Networking type energy storage transient stability optimization control method and system considering reactive power degradation

Abstract

The invention discloses a network construction type energy storage transient stability optimization control method and system considering reactive power degradation, and belongs to the field of power system transient stability control. According to the method, a network construction type energy storage grid-connected system model is constructed, a reactive power degradation effect dynamically triggered by a reactive power control loop is analyzed, and an active power loop optimization control equation is established according to the reactive power degradation effect. On the basis, a self-adaptive torque adjusting module is embedded in an active control module, and when it is monitored that the internal voltage of the inverter is reduced to 50% of a rated value, the reference torque is automatically and dynamically corrected so as to improve the power angle transient stability margin of the system. Simulation results show that the method can effectively restrain the instability of the network construction type energy storage power angle, obviously enhance the transient stability of the system, and guarantee the safe and reliable operation of the power grid.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system transient stability control, in particular to a network-type energy storage transient stability optimization control method and system considering reactive power degradation. BACKGROUND

[0002] With the high proportion of new energy power generation equipment accessing the power grid and the formation of the power system, the key role of network-type energy storage devices in maintaining the dynamic stability of the power system is increasingly prominent. However, traditional network-type energy storage has significant challenges in transient synchronous stability. For example, in the fault state of the network-type energy storage system, the internal voltage drop of the inverter caused by the reactive power regulation mechanism will exacerbate the imbalance between active power supply and demand, significantly weakening the transient stability margin of the system. However, traditional methods rely on idealized network models or single control dimensions, and do not fully consider the negative effects of the reactive power control loop on transient characteristics. Therefore, a new network-type energy storage control method that considers the degradation effects of network-type energy storage reactive power control is needed.

[0003] Currently, there is little research on the degradation effects of the reactive power control loop of network-type energy storage systems. Patent application CN119171479A provides a control method for network-type energy storage systems based on virtual inertia and virtual damping, which can reduce the demand for energy storage, active power oscillation, and control frequency oscillation. Patent application CN118432136A proposes a network-type energy storage frequency control method suitable for weak grids, which builds a frequency and power cascade control structure for frequency regulation and power distribution control, improves the dynamic characteristics of the system, and improves the power quality of new power systems. As can be seen, there is a lack of research on the degradation effects of the reactive power control loop of network-type energy storage systems in the prior art. Therefore, a method that considers the degradation effects of the reactive power control loop on network-type energy storage transient stability control is needed. SUMMARY

[0004] To overcome the deficiencies of the prior art, the present application aims to provide a network-type energy storage transient stability optimization control method and system considering reactive power degradation. This method embeds an adaptive torque adjustment module in the active power control loop of traditional network-type energy storage control under the premise of considering the degradation effects of the reactive power control loop of network-type energy storage systems, and dynamically corrects the reference torque to ensure the stability of the power angle during system faults, improving the transient stability of network-type energy storage systems.

[0005] To achieve the above-mentioned purpose, the technical solutions of the present application are as follows: In a first aspect, the present application provides a network-type energy storage transient stability optimization control method considering reactive power degradation effects. The method specifically includes the following steps: S1: Model the network-type energy storage power station grid-connected system.

[0006] According to the actual grid parameters, the grid-connected system model is constructed, which contains active power control module, governor module, reactive power control module, virtual impedance control module, coordinate transformation module, double closed-loop control module, PWM module, DC power supply, three-phase full-bridge inverter circuit, filter inductor, filter capacitor, the sum of equivalent inductance and line inductance of transformer, the sum of equivalent resistance, and AC grid. abc / dq dq / abc

[0007] Based on the multi-time scale decomposition and singular perturbation theory, the dynamic characteristics of the system are analyzed: the voltage and current double closed-loop control system is equivalent to an ideal transfer link, so that the output voltage amplitude and phase of the inverter are approximately equal to the control command value; the fast changing state variables of inductor current and capacitor voltage in the LC filter link are ignored, and the algebraic expressions of active power P e and reactive power Q e are derived, as well as the swing equation of grid-connected type control and the mathematical equation of reactive control loop.

