specifically: according to the power difference before and after the voltage dip and the power-voltage characteristic curve of the PV, the voltage difference of the PV before and after the voltage dip is obtained; based on the voltage difference and combined with the voltage-current characteristic curve of the PV, the current difference of the PV output before and after the fault is obtained, and the current difference value is compensated to the current reference value on the DC side.

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

[0020]

[0021] where, ΔP is the power difference, C 1 are C respectively 2 is the inherent gain coefficient of the PV panel, V MPPT is the PV panel voltage at maximum power tracking, V oc is the open-circuit voltage of the PV panel, I sc is the reverse saturation current.

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

[0023] Further, the grid connection point voltage is detected in real time, and it is judged whether the grid connection point voltage is qualified. Specifically, a decoupled double synchronous reference frame phase-locked loop is used to collect the positive and negative sequence voltages of the grid connection point. When the positive sequence voltage dip depth of the grid connection point reaches below the preset threshold, it is determined that the grid connection point voltage is unqualified.

[0024] According to the second aspect of the embodiments of the present invention, a two-stage PV grid-connected system double-layer low voltage ride-through control system is provided, including:

[0025] A grid connection point voltage real-time monitoring module, which is used to detect the grid connection point voltage in real time and judge whether the grid connection point voltage is qualified;

[0026] An AC layer low voltage ride-through module, which is used to generate a current command with the goal of boosting the positive sequence voltage of the grid connection point and reducing the negative sequence voltage of the grid connection point when the grid connection point voltage is unqualified, and realizes the control of the inverter voltage and current through the positive and negative sequence current inner loops and the phase-locked loop;

[0027] A remaining capacity detection module, which is used to determine whether there is remaining capacity in the subsequent-stage inverter based on the generated current command after the positive and negative sequence voltage support is realized in the AC layer. If there is remaining capacity, it calculates the remaining capacity and generates an active power command to be sent to the DC layer.

[0028] An information sharing and DC-side voltage stabilization module, which is used to share the command to the previous-stage inverter after the subsequent-stage inverter obtains the output active power command. The previous-stage inverter compensates the current reference value on the DC side during the low voltage ride-through period according to the PV output characteristic curve.

[0029] According to the third aspect of the embodiments of the present invention, an electronic device is provided, including a memory, a processor, and a computer program running on the memory. When the processor executes the program, the two-stage PV grid-connected system double-layer low voltage ride-through control method described above is implemented.

[0030] According to the fourth aspect of the embodiments of the present invention, a non-transitory computer-readable storage medium is provided, on which a computer program is stored. When the program is executed by a processor, the two-stage PV grid-connected system double-layer low voltage ride-through control method described above is implemented.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] The present invention provides a two-stage PV grid-connected system double-layer low voltage ride-through control method and system. By sharing the active power command output by the AC layer with the DC layer converter, the PV actively adjusts the output active power according to this command to ensure the stability of the DC-side voltage. At the same time, using the characteristic curve of the PV output, the current reference value on the DC side during the low voltage ride-through period is compensated, shortening the transient process on the DC side during the low voltage ride-through period and reducing the time for the DC-side voltage to reach stability.

[0033] Advantages of additional aspects of the present invention will be partially given in the following description, partially become apparent from the following description, or be learned through the practice of the present invention. Description of the Drawings

[0034] The specification drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0035] Figure 1 It is a flowchart of a two-stage PV grid-connected system double-layer low voltage ride-through control method described in the embodiments of the present invention;

[0036] Figure 2 It is the DC-side boost inverter control structure described in the embodiments of the present invention;

[0037] Figure 3 This is the graph of the rapid stabilization result of the DC-side voltage in the embodiments of the present invention. Specific embodiments

[0038] The present invention will be further described below in conjunction with the drawings and embodiments.

