Method and system for adjusting node impedance matrix of high-proportion wind power system containing current limiter

Abstract

The invention discloses a method and system for adjusting a node impedance matrix of a high-proportion wind power system containing a current limiter, and the method comprises the steps: calculating equivalent impedance before and after a fault of a doubly-fed fan, and further modifying an expansion node impedance matrix of a system containing a generator; modifying a system node impedance matrix after the current limiter is input; and calculating the short-circuit current of each node of the system according to the modified system node impedance matrix. In the working process, impedance deviation caused by the fact that a crowbar resistor is started when the doubly-fed fan breaks down seriously is considered, and the impedance of the current limiter is equivalent to a parallel impedance branch, so that the calculation process of a system node impedance matrix is simplified; the calculation efficiency of the short-circuit current of the large-scale wind power plant is improved, and the precision is ensured to be within an acceptable range.

Description

Technical Field

[0001] The present invention relates to an electric power system, and in particular to a method and system for adjusting a node impedance matrix of a high-ratio wind power system including a current limiter. Background Art

[0002] At present, my country has become the country with the largest installed capacity of wind power in the world, and wind power has become one of the main energy sources of the power system. my country's wind power mainly presents large-scale and intensive development, and many million-kilowatt wind farms have emerged. Doubly fed wind turbines (DFIGs) are the most widely used wind turbines. Their fault characteristics are affected by the control strategy of the rotor-side converter and have different fault currents from traditional synchronous generators, thus posing a threat to the setting and reliable operation of the relay protection equipment of the power system.

[0003] Fault current limiter (FCL) is considered to be an effective measure to suppress short-circuit current. Under normal operating conditions, it shows a low impedance or superconducting state to the outside; under fault conditions, FCL can quickly switch from a low impedance state to a high impedance state, suppressing excessive short-circuit current by increasing the impedance in the loop. Due to the high production, installation and maintenance costs of FCL, its promotion and application in actual production is restricted to a certain extent. Therefore, the location and capacity of FCL in the system need to be optimized to save costs.

[0004] However, in power systems with a high proportion of wind power, the calculation and suppression of short-circuit currents face new challenges. Due to the crowbar startup of the rotor side of the doubly fed wind turbine under severe faults, a crowbar resistor with a large resistance will be put into the rotor winding, and the rotor side converter will be locked at the same time. After the crowbar is started, the doubly fed wind turbine loses the rotor voltage excitation and can be equivalent to an asynchronous motor with a certain slip. Therefore, for the calculation of short-circuit current in the power system, after the fault occurs, the node connected to the doubly fed wind turbine is converted from the power node to the load node of the asynchronous motor. This transformation will change the current distribution characteristics of the system, especially the self-impedance of the node connected to the wind power.

[0005] Therefore, when configuring FCL to suppress short-circuit current in a system with a high proportion of wind power, it is necessary not only to consider the impact of FCL on the system node impedance matrix, but also to take into account the impedance change of wind power before and after the fault. If the impact of the wind power crowbar control strategy is ignored, the calculation of the system extended impedance matrix including the generator impedance will be inaccurate, which will lead to deviations in the short-circuit current calculation, threatening the safe and stable operation of the power system.

[0006] In the prior art, Chinese patent CN201610590130.4 provides a method for calculating the node impedance matrix of the fault port of a distribution line, ignoring the line impedance of the parallel branch and the series branch after the fault port in the distribution line, adding the load impedance of the parallel branch to the corresponding node, merging the load impedance of the series branch after the fault port to the fault port node, and obtaining the equivalent circuit of the fault main circuit; the equivalent circuit of the fault main circuit is represented by the line loop impedance matrix and the parallel branch node admittance matrix; calculating the parallel branch node admittance matrix of each node; and calculating the fault port node impedance matrix according to the equivalent circuit of the fault main circuit. However, the patent does not consider the impedance change of the wind turbine access node, and ignores the impedance change of the series connection in the line, so it is impossible to accurately calculate the impedance matrix after the current limiter is put into use.

