A novel power system fault ride-through control method and control device

Abstract

The application relates to the technical field of power system control, in particular to a fault ride-through control method and a control device of a novel power system, which comprises the following steps: based on the voltage parameters of a wind farm output side, a wind farm grid connection side and a grid connection side node, corresponding regulation and control parameters are obtained by analysis, so that the dynamic regulation and control of a PR controller are realized; when a system fault occurs, the control parameters can be quickly adjusted, so that the quick compensation under the fault condition is realized, the effectiveness of the fault ride-through control is improved, and when the wind farm is normally operated, the corresponding control parameters can be matched based on various harmonic conditions, the harmonic is suppressed, and the stability and purity of the overall power grid operation are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system control, in particular to a fault ride-through control method and control device of a new power system. BACKGROUND

[0002] The new power system is a modernized power system built to address energy transformation, sustainable development, and climate change challenges. Compared with traditional power systems, it has more flexibility, intelligence, low carbon, distribution, and diversification. The core goal of the new power system is to achieve more efficient, cleaner, and more reliable energy supply, and to address complex challenges such as future power demand and climate change. At present, with the continuous development of clean energy, new clean energy generation has volatility, intermittency and uncontrollability, which increases the difficulty of wind power in parallel.

[0003] Fault ride-through control of the power system refers to maintaining parallel operation or safely transitioning according to a specific strategy when a fault occurs in power generation equipment or key power equipment, avoiding immediate off-grid shutdown damage to the power grid or equipment. Its core purpose is to ensure stable system operation and quickly recover normal control mechanisms after fault removal.

[0004] The disclosure document "CN119093461A Fault Ride-Through Control Method and Fault Ride-Through Control Device for Wind Power Flexible HVDC" sets the PI control coefficient in the fault ride-through control process according to a predetermined linear relationship, thereby achieving the effectiveness of fault ride-through control. However, due to the low dynamic tracking accuracy of PI control, especially when facing AC signals, it is easily affected by wind power generation frequency fluctuations, which in turn leads to a decrease in control accuracy. In proportional-resonant control, although the proportional control coefficient is a fixed value, and the resonance coefficient is calculated through the resonance frequency and the filter parameter, this method ignores the influence of the resonance frequency strength. This can cause deviations in the resonance control part during the fault ride-through process, thereby amplifying high-frequency noise, reducing control accuracy, and possibly having an adverse effect on subsequent links. SUMMARY

[0005] In view of the above, it is necessary to provide a fault ride-through control method and control device for a new power system to solve the above problems.

[0006] The first aspect of the present application provides a fault ride-through control method for a new power system, the method comprising:

[0007] Collecting voltage parameters of the wind farm output side, the wind farm grid side, and the grid side node;

[0008] The voltage parameters of the wind farm grid-side in a cycle of electrical signals are analyzed in the frequency domain, and based on the energy proportion and frequency distribution of each harmonic component of the voltage, a harmonic control coefficient of each harmonic component of the voltage parameters is determined;

[0009] The deviation distribution of the voltage parameters of the wind farm grid-side and the grid-side node in the cycle of electrical signals is compared, and the harmonic control coefficient is combined to determine the grid-connection deviation of the cycle of electrical signals;

[0010] The voltage parameters of the wind farm output side in the cycle of electrical signals are converted from three-phase voltage to two-phase voltage, and based on the distribution similarity between any two-phase voltage of the wind farm grid-side in the time window corresponding to the current cycle of electrical signals and the comparison of the high-frequency and low-frequency energy of the two-phase voltage, a fault determination coefficient of the cycle of electrical signals is determined to obtain a fault determination result of the cycle of electrical signals;

[0011] The fault determination result, the fault determination coefficient and the grid-connection deviation are used to determine a proportional control coefficient of the next cycle of electrical signals and a resonance control coefficient of each resonance controller.

[0012] The harmonic control coefficient of each harmonic component of the voltage parameters is determined as follows:

[0013] The frequency domain response envelope of the voltage parameters of the current cycle of electrical signals and the previous W cycles of electrical signals is obtained, where W is a preset value;

[0014] The frequency of the frequency component of the envelope of each harmonic component is compared with the frequency corresponding to each harmonic component, and then one-half of the 3dB bandwidth corresponding to each harmonic component is added;

[0015] The negative correlation mapping of the addition result of each harmonic component is positively fused with the energy proportion to obtain the harmonic control coefficient of each harmonic component.

[0016] The process of determining the grid-connection deviation of the cycle of electrical signals is as follows:

[0017] The voltage parameters of the wind farm grid-side and the grid-side node at each sampling time in the cycle of electrical signals are subtracted to obtain a difference vector;

[0018] The module length of the vector sum of the difference vectors corresponding to all sampling times in the cycle of electrical signals is calculated, and is positively fused with the dispersion degree of the module lengths of the difference vectors corresponding to all sampling times in the cycle of electrical signals and the cumulative sum of the harmonic control coefficients of all harmonic components in the cycle of electrical signals to obtain the grid-connection deviation of the cycle of electrical signals.

