Centralized photovoltaic grid-connected system with super capacitor and high voltage ride-through control method and system thereof

Abstract

This invention discloses a centralized photovoltaic grid-connected system with a supercapacitor and its high-voltage ride-through control method and system. The system includes a centralized photovoltaic array, a supercapacitor, an H-bridge converter, a DC / AC grid-connected inverter, and a DC bus. The supercapacitor is connected to the H-bridge converter and, after passing through a filter circuit, is connected in series with the centralized photovoltaic array and then connected to the DC bus. The input terminal of the DC / AC grid-connected inverter is connected to the DC bus, and its output terminal is connected to the power grid after passing through an LC filter circuit. This invention uses multivariate fault diagnosis criteria for real-time fault judgment and operating mode switching. Through adaptive control of the supercapacitor H-bridge output voltage and optimized control strategies of the DC / AC grid-connected inverter, it improves the system's active support capability, avoids power drop in the centralized photovoltaic system, and achieves high-voltage fault ride-through.

Description

Technical Field

[0001] This invention relates to the field of high voltage ride-through in centralized photovoltaic grid-connected systems, and particularly to a topology of a centralized photovoltaic grid-connected system containing a supercapacitor and a high voltage ride-through control method. Background Technology

[0002] Centralized photovoltaic (PV) inverter systems are key equipment for the large-scale development of PV energy in my country, and are widely used in some PV-rich areas, such as the Northwest region. This type of system has a single-pole architecture, large installed capacity, and relatively simple control, but poor flexibility. In actual operation, some PV-rich areas frequently experience significant active power drops during high-voltage ride-through, seriously affecting grid frequency stability and threatening grid security. Therefore, improving the system's high-voltage ride-through capability has become an urgent issue to ensure the absorption of new energy and grid stability.

[0003] However, existing high-voltage ride-through methods for photovoltaic inverter systems have the following problems:

[0004] (1) There is a lot of research on two-stage architecture, but not enough research on single-stage architecture. Existing research mostly focuses on two-stage topologies in which the photovoltaic array is connected to the DC bus through a DC / DC circuit. However, this type of topology is mostly used in distributed photovoltaic power stations and residential photovoltaic applications, and is not suitable for high-power centralized photovoltaic array scenarios.

[0005] (2) The control strategy is too simple and the fault diagnosis and response are lagging. The existing high voltage ride-through control method is easily affected by grid noise or instantaneous spikes, which can lead to misjudgment or delay. At the same time, the control strategy has not been optimized and the coordination between the inverter and the photovoltaic array is poor, making it impossible to achieve fast mode switching.

[0006] (3) The system architecture is rigid and lacks a dynamic voltage support mechanism. The existing centralized photovoltaic system topology lacks instantaneous voltage support, which makes it impossible for the DC bus voltage to be adaptively adjusted. This forces the power output of the photovoltaic array to be reduced, limiting its reliability in high voltage ride-through scenarios. Summary of the Invention

[0007] The technical problem to be solved by this invention is that the two-stage topology in the prior art is not suitable for high-power centralized photovoltaic array scenarios, and the existing control strategies are simple and lack dynamic voltage support mechanisms. Therefore, this invention proposes a centralized photovoltaic grid-connected system with supercapacitors and its control strategy.

[0008] To solve the above technical problems, the present invention adopts the following technical solution:

[0009] First, this invention proposes a centralized photovoltaic grid-connected system with a supercapacitor. The system includes a centralized photovoltaic array, a supercapacitor, an H-bridge converter, a DC / AC grid-connected inverter, and a DC bus, with the following connection relationship:

[0010] One end of the output of the centralized photovoltaic array is directly connected to the DC bus, and the other end is connected to the output of the H-bridge converter.

[0011] The output terminal of the supercapacitor is connected to the input terminal of the H-bridge converter. After passing through a filter circuit, one end of the output of the H-bridge converter is connected to the photovoltaic array, and the other end is connected to the DC bus, so that the supercapacitor and the centralized photovoltaic array are connected in series through the H-bridge converter.

[0012] The input terminal of the DC / AC grid-connected inverter is connected to the DC bus, and its output terminal is connected to the power grid after passing through an LC filter circuit.

