New energy sending end power grid voltage stability prevention and control method, system and device and storage medium

Abstract

The invention discloses a new energy sending end power grid voltage stability prevention and control method, system and device, and a storage medium. The method comprises the steps of obtaining an anticipated fault set under any operation scene of a new energy sending end power grid; performing multi-dimensional stability analysis on the voltage under each anticipated fault, and screening out a key anticipated fault set with any type of voltage instability risk; if the key anticipated fault set is not empty, triggering a prevention and control mechanism, and constructing a prevention and control optimization model by taking minimum control cost as a target function; and solving the prevention and control optimization model to obtain an optimal prevention and control strategy. According to the method, the prevention and control optimization model containing various voltage stability constraints is established, and the distributed optimization algorithm is adopted for solving, so that the static voltage stability, the small interference voltage stability and the large interference voltage stability of the sending-end power grid can be ensured.

Description

Technical Field

[0001] This invention relates to the technical field of power system operation, and in particular to a method, system, equipment, and storage medium for voltage stability prevention and control of new energy power grids. Background Technology

[0002] The weak overcurrent capacity of renewable energy converters, lacking the dynamic reactive power support capabilities of conventional synchronous power supplies, and the reduced short-circuit capacity and grid strength in areas with large-scale renewable energy grid integration, can lead to excessive short-circuit currents and insufficient overall dynamic reactive power support in the new power electronic grid. Furthermore, the narrow voltage tolerance range of converters reduces the low / high voltage ride-through capability of renewable energy units. When transient power frequency overvoltages occur due to external faults, they can cause large-scale cascading grid disconnection faults in renewable energy units, further impacting the safety and stability of the power grid. For the sending-end grid connected to the main grid via asynchronous interconnection, voltage stability issues can also affect its DC power output, thereby impacting the frequency stability of both the sending and receiving grids. Therefore, implementing preventative control measures for the sending-end grid to ensure its voltage stability under various operating modes is of great significance.

[0003] Currently, voltage stability prevention and control in power grids mainly focuses on static voltage stability. However, in high-penetration renewable energy power grids, dynamic voltage stability is a more significant concern due to the strong nonlinearity of power electronic devices. Dynamic voltage stability encompasses both small-disturbance voltage stability and large-disturbance voltage stability. This invention proposes a novel preventive control method for high-penetration renewable energy sending-end power grids that considers multiple voltage stability constraints, thereby providing decision support for the stable operation of the power system. Summary of the Invention

[0004] In view of the aforementioned existing problems, this invention is proposed. Therefore, this invention provides a method, system, device, and storage medium for preventing and controlling voltage stability in the power grid at the new energy sending end, addressing the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, embodiments of the present invention provide a method for preventing and controlling voltage stability in a new energy power grid, comprising: acquiring a set of anticipated faults under any operating scenario of the new energy power grid; A multi-dimensional stability analysis was performed on the voltage under each of the anticipated faults to identify a set of key anticipated faults that pose a risk of voltage instability in any type. If the set of key anticipated faults is not empty, a preventive control mechanism is triggered, and a preventive control optimization model is constructed with the goal of minimizing control costs. The optimal prevention and control strategy is obtained by solving the aforementioned prevention and control optimization model.

[0006] As a preferred embodiment of the voltage stability prevention and control method for the new energy power grid described in this invention, the step of performing multi-dimensional stability analysis on the voltage under each anticipated fault to screen out a set of key anticipated faults with any type of voltage instability risk includes: The static voltage stability of the power grid under the various anticipated faults was analyzed, and key anticipated faults with the risk of static voltage instability were screened out. The system linearization model under each of the aforementioned contingent faults is evaluated to identify key contingent faults that pose a risk of small disturbance voltage instability. The system state after each anticipated fault is cleared is solved. If there is no real feasible solution for the AC bus voltage, the key anticipated faults with the risk of large disturbance voltage instability are screened out.

[0007] As a preferred embodiment of the new energy power grid voltage stability prevention and control method of the present invention, the static voltage stability of the power grid under each anticipated fault is analyzed, and key anticipated faults with static voltage instability risk are identified, including: A continuous power flow model of the power grid containing new energy sources with a high proportion of voltage source converters is constructed, and the control mode of the voltage source converters is configured, taking into account the operating constraints of the upper limit of the converter's internal potential and the upper limit of the output current. For each anticipated fault, the system load is parameterized based on the continuous power flow model, and the load and power supply are expressed as linear functions of the load growth parameters. Augmented power flow equations are constructed through the local parameterized continuous power flow algorithm, and the maximum load-bearing parameters under the corresponding anticipated fault are calculated. If the maximum load-bearing parameter is less than the first threshold, it is determined that the static voltage stability of the system is insufficient under the current anticipated fault, and the current anticipated fault is included in the set of key anticipated faults with the risk of static voltage instability.

[0008] As a preferred embodiment of the new energy sending-end grid voltage stability prevention and control method of the present invention, the following is provided: the system linearization model under each anticipated fault is evaluated, and the key anticipated faults with small disturbance voltage instability risk are screened out, including: constructing a sending-end grid dynamic model that includes synchronous generators, voltage source converters and static loads. For each anticipated fault, the dynamic model of the sending-end power grid is linearized at the corresponding operating point to construct an extended Jacobian matrix. The state variables of the extended Jacobian matrix include the transient electromotive force of the synchronous generator, the d-axis and q-axis output current components of the voltage source converter, and the phase-locked loop phase. If the extended Jacobian matrix is ​​singular, it is determined that the system has a small disturbance voltage instability risk under the anticipated fault, and it is included in the set of critical anticipated faults.