[0019] The dispersion degree is calculated by the variance of the module lengths of the difference vectors corresponding to all sampling times in the cycle of electrical signals.

[0020] The specific process of determining the fault judgment coefficient of the electrical signal period is:

[0021] Obtain the similarity between any two-phase voltages of the wind farm grid-connected side in the time window corresponding to the electrical signal period, and obtain the range value of all similarities obtained in the current time window;

[0022] Calculate the ratio between the high-frequency energy and the low-frequency energy of the two-phase voltages after conversion in the current time window, and the result of forward fusion of the range value and the ratio is taken as the fault judgment coefficient of the electrical signal period.

[0023] The step of obtaining the fault judgment result of the electrical signal period is:

[0024] The voltage parameters of each electrical signal period of the historical known fault are composed into a known fault sample, the threshold value of the fault judgment coefficient of the known fault sample is obtained, the electrical signal period with the fault judgment coefficient greater than the threshold value is judged as a real fault interval, otherwise, the electrical signal period is judged as normal.

[0025] The specific process of determining the proportional control coefficient of the next electrical signal period is:

[0026] Based on the fault judgment result, a fault scaling coefficient is determined;

[0027] The product of the fault scaling coefficient and the preset proportional control coefficient value at the initial time is calculated, the normalized value of the fault judgment coefficient is taken as the weight of the product, the difference between the natural number 1 and the normalized value of the fault judgment coefficient is taken as the weight of the proportional control coefficient at the current time, and the next signal period proportional control coefficient is obtained by weighted sum of the product and the proportional control coefficient.

[0028] The specific process of determining the fault scaling coefficient is:

[0029] When the electrical signal period is judged as a real fault interval, the first preset value is taken as the corresponding fault scaling coefficient, otherwise, the second preset value is taken as the corresponding fault scaling coefficient; wherein the first preset value is greater than the second preset value.

[0030] The specific formula of the resonance control coefficient of each resonance controller is:

[0031]

[0032] In the formula, indicates the resonance control coefficient of the kth resonance controller corresponding to the next electrical signal period; indicates the proportional control coefficient of the rth resonance controller obtained by using the frequency domain analysis method; indicates the fault scaling coefficient; a normalized value representing a grid deviation of a current electrical signal cycle; a normalized value representing a harmonic control coefficient of a kth harmonic corresponding to a current electrical signal cycle; a preset adjustment step of the kth resonant controller.

[0033] In a second aspect, the embodiments of the present application further provide a novel fault ride-through control device for a power system, 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.

[0034] The present application has at least the following beneficial effects:

[0035] The application firstly collects the voltage key signals of the wind farm and the power grid accurately, which is the basis for system stability and fault diagnosis. The information of each node can help identify the differences between the wind farm and the power grid, especially the impact on voltage when the wind speed changes or the power grid fails. The voltage parameters at the grid-connected side of the wind farm are analyzed in the frequency domain. Based on the energy proportion and frequency distribution of each harmonic component of the voltage, the harmonic control coefficient of each harmonic component of the voltage parameter is determined. When the wind farm is connected to the power grid, the harmonic content of the voltage is an important factor affecting power quality. The determination of the harmonic control coefficient helps to suppress the harmonic influence, thereby ensuring that the wind farm does not cause excessive disturbance to the power grid when connected, and reducing the response lag when the power grid fails. By comparing the deviation distribution of the voltage parameters of the grid-connected side and the grid-connected side nodes in the electric signal cycle, and combining the harmonic control coefficient, the grid-connected deviation of the electric signal cycle is determined. By describing the potential impact of voltage fluctuations on the stability of the power grid, it provides a data basis for effectively eliminating or reducing the grid-connected deviation, avoids excessive interference of wind farm fluctuations on the power grid, and enhances the fault tolerance of the power grid.

[0036] The implementation of the application can enhance the fault ride-through capability of the wind farm, especially when the power grid experiences short-term fluctuations, power outages or other faults. The wind farm can remain connected to the grid under these conditions, reducing the impact on the power grid. By adjusting the control coefficient and regulating the harmonic in real time, the power quality of the wind farm can be improved, reducing harmonic interference in the power grid, making the stability of the wind farm and the power grid stronger. This control strategy enables the wind farm to remain stable when the power grid fails, ensuring that the power grid is not subjected to excessive impact, thereby improving the fault tolerance and operational efficiency of the entire power grid. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1A step flow chart of a novel power system fault ride-through control method is provided for an embodiment of the present application.