[0007] Chinese patent CN201810947374.2 provides a new method of Gauss-Jordan elimination for quickly obtaining the node impedance matrix of the power system, which is about 65% faster than the traditional Gauss-Jordan elimination method. However, this patent only calculates the node impedance matrix of the traditional power system, and does not involve the impedance matrix calculation of the power system with current limiters and doubly fed wind turbines. Summary of the invention

[0008] In response to the above problems, the present invention provides a method and system for adjusting the node impedance matrix of a high-proportion wind power system containing a current limiter, which can quickly modify the system node impedance matrix after the current limiter and the doubly fed wind turbine crowbar are put into operation, thereby ensuring safe and stable operation of the power system.

[0009] The technical solution of the present invention is: a method for adjusting a node impedance matrix of a high-ratio wind power system including a current limiter, comprising:

[0010] Step 1: Calculate the steady-state impedance of the doubly-fed wind turbine before and after the fault, and then modify the system extended node impedance matrix including the generator;

[0011] Step 2: based on step 1, modify the system node impedance matrix after the current limiter is put into use;

[0012] Step three, calculate the short-circuit current of each node in the system according to the modified system node impedance matrix.

[0013] In step 1, the steady-state impedance z of the doubly fed wind turbine before the fault pre for:

[0014] z pre =R s +jω s σL s

[0015] In the formula, R s represents the stator resistance; j represents the imaginary unit; ωs represents the stator angular frequency; σ represents the leakage magnetic coefficient of the doubly fed fan; L s represents the stator inductance.

[0016] In step 1, the steady-state impedance z of the doubly fed wind turbine after failure fault for:

[0017] z fault =R s +jω s L eq∞

[0018] Where, L eq∞ It represents the equivalent steady-state inductance of the doubly-fed wind turbine after crowbar starting.

[0019] In step 2, when FCL is activated, the equivalent impedance z eq When connected in parallel to the network, the system node impedance matrix is ​​modified according to the following formula:

[0020]

[0021] In the formula, the variable Z xy,n represents the xth row and yth column element in the system node impedance matrix when n FCLs are activated; Z xk,n-1 represents the xth row and kth column element in the system node impedance matrix when n-1 FCLs are activated; Z xi,n-1 represents the xth row and ith column element in the system node impedance matrix when n-1 FCLs are activated; Z yk,n-1 represents the element in the yth row and kth column of the system node impedance matrix when n-1 FCLs are activated; Z yi,n-1 represents the element in the yth row and ith column of the system node impedance matrix when n-1 FCLs are activated; Z ii,n-1 represents the element in the ith row and ith column of the system node impedance matrix when n-1 FCLs are activated; Z kk,n-1 represents the kth row and kth column element in the system node impedance matrix when n-1 FCLs are activated; Z ki,n-1 represents the element in the kth row and ith column of the system node impedance matrix when n-1 FCLs are activated; z eq,n-1 represents the equivalent impedance of the n-1th FCL; the subscripts x and y represent any node numbers in the network, and the subscripts k and i represent the head node and the end node of the line where the current limiter is installed.

[0022] Equivalent impedance z eq as follows:

[0023]

[0024] In the formula, z line is the line impedance, z FCLis the current limiter impedance.

[0025] After FCL is activated, the change in self-impedance of all nodes is:

[0026]

[0027] In the formula, ΔZ xx,n It represents the change of the element in the xth row and xth column in the system node impedance matrix when n FCLs are activated.

[0028] In step 3, when a short-circuit fault occurs at node k in the system, its FCL is activated at line n, and the short-circuit current calculation formula of node k is:

[0029]

[0030] In the formula, I k,n represents the short-circuit current at node k, U k represents the voltage of node k before the fault, Z kk,n represents the node impedance matrix including FCL, I b Indicates the reference current.

