Power quality compensation method and device for new energy access to power grid

Abstract

The application relates to the technical field of intelligent optimization compensation of transformers, in particular to a power quality compensation method and device for new energy access to a power grid, which comprises the following steps: connecting a dynamic voltage compensation converter in series at the low-voltage side of a transformer, connecting a high-power bidirectional converter in parallel at the terminal load side, collecting voltages at each moment in each cycle at the low-voltage side of the transformer, and recording the voltages as transformer voltages; collecting load currents and load voltages at each moment in each cycle at the terminal load side; determining the influence weight of each cycle harmonic disturbance, the influence weight of reactive power disturbance and the influence weight of voltage out-of-limit; constructing a target function; using an intelligent optimization algorithm and combining the target function, obtaining the optimal power factor, each harmonic current component and each transformer voltage in the current cycle, and performing transformer voltage compensation, reactive compensation and harmonic current compensation on the current cycle respectively. Therefore, the overall stability of power quality is improved.

Description

Technical Field

[0001] This application relates to the field of intelligent optimization and compensation technology for transformers, specifically to a power quality compensation method and equipment for new energy grid access. Background Technology

[0002] The grid connection of renewable energy sources such as photovoltaic and wind power into the power system can lead to a decline in power quality. Power quality issues affect the normal operation of power equipment and, in severe cases, can cause three-phase imbalance, large voltage fluctuations, and harmonics, posing a serious threat to the stability and reliability of the power grid. Power electronic converters can regulate power to solve power quality problems, ensuring that the output meets the frequency and voltage requirements of user loads. Integrated series-parallel voltage source converters can dynamically respond to real-time conditions such as load changes and harmonic fluctuations in the power system. Series voltage source converters can adjust voltage fluctuations in real time to balance voltage stability; while parallel voltage source converters can provide timely compensation when load fluctuations or reactive power demand changes occur, ensuring the stability of the power system.

[0003] Existing intelligent compensation methods often only target one type of power quality problem for detection and management. They rely on a single control strategy, lack flexibility, cannot effectively cope with complex multi-objective optimization problems, and suffer from low power quality stability. Summary of the Invention

[0004] To address the aforementioned technical problems, the purpose of this application is to provide a power quality compensation method and equipment for integrating new energy sources into the power grid. The specific technical solution adopted is as follows:

[0005] In a first aspect, embodiments of this application provide a power quality compensation method for new energy grid integration, the method comprising the following steps:

[0006] A dynamic voltage compensation converter is connected in series on the low-voltage side of the transformer, and a high-power bidirectional converter is connected in parallel on the terminal load side. The voltage at each moment in each cycle on the low-voltage side of the transformer is collected and recorded as the transformer voltage; the load current and load voltage at each moment in each cycle on the terminal load side are collected.

[0007] Based on the load current at all times within each cycle, the harmonic current components are obtained to obtain the total harmonic distortion rate of each cycle; by the degree of variation of the total harmonic distortion rate of each cycle relative to the historical cycle, the influence weight of harmonic disturbances in each cycle is determined.

[0008] Based on the load current and the load voltage, the power factor of each cycle on the terminal load side is obtained, and the influence weight of reactive power disturbance in each cycle is determined by the degree of deviation between the power factor of each cycle and the historical cycle.

[0009] determine an influence weight of voltage out-of-limit of each cycle based on a difference degree of transformer voltage fluctuation of each cycle compared with historical cycles;

[0010] calculate a current power quality state index based on the transformer voltage, load current and load voltage collected in each cycle, combine the determined influence weight of harmonic disturbance, influence weight of reactive power disturbance and influence weight of voltage out-of-limit to build a multi-objective optimization objective function containing total harmonic distortion, power factor and transformer voltage deviation;

[0011] use intelligent optimization algorithm to combine the objective function to obtain optimal power factor, each harmonic current component and each transformer voltage of the current cycle, and perform transformer voltage compensation, reactive compensation and harmonic current compensation on the current cycle.

