Fault simulation calculation method and system for network construction type fan access system

Abstract

The invention discloses a fault simulation calculation method and system for a network construction type fan access system, and relates to the field of power system fault simulation modeling, a network construction type fan comprises a wind turbine generator set body and a network construction type inverter power supply, based on a network construction type inverter power supply control strategy, an active and reactive power simulation calculation model is established, and the network construction type fan access system is established. Further establishing an equivalent model when the network-forming type inverter power supply has a fault; based on the fault equivalence model, according to the network structure of the power distribution network, establishing a composite sequence network equivalence model under the fault condition of the power distribution network containing the constructed network type inverter power supply; obtaining a loop equation set formed by a universal matrix based on the composite sequence network equivalent model; and simultaneously establishing the loop equation set and the fault equivalent model of the network construction type power supply, and solving the fault quantity by adopting an iterative calculation method according to the output power and current characteristics of the network construction type power supply and the constraint of the relationship between the power and the voltage. The problem that a traditional fault analysis and calculation method based on a synchronous machine power supply cannot adapt to a network construction type fan access scene is solved.

Description

Technical Field

[0001] This invention relates to the field of power system fault simulation modeling, and in particular to a fault simulation calculation method and system for a grid-connected wind turbine system. Background Technology

[0002] The statements in this section are merely background information relating to this disclosure and do not necessarily constitute prior art.

[0003] Traditional power grid fault analysis typically relies on the symmetrical component method and the superposition theorem, assuming a steady-state state at power frequency. It calculates the current and voltage distribution at the fault point by establishing an equivalent model of the power grid and considering the fault type. However, this method fails to consider different types of renewable energy integration and assumes the system is in an ideal symmetrical state. In particular, it struggles to characterize the nonlinear response of power electronic equipment and the dynamic characteristics of multi-source collaborative interaction after grid-connected renewable energy integration. Renewable energy sources are often calculated as constant current sources or voltage sources in series impedance. While this partially reflects the fault current contribution of renewable energy sources, it neglects the dynamic control logic of power electronic equipment, resulting in poor accuracy of the calculation results.

[0004] In reality, with a large number of synchronous power sources being replaced by new energy sources, conventional grid-connected new energy sources cannot compensate for the reduction in system inertia, strength, and short-circuit capacity. Regarding wind turbines, grid-connected wind turbines with voltage and frequency support capabilities can actively support the power grid and will inevitably become an important component of future power systems. Current research rarely focuses on fault simulation modeling and analysis calculations for systems with virtual synchronous grid-connected wind turbine power sources, making it impossible to obtain accurate electrical quantity distributions in the network under such power source access conditions. Furthermore, the integration of numerous new energy sources into the grid also places higher demands on real-time grid simulation testing. Summary of the Invention

[0005] To overcome the shortcomings of existing fault simulation calculation technologies, this invention provides a fault simulation calculation method and system for grid-connected wind turbine systems, which realizes rapid fault simulation after grid-connected new energy sources are connected, and can be used to support real-time simulation testing technology for new energy access systems.

[0006] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: In a first aspect, the present invention provides a fault simulation calculation method for a grid-connected wind turbine system, wherein the grid-connected wind turbine includes a wind turbine generator body and a grid-connected inverter power supply, and the method includes the following steps: Based on the control strategy of the virtual synchronous machine type of grid-type inverter, the characteristics of the output power of the grid-type inverter under the steady state of the distribution network fault are analyzed, and the active and reactive power simulation calculation model of the grid-type inverter under fault is established. Then, based on the correlation between the output current and power of the grid-type inverter, the equivalent model of the grid-type inverter fault is established. Based on the fault equivalent model of the grid-type inverter power supply, a composite sequence network equivalent model under the fault conditions of the distribution network containing the grid-type inverter power supply is established according to the distribution network structure. Based on the composite sequence network equivalent model, a set of loop equations composed of a generalized matrix is ​​obtained according to the circuit theorem; By combining the aforementioned set of loop equations with the equivalent fault model of the grid-connected inverter, and based on the output power and current characteristics of the grid-connected inverter and the constraints of the power-voltage relationship, an iterative calculation method is used to solve for the fault quantities.