[0031] A node impedance matrix adjustment system for a high-ratio wind power system including a current limiter, comprising:

[0032] A calculation module is used to calculate the equivalent impedance of the doubly-fed wind turbine before and after the fault, and then modify the system extended node impedance matrix including the generator;

[0033] A modification module is used to modify the system node impedance matrix after the current limiter is put into use;

[0034] The current module is used to calculate the short-circuit current of each node of the system according to the modified system node impedance matrix.

[0035] In the calculation module,

[0036] Steady-state impedance z of a doubly-fed wind turbine before fault pre for:

[0037] z pre =R s +jω s σL s

[0038] In the formula, R s represents the stator resistance; j represents the imaginary unit; ω s represents the stator angular frequency; σ represents the leakage magnetic coefficient of the doubly fed fan; L s represents the stator inductance;

[0039] Steady-state impedance z of a doubly-fed wind turbine after a fault fault for:

[0040] z fault =R s +jω s L eq∞

[0041] Where, L eq∞ It represents the equivalent steady-state inductance of the doubly-fed wind turbine after crowbar starting.

[0042] In the modification module,

[0043] When FCL is activated, the equivalent impedance z eq When connected in parallel to the network, the system node impedance matrix is ​​modified according to the following formula:

[0044]

[0045] In the formula, the variable Z xy,n represents the xth row and yth column element in the system node impedance matrix when n FCLs are activated; Z xk,n-1 represents the xth row and kth column element in the system node impedance matrix when n-1 FCLs are activated; Z xi,n-1 represents the xth row and ith column element in the system node impedance matrix when n-1 FCLs are activated; Z yk,n-1 represents the element in the yth row and kth column of the system node impedance matrix when n-1 FCLs are activated; Z yi,n-1 represents the element in the yth row and ith column of the system node impedance matrix when n-1 FCLs are activated; Z ii,n-1 represents the element in the ith row and ith column of the system node impedance matrix when n-1 FCLs are activated; Z kk,n-1 represents the kth row and kth column element in the system node impedance matrix when n-1 FCLs are activated; Z ki,n-1 represents the element in the kth row and ith column of the system node impedance matrix when n-1 FCLs are activated; z eq,n-1 represents the equivalent impedance of the n-1th FCL; the subscripts x and y represent any node numbers in the network, and the subscripts k and i represent the head node and the end node of the line where the current limiter is installed;

[0046] Among them, the equivalent impedance z eq as follows:

[0047]

[0048] In the formula, z line is the line impedance, z FCL is the current limiter impedance.

[0049] In operation, the present invention takes into account the impedance deviation caused by starting the crowbar resistor of the doubly fed wind turbine under severe fault conditions, and equates the current limiter impedance to a parallel impedance branch, thereby simplifying the calculation process of the system node impedance matrix, improving the efficiency of short-circuit current calculation in large-scale wind farms while ensuring its accuracy is within an acceptable range. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a flow chart of the method of the present invention,

[0051] Figure 2 This is the schematic diagram of the equivalent impedance of the doubly fed wind turbine before and after the fault.

[0052] Figure 3 This is a comparison chart of the short-circuit current of each 33kV node in the system before and after the use of FCL. DETAILED DESCRIPTION

[0053] like Figure 1 As shown, the present invention proposes a method for adjusting the node impedance matrix of a high-ratio wind power system including a current limiter, and the steps are as follows:

[0054] Step 1: Calculate the steady-state impedance of the doubly-fed wind turbine before and after the fault, and then modify the system extended node impedance matrix including the generator;

[0055] Step 2: Based on step 1, modify the system node impedance matrix after the current limiter is put into use;

[0056] Step three, calculate the short-circuit current of each node in the system according to the modified system node impedance matrix.

