CN106066918B - Short-circuit current calculation method containing distributed power supply and nonlinear load - Google Patents
Short-circuit current calculation method containing distributed power supply and nonlinear load Download PDFInfo
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Abstract
The invention discloses a homotopy-based short-circuit current calculation method containing distributed power supplies and nonlinear loads, wherein the distributed power supplies are used as nodes, and a power distribution network system model is constructed according to the connection mode and parameters of each electrical element in a power distribution network; solving the short-circuit current of the load model of the power distribution network by adopting an iterative compensation current method, judging whether the solved short-circuit current is converged, if not, entering the next step, otherwise, storing the result and stopping calculation; converting all constant power loads into a constant impedance load model, calculating short-circuit current by using an iterative compensation current method, and calculating the short-circuit voltage value of each node in the power distribution network system; and constructing a homotopy equation, constructing an admittance matrix by using the calculated short-circuit voltage value and the current value, and solving and updating the admittance matrix by using a continuity method to obtain a convergence short-circuit current solution. The invention improves the short circuit calculation performance in two aspects of convergence and solving precision.
Description
Technical Field
The invention relates to a homotopy-based short-circuit current calculation method comprising a distributed power supply and a nonlinear load.
Background
In recent years, green renewable energy sources such as wind energy and solar energy have been rapidly developed, and distributed power generation technologies using the green renewable energy sources as carriers have also been vigorously developed. The access of the distributed power supply changes the topological structure of the power distribution network, so that electric energy can flow in two directions, and more challenges are brought to the operation and maintenance of the power distribution network.
Specifically, the influence of the method is twofold. On the one hand, the distributed power supply carries out electric energy local compensation at the load center, thereby reduces the loss that the electric energy flows in the circuit and arouses, improves the supply voltage quality simultaneously, improves the power supply reliability, and on the other hand, when short-circuit fault takes place, distributed power supply can supply short-circuit current to the trouble node for fault current increases, and the short-circuit path changes, influences relay protection system's normal operating.
Achieving accurate power distribution system short circuit analysis typically requires accurate construction based on a power distribution element model. In the traditional calculation of the short circuit of the power distribution network, a load model usually adopts a constant impedance model or directly ignores the load so as to simplify the calculation of the short circuit. However, the simplification of the load model may greatly affect the accuracy of the short circuit calculation result of the power system. When a short-circuit fault occurs, the system voltage will drop, and the power consumed by the load will affect the system power consumption balance, thereby affecting the short-circuit current result. When the actual load model in the system is a constant current model, if a constant impedance model is adopted, the power consumption is proportional to the square of the voltage, and thus is lower than the actual power consumption. Similarly, when the actual load is a constant power model, the electric energy consumption is more than that of the actual electric energy, so that the unbalanced power supply and consumption is increased, and the accuracy of the short circuit calculation result is influenced.
Two methods can be used for calculating the short-circuit current, and the calculation accuracy is consistent, and the two methods are respectively a sequence component method and a phase component method.
The sequence component method expresses three-phase elements in the system by positive sequence, negative sequence and zero sequence, and realizes the decoupling among the three sequences. However, this approach is not suitable for asymmetric distribution networks. Mutual coupling effect between the sequential networks is caused by unequal mutual coupling among phases, and the symmetrical component method has no advantage; another reason for not using the symmetric component method is that the failed phase is limited. For example, the analysis of line-to-ground faults using the symmetric component method is limited to a-phase grounding. If a single phase branch line is connected to phase b or phase c and the short circuit current needs to be calculated, the symmetrical component method is stranded.
The phase component method adopts three-phase modeling for elements in the network, and develops a node admittance matrix correction method, a superposition method, a compensation current method and the like to carry out short-circuit current analysis based on the phase component method.
The node admittance matrix correction method simulates short circuit by accessing small impedance at a fault node, modifies a system node admittance matrix according to the short circuit, and adopts a load flow calculation method to calculate the short circuit. The method needs to continuously modify the node admittance matrix in the iterative process, and has low computational efficiency for a large system.
Although the superposition method and the compensation current method reduce the calculation amount to a certain extent, the research on the load model is relatively lacked, the load is always treated as a constant impedance model, and when the load is a composite model of constant impedance, constant power and constant current, iteration is not converged.
Disclosure of Invention
In order to solve the problems, the invention provides a homotopy-based short-circuit current calculation method containing a distributed power supply and a nonlinear load.