[0007] In a further technical solution, the grid-type inverter power supply adopts positive and negative sequence separation control, and the negative sequence loop adopts a control method to suppress negative sequence current.

[0008] A further technical solution is that, under steady-state conditions during a distribution network fault, the reactive power of the grid-connected inverter power supply satisfies the following formula:

[0009] in, Reactive power This is a reference value for reactive power. The voltage regulation coefficient is used to reflect the reactive power-voltage droop characteristics. This is the system voltage reference value. This refers to the voltage between the step-up transformer and the filter inductor of the grid-type inverter power supply.

[0010] A further technical solution is that the relationship between the positive sequence current and power output of the grid-type inverter is as follows:

[0011] The output negative sequence current is:

[0012] in, It is a positive sequence current. It is a negative sequence current. The apparent power delivered by a grid-connected inverter to the grid connection point. The voltage phasor between the step-up transformer and the filter inductor of the grid-type inverter power supply; It is a conjugate phasor.

[0013] A further technical solution is that the composite sequence network equivalent model of the grid-connected inverter power supply under the fault conditions of the distribution network consists of the positive sequence network of the grid-connected inverter power supply and the negative sequence network without power supply.

[0014] A further technical solution is that the system of loop equations formed by the generalized matrix is ​​as follows:

[0015] in, for The corrected loop impedance matrix, For the number of loop circuits, for The loop current vector, A for The correlation matrix between loop current and DG branch, for The voltage vector of the distribution network voltage source. for Output current vector of a grid-type inverter.

[0016] A further technical solution is that the constraint on the power-voltage relationship is expressed as follows:

[0017] in, Active power For the step-up transformer reactance of the grid-type inverter power supply, This refers to the voltage between the step-up transformer and the filter inductor in a grid-type inverter power supply. This is the positive sequence voltage at the grid connection point. phasor and The phase difference; The convergence criterion for iterative computation methods is:

[0018] in, It is a function with maximum value. For the first i Individual network-type DG The difference between the current amplitude and the amplitude of the previous iteration. For the first Individual network-type DG The difference between the current amplitude and the amplitude of the previous iteration. The threshold for the convergence criterion.

[0019] Secondly, this invention provides a fault simulation calculation system for a grid-connected wind turbine system. The grid-connected wind turbine includes a wind turbine generator body and a grid-connected inverter power supply. The system includes: The fault equivalent model construction module is configured as follows: based on the control strategy of the grid-type inverter power supply of virtual synchronous machine type, analyze the characteristics of the output power of the grid-type inverter power supply under the steady state of the distribution network fault, and establish the active and reactive power simulation calculation model of the grid-type inverter power supply under fault; then, based on the correlation between the output current and power of the grid-type inverter power supply, establish the fault equivalent model of the grid-type inverter power supply. The fault equivalent circuit construction module is configured to: based on the fault equivalent model of the grid-type inverter power supply, establish a composite sequence network equivalent model under the fault conditions of the distribution network containing the grid-type inverter power supply according to the distribution network structure; A generalized matrix form equation system construction module is configured to: obtain a system of loop equations composed of a generalized matrix based on the composite sequence network equivalent model and according to the circuit theorem; The fault electrical quantity calculation module is configured to: combine the circuit equations and the fault equivalent model of the grid-type inverter power supply, and solve for the fault quantity using an iterative calculation method based on the output power and current characteristics of the grid-type inverter power supply and the constraints of the power-voltage relationship.

[0020] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the fault simulation calculation method for a grid-connected wind turbine system as described in the first aspect.

[0021] Fourthly, the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps in the fault simulation calculation method for a grid-connected wind turbine system as described in the first aspect.

