New energy equipment low-voltage ride-through transient synchronous stability analysis method based on improved equal-area principle

Abstract

The invention discloses a new energy equipment low-voltage ride-through transient synchronous stability analysis method based on an improved equal-area principle. The method comprises the following steps: performing transient modeling on a new energy grid-connected system considering a complete low-voltage ride-through process; solving a stable working point of the system at the stage 1 and an unstable equilibrium point of the system at the initial moment of the stage 3; normalizing the differential algebraic equations at the initial moments of the stage 2 and the stage 3 into the form of a generalized swing equation, and solving each equivalent coefficient; at the initial moment of the stage 3, the critical cutting angle of the system is calculated through the first-time equal-area approximation principle, the second-time equal-area approximation principle and the third-time equal-area approximation principle, and the critical cutting angle of third-time approximation serves as an output result based on the improved equal-area principle; and calculating the trajectory of the new energy grid-connected system during the fault duration, and outputting the critical clearing time of the new energy grid-connected system in combination with the numerical trajectory and the analytically calculated critical clearing angle, thereby helping to take measures in time to ensure the safe and stable operation of the power system.

Description

Technical Field

[0001] This invention belongs to the field of transient stability operation and control of new power systems, and more specifically, relates to a method for analyzing the low voltage ride-through transient synchronous stability of new energy equipment based on the improved equal area principle. Background Technology

[0002] The vigorous development of new energy sources has become an inevitable trend in my country. In recent years, the installed capacity of new energy sources has been increasing, bringing many new problems to the new power system and posing numerous challenges to its stable operation.

[0003] Unlike synchronous generators, renewable energy equipment has insufficient overcurrent capacity. When faced with strong fault disturbances, to avoid overcurrent, the equipment risks disconnecting from the grid, which significantly impacts system stability. To ensure renewable energy equipment can operate without disconnecting from the grid and maintain system stability, various countries have introduced corresponding grid connection guidelines. my country's grid connection guidelines stipulate that when the terminal voltage of renewable energy equipment is below 0.8 pu, the equipment will adopt low-voltage ride-through control to support the terminal voltage level. After the fault is cleared, the renewable energy equipment will adopt ramp-up control; and after the initial active power output is restored, it will finally switch to conventional control. Therefore, during the entire low-voltage ride-through process, renewable energy equipment exhibits sequential switching, strong nonlinearity, and multi-timescale characteristics. For such a complex renewable energy transient switching system, ensuring its safe and stable operation and quickly and accurately calculating its critical disconnection time becomes a challenging problem.

[0004] The calculation of critical cutoff time for a system mainly falls into two categories: numerical calculation and analytical calculation. Numerical simulation methods typically consume significant computational resources and are time-consuming, hindering rapid decision-making. Analytical calculations, on the other hand, can quickly aid decision-making. Currently, the main methods include the equal-area method and the Lyapunov method. These two types of methods generally ignore the influence of damping terms and are widely used in traditional synchronous machine systems. In renewable energy grid-connected systems, the damping term exhibits both magnitude and positive / negative variations; ignoring the damping term often leads to significant errors. Furthermore, due to the frequency jumps in the phase-locked loop, directly using these two types of methods also introduces substantial errors. Therefore, based on a deep understanding of the characteristics of renewable energy grid-connected systems, it is necessary to improve existing analytical methods to suit current application scenarios, thereby providing guidance for implementing transient control measures.

[0005] Meanwhile, artificial intelligence algorithms have been introduced into the assessment of power grid transient stability, but training the equipment as a "black box" makes the internal physical mechanisms almost invisible; moreover, the massive amounts of high-fidelity data required to supply the model consume significant computing resources. This results in two main drawbacks: first, it fails to elicit intuitive and explainable physical causes; second, the computation time is too long, making it difficult to support real-time analysis and second-level decision-making for large power grids.

[0006] There is an urgent need to propose a novel and efficient theoretical method for the critical disconnection time of grid-connected new energy equipment systems that take into account the complete low-voltage ride-through process. Summary of the Invention

[0007] To address the shortcomings and improvement needs of existing methods, this invention provides a method for analyzing the low-voltage ride-through transient synchronous stability of new energy equipment based on an improved equal-area principle. Its purpose is to quickly and accurately calculate the critical disconnection time of the new energy grid-connected system, providing guidance for timely system intervention and ensuring the stable operation of the power system.

