Power distribution network weighted current differential protection method based on distributed photovoltaic fault current regulation and control

Abstract

According to the power distribution network weighted current differential protection method based on distributed photovoltaic fault current regulation and control, voltage and current signals on the two sides of a power distribution network line are collected in real time, and through fine signal processing steps including filtering, Fourier transform and sequence component decomposition, accurate recognition of fault current and rapid judgment of the fault direction are achieved; by adjusting the current reference value of the inverter, the distribution coefficients of the positive and negative sequence current are equal, and the influence of the negative sequence current on the protection performance is effectively eliminated; the Bergeron model is utilized to accurately deduce the current, the synchronization error is considered to perform weighting processing, and the weighting processing and the local actually measured current jointly form a weighting differential protection criterion, so that the selectivity and the reliability of the power distribution network protection are remarkably improved, and the correctness and the quickness of the protection action can also be ensured under the distributed photovoltaic high permeability; the problem that a traditional protection method is insufficient in protection selectivity in the distributed photovoltaic power distribution network is solved, and powerful technical support is provided for safe and stable operation of the power distribution network.

Description

Technical Field

[0001] The present invention relates to the technical field of power system protection and control, and in particular to a weighted current differential protection method for a distribution network based on distributed photovoltaic fault current regulation. Background Art

[0002] With the rapid development of renewable energy technology, the penetration rate of distributed photovoltaic (DG) in the distribution network has continued to increase, making the traditional single-power distribution network gradually present the distinctive characteristics of a multi-power active distribution network. This change has put forward higher requirements for the protection and control of the distribution network.

[0003] In traditional distribution networks, the widely used three-stage overcurrent protection (current quick-break protection, time-limited quick-break protection and time-limited overcurrent protection) was once the mainstream solution for distribution network protection due to its simplicity and reliability. However, with the access of distributed photovoltaics, the short-circuit current distribution in the distribution network has changed significantly, and the traditional three-stage overcurrent protection can no longer meet the requirements of protection selectivity.

[0004] Although longitudinal protection (such as current differential protection) has absolute selectivity and can accurately distinguish between internal and external faults, its large-scale application is limited due to the large number and wide range of distribution network points. Except for a very small number of important distribution lines, they generally do not have the communication conditions required for longitudinal protection.

[0005] The access of distributed photovoltaics not only changes the power structure of the distribution network, but also introduces the nonlinear characteristics and control strategies of power electronic equipment, making the fault characteristics in the distribution network more complicated. In particular, when a fault occurs, distributed photovoltaics may generate a large fault current, which poses a challenge to the rapid and accurate action of the protection device.

[0006] The fifth generation of mobile communication technology 5G (5th Generation Mobile Communication Technology) provides a new solution for distribution network protection with its low latency, high bandwidth and large connection characteristics. The application of 5G effectively solves the communication problems in the distribution network and creates conditions for the widespread application of longitudinal protection in the distribution network.

[0007] Although some studies have attempted to use the flexible regulation characteristics of distributed photovoltaics to optimize distribution network protection, these methods often have problems such as complex calculations, poor real-time performance, or weak adaptability. For example, although the proportional braking current differential protection method can reliably distinguish internal and external faults, its performance may be affected when dealing with the complex fault characteristics caused by distributed photovoltaic access.

[0008] In summary, the existing distribution network protection technology has many shortcomings in dealing with the challenges brought by distributed photovoltaic access. How to make full use of the flexible regulation characteristics of distributed photovoltaics and combine advanced communication technology to build a fast, reliable and adaptable distribution network protection method is an urgent problem to be solved.

[0009] The present invention is proposed based on the above background, and aims to achieve protection control coordinated with highly controllable power electronic equipment through a distribution network protection method based on distributed photovoltaic fault current regulation, improve the operation reliability of distributed photovoltaic distribution network lines, and ensure the safe and stable operation of the power system. Summary of the invention

[0010] The technical problem to be solved by the present invention is to provide a weighted current differential protection method for distribution network based on distributed photovoltaic fault current regulation, so as to solve the problem in the field of distribution network line protection and control containing distributed photovoltaics that the short-circuit current distribution changes due to the access of distributed photovoltaics, making the traditional three-stage overcurrent protection unable to meet the protection selectivity requirements.

[0011] In order to solve the above technical problems, the technical solution adopted by the present invention is: a weighted current differential protection method for distribution network based on distributed photovoltaic fault current regulation, comprising the following steps: Step 1: Collect three-phase voltage and current signals in real time at the protection installations on both sides of the distribution network line, filter the collected three-phase voltage and current signals through the mean filtering algorithm to obtain filtered three-phase voltage and current signals, convert the filtered three-phase voltage and current signals into phasor form through Fourier transform, and perform sequence component decomposition to obtain positive sequence, negative sequence and zero sequence voltage and current components; Step 2: Calculate the positive sequence current mutation on both sides, and compare the positive sequence current mutation on both sides with the preset threshold value. When the positive sequence current mutation on both sides exceeds the threshold value, it is determined that a fault has occurred. Further, according to the phase difference between the negative sequence and zero sequence voltage and current, it is determined whether the fault occurs in the positive direction. Step 3: If the fault occurs in the positive direction, the protection is activated and the negative sequence suppression control strategy of the distributed photovoltaic grid-connected converter is temporarily shielded. The phase angle of the converter phase-locked loop is adjusted to make the positive and negative sequence current distribution coefficients equal by adjusting the d-axis and q-axis current reference values ​​in the inverter current inner loop of the distributed photovoltaic equipment. Step 4: After adjusting the current reference value, re-collect the three-phase current signal at the protection installation, perform Karenbauer phase modulus transformation, deduce the obtained modulus data to the other end of the line based on the Berelon distributed parameter line model, and then perform Karenbauer phase modulus inverse transformation on the deduced modulus data to obtain the deduced three-phase current phasor; Step 5: Calculate the synchronization error angle according to the timing error of the protection on both sides and the inherent delay of the communication channel, perform synchronization error weighting processing on the deduced current phasor, and input the weighted current phasor data and the local real-time collected current phasor data into the current differential protection judgment criterion to determine whether the fault has actually occurred and instruct the protection to perform the corresponding action strategy.

