Generalized electromagnetic transient simulation decoupling method and system for asynchronous motor loads

Abstract

The application discloses a general electromagnetic transient simulation decoupling method and system for asynchronous motor load, comprising the following steps: determining a single-phase simplified equivalent circuit of an asynchronous motor decoupling model; obtaining an asynchronous motor load-grid electromagnetic transient simulation interface through the single-phase simplified equivalent circuit; and based on the asynchronous motor load-grid electromagnetic transient simulation interface and a d-q model, performing electromagnetic transient simulation on the asynchronous motor load, so that the problem of too many iteration times of full-network equation solving of electromagnetic transient simulation of a power system containing a large number of asynchronous motor loads is solved, and the problems of low simulation efficiency and poor interface numerical stability are solved.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic transient simulation, specifically to a general electromagnetic transient simulation decoupling method and system for asynchronous motor loads. Background Technology

[0002] Load models play a crucial role in studying the transient and voltage stability of large-scale power systems. From a system perspective, motor loads account for more than 50% of the total load in a power system; therefore, motor load models are commonly used to represent dynamic load models in electromagnetic transient simulations. When a system contains a large number of motor loads, their dynamic characteristics significantly affect the simulation results. To improve simulation efficiency, asynchronous motors in power system simulations typically use lumped parameter models (ignoring the motor's geometric complexity, eddy currents, saturation, and hysteresis effects), including phase domain (PD) models, voltage-behind-reactance (VBR) models, and dq models.

[0003] (1) In the PD model, the motor variables are all represented in the abc coordinate system. The stator and rotor circuits are directly connected to the external network. The motor variables and the external network are solved at the same time, which has good numerical stability. However, since the inductance matrix parameters of the PD model will change with the rotor position, the computational complexity of the PD model is high.

[0004] (2) In the VBR model, stator variables are represented by abc coordinates, while rotor variables are represented by dq coordinates. The motor is equivalent to a voltage source connected in series with the RL branch. The stator of the VBR model can be directly connected to the external network, and the motor state variables and network equations can be solved simultaneously, improving numerical stability. However, this comes at the cost of time-varying RL parameters.

[0005] (3) Applying the Park transformation to the PD model yields the dq model, which has the advantage of providing a constant inductance matrix in the dq coordinate system, resulting in higher simulation efficiency. The dq model is the most widely used model in asynchronous motors and is widely employed in commercial electromagnetic transient simulation software such as PSCAD / EMTDC, EMTP-RV, and Matlab / Simulink.

[0006] Prior art related to this invention

[0007] The Norton current source method is a motor-grid interface method used in the commercial software PSCAD / EMTDC.

[0008] The Norton current source method models the asynchronous motor as an equivalent of a Norton current source connected to the power grid. This type of motor-grid interface is as follows: Figure 2As shown. Injected current I m (t) is calculated using the stator terminal voltage of the asynchronous motor from the previous time step, which means there is a time step delay in calculating the asynchronous motor variables. This can lead to numerical instability, especially when the asynchronous motor is in a near-open-circuit state. To improve numerical stability and prevent the asynchronous motor from being completely open-circuited, a port characteristic impedance r″ is introduced in the motor-network interface. The effect of this increased resistance is then reflected by the additional current I injected into the stator port of the asynchronous motor. c (t) source to compensate.

[0009] Disadvantage of technique 1: Due to the injected current I m (t) is calculated based on the stator terminal voltage of the previous time step, therefore the injected current I m The calculation of (t) involves a step delay. Mathematically, this delay is equivalent to an explicit method in numerical integration, and this factor may affect the numerical stability of the simulation. To ensure the numerical stability and accuracy of the interface, this method requires adjustment of the injected current I. m Solving for (t) requires multiple iterations, meaning the overall motor-grid equations need to be solved multiple times. When the system is very large, the order of the overall motor-grid equations is very high, making the efficiency of solving the overall motor-grid equations multiple times extremely low.

[0010] Prior art related to this invention

[0011] The network iteration method is a motor-grid interface method used in the commercial software EMTP-RV.

[0012] In EMTP-RV, the asynchronous motor model and network equations are solved simultaneously using Newton's iteration method. Furthermore, in the EMTP-RV asynchronous motor model, convergent solutions to the motor equations for each time step are obtained through iterative cycles of speed and voltage. The convergence criteria for these two cycles are controlled by a user-specified error bias.

[0013] The disadvantage of technique 2 is that solving the simultaneous iterative equations of the asynchronous motor and the network at each time step usually requires more computational resources. As the size of the network equations increases, the overall simulation efficiency will decrease significantly. Summary of the Invention

[0014] To address the problem of excessive iterations in solving the network equations for electromagnetic transient simulations of power systems with a large number of asynchronous motor loads, leading to low simulation efficiency and poor numerical stability at the interface, this invention provides a general electromagnetic transient simulation decoupling method and system for asynchronous motor loads. The method includes:

[0015] Determine the single-phase equivalent circuit of the decoupling model of the asynchronous motor;

[0016] By merging the asynchronous motor impedance in the single-phase equivalent circuit and using lumped parameters to represent the distributed parameter decoupling elements, the single-phase equivalent circuit is simplified, and a single-phase simplified equivalent circuit of the asynchronous motor decoupling model is obtained.

[0017] The asynchronous motor load-grid electromagnetic transient simulation interface is obtained through the single-phase simplified equivalent circuit.

[0018] Based on the asynchronous motor load-grid electromagnetic transient simulation interface and dq model, the electromagnetic transient simulation of the asynchronous motor load is performed. At the current simulation moment, the historical current sources of the decoupling components are updated according to the system node voltages. The stator three-phase voltage and rotor three-phase voltage are transformed by Park to obtain the stator voltage and rotor voltage in the dq reference frame. Based on the stator voltage and rotor voltage, the state equation of the asynchronous motor is solved to obtain the stator current and rotor current in the dq reference frame.

[0019] By obtaining the stator three-phase current through the Park inverse transformation of the stator current, and transferring the stator three-phase current to the current source, the stator side interface circuit of the asynchronous motor is solved to obtain the stator side voltage of the asynchronous motor.

[0020] When the state equation of the asynchronous motor satisfies the error condition, the node conductance matrix of the system is updated based on the characteristic conductance of the decoupling element, and the right-hand term current of the node voltage equation of the system is updated based on the historical current source of the stator side of the decoupling element and the historical current source of the compensation capacitor.

[0021] The node voltages of the system are obtained based on the node conductance matrix and the current on the right-hand side of the node voltage equation; the historical current sources of the system compensation capacitors are updated using the node voltages.

[0022] Based on the preset step size, update the current simulation time, and perform another electromagnetic transient simulation of the asynchronous motor load. When the current simulation time is greater than the simulation time, end the simulation.