[0038] Figure 2 A flow chart for obtaining proportional control coefficients and resonance control coefficients of a next electric signal cycle is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0039] In the description of the embodiments of the present application, the words "exemplary", "or", "for example", and the like are used to mean serving as an example, instance, or illustration. Any embodiment or design presented as "exemplary" or "for example" in the embodiments of the present application should not be construed as preferred or advantageous over other embodiments or design solutions. Rather, the use of "exemplary", "or", "for example", and the like is intended to present concepts in a particular manner.

[0040] 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 the present application belongs. The terminology used in the specification of the present application is only for the purpose of describing specific embodiments and is not intended to limit the present application.

[0041] In addition, it should be pointed out that the terms "first", "second" in the present application and the drawings are used to distinguish similar objects, and are not used to describe a specific order or sequence. The methods disclosed in the embodiments of the present application or the methods shown in the flow charts include one or more steps for implementing the methods, and the execution order of the steps can be interchanged with each other without departing from the scope of the present application, and some steps can also be deleted.

[0042] 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 the present application belongs.

[0043] The specific schemes of a novel power system fault ride-through control method and control device provided by the present application will be specifically described below in combination with the drawings.

[0044] The present application focuses on a novel power system for wind power generation, and the basic wind power generation system is constituted as follows:

[0045] Wind turbine generator set: mainly realizes the wind power generator for converting wind power into electric power, different wind turbine generators are selected according to the actual wind field situation, and in the preferred embodiment, each wind turbine generator is a direct-drive permanent magnet synchronous wind turbine generator set (PMSG), and the rated capacity is 4.5 WM.

[0046] Wind power transformer: for each wind turbine generator set, the voltage of the wind power generator is boosted to reduce the loss of the line in transmission.

[0047] Intermediate transformer: for the integration of the voltage of multiple wind turbine generators, to avoid multiple line transmission, improve the voltage, in order to facilitate long distance transmission.

[0048] Battery pack: when the wind power does not meet the grid connection demand and the overall power benefit is low, the wind power is stored to improve the stability of grid connection and avoid waste of electric energy. At the same time, when there is voltage and frequency deviation between the wind farm and the power grid, the battery pack output is used to compensate for the deviation, especially in the process of fault ride-through control, the output of the battery pack needs to be improved to reduce the impact of wind farm fault on the power grid.

[0049] Grid connection module: the output of wind power is usually electric energy, which is connected to the grid through the grid connection module using an inverter to realize the consistency of voltage, frequency and phase of the grid side with the grid, and improve the stability of the grid operation. In the grid connection module, it mainly includes rectifier, phase-locked loop, voltage loop, current loop, inverter and PR controller.

[0050] The grid connection module mainly realizes the connection of the electric energy generated by the wind farm with the power grid. The power failure of the present application mainly refers to the failure of the wind farm, and the fault ride-through control specifically refers to the reasonable control of the grid connection module when the wind farm fails, which reduces the impact of the wind farm failure on the power grid and improves the stability and purity of the power grid operation.

[0051] In the fault ride-through control, the PR control module is mainly used to control the three elements of the AC grid (voltage, frequency and phase). Due to the uncertainty of the wind farm, the change of the electrical parameters caused by the actual fault (short circuit fault) has the characteristics of suddenness and strong destructive power, which leads to the deviation between the parameter calculation in the traditional PR control and the actual demand, affecting the effectiveness of the fault ride-through control.

[0052] Please refer to Figure 1 , which shows the step flow chart of a new type of power system fault ride-through control method provided by an embodiment of the present application, which comprises the following steps:

[0053] Step 1: Collect the voltage parameters of the wind farm output side, the wind farm grid side and the grid side node.

[0054] In the process of wind farm grid connection, in order to realize the fault ride-through control, the electrical parameter information of the grid connection needs to be obtained in real time, so the electrical parameter information of the wind farm output side (grid connection module input), the wind farm grid side (grid connection module output) and the grid side node (the interface of the power grid and the wind farm) is obtained. Among them, the electrical parameter mainly includes voltage information, and the voltage is complex parameter information, including real-time voltage value and phase information; in this embodiment, the Hall voltage sensor is used to obtain the electrical parameter information.

[0055] In order to more accurately obtain the electrical parameter information of the wind farm operation and grid deviation, the sampling frequency of the sensor is 5 kHz, and the collected electrical parameter information is analyzed to improve the effective grid control of the wind farm in normal operation and when the wind farm fails.

[0056] Step two: frequency domain analysis of the voltage parameters of the wind farm grid side according to the electrical signal period, based on the energy proportion and frequency distribution of each harmonic component of the voltage, determine the harmonic control coefficient of each harmonic component of the voltage parameter.