[0012] In a preferred solution, the process of obtaining the sequence component voltage and current in Step 1 includes: Step 1.1: Real-time acquisition of three-phase voltage and current signals at the protection installations on both sides of the AC line of the distribution network. The sampling rate f m The sampling data of 20ms before and after the fault is saved, and the voltage and current data with an array length of 2000 bits are obtained. U ma , U mb , U mc ]、[ I ma , I mb , I mc ]、[ U na , U nb , U nc ]、[ I na , I nb , I nc ], where m and n correspond to the distributed photovoltaic protection installation location and the system side protection installation location; Step 1.2: Sample the voltage and current signal data obtained in Step 1.1. U ma , U mb , U mc ]、[ I ma , I mb , I mc ]、[ U na , U nb , U nc ]、[ I na , I nb, I nc ] to filter and obtain the corresponding filtered signal data [ U ’ ma, , U ’ mb , U ’ mc ]、[ I ’ ma , I ’ mb , I ’ mc ]、[ U ’ na , U ’ nb , U ’ nc ]、[ I ’ na , I ’ nb , I ’ nc ], the filtering algorithm expression used is as follows: (1) in, U ’ ma,p , U ’ mb,p , U ’ mc,p , I ’ ma,p , I ’ mb,p , I ’ mc,p , U ’ na,p , U ’ nb,p , U ’ nc,p , I ’ na,p ,I ’ nb,p , I ’ nc,p is the voltage and current data signal [ U ’ ma, , U ’ mb , U ’ mc ]、[ I ’ ma , I ’ mb , I ’ mc ]、[ U ’ na , U ’ nb , U ’ nc ]、[ I ’ na , I ’ nb , I ’ nc ] corresponding to the filtered p-th voltage and current signal data; U ma,p-M , U mb,p-M , U mc,p-M , U na,p-M , U nb,p-M , U nc,p-M , I ma,p-M , I mb,p-M , I mc,p-M , I na,p-M , I nb,p-M , I nc,p-M is an array signal[ U ma , U mb , Umc ]、[ I ma , I mb , I mc ]、[ U na , U nb , U nc ]、[ I na , I nb , I nc ] p - M data; p and M are the voltage and current numbers after filtering, ranging from 0 to 3999, a total of 4000 data, p=M+10; is the power frequency, take 50Hz; Step 1.3: The signal data after filtering in Step 1.2 is converted into phasor form through Fourier transform, and the voltage phasor data is [ ] as an example, the steps are: (2) (3) Where N is the number of samples in a signal period T, which is set to 2000; i is set to 1 to obtain the sinusoidal component of the fundamental component and cosine components , is the voltage signal data[ U ’ ma ]; n is the sampling sequence number, ranging from 1 to 3999; The remaining voltage and current phasors are calculated in the same way, and the voltage and current phasor data can be obtained [ , , ]、[ , , ]、[ , , ]、[ , , ]; Step 1.4: Perform sequence component decomposition on the voltage and current phasor data obtained by Fourier transform in Step 1.3 to obtain the corresponding positive sequence component, negative sequence component, and zero sequence component. The sequence component decomposition is as follows: (4) In the formula, [ , , , , , ] are respectively the positive sequence component, negative sequence component and zero sequence component data groups corresponding to the current signal data on both sides of the line; [ , , , , , ] are the data groups of positive sequence component, negative sequence component and zero sequence component corresponding to the voltage signal respectively; is the rotation factor, and the expression is .

[0013] In a preferred solution, when the positive sequence current mutations on both sides exceed the preset threshold values ​​in Step 2, it is determined that a fault has occurred, and the specific steps of the determination include: Step 2.1: Calculate the sequence current mutation and threshold value on both sides , the calculation formula is as follows: (5) Where N is the number of samples in a signal cycle T, which is set to 2000; n is the sampling sequence number, from 2001 to 3999; , , , , , is the current sequence component data set[ , , , , , ] the nth sequence current data value in each sequence; , , , , , For the corresponding n The calculated values ​​of each sequence current mutation are combined into a data set of each sequence current mutation as [ , , , , , ]; Step 2.2: Compare the magnitude of the positive sequence current mutation on both sides calculated in real time with the threshold setting value. When the following relationship is satisfied, the protection is judged to be activated and the direction determination process is entered: (6) (7) In the formula, , for , The effective value of is the threshold setting value; is the rated current; Step 2.3: Calculate the angle between the zero-sequence voltage and the zero-sequence current and the angle between the negative-sequence voltage and the negative-sequence current. When these two angles meet the following preset conditions, it is determined that the fault occurred in the positive direction: (8) Where arg is the angle between the two phasors.

[0014] In a preferred solution, the control method for shielding the negative sequence suppression control strategy of the distributed photovoltaic grid-connected converter in Step 3 includes: Step 3.1: When the protection is activated, the distributed photovoltaic shields the 20ms negative sequence suppression strategy and sets the phase-locked loop to track the voltage phase angle Replace ; Step 3.2: Calculate the positive-sequence and negative-sequence current distribution coefficients in real time through the positive-sequence current mutation on both sides to obtain the effective value of the control target value , the calculation formula is: (9) In the formula, is the positive sequence distribution coefficient; is the negative sequence distribution coefficient; Step 3.3: Calculate the current inner loop d and q axis reference values ​​in the internal control link of the distributed photovoltaic inverter. To input the above current inner loop d and q axis reference values ​​into the grid-connected inverter, the calculation formula is: (10) In the formula, , Input the reference value of the current loop under the new control strategy; is the impedance angle.

[0015] In a preferred solution, the voltage and current deduction method based on the Berelon distributed parameter line model in Step 4 includes: Step 4.1: Re-collect the three-phase voltage and current signals at the protection installation on both sides of the AC line of the distribution network. The sampling rate f mThe sampling data is stored at 1 MHz for 20 ms, and the voltage and current arrays with an array length of 2000 bits are obtained. , , ] 、[ , , ]、[ , , ]、[ , , ], the obtained voltage and current array is transformed into Karenbauer phase mode, and the expression is: (11) Where: , , , , , They are the 1-mode component, 2-mode component and 0-mode component obtained by Karenbauer phase mode transformation of the current signals on both sides; , , , , , They are the 1-mode component, 2-mode component, and 0-mode component obtained by Karenbauer phase-mode transformation of the voltage signal; Step 4.2: The voltage and current modulus data collected on the m side are deduced to the n side through the Berelon model, and the deduced current modulus data of 1 mode, 2 mode, and 0 mode can be obtained. , , ]; Modulus data of voltage 1 mode, 2 mode, and 0 mode[ , , ]; The voltage and current modulus data collected on the n side are deduced to the m side through the Berelon model, and the deduced current modulus numbers of 1 mode, 2 mode, and 0 mode can be obtained [ , , ]; Modulus data of voltage 1 mode, 2 mode, and 0 mode[ , , ], the derivation expression of the Berelon model is: (12) In the formula, (13) (14) (15) (16) In the formula, Z c is the line wave impedance, R is the line resistance, The delay factor acts to delay the data sequence , , v is the speed of light, l is the line length; Step 4.3: Perform Karenbauer phase inverse transformation on the voltage and current modulus data deduced on both sides to obtain the voltage and current phasors deduced on the m side [ , , ]、[ , , ]; voltage and current phasors derived on the n side [ , , ]、[ , , ], the calculation formula is as follows: (17) In a preferred solution, the step of calculating the synchronization error angle in Step 5 to perform weighted processing on the deduced current phasor, and inputting the weighted current phasor data and the local real-time collected current phasor data into the judgment step of the current differential protection includes: Step 5.1: Based on the timing error and the inherent delay of the channel, the synchronous error angle of the electrical quantities on both sides can be calculated. for: (18) In the formula, is the timing error between the two sides, is the inherent delay of the channel; Step 5.2: Construct a weighted phasor of unit length based on the calculated synchronization error angle , the deduced current phasor is weighted and combined with the local measured current to construct a weighted differential current and weighted braking current ,in For three phases a, b, and c, the constructed expression is: (19) (20); Step 5.3: Compare the weighted differential current and weighted braking current of the constructed m-side. If the weighted differential current is greater than the weighted braking current, the protection will be activated, otherwise the protection will be locked. The same is true for the n-side. The protection criterion is: , a phase action; , b phase action; , c phase action; among them, k is the reliability coefficient, and the actual engineering value is 0.5~0.8; , , , , , The modulus of the phasor is obtained by adding the weighted differential current of each phase on both sides m and n; , , , , , Calculate the modulus value of the phasor for the weighted braking current of each phase on both sides m and n; , , , , , Obtain the modulus value of the phasor for the measured current of each phase on both sides m and n; , , , , , The modulus of the phasor is obtained by weighted deduction of the current of each phase on both sides of m and n.