[0023] Furthermore, the single-phase equivalent circuit of the decoupling model of the asynchronous motor is determined, including:

[0024] Determine the input data and relevant baseline values ​​used to construct the decoupled model of the asynchronous motor;

[0025] Using the input data and relevant benchmark values, as well as the single-phase circuit topology of the original asynchronous motor model, the single-phase equivalent circuit of the decoupled asynchronous motor model is determined.

[0026] Furthermore, by merging the impedance of the asynchronous motor and using lumped parameters to represent the distributed parameter decoupling elements, the single-phase equivalent circuit is simplified, resulting in a simplified single-phase equivalent circuit of the asynchronous motor decoupling model, including:

[0027] The impedance of an asynchronous motor can be combined using the following formula:

[0028]

[0029] Among them, Z im z is the equivalent impedance of the asynchronous motor. s For the stator equivalent impedance, z r Z is the rotor equivalent impedance. m It is the excitation impedance;

[0030] The distributed parameter decoupling element is represented by a π-type lumped parameter, where the equivalent impedance X of the decoupling element is... d Equivalent susceptance B of decoupling element d The calculation formula is:

[0031]

[0032] Among them, z c The characteristic impedance of the decoupling element is given by γ, the propagation constant of the transmission line is given by j (the imaginary unit), and ω is the angular velocity of synchronization. d For decoupling the inductor, C d For decoupling components, capacitors;

[0033] The single-phase simplified equivalent circuit of the asynchronous motor decoupling model is obtained through the above method.

[0034] Furthermore, the asynchronous motor load-grid electromagnetic transient simulation interface specifically includes: one asynchronous motor equation solving module and three circuit modules;

[0035] The three circuit modules are the stator-side interface circuit of the asynchronous motor, the grid-side interface circuit of the asynchronous motor, and the external power grid; the grid-side interface circuit of the asynchronous motor is directly connected to the external power grid, and the connection node is k; the stator-side interface circuit of the asynchronous motor contains one node, which is m.

[0036] The characteristic conductance G of the decoupling element in the asynchronous motor grid-side interface circuit c and decoupling element grid-side historical current source I k G, the interface circuit with the stator side of the asynchronous motor c and decoupling element stator side historical current source I m These are collectively referred to as decoupling elements.

[0037] Furthermore, based on the aforementioned asynchronous motor load-grid electromagnetic transient simulation interface and dq model, the electromagnetic transient simulation of the asynchronous motor load is performed. At the current simulation moment, the historical current sources of the decoupling components are updated according to the system node voltages, including:

[0038] Start the electromagnetic transient simulation of the asynchronous motor load, setting the simulation time t=0;

[0039] Advance the simulation time step by one step, update the simulation time: t = t + Δt, set the iteration count to zero, and let j = 0;

[0040] Based on the system node voltage U obtained at time t-Δt, the historical current sources of the decoupling elements are updated, specifically as follows:

[0041] I m (t-Δt)=I m (t-2Δt)+α(-2G c u k (t-Δt)+I k (t-2Δt)-I m (t-2Δt))

[0042] I k (t-Δt)=I k (t-2Δt)+α(-2G c u m (t-Δt)+I m (t-2Δt)-I k (t-2Δt))

[0043] Among them, u k It is the voltage at node k, u m Let α be the voltage at node m, and α∈[0,1] be the interpolation coefficients.

[0044] Furthermore, the stator three-phase voltage and rotor three-phase voltage are transformed by Park to obtain the stator voltage and rotor voltage in the dq reference frame, including:

[0045] Let the iteration number j = j + 1, and take the stator three-phase voltage v obtained in the previous iteration. abcs (t) and rotor three-phase voltage v abcr (t), after Park transformation, outputs the stator voltage v in the dq reference frame. dqs (t) and rotor voltage v dqr (t), the calculation formula is as follows;

[0046] v qds =Kv abcs

[0047] v qdr =Kv abcr

[0048] Wherein, the Park transformation matrix K is

[0049]

[0050] In the above formula, θ dq It is the rotation angle.

[0051] Furthermore, based on the stator voltage and rotor voltage, the state equations of the asynchronous motor are solved to obtain the stator current and rotor current in the dq reference frame, including:

[0052] The state equations of the stator and rotor in the dq reference frame are as follows

[0053]

[0054]

[0055] in,

[0056]

[0057] Wherein, the subscript abc indicates that the variable is in the abc reference frame, the subscript dq indicates that the variable is in the dq0 reference frame, v and i are column vectors, the subscript s represents the stator, the subscript r represents the rotor, λ is the flux linkage, ω is the synchronous angular velocity, and ω r It is the rotor angular velocity;

[0058] The relationship between the magnetic flux linkage λ and the current i of the stator and rotor in the dq reference frame is as follows:

[0059]

[0060] The module for solving the state equations of an asynchronous motor obtains the stator current i at time t. dqs and rotor current i dqr , where matrix element L dqs ~L dqr These are the inductance matrix elements of the asynchronous motor, calculated by the asynchronous motor state equation solving module.

[0061] Furthermore, by obtaining the stator three-phase current through the stator current inverse Park transform, and transferring the stator three-phase voltage to the current source, the stator-side interface circuit of the asynchronous motor is solved to obtain the stator-side voltage of the asynchronous motor, including:

[0062] The stator current i dqs The stator three-phase current i is obtained through the inverse Park transform. abcs The stator three-phase current i abcs Transmitted to current source I s Solve the stator-side interface circuit of the asynchronous motor and output the stator-side voltage v of the asynchronous motor at time t. abcs ,

[0063] The formula for calculating the inverse Park transform is as follows:

[0064] i abcs =K -1 i qds

[0065] The calculation formula for solving the stator-side interface circuit of a single-phase asynchronous motor is as follows:

[0066] (G c +G s )v m (t)=I s (t)-I m (t)

[0067] Solve the above equation separately for phases a, b, and c, and output the stator-side three-phase voltage v at time t. abcs =[v ma v mb v mc ] T .

[0068] Furthermore, when the asynchronous motor state equation satisfies the error condition, the system's node conductance matrix is ​​updated based on the characteristic conductance of the decoupling element, and the right-hand side current of the system's node voltage equation is updated based on the historical current sources of the decoupling element stator side and the historical current sources of the compensation capacitor, including:

[0069] According to the stator current i dqs Rotor current i dqr and stator side three-phase voltage v abcs Determine whether the solution to the state equation of the asynchronous motor meets the error condition. If the error condition is met...

[0070]

[0071] Then the asynchronous motor state equation solving module and the asynchronous motor stator side interface circuit complete the solution, and update the nodal conductance matrix G of the system at time t.

