A network configuration type SVG simulation method and system considering dynamic characteristics of direct current side capacitor

Abstract

The application discloses a network-configuration type SVG simulation method and system considering dynamic characteristics of a direct-current side capacitor, and belongs to the technical field of power grids. The method comprises the following steps: based on a control link of a network-configuration type SVG, a network-configuration type SVG simulation model is established; each link of the simulation model is solved, and a differential equation in the simulation model is linearly converted into an algebraic equation based on a trapezoidal integral method for solving; and the response characteristics of the network-configuration type SVG under various working conditions are simulated according to the solutions of each link of the simulation model. The application can accurately simulate the response characteristics of the network-configuration type SVG under various working conditions, avoids the problem that the simulation result is excessively optimistic due to rough capacitor processing in the prior art model, and improves the credibility of the simulation result.

Description

Technical Field

[0001] This invention relates to the field of power grid technology, and more specifically, to a grid-type SVG simulation method and system that takes into account the dynamic characteristics of DC-side capacitors. Background Technology

[0002] With the accelerated grid connection of new energy sources, the voltage support capacity of the power grid continues to weaken. New energy units have weak tolerance and poor resistance to voltage disturbances; a voltage drop exceeding 20% ​​can trigger a chain reaction of grid disconnections (such as the Nan'ao blackout). Simultaneously, the equipment relies on phase-locked loops (PLLs) to lock onto the grid phase, requiring a short-circuit ratio greater than 1.5 at the grid connection point. Compared to conventional SVG (Static Var Generator) systems that rely on PLLs, grid-connected SVGs employ a grid-connected strategy, enabling them to automatically generate internal potential amplitude and phase. They operate without PLLs, can operate stably in weak grid environments, and can provide instantaneous short-circuit currents exceeding three times the rated current after a fault, offering extremely strong voltage support capabilities and significantly improving the short-circuit ratio at the grid connection point. They are widely used in new energy power plants and remote load centers.

[0003] To assess the effectiveness of equipment and ensure its safe and stable operation after grid connection, large power grid simulation analysis is indispensable as an important basis for understanding power grid characteristics, analyzing planning schemes, verifying defense measures, and specifying operating modes.

[0004] Existing network-type SVG simulation models follow the modeling approach of grid-type SVG, failing to consider the charging and discharging characteristics of DC capacitors or simulating them only with a single, limited integral element. However, unlike grid-type SVGs, which only provide weak reactive power support, network-type SVGs provide both inertial response and extremely strong reactive power support during faults. Since the DC capacitor is its primary primary energy source, the impact of DC voltage changes caused by charging and discharging on the control characteristics must be accurately simulated; otherwise, it will lead to overly optimistic simulation results and unusable simulation results, among other serious problems. Summary of the Invention

[0005] To address the above problems, this invention proposes a network-based SVG simulation method that considers the dynamic characteristics of the DC-side capacitor, comprising:

[0006] A simulation model of a network-based SVG is established based on the control loop of the network-based SVG.

[0007] The simulation model is solved by solving each component, and the differential equations are linearized into algebraic equations based on the trapezoidal integral method.

[0008] Based on the solutions of each stage of the simulation model, the response characteristics of the simulated mesh SVG under various working conditions are simulated.

[0009] Optional control elements for network-type SVG include:

[0010] Virtual inertia and damping control, DC side voltage control, virtual excitation control, overcurrent limiting, and grid connection interface.

[0011] Optional simulation models include: virtual inertia and damping control model, DC side voltage control model, virtual excitation control model, overcurrent limiting model and grid connection interface model;

[0012] The DC-side voltage control model simulates the voltage changes caused by the charging and discharging of the DC capacitor based on the active power measurements exchanged between the grid-type SVG and the system, and generates active power increments. The DC-side voltage control model also considers the effects of DC capacitor undervoltage and overvoltage protection.

[0013] The virtual damping control model generates a virtual internal potential phase angle reference value for a grid-type SVG based on the input active power increment, active power measurement value, and active power reference value.

[0014] The virtual excitation control model selects constant reactive power control or constant voltage control, and generates a reference value for the virtual internal potential amplitude of the grid-type SVG based on the measured values ​​of reactive power or voltage and the reference values ​​of reactive power or voltage. The virtual excitation control model considers the constraint of DC capacitor voltage on the modulation capability of the grid-type SVG.

[0015] The overcurrent limiting model generates the virtual internal potential amplitude and the actual phase angle value based on the virtual internal potential amplitude, the phase angle reference value, and the device overcurrent limit.

[0016] The grid connection interface model generates active and reactive current components injected into the grid based on the virtual internal potential and the magnitude of the connection reactance.

[0017] Optional DC-side voltage control model, including the following components:

[0018] Based on the active power measurements exchanged between the network-type SVG and the system, the DC capacitor voltage V is calculated. dc The calculation formula is as follows:

[0019]

[0020] Among them, P ref For the active power reference value exchanged between the grid-type SVG and the system, C is the size of the DC capacitor, and P is the active power measurement value of the grid-type SVG;

[0021] The active power increment ΔP is calculated based on DC voltage using the following formula:

[0022]

[0023] Among them, K P K is the proportional gain coefficient of the PI controller. IThe integral gain coefficient of the PI controller;

[0024] Among them, K P and K I Adjustments are made by identifying each stage and verifying the whole process. The least squares method is used to fit the identified stages.

[0025] The operating state of a grid-type SVG is determined based on DC voltage, and the calculation formula is as follows:

[0026]

[0027] Among them, I MODE If the value is 1, then the real part I of the injected grid current in the grid-type SVG is 1. X and the imaginary part I of the injected grid current in the grid-type SVG Y Normal output, I MODE If it is 0, then I X and I Y Output set to 0, V H T is the threshold for DC capacitor overvoltage protection operation. H For the DC capacitor overvoltage protection operation delay, V L T is the threshold for DC capacitor undervoltage protection operation. L This is a delay in the operation of the DC capacitor undervoltage protection.

[0028] Optional, the virtual inertia and damping control model includes the following components:

[0029] The virtual rotational speed is calculated based on the active power increment, measured active power, and active power baseline value. The calculation formula is as follows:

[0030]

[0031] Where ω0 is the rated speed of the system, J is the virtual moment of inertia, D is the virtual damping coefficient, and ω is the virtual speed of the SVG;

[0032] The virtual phase is generated based on the virtual rotational speed, and the calculation formula is as follows:

[0033]

[0034] Optional, the virtual excitation control model includes the following components:

[0035] Based on the measured voltage or reactive power reference value of the SVG access point in a grid-type SVG, the no-load excitation electromotive force is calculated using the following formula:

[0036]

[0037] Where K is the series PI gain coefficient, K VFor proportional-integral selection factors, T1, T2, T3, and T4 are the time constants of the series PI converter, and K is the coefficient of performance. PQ K is the proportional gain coefficient of the PI controller. IQ The integral gain coefficient of the PI controller;

[0038] Where K, K V K PQ and K IQ Adjustments are made by identifying each stage and verifying the whole process. The least squares method is used to fit the identified stages.

[0039] Calculate the limiting value E' based on the no-load excitation electromotive force. q The calculation formula is as follows:

[0040]

[0041] Among them, E' q i is the initial value before the transient potential is limited. d x is the DC current component. d For synchronous reactance, x' d For direct-axis transient reactance, T′ d0 The direct-axis open-circuit transient time constant;

[0042] The virtual internal potential amplitude is calculated based on the pre-limiting value and the DC capacitor voltage. The calculation formula is as follows:

[0043]

[0044] In the formula, K lim For overmodulation coefficients, piecewise functions are required to represent them for certain types of generator sets;

[0045] Among them, K lim Adjustments are made by identifying each stage and verifying the whole process. The least squares method is used to fit the identified stages.

[0046] Optional, the overcurrent limiting model and grid connection interface model include the following components:

[0047] The grid-connected current is calculated based on the virtual internal potential and connection reactance, using the following formula:

[0048]

[0049] Among them, X T To connect the reactance, V x V is the measured real part of the grid connection point current. y E represents the imaginary part of the grid connection point current. x E is the real part of the virtual internal potential. y This represents the imaginary part of the virtual internal potential.

[0050] If I is greater than the overcurrent limit requirement Imax, then the total amplitude of the virtual impedance is obtained based on the magnitude of the limiting current, the voltage deviation, and the current limit value, and the virtual resistance R is calculated. v Size, calculated using the following formula:

[0051]

[0052] R v =kX v (12)

[0053] Among them, X v Let k be the virtual reactance, and k be the ratio of virtual resistance to virtual reactance.

[0054] By R v and X v The current reference value after current limiting is calculated using the following formula:

[0055]

[0056] Optionally, the differential equations are linearized into algebraic equations using the trapezoidal integral method, and the solution formula is as follows:

[0057] dy / dt=f(y)(14)

[0058]

[0059] Where y0 is the current value, y is the value to be solved, and h is the simulation step size.

[0060] Furthermore, this invention also proposes a network-based SVG simulation system that considers the dynamic characteristics of DC-side capacitors, comprising:

[0061] The modeling unit is used to establish a simulation model of the network-based SVG for the control loop.

[0062] The solution unit is used to solve each part of the simulation model, wherein the differential equations are linearized into algebraic equations based on the trapezoidal integral method for solution.

[0063] The simulation unit is used to simulate the response characteristics of the mesh-type SVG under various working conditions based on the solutions of each part of the simulation model.

[0064] Optional control elements for network-type SVG include:

[0065] Virtual inertia and damping control, DC side voltage control, virtual excitation control, overcurrent limiting, and grid connection interface.

[0066] Optional simulation models include: virtual inertia and damping control model, DC side voltage control model, virtual excitation control model, overcurrent limiting model and grid connection interface model;

[0067] The DC-side voltage control model simulates the voltage changes caused by the charging and discharging of the DC capacitor based on the active power measurements exchanged between the grid-type SVG and the system, and generates active power increments. The DC-side voltage control model also considers the effects of DC capacitor undervoltage and overvoltage protection.

[0068] The virtual damping control model generates a virtual internal potential phase angle reference value for a grid-type SVG based on the input active power increment, active power measurement value, and active power reference value.

[0069] The virtual excitation control model selects constant reactive power control or constant voltage control, and generates a reference value for the virtual internal potential amplitude of the grid-type SVG based on the measured values ​​of reactive power or voltage and the reference values ​​of reactive power or voltage. The virtual excitation control model considers the constraint of DC capacitor voltage on the modulation capability of the grid-type SVG.

[0070] The overcurrent limiting model generates the virtual internal potential amplitude and the actual phase angle value based on the virtual internal potential amplitude, the phase angle reference value, and the device overcurrent limit.

[0071] The grid connection interface model generates active and reactive current components injected into the grid based on the virtual internal potential and the magnitude of the connection reactance.

[0072] Optional DC-side voltage control model, including the following components:

[0073] Based on the active power measurements exchanged between the network-type SVG and the system, the DC capacitor voltage V is calculated. dc The calculation formula is as follows:

[0074]

[0075] Among them, P ref For the active power reference value exchanged between the grid-type SVG and the system, C is the size of the DC capacitor, and P is the active power measurement value of the grid-type SVG;

[0076] The active power increment ΔP is calculated based on DC voltage using the following formula:

[0077]

[0078] Among them, K P K is the proportional gain coefficient of the PI controller. I The integral gain coefficient of the PI controller;

[0079] Among them, K P and K IAdjustments are made by identifying each stage and verifying the whole process. The least squares method is used to fit the identified stages.

[0080] The operating state of a grid-type SVG is determined based on DC voltage, and the calculation formula is as follows:

[0081]

[0082] Among them, I MODE If the value is 1, then the real part I of the injected grid current in the grid-type SVG is 1. X and the imaginary part I of the injected grid current in the grid-type SVG Y Normal output, I MODE If it is 0, then I X and I Y Set the output to 0.

[0083] Optional, the virtual inertia and damping control model includes the following components:

[0084] The virtual rotational speed is calculated based on the active power increment, measured active power, and active power baseline value. The calculation formula is as follows:

[0085]

[0086] Where ω0 is the rated speed of the system, J is the virtual moment of inertia, D is the virtual damping coefficient, and ω is the virtual speed of the SVG;

[0087] The virtual phase is generated based on the virtual rotational speed, and the calculation formula is as follows:

[0088]

[0089] Optional, the virtual excitation control model includes the following components:

[0090] Based on the measured voltage or reactive power reference value of the SVG access point in a grid-type SVG, the no-load excitation electromotive force is calculated using the following formula:

[0091]

[0092] Where K is the series PI gain coefficient, K V For proportional-integral selection factors, T1, T2, T3, and T4 are the time constants of the series PI converter, and K is the coefficient of performance. PQ K is the proportional gain coefficient of the PI controller. IQ The integral gain coefficient of the PI controller;

[0093] Among them, K, K V K PQ and K IQAdjustments were made by identifying each stage individually and verifying the overall process. The identification of each stage was performed using the least squares method for fitting. The pre-limiting value E' was calculated based on the no-load excitation electromotive force. q The calculation formula is as follows:

[0094]

[0095] Among them, E' q i is the initial value before the transient potential is limited. d x is the DC current component. d For synchronous reactance, x' d For direct-axis transient reactance, T′ d0 The direct-axis open-circuit transient time constant;

[0096] The virtual internal potential amplitude is calculated based on the pre-limiting value and the DC capacitor voltage. The calculation formula is as follows:

[0097]

[0098] In the formula, K lim For overmodulation coefficients, piecewise functions are required to represent them for certain types of generator sets;

[0099] Among them, K lim Adjustments are made by identifying each stage and verifying the whole process. The least squares method is used to fit the identified stages.

[0100] Optional, the overcurrent limiting model and grid connection interface model include the following components:

[0101] The grid-connected current is calculated based on the virtual internal potential and connection reactance, using the following formula:

[0102]

[0103] Among them, X T To connect the reactance, V x V is the measured real part of the grid connection point current. y E represents the imaginary part of the grid connection point current. x E is the real part of the virtual internal potential. y This represents the imaginary part of the virtual internal potential.

[0104] If I is greater than the overcurrent limit requirement Imax, then the total amplitude of the virtual impedance is obtained based on the magnitude of the limiting current, the voltage deviation, and the current limit value, and the virtual resistance R is calculated. v Size, calculated using the following formula:

[0105]

[0106] R v =kX v (12)

[0107] Among them, X v Let k be the virtual reactance, and k be the ratio of virtual resistance to virtual reactance.

[0108] By R v and X v The current reference value after current limiting is calculated using the following formula:

[0109]

[0110] Optionally, the differential equations are linearized into algebraic equations using the trapezoidal integral method, and the solution formula is as follows:

[0111] dy / dt=f(y)(14)

[0112]

[0113] Where y0 is the current value, y is the value to be solved, and h is the simulation step size.

[0114] In another aspect, the present invention also provides a computing device, comprising: one or more processors;

[0115] A processor is used to execute one or more programs;

[0116] When the one or more programs are executed by the one or more processors, the method described above is implemented.

[0117] In another aspect, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the method described above.

[0118] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0119] This invention provides a simulation method for a networked SVG that considers the dynamic characteristics of the DC-side capacitor. The method includes: establishing a simulation model of the networked SVG based on its control loop; solving each element of the simulation model, where the differential equations are linearized into algebraic equations using the trapezoidal integral method; and simulating the response characteristics of the networked SVG under various operating conditions based on the solutions of each element of the simulation model. This invention can accurately simulate the response characteristics of the networked SVG under various operating conditions, avoiding the problem of overly optimistic simulation results caused by the coarse handling of capacitors in existing models, thus improving the reliability of the simulation results. Attached Figure Description

[0120] Figure 1 This is a flowchart of the method of the present invention;

[0121] Figure 2This is a schematic diagram of a simulation model for an embodiment of the method of the present invention;

[0122] Figure 3 This is a schematic diagram of a single-machine system according to an embodiment of the method of the present invention;

[0123] Figure 4 (a)-(d) are comparison charts of the simulation results of active power output, reactive power output, system voltage and system frequency of the device in the embodiment of the method of the present invention with those of the existing method, respectively.

[0124] Where P is the measured active power value of the grid-type SVG; P ref Q is the reference value for active power of the grid-type SVG; Q is the measured value for reactive power of the grid-type SVG; ref V is the reactive power reference value for a grid-connected SVG; V is the measured voltage value at the grid-connected SVG connection point; V ref V is the reference voltage value for the SVG access point in a grid-connected system; ΔP is the active power difference value of the DC voltage control output; dc This is the measured value of the DC side voltage; V dcref This is the reference value for the DC-side voltage; θ ref θ is the virtual internal potential phase angle reference value; E is the actual virtual internal potential phase angle value; ref E is the reference value for the virtual internal potential amplitude; E is the actual value for the virtual internal potential amplitude; I x Inject the real part of the grid current into the grid-type SVG. Detailed Implementation

[0125] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0126] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0127] Example 1:

[0128] This invention proposes a network-based SVG simulation method S100 that considers the dynamic characteristics of DC-side capacitors, such as... Figure 1 As shown, it includes:

[0129] S101, Based on the control loop of the networked SVG, establish a simulation model of the networked SVG;

[0130] S102, Solve each part of the simulation model, wherein the differential equations are linearized into algebraic equations based on the trapezoidal integral method and solved.

[0131] S103, based on the solutions of each component of the simulation model, simulates the response characteristics of the mesh-type SVG under various working conditions.

[0132] The established simulation model, such as Figure 2 As shown, it includes sub-models such as virtual inertia and damping control, DC side voltage control, virtual excitation control, and overcurrent limiting. Among them, the DC-side voltage control model simulates the voltage changes caused by the charging and discharging of the DC capacitor based on the active power measurements exchanged between the grid-type SVG and the system, and generates the active power increment. The model must consider the impact of DC capacitor undervoltage and overvoltage protection. The virtual damping control model generates the virtual internal potential phase angle reference value of the grid-type SVG based on the input active power increment, active power measurement, and active power reference value. The virtual excitation control model can choose constant reactive power control or constant voltage control. Based on the reactive power or voltage measurement and reactive power or voltage reference value, it generates the virtual internal potential amplitude reference value of the grid-type SVG. The model must consider the constraint of DC capacitor voltage on the modulation capability of the grid-type SVG. The overcurrent limiting model forms the actual values ​​of virtual internal potential amplitude and phase angle based on virtual internal potential amplitude, phase angle reference value, and equipment overcurrent limit. The grid-connected interface model generates the active current and reactive current components injected into the grid based on the virtual internal potential and the magnitude of the connection reactance, which are manifested externally as voltage source characteristics.

[0133] The DC-side voltage control model mainly includes the following components:

[0134] Calculation of DC capacitor voltage V based on active power measurements exchanged between the network-type SVG and the system. dc The calculation formula is as follows:

[0135]

[0136] In the formula, P ref The active power reference value for the network-type SVG and system exchange is given, where C is the size of the DC capacitor. C is a design parameter that can be obtained from the manufacturer or maintenance provider.

[0137] The formula for calculating the active power increment ΔP based on DC voltage is as follows:

[0138]

[0139] In the formula, KP is the proportional gain coefficient of the PI controller, and KI is the integral gain coefficient of the PI controller. KP and KI are operating parameters that can be obtained by requesting information from the maintenance provider. KP and KI can be adjusted through segmented identification and overall verification; the identification segment can be fitted using the least squares method.

[0140] The calculation method for determining the operating state of a grid-type SVG based on DC voltage is as follows:

[0141]

[0142] Among them, I MODE If the value is 1, then the real part I of the injected grid current in the grid-type SVG is 1. X and the imaginary part I of the injected grid current in the grid-type SVG Y Normal output, I MODE If it is 0, then I X and I Y Output set to 0, V H T is the threshold for DC capacitor overvoltage protection operation. H For the DC capacitor overvoltage protection operation delay, V L T is the threshold for DC capacitor undervoltage protection operation. L This is a delay in the operation of the DC capacitor undervoltage protection.

[0143] Virtual inertia and damping control mainly includes the following aspects:

[0144] The virtual rotational speed is calculated based on the active power increment, measured active power, and active power reference value. The calculation formula is as follows:

[0145]

[0146] In the formula, J is the virtual moment of inertia, D is the virtual damping coefficient, and ω is the virtual rotational speed of the SVG. J and D are design parameters, which can be obtained by consulting the manufacturer or maintenance provider.

[0147] The virtual phase is generated based on the virtual rotation speed, and its calculation formula is as follows:

[0148]

[0149] Virtual excitation control mainly includes the following components:

[0150] The no-load excitation electromotive force is calculated based on the measured voltage or reactive power reference value of the SVG access point in a grid-type system. The calculation formula is as follows:

[0151]

[0152] In the formula, K is the series PI gain coefficient, K VFor proportional-integral (PI) selection factors, T1, T2, T3, T4 are the time constants of the series PI converter, and K... PQ K is the proportional gain coefficient of the PI controller. IQ Here, K and K are the integral gain coefficients of the PI controller. V K PQ K IQ T1, T2, T3, and T4 are operating parameters, which can be obtained by requesting information from the operations and maintenance provider. K, K V K PQ K IQ Adjustments can be made by identifying each step separately and verifying the whole process; for the identification step, the least squares method can be used for fitting.

[0153] Calculate the limiting value E' based on the no-load excitation electromotive force. q The calculation formula is as follows:

[0154]

[0155] In the formula, E' q The transient potential is the initial value before limiting, id is the DC current component, and x is the current component before limiting. d For synchronous reactance, x' d For direct-axis transient reactance, T′ d0 Let x be the direct-axis open-circuit transient time constant. d , x' d and T′ d0 Design parameters can be obtained by requesting information from the manufacturer or maintenance provider. d It can be calculated based on (10).

[0156] The virtual internal potential amplitude is calculated based on the pre-limiting value and the DC capacitor voltage. The calculation formula is as follows:

[0157]

[0158] In the formula, K lim Overmodulation coefficient

[0159] K lim Adjustments are made by identifying each stage and verifying the whole process. The least squares method is used to fit the identified stages.

[0160] In the simulation, the overcurrent limiting and grid-connected interface model mainly includes the following components:

[0161] The grid-connected current is calculated based on the virtual internal potential and connection reactance, and the calculation formula is as follows:

[0162]

[0163] Among them, X T To connect the reactance, Vx V is the measured real part of the grid connection point current. y E represents the imaginary part of the grid connection point current. x E is the real part of the virtual internal potential. y This represents the imaginary part of the virtual internal potential. Where X... T Design parameters can be obtained by requesting information from the manufacturer or maintenance provider.

[0164] If I is greater than the overcurrent limit requirement I max Then, based on the magnitude of the limiting current, the voltage deviation, and the current limiting value, the total amplitude of the virtual impedance is obtained, and the virtual resistance R is calculated. v Size, its calculation formula is:

[0165]

[0166] R v =kX v (12)

[0167] In the formula, X v Let k be the virtual reactance, and k be the ratio of virtual resistance to virtual reactance.

[0168] By R v X v The formula for calculating the reference current value after current limiting is as follows:

[0169]

[0170] The differential equations in each stage can be solved by linearizing the differences using the trapezoidal integration method (transforming Equation 14 into Equation 15 for solution). The method is as follows:

[0171] dy / dt=f(y)(14)

[0172]

[0173] In the formula, y0 is the current value, y is the value to be solved, and h is the simulation step size.

[0174] The segment identification and overall verification comparison of the operating conditions include the following: voltage drop at the grid connection point of the grid-connected SVG by 0.05, 0.2, 0.5 and 0.8 per unit, voltage increase by 0.05, 0.1 and 0.2 per unit, and frequency drop by 0.25 Hz.

[0175] The comparison includes the active and reactive power outputs of the mesh-type SVG.

[0176] The method described in this invention has been implemented in the PSD-BPA simulation software, and the stand-alone system built is as follows: Figure 3As shown, active and reactive load disturbances are added at the installation point of the grid-type SVG, and the support capacity of the grid-type SVG for the power grid is observed. The results of the proposed method are compared with those of existing methods. Figure 4 As shown in (a)-(d).

[0177] Comparing the active and reactive power outputs of the grid-type SVG after the disturbance, as well as the voltage and frequency of the disturbed node, the simulation results of the two existing methods are not significantly different. The simulation results are both quite optimistic, with good system voltage and frequency, and the system can provide long-term support based on the response characteristics in the early stage of the fault. There is no risk to the system.

[0178] However, the actual equipment response characteristics can be divided into three typical stages. In the early stage of the fault, the simulation results of the method proposed in this invention are not significantly different from existing methods, both providing strong active and reactive power support capabilities. In the middle stage of the fault, as the DC capacitor discharges continuously, the DC side voltage decreases. Due to the limitations of the equipment itself, PWM no longer has the ability to modulate the DC side voltage to the required AC side voltage. The method proposed in this invention can simulate this well, and the active and reactive power output of the equipment is limited. In the later stage of the fault, the DC side capacitor voltage is too low. Due to equipment protection requirements, the grid-type SVG will be disconnected from the power grid, lacking any active or reactive power support capabilities. The method proposed in this invention correctly reflects this operating characteristic, and the system voltage and frequency continue to deteriorate, posing a risk of instability.

[0179] Example 2:

[0180] This invention also proposes a network-based SVG simulation system 200 that considers the dynamic characteristics of DC-side capacitors, comprising:

[0181] Modeling unit 201 is used to establish a simulation model of the network-type SVG based on the control loop of the network-type SVG.

[0182] The solution unit 202 is used to solve each part of the simulation model, wherein the differential equations are linearized into algebraic equations based on the trapezoidal integral method for solution.

[0183] Simulation unit 203 is used to simulate the response characteristics of the network-type SVG under various working conditions based on the solutions of each part of the simulation model.

[0184] The control components of a mesh-based SVG include:

[0185] Virtual inertia and damping control, DC side voltage control, virtual excitation control, overcurrent limiting, and grid connection interface.

[0186] The simulation models include: virtual inertia and damping control model, DC side voltage control model, virtual excitation control model, overcurrent limiting model, and grid connection interface model.

[0187] The DC-side voltage control model simulates the voltage changes caused by the charging and discharging of the DC capacitor based on the active power measurements exchanged between the grid-type SVG and the system, and generates active power increments. The DC-side voltage control model also considers the effects of DC capacitor undervoltage and overvoltage protection.

[0188] The virtual damping control model generates a virtual internal potential phase angle reference value for a grid-type SVG based on the input active power increment, active power measurement value, and active power reference value.

[0189] The virtual excitation control model selects constant reactive power control or constant voltage control, and generates a reference value for the virtual internal potential amplitude of the grid-type SVG based on the measured values ​​of reactive power or voltage and the reference values ​​of reactive power or voltage. The virtual excitation control model considers the constraint of DC capacitor voltage on the modulation capability of the grid-type SVG.

[0190] The overcurrent limiting model generates the virtual internal potential amplitude and the actual phase angle value based on the virtual internal potential amplitude, the phase angle reference value, and the device overcurrent limit.

[0191] The grid connection interface model generates active and reactive current components injected into the grid based on the virtual internal potential and the magnitude of the connection reactance.

[0192] Optional DC-side voltage control model, including the following components:

[0193] Based on the active power measurements exchanged between the network-type SVG and the system, the DC capacitor voltage V is calculated. dc The calculation formula is as follows:

[0194]

[0195] Among them, P ref For the active power reference value exchanged between the grid-type SVG and the system, C is the size of the DC capacitor, and P is the active power measurement value of the grid-type SVG;

[0196] The active power increment ΔP is calculated based on DC voltage using the following formula:

[0197]

[0198] Among them, K P K is the proportional gain coefficient of the PI controller. I The integral gain coefficient of the PI controller;

[0199] Among them, K P and K I Adjustments are made by identifying each stage and verifying the whole process. The least squares method is used to fit the identified stages.

[0200] The operating state of a grid-type SVG is determined based on DC voltage, and the calculation formula is as follows:

[0201]

[0202] Among them, I MODE If the value is 1, then the real part I of the injected grid current in the grid-type SVG is 1. X and the imaginary part I of the injected grid current in the grid-type SVG Y Normal output, I MODE If it is 0, then I X and I Y Output set to 0, V H T is the threshold for DC capacitor overvoltage protection operation. H For the DC capacitor overvoltage protection operation delay, V L T is the threshold for DC capacitor undervoltage protection operation. L This is a delay in the operation of the DC capacitor undervoltage protection.

[0203] The virtual inertia and damping control model includes the following components:

[0204] The virtual rotational speed is calculated based on the active power increment, measured active power, and active power baseline value. The calculation formula is as follows:

[0205]

[0206] Where ω0 is the rated speed of the system, J is the virtual moment of inertia, D is the virtual damping coefficient, and ω is the virtual speed of the SVG;

[0207] The virtual phase is generated based on the virtual rotational speed, and the calculation formula is as follows:

[0208]

[0209] The virtual excitation control model includes the following components:

[0210] Based on the measured voltage or reactive power reference value of the SVG access point in a grid-type SVG, the no-load excitation electromotive force is calculated using the following formula:

[0211]

[0212] Where K is the series PI gain coefficient, K V For proportional-integral selection factors, T1, T2, T3, and T4 are the time constants of the series PI converter, and K is the coefficient of performance. PQ K is the proportional gain coefficient of the PI controller. IQ The integral gain coefficient of the PI controller;

[0213] Among them, K, K V K PQ and K IQAdjustments were made by identifying each stage individually and verifying the overall process. The identification of each stage was performed using the least squares method for fitting. The pre-limiting value E' was calculated based on the no-load excitation electromotive force. q The calculation formula is as follows:

[0214]

[0215] Among them, E' q i is the initial value before the transient potential is limited. d x is the DC current component. d For synchronous reactance, x' d For direct-axis transient reactance, T′ d0 The direct-axis open-circuit transient time constant;

[0216] The virtual internal potential amplitude is calculated based on the pre-limiting value and the DC capacitor voltage. The calculation formula is as follows:

[0217]

[0218] In the formula, K lim For overmodulation coefficients, piecewise functions are required to represent them for certain types of generator sets;

[0219] Among them, K lim Adjustments are made by identifying each stage and verifying the whole process. The least squares method is used to fit the identified stages.

[0220] The overcurrent limiting model and grid connection interface model include the following components:

[0221] The grid-connected current is calculated based on the virtual internal potential and connection reactance, using the following formula:

[0222]

[0223] Among them, X T To connect the reactance, V x V is the measured real part of the grid connection point current. y E represents the imaginary part of the grid connection point current. x E is the real part of the virtual internal potential. y This represents the imaginary part of the virtual internal potential.

[0224] If I is greater than the overcurrent limit requirement Imax, then the total amplitude of the virtual impedance is obtained based on the magnitude of the limiting current, the voltage deviation, and the current limit value, and the virtual resistance R is calculated. v Size, calculated using the following formula:

[0225]

[0226] R v =kX v (12)

[0227] Among them, X v Let k be the virtual reactance, and k be the ratio of virtual resistance to virtual reactance.

[0228] By R v and X v The current reference value after current limiting is calculated using the following formula:

[0229]

[0230] The solution formula for the differential equation, which is linearized into an algebraic equation using the trapezoidal integral method, is as follows:

[0231] dy / dt=f(y)(14)

[0232]

[0233] Where y0 is the current value, y is the value to be solved, and h is the simulation step size.

[0234] This invention can accurately simulate the response characteristics of network-type SVG under various working conditions, avoiding the problem of overly optimistic simulation results caused by the coarse handling of capacitance in existing models, and improving the reliability of simulation results.

[0235] Example 3:

[0236] Based on the same inventive concept, this invention also provides a computer device, which includes a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions from the computer storage medium to implement corresponding method flows or corresponding functions, thereby implementing the steps of the methods in the above embodiments.

[0237] Example 4:

[0238] Based on the same inventive concept, this invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the method in the above embodiments.

[0239] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0240] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0241] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0242] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0243] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0244] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A network-based SVG simulation method considering the dynamic characteristics of DC-side capacitors, characterized in that, include: A simulation model of a network-based SVG is established based on the control loop of the network-based SVG. The simulation model is solved by solving each component, and the differential equations are linearized into algebraic equations based on the trapezoidal integral method. Based on the solutions of each component of the simulation model, the response characteristics of the simulated mesh SVG under various working conditions are simulated. The control mechanism of the mesh-type SVG includes: Virtual inertia and damping control, DC side voltage control, virtual excitation control, overcurrent limiting, and grid connection interface; The simulation model includes: a virtual inertia and damping control model, a DC side voltage control model, a virtual excitation control model, an overcurrent limiting model, and a grid connection interface model; The DC-side voltage control model simulates the voltage changes caused by the charging and discharging of the DC capacitor based on the active power measurements exchanged between the grid-type SVG and the system, and generates active power increments. The DC-side voltage control model also considers the effects of DC capacitor undervoltage and overvoltage protection. The virtual damping control model generates a virtual internal potential phase angle reference value for a grid-type SVG based on the input active power increment, active power measurement value, and active power reference value. The virtual excitation control model selects constant reactive power control or constant voltage control, and generates a reference value for the virtual internal potential amplitude of the grid-type SVG based on the measured values ​​of reactive power or voltage and the reference values ​​of reactive power or voltage. The virtual excitation control model considers the constraint of DC capacitor voltage on the modulation capability of the grid-type SVG. The overcurrent limiting model generates the virtual internal potential amplitude and the actual phase angle value based on the virtual internal potential amplitude, the phase angle reference value, and the device overcurrent limit. The grid connection interface model generates active and reactive current components injected into the grid based on the virtual internal potential and the magnitude of the connection reactance.

2. The mesh-based SVG simulation method according to claim 1, characterized in that, The DC-side voltage control model includes the following components: Calculate the DC capacitor voltage based on the active power measurements exchanged between the network-type SVG and the system. V dc The calculation formula is as follows: (1) in, P ref To facilitate the exchange of active power reference values ​​between the network-type SVG and the system, C The size of the DC capacitor. P This refers to the active power measurement value of a grid-type SVG; The active power increment ΔP is calculated based on DC voltage using the following formula: in, K P for PI Controller proportional gain coefficient, K I for PI Controller integral gain coefficient; in, K P and K I Adjustments are made by identifying each stage and verifying the whole process. The least squares method is used to fit the identified stages. The operating state of a grid-type SVG is determined based on DC voltage, and the calculation formula is as follows: (3) in, I MODE If the value is 1, then the real part of the injected grid current in the grid-type SVG is 1. I X and the imaginary part of the injected grid current in the grid-type SVG I Y Normal output, I MODE If it is 0, then I X and I Y Output set to 0, V H T is the threshold for DC capacitor overvoltage protection operation. H For the DC capacitor overvoltage protection operation delay, V L T is the threshold for DC capacitor undervoltage protection operation. L This is a delay in the operation of the DC capacitor undervoltage protection.

3. The mesh-based SVG simulation method according to claim 1, characterized in that, The virtual inertia and damping control model includes the following components: The virtual rotational speed is calculated based on the active power increment, measured active power, and active power baseline value. The calculation formula is as follows: (4) Where ω0 is the system's rated speed, J For virtual rotational inertia, D This is the virtual damping coefficient. ω For SVG virtual rotation speed; The virtual phase is generated based on the virtual rotational speed, and the calculation formula is as follows: (5)。 4. The mesh-based SVG simulation method according to claim 1, characterized in that, The virtual excitation control model includes the following components: Based on the measured voltage or reactive power reference value of the SVG access point in a grid-type SVG, the no-load excitation electromotive force is calculated using the following formula: (6) in, K For series PI Gain coefficient, K V Choosing factors for proportional integrals T 1 , T 2 , T 3 and T 4 They are connected in series. PI Time constant, K PQ for PI Controller proportional gain coefficient, K IQ for PI Controller integral gain coefficient; in, K , K V , K PQ and K IQ Adjustments are made by identifying each stage and verifying the whole process. The least squares method is used to fit the identified stages. Calculation of the limiting value based on the no-load excitation electromotive force The calculation formula is as follows: (7) in, This is the previous value for the transient potential limiting. i d It is the DC current component. x d For synchronization reactance, For direct-axis transient reactance, The direct-axis open-circuit transient time constant; The virtual internal potential amplitude is calculated based on the pre-limiting value and the DC capacitor voltage. The calculation formula is as follows: (8) In the formula, K lim For overmodulation coefficients, piecewise functions are required to represent them for certain types of generator sets; in, K lim Adjustments are made by identifying each stage and verifying the whole process. The least squares method is used to fit the identified stages.

5. The mesh-based SVG simulation method according to claim 1, characterized in that, The overcurrent limiting model and grid connection interface model include the following components: The grid-connected current is calculated based on the virtual internal potential and connection reactance, using the following formula: (9) (10) in, X T To connect the reactor, V x This is the measured value of the real part of the grid connection point current. V y This is the measured value of the imaginary part of the grid connection point current. E x The real part of the virtual internal potential. E y This represents the imaginary part of the virtual internal potential. like I Greater than the overcurrent limit requirement Imax Then, based on the magnitude of the limiting current, the voltage deviation, and the current limiting value, the total amplitude of the virtual impedance is obtained, and the virtual resistance is calculated. R v Size, calculated using the following formula: (11) (12) in, X v For virtual reactance, k This represents the ratio of virtual resistance to virtual reactance. By R v and X v The current reference value after current limiting is calculated using the following formula: (13)。 6. The mesh-based SVG simulation method according to claim 1, characterized in that, The solution formula for the differential equation, which is linearized into an algebraic equation using the trapezoidal integral method, is as follows: (14) (15) in, y 0 is the current value. y The value to be solved is... h This is the simulated step size.