[0009] As a preferred embodiment of the new energy power grid voltage stability prevention and control method of the present invention, the system state after each anticipated fault is cleared is solved. If there is no real feasible solution for the AC bus voltage, the key anticipated faults with the risk of large disturbance voltage instability are screened out, including: For each anticipated fault, establish a post-fault power flow equation that includes the dynamics of the synchronous generator transient electromotive force, the current limiting characteristics of the voltage source converter, and the DC power output response. During the fault phase, the voltage source converter increases the output current to maintain stable power output, and the output current is within the maximum limit value; At the fault clearing moment, based on the fault duration, the transient electromotive force expression of the synchronous machine and the AC bus power balance equation are combined to construct a set of nonlinear power flow equations after fault clearing; the set of power flow equations is solved to obtain the mathematical solution of the AC bus voltage amplitude. If the amplitude of the AC bus voltage does not have a real solution, it is determined that the system has experienced a large disturbance voltage collapse under the anticipated fault, and it is included in the set of key anticipated faults with the risk of large disturbance voltage instability.

[0010] The beneficial effects of this preferred technical solution are that it can screen out three types of key anticipated faults of instability, and achieve risk-oriented precise prevention and control, preventing cascading grid disconnection or voltage collapse due to ignoring a certain type of dynamic process.

[0011] As a preferred embodiment of the voltage stability prevention and control method for the new energy power grid at the sending end described in this invention, the construction of a prevention and control optimization model with minimizing control cost as the objective function includes: the objective function of the prevention and control optimization model is expressed as: in, , , , , These represent the generator's active power output, reactive power output, reactive power injected by the adjustable capacitor, reactive power injected by the adjustable reactor, and the turns ratio of the on-load tap-changing transformer, respectively; the operating variables in the normal operating state before preventive control are indicated by the subscript 0, and the variables in the normal operating state after preventive control are indicated by the subscript 0. This indicates the amount of active power cut by the load node; , , , , These represent the number of generator nodes, the number of system nodes, the number of adjustable capacitor banks, the number of adjustable reactor banks, and the number of on-load tap-changing transformers, respectively. , , , , , These represent the weights of each control measure; The constraints of the prevention and control optimization model include normal operation constraints, multi-dimensional voltage stability constraints under critical faults, and new energy operation constraints.

[0012] The beneficial effects of this preferred technical solution are that it constructs an optimization model with the objective function of minimizing control costs, assigns differentiated weights to different control methods, prioritizes low-cost measures, and reduces high-cost operations.

[0013] As a preferred embodiment of the voltage stability prevention and control method for the new energy power grid at the sending end described in this invention, the optimal prevention and control strategy obtained by solving the prevention and control optimization model includes: The large-scale power grid is divided into multiple sub-networks, and a local optimization model for each sub-network is constructed. The complementary gap of the local optimization model for each sub-network is calculated. If the complementary gap is less than the allowable error, the optimization result is output; if the complementary gap is not less than the allowable error, it is determined whether the maximum number of iterations of the decomposition coordination interior point method has been reached. If the maximum number of iterations is reached, the algorithm fails to converge, terminates, and displays a failure message; if the maximum number of iterations is not reached, the control variables and dual variables of each subnet are updated according to the current iteration results until the iterative coordination converges and the optimal prevention and control strategy is output.

[0014] Secondly, the present invention provides a voltage stability prevention and control system for a new energy power grid, comprising: a fault acquisition module, used to acquire a set of anticipated faults under any operating scenario of the new energy power grid; The fault screening module is used to perform multi-dimensional stability analysis on the voltage under each anticipated fault and screen out a set of key anticipated faults that have any type of voltage instability risk. The optimization model building module is used to trigger the prevention and control mechanism if the set of key anticipated faults is not empty, and to build a prevention and control optimization model that considers multi-dimensional voltage stability constraints and new energy operation constraints under key anticipated faults with the objective function of minimizing control costs. The optimization module is used to solve the prevention and control optimization model to obtain the optimal prevention and control strategy.

[0015] Thirdly, the present invention provides an electronic device, comprising: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, they implement the steps of the new energy power grid voltage stability prevention and control method.

[0016] Fourthly, the present invention provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the new energy power grid voltage stability prevention and control method.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention can screen out key anticipated faults with static voltage stability problems, as well as key anticipated faults with small disturbance voltage stability problems and large disturbance voltage stability problems. Furthermore, it establishes a preventive control optimization model that includes multiple voltage stability constraints and uses a distributed optimization algorithm to solve it, which can fully guarantee the static voltage stability, small disturbance voltage stability and large disturbance voltage stability of the sending-end power grid. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a schematic flowchart of a method for preventing and controlling voltage stability in a new energy power grid according to an embodiment of the present invention. Figure 2 This is a flowchart illustrating the solution process for a preventive control method for voltage stability prevention control of a new energy power grid, as described in one embodiment of the present invention. Figure 3 This is a schematic diagram of a new energy source connected to the grid via a voltage source converter, according to an embodiment of the present invention, which describes a method for preventing and controlling voltage stability in the power grid at the new energy sending end. Figure 4 This is a flowchart of static voltage stability analysis based on the continuous power flow method for a new energy power grid voltage stability prevention and control method according to an embodiment of the present invention. Figure 5 This is a dynamic model diagram of the power grid considering voltage source converter access in a new energy power grid voltage stability prevention and control method according to an embodiment of the present invention. Figure 6 This is a schematic diagram of an IEEE 236-node system for a new energy power grid voltage stability prevention and control method according to an embodiment of the present invention; Figure 7 This is a structural diagram of the IEEE 118-node system for a new energy power grid voltage stability prevention and control method according to an embodiment of the present invention. Detailed Implementation