[0072] Furthermore, based on the node conductance matrix and the current on the right-hand side of the node voltage equation, the node voltage of the system is obtained; using the node voltage, the historical current source of the system compensation capacitor is updated, including:

[0073] Based on the nodal conductance matrix G, the right-hand side term I of the nodal voltage equation is obtained. Solve the system nodal voltage equation at time t:

[0074] GU=I

[0075] Output the node voltage U of the system at time t;

[0076] The historical current source of the system compensation capacitor is updated using the node voltage, specifically using the following formula:

[0077]

[0078] Furthermore, based on the preset step size, the current simulation time is updated, and the electromagnetic transient simulation of the asynchronous motor load is performed again. The simulation ends when the current simulation time exceeds the simulation time, including:

[0079] If the current simulation time t is greater than the simulation time T, then the simulation ends.

[0080] This invention also provides a general electromagnetic transient simulation decoupling system for asynchronous motor loads, comprising:

[0081] Equivalent circuit module, used to determine the single-phase equivalent circuit of the decoupling model of the asynchronous motor;

[0082] A simplification module is used to simplify the single-phase equivalent circuit by merging the asynchronous motor impedance in the single-phase equivalent circuit and using lumped parameters to represent the distributed parameter decoupling elements, thereby obtaining a single-phase simplified equivalent circuit of the asynchronous motor decoupling model.

[0083] The simulation interface acquisition module is used to obtain the asynchronous motor load-grid electromagnetic transient simulation interface through the single-phase simplified equivalent circuit.

[0084] The first simulation module is used to perform electromagnetic transient simulation of the asynchronous motor load based on the asynchronous motor load-grid electromagnetic transient simulation interface and dq model. At the current simulation moment, it updates the historical current source of the decoupling element according to the system node voltage; it obtains the stator voltage and rotor voltage in the dq reference frame by performing Park transformation on the stator three-phase voltage and rotor three-phase voltage; and it solves the state equation of the asynchronous motor according to the stator voltage and rotor voltage to obtain the stator current and rotor current in the dq reference frame.

[0085] The second simulation module is used to obtain the stator three-phase current by passing the stator current through the Park inverse transformation, and then pass the stator three-phase current to the current source to solve the stator side interface circuit of the asynchronous motor and obtain the stator side voltage of the asynchronous motor.

[0086] The third simulation module is used to update the node conductance matrix of the system based on the characteristic conductance of the decoupling element when the state equation of the asynchronous motor satisfies the error condition, and to update the right-hand term current of the node voltage equation of the system based on the historical current source of the stator side of the decoupling element and the historical current source of the compensation capacitor.

[0087] The fourth simulation module is used to obtain the node voltage of the system based on the node conductance matrix and the current on the right-hand side of the node voltage equation; and to update the historical current source of the system compensation capacitor using the node voltage.

[0088] The iteration module is used to update the current simulation time according to the preset step size, and then perform electromagnetic transient simulation of the asynchronous motor load again. The simulation ends when the current simulation time is longer than the simulation time. Attached Figure Description

[0089] Figure 1 This is a flowchart illustrating a general electromagnetic transient simulation decoupling method for asynchronous motor loads provided by the present invention.

[0090] Figure 2 This invention relates to the Norton current source method interface circuit used in PSCAD;

[0091] Figure 3 This invention relates to a single-phase circuit of the original model of an asynchronous motor;

[0092] Figure 4 This invention relates to a single-phase equivalent circuit of the decoupling model of an asynchronous motor.

[0093] Figure 5 This invention relates to a single-phase simplified equivalent circuit of the decoupling model of an asynchronous motor.

[0094] Figure 6 This invention relates to an asynchronous motor load-grid electromagnetic transient simulation interface;

[0095] Figure 7 This invention relates to the simulation results of the East China power grid;

[0096] Figure 8 This is a schematic diagram of a general electromagnetic transient simulation decoupling system for asynchronous motor loads provided by the present invention. Detailed Implementation

[0097] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0098] Example 1

[0099] The method provided in the first embodiment of the present invention will be described in detail.

[0100] Step S101: Determine the single-phase equivalent circuit of the asynchronous motor decoupling model.

[0101] Determine the input data and relevant benchmark values ​​used to construct the decoupling model of the asynchronous motor; using the input data and relevant benchmark values, and as follows... Figure 3Given the single-phase circuit topology of the original asynchronous motor model, determine the single-phase equivalent circuit of the decoupled asynchronous motor model, such as... Figure 4 As shown.

[0102] Step S102: By merging the asynchronous motor impedance in the single-phase equivalent circuit and using lumped parameters to represent the distributed parameter decoupling elements, the single-phase equivalent circuit is simplified to obtain the single-phase simplified equivalent circuit of the asynchronous motor decoupling model.

[0103] The impedance of an asynchronous motor can be combined using the following formula:

[0104]

[0105] Among them, Z im z is the equivalent impedance of the asynchronous motor. s For the stator equivalent impedance, z r Z is the rotor equivalent impedance. m It is the excitation impedance;

[0106] The distributed parameter decoupling element is represented by a π-type lumped parameter, where the equivalent impedance X of the decoupling element is... d Equivalent susceptance B of decoupling element d The calculation formula is:

[0107]

[0108] Among them, z c The characteristic impedance of the decoupling element is given by γ, the propagation constant of the transmission line is given by j (the imaginary unit), and ω is the angular velocity of synchronization. d For decoupling the inductor, C d For decoupling components, capacitors;

[0109] The simplified single-phase equivalent circuit of the decoupled asynchronous motor model is obtained through the above method, such as... Figure 5 As shown.

[0110] Step S103: Obtain the asynchronous motor load-grid electromagnetic transient simulation interface through the single-phase simplified equivalent circuit.

[0111] Asynchronous motor load-grid electromagnetic transient simulation interface, such as Figure 6 As shown, for the sake of simplicity, Figure 6 A single-phase circuit was demonstrated. Figure 6 The interface shown contains one asynchronous motor equation solving module and three circuit modules;

[0112] The three circuit modules are the stator-side interface circuit of the asynchronous motor, the grid-side interface circuit of the asynchronous motor, and the external power grid; the grid-side interface circuit of the asynchronous motor is directly connected to the external power grid, and the connection node is k; the stator-side interface circuit of the asynchronous motor contains one node, which is m.

[0113] The characteristic conductance G of the decoupling element in the asynchronous motor grid-side interface circuit c and decoupling element grid-side historical current source I k G, the interface circuit with the stator side of the asynchronous motor c and decoupling element stator side historical current source I m These are collectively referred to as decoupling elements. Figure 6 The calculation expressions and meanings of the circuit parameters are as follows:

[0114] —The compensated equivalent conductance is discretized using the trapezoidal method;

[0115] —Characteristic conductance of decoupling elements;

[0116] —Stator port characteristic conductance discretized using the trapezoidal method;

[0117] I sheq —The historical current source of the compensation capacitor;

[0118] I k —Decoupling the historical current source on the grid side of the component;

[0119] I m —Historical current sources on the stator side of the decoupling element;

[0120] I s —Equivalent current source of three-phase stator current;

[0121] V s — Stator three-phase voltage equivalent voltage source.