[0008] To achieve the above objectives, according to a first aspect of the present invention, an improved equal-area method suitable for low-voltage ride-through transient synchronization stability analysis of new energy equipment is provided, which mainly includes the following steps: (1) A transient switching model is constructed for the renewable energy grid-connected system under the complete low-voltage ride-through process. The system is divided into four stages according to the time sequence of the fault occurrence: pre-fault stage (stage 1), fault duration stage (stage 2), pre-fault recovery stage (stage 3), and post-fault recovery stage (stage 4). When the fault occurs, since the terminal voltage is lower than 0.8 pu, the renewable energy grid-connected system will switch to low-voltage ride-through control, and the system will switch from stage 1 to stage 2. When the fault is cleared, the renewable energy reactive power control resumes normal control, and the active power control adopts ramp control, and the system switches from stage 2 to stage 3. When the active power output recovers to the initial level, the renewable energy active power control resumes normal control, and the system switches from stage 3 to stage 4. For each stage, the differential equations and algebraic equations of the system are constructed, which together constitute the transient switching model of the renewable energy grid-connected system.

[0009] (2) Solve for the stable operating point of the system in stage 1. f The unstable equilibrium point at the initial moment of stage 1 and stage 3. f 3,u For the system of differential-algebraic equations in stage 1, setting the differential terms to 0 and solving the system of equations simultaneously yields the stable operating point for stage 1. f 1, its value range is less than π / 2. For the initial time of stage 3 (i.e. i d3 = i d2 By setting the differential terms in the system of differential algebraic equations to 0 and solving the system simultaneously, we can obtain the unsteady equilibrium point of stage 3. f 3,u Its value range is greater than π / 2.

[0010] (3) Normalize the differential algebraic equations at the initial time of stage 2 and stage 3 into the form of generalized swing equations, and solve for each equivalent coefficient.

[0011] (4) For the new energy grid-connected system at the initial moment of stage 3, the critical cut-off angle of the system is calculated using the first equal area approximation principle. f cr 1 .

[0012] (5) For the new energy grid-connected system at the initial moment of stage 3, the critical cut-off angle of the system is calculated using the second equal area approximation principle. f cr 2 .

[0013] (6) For the new energy grid-connected system at the initial moment of stage 3, the critical cut-off angle of the system is calculated using the third equal area approximation principle. f cr 3 .

[0014] (7) The trajectory of the new energy grid-connected system during the fault duration, obtained using the classic fourth-order Runge-Kuta method, with a step size of The step size can be adjusted according to the required computational accuracy and speed. In multiple simulations, the fault duration is set to gradually increase, and when the trajectory... f Just greater than f cr If we record the time as T, then T- As the critical resection time of the system.

[0015] The present invention also provides an electronic device, comprising: a computer-readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used to read executable instructions stored in the computer-readable storage medium and execute the above-described method.

[0016] The present invention also provides a computer-readable storage medium storing computer instructions for causing a processor to perform the above-described method.

[0017] The present invention also provides a computer program product, including a computer program or instructions that, when executed by a processor, implement the above-described method.

[0018] Overall, compared with the prior art, the technical solutions conceived in this invention can adapt to the sequential switching, strong nonlinearity, and multi-timescale characteristics of new energy equipment. Through this method, the critical cut-off time of the system can be calculated more quickly and accurately, providing a scientific basis and technical support for the safe and stable operation of new energy power systems. Attached Figure Description

[0019] Figure 1 A flowchart of an improved equal-area-based low-voltage ride-through transient synchronization stability analysis method for new energy equipment provided in an embodiment of the present invention; Figure 2 This is a topology diagram of a VSC grid-connected system under a DC voltage time scale provided in an embodiment of the present invention; Figure 3 The present invention provides a time-domain simulation diagram for verifying system stability and instability when a grid voltage fault occurs, based on the critical clearing time calculated using an improved equal-area method. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0021] In this invention, the terms "first," "second," etc. (if present) in the invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0022] New power systems incorporating renewable energy equipment exhibit significantly different transient stability characteristics compared to traditional power systems centered on synchronous generators. Traditional synchronous generator systems can be accurately described using classical swing equations, and their physical mechanisms are clear. In contrast, renewable energy equipment generally employs complex sequential control strategies involving multiple time scales, containing numerous nonlinear control elements. This characteristic not only exacerbates the system's nonlinearity and strong coupling but also makes it difficult to calculate its critical cut-off time, thus greatly increasing the difficulty of ensuring the stable operation of renewable energy grid-connected systems. Therefore, to quickly and accurately calculate the critical cut-off time of renewable energy grid-connected systems during low-voltage ride-through and ensure the stable and safe operation of the power system, this invention proposes an improved equal-area transient synchronous stability analysis method for renewable energy equipment based on low-voltage ride-through. This method can improve the efficiency and accuracy of calculating the critical cut-off time of renewable energy grid-connected systems and guide timely transient control measures to ensure the safe and stable operation of the power system.