[0039] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0040] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

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

[0042] In one or more embodiments, as Figure 1 shown, the solution provided by this embodiment

[0043] Step 1: Real-time detect the grid connection point voltage and determine whether the grid connection point voltage is qualified;

[0044] In specific implementation, the specific processing procedure of step 1 is as follows:

[0045] Apply a Decoupled Double Synchronous Reference Frame Phase-Locked Loop (DDSRF-PLL) to collect the positive and negative sequence voltages of the grid connection point and monitor in real time whether there is a voltage dip. If the dip depth of the positive sequence voltage at the grid connection point reaches below 0.9 p.u., the photovoltaic grid-connected system enters the low voltage ride-through control mode.

[0046] Step 2: When the grid connection point voltage is unqualified, generate a current command with the goal of increasing the positive sequence voltage and decreasing the negative sequence voltage of the grid connection point, and realize the control of the inverter voltage and current through the positive and negative sequence current inner loops and the phase-locked loop;

[0047] In specific implementation, the specific processing procedure of step 2 is as follows:

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

[0049]

[0050] Among them, v + represents the positive sequence component of the grid connection 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] Among them, v - represents the negative sequence component of the grid connection point voltage; i - represents the negative sequence component of the inverter output current; is the negative sequence component of the grid-side voltage.

[0054] By transforming the above formulas, we can get:

[0055]

[0056] Among them, 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 connection point voltage; ω is the angular frequency at the power grid power frequency; is the active and reactive positive sequence current command output by the inverter.

[0057]

[0058] Among them, 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 connection point voltage; is the active and reactive negative sequence current command output by the inverter.

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

[0060]

[0061] Among them, V a 、V b 、V c are the amplitudes of the a, b, and c phase voltages at the grid connection point; is the phase angle difference between positive and negative sequence voltages.

[0062] When an asymmetric fault occurs, to keep the system operating within a safe range, the phase voltages at the grid connection point should be specified with maximum and minimum limits. At the same time, to achieve the goal of increasing the positive sequence voltage and reducing the negative sequence voltage at the grid connection point, the maximum and minimum values of the phase voltages should be relatively close. At this time, the voltages of the maximum and minimum phases can be expressed as:

[0063]

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

[0065]

[0066] Solving the above formula, the current commands output by the subsequent-stage inverter with the goal of increasing the positive sequence voltage and reducing the negative sequence voltage at the grid connection point are:

[0067]

[0068] where, and are respectively the reference values of the positive and negative sequence voltages at the grid connection 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 connection point voltage; ω is the angular frequency at the power grid power frequency; are respectively 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 connection point voltage; X g and R g are the reactance and resistance values in the line; is the oscillation limit 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 phase angle; are respectively the active and reactive negative sequence current commands output by the inverter.

[0069] and can be specifically expressed as:

[0070]

[0071] where,

[0072] Step 3: After the AC layer realizes positive and negative sequence voltage support, based on the generated current command, determine whether there is remaining capacity in the subsequent inverter. If there is remaining capacity, calculate the remaining capacity and generate an active power command to send to the DC layer;

[0073] In specific implementation, the specific processing procedure of the said Step 3 is as follows:

[0074] At this time, the current command output by the subsequent inverter is generated. If the output active current command is greater than 0, then it can be obtained how much active power the inverter can still output as the active power reference value to be transmitted to the DC layer:

[0075]

[0076] Step 4: After the subsequent inverter obtains the output active power command, share the command with the previous inverter, and the previous inverter compensates the current reference value on the DC side during the low voltage ride through period according to the PV output characteristic curve.

[0077] In specific implementation, the specific processing procedure of the said Step 4 is as follows:

[0078] After the subsequent inverter obtains the output active power, share the command with the previous inverter. According to the power difference before and after the voltage dip and the P-V characteristic curve of the PV, the voltage difference of the PV before and after the voltage dip can be obtained. Then, according to the V-I characteristic curve of the PV, the current difference of the PV output before and after the fault can be obtained, and compensating this current difference value to the current reference value on the DC side can make the DC side voltage reach stability quickly during the low voltage ride through period.

