Method, device and equipment for determining dynamic security domain of micro-grid and medium

Abstract

The embodiment of the invention provides a micro-grid dynamic security domain determination method, device and equipment and a medium, and the method comprises the steps: determining a dominant stability domain boundary estimation equation based on a transient synchronization model of a micro-grid; and determining the dynamic security domain of the micro-grid based on the dominant stability domain boundary estimation equation. The technical scheme provided by the embodiment of the invention is suitable for a complex micro-grid scene for controlling variable dimension expansion, and a unified, quantifiable and executable technical path is provided for transient synchronization stability evaluation and regulation.

Description

Methods, devices, equipment and media for determining the dynamic security domain of microgrids Technical Field

[0001] This application provides embodiments in the field of power system security and stability analysis technology, and particularly relates to a method for determining the dynamic security domain of a microgrid. Background Technology

[0002] Microgrids, as a key component in building new power systems, play a crucial role in promoting the consumption of distributed energy and driving energy transition. On the power source side, renewable energy sources with power electronic interfaces have become the main power source, exchanging energy with the grid through various controllers. Their dynamic characteristics are highly dependent on control strategies and parameters. On the load side, new flexible loads such as hydrogen production by electricity and ammonia synthesis have a large power regulation range. Coupled with the volatility of renewable energy output, this results in frequent power changes on both the source and load sides, leading to high uncertainty in system power flow. Compared to large power grids dominated by synchronous machines, all-renewable energy microgrids have smaller transient synchronization stability margins and increased instability risks. Traditional dynamic safety domain estimation methods and control techniques used to improve transient synchronization stability face adaptation challenges. Current research has proposed manifold, energy function, and sum-of-squares estimation methods for judging the transient synchronization stability of microgrids or high-proportion renewable energy systems. However, in all-renewable energy microgrid scenarios where renewable energy, energy storage, and flexible loads such as hydrogen production by water electrolysis coexist with grid-type / grid-connected renewable energy, are relatively limited in scope. Furthermore, the adjustable resource dimension in all renewable energy microgrids has been significantly expanded, including controller parameters for new energy and energy storage, as well as flexible loads, which can all be used as control variables. However, existing research has not yet formed a clear and unified definition of the dynamic security domain, and the corresponding evaluation methods still need to be improved. Summary of the Invention

[0003] This application provides a method for determining the dynamic security domain of a microgrid, which addresses the technical problems in related technologies such as insufficient characterization of the dynamic operating characteristics of multi-energy coupled nodes and inadequate disclosure of power grid characteristics in integrated energy scenarios.

[0004] In a first aspect, embodiments of this application provide a method for determining the dynamic security domain of a microgrid, including:

[0005] Based on the transient synchronization model of microgrids, the boundary estimation equation of the dominant stability domain is determined;

[0006] Based on the dominant stability domain boundary estimation equation, the dynamic security domain of the microgrid is determined.

[0007] This approach first constructs a transient synchronization model reflecting the coupling relationships between grid-connected / grid-based new energy sources, energy storage systems, and flexible loads (such as water electrolysis hydrogen production units) in a fully renewable energy microgrid. Based on this, the dominant instability mode of the system under fault disturbances is extracted, and the corresponding dominant stability domain boundary estimation equation is established. Subsequently, this equation is used to define the stable operating boundary of the microgrid in the injected active current reference value space and the controller parameter space, thereby generating a dynamic safety domain with clear physical meaning and mathematical expression. This method is applicable to complex microgrid scenarios with high uncertainty on both the source and load sides and expanded dimensions of control variables, providing a unified, quantifiable, and executable technical path for transient synchronization stability assessment and control.

[0008] In one possible implementation, based on a transient synchronization model of the microgrid, the dominant stability domain boundary estimation equations are determined, including:

[0009] Calculate all equilibrium points in the transient synchronization model and the corresponding stable manifolds of the equilibrium points;

[0010] Based on the stable manifold at the equilibrium point, the boundary estimation equation of the dominant stable domain corresponding to the equilibrium point is determined by comparing the limit cut-off time. The limit cut-off time is the shortest time taken for the system state trajectory point to change from satisfying the transient synchronous stability discrimination equation to being less than zero or equal to zero in a given fault simulation.