[0013] Furthermore, this invention proposes a centralized photovoltaic grid-connected system that uses the d-axis component of the grid voltage and its variation as a multivariate fault diagnosis criterion for real-time fault judgment, switching between normal operation mode and high-voltage ride-through mode.

[0014] In normal operating mode, the centralized photovoltaic array operates at maximum power point, and the DC / AC grid-connected inverter maintains system stability by adjusting its own modulation ratio, providing voltage regulation and power to the supercapacitor while assisting in grid frequency regulation.

[0015] In high voltage ride-through mode, the supercapacitor actively supports the DC / AC grid-connected inverter through the H-bridge converter, while the centralized photovoltaic array still operates at its maximum power point.

[0016] Furthermore, the system performs real-time fault diagnosis using multivariate fault diagnosis criteria. The fault initiation criterion is as follows:

[0017] (1)

[0018] Where u sdN u, the d-axis component of the grid voltage sd Rated values, k1 is the high voltage ride-through threshold coefficient, k2 and k3 are the lower and upper limits of the grid voltage change rate, respectively, to filter instantaneous noise or spikes;

[0019] The fault recovery criterion is:

[0020] (2)

[0021] Where Δk is the hysteresis width coefficient, which prevents the system from jittering near the critical point, and k4 is the upper limit threshold for fault recovery of the grid voltage change rate, indicating that the system tends to be stable and there is no risk of immediate rebound.

[0022] Furthermore, the d-axis component u of the grid voltage sd The following coordinate transformation is performed after collecting the three-phase grid voltage:

[0023] (3)

[0024] Among them, u sq U represents the q-axis component of the grid voltage. sA u sB and u sC These represent the voltages of the three-phase power grid.

[0025] The control method includes the following parts:

[0026] S1) Centralized photovoltaic array maximum power point tracking control;

[0027] S2) Supercapacitor H-bridge output voltage adaptive control: The output voltage reference value is adaptively adjusted according to the grid voltage. A dual closed-loop control strategy of voltage outer loop and current inner loop is adopted to generate the drive signal of the H-bridge converter.

[0028] S3) Optimized control of DC / AC grid-connected inverter: Extract the output voltage of the supercapacitor H-bridge and the reference voltage of the centralized photovoltaic control output as the reference value of the DC voltage outer loop. Adopt the decoupled dual closed-loop control strategy of DC bus voltage feedforward, bus voltage outer loop and grid-side current inner loop to generate the grid-connected inverter pulse width modulation signal.

[0029] The supercapacitor is connected in series to the DC bus via an H-bridge converter. The supercapacitor's output voltage is adjusted to cope with sudden voltage spikes in the power grid. Specific operating modes include:

[0030] Normal operating mode: When the grid voltage is within the high voltage crossing threshold range, the centralized photovoltaic system operates at the maximum power point, the supercapacitor output voltage is 0, the DC / AC grid-connected inverter maintains system stability by adjusting its own modulation ratio, and the DC bus voltage is stabilized at the maximum power point voltage of the photovoltaic array.

[0031] High Voltage Ride-Through Mode: When the grid voltage exceeds the high voltage ride-through threshold, the inverter voltage exceeds the regulation range of the DC / AC grid-connected inverter. The supercapacitor outputs a DC voltage with the same polarity as the maximum power point voltage of the photovoltaic array through the H-bridge converter, providing voltage support for the grid-connected inverter. The centralized photovoltaic system still operates at the maximum power point. At this time, the DC bus voltage is the sum of the maximum power point voltage of the photovoltaic array and the output voltage of the supercapacitor.

[0032] To achieve adaptive control of the supercapacitor H-bridge output voltage, this invention detects the grid voltage in real time and adjusts the output reference voltage value, specifically including:

[0033] S2.1) Collect the three-phase power grid voltage u sA u sB and u sC And the d-axis component of the grid voltage is obtained through coordinate transformation, and the calculation formula is given by equation (1);

[0034] S2.2) Calculate the output reference voltage value u Co_ref The calculation formula is:

[0035] (4)

[0036] Where u pvN u is the rated maximum power point voltage of the centralized photovoltaic array. sdN The rated value of the d-axis component of the grid voltage;