[0019] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0020] Example 1, referring to Figures 1-5 This is one embodiment of the present invention, which provides a method for preventing and controlling voltage stability in the power grid at the new energy sending end, such as... Figure 1 As shown, it includes: S100: Obtain the set of anticipated faults under any operating scenario of the new energy power grid; S200: Perform multi-dimensional stability analysis on the voltage under each anticipated fault to screen out the set of key anticipated faults that pose a risk of voltage instability in any type; S300: If the set of critical anticipated faults is not empty, a preventive control mechanism is triggered, and a preventive control optimization model is constructed with the goal of minimizing control costs. S400: Solve the prevention and control optimization model to obtain the optimal prevention and control strategy.

[0021] It should be noted that renewable energy sources connected to the grid via power electronic converters have limited overcurrent capacity and cannot provide effective dynamic reactive power support like traditional synchronous generators. Converters are sensitive to voltage fluctuations and have a narrow voltage tolerance range, making renewable energy units prone to low / high voltage ride-through failures during transient power frequency overvoltages, leading to large-scale grid disconnection. For renewable energy sending-end grids connected to the main grid via DC asynchronous connections, voltage stability issues directly affect DC power transmission, subsequently impacting the frequency stability of both sending and receiving end grids. Current voltage stability prevention and control primarily focuses on static voltage stability, neglecting the small-disturbance and large-disturbance voltage stability issues caused by high proportions of power electronic equipment. This invention targets high-penetration renewable energy power grids. It employs a continuous power flow method considering renewable energy control methods and operational constraints to analyze anticipated grid faults and identify key anticipated faults with static voltage stability issues. A small-disturbance voltage stability analysis method based on the singularity-induced method is used to further identify key anticipated faults with small-disturbance voltage stability issues. A large-disturbance voltage stability analysis method based on power flow feasible solutions is then used to identify key anticipated faults with large-disturbance voltage stability issues. This constructs a set of key anticipated faults with static, small-disturbance, and large-disturbance voltage stability problems. Then, with the objective function of minimizing control cost, a preventative control optimization model considering static voltage stability constraints, small-disturbance voltage stability constraints, large-disturbance voltage stability constraints, and renewable energy operation constraints under key anticipated faults is constructed. Considering that the difficulty of solving this optimization model increases with the scale of the power grid and the presence of multiple constraints, a decomposition and coordination algorithm is proposed to solve the aforementioned preventative control optimization model.

[0022] In this embodiment of the invention, the set of faults preset in step S100 can be the faults that the power grid determines to occur frequently based on its operating experience; otherwise, the N-1 faults and N-2 faults with a higher probability of occurrence in the power grid are taken as the set of anticipated faults.

[0023] In this embodiment of the invention, step S200 performs a multi-dimensional stability analysis on the voltage under each anticipated fault, and filters out the set of key anticipated faults that pose any type of voltage instability risk, including: The static voltage stability of the power grid under various anticipated faults was analyzed, and key anticipated faults with the risk of static voltage instability were screened out. The system linearization model under each anticipated fault is evaluated, and key anticipated faults with small disturbance voltage instability risk are screened out. The system state after each anticipated fault is cleared is solved. If there is no real feasible solution for the AC bus voltage, the key anticipated faults with the risk of large disturbance voltage instability are screened out.

[0024] In this embodiment of the invention, step S200 analyzes the static voltage stability of the power grid under various anticipated faults, and identifies key anticipated faults with the risk of static voltage instability, including: A continuous power flow model of the power grid containing new energy sources with a high proportion of voltage source converters is constructed, and the control mode of the voltage source converters is configured, taking into account the operating constraints of the upper limit of the converter's internal potential and the upper limit of the output current. For each anticipated fault, the system load is parameterized based on the continuous power flow model, and the load and power supply are expressed as linear functions of the load growth parameters. Augmented power flow equations are constructed through the local parameterized continuous power flow algorithm, and the maximum load-bearing parameters under the corresponding anticipated fault are calculated. If the maximum load-bearing parameter is less than the first threshold, it is determined that the static voltage stability of the system is insufficient under the current anticipated fault, and the current anticipated fault is included in the set of key anticipated faults with the risk of static voltage instability.

[0025] It should be noted that, in this embodiment of the invention, the first threshold can be set to 0.1 based on actual engineering experience.

[0026] Furthermore, such as Figure 3 As shown, the main equipment in a grid-connected circuit for new energy sources includes a converter, a filter, and a transformer. (See diagram.) U S This refers to the voltage amplitude at point S on the AC bus. U C The internal potential of point C in the AC converter is measured. δ for U C and U S The phase difference between them; P S , Q S and P C , Q C These are the active power and reactive power at AC bus S and AC measurement point C of the converter, respectively; P d , U d These represent the active power and voltage on the DC side of the converter, respectively. P dc , Q dc These represent the DC output power; R C , X C These are the equivalent resistance and reactance at AC measurement point C of the converter (including the equivalent reactance of the converter transformer). Xf For filter reactance; The output current phasor at point C of the AC converter is given.