[0012] In one embodiment, the determination of the influence weight of harmonic disturbance of each cycle includes:

[0013] calculate a ratio of total harmonic distortion of each cycle to an average of total harmonic distortions of all previous cycles, denoted as a first ratio, when the first ratio is greater than or equal to a value of 1, the influence weight of corresponding cycle harmonic disturbance is 1, otherwise, the influence weight of corresponding cycle harmonic disturbance is the first ratio.

[0014] In one embodiment, the determination of the influence weight of reactive power disturbance of each cycle includes:

[0015] calculate a ratio of the power factor of each cycle to an average of power factors of all previous cycles, denoted as a second ratio, and the influence weight of reactive power disturbance of each cycle is a normalized result of the second ratio.

[0016] In one embodiment, the determination of the influence weight of voltage out-of-limit of each cycle includes:

[0017] calculate a ratio of transformer voltage variance of all time points of each cycle to an average of transformer voltage variances of all previous cycles, denoted as a third ratio, if the third ratio is greater than or equal to a value of 1, the influence weight of corresponding cycle voltage out-of-limit is a value of 1, otherwise, the influence weight of corresponding cycle voltage out-of-limit is the third ratio.

[0018] In one embodiment, the expression of the objective function is:

[0019]

[0020] In the formula, is a target function value of the jth cycle, , , These are the weights of the impact of harmonic disturbance, reactive power disturbance, and voltage over-limit in the j-th cycle, respectively. Let be the total harmonic distortion rate of the j-th period; Let be the power factor in the j-th cycle; This represents the i-th transformer voltage sample value in the j-th cycle. The average voltage over the period is N, where N is the number of sampling points. This is the effective value of the rated voltage on the low-voltage side of the transformer;

[0021] The specific calculation method is as follows: ,in Let M be the effective value of the kth harmonic current component in the jth period, M be the total number of harmonic current components, and V be the effective value of the fundamental component in the jth period.

[0022] In one embodiment, the initial particles of the intelligent optimization algorithm are: each harmonic current component, power factor, and transformer voltage of each cycle, which are preset a number of cycles before each cycle.

[0023] In one embodiment, the transformer voltage compensation includes:

[0024] The optimized transformer voltage at each moment of the current period is obtained using the Clarke transform. Components and The components are denoted as follows: and Based on the preset rated voltage amplitude And the phase angle θ at the current moment, the transformer voltage compensation at each moment Axial components and The calculation method for shaft components is as follows:

[0025]

[0026]

[0027] In the formula, It is a trigonometric sine function. It is a trigonometric cosine function. This is the fundamental phase angle of the power grid obtained through a phase-locked loop.

[0028] In one embodiment, the reactive power compensation amount is calculated as follows:

[0029] In the formula, This is the amount of reactive power compensation for the current cycle. This represents the active power collected in the current cycle. The power factor collected in the current cycle. The power factor optimized for the current cycle.

[0030] In one embodiment, the compensation amount of the harmonic current compensation is a difference between each optimal harmonic current component and a preset target harmonic current value.

[0031] In a second aspect, the embodiments of the present application further provide an electric energy quality compensation device for new energy access to a power grid, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, and the processor implements the steps of the method in any of the above aspects when executing the computer program.

[0032] The present application has at least the following beneficial effects:

[0033] The application collects the voltage at each moment in each cycle at the low-voltage side of the transformer, denoted as the transformer voltage; collects the load current and load voltage at each moment in each cycle at the terminal load side; obtains each harmonic current component based on the load current at all moments in each cycle, and obtains the total harmonic distortion rate of each cycle; determines the influence weight of harmonic disturbance of each cycle through the variation degree of the total harmonic distortion rate of each cycle relative to the historical cycle; evaluates the influence degree of harmonic current disturbance and improves the accuracy of subsequent harmonic current compensation; obtains the power factor of each cycle at the terminal load side based on the load current and the load voltage, and determines the influence weight of reactive power disturbance of each cycle by using the deviation degree of the power factor of each cycle relative to the historical cycle; the influence weight of reactive power disturbance reflects the urgency of reactive power compensation of each cycle, and embodies the imbalance of power grid load and the instability of power grid operation, thereby providing a reference for the determination of subsequent reactive power compensation; determines the influence weight of voltage out-of-limit of each cycle based on the difference degree of transformer voltage fluctuation of each cycle relative to the historical cycle; the influence weight of voltage out-of-limit of each cycle reflects the instability degree of transformer voltage of each cycle, thereby improving the reliability of transformer voltage compensation; real-time preliminary voltage compensation is performed at the low-voltage side of the transformer, real-time preliminary reactive power compensation and harmonic current compensation are respectively performed at the terminal load side, a target function is constructed based on the total harmonic distortion rate, the power factor, the transformer voltage fluctuation of each cycle, and in combination with the influence weight of harmonic disturbance, the influence weight of reactive power disturbance, and the influence weight of voltage out-of-limit of each cycle; the construction of the target function integrates various power quality problems, and can solve power quality problems from multiple aspects; the optimal power factor, each harmonic current component, and each transformer voltage of the current cycle are obtained by using an intelligent optimization algorithm in combination with the target function, and transformer voltage compensation, reactive power compensation, and harmonic current compensation are respectively performed on the current cycle. The power quality is significantly optimized, the loss of the power system can be effectively reduced in terms of the power factor, the reactive power, the harmonic, and the voltage stability, and the overall efficiency of the power system and the stability of the power quality are improved. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0035] Figure 1 A step flow chart of a power quality compensation method for new energy access to a power grid provided by an embodiment of the present application;

[0036] Figure 2 A flow chart is determined for the objective function. DETAILED DESCRIPTION

[0037] In order to further clarify the technical means and effects taken by the present application to achieve the predetermined inventive objectives, the specific implementation, structure, features and effects of the power quality compensation method and device for new energy access to power grid according to the present application are described in detail below in combination with the drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0038] 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.

[0039] The specific scheme of the power quality compensation method and device for new energy access to power grid provided by the present application is specifically described below in combination with the drawings.

[0040] Please refer to Figure 1 , which shows the step flow chart of the power quality compensation method for new energy access to power grid provided by one embodiment of the present application, which includes the following steps:

[0041] S1, a dynamic voltage compensation converter is connected in series at the low-voltage side of the transformer, a high-power bidirectional converter is connected in parallel at the terminal load side, the voltage at each time in each cycle at the low-voltage side of the transformer is collected and recorded as the transformer voltage, and the load current and load voltage at each time in each cycle at the terminal load side are collected.

[0042] In this embodiment, a dynamic voltage compensation converter based on PWM (Pulse Width Modulation) control is connected in series at the low-voltage side of the transformer for suppressing low-order harmonics and voltage fluctuations of the transformer output voltage, and the converter is connected with the low-voltage bus through a phase-shift transformer. A voltage transformer with a transformation ratio of 400V / 100V is installed at the three-phase four-wire bus at the low-voltage side of the transformer to collect the bus voltage signal at each time in each cycle, which is recorded as the transformer voltage. At the same time, a high-power bidirectional converter is connected in parallel at the terminal load side for compensating the load harmonic current and reactive power. A closed-loop Hall sensor is used to collect the current signal at each time in each cycle at the load side, which is recorded as the load current, and a voltage transformer with a transformation ratio of 220V / 5V is used to collect the voltage signal at each time in each cycle at the load side, which is recorded as the load voltage. In this embodiment, the transformer voltage, load voltage and load current are synchronously collected, and the sampling frequency is 5kHz, and each 10ms is a processing period. The implementer can set the sampling frequency and the length of the period according to the actual situation, which is not limited in this embodiment.

[0043] The transformer voltage at all times in each cycle is taken as the input of a low-pass filter to eliminate high-frequency noise, and the output is the denoised transformer voltage at all times in each cycle. The denoised transformer voltage is normalized by using the maximum-minimum value normalization method. The load current at all times in each cycle and the load voltage at all times in each cycle are denoised and normalized by using the same denoising and normalization method as the transformer voltage at all times in each cycle. The denoised and normalized transformer voltage, load current, and load voltage at all times in each cycle are obtained. The low-pass filter and the maximum-minimum value normalization method are both known technologies, and thus will not be described in detail in this embodiment.

