Time domain distance protection method and system for photovoltaic power stations connected to double-circuit lines on the same tower

Abstract

The present invention relates to a time-domain distance protection method and system for photovoltaic power stations connected to a double-circuit line on the same tower. The method comprises: taking into account the impact of the photovoltaic power station connected to the double-circuit line on the electrical quantity of the double-circuit line on the same tower and the impact of the mutual inductance of the double-circuit line itself, constructing a sequence component fault distance model; optimizing the sequence component fault distance model by utilizing the relationship between the zero-sequence current of the fault loop and the fault point current; setting a first relevant electrical parameter involved in the sequence component fault distance optimization model to a preset fixed value, obtaining a measured value of a second relevant electrical parameter involved in the sequence component fault distance optimization model, and then performing discretization processing to obtain an actual fault distance; and comparing the actual fault distance with the set distance to determine whether to execute a time-domain distance protection action. The present invention improves the calculation accuracy of the fault distance and ensures the safe and stable operation of the double-circuit line on the same tower when the photovoltaic power station is connected.

Description

Technical Field

[0001] The present invention relates to the field of power grid fault distance protection, and in particular to a time domain distance protection method and system for a photovoltaic power station connected to a double-circuit line on the same tower. Background Art

[0002] With the rise of new energy, photovoltaic power stations are widely used in power grids. However, due to the large uncertainty and volatility of photovoltaic power stations, the power frequency distance protection method cannot accurately determine the location and severity of the fault when the photovoltaic power station is connected to the line. In addition, the intermittent and random volatility of the photovoltaic power station itself makes the fault current difficult to predict. After connecting to the double-circuit line on the same tower, the topology of the double-circuit line on the same tower will change, and it will also affect the changes in the original electrical quantity amplitude, phase angle and other parameters of the power grid, thereby causing the protection to refuse to operate or malfunction. Therefore, seeking an effective distance protection scheme for the connection of photovoltaic power stations to the double-circuit line on the same tower, taking into account the impact of the photovoltaic power station connection on the parameters of the double-circuit line on the same tower and the impact of the mutual inductance of the double-circuit line on the same tower itself, is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0003] The present invention provides a time domain distance protection method and system for a photovoltaic power station connected to a double-circuit line on the same tower, so as to solve at least one of the above technical problems.

[0004] The present invention solves the above technical problems with the following technical solution: A time domain distance protection method for photovoltaic power stations connected to double-circuit lines on the same tower, comprising:

[0005] S1, taking into account the impact of the photovoltaic power station connected to the double-circuit line on the electrical quantity of the double-circuit line on the same tower and the influence of the mutual inductance of the double-circuit line on the same tower, a sequence component fault distance model for the photovoltaic power station connected to the double-circuit line on the same tower is constructed;

[0006] S2, optimizing the sequence component fault distance model by using the relationship between the zero-sequence current of the fault line and the fault point current in the double-circuit line connected to the same tower by the photovoltaic power station, to obtain a sequence component fault distance optimization model;

[0007] S3: Setting a first relevant electrical parameter involved in the sequence component fault distance optimization model to a preset fixed value, and starting the photovoltaic power station connected to the double-circuit line on the same tower to obtain a measured value of a second relevant electrical parameter involved in the sequence component fault distance optimization model; substituting the preset fixed value of the first relevant electrical parameter and the measured value of the second relevant electrical parameter into the sequence component fault distance optimization model and performing time-domain discretization processing to obtain an actual fault distance from the photovoltaic power station side protection to the fault point under the preset fixed value of the first relevant electrical parameter;

[0008] S4, comparing the actual fault distance from the photovoltaic power station side protection to the fault point with the set distance under the preset fixed value of the first relevant electrical parameter to determine whether to perform the time domain distance protection action under the preset fixed value of the first relevant electrical parameter.

[0009] On the basis of the above technical solution, the present invention can also be improved as follows.

[0010] Preferably, the S1 is specifically:

[0011] Construct a fault distance model for photovoltaic power stations connected to double-circuit lines on the same tower;

[0012] The positive and negative zero-sequence currents in the fault loop of the double-circuit line connected to the same tower are taken into account and substituted into the fault distance model to obtain the sequence component fault distance model.

[0013] Preferably, the photovoltaic power station is connected to a double-circuit line on the same tower, including line I and line II. If line I fails, the faulty line is line I, and:

[0014] The fault distance model is expressed as:

[0015] ;

[0016] in, Indicates the voltage on the photovoltaic power station side when the photovoltaic power station is connected to a double-circuit line on the same tower. Indicates the current of the I loop close to the photovoltaic power station side, Indicates the zero-sequence current of the II loop close to the photovoltaic power station side, and Respectively represent the resistance and inductance per unit length of the I loop line, and Respectively represent the mutual resistance and mutual inductance per unit length of the I loop line, Indicates the actual fault distance from the PV power station protection to the fault point. represents the fault point current, represents the transition resistance of the fault point, Indicates time.