[0016] The weighted current differential protection method for distribution network based on distributed photovoltaic fault current regulation provided by the present invention has the following beneficial effects: 1. The present invention solves the problem in the field of line protection and control of distribution networks containing distributed photovoltaics that the short-circuit current distribution changes due to the access of distributed photovoltaics, making the traditional three-stage overcurrent protection unable to meet the protection selectivity requirements, the distribution network points are numerous and wide and do not have the communication conditions required for longitudinal protection, and the fault characteristics of distributed photovoltaics may cause misjudgment or refusal of protection actions during faults in the area. It solves the protection problems caused by the access of distributed photovoltaics and enhances the reliability of protection; 2. The protection criterion setting of the protection method of the present invention is simple and easy: first, the three-phase voltage and current data at the protection installations on both sides of the distribution network line are collected in real time, and the collected three-phase voltage and current data are denoised by a filtering algorithm. The denoised three-phase voltage and current data are transformed into a phasor form by a Fourier algorithm, and then the sequence component is decomposed; secondly, the current mutation amount is calculated to determine whether a fault has occurred, and as a basis for the protection start-up determination, the angle between the zero-sequence and negative-sequence voltage and current is calculated to determine whether the fault has occurred in the positive direction; thirdly, the distributed photovoltaic control is adjusted to achieve equal distribution coefficients of positive and negative sequence currents, and finally the electrical quantity is deduced by the Berelon model, and a weighted current differential protection criterion is formed taking into account the synchronization error; compared with the existing differential protection technology, the method of the present invention is fully adapted to the distribution network containing distributed photovoltaics, and has a strong ability to resist synchronization errors, and is immune to capacitor currents; the present invention takes into account both economy and reliability, and has a strong engineering practical value; 3. The present invention innovatively proposes to achieve a balance between the positive and negative sequence current distribution coefficients by regulating the d-axis and q-axis current reference values ​​in the inverter current inner loop of the distributed photovoltaic equipment, thereby improving the accuracy of fault detection and protection, and enhancing the regulation potential of the distributed photovoltaic (DG) fault current that is ignored by the traditional distribution network protection method; 4. The present invention achieves a balance between the positive and negative sequence current distribution coefficients by short-term shielding of the negative sequence suppression control strategy of the distributed photovoltaic grid-connected converter and adjusting the phase angle of the phase-locked loop. This control strategy not only improves the accuracy of fault detection, but also makes full use of the flexible control capability of distributed photovoltaics; 5. The present invention introduces a weighted current differential protection criterion while taking into account the inter-station communication delay and synchronization error in the distribution network. This criterion calculates the synchronization error angle, weights the synchronization error of the deduced current data, and then inputs the differential protection criterion together with the local real-time collected current data, thereby improving the sensitivity and reliability of the protection; 6. The present invention takes into account the actual situation of inter-station communication in the distribution network and creatively proposes a weighted differential protection criterion. This criterion solves the problem of protection misoperation or refusal to operate caused by communication delay and synchronization error through weighted processing of synchronization error, thereby improving the reliability of protection. 7. The present invention adopts the Berelon distributed parameter line model in the current deduction process, which effectively eliminates the influence of capacitive current and makes the current deduction more accurate. The application of this model in distribution network protection is novel and helps to improve the performance of the protection method; 8. The present invention combines the Berelon model with the Karenbauer phase mode transformation for the deduction and inverse transformation of the distribution network current. This method not only simplifies the calculation process, but also improves the accuracy of current deduction, providing a new technical approach for distribution network protection; 9. The present invention adjusts the positive and negative sequence current distribution coefficients by regulating the inner loop of the inverter current of the distributed photovoltaic equipment, thereby improving the sensitivity and selectivity of the protection; 10. The present invention not only focuses on fault detection and location, but also realizes the coordination of protection and control by regulating the fault current of distributed photovoltaics. This comprehensive protection and regulation strategy is innovative in the field of distribution network protection; 11. The present invention not only realizes the effective regulation of fault current, but also realizes the rapid and accurate detection of faults through the weighted current differential protection criterion. This multi-objective coordinated control and protection method has significant creativity in the field of distribution network protection; 12. The present invention provides a new protection method for the distribution network containing distributed photovoltaics, which ensures the safe and stable operation of the power system. It is of great significance to promote the widespread application of renewable energy and ensure the safe and stable operation of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below in conjunction with the accompanying drawings and implementation examples: Figure 1 A flowchart of the method for protecting the invention; Figure 2 It is a simulation diagram of the 10kV power distribution system of the present invention; Figure 3 This is a schematic diagram of the action of the starting criterion for single-phase grounding fault according to Embodiment 2 of the present invention; Figure 4 This is a schematic diagram of the magnitude of the positive and negative sequence current distribution coefficients of a single-phase grounding fault in Example 2 of the present invention; Figure 5 This is a schematic diagram of the operation of the weighted current differential protection for a single-phase ground fault in Embodiment 2 of the present invention; Figure 6 This is a schematic diagram of the action of the phase-to-phase fault starting criterion in Embodiment 3 of the present invention; Figure 7 This is a schematic diagram of the magnitude of the positive and negative sequence current distribution coefficients of the interphase fault in Embodiment 3 of the present invention; Figure 8 This is a schematic diagram of the operation of the phase-to-phase fault weighted current differential protection according to Embodiment 3 of the present invention. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments: Example 1 like Figure 1 As shown, the weighted current differential protection method for distribution network based on distributed photovoltaic fault current regulation includes the following steps: Step 1: Collect three-phase voltage and current signals in real time at the protection installations on both sides of the distribution network line, filter the collected three-phase voltage and current signals through the mean filtering algorithm to obtain filtered three-phase voltage and current signals, convert the filtered three-phase voltage and current signals into phasor form through Fourier transform, and perform sequence component decomposition to obtain positive sequence, negative sequence and zero sequence voltage and current components; Step 2: Calculate the positive sequence current mutation on both sides, and compare the positive sequence current mutation on both sides with the preset threshold value. When the positive sequence current mutation on both sides exceeds the threshold value, it is determined that a fault has occurred. Further, according to the phase difference between the negative sequence and zero sequence voltage and current, it is determined whether the fault occurs in the positive direction. Step 3: If the fault occurs in the positive direction, the protection is activated and the negative sequence suppression control strategy of the distributed photovoltaic grid-connected converter is temporarily shielded. The phase angle of the converter phase-locked loop is adjusted to make the positive and negative sequence current distribution coefficients equal by adjusting the d-axis and q-axis current reference values ​​in the inverter current inner loop of the distributed photovoltaic equipment. Step 4: After adjusting the current reference value, re-collect the three-phase current signal at the protection installation, perform Karenbauer phase modulus transformation, deduce the obtained modulus data to the other end of the line based on the Berelon distributed parameter line model, and then perform Karenbauer phase modulus inverse transformation on the deduced modulus data to obtain the deduced three-phase current phasor; Step 5: Calculate the synchronization error angle according to the timing error of the protection on both sides and the inherent delay of the communication channel, perform synchronization error weighting processing on the deduced current phasor, and input the weighted current phasor data and the local real-time collected current phasor data into the current differential protection judgment criterion to determine whether the fault has actually occurred and instruct the protection to perform the corresponding action strategy.