[0044] S2, based on the load current at all times in each cycle, obtains each harmonic current component to obtain the total harmonic distortion rate of each cycle; and determines the influence weight of the harmonic disturbance of each cycle through the variation degree of the total harmonic distortion rate of each cycle relative to the historical cycle.

[0045] With a high proportion of photovoltaic access to the distribution network, due to the randomness and strong dispersion of photovoltaic, the stability of power quality is greatly affected, and the complexity of power quality disturbance is high. In order to deal with power quality problems, power electronic converters are usually used to adjust power and compensate current and voltage to ensure the stability of power quality. The traditional compensation method is difficult to cope with the real-time influence of photovoltaic access on power quality, so it is difficult to compensate in time to ensure the stability of power quality. At the same time, the traditional compensation method often relies on a single control strategy, and the compensation for power quality fluctuations caused by photovoltaic access lacks sufficient flexibility and comprehensiveness.

[0046] In the distribution network, there may be multiple problems affecting power quality at the same time, and the changes of voltage and current are the final result caused by the mutual influence of multiple problems. At this time, the calculation of compensation amount according to this result will cause a certain relief to various problems after compensation, but it is difficult to solve all problems or achieve an optimal balance state at the same time. Therefore, the transformer voltage, reactive power, and harmonic are analyzed in this embodiment, and multi-objective optimization is continued according to the result after compensation to achieve the final optimal compensation.

[0047] In the distribution network, the common problems affecting power quality include reactive power, harmonic, and voltage out-of-limit problem, so certain voltage and current compensation is needed to ensure that the power quality meets the requirements of the power supply system. In order to calculate the voltage and current compensation amount, the effective value of voltage and current, active power, reactive power, and harmonic current in each cycle need to be calculated according to the collected voltage and current data.

[0048] In this embodiment, the normalized load current at all times in each cycle is first processed using a fast Fourier transform algorithm to obtain the corresponding frequency domain data, the harmonic current components of each cycle are obtained, and the total harmonic distortion rate of the load current in each cycle is calculated. The fast Fourier transform algorithm, the acquisition of harmonic current components, and the calculation of the total harmonic distortion rate are all existing known technologies, and the specific process will not be described in detail.

[0049] Among the various issues affecting power quality, the greater the degree of variation in the corresponding parameters relative to historical periods, the more severe the impact on power quality. Therefore, in subsequent multi-objective optimization, these issues require greater weight to enhance compensation for disturbances and improve power quality. Thus, it is necessary to calculate the corresponding impact weights based on the variation of various issues, specifically:

[0050] , It is the first The influence weight of harmonic disturbances within each period For the first The total harmonic distortion rate of each cycle is the same as the previous one. The ratio of the average total harmonic distortion (THD) over each period is denoted as the first ratio. It can be understood that the smaller the THD, the smaller the degree of harmonic disturbance, and therefore the smaller the impact of harmonics on power quality. The corresponding influence weight is then determined accordingly. The smaller it is.

[0051] S3. Based on the load current and the load voltage, obtain the power factor of each cycle on the terminal load side, and determine the influence weight of reactive power disturbance in each cycle by utilizing the degree of deviation between the power factor of each cycle and the historical cycle.

[0052] Based on the normalized load voltage and load current at all times in each cycle, the active power and reactive power of each cycle are calculated, and the power factor of each cycle is calculated. It should be noted that the calculation of active power, reactive power and power factor of each cycle are all existing known technologies, and the specific process will not be described in detail.

[0053] , It is the first The weighting of the impact of reactive power disturbance within each cycle. It is a normalization function. For the first The power factor of each cycle is the same as the previous one. The ratio of the average power factor over each period is denoted as the second ratio. It can be understood that the greater the impact of reactive power disturbances on power quality, the smaller the corresponding power factor, and thus the greater the corresponding impact weight. The larger it gets, the bigger it becomes.

[0054] S4, determining the influence weight of voltage out-of-limit of each cycle based on the difference degree of transformer voltage fluctuation of each cycle compared with historical cycles.

