Construction method and device of voltage source converter grid-connected system parameter feasible region

Abstract

The invention provides a voltage source converter grid-connected system parameter feasible region construction method and device, and relates to the field of power system transient stability analysis, and the method comprises the steps: constructing a grid-connected system simplified mathematical model according to a topological structure of a voltage source converter grid-connected system; deriving the simplified mathematical model of the grid-connected system to obtain a second-order equivalent dynamic equation; and performing numerical integration and equal area calculation on the second-order equivalent dynamic equation to determine a voltage source converter grid-connected system parameter feasible region. According to the method, the parameter feasible region of the voltage source converter in the whole fault process can be constructed aiming at the transient synchronous stability problem caused by the weak connection system of the voltage source converter in the whole fault process.

Description

Technical Field

[0001] The present application relates to the field of power system transient stability analysis, and specifically to a method and device for constructing a parameter feasible region of a voltage source converter grid-connected system. Background Art

[0002] At present, new energy has become a key component of the new power system. However, due to the uneven distribution between new energy resources and electricity loads, new energy grid-connected devices often operate in areas with weak power grids. In this case, complex coupling effects will occur between new energy grid-connected devices and weak power grids, thus triggering serious system stability problems.

[0003] The low-voltage ride-through control of new energy adjusts the output current according to the terminal voltage amplitude. The traditional transient stability analysis based on the constant current assumption does not conform to the actual situation and may cause misjudgment of the analysis results. After the voltage source converter (VSC) is subjected to large disturbances such as grid faults, it is prone to trigger system transient synchronous stability problems. Since there is less research on the VSC current injection in the non-current limiting control mode, the parameter analysis of such problems will affect the system transient stability.

[0004] When a fault occurs, the system may lose transient stability, but after the fault is cleared, the system may recover transient stability. Therefore, simply studying the stability during the fault period has certain limitations.

[0005] This section aims to provide background or context for the embodiments of the present invention described in the claims. The descriptions herein are not admitted to be prior art merely because they are included in this section. Summary of the Invention

[0006] Aiming at the problems in the prior art, the present application provides a method and device for constructing a parameter feasible region of a voltage source converter grid-connected system, which can construct a parameter feasible region of the voltage source converter during the whole process of a fault for the transient synchronous stability problem caused by the weak connection system of the voltage source converter during the whole process of a fault.

[0007] To solve the above technical problems, the present application provides the following technical solutions:

[0008] In a first aspect, the present application provides a method for constructing a parameter feasible region of a voltage source converter grid-connected system, including:

[0009] Constructing a simplified mathematical model of the grid-connected system according to the topological structure of the voltage source converter grid-connected system;

[0010] Deriving the simplified mathematical model of the grid-connected system to obtain a second-order equivalent dynamic equation;

[0011] Numerically integrate the second-order equivalent dynamic equation and perform equal-area calculation to determine the feasible region of the parameters of the voltage-source converter grid-connected system.

[0012] Furthermore, the simplified mathematical model of the grid-connected system includes a pre-fault model; constructing the simplified mathematical model of the grid-connected system according to the topological structure of the voltage-source converter grid-connected system includes:

[0013] Obtain the phase angle of the phase-locked loop, the fault voltage component, the q-axis component of the grid connection point voltage, the component of the active power before filtering, and the component of the active power after filtering according to the topological structure;

[0014] Calculate the first-derivative integral term according to the phase angle of the phase-locked loop, the fault voltage component, the q-axis component of the grid connection point voltage, the component of the active power before filtering, and the component of the active power after filtering;

[0015] Calculate the reference term of the injected current power according to the component of the AC voltage after filtering, the component of the grid connection point voltage, the reference value of the AC voltage, the reference value of the active power, the component of the active power after filtering, and the first-derivative integral term;

[0016] Construct the pre-fault model according to the first-derivative integral term and the reference term of the injected current power.

[0017] Furthermore, the simplified mathematical model of the grid-connected system includes a fault-in-progress model; constructing the simplified mathematical model of the grid-connected system according to the topological structure of the voltage-source converter grid-connected system includes:

[0018] Obtain the non-linear equation during the fault according to the low-voltage ride-through coefficient and the current limit value;

[0019] Substitute the relationship function between the d-axis component and the q-axis component in the reference term of the injected current power into the non-linear equation during the fault to obtain the fault-in-progress model.

[0020] Furthermore, the simplified mathematical model of the grid-connected system includes a post-fault model; constructing the simplified mathematical model of the grid-connected system according to the topological structure of the voltage-source converter grid-connected system includes:

[0021] Derive the reference value term of the active power based on the recovery coefficient for the given reference value of the system active power;

[0022] Substitute the reference value term of the active power into the pre-fault model to obtain the post-fault model.

[0023] Furthermore, deriving the second-order equivalent dynamic equation from the simplified mathematical model of the grid-connected system includes:

[0024] Derive the equivalent inertia, equivalent damping, equivalent virtual mechanical power, and equivalent virtual electromagnetic power from the simplified mathematical model of the grid-connected system;

[0025] Determine the second-order equivalent dynamic equation according to the equivalent inertia, equivalent damping, equivalent virtual mechanical power, and equivalent virtual electromagnetic power; wherein, the second-order equivalent dynamic equation includes a pre-fault equation, a fault equation, and a post-fault equation.

[0026] Further, the numerical integration and equal-area calculation of the second-order equivalent dynamic equation to determine the feasible region of the voltage source converter grid-connected system parameters includes:

[0027] Perform numerical integration and equal-area calculation on the pre-fault equation and the fault equation to obtain the accelerating area;

[0028] Perform numerical integration and equal-area calculation on the post-fault equation to obtain the decelerating area;

[0029] If the accelerating area is not greater than the decelerating area, it is determined that the voltage source converter grid-connected system is transiently stable after the fault is removed;

[0030] If the accelerating area is greater than the decelerating area, it is determined that the voltage source converter grid-connected system is transiently unstable after the fault is removed;

[0031] Determine the feasible region of the voltage source converter grid-connected system parameters according to whether the voltage source converter grid-connected system is transiently stable after the fault is removed.

[0032] In a second aspect, the present application provides a device for constructing a feasible region of voltage source converter grid-connected system parameters, including:

[0033] A simplified model construction unit for constructing a simplified mathematical model of the grid-connected system according to the topological structure of the voltage source converter grid-connected system;

[0034] A dynamic equation generation unit for differentiating the simplified mathematical model of the grid-connected system to obtain a second-order equivalent dynamic equation;

[0035] A feasible region determination unit for performing numerical integration and equal-area calculation on the second-order equivalent dynamic equation to determine the feasible region of the voltage source converter grid-connected system parameters.

[0036] Further, the simplified mathematical model of the grid-connected system includes a pre-fault model; the simplified model construction unit includes:

[0037] A phase angle component acquisition module for obtaining the phase angle of the phase-locked loop, the fault voltage component, the q-axis component of the grid connection point voltage, the component before active power filtering, and the component after active power filtering according to the topological structure;

[0038] A derivative integral determination module, configured to calculate a first derivative integral term according to the phase angle of the phase-locked loop, the fault voltage component, the q-axis component of the grid-connected point voltage, the component of the active power before filtering, and the component of the active power after filtering;

[0039] A power reference determination module, configured to calculate an injected current power reference term according to the component of the AC voltage after filtering, the grid-connected point voltage component, the AC voltage reference value, the active power reference value, the component of the active power after filtering, and the first derivative integral term;

[0040] A pre-fault model construction module, configured to determine the pre-fault model according to the first derivative integral term and the injected current power reference term.

[0041] Further, the simplified mathematical model of the grid-connected system includes a mid-fault model; the simplified model construction unit includes:

[0042] An equation determination module, configured to obtain a mid-fault non-linear equation according to the low voltage ride-through coefficient and the current limit value;

[0043] A mid-fault model construction module, configured to substitute the relationship function between the d-axis component and the q-axis component in the injected current power reference term into the mid-fault non-linear equation to obtain the mid-fault model.

[0044] Further, the simplified mathematical model of the grid-connected system includes a post-fault model; the simplified model construction unit includes:

[0045] A reference value term generation module, configured to take the derivative of the system-given active power reference value based on the recovery coefficient to obtain an active power reference value term;

[0046] A post-fault model construction module, configured to substitute the active power reference value term into the pre-fault model to obtain the post-fault model.

[0047] Further, the dynamic equation generation unit includes:

[0048] A model derivative module, configured to take the derivative of the simplified mathematical model of the grid-connected system to obtain an equivalent inertia, an equivalent damping, an equivalent virtual mechanical power, and an equivalent virtual electromagnetic power;

[0049] A dynamic equation generation module, configured to determine the second-order equivalent dynamic equation according to the equivalent inertia, the equivalent damping, the equivalent virtual mechanical power, and the equivalent virtual electromagnetic power; wherein, the second-order equivalent dynamic equation includes a pre-fault equation, a mid-fault equation, and a post-fault equation.

[0050] Further, the feasible region determination unit includes:

[0051] An acceleration area calculation module, configured to perform numerical integration and equal area calculation on the pre-fault equation and the in-fault equation to obtain an acceleration area;

[0052] A deceleration area calculation module, configured to perform numerical integration and equal area calculation on the post-fault equation to obtain a deceleration area;

[0053] A transient stability determination module, configured to determine that the voltage source converter grid-connected system is transiently stable after fault removal if the acceleration area is not greater than the deceleration area;

[0054] A transient instability determination module, configured to determine that the voltage source converter grid-connected system is transiently unstable after fault removal if the acceleration area is greater than the deceleration area;

[0055] A feasible region determination module, configured to determine a feasible region of voltage source converter grid-connected system parameters according to whether the voltage source converter grid-connected system is transiently stable after fault removal.

[0056] In a third aspect, the present application provides an electronic device including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the steps of the method for constructing a feasible region of voltage source converter grid-connected system parameters are implemented.

[0057] In a fourth aspect, the present application provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method for constructing a feasible region of voltage source converter grid-connected system parameters are implemented.

[0058] In a fifth aspect, the present application provides a computer program product, including a computer program / instructions. When the computer program / instructions are executed by a processor, the steps of the method for constructing a feasible region of voltage source converter grid-connected system parameters are implemented.

[0059] Aiming at the problems in the prior art, the method and device for constructing a feasible region of voltage source converter grid-connected system parameters provided by the present application can establish and verify a system model of the voltage source converter grid-connected system under the whole process of fault under an assumption, and simplify the system model based on control structures such as an outer loop - phase-locked loop; carry out system transient stability analysis based on the equal area rule and numerical integration method, and consider the low-voltage ride-through coefficient - active current feasible region under the non-limiting case to ensure that the system provides stable and effective support capabilities within the feasible region. Description of the Drawings

[0060] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0061] Figure 1 This is the main circuit structure and control system of the WG-VSC in the embodiments of this application;

[0062] Figure 2 This is the transient instability simulation phenomenon in the embodiments of this application;

[0063] Figure 3 This is the mechanism process of revealing the whole fault process by the equal area criterion in the embodiments of this application;

[0064] Figure 4 This is the feasible region of the low-voltage ride-through coefficient K - active current i tdref in the embodiments of this application;

[0065] Figure 5 This is the feasible region of K - i tdref when the cut-off time is 0.3s, 0.4s, and 0.5s in the embodiments of this application;

[0066] Figure 6 This is the flowchart of the method for constructing the feasible region of the parameters of the voltage source converter grid-connected system in the embodiments of this application;

[0067] Figure 7 This is the flowchart of constructing the pre-fault model in the embodiments of this application;

[0068] Figure 8 This is the flowchart of constructing the in-fault model in the embodiments of this application;

[0069] Figure 9 This is the flowchart of constructing the post-fault model in the embodiments of this application;

[0070] Figure 10 This is the flowchart of obtaining the second-order equivalent dynamic equation in the embodiments of this application;

[0071] Figure 11 This is the flowchart of determining the feasible region of the parameters of the voltage source converter grid-connected system in the embodiments of this application;

[0072] Figure 12 This is the structural diagram of the device for constructing the feasible region of the parameters of the voltage source converter grid-connected system in the embodiments of this application;

[0073] Figure 13 This is the structural diagram of one of the simplified model construction units in the embodiments of this application;

[0074] Figure 14 This is the structure diagram of the second simplified model construction unit in the embodiments of the present application;

[0075] Figure 15 This is the structure diagram of the third simplified model construction unit in the embodiments of the present application;

[0076] Figure 16 This is the structure diagram of the dynamic equation generation unit in the embodiments of the present application;

[0077] Figure 17 This is the structure diagram of the feasible region determination unit in the embodiments of the present application;

[0078] Figure 18 This is the schematic structural diagram of the electronic device in the embodiments of the present application. Specific Embodiments

[0079] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer and more understandable, the following further elaborates on the embodiments of the present invention in conjunction with the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but do not limit the present invention.

[0080] The information collected in the technical solutions of the present application is information and data authorized by the user or fully authorized by all parties. Moreover, for the processing of relevant data, such as collection, storage, use, processing, transmission, provision, disclosure, and application, etc., all comply with the relevant laws, regulations, and standards of relevant countries and regions, adopt necessary confidentiality measures, do not violate public order and good customs, and provide corresponding operation entrances for users to choose to authorize or reject.

[0081] Provide corresponding operation entrances for users to choose to agree or reject the automated decision-making results; if the user chooses to reject, then enter the expert decision-making process.

[0082] In one embodiment, referring to Figure 6 , in order to be able to address the transient synchronization stability problem caused by a weak-connected system of a voltage source converter throughout the entire fault process and construct the parameter feasible region of the voltage source converter throughout the entire fault process, the present application provides a method for constructing the parameter feasible region of a voltage source converter grid-connected system, including:

[0083] S101: Construct a simplified mathematical model of the grid-connected system according to the topological structure of the voltage source converter grid-connected system;

[0084] S102: Take the derivative of the simplified mathematical model of the grid-connected system to obtain a second-order equivalent dynamic equation;

[0085] S103: Perform numerical integration and equal-area calculation on the second-order equivalent dynamic equation, and determine the parameter feasible region of the voltage source converter grid-connected system.

[0086] It is understandable that the embodiment of the present application discloses a method for constructing a feasible region of parameters of a voltage source converter grid-connected system, which considers the dynamic interaction between the outer loop and the phase-locked loop control links, and the low-voltage ride-through coefficient and active current during a fault without amplitude limitation, further enhancing the stable support ability of the voltage source converter grid-connected system throughout the entire fault process.

[0087] First, regarding the low-frequency oscillation stability problem of the system after the weak-grid connected voltage source converter (WG-VSC) is grid-connected under different working conditions, the embodiment of the present application constructs a WG-VSC system model at the transient stability analysis time scale based on the multi-time scale model simplification principle, and builds a detailed electromagnetic transient model of the WG-VSC system to verify the effectiveness of the above WG-VSC system model. The WG-VSC system model considers the influence of different control dynamics on the system in three stages: before the fault, during the fault, and after the fault, and simplifies and reduces the order. To simplify the analysis process, the following common assumptions are considered:

[0088] 1) The current loop bandwidth is much higher than the outer loop and PLL bandwidth, so the dynamic process of the current inner loop is ignored, that is, it is considered that before the VSC outer loop and PLL act, the d-axis and q-axis currents I td , I tq have completed the tracking of the reference values I tdref , I tqref ;

[0089] 2) The electromagnetic transient processes of the LC filter and the AC network are ignored. Such links only affect the dynamic characteristics of the system at the high-frequency time scale.

[0090] Based on the above assumptions, a simplified mathematical model of the WG-VSC system for analyzing the entire fault process can be obtained for transient stability analysis. Among them, the simplified mathematical model includes a pre-fault model, a fault model, and a post-fault model.

[0091] Secondly, the second derivative of the simplified mathematical model is obtained to get the second-order equivalent dynamic equation. Taking the second-order equivalent dynamic equation as the core, based on the method combining numerical integration and the equal-area rule, the transient synchronous instability condition of the WG-VSC system is analyzed to obtain the corresponding accelerating area and decelerating area.

[0092] Then, the given values of the low-voltage ride-through coefficient and active current during the fault will affect the transient stability state of the system after the fault is cleared. Considering the feasible region of the low-voltage ride-through coefficient - active current without amplitude limitation to ensure that the system provides stable reactive power support within the feasible region.

[0093] Finally, the impact of the fault clearing time on the low-ride-through coefficient - active current feasible region of the WG-VSC system is analyzed.

[0094] As can be seen from the above description, the method and device for constructing the feasible region of the parameters of the voltage source converter grid-connected system provided by this application can establish and verify the system model of the voltage source converter grid-connected system under the whole fault process under the hypothesis, and simplify the system model based on control structures such as the outer loop - phase-locked loop; the transient stability analysis of the system is carried out based on the equal area rule and numerical integration method, considering the low-ride-through coefficient - active current feasible region in the case of no clipping to ensure that the system provides stable and effective support within the feasible region.

[0095] In one embodiment, refer to Figure 7 , the simplified mathematical model of the grid-connected system includes a pre-fault model; the construction of the simplified mathematical model of the grid-connected system according to the topological structure of the voltage source converter grid-connected system includes:

[0096] S201: Obtain the phase angle of the phase-locked loop, the fault voltage component, the q-axis component of the grid connection point voltage, the component of the active power before filtering, and the component of the active power after filtering according to the topological structure;

[0097] S202: Calculate the first derivative integral term according to the phase angle of the phase-locked loop, the fault voltage component, the q-axis component of the grid connection point voltage, the component of the active power before filtering, and the component of the active power after filtering;

[0098] S203: Calculate the reference term of the injected current power according to the component of the AC voltage after filtering, the component of the grid connection point voltage, the reference value of the AC voltage, the reference value of the active power, the component of the active power after filtering, and the first derivative integral term;

[0099] S204: Construct the pre-fault model according to the first derivative integral term and the reference term of the injected current power.

[0100] It can be understood that specifically, the construction process of the simplified mathematical model corresponding to the topological structure of the WG-VSC system is as follows:

[0101] Simplify the weakly-connected VSC grid-connected system based on the "phase-locked loop - outer loop" control, ignore the high-frequency dynamics in the system transient process, and establish a simplified mathematical model of the weakly-connected VSC grid-connected system under the whole fault process (also called the simplified mathematical model of the grid-connected system).

[0102] Figure 1 The main circuit topology and control system of the WG-VSC system are shown. The source side includes the input power P ref , the source side capacitor C, and the DC voltage U dc ; the VSC is connected to the grid through an LC filter, and the filter inductance and capacitance are L f and Cf ; The voltage at the point of common coupling (PCC) on the AC side is V t ∠θ t , and the grid voltage is V s ∠0°; Z g1 and Z g2 are the equivalent grid-side impedances, Z g1 = R g1 + jX g1 , Z g2 = R g2 + jX g2 .

[0103] Considering the entire fault process, it can be divided into three stages: before the fault, during the fault, and after the fault, to construct the system model respectively. Among them, the construction process of the model before the fault (t < t0) is as follows:

[0104] The active current and reactive current are generated by active power control (P control) and AC voltage control (V t control). To filter out high-frequency disturbances, usually the detected values of active power P and AC voltage V t are low-pass filtered. Among them, T P and T V are the filter constants. Establish the differential-algebraic equation (DAE) of the WG-VSC system.

[0105]

[0106] In the formula, θ pll is the phase angle of the phase-locked loop, k p and k i are the proportional and integral coefficients of the phase-locked loop respectively, k p1 and k i1 are the proportional and integral coefficients of the active outer loop respectively, k p2 and k i2 are the proportional and integral coefficients of the reactive outer loop respectively, V F is the fault voltage component, V td is the d-axis component of the voltage at the point of common coupling, V tq is the q-axis component of the voltage at the point of common coupling, x pll is the integral term of V tq , P, P f and P ref are the components of the active power before filtering, after filtering, and the reference value respectively, x P is the integral term of P - P f , V t is the AC voltage, V tfis the filtered component of the AC voltage, V tdf , V tqf are the d-axis component and q-axis component respectively, V tref is the AC voltage reference value, x v is V tref -V t is the integral term of, R e and X e are the equivalent resistance and reactance of the power grid respectively, i tdref and i tqref are the active and reactive components of the injected current at this stage respectively, P ref is the active power reference value. V td and V tq are expressed as:

[0107] As can be seen from the above description, the method and device for constructing the feasible region of the parameters of the voltage source converter grid-connected system provided by this application can construct a simplified mathematical model of the grid-connected system according to the topological structure of the voltage source converter grid-connected system.

[0108] In one embodiment, referring to Figure 8 , the simplified mathematical model of the grid-connected system includes a model during a fault; the constructing of the simplified mathematical model of the grid-connected system according to the topological structure of the voltage source converter grid-connected system includes:

[0109] S301: Obtain the nonlinear equation during the fault according to the low voltage ride through coefficient and the current limit value;

[0110] S302: Substitute the relationship function between the d-axis component and the q-axis component in the injected current power reference term into the nonlinear equation during the fault to obtain the model during the fault.

[0111] It can be understood that during the fault and when the limit is not triggered (t0 < t < t F ), the construction process of the model during the fault is as follows: Considering that after the fault occurs, the voltage at the PCC point drops. Therefore, in order to prevent the reactive injected current from exceeding the limit value, under the low voltage ride through (LVRT) strategy (B), the mathematical model of the WG-VSC system only includes the PLL dynamics. Among them, the application of the low voltage ride through strategy in the embodiments of this application can be understood as: providing corresponding low voltage strategies during the network low voltage stage caused by the fault to perform reactive power support, so as to ensure the transient stability during the whole process of the fault.

[0112]

[0113] In the formula, K is the low ride through coefficient, I max is the current limit value.

[0114] A non-linear model (also known as a non-linear equation) of the system during a fault can be obtained:

[0115]

[0116] Wherein, i tqref = f(K, i tdref ) is a function of i tqref with respect to K and i tdref after considering the low voltage ride-through strategy (B), and x1 is the aforementioned θ pll . Equation (C) can be transformed into Equation (D):

[0117]

[0118] As can be seen from the above description, the method and device for constructing the feasible region of the parameters of the voltage source converter grid-connected system provided by the present application can construct a simplified mathematical model of the grid-connected system according to the topological structure of the voltage source converter grid-connected system.

[0119] In one embodiment, referring to Figure 9 , the simplified mathematical model of the grid-connected system includes a post-fault model; the constructing of the simplified mathematical model of the grid-connected system according to the topological structure of the voltage source converter grid-connected system includes:

[0120] S401: Derive the reference value of the given active power of the system based on the recovery coefficient to obtain the reference value term of the active power;

[0121] S402: Substitute the reference value term of the active power into the pre-fault model to obtain the post-fault model.

[0122] It can be understood that the construction process of the post-fault model is as follows: after the fault is removed, the voltage at the PCC point increases, and the active current and reactive current switch to the normal operation control strategy. When the recovery coefficient τ = 0, it means that P ref directly returns to the given value; when τ ≠ 0, it means that P ref needs to return to the given value at a certain rate. At this time, the following equation needs to be added to the system DAE equation (A):

[0123]

[0124] Wherein, P in represents the reference value of the active power given to the system control after P ref returns at the rate of the recovery coefficient τ. At this time, the system DAE equation is transformed into:

[0125]

[0126] Among them, the specific symbol meanings are as described above.

[0127] Most of the existing technologies focus on the transient stability analysis during faults, while ignoring the system transient stability throughout the entire fault process. However, when the fault is cleared and how to set the low-ride-through coefficient and active current during the fault will affect the system transient stability. Taking the example in Table 1 as an illustration, the simulation diagram is as shown in Figure 2 and the specific system parameters are shown in Table 2. Among them, Figure 2 the black line segment in represents the simulation results generated using the detailed electromagnetic transient simulation switch model (existing technology model), and the red line segment represents the simulation results generated using the mathematical large-signal model provided in this application. The simulation results of the two can be compared.

[0128] Table 1 Simulation Example

[0129]

[0130] Table 2 System Parameters

[0131]

[0132] 1) The electromagnetic transient simulation results based on the detailed switch model are highly coincident with the time-domain simulation results of the simplified mathematical analysis models (A) - (F), verifying the feasibility and effectiveness of the mathematical models (A) - (F) in analyzing the transient instability problem of the WG-VSC system after a fault.

[0133] 2) Without triggering the limit, considering the LVRT strategy, from Case1, Case3, and Case4, it can be seen that the setting of the active current i tdref and the low-ride-through coefficient K will affect the transient stability results of the system after a fault. Therefore, constructing the feasible region of the low-ride-through coefficient K - active current i tdref is beneficial to ensuring the transient stability of the system throughout the entire fault process. In addition, from Case1 and Case2, it can be seen that the fault clearing time will further affect the stability results.

[0134] As can be seen from the above description, the method and device for constructing the feasible region of the voltage source converter grid-connected system parameters provided in this application can construct a simplified mathematical model of the grid-connected system according to the topological structure of the voltage source converter grid-connected system.

[0135] In one embodiment, referring to Figure 10 , taking the derivative of the simplified mathematical model of the grid-connected system to obtain the second-order equivalent dynamic equation includes:

[0136] S501: Taking the derivative of the simplified mathematical model of the grid-connected system to obtain the equivalent inertia, equivalent damping, equivalent virtual mechanical power, and equivalent virtual electromagnetic power;

[0137] S502: Determine the second-order equivalent dynamic equation according to the equivalent inertia, equivalent damping, equivalent virtual mechanical power, and equivalent virtual electromagnetic power; where the second-order equivalent dynamic equation includes a pre-fault equation, a fault equation, and a post-fault equation.

[0138] It can be understood that by taking the derivatives of equations (A), (D), and (F) in the previous steps respectively, and substituting (B) and (E) into the derivative results, the unified second-order equivalent dynamic equation (G) is obtained.

[0139]

[0140] In the formula, J, D, P meq and P eeq respectively represent equivalent inertia, equivalent damping, equivalent virtual mechanical power, and equivalent virtual electromagnetic power.

[0141] The specific P meq and P eeq analytical expressions in the system are different under different fault stages, as shown in Table 3 below.

[0142] Table 3 Analytical expressions of P meq and P eeq during the whole fault process

[0143]

[0144] In the table, P meq0 , P meq1 and P meq2 respectively represent the equivalent virtual mechanical power expressions before, during, and after the fault. P eeq0 , P eeq1 and P eeq2 respectively represent the equivalent virtual electromagnetic power expressions before, during, and after the fault.

[0145] During Figure 3 the transient process in the whole fault process shown is as follows:

[0146] First, at t = t0, δ = δ0, a system fault occurs, P meq1 > P eeq1 , δ starts to accelerate until the fault clearing point C, forming an equivalent acceleration area S acc ; Second, at t = t F , δ = δ F , the system fault is cleared, P meq2 < P eeq2 , δ starts to decelerate until P meq2 = P eeq2 , that is, δ = δ F , forming an equivalent maximum deceleration area S dec .

[0147] Due to P meq0 and P meq2 The expressions are very complex, so the method combining the equal - area method and numerical integration is used to calculate S acc and S dec .

[0148] As can be seen from the above description, the method and device for constructing the feasible region of the parameters of the voltage - source converter grid - connected system provided by this application can derive the simplified mathematical model of the grid - connected system to obtain the second - order equivalent dynamic equation.

[0149] In one embodiment, referring to Figure 11 , the numerical integration and equal - area calculation are performed on the second - order equivalent dynamic equation, and the feasible region of the parameters of the voltage - source converter grid - connected system is determined, including:

[0150] S601: Perform numerical integration and equal - area calculation on the pre - fault equation and the in - fault equation to obtain the accelerating area;

[0151] S602: Perform numerical integration and equal - area calculation on the post - fault equation to obtain the decelerating area;

[0152] S603: If the accelerating area is not greater than the decelerating area, it is determined that the voltage - source converter grid - connected system is transiently stable after the fault is cleared;

[0153] S604: If the accelerating area is greater than the decelerating area, it is determined that the voltage - source converter grid - connected system is transiently unstable after the fault is cleared;

[0154] S605: Determine the feasible region of the parameters of the voltage - source converter grid - connected system according to whether the voltage - source converter grid - connected system is transiently stable after the fault is cleared.

[0155] It can be understood that with the second - order dynamic equation (G) as the core, based on the method combining numerical integration and the equal - area rule, the generation mechanism of the transient synchronous instability phenomenon of the WG - VSC system is revealed, and the corresponding accelerating and decelerating areas are analyzed. The brief steps are as follows:

[0156] When a fault occurs, the system is in the in - fault stage, and the expression of the accelerating area is:

[0157] S acc = S acc + 1 / 2×(P meq1,F - P eeq1,F + P meq1,0 - P eeq1,0 )×(θ F - θ0) (H)

[0158] In the formula, S accFor the accelerating area, P meq1,F and P meq1,0 respectively represent the equivalent mechanical power at θ F and θ0 moments, P eeq1,F and P eeq1,0 respectively represent the equivalent electromagnetic power at θ F and θ0 moments.

[0159] When the fault is removed, the system is in the post - fault stage, and the decelerating area expression is:

[0160] S dec = S dec + 1 / 2×(P meq2,C - P eeq2,C + P meq2,F - P eeq2,F )×(θ C - θ F ) (I)

[0161] In the formula, S dec is the accelerating area, P meq2,F and P meq2,C respectively represent the equivalent mechanical power at θ F and θ C moments, P eeq2,F and P eeq2,C respectively represent the equivalent electromagnetic power at θ F and θ C moments.

[0162] If S acc ≤ S dec , the system can recover transient stability after the fault is removed; if S acc > S dec , the system will be transiently unstable after the fault is removed. Based on the above process, the transient stability during the whole fault process can be described and analyzed.

[0163] Next, considering the system stability after the low - voltage ride - through strategy, it is mainly affected by the parameter low - voltage ride - through coefficient K and the d - axis component i tdref of the injected current. Next, for equations (H) and (I) in step (2), a method combining numerical integration and the equal - area criterion will be used to calculate point by point, record the transient stability points, and thus construct the feasible region of K - i tdref so that the system transient stability during the whole fault process can be guaranteed within this region. If the post - fault injected active current and the set reactive low - voltage ride - through coefficient are within this feasible region, the transient stability during the whole fault process is ensured.

[0164] Based on this current feasible region, the influence of the cut - off time on K - i tdrefImpact on the feasible region. The cut-off time affects the specific values of analytical expressions such as the equivalent electromagnetic power and equivalent mechanical power during the pre-fault, fault, and post-fault stages, thereby further affecting K-i tdref The regional scope of the feasible region affects the transient stability of the system.

[0165] For example, when a specific set of operating conditions is selected, that is, a specific set of data for (K, i tdref ) is determined, the current specific operating conditions and equilibrium point information can be determined. Based on the method combining numerical integration and the equal-area criterion, the acceleration and deceleration areas under the current operating conditions are calculated through the previous steps (H) and (I) to judge the transient stability of the WG-VSC system at this time. When it is judged as transient instability, the current operating point and the specific data of (K, i tdref ) are discarded; when it is judged as transient stability, the specific data of (K, i tdref ) at this time are recorded. The remaining operating condition points are calculated repeatedly, and the current feasible region range of K-i tdref is formed point by point. This feasible region range includes all the (K, i tdref ) data corresponding to the transient stability conditions.

[0166] The steps are described as follows:

[0167] 1) Determine a specific set of data for (K, i tdref ) to determine the current specific operating conditions and equilibrium point information;

[0168] 2) Based on the method combining numerical integration and the equal-area criterion, calculate the acceleration and deceleration areas under the current operating conditions through equations (H) and (I) to judge the transient stability of the WG-VSC system at this time;

[0169] 3) When it is judged as transient instability, the current operating point and the specific data of (K, i tdref ) are discarded; when it is judged as transient stability, the specific data of (K, i tdref ) at this time are recorded. The remaining operating condition points are calculated repeatedly, and the current feasible region range of K-i tdref is formed point by point. This feasible region range includes all the (K, i tdref ) data corresponding to the transient stability conditions.

[0170] Taking a wind farm as an example, based on the "Technical Regulations for Wind Farms Connected to the Power System" GB / T 19963.1-2021, the value range of K is such that K can control the system stability within the range of 1 to 3 and play the role of low-voltage support under faults. Based on Algorithm 1, the feasible region (also known as the feasible stable region) of the low-voltage ride-through coefficient K - active current i tdref can be constructed as shown in Appendix Figure 4 .

[0171] See Figure 5 , considering that the feasible region of K-i tdref constructed during the fault is affected by the fault clearing time, a specific analysis is carried out. Taking the data in Table 2 as an example, the feasible regions of K-i tdref are constructed when the clearing times are t = 0.3 s, t = 0.4 s, and t = 0.5 s, as shown in the following figure. It can be seen that: (1) As the clearing time shortens, at the same low-ride-through coefficient, the corresponding value range of i tdref increases; (2) As the low-ride-through coefficient K increases, more active current can be injected during the fault, which also represents an improvement in the system stability performance.

[0172] Based on the same inventive concept, the embodiment of the present application also provides a device for constructing the feasible region of the parameters of the voltage source converter grid-connected system, which can be used to implement the method described in the above embodiment, as described in the following embodiment. Since the principle of solving problems by the device for constructing the feasible region of the parameters of the voltage source converter grid-connected system is similar to that of the method for constructing the feasible region of the parameters of the voltage source converter grid-connected system, the implementation of the device for constructing the feasible region of the parameters of the voltage source converter grid-connected system can refer to the implementation of the method for determining the software performance benchmark, and the repeated parts will not be described again. Hereinafter, the term "unit" or "module" can be a combination of software and / or hardware that can implement a predetermined function. Although the systems described in the following embodiments are preferably implemented in software, the implementation in hardware, or a combination of software and hardware, is also possible and contemplated.

[0173] In one embodiment, see Figure 12 , in order to be able to construct the parameter feasible region of the voltage source converter under the whole process of the fault for the transient synchronization stability problem caused by the voltage source converter weak connection system in the whole process of the fault, the present application provides a device for constructing the feasible region of the parameters of the voltage source converter grid-connected system, including: a simplified model construction unit 1201, a dynamic equation generation unit 1202, and a feasible region determination unit 1203.

[0174] The simplified model construction unit 1201 is configured to construct a simplified mathematical model of the grid-connected system according to the topological structure of the voltage source converter grid-connected system;

[0175] The dynamic equation generation unit 1202 is configured to derive the simplified mathematical model of the grid-connected system to obtain a second-order equivalent dynamic equation;

[0176] The feasible region determination unit 1203 is configured to perform numerical integration and equal area calculation on the second-order equivalent dynamic equation, and determine the feasible region of the parameters of the voltage source converter grid-connected system.

[0177] In one embodiment, see Figure 13, the simplified mathematical model of the grid-connected system includes a pre-fault model; the simplified model construction unit 1201 includes: a phase angle component acquisition module 1301, a derivative integral determination module 1302, a power reference determination module 1303, and a pre-fault segment model construction module 1304.

[0178] The phase angle component acquisition module 1301 is used to obtain the phase angle of the phase-locked loop, the fault voltage component, the q-axis component of the grid connection point voltage, the component of the active power before filtering, and the component of the active power after filtering according to the topological structure;

[0179] The derivative integral determination module 1302 is used to calculate the first-order derivative integral term according to the phase angle of the phase-locked loop, the fault voltage component, the q-axis component of the grid connection point voltage, the component of the active power before filtering, and the component of the active power after filtering;

[0180] The power reference determination module 1303 is used to calculate the injected current power reference term according to the component of the AC voltage after filtering, the grid connection point voltage component, the AC voltage reference value, the active power reference value, the component of the active power after filtering, and the first-order derivative integral term;

[0181] The pre-fault segment model construction module 1304 is used to determine the pre-fault model according to the first-order derivative integral term and the injected current power reference term.

[0182] In one embodiment, referring to Figure 14 , the simplified mathematical model of the grid-connected system includes a fault-in model; the simplified model construction unit 1201 includes: an equation determination module 1401 and a fault-middle segment model construction module 1402.

[0183] The equation determination module 1401 is used to obtain the non-linear equation during the fault according to the low voltage ride-through coefficient and the current limit value;

[0184] The fault-middle segment model construction module 1402 is used to substitute the relationship function between the d-axis component and the q-axis component in the injected current power reference term into the non-linear equation during the fault to obtain the fault-in model.

[0185] In one embodiment, referring to Figure 15 , the simplified mathematical model of the grid-connected system includes a post-fault model; the simplified model construction unit 1201 includes: a reference value term generation module 1501 and a post-fault segment model construction module 1502.

[0186] The reference value term generation module 1501 is used to take the derivative of the system-given active power reference value based on the recovery coefficient to obtain the active power reference value term;

[0187] The post-fault segment model construction module 1502 is used to substitute the active power reference value term into the pre-fault model to obtain the post-fault model.

[0188] In one embodiment, referring to Figure 16 , the dynamic equation generation unit 1202 includes: a model derivative module 1601 and a dynamic equation generation module 1602.

[0189] The model derivative module 1601 is used to derive the simplified mathematical model of the grid-connected system to obtain the equivalent inertia, equivalent damping, equivalent virtual mechanical power, and equivalent virtual electromagnetic power.

[0190] The dynamic equation generation module 1602 is used to determine the second-order equivalent dynamic equation according to the equivalent inertia, equivalent damping, equivalent virtual mechanical power, and equivalent virtual electromagnetic power; wherein, the second-order equivalent dynamic equation includes a pre-fault equation, a fault equation, and a post-fault equation.

[0191] In one embodiment, referring to Figure 17 , the feasible region determination unit 1203 includes: an acceleration area calculation module 1701, a deceleration area calculation module 1702, a transient stability determination module 1703, a transient instability determination module 1704, and a feasible region determination module 1705.

[0192] The acceleration area calculation module 1701 is used to perform numerical integration and equal area calculation on the pre-fault equation and the fault equation to obtain the acceleration area.

[0193] The deceleration area calculation module 1702 is used to perform numerical integration and equal area calculation on the post-fault equation to obtain the deceleration area.

[0194] The transient stability determination module 1703 is used to determine that the voltage source converter grid-connected system is transiently stable after fault removal if the acceleration area is not greater than the deceleration area.

[0195] The transient instability determination module 1704 is used to determine that the voltage source converter grid-connected system is transiently unstable after fault removal if the acceleration area is greater than the deceleration area.

[0196] The feasible region determination module 1705 is used to determine the parameter feasible region of the voltage source converter grid-connected system according to whether the voltage source converter grid-connected system is transiently stable after fault removal.

[0197] From a hardware level, in order to be able to construct the parameter feasible region of the voltage source converter under the entire fault process for the transient synchronization stability problem caused by the weak connection system of the voltage source converter, this application provides an embodiment of an electronic device for implementing all or part of the content in the method for constructing the parameter feasible region of the voltage source converter grid-connected system. The electronic device specifically includes the following content:

[0198] A processor, a memory, a communications interface, and a bus; wherein, the processor, the memory, and the communications interface complete communication with each other through the bus; the communications interface is used to implement information transmission between the device for constructing the feasible region of the voltage source converter grid-connected system parameters and related devices such as the core business system, the user terminal, and the relevant database, etc.; this logic controller can be a desktop computer, a tablet computer, a mobile terminal, etc., and this embodiment is not limited thereto. In this embodiment, this logic controller can be implemented with reference to the embodiments of the method for constructing the feasible region of the voltage source converter grid-connected system parameters and the embodiments of the device for constructing the feasible region of the voltage source converter grid-connected system parameters, and the content thereof is incorporated herein, and the repeated parts will not be elaborated again.

[0199] It can be understood that the user terminal can include a smart phone, a tablet electronic device, a network set-top box, a portable computer, a desktop computer, a personal digital assistant (PDA), a vehicle-mounted device, a smart wearable device, etc. Among them, the smart wearable device can include smart glasses, a smart watch, a smart bracelet, etc.

[0200] In practical applications, part of the method for constructing the feasible region of the voltage source converter grid-connected system parameters can be executed on the electronic device side as described above, or all operations can be completed in the client device. Specifically, it can be selected according to the processing capacity of the client device and the limitations of the user usage scenario, etc. This application does not make any limitations in this regard. If all operations are completed in the client device, the client device may further include a processor.

[0201] The above-mentioned client device can have a communication module (i.e., a communication unit), and can be communicatively connected to a remote server to realize data transmission with the server. The server can include a server on the task scheduling center side, and in other implementation scenarios, it can also include a server on the intermediate platform, such as a server on a third-party server platform communicatively linked to the task scheduling center server. The server can include a single computer device, or can include a server cluster composed of multiple servers, or a server structure of a distributed device.

[0202] Figure 18 This is a schematic block diagram of the system composition of the electronic device 9600 according to an embodiment of the present application. As Figure 18 shown, the electronic device 9600 can include a central processing unit 9100 and a memory 9140; the memory 9140 is coupled to the central processing unit 9100. It should be noted that this Figure 18is exemplary; other types of structures can also be used to supplement or replace this structure to achieve telecommunication functions or other functions.

[0203] In one embodiment, the function of constructing the feasible region of the parameters of the voltage source converter grid-connected system can be integrated into the central processing unit 9100. Among them, the central processing unit 9100 can be configured to perform the following controls:

[0204] S101: Construct a simplified mathematical model of the grid-connected system according to the topological structure of the voltage source converter grid-connected system;

[0205] S102: Differentiate the simplified mathematical model of the grid-connected system to obtain a second-order equivalent dynamic equation;

[0206] S103: Perform numerical integration and equal-area calculation on the second-order equivalent dynamic equation, and determine the feasible region of the parameters of the voltage source converter grid-connected system.

[0207] From the above description, it can be seen that the method and device for constructing the feasible region of the parameters of the voltage source converter grid-connected system provided by this application can establish and verify the system model of the voltage source converter grid-connected system under the assumption during the whole process of the fault, simplify the system model based on control structures such as the outer loop - phase-locked loop; carry out the transient stability analysis of the system based on the equal-area rule and the method of numerical integration, and consider the feasible region of the low-voltage ride-through coefficient - active current under the non-limiting situation to ensure that the system provides stable and effective support within the feasible region.

[0208] In another embodiment, the device for constructing the feasible region of the parameters of the voltage source converter grid-connected system can be separately configured from the central processing unit 9100. For example, the device for constructing the feasible region of the parameters of the voltage source converter grid-connected system of the data composite transmission device can be configured as a chip connected to the central processing unit 9100, and the function of the method for constructing the feasible region of the parameters of the voltage source converter grid-connected system can be realized through the control of the central processing unit.

[0209] As Figure 18 shown, the electronic device 9600 may further include: a communication module 9110, an input unit 9120, an audio processor 9130, a display 9160, and a power supply 9170. It should be noted that the electronic device 9600 does not necessarily have to include all the components shown in Figure 18 ; in addition, the electronic device 9600 may further include components not shown in Figure 18 , and reference can be made to the prior art.

[0210] As Figure 18As shown, the central processing unit 9100, sometimes also referred to as a controller or operation control, may include a microprocessor or other processor device and / or logic device. The central processing unit 9100 receives inputs and controls the operation of the various components of the electronic device 9600.

[0211] Among them, the memory 9140 can be, for example, one or more of a buffer, a flash memory, a hard drive, a removable medium, a volatile memory, a non-volatile memory, or other suitable devices. It can store the above-mentioned failure-related information, and can also store programs for executing relevant information. And the central processing unit 9100 can execute the programs stored in the memory 9140 to implement information storage or processing, etc.

[0212] The input unit 9120 provides inputs to the central processing unit 9100. The input unit 9120 is, for example, a key or a touch input device. The power supply 9170 is used to supply power to the electronic device 9600. The display 9160 is used to display display objects such as images and texts. The display can be, for example, an LCD display, but is not limited thereto.

[0213] The memory 9140 can be a solid-state memory, for example, a read-only memory (ROM), a random access memory (RAM), a SIM card, etc. It can also be a memory that stores information even when powered off, can be selectively erased, and has more data. Examples of such a memory are sometimes referred to as EPROMs, etc. The memory 9140 can also be some other type of device. The memory 9140 includes a buffer memory 9141 (sometimes referred to as a buffer). The memory 9140 can include an application / function storage unit 9142, which is used to store application programs and function programs or the processes for operating the electronic device 9600 through the central processing unit 9100.

[0214] The memory 9140 can also include a data storage unit 9143, which is used to store data, such as contacts, digital data, pictures, sounds, and / or any other data used by the electronic device. The driver storage unit 9144 of the memory 9140 can include various drivers of the electronic device for communication functions and / or for performing other functions of the electronic device (such as a messaging application, an address book application, etc.).

[0215] The communication module 9110 is a transmitter / receiver that transmits and receives signals via the antenna 9111. The communication module (transmitter / receiver) 9110 is coupled to the central processing unit 9100 to provide input signals and receive output signals, which can be the same as in the case of a conventional mobile communication terminal.

[0216] Based on different communication technologies, in the same electronic device, multiple communication modules 9110 can be provided, such as a cellular network module, a Bluetooth module, and / or a wireless local area network module, etc. The communication module (transmitter / receiver) 9110 is also coupled to a speaker 9131 and a microphone 9132 via an audio processor 9130 to provide an audio output via the speaker 9131 and receive an audio input from the microphone 9132, thereby implementing normal telecommunication functions. The audio processor 9130 may include any suitable buffers, decoders, amplifiers, etc. Additionally, the audio processor 9130 is also coupled to a central processor 9100, so that recording can be performed on the local device through the microphone 9132, and the sound stored on the local device can be played through the speaker 9131.

[0217] Embodiments of the present application also provide a computer-readable storage medium capable of implementing all steps in the method for constructing the parameter feasible region of a voltage source converter grid-connected system where the execution subject in the above embodiments is a server or a client. A computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, all steps in the method for constructing the parameter feasible region of a voltage source converter grid-connected system where the execution subject in the above embodiments is a server or a client are implemented. For example, when the processor executes the computer program, the following steps are implemented:

[0218] S101: Construct a simplified mathematical model of the grid-connected system according to the topological structure of the voltage source converter grid-connected system;

[0219] S102: Take the derivative of the simplified mathematical model of the grid-connected system to obtain a second-order equivalent dynamic equation;

[0220] S103: Perform numerical integration and equal area calculation on the second-order equivalent dynamic equation, and determine the parameter feasible region of the voltage source converter grid-connected system.

[0221] As can be seen from the above description, the method and device for constructing the parameter feasible region of a voltage source converter grid-connected system provided by the present application can establish and verify the system model of the voltage source converter grid-connected system under the assumed conditions during the entire fault process, simplify the system model based on control structures such as an outer loop - phase-locked loop; perform transient stability analysis of the system based on the equal area rule and the numerical integration method, and consider the low-voltage ride-through coefficient - active current feasible region in the case of no clipping to ensure that the system provides stable and effective support capabilities within the feasible region.

[0222] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, an apparatus, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, 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.) that contain computer-usable program code.

[0223] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatus (devices), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0224] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0225] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0226] Specific embodiments are applied in the present invention to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for constructing the feasible region of parameters of a voltage source converter grid-connected system, characterized in that Including: Construct a simplified mathematical model of the grid-connected system according to the topological structure of the voltage-source converter grid-connected system; Differentiate the simplified mathematical model of the grid-connected system to obtain a second-order equivalent dynamic equation; Perform numerical integration and equal-area calculation on the second-order equivalent dynamic equation to determine the feasible region of the parameters of the voltage-source converter grid-connected system.

2. The method for constructing the feasible region of the parameters of the voltage source converter grid-connected system according to claim 1, wherein The simplified mathematical model of the grid-connected system includes a pre-fault model; the construction of the simplified mathematical model of the grid-connected system according to the topological structure of the voltage-source converter grid-connected system includes: Obtain the phase angle of the phase-locked loop, the fault voltage component, the q-axis component of the grid-connected point voltage, the component of the active power before filtering, and the component of the active power after filtering according to the topological structure; Calculate the first-order derivative integral term according to the phase angle of the phase-locked loop, the fault voltage component, the q-axis component of the grid-connected point voltage, the component of the active power before filtering, and the component of the active power after filtering; Calculate the reference term of the injected current power according to the component of the AC voltage after filtering, the component of the grid-connected point voltage, the reference value of the AC voltage, the reference value of the active power, the component of the active power after filtering, and the first-order derivative integral term; Construct the pre-fault model according to the first-order derivative integral term and the reference term of the injected current power.