[0023] The specific implementation process is as follows: Figure 1 As shown: (1) Nonlinear transient switching modeling is performed for the new energy grid-connected system. The control block diagram and topology of the VSC grid-connected system under the voltage-time scale are as follows: Figure 2 As shown, its transient switching model will be constructed. U dci This is the DC capacitor voltage.i di Active current, i qi It is reactive current. f i For phase-locked loop phase, oh i Let i be the phase-locked loop frequency, i = 1, 2, 3, 4, 5, where each number represents the current stage. In stage 1, the renewable energy grid-connected system adopts conventional control, considering capacitor dynamics, DC voltage control dynamics, terminal voltage control dynamics, and phase-locked loop control dynamics, resulting in a 5th-order model. The selected state variable is […]. U dc1 , i d1 , i q1 , f 1, oh [1] Its differential-algebraic equation is as follows:

[0024] in, C Indicates the size of the DC capacitor. P in The constant power input to the DC capacitor. k pdc and k idc These represent the proportional and integral coefficients for DC voltage control, respectively. k pV and k iV These represent the proportional and integral coefficients for terminal voltage control, respectively. k ppll and k ipll These represent the proportional coefficient and integral coefficient of the phase-locked loop control, respectively. X g This refers to the connection reactance between the VSC and the power system. U t1 The magnitude of the terminal voltage. u td1 and u tq1 These represent the terminal voltages at... d shaft and q The components below the axis, P e1 This indicates the electromagnetic output power. Represents state quantities The derivative, where the upper label is " "" indicates differentiation. Additionally, the grid voltage before the fault... U g1 =1 pu.

[0025] In Phase 2, the new energy grid-connected system adopts low-voltage ride-through control, considering only the dynamics of phase-locked loop control, which manifests as a second-order model. The selected state variable is […]. f 2, oh [2] Its differential-algebraic equation is as follows:

[0026] in, u td2 and u tq2 These represent the terminal voltages at... d shaft and q The component below the shaft, the voltage after the fault drop U g2 It is a constant. U g2 < U g1 .

[0027] According to low voltage ride-through control, its current command value i d2 and i q2 This is a constant value, calculated at the initial moment of the fault occurrence, as shown below:

[0028] in, U t2 The magnitude of the terminal voltage. K This represents the reactive power proportional injection coefficient, which is a constant. I max This represents the capacity of the converter and is also a constant.

[0029] In Phase 3, the active power control of the renewable energy grid-connected system adopts ramp control, while reactive power control reverts to terminal voltage control. Considering the dynamics of phase-locked loop control, terminal voltage control, and ramp control, a fourth-order model is adopted, and the state variables are selected as […]. i d3 , i q3 , f 3, oh [3] Its differential-algebraic equation is as follows:

[0030] in, u td3 and u tq3 These represent the terminal voltages at... d shaft and q The components below the axis, U t3The voltage amplitude after the fault is cleared. U g3 It is a constant. U g3 = U g1 =1 pu. Climbing coefficient K ramp It is a constant.

[0031] In Phase 4, the new energy grid-connected system adopts conventional control, considering capacitor dynamics, DC voltage control dynamics, terminal voltage control dynamics, and phase-locked loop control dynamics, exhibiting a 5th-order model, similar to Phase 1, only differing in digital subscripts. The selected state variables are [ U dc4 , i d4 , i q4 , f 4, oh [4] Its differential-algebraic equation is as follows:

[0032] in, u td4 and u tq4 These represent the terminal voltages at... d shaft and q The components below the axis, U t4 The magnitude of the terminal voltage. P e4 This indicates the electromagnetic output power.