[0057] In the process of grid connection control of wind farm, the electrical parameters of wind farm grid connection output should be consistent with the electrical parameters of large power grid, so as to realize effective grid connection and improve the effectiveness of large power grid operation. According to the droop characteristic curve of wind farm output, the frequency and voltage of wind farm grid connection can be adjusted according to the size of active power and reactive power. Therefore, through the deviation of the electrical parameters of wind farm grid side and the electrical parameters of grid side node, the grid connection control of wind farm can be realized. When fault occurs, the traditional PR control still uses the same calculation method to obtain the control parameters (Kp is usually a fixed value, and Kr is calculated only by the resonance frequency), which leads to the failure of effective fault ride-through control in the actual process. Therefore, according to the actual deviation analysis, the control parameters of PR control are dynamically adjusted.

[0058] In the process of wind power grid connection control, the phase difference can be controlled by phase-locked loop, so it is necessary to adjust the voltage amplitude and frequency to be consistent with the large power grid, mainly through the adjustment of active power and reactive power output by wind farm. This application focuses on the grid connection control of voltage and realizes the fault ride-through control of voltage.

[0059] In the process of wind power grid connection control, by analyzing the voltage parameters of wind farm grid side, the harmonic control coefficient can be obtained, so as to realize the effective control of voltage waveform. The electrical energy generated by wind farm needs to be converted through grid connection module to make it consistent with the electrical parameters of large power grid. However, due to the uncertainty of wind farm and possible faults, the voltage of grid side often deviates. Therefore, these deviations must be analyzed.

[0060] In ideal conditions, the voltage of wind farm grid side should be a pure sine wave signal, its amplitude should be consistent with the voltage of large power grid, and the frequency and phase should be basically matched. However, due to the volatility of wind farm and the interference of nonlinear devices caused by faults, harmonic components may be generated in the voltage signal. These harmonic components will affect the stability of voltage, so the resonance controller in PR controller needs to be adjusted to suppress harmonics and improve the stability of voltage output.

[0061] Since the voltage parameter is collected in real time, the voltage frequency of the wind farm output may fluctuate at 50 Hz, and thus the electric signal period in the present application is set to 20 ms; voltage data of W electric signal periods before the current electric signal period is selected to construct a local voltage sequence, and W electric signal periods before the current electric signal period are selected to form a current time window. (The current electric signal period refers to the most recent complete electric signal period from the current time, and if the current period is not completed, the data of the last complete period is used.) In the present embodiment, W is set to 10. Then, the local voltage sequence is analyzed in the frequency domain using fast Fourier transform (FFT), and each frequency domain response envelope is obtained through an envelope extraction method. The frequency corresponding to the peak value in each envelope is the envelope frequency component, and the maximum frequency component of the peak value in the envelope is considered to be the fundamental frequency.

[0062] When the wind farm is greatly affected by uncertainty or faults, many harmonic components will appear in the frequency domain response, which are usually integer multiples of the fundamental frequency and will cause the overall harmonic component to occupy a large amplitude in the frequency domain response. Therefore, the harmonic control coefficient of each harmonic component needs to be calculated, specifically: comparing the frequency corresponding to the frequency component of each harmonic component envelope with the frequency corresponding to each harmonic, and then adding one-half of the 3dB bandwidth corresponding to each harmonic component; the negative correlation mapping of the addition result of each harmonic component is positively fused with the energy ratio to obtain the harmonic control coefficient of each harmonic component.

[0063] In the present embodiment, the difference absolute value of two variables is used to calculate the comparison of the two variables; the negative correlation mapping of the variable is calculated by the reciprocal of the variable; and the multiplication calculation method is used for the positive fusion of multiple variables. Specifically, the specific expression of the harmonic control coefficient of the kth harmonic component in the current electric signal period is:

[0064]

[0065] In the formula, The energy ratio of the current harmonic component, i.e., the ratio of the frequency domain response energy of the kth harmonic envelope frequency component to the fundamental frequency domain response energy; represents the frequency corresponding to the frequency component of the envelope of the kth harmonic component, represents the number of harmonics, represents the frequency corresponding to the fundamental frequency, represents the 3dB bandwidth of the envelope of the kth harmonic component, i.e., the frequency domain width corresponding to a half decrease in peak energy.

[0066] ​In the analysis of the harmonic regulation coefficient, the key is to evaluate the proportion of the energy of the harmonic component. When the proportion of the energy is larger, it means that the influence of the harmonic on the overall voltage waveform is more significant, and therefore the suppression of the harmonic needs to be strengthened. At the same time, by analyzing the frequency deviation of the harmonic component, the influence of the frequency shift on the voltage waveform can be measured; the smaller the frequency shift is, the more concentrated the interference frequency is on the harmonic, and the greater the interference degree is. Therefore, the suppression of these frequency components should be increased, so as to improve the stability of the voltage waveform.

[0067] Step three: comparing the deviation distribution of the voltage parameters of the nodes at the grid-connection side and the grid-connected side of the wind farm in the electrical signal cycle, and combining the harmonic regulation coefficient, the grid-connection deviation of the electrical signal cycle is determined.