[0122] Step S104: Based on the asynchronous motor load-grid electromagnetic transient simulation interface and dq model, perform electromagnetic transient simulation of the asynchronous motor load. At the current simulation moment, update the historical current source of the decoupling element according to the system node voltage; transform the stator three-phase voltage and rotor three-phase voltage through Park transformation to obtain the stator voltage and rotor voltage in the dq reference frame; solve the asynchronous motor state equation based on the stator voltage and rotor voltage to obtain the stator current and rotor current in the dq reference frame.

[0123] Start the electromagnetic transient simulation of the asynchronous motor load, setting the simulation time t=0;

[0124] Advance the simulation time step by one step, update the simulation time: t = t + Δt, set the iteration count to zero, and let j = 0;

[0125] Based on the system node voltage U obtained at time t-Δt, the historical current sources of the decoupling elements are updated, specifically as follows:

[0126] I m (t-Δt)=I m (t-2Δt)+α(-2G c u k (t-Δt)+I k (t-2Δt)-I m (t-2Δt))

[0127] I k (t-Δt)=I k (t-2Δt)+α(-2G c u m (t-Δt)+I m (t-2Δt)-I k (t-2Δt))

[0128] Among them, u k It is the voltage at node k, u m Let α be the voltage at node m, and α∈[0,1] be the interpolation coefficients.

[0129] Let the iteration number j = j + 1, and take the stator three-phase voltage v obtained in the previous iteration. abcs (t) and rotor three-phase voltage v abcr (t), after Park transformation, outputs the stator voltage v in the dq reference frame. dqs (t) and rotor voltage v dqr (t), the calculation formula is as follows;

[0130] v qds =Kv abcs

[0131] v qdr =Kv abcr

[0132] Wherein, the Park transformation matrix K is

[0133]

[0134] In the above formula, θ dq It is the rotation angle.

[0135] The state equations of the stator and rotor in the dq reference frame are as follows

[0136]

[0137]

[0138] in,

[0139]

[0140] Wherein, the subscript abc indicates that the variable is in the abc reference frame, the subscript dq indicates that the variable is in the dq0 reference frame, v and i are column vectors, the subscript s represents the stator, the subscript r represents the rotor, λ is the flux linkage, ω is the synchronous angular velocity, and ω r It is the rotor angular velocity;

[0141] The relationship between the magnetic flux linkage λ and the current i of the stator and rotor in the dq reference frame is as follows:

[0142]

[0143] The module for solving the state equations of an asynchronous motor obtains the stator current i at time t. dqs and rotor current i dqr , where matrix element L dqs ~L dqr These are the inductance matrix elements of the asynchronous motor, calculated by the asynchronous motor state equation solving module.

[0144] Step S105: Obtain the stator three-phase current by performing the stator current inverse Park transformation, transfer the stator three-phase current to the current source, solve the stator side interface circuit of the asynchronous motor, and obtain the stator side voltage of the asynchronous motor.

[0145] The stator current i dqs The stator three-phase current i is obtained through the inverse Park transform. abcs The stator three-phase current i abcs Transmitted to current source I s Solve the stator-side interface circuit of the asynchronous motor and output the stator-side voltage v of the asynchronous motor at time t. abcs ,

[0146] The formula for calculating the inverse Park transform is as follows:

[0147] i abcs =K -1 i qds

[0148] The calculation formula for solving the stator-side interface circuit of a single-phase asynchronous motor is as follows:

[0149] (G c +G s )v m (t)=I s (t)-I m (t)

[0150] Solve the above equation separately for phases a, b, and c, and output the stator-side three-phase voltage v at time t. abcs =[v ma v mb v mc ] T .

[0151] Step S106: When the state equation of the asynchronous motor satisfies the error condition, update the node conductance matrix of the system based on the characteristic conductance of the decoupling element, and update the right-hand term current of the node voltage equation of the system based on the historical current source of the stator side of the decoupling element and the historical current source of the compensation capacitor.

[0152] According to the stator current i dqs Rotor current i dqr and input stator side three-phase voltage v abcs Determine whether the solution to the state equation of the asynchronous motor meets the error condition. If the error condition is met...

[0153]

[0154] Then the asynchronous motor state equation solving module and the asynchronous motor stator side interface circuit complete the solution, and update the nodal conductance matrix G of the system at time t.

[0155] Step S107: Obtain the node voltage of the system based on the node conductance matrix and the current on the right-hand side of the node voltage equation; update the historical current source of the system compensation capacitor using the node voltage.

[0156] Based on the nodal conductance matrix G, the right-hand side term I of the nodal voltage equation is obtained, and then solved. t System node voltage equations at time:

[0157] GU=I

[0158] Output the node voltage U of the system at time t;

[0159] The historical current source of the system compensation capacitor is updated using the node voltage, specifically using the following formula:

[0160]

[0161] Step S108: Update the current simulation time according to the preset step size, and perform electromagnetic transient simulation of the asynchronous motor load again. When the current simulation time is greater than the simulation time, end the simulation.

[0162] Determine if the simulation has ended. If the current simulation time t is greater than the simulation time T, then end the simulation.

[0163] Example 2

[0164] The technical solution is divided into two main steps: Steps 1 to 5 are the derivation and establishment of the asynchronous motor load model; Steps 6 to 17 are the process of using the asynchronous motor load model to perform electromagnetic transient simulation.

[0165] Step 1:

[0166] Input the load simulation parameters for the asynchronous motor.

[0167] Enter the following given parameters:

[0168] P load —Active power (per unit) at load nodes;

[0169] Q load —Reactive power at load nodes (per unit);

[0170] U load —Load node voltage (per unit);

[0171] P n —Rated power (MW);

[0172] V n —Rated line voltage RMS value (kV);

[0173] ω base —Reference frequency (Hz);

[0174] R s —Stator resistance (per unit);

[0175] R r —Rotor resistance (per unit);

[0176] L m —Magnetic inductance (per unit value);

[0177] L s —Stator leakage inductance (per unit value);

[0178] L r —Rotor leakage inductance (per unit);

[0179] X s —Stator reactance (per unit);

[0180] X r —Rotor reactance (per unit);

[0181] X m —Magnetic reactance (per unit);

[0182] s——Initial slip (0 <s<1);

[0183] ks —Stator leakage inductance distribution ratio (0 <k s <1);

[0184] Δt — Simulation step size (seconds);

[0185] Among them, P load Q load and U load It is usually obtained from the results of power flow calculations.

[0186] Step 2: Input the parameters from Step 1, and output the relevant reference values ​​for the asynchronous motor (used for calculating the relevant nominal values ​​in Steps 3 and 4).