[0037] S2.3) Acquire the output voltage u of the H-bridge converter Co The reference value i for generating the output current is obtained by using voltage closed-loop control. Lo_ref :

[0038] (5)

[0039] Among them G uo (s) is the closed-loop controller for the output voltage of the H-bridge converter;

[0040] S2.4) Acquire the output current i of the H-bridge converter L A voltage modulation signal u is generated using current closed-loop control. f :

[0041] (6)

[0042] Among them G io (s) is the closed-loop controller for the output current of the H-bridge converter;

[0043] S2.5) Introduce supercapacitor voltage feedforward to calculate the H-bridge converter switching duty cycle d. H =u f / u C To generate the PWM signal for the H-bridge converter, where u C This is the voltage of the supercapacitor.

[0044] Furthermore, to achieve DC / AC grid-connected inverter control, this invention employs a dual closed-loop control strategy consisting of an outer loop for DC bus voltage and an inner loop for grid-side current, and introduces bus voltage feedforward, specifically including:

[0045] S3.1) Signal Acquisition and Coordinate Transformation: Sampling DC bus voltage u dc H-bridge converter output voltage u Co Three-phase grid voltage u sA u sB and u sC Three-phase grid current i sA i sB and i sC And the dq-axis component u of the grid voltage is obtained through coordinate transformation. sd u sq dq-axis component of grid current i sd i sq The coordinate transformation matrix is ​​given by equation (3);

[0046] S3.2) DC bus voltage outer loop control: A PI controller is used, and its output is used as the reference value i for the current inner loop. sd_ref and i sq_ref The DC bus voltage reference u dc_ref The photovoltaic output voltage reference value u pv_ref With H-bridge converter output voltage u Co The sum of i sq_ref To achieve a unity power factor of 0 for grid connection, the specific calculation formula is as follows:

[0047] (7)

[0048] Among them G udc (s) is the DC bus voltage outer loop controller;

[0049] S3.3) Grid-side current inner loop control: A PI controller is used, and the output u of the current inner loop PI controller is... sd_pi u sq_pi for:

[0050] (8)

[0051] Among them G id (s), G iq (s) is the grid-side current inner loop controller; to further resolve dq-axis coupling, a feedforward decoupling term is introduced, and the inverter's dq-axis voltage command u sd_inv u sq_inv The calculation formula is as follows:

[0052] (9)

[0053] S3.4) Inverse coordinate transformation and bus voltage feedforward: Inverse Park transformation is adopted, and DC bus voltage feedforward is introduced to generate the grid-connected inverter pulse width modulation signal u. sα_inv u sβ_inv The calculation formula is as follows:

[0054] (10)

[0055] Where K is the feedforward gain coefficient.

[0056] Secondly, the present invention also proposes a computer program product, including a computer program / instructions that, when executed by a processor, implement the steps of the method described in the present invention.

[0057] Furthermore, the present invention also proposes an electronic system comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the steps of the method described in the present invention.

[0058] Finally, the present invention provides a computer-readable storage medium storing computer instructions for causing the computer to perform the steps of the method described in the present invention.

[0059] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0060] By adopting the centralized photovoltaic grid-connected system topology with supercapacitors and the high-voltage ride-through control strategy provided by this invention, when the grid voltage suddenly rises, the system switches modes, the supercapacitor is immediately put into operation, and the centralized photovoltaic system still maintains maximum power point operation, thus avoiding power drop. Attached Figure Description

[0061] Figure 1 This is a topology diagram of the centralized photovoltaic grid-connected system containing supercapacitors according to the present invention.

[0062] Figure 2 This is a schematic diagram of the high-voltage ride-through operating mode switching process of the present invention.

[0063] Figure 3 This is a block diagram showing the switching of the working mode for the adaptive control of the supercapacitor H-bridge output voltage of the present invention.

[0064] Figure 4 This is the block diagram of the optimized control of the DC / AC grid-connected inverter of the present invention.