[0068] The above steps focus on the analysis of the voltage at the grid-connection side of the wind farm, and then the harmonic regulation coefficient corresponding to each harmonic component is obtained. Since the voltage at the grid-connection side of the wind farm is directly connected to the large power grid, the voltage difference between the two will directly affect the effect of the grid-connection control. Therefore, it is necessary to further analyze the voltage deviation between the two in order to provide more accurate adjustment basis for the grid-connection control.

[0069] When the harmonic interference is serious, the voltage fluctuation at the grid-connection side of the wind farm will cause the deviation between the voltage at the grid-connection side and the voltage at the grid-connected side to increase. In the current electrical signal cycle, the voltage at each sampling time can be expressed in complex form (including voltage amplitude and phase), and therefore the voltage at each sampling time can be regarded as a voltage vector. When the harmonic interference is strong, the difference between the voltage vector at the grid-connection side and the voltage vector at the grid-connected side will become more significant. The difference vector obtained by subtracting the voltage vector at the grid-connected side from the voltage vector at the grid-connection side can measure the deviation between the voltage signal at the grid-connection side and the voltage signal at the grid-connected side during the grid-connection process; the sequence composed of the difference vectors at all sampling times is regarded as the difference vector sequence.

[0070] Based on the analysis of the difference vector sequence in the current electrical signal cycle, the grid-connection deviation in the current electrical signal cycle is obtained, and specifically:

[0071] The module length of the vector sum of the difference vectors corresponding to all sampling times in the current electrical signal cycle is calculated, and is fused forward with the dispersion degree of the module length of the difference vectors corresponding to all sampling times in the difference vector sequence in the current electrical signal cycle, and the cumulative sum of the harmonic regulation coefficients of all harmonic components in the current electrical signal cycle, to obtain the grid-connection deviation in the current electrical signal cycle.

[0072] In this embodiment, the dispersion degree is calculated by using the variance, and the specific formula of the grid-connection deviation in the current electrical signal cycle is:

[0073]

[0074] In the formula, a grid-connection deviation of a current electrical signal cycle, a vector sum of all sampling time corresponding difference vectors in a current electrical signal cycle, an exponential function with a natural constant e as a base, a variance of all sampling time corresponding difference vector lengths in a difference vector sequence in a current electrical signal cycle, a summation function, a harmonic control coefficient of a kth harmonic component in a current electrical signal cycle; a vector sum of all sampling time corresponding difference vectors in a current electrical signal cycle, and a result of forward fusion of a variance of all sampling time corresponding difference vector lengths in a difference vector sequence in a current electrical signal cycle, and an accumulated sum of harmonic control coefficients of all harmonic components in a current electrical signal cycle. It should be noted that when a single harmonic component occupies less than one percent (20 dB) of the energy of the fundamental wave, it will no longer be analyzed.

[0075] Thus, according to the voltage deviation between the overall wind farm grid-side and the grid-side node, when the overall wind farm is seriously interfered by harmonics, the voltage difference vector at each sampling time in a single electrical signal cycle will fluctuate greatly, and the deviation coupling is basically consistent, so that the length of the sum of the difference vector sequence is large, and the value of the corresponding harmonic control coefficient is large, and finally the grid-connection deviation between the wind farm grid-side and the grid-side node is large.

[0076] Step four: the voltage parameter of the wind farm output side of the electrical signal cycle is converted from three-phase voltage to two-phase voltage, according to the distribution similarity between any two-phase voltage of the wind farm grid-side in the time window corresponding to the current electrical signal cycle, and the comparison of the high and low frequency energy of the two-phase voltage, the fault determination coefficient of the electrical signal cycle is determined, and the fault determination result of the electrical signal cycle is obtained.

[0077] In actual operation, the voltage change of the wind farm output side can more directly reflect the running state of the wind farm and whether a fault has occurred. Therefore, the running state of the wind farm can be evaluated according to the change of the voltage of the wind farm output side, and the parameters of the PR controller are adjusted accordingly to better cope with the grid-connection deviation and optimize the running effect.

[0078] In the process of wind turbine power generation, the wind drives the rotor to cut the internal permanent magnet to generate induced voltage and induced current, that is, the electricity generated by the wind turbine is alternating current. Therefore, in the actual operation of the wind farm, due to uneven wind distribution, the frequency of the overall alternating current is not consistent, and there are many interference waves, so the overall performance is more interference with many waves, which has a great impact. When the wave is within a certain fluctuation range, the grid-connected module has a certain filtering device, which can correct the voltage. At the same time, when the wind power is transmitted in the wind farm, line faults occur, especially short circuit faults, which account for 95% of the overall line faults. Therefore, the present application mainly analyzes the short circuit fault, which will cause voltage imbalance and voltage fluctuation.

[0079] Firstly, the differences of the three-phase electricity at the output side of the current wind farm are analyzed, and the Clarke transformation is used to convert the three-phase electricity into two-phase electricity for analyzing the frequency domain distribution. When a line fault occurs, the three-phase electricity shows voltage imbalance, which is usually caused by one-way short circuit fault. At the same time, in the case of two-phase electricity, the voltage will decay quickly, and in the frequency domain, the proportion of high-frequency components will increase significantly.