[0187]

[0188]

[0189]

[0190]

[0191]

[0192] Among them, V base Voltage reference value, I base It is the current reference value, Z base It is the impedance reference value, L base It is the inductance reference value, C base This is the reference value for the capacitor.

[0193] Step 3: Decoupling Model Simplification Equivalent Circuit Establishment Module. Input the parameters obtained in Steps 1 and 2 and the relevant reference values ​​of the asynchronous motor. Figure 3 The single-phase circuit topology of the original asynchronous motor model, output Figure 4 The single-phase simplified equivalent circuit topology and parameters of the decoupling model of an asynchronous motor.

[0194] Figure 3 This is a single-phase circuit representing the original model of an asynchronous motor, commonly found in electrical machinery textbooks. U load It is the load node voltage, S dload It refers to dynamic load power flow, where j represents the imaginary unit, and X... s It is the stator reactance, R s It is the stator resistance, X m It is the magnetizing reactance, X r It is the rotor reactance, R r s is the rotor resistance, and s is the slip. Figure 4 For the decoupling model of an asynchronous motor, a single-phase equivalent circuit is provided, where y sh It is compensation admittance, B dIt is the equivalent susceptance of the decoupling element, Δx represents the differential component, and k s It is the stator leakage inductance distribution ratio.

[0195] Will Figure 3 Partial stator reactance X in the original circuit s (The allocation ratio is k) s Equivalent susceptance B of the decoupling element d Combined, using distributed parameter representation, decoupled components are constructed to form Figure 4 The decoupling model shown is a single-phase equivalent circuit topology.

[0196] According to the transmission line equation, in order for the decoupling element to have a natural one-step delay Δt, the inductance L of the decoupling element... d and decoupling element capacitor C d Need to meet

[0197]

[0198] L d and C d Determined by the following formula:

[0199]

[0200]

[0201] Will Figure 4 The circuit is simplified to Figure 5 The single-phase simplified equivalent circuit topology of the decoupling model of the asynchronous motor is shown.

[0202] The topology simplification method and parameter calculation formula are as follows:

[0203] (1) Combine the impedances of asynchronous motors:

[0204]

[0205] Z im This represents the equivalent impedance of an asynchronous motor. Where Z... s =R s +j(1-k s )X s It is the stator equivalent impedance, Z r =R r / s+jX r It is the rotor equivalent impedance, Z m =jX m s is the magnetizing impedance, and s is the slip.

[0206] (2) The distributed parameter decoupling element is represented by a π-type lumped parameter, where the equivalent reactance X of the decoupling element is... d Equivalent susceptance B of decoupling element dThe calculation formula is

[0207]

[0208] In equation (10), sinh represents the hyperbolic sine function, cosh represents the hyperbolic cosine function, and j is the imaginary unit. Equations (9) and (10) are... Figure 4 The parameters of the single-phase simplified equivalent circuit of the decoupled asynchronous motor model shown are given.

[0209] Step 4: Input the single-phase simplified equivalent circuit topology and parameters of the asynchronous motor decoupling model from Step 3, and output the compensation parameter C. sh or L sh .

[0210] List Figure 5 Circuit node voltage equations.

[0211]

[0212] The calculation formulas for each element in the above formula are as follows:

[0213]

[0214]

[0215] y 21 =y 12 (14)

[0216]

[0217]

[0218] i2 = 0 (17)

[0219] u1 = U load (18)

[0220] Where the subscripts 1 and 2 represent nodes 1 and 2, y 11 ~y 22 These are elements of the admittance matrix, where u is the node voltage and i is the node injected current. * Indicates complex conjugation. P load Q is the active power of the load node; load It is the reactive power of the load node; U load It is the load node voltage.

[0221] u2 and y sh These are the unknowns in the equation. Solving the nodal voltage and power equations yields u2 and y. sh .

[0222] By y shThe formula for calculating the compensation parameters for a delta connection is:

[0223]

[0224] Among them, C sh It is a compensation capacitor, L sh It is a compensating inductance. Im(.) indicates taking the imaginary part of the complex number.

[0225] Step 5: Input the single-phase equivalent circuit and its parameters of the asynchronous motor decoupling model obtained in Steps 1 to 4, and output the asynchronous motor load-grid electromagnetic transient simulation interface and its parameters for the simulation process in Steps 6 to 17.

[0226] Asynchronous motor load-grid electromagnetic transient simulation interface, such as Figure 6 As shown. For the sake of simplicity, Figure 6 A single-phase circuit was demonstrated. Figure 6 The interface shown contains one asynchronous motor equation solving module and three circuit modules: an asynchronous motor stator-side interface circuit, an asynchronous motor grid-side interface circuit, and an external power grid. The asynchronous motor grid-side interface circuit is directly connected to the external power grid, with node k as the connection point. The asynchronous motor stator-side interface circuit contains one node, which is m. The G... c and I k G, the interface circuit with the stator side of the asynchronous motor c and I m These are collectively referred to as decoupling elements. Figure 6 The calculation expressions and meanings of the circuit parameters are as follows:

[0227] —The compensated equivalent conductance is discretized using the trapezoidal method;

[0228] —Characteristic conductance of decoupling elements;

[0229] —Stator port characteristic conductance discretized using the trapezoidal method;

[0230] I sheq —The historical current source of the compensation capacitor;

[0231] I k —Decoupling the historical current source on the grid side of the component;

[0232] I m —Historical current sources on the stator side of the decoupling element;

[0233] I s —Equivalent current source of three-phase stator current;

[0234] V s— Stator three-phase voltage equivalent voltage source.

[0235] Step 6: Start the electromagnetic transient simulation of the asynchronous motor load, and set the simulation time t = 0.

[0236] Step 7: Advance the simulation time by one step and update the simulation time: t = t + Δt. Set the iteration count to zero and let j = 0.

[0237] Step 8: Update the historical current source of the decoupling element based on the system node voltage U obtained at time t-Δt (from step 15 of the previous time step).

[0238] I m (t-Δt)=I m (t-2Δt)+α(-2G c u k (t-Δt)+I k (t-2Δt)-I m (t-2Δt)) (20)

[0239] I k (t-Δt)=I k (t-2Δt)+α(-2G c u m (t-Δt)+I m (t-2Δt)-I k (t-2Δt)) (21)

[0240] Among them, u k It is the voltage at node k, u m α is the voltage at node m, and α∈[0,1] are the interpolation coefficients, which are determined by the required interpolation time in the simulation.

[0241] Will I k (t-Δt) is transmitted to the controlled current source I of the asynchronous motor's grid-side interface circuit. k . Will I m (t-Δt) is transmitted to the controlled current source I of the stator-side interface circuit of the asynchronous motor. m .