[0011] In one possible implementation, the dynamic security domain of the microgrid is determined based on the dominant stability domain boundary estimation equation, including:

[0012] The initial dynamic security domain is determined based on the transient synchronization model of the microgrid;

[0013] Set up the initial space for searching the initial dynamic security domain;

[0014] Substituting the points in the initial space into the dominant stability domain boundary estimation equation, the boundary of the initial dynamic security domain is determined, and the dynamic security domain is obtained.

[0015] In this scheme, the initial dynamic safety domain consists of the region within the microgrid's current operating point and its neighborhood that satisfies small-disturbance stability. The initial space is set based on the actual adjustable resource range of the system, including the upper and lower limits of the converter active current reference value and the feasible range of key controller parameters (such as virtual inertia, damping coefficient, and droop gain). After discretizing and sampling the initial space, each sampling point is input as the system operating state into the boundary estimation equation of the dominant stability domain. Its stability is determined by numerical criteria (such as whether the phase trajectory converges to the equilibrium point), thereby outlining the precise boundary of the dynamic safety domain. This process avoids the dependence on conservatism in the traditional energy function method and improves the compactness and engineering applicability of the boundary estimation.

[0016] In one possible implementation, points in the initial space are substituted into the dominant stability domain boundary estimation equation to determine the boundary of the initial dynamic security domain, thus obtaining the dynamic security domain, which includes:

[0017] For each point in the initial space, a predetermined fault is simulated, and the points are substituted into the boundary estimation equation of the dominant stability domain to obtain the phase trajectory points after the predetermined fault is removed.

[0018] This scheme employs typical disturbance types such as three-phase short circuits or line breaks for the predetermined fault, with the fault duration fixed at a preset value (e.g., 0.1 seconds). Under the system parameter configuration corresponding to each sampling point, time-domain simulation is performed to record the time response sequence of key system state variables (e.g., voltage phase angle difference, frequency deviation) after fault clearance. This sequence is mapped to the phase plane, and its initial segment trajectory points are extracted and substituted into the dominant stability domain boundary estimation equation. If the trajectory point is located within the stable region defined by the estimation equation, the sampling point is determined to belong to the dynamic safety domain. This method significantly reduces computational complexity by replacing global stability judgment with local trajectory characteristics.

[0019] In one possible implementation, the dynamic security domain includes a first dynamic security domain and / or a second dynamic security domain, and the initial space includes a first initial space and a second initial space. Then, setting an initial space for searching the initial dynamic security domain includes:

[0020] Generate a first initial space for the first dynamic security domain; and / or

[0021] A second initial space is generated for the second dynamic security domain, wherein the first initial space is used to characterize the search space for the injected active current reference value for the first dynamic security domain, and the second initial space is used to characterize the search space for the controllable parameters for the second dynamic security domain.

[0022] This scheme employs a two-domain approach: the first dynamic security domain focuses on the feasibility of power dispatch at the operational level, with its boundary determined by converter output capacity and power flow constraints; the second dynamic security domain focuses on the robustness of parameters at the control level, with its boundary determined by the dynamic response characteristics of the controller. These two security domains correspond to different sets of decision variables, supporting hierarchical optimization: the operational dispatch layer adjusts the active current reference value, and the control configuration layer tunes the controller parameters. This dual-domain structure is compatible with the microgrid's "operation-control" collaborative optimization architecture, improving resource utilization efficiency.

[0023] In one possible implementation, the first dynamic safety domain consists of all active current reference values ​​that satisfy the following condition:

[0024] The system operating at this active current reference value, after a predetermined fault occurs and is cleared, has its state trajectory point located within the transient synchronous stability region defined by the dominant stability region boundary estimation equation.

[0025] The first initial space is a set of active current reference values ​​discretized within the range of zero to three times the rated current.

[0026] In one possible implementation, the second dynamic security domain consists of all controllable parameters that satisfy the following conditions:

[0027] The system operating with this set of controllable parameters, after the occurrence and removal of a predetermined fault, has its state trajectory point located within the transient synchronous stability region defined by the dominant stability region boundary estimation equation;

[0028] The second initial space is a set of combinations of proportional control parameters and integral control parameters discretized within the range of zero to ten times the rated parameters.