[0019] In this embodiment, the process of obtaining the sequence component voltage and current in Step 1 includes: Step 1.1: Real-time acquisition of three-phase voltage and current signals at the protection installations on both sides of the AC line of the distribution network. The sampling rate f m The sampling data of 20ms before and after the fault is saved, and the voltage and current data with an array length of 2000 bits are obtained. U ma , U mb , U mc ]、[ I ma , I mb , I mc ]、[ Una , U nb , U nc ]、[ I na , I nb , I nc ], where m and n correspond to the distributed photovoltaic protection installation location and the system side protection installation location; Step 1.2: Sample the voltage and current signal data obtained in Step 1.1. U ma , U mb , U mc ]、[ I ma , I mb , I mc ]、[ U na , U nb , U nc ]、[ I na , I nb , I nc ] to filter and obtain the corresponding filtered signal data [ U ’ ma, , U ’ mb , U ’ mc ]、[ I ’ ma , I ’ mb , I ’ mc ]、[ U ’ na , U ’ nb , U ’ nc ]、[ I ’ na , I ’nb , I ’ nc ], the filtering algorithm expression used is as follows: (1) in, U ’ ma,p , U ’ mb,p , U ’ mc,p , I ’ ma,p , I ’ mb,p , I ’ mc,p , U ’ na,p , U ’ nb,p , U ’ nc,p , I ’ na,p , I ’ nb,p , I ’ nc,p is the voltage and current data signal [ U ’ ma, , U ’ mb , U ’ mc ]、[ I ’ ma , I ’ mb , I ’ mc ]、[ U ’ na , U ’ nb , U ’ nc ]、[ I ’na , I ’ nb , I ’ nc ] corresponding to the filtered p-th voltage and current signal data; U ma,p-M , U mb,p-M , U mc,p-M , U na,p-M , U nb,p-M , U nc,p-M , I ma,p-M , I mb,p-M , I mc,p-M , I na,p-M , I nb,p-M , I nc,p-M is an array signal[ U ma , U mb , U mc ]、[ I ma , I mb , I mc ]、[ U na , U nb , U nc ]、[ I na , I nb , I nc ] p - M data; p and M are the voltage and current numbers after filtering, ranging from 0 to 3999, a total of 4000 data, p=M+10; is the power frequency, take 50Hz; Step 1.3: The signal data after filtering in Step 1.2 is converted into phasor form through Fourier transform, and the voltage phasor data is [ ] as an example, the steps are: (2) (3) Where N is the number of samples in a signal period T, which is set to 2000; i is set to 1 to obtain the sinusoidal component of the fundamental component and cosine components , is the voltage signal data[ U ’ ma ]; n is the sampling sequence number, ranging from 1 to 3999; The remaining voltage and current phasors are calculated in the same way, and the voltage and current phasor data can be obtained [ , , ]、[ , , ]、[ , , ]、[ , , ]; Step 1.4: Perform sequence component decomposition on the voltage and current phasor data obtained by Fourier transform in Step 1.3 to obtain the corresponding positive sequence component, negative sequence component, and zero sequence component. The sequence component decomposition is as follows: (4) In the formula, [ , , , , , ] are respectively the positive sequence component, negative sequence component and zero sequence component data groups corresponding to the current signal data on both sides of the line; [ , , , , , ] are the data groups of positive sequence component, negative sequence component and zero sequence component corresponding to the voltage signal respectively; is the rotation factor, and the expression is .

[0020] Furthermore, in Step 2, when the positive sequence current mutation amounts on both sides exceed the preset threshold value, it is determined that a fault has occurred, and the specific steps of the determination include: Step 2.1: Calculate the sequence current mutation and threshold value on both sides , the calculation formula is as follows: (5) Where N is the number of samples in a signal cycle T, which is set to 2000; n is the sampling sequence number, from 2001 to 3999; , , , , , is the current sequence component data set[ , , , , , ] the nth sequence current data value in each sequence; , , , , , For the corresponding n The calculated values ​​of each sequence current mutation are combined into a data set of each sequence current mutation as [ , , , , , ]; Step 2.2: Compare the magnitude of the positive sequence current mutation on both sides calculated in real time with the threshold setting value. When the following relationship is satisfied, the protection is judged to be activated and the direction determination process is entered: (6) (7) In the formula, , for , The effective value of is the threshold setting value; is the rated current; Step 2.3: Calculate the angle between the zero-sequence voltage and the zero-sequence current and the angle between the negative-sequence voltage and the negative-sequence current. When these two angles meet the following preset conditions, it is determined that the fault occurred in the positive direction: (8) Where arg is the angle between the two phasors.