[0242] Step 9: Let the iteration number j = j + 1, and input the stator three-phase voltage v calculated in the previous iteration. abcs (t) and rotor three-phase voltage v abcr (t), after Park transformation, outputs the stator-rotor voltage v in the dq reference frame. dqs (t) and v dqr (t), the calculation formula is as follows:

[0243] v qds =Kv abcs (twenty two)

[0244] v qdr =Kv abcr (twenty three)

[0245] Where the Park transformation matrix K is

[0246]

[0247] In the above formula, θ dq It is the rotation angle.

[0248] Step 10: Enter v from step 9 dqs (t) and v dqr (t), the module for solving the state equation of the asynchronous motor, outputs the stator current i in the dq reference frame. dqs and rotor current i dqr .

[0249] The state equations of the stator and rotor in the dq model can be written as follows:

[0250]

[0251]

[0252] in

[0253]

[0254] Wherein, the subscript abc indicates that the variable is in the abc reference frame. The subscript dq indicates that the variable is in the dq0 reference frame; v and i are column vectors (a three-dimensional column vector of abc or a three-dimensional column vector of dq0); the subscript s represents the stator, and the subscript r represents the rotor. λ is the flux linkage, ω is the synchronous angular velocity, and ω r It is the rotor angular velocity.

[0255] The relationship between the magnetic flux linkage λ and the current i of the stator and rotor in the dq reference frame is as follows:

[0256]

[0257] The module for solving the state equations of an asynchronous motor is used to obtain the i-th equation at time t. dqs and i dqr Among them, matrix element L dqs ~L dqr These are the inductance matrix elements of the asynchronous motor, calculated by the asynchronous motor state equation solving module.

[0258] Step 11: Input i from step 10 dqs , change i dqs i is obtained through the inverse Park transform abcs , change i abcs Passed to Figure 6 Current source I in s Solve the stator-side interface circuit of the asynchronous motor and output the stator-side voltage v of the asynchronous motor at time t. abcs .

[0259] The formula for calculating the inverse Park transform is as follows:

[0260] i abcs =K -1 i qds (29)

[0261] The calculation formula for solving the stator-side interface circuit (single phase) of an asynchronous motor is as follows:

[0262] (G c +G s )v m (t)=I s (t)-I m (t) (30)

[0263] Solve the above equation separately for phases a, b, and c, and output the stator-side three-phase voltage v at time t. abcs =[v ma v mb v mc ] T .

[0264] Step 12: Input the stator current i from step 10 dqs and rotor current i dqr Input the stator-side three-phase voltage v from step 11. abcs Determine whether the solution to the state equation of the asynchronous motor meets the error conditions.

[0265] If the error condition is met

[0266]

[0267] If the asynchronous motor state equation solving module and the asynchronous motor stator-side interface circuit have completed their solutions, proceed to step 13; otherwise, return to step 9, update the stator three-phase voltage, and let... The next iteration of the asynchronous motor state equation solving module and the asynchronous motor stator-side interface circuit is performed. The superscript (j) indicates the j-th iteration.

[0268] Step 13: Input G obtained in step 5 sh and G c Update the node conductance matrix G of the system at time t (where “system” refers to the overall circuit consisting of the asynchronous motor grid-side interface circuit and the external power grid, the same below).

[0269] Step 14: Input the I obtained in step 8 mInput compensation capacitor historical current source I sheq (From step 16 of the previous time step), update the right-hand side I of the nodal voltage equation of the system at time t.

[0270] Step 15: Input the system node conductance matrix G obtained in Step 13, input the right-hand side I of the node voltage equation obtained in Step 14, and solve the system node voltage equation at time t:

[0271] GU=I (32)

[0272] Output the system node voltage U at time t.

[0273] Step 16: Input the system node voltage U obtained in Step 15, update the relevant system electrical quantities, and update the historical current source I of the system compensation capacitor. sheq This is used for calculation in step 14 of the next time step.

[0274]

[0275] Step 17: Determine if the simulation has ended. If t is less than the simulation time T, return to step 7 and calculate the next step size. Otherwise, end the simulation.

[0276] Example 3

[0277] Electromagnetic transient simulation test of East China Power Grid: In the electromagnetic transient simulation program, the proposed asynchronous motor decoupling model is implemented by programming, and electromagnetic transient simulation calculation tasks of East China Power Grid are carried out based on this model.

[0278] The East China Power Grid comprises five provincial grids: Jiangsu, Zhejiang, Shanghai, Anhui, and Fujian, with a total of 2,328 asynchronous motors, constituting a large-scale regional power grid. The simulation test condition is as follows: at time 3.0s, a metallic ground fault of phase A occurs at a 525kV node, with a fault duration of 100ms. The model uses a 50us step size and a simulation time of 10s.

[0279] Taking a 230kV, 140+j50MV·A load node (dynamic load ratio of 0.58) near a certain fault point as an example, its dynamic load active and reactive power waveforms are as follows: Figure 7 As shown.

[0280] Figure 7 The results show that the steady-state results of the proposed model are consistent with the power flow calculation results, and the dynamic process simulation results of the proposed model are consistent with the reference model (traditional dq model of asynchronous motor). The proposed model can operate stably in a real large power grid example that includes DC and a large number of new energy equipment. It can accurately simulate the steady-state and load dynamic characteristics of large-scale power grids after faults, and the simulation accuracy meets the engineering requirements.

[0281] The test showed that the reference model took 5126 seconds to compute, while the proposed model took 3397 seconds, resulting in a speedup of 1.51. This demonstrates that the proposed model can significantly improve simulation efficiency.

[0282] Based on the same inventive concept, this invention also provides a general electromagnetic transient simulation decoupling system 800 for asynchronous motor loads, such as... Figure 8 As shown, it includes:

[0283] Equivalent circuit module 810 is used to determine the single-phase equivalent circuit of the decoupling model of the asynchronous motor;

[0284] The simplification module 820 is used to simplify the single-phase equivalent circuit by merging the asynchronous motor impedance in the single-phase equivalent circuit and using lumped parameters to represent the distributed parameter decoupling elements, thereby obtaining a single-phase simplified equivalent circuit of the asynchronous motor decoupling model.

[0285] The simulation interface acquisition module 830 is used to obtain the asynchronous motor load-grid electromagnetic transient simulation interface through the single-phase simplified equivalent circuit.

[0286] The first simulation module 840 is used to perform electromagnetic transient simulation of the asynchronous motor load based on the asynchronous motor load-grid electromagnetic transient simulation interface and the dq model. At the current simulation moment, it updates the historical current source of the decoupling element according to the system node voltage; it transforms the stator three-phase voltage and rotor three-phase voltage through Park transformation to obtain the stator voltage and rotor voltage in the dq reference frame; and it solves the state equation of the asynchronous motor based on the stator voltage and rotor voltage to obtain the stator current and rotor current in the dq reference frame.