[0017] Preferably, the positive and negative zero-sequence currents in the fault loop of the double-circuit line connected to the same tower by the photovoltaic power station are expressed as:

[0018] ;

[0019] in, 、 and Respectively represent the zero-sequence current, positive-sequence current and negative-sequence current of the I loop close to the photovoltaic power station side;

[0020] The sequence component fault distance model is expressed as:

[0021] ;

[0022] in, and They represent the zero-sequence resistance and positive-sequence resistance per unit length of the I-loop line, and Respectively represent the zero-sequence inductance and positive-sequence inductance per unit length of the I-circuit line; in a double-circuit line on the same tower, , , It represents the negative sequence resistance per unit length of the I loop line, It represents the negative sequence inductance per unit length of the I loop.

[0023] Preferably, in S2, the relationship between the zero-sequence current of the fault line in the double-circuit line connected to the same tower and the fault point current is expressed as:

[0024] ;

[0025] in, represents a complex coefficient, and , and Respectively The real and imaginary parts of

[0026] The sequence component fault distance optimization model is expressed as:

[0027] ;

[0028] in, and They represent the zero-sequence resistance compensation coefficient and the zero-sequence inductance compensation coefficient on the I loop, respectively, and the zero-sequence resistance compensation coefficient and the zero-sequence inductance compensation coefficient are expressed as:

[0029] .

[0030] Preferably, in S3, the first relevant electrical parameter is ; The second related electrical parameters include: 、 、 、 、 、 、 、 and ;

[0031] Substituting the preset fixed value of the first relevant electrical parameter and the measured value of the second relevant electrical parameter into the sequence component fault distance optimization model, a time-domain-based discretization process is performed, specifically:

[0032] Substitute the preset fixed value of the first relevant electrical parameter and the measured value of the second relevant electrical parameter into the sequence component fault distance optimization model to obtain a simplified sequence component fault distance model; the simplified sequence component fault distance model is expressed as:

[0033] ;

[0034] in, 、 and are coefficients of the sequence component fault distance optimization model, and:

[0035] ;

[0036] The simplified model of sequence component fault distance is discretized based on the time domain by using difference instead of differentiation to obtain the actual fault distance of the fault point protected on the photovoltaic power station side under the preset fixed value of the first relevant electrical parameter.

[0037] Preferably, in S4, the criterion for executing the time domain distance protection action is: ;in, Indicates the set distance.

[0038] Preferably, after S3, the method further includes:

[0039] S5, changing the preset fixed value of the first relevant electrical parameter multiple times, and executing S3 after each change of the preset fixed value of the first relevant electrical parameter, to obtain an actual fault distance from the photovoltaic power station side protection to the fault point under the multiple different preset fixed values ​​of the first relevant electrical parameter;

[0040] The actual fault distance from the photovoltaic power station side protection to the fault point under each different preset fixed value of the first relevant electrical parameter is compared with the set distance to determine whether the time domain distance protection action is performed under each different preset fixed value of the first relevant electrical parameter, and to calculate the error between the actual fault distance and the set distance.

[0041] Preferably, the preset fixed value of the first relevant electrical parameter has a value range of 0-300Ω.

[0042] Based on the above-mentioned time domain distance protection method for photovoltaic power stations connected to double-circuit lines on the same tower, the present invention also provides a time domain distance protection system for photovoltaic power stations connected to double-circuit lines on the same tower.

[0043] The time domain distance protection system for photovoltaic power stations connected to double-circuit lines on the same tower includes:

[0044] A modeling module is used to consider the impact of the photovoltaic power station connected to the double-circuit line on the electrical quantity of the double-circuit line and the mutual inductance of the double-circuit line itself, and to build a sequence component fault distance model for the photovoltaic power station connected to the double-circuit line on the same tower;

[0045] An optimization module is used to optimize the sequence component fault distance model by using the relationship between the zero-sequence current of the fault loop and the fault point current in the double-circuit line connected to the same tower of the photovoltaic power station, so as to obtain a sequence component fault distance optimization model;

[0046] A calculation module is configured to set a first relevant electrical parameter involved in the sequence component fault distance optimization model to a preset fixed value, and to start operation of a photovoltaic power station connected to a double-circuit line on the same tower, to obtain a measured value of a second relevant electrical parameter involved in the sequence component fault distance optimization model; substitute the preset fixed value of the first relevant electrical parameter and the measured value of the second relevant electrical parameter into the sequence component fault distance optimization model, and then perform time-domain-based decentralization processing to obtain an actual fault distance from the photovoltaic power station side protection to the fault point under the preset fixed value of the first relevant electrical parameter;

[0047] A protection module is used to compare the actual fault distance from the photovoltaic power station side protection to the fault point with the set distance under the preset fixed value of the first relevant electrical parameter, so as to determine whether to perform a time domain distance protection action under the preset fixed value of the first relevant electrical parameter.