[0029] In one possible implementation, a predetermined fault is simulated for each point in the initial space, and substituted into the dominant stability domain boundary estimation equation to obtain the phase trajectory points after the predetermined fault is cleared, including:

[0030] The first phase trajectory point after a predetermined fault clearance is determined based on the current reference value in the first initial space; and / or

[0031] The second phase trajectory point after the predetermined fault is cleared is determined based on the controllable parameters in the second initial space.

[0032] This scheme uses a first initial space where controller parameters are fixed and only the active current reference value is varied to obtain the corresponding first-phase trajectory point set, which is used to characterize the impact of the operating point on transient stability. In a second initial space, the operating point is fixed and only the controller parameters are varied to obtain the corresponding second-phase trajectory point set, which is used to characterize the adjustment effect of the control strategy on the stability margin. Both types of trajectory points are input into the same dominant stability domain boundary estimation equation, achieving a joint mapping of multidimensional variables to the safety domain.

[0033] In one possible implementation, the method also includes:

[0034] A transient synchronization stability margin extension strategy is generated based on dynamic security domains.

[0035] In this scheme, the area or volume of the dynamic safety domain is used as a quantitative indicator of stability margin. When the current operating point is detected to be close to the boundary of the safety domain, the margin expansion process is initiated. This strategy improves the system's anti-disturbance capability by adjusting adjustable resources to move the operating point into the safety domain and expanding the coverage of the safety domain.

[0036] In one possible implementation, when the dynamic security domain includes a first dynamic security domain and a second dynamic security domain, a transient synchronization stability margin extension strategy is generated based on the dynamic security domain, including:

[0037] Adjust the controllable parameters based on the second dynamic security domain until the area increment of the adjusted second dynamic security domain is less than the preset increment.

[0038] Adjust the active current reference value of the converter based on the first dynamic safety domain.

[0039] This scheme first performs a gradient ascent search within the controller parameter space to maximize the area of ​​the second dynamic safety region. Parameter adjustment stops when the area increment from a single iteration falls below a threshold (e.g., 1%). Subsequently, under the updated control parameters, the first dynamic safety region is recalculated, and the current active current reference value is shifted towards the center of the safety region to ensure the operating point is in a high-margin region. This two-stage strategy prioritizes optimizing the control structure before optimizing the operating point, conforming to the engineering logic of "control first, then adjust."

[0040] In one possible implementation, the preset increment is 10%, and the controllable parameters are adjusted based on the second dynamic security domain until the area increment of the adjusted second dynamic security domain is less than the preset increment, including:

[0041] If the area of ​​the second dynamic safety domain obtained after the previous adjustment is less than 110% of the area of ​​the second dynamic safety domain obtained after the next adjustment, the adjustment of the controllable parameters shall be stopped.

[0042] In one possible implementation, the transient synchronization model is constructed as follows:

[0043] Acquire microgrid information, including at least the microgrid system topology, operating mode, equipment control strategy, and microgrid parameters;

[0044] A transient synchronization model of a microgrid is established based on microgrid information.

[0045] This scheme collects various types of information from each node in the microgrid and transforms them into a coupled system of differential equations and algebraic constraints, forming a transient synchronization model that can reflect the dynamic characteristics of multiple time scales, thus providing an accurate physical basis for the construction of the dynamic security domain.

[0046] Secondly, embodiments of this application provide a microgrid dynamic security domain determination device, comprising:

[0047] The module is used to determine the boundary estimation equations of the dominant stability domain based on the transient synchronization model of the microgrid;

[0048] The processing module is used to determine the dynamic security domain of the microgrid based on the dominant stability domain boundary estimation equation.

[0049] Thirdly, embodiments of this application provide an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, it implements the method provided in embodiments of this application.

[0050] Fourthly, embodiments of this application provide a computer-readable storage medium, characterized in that it stores a computer program thereon, which, when executed in a computer, causes the computer to perform the method provided in embodiments of this application. Attached Figure Description

[0051] Figure 1 is a flowchart of a method for determining the dynamic security domain of a microgrid according to an embodiment of this application;

[0052] Figure 2 is a schematic diagram of a microgrid system provided in an embodiment of this application;

[0053] Figure 3 is a schematic diagram of another microgrid system provided in an embodiment of this application;

[0054] Figure 4 is a schematic diagram of the calculation results of the Type II dynamic security domain provided in the embodiment of this application;

[0055] Figure 5 is a structural block diagram of a microgrid dynamic security domain determination method device provided in an embodiment of this application;