[0027] Furthermore, according to Figure 3 The relationship between the power provided by the new energy source and the voltage and current can be obtained as follows: in, The magnitude of the VSC grid-connected impedance; It is the impedance angle.

[0028] Reference Figure 4 In an optional embodiment, it is assumed that a high proportion of renewable energy grids have The nodes are mostly powered by voltage source converters (VSCs), employing constant voltage and constant reactive power control or reactive power-voltage droop control, and taking into account... and Constraints, corresponding nodes Injection power and This indicates that a small portion of the power supplies are traditional synchronous machine power supplies, used as balancing nodes or PV nodes, corresponding to the nodes. Injection power and This indicates that the node load and This indicates that the node DC power output and In other words, the first [unit / item] in the power grid The power balance equations for each node are as follows: in, , They are nodes The imbalance between active and reactive power; , They are nodes and nodes The voltage amplitude; , They are nodes and nodes The electrical conductance and susceptance between them; For nodes and nodes The phase angle difference between them.

[0029] Using the continuous power flow method, the parameterized load and power supply can be expressed as: in, , , , , These are the parameterized active power of the load, reactive power of the load, active power of the synchronous machine power supply, and active and reactive power of the VSC power supply, respectively. , , , , For the corresponding initial rate; , , , , This corresponds to the power increment; These are load parameters.

[0030] The active and reactive power transmitted between the new energy source and the AC system during steady-state operation is affected by the amplitude of the converter output current. On the one hand, it is limited by the internal potential of the VSC. The limitations are as follows: The relationship between the power provided by new energy sources and voltage and current, the VSC internal potential constraints, and the output current constraints are expressed as follows: in, This represents the upper limit of the converter voltage modulation. This represents the upper limit of the actual input current to the AC system of the converter.

[0031] When it needs to be explained, It can be the minimum value of current limits such as the maximum current of new energy delivered to the AC system, the maximum current allowed by the VSC device itself, and the maximum current of the control output.

[0032] From this, we can obtain the parameterized power balance equation. Combining the above VSC internal potential constraint and output current constraint equations, we can obtain the mathematical model of continuous power flow in a power grid containing a VSC source, which can be simplified as follows: in, The power flow equations are parameterized. U The node voltage magnitude state vector; θ The node voltage phase angle state vector; For VSC U C and I C constraint functions; This is the operating constraint function for the synchronous generator, including excitation current and output current constraints.

[0033] Furthermore, to ensure that the extended Jacobian matrix is ​​nonsingular at the bifurcation point, local parameterization is employed to construct the augmented power flow equations as follows: in, For nodes The state variables are selected by choosing the voltage of the node with the most severe voltage drop as a continuous parameter. For nodes Elements in the voltage tangent vector; Δ s To calculate the step size.

[0034] In this embodiment of the invention, step S200 evaluates the system linearization model under each anticipated fault and screens out the key anticipated faults with small disturbance voltage instability risk, including: constructing a dynamic model of the sending-end power grid that includes synchronous generators, voltage source converters and static loads; For each anticipated fault, the dynamic model of the sending-end power grid is linearized at the corresponding operating point to construct an extended Jacobian matrix. The state variables of the extended Jacobian matrix include the transient electromotive force of the synchronous generator, the d-axis and q-axis output current components of the voltage source converter, and the phase-locked loop phase. If the extended Jacobian matrix is ​​singular, it is determined that the system has a small disturbance voltage instability risk under the anticipated fault, and it is included in the set of critical anticipated faults.

[0035] Furthermore, when new energy sources are connected to the power system via VSC, the equivalent schematic diagram is as follows: Figure 5 As shown.

[0036] Reference Figure 5 , P SG and Q SG These represent the output active power and reactive power, respectively. and φ These represent the magnitude and phase of the system's equivalent impedance, respectively. and These represent the amplitude and phase of the AC bus voltage, respectively. The equivalent electromotive force of the synchronous power supply; P VSC and Q VSC These are the active and reactive power outputs of the VSC, respectively. This is the DC current of VSC; U VSC VSC is the DC voltage; This refers to the short-circuit voltage of the VSC converter transformer. For VSC converter ratio; P load and Q load These represent the active power and reactive power of the load, respectively.

[0037] Furthermore, to perform small-disturbance voltage stability analysis on the system, it is necessary to obtain the extended Jacobian block matrix J. net Therefore, a quasi-steady-state model of the system needs to be established. Considering the ontological models of each dynamic component, the derivation process of the quasi-steady-state model of the system is as follows: The Thevenin equivalent model is used to simulate the impact of the synchronous power source on the load node voltage, i.e., the voltage source in series impedance form. The output active and reactive power of the synchronous generator are as follows: The quasi-steady-state equations of VSC are shown below: in, I VSC and These represent the amplitude and phase of the AC output current of the VSC, respectively. and These are the AC output currents of VSC. shaft and Axial components; and These are the AC output currents of VSC. d shaft and q Axial components; θ PLL This refers to the output phase of the phase-locked loop (PLL).

[0038] The load model is represented as follows: in, U 0, P 0, Q 0 represents the voltage, active power, and reactive power of the system under rated operating conditions; It represents the proportionality coefficient of constant impedance load, constant current load, and constant power load in active load; It represents the ratio coefficient of constant impedance load, constant current load and constant power load in reactive load.