[0287] The second simulation module 850 is used to obtain the stator three-phase current by passing the stator current under the dq reference frame through the Park inverse transformation, and to transfer the stator three-phase current to the current source to solve the stator side interface circuit of the asynchronous motor and obtain the stator side voltage of the asynchronous motor.

[0288] The third simulation module 860 is used to update the node conductance matrix of the system based on the characteristic conductance of the decoupling element when the state equation of the asynchronous motor satisfies the error condition, and to update the right-hand term current of the node voltage equation of the system based on the historical current source of the stator side of the decoupling element and the historical current source of the compensation capacitor.

[0289] The fourth simulation module 870 is used to obtain the node voltage of the system based on the node conductance matrix and the current on the right-hand side of the node voltage equation; and to update the historical current source of the system compensation capacitor using the node voltage.

[0290] The iteration module 880 is used to update the current simulation time according to the preset step size, and to perform electromagnetic transient simulation of the asynchronous motor load again. When the current simulation time is greater than the simulation time, the simulation ends.

[0291] This invention provides a general electromagnetic transient simulation decoupling method and system for asynchronous motor loads, which can naturally decouple the asynchronous motor circuit from the external power grid. The resulting effects include:

[0292] (1) Improved simulation efficiency. In the provided decoupled model, the asynchronous motor circuit and the external power grid are independent of each other. The asynchronous motor circuit is calculated iteratively on its own without having to solve equations simultaneously with the external power grid. Therefore, the external power grid does not need to perform multiple iterative calculations due to the presence of the asynchronous motor, thus improving the simulation efficiency.

[0293] (2) It has good numerical stability. The provided decoupling model combines the extracted stator leakage inductance with the compensation capacitor to construct a decoupling element with natural delay. The delay of the decoupling element matches the simulation step size. Therefore, the asynchronous motor and the external power grid are naturally decoupled, and the motor-power grid interface can ensure good numerical stability.

[0294] (3) Universality and simplicity: The asynchronous motor load model provided by this invention can use different asynchronous motor state equation solution modules, thus possessing universality. In addition, the provided model can automatically configure the parameters of decoupling components and compensation capacitors according to the active and reactive power of the load node set by the user, so that the power results of electromagnetic transient simulation match the power of the load node given in the power flow calculation, thus possessing simplicity.

[0295] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A general electromagnetic transient simulation decoupling method for asynchronous motor loads, characterized in that, include: Determine the single-phase equivalent circuit of the decoupling model of the asynchronous motor; By merging the asynchronous motor impedance in the single-phase equivalent circuit and using lumped parameters to represent the distributed parameter decoupling elements, the single-phase equivalent circuit is simplified, and a single-phase simplified equivalent circuit of the asynchronous motor decoupling model is obtained. The asynchronous motor load-grid electromagnetic transient simulation interface is obtained through the single-phase simplified equivalent circuit. Based on the asynchronous motor load-grid electromagnetic transient simulation interface and dq model, the electromagnetic transient simulation of the asynchronous motor load is performed. At the current simulation moment, the historical current sources of the decoupling components are updated according to the system node voltages. The stator three-phase voltage and rotor three-phase voltage are transformed by Park to obtain the stator voltage and rotor voltage in the dq reference frame. Based on the stator voltage and rotor voltage, the state equation of the asynchronous motor is solved to obtain the stator current and rotor current in the dq reference frame. By obtaining the stator three-phase current through the Park inverse transformation of the stator current, and transferring the stator three-phase current to the current source, the stator side interface circuit of the asynchronous motor is solved to obtain the stator side voltage of the asynchronous motor. When the state equation of the asynchronous motor satisfies the error condition, the node conductance matrix of the system is updated based on the characteristic conductance of the decoupling element, and the right-hand term current of the node voltage equation of the system is updated based on the historical current source of the stator side of the decoupling element and the historical current source of the compensation capacitor. The node voltages of the system are obtained based on the node conductance matrix and the current on the right-hand side of the node voltage equation. The historical current source of the system compensation capacitor is updated using the node voltage; Based on the preset step size, update the current simulation time, and perform another electromagnetic transient simulation of the asynchronous motor load. When the current simulation time is greater than the simulation time, end the simulation.

2. The method according to claim 1, characterized in that, Determine the single-phase equivalent circuit of the decoupling model of the asynchronous motor, including: Determine the input data and relevant baseline values ​​used to construct the decoupled model of the asynchronous motor; Using the input data and relevant benchmark values, as well as the single-phase circuit topology of the original asynchronous motor model, the single-phase equivalent circuit of the decoupled asynchronous motor model is determined.

3. The method according to claim 1, characterized in that, By merging the impedance of the asynchronous motor and using lumped parameters to represent the distributed parameter decoupling elements, the single-phase equivalent circuit is simplified, resulting in a simplified single-phase equivalent circuit for the asynchronous motor decoupling model, including: The impedance of an asynchronous motor can be combined using the following formula: Among them, Z im z is the equivalent impedance of the asynchronous motor. s For the stator equivalent impedance, z r Z is the rotor equivalent impedance. m It is the excitation impedance; The distributed parameter decoupling element is represented by a π-type lumped parameter, where the equivalent impedance X of the decoupling element is... d Equivalent susceptance B of decoupling element d The calculation formula is: Among them, z c The characteristic impedance of the decoupling element is given by γ, the propagation constant of the transmission line is given by j (the imaginary unit), and ω is the angular velocity of synchronization. d For decoupling the inductor, C d For decoupling components, capacitors; The single-phase simplified equivalent circuit of the asynchronous motor decoupling model is obtained through the above method.

4. The method according to claim 1, characterized in that, The asynchronous motor load-grid electromagnetic transient simulation interface specifically includes: one asynchronous motor equation solving module and three circuit modules; The three circuit modules are the stator-side interface circuit of the asynchronous motor, the grid-side interface circuit of the asynchronous motor, and the external power grid; the grid-side interface circuit of the asynchronous motor is directly connected to the external power grid, and the connection node is k; the stator-side interface circuit of the asynchronous motor contains one node, which is m. The characteristic conductance G of the decoupling element in the asynchronous motor grid-side interface circuit c and decoupling element grid-side historical current source I k G, the interface circuit with the stator side of the asynchronous motor c and decoupling element stator side historical current source I m These are collectively referred to as decoupling elements.

5. The method according to claim 1, characterized in that, Based on the aforementioned asynchronous motor load-grid electromagnetic transient simulation interface and dq model, the electromagnetic transient simulation of the asynchronous motor load is performed. At the current simulation moment, the historical current sources of the decoupling components are updated according to the system node voltages, including: Start the electromagnetic transient simulation of the asynchronous motor load, setting the simulation time t=0; Advance the simulation time step by one step, update the simulation time: t = t + Δt, set the iteration count to zero, and let j = 0; Based on the system node voltage U obtained at time t-Δt, the historical current sources of the decoupling elements are updated, specifically as follows: I m (t-Δt)=I m (t-2Δt)+α(-2G c u k (t-Δt)+I k (t-2Δt)-I m (t-2Δt)) I k (t-Δt)=I k (t-2Δt)+α(-2G c u m (t-Δt)+I m (t-2Δt)-I k (t-2Δt)) Among them, u k It is the voltage at node k, u m Let α be the voltage at node m, and α∈[0,1] be the interpolation coefficients.