[0008] (1); In the formula: G = R s / ( R s 2 + X s 2 ), B =- X s / ( R s 2 + X s 2 ), R s +j X s =( R g + R v )+j( X g + X v ), R g is the line resistance, R v is the virtual resistance, X g is the line inductance corresponding to the reactance, X ​​v The reactance corresponding to the virtual inductance; V g This is the magnitude of the grid voltage (with the grid voltage phase angle as the reference phase angle). E The voltage amplitude inside the inverter is determined by the grid voltage phase angle according to the convention of setting the grid synchronous coordinate system. V g Considered as the reference phase angle, the power angle δ Considered as the internal voltage of the inverter E With grid-side voltage V g The phase angle difference satisfies the following mathematical expression: (2); In the formula: ω 0 represents the rated synchronous angular velocity of the power grid. ω 1 represents the angular velocity of the grid-connected energy storage system.

[0009] The swing equation for grid-type control is: (3); In the formula: J v1 This is virtual inertia; D p This is the virtual damping coefficient; T em For output torque, it can be achieved through T em = P e / ω 0 calculation, reference active power P ref Generated by the speed governor, its calculation method is as follows: (4); Combining these, we can obtain: (5); In the formula: D p = D v1 + K f / ω 0, D p For equivalent damping; T 0= P 0 / ω 0.

[0010] The mathematical equation for the reactive power control loop is: (6); In the formula: K=1 / K i , K i is the voltage integral coefficient; D q is Q - V is the droop coefficient; E 0, Q 0 are the reference voltage and reference reactive power, respectively.

[0011] S2: Analysis of reactive power degradation effect and establishment of active power loop optimization control equation.

[0012] The derivative equation of the internal voltage E of the inverter is converted into a quasi-steady-state equation, and the network-form control model obtained in step S1 is simplified into the form of "second-order derivative equation + quasi-steady-state equation".

[0013] Taking E as a parameter variable, the derivative equation of the internal voltage E of the inverter can be converted into a quasi-steady-state equation. The network-form control model in equations (4)-(6) is simplified into a second-order derivative equation plus a quasi-steady-state equation, as shown below: (7); (8); The transient equivalent circuit (including the equivalent circuit without considering reactive power control and the equivalent circuit considering reactive power control) of the network-form energy storage connected to the grid and the active power P - power angle δ curve are constructed, and the coordinate translation improvement method is adopted to make the power angle related equation satisfy the characteristics of an odd function, so as to accurately analyze the transient power angle problem.

[0014] The improved method of coordinate translation is adopted, so that equation (9) is an odd function: (9); In the equation, δ t = δ + φ- π / 2 , Z and φ are the line impedance and impedance angle, respectively.

[0015] The transient equivalent circuit and P - power angle δ curve are combined to analyze the reactive power degradation effect: when the grid fails, the amplitude difference between the network-form energy storage and the grid voltage leads to a sudden increase in the output reactive power of the energy storage, and the internal voltage E of the inverter decreases; after the fault is cleared, E cannot be restored immediately, so that P- δ Maximum value of the curve P max Reduction, causing the area of the acceleration zone to increase when a fault occurs, and the area of the deceleration zone to decrease after the fault is cleared, which may lead to the maximum power angle δ max Exceeding the unstable equilibrium point δ u , triggering transient power angle instability.

[0016] Based on the quasi-steady-state equation, the reference torque T ref after a fault is established E The active power control optimization equation that relates to the internal voltage (10) is established. In the equation: δ t0 is the initial power angle, V g1 is the grid-side voltage after a fault.

[0017] S3: Active power control module optimization.

[0018] An adaptive torque adjustment module is embedded in the active power control module of the grid-forming energy storage system, which has two working states: "optimization control unstarted state" and "optimization control started state": Optimization control unstarted state: the reference torque T ref output by the governor P ref is generated through 1 / ω 0 operation; the deviation value between T ref and the actual electromagnetic torque T e is input into the equivalent damping D p link (simulating system damping characteristics, suppressing power oscillation), virtual inertia J v1 integral link (simulating synchronous generator rotor inertia, delaying frequency change rate), 1 / S integral link, and finally the phase angle of the grid-forming energy storage is obtained θ g , participating in power angle stability control.