[0039] The power balance equation for the AC bus is: Furthermore, by linearizing the quasi-steady-state model of the new energy power system, we can obtain: Among them, J net To extend the Jacobian block matrix; Δ θ s Δ represents the phase change of the AC bus voltage. U s J represents the change in amplitude of the AC bus voltage. nx is the linearized matrix of the state variables; Δx is the vector composed of the state variables, mainly including the transient electromotive force of the synchronous generator. VSC output AC current and and the output of the phase-locked loop (PLL) θ PLL .

[0040] The extended Jacobian matrix can be represented as: Reference Figure 5 Voltage stability under small disturbances can be determined using the following formula: in, This indicates that the system voltage is stable. This indicates that the system voltage is unstable.

[0041] In an optional embodiment, it is assumed that the apparent power of the VSC is S VSC The power factor is cos( θ s - θ v The load power factor is The power balance equation can be written as follows: The relationship between the apparent power of VSC and the alternating current is as follows: Therefore, we can conclude that: in, Furthermore, considering the switching effect of the compensation capacitor, assuming that the steady-state value of the AC bus voltage can always be maintained at the rated value under different operating conditions, the above determinant can be used as a function of the variable... S VSC The quadratic equation in one variable. When the system is critically stable, it can be expressed as: Solve the equation and select the positive root in the result; this is the critical stable condition of the system. S VSC The value is shown in the following formula: Under critical stability conditions, the active power of the VSC is: When the output power of the VSC exceeds the critical value, matrix J net The determinant value will be less than 0, which means that the system will experience small disturbance voltage instability.

[0042] The capacity constraints of the new energy units connected to the system are analyzed based on the calculation formulas for the system when it is critically stable and under critical stability conditions. This capacity can be used as a capacity constraint for new energy in subsequent preventive control to maintain stable voltage under small disturbances.

[0043] In this embodiment of the invention, step S200 solves for the system state after each anticipated fault is cleared. If there is no real feasible solution for the AC bus voltage, the key anticipated faults with the risk of large disturbance voltage instability are screened out, including: For each anticipated fault, establish a post-fault power flow equation that includes the dynamics of the synchronous generator transient electromotive force, the current limiting characteristics of the voltage source converter, and the DC power output response. During the fault phase, the voltage source converter increases the output current to maintain stable power output, and the output current is within the maximum limit value; At the fault clearing moment, based on the fault duration, the transient electromotive force expression of the synchronous machine and the AC bus power balance equation are combined to construct a set of nonlinear power flow equations after fault clearing; the power flow equations are solved to obtain the mathematical solution of the AC bus voltage amplitude. If the AC bus voltage amplitude does not have a real solution, it is determined that the system has experienced a large disturbance voltage collapse under the anticipated fault, and it is included in the set of key anticipated faults with the risk of large disturbance voltage instability.

[0044] Furthermore, refer to Figure 5 When a fault occurs on the bus of the new energy access system, the differential equation of the transient electromotive force of the synchronous machine is as follows: Furthermore, assuming the d-axis synchronous reactance and the q-axis synchronous reactance are equal, that is... Because the AC bus voltage is very low during a short-circuit fault, the excitation system is usually at its peak excitation value, as shown in the following formula: The time-domain expression for the transient electromotive force of the synchronous machine is: in, The transient time constant of the synchronizing machine; This is the excitation electromotive force of the synchronous machine; x d For d-axis synchronous reactance; The transient reactance along the d-axis; This refers to the d-axis current of the synchronous machine. This is the maximum output limit for the excitation system.

[0045] During the fault phase, the outer loop controller of the VSC fully activates, attempting to increase the VSC output current to maintain a constant output power. Normally, under a three-phase ground fault condition at the VSC outlet, the VSC output current quickly reaches its maximum limit. in, This is the maximum AC current limit for VSC.

[0046] At the moment the fault is cleared, it should be noted that some DC power is transmitted via LCC and some via VSC. The portion transmitted via LCC will be blocked due to the decrease in bus voltage, resulting in zero DC output power for this part. The portion transmitted via VSC may not be blocked immediately due to reactive power control. Let's assume its transmitted DC power is... Therefore, at this moment, the load borne by the synchronous machine and VSC is the greatest, and voltage instability is most likely to occur. If the fault duration is Δ...t Then, the system power flow equation at the time of fault clearing is as follows: Solve the system power flow equations at the moment the fault is cleared to obtain the magnitude and phase of the AC bus voltage at that moment. If there is no real solution for the magnitude of the AC bus voltage, it indicates that the system will experience voltage collapse and is in a state of large disturbance voltage instability.

[0047] It should be noted that, in order to analyze the impact of new energy access on the stability of the system under large disturbance voltage, the output power of the new energy in steady state is changed, and the power flow equation of the system at the time of fault clearance is solved. The curve of the AC bus voltage at the time of short-circuit fault clearance as a function of the steady-state output power of the new energy can be obtained. From this, the maximum allowable access capacity of new energy under large disturbance voltage stability can be obtained.

[0048] It should be noted that the goal of voltage stability prevention and control is often to ensure sufficient voltage stability of the system under normal operating conditions and under anticipated fault conditions with the least possible control cost. Its control measures include adjusting the active and reactive power output of generators, switching adjustable capacitors and reactors, adjusting the tap changers of on-load tap-changing transformers, and shedding loads.