6. The method according to claim 1, characterized in that, The stator three-phase voltage and rotor three-phase voltage are transformed by Park to obtain the stator voltage and rotor voltage in the dq reference frame, including: Let the iteration number j = j + 1, and take the stator three-phase voltage v obtained in the previous iteration. abcs (t) and rotor three-phase voltage v abcr (t), after Park transformation, outputs the stator voltage v in the dq reference frame. dqs (t) and rotor voltage v dqr (t), the calculation formula is as follows; v qds =Kv abcs v qdr =Kv abcr Wherein, the Park transformation matrix K is In the above formula, θ dq It represents the rotation angle, and the subscript abc indicates that the variable is a variable in the abc reference frame.

7. The method according to claim 1, characterized in that, Based on the stator voltage and rotor voltage, solve the state equations of the asynchronous motor to obtain the stator current and rotor current in the dq reference frame, including: The state equations of the stator and rotor in the dq reference frame are as follows in, Wherein, the subscript abc indicates that the variable is in the abc reference frame, the subscript dq indicates that the variable is in the dq0 reference frame, v and i are column vectors, the subscript s represents the stator, the subscript r represents the rotor, λ is the flux linkage, ω is the synchronous angular velocity, and ω r It is the rotor angular velocity; The relationship between the magnetic flux linkage λ and the current i of the stator and rotor in the dq reference frame is as follows: The module for solving the state equations of an asynchronous motor obtains the stator current i at time t. dqs and rotor current i dqr , where matrix element L dqs ~L dqr These are the inductance matrix elements of the asynchronous motor, calculated by the asynchronous motor state equation solving module.

8. The method according to claim 1, characterized in that, By obtaining the stator three-phase current through the stator current inverse Park transform, and transferring the stator three-phase voltage to the current source, the stator-side interface circuit of the asynchronous motor is solved to obtain the stator-side voltage of the asynchronous motor, including: The stator current i dqs The stator three-phase current i is obtained through the inverse Park transform. abcs The stator three-phase current i abcs Transmitted to current source I s Solve the stator-side interface circuit of the asynchronous motor and output the stator-side voltage v of the asynchronous motor at time t. abcs , The formula for calculating the inverse Park transform is as follows: i abcs =K -1 i qds The calculation formula for solving the stator-side interface circuit of a single-phase asynchronous motor is as follows: (G c +G s )v m (t)=I s (t)-I m (t) Solve the above equation separately for phases a, b, and c, and output the stator-side three-phase voltage v at time t. abcs =[v ma v mb v mc ] T ; In this context, the subscript abc indicates that the variable is a variable in the abc reference frame, and the subscript dq indicates that the variable is a variable in the dq0 reference frame.

9. The method according to claim 1, characterized in that, When the state equation of the asynchronous motor satisfies the error condition, the nodal conductance matrix of the system is updated based on the characteristic conductance of the decoupling element, and the right-hand side current of the nodal voltage equation of the system is updated based on the historical current source on the stator side of the decoupling element and the historical current source of the compensation capacitor, including: According to the stator current i dqs Rotor current i dqr and stator side three-phase voltage v abcs Determine whether the solution to the state equation of the asynchronous motor meets the error condition. If the error condition is met... Then the asynchronous motor state equation solving module and the asynchronous motor stator side interface circuit complete the solution, and update the nodal conductance matrix G of the system at time t; In this context, the subscript abc indicates that the variable is a variable in the abc reference frame, and the subscript dq indicates that the variable is a variable in the dq0 reference frame.

10. The method according to claim 1, characterized in that, The node voltages of the system are obtained based on the node conductance matrix and the current on the right-hand side of the node voltage equation. The historical current source of the system compensation capacitor is updated based on the node voltage, including: Based on the nodal conductance matrix G, the right-hand side term I of the nodal voltage equation is obtained. Solve the system nodal voltage equation at time t: GU=I Output the node voltage U of the system at time t; The historical current source of the system compensation capacitor is updated using the node voltage, specifically using the following formula:

11. The method according to claim 1, characterized in that, Based on the preset step size, update the current simulation time, and perform another electromagnetic transient simulation of the asynchronous motor load. The simulation ends when the current simulation time exceeds the simulation time, including: If the current simulation time t is greater than the simulation time T, then the simulation ends.

12. A general electromagnetic transient simulation decoupling system for asynchronous motor loads, characterized in that, include: Equivalent circuit module, used to determine the single-phase equivalent circuit of the decoupling model of the asynchronous motor; A simplification module is used to simplify the single-phase equivalent circuit by merging the asynchronous motor impedance in the single-phase equivalent circuit and using lumped parameters to represent the distributed parameter decoupling elements, thereby obtaining a single-phase simplified equivalent circuit of the asynchronous motor decoupling model. The simulation interface acquisition module is used to obtain the asynchronous motor load-grid electromagnetic transient simulation interface through the single-phase simplified equivalent circuit. The first simulation module is used to perform electromagnetic transient simulation of the asynchronous motor load based on the asynchronous motor load-grid electromagnetic transient simulation interface and dq model. At the current simulation moment, it updates the historical current source of the decoupling element according to the system node voltage; it obtains the stator voltage and rotor voltage in the dq reference frame by performing Park transformation on the stator three-phase voltage and rotor three-phase voltage; and it solves the state equation of the asynchronous motor according to the stator voltage and rotor voltage to obtain the stator current and rotor current in the dq reference frame. The second simulation module is used to obtain the stator three-phase current by passing the stator current through the Park inverse transformation, and then pass the stator three-phase current to the current source to solve the stator side interface circuit of the asynchronous motor and obtain the stator side voltage of the asynchronous motor. The third simulation module is used to update the node conductance matrix of the system based on the characteristic conductance of the decoupling element when the state equation of the asynchronous motor satisfies the error condition, and to update the right-hand term current of the node voltage equation of the system based on the historical current source of the stator side of the decoupling element and the historical current source of the compensation capacitor. The fourth simulation module is used to obtain the node voltages of the system based on the node conductance matrix and the current in the right-hand side of the node voltage equation. The historical current source of the system compensation capacitor is updated using the node voltage; The iteration module is used to update the current simulation time according to the preset step size, and then perform electromagnetic transient simulation of the asynchronous motor load again. The simulation ends when the current simulation time is longer than the simulation time.

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