[0019] Optimization control started state: when the internal voltage of the inverter is monitored E to decrease to 50% of the rated value, this state is started. First, the difference between the reference voltage V 0 and the grid-side voltage V g is input into the 1 / Kv After proportional control adjustment, the reactive power is compared with the reference reactive power. Q 0 and actual reactive power Q e The differences are added together, and the resulting signal is processed by... K i After the voltage integration stage accumulates the data, it is compared with the reference voltage. E 0-phase addition generates internal voltage E ; then, E With real-time monitoring of grid-side voltage after fault V g1 Substitute the active power expression from step S1 to calculate the initial power angle. δ t0 Then δ t0 , E , V g1 Substituting into the active power control optimization equation, the corrected reference torque is obtained. T ref The subsequent signal processing procedure is the same as in the "optimized control not started state", through dynamic correction. T ref Ensure initial power angle stability and suppress power angle loss of synchronization.

[0020] Secondly, this invention provides a grid-connected energy storage transient stability optimization control system that considers reactive power degradation effects. The system includes a grid-connected system modeling module, a reactive power degradation analysis and optimization equation construction module, and an active power control optimization module. The functions of each module are as follows: Grid-connected system modeling module: Based on actual grid parameters, a grid-connected system model of the grid-connected energy storage power station is constructed. Based on multi-timescale decomposition and singular perturbation theory, the voltage and current dual closed-loop control system is equivalent to an ideal transmission link. The rapidly changing state variables in the LC filter link are ignored, and the system output active power is derived. P e reactive power Q e The algebraic expression of the control, as well as the swing equation of the network control and the mathematical equation of the reactive power control loop.

[0021] Reactive power degradation analysis and optimization equation construction module: This module constructs the inverter's internal voltage... E The derivative equation is transformed into a quasi-steady-state equation, simplifying the network control model; through transient equivalent circuit and P - δ The curve analysis shows the deteriorating effect of the reactive power control loop on transient angular stability (the area of ​​the acceleration zone increases during a fault, and the area of ​​the deceleration zone decreases after the fault is cleared). The coordinate translation improvement method is used to handle the power angle correlation equation, and the active power control optimization equation is established based on the quasi-steady-state equation.

[0022] Active control optimization module: contains an adaptive torque adjustment unit for real-time monitoring of the internal voltage of the inverter E ; when E decreases to 50% of the rated value, start the optimization control based on the active control optimization equation, combined with the real-time monitoring of E and the post-fault grid-side voltage V g1 calculate the initial power angle δ t0 , dynamically correct the reference torque T ref , and improve the system transient stability margin.

[0023] In a third aspect, the application provides a network-type energy storage transient stability optimization control method considering reactive power degradation effects, or the application of the network-type energy storage transient stability optimization control system considering reactive power degradation effects in a new energy high-proportion access power system. It is used to deal with the transient power angle instability problem caused by three-phase short-circuit fault of the grid during the network-type energy storage grid-connected operation, realizes online monitoring and optimization control of the power system, enhances the transient stability of the network-type energy storage system, and improves the overall reliability of the power system.

[0024] Advantages and beneficial effects of the application: The application is aimed at the transient power angle instability problem caused by the dynamic of the reactive power control loop of the network-type energy storage during the grid fault, fully considers the influence of the reactive power control loop on the transient angle stability, and proposes a method of optimizing the active control module of the traditional network-type energy storage control. By real-time monitoring of the post-fault voltage of the grid and the internal voltage of the inverter, when the internal voltage of the inverter decreases to half of the rated value, the optimization control is started to dynamically reduce the reference torque of the system, to improve the transient stability margin of the power angle, so as to achieve the purpose of improving the transient stability of the network-type energy storage system. The scheme is suitable for online monitoring and optimization control of the power system, can effectively enhance the transient stability of the network-type energy storage system, and thus improve the overall reliability and stability of the power system, and build a strong protection for the safe operation of the grid. Specifically: 1. The application first considers the degradation effect of the reactive power control loop of the network-type energy storage system, breaks through the limitation of the traditional control method which relies on idealized model and ignores the negative influence of reactive power control on transient characteristics, and accurately captures the transient power angle instability risk caused by the internal voltage drop of the inverter during the fault.

[0025] 2. The application embeds an adaptive torque adjustment module in the active control module, takes the internal voltage of the inverter E = 50% of the rated value as the starting threshold, dynamically corrects the reference torque T refThe power angle instability during the transient period can be effectively inhibited, and the transient stability margin of the grid-constructed energy storage system is significantly improved.