[0049] In this embodiment of the invention, step S300, which uses minimizing control cost as the objective function, involves constructing a preventive control optimization model, where the objective function of the preventive control optimization model is expressed as: in, , , , , These represent the generator's active power output, reactive power output, reactive power injected by the adjustable capacitor, reactive power injected by the adjustable reactor, and the turns ratio of the on-load tap-changing transformer, respectively; the operating variables in the normal operating state before preventive control are indicated by the subscript 0, and the variables in the normal operating state after preventive control are indicated by the subscript 0. This indicates the amount of active power cut by the load node; , , , , These represent the number of generator nodes, the number of system nodes, the number of adjustable capacitor banks, the number of adjustable reactor banks, and the number of on-load tap-changing transformers, respectively. , , , , , These represent the weights of each control measure; The constraints of the prevention and control optimization model include normal operation constraints, multi-dimensional voltage stability constraints under critical faults, and new energy operation constraints.

[0050] Specifically, the interconnected power grid after preventive control measures need to meet the feasibility constraints under normal operating conditions, including: The system power flow equations under normal operating conditions after preventive control measures are expressed as follows: The voltage transformation equation after introducing a virtual node in the on-load tap-changing transformer branch is expressed as: The upper and lower limit constraints of each control variable and state variable in preventive control are expressed as follows: The internal potential constraint of the VSC converter is expressed as: The output current constraint of the VSC converter is expressed as: in, , , , , , These represent the active and reactive power output from new energy sources (which will be used as optimization variables), the active and reactive loads at each load node in the system, and the active and reactive power transmitted via DC. , , These represent the system node voltage magnitude, and their real and imaginary parts, respectively. , These represent the real and imaginary parts of the virtual node voltage phasor introduced into the branch of the on-load tap-changing transformer, respectively. Indicates the first regional power grid The set of connecting lines contained in a cross section; Represents nodes A collection of connected branch lines; Represents nodes A collection of connected on-load tap-changing transformer branches; N D This indicates the node in the system that is connected to the converter; , , , These represent the active and reactive power on the line branch and the active and reactive power on the on-load tap-changing transformer branch, respectively.

[0051] It should be noted that the voltage stability prevention control proposed in this invention is for the case of high-penetration renewable energy access in the sending-end power grid. Therefore, the DC power delivered by the sending-end power grid can be considered unchanged before and after the prevention control; voltage stability prevention control is achieved solely through adjustments to the internal control variables of the sending-end power grid itself. Furthermore, the maximum constraint on the renewable energy access capacity can be obtained through the preceding small-disturbance voltage stability analysis and large-disturbance voltage stability analysis.

[0052] Furthermore, a load growth state with small disturbance voltage stability requirements is considered a special case of the anticipated fault state. The voltage stability constraints, control variable constraints, state variable constraints, renewable energy internal potential constraints, and output current constraints under the anticipated fault are as follows: Among them, the superscripts of each variable c This indicates that the variable belongs to the expected fault state after preventive control. Indicates the system at the 1st c The expected load margin that needs to be met under a contingent fault can be determined based on the actual engineering requirements.

[0053] It should be noted that for voltage stability prevention and control issues, the requirement is that after prevention and control, if a anticipated fault occurs under normal operating conditions, the system should still maintain the expected voltage stability without applying new control measures. That is, the reactive power injection by the adjustable capacitor, the reactive power injection by the adjustable reactor, the turns ratio of the on-load tap-changing transformer, and the load shedding should all remain at the values ​​of the normal operating conditions after prevention and control under the anticipated fault condition.

[0054] In this embodiment of the invention, step S400, which involves solving the prevention and control optimization model to obtain the optimal prevention and control strategy, includes: The large-scale power grid is divided into multiple sub-networks, and a local optimization model for each sub-network is constructed. The complementary gap of the local optimization model for each sub-network is calculated. If the complementary gap is less than the allowable error, the optimization result is output; if the complementary gap is not less than the allowable error, it is determined whether the maximum number of iterations of the decomposition coordination interior point method has been reached. If the maximum number of iterations is reached, the algorithm fails to converge, terminates, and displays a failure message; if the maximum number of iterations is not reached, the control variables and dual variables of each subnet are updated according to the current iteration results until the iterative coordination converges and the optimal prevention and control strategy is output.

[0055] It should be noted that modern large-scale power grids are characterized by hierarchical and regional management, with each dispatch center only responsible for maintaining and managing its own power grid data. If the preventive control optimization model is solved using traditional centralized optimization algorithms, the problem of splicing basic data will inevitably arise. Moreover, with the increasing scale of the power grid, the preventive control optimization model may also encounter convergence problems. Existing multi-regional distributed algorithms can effectively solve these problems. Among distributed algorithms, the Auxiliary Problem Principle (APP) algorithm is the most widely used. However, after comparing the APP algorithm with the decomposition and coordination interior point method, some scholars have found that the decomposition and coordination interior point method has advantages over the APP algorithm in terms of computation time, accuracy of the objective function, and number of iterations.

[0056] Reference Figure 2 In a preferred embodiment, based on the establishment of a preventive control model that considers small disturbance voltage stability, large disturbance voltage stability and static voltage stability, the present invention establishes a corresponding decomposition coordination optimization model in view of the current characteristics of the power grid's hierarchical and zoned management, and solves it using the decomposition coordination interior point method.

[0057] In one possible implementation, a set of anticipated faults is formed by setting possible faults based on the current power grid operating status. Analyze the static voltage stability and dynamic voltage stability under each anticipated fault. If any fault causes system instability, preventive control measures must be taken. In the preventive control optimization process, a preventive control optimization model is established and solved using the decomposition and coordination interior point method. If no preventive control measures are required, the control results are directly output. By adjusting the control variables, the system remains stable under all anticipated faults, and the optimized control strategy is applied to the actual system.