[0033] (2) Solve for the stable operating point of the system in stage 1. f The unstable equilibrium point at the initial moment of stage 1 and stage 3. f 3,u For the system of differential-algebraic equations in stage 1, setting the differential terms to 0 and solving the system of equations simultaneously yields the stable operating point for stage 1. f 1, its value range is less than π / 2. For the initial time of stage 3 (i.e. i d3 = i d2 By setting the differential terms in the system of differential algebraic equations to 0 and solving the system simultaneously, we can obtain the unsteady equilibrium point of stage 3. f 3,u Its value range is greater than π / 2.

[0034] (3) Normalize the differential-algebraic equations at the initial moments of stages 2 and 3 into the form of generalized oscillation equations, and solve for each equivalent coefficient. The form of the generalized oscillation equation for stage 2 is as follows:

[0035] Among them, the equivalent inertia coefficient of the system in stage 2 M 2. Equivalent mechanical power P meq2 Equivalent electromagnetic power P eq2 Equivalent damping coefficient D The expression for 2 is:

[0036] The generalized swing equation for the initial moment of stage 3 is as follows:

[0037] Among them, the equivalent inertia coefficient of the system at the initial moment of stage 3 M 3. Equivalent mechanical power P meq3 Equivalent electromagnetic power P eq3 Equivalent damping coefficient D The expression for 3 is:

[0038] Because the system current at the initial moment of stage 3 i d3 = i d2 ,So P meq3 = P meq2 .

[0039] (4) For the new energy grid-connected system at the initial moment of stage 3, the critical cut-off angle of the system is calculated using the first equal area approximation principle. f cr 1 In the first approximation, damping effects are neglected ( D 2 and D 3) The impact of the fault occurrence / clearance, and the frequency jumps at the fault occurrence / clearance point. From the initial operating point of the fault. f 1 to fault clearing angle f cr 1 The acceleration area of ​​the system is From the fault removal angle f cr 1 Unstable equilibrium point at the initial moment of stage 3 f 3,u The deceleration area of ​​the system is According to the equal area rule, to ensure stability at the initial moment of stage 3, the following conditions must be met: Therefore, the first approximate expression for the critical resection angle can be obtained as: .

[0040] (5) For the new energy grid-connected system at the initial moment of stage 3, the critical cut-off angle of the system is calculated using the second equal area approximation principle. f cr 2 In the second approximation, the damping effect is neglected ( D 2 and D The impact of 3) is considered, but the frequency jump at the time of fault occurrence / clearance is taken into account. Network equations This holds true in all stages, differing only in the subscripts. The frequency jumps in the system are caused by... u tq The result is that and phase f The numbers are always consecutive, differing only in their subscripts. Therefore, it can be determined based on... U g and i d The mutation can be used to obtain the jump variables at the time of fault occurrence / clearance. Its expression is: Since the damping term is neglected, the system energy is conserved at the initial moments of stages 2 and 3, making it a conservative system. Therefore, an energy function can be constructed. The system frequency jumps from 0 to [value] at the initial moment of phase 2. oh 1, its expression is: Therefore, the constant energy value for stage 2 can be obtained. Similarly, the constant energy value for stage 3 can be obtained. .make t c Indicates the time when the fault is cleared. f cr 2 Let represent the critical cut-off angle for the second approximation. Based on the energy conservation in stage 2, the frequency expression before the fault clearing time can be obtained: Similarly, the frequency expression after the fault clearing time can be obtained as follows: At the fault clearing moment, the frequency jump variable Therefore, the approximate expression for the critical resection angle using the second equal-area method can be obtained as follows:

[0041] (6) For the new energy grid-connected system at the initial moment of stage 3, the critical cut-off angle of the system is calculated using the third equal area approximation principle. f cr3 In the third approximation, damping effect is also taken into account ( D 2 and D The impact of 3) also considers the frequency jumps at the time of fault occurrence / clearance. Let S d The third approximation represents the energy consumed by the damping term. It considers the same kinetic energy change as the second approximation, but in the third approximation, a portion of the potential energy is allocated for damping energy dissipation. S d According to the law of conservation of energy, we have:

[0042] The expression for the damping dissipation term is as follows: Using the second approximation of the frequency expression and the critical cutoff angle, the energy dissipated by the damping term can be estimated as follows:

[0043] Finally, the critical resection angle expression approximated by the third equal area principle can be obtained as follows:

[0044] The critical cut-off angle of the third approximation is used as the output of the improved equal area principle, i.e. f cr = f cr 3 .