[0048] The beneficial effects of the present invention are as follows: in the time domain distance protection method and system for connecting a photovoltaic power station to a double-circuit line on the same tower of the present invention, the influence of the photovoltaic power station on the electrical quantity of the line after the photovoltaic power station is connected to the double-circuit line on the same tower and the influence of the mutual inductance of the double-circuit line on the same tower are first taken into account to construct a sequence component fault distance model for connecting the photovoltaic power station to the double-circuit line on the same tower, then the relationship between the zero-sequence current on both sides of the line and the fault point current after the photovoltaic power station is connected is used to optimize the sequence component fault distance model, then the sequence component fault distance optimization model is discretized by setting and measuring the values ​​of relevant electrical parameters to calculate the actual distance, and finally the actual distance is compared with the set distance to determine whether to execute the time domain distance protection action; the present invention optimizes the traditional time domain distance protection method, solves the problem of inaccurate protection caused by the influence of the photovoltaic power station on the line after the photovoltaic power station is connected to the double-circuit line on the same tower and the influence of the mutual inductance of the double-circuit line on the same tower, improves the calculation accuracy of the fault distance, and ensures that the double-circuit line on the same tower with the photovoltaic power station connected can operate safely and stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1This is a flow chart of the time domain distance protection method for a photovoltaic power station connected to a double-circuit line on the same tower according to the present invention;

[0050] Figure 2 This is a schematic diagram of the photovoltaic power station connected to the double-circuit line on the same tower;

[0051] Figure 3 This is a network diagram of the zero-sequence current of the I circuit during a single-phase grounding fault after the photovoltaic power station is connected to the double-circuit line on the same tower;

[0052] Figure 4 This is a simulation diagram of the zero-sequence current amplitude and phase angle changes on both sides of the double-circuit line on the same tower before and after the photovoltaic power station is connected to the double-circuit line on the same tower;

[0053] Figure 5 Schematic diagram of the relationship between the fault point current and the zero-sequence current on the photovoltaic power station side and the system side;

[0054] Figure 6 This is a structural block diagram of the time domain distance protection system for a photovoltaic power station connected to a double-circuit line on the same tower according to the present invention. DETAILED DESCRIPTION

[0055] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0056] like Figure 1 As shown in Figure 1, the time domain distance protection method for a photovoltaic power station connected to a double-circuit line on the same tower includes:

[0057] S1, taking into account the impact of the photovoltaic power station connected to the double-circuit line on the electrical quantity of the double-circuit line on the same tower and the influence of the mutual inductance of the double-circuit line on the same tower, a sequence component fault distance model for the photovoltaic power station connected to the double-circuit line on the same tower is constructed;

[0058] S2, optimizing the sequence component fault distance model by using the relationship between the zero-sequence current of the fault line and the fault point current in the double-circuit line connected to the same tower by the photovoltaic power station, to obtain a sequence component fault distance optimization model;

[0059] S3: Setting a first relevant electrical parameter involved in the sequence component fault distance optimization model to a preset fixed value, and starting the photovoltaic power station connected to the double-circuit line on the same tower to obtain a measured value of a second relevant electrical parameter involved in the sequence component fault distance optimization model; substituting the preset fixed value of the first relevant electrical parameter and the measured value of the second relevant electrical parameter into the sequence component fault distance optimization model and performing time-domain discretization processing to obtain an actual fault distance from the photovoltaic power station side protection to the fault point under the preset fixed value of the first relevant electrical parameter;

[0060] S4, comparing the actual fault distance from the photovoltaic power station side protection to the fault point with the set distance under the preset fixed value of the first relevant electrical parameter to determine whether to perform the time domain distance protection action under the preset fixed value of the first relevant electrical parameter.

[0061] The following is a detailed description of each step:

[0062] In some embodiments, the S1 is specifically:

[0063] Construct a fault distance model for photovoltaic power stations connected to double-circuit lines on the same tower;

[0064] The positive and negative zero-sequence currents in the fault loop of the double-circuit line connected to the same tower are taken into account and substituted into the fault distance model to obtain the sequence component fault distance model.

[0065] Specifically, the line after the photovoltaic power station is connected to the double-circuit line on the same tower is as follows Figure 2 As shown. Among them, the photovoltaic power station PV is connected to the double-circuit line on the same tower through a transformer; the photovoltaic power station connected to the double-circuit line on the same tower includes line I and line II, line I and line II are close to the photovoltaic power station side as the M side, and line I and line II are close to the system side as the N side; on line I, the photovoltaic power station side protection is protection 1, and the system side protection is protection 2. Photovoltaic power station parameter settings: the sampling frequency is 10kHz, the rated capacity of the photovoltaic power station is 20MW, the photovoltaic power station is connected to the system after the transformer is stepped up, the voltage levels of the photovoltaic power station side and the system side are both set to 220kV, and the total length of the double-circuit line on the same tower is set to 100km. Taking line I as an example for analysis, the protection range of line I is 80% of the total length of the line. Since the total length of the double-circuit line on the same tower connected to the photovoltaic power station is km. Therefore, the set distance for = *80%=80km. This embodiment takes the case of a ground fault in phase A of loop I as an example, and the excess resistance at the fault point f is (The resistance at the fault point is called the transition resistance). The fault loop in the double-circuit line connected to the same tower of the photovoltaic power station is the I loop, and:

[0066] The fault distance model is expressed as:

[0067] ; (1)

[0068] in, Indicates the voltage on the photovoltaic power station side when the photovoltaic power station is connected to a double-circuit line on the same tower. is the resistance voltage on the I loop, is the inductor voltage on the I loop, is the resistance voltage at the fault point on line I, is the mutual inductance resistance voltage of loop II to loop I, is the mutual inductance voltage of loop II to loop I;

[0069] Indicates the current of the I loop close to the photovoltaic power station side, Indicates the zero-sequence current of the II loop close to the photovoltaic power station side, and Respectively represent the resistance and inductance per unit length of the I loop line, and Respectively represent the mutual resistance and mutual inductance per unit length of the I loop line, Indicates the actual fault distance from the PV power station protection to the fault point. represents the fault point current, represents the transition resistance of the fault point, Indicates time.

[0070] Furthermore, considering the positive and negative zero-sequence currents in the fault loop of the double-circuit line connected to the same tower, the positive and negative zero-sequence currents in the fault loop of the double-circuit line connected to the same tower can be expressed as:

[0071] ; (2)

[0072] in, 、 and Respectively represent the zero-sequence current, positive-sequence current and negative-sequence current of the I loop close to the photovoltaic power station side;

[0073] Substituting Equation (2) into Equation (1) yields the sequence component fault distance model. Since this embodiment takes the ground fault of phase A of loop I as an example, the sequence component fault distance model specifically represents the phase A voltage near protection 1 on the photovoltaic power station side using sequence components.

[0074] The sequence component fault distance model is expressed as:

[0075] ; (3)

[0076] in, and They represent the zero-sequence resistance and positive-sequence resistance per unit length of the I-loop line, and Respectively represent the zero-sequence inductance and positive-sequence inductance per unit length of the I-circuit line; in a double-circuit line on the same tower, generally, , , It represents the negative sequence resistance per unit length of the I loop line, It represents the negative sequence inductance per unit length of the I loop.

[0077] The network diagram of the zero-sequence current of the I circuit during a single-phase grounding fault after the photovoltaic power station is connected to the double-circuit line on the same tower is as follows: Figure 3 As shown; Figure 3 middle, Indicates the zero-sequence current of the I loop close to the system side, represents the zero-sequence capacitance per unit length of the I loop line, Indicates the capacitive current of the I loop close to the head end of the photovoltaic power station side, Indicates the capacitive current at the end of the I loop close to the photovoltaic power station side, Indicates the capacitive current of the I loop close to the system side head end, represents the capacitive current of the I loop close to the end of the system side, Indicates the unit impedance of the photovoltaic power station side, Indicates the unit impedance on the system side.

[0078] In some embodiments, for the sequence component fault distance model obtained above, by starting the normal operation of the photovoltaic power station connected to the double-circuit line on the same tower and the single-phase grounding short circuit fault (i.e., phase A grounding fault), the zero-sequence currents on both sides of the line connected to the photovoltaic power station are obtained respectively, and the relationship between the zero-sequence current of the I loop in the sequence component and the fault point current is further optimized, thereby optimizing the sequence component fault distance model.

[0079] Due to the fault point current It cannot be measured, so it needs to be treated equivalently.

[0080] Depend on Figure 3 It can be seen that: , here It indicates the zero sequence current at the fault point. It can be seen that after the photovoltaic power station is connected to the double-circuit line on the same tower, the capacitive current will cause and Then we can simulate and verify the specific situation after the photovoltaic power station is connected to the double-circuit line on the same tower. The simulation results are as follows: Figure 4 shown.

[0081] The single-phase grounding fault of the double-circuit line with and without the photovoltaic power station connected to the same tower is simulated, and the changes in the line simulation situation can be observed. When the photovoltaic power station is not connected, the current amplitude and phase angle on both sides of the line are basically the same. However, when the photovoltaic power station is connected, it can be clearly observed that the zero-sequence current amplitude and phase angle on the photovoltaic power station side change, such as Figure 4 shown; among them, Figure 4(a) is a simulation diagram of the zero-sequence current amplitude change on both sides of the double-circuit line on the same tower (the photovoltaic power station side and the system side) after the photovoltaic power station is connected to the double-circuit line on the same tower. Figure 4 (b) is a simulation diagram of the zero-sequence current amplitude change on both sides of the double-circuit line on the same tower when the photovoltaic power station is not connected to the double-circuit line on the same tower (that is, before the photovoltaic power station is connected to the double-circuit line on the same tower). Figure 4 (c) is the simulated change diagram of the zero-sequence current phase angle on both sides of the double-circuit line on the same tower after the photovoltaic power station is connected to the double-circuit line on the same tower. Figure 4 (d) is a simulated change diagram of the zero-sequence current phase angle on both sides of the double-circuit line on the same tower when the photovoltaic power station is not connected to the double-circuit line on the same tower. And according to the relationship between the current changes on the photovoltaic power station side and the system side and the current flowing through the fault point, it can be clearly observed that the current flowing through the fault point Affected by the amplitude and phase angle after the photovoltaic power station is connected, such as Figure 5 shown; among them, Figure 5 (a) is a schematic diagram of the relationship between the zero-sequence current and the fault current on both sides of the double-circuit line on the same tower after the photovoltaic power station is connected to the double-circuit line on the same tower. Figure 5 (b) is a schematic diagram of the relationship between the zero-sequence current and the fault current on both sides of the double-circuit line on the same tower when the photovoltaic power station is not connected to the double-circuit line on the same tower.