[0021] Furthermore, the control method for shielding the negative sequence suppression control strategy of the distributed photovoltaic grid-connected converter in Step 3 includes: Step 3.1: When the protection is activated, the distributed photovoltaic shields the 20ms negative sequence suppression strategy and sets the phase-locked loop to track the voltage phase angle Replace ; Step 3.2: Calculate the positive-sequence and negative-sequence current distribution coefficients in real time through the positive-sequence current mutation on both sides to obtain the effective value of the control target value , the calculation formula is: (9) In the formula, is the positive sequence distribution coefficient; is the negative sequence distribution coefficient; Step 3.3: Calculate the current inner loop d and q axis reference values ​​in the internal control link of the distributed photovoltaic inverter. To input the above current inner loop d and q axis reference values ​​into the grid-connected inverter, the calculation formula is: (10) In the formula, , Input the reference value of the current loop under the new control strategy; is the impedance angle.

[0022] Furthermore, the voltage and current deduction method based on the Berelon distributed parameter line model in Step 4 includes: Step 4.1: Re-collect the three-phase voltage and current signals at the protection installation on both sides of the AC line of the distribution network. The sampling rate f m The sampling data is stored at 1 MHz for 20 ms, and the voltage and current arrays with an array length of 2000 bits are obtained. , , ] 、[ , , ]、[ , , ]、[ , , ], the obtained voltage and current array is transformed into Karenbauer phase mode, and the expression is: (11) Where: , , , , , They are the 1-mode component, 2-mode component and 0-mode component obtained by Karenbauer phase mode transformation of the current signals on both sides; , , , , , They are the 1-mode component, 2-mode component, and 0-mode component obtained by Karenbauer phase-mode transformation of the voltage signal; Step 4.2: The voltage and current modulus data collected on the m side are deduced to the n side through the Berelon model, and the deduced current modulus data of 1 mode, 2 mode, and 0 mode can be obtained. , , ]; Modulus data of voltage 1 mode, 2 mode, and 0 mode[ , , ]; The voltage and current modulus data collected on the n side are deduced to the m side through the Berelon model, and the deduced current modulus numbers of 1 mode, 2 mode, and 0 mode can be obtained [ , , ]; Modulus data of voltage 1 mode, 2 mode, and 0 mode[ , , ], the derivation expression of the Berelon model is: (12) In the formula, (13) (14) (15) (16) In the formula, Z c is the line wave impedance, R is the line resistance, The delay factor acts to delay the data sequence , , v is the speed of light, l is the line length; Step 4.3: Perform Karenbauer phase inverse transformation on the voltage and current modulus data deduced on both sides to obtain the voltage and current phasors deduced on the m side [ , , ]、[ , , ]; voltage and current phasors derived on the n side [ , , ]、[ , , ], the calculation formula is as follows: (17) Furthermore, the step of calculating the synchronization error angle in Step 5 to perform weighted processing on the deduced current phasor, and inputting the weighted current phasor data and the local real-time collected current phasor data into the judgment step of the current differential protection includes: Step 5.1: Based on the timing error and the inherent delay of the channel, the synchronous error angle of the electrical quantities on both sides can be calculated. for: (18) In the formula, is the timing error between the two sides, is the inherent delay of the channel; Step 5.2: Construct a weighted phasor of unit length based on the calculated synchronization error angle , the deduced current phasor is weighted and combined with the local measured current to construct a weighted differential current and weighted braking current ,in For three phases a, b, and c, the constructed expression is: (19) (20); Step 5.3: Compare the weighted differential current and weighted braking current of the constructed m-side. If the weighted differential current is greater than the weighted braking current, the protection will be activated, otherwise the protection will be locked. The same is true for the n-side. The protection criterion is: , a phase action; , b phase action; , c phase action; among them, k is the reliability coefficient, and the actual engineering value is 0.5~0.8; , , , , , The modulus of the phasor is obtained by adding the weighted differential current of each phase on both sides m and n; , , , , , Calculate the modulus value of the phasor for the weighted braking current of each phase on both sides m and n; , , , , , Obtain the modulus value of the phasor for the measured current of each phase on both sides m and n; , , , , , The modulus of the phasor is obtained by weighted deduction of the current of each phase on both sides of m and n.

[0023] Example 2 In the other two preferred embodiments, based on the above embodiment 1, in order to verify the effectiveness of the present invention, we built the following simulation platform on the PSCAD / EMTDC platform: Figure 2 The 10kV distribution network line model shown in the figure includes multiple lines, and the specific parameters are as follows: the length of the mn line is 20km, the length of the no line is 10km, the length of the mp line is 15km, and the length of the pq line is 15km; the line impedance is set to 0.345+j0.27Ω / km; the system voltage level is 10kV, and multiple distributed photovoltaic (DG) power sources are connected, among which the capacity of DG1 is 10MVA, the capacity of DG2 is 5MVA, and the capacity of DG3 and DG4 are both 2MVA; the distributed photovoltaic adopts the PQ control strategy, and the power factor is set to 0.95; the load model adopts the voltage-frequency model, and the specific parameters are P0=20MW, Q0=5MVAR; Figures 3~8 As shown, a single-phase metallic grounding fault is set at 2 km on the line mn and 2 km on the line no outside the area, and an example analysis is performed on the protection method proposed in the present invention under the faults inside and outside the area.

[0024] A metallic single-phase grounding fault occurs at 2 km on line mn. The fault occurs at 2 seconds, the timing error between m and n is 2 ms, and the inherent delay of the channel is 3 ms.

[0025] Step 1: Step 1: Collect the voltage and current signals on the line in real time at the local protection installation, save the sampling data for 2ms, and obtain the sampling voltage and current data set [ U ma , U mb , U mc ]、[ I ma , I mb , I mc ]、[ U na , U nb , U nc ]、[ I na , I nb , I nc ]; Step 2: Filter the voltage and current signal data obtained in step 1 to obtain a signal array [ U ’ ma , U ’ mb , U ’ mc ],、[ I ’ ma , I ’ mb , I ’ mc ]、[ U ’ na , U ’ nb , U ’ nc ]、[ I ’ na , I ’ nb , I ’ nc ]; Step 3: Perform Fourier transform on the signal data filtered in step 2 to obtain voltage and current phasor data [ , , ]、[ , , ]、[ , , ]、[ , , ]; Step 4: Decompose the sequence components to obtain the sequence voltage and current components respectively: , , , , , ]、[ , , , , , ].