[0026] 3, MATLAB / Simulink simulation verification: in the three-phase short-circuit fault (the voltage of the power grid side is reduced to 20% of the rated value, and the fault is cleared) scene, the internal voltage of the system adopting the control method of the application can gradually recover to the steady state before the fault, and the power angle returns to the steady state value before the fault within 13s; while the internal voltage of the system adopting the traditional control method oscillates and loses stability, and the power angle is seriously out of step.

[0027] 4, The application is suitable for online monitoring and optimal regulation and control of a power system, can effectively enhance the transient stability of the grid-constructed energy storage in the power system with high proportion of new energy access, and further improve the overall reliability of the power system, thereby providing protection for safe operation of the power grid. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a grid-connected topology structure diagram of the grid-constructed energy storage power station; Figure 2 is an equivalent circuit diagram of grid-constructed energy storage; Figure 3 is a power angle curve of the grid-constructed energy storage during the transient period; P - δ curve diagram; Figure 4 is an optimal control block diagram for improving the transient stability of the grid-constructed energy storage; Figure 5 is a simulation voltage waveform diagram of the grid-constructed energy storage system; Figure 6 is a simulation power angle waveform diagram of the grid-constructed energy storage system.

[0029] In the figure: 1, active power control module;2, speed regulator module;3, reactive power control module;4, virtual impedance control module;5, abc / dq coordinate transformation;6, double closed loop control;7, dq / abc coordinate transformation;8, PWM module;9, DC power supply;10, three-phase full-bridge inverter circuit;11, filter inductor;12, filter capacitor;13, the sum of the equivalent inductance of the transformer and the line inductance;14, the sum of the equivalent resistance;15, AC power grid. DETAILED DESCRIPTION

[0030] The technical solutions of the application will be further described in detail below in combination with the drawings and specific embodiments.

[0031] At the same time, it should be noted that the embodiments described herein are only used for exemplary explanation of the core idea of the application and do not constitute any limitation on the protection scope of the application.

[0032] Embodiment 1 The application proposes a network-constructed energy storage transient stability optimization control method and system considering reactive power degradation, which specifically comprises the following three steps: Step S1: According to the actual power grid situation, the network-constructed energy storage power station grid-connected system modeling is carried out.

[0033] Figure 1 The network-constructed energy storage system grid-connected topology diagram is shown in the application. The network-constructed energy storage grid-connected system is composed of the following modules: active power control module 1, speed regulator module 2, reactive power control module 3, virtual impedance control module 4, abc / dq coordinate transformation 5, double closed-loop control 6, dq / abc coordinate transformation 7, PWM module 8, DC power supply 9, three-phase full-bridge inverter circuit 10, filter inductor 11, filter capacitor 12, the sum of transformer equivalent inductance and line inductance 13, the sum of equivalent resistances 14, AC power grid 15.

[0034] In the study of the dynamic characteristics of the above network-constructed energy storage power station grid-connected system model, the analysis method based on multi-time scale decomposition and singular perturbation theory is used, that is, in the analysis of the slow dynamic process of the system, the fast-changing state quantity is regarded as having converged to the quasi-steady state. Therefore, the voltage and current double closed-loop control system of the model can be equivalent to an ideal transmission link, so that the output voltage amplitude and phase of the inverter are approximately equal to the control command value. At the same time, the fast-changing state quantities of the inductor current and capacitor voltage in the LC filter link are ignored, so that the active power P e and reactive power Q e of the system output can be derived as: (1); In the formula: G = R s / ( R s 2 + X s 2 ), B =- X s / ( R s 2 + X s 2 ), R s +j X s =( R g +R v ) + j ( 0 X g + X v ). According to the setting convention of the grid synchronous coordinate system, the phase angle of the grid voltage V g is regarded as the reference phase angle, and the power angle δ is regarded as the phase angle difference between the internal voltage of the inverter and the grid-side voltage E V g , which satisfies the following mathematical expression: (2) ; In the formula: ω 0 is the rated synchronous angular velocity of the grid, ω 1 is the angular velocity of the grid-connected energy storage system of the grid-forming type.

[0035] The swing equation of the grid-forming control is: (3) ; In the formula: J v1 is the virtual inertia; D p is the virtual damping coefficient; T em is the output torque, which can be calculated by T em = P e / ω 0, P ref is the reference active power generated by the speed governor, and the calculation method is as follows: (4) ; In combination, the following can be obtained: (5) ; In the formula: D p = D v1 + K f / ω 0, D p is the equivalent damping; T 0= P 0 / ω 0.