[0058] Furthermore, the solution obtained by decomposing the consistent interior point method includes the following steps: A decomposition and coordination optimization model is established, which divides the entire power system into multiple subnets and constructs a local optimization model for each subnet. Each subnet contains local optimization objectives and constraints. Input the parameters required for the decomposition and coordination interior point method, and calculate the complementary gap of the local optimization model of each subnet; If the complementary gap is less than the allowable error, the optimized result is output; if the complementary gap is not less than the allowable error, the optimized result is output. When the complementary gap is not less than the allowable error, if the iterative calculation reaches the maximum number of iterations of the decomposition coordination interior point method, the algorithm will not converge; if the iterative calculation does not reach the maximum number of iterations of the decomposition coordination interior point method, the original variables and dual variables of each subnet will be updated, and the complementary gap will be recalculated. The optimal prevention and control strategy is output when the convergence condition is met.

[0059] The above is a schematic scheme of a new energy power grid voltage stability prevention and control method according to this embodiment. It should be noted that the technical solution of this new energy power grid voltage stability prevention and control system belongs to the same concept as the technical solution of the aforementioned new energy power grid voltage stability prevention and control method. Details not described in detail in the technical solution of the new energy power grid voltage stability prevention and control system in this embodiment can be found in the description of the technical solution of the aforementioned new energy power grid voltage stability prevention and control method.

[0060] This embodiment of a new energy power grid voltage stability prevention and control system includes: The fault acquisition module is used to acquire a set of anticipated faults under any operating scenario of the new energy power grid; The fault screening module is used to perform multi-dimensional stability analysis on the voltage under each anticipated fault and screen out the set of key anticipated faults that have any type of voltage instability risk. The optimization model building module is used to trigger the preventive control mechanism if the set of key anticipated faults is not empty. With minimizing the control cost as the objective function, it builds a preventive control optimization model that considers multi-dimensional voltage stability constraints and new energy operation constraints under key anticipated faults. The optimization module is used to solve the prevention and control optimization model to obtain the optimal prevention and control strategy.

[0061] This embodiment also provides an electronic device applicable to the voltage stability prevention and control method of the new energy transmission grid, including: The system includes a memory and a processor. The memory stores computer-executable instructions, and the processor executes these instructions to implement the voltage stability prevention and control method for the new energy transmission grid as proposed in the above embodiments.

[0062] This embodiment also provides a storage medium storing a computer program, which, when executed by a processor, implements the method for preventing and controlling voltage stability of the new energy transmission grid as proposed in the above embodiments.

[0063] The storage medium proposed in this embodiment and the method for preventing and controlling voltage stability of the new energy power grid proposed in the above embodiments belong to the same inventive concept. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0064] Based on the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0065] Example 2, refer to Figures 6-7 This is one embodiment of the present invention. In this embodiment, the IEEE 236-node system is used as the test system to verify the correctness and effectiveness of the present invention.

[0066] It should be noted that the IEEE 236-node system used in this embodiment consists of two IEEE 118-node systems, as shown in the schematic diagram below. Figure 6 As shown. Each circle represents an IEEE 118-node system unit, and its construction process is as follows: Let the area number be n Then each regional node i The corresponding number for the original IEEE 118-node system is i +( n-1)×118, the system data in each sub-region is the same as the original IEEE 118 node system data. The cross-sectional information between the two regions is shown in Table 1, and the topology diagram of each IEEE 118 node system is shown below. Figure 7 As shown.

[0067] Table 1. Cross-sectional information of each system

[0068] First, the voltage stability analysis of the test system is performed using the dynamic and static voltage stability analysis methods proposed in this invention, which yields key anticipated faults. For these key anticipated faults, the voltage stability prevention control strategy proposed in this invention is then used for calculation. Simulation results are shown in Table 2. During the simulation, it was found that the prevention control process only requires one iteration to ensure that the system meets the voltage stability requirements under both normal operating conditions and anticipated fault conditions, verifying the correctness and effectiveness of the algorithm of the prevention control model proposed in this invention.

[0069] Table 2 Simulation Results of Prevention and Control

[0070] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preventing and controlling voltage stability in a new energy transmission grid, characterized in that, include: Obtain the set of anticipated faults under any operating scenario of the renewable energy power grid; A multi-dimensional stability analysis was performed on the voltage under each of the anticipated faults to identify a set of key anticipated faults that pose a risk of voltage instability in any type. If the set of key anticipated faults is not empty, a preventive control mechanism is triggered, and a preventive control optimization model is constructed with the goal of minimizing control costs. The optimal prevention and control strategy is obtained by solving the aforementioned prevention and control optimization model.

2. The method for preventing and controlling voltage stability in the power grid at the new energy sending end as described in claim 1, characterized in that, The multi-dimensional stability analysis of the voltage under each anticipated fault, and the selection of a set of key anticipated faults with any type of voltage instability risk, include: The static voltage stability of the power grid under the various anticipated faults was analyzed, and key anticipated faults with the risk of static voltage instability were screened out. The system linearization model under each of the aforementioned contingent faults is evaluated to identify key contingent faults that pose a risk of small disturbance voltage instability. The system state after each anticipated fault is cleared is solved. If there is no real feasible solution for the AC bus voltage, the key anticipated faults with the risk of large disturbance voltage instability are screened out.