[0082] When there is no photovoltaic power station connected and only the double-circuit line on the same tower is in operation, the zero-sequence network impedance angles on both sides of the fault point are approximately equal, and the zero-sequence currents flowing through the double-circuit line on both sides of the same tower are approximately in phase, so 3 and There is only one real coefficient difference between ,Right now and The relationship between can be expressed as: .Will Substituting into formula (1) we can get the fault distance optimization model of the double-circuit transmission line on the same tower without access to the photovoltaic power station. The fault distance optimization model of the double-circuit transmission line on the same tower without access to the photovoltaic power station is expressed as:

[0083] ; (4)

[0084] When a photovoltaic power station is connected to a double-circuit line on the same tower, due to the weak feedback and randomness of photovoltaics, when a single-phase grounding fault occurs in the double-circuit line on the same tower, the amplitude and phase angle of the zero-sequence current on both sides of the double-circuit line on the same tower will change, resulting in a phase difference in the zero-sequence current on both sides of the double-circuit line on the same tower. and The relationship between the two cannot be expressed in terms of real coefficients. Instead, complex coefficients should be used express: ;Will as well as (From formula (2) Substituting the transformed data into formula (3) yields:

[0085] ; (5)

[0086] because represents a complex coefficient, and , and Respectively The real and imaginary parts of

[0087] The sequence component fault distance optimization model is expressed as:

[0088] ; (6)

[0089] in, and They represent the zero-sequence resistance compensation coefficient and the zero-sequence inductance compensation coefficient on the I loop, respectively, and the zero-sequence resistance compensation coefficient and the zero-sequence inductance compensation coefficient are expressed as:

[0090] . (7)

[0091] In some embodiments, in S3, the first relevant electrical parameter is ; The second related electrical parameters include: 、 、 、 、 、 、 、 and .

[0092] The photovoltaic power station is started to connect to the double-circuit line on the same tower to obtain the measured value of the second relevant electrical parameter involved in the sequence component fault distance optimization model, specifically:

[0093] Obtain the voltage and current on the photovoltaic power station side and the inductance and resistance of the double-circuit line on the same tower when the photovoltaic power station is connected to the double-circuit line in normal operation. Obtain the voltage and current data of the photovoltaic power station connected to the double-circuit line on the same tower after a fault occurs, so as to calculate the zero-sequence current on the photovoltaic power station side and the zero-sequence current on the system side after the fault occurs, and obtain the zero-sequence resistance and zero-sequence inductance of the double-circuit line on the same tower. Based on the zero-sequence resistance and zero-sequence inductance of the double-circuit line on the same tower, calculate the zero-sequence resistance compensation coefficient and zero-sequence inductance compensation coefficient, as well as the mutual resistance and mutual inductance of the II loop to the I loop.

[0094] The present invention can directly obtain the zero-sequence resistance per unit length of the line on the I circuit by simulating the normal operation of the double-circuit line on the same tower connected to the photovoltaic power station. , Positive sequence resistance per unit length of line on I loop , zero-sequence inductance per unit length of line on I loop , the positive sequence inductance per unit length of the line on the I loop , Mutual resistance per unit length of line on I loop , Mutual inductance per unit length of line on I loop ;Will 、 、 、 、 、 Substituting these measured values ​​into formula (7) can obtain the zero-sequence resistance compensation coefficient on the I loop: and zero-sequence inductance compensation coefficient Then, when a fault occurs in the double-circuit line connected to the photovoltaic power station, the voltage of the I circuit close to the photovoltaic power station during the fault period can be directly obtained. 、The current of I loop close to the photovoltaic power station side and the current of the II loop close to the photovoltaic power station side ,Will and Through FFT component analysis, we can get the zero-sequence current of the I loop close to the photovoltaic power station side. Zero sequence current of line II close to the photovoltaic power station The actual fault distance when a fault occurs in a double-circuit line on the same tower after the photovoltaic power station is connected is then calculated. This improves the accuracy of the fault distance calculation based on more factors, solving the problem of inaccurate protection caused by the impact of the photovoltaic power station on the double-circuit line on the same tower and the mutual inductance of the double-circuit line itself when the photovoltaic power station is connected to the double-circuit line on the same tower.