[0079] Furthermore, in order to quickly stabilize the DC side voltage under asymmetric faults, the DC layer will generate a compensation current ΔI according to ΔP, where ΔP is the active power reference value P ref shared by the AC layer and the power difference at the maximum power point P MPPT To establish the analytical relationship between ΔP and ΔI, an intermediate variable ΔV needs to be obtained. According to the P-V characteristic curve of the PV array, the voltage difference ΔV of the DC side can be obtained. Then, by substituting ΔV into the V-I characteristic curve of the PV array, the compensation current ΔI of the boost converter can be deduced to achieve the rapid stability of the DC link voltage. The detailed implementation is as follows:

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

[0081]

[0082] Performing second-order Taylor expansion on the above formula can obtain the analytical relationship expression between ΔP and ΔV:

[0083]

[0084] Using the active power command shared by the AC layer, the DC layer can calculate ΔV through the power difference:

[0085]

[0086] Similar to the processing of the above P-V characteristic curve, the V-I characteristic curve of the photovoltaic panel can also be expanded by the second-order Taylor series to obtain the relationship expression between ΔI and ΔV:

[0087]

[0088] Where:

[0089]

[0090] Substituting the variable ΔV into the above expression of the compensation current, the injection value of the complete compensation current can be obtained:

[0091]

[0092] Furthermore, the duty cycle of the boost inverter under asymmetric faults can be expressed as:

[0093]

[0094] As Figure 2 shown, it shows the DC-side boost inverter control structure described in this embodiment; as Figure 3 shown, it shows the DC-side voltage fast stabilization result graph described in this embodiment.

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

[0096] A grid connection point voltage real-time monitoring module, which is used to detect the grid connection point voltage in real time and judge whether the grid connection point voltage is qualified;

[0097] An AC layer low voltage ride-through module, which is used to generate a current command with the goal of boosting the positive sequence voltage of the grid connection point and reducing the negative sequence voltage of the grid connection point when the grid connection point voltage is unqualified, and realizes the control of the inverter voltage and current through the positive and negative sequence current inner loops and the phase-locked loop;

[0098] A remaining capacity detection module, which is used to judge whether the subsequent inverter has remaining capacity based on the generated current command after the AC layer realizes positive and negative sequence voltage support. If there is remaining capacity, calculate the remaining capacity and generate an active power command to send to the DC layer;

[0099] An information sharing and DC-side voltage stabilization module, which is used for the subsequent-stage inverter to share the obtained active power command with the previous-stage inverter after obtaining the output active power command, and the previous-stage inverter compensates the current reference value on the DC side during the low-ride period according to the PV output characteristic curve.

[0100] Furthermore, the relevant technical details of the system in this embodiment have been described in detail in Embodiment 1, so they will not be elaborated here.

[0101] In more embodiments, there is also provided:

[0102] An electronic device, including a memory, a processor, and computer instructions stored on the memory and running on the processor. When the computer instructions are run by the processor, the method described in Embodiment 1 is completed. For the sake of brevity, it will not be elaborated here.

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

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

[0105] A computer-readable storage medium for storing computer instructions, which when executed by the processor, complete the method described in Embodiment 1.

[0106] The method in Embodiment 1 can be directly embodied as being executed by a hardware processor, or by a combination of hardware and software modules in the processor. The software module may be located in a mature storage medium in the art such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, or an electrically erasable programmable memory, a register, etc. This storage medium is located in the memory, and the processor reads the information in the memory and combines its hardware to complete the steps of the above method. To avoid repetition, it will not be described in detail here.

[0107] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A two-level photovoltaic grid-connected system double-layer low voltage ride-through control method, characterized in that: include: Conduct real-time detection of the grid connection point voltage and determine whether the grid connection point voltage is qualified; When the grid connection point voltage is unqualified, the current command is generated with the goal of increasing the positive sequence voltage at the grid connection point and reducing the negative sequence voltage at the grid connection point, and the inverter voltage and current are controlled through the positive and negative sequence current inner loop and the phase-locked loop; After the AC layer realizes positive and negative sequence voltage support, it determines whether the subsequent inverter has residual capacity based on the generated current command. If there is residual capacity, it calculates the residual capacity and generates active power command to send to the DC layer. After obtaining the output active power instruction, the rear inverter shares the instruction with the front inverter. The front inverter compensates the current reference value of the DC side during the low-power period according to the photovoltaic output characteristic curve.