[0055] The disturbance of voltage is real-time, and the voltage is also constantly fluctuating as an approximate sine wave, so the fluctuation of voltage is measured by the variance of transformer voltage data in each cycle, and the voltage out-of-limit problem, i.e. the excessive or insufficient fluctuation of voltage, exceeds the normal fluctuation range, so the variance can also reflect the voltage out-of-limit, and the calculation method of the influence weight of voltage out-of-limit is:

[0056] , is the influence weight of voltage out-of-limit in the first cycle, is the third ratio, , is the variance of transformer voltage in the first cycle, is the mean value of transformer voltage variance of the previous cycles. It can be understood that when the voltage out-of-limit is more serious, the disturbance to power quality is more serious, and the corresponding transformer voltage variance is also larger, so the corresponding influence weight is also larger.

[0057] S5, calculating the current power quality state index based on the transformer voltage, load current and load voltage collected in each cycle, and combining the influence weight of harmonic disturbance, the influence weight of reactive power disturbance and the influence weight of voltage out-of-limit, to build a multi-objective optimization objective function containing total harmonic distortion, power factor and transformer voltage deviation.

[0058] In order to realize the comprehensive optimal management of power quality, the embodiment discards the single target independent compensation mode, and adopts the multi-objective joint optimization strategy. After collecting the current voltage and current data, the physical compensation action is not immediately executed, but the target function reflecting the comprehensive index of power quality is first constructed. The target function comprehensively considers the influence of three dimensions of harmonic, reactive power and voltage fluctuation, and uses the weight coefficients determined in steps S2 to S4 to dynamically adjust the optimization priority of each dimension, thereby providing a mathematical model basis for subsequent calculation of optimal compensation instructions.

[0059] In the process of collection, the transformer voltage at each time in each cycle and the load current and load voltage at each time in each cycle at the terminal load side are also collected in the embodiment. To optimize the transformer voltage compensation, reactive power compensation and harmonic current compensation in the current cycle, the transformer voltage, load current and load voltage collected in the previous G cycles of the current cycle are first obtained in the embodiment, and the fundamental component and each harmonic current component are obtained based on the load current by using the fast Fourier transform algorithm. In the embodiment, G = 60, and the implementer can set it according to the actual situation.

[0060] At the terminal load side, the power factor of each cycle in the previous G cycles and each harmonic current component of each cycle are obtained based on the load voltage and load current collected in each cycle, and the transformer voltage collected at each time in each cycle in the previous G cycles is obtained.

[0061] The historical data of the previous G cycles of the current cycle are obtained, including the power factor, harmonic current component and transformer voltage. The power factor of each cycle, all harmonic current components and all transformer voltages are used as the initial particles of the intelligent optimization algorithm. When compensation is performed for each cycle, due to different power quality disturbance conditions, there is a certain difference in the target function used. For example, the target function of the first cycle is constructed based on each harmonic current component, power factor and each transformer voltage, and the specific expression of the target function is as follows:

[0062]

[0063] In the formula, f j is the target function value of the jth cycle, , , , are the influence weights of the harmonic disturbance, reactive power disturbance and voltage out-of-limit of the jth cycle respectively; is the total harmonic distortion rate of the jth cycle; is the power factor of the jth cycle; is the ith transformer voltage sampling value of the jth cycle, is the average voltage in the cycle, and N is the number of sampling points; is the rated voltage effective value of the low-voltage side of the transformer, and the value of the embodiment is 220V.

[0064] The specific calculation method of is as follows: wherein is the effective value of the kth harmonic current component of the jth cycle, M is the total number of harmonic current components, and V is the effective value of the fundamental component of the jth cycle. If the value of the target function is smaller, it means that the comprehensive index of power quality is better. ​

[0065] The flowchart for determining the objective function is as follows: Figure 2 As shown.

[0066] It is understandable that, in order to ensure power quality after compensation, it is necessary to minimize the power quality disturbances caused by harmonics, reactive power, and voltage over-limits, and to maximize the difference in disturbance changes before and after compensation. Therefore, the objective function mentioned above is used to optimize the objective function so that it is greater than 0 and reaches its minimum value, that is, the closer the objective function is to 0, the better.