[0057] Step 1: Calculate the equivalent impedance of the doubly-fed wind turbine before and after the fault, and modify the system extended node impedance matrix containing the generator (this is the change of the self-impedance element, that is, the diagonal elements in the system extended node impedance matrix, and only the corresponding elements need to be replaced);

[0058] Based on the system extended node impedance matrix including the generator calculated in step one, step two further calculates the system node impedance matrix after the current limiter is put into operation;

[0059] Based on step 2, step 3 uses the impedance matrix to calculate the short-circuit current of each node in the system.

[0060] Step 1: Calculate the steady-state impedance of the doubly-fed wind turbine before and after the fault.

[0061] When a system fault occurs, the terminal voltage of the wind turbine will drop, causing a large transient electromotive force to be induced in its rotor winding. In severe faults, this transient electromotive force may exceed the maximum output voltage of the inverter on the rotor side of the wind turbine, resulting in overcurrent in the rotor winding, and in severe cases, the inverter will burn out. For this reason, a crowbar circuit is usually configured in the doubly fed wind turbine. When the rotor current is detected to be too high, the crowbar circuit is put into operation and the rotor side inverter is locked. The crowbar circuit is generally activated within 3-5ms after the fault occurs. Subsequently, the doubly fed wind turbine operates as an asynchronous induction motor with a certain slip. During the electromagnetic transient process, the rotor speed is usually considered to be constant due to the large rotational inertia of the rotor. If the delay of the crowbar activation is further ignored, the fault response of the DFIG can be regarded as a voltage step signal on a linear system. Therefore, it can be described by a system of linear differential equations with constant coefficients.

[0062] Using the motor convention, the doubly fed wind turbine can be described by the following mathematical model in the stator stationary coordinate system:

[0063]

[0064] In the formula, Represent the stator and rotor voltages respectively; Represent the stator and rotor currents respectively; Respectively represent the stator and rotor flux; R s , R r Respectively represent the stator and rotor resistance; L s , L r Respectively represent the stator and rotor inductance; L m represents mutual inductance; d represents the derivative symbol, t represents time, j represents the imaginary unit; ω r Indicates the rotor angular frequency.

[0065] Eliminating the rotor current and stator flux in the above stator-rotor voltage equations, we can obtain:

[0066]

[0067] Where, σ represents the magnetic leakage coefficient of the doubly fed wind turbine.

[0068] The above formula shows that the stator current of the doubly fed wind turbine is determined by the stator voltage and the dynamics of the rotor side flux. The last term in the above formula can be expressed as the internal potential of the doubly fed wind turbine, which is determined by the rotor side control strategy. In steady-state operation, the internal potential is considered to be constant, so the wind turbine can be equivalent to a steady-state impedance, such as Figure 2 a). The steady-state impedance of the doubly fed wind turbine before fault can be expressed as:

[0069] z pre =R s +jω sσL s (4)

[0070] In the formula, ω s represents the stator angular frequency.

[0071] The short-circuit current calculation of the power system is mainly for the periodic component, that is, the steady-state component of the short-circuit current. Once the crowbar short-circuits the rotor-side converter, the DFIG is equivalent to a passive component that can be represented by inductance. According to the stator and rotor voltage equations of the doubly fed wind turbine, the rotor voltage can be expressed as follows:

[0072]

[0073] In the formula, R re is the equivalent resistance including the crowbar resistance and the rotor resistance, represents the stator flux in the rotor coordinate system, Represents the rotor current in the rotor coordinate system. The first term in the above equation is the open-circuit rotor voltage induced by the stator flux. The second term reflects the dynamics of the rotor current. Since the crowbar short-circuits the RSC (i.e., a short-circuit fault occurs in the rotor-side converter (RSC) in the power system), after all transient components have decayed, the rotor current is completely induced by the stator flux. Therefore, the steady-state stator flux and rotor current after the fault are described by the following equation:

[0074]

[0075] In the formula, represents the steady-state component of the stator flux, Represents the steady-state component of the rotor current.