In order to achieve the purpose, the invention adopts the following technical scheme:
a short-circuit current calculation method based on homotopy and comprising a distributed power supply and a nonlinear load comprises the following steps:
(1) taking the distributed power supply as a node, constructing a power distribution network system model according to the connection mode and parameters of each electrical element in the power distribution network, and performing load flow calculation;
(2) solving the short-circuit current of the load model of the power distribution network by adopting an iterative compensation current method, judging whether the solved short-circuit current is converged, if not, entering the step (3), otherwise, storing the result and stopping calculation;
(3) converting all constant power loads into a constant impedance load model, calculating short-circuit current by using an iterative compensation current method, and calculating the short-circuit voltage value of each node in the power distribution network system;
(4) and constructing a homotopy equation, constructing an admittance matrix by using the calculated short-circuit voltage value and the current value, and solving and updating the admittance matrix by using a continuity method to obtain a convergence short-circuit current solution.
In the step (1), the distributed power source includes a synchronous generator, an asynchronous generator and a distributed power source connected to the grid through an inverter, and is regarded as a PV node, a PQ node or a PI node, and when the distributed power source is used as the PV node to calculate that the short-circuit current is not converged, the distributed power source is converted into the PQ node.
In the step (1), the load is constructed into a constant power model, a constant current model, a constant impedance model or a ZIP model formed by combination.
In the step (1), the electrical components further include a transformer, a voltage regulator and a capacitor.
In the step (1), a fault model is constructed, and for a three-phase earth fault, a single-phase earth fault and an interphase fault, impedance with a corresponding resistance value is accessed to a fault node to carry out a short-circuit fault model.
In the step (2), the short-circuit current at the fault node is calculated by adopting a Thevenin equivalent method.
In the step (3), after the current at the fault point is solved, the system node current injection is updated, that is, the short-circuit current at the fault point is added to the system current injection vector before the fault as the negative current injection.
In the step (3), the constant power load is converted into a constant impedance model, all the constant power load parts in the network are converted into the constant impedance model, a system node admittance matrix is established, an equivalent system current injection vector including the transformer substation, the distributed power supply, the load and the short-circuit current is calculated, and the short-circuit voltage value of each node of the network is calculated.
In the step (4), initial values and step lengths of continuous parameters are set, a parameterized admittance matrix is established, system current injection is calculated through a parameter equation, the node voltage value is used as an initial solution, the values of the continuous parameters are gradually increased, and network node voltages under different continuous parameter values are solved.
And (4) judging whether the network node voltage is converged, if so, solving the current of each branch, otherwise, adopting a step length control strategy, adjusting the step length of the continuous parameters, reestablishing the parameterized admittance matrix, and solving the current of each branch in the power distribution network until the continuous parameters are 1, otherwise, renewing the continuous parameters and continuously establishing the parameterized admittance matrix.
The invention has the beneficial effects that:
(1) the invention provides a compensation current method using homotopy enhancement to solve the problem, so that the performance of short circuit calculation is improved in two aspects of convergence and solving precision;
(2) by introducing an auxiliary function and an auxiliary parameter, the difficult problem which is difficult to solve is converted into a simple problem, the solution of the solved simple problem is taken as a starting point, the original difficult problem is gradually reduced from 0 to 1 through the auxiliary parameter, and an estimation method of an initial point is provided by a homotopy method, so that the initial point is closer to a real solution;
(3) the problem of processing short circuit calculation of a power distribution system containing a nonlinear load is that the method has good convergence and stronger robustness compared with the traditional method, and when the system contains a constant-power load, the traditional short circuit calculation method can have the problem of non-convergence;
(4) the method has wide application range and can be used for processing various load models in the power distribution network;
(5) the influence of different load models on the calculated value of the short-circuit current is emphasized, and a more accurate setting value is provided for relay protection.
Drawings
FIG. 1 is a system diagram of an IEEE-13 node;
FIG. 2 is a single line diagram of an IEEE-8500 node;
FIG. 3 is a flow chart of a three-stage general theory enhanced short circuit current algorithm
FIG. 4 is a homotopy process flow diagram;
FIG. 5 is a schematic diagram of a three-phase ground fault;
FIG. 6 is a schematic diagram of the convergence of an IEEE-13 node algorithm in a three-phase short-circuit fault iteration process;
FIG. 7 is a diagram illustrating convergence of an example iteration process of an IEEE-8500 node.