[0056] Figure 6 is a schematic diagram of an electronic device structure provided in an embodiment of this application. Detailed Implementation

[0057] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] Microgrids are a crucial component in building new power systems and an important pathway to achieving distributed energy consumption and promoting energy transition. On the power source side, renewable energy sources with power electronic interfaces become the main power source. Unlike the physical rotor motion driven by the mechanical and electromagnetic imbalance torque of synchronous machines, they exchange energy with the grid through various controllers. Their dynamic characteristics are highly dependent on the selected control strategies and parameters. On the load side, new flexible loads such as hydrogen production by electricity and ammonia synthesis have a wide power adjustment range. Coupled with the fluctuations in renewable energy output, power changes on both the source and load sides lead to frequent system power flow variations. Therefore, compared to large power grids dominated by synchronous machines, all-renewable energy microgrids have smaller transient synchronization stability margins and are more prone to instability accidents. Traditional dynamic safety domain estimation methods and extended control techniques for improving transient synchronization stability face many challenges.

[0059] Currently, research has developed manifold, energy function, and sum-of-squares estimation methods for determining the transient synchronization stability of microgrids or high-proportion renewable energy systems. However, research on transient synchronization stability determination methods for all-renewable energy microgrids with coexisting flexible loads such as renewable energy, energy storage, and hydrogen production via water electrolysis is limited. Furthermore, unlike large power grids dominated by synchronous machines, all-renewable energy microgrids incorporate adjustable resources such as renewable energy and energy storage controller parameters, as well as flexible loads, into their control resources. This increases the dimensions of transient synchronization stability control, and existing dynamic security domains for transient synchronization stability in all-renewable energy microgrids lack clear definition, resulting in incomplete dynamic security domain assessment methods.

[0060] Figure 1 is a flowchart of a method for determining the dynamic security domain of a microgrid according to an embodiment of this application. Its core lies in constructing a mathematical model that accurately reflects the transient synchronization characteristics of a high-proportion renewable energy microgrid, and deriving a calculable and executable stability boundary equation based on this model. Then, the transient synchronization stability of the system is quantitatively determined by substituting the phase trajectory points with the boundary equation. This method can be executed by a device for determining the dynamic security domain of a microgrid, which can be implemented by software and / or hardware, and can be configured in electronic devices such as computers.

[0061] As shown in Figure 1, the technical solution provided in this application includes the following steps:

[0062] S110: Based on the transient synchronization model of microgrids, determine the boundary estimation equation of the dominant stability domain.

[0063] In practical implementation, the first step is to obtain complete system information of the target microgrid. This information includes, but is not limited to, the microgrid's electrical topology, the connections between nodes, the types of distributed power sources and their control strategies, the dynamic characteristics of flexible loads, line impedance parameters, transformer turns ratios and short-circuit capacities, and the control parameter ranges of various power electronic converters. Information such as the system topology, operating mode, equipment control strategies, and parameters of the all-renewable energy microgrid is then obtained. A transient synchronization model of the all-renewable energy system, including grid-connected wind / solar renewable energy, grid-connected energy storage, and water electrolysis for hydrogen production, is then established to provide an accurate mathematical foundation for subsequent analysis.

[0064] In one example, information such as the system topology, operation mode, equipment control strategy, and parameters of a fully renewable energy microgrid is obtained. A transient synchronization model of the fully renewable energy system, including grid-connected wind / solar renewable energy, grid-connected energy storage, and flexible loads such as water electrolysis for hydrogen production, is established. Taking the system shown in Figures 2 and 3 as an example, the microgrid includes grid-connected renewable energy, energy storage, and flexible loads. The grid-connected renewable energy, grid-connected energy storage, and flexible loads are interconnected through converters and described using nonlinear differential equations. The microgrid lines are described using algebraic equations. The grid-connected renewable energy, energy storage, and flexible load equipment such as water electrolysis for hydrogen production use phase-locked loops (PLLs) to lock the phase and provide a control reference coordinate system. Externally, they appear as current sources and can be described using differential equations and output equations. The differential equations are as follows:

[0065]

[0066] Where d() / dt represents the derivative of the state variable with respect to time, , These represent the output angle and integrator output variables of the phase-locked control loop for grid-connected new energy, energy storage, and flexible load equipment, respectively. , , These represent the integral output of the DC voltage control, the square of the DC voltage, and the reference value of the DC voltage, respectively. The reference value of the DC voltage is typically 1.0 pu; k p1 , k i1 For the proportional and integral control parameters of the phase-locked loop; k i2 k is the DC voltage integral control parameter. p2 P is the DC voltage proportional control parameter. ref For power reference value, C f For mesh-type equipment, filter capacitors are used. ω0 is the power frequency, i.e., 2π × 50Hz; u td and u tq For the voltage at the point of common coupling U t Components on the dq axis; i d and i q It is the component of the current on the dq axis; and Reference value of current on the dq axis; L g This is the equivalent impedance of the equivalent power grid.