[0026] Step 2: Step 1: Set the threshold , calculate the sequence current mutation data of both sides at 2.002s; Step 2: The effective value of the positive sequence current mutation at 2.002s , , exceeding the threshold , determine the fault occurs, such as Figure 3 As shown; Step 3: At this time is 60°, If the angle is 40° within the setting range, the fault is judged to occur in the positive direction and the protection is activated.

[0027] Step 3: Step 1: When the protection is activated, the distributed photovoltaic system temporarily blocks the 20ms negative sequence suppression strategy and sets the positive sequence voltage phase angle of the grid-connected point tracked by the phase-locked loop Replace ; Step 2: The current mutation on both sides is decomposed by sequence components to obtain the effective value of the positive sequence current mutation: and , calculate the positive sequence current distribution coefficient , effective value of the negative sequence current mutation on the n side , calculate the control target ; Step 3: Calculate the d-axis reference value of the inner current loop in the internal control link of the distributed photovoltaic inverter , q-axis reference value , the calculated d-axis reference value and q-axis reference value are input into the control, and the positive sequence current distribution coefficient is adjusted to be equal to the negative sequence current distribution coefficient, such as Figure 4 As shown; Step 4: Step 1: Re-collect the three-phase voltage and current signals at the protection installation on both sides of the AC line of the distribution network, store the sampling data for 20ms, and obtain the voltage and current arrays [ u ’’ ma , u ’’ mb , u ’’ mc ]、[ i ’’ ma , ii ’’ mb , i ’’ mc ]、[ u ’’na , u ’’ nb , u ’’ nc ]、[ i ’’ na , i ’’ nb , i ’’ nc ]; The voltage and current data are transformed by Karenbauer phase modulus to obtain the voltage and current modulus data respectively: , , ]、[ , , ]; Step 2: The voltage and current modulus data collected on the m side are extrapolated to the n side through the Berelon model to obtain the extrapolated voltage and current modulus data [ , , ]、[ , , ]; The voltage and current modulus data collected on the n side are deduced to the m side through the Berelon model, and the deduced voltage and current modulus data can be obtained [ , , ]、[ , , ]; Step 3: Perform Karenbauer phase inverse transformation on the voltage and current modulus data deduced on both sides to obtain the m-side deduced current phasor data [ , , ]; Current phasor data derived on the n side [ , , ].

[0028] Step 5: Step 1: Calculate the timing error between m and n: , channel intrinsic delay , calculate the synchronous error angle of the electrical quantities on both sides as ; Step 2: Construct a weighted phasor of unit length based on the calculated synchronization error angle ; Input the processed currents on the m side and the n side into the differential protection criterion at the same time. Taking the A phase on the m side as an example, the simulation results are as follows: Figure 5 As shown, the effective value of the differential current of phase A on side m is 400A, and the product of the braking current of phase A on side m and the braking coefficient is 50A, so the protection can operate reliably.

[0029] Example 3 In another preferred embodiment, based on the above embodiments 1 and 2, a BC phase metallic fault occurs at 10 km on line mn, the fault occurs at 2 seconds, the timing error between m and n is 1.5 ms, and the inherent delay of the channel is 4 ms.

[0030] Step 1: Step 1: Collect the voltage and current signals on the line in real time at the local protection installation, save the sampling data for 2ms, and obtain the sampling voltage and current data set [ U ma , U mb , U mc ]、[ I ma , I mb , I mc ]、[ U na , U nb , U nc ]、[ I na , I nb , I nc ]; Step 2: Filter the voltage and current signal data obtained in step 1 to obtain a signal array [ U ’ ma , U ’ mb , U ’ mc ],、[ I ’ ma , I ’ mb , I ’ mc ]、[ U ’ na , U’ nb , U ’ nc ]、[ I ’ na , I ’ nb , I ’ nc ]; Step 3: Perform Fourier transform on the signal data filtered in step 2 to obtain voltage and current phasor data [ , , ]、[ , , ]、[ , , ]、[ , , ]; Step 4: Decompose the sequence components to obtain the sequence voltage and current components respectively: , , , , , ]、[ , , , , , ].

[0031] Step 2: Step 1: Set the threshold , calculate the sequence current mutation data of both sides at 2.002s; Step 2: The effective value of the positive sequence current mutation at 2.002s , , exceeding the threshold , determine the fault occurs, such as Figure 6 As shown; Step 3: At this time is 78°, If the angle is 62° within the setting range, it is judged that the fault occurs in the positive direction and the protection is activated.

[0032] Step 3: Step 1: When the protection is activated, the distributed photovoltaic system temporarily blocks the 20ms negative sequence suppression strategy and sets the positive sequence voltage phase angle of the grid-connected point tracked by the phase-locked loop Replace ; Step 2: The current mutation on both sides is decomposed by sequence components to obtain the effective value of the positive sequence current mutation: and , calculate the positive sequence current distribution coefficient , effective value of the negative sequence current mutation on the n side , calculate the control target ; Step 3: Calculate the d-axis reference value of the inner current loop in the internal control link of the distributed photovoltaic inverter , q-axis reference value , the calculated d-axis reference value and q-axis reference value are input into the control, and the positive sequence current distribution coefficient is adjusted to be equal to the negative sequence current distribution coefficient, such as Figure 7 shown.

[0033] Step 4: Step 1: Re-collect the three-phase voltage and current signals at the protection installation on both sides of the AC line of the distribution network, store the sampling data for 20ms, and obtain the voltage and current arrays [ u ’’ ma , u ’’ mb , u ’’ mc ]、[ i ’’ ma , ii ’’ mb , i ’’ mc ]、[ u ’’ na , u ’’ nb , u ’’ nc ]、[ i ’’ na , i ’’ nb , i ’’ nc ]; The voltage and current data are transformed by Karenbauer phase modulus to obtain the voltage and current modulus data respectively: , , ]、[ , , ]; Step 2: The voltage and current modulus data collected on the m side are extrapolated to the n side through the Berelon model to obtain the extrapolated voltage and current modulus data [ , , ]、[ , , ]; The voltage and current modulus data collected on the n side are deduced to the m side through the Berelon model, and the deduced voltage and current modulus data can be obtained [ , , ]、[ , , ]; Step 3: Perform Karenbauer phase inverse transformation on the voltage and current modulus data deduced on both sides to obtain the m-side deduced current phasor data [ , , ]; Current phasor data derived on the n side [ , , ].

[0034] Step 5: Step 1: Calculate the timing error between m and n: , channel intrinsic delay , calculate the synchronous error angle of the electrical quantities on both sides as ; Step 2: Construct a weighted phasor of unit length based on the calculated synchronization error angle ; Input the processed currents on the m side and the n side into the differential protection criterion at the same time. Taking the B and C phases on the m side as an example, the simulation results are as follows: Figure 8 As shown, the effective value of the differential current of phase B on side m is 480A, the product of the braking current of phase B on side m and the braking coefficient is 70A, the effective value of the differential current of phase C on side m is 410A, the product of the braking current of phase C on side m and the braking coefficient is 80A, so the protection can operate reliably.