[0095] Substituting the preset fixed value of the first relevant electrical parameter and the measured value of the second relevant electrical parameter into the sequence component fault distance optimization model, a time-domain-based discretization process is performed, specifically:

[0096] Substitute the preset fixed value of the first relevant electrical parameter and the measured value of the second relevant electrical parameter into the sequence component fault distance optimization model to obtain a simplified sequence component fault distance model; the simplified sequence component fault distance model is expressed as:

[0097] ; (8)

[0098] in, 、 and are coefficients of the sequence component fault distance optimization model, and:

[0099] ; (9)

[0100] The simplified model of sequence component fault distance is discretized based on the time domain using difference instead of differentiation to obtain the actual fault distance from the photovoltaic power station side protection to the fault point under the preset fixed value of the first relevant electrical parameter.

[0101] Discretize Equation (8), that is, use difference instead of differential. According to the three-point differential formula, at each sampling moment The differential of can be solved by the difference between the previous sampling moment and the next sampling moment, where is the sampling time interval. According to the three-point differential formula, the discrete-time signal can be expressed as:

[0102] ; (10)

[0103] According to formula (10), the actual fault distance from the photovoltaic power station side protection to the fault point under the preset fixed value of the first relevant electrical parameter (transition resistance) can be calculated.

[0104] In some embodiments, in S4, the criterion for executing the time domain distance protection action is: ;in, Indicates the set distance.

[0105] Specifically, the actual fault distance obtained after fitting is calculated and set distance Compare, if satisfied , the protection is activated, otherwise the protection is inactivated.

[0106] In some embodiments, after S3, the method further includes:

[0107] S5, changing the preset fixed value of the first relevant electrical parameter multiple times, and executing S3 after each change of the preset fixed value of the first relevant electrical parameter, to obtain an actual fault distance from the photovoltaic power station side protection to the fault point under the multiple different preset fixed values ​​of the first relevant electrical parameter;

[0108] The actual fault distance from the photovoltaic power station side protection to the fault point under each different preset fixed value of the first relevant electrical parameter is compared with the set distance to determine whether the time domain distance protection action is performed under each different preset fixed value of the first relevant electrical parameter, and to calculate the error between the actual fault distance and the set distance.

[0109] Specifically, according to S3, when a transition resistance value is set, the corresponding actual fault distance can be calculated. Since when a double-circuit line on the same tower fails, its transition resistance is generally between 0 and 300Ω. Therefore, when a single-phase grounding fault occurs in the set line, different transition resistance values ​​(0 to 300Ω) correspond to different fault locations (0 to 100km), changes in the amplitude, phase angle and mutual inductance parameters of the electrical quantities related to line I and line II; by repeating S3 for different transition resistance values, multiple actual fault distances can be calculated, thereby performing time domain distance protection judgment and calculating the distance to be set. The error degree is small, and multiple data can more accurately reflect that this method has better protection performance.

[0110] Based on the above-mentioned time domain distance protection method for photovoltaic power stations connected to double-circuit lines on the same tower, the present invention also provides a time domain distance protection system for photovoltaic power stations connected to double-circuit lines on the same tower.

[0111] like Figure 6 As shown in Figure 1, the time domain distance protection system for a photovoltaic power station connected to a double-circuit line on the same tower includes:

[0112] A modeling module is used to consider the impact of the photovoltaic power station connected to the double-circuit line on the electrical quantity of the double-circuit line on the same tower, as well as the influence of the mutual inductance of the double-circuit line itself, and to build a sequence component fault distance model for the photovoltaic power station connected to the double-circuit line on the same tower;

[0113] An optimization module is used to optimize the sequence component fault distance model by using the relationship between the zero-sequence current of the fault loop and the fault point current in the double-circuit line connected to the same tower of the photovoltaic power station, so as to obtain a sequence component fault distance optimization model;

[0114] A calculation module is configured to set a first relevant electrical parameter involved in the sequence component fault distance optimization model to a preset fixed value, and to start operation of a photovoltaic power station connected to a double-circuit line on the same tower, to obtain a measured value of a second relevant electrical parameter involved in the sequence component fault distance optimization model; substitute the preset fixed value of the first relevant electrical parameter and the measured value of the second relevant electrical parameter into the sequence component fault distance optimization model, and then perform time-domain discretization processing to obtain an actual fault distance from the photovoltaic power station side protection to the fault point under the preset fixed value of the first relevant electrical parameter;

[0115] A protection module is used to compare the actual fault distance from the photovoltaic power station side protection to the fault point with the set distance under the preset fixed value of the first relevant electrical parameter, so as to determine whether to perform a time domain distance protection action under the preset fixed value of the first relevant electrical parameter.

[0116] The specific functions of each module in the time domain distance protection system for photovoltaic power stations connected to double-circuit lines on the same tower of the present invention are described in detail in the time domain distance protection method for photovoltaic power stations connected to double-circuit lines on the same tower of the present invention, which will not be repeated here.