[0036] The mathematical equation of the reactive power control loop is: (6) ; In the formula: K =1 / ​K i , K i is the voltage integral coefficient; D q is Q - V the droop coefficient; E 0, Q 0are the reference voltage and reference reactive power, respectively.

[0037] Step S2: Analysis of the reactive power degradation effect of the grid-forming energy storage and establishment of the active power loop optimization control equation.

[0038] Taking E as a parameter variable, the derivative equation of the inverter internal voltage E can be converted into a quasi-steady-state equation. The grid-forming control model in equations (4)-(6) is simplified into a second-order derivative equation plus a quasi-steady-state equation, as shown below: (7); (8); In order to study the transient characteristics of the grid-forming energy storage system and construct the active power control optimization equation, equation (7) needs to be further processed to obtain equation (9). In the transient state, the grid-forming converter can be represented by a voltage source to establish the transient equivalent circuit of the system. As shown in Figure 2 , where Figure 2 (a) in (a) is the grid-connected equivalent circuit without considering reactive power control, Figure 2 (b) in (b) is the grid-connected equivalent circuit considering reactive power control, V g is the grid phase voltage amplitude, Z is the equivalent line impedance. At the same time, the active power P -power angle δ curve needs to be constructed to analyze the transient power angle problem in the distribution network, as shown in Figure 3 , where Figure 3 (a) in (a) is the P - δ curve with constant inverter internal voltage, Figure 3 (b) in (b) is the P - δ curve considering the influence of the reactive power control loop. Since the resistance in the distribution network cannot be ignored, otherwise it will lead to the active power no longer being an odd function of the power angle. Therefore, the improved method of coordinate translation is adopted here, so that equation (9) is an odd function: (9); In the formula: δ t = δ +φ- π / 2 , Z and φ These are the line impedance and the impedance angle, respectively.

[0039] Based on coordinate translation, Figure 2 The active power P and power angle in model (a) δ Relationships such as Figure 3 As shown in (a) above. Curve I represents the curve before and after the fault. P - δ Relationship, curve II represents the fault condition. P - δ The curve has a stable equilibrium point. δ s and unstable equilibrium points δ u The Extended Equal Area Criterion (EEAC) can intuitively explain the transient angular stability criterion: before the fault, the system... δ s During operation, if a fault occurs, the operating point jumps to curve II, causing an imbalance in active power. δ Acceleration; at the critical work angle δ c Clear the fault and return the running point to curve I. δ slow down. δ max Given the maximum power angle after the fault, and ignoring damping losses, the transient angular stability criterion is calculated based on the acceleration area S1 equaling the deceleration area S2. δ max < δ u .

[0040] When considering the impact of reactive power control loops, use Figure 2 (b) in the diagram represents the equivalent circuit of grid-connected energy storage. Due to the voltage amplitude difference between the grid-connected energy storage and the grid, a ground fault causes a sudden increase in reactive power output from the grid-connected energy storage, leading to a voltage spike within the inverter. E Reduced. After the fault is cleared, E Unable to recover immediately, making P - δ Maximum values ​​of curves I and II P max1 and P max2 They will be reduced to P max1 and P max2 This results in an increased acceleration zone area during fault detection and a decreased deceleration zone area after fault clearance. This could lead to a decrease in the maximum power angle within the same fault clearance time. δ max Greater than δ uThis is called the degradation effect of the reactive control loop on transient angle stability. Therefore, it is necessary to consider the degradation effect of the reactive control loop in the control of grid-connected energy storage systems.

[0041] The derivative equation of the internal voltage E can be regarded as a quasi-steady-state equation. From equations (8) and (9), it can be seen that the reference torque T ref after the fault is related to the internal voltage E , which can be described by equation (10), which is the active control optimization equation of the present application: (10); In the equation: δ t0 is the initial power angle, V g1 is the grid-side voltage after the fault.

[0042] Step S3: using the control method of the present application to optimize the active control module of the grid-connected energy storage system.