The specific implementation mode is as follows:
the invention is further described with reference to the following figures and examples.
1 System modeling
1.1 distributed Power Steady State model
Distributed power sources include synchronous generators, asynchronous generators, and distributed power sources that are connected to the grid via inverters, which may be considered PV nodes, PQ nodes, or PI nodes. In this patent, the distributed power source will switch to the PQ node when the misconvergence occurs as the PV node to calculate the short circuit current.
1.2 load model
Generally, the load model includes a constant power model, a constant current model, a constant impedance model, and a combined load model (ZIP). Three-phase loads can ground a balanced or unbalanced star or angular ungrounded and single or two-tank ground. The combined load model can be expressed by the following two formulas
Wherein U isNAt rated voltage, PN、QNRated active and reactive power, ap、bp、cp、aq、bq、cqIs a coefficient and satisfies ap+bp+cp＝1，aq+bq+cq1. (1) The load is composed of three parts, the first part represents a constant impedance load, the second part represents a constant current load, and the third part represents a constant power load.
1.3 Transformer model
A detailed transformer model is necessary for the analysis and calculation of the short-circuit current. In particular, the model should include: three-phase tap, iron core loss and copper loss, exciting current, insulating phase-changing device and neutral point grounding impedance.
The short-circuit impedance and exciting current of the transformer are used for calculating the admittance matrix, the grounding types of the three-phase transformer comprise YN-YN, YN-Y, YN-D, Y-YN, Y-Y, Y-D, D-YN, D-Y, D-D and the like, and the impedance matrix of the transformer has different expression forms for different wiring forms, as shown in a table 1-1. Wherein U isNAt rated voltage, PN、QNRated active and reactive power, ap、bp、cp、aq、bq、cqIs a coefficient and satisfies ap+bp+cp＝1，aq+bq+cq1. (1) The load is composed of three parts, the first part represents a constant impedance load, the second part represents a constant current load, and the third part represents a constant power load.
TABLE 1-1 admittance matrix of distribution transformers
1.3 Transformer model
A detailed transformer model is necessary for the analysis and calculation of the short-circuit current. In particular, the model should include: three-phase tap, iron core loss and copper loss, exciting current, insulating phase-changing device and neutral point grounding impedance.
The short-circuit impedance and the exciting current of the transformer are used for calculating the admittance matrix, and the grounding types of the three-phase transformer comprise YN-YN, YN-Y, YN-D, Y-YN, Y-Y, Y-D, D-YN, D-Y, D-D and the like.
1.4 pressure regulator model
The voltage regulator may be single phase or three phase. The single-phase voltage regulator may also be Y-coupled, delta-coupled, or on-delta-coupled, in addition to operating as a single-phase device. The voltage regulator and the controller make the output voltage change along with the change of the load.
The staged voltage regulator consists of an autotransformer and an on-load voltage regulation tap. The voltage is varied by changing the tap of the series winding of the autotransformer. The position of the tap is determined by the control circuit (line drop compensator). The purpose of the line drop compensator is to simulate the drop in voltage of the distribution line from the voltage regulator to the load center.
Three single-phase hierarchical formula voltage regulator can connect into a three-phase hierarchical formula voltage regulator. When three single phase regulators are combined, each regulator has its own compensation circuit, so that the tap of each regulator varies independently.
The interior of each phase winding of the three-phase voltage regulator is connected to the regulator housing. Three-phase regulators are operated in tandem so that the tap changes are consistent across all windings, thus requiring only one compensation circuit. For this case, an engineer is required to decide which set of current and voltage the compensation circuit draws. Three-phase voltage regulators can only be connected in a star or closed triangle.
1.5 capacitor model
Parallel capacitors are commonly used in power distribution systems for voltage regulation and to provide reactive support. The capacitor bank can be represented by a constant susceptance, connected as Y or as delta. Similar to the load model, all the capacitor banks are represented by a three-phase capacitor bank model, and the single-phase and two-phase capacitor bank models are obtained by setting the missing current to zero.
1.6 Fault model
Short-circuit faults can be classified into three-phase ground faults, single-phase ground faults, and phase-to-phase faults. For different fault types, the fault node can be connected with the impedance with the corresponding resistance value to carry out short-circuit fault modeling. When a three-phase earth fault occurs at k points in the system, the corresponding three phases Z of A, B and C are shown in FIG. 5FAnd ZgThe four parameters all take values close to zero; when AB interphase short circuit occurs, the A phase Z is connectedFAnd B phase ZFSet close to zero, and C phase ZFAnd ZgSet to infinity. By changing three phases Z of A, B and CFAnd ZgThe values of the four parameters can simulate different types of short-circuit faults.
TABLE 1-2 Fault model matrix
2 iterative compensation current method
2.1 short-circuit current at fault point
For short circuit current at fault nodeWe use the method of donning the vernan equivalent to perform the calculation. Wherein the Thevenin equivalent open-circuit voltage is the node voltage value in normal operation in the network before the faultInjecting unit current of 1+ j0A into one node at a time according to the sequence ABC at the fault bus, setting the current injected into other nodes to be zero, and setting the current to be zero according to the formula V-Ybus - 1IinjSolving for node voltage (Y)bus -1Formed when the tidal current is solved for the system node admittance matrix), the node phase voltage value corresponding to the fault bus is ZeqThe process is repeated (the number of times is the number of phases at the fault bus) until ZeqAnd (4) forming.
Considering fault impedance matrix in interphase short circuitWithout meaning, we do norton equivalence on thevenin equivalent circuits. And is provided with
Can calculate the voltage of the fault port
Wherein I is an identity matrix.
The fault node short circuit current can be obtained by the following formula:
2.2 network non-fault point short-circuit voltage current
After the current at the fault point is solved, the current injection of the system node is updated, namely the short-circuit current at the fault point is added as negative current injection to the current injection vector of the system before the faultIn (1).Can be solved by solving the power flow [36-38 ]]And (5) obtaining a solution. For example, when a three-phase short-circuit fault occurs in the system, there are
Wherein the content of the first and second substances,the fault node short-circuit current obtained by solving (3-3) is a 3 x 1 matrix;is a vector added to the system current injection vector.
The node voltage of the entire post-fault network can be calculated by:
wherein the content of the first and second substances,for the post-fault network node voltage, YbusFor the network admittance matrix, the fault is consistent before and after,and injecting the current of the system after the fault, including equivalent current injection of a transformer substation, a distributed power supply, short-circuit current and a load.Continuously correcting according to the voltage value of the node in the iterative process, and calculating the difference between the two short-circuit voltage calculation resultsAnd comparing the convergence precision to judge the convergence.
From post-fault network voltageThe short-circuit current of each branch of the network can be solved by the following formula
Wherein the content of the first and second substances,Yentryis the admittance matrix of the line elements in the system, with dimension 3 x 3.
3 homotopy method
The homotopy method is generally used for solving the nonlinear problem and has a good effect on the difficult problem that the initial point is not easy to estimate. The homotopic method has the idea that the difficult problem which is difficult to solve is converted into a simple problem by introducing an auxiliary function and an auxiliary parameter, the solution of the solved simple problem is taken as a starting point, and the original difficult problem is gradually reduced by the change of the auxiliary parameter from 0 to 1. The homotopy method provides an estimation method of the initial point, so that the initial point is closer to the true solution. Many homotopy methods are used to solve not only the local convergence problem of iterative methods, but also to find multiple solutions. It is therefore considered a unified, more general approach.
The homotopy method also becomes an embedded path tracking method, and is a robust numerical method for solving a nonlinear algebraic equation system. Unlike newton's method and its variants, which rely on function information defining specific points in the domain, homotopy method utilizes the true and global mapping features that homotopy holds, and is thus a global method.
In an electric power system, when a short-circuit fault occurs, the convergence domain of the short-circuit solution of the system becomes smaller than that in a normal operation state, and even when a fault node contains a constant-power load, the short-circuit solution does not exist. The traditional iterative short circuit calculation method has a good effect on linear constant impedance load calculation, but when a system contains constant power load, the methods have great limitations, cannot process more complex and nonlinear load models, and can cause the problem that short circuit calculation cannot be converged. At this time, the load model is properly transformed and finally restored by adopting a homotopy method, so that the problem of short circuit convergence can be effectively solved.
For nonlinear algebraic equations, the homotopy method has global convergence. To solve the difficult problem f (x) ═ 0, we choose a simple problem G (x) ═ 0, G: R that is easy to solve or solves the known onen→RnAnd embedding the continuous parameter λ into the complex problem f (x) ═0, constructing a high-dimensional homotopy equation:
H(x，λ)：Rn×R→Rn，x∈Rn,λ∈R (8)
the homotopy equation satisfies the following two boundary conditions:
1.H(x,0)＝G(x)
2.H(x,1)＝F(x)
that is, when λ is 0, the solution of the homotopic equation H (x,0) ═ g (x) ═ 0 is a solution of the simple problem, and when λ is 1, H (x,1) ═ f (x) ═ 0 is a solution of the to-be-solved difficult problem f (x) ═ 0. H (x, λ) represents a system of equations containing n equations, and there are n +1 unknowns. From a computational perspective, the homotopy method can be viewed as starting from an initial point in solution space(suppose thatSolution to the simple problem H (x,0) by tracing the implicit curve C(s) epsilon H-1(0) The solution of the difficult problem H (x,1) is tracked until λ ═ 1. If this process is successful, then the solution for F (x) is available.
To construct the homotopy equation H (x, λ) for the general problem, we define the following famous linear convex homotopy equation:
H(x,λ)＝λF(x)+(1-λ)G(x). (9)
the homotopic equation of the linear convex is also used for solving the problem of the non-convergence of short circuit calculation in the power distribution network. For short circuit calculation, a simple problem is that a constant power load is converted into a fault equation (6) under a constant impedance load, and a method for solving a power flow, such as an implicit Z-bus Gaussian method, can be used for solving; the difficult problem is the fault equation (6) under the ZIP load model, and the solution obtained when the parameter lambda is gradually increased and is 1 is the short circuit solution under the ZIP load to be obtained by taking the short circuit solution obtained under the constant impedance load as a starting point.
4. Distribution network short circuit calculation method based on homotopy method
The basic idea of the homotopy method is to establish a set of parametric equations, so that the system is easy to solve when λ is 0, and is an original difficult-to-solve system when λ is 1. The homotopy method is applied to short circuit calculation, the simple problem is a short circuit equation (6) when all loads are constant impedance models, an implicit Zbus Gaussian method can be used for solving, and the difficult problem is the short circuit equation (6) when the load model is ZIP. To this end we define the following parameter vector:
for current injection vectors of the network under ZIP load after fault,network current injection for converting constant power load into constant impedance load. Likewise, Ybus(zip)For network node admittance matrices under ZIP load, Ybus(z)The network node admittance matrix is converted into a constant impedance load for the constant power part. We note that the above parameter vector has the following characteristics:
when the lambda is equal to 0, the magnetic flux,
Ybus(λ)＝Ybus(z)；
when the lambda is equal to 1, the total number of the two groups,
Ybus(λ)＝Ybus(zip)。
the short circuit calculation equation with parameters is:
for the above parameterized short circuit equation, the following features are provided:
(1) when lambda is equal to 0, the parameterized short-circuit equation (9) is consistent with the short-circuit equation (6) under the constant-power load conversion constant-impedance model;
(2) when λ is 1, the above-described parameterized short circuit equation (9) is consistent with the short circuit equation under ZIP load.
The key factor affecting the efficiency of the short circuit calculation is the choice of the step size Δ λ. Conservative choices take a constant, smaller step size during the continuity method to ensure convergence of the algorithm. However, this requires many iterations, which reduces the computational efficiency. If a larger step size is selected, the short circuit calculation may suffer from non-convergence. The present invention adopts a strategy of step size control to solve the problem. The size of the step size Δ λ is determined according to the number of iterations required in the last successive process. If the iteration times are more, setting the step length delta lambda in the next continuous process to be smaller than the step length delta lambda in the last continuous process; if the number of iterations is small, the step size for the next step is larger than the last one. In addition to this, at a certain λiWhen short circuit is not converged, a strategy of reducing the step length by half (delta lambda) is adoptedi+1＝ΔλiAnd/2) ensuring the convergence of short circuit calculation. And a real-time dynamic adjustment strategy is adopted for the step length delta lambda, so that the convergence of the algorithm is ensured, and the short circuit calculation efficiency is improved. In practice, if the step size Δ λ is adjusted multiple times, the parameter λ may not grow exactly to 1. In this case, | lambda-1 | ≦ 10-4As an approximate judgment criterion of λ 1.
Example analysis
In order to verify the correctness and the validity of the method, the method is applied to the standard calculation example IEEE-13 and IEEE-8500 node system for verification. Table 1 shows values of short-circuit current at failure of IEEE-13 node, and tables 2, 3 and 4 show values of short-circuit current at failure of IEEE-8500 node.
TABLE 1 short-circuit Current values at Fault of IEEE-13 nodes
As can be seen from Table 1, under the constant impedance load model, the short-circuit current calculated by the method provided by the invention is basically consistent with the calculation result of OpenDSS [ ], and the accuracy of the algorithm provided by the invention is verified. On the other hand, when the load model is ZIP, the short-circuit current generally has a smaller value than that of the constant impedance load model. Therefore, when a constant impedance load model is used in short circuit calculation, the calculation result is conservative, the safety of the system is guaranteed, and the investment of a relay protection system is increased.
TABLE 2IEEE-8500 node values of short-circuit current at fault
It can be seen that when the coincidence model is in the form of constant impedance, the short circuit current value is generally higher. In addition, when the load ratios of constant power, constant current and constant impedance are different in the system, the short-circuit current value is also greatly different, and the higher the ratio of the constant power load to the constant current load is, the smaller the short-circuit current value is, as shown in table 3. Therefore, in the short circuit calculation, the modeling of the load has very important significance.
TABLE 3 short-circuit Current value at Fault of IEEE-8500 node
In order to prove the robustness of the homotopy enhanced short circuit calculation method, 10 distributed generators are connected into an IEEE-8500 node calculation example, and short circuit faults are tested at different nodes. Short-circuit current values when three-phase ground faults occur under different load models are summarized as shown in table 4.
TABLE 4 short-circuit Current value at Fault of IEEE-8500 node
Fig. 6 shows the voltage difference variation of two adjacent computations in the iteration process when λ is 1 and the load in the network is a ZIP model, and it can be clearly seen that the iterative compensation current method diverges and the homonymous robust short circuit computation method converges.
For the phase-B grounding fault, the traditional iterative compensation current method diverges, but the homotopy-enhanced short-circuit current calculation method provided by the invention is reliable in convergence, and can solve a short-circuit solution, as shown in FIG. 7.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.
Claims (10)
1. A homotopy-based short-circuit current calculation method comprising a distributed power supply and a nonlinear load is characterized by comprising the following steps: the method comprises the following steps:
(1) taking the distributed power supply as a node, constructing a power distribution network system model according to the connection mode and parameters of each electrical element in the power distribution network, and performing load flow calculation; the power distribution network system model comprises a distributed power supply steady-state model, a load model, a transformer model, a voltage regulator model, a capacitor model and a fault model;
(2) solving the short-circuit current of the load model of the power distribution network by adopting an iterative compensation current method, judging whether the solved short-circuit current is converged, if not, entering the step (3), otherwise, storing the result and stopping calculation;
(3) converting all constant power loads into a constant impedance load model, calculating short-circuit current by using an iterative compensation current method, and calculating the short-circuit voltage value of each node in the power distribution network system;
(4) constructing a homotopy equation, constructing an admittance matrix by using the calculated short-circuit voltage value and the current value, and solving and updating the admittance matrix by using a continuity method to obtain a convergence short-circuit current solution;
the transformer model comprises three-phase taps, iron core loss and copper loss, exciting current, an insulating commutation device and neutral point grounding impedance, wherein an admittance matrix is calculated by using the short-circuit impedance and the exciting current of the transformer, the grounding type of the three-phase transformer comprises YN-YN, YN-Y, YN-D, Y-YN, Y-Y, Y-D, D-YN, D-Y and D-D, and the impedance matrix of the transformer has different expression forms for different wiring forms;
the stepped voltage regulator consists of an autotransformer and a load voltage regulation tap, the voltage is changed by changing the tap of a series winding of the autotransformer, the position of the tap is determined by a control circuit, and the line voltage drop compensator aims to simulate the voltage drop of a distribution line from the voltage regulator to a load center; three single-phase hierarchical formula voltage regulator can connect into a three-phase hierarchical formula voltage regulator, and when three single-phase voltage regulator combination was in the same place, every voltage regulator all had self compensating circuit, and the tap of every voltage regulator changes alone, and every phase winding of three-phase voltage regulator is inside all to be connected the voltage regulator casing, and the three-phase voltage regulator is the operation in coordination, and the change of tap keeps unanimous on all windings, only needs a compensating circuit.
2. The homotopy-based short-circuit current calculation method comprising a distributed power supply and a nonlinear load as claimed in claim 1, characterized in that: in the step (1), the distributed power source includes a synchronous generator, an asynchronous generator and a distributed power source connected to the grid through an inverter, and is regarded as a PV node, a PQ node or a PI node, and when the distributed power source is used as the PV node to calculate that the short-circuit current is not converged, the distributed power source is converted into the PQ node.