[0080] According to the above analysis, the fault determination coefficient of the current electric signal period is obtained. Specifically, the similarity between the voltage sequences corresponding to any two phases at the grid-connected side of the wind farm in the time window is obtained, and the range of all similarities obtained in the current time window is obtained. The ratio between the high-frequency energy and the low-frequency energy of the converted two-phase voltage in the current time window is calculated, and the result of the forward fusion of the range and the ratio is taken as the fault determination coefficient of the current electric signal period. In this embodiment, the inverse of the DTW distance between the voltage sequences corresponding to any two phases at the grid-connected side of the wind farm in the time window is taken as the similarity thereof; the multiplication calculation method is used for forward fusion of multiple variables; it should be noted that in order to prevent the DTW distance from being 0 and the similarity from being meaningless, a preset positive number other than 0 needs to be added in the denominator, and the preset parameter value is 0.01 in this embodiment.

[0081] It should be noted that the high-frequency energy and the low-frequency energy of the converted two-phase voltage in the current time window, that is, the frequency domain analysis of the converted voltage, the definition interval of the low-frequency is 0~100Hz, and the definition interval of the high-frequency is above 100Hz. The frequency domain response curve in the corresponding range is integrated to obtain the corresponding high-frequency energy and low-frequency energy.

[0082] When analyzing the voltage parameters on the output side of the wind farm, first, the corresponding fault determination coefficient is calculated by studying the time domain distribution of three-phase electricity and the frequency domain characteristics of the converted two-phase electricity. When the wind power line fails, the voltage of three-phase electricity will be unbalanced, especially single-phase short-circuit fault, which may cause the voltage to decay rapidly, and thus increase the difference in similarity of three-phase electricity. At the same time, due to the existence of line short-circuit fault, the energy proportion of high-frequency component in the frequency domain response will increase significantly, thereby causing the fault determination coefficient to be high in the current time window. On the contrary, in the case of no line fault and only harmonic interference, although the three-phase voltage will be affected by a certain harmonic, the voltage deviation is small, or the harmonic interference is relatively coupled, and the difference in similarity of three-phase voltage is small. In addition, compared with the fundamental frequency component, the energy proportion of harmonic component is low, so the proportion of high-frequency energy is relatively small, resulting in a low value of the fault determination coefficient.

[0083] The present application collects 1000 groups of voltage parameters of known fault signal periods, including line fault, harmonic interference and artificially labeled data of normal line transmission, to obtain the corresponding fault determination coefficient of each group. The threshold segmentation method is used to obtain the score (F1-Scorce) of the corresponding threshold value through accuracy and recall rate, and the threshold value with the maximum score is selected as the segmentation threshold. If the fault determination coefficient in the current signal period is greater than the threshold value, it is determined as a real fault interval, which needs to be amplified and regulated, and the others are marked as normal interval for normal regulation.

[0084] Step five: using the fault judgment result, the fault determination coefficient and the grid-connection deviation, to determine the proportional control coefficient of the next signal period and the resonance control coefficient of each resonance controller.

[0085] Based on the voltage parameter data of the wind farm output side, the wind farm grid-connection side and the grid-connection side node, the corresponding harmonic interference situation and fault determination result are obtained. Further, the control parameters of the PR controller need to be adjusted. In the present application, the PR controller is composed of a proportional controller and multiple harmonic controllers, aiming to realize the through control of the fault.

[0086] Specifically, first, the proportional parameter in the operation process of the PR controller is adjusted, and the specific formula is:

[0087]

[0088] In the formula, represents the proportional control coefficient of the next signal period, represents the preset fault expansion coefficient, which is set to the first preset value when the current signal period is determined as a real fault interval, and is set to the second preset value otherwise; normalized value of current electric signal cycle fault determination coefficient, in the embodiment, the normalization method is: obtaining the maximum value of the fault determination coefficient, and the ratio of each fault determination coefficient to the obtained maximum value is taken as the normalization result of each fault determination coefficient; proportional control coefficient value set at the initial moment, which is set to 1 in the embodiment; proportional control coefficient value calculated at the current time window.

[0089] It should be noted that in the real fault case, the fault scaling coefficient is set to be larger in the embodiment, so as to realize fast compensation and response; and for other non-fault states (for example, noise interference that may occur during operation), since these situations are usually accompanied by smaller intensity and shorter duration, a smaller fault scaling coefficient is adopted to avoid overreaction to the system, therefore, the first preset value is greater than the second preset value in the embodiment, the first preset value is 3, and the second preset value is 1, and the preset fault scaling coefficient in the embodiment is obtained through historical experiments, which will not be described in detail.