[0043] Figure 4 is the optimization control block diagram of the present application for improving the transient stability of the grid-connected energy storage system. The operations included in the block diagram are: operation one is the integral link of 1 ω 0, operation two is the damping coefficient D p link, operation three is the integral link of virtual inertia J v1 , operation four is the integral link of 1 / S, operation five is the proportional link of K v , operation six is the voltage integral link of K i , and operation seven is the optimization control link of equation (10).

[0044] The optimization control target of the optimization control module is to achieve the same steady-state operating point as before the fault. The module has two working states, namely, the optimization control non-start state 1 and the optimization control start state 2. State 2 is started when the system detects that the internal voltage E of the inverter is reduced to half of the rated value. In state 1, the reference torque T ref is generated by operation one in the active optimization control module with the reference active power P ref as the input quantity given by the governor. Then the reference torque T ref is compared with the actual electromagnetic torque T eThe difference is introduced into the operation two links. The link is used to simulate the damping characteristics of the system, and suppress the power oscillation in the transient process. The processed signal is input to operation three, and the inertia characteristics of the rotor of the synchronous generator are simulated through virtual inertia, so as to delay the frequency change rate of the system. Finally, the network type energy storage phase angle is obtained through the integral operation four θ g , and the power angle stability control of the system is participated.

[0045] And the reference torque T ref of the optimization control module in state 2 is adjusted by the following two steps: First step: the difference between the reference voltage V 0 and the grid-side voltage V g is adjusted through operation five, and then the difference between the reference reactive power Q 0 and the actual reactive power Q e is added, the obtained signal is input to operation six for cumulative operation, and the integral output signal is added to the reference voltage E 0, and finally the internal voltage E is generated.

[0046] Second step: the internal voltage E of the inverter is input to operation seven optimization control module, the internal voltage E and the measured grid-side voltage V g1 after the fault are substituted into the upper formula in formula (10) to calculate the initial power angle δ t0 , and then the calculated δ t0 and the known E , V g1 are substituted into the lower formula of formula (10), so that the reference torque T ref is obtained. In state 2 mode, the subsequent work of the active power optimization control module is consistent with state 1.

[0047] From the above analysis, when the optimization control module is in state 2, the reference torque T ref is adjusted in real time through the above method to ensure the stability of the initial power angle of the system, so as to achieve the optimization control target, suppress the power angle out-of-step phenomenon, and solve the network type control transient power angle stability problem, and improve the transient stability of the network type energy storage control power system.

[0048] This invention optimizes the active power control loop of traditional grid-type energy storage control by considering the influence of the reactive power control loop, using a dynamic torque optimization method. When the system detects that the inverter's internal voltage drops to 50% of its rated value, the optimized control of this invention reduces the input reference torque to suppress the risk of power angle instability during transient periods, thereby improving the transient power angle stability of the grid-type control. A grid-type energy storage control system connected to an infinite three-phase voltage source was established as the research system in MATLAB / Simulink simulation. For the three-phase short-circuit fault scenario, the grid-side voltage... V g The voltage drops to 20% of the rated value at 10 seconds, and the system is set to clear the fault at 10.3 seconds. Simultaneously, the inverter's internal voltage is adjusted under permanent system fault conditions. E Real-time monitoring of the voltage inside the inverter. E When the input reference torque is reduced to half of the rated value, the optimized control loop of this invention is activated to reduce the input reference torque. The internal voltage and fault power angle of the grid-type energy storage system are also monitored. Simulation results are as follows: Figure 5 and Figure 6 As shown, where Figure 5 It is the internal voltage waveform of the fault. Figure 6 This is the fault angle waveform. Figure 5 As can be seen, when using traditional control methods in a grid-type energy storage system, the internal voltage oscillates and becomes unstable after the fault is cleared. However, when the system adopts the optimized control method of this invention, the internal voltage gradually returns to its pre-fault steady state after the system fault is cleared in 10.3 seconds. The fault power angle waveform is shown below. Figure 6 As shown, when using traditional control methods, grid-type energy storage systems experience severe power angle instability. However, when the optimized control method proposed in this invention is adopted, the system's power angle returns to its pre-fault steady-state value within 13 seconds. Simulation results demonstrate the significant optimization effect of the proposed optimized control method.