7. A network-based SVG simulation system considering the dynamic characteristics of DC-side capacitance, characterized in that, include: The modeling unit is used to establish a simulation model of the network-based SVG for the control loop. The solution unit is used to solve each part of the simulation model, wherein the differential equations are linearized into algebraic equations based on the trapezoidal integral method for solution. The simulation unit is used to simulate the response characteristics of the mesh-type SVG under various working conditions based on the solutions of each part of the simulation model. The control mechanism of the mesh-type SVG includes: Virtual inertia and damping control, DC side voltage control, virtual excitation control, overcurrent limiting, and grid connection interface; The simulation model includes: a virtual inertia and damping control model, a DC side voltage control model, a virtual excitation control model, an overcurrent limiting model, and a grid connection interface model; The DC-side voltage control model simulates the voltage changes caused by the charging and discharging of the DC capacitor based on the active power measurements exchanged between the grid-type SVG and the system, and generates active power increments. The DC-side voltage control model also considers the effects of DC capacitor undervoltage and overvoltage protection. The virtual damping control model generates a virtual internal potential phase angle reference value for a grid-type SVG based on the input active power increment, active power measurement value, and active power reference value. The virtual excitation control model selects constant reactive power control or constant voltage control, and generates a reference value for the virtual internal potential amplitude of the grid-type SVG based on the measured values ​​of reactive power or voltage and the reference values ​​of reactive power or voltage. The virtual excitation control model considers the constraint of DC capacitor voltage on the modulation capability of the grid-type SVG. The overcurrent limiting model generates the virtual internal potential amplitude and the actual phase angle value based on the virtual internal potential amplitude, the phase angle reference value, and the device overcurrent limit. The grid connection interface model generates active and reactive current components injected into the grid based on the virtual internal potential and the magnitude of the connection reactance.

8. The mesh-based SVG simulation system according to claim 7, characterized in that, The DC-side voltage control model includes the following components: Calculate the DC capacitor voltage based on the active power measurements exchanged between the network-type SVG and the system. V dc The calculation formula is as follows: (1) in, P ref To facilitate the exchange of active power reference values ​​between the network-type SVG and the system, C The size of the DC capacitor. P This refers to the active power measurement value of a grid-type SVG; The active power increment ΔP is calculated based on DC voltage using the following formula: (2) in, K P for PI Controller proportional gain coefficient, K I for PI Controller integral gain coefficient; in, K P and K I Adjustments are made by identifying each stage and verifying the whole process. The least squares method is used to fit the identified stages. The operating state of a grid-type SVG is determined based on DC voltage, and the calculation formula is as follows: (3) in, I MODE If the value is 1, then the real part of the injected grid current in the grid-type SVG is 1. I X and the imaginary part of the injected grid current in the grid-type SVG I Y Normal output, I MODE If it is 0, then I X and I Y Output set to 0, V H T is the threshold for DC capacitor overvoltage protection operation. H For the DC capacitor overvoltage protection operation delay, V L T is the threshold for DC capacitor undervoltage protection operation. L This is a delay in the operation of the DC capacitor undervoltage protection.

9. The mesh-based SVG simulation system according to claim 7, characterized in that, The virtual inertia and damping control model includes the following components: The virtual rotational speed is calculated based on the active power increment, measured active power, and active power baseline value. The calculation formula is as follows: (4) Where ω0 is the system's rated speed, J For virtual rotational inertia, D This is the virtual damping coefficient. ω For SVG virtual rotation speed; The virtual phase is generated based on the virtual rotational speed, and the calculation formula is as follows: (5)。 10. The mesh-based SVG simulation system according to claim 7, characterized in that, The virtual excitation control model includes the following components: Based on the measured voltage or reactive power reference value of the SVG access point in a grid-type SVG, the no-load excitation electromotive force is calculated using the following formula: (6) in, K For series PI Gain coefficient, K V Choosing factors for proportional integrals T 1 , T 2 , T 3 and T 4 They are connected in series. PI Time constant, K PQ for PI Controller proportional gain coefficient, K IQ for PI Controller integral gain coefficient; in, K , K V , K PQ and K IQ Adjustments were made by identifying each stage individually and verifying the overall process. The identification of each stage was performed using the least squares method for fitting; the limiting value was calculated based on the no-load excitation electromotive force. The calculation formula is as follows: (7) in, This is the previous value for the transient potential limiting. i d It is the DC current component. x d For synchronization reactance, For direct-axis transient reactance, The direct-axis open-circuit transient time constant; The virtual internal potential amplitude is calculated based on the pre-limiting value and the DC capacitor voltage. The calculation formula is as follows: (8) In the formula, K lim For overmodulation coefficients, piecewise functions are required to represent them for certain types of generator sets; in, K lim Adjustments are made by identifying each stage and verifying the whole process. The least squares method is used to fit the identified stages.

11. The mesh-based SVG simulation system according to claim 7, characterized in that, The overcurrent limiting model and grid connection interface model include the following components: The grid-connected current is calculated based on the virtual internal potential and connection reactance, using the following formula: (9) (10) in, X T To connect the reactor, V x This is the measured value of the real part of the grid connection point current. V y This is the measured value of the imaginary part of the grid connection point current. E x The real part of the virtual internal potential. E y This represents the imaginary part of the virtual internal potential. like I Greater than the overcurrent limit requirement Imax Then, based on the magnitude of the limiting current, the voltage deviation, and the current limiting value, the total amplitude of the virtual impedance is obtained, and the virtual resistance is calculated. R v Size, calculated using the following formula: (11) (12) in, X v For virtual reactance, k This represents the ratio of virtual resistance to virtual reactance. By R v and X v The current reference value after current limiting is calculated using the following formula: (13)。 12. The mesh-based SVG simulation system according to claim 7, characterized in that, The solution formula for the differential equation, which is linearized into an algebraic equation using the trapezoidal integral method, is as follows: (14) (15) in, y 0 is the current value. y The value to be solved is... h This is the simulated step size.

13. A computer device, characterized in that, include: One or more processors; A processor is used to execute one or more programs; When the one or more programs are executed by the one or more processors, the method described in any one of claims 1-6 is implemented.

14. A computer-readable storage medium, characterized in that, It contains a computer program, which, when executed, implements the method as described in any one of claims 1-6.

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