[0045] (7) The trajectory of the new energy grid-connected system during the fault duration, obtained using the classic fourth-order Runge-Kuta method, with a step size of The step size can be adjusted according to the required computational accuracy and speed. In multiple simulations, the fault duration is set to gradually increase, and when the trajectory... f Just greater than f cr If we record the time as T, then T- As the critical resection time of the system.

[0046] The embodiments of the present invention employ a VSC grid-connected system under a DC voltage time scale, and its topology and control block diagram are as follows: Figure 2 As shown in Table 1, the approximate estimation results of the cubic equal area method under different working conditions and the critical resection angle results obtained from numerical simulation are obtained according to the above calculation method. The corresponding critical resection time results are shown in Table 2. f cr EMT The critical cut-off angle calculated by numerical simulation. t cr EMTThis represents the critical cut-off time calculated by numerical simulation. It can be seen that the error of the cubic equal-area method decreases successively. To verify the effectiveness of the method, under condition 1 (the fault occurs at 0.5s), U g2 =0.2 pu, i d2 =0.4pu), and time-domain simulation was performed based on the critical cut-off time calculated according to the improved equal area principle, and both stable and unstable waveforms were analyzed, such as Figure 3 As shown, the critical cut-off time calculated based on the improved equal-area method is in excellent agreement with the numerical simulation results, demonstrating high accuracy. The proposed improved equal-area method for analyzing the low-voltage ride-through transient synchronization stability of new energy equipment can quickly and accurately calculate the system's critical cut-off time.

[0047] Table 1. Calculation results of the critical resection angle based on the three-dimensional equal-area approximation and numerical simulation.

[0048] Table 2. Calculation results of critical resection time based on three equal-area approximations and numerical simulations.

[0049] In summary, this invention proposes an improved method for analyzing the transient synchronous stability of new energy equipment during low-voltage ride-through based on equal-area conditions. This method can quickly and accurately calculate the critical disconnection time of the new energy grid-connected system during low-voltage ride-through and guide timely implementation of transient control measures to ensure the safe and stable operation of the power system.

[0050] Example 2 The present invention also relates to an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the method described above.

[0051] The electronic device can be a desktop computer, laptop, handheld computer, or cloud server, etc. The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The memory can be used to store computer programs and / or modules. The processor performs various functions of the electronic device by running or executing the computer programs and / or modules stored in the memory, and by accessing data stored in the memory.

[0052] Example 3 The present invention also relates to a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described above.

[0053] Specifically, the memory may include high-speed random access memory, as well as non-volatile memory, such as hard disks, RAM, plug-in hard disks, smart media cards (SMC), secure digital (SD) cards, flash cards, at least one disk storage device, flash memory device, or other volatile solid-state storage devices.

[0054] Example 4 This invention provides a computer program product or computer program that includes computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computer device to perform the steps of the method described in the above embodiments of this invention.

[0055] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. It should be noted that the terms "in one embodiment," "for example," and "again" in this invention are intended to illustrate the invention and are not intended to limit the invention.

[0056] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for analyzing the transient synchronization stability of new energy equipment during low-voltage ride-through based on an improved equal-area principle, characterized in that, Includes the following steps: (1) Taking into account the complete low voltage ride-through process, the system is divided into four stages according to the time sequence of the fault occurrence: the early stage of the fault, i.e., stage 1; the fault duration, i.e., stage 2; the early stage of the fault recovery, i.e., stage 3; and the late stage of the fault recovery, i.e., stage 4. The division rule is as follows: when the fault occurs, since the terminal voltage is lower than 0.8 pu, the new energy grid-connected system will switch to low voltage ride-through control, and the system will switch from stage 1 to stage 2; when the fault is cleared, the reactive power control of the new energy will resume normal control, and the active power control will adopt ramp control, and the system will switch from stage 2 to stage 3; when the active power output recovers to the initial level, the active power control of the new energy will resume normal control, and the system will switch from stage 3 to stage 4. For each stage, construct a system of differential-algebraic equations for the system; (2) Set the differential terms in the differential algebraic equations of stage 1 and stage 3 to 0 respectively, and solve for the stable operating point of the system in stage 1. φ The unstable equilibrium point at the initial moment of stage 1 and stage 3. φ 3,u ; (3) Normalize the differential algebraic equations at the initial time of stage 2 and stage 3 into the form of generalized swing equations, and solve for each equivalent coefficient; (4) For the new energy grid-connected system at the initial moment of stage 3, without considering the damping effect and the frequency jump at the moment of fault occurrence / clearance, according to the energy conservation of the system, the acceleration area will be equal to the deceleration area. The critical cut-off angle of the system is calculated by using the first equal area approximation principle. φ cr 1 ; (5) For the new energy grid-connected system at the initial moment of stage 3, without considering the damping effect but taking into account the frequency jump at the moment of fault occurrence / clearance, the frequency correction is considered based on the first equal area approximation. According to the energy conservation principle, the critical cut-off angle of the system is calculated using the second equal area approximation principle. φ cr 2 ; (6) For the new energy grid-connected system at the initial moment of stage 3, considering both the damping effect and the frequency jump at the moment of fault occurrence / clearance, and taking into account the same kinetic energy change as the second equal area approximation, a portion of the potential energy is allocated for damping energy dissipation. The dissipated energy is estimated by using the result of the second equal area approximation, and the critical cut-off angle of the system is calculated by using the principle of the third equal area approximation. φ cr 3 The critical cut-off angle of the third approximation is used as the output of the improved equal-area method, i.e. φ cr = φ cr 3 ; (7) The trajectory of the system during the fault duration is numerically calculated using the classical fourth-order Runge-Kuta method, combined with the critical clearing angle calculated analytically. φ cr The critical resection time of the system is determined.