[0067] Furthermore, flexible load equipment such as grid-based new energy, grid-based energy storage, and water electrolysis for hydrogen production employs virtual synchronous control or droop control to lock the phase and provide a control reference coordinate system. Externally, it manifests as a voltage source and can be described using differential equations and output equations. The differential equation is as follows:

[0068]

[0069] Where d() / dt represents the derivative of the state variable with respect to time, , These represent the angle and frequency of the virtual synchronous control output, respectively. , , These represent the output of the DC voltage control integrator, the square of the DC voltage, and the reference value of the DC voltage, respectively. The reference value of the DC voltage is generally 1.0 pu; M and D are the inertia and damping control parameters of the virtual synchronous control. This is a power reference value; These are DC voltage integral control parameters. These are the proportional control parameters for DC voltage. These are the port voltage and the equivalent grid voltage amplitude, respectively.

[0070] By combining the models of grid-connected equipment, network-structured equipment, and lines, and incorporating the acquired information on the system topology, operating mode, equipment control strategies, and parameters of the all-renewable energy microgrid into the equations, a white-box model of the all-renewable energy microgrid is obtained, and a nonlinear transient synchronization model of the system is constructed. At this point, the component u of the voltage at the point of common coupling of the grid-connected equipment on the q-axis of the phase-locked loop is... tq for:

[0071]

[0072] Among them, I Lk Z LiK V Mj These are the phasor forms of voltage, line impedance, and node voltage, respectively. These represent the phase-locked angle, dq-axis current angle, and line impedance angle of the i-th wire in the network, respectively. | | represents the amplitude of the phasor; Re and Im represent the real and imaginary parts, respectively.

[0073] Furthermore, the electromagnetic power of the network-type equipment is:

[0074]

[0075] in, , , These represent the synchronous control angle of the i-th network-type device, the dq-axis current angle, and the line impedance angle, respectively. M It is in phasor form for line admittance.

[0076] After establishing the transient synchronization model, the derivation of the dominant stability domain boundary estimation equation is performed. Based on the transient synchronization white-box mathematical model of a fully renewable energy system including flexible loads such as grid-connected wind / solar new energy, energy storage, and water electrolysis for hydrogen production, the stability domain boundary of the fully renewable energy system is calculated based on manifold theory. Furthermore, according to the calculation method of the Jacobian matrix, the estimated value of the stable manifold can be obtained. Based on this, a stability discrimination index and judgment criterion can be proposed. The high-dimensional phase trajectory points in the system fault are substituted into the defined transient synchronization stability discrimination equation to determine whether the system is stable at this time. The dominant stability domain boundary estimation equation can be determined according to the corresponding minimum limit cut-off time, that is, by comparing the limit cut-off times corresponding to each equilibrium point, the dominant Type I equilibrium point and its corresponding stability domain boundary estimation equation are determined.

[0077] Specifically, based on the transient synchronous white-box mathematical model of a fully renewable energy system including flexible loads such as grid-connected wind / solar new energy, energy storage, and water electrolysis for hydrogen production, the stability domain boundary of the fully renewable energy system is calculated based on manifold theory, satisfying:

[0078]

[0079] in, W represents the boundary of the stable region. S Represents the unstable equilibrium point x u The stable manifold.

[0080] Furthermore, based on the method for calculating the Jacobian matrix, the stable manifold W can be obtained. S The estimated value is:

[0081]

[0082] Among them, v T i Let be the eigenvector of the Jacobian matrix, and Q be the second-order estimated parameter matrix. Q is the standard numerical process of the local manifold theory of nonlinear systems, which has mature applications in the stability analysis of control systems and power systems. Therefore, the specific calculation method will not be described in detