Method and system for determining short-circuit current in power systems containing renewable energy power plants

Abstract

This invention discloses a method and system for determining the short-circuit current of a power system containing renewable energy power plants, belonging to the field of power system short-circuit current calculation technology. The method includes: establishing positive-sequence and negative-sequence short-circuit models for the renewable energy units; establishing positive-sequence and negative-sequence short-circuit models for the renewable energy power plants; obtaining basic parameters of the power network portion of the power system; based on the basic parameters of the power network and the positive-sequence and negative-sequence short-circuit models of the renewable energy power plants, establishing a simplified composite sequence network model of the power system including the renewable energy power plants and the power network; and iteratively calculating the simplified composite sequence network model of the power system to obtain the short-circuit current of the renewable energy power plants and each branch of the power system. This invention solves for the short-circuit current of renewable energy power plants using the obtained simplified composite sequence network model, overcoming the limitations of existing short-circuit current calculation methods.

Description

Technical Field

[0001] This invention relates to the field of power system short-circuit current calculation technology, and more specifically, to a method and system for determining the short-circuit current of a power system containing new energy power plants. Background Technology

[0002] (1) Traditional methods for calculating short-circuit current in power systems include the following:

[0003] 1) Symmetric component method, specifically including:

[0004] Power system faults include three-phase symmetrical faults and asymmetrical faults. Generally, the symmetrical component method is used to analyze different types of faults. This method decomposes the unbalanced voltage and current after a fault into three sets of balanced three-phase components: positive sequence, negative sequence, and zero sequence. Each set of electrical quantities can be described using a single-phase circuit. The symmetrical component method is widely used in the calculation of short-circuit currents in traditional AC systems. It typically uses a sequence network for calculation and divides the system model at the fault point into two parts: the power system network and the fault circuit.

[0005] Faulty circuits are described using sequence admittance matrices. For example, for a three-phase fault, the equivalent admittance matrix Y of the faulty circuit is... f for:

[0006]

[0007] Here Z fn Z is the fault impedance between the phase line at the fault point and its neutral point. ng The fault impedance is between the neutral point and ground; for a single-phase fault, the equivalent admittance matrix Y of the fault circuit is... f for:

[0008]

[0009] Among them, Z fg This is the impedance between the fault point and ground; when there is a metallic grounding, this impedance is approximately zero.

[0010] 2) Fault analysis based on the superposition method, specifically including:

[0011] The principle of using the superposition method for fault analysis is as follows: the system after the fault is divided into two parts as shown in Figure 1(a). The fault circuit is equivalent to the fault current source. Then, Figure 1(a) can be equivalent to (b), and further equivalent to the sum of the two parts (c) and (d).

[0012] Step 1: Equivalent the original network before the fault to the fault port determined by the fault type. This can be done by first performing Thevenin equivalence and then converting it to Norton equivalence. That is, converting Figure 1(a) to (e).

[0013] Step 2: Connect the fault circuit and the Norton equivalent circuit at the fault port, and solve for the fault voltage at the fault port using the following formula.

[0014] V f =(Y eq +Y f ) -1 I eq (0) (2-3)

[0015] Then, the fault current at the fault port is calculated using the following formula.

[0016] I f =Y f (Y eq +Y f ) -1 I eq (0) (2-4)

[0017] Step 3: Based on the fault current at the fault port, calculate the fault electrical quantities of other nodes in the entire network, and then add them together with the components before the fault. That is, the voltage V of any node in the system after the fault can be expressed as...

[0018] V = V (0) +V′ (2-5)

[0019] Where V (0) V' is the component determined by the pre-fault power flow in Figure 1(c), and V' is the component determined by the fault current I in Figure 1(d). f The weight of the decision.

[0020] (2) Equivalent models for new energy power plants in short-circuit calculations include:

[0021] Due to the fault characteristics of new energy generating units, they exhibit voltage-controlled current source behavior during steady-state operation after a fault, which is related to the unit's fault ride-through control strategy and steady-state power. Therefore, the short-circuit current calculation model for new energy generating units uses a voltage-controlled current source to describe it.

[0022] Generally, new energy power plants are represented by a single equivalent generating unit, also known as the "single-unit multiplication" model. The circuitry and control structure (including fault ride-through control strategy) of the equivalent generating unit are the same as those of a single generating unit. The rated capacity of the equivalent generating unit is equal to the rated capacity of the power plant. The output power of the equivalent generating unit under normal conditions is equal to the total output power of all generating units in the power plant. The control strategy of the equivalent generating unit under fault ride-through is also consistent with that of a single generating unit. The short-circuit current calculation model for a new energy power plant is the same as the short-circuit current calculation model for this equivalent generating unit.

[0023] (3) Short-circuit current calculation methods for power systems containing new energy sources, including:

[0024] Due to the applicability issues of the superposition principle, iterative calculations must be performed based on the node voltage equations of the entire system.

[0025] 1) The iterative method is used to calculate symmetric faults, specifically including:

[0026] Solving the problem by starting with the entire network before decomposition, we write the nodal voltage equations for the entire network:

[0027]

[0028] Where f is the faulty node and G is the new energy grid-connected node; for any node j, U j Let I be the voltage phasor at node j. j Let be the current phasor injected at node j. The injected current on the right-hand side of this equation is provided by both the synchronous generator and the renewable energy plant. For the synchronous generator, the injected current is constant and is the current source current after Norton equivalent of the subtransient electromotive force and subtransient reactance; for the renewable energy plant, it is the actual output current under a certain state, and its value is determined by the grid connection point voltage.

[0029] The voltage phasors of each node in the network are calculated using equation (2-6). The output current of the renewable energy power station is then obtained using the calculated node voltage phasors, and the injected current column vector in equation (2-6) is updated. The calculation process is as follows: Figure 2 As shown. Iterative calculations are performed using this method until the voltages of all nodes in the network converge. Given the accurate voltages of each node in the network, the short-circuit current on each line can be calculated. The current of lines directly connected to the renewable energy power station can be calculated based on the functional relationship between its voltage and current. The short-circuit current of lines not directly connected to the renewable energy power station is:

[0030] I jk =(V j -V k ) / z jk (2-7)

[0031] Among them, z jk I represents the line impedance between nodes j and k. jk Let be the line current between nodes j and k.

[0032] 2) Iterative methods are used to calculate asymmetric faults, including:

[0033] Since there is no coupling relationship in the positive and negative zero-order networks, the node admittance matrix formed without considering fault boundary conditions is:

[0034]

[0035] in, These are the zero-sequence, positive-sequence, and negative-sequence node voltage phasor matrices, respectively. These are the phasor matrices of the injected node currents for zero-sequence, positive-sequence, and negative-sequence, respectively. These are the admittance matrices for the zero-order, positive-order, and negative-order nodes, respectively.

[0036] Each sequence network is connected by fault points containing electrical relationships. To reflect this connection, fault points and zero-potential points are added to each sequence network shown in Equation (2-8). The connection method of fault points and zero potentials between sequences is adjusted according to the fault type, and the positive-sequence zero-potential point is eliminated (grounded to eliminate the singularity of node admittance), resulting in the node voltage equations with a dimension of 3n+5:

[0037]

[0038] Among them, Y αβ (α,β∈{(0),(1),(2)}andα≠β) is the node admittance matrix between different orders; Y αα These are the admittance matrices of nodes with the same order.

[0039] After formulating the network node voltage equations, the next steps are similar to those for three-phase short-circuit faults. Assuming each node voltage has initial values ​​(which can be obtained from power flow calculations), calculate the sequence currents output by the renewable energy source. The synchronous generator power supply only acts as a positive-sequence current injection element in the network, and therefore only in... The current in the inverter power supply may appear at a constant value, while the current in the new energy inverter power supply may also appear at a constant value. In this process, the node injection current at k iterations is obtained from the node voltage at k iterations. Combined with the node admittance matrix, the node voltage is calculated as the state at k+1 iterations. This process is repeated until the node voltages converge to the specified accuracy.

[0040] In summary, the above method is used to calculate the short-circuit current of a power system. The matrix size is relatively large, but the nodal admittance matrix does not change during the iteration process. Therefore, the inversion operation of the admittance matrix only needs to be performed once.

[0041] For renewable energy systems, the superposition principle has applicability issues. Because renewable energy units exhibit characteristics of voltage-controlled current sources in steady-state operation after a fault, the relationship between their output current and grid connection voltage is non-linear. Even if network decomposition using the superposition principle is possible, a renewable energy current source will still appear in the fault component network, and this current source varies with the grid connection voltage, making it impossible to represent using a constant current source.

[0042] Existing equivalent methods for short-circuit current calculations in renewable energy power plants only consider the circuit and control structures before and after equivalence, as well as the consistency of steady-state capacity and power. For short-circuit current calculations, they do not fully account for the differences in fault output current caused by differences in steady-state power among different units. Therefore, using only an equivalent method that averages steady-state power may not be sufficient to ensure the consistency of short-circuit currents at the power plant.

[0043] For negative sequence models of new energy power plants, equivalent impedance is generally used for description, but practical calculation formulas are lacking.

[0044] The iterative method is suitable for accurate calculation of positive sequence short-circuit current. However, for asymmetrical faults, if detailed models of each sequence network are formed and iterative calculations are performed simultaneously, the dimension of the impedance matrix reaches about three times the number of power grid nodes, resulting in a large amount of computation and affecting the efficiency of short-circuit current calculation. Summary of the Invention

[0045] To address the above problems, this invention proposes a method for determining the short-circuit current of a power system containing renewable energy power plants, comprising:

[0046] Obtain the basic parameters of each new energy unit in the new energy power station in the power system, and establish the positive sequence short circuit model and negative sequence short circuit model of the new energy unit based on the basic parameters of the new energy unit and the low voltage ride-through control logic of the new energy unit.

[0047] Obtain the basic parameters of the new energy power station, and based on the basic parameters of the new energy power station and the positive sequence short circuit model and negative sequence short circuit model of the new energy unit, establish the positive sequence short circuit model and negative sequence short circuit model of the new energy power station.

[0048] Obtain the basic parameters of the power network portion of the power system, and based on the basic parameters of the power network and the positive-sequence short-circuit model and negative-sequence short-circuit model of the new energy power station, establish a simplified composite sequence network model of the power system including the new energy power station and the power network.

[0049] The simplified composite sequence network model of the power system is iteratively calculated to obtain the short-circuit current of the new energy power stations and each branch of the power system.

[0050] Optionally, a positive-sequence short-circuit model for the aforementioned new energy power station is established, including:

[0051] The positive sequence short-circuit calculation model for the k-th unit in a renewable energy power plant is represented using a voltage-controlled current source, as shown in the following formula:

[0052]

[0053] in, Let be the positive sequence short-circuit current of the k-th unit. Let i be the positive sequence voltage at the terminal of the k-th unit. refGk This is the reference current value for the k-th generating unit during normal operation.

[0054] Among them, i refGk =P refk -jQ refk P refk Q is the active power reference value when the k-th unit is operating normally. refk Here is the reactive power reference value when the k-th generating unit is operating normally, k = 1 to M;

[0055] For a new energy power station consisting of M units of the same model, use one equivalent generator to perform equivalent calculations to determine the sum of the positive sequence currents of each unit, which is the positive sequence short-circuit current of the new energy power station. The formula is as follows:

[0056]

[0057] Based on the sum of the positive-sequence currents of each unit, the relationship curve between the positive-sequence current and positive-sequence voltage of the equivalent machine is obtained and named as function g. The positive-sequence short-circuit model is determined, and the formula is as follows:

[0058]

[0059] in, This refers to the positive sequence short-circuit current of the aforementioned new energy power station. Let g be the positive sequence voltage of the node of the new energy power station, and g be the positive sequence voltage relationship curve function of the new energy power station.

[0060] Optionally, a negative-sequence short-circuit model for the new energy power station is established, including:

[0061] The formula for determining the negative-order equivalent admittance is as follows:

[0062]

[0063] in, For the negative sequence equivalent admittance of the k-th unit, L t K is the sum of the filter inductance of the grid-side converter and the leakage inductance of the transformer substation. i and T i These represent the proportional gain and integral time constant of the grid-side converter of the generator unit, respectively, where ω0 is the power frequency angular frequency, and K... m and T m Let be the equivalent gain and equivalent delay time of PMW, respectively, and j be the node;

[0064] For a new energy power station consisting of M generators of the same model, an equivalent negative sequence admittance is determined using one equivalent generator, as shown in the following formula:

[0065]

[0066] The equivalent negative-order admittance satisfies the following formula:

[0067]

[0068] in, This refers to the negative sequence short-circuit current of the aforementioned new energy power station. This refers to the negative sequence voltage of the new energy power station node. The equivalent negative sequence admittance of the new energy power station.

[0069] Optional, simplified composite sequence network models include:

[0070] The model excludes positive / negative sequence network models and zero sequence network models of power systems at renewable energy power plants; includes positive / negative sequence network models of power systems at renewable energy power plants; includes a sequence network combination model of power systems at renewable energy power plants; and includes a composite sequence network model of renewable energy power plants.

[0071] Optional, negative-sequence network models excluding the power systems of renewable energy power plants are as follows:

[0072]

[0073] in, This represents the negative-sequence self-admittance of a typical power grid node. and This refers to the negative-sequence mutual admittance between the new energy power station node and the general power grid node. and This refers to the negative-sequence mutual admittance between the fault point and a general power grid node. The negative-order self-admittance of the new energy power station node is given. The negative-order self-admittance of the fault point. and The negative-order mutual admittance between the new energy power station node and the fault point is given. This refers to the negative sequence voltage of a typical power grid node. This refers to the negative sequence voltage of the new energy power station node. The negative sequence voltage at the fault point. This represents the negative sequence current at the fault point.

[0074] Optional, positive-sequence network models excluding the power systems of renewable energy power plants are as follows:

[0075]

[0076] in, This represents the positive sequence voltage of a typical power grid node. This refers to the positive sequence voltage of the new energy power station node. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point.

[0077] Optionally, a zero-sequence network model excluding the power system of renewable energy power plants can be established, including:

[0078] The zero-sequence network model in impedance matrix form is established as follows:

[0079] in, This refers to the zero-sequence voltage of a typical power grid node. The zero-sequence voltage at the fault point. This refers to the zero-sequence self-impedance of a typical power grid node. and This refers to the zero-sequence mutual impedance between the fault point and a general power grid node. The zero-sequence self-impedance at the fault point, This refers to the zero-sequence current at the fault point.

[0080] Based on the zero-sequence network model in impedance matrix form, the equivalent relationship between fault point voltage and current is extracted, i.e., the zero-sequence network model of the power system excluding new energy power plants, as follows:

[0081]

[0082] Optional, a positive-sequence network model including the power system of new energy power plants, is as follows:

[0083]

[0084] in, This represents the positive sequence voltage of a typical power grid node. This refers to the positive sequence voltage of the new energy power station node. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point.

[0085] Optional, a negative-sequence network model including the power system of new energy power plants, is as follows:

[0086]

[0087] in, The negative sequence voltage at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative sequence current at the fault point.

[0088] Optionally, a negative-sequence network model of the power system including new energy power plants is established, including:

[0089] In the negative-sequence network model excluding the power system of renewable energy power plants, self-admittance is added to the original renewable energy power plant nodes. The following admittance matrix is ​​obtained:

[0090]

[0091] Inverting the admittance matrix, we get:

[0092]

[0093] Based on the inverse admittance matrix, a negative-order network model in impedance matrix form is established as follows:

[0094]

[0095] Based on the negative-sequence network model in impedance matrix form, the equivalent relationship between fault point voltage and current is extracted, i.e., the negative-sequence network model of the power system including new energy power plants, as follows:

[0096]

[0097] in, The negative sequence voltage at the fault point. This is the negative sequence current at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative-sequence self-admittance of a typical power grid node. and This refers to the negative-sequence mutual admittance between the new energy power station node and the general power grid node. and This refers to the negative-sequence mutual admittance between the fault point and a general power grid node. The negative-order self-admittance of the new energy power station node is given. The negative-order self-admittance of the fault point. and The negative-order mutual admittance between the new energy power station node and the fault point is given. This refers to the negative sequence voltage of a typical power grid node. This refers to the negative sequence voltage of the new energy power station node. This refers to the negative sequence short-circuit current of the aforementioned new energy power station. This represents the positive sequence current at a typical power grid node. This is the negative-sequence self-impedance of a typical power grid node. and This refers to the negative-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the negative-sequence mutual impedance between the fault point and a general power grid node. The negative sequence self-impedance of the new energy power station node is given. The negative sequence self-impedance of the fault point. and The negative sequence mutual impedance is the impedance between the node of the new energy power station and the fault point.

[0098] Optional, a sequence network model including the power system of new energy power plants is as follows:

[0099]

[0100] in, The zero-sequence voltage at the fault point. The equivalent zero-sequence impedance at the fault point, The zero-sequence current at the fault point. This represents the positive sequence voltage of a typical power grid node. This refers to the positive sequence voltage of the new energy power station node. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point. This represents the positive sequence voltage of a typical power grid node. The negative sequence voltage at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative sequence current at the fault point.

[0101] Optional, composite sequence network model, as follows:

[0102]

[0103] The formulas for calculating matrices A1, A2, B1, and B2 are as follows:

[0104]

[0105] in, This represents the positive sequence voltage of a typical power grid node. This refers to the positive sequence voltage of the new energy power station node. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point. The zero-sequence voltage at the fault point. Let g be the negative sequence voltage at the fault point, and g be the positive sequence voltage relationship curve function of the new energy power station. The negative sequence voltage at the fault point. Y is the negative sequence current at the fault point. f Let I be the sequence admittance matrix of the faulty circuit, and let I be the identity matrix.

[0106] Optionally, iterative calculations are performed on the simplified composite sequence network model of the power system to obtain the short-circuit currents of the new energy power plants and each branch of the power system, including:

[0107] The composite sequence network model is iterated for the n=1th time to obtain the positive sequence voltage of the new energy power station grid connection point calculated in the n=1th iteration. According to the positive sequence voltage of the grid connection point of the new energy power station Determine the positive sequence current injected into the new energy power station.

[0108] According to the above The composite sequence network model is iterated for the (n+1)th time to obtain the positive sequence voltage of the new energy power station grid connection point calculated in the (n+1)th iteration.

[0109] judge and If the absolute value of the difference meets the preset threshold, and if so, the short-circuit current of the new energy power station and each branch is determined based on the positive / negative sequence network model and zero sequence network model of the power system without new energy power stations, the positive / negative sequence network model of the power system with new energy power stations, and the sequence network combined model of the power system with new energy power stations.

[0110] Furthermore, this invention also proposes a system for determining the short-circuit current of a power system containing new energy power plants, comprising:

[0111] The first model building module is used to obtain the basic parameters of each new energy unit in the new energy power station in the power system, and to establish the positive sequence short circuit model and negative sequence short circuit model of the new energy unit based on the basic parameters of the new energy unit and the low voltage ride-through control logic of the new energy unit.

[0112] The second model building module is used to obtain the basic parameters of the new energy power station, and to establish the positive sequence short circuit model and negative sequence short circuit model of the new energy power station based on the basic parameters of the new energy power station and the positive sequence short circuit model and negative sequence short circuit model of the new energy unit.

[0113] The third model building module is used to obtain the basic parameters of the power network part of the power system, and based on the basic parameters of the power network and the positive sequence short circuit model and negative sequence short circuit model of the new energy power station, to establish a simplified composite sequence network model of the power system including the new energy power station and the power network.

[0114] The iterative calculation module is used to perform iterative calculations on the simplified composite sequence network model of the power system to obtain the short-circuit current of the new energy power stations and each branch of the power system.

[0115] Optionally, the second model building module establishes a positive-sequence short-circuit model of the new energy power station, including:

[0116] The positive sequence short-circuit calculation model for the k-th unit in a renewable energy power plant is represented using a voltage-controlled current source, as shown in the following formula:

[0117]

[0118] in, Let be the positive sequence short-circuit current of the k-th unit. Let i be the positive sequence voltage at the terminal of the k-th unit. refGk This is the reference current value for the k-th generating unit during normal operation.

[0119] Among them, i refGk =P refk -jQ refk P refk Q is the active power reference value when the k-th unit is operating normally. refk Here is the reactive power reference value when the k-th generating unit is operating normally, k = 1 to M;

[0120] For a new energy power station consisting of M units of the same model, use one equivalent generator to perform equivalent calculations to determine the sum of the positive sequence currents of each unit, which is the positive sequence short-circuit current of the new energy power station. The formula is as follows:

[0121]

[0122] Based on the sum of the positive-sequence currents of each unit, the relationship curve between the positive-sequence current and positive-sequence voltage of the equivalent machine is obtained and named as function g. The positive-sequence short-circuit model is determined, and the formula is as follows:

[0123]

[0124] in, This refers to the positive sequence short-circuit current of the aforementioned new energy power station. Let g be the positive sequence voltage of the node of the new energy power station, and g be the positive sequence voltage relationship curve function of the new energy power station.

[0125] Optionally, the second model building module establishes a negative-sequence short-circuit model for the new energy power station, including:

[0126] The formula for determining the negative-order equivalent admittance is as follows:

[0127]

[0128] in, For the negative sequence equivalent admittance of the k-th unit, L t K is the sum of the filter inductance of the grid-side converter and the leakage inductance of the transformer substation. i and T i These represent the proportional gain and integral time constant of the grid-side converter of the generator unit, respectively, where ω0 is the power frequency angular frequency, and K... m and Tm Let be the equivalent gain and equivalent delay time of PMW, respectively, and j be the node;

[0129] For a new energy power station consisting of M generators of the same model, an equivalent negative sequence admittance is determined using one equivalent generator, as shown in the following formula:

[0130]

[0131] The equivalent negative-order admittance satisfies the following formula:

[0132]

[0133] in, This refers to the negative sequence short-circuit current of the aforementioned new energy power station. This refers to the negative sequence voltage of the new energy power station node. The equivalent negative sequence admittance of the new energy power station.

[0134] Optional, simplified composite sequence network models include:

[0135] The model excludes positive / negative sequence network models and zero sequence network models of power systems at renewable energy power plants; includes positive / negative sequence network models of power systems at renewable energy power plants; includes a sequence network combination model of power systems at renewable energy power plants; and includes a composite sequence network model of renewable energy power plants.

[0136] Optional, negative-sequence network models excluding the power systems of renewable energy power plants are as follows:

[0137]

[0138] in, This represents the negative-sequence self-admittance of a typical power grid node. and This refers to the negative-sequence mutual admittance between the new energy power station node and the general power grid node. and This refers to the negative-sequence mutual admittance between the fault point and a general power grid node. The negative-order self-admittance of the new energy power station node is given. The negative-order self-admittance of the fault point. and The negative-order mutual admittance between the new energy power station node and the fault point is given. This refers to the negative sequence voltage of a typical power grid node. This refers to the negative sequence voltage of the new energy power station node. The negative sequence voltage at the fault point. This represents the negative sequence current at the fault point.

[0139] Optional, positive-sequence network models excluding the power systems of renewable energy power plants are as follows:

[0140]

[0141] in, This represents the positive sequence voltage of a typical power grid node. This refers to the positive sequence voltage of the new energy power station node. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point.

[0142] Optionally, a zero-sequence network model excluding the power system of renewable energy power plants can be established, including:

[0143] The zero-sequence network model in impedance matrix form is established as follows:

[0144] in, This refers to the zero-sequence voltage of a typical power grid node. The zero-sequence voltage at the fault point. This refers to the zero-sequence self-impedance of a typical power grid node. and This refers to the zero-sequence mutual impedance between the fault point and a general power grid node. The zero-sequence self-impedance at the fault point, This refers to the zero-sequence current at the fault point.

[0145] Based on the zero-sequence network model in impedance matrix form, the equivalent relationship between fault point voltage and current is extracted, i.e., the zero-sequence network model of the power system excluding new energy power plants, as follows:

[0146]

[0147] Optional, a positive-sequence network model including the power system of new energy power plants, is as follows:

[0148]

[0149] in, This represents the positive sequence voltage of a typical power grid node. This refers to the positive sequence voltage of the new energy power station node. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point.

[0150] Optional, a negative-sequence network model including the power system of new energy power plants, is as follows:

[0151]

[0152] in, The negative sequence voltage at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative sequence current at the fault point.

[0153] Optionally, a negative-sequence network model of the power system including new energy power plants is established, including:

[0154] In the negative-sequence network model excluding the power system of renewable energy power plants, self-admittance is added to the original renewable energy power plant nodes. The following admittance matrix is ​​obtained:

[0155]

[0156] Inverting the admittance matrix, we get:

[0157]

[0158] Based on the inverse admittance matrix, a negative-order network model in impedance matrix form is established as follows:

[0159]

[0160] Based on the negative-sequence network model in impedance matrix form, the equivalent relationship between fault point voltage and current is extracted, i.e., the negative-sequence network model of the power system including new energy power plants, as follows:

[0161]

[0162] in, The negative sequence voltage at the fault point. This is the negative sequence current at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative-sequence self-admittance of a typical power grid node. and This refers to the negative-sequence mutual admittance between the new energy power station node and the general power grid node. and This refers to the negative-sequence mutual admittance between the fault point and a general power grid node. The negative-order self-admittance of the new energy power station node is given. The negative-order self-admittance of the fault point. and The negative-order mutual admittance between the new energy power station node and the fault point is given. This refers to the negative sequence voltage of a typical power grid node. This refers to the negative sequence voltage of the new energy power station node. This refers to the negative sequence short-circuit current of the aforementioned new energy power station. This represents the positive sequence current at a typical power grid node. This is the negative-sequence self-impedance of a typical power grid node. and This refers to the negative-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the negative-sequence mutual impedance between the fault point and a general power grid node. The negative sequence self-impedance of the new energy power station node is given. The negative sequence self-impedance of the fault point. and The negative sequence mutual impedance is the impedance between the node of the new energy power station and the fault point.

[0163] Optional, a sequence network model including the power system of new energy power plants is as follows:

[0164]

[0165] in, The zero-sequence voltage at the fault point. The equivalent zero-sequence impedance at the fault point, The zero-sequence current at the fault point. This represents the positive sequence voltage of a typical power grid node. This refers to the positive sequence voltage of the new energy power station node. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point. This represents the positive sequence voltage of a typical power grid node. The negative sequence voltage at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative sequence current at the fault point.

[0166] Optional, composite sequence network model, as follows:

[0167]

[0168] The formulas for calculating matrices A1, A2, B1, and B2 are as follows:

[0169]

[0170] in, This represents the positive sequence voltage of a typical power grid node. This refers to the positive sequence voltage of the new energy power station node. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point. The zero-sequence voltage at the fault point. Let g be the negative sequence voltage at the fault point, and g be the positive sequence voltage relationship curve function of the new energy power station. The negative sequence voltage at the fault point. Y is the negative sequence current at the fault point. f Let I be the sequence admittance matrix of the faulty circuit, and let I be the identity matrix.

[0171] Optionally, the iterative calculation module performs iterative calculations on the simplified composite sequence network model of the power system to obtain the short-circuit currents of the new energy power plants and each branch of the power system, including:

[0172] The composite sequence network model is iterated for the n=1th time to obtain the positive sequence voltage of the new energy power station grid connection point calculated in the n=1th iteration. According to the positive sequence voltage of the grid connection point of the new energy power station Determine the positive sequence current injected into the new energy power station.

[0173] According to the above The composite sequence network model is iterated for the (n+1)th time to obtain the positive sequence voltage of the new energy power station grid connection point calculated in the (n+1)th iteration.

[0174] judge and If the absolute value of the difference meets the preset threshold, and if so, the short-circuit current of the new energy power station and each branch is determined based on the positive / negative sequence network model and zero sequence network model of the power system without new energy power stations, the positive / negative sequence network model of the power system with new energy power stations, and the sequence network combined model of the power system with new energy power stations.

[0175] In another aspect, the present invention also provides a computing device, comprising: one or more processors;

[0176] A processor is used to execute one or more programs;

[0177] When the one or more programs are executed by the one or more processors, the method described above is implemented.

[0178] In another aspect, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the method described above.

[0179] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0180] This invention provides a method for determining the short-circuit current of a power system containing renewable energy power plants. The method includes: acquiring the basic parameters of each renewable energy unit within the renewable energy power plant in the power system; establishing positive-sequence and negative-sequence short-circuit models of the renewable energy units based on the basic parameters and the low-voltage ride-through control logic of the renewable energy units; acquiring the basic parameters of the renewable energy power plant; establishing positive-sequence and negative-sequence short-circuit models of the renewable energy power plant based on the basic parameters of the renewable energy power plant and the positive-sequence and negative-sequence short-circuit models of the renewable energy units; acquiring the basic parameters of the power network portion of the power system; establishing a simplified composite sequence network model of the power system including the renewable energy power plant and the power network based on the basic parameters of the power network and the positive-sequence and negative-sequence short-circuit models of the renewable energy power plant; and iteratively calculating the simplified composite sequence network model of the power system to obtain the short-circuit current of the renewable energy power plant and each branch of the power system. This invention solves for the short-circuit current of the renewable energy power plant using the obtained simplified composite sequence network model, overcoming the limitations of existing short-circuit current calculation methods. Attached Figure Description

[0181] Figure 1(a) shows the equivalent circuit diagram of the power system after the fault;

[0182] Figure 1(b) is the equivalent circuit diagram of the fault circuit simulated by the fault current;

[0183] Figure 1(c) is a schematic diagram of the result of a power source acting alone in a power system;

[0184] Figure 1(d) is a schematic diagram of the effect of fault current acting alone in a power system;

[0185] Figure 1(e) is the Norton equivalent circuit replacement circuit diagram of the power system after the fault.

[0186] Figure 2 A schematic diagram illustrating the fault process analysis using the iterative method;

[0187] Figure 3 This is a flowchart of the method of the present invention;

[0188] Figure 4 This is a typical new energy grid-connected system topology diagram according to an embodiment of the present invention;

[0189] Figure 5 The active current curves of the new energy generating unit and the power station under different voltage levels are shown in the figure.

[0190] Figure 6 This is a typical new energy grid-connected system topology diagram of the present invention;

[0191] Figure 7 This is a structural diagram of the system of the present invention. Detailed Implementation

[0192] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0193] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0194] Example 1:

[0195] This invention proposes a method for determining the short-circuit current of a power system containing renewable energy power plants, such as... Figure 3 As shown, it includes:

[0196] Step 1: Obtain the basic parameters of each new energy unit in the new energy power station in the power system. Based on the basic parameters of the new energy unit and the low voltage ride-through control logic of the new energy unit, establish the positive sequence short circuit model and negative sequence short circuit model of the new energy unit.

[0197] Step 2: Obtain the basic parameters of the new energy power station. Based on the basic parameters of the new energy power station and the positive sequence short circuit model and negative sequence short circuit model of the new energy unit, establish the positive sequence short circuit model and negative sequence short circuit model of the new energy power station.

[0198] Step 3: Obtain the basic parameters of the power network in the power system. Based on the basic parameters of the power network and the positive sequence short-circuit model and negative sequence short-circuit model of the new energy power station, establish a simplified composite sequence network model of the power system including the new energy power station and the power network.

[0199] Step 4: Iteratively calculate the simplified composite sequence network model of the power system to obtain the short-circuit current of the new energy power stations and each branch of the power system.

[0200] Steps 1, 2, 3, and 4 are detailed below:

[0201] (1) Establish a positive sequence short-circuit calculation model for new energy power plants;

[0202] Based on the low-voltage ride-through control logic of new energy units, the positive-sequence short-circuit calculation model of the k-th unit in the power station is represented by a voltage-controlled current source, namely:

[0203]

[0204] in, This is the positive sequence short-circuit current. This is the positive sequence voltage at the machine terminal; i refGk The current reference value during normal operation can be approximated by the active power reference value P during normal operation. refk Reactive power reference value Q refk To perform the calculation, that is:

[0205] i refGk =P refk -jQ refk (2-11)

[0206] Considering the widely adopted low-voltage ride-through control logic, the relationship between the positive-sequence short-circuit current and the positive-sequence voltage at the generator terminals of a new energy unit is as follows:

[0207]

[0208] Where VL is the voltage threshold value for entering low voltage ride-through control, and KQ is the reactive current coefficient for low voltage ride-through control.

[0209] A new energy power station consisting of M units of the same model will be equivalently managed using one generator set. Its positive sequence current will be the sum of the positive sequence currents of all units, i.e.:

[0210]

[0211] Based on the given normal operating power values ​​of each unit, it is approximately assumed that the positive sequence voltage at each unit terminal is equal to the positive sequence voltage at the station port. Equation (2-13) is used to obtain the positive sequence current-positive sequence voltage relationship curve of the equivalent unit, which is named function g, i.e.:

[0212]

[0213] (2) Establish a negative sequence short-circuit calculation model for new energy power plants;

[0214] This part needs to be considered when calculating asymmetric faults, but can be omitted when calculating symmetric faults.

[0215] Let the negative sequence equivalent admittance of the k-th renewable energy unit in the renewable energy power station be... For new energy generating units with known parameters, the negative-sequence equivalent admittance is calculated using the following formula:

[0216]

[0217] Where Lt is the sum of the filter inductance of the grid-side converter and the leakage inductance of the transformer, Ki and Ti are the proportional coefficient and integral time constant of the grid-side converter, respectively, w0 is the power frequency angular frequency, and Km and Tm are the equivalent gain and equivalent delay time of the PMW, respectively.

[0218] For new energy units with unknown parameters, such as manufacturer's digital packaging model or physical controller model, the negative sequence equivalent admittance can be obtained through the following steps: build a simplified electromagnetic transient simulation model of "new energy unit - Thevenin equivalent circuit"; apply a small amplitude power frequency negative sequence voltage to the voltage source, and perform Fourier transform on the simulation results of the unit port voltage and current to extract the power frequency negative sequence component; divide the power frequency negative sequence phasor in the current and voltage to obtain the negative sequence equivalent admittance.

[0219] For a new energy power station consisting of M units of the same model, an equivalent unit is used for equivalence analysis. Assuming that the negative-sequence admittance of each unit is approximately equal, the equivalent negative-sequence admittance of the new energy power station can be considered as the parallel value of multiple individual unit negative-sequence admittances, i.e.:

[0220]

[0221] The equivalent negative sequence admittance of this new energy power station satisfies:

[0222]

[0223] (3) Establish a simplified composite sequence network model that includes new energy power stations;

[0224] The nodes in the system are divided into three categories: conventional nodes, renewable energy grid-connected nodes, and fault points. If some conventional nodes are connected to synchronous generators, they are represented by Norton equivalents as a parallel model of a fixed current source injected into the node and an equivalent admittance. Renewable energy grid-connected nodes are the network nodes connected to renewable energy power plants. Renewable energy power plants are represented by a voltage-controlled current source model in positive sequence, an equivalent impedance model in negative sequence, and an open circuit in zero sequence.

[0225] 1) Positive and negative sequence network models excluding new energy power station systems;

[0226] Without considering the renewable energy power plant model, similar to conventional power systems, the grid node admittance matrix Y is first established based on the circuit topology parameters. n According to Y n Establish the negative-order network node voltage equations described by the admittance matrix, namely:

[0227]

[0228] In addition, for Y n Inverse the equations and establish the nodal voltage equations of the positive-order network described by the impedance matrix, i.e.:

[0229]

[0230] 2) Zero-sequence network model excluding new energy power station systems;

[0231] When calculating asymmetrical faults, this part needs to be considered, while it can be omitted when calculating symmetrical faults. The 35kV grid-connected nodes of renewable energy power plants are generally connected to the high-voltage grid via step-up transformers, and the 35kV side typically uses a transformer delta connection, which is equivalent to a short circuit to ground under zero-sequence conditions. Therefore, by eliminating the renewable energy 35kV grid-connected nodes from the admittance matrix in equation (2-18), a zero-sequence admittance matrix is ​​formed. Then, by inverting the matrix, the zero-sequence network node voltage equation described by the impedance matrix is ​​established, i.e.:

[0232]

[0233] Further simplifying the fault point, the voltage and current relationship at the fault point is extracted:

[0234]

[0235] 3) A forward-order network model including new energy power station systems;

[0236] Since the positive sequence short-circuit calculation models for each renewable energy power station are nonlinear models described by functions, it is necessary to add this nonlinear model to each renewable energy grid-connected node in the original positive sequence network described by equation (2-19) to establish the node voltage equations of the positive sequence network:

[0237]

[0238] 4) Negative-order network model including new energy power station systems;

[0239] When calculating asymmetric faults, this part needs to be considered, while the calculation of symmetric faults can omit this part. When describing renewable energy power plants using negative-sequence equivalent admittance, a self-admittance needs to be added to each renewable energy grid-connected node in the original negative-sequence network described by equation (2-18), that is:

[0240]

[0241] Then, by inverting the matrix, the node voltage equations of the negative-order network described by the impedance matrix are established, namely:

[0242]

[0243] Further simplifying the fault point, the voltage and current relationship at the fault point is extracted:

[0244]

[0245] 5) Including the sequential network connection of new energy power station systems;

[0246] Combining equations (2-21), (2-22), and (2-25) yields the nodal voltage equations for the detailed model containing the positive-sequence network, as well as the simplified models for the negative-sequence and zero-sequence networks:

[0247]

[0248] In the calculation of symmetric faults, the correlation matrices and variables of zero-order and negative-order networks can be removed.

[0249] 6) Combined with the faulty circuit, a composite sequence network model is obtained;

[0250] The faulty circuit is modeled with ordered coupling and described using the admittance matrix Yf, which satisfies:

[0251]

[0252] Combining equations (2-26) and (2-27), we derive the following:

[0253]

[0254] The expressions for some of the submatrices are as follows:

[0255]

[0256] In the calculation of symmetric faults, the zero-order and negative-order matrices and variables can be removed.

[0257] (4) Short-circuit current iterative calculation based on composite sequence network model;

[0258] 1) Perform the n=1th iteration calculation, i.e., according to equation (2-28), first consider that none of the new energy power stations have entered the low voltage ride-through state, that is, the current injected into the grid by the new energy power stations is given according to their steady-state power, and calculate the positive sequence voltage of the new energy grid connection node.

[0259] 2) Based on the nth calculation Calculate the positive sequence current injected into the power grid.

[0260] 3) According to Calculate using equation (2-28) Determine if it satisfies Where ε is a pre-set threshold value. If the condition is not met, let n = n + 1 and return to step 2); if it is met, proceed to step 4.

[0261] 4) Based on equation (2-28), calculate the positive sequence voltage of all nodes in the power grid, and the sequence voltage of each fault point; based on the sequence voltage of each fault point, calculate the sequence current of each fault point using equation (2-27); based on the negative sequence current of the fault point, calculate the negative sequence voltage of all nodes using equation (2-24); based on the zero sequence current of the fault point, calculate the zero sequence voltage of all nodes using equation (2-20); finally, based on the sequence voltage of all nodes, calculate the sequence current of all branches using equation (2-7). This completes the calculation of the fault voltage and fault current for the entire power grid. If necessary, the sequence components can be converted into three-phase effective values.

[0262] In the calculation of symmetrical faults, the calculation content of zero sequence and negative sequence can be removed.

[0263] The invention will now be verified using specific examples:

[0264] In this example, the topology of the new energy power station grid connection system is as follows: Figure 4 As shown, Figure 4 It includes two new energy power stations and their step-up transformers, a Thevenin equivalent power source for one synchronous generator, three connection impedances, and two nodal loads.

[0265] The positive-sequence short-circuit model for renewable energy power plants contains a key parameter: the positive-sequence active current-positive-sequence voltage characteristic curve. The calculation results in this example are as follows: Figure 5 As shown in the figure, the terminal voltage varies between 0.2 and 1.0. The active current of each unit is shown as the thin solid line, and the overall output active current of the station is shown as the thick dashed line. The thick dashed line can be used as some key parameters of the positive sequence short circuit calculation model.

[0266] against Figure 4 The equivalent circuit established for the new energy grid-connected system is as follows: Figure 6 As shown, two new energy power stations are described using positive-sequence and negative-sequence models and their switching switches, respectively. The step-up transformer is described using its short-circuit impedance and zero-sequence branch, and one synchronous generator is described using the Norton equivalent circuit.

[0267] (1) Calculation conditions for the example;

[0268] Typical power grid topology including renewable energy power plants is as follows: Figure 4 As shown, the equipment on the new energy power station side includes one equivalent full-power converter, with the converter parameters equivalent to the 35kV side; the equipment on the system side includes a 35 / 115kV step-up transformer, the impedance ZL from the step-up transformer to the fault point, the equivalent voltage source Vg on the system side, and the impedance Zg from the system power supply to the fault point.

[0269] The rated capacity of the new energy power station is 50MW, including 25 units, with a power of 2MW per unit. The steady-state active current Id0 of each unit during normal operation is shown in Table 1.

[0270] Table 1

[0271]

[0272]

[0273] The parameters of the 2MW direct-drive wind turbine and related systems are shown in Table 2. In the calculation, the per-unit system is used, and the rated capacity of the wind farm is set as the baseline capacity of the system.

[0274] Table 2

[0275] parameter unit value parameter unit value <![CDATA[S B ]]> MVA 50 <![CDATA[V B ]]> kV 35 <![CDATA[S G ]]> MVA 2 <![CDATA[V G ]]> kV 0.69 <![CDATA[K p ]]> pu 1.5 <![CDATA[T i ]]> s 0.1 <![CDATA[K pll ]]> pu 50 <![CDATA[T pll ]]> s 0.01 <![CDATA[K m ]]> pu 1.2 <![CDATA[T m ]]> s <![CDATA[1.5×10 -3 ]]> <![CDATA[K Q ]]> pu 1.5 <![CDATA[V L ]]> pu 0.9 <![CDATA[L t ]]> pu 0.5 <![CDATA[Z T1 ]]> pu 0+j0.15 <![CDATA[Z L1 ]]> pu 0+j0.05 <![CDATA[Z T2 ]]> pu 0+j0.15 <![CDATA[Z L2 ]]> pu 0+j0.05 <![CDATA[Z L3 ]]> pu 0+j0.05 <![CDATA[Z n1 ]]> pu 0-j3.0 <![CDATA[Z n2 ]]> pu 0+j1.5 <![CDATA[V s ]]> pu 1.0 <![CDATA[Z s ]]> pu 0+j0.1

[0276] Based on the above calculation conditions, the specific calculation process for this example is given below.

[0277] (2) Establish a positive sequence short-circuit calculation model for new energy power plants;

[0278] First, based on equation (2-12), substitute the steady-state active power of each unit under normal operation as shown in Table 1 (assuming the steady-state reactive power is 0 at this time), and the parameters KQ and VL in Table 2, to calculate the relationship between the positive-sequence active current and the positive-sequence voltage at the generator terminals for each unit. On this basis, given a generator terminal voltage variation between 0.2 and 1.0, calculate the active and reactive currents of each unit under fault conditions, where the reactive current of each unit is equal, and the active currents are as follows: Figure 4 The solid blue line indicates this. Next, based on equation (2-13), the overall output active current of the power station is calculated, as follows: Figure 4 As shown by the solid red line, this red curve can be used as some key parameters of the positive sequence short-circuit calculation model and used for subsequent whole-network short-circuit calculations.

[0279] (3) Establish a negative sequence short-circuit calculation model for new energy power plants;

[0280] Based on equation (2-15), substituting the electrical and control parameters of the new energy units shown in Table 2, the negative-sequence equivalent admittance of a single unit is obtained, and the negative-sequence equivalent admittance of the entire power station is obtained based on equation (2-16). The parameters of the two power stations are the same, and the calculated magnitude of the negative-sequence equivalent impedance of the power station is 0.53 pu, with a phase angle of 6.1 degrees.

[0281] (4) Establish and simplify a composite sequence network model that includes new energy power stations;

[0282] For this example system, its equivalent circuit is constructed as follows: Figure 6 As shown below, the process of establishing the composite sequence network model will be introduced.

[0283] 1) Positive and negative sequence network models excluding new energy power station systems;

[0284] The power network excluding renewable energy power plants has a total of 6 nodes, including 3 conventional nodes, 2 renewable energy grid-connected nodes, and 1 fault node. The node voltage and current sequences are as follows:

[0285]

[0286] Establish its positive and negative node admittance matrices Both have the same expression, namely:

[0287]

[0288] By inverting the matrix, negative-order and positive-order network node voltage equations in the form of equations (2-18) and (2-19) can be established respectively.

[0289] 2) Zero-sequence network model excluding new energy power station systems;

[0290] Considering the zero-sequence model of the low-voltage side angle-connected windings of the two step-up transformers, the 35kV renewable energy grid connection node is eliminated, where the node voltage and current sequences are as follows:

[0291]

[0292] Corresponding nodal admittance matrix for:

[0293]

[0294] By inverting and simplifying the matrix, the zero-sequence network node voltage equations of the form (2-21) can be established.

[0295] 3) A forward-order network model including new energy power station systems;

[0296] Using the positive-sequence nonlinear model of the new energy power station obtained by fitting in step (2) of the example, the voltage equation of the grid positive-sequence network node shown in equation (2-22) is established.

[0297] 4) Negative-order network model including new energy power station systems;

[0298] Using the negative-sequence equivalent impedance model of the new energy power station obtained in step (3) of the example, the node voltage equation of the negative-sequence network of the power grid shown in equation (2-25) is established.

[0299] 5) Including the sequential network connection of new energy power station systems;

[0300] By combining the equations, we obtain the sequence network node voltage equation of the system containing new energy power stations, as shown in equation (2-26).

[0301] 6) Combined with the faulty circuit, a composite sequence network is obtained;

[0302] Under three-phase faults, the fault circuit is described by the admittance matrix, and its value is shown in Equation (2-1); under single-phase faults, the fault circuit is described by the admittance matrix, and its value is shown in Equation (2-2); finally, the composite sequence network node voltage equations shown in Equations (2-28) and (2-29) are obtained by combining them.

[0303] (5) Short-circuit current iterative calculation based on composite sequence network model;

[0304] 1) Three-phase fault;

[0305] First, iterative calculations were performed using equation (2-28), with a preset terminal voltage deviation limit of 0.02 pu. The calculation results converged, and the number of iterations was 3. Second, short-circuit currents were calculated successively using equations (2-24), (2-25), (2-20), and (2-7). The final short-circuit current sequence components of each branch are shown in Table 3.

[0306] Table 3

[0307]

[0308] 2) Single-phase fault;

[0309] First, iterative calculations were performed using equation (2-28), with a preset terminal voltage deviation limit of 0.02 pu. The calculation results converged, and the number of iterations was 7. Second, short-circuit currents were calculated successively using equations (2-24), (2-25), (2-20), and (2-7). The final short-circuit current sequence components of each branch are shown in Table 4.

[0310] Table 4

[0311]

[0312]

[0313] This invention addresses the short-circuit calculation problem in new energy power systems. It overcomes the limitations of existing short-circuit current calculation methods in three aspects: equivalent models for new energy power plants, negative-sequence equivalent admittance of new energy power plants, and iterative calculation procedures for short-circuit current. Specifically, it achieves the following:

[0314] (1) The proposed equivalent model for new energy power plants, based on fitting the overall fault output characteristics of the power plant, calculates the output current of units with different initial powers at different voltage drop depths and obtains the overall output current characteristics of the power plant, which serve as key parameters for the positive-sequence short-circuit calculation model of the equivalent unit, based on the single-unit equivalent model of the power plant. Compared with the current method that only performs single-unit equivalent model based on equivalent initial power, this equivalent model takes into account the influence of internal unit differences on short-circuit current characteristics, which can improve the calculation accuracy of the positive-sequence short-circuit current contributed by new energy power plants.

[0315] (2) The proposed general negative sequence equivalent admittance model for full-power converter type new energy power stations is a practical calculation formula that reflects the dominant influencing factors on its negative sequence short-circuit current characteristics and has good calculation accuracy and efficiency. For new energy power stations where accurate parameters cannot be obtained, a practical method for measuring negative sequence impedance through small signal negative sequence disturbance is proposed.

[0316] (3) A simplified negative-sequence and zero-sequence network model is proposed to be combined with a detailed positive-sequence network model to form a simplified composite sequence network model. Its node impedance matrix has a low dimension, which can reduce the scale of iterative calculation and improve the efficiency of short-circuit current calculation. The key point is that, based on the passive characteristics of the negative-sequence and zero-sequence networks of the new energy system, they are equivalent to the fault nodes; while for the positive-sequence network that needs to be iteratively calculated, the complete model is retained.

[0317] Example 2:

[0318] The present invention also provides a system 200 for determining the short-circuit current of a power system containing new energy power plants, such as... Figure 7 As shown, it includes:

[0319] The first model building module 201 is used to obtain the basic parameters of each new energy unit in the new energy power station in the power system, and to establish the positive sequence short circuit model and negative sequence short circuit model of the new energy unit based on the basic parameters of the new energy unit and the low voltage ride-through control logic of the new energy unit.

[0320] The second model building module 202 is used to obtain the basic parameters of the new energy power station, and to establish the positive sequence short circuit model and negative sequence short circuit model of the new energy power station based on the basic parameters of the new energy power station and the positive sequence short circuit model and negative sequence short circuit model of the new energy unit.

[0321] The third model building module 203 is used to obtain the basic parameters of the power network part of the power system, and based on the basic parameters of the power network and the positive sequence short circuit model and negative sequence short circuit model of the new energy power station, to establish a simplified composite sequence network model of the power system including the new energy power station and the power network.

[0322] The iterative calculation module 204 is used to perform iterative calculations on the simplified composite sequence network model of the power system to obtain the short-circuit current of the new energy power stations and each branch of the power system.

[0323] The second model building module establishes the positive-sequence short-circuit model of the new energy power station, including:

[0324] The positive sequence short-circuit calculation model for the k-th unit in a renewable energy power plant is represented using a voltage-controlled current source, as shown in the following formula:

[0325]

[0326] in, Let be the positive sequence short-circuit current of the k-th unit. Let i be the positive sequence voltage at the terminal of the k-th unit. refGk This is the reference current value for the k-th generating unit during normal operation.

[0327] Among them, i refGk =P refk -jQ refk P refk Q is the active power reference value when the k-th unit is operating normally. refk Here is the reactive power reference value when the k-th generating unit is operating normally, k = 1 to M;

[0328] For a new energy power station consisting of M units of the same model, use one equivalent generator to perform equivalent calculations to determine the sum of the positive sequence currents of each unit, which is the positive sequence short-circuit current of the new energy power station. The formula is as follows:

[0329]

[0330] Based on the sum of the positive-sequence currents of each unit, the relationship curve between the positive-sequence current and positive-sequence voltage of the equivalent machine is obtained and named as function g. The positive-sequence short-circuit model is determined, and the formula is as follows:

[0331]

[0332] in, This refers to the positive sequence short-circuit current of the aforementioned new energy power station. Let g be the positive sequence voltage of the node of the new energy power station, and g be the positive sequence voltage relationship curve function of the new energy power station.

[0333] The second model building module establishes a negative-sequence short-circuit model for the new energy power station, including:

[0334] The formula for determining the negative-order equivalent admittance is as follows:

[0335]

[0336] in, For the negative sequence equivalent admittance of the k-th unit, L t K is the sum of the filter inductance of the grid-side converter and the leakage inductance of the transformer substation. i and T i These represent the proportional gain and integral time constant of the grid-side converter of the generator unit, respectively, where ω0 is the power frequency angular frequency, and K... m and T m Let be the equivalent gain and equivalent delay time of PMW, respectively, and j be the node;

[0337] For a new energy power station consisting of M generators of the same model, an equivalent negative sequence admittance is determined using one equivalent generator, as shown in the following formula:

[0338]

[0339] The equivalent negative-order admittance satisfies the following formula:

[0340]

[0341] in, This refers to the negative sequence short-circuit current of the aforementioned new energy power station. This refers to the negative sequence voltage of the new energy power station node. The equivalent negative sequence admittance of the new energy power station.

[0342] The simplified composite sequence network model includes:

[0343] The model excludes positive / negative sequence network models and zero sequence network models of power systems at renewable energy power plants; includes positive / negative sequence network models of power systems at renewable energy power plants; includes a sequence network combination model of power systems at renewable energy power plants; and includes a composite sequence network model of renewable energy power plants.

[0344] The negative-sequence network model, excluding the power system of new energy power plants, is as follows:

[0345]

[0346] in, This represents the negative-sequence self-admittance of a typical power grid node. and This refers to the negative-sequence mutual admittance between the new energy power station node and the general power grid node. and This refers to the negative-sequence mutual admittance between the fault point and a general power grid node. The negative-order self-admittance of the new energy power station node is given. The negative-order self-admittance of the fault point. and The negative-order mutual admittance between the new energy power station node and the fault point is given. This refers to the negative sequence voltage of a typical power grid node. This refers to the negative sequence voltage of the new energy power station node. The negative sequence voltage at the fault point. This represents the negative sequence current at the fault point.

[0347] The positive-sequence network model, excluding the power system of new energy power plants, is as follows:

[0348]

[0349] in, This represents the positive sequence voltage of a typical power grid node. This refers to the positive sequence voltage of the new energy power station node. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point. This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point.

[0350] Among them, establishing a zero-sequence network model excluding the power system of new energy power plants includes:

[0351] The zero-sequence network model in impedance matrix form is established as follows:

[0352] in, This refers to the zero-sequence voltage of a typical power grid node. The zero-sequence voltage at the fault point. This refers to the zero-sequence self-impedance of a typical power grid node. and This refers to the zero-sequence mutual impedance between the fault point and a general power grid node. The zero-sequence self-impedance at the fault point, This refers to the zero-sequence current at the fault point.

[0353] Based on the zero-sequence network model in impedance matrix form, the equivalent relationship between fault point voltage and current is extracted, i.e., the zero-sequence network model of the power system excluding new energy power plants, as follows:

[0354]

[0355] The positive-sequence network model for the power system of renewable energy power plants is as follows:

[0356]

[0357] in, This represents the positive sequence voltage of a typical power grid node. This refers to the positive sequence voltage of the new energy power station node. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point.

[0358] The negative-order network model for the power system of new energy power plants is as follows:

[0359]

[0360] in, The negative sequence voltage at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative sequence current at the fault point.

[0361] Among them, establishing a negative-sequence network model for the power system of new energy power plants includes:

[0362] In the negative-sequence network model excluding the power system of renewable energy power plants, self-admittance is added to the original renewable energy power plant nodes. The following admittance matrix is ​​obtained:

[0363]

[0364] Inverting the admittance matrix, we get:

[0365]

[0366] Based on the inverse admittance matrix, a negative-order network model in impedance matrix form is established as follows:

[0367]

[0368] Based on the negative-sequence network model in impedance matrix form, the equivalent relationship between fault point voltage and current is extracted, i.e., the negative-sequence network model of the power system including new energy power plants, as follows:

[0369]

[0370] in, The negative sequence voltage at the fault point. This is the negative sequence current at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative-sequence self-admittance of a typical power grid node. and This refers to the negative-sequence mutual admittance between the new energy power station node and the general power grid node. and This refers to the negative-sequence mutual admittance between the fault point and a general power grid node. The negative-order self-admittance of the new energy power station node is given. The negative-order self-admittance of the fault point. and The negative-order mutual admittance between the new energy power station node and the fault point is given. This refers to the negative sequence voltage of a typical power grid node. This refers to the negative sequence voltage of the new energy power station node. This refers to the negative sequence short-circuit current of the aforementioned new energy power station. This represents the positive sequence current at a typical power grid node. This is the negative-sequence self-impedance of a typical power grid node. and This refers to the negative-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the negative-sequence mutual impedance between the fault point and a general power grid node. The negative sequence self-impedance of the new energy power station node is given. The negative sequence self-impedance of the fault point. and The negative sequence mutual impedance is the impedance between the node of the new energy power station and the fault point.

[0371] The sequence network connection model including the power system of new energy power plants is as follows:

[0372]

[0373] in, The zero-sequence voltage at the fault point. The equivalent zero-sequence impedance at the fault point, The zero-sequence current at the fault point. This represents the positive sequence voltage of a typical power grid node. This refers to the positive sequence voltage of the new energy power station node. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point. This represents the positive sequence voltage of a typical power grid node. The negative sequence voltage at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative sequence current at the fault point.

[0374] The composite sequence network model is described below:

[0375]

[0376] The formulas for calculating matrices A1, A2, B1, and B2 are as follows:

[0377]

[0378] in, This represents the positive sequence voltage of a typical power grid node. This refers to the positive sequence voltage of the new energy power station node. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point. The zero-sequence voltage at the fault point. Let g be the negative sequence voltage at the fault point, and g be the positive sequence voltage relationship curve function of the new energy power station. The negative sequence voltage at the fault point. Y is the negative sequence current at the fault point. f Let I be the sequence admittance matrix of the faulty circuit, and let I be the identity matrix.

[0379] The iterative calculation module performs iterative calculations on the simplified composite sequence network model of the power system to obtain the short-circuit currents of the new energy power plants and each branch of the power system, including:

[0380] The composite sequence network model is iterated for the n=1th time to obtain the positive sequence voltage of the new energy power station grid connection point calculated in the n=1th iteration. According to the positive sequence voltage of the grid connection point of the new energy power station Determine the positive sequence current injected into the new energy power station.

[0381] According to the above The composite sequence network model is iterated for the (n+1)th time to obtain the positive sequence voltage of the new energy power station grid connection point calculated in the (n+1)th iteration.

[0382] judge and If the absolute value of the difference meets the preset threshold, and if so, the short-circuit current of the new energy power station and each branch is determined based on the positive / negative sequence network model and zero sequence network model of the power system without new energy power stations, the positive / negative sequence network model of the power system with new energy power stations, and the sequence network combined model of the power system with new energy power stations.

[0383] Example 3:

[0384] Based on the same inventive concept, this invention also provides a computer device, which includes a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in the computer storage medium to implement corresponding method flows or corresponding functions, thereby implementing the steps of the methods in the above embodiments.

[0385] Example 4:

[0386] Based on the same inventive concept, this invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the method in the above embodiments.

[0387] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0388] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in one or more blocks of the flowchart illustrations and / or one or more blocks of the block diagrams.

[0389] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means that implement the functions specified in one or more flowcharts and / or one or more block diagrams.

[0390] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide steps for implementing the functions specified in one or more flowcharts and / or one or more block diagrams.

[0391] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0392] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for determining the short-circuit current of a power system containing renewable energy power plants, characterized in that, The method includes: Obtain the basic parameters of each new energy unit in the new energy power station in the power system, and establish the positive sequence short circuit model and negative sequence short circuit model of the new energy unit based on the basic parameters of the new energy unit and the low voltage ride-through control logic of the new energy unit. Obtain the basic parameters of the new energy power station, and based on the basic parameters of the new energy power station and the positive sequence short circuit model and negative sequence short circuit model of the new energy unit, establish the positive sequence short circuit model and negative sequence short circuit model of the new energy power station. Obtain the basic parameters of the power network portion of the power system, and based on the basic parameters of the power network and the positive-sequence short-circuit model and negative-sequence short-circuit model of the new energy power station, establish a simplified composite sequence network model of the power system including the new energy power station and the power network. The simplified composite sequence network model of the power system is iteratively calculated to obtain the short-circuit current of the new energy power stations and each branch of the power system; The simplified composite sequence network model includes: Excluding positive / negative sequence network models and zero sequence network models of power systems in renewable energy power plants; including positive / negative sequence network models of power systems in renewable energy power plants; including sequence network combination models of power systems in renewable energy power plants and composite sequence network models of renewable energy power plants. The composite sequence network model is as follows: Among them, matrix , , , The calculation formula is as follows: in, This represents the positive sequence voltage of a typical power grid node. This represents the positive sequence voltage of the new energy power station nodes. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point. This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point. The zero-sequence voltage at the fault point. The negative sequence voltage at the fault point. Let be the positive sequence voltage relationship curve function of the aforementioned new energy power station. The negative sequence voltage at the fault point. This is the negative sequence current at the fault point. Here is the order admittance matrix of the faulty circuit. It is the identity matrix. The zero-sequence self-impedance at the fault point, The equivalent negative sequence impedance at the fault point; The iterative calculation of the simplified composite sequence network model of the power system to obtain the short-circuit current of the new energy power plants and each branch of the power system includes: The composite sequence network model is iterated for the n=1th time to obtain the positive sequence voltage of the new energy power station grid connection point calculated in the n=1th iteration. According to the positive sequence voltage of the grid connection point of the new energy power station Determine the positive sequence current injected into the new energy power station. ; According to the above The composite sequence network model is iterated for the (n+1)th time to obtain the positive sequence voltage of the new energy power station grid connection point calculated in the (n+1)th iteration. ; judge and If the absolute value of the difference meets the preset threshold, and if so, the short-circuit current of the new energy power station and each branch is determined based on the positive / negative sequence network model and zero sequence network model of the power system without new energy power stations, the positive / negative sequence network model of the power system with new energy power stations, and the sequence network combined model of the power system with new energy power stations.

2. The method according to claim 1, characterized in that, Establishing the positive-sequence short-circuit model for the aforementioned new energy power station includes: The positive sequence short-circuit calculation model for the k-th unit in a renewable energy power plant is represented using a voltage-controlled current source, as shown in the following formula: in, Let be the positive sequence short-circuit current of the k-th unit. Let be the positive sequence voltage at the terminal of the k-th generating unit. This is the reference current value for the k-th generating unit during normal operation. in, , This is the active power reference value when the k-th unit is operating normally. Here is the reactive power reference value when the k-th generating unit is operating normally, k=1~M; For a new energy power station consisting of M units of the same model, use one equivalent generator to perform equivalent calculations to determine the sum of the positive sequence currents of each unit, which is the positive sequence short-circuit current of the new energy power station. The formula is as follows: Based on the sum of the positive-sequence currents of each unit, the relationship curve between the positive-sequence current and positive-sequence voltage of the equivalent machine is obtained and named as function g. The positive-sequence short-circuit model is determined, and the formula is as follows: in, This refers to the positive sequence short-circuit current of the aforementioned new energy power station. This represents the positive sequence voltage of the new energy power station nodes. Let be the positive sequence voltage relationship curve function of the new energy power station.

3. The method according to claim 1, characterized in that, Establishing a negative-sequence short-circuit model for the aforementioned new energy power station includes: The formula for determining the negative-order equivalent admittance is as follows: in, Let be the negative-sequence equivalent admittance of the k-th unit. This is the sum of the filter inductance of the grid-side converter and the leakage inductance of the transformer substation. and These are the proportional gain and integral time constant of the grid-side converter of the generating unit, respectively. It is the power frequency angular frequency. and These are the equivalent gain and equivalent delay time of the PWM, respectively. For a new energy power station consisting of M generators of the same model, an equivalent negative sequence admittance is determined using one equivalent generator, as shown in the following formula: The equivalent negative-order admittance satisfies the following formula: in, This refers to the negative sequence short-circuit current of the aforementioned new energy power station. This refers to the negative sequence voltage of the new energy power station nodes. The equivalent negative sequence admittance of the new energy power station.

4. The method according to claim 1, characterized in that, The negative-order network model of the power system excluding new energy power plants is as follows: in, This represents the negative-sequence self-admittance of a typical power grid node. and This refers to the negative-sequence mutual admittance between new energy power plant nodes and general power grid nodes. and This refers to the negative-sequence mutual admittance between the fault point and a general power grid node. The negative-order self-admittance of the new energy power station node is given. The negative-order self-admittance of the fault point. and The negative-order mutual admittance between the new energy power station node and the fault point is given. This refers to the negative sequence voltage of a typical power grid node. This refers to the negative sequence voltage of the new energy power station node. The negative sequence voltage at the fault point. This represents the negative sequence current at the fault point.

5. The method according to claim 1, characterized in that, The positive sequence network model of the power system excluding new energy power plants is as follows: in, This represents the positive sequence voltage of a typical power grid node. This represents the positive sequence voltage of the new energy power station nodes. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point. This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point.

6. The method according to claim 1, characterized in that, The zero-sequence network model excluding the power system of new energy power plants includes: The zero-sequence network model in impedance matrix form is established as follows: in, This refers to the zero-sequence voltage of a typical power grid node. The zero-sequence voltage at the fault point. This refers to the zero-sequence self-impedance of a typical power grid node. and This refers to the zero-sequence mutual impedance between the fault point and a general power grid node. The zero-sequence self-impedance at the fault point, This refers to the zero-sequence current at the fault point. Based on the zero-sequence network model in impedance matrix form, the equivalent relationship between fault point voltage and current is extracted, i.e., the zero-sequence network model of the power system excluding new energy power plants, as follows: 。 7. The method according to claim 1, characterized in that, The positive sequence network model of the power system including new energy power plants is as follows: in, This represents the positive sequence voltage of a typical power grid node. This represents the positive sequence voltage of the new energy power station nodes. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point. This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point. Let be the positive sequence voltage relationship curve function of the new energy power station.

8. The method according to claim 1, characterized in that, The negative-order network model of the power system including new energy power plants is as follows: in, The negative sequence voltage at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative sequence current at the fault point.

9. The method according to claim 8, characterized in that, Establish a negative-sequence network model for the power system including new energy power plants, including: In the negative-sequence network model excluding the power system of renewable energy power plants, self-admittance is added to the original renewable energy power plant nodes. The following admittance matrix is ​​obtained: Inverting the admittance matrix, we get: Based on the inverse admittance matrix, a negative-order network model in impedance matrix form is established as follows: Based on the negative-sequence network model in impedance matrix form, the equivalent relationship between fault point voltage and current is extracted, i.e., the negative-sequence network model of the power system including new energy power plants, as follows: in, The negative sequence voltage at the fault point. This is the negative sequence current at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative-sequence self-admittance of a typical power grid node. and This refers to the negative-sequence mutual admittance between the new energy power station node and the general power grid node. and This refers to the negative-sequence mutual admittance between the fault point and a general power grid node. The negative-order self-admittance of the new energy power station node is given. The negative-order self-admittance of the fault point. and The negative-order mutual admittance between the new energy power station node and the fault point is given. This refers to the negative sequence voltage of a typical power grid node. This refers to the negative sequence voltage of the new energy power station node. This refers to the negative sequence short-circuit current of the aforementioned new energy power station. This represents the positive sequence current at a typical power grid node. This is the negative-sequence self-impedance of a typical power grid node. and This refers to the negative-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the negative-sequence mutual impedance between the fault point and a general power grid node. The negative sequence self-impedance of the new energy power station node is given. and The negative sequence mutual impedance is the impedance between the node of the new energy power station and the fault point. The equivalent negative sequence admittance of the new energy power station.

10. The method according to claim 1, characterized in that, The sequence network connection model of the power system including new energy power stations is as follows: in, The zero-sequence voltage at the fault point. The equivalent zero-sequence impedance at the fault point, The zero-sequence current at the fault point. This represents the positive sequence voltage of a typical power grid node. This represents the positive sequence voltage of the new energy power station nodes. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point. This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point. The negative sequence voltage at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative sequence current at the fault point.

11. A system for determining the short-circuit current of a power system containing new energy power plants, characterized in that, The system includes: The first model building module is used to obtain the basic parameters of each new energy unit in the new energy power station in the power system, and to establish the positive sequence short circuit model and negative sequence short circuit model of the new energy unit based on the basic parameters of the new energy unit and the low voltage ride-through control logic of the new energy unit. The second model building module is used to obtain the basic parameters of the new energy power station, and to establish the positive sequence short circuit model and negative sequence short circuit model of the new energy power station based on the basic parameters of the new energy power station and the positive sequence short circuit model and negative sequence short circuit model of the new energy unit. The third model building module is used to obtain the basic parameters of the power network part of the power system, and based on the basic parameters of the power network and the positive sequence short circuit model and negative sequence short circuit model of the new energy power station, to establish a simplified composite sequence network model of the power system including the new energy power station and the power network. The iterative calculation module is used to perform iterative calculations on the simplified composite sequence network model of the power system to obtain the short-circuit current of the new energy power stations and each branch of the power system. The simplified composite sequence network model includes: Excluding positive / negative sequence network models and zero sequence network models of power systems in renewable energy power plants; including positive / negative sequence network models of power systems in renewable energy power plants; including sequence network combination models of power systems in renewable energy power plants and composite sequence network models of renewable energy power plants. The composite sequence network model is as follows: Among them, matrix , , , The calculation formula is as follows: in, This represents the positive sequence voltage of a typical power grid node. This represents the positive sequence voltage of the new energy power station nodes. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point. This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point. The zero-sequence voltage at the fault point. The negative sequence voltage at the fault point. Let be the positive sequence voltage relationship curve function of the aforementioned new energy power station. The negative sequence voltage at the fault point. This is the negative sequence current at the fault point. Here is the order admittance matrix of the faulty circuit. It is the identity matrix. The zero-sequence self-impedance at the fault point, The equivalent negative sequence impedance at the fault point; The iterative calculation of the simplified composite sequence network model of the power system to obtain the short-circuit current of the new energy power plants and each branch of the power system includes: The composite sequence network model is iterated for the n=1th time to obtain the positive sequence voltage of the new energy power station grid connection point calculated in the n=1th iteration. According to the positive sequence voltage of the grid connection point of the new energy power station Determine the positive sequence current injected into the new energy power station. ; According to the above The composite sequence network model is iterated for the (n+1)th time to obtain the positive sequence voltage of the new energy power station grid connection point calculated in the (n+1)th iteration. ; judge and If the absolute value of the difference meets the preset threshold, and if so, the short-circuit current of the new energy power station and each branch is determined based on the positive / negative sequence network model and zero sequence network model of the power system without new energy power stations, the positive / negative sequence network model of the power system with new energy power stations, and the sequence network combined model of the power system with new energy power stations.

12. The system according to claim 11, characterized in that, Establishing the positive-sequence short-circuit model for the aforementioned new energy power station includes: The positive sequence short-circuit calculation model for the k-th unit in a renewable energy power plant is represented using a voltage-controlled current source, as shown in the following formula: in, Let be the positive sequence short-circuit current of the k-th unit. Let be the positive sequence voltage at the terminal of the k-th generating unit. This is the reference current value for the k-th generating unit during normal operation. in, , This is the active power reference value when the k-th unit is operating normally. Here is the reactive power reference value when the k-th generating unit is operating normally, k=1~M; For a new energy power station consisting of M units of the same model, use one equivalent generator to perform equivalent calculations to determine the sum of the positive sequence currents of each unit, which is the positive sequence short-circuit current of the new energy power station. The formula is as follows: Based on the sum of the positive-sequence currents of each unit, the relationship curve between the positive-sequence current and positive-sequence voltage of the equivalent machine is obtained and named as function g. The positive-sequence short-circuit model is determined, and the formula is as follows: in, This refers to the positive sequence short-circuit current of the aforementioned new energy power station. This represents the positive sequence voltage of the new energy power station nodes. Let be the positive sequence voltage relationship curve function of the new energy power station.

13. The system according to claim 11, characterized in that, Establishing a negative-sequence short-circuit model for the aforementioned new energy power station includes: The formula for determining the negative-order equivalent admittance is as follows: in, Let be the negative-sequence equivalent admittance of the k-th unit. This is the sum of the filter inductance of the grid-side converter and the leakage inductance of the transformer substation. and These are the proportional gain and integral time constant of the grid-side converter of the generating unit, respectively. It is the power frequency angular frequency. and These are the equivalent gain and equivalent delay time of the PWM, respectively. For a new energy power station consisting of M generators of the same model, an equivalent negative sequence admittance is determined using one equivalent generator, as shown in the following formula: The equivalent negative-order admittance satisfies the following formula: in, This refers to the negative sequence short-circuit current of the aforementioned new energy power station. This refers to the negative sequence voltage of the new energy power station nodes. The equivalent negative sequence admittance of the new energy power station.

14. The system according to claim 11, characterized in that, The negative-order network model of the power system excluding new energy power plants is as follows: in, This represents the negative-sequence self-admittance of a typical power grid node. and This refers to the negative-sequence mutual admittance between new energy power plant nodes and general power grid nodes. and This refers to the negative-sequence mutual admittance between the fault point and a general power grid node. The negative-order self-admittance of the new energy power station node is given. The negative-order self-admittance of the fault point. and The negative-order mutual admittance between the new energy power station node and the fault point is given. This refers to the negative sequence voltage of a typical power grid node. This refers to the negative sequence voltage of the new energy power station node. The negative sequence voltage at the fault point. This represents the negative sequence current at the fault point.

15. The system according to claim 11, characterized in that, The positive sequence network model of the power system excluding new energy power plants is as follows: in, This represents the positive sequence voltage of a typical power grid node. This represents the positive sequence voltage of the new energy power station nodes. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point. This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point.

16. The system according to claim 11, characterized in that, The zero-sequence network model excluding the power system of new energy power plants includes: The zero-sequence network model in impedance matrix form is established as follows: in, This refers to the zero-sequence voltage of a typical power grid node. The zero-sequence voltage at the fault point. This refers to the zero-sequence self-impedance of a typical power grid node. and This refers to the zero-sequence mutual impedance between the fault point and a general power grid node. The zero-sequence self-impedance at the fault point, This refers to the zero-sequence current at the fault point. Based on the zero-sequence network model in impedance matrix form, the equivalent relationship between fault point voltage and current is extracted, i.e., the zero-sequence network model of the power system excluding new energy power plants, as follows: 。 17. The system according to claim 11, characterized in that, The positive sequence network model of the power system including new energy power plants is as follows: in, This represents the positive sequence voltage of a typical power grid node. This represents the positive sequence voltage of the new energy power station nodes. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point. This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point. Let be the positive sequence voltage relationship curve function of the new energy power station.

18. The system according to claim 11, characterized in that, The negative-order network model of the power system including new energy power plants is as follows: in, The negative sequence voltage at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative sequence current at the fault point.

19. The system according to claim 18, characterized in that, Establish a negative-sequence network model for the power system including new energy power plants, including: In the negative-sequence network model excluding the power system of renewable energy power plants, self-admittance is added to the original renewable energy power plant nodes. The following admittance matrix is ​​obtained: Inverting the admittance matrix, we get: Based on the inverse admittance matrix, a negative-order network model in impedance matrix form is established as follows: Based on the negative-sequence network model in impedance matrix form, the equivalent relationship between fault point voltage and current is extracted, i.e., the negative-sequence network model of the power system including new energy power plants, as follows: in, The negative sequence voltage at the fault point. This is the negative sequence current at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative-sequence self-admittance of a typical power grid node. and This refers to the negative-sequence mutual admittance between the new energy power station node and the general power grid node. and This refers to the negative-sequence mutual admittance between the fault point and a general power grid node. The negative-order self-admittance of the new energy power station node is given. The negative-order self-admittance of the fault point. and The negative-order mutual admittance between the new energy power station node and the fault point is given. This refers to the negative sequence voltage of a typical power grid node. This refers to the negative sequence voltage of the new energy power station node. This refers to the negative sequence short-circuit current of the aforementioned new energy power station. This represents the positive sequence current at a typical power grid node. This is the negative-sequence self-impedance of a typical power grid node. and This refers to the negative-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the negative-sequence mutual impedance between the fault point and a general power grid node. The negative sequence self-impedance of the new energy power station node is given. and The negative sequence mutual impedance is the impedance between the node of the new energy power station and the fault point. The equivalent negative sequence admittance of the new energy power station.

20. The system according to claim 11, characterized in that, The sequence network connection model of the power system including new energy power stations is as follows: in, The zero-sequence voltage at the fault point. The equivalent zero-sequence impedance at the fault point, The zero-sequence current at the fault point. This represents the positive sequence voltage of a typical power grid node. This represents the positive sequence voltage of the new energy power station nodes. The positive sequence voltage at the fault point. This represents the positive-sequence self-impedance of a typical power grid node. and This refers to the positive-sequence mutual impedance between the new energy power station node and the general power grid node. and This refers to the positive-sequence mutual impedance between the fault point and a general power grid node. The positive-sequence self-impedance of the new energy power station node is given. and The positive-sequence mutual impedance between the nodes of the new energy power station and the fault point is given. The positive-sequence self-impedance of the fault point. This represents the positive sequence current at a typical power grid node. This represents the positive sequence current at the fault point. The negative sequence voltage at the fault point. This is the equivalent negative sequence impedance at the fault point. This represents the negative sequence current at the fault point.

21. A computer device, characterized in that, include: One or more processors; A processor is used to execute one or more programs; When the one or more programs are executed by the one or more processors, the method described in any one of claims 1-10 is implemented.

22. A computer-readable storage medium, characterized in that, It contains a computer program, which, when executed, implements the method as described in any one of claims 1-10.

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