2. The two-stage photovoltaic grid-connected system double-layer low voltage ride-through control method according to claim 1, characterized in that: The current command is generated with the goal of increasing the positive sequence voltage of the grid connection point and reducing the negative sequence voltage of the grid connection 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. Specifically, when an asymmetric fault occurs, the maximum and minimum limits of the grid connection point phase voltage are determined based on the preset strategy, so that the maximum and minimum limits of the grid connection point phase voltage are relatively close, wherein the preset strategy is specifically expressed by the following formula: Among them, V max With V min are the maximum and minimum values ​​of the grid-connected point voltage respectively; γ max With γ min is the maximum and minimum value of the cosine of the phase angle difference between the positive and negative sequence voltages of the three phases, V + is the amplitude of the positive sequence component of the grid connection point voltage, V - is the amplitude of the negative sequence component of the grid connection point voltage, is the phase angle between positive and negative sequence voltages.

3. The double-layer low voltage ride through control method for a two-stage photovoltaic grid-connected system according to claim 1 or 2, characterized in that: The generated current instruction is specifically expressed as follows: in, and They are the reference values ​​of positive and negative sequence voltages at the grid connection point, respectively; 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 connection point voltage; ω is the angular frequency at the power frequency of the grid; They are respectively 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 connection point voltage; X g With R g are the reactance and resistance values ​​in the line; is the oscillation limit of the DC side voltage; V dc is the DC side voltage value; ε max is the maximum cosine value of the angle between the positive and negative sequence currents; They are respectively the active and reactive negative sequence current instructions output by the inverter.

4. The double-layer low voltage ride through control method for a two-stage photovoltaic grid-connected system according to claim 1, characterized in that: The front-stage inverter compensates the current reference value of the DC side during the low-breakthrough period 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 combined with 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 is compensated to the current reference value of the DC side.

5. The double-layer low voltage ride through control method for a two-stage photovoltaic grid-connected system as claimed in claim 4, characterized in that: The current difference is specifically expressed as: Where ΔP is the power difference, C1 and C2 are the inherent gain coefficients of the photovoltaic panel, and V MPPT is the photovoltaic panel voltage during maximum power tracking, V oc is the open circuit voltage of the photovoltaic panel, I sc is the reverse saturation current.

6. The double-layer low voltage ride through control method for a two-stage photovoltaic grid-connected system according to claim 4, 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.

7. The double-layer low voltage ride through control method for a two-stage photovoltaic grid-connected system according to claim 1, characterized in that: The grid connection point voltage is detected in real time and whether the grid connection point voltage is qualified is determined. 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 drop depth of the positive sequence voltage of the grid connection point reaches below a preset threshold, the grid connection point voltage is determined to be unqualified.

8. Two-stage photovoltaic grid-connected system 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 instructions when the grid connection point voltage is unqualified, with the goal of increasing the positive sequence voltage at the grid connection point and reducing the negative sequence voltage at the grid connection point, and to control the inverter voltage and current through the positive and negative sequence current inner loop and the phase-locked loop; The remaining capacity detection module is used to determine whether the subsequent inverter has remaining capacity based on the generated current command after the AC layer realizes positive and negative sequence voltage support. 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 for the rear-stage inverter to share the output active power instruction with the front-stage inverter after obtaining the output active power instruction. The front-stage inverter compensates the current reference value of the DC side during the low-power period according to the photovoltaic output characteristic curve.

9. An electronic device comprising a memory, a processor and a computer program stored and running on the memory, characterized in that: When the processor executes the program, the double-layer low voltage ride-through control method for the two-stage photovoltaic grid-connected system is implemented as described in any one of claims 1-7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, a double-layer low voltage ride-through control method for a two-stage photovoltaic grid-connected system is implemented as described in any one of claims 1-7.

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