[0065] Figure 5 This is a diagram showing the key output waveforms of each module in the high-voltage ride-through switching of the system of this invention. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the application will be further described in detail below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments involved in this invention. All non-innovative embodiments based on these embodiments by other researchers in the art are within the protection scope of this invention. Furthermore, the step numbers in the embodiments of this invention are only set for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0067] Example 1: In one embodiment of the present invention, a topology incorporating a supercapacitor and a novel high-voltage ride-through control method are proposed for a centralized photovoltaic grid-connected system with a maximum power of 53kW. The system structure is as follows. Figure 1 As shown, it includes: a centralized photovoltaic array, a supercapacitor, an H-bridge converter, a DC / AC grid-connected inverter, a power grid, and a DC bus.

[0068] Specifically, one end of the output of the centralized photovoltaic array is directly connected to the DC bus, and the other end is connected to the output of the H-bridge converter; the output of the supercapacitor is connected to the input of the H-bridge converter, and the output of the H-bridge converter is connected to the photovoltaic array at one end after passing through the filter circuit, and connected to the DC bus at the other end, so that the supercapacitor and the centralized photovoltaic array are in series through the H-bridge converter; the input of the DC / AC grid-connected inverter is connected to the DC bus, and its output is connected to the grid after passing through the LC filter circuit.

[0069] according to Figure 1 The present invention provides a high-voltage ride-through control method for the system modules shown, comprising the following parts:

[0070] S1) The perturbation observation method is used for maximum power point tracking control of the centralized photovoltaic array;

[0071] S2) Supercapacitor H-bridge output voltage adaptive control;

[0072] S3) Optimized control of DC / AC grid-connected inverters;

[0073] The high-voltage ride-through working mode switching method provided in this embodiment is as follows: Figure 2 As shown, the system uses a fault initiation criterion to determine whether a high-voltage fault has occurred, thus deciding whether to switch from normal operating mode to high-voltage ride-through mode. Then, a fault recovery criterion is used to determine whether the fault has been recovered, deciding whether to switch back to normal operating mode. The fault initiation criterion is:

[0074]

[0075] According to national high-voltage ride-through regulations, photovoltaic power stations are required to have the capability to operate continuously for 500ms when the AC side voltage is not higher than 1.3 pu, and for 10s when it is not higher than 1.2 pu. In this embodiment, the high-voltage ride-through threshold coefficient k1 = 1.3 is selected. To avoid interference such as noise spikes and improve the reliability of fault diagnosis, the upper and lower limit thresholds of the rate of change are selected as k3 = 10 and k2 = 0.1.

[0076] The fault recovery criterion is:

[0077]

[0078] To prevent the system from oscillating at the switching point, the hysteresis width coefficient Δk = 0.1 is selected in this embodiment; to avoid the system from rebounding after the fault is recovered, the upper limit of the rate of change k4 ≈ 0 is selected, and k4 = 0.1 is taken in this embodiment.

[0079] In this embodiment, the voltage at the maximum power point of the centralized photovoltaic system is 725V. The specific steps of the perturbation observation method mentioned in S1 are as follows:

[0080] S1.1) Voltage perturbation application: In each control cycle, a small perturbation is applied to the output reference voltage of the photovoltaic array in fixed steps, that is, the current reference voltage value u is changed. pv_ref (k)= u pv_ref (k-1)±△u, where △u is the preset voltage disturbance step size, set to 0.1V;

[0081] S1.2) Power Sampling and Calculation: Real-time sampling of the output voltage u of the photovoltaic array pv (k) and output current i pv (k), and calculate the output power P at the current time. pv (k)= u pv (k)×i pv (k);

[0082] S1.3) Power change calculation: The current output power P pv (k) and the output power P of the previous cycle pv Compare with (k-1) and calculate the power change ΔP = P pv (k)- P pv (k-1);

[0083] S1.4) Disturbance direction decision: If ΔP>0, it means that the power change direction is consistent with the voltage disturbance direction of the previous cycle, and the voltage disturbance direction will be maintained in the next cycle; if ΔP<0, it means that the power change direction is opposite to the voltage disturbance direction of the previous cycle, and the voltage disturbance direction will be reversed immediately in the next cycle.

[0084] By continuously repeating the above steps, the operating point of the photovoltaic array is dynamically stabilized near the maximum power point.