[0090] In the proportional control coefficient adjustment process, when it is determined that a real fault occurs, the proportional control coefficient needs to be increased at this time, since the fault interferes with the normal operation of the power grid at this time, increasing the proportional control coefficient helps to enhance the voltage compensation capability, so that the voltage of the wind farm access point can be quickly stabilized and consistent with the voltage of the large power grid; meanwhile, the term is introduced to avoid rapid changes in the value of the proportional control coefficient in adjacent two electric signal cycles, causing the regulated voltage to oscillate.

[0091] A plurality of resonance controllers are included in the PR controller, and each resonance controller can suppress the corresponding resonance wave, so as to realize effective regulation and control of the grid-connected voltage. For the kth resonance controller, and are normalized respectively to obtain , ; in the embodiment, the maximum-minimum normalization method is selected, and the specific formula of the resonance control coefficient of the kth resonance controller is:

[0092]

[0093] In the formula, represents the resonance control coefficient of the kth resonance controller corresponding to the next electric signal cycle; represents the proportional control coefficient of the rth resonance controller obtained by using the frequency domain analysis method; represents the fault scaling coefficient, which is consistent with the Kp adjustment; represents the normalized value of the grid-connected deviation of the current electric signal cycle; a normalized value of the harmonic control coefficient corresponding to the kth harmonic in the current electrical signal cycle; a step length of the kth resonance controller, usually taking a value of a step length of the kth resonance controller, usually taking a value of , and in the embodiment, the value is The proportional control coefficient of the rth resonance controller obtained by using the frequency domain analysis method is a known technology in the art, and the present application will not be described here.

[0094] The flowchart for obtaining the proportional control coefficient and the resonance control coefficient of the next electrical signal cycle is shown in Figure 2 .

[0095] In the harmonic control process, the resonance control coefficient is calculated based on the traditional method as the reference, and the harmonic control coefficient of the harmonic distribution is obtained at this time. When the energy proportion corresponding to the current harmonic and the frequency deviation are small, it means that the harmonic frequency has a greater impact, and the value of the corresponding resonance control coefficient is larger. Therefore, the harmonic control coefficient corresponding to the harmonic needs to be increased to achieve suppression of the harmonic. At the same time, the grid deviation of the overall wind farm grid-side and grid-side nodes in the current cycle is measured. If the overall grid deviation is large, it means that the harmonic interference is serious, and the resonance control coefficient needs to be further amplified to improve the suppression of the harmonic. On the contrary, when the overall harmonic interference is small, the harmonic control coefficient is basically zero, and the voltage of the wind farm grid-side and grid-side nodes is basically consistent, and the value of the grid deviation is small. Therefore, the resonance control coefficient calculated based on the traditional method is sufficient to suppress a small amount of small amplitude harmonics.

[0096] Therefore, based on the voltage deviation of the wind farm during grid connection, the real-time control amount can be obtained. In order to compensate for the voltage deviation, the corresponding reactive power is needed to adjust the grid voltage based on the wind farm battery, and the calculated voltage PR control parameters, i.e. Kp and Kr parameters, are brought into the actual controller. Therefore, when the system fails, the corresponding control parameters can be quickly adjusted to improve the output of the battery, thereby reducing the impact of line faults on wind farm grid connection, thereby achieving effective fault ride-through control.

[0097] Based on the same inventive concept as the above method, the present embodiment also provides a new type of power system fault ride-through control device, which comprises a memory, a processor, and a computer program stored in the memory and running on the processor. The processor executes the computer program to implement the steps of any one of the above new type of power system fault ride-through control methods.

[0098] The computer program product of the present application can be a computer program implemented on one or more computers. The program instructions can be stored on a computer-readable medium, such as a floppy disk, CD-ROM, and the like. The computer program product can also include computer programs that are transmitted over a network via, for example, telephone line, LAN, wireless instrument, or others. Accordingly, the computer program product of the present application can be an article of manufacture including a computer usable medium having computer readable program code means distributed therein. The computer readable program code means is means for causing a computer to operate in a specific and predefined manner. The present application can also be embodied in a computer readable medium including transitory signals. Accordingly, the present application can be a product, an article of manufacture, and / or a machine. The present application can also be embodied in any computer readable medium for use in

[0099] It is apparent that a person skilled in the art can make various modifications to the application described in the embodiment without departing from the scope of the application. Therefore, the above described embodiments of the application are intended to be illustrative only and the true scope of the application is indicated by the appended claims.