[0035] In summary, the weighted current differential protection method for distribution network based on distributed photovoltaic fault current regulation proposed in the present invention is a major technological innovation to cope with the challenges of the complexity of modern power grids and distributed energy access. It not only solves the limitations of traditional protection means in distributed photovoltaic access scenarios, but also flexibly regulates the fault current of distributed photovoltaic equipment, combined with a series of innovative strategies and technical means such as the Berelon distributed parameter line model, to achieve a highly reliable and fast-response distribution network protection solution, effectively overcome the limitations of the existing technology, and significantly improve the protection performance, reliability and response speed of the distribution network; the core of the present invention lies in its multi-level solution: from the flexible regulation of the fault current of distributed photovoltaic equipment, to the precise current deduction based on the Berelon model, to the innovative application of weighted differential protection criteria, each step is closely connected, and together constitute an efficient and intelligent distribution network protection system; this multi-objective coordinated control and protection method not only ensures When a fault occurs, the fault area can be located and isolated quickly and accurately, and the impact on non-fault areas is minimized, thereby improving the operating efficiency and stability of the entire distribution network. In addition, the present invention fully considers the limitations of communication conditions in the distribution network, and effectively reduces the risk of protection misoperation or refusal to operate due to communication delays and synchronization errors through weighted processing of synchronization errors in weighted differential protection criteria. This innovation is of great significance for improving the practicality and reliability of distribution network protection systems, especially in the context of large-scale distributed photovoltaic access and rapid development of smart grids, its application value is more prominent. The proposal and application of the present invention not only brings new technical approaches and solutions to the field of distribution network protection, but also provides strong technical support and guarantee for the construction and development of future smart grids. With the continuous development of distributed energy and smart grid technologies, the relevant technologies and methods of the present invention will be more widely used and promoted, contributing greater strength to the sustainable development of the power industry.

Claims

1. A weighted current differential protection method for distribution network based on distributed photovoltaic fault current regulation, characterized in that: The method comprises the following steps: Step 1: Collect three-phase voltage and current signals in real time at the protection installations on both sides of the distribution network line, filter the collected three-phase voltage and current signals through the mean filtering algorithm to obtain filtered three-phase voltage and current signals, convert the filtered three-phase voltage and current signals into phasor form through Fourier transform, and perform sequence component decomposition to obtain positive sequence, negative sequence and zero sequence voltage and current components; Step 2: Calculate the positive sequence current mutation on both sides, and compare the positive sequence current mutation on both sides with the preset threshold value. When the positive sequence current mutation on both sides exceeds the threshold value, it is determined that a fault has occurred. Further, according to the phase difference between the negative sequence and zero sequence voltage and current, it is determined whether the fault occurs in the positive direction. Step 3: If the fault occurs in the positive direction, the protection is activated and the negative sequence suppression control strategy of the distributed photovoltaic grid-connected converter is temporarily shielded. The phase angle of the converter phase-locked loop is adjusted to make the positive and negative sequence current distribution coefficients equal by adjusting the d-axis and q-axis current reference values ​​in the inverter current inner loop of the distributed photovoltaic equipment. Step 4: After adjusting the current reference value, re-collect the three-phase current signal at the protection installation, perform Karenbauer phase modulus transformation, deduce the obtained modulus data to the other end of the line based on the Berelon distributed parameter line model, and then perform Karenbauer phase modulus inverse transformation on the deduced modulus data to obtain the deduced three-phase current phasor; Step 5: Calculate the synchronization error angle according to the timing error of the protection on both sides and the inherent delay of the communication channel, perform synchronization error weighting processing on the deduced current phasor, and input the weighted current phasor data and the local real-time collected current phasor data into the current differential protection judgment criterion to determine whether the fault has actually occurred and instruct the protection to perform the corresponding action strategy.

2. The weighted current differential protection method for distribution network based on distributed photovoltaic fault current regulation according to claim 1 is characterized in that: The process of obtaining the sequence component voltage and current in Step 1 includes: Step 1.1: Real-time acquisition of three-phase voltage and current signals at the protection installations on both sides of the AC line of the distribution network. The sampling rate f m The sampling data of 20ms before and after the fault is saved, and the voltage and current data with an array length of 2000 bits are obtained. U ma , U mb , U mc ]、[ I ma , I mb , I mc ]、[ U na , U nb , U nc ]、[ I na , I nb , I nc ], where m and n correspond to the distributed photovoltaic protection installation location and the system side protection installation location; Step 1.2: Sample the voltage and current signal data obtained in Step 1.

1. U ma , U mb , U mc ]、[ I ma , I mb , I mc ]、[ U na , U nb , U nc ]、[ I na , I nb , I nc ] to filter and obtain the corresponding filtered signal data [ U ’ ma, , U ’ mb , U ’ mc ]、[ I ’ ma , I ’ mb , I ’ mc ]、[ U ’ na , U ’ nb , U ’ nc ]、[ I ’ na , I ’ nb , I ’ nc ], the filtering algorithm expression used is as follows: （1）； in, U ’ ma,p , U ’ mb,p , U ’ mc,p , I ’ ma,p , I ’ mb,p , I ’ mc,p , U ’ na,p , U ’ nb,p , U ’ nc,p , I ’ na,p , I ’ nb,p , I ’ nc,p is the voltage and current data signal [ U ’ ma, , U ’ mb , U ’ mc ]、[ I ’ ma , I ’ mb , I ’ mc ]、[ U ’ na , U ’ nb , U ’ nc ]、[ I ’ na , I ’ nb , I ’ nc ] corresponding to the filtered p-th voltage and current signal data; U ma,p-M , U mb,p-M , U mc,p-M , U na,p-M , U nb,p-M , U nc,p-M , I ma,p-M , I mb,p-M , I mc,p-M , I na,p-M , I nb,p-M , I nc,p-M is an array signal[ U ma , U mb , U mc ]、[ I ma , I mb , I mc ]、[ U na , U nb , U nc ]、[ I na , I nb , I nc ] p - M data; p and M are the voltage and current numbers after filtering, ranging from 0 to 3999, a total of 4000 data, p=M+10; is the power frequency, take 50Hz; Step 1.3: The signal data after filtering in Step 1.2 is converted into phasor form through Fourier transform, and the voltage phasor data is [ ] as an example, the steps are: （2）； （3）； Where N is the number of samples in a signal period T, which is set to 2000; i is set to 1 to obtain the sinusoidal component of the fundamental component and cosine components , is the voltage signal data[ U ’ ma ]; n is the sampling sequence number, ranging from 1 to 3999; The remaining voltage and current phasors are calculated in the same way, and the voltage and current phasor data can be obtained [ , , ]、[ , , ]、[ , , ]、[ , , ]; Step 1.4: Perform sequence component decomposition on the voltage and current phasor data obtained by Fourier transform in Step 1.3 to obtain the corresponding positive sequence component, negative sequence component, and zero sequence component. The sequence component decomposition is as follows: （4）； In the formula, [ , , , , , ] are respectively the positive sequence component, negative sequence component and zero sequence component data groups corresponding to the current signal data on both sides of the line; [ , , , , , ] are the data groups of positive sequence component, negative sequence component and zero sequence component corresponding to the voltage signal respectively; is the rotation factor, and the expression is .