[0076] If we further replace the rotor current in the above formula with the stator flux and stator current, we can deduce:

[0077]

[0078] In the formula, represents the steady-state component of the stator current, L eq∞ It represents the equivalent steady-state inductance of the doubly-fed wind turbine after crowbar starting.

[0079] The above formula expresses the relationship between the steady-state stator current and stator flux of the doubly fed wind turbine after a fault. It can be observed that when the wind turbine slip and crowbar resistance are determined, the coefficient is a constant, so it can be expressed as the steady-state equivalent inductance of the doubly fed wind turbine. The steady-state equivalent circuit after the fault is as follows: Figure 2 b). Before the fault, the doubly fed wind turbine can be equivalent to a series connection of a controlled voltage source and an equivalent impedance; after the fault, the crowbar is activated to make it an induction motor with a certain slip, and its steady-state characteristics can be represented by a steady-state equivalent inductance related to the slip and crowbar resistance.

[0080] The steady-state impedance of a doubly-fed wind turbine after a fault can be expressed as:

[0081] z fault =R s +jω s L eq∞ (8)

[0082] Therefore, the impedance of the doubly fed wind turbine changes after the fault, which will change the self-impedance of the connected node for short-circuit current calculation. For the system impedance matrix, the self-impedance of the node to which the doubly fed wind turbine is connected (i.e., the impedance before the fault) can be replaced with the impedance after the fault. The equivalent impedance of the doubly fed wind turbine before and after the fault can be directly applied to the node impedance matrix of the power system, providing a model basis for the short-circuit current calculation of large-scale systems with a high proportion of wind power.

[0083] The existing calculation only calculates the short-circuit current after the double-fed wind turbine fails and obtains its time domain expression, but does not derive the equivalent impedance change before and after the crowbar start of the double-fed wind turbine. The present invention derives the steady-state impedance of the double-fed wind turbine after the crowbar start by analyzing the relationship between the steady-state stator current and the stator flux after the double-fed wind turbine fails.

[0084] Step 2: Modify the system node impedance matrix after the current limiter is put into use.

[0085] The fundamental principle of the current limiter is to put an impedance in series in the network when a short circuit occurs in the system, so as to achieve the purpose of limiting the short circuit current. kk In terms of FCL activation, it is equivalent to increasing the impedance of a line in the network by z. FCL , so the node impedance matrix network needs to be updated. Usually, it is necessary to first update the node admittance matrix and then invert it to obtain the node impedance matrix. However, as the system scale increases and the number of nodes increases, the amount of inversion calculation increases exponentially. The present invention uses the Thevenin equivalent circuit to connect the z FCL It is equivalent to a parallel impedance, avoiding the inversion operation.

[0086] When FCL is activated, it is equivalent to a current limiter impedance z FCL Connected in series on the line between nodes k and i, the line impedance increases. Assume that an equivalent impedance z eq Connect in parallel on the line, and make the impedance between nodes k and i the same as in series, that is,

[0087]

[0088] In the formula, z line is the line impedance, z FCL is the current limiter impedance.

[0089] Therefore, when FCL is activated, it can be equivalent to the equivalent impedance z eq Connecting to the network in parallel is equivalent to adding a new branch. The system node impedance matrix can be modified according to the following formula

[0090]

[0091] In the formula, the variable Z xy,n represents the xth row and yth column element in the system node impedance matrix when n FCLs are activated; Z xk,n-1 represents the xth row and kth column element in the system node impedance matrix when n-1 FCLs are activated; Z xi,n-1 represents the xth row and ith column element in the system node impedance matrix when n-1 FCLs are activated; Z yk,n-1 represents the element in the yth row and kth column of the system node impedance matrix when n-1 FCLs are activated; Z yi,n-1 represents the element in the yth row and ith column of the system node impedance matrix when n-1 FCLs are activated; Z ii,n-1 represents the element in the ith row and ith column of the system node impedance matrix when n-1 FCLs are activated; Z kk,n-1 represents the kth row and kth column element in the system node impedance matrix when n-1 FCLs are activated; Z ki,n-1 represents the element in the kth row and ith column of the system node impedance matrix when n-1 FCLs are activated; z eq,n-1 represents the equivalent impedance of the n-1th FCL; in particular, the subscripts x and y represent any node numbers in the network, and the subscripts k and i represent the head node and the end node of the line where the current limiter is installed.