Claims

1. A method for fault ride-through control of a novel power system, characterized by, The method comprises the following steps: Collecting voltage parameters of wind farm output side, wind farm grid side and grid side nodes; Performing frequency domain analysis on the voltage parameters of the wind farm grid side according to the electric signal cycle, determining the harmonic control coefficient of each harmonic component of the voltage parameters based on the energy proportion and frequency distribution of each harmonic component of the voltage parameters; Comparing the deviation distribution of the voltage parameters of the wind farm grid side and the grid side nodes in the electric signal cycle, and determining the grid deviation of the electric signal cycle in combination with the harmonic control coefficient; Converting the voltage parameters of the wind farm output side in the electric signal cycle from three-phase voltage to two-phase voltage, determining the fault judgment coefficient of the electric signal cycle according to the distribution similarity between any two-phase voltage of the wind farm grid side in the time window corresponding to the current electric signal cycle, and the comparison of the high-frequency energy and the low-frequency energy of the two-phase voltage, and obtaining the fault judgment result of the electric signal cycle; Determining the proportional control coefficient of the next electric signal cycle and the resonance control coefficient of each resonance controller by using the fault judgment result, the fault judgment coefficient and the grid deviation.

2. A novel fault ride-through control method of a power system according to claim 1, characterized in that, The determination of the harmonic control coefficient of each harmonic component of the voltage parameters is specifically: Obtaining the frequency domain response envelope of the voltage parameters of the current electric signal cycle and the previous W electric signal cycles, wherein W is a preset value; Comparing the frequency corresponding to the frequency component of the envelope of each harmonic component with the frequency corresponding to each harmonic component, and then adding one-half of the 3dB bandwidth corresponding to each harmonic component; Mapping the negative correlation of the addition result of each harmonic component to the energy proportion to obtain the harmonic control coefficient of each harmonic component.

3. A novel fault ride through control method of power system as claimed in claim 1, wherein, The process of determining the grid deviation of the electric signal cycle is: Subtracting the voltage parameters of the wind farm grid side and the grid side nodes at each sampling time in the electric signal cycle to obtain a difference vector; Calculating the module length of the vector sum of the difference vectors corresponding to all sampling times in the electric signal cycle, and performing forward fusion with the dispersion degree of the module lengths of the difference vectors corresponding to all sampling times in the electric signal cycle, and the cumulative sum of the harmonic control coefficients of all harmonic components in the electric signal cycle to obtain the grid deviation of the electric signal cycle.

4. A method of fault ride-through control of a new power system according to claim 3, characterized in that, The dispersion degree is calculated by the variance of the module lengths of the difference vectors corresponding to all sampling times in the electric signal cycle.

5. A novel fault ride through control method of power system as claimed in claim 1, wherein, The specific process of determining the fault judgment coefficient of the electric signal cycle is: Obtaining the similarity between any two-phase voltage of the wind farm grid side in the time window corresponding to the electric signal cycle, and obtaining the range value of all similarities obtained in the current time window; Calculating the ratio between the high-frequency energy and the low-frequency energy of the converted two-phase voltage in the current time window, and performing forward fusion of the range value and the ratio to obtain the fault judgment coefficient of the electric signal cycle.

6. A novel fault ride through control method of power system as claimed in claim 1, wherein, The step of obtaining the fault judgment result of the electric signal cycle is: Grouping the voltage parameters of each electric signal cycle of the historical known fault into a known fault sample, performing threshold segmentation on the fault judgment coefficient of the known fault sample to obtain a segmentation threshold, and judging the electric signal cycle with the fault judgment coefficient greater than the segmentation threshold as a real fault interval; Otherwise, the electric signal cycle is judged as normal.

7. A novel fault ride-through control method of power system according to claim 6, characterized by, The proportional control coefficient of the next electric signal period is determined, specifically: Based on the fault judgment result, a fault scaling coefficient is determined; A product of the fault scaling coefficient and a preset proportional control coefficient value at an initial time is calculated, a normalized value of the fault determination coefficient is taken as a weight of the product, a difference between a natural number 1 and the normalized value of the fault determination coefficient is taken as a weight of the proportional control coefficient at the current time, and a weighted sum of the product and the proportional control coefficient is obtained to obtain the proportional control coefficient of the next signal period.

8. A novel fault ride-through control method of power system according to claim 7, characterized by, The process of determining the fault scaling coefficient is specifically: When the electric signal period is judged as a real fault interval, a first preset value is taken as the corresponding fault scaling coefficient; otherwise, a second preset value is taken as the corresponding fault scaling coefficient; wherein the first preset value is greater than the second preset value.

9. A novel fault ride-through control method of power system according to claim 8, characterized by, The specific formula of the resonance control coefficient of each resonance controller is: ； In the formula, represents the resonance control coefficient corresponding to the kth resonance controller in the next electric signal period; represents the proportional control coefficient of the rth resonance controller obtained by using the frequency domain analysis method; represents the fault scaling coefficient; represents the normalized value of the grid-connected deviation in the current electric signal period; represents the normalized value of the harmonic control coefficient corresponding to the kth harmonic in the current electric signal period; represents the preset adjustment step of the kth resonance controller.

10. A novel fault ride-through control device for power systems, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, The processor implements the steps of the method of any one of claims 1-9 when executing the computer program.

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