3. The weighted current differential protection method for distribution network based on distributed photovoltaic fault current regulation according to claim 1 is characterized in that: In Step 2, when the positive sequence current mutations on both sides exceed the preset threshold value, it is determined that a fault has occurred. The specific steps of the determination include: Step 2.1: Calculate the sequence current mutation and threshold value on both sides , the calculation formula is as follows: （5）； Where N is the number of samples in a signal cycle T, which is set to 2000; n is the sampling sequence number, from 2001 to 3999; , , , , , is the current sequence component data set[ , , , , , ] the nth sequence current data value in each sequence; , , , , , For the corresponding n The calculated values ​​of each sequence current mutation are combined into a data set of each sequence current mutation as [ , , , , , ]; Step 2.2: Compare the magnitude of the positive sequence current mutation on both sides calculated in real time with the threshold setting value. When the following relationship is satisfied, the protection is judged to be activated and the direction determination process is entered: （6）； （7）； In the formula, , for , The effective value of is the threshold setting value; is the rated current; Step 2.3: Calculate the angle between the zero-sequence voltage and the zero-sequence current and the angle between the negative-sequence voltage and the negative-sequence current. When these two angles meet the following preset conditions, it is determined that the fault occurred in the positive direction: （8）； Where arg is the angle between the two phasors.

4. The weighted current differential protection method for distribution network based on distributed photovoltaic fault current regulation according to claim 1 is characterized in that: The control method for shielding the negative sequence suppression control strategy of the distributed photovoltaic grid-connected converter in Step 3 includes: Step 3.1: When the protection is activated, the distributed photovoltaic shields the 20ms negative sequence suppression strategy and sets the phase-locked loop to track the voltage phase angle Replace ; Step 3.2: Calculate the positive-sequence and negative-sequence current distribution coefficients in real time through the positive-sequence current mutation on both sides to obtain the effective value of the control target value , the calculation formula is: （9）； In the formula, is the positive sequence distribution coefficient; is the negative sequence distribution coefficient; Step 3.3: Calculate the current inner loop d and q axis reference values ​​in the internal control link of the distributed photovoltaic inverter. To input the above current inner loop d and q axis reference values ​​into the grid-connected inverter, the calculation formula is: （10）； In the formula, , Input the reference value of the current loop under the new control strategy; is the impedance angle.

5. The weighted current differential protection method for distribution network based on distributed photovoltaic fault current regulation according to claim 1 is characterized in that: The voltage and current deduction method based on the Berelon distributed parameter line model in Step 4 includes: Step 4.1: Re-collect the three-phase voltage and current signals at the protection installation on both sides of the AC line of the distribution network. The sampling rate f m The sampling data is stored at 1 MHz for 20 ms, and the voltage and current arrays with an array length of 2000 bits are obtained. , , ]、[ , , ]、[ , , ]、[ , , ], the obtained voltage and current array is transformed into Karenbauer phase mode, and the expression is: （11）； Where: , , , , , They are the 1-mode component, 2-mode component and 0-mode component obtained by Karenbauer phase mode transformation of the current signals on both sides; , , , , , They are the 1-mode component, 2-mode component, and 0-mode component obtained by Karenbauer phase-mode transformation of the voltage signal; Step 4.2: The voltage and current modulus data collected on the m side are deduced to the n side through the Berelon model, and the deduced current modulus data of 1 mode, 2 mode, and 0 mode can be obtained. , , ]; Modulus data of voltage 1 mode, 2 mode, and 0 mode[ , , ]; The voltage and current modulus data collected on the n side are deduced to the m side through the Berelon model, and the deduced current modulus numbers of 1 mode, 2 mode, and 0 mode can be obtained [ , , ]; Modulus data of voltage 1 mode, 2 mode, and 0 mode[ , , ], the derivation expression of the Berelon model is: （12）； In the formula, （13）； （14）； （15）； （16）； In the formula, Z c is the line wave impedance, R is the line resistance, The delay factor acts to delay the data sequence , , v is the speed of light, l is the line length; Step 4.3: Perform Karenbauer phase inverse transformation on the voltage and current modulus data deduced on both sides to obtain the voltage and current phasors deduced on the m side [ , , ]、[ , , ]; voltage and current phasors derived on the n side [ , , ]、[ , , ], the calculation formula is as follows: （17）。 6. The weighted current differential protection method for distribution network based on distributed photovoltaic fault current regulation according to claim 1 is characterized in that: The step of calculating the synchronization error angle in Step 5 to perform weighted processing on the deduced current phasor, and inputting the weighted current phasor data and the local real-time collected current phasor data into the judgment step of the current differential protection includes: Step 5.1: Based on the timing error and the inherent delay of the channel, the synchronous error angle of the electrical quantities on both sides can be calculated. for: （18）； In the formula, is the timing error between the two sides, is the inherent delay of the channel; Step 5.2: Construct a weighted phasor of unit length based on the calculated synchronization error angle , the deduced current phasor is weighted and combined with the local measured current to construct a weighted differential current and weighted braking current ,in For three phases a, b, and c, the constructed expression is: （19）； （20）； Step 5.3: Compare the weighted differential current and weighted braking current of the constructed m-side. If the weighted differential current is greater than the weighted braking current, the protection will be activated, otherwise the protection will be locked. The same is true for the n-side. The protection criterion is: , a phase action; , b phase action; , c phase action; among them, k is the reliability coefficient, and the actual engineering value is 0.5~0.8; , , , , , The modulus of the phasor is obtained by adding the weighted differential current of each phase on both sides m and n; , , , , , Calculate the modulus value of the phasor for the weighted braking current of each phase on both sides m and n; , , , , , Obtain the modulus value of the phasor for the measured current of each phase on both sides m and n; , , , , , The modulus of the phasor is obtained by weighted deduction of the current of each phase on both sides of m and n.

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