[0085] In this embodiment, a 99.5F supercapacitor with a rated capacity of 600V is selected. The adaptive control of the supercapacitor H-bridge output voltage mentioned in S2 is as follows: Figure 3 As shown, the specific steps are as follows:

[0086] S2.1) Collect the three-phase power grid voltage u sA u sB and u sC The d-axis component of the grid voltage is obtained through coordinate transformation;

[0087] S2.2) Calculate the output reference voltage value u Co_ref In normal working mode u Co_ref =0, and according to the calculation formula in high voltage ride-through mode, we can obtain:

[0088]

[0089] S2.3) Acquire the output voltage u of the H-bridge converter Co The reference value i for generating the output current is obtained by using voltage closed-loop control. Lo_ref Its voltage outer loop controller G uo The transfer function (s) is as follows:

[0090]

[0091] Among them, K p1 K represents the proportional gain. i1 Indicates integral gain. This represents the Laplace transform variable. In this embodiment, the parameters are selected as follows: K p1 =0.5, K i1 =50;

[0092] S2.4) Acquire the output current i of the H-bridge converter L A voltage modulation signal u is generated using current closed-loop control. f Its current closed-loop controller G io (s) parameter is selected as: K p2 =5,K i2 =300;

[0093] S2.5) Introduce supercapacitor voltage feedforward to calculate the H-bridge converter switching duty cycle d. H =u f / u C To generate the PWM signal for the H-bridge converter, where u C =600V.

[0094] In this embodiment, the optimized control of the DC / AC grid-connected inverter is as follows: Figure 4 As shown, the specific steps are as follows:

[0095] S3.1) Signal Acquisition and Coordinate Transformation: Sampling DC bus voltage u dc H-bridge converter output voltage u Co Three-phase grid voltage u sA u sB and u sC Three-phase grid current i sA i sB and i sC And the dq-axis component u of the grid voltage is obtained through coordinate transformation. sd u sq dq-axis component of grid current i sd i sq ;

[0096] S3.2) DC bus voltage outer loop control: A PI controller is used, and its output is used as the reference value i for the current inner loop. sd_ref and i sq_ref Keep i sq_ref =0 to ensure unity power factor grid connection. Under normal operating conditions, the DC bus voltage reference value of the voltage loop is the output voltage reference value u of the centralized photovoltaic maximum power point tracking control. pv_ref With H-bridge converter output voltage u Co The sum; in high voltage ride-through mode, maintain u pv_ref =u MPP =725V, allowing the photovoltaic system to operate at maximum power. The DC bus voltage outer loop controller G... udc (s) parameter is selected as: K p3 =0.1, K i3 =100;

[0097] S3.3) Grid-side current inner loop control: A PI controller is used, and the output u of the current inner loop PI controller is... sd_pi u sq_pi Among them, the grid-side current inner loop controller G id (s), G iq (s) parameter is selected as: K p4 = K p5 =22.201, K i4 = K i5 =49348; The calculated value of the decoupling feedforward coefficient is:

[0098]

[0099] S3.4) Inverse coordinate transformation and bus voltage feedforward: Inverse Park transformation is adopted, and DC bus voltage feedforward is introduced to generate the grid-connected inverter pulse width modulation signal u. sα_inv u sβ_inv In this embodiment, the feedforward gain coefficient K=1.48.

[0100] In summary, after adopting the proposed topology and high-voltage ride-through control strategy, the key output waveforms of each module during high-voltage ride-through operation switching are as follows: Figure 5 As shown, when the grid voltage suddenly rises, the system switches modes, the supercapacitor is immediately put into operation, and the centralized photovoltaic system continues to operate at its maximum power point, thus avoiding a power drop.

[0101] Example 2: This example proposes a computer program product, including a computer program / instructions, which, when executed by a processor, implements the steps of the method described in this invention.

[0102] Example 3: This example proposes an electronic system, including: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the method steps of the present invention.

[0103] It should be noted that the electronic system can use terminal devices such as desktop computers, laptops, or cloud servers. Furthermore, terminal devices include, but are not limited to, processors and memory. For example, terminal devices can also include input / output devices, network access devices, and buses.

[0104] Furthermore, the processor can be a central processing unit (CPU). Of course, depending on the actual use, other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), off-the-shelf programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. can also be used. The general-purpose processor can be a microprocessor or any conventional processor, etc., and this application does not limit it in this regard.