[0117] In the time-domain distance protection method and system for connecting a photovoltaic power station to a double-circuit line on the same tower of the present invention, the influence of the photovoltaic power station on the electrical quantity of the line after the photovoltaic power station is connected to the double-circuit line on the same tower and the influence of the mutual inductance of the double-circuit line on the same tower are first taken into account to construct a sequence component fault distance model for the photovoltaic power station connected to the double-circuit line on the same tower. Then, the sequence component fault distance model is optimized by using the relationship between the zero-sequence current on both sides of the line and the fault point current after the photovoltaic power station is connected. Then, the sequence component fault distance optimization model is discretized by setting and measuring the values ​​of relevant electrical parameters to calculate the actual distance. Finally, the actual distance is compared with the set distance to determine whether to execute the time-domain distance protection action. The present invention optimizes the traditional time-domain distance protection method, solves the problem of inaccurate protection caused by the influence of the photovoltaic power station on the line after the photovoltaic power station is connected to the double-circuit line on the same tower and the influence of the mutual inductance of the double-circuit line on the same tower, improves the calculation accuracy of the fault distance, and ensures the safe and stable operation of the double-circuit line on the same tower when the photovoltaic power station is connected.

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A time domain distance protection method for photovoltaic power stations connected to double-circuit lines on the same tower, characterized in that: include: S1, taking into account the impact of the photovoltaic power station connected to the double-circuit line on the electrical quantity of the double-circuit line on the same tower and the influence of the mutual inductance of the double-circuit line on the same tower, a sequence component fault distance model for the photovoltaic power station connected to the double-circuit line on the same tower is constructed; S2, optimizing the sequence component fault distance model by using the relationship between the zero-sequence current of the fault line and the fault point current in the double-circuit line connected to the same tower by the photovoltaic power station, to obtain a sequence component fault distance optimization model; S3: Setting a first relevant electrical parameter involved in the sequence component fault distance optimization model to a preset fixed value, and starting the photovoltaic power station connected to the double-circuit line on the same tower to obtain a measured value of a second relevant electrical parameter involved in the sequence component fault distance optimization model; substituting the preset fixed value of the first relevant electrical parameter and the measured value of the second relevant electrical parameter into the sequence component fault distance optimization model and performing time-domain discretization processing to obtain an actual fault distance from the photovoltaic power station side protection to the fault point under the preset fixed value of the first relevant electrical parameter; S4, comparing the actual fault distance from the photovoltaic power station side protection to the fault point with the set distance under the preset fixed value of the first relevant electrical parameter to determine whether to perform a time domain distance protection action under the preset fixed value of the first relevant electrical parameter; The first relevant electrical parameter is ; Indicates the transition resistance of the fault point; The photovoltaic power station is connected to a double-circuit line on the same tower, including line I and line II. If line I fails, the faulty line is line I. The second related electrical parameters include: 、 、 、 、 、 、 、 and ; 、 、 、 、 、 、 、 and They respectively represent the current of the I loop close to the photovoltaic power station side, the zero-sequence current of the I loop close to the photovoltaic power station side, the zero-sequence resistance of the unit length line on the I loop, the positive-sequence resistance of the unit length line on the I loop, the zero-sequence inductance of the unit length line on the I loop, the positive-sequence inductance of the unit length line on the I loop, the mutual resistance of the unit length line on the I loop, the mutual inductance of the unit length line on the I loop, and the zero-sequence current of the II loop close to the photovoltaic power station side.

2. The time domain distance protection method for photovoltaic power station access to double-circuit lines on the same tower according to claim 1 is characterized in that: The S1 is specifically: Construct a fault distance model for photovoltaic power stations connected to double-circuit lines on the same tower; The positive and negative zero-sequence currents in the fault loop of the double-circuit line connected to the same tower are taken into account and substituted into the fault distance model to obtain the sequence component fault distance model.

3. The time domain distance protection method for accessing a photovoltaic power station to a double-circuit line on the same tower according to claim 2, characterized in that: The fault distance model is expressed as: ； in, Indicates the voltage on the photovoltaic power station side when the photovoltaic power station is connected to a double-circuit line on the same tower. and Respectively represent the resistance and inductance per unit length of the I loop line, Indicates the actual fault distance from the PV power station protection to the fault point. represents the fault point current, Indicates time.

4. The time domain distance protection method for photovoltaic power station access to double-circuit lines on the same tower according to claim 3 is characterized in that: The positive and negative zero-sequence currents in the fault loop of the double-circuit line connected to the same tower of a photovoltaic power station are expressed as: ； in, and Respectively represent the positive sequence current and negative sequence current of the I loop close to the photovoltaic power station side; The sequence component fault distance model is expressed as: ； Among them, in the double-circuit line on the same tower, , , It represents the negative sequence resistance per unit length of the I loop line, It represents the negative sequence inductance per unit length of the I loop.