[0067] S6. Using an intelligent optimization algorithm and the objective function, obtain the optimal power factor, harmonic current components, and transformer voltage for the current cycle, and perform transformer voltage compensation, reactive power compensation, and harmonic current compensation for the current cycle.

[0068] Assuming the j-th period is the current period, this embodiment utilizes the objective function, combined with all initial particles, and employs a multi-objective particle swarm optimization algorithm for optimization, where the number of particles is... Maximum number of iterations In this embodiment The implementer can set the inertia weights themselves. Initial learning factor Each particle's initial velocity is set to 0. A multi-objective particle swarm optimization algorithm is used to output the first particle. The optimal power factor, harmonic current components, and transformer voltage values ​​are determined during energy compensation in each cycle. The multi-objective particle swarm optimization algorithm is a well-known existing technology, and its specific process will not be elaborated upon. Based on the harmonic current components in the optimal solution, harmonic current compensation can be performed; based on the power factor in the optimal solution, reactive power disturbance compensation can be performed; and based on the transformer voltage values ​​in the optimal solution, voltage compensation on the low-voltage side of the transformer can be performed. The specific compensation method is as follows:

[0069] For transformer voltage compensation, firstly, the Clarke transform is used to obtain the optimized transformer voltage at each moment of the current period. Components and Component, denoted as and In order to calculate the compensation amount, the rated voltage amplitude of the system standard is set. This corresponds to an effective value of 220V. The fundamental phase angle θ output in real time by the phase-locked loop is used to construct a reference voltage trajectory.

[0070] α-axis component of transformer voltage compensation and β-axis components The reference value is subtracted from the actual value to obtain the value. The specific calculation formula is as follows:

[0071]

[0072]

[0073] is a trigonometric sine function, is a trigonometric cosine function, is a grid fundamental phase angle obtained through a phase-locked loop.

[0074] The calculation method of compensation for reactive power disturbance, i.e., reactive compensation, is as follows: , wherein, is a compensation amount of reactive compensation in the current period, is an active power collected in the current period, is a power factor collected in the current period, is an optimized power factor in the current period.

[0075] The compensation amount for each harmonic current component is the difference between each harmonic current component in the optimal solution and a preset target harmonic current value, wherein, for even harmonics, the target harmonic current value is 3% of the fundamental component, and for odd harmonics, the target harmonic current value is 5% of the fundamental component. The implementer can set it according to the actual situation, which is not limited in the embodiment.

[0076] Based on the same inventive concept as the above method, the embodiment of the present application also provides a power quality compensation device for new energy access to a power grid, which comprises a memory, a processor, and a computer program stored in the memory and running on the processor, and the processor implements the steps of any one of the methods in the above power quality compensation method for new energy access to a power grid when executing the computer program.

[0077] It should be noted that the above sequence of the embodiments of the present application is only for description, and does not represent the advantages and disadvantages of the embodiments. The above describes specific embodiments of the present application. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multi-task processing and parallel processing are possible or can be advantageous.

[0078] Each embodiment in the present specification is described in a progressive manner, and the same or similar parts between each embodiment can be referred to each other. Each embodiment mainly describes the differences from other embodiments.

[0079] The above is only the preferred embodiment of the present application, and does not limit the present application. Any modification, equivalent replacement, improvement, etc. made within the principles of the present application shall be included in the protection scope of the present application.