[0092] Equation (10) shows that each time a FCL is activated, the system node impedance matrix needs to be modified.

[0093] For short-circuit current calculation, only the diagonal elements of the node impedance matrix need to be modified. After FCL is activated, the change in self-impedance of all nodes is:

[0094]

[0095] In the formula, ΔZ xx,n It represents the change of the element in the xth row and xth column in the system node impedance matrix when n FCLs are activated.

[0096] Step 2 is a method for modifying each element in the system node impedance matrix Z, and the final output is the Z matrix. Among them, formula (10) represents the modification operation of the Z matrix. Formula (11) is a simplified version of formula (10). Since only the diagonal elements of the Z matrix are needed to calculate the short-circuit current, formula (11) can be used directly to modify the diagonal elements.

[0097] Step three, calculate the short-circuit current of each node in the system according to the modified system node impedance matrix.

[0098] The factors that determine the system short-circuit current level include the node impedance matrix Z of the system network information S and the node voltage before the fault. When a short-circuit fault occurs at node k in the system, its FCL is activated at line n, and the short-circuit current calculation formula of node k is:

[0099]

[0100] In the formula, I k,n represents the short-circuit current of node k, subscript k represents the node where the fault occurs, subscript n represents the line where the FCL is installed, and U k represents the voltage of node k before the fault, Z kk,n The node impedance matrix (Z kk,n is an element in the Z matrix), I b Indicates the reference current.

[0101] The present invention also provides a high-ratio wind power system node impedance matrix adjustment system including a current limiter, comprising:

[0102] A calculation module is used to calculate the equivalent impedance of the doubly-fed wind turbine before and after the fault, and then modify the system extended node impedance matrix including the generator;

[0103] A modification module is used to modify the system node impedance matrix after the current limiter is put into use;

[0104] The current module is used to calculate the short-circuit current of each node of the system according to the modified system node impedance matrix.

[0105] In the calculation module,

[0106] Steady-state impedance z of a doubly-fed wind turbine before fault pre for:

[0107] z pre =R s +jω s σL s

[0108] In the formula, R s represents the stator resistance; j represents the imaginary unit; ω s represents the stator angular frequency; σ represents the leakage magnetic coefficient of the doubly fed fan; L s represents the stator inductance;

[0109] Steady-state impedance z of a doubly-fed wind turbine after a fault fault for:

[0110] zfault =R s +jω s L eq∞

[0111] Where, L eq∞ It represents the equivalent steady-state inductance of the doubly-fed wind turbine after crowbar starting.

[0112] In the modification module,

[0113] When FCL is activated, the equivalent impedance z eq When connected in parallel to the network, the system node impedance matrix is ​​modified according to the following formula:

[0114]

[0115] In the formula, the variable Z xy,n represents the xth row and yth column element in the system node impedance matrix when n FCLs are activated; Z xk,n-1 represents the xth row and kth column element in the system node impedance matrix when n-1 FCLs are activated; Z xi,n-1 represents the xth row and ith column element in the system node impedance matrix when n-1 FCLs are activated; Z yk,n-1 represents the element in the yth row and kth column of the system node impedance matrix when n-1 FCLs are activated; Z yi,n-1 represents the element in the yth row and ith column of the system node impedance matrix when n-1 FCLs are activated; Z ii,n-1 represents the element in the ith row and ith column of the system node impedance matrix when n-1 FCLs are activated; Z kk,n-1 represents the kth row and kth column element in the system node impedance matrix when n-1 FCLs are activated; Z ki,n-1 represents the element in the kth row and ith column of the system node impedance matrix when n-1 FCLs are activated; z eq,n-1 represents the equivalent impedance of the n-1th FCL; the subscripts x and y represent any node numbers in the network, and the subscripts k and i represent the head node and the end node of the line where the current limiter is installed;

[0116] Among them, the equivalent impedance z eq as follows:

[0117]

[0118] In the formula, z line is the line impedance, z FCL is the current limiter impedance.