Claims

1. A network-configuration type energy storage transient stability optimization control method considering reactive degradation effect, characterized in that: Comprising the following steps: S1: according to the actual power grid parameters, the grid-connected system model of the grid-connected type energy storage power station is constructed: the grid-connected system model contains active power control module, speed regulator module, reactive power control module, virtual impedance control module, coordinate transformation module, double closed loop control module, PWM module, DC power supply, three-phase full-bridge inverter circuit, filter assembly and grid equivalent assembly, based on multi-time scale decomposition and singular perturbation theory, the voltage and current double closed loop control system in the grid-connected system model is equivalent to an ideal transfer link, the rapidly changing state quantity in the LC filter link is ignored, and the algebraic expression of the system output active power P e , reactive power Q e , swing equation of grid-connected type control and mathematical equation of reactive control loop are derived; S2: analyze the reactive power degradation effect of the network-structured energy storage, convert the derivative equation of the inverter internal voltage E into a quasi-steady-state equation: simplify the network-structured control model obtained in step S1, process the power angle related equation by using the coordinate translation improvement method, combine the transient equivalent circuit with P - delta curve analyze the degradation effect of the reactive power control loop on the transient angle stability, establish an active power control optimization equation based on the quasi-steady-state equation, wherein the active power control optimization equation represents the relationship between the reference torque T ref and the internal voltage E after the fault; S3: Embedding adaptive torque regulation module in the active power control module of the network-constructed energy storage system: the adaptive torque regulation module is provided with two states of optimization control non-starting and starting, when the internal voltage E of the inverter is monitored to reduce to 50% of the rated value, the optimization control state is started, based on the active power control optimization equation obtained in step S2, combined with the real-time monitored internal voltage E and the post-fault grid-side voltage V g1 , calculate the initial power angle delta t0 and dynamically correct the reference torque T ref , suppress the power angle instability during the transient state.

2. The network-forming energy storage transient stability optimization control method considering reactive degradation effect according to claim 1, characterized in that: In step S1, the active power P e , the reactive power Q e The algebraic expression of the active power (1); In the formula: G R s R s 2 X s 2 B X s R s 2 X s 2 R s X s R g R v X g X v R g is the line resistance, R v is the virtual resistance, X g is the reactance corresponding to the line inductance, X v is the reactance corresponding to the virtual inductance; V g is the grid voltage amplitude, E is the internal voltage amplitude of the inverter, delta is the power angle, and delta =∠ E -∠ V g , ∠ E is the phase angle of the internal voltage of the inverter, ∠ V g is the phase angle of the grid voltage; the power angle delta is considered as the phase angle difference between the internal voltage of the inverter E and the grid-side voltage V g satisfies the following mathematical expression:​​​​​​​​​​​​​​ (2)； In the formula: omega 0 is the rated synchronous angular velocity of the power grid, omega 1 is the angular velocity of the grid-forming energy storage grid-connected system.

3. The network-forming energy storage transient stability optimization control method considering reactive degradation effect according to claim 2, characterized in that: In step S1, the swing equation of the network-forming control satisfies: (3)； where: J v1 is the virtual inertia; D p is the virtual damping coefficient; T em is the output torque, which is calculated by T em P e omega 0, the reference active power P ref is generated by the governor, the calculation method of which is as follows:​​ (4)； In combination, we obtain: (5)； wherein: D p = D v1 + K f / omega 0, D p is the equivalent damping; T 0= P 0 / omega 0.

4. The method of claim 3, wherein the method is characterized by: In step S1, the reactive power control loop mathematical equation satisfies: (6)； wherein: K =1 / K i , K i is a voltage integration coefficient; D q is Q - V a droop coefficient; E 0, Q 0 are a reference voltage and a reference reactive power, respectively.

5. The method of claim 4, wherein the method is characterized by: In the coordinate translation improvement method in step S2, define delta t = delta + phi- π / 2 , Z and phi are the line impedance and impedance angle, respectively, so that the power angle correlation equation satisfies the odd function property: Will E As a parameter variable, the internal voltage of the inverter E The derivative equation is transformed into a quasi-steady-state equation; the network control model in equations (4)-(6) is simplified to a second-order derivative equation plus a quasi-steady-state equation, as shown below: (7)； (8)； Further processing of formula (7) obtains formula (9); an improved method of coordinate translation is adopted, so that formula (9) is an odd function: (9)； where: delta t = delta + phi- π / 2 , Z and phi are the line impedance and the impedance angle, respectively.