3. The method for preventing and controlling voltage stability in the power grid at the new energy sending end as described in claim 2, characterized in that, An analysis of the static voltage stability of the power grid under the aforementioned contingent faults identified key contingent faults with a risk of static voltage instability as follows: A continuous power flow model of the power grid containing new energy sources with a high proportion of voltage source converters is constructed, and the control mode of the voltage source converters is configured, taking into account the operating constraints of the upper limit of the converter's internal potential and the upper limit of the output current. For each anticipated fault, the system load is parameterized based on the continuous power flow model, and the load and power supply are expressed as linear functions of the load growth parameters. Augmented power flow equations are constructed through the local parameterized continuous power flow algorithm, and the maximum load-bearing parameters under the corresponding anticipated fault are calculated. If the maximum load-bearing parameter is less than the first threshold, it is determined that the static voltage stability of the system is insufficient under the current anticipated fault, and the current anticipated fault is included in the set of key anticipated faults with the risk of static voltage instability.

4. The method for preventing and controlling voltage stability in the power grid at the new energy sending end as described in claim 3, characterized in that, The system linearization model under each of the aforementioned contingent faults was evaluated, and key contingent faults with small disturbance voltage instability risk were screened out, including: constructing a dynamic model of the sending-end power grid that includes synchronous generators, voltage source converters and static loads; For each anticipated fault, the dynamic model of the sending-end power grid is linearized at the corresponding operating point to construct an extended Jacobian matrix. The state variables of the extended Jacobian matrix include the transient electromotive force of the synchronous generator, the d-axis and q-axis output current components of the voltage source converter, and the phase-locked loop phase. If the extended Jacobian matrix is ​​singular, it is determined that the system has a small disturbance voltage instability risk under the anticipated fault, and it is included in the set of critical anticipated faults.

5. The voltage stability prevention and control method for the new energy transmission grid as described in claim 4, characterized in that, Solving for the system state after clearing each anticipated fault, if there is no real feasible solution for the AC bus voltage, the key anticipated faults with the risk of large disturbance voltage instability are identified as follows: For each anticipated fault, establish a post-fault power flow equation that includes the dynamics of the synchronous generator transient electromotive force, the current limiting characteristics of the voltage source converter, and the DC power output response. During the fault phase, the voltage source converter increases the output current to maintain stable power output, and the output current is within the maximum limit value; At the fault clearing moment, based on the fault duration, the transient electromotive force expression of the synchronous machine and the AC bus power balance equation are combined to construct a set of nonlinear power flow equations after fault clearing; the set of power flow equations is solved to obtain the mathematical solution of the AC bus voltage amplitude. If the amplitude of the AC bus voltage does not have a real solution, it is determined that the system has experienced a large disturbance voltage collapse under the anticipated fault, and it is included in the set of key anticipated faults with the risk of large disturbance voltage instability.

6. The voltage stability prevention and control method for the new energy transmission grid as described in claim 5, characterized in that, The preventive control optimization model is constructed with minimizing control costs as the objective function. The objective function of the preventive control optimization model is expressed as: in, , , , , These represent the generator's active power output, reactive power output, reactive power injected by the adjustable capacitor, reactive power injected by the adjustable reactor, and the turns ratio of the on-load tap-changing transformer, respectively; the operating variables in the normal operating state before preventive control are indicated by the subscript 0, and the variables in the normal operating state after preventive control are indicated by the subscript 0. This indicates the amount of active power cut by the load node; , , , , These represent the number of generator nodes, the number of system nodes, the number of adjustable capacitor banks, the number of adjustable reactor banks, and the number of on-load tap-changing transformers, respectively. , , , , , These represent the weights of each control measure; The constraints of the prevention and control optimization model include normal operation constraints, multi-dimensional voltage stability constraints under critical faults, and new energy operation constraints.

7. The voltage stability prevention and control method for the new energy transmission grid as described in claim 6, characterized in that, Solving the aforementioned prevention and control optimization model yields the following optimal prevention and control strategies: The large-scale power grid is divided into multiple sub-networks, and a local optimization model for each sub-network is constructed. The complementary gap of the local optimization model for each sub-network is calculated. If the complementary gap is less than the allowable error, the optimization result is output; if the complementary gap is not less than the allowable error, it is determined whether the maximum number of iterations of the decomposition coordination interior point method has been reached. If the maximum number of iterations is reached, the algorithm fails to converge, terminates, and displays a failure message; if the maximum number of iterations is not reached, the control variables and dual variables of each subnet are updated according to the current iteration results until the iterative coordination converges and the optimal prevention and control strategy is output.

8. A voltage stability prevention and control system for a new energy transmission grid, applied to the method described in any one of claims 1-7, characterized in that, include: The fault acquisition module is used to acquire a set of anticipated faults under any operating scenario of the new energy power grid; The fault screening module is used to perform multi-dimensional stability analysis on the voltage under each anticipated fault and screen out a set of key anticipated faults that have any type of voltage instability risk. The optimization model building module is used to trigger the prevention and control mechanism if the set of key anticipated faults is not empty, and to build a prevention and control optimization model that considers multi-dimensional voltage stability constraints and new energy operation constraints under key anticipated faults with the objective function of minimizing control costs. The optimization module is used to solve the prevention and control optimization model to obtain the optimal prevention and control strategy.

9. An electronic device, comprising: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, they implement the steps of the new energy power grid voltage stability prevention and control method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the new energy power grid voltage stability prevention and control method according to any one of claims 1 to 7.

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