[0119] The present invention takes into account the impedance deviation caused by starting the crowbar resistor when the doubly fed wind turbine is in a serious fault state, and equates the current limiter impedance to a parallel impedance branch, thereby simplifying the calculation process of the system node impedance matrix, improving the efficiency of short-circuit current calculation in large-scale wind farms while ensuring its accuracy is within an acceptable range.

[0120] Specific example:

[0121] The standard IEEE 30-node system with wind power is used as an example. Assuming that the maximum short-circuit current of the 33kV node is 10kA, the nodes with short-circuit current exceeding the standard and their short-circuit current levels calculated by the method proposed in the present invention are shown in Table 1. Current limiters with impedance values ​​of 0.27pu and 0.59pu are arranged on line 14 and line 16 respectively. The short-circuit current comparison of each node in the system before and after the current limiter is activated is calculated by the method proposed in the present invention. Figure 3 Obviously, FCL can effectively control the short-circuit current level of all nodes below 10kA, which proves the effectiveness of this method.

[0122] Table 1 Short-circuit current calculation results

[0123]

[0124] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be covered by the scope of the claims of the present invention.

Claims

1. A method for adjusting the node impedance matrix of a high-ratio wind power system including a current limiter, characterized in that: include: Step 1: Calculate the steady-state impedance of the doubly-fed wind turbine before and after the fault, and then modify the system extended node impedance matrix including the generator; Step 2: based on step 1, modify the system node impedance matrix after the current limiter is put into use; Step three, calculate the short-circuit current of each node in the system according to the modified system node impedance matrix.

2. The method for adjusting the node impedance matrix of a high-ratio wind power system with a current limiter according to claim 1, characterized in that: In step 1, the steady-state impedance z of the doubly fed wind turbine before the fault pre for: z pre =R s +jω s σL s In the formula, R s represents the stator resistance; j represents the imaginary unit; ω s represents the stator angular frequency; σ represents the leakage magnetic coefficient of the doubly fed fan; L s represents the stator inductance.

3. The method for adjusting the node impedance matrix of a high-ratio wind power system with a current limiter according to claim 2, characterized in that: In step 1, the steady-state impedance z of the doubly fed wind turbine after failure fault for: from fault =R s +jω s L eq∞ Where, L eq∞ It represents the equivalent steady-state inductance of the doubly-fed wind turbine after crowbar starting.

4. The method for adjusting the node impedance matrix of a high-ratio wind power system with a current limiter according to claim 1, characterized in that: In step 2, when FCL is activated, the equivalent impedance z eq When connected in parallel to the network, the system node impedance matrix is ​​modified according to the following formula: In the formula, the variable Z xy,n represents the xth row and yth column element in the system node impedance matrix when n FCLs are activated; Z xk,n-1 represents the xth row and kth column element in the system node impedance matrix when n-1 FCLs are activated; Z xi,n-1 represents the xth row and ith column element in the system node impedance matrix when n-1 FCLs are activated; Z yk,n-1 represents the element in the yth row and kth column of the system node impedance matrix when n-1 FCLs are activated; Z yi,n-1 represents the element in the yth row and ith column of the system node impedance matrix when n-1 FCLs are activated; Z ii,n-1 represents the element in the ith row and ith column of the system node impedance matrix when n-1 FCLs are activated; Z kk,n-1 represents the kth row and kth column element in the system node impedance matrix when n-1 FCLs are activated; Z ki,n-1 represents the element in the kth row and ith column of the system node impedance matrix when n-1 FCLs are activated; z eq,n-1 represents the equivalent impedance of the n-1th FCL; the subscripts x and y represent any node numbers in the network, and the subscripts k and i represent the head node and the end node of the line where the current limiter is installed.