[0022] The above one or more technical solutions have the following beneficial effects: This invention analyzes the characteristics of active and reactive power output by grid-type inverters during distribution network faults, based on the control strategy of virtual synchronous machine-based grid-type inverters. A composite-sequence network fault simulation model for grid-type inverters connected to the distribution network is established, deriving a generalized matrix-form loop equation set for the distribution network, including the positive-sequence voltage at the grid connection point. Furthermore, based on the output power and current characteristics of the grid-type inverter and the constraints of the power-voltage relationship, an iterative calculation method for fault electrical quantities is proposed. A simulation model built using PSCAD is used to verify the accuracy of the proposed fault calculation method. This invention solves the problem that traditional fault analysis and calculation methods based on synchronous machine power supplies cannot adapt to the scenario of grid-type inverters connected to the distribution network.

[0023] This invention addresses the problem that traditional fault analysis and calculation methods based on synchronous power supplies cannot adapt to the scenario of grid-connected inverters accessing distribution networks. The proposed distribution network fault calculation method is based on active power-frequency and reactive power-voltage relationships, and can converge quickly under both symmetrical and asymmetrical fault conditions. It has high calculation accuracy and is universal for network results of multiple DG access and different distribution networks. It improves the theoretical framework for short-circuit current simulation calculation of distribution networks with grid-connected inverters, provides theoretical support for fault analysis and protection design of active distribution networks, and ensures the safe and reliable operation of distribution networks. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 This is a flowchart of a fault simulation calculation method for a grid-connected wind turbine system according to an embodiment of the present invention; Figure 2 This is the active-frequency control link of the outer loop control structure of the virtual synchronous machine-type grid-type inverter power supply in this embodiment of the invention; Figure 3 This is the reactive power-voltage control link of the outer loop control structure of the virtual synchronous machine-type grid-type inverter power supply in this embodiment of the invention; Figure 4 This is a typical power distribution network structure diagram according to an embodiment of the present invention; Figure 5 This is a typical equivalent circuit diagram of a power distribution network fault according to an embodiment of the present invention. Detailed Implementation

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0028] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0029] Example 1 For example Figure 1 As shown in the figure, this embodiment discloses a fault simulation calculation method for a grid-connected wind turbine system. The grid-connected wind turbine includes a wind turbine generator body and a grid-connected inverter power supply. The method includes the following steps: S1: Based on the control strategy of the virtual synchronous machine type of grid-type inverter, the characteristics of the output power of the grid-type inverter under the steady state of the distribution network fault are analyzed, and the active and reactive power simulation calculation model of the grid-type inverter under fault is established; then, based on the correlation between the output current and power of the grid-type inverter, the equivalent model of the grid-type inverter fault is established. In this embodiment, the grid-connected wind turbine includes a wind turbine body and a grid-connected inverter. The wind turbine body includes a wind turbine and a generator. In the fault simulation calculation, the grid-connected inverter directly participates in the calculation of the electrical quantities of the power grid. Therefore, the steps of this invention can be directly applied to the grid-connected fault analysis of the grid-connected wind turbine.

[0030] The grid-connected inverter employs a virtual synchronous machine control strategy, directly utilizing the power outer loop to control the voltage amplitude and phase. The power outer loop is divided into two parts: an active / frequency loop and a reactive / voltage loop. The former is a droop control with inertial characteristics, based on the control objective, i.e., the active power reference value. and system frequency reference value Output frequency , The voltage phase is obtained after integration. The latter simulates a voltage regulation process with inertial characteristics, based on a reactive power reference value. and system voltage reference value Given voltage amplitude The outer ring structure is as follows Figure 2 , Figure 3 As shown, the control equation is shown in equation (1).

[0031] (1) in, For virtual rotational inertia, For frequency The first derivative with respect to time, The detected active power, The damping coefficient is used to reflect the droop characteristics of the active-frequency loop. The integral coefficient is... Equivalent internal potential The first derivative with respect to time, The detected reactive power, The voltage regulation coefficient is used to reflect the reactive power-voltage loop droop characteristics. This is the voltage at the LC filter, which is also the voltage at the inverter power supply port of the grid.

[0032] It should be noted that the above governing equations are in the time domain. Figure 2 , Figure 3 It is in the frequency domain. Figure 2 , Figure 3 middle It represents a complex frequency and describes the frequency domain characteristics of a signal.

[0033] The characteristics of the active power output of a grid-type inverter during a distribution network fault are as follows: For distribution network systems, distribution network faults constitute high-power disturbances. Under conditions of power generation and consumption imbalance, synchronous motor power supplies mitigate the power imbalance by varying the rotor speed, while inverter power supplies also adjust their output power according to control strategies. The system frequency dynamically changes during this process, eventually reaching a steady state and returning to near the system's rated frequency. For the current distribution network, the synchronous motor power supply on the main grid side is equivalent to an ideal power supply in series with an impedance, playing a decisive role in frequency during high-power disturbances. The steady-state system frequency deviation expression is as follows: (2) in, The steady-state deviation of the system frequency. for System frequency deviation at time t, This represents the deviation between power generation and power consumption during disturbances. The rated power of the system, The equivalent droop coefficient of the system characterizes the degree of frequency change caused by power abrupt changes; is the damping coefficient.

[0034] Since the capacity of the main grid is usually much larger than that of the distribution grid, and can often be considered equivalent to an ideal voltage source, the main grid can react quickly when power disturbances occur in the distribution grid, outputting the power required by the distribution grid. , For small constants, The effect of [the system's frequency deviation] is relatively negligible. Therefore, the frequency deviation when the system reaches steady state is approximately 0, and the frequency in fault steady state is 50Hz. Thus, the output active power can be obtained as: (3) Reactive power of grid-connected inverters during steady-state fault conditions in the distribution network Satisfy the following formula: (4) in, This is a reference value for reactive power. The voltage regulation coefficient is used to reflect the reactive power-voltage droop characteristics. This is the system voltage reference value. This refers to the voltage between the step-up transformer and the filter inductor of the grid-type inverter power supply.

[0035] Grid-connected inverter output positive sequence current The relationship between power and strength is as follows: (5) Output negative sequence current for: (6) in, The apparent power delivered by a grid-connected inverter to the grid connection point. , The imaginary unit; The voltage phasor between the step-up transformer and the filter inductor of the grid-type inverter power supply; These are conjugate phasors. Based on the above current expression, in the positive sequence network, its equivalent is a controlled current source, while in the negative sequence network, it is an open circuit.

[0036] The equivalent model of the composite sequence network under fault conditions in a distribution network with a grid-connected inverter consists of the positive sequence network of the grid-connected inverter and the negative sequence network without power sources. Due to the adoption of a negative sequence current suppression control strategy, the negative sequence network does not contain power sources and is in equivalent impedance form, connected in series with the transition resistor from the negative sequence port.

[0037] S2: Based on the fault equivalent model of the grid-type inverter power supply, and according to the distribution network structure, establish a composite sequence network equivalent model under the fault conditions of the distribution network containing the grid-type inverter power supply. like Figure 4 As shown, a typical distribution network structure is selected, with two outgoing lines connected in parallel on the distribution network side. There are a total of 4 loads and 5 lines, namely line 1-1, line 1-2, line 2-1, line 2-2, and line 2-3. The grid-connected inverter (DG) is connected to the distribution network between line 2-1 and line 2-2, and the fault point is located at F upstream of the grid connection point.

[0038] for Figure 4 The typical distribution network shown has a composite sequence network equivalent model (i.e., distribution network fault equivalent circuit) under a two-phase-to-phase short-circuit fault, as follows: Figure 5 As shown. In the equivalent circuit of a distribution network fault, The equivalent internal potential of the main grid-side synchronous power supply; The equivalent impedance of the power supply of the main grid-side synchronous machine; The equivalent impedance of the outgoing lines 1-1 and 1-2; This is the equivalent impedance of line 2-1; This is the equivalent impedance of line 2-2; The equivalent impedance of line 2-3; The equivalent impedance of load 2; The equivalent impedance of load 3; The equivalent impedance of load 4; The equivalent impedance of the circuit to the right of the blue dashed line; is a constant representing the proportion of the fault location to the line segment, with a value range of (0,1). The equivalent potential of a grid-connected inverter power supply. This refers to the equivalent internal impedance of a grid-connected inverter, including the grid-connected transformer portion. This refers to the output current of a grid-type inverter.

[0039] S3: Based on the composite sequence network equivalent model, the loop equation system composed of the generalized matrix is ​​obtained according to the circuit theorem; In this embodiment, based on the equivalent model of the composite sequence network of the distribution network, the loop current equations and additional equations composed of the generalized matrix of the distribution network are written. The additional equations are the equations relating the branch currents of the DG grid-connected circuits to the loop currents. Solving the loop current equations and the additional equations simultaneously, the fault electrical quantity equations are obtained: (7) in, for The corrected loop impedance matrix, The number of loop circuits; for The loop current vector; A for The correlation matrix between loop current and DG branch; for The voltage vector of the distribution network voltage source; for Grid-type inverter output current The vector formed by these vectors.

[0040] S4: Combine the aforementioned loop equations with the equivalent fault model of the grid-connected inverter power supply, and use an iterative calculation method to solve for the fault quantities based on the output power and current characteristics of the grid-connected inverter power supply and the constraints of the power-voltage relationship.

[0041] In this embodiment, the expression (5) of the fault equivalent model of the grid-type inverter power supply is used to determine the output current of the grid-type inverter power supply. Set the value to zero as the initial value, substitute it into equation (7) to calculate the loop current value, calculate the grid-connected voltage of the grid-connected inverter based on the loop current, calculate the power after the fault and the voltage at the grid-connected inverter port according to equations (3), (4), and (8), calculate the new output current of the grid-connected inverter based on equation (5), and resubstitute it into equation (7) to calculate the grid-connected voltage. Use the convergence criterion equation (9) to determine whether the calculation result is converged. If the calculation result is converged, the operation ends; if the calculation result is not converged, substitute the new output current of the grid-connected inverter into equation (6) and repeat the above calculation process until the convergence condition is met, and then end the operation.

[0042] (8) (9) in, For the step-up transformer reactance of the grid-type inverter power supply, This is the positive sequence voltage at the grid connection point. phasor and The phase difference, It is a function with maximum value. This represents the difference between the calculated grid-connected voltage values ​​before and after the connection. For the first i Individual network-type DG The difference between the current amplitude and the amplitude of the previous iteration. For the first Individual network-type DG The difference between the current amplitude and the amplitude of the previous iteration. The threshold for the convergence criterion is a constant, and in this embodiment, it is taken as... The convergence condition is that the difference between the calculated voltage values ​​at the grid connection point in two consecutive calculations does not exceed [a certain threshold]. .

[0043] In summary, this invention analyzes the characteristics of the output power of grid-type inverters during distribution network faults based on the control strategy of virtual synchronous machines, derives the electrical quantity constraint relationships of grid-type inverters during faults, establishes an equivalent model of a composite sequence network of a distribution network containing grid-type inverters based on the distribution network structure, obtains a set of equations composed of a generalized loop matrix using circuit theorems, and proposes an iterative calculation method for fault electrical quantities based on the constraints of the output power and current characteristics and the power-voltage relationship of the grid-type inverters, thereby achieving accurate solutions for fault electrical quantities.

[0044] Once the parameters of the distribution network system are determined, Figure 4 When a two-phase short-circuit fault occurs at fault point F, the implementation status of the proposed fault calculation method can be obtained by calculating and solving the fault quantity of the distribution network using the proposed fault calculation method.

[0045] This invention builds a system in PSCAD / EMTDC as follows: Figure 4 The simulation model shown is based on a distribution network rated voltage of 10kV; a line parameter per unit length of 0.125+j0.095Ω / km; and impedances of lines 1 to 5 of 0.250+j0.190Ω, 0.500+j0.380Ω, 0.625+j0.475Ω, 0.600+j0.456Ω, and 0.375+j0.285Ω, respectively. A 2MW grid-connected inverter is connected to the distribution network between lines 2-1 and 2-2. =0.6.

[0046] Table 1 shows the calculation and simulation results of relevant fault quantities when a two-phase short-circuit fault occurs at fault point F. The amplitude error of the proposed calculation method is within 2%, and the angle error is within... Within this range, the proposed method can calculate the fault electrical quantities of the system relatively accurately.

[0047] Table 1 Two-phase short circuit at point F (A phase value)

[0048] Simulation results demonstrate that this invention addresses the problem that traditional fault analysis and calculation methods based on synchronous power supplies cannot adapt to the scenario of grid-connected inverters accessing distribution networks. The proposed distribution network fault calculation method is based on active power-frequency and reactive power-voltage relationships, and can converge quickly under different fault conditions with high calculation accuracy. It improves the theoretical framework for short-circuit current calculation in distribution networks containing grid-connected inverters, provides theoretical support for fault analysis and protection design of active distribution networks, and ensures the safe and reliable operation of distribution networks.

[0049] Research has revealed that, without considering current limiting, when the distribution network reaches steady state after a fault, the frequency of the voltage at the grid connection point of the grid-connected inverter remains unchanged, and the active power output of the grid-connected inverter remains unchanged, consistent with the active power reference value. However, due to the significant voltage drop after the fault, the reactive power at the fault steady state differs from the initial value. Based on the control strategy of the virtual synchronous machine type grid-connected inverter, the formula for calculating the reactive power at the fault steady state can be obtained. Based on this, an equivalent fault model of the grid-connected inverter is established, and the fault electrical quantity equations are solved using an iterative calculation method.

[0050] Example 2 This embodiment discloses a fault simulation calculation system for a grid-connected wind turbine system. The grid-connected wind turbine includes a wind turbine generator body and a grid-connected inverter power supply. The system includes: The fault equivalent model construction module is configured as follows: based on the control strategy of the grid-type inverter power supply of virtual synchronous machine type, analyze the characteristics of the output power of the grid-type inverter power supply under the steady state of the distribution network fault, and establish the active and reactive power simulation calculation model of the grid-type inverter power supply under fault; then, based on the correlation between the output current and power of the grid-type inverter power supply, establish the fault equivalent model of the grid-type inverter power supply. The fault equivalent circuit construction module is configured to: based on the fault equivalent model of the grid-type inverter power supply, establish a composite sequence network equivalent model under the fault conditions of the distribution network containing the grid-type inverter power supply according to the distribution network structure; A generalized matrix form equation system construction module is configured to: obtain a system of loop equations composed of a generalized matrix based on the composite sequence network equivalent model and according to the circuit theorem; The fault electrical quantity calculation module is configured to: combine the circuit equations and the fault equivalent model of the grid-type inverter power supply, and solve for the fault quantity using an iterative calculation method based on the output power and current characteristics of the grid-type inverter power supply and the constraints of the power-voltage relationship.

[0051] Example 3 The purpose of this embodiment is to provide a computing device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the method of Embodiment 1.

[0052] Example 4 The purpose of this embodiment is to provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the steps of the method of Embodiment 1.

[0053] The steps and methods involved in the apparatuses of Embodiments 3 and 4 above correspond to those in Embodiment 1. For specific implementation details, please refer to the relevant description section of Embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood as including any medium capable of storing, encoding, or carrying an instruction set for execution by a processor and enabling the processor to perform any of the methods in this invention.

[0054] Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any particular combination of hardware and software.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0056] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A fault simulation calculation method for a grid-connected wind turbine system, characterized in that, Grid-connected wind turbines include the wind turbine generator body and a grid-connected inverter power supply. The method includes the following steps: Based on the control strategy of the virtual synchronous machine type of grid-type inverter, the characteristics of the output power of the grid-type inverter under the steady state of the distribution network fault are analyzed, and the active and reactive power simulation calculation model of the grid-type inverter under fault is established. Then, based on the correlation between the output current and power of the grid-type inverter, the equivalent model of the grid-type inverter fault is established. Based on the fault equivalent model of the grid-type inverter power supply, a composite sequence network equivalent model under the fault conditions of the distribution network containing the grid-type inverter power supply is established according to the distribution network structure. Based on the composite sequence network equivalent model, a set of loop equations composed of a generalized matrix is ​​obtained according to the circuit theorem; By combining the aforementioned set of loop equations with the equivalent fault model of the grid-connected inverter, and based on the output power and current characteristics of the grid-connected inverter and the constraints of the power-voltage relationship, an iterative calculation method is used to solve for the fault quantities.

2. The fault simulation calculation method for a grid-connected wind turbine system as described in claim 1, characterized in that, The grid-type inverter power supply adopts positive and negative sequence separation control, and the negative sequence loop adopts a control method to suppress negative sequence current.

3. The fault simulation calculation method for a grid-connected wind turbine system as described in claim 1, characterized in that, During steady-state operation of a distribution network fault, the reactive power of a grid-connected inverter power supply satisfies the following equation: in, Reactive power This is a reference value for reactive power. The voltage regulation coefficient is used to reflect the reactive power-voltage droop characteristics. This is the system voltage reference value. This refers to the voltage between the step-up transformer and the filter inductor of the grid-type inverter power supply.

4. The fault simulation calculation method for a grid-connected wind turbine system as described in claim 1, characterized in that, The relationship between the positive sequence current and power output of the grid-type inverter is as follows: The output negative sequence current is: in, It is a positive sequence current. It is a negative sequence current. The apparent power delivered by a grid-connected inverter to the grid connection point. The voltage phasor between the step-up transformer and the filter inductor of the grid-type inverter power supply; It is a conjugate phasor.

5. The fault simulation calculation method for a grid-connected wind turbine system as described in claim 1, characterized in that, The composite sequence network equivalent model of the inverter power supply under the fault conditions of the distribution network consists of the positive sequence network of the inverter power supply with the structured grid and the negative sequence network without the power supply.

6. The fault simulation calculation method for a grid-connected wind turbine system as described in claim 1, characterized in that, The system of loop equations formed by the generalized matrix is ​​as follows: in, for The corrected loop impedance matrix, For the number of loop circuits, for The loop current vector, A for The correlation matrix between loop current and DG branch, for The voltage vector of the distribution network voltage source. for Output current vector of a grid-type inverter.

7. The fault simulation calculation method for a grid-connected wind turbine system as described in claim 1, characterized in that, The constraint on the power-voltage relationship is expressed as follows: in, Active power For the step-up transformer reactance of the grid-type inverter power supply, This refers to the voltage between the step-up transformer and the filter inductor in a grid-type inverter power supply. This is the positive sequence voltage at the grid connection point. phasor and The phase difference; The convergence criterion for iterative computation methods is: in, It is a function with maximum value. For the first i Individual network-type DG The difference between the current amplitude and the amplitude of the previous iteration. For the first Individual network-type DG The difference between the current amplitude and the amplitude of the previous iteration. The threshold for the convergence criterion.

8. A fault simulation calculation system for a grid-connected wind turbine system, characterized in that, Grid-type wind turbines include the wind turbine generator body and a grid-type inverter power supply. The system includes: The fault equivalent model construction module is configured as follows: based on the control strategy of the grid-type inverter power supply of virtual synchronous machine type, analyze the characteristics of the output power of the grid-type inverter power supply under the steady state of the distribution network fault, and establish the active and reactive power simulation calculation model of the grid-type inverter power supply under fault; then, based on the correlation between the output current and power of the grid-type inverter power supply, establish the fault equivalent model of the grid-type inverter power supply. The fault equivalent circuit construction module is configured to: based on the fault equivalent model of the grid-type inverter power supply, establish a composite sequence network equivalent model under the fault conditions of the distribution network containing the grid-type inverter power supply according to the distribution network structure; A generalized matrix form equation system construction module is configured to: obtain a system of loop equations composed of a generalized matrix based on the composite sequence network equivalent model and according to the circuit theorem; The fault electrical quantity calculation module is configured to: combine the circuit equations and the fault equivalent model of the grid-type inverter power supply, and solve for the fault quantity using an iterative calculation method based on the output power and current characteristics of the grid-type inverter power supply and the constraints of the power-voltage relationship.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the fault simulation calculation method for a grid-type wind turbine access system as described in any one of claims 1-7.

10. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the fault simulation calculation method for a grid-type wind turbine access system as described in any one of claims 1-7.

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