Claims

1. A power quality compensation method for new energy grid connection, characterized in that, The method includes the following steps: A dynamic voltage compensation converter is connected in series on the low-voltage side of the transformer, and a high-power bidirectional converter is connected in parallel on the terminal load side. The voltage at each moment in each cycle on the low-voltage side of the transformer is collected and recorded as the transformer voltage; the load current and load voltage at each moment in each cycle on the terminal load side are collected. Based on the load current at all times within each cycle, the harmonic current components are obtained to obtain the total harmonic distortion rate of each cycle; by the degree of variation of the total harmonic distortion rate of each cycle relative to the historical cycle, the influence weight of harmonic disturbances in each cycle is determined. Based on the load current and the load voltage, the power factor of each cycle on the terminal load side is obtained, and the influence weight of reactive power disturbance in each cycle is determined by the degree of deviation between the power factor of each cycle and the historical cycle. Based on the degree of difference in transformer voltage fluctuations between each cycle and historical cycles, the impact weight of voltage exceeding the limit in each cycle is determined; Based on the transformer voltage, load current and load voltage collected in each cycle, the current power quality status index is calculated. Combined with the determined influence weights of harmonic disturbances, reactive power disturbances and voltage over-limits in each cycle, a multi-objective optimization objective function including total harmonic distortion, power factor and transformer voltage deviation is constructed. Using intelligent optimization algorithms and the objective function, the optimal power factor, harmonic current components, and transformer voltages for the current cycle are obtained. Transformer voltage compensation, reactive power compensation, and harmonic current compensation are then performed for the current cycle. The expression for the objective function is: In the formula, Let j be the objective function value in the j-th period. , , These are the weights of the impact of harmonic disturbance, reactive power disturbance, and voltage over-limit in the j-th cycle, respectively. Let be the total harmonic distortion rate of the j-th period; Let be the power factor in the j-th cycle; This represents the i-th transformer voltage sample value in the j-th cycle. The average voltage over the period is N, where N is the number of sampling points. This is the effective value of the rated voltage on the low-voltage side of the transformer; The specific calculation method is as follows: ,in Let M be the effective value of the kth harmonic current component in the jth period, M be the total number of harmonic current components, and V be the effective value of the fundamental component in the jth period.

2. The power quality compensation method for new energy grid connection as described in claim 1, characterized in that, The determination of the influence weights of each periodic harmonic disturbance includes: The ratio of the total harmonic distortion rate of each period to the mean of the total harmonic distortion rates of all previous periods is calculated and denoted as the first ratio. When the first ratio is greater than or equal to 1, the influence weight of the harmonic disturbance of the corresponding period is 1; otherwise, the influence weight of the harmonic disturbance of the corresponding period is the first ratio.

3. The power quality compensation method for new energy grid access as described in claim 1, characterized in that, The determination of the impact weights of reactive power disturbances in each cycle includes: The ratio of the power factor of each cycle to the mean of the power factors of all previous cycles is calculated and denoted as the second ratio. The influence weight of reactive power disturbance in each cycle is the normalized result of the second ratio.

4. The power quality compensation method for new energy grid connection as described in claim 1, characterized in that, The determination of the impact weight of voltage exceedance in each cycle includes: Calculate the ratio of the transformer voltage variance at all times in each cycle to the mean of the transformer voltage variance in all previous cycles, and denot it as the third ratio. If the third ratio is greater than or equal to 1, the influence weight of the voltage exceeding the limit in the corresponding cycle is 1; otherwise, the influence weight of the voltage exceeding the limit in the corresponding cycle is the third ratio.

5. The power quality compensation method for new energy grid access as described in claim 1, characterized in that, The initial particles of the intelligent optimization algorithm are: each harmonic current component, power factor, and transformer voltage of each cycle, which are preset in a certain number of cycles before each cycle.

6. The power quality compensation method for new energy grid connection as described in claim 1, characterized in that, The transformer voltage compensation includes: The optimized transformer voltage at each moment of the current period is obtained using the Clarke transform. Components and The components are denoted as follows: and Based on the preset rated voltage amplitude And the phase angle θ at the current moment, the transformer voltage compensation at each moment Axial components and The calculation method for shaft components is as follows: In the formula, It is a trigonometric sine function. It is a trigonometric cosine function. This is the fundamental phase angle of the power grid obtained through a phase-locked loop.

7. The power quality compensation method for new energy grid access as described in claim 1, characterized in that, The calculation method for the reactive power compensation amount is as follows: In the formula, This is the amount of reactive power compensation for the current cycle. This represents the active power collected in the current cycle. The power factor collected in the current cycle. This is the optimized power factor for the current cycle.

8. The power quality compensation method for new energy grid access as described in claim 1, characterized in that, The compensation amount of the harmonic current compensation is the difference between each optimal harmonic current component and the preset target harmonic current value.

9. A power quality compensation device for new energy grid connection, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1-8.

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