6. The method of claim 5, wherein the method is characterized by: The adaptive torque adjustment module in step S3 includes two working states of an optimal control non-starting state and an optimal control starting state, and the specific control method is: reference torque T ref reference active power output by the governor P ref through 1 omega an operation link to generate the reference torque T ref and the deviation value of the actual electromagnetic torque T e , through equivalent damping D p link, virtual inertia J v1 integral link and 1 / S integral operation link, to obtain the phase angle of the grid-forming energy storage theta g ​ In the optimized control starting state, the starting condition is that the system monitors the internal voltage of the inverter E to 50% of its rated value; in this state, the internal voltage of the inverter is first generated by the reactive power control module E ; the internal voltage of the inverter E and the post-fault grid-side voltage V g1 The initial power angle is calculated as delta t0 ; Then the initial power angle delta t0 Inverter internal voltage E and grid-side voltage after fault V g1 Substituting into the active power control optimization equation, the corrected reference torque is calculated. T ref The subsequent correction reference torque T ref With actual electromagnetic torque T e The process for handling deviation values ​​is the same as that for when optimization control is not activated, and it is achieved through dynamic correction. T ref To ensure initial power angle stability and suppress power angle loss of synchronization; in the active power control optimization equation, the reference torque T ref The value is determined by the initial power angle. delta t0 Inverter internal voltage E and grid-side voltage after fault V g1 It was jointly determined that, among which delta t0 The initial power angle, V g1 This refers to the voltage on the grid side after the fault. The active power control optimization equation is: (10)； In the formula: delta t0 is the initial power angle, V g1 is the post-fault grid-side voltage.

7. A network-configuration type energy storage transient stability optimization control system considering reactive degradation effect, characterized in that: Comprising a grid-connected system modeling module, a reactive power degradation analysis and optimization equation construction module, and an active power control optimization module; The grid-connected system modeling module is configured to construct a grid-connected system model of the grid-connected energy storage power station according to actual grid parameters, and derive an algebraic expression of active power output of the system P e , and a swing equation and a reactive power control loop mathematical equation of grid-connected control Q e ​ The reactive power degradation analysis and optimization equation construction module is used to analyze the reactive power degradation effect of the network-forming energy storage, simplify the network-forming control model, and establish the active power control optimization equation; The active control optimization module comprises an adaptive torque adjustment unit for monitoring the internal voltage of the inverter E When E When the voltage drops to 50% of the rated value, the reference torque is dynamically corrected based on the active control optimization equation T ref , the system transient stability margin is improved; The control system is realized by the control method in any one of claims 1 to 6, wherein the grid-connected system modeling module corresponds to the modeling and derivation process of step S1, the reactive power degradation analysis and optimization equation construction module corresponds to the degradation analysis and equation establishment process of step S2, and the active power control optimization module corresponds to the adaptive torque adjustment process of step S3; the three modules are sequentially progressive and data intercommunicate, forming a "modeling-analysis-control" closed-loop optimization system to improve the stability of the network-forming energy storage system under transient operating conditions.

8. The network-forming energy storage transient stability optimization control system considering the effect of reactive degradation of claim 7, wherein: The grid-connected system modeling module is based on multi-time scale decomposition and singular perturbation theory, and equivalent to an ideal transfer link for the voltage and current double-loop control system in the grid-connected system model, and ignores the fast-changing state quantity in the LC filter link.

9. The network-forming energy storage transient stability optimization control system considering the effect of reactive degradation of claim 8, wherein: The reactive deterioration analysis and optimization equation construction module constructs a transient equivalent circuit and P - For dealing with the transient power angle instability problem caused by three-phase short-circuit fault of the grid-connected energy storage in the power system, to realize online monitoring and optimization control of the power system, and to enhance the transient stability of the grid-connected energy storage system to improve the overall reliability of the power system. The curve is analyzed to analyze the deterioration influence of the reactive control loop on the transient angle stability, and the deterioration influence is manifested as an increase in the acceleration area during the fault and a decrease in the deceleration area after the fault is cleared.

10. The network-forming energy storage transient stability optimization control method considering reactive degradation effects according to any one of claims 1-6, or the application of the network-forming energy storage transient stability optimization control system considering reactive degradation effects according to any one of claims 7-9 in a new energy high proportion access power system, characterized in that: ​

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