[0105] Furthermore, the memory can be an internal storage unit of the terminal device, such as the hard disk or RAM of the terminal device, or an external storage device of the terminal device, such as a plug-in hard disk, smart memory card (SMC), secure digital card (SD), or flash memory card (FC) equipped on the terminal device. In addition, the memory can also be a combination of the internal storage unit and the external storage device of the terminal device. The memory is used to store computer programs and other programs and data required by the terminal device. The memory can also be used to temporarily store data that has been output or will be output. This application does not limit this.

[0106] Furthermore, through this electronic system, any one of the methods described in the above embodiments can be stored in the memory of the electronic system and loaded and executed on the processor of the terminal device for convenient use.

[0107] Example 4: This example also discloses a computer-readable storage medium, which stores a computer program, wherein when the computer program is executed by a processor, it employs the steps of any of the methods described in the above examples.

[0108] The computer program can be stored in a computer-readable medium. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or certain middleware. The computer-readable medium includes any entity or device capable of carrying computer program code, recording media, USB flash drive, portable hard drive, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the computer-readable medium includes, but is not limited to, the above-mentioned components.

[0109] It should be further explained that the control methods in the above embodiments are stored in the computer-readable storage medium and loaded and executed on the processor through this computer-readable storage medium, so as to facilitate the storage and application of the above methods.

[0110] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0111] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A centralized photovoltaic grid-connected system containing supercapacitors, characterized in that, include: The system includes a centralized photovoltaic array, a supercapacitor, an H-bridge converter, a DC / AC grid-connected inverter, and a DC bus. One end of the output of the centralized photovoltaic array is directly connected to the DC bus, and the other end is connected to the output of the H-bridge converter. The output terminal of the supercapacitor is connected to the input terminal of the H-bridge converter. After passing through a filter circuit, one end of the output of the H-bridge converter is connected to the photovoltaic array, and the other end is connected to the DC bus, so that the supercapacitor and the centralized photovoltaic array are connected in series through the H-bridge converter. The input terminal of the DC / AC grid-connected inverter is connected to the DC bus, and its output terminal is connected to the power grid after passing through an LC filter circuit. The system responds to sudden rises in grid voltage by adjusting the output voltage of the supercapacitor, uses the d-axis component of the grid voltage and its change as a multivariate fault diagnosis criterion for real-time fault judgment, and switches between normal operation mode and high voltage ride-through mode.

2. A centralized photovoltaic grid-connected system with supercapacitors according to claim 1, characterized in that, The multivariate fault diagnosis criteria include fault initiation criteria and fault recovery criteria, as detailed below: The fault initiation criterion is: (1) The fault recovery criterion is: (2) Where u sdN u, the d-axis component of the grid voltage sd The rated values ​​are: k1 is the high voltage ride-through threshold coefficient, k2 and k3 are the lower and upper limits of the grid voltage change rate, respectively, to filter instantaneous noise or spikes; Δk is the hysteresis width coefficient to prevent the system from jittering near the critical point, and k4 is the upper limit threshold for grid voltage change rate fault recovery.

3. A centralized photovoltaic grid-connected system with a supercapacitor according to claim 2, characterized in that, d-axis component of grid voltage u sd By collecting the three-phase power grid voltage u sA u sB and u sC The following coordinate transformation was then performed to obtain: (3) Among them, u sq U represents the q-axis component of the grid voltage. sA u sB and u sC These represent the voltages of the three-phase power grid.

4. A centralized photovoltaic grid-connected system with a supercapacitor as described in claim 1, characterized in that, The system switches between normal operating mode and high voltage ride-through mode as follows: Normal operating mode: When the grid voltage is within the high voltage crossing threshold range, the centralized photovoltaic system operates at the maximum power point, the supercapacitor output voltage is 0, the DC / AC grid-connected inverter maintains system stability by adjusting its own modulation ratio, and the DC bus voltage is stabilized at the maximum power point voltage of the photovoltaic array. High Voltage Ride-Through Mode: When the grid voltage exceeds the high voltage ride-through threshold, the inverter voltage exceeds the regulation range of the DC / AC grid-connected inverter. The supercapacitor outputs a DC voltage with the same polarity as the maximum power point voltage of the photovoltaic array through the H-bridge converter, providing voltage support for the grid-connected inverter. The centralized photovoltaic system still operates at the maximum power point. At this time, the DC bus voltage is the sum of the maximum power point voltage of the photovoltaic array and the output voltage of the supercapacitor.