3. The homotopy-based short-circuit current calculation method comprising a distributed power supply and a nonlinear load as claimed in claim 1, characterized in that: in the step (1), the load is constructed into a constant power model, a constant current model, a constant impedance model or a ZIP model formed by combination.
4. The homotopy-based short-circuit current calculation method comprising a distributed power supply and a nonlinear load as claimed in claim 1, characterized in that: in the step (1), the electrical components further include a transformer, a voltage regulator and a capacitor.
5. The homotopy-based short-circuit current calculation method comprising a distributed power supply and a nonlinear load as claimed in claim 1, characterized in that: in the step (1), a fault model is constructed, and for a three-phase earth fault, a single-phase earth fault and an interphase fault, impedance with a corresponding resistance value is accessed to a fault node to carry out a short-circuit fault model.
6. The homotopy-based short-circuit current calculation method comprising a distributed power supply and a nonlinear load as claimed in claim 1, characterized in that: in the step (2), the short-circuit current at the fault node is calculated by adopting a Thevenin equivalent method.
7. The homotopy-based short-circuit current calculation method comprising a distributed power supply and a nonlinear load as claimed in claim 1, characterized in that: in the step (3), after the current at the fault point is solved, the system node current injection is updated, that is, the short-circuit current at the fault point is added to the system current injection vector before the fault as the negative current injection.
8. The homotopy-based short-circuit current calculation method comprising a distributed power supply and a nonlinear load as claimed in claim 1, characterized in that: in the step (3), the constant power load is converted into a constant impedance model, all the constant power load parts in the network are converted into the constant impedance model, a system node admittance matrix is established, an equivalent system current injection vector including the transformer substation, the distributed power supply, the load and the short-circuit current is calculated, and the short-circuit voltage value of each node of the network is calculated.
9. The homotopy-based short-circuit current calculation method comprising a distributed power supply and a nonlinear load as claimed in claim 1, characterized in that: in the step (4), initial values and step lengths of continuous parameters are set, a parameterized admittance matrix is established, system current injection is calculated through a parameter equation, the node voltage value is used as an initial solution, the values of the continuous parameters are gradually increased, and network node voltages under different continuous parameter values are solved.
10. The homotopy-based short-circuit current calculation method comprising a distributed power supply and a nonlinear load as claimed in claim 1, characterized in that: and (4) judging whether the network node voltage is converged, if so, solving the current of each branch, otherwise, adopting a step length control strategy, adjusting the step length of the continuous parameters, reestablishing the parameterized admittance matrix, and solving the current of each branch in the power distribution network until the continuous parameters are 1, otherwise, renewing the continuous parameters and continuously establishing the parameterized admittance matrix.
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| CN107732905B (en) * | 2017-10-19 | 2020-09-08 | 国家电网公司 | Short-circuit current calculation method for grid-connected distributed power supply of current transformer |
| CN110460059B (en) * | 2019-07-26 | 2023-02-03 | 国网山东省电力公司泰安供电公司 | Power flow calculation method for power system |
| CN110783897A (en) * | 2019-09-25 | 2020-02-11 | 北京交通大学 | GPU acceleration-based power grid short-circuit current parallel computing method and system |
| CN111625914A (en) * | 2020-05-25 | 2020-09-04 | 广东电网有限责任公司 | Short-circuit current calculation method and system |
| CN113420522A (en) * | 2021-07-21 | 2021-09-21 | 北京华大九天科技股份有限公司 | Method for calculating circuit node charge of linear capacitor in circuit |
| CN114188945B (en) * | 2022-02-17 | 2022-06-14 | 国网江西省电力有限公司电力科学研究院 | Method and device for calculating short-circuit current of power distribution network containing photovoltaic power supply |
| CN115173416A (en) * | 2022-09-08 | 2022-10-11 | 国网江西省电力有限公司电力科学研究院 | Distribution network short circuit total current calculation method and system considering distributed power supply |
| CN116227250B (en) * | 2023-05-10 | 2023-07-21 | 国网冀北电力有限公司 | Power flow solution space boundary calculation method and device for knowledge graph power system |
| CN116613752B (en) * | 2023-07-20 | 2023-11-14 | 中国电力科学研究院有限公司 | New energy affected range and voltage calculation method and system under main network fault |
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