3. The method for constructing the feasible region of the parameters of the voltage source converter grid-connected system according to claim 2, characterized in that The simplified mathematical model of the grid-connected system includes a fault-in model; the construction of the simplified mathematical model of the grid-connected system according to the topological structure of the voltage-source converter grid-connected system includes: Obtain the non-linear equation during the fault according to the low-voltage ride-through coefficient and the current limit value; Substitute the relationship function between the d-axis component and the q-axis component in the reference term of the injected current power into the non-linear equation during the fault to obtain the fault-in model.

4. The method for constructing the feasible region of the parameters of the voltage source converter grid-connected system according to claim 2, characterized in that, The simplified mathematical model of the grid-connected system includes a post-fault model; the construction of the simplified mathematical model of the grid-connected system according to the topological structure of the voltage-source converter grid-connected system includes: Differentiate the reference value of the given active power of the system based on the recovery coefficient to obtain the reference term of the active power; Substitute the reference term of the active power into the pre-fault model to obtain the post-fault model.

5. The method for constructing the parameter feasible region of the voltage source converter grid-connected system according to claim 1, characterized in that, The differentiation of the simplified mathematical model of the grid-connected system to obtain a second-order equivalent dynamic equation includes: Differentiate the simplified mathematical model of the grid-connected system to obtain the equivalent inertia, equivalent damping, equivalent virtual mechanical power, and equivalent virtual electromagnetic power; Determine the second-order equivalent dynamic equation according to the equivalent inertia, equivalent damping, equivalent virtual mechanical power, and equivalent virtual electromagnetic power; wherein, the second-order equivalent dynamic equation includes a pre-fault equation, a fault-in equation, and a post-fault equation.

6. The method for constructing the feasible region of the parameters of the voltage source converter grid-connected system according to claim 5, characterized in that The numerical integration and equal-area calculation of the second-order equivalent dynamic equation to determine the feasible region of the parameters of the voltage-source converter grid-connected system includes: Perform numerical integration and equal-area calculation on the pre-fault equation and the fault-in equation to obtain the accelerating area; Perform numerical integration and equal-area calculation on the post-fault equation to obtain the decelerating area; If the accelerating area is not greater than the decelerating area, it is determined that the voltage-source converter grid-connected system is transiently stable after the fault is cleared; If the accelerating area is greater than the decelerating area, it is determined that the voltage-source converter grid-connected system is transiently unstable after the fault is cleared; Determine the feasible region of the parameters of the voltage source converter grid-connected system according to whether the transient state of the voltage source converter grid-connected system is stable after the fault is removed.

7. A device for constructing the feasible region of parameters of a voltage source converter grid-connected system, characterized in that, Including: A simplified model construction unit for constructing a simplified mathematical model of the grid-connected system according to the topological structure of the voltage source converter grid-connected system; A dynamic equation generation unit for differentiating the simplified mathematical model of the grid-connected system to obtain a second-order equivalent dynamic equation; A feasible region determination unit for performing numerical integration and equal area calculation on the second-order equivalent dynamic equation to determine the feasible region of the parameters of the voltage source converter grid-connected system.

8. The device for constructing the feasible region of the parameters of the voltage source converter grid-connected system according to claim 7, characterized in that, The simplified mathematical model of the grid-connected system includes a pre-fault model; the simplified model construction unit includes: A phase angle component acquisition module for acquiring the phase angle of the phase-locked loop, the fault voltage component, the q-axis component of the grid connection point voltage, the component before active power filtering, and the component after active power filtering according to the topological structure; A derivative integral determination module for calculating a first derivative integral term according to the phase angle of the phase-locked loop, the fault voltage component, the q-axis component of the grid connection point voltage, the component before active power filtering, and the component after active power filtering; A power reference determination module for calculating an injected current power reference term according to the component after AC voltage filtering, the grid connection point voltage component, the AC voltage reference value, the active power reference value, the component after active power filtering, and the first derivative integral term; A pre-fault segment model construction module for determining the pre-fault model according to the first derivative integral term and the injected current power reference term.

9. The device for constructing the feasible region of the voltage source converter grid-connected system parameters according to claim 8, characterized in that, The simplified mathematical model of the grid-connected system includes a fault model; the simplified model construction unit includes: An equation determination module for obtaining a non-linear equation during the fault according to the low voltage ride-through coefficient and the current limit value; A fault segment model construction module for substituting the relationship function between the d-axis component and the q-axis component in the injected current power reference term into the non-linear equation during the fault to obtain the fault model.

10. The device for constructing the feasible region of the parameters of the voltage source converter grid-connected system according to claim 8, characterized in that, The simplified mathematical model of the grid-connected system includes a post-fault model; The simplified model construction unit includes: A reference value term generation module for differentiating the system given active power reference value based on the recovery coefficient to obtain an active power reference value term; A post-fault segment model construction module for substituting the active power reference value term into the pre-fault model to obtain the post-fault model.

11. The device for constructing the feasible region of the parameters of the voltage source converter grid-connected system according to claim 7, characterized in that, The dynamic equation generation unit includes: A model differentiation module for differentiating the simplified mathematical model of the grid-connected system to obtain an equivalent inertia, an equivalent damping, an equivalent virtual mechanical power, and an equivalent virtual electromagnetic power; A dynamic equation generation module for determining the second-order equivalent dynamic equation according to the equivalent inertia, the equivalent damping, the equivalent virtual mechanical power, and the equivalent virtual electromagnetic power; wherein, the second-order equivalent dynamic equation includes a pre-fault equation, a fault equation, and a post-fault equation.

12. The device for constructing the feasible region of the parameters of the voltage source converter grid-connected system according to claim 11, characterized in that, The feasible region determination unit includes: An acceleration area calculation module for performing numerical integration and equal area calculation on the pre-fault equation and the fault equation to obtain an acceleration area; A deceleration area calculation module for performing numerical integration and equal area calculation on the post-fault equation to obtain a deceleration area; A transient stability determination module, configured to determine that the voltage source converter grid-connected system is transiently stable after fault removal if the accelerating area is not greater than the decelerating area; A transient instability determination module, configured to determine that the voltage source converter grid-connected system is transiently unstable after fault removal if the accelerating area is greater than the decelerating area; A feasible region determination module, configured to determine the feasible region of the voltage source converter grid-connected system parameters according to whether the voltage source converter grid-connected system is transiently stable after fault removal.

13. An electronic device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the program, the steps of the method for constructing the feasible region of the voltage source converter grid-connected system parameters according to any one of claims 1 to 6 are implemented.

14. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, the steps of the method for constructing the feasible region of the voltage source converter grid-connected system parameters according to any one of claims 1 to 6 are implemented.

15. A computer program product, comprising a computer program / instructions, characterized in that, When the computer program / instructions are executed by the processor, the steps of the method for constructing the feasible region of the voltage source converter grid-connected system parameters according to any one of claims 1 to 6 are implemented.

Images