5. A high-voltage ride-through control method for a centralized photovoltaic grid-connected system containing supercapacitors, applied to the system described in any one of claims 1-4, characterized in that, Includes the following steps: S1, Centralized photovoltaic array maximum power point tracking control; S2. Supercapacitor H-bridge output voltage adaptive control: The output voltage reference value is adaptively adjusted according to the grid voltage. A dual closed-loop control strategy of voltage outer loop and current inner loop is adopted to generate the drive signal of the H-bridge converter. S3, DC / AC grid-connected inverter optimized control: Extract the output voltage of the supercapacitor H-bridge and the output reference voltage of the centralized photovoltaic control as the reference value of the DC voltage outer loop, and adopt a decoupled dual closed-loop control strategy of DC bus voltage feedforward, bus voltage outer loop and grid-side current inner loop to generate the grid-connected inverter pulse width modulation signal.

6. The method according to claim 5, characterized in that, The adaptive control of the supercapacitor H-bridge output voltage specifically includes: S2.1, Acquire three-phase grid voltage u sA u sB and u sC The d-axis component of the grid voltage is obtained through coordinate transformation; S2.2 Calculate the output reference voltage value u Co_ref The calculation formula is: (4) Where u pvN u is the rated maximum power point voltage of the centralized photovoltaic array. sdN The rated value of the d-axis component of the grid voltage; S2.3, Acquire the output voltage u of the H-bridge converter Co The reference value i for generating the output current is obtained by using voltage closed-loop control. Lo_ref : (5) Among them G uo (s) is the closed-loop controller for the output voltage of the H-bridge converter; S2.4, Acquire the output current i of the H-bridge converter L A voltage modulation signal u is generated using current closed-loop control. f : (6) Among them G io (s) is the closed-loop controller for the output current of the H-bridge converter; S2.

5. Introduce supercapacitor voltage feedforward and calculate the switching duty cycle d of the H-bridge converter. H =u f / u C To generate the PWM signal for the H-bridge converter, where u C This is the voltage of the supercapacitor.

7. The method according to claim 6, characterized in that, The control of the DC / AC grid-connected inverter specifically includes: S3.1 Signal Acquisition and Coordinate Transformation: Sampling DC bus voltage u dc H-bridge converter output voltage u Co Three-phase grid voltage u sA u sB and u sC Three-phase grid current i sA i sB and i sC And the dq-axis component u of the grid voltage is obtained through coordinate transformation. sd u sq dq-axis component of grid current i sd i sq ; S3.2, DC bus voltage outer loop control: A PI controller is used, and its output serves as the reference value i for the current inner loop. sd_ref and i sq_ref The DC bus voltage reference u dc_ref The photovoltaic output voltage reference value u pv_ref With H-bridge converter output voltage u Co The sum of i sq_ref To achieve a unity power factor of 0 for grid connection, the specific calculation formula is as follows: (7) Among them G udc (s) is the DC bus voltage outer loop controller; S3.3, Grid-side current inner loop control: A PI controller is used, and the output u of the current inner loop PI controller is... sd_pi u sq_pi for: (8) Among them G id (s), G iq (s) is the grid-side current inner loop controller; To further address dq-axis coupling, a feedforward decoupling term is introduced, and the inverter's dq-axis voltage command u... sd_inv u sq_inv The calculation formula is as follows: (9) S3.4 Inverse Coordinate Transformation and Bus Voltage Feedforward: Inverse Park transformation is adopted, and DC bus voltage feedforward is introduced to generate the grid-connected inverter pulse width modulation signal u. sα_inv u sβ_inv The calculation formula is as follows: (10) Where K is the feedforward gain coefficient.

8. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method described in claims 5-7.

9. An electronic system comprising: At least one processor; And a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, characterized in that the instructions are executed by the at least one processor to enable the at least one processor to perform the method steps of any one of claims 5-7.

10. A computer-readable storage medium storing computer instructions, characterized in that, The computer instructions are used to cause the computer to perform the steps of the method described in any one of claims 5-7.

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