5. The method for adjusting the node impedance matrix of a high-ratio wind power system with a current limiter according to claim 4, characterized in that: Equivalent impedance z eq as follows: In the formula, z line is the line impedance, z FCL is the current limiter impedance.

6. The method for adjusting the node impedance matrix of a high-ratio wind power system with a current limiter according to claim 4, characterized in that: After FCL is activated, the change in self-impedance of all nodes is: In the formula, ΔZ xx,n It represents the change of the element in the xth row and xth column in the system node impedance matrix when n FCLs are activated.

7. The method for adjusting the node impedance matrix of a high-ratio wind power system with a current limiter according to claim 1, characterized in that: In step 3, when a short-circuit fault occurs at node k in the system, its FCL is activated at line n, and the short-circuit current calculation formula of node k is: In the formula, I k,n represents the short-circuit current at node k, U k represents the voltage of node k before the fault, Z kk,n represents the node impedance matrix including FCL, I b Indicates the reference current.

8. A high-ratio wind power system node impedance matrix adjustment system with a current limiter, characterized in that: include: A calculation module is used to calculate the equivalent impedance of the doubly-fed wind turbine before and after the fault, and then modify the system extended node impedance matrix including the generator; A modification module is used to modify the system node impedance matrix after the current limiter is put into use; The current module is used to calculate the short-circuit current of each node of the system according to the modified system node impedance matrix.

9. The high-ratio wind power system node impedance matrix adjustment system with current limiter according to claim 8, characterized in that: In the calculation module, Steady-state impedance z of a doubly-fed wind turbine before fault pre for: z pre =R s +jω s σL s In the formula, R s represents the stator resistance; j represents the imaginary unit; ω s represents the stator angular frequency; σ represents the leakage magnetic coefficient of the doubly fed fan; L s represents the stator inductance; Steady-state impedance z of a doubly-fed wind turbine after a fault fault for: from fault =R s +jω s L eq∞ Where, L eq∞ It represents the equivalent steady-state inductance of the doubly-fed wind turbine after crowbar starting.

10. The high-ratio wind power system node impedance matrix adjustment system with current limiter according to claim 8, characterized in that: In the modification module, When FCL is activated, the equivalent impedance z eq When connected in parallel to the network, the system node impedance matrix is ​​modified according to the following formula: In the formula, the variable Z xy,n represents the xth row and yth column element in the system node impedance matrix when n FCLs are activated; Z xk,n-1 represents the xth row and kth column element in the system node impedance matrix when n-1 FCLs are activated; Z xi,n-1 represents the xth row and ith column element in the system node impedance matrix when n-1 FCLs are activated; Z yk,n-1 represents the element in the yth row and kth column of the system node impedance matrix when n-1 FCLs are activated; Z yi,n-1 represents the element in the yth row and ith column of the system node impedance matrix when n-1 FCLs are activated; Z ii,n-1 represents the element in the ith row and ith column of the system node impedance matrix when n-1 FCLs are activated; Z kk,n-1 represents the kth row and kth column element in the system node impedance matrix when n-1 FCLs are activated; Z ki,n-1 represents the element in the kth row and ith column of the system node impedance matrix when n-1 FCLs are activated; z eq,n-1 represents the equivalent impedance of the n-1th FCL; the subscripts x and y represent any node numbers in the network, and the subscripts k and i represent the head node and the end node of the line where the current limiter is installed; Among them, the equivalent impedance z eq as follows: In the formula, z line is the line impedance, z FCL is the current limiter impedance.

Images