2. The transient synchronous stability analysis method as described in claim 1, characterized in that, The system of differential-algebraic equations constructed in each stage are as follows: Phase 1: Phase 2: Phase 3: Phase 4: in, U dci This is the DC capacitor voltage. i di Active current, i qi It is reactive current. φ i For phase-locked loop phase, ω i The frequency of the phase-locked loop (PLL) U ti The magnitude of the terminal voltage. u tdi and u tqi These represent the terminal voltages at... d shaft and q The components below the axis, P ei Indicates electromagnetic output power. U gi The voltage is the grid voltage, i = 1, 2, 3, 4, 5, where the number represents the current stage. C Indicates the size of the DC capacitor. P in The constant power input to the DC capacitor. k pdc and k idc These represent the proportional and integral coefficients for DC voltage control, respectively. k pV and k iV These represent the proportional and integral coefficients for terminal voltage control, respectively. k ppll and k ipll These represent the proportional and integral coefficients of the phase-locked loop control, respectively. X g For the connection reactance between VSC and the power system, K This represents the reactive power proportional injection coefficient. I max Indicates the capacity of the converter. K ramp Indicates the gradeability coefficient. Represents state quantities The derivative, where the upper label is " "" indicates differentiation operation.

3. The transient synchronization stability analysis method as described in claim 2, characterized in that, By setting the differential terms in the system of differential-algebraic equations for stage 1 to 0 and solving the system of equations simultaneously, the stable operating point for stage 1 can be obtained. φ 1. Its value range is less than π / 2.

4. The transient synchronization stability analysis method as described in claim 2, characterized in that, For the initial time of phase 3 (i.e. i d3 = i d2 By setting the differential terms in the system of differential algebraic equations to 0 and solving the system of equations simultaneously, we can obtain the unsteady equilibrium point of stage 3. φ 3,u Its value range is greater than π / 2.

5. The transient synchronization stability analysis method as described in claim 1, characterized in that, By analogy with a synchronous machine, the differential-algebraic equations of stage 2 can be written in the form of a rocking equation, yielding its equivalent inertia coefficient, equivalent mechanical power, and equivalent electromagnetic power: in, M 2 represents the equivalent inertia coefficient of the system in stage 2. P meq2 For equivalent mechanical power, P eq2 For equivalent electromagnetic power, D 2 represents the equivalent damping coefficient; Similarly, the swing equation at the initial moment of stage 3 is as follows: in, M 3 represents the equivalent inertia coefficient of the system in stage 3. P meq3 For equivalent mechanical power, P eq3 For equivalent electromagnetic power, D 3 represents the equivalent damping coefficient.

6. The transient synchronization stability analysis method as described in claim 1, characterized in that, The fault trajectory of the multi-machine system obtained by the classic fourth-order Runge-Kuta method has a step size of The step size is adjusted according to the required calculation accuracy and speed; in multiple simulations, the fault duration is set to gradually increase, when the trajectory... φ Greater than φ cr Record the time as T- As the critical resection time of the system.

7. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1 to 6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1 to 6.

9. A computer program product, comprising a computer program or instructions, characterized in that, When the computer program or instructions are executed by a processor, they implement the steps of the method as described in any one of claims 1 to 6.

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