5. The time domain distance protection method for photovoltaic power station access to double-circuit lines on the same tower according to claim 4 is characterized in that: In S2, the relationship between the zero-sequence current of the fault line in the double-circuit line connected to the same tower and the current at the fault point is expressed as: ； in, represents a complex coefficient, and , and Respectively The real and imaginary parts of The sequence component fault distance optimization model is expressed as: ； in, and They represent the zero-sequence resistance compensation coefficient and the zero-sequence inductance compensation coefficient on the I loop, respectively, and the zero-sequence resistance compensation coefficient and the zero-sequence inductance compensation coefficient are expressed as: 。 6. The time domain distance protection method for photovoltaic power station accessed to a double-circuit line on the same tower according to claim 5, characterized in that: In S3, the preset fixed value of the first relevant electrical parameter and the measured value of the second relevant electrical parameter are substituted into the sequence component fault distance optimization model and then discretized based on the time domain, specifically: Substitute the preset fixed value of the first relevant electrical parameter and the measured value of the second relevant electrical parameter into the sequence component fault distance optimization model to obtain a simplified sequence component fault distance model; the simplified sequence component fault distance model is expressed as: ； in, 、 and are coefficients of the sequence component fault distance optimization model, and: ； The simplified model of sequence component fault distance is discretized based on the time domain by using difference instead of differentiation to obtain the actual fault distance from the photovoltaic power station side protection to the fault point under the preset fixed value of the first relevant electrical parameter.

7. The time domain distance protection method for photovoltaic power station accessed to a double-circuit line on the same tower according to claim 6, characterized in that: In S4, the criterion for executing the time domain distance protection action is: ;in, Indicates the set distance.

8. The time domain distance protection method for photovoltaic power station accessed to a double-circuit line on the same tower according to claim 6, characterized in that: After S3, it also includes: S5, changing the preset fixed value of the first relevant electrical parameter multiple times, and executing S3 after each change of the preset fixed value of the first relevant electrical parameter, to obtain an actual fault distance from the photovoltaic power station side protection to the fault point under the multiple different preset fixed values ​​of the first relevant electrical parameter; The actual fault distance from the photovoltaic power station side protection to the fault point under each different preset fixed value of the first relevant electrical parameter is compared with the set distance to determine whether the time domain distance protection action is performed under each different preset fixed value of the first relevant electrical parameter, and to calculate the error between the actual fault distance and the set distance.

9. The time domain distance protection method for photovoltaic power station accessed to a double-circuit line on the same tower according to any one of claims 6 to 8, characterized in that: The preset fixed value of the first relevant electrical parameter has a value range of 0-300Ω.

10. The time domain distance protection system for photovoltaic power stations connected to double-circuit lines on the same tower is characterized by: include: A modeling module is used to consider the impact of the photovoltaic power station connected to the double-circuit line on the electrical quantity of the double-circuit line on the same tower, as well as the influence of the mutual inductance of the double-circuit line itself, and to build a sequence component fault distance model for the photovoltaic power station connected to the double-circuit line on the same tower; An optimization module is used to optimize the sequence component fault distance model by using the relationship between the zero-sequence current of the fault loop and the fault point current in the double-circuit line connected to the same tower of the photovoltaic power station, so as to obtain a sequence component fault distance optimization model; A calculation module is configured to set a first relevant electrical parameter involved in the sequence component fault distance optimization model to a preset fixed value, and to start operation of a photovoltaic power station connected to a double-circuit line on the same tower to obtain a measured value of a second relevant electrical parameter involved in the sequence component fault distance optimization model; substitute the preset fixed value of the first relevant electrical parameter and the measured value of the second relevant electrical parameter into the sequence component fault distance optimization model, and then perform time-domain discretization processing to obtain an actual fault distance from the photovoltaic power station side protection to the fault point under the preset fixed value of the first relevant electrical parameter; a protection module, configured to compare an actual fault distance from the photovoltaic power station side protection to the fault point with a set distance under a preset fixed value of the first relevant electrical parameter, so as to determine whether to perform a time domain distance protection action under the preset fixed value of the first relevant electrical parameter; The first relevant electrical parameter is ; Indicates the transition resistance of the fault point; The photovoltaic power station is connected to a double-circuit line on the same tower, including line I and line II. If line I fails, the faulty line is line I. The second related electrical parameters include: 、 、 、 、 、 、 、 and ; 、 、 、 、 、 、 、 and They respectively represent the current of the I loop close to the photovoltaic power station side, the zero-sequence current of the I loop close to the photovoltaic power station side, the zero-sequence resistance of the unit length line on the I loop, the positive-sequence resistance of the unit length line on the I loop, the zero-sequence inductance of the unit length line on the I loop, the positive-sequence inductance of the unit length line on the I loop, the mutual resistance of the unit length line on the I loop, the mutual inductance of the unit length line on the I loop, and the zero-sequence current of the II loop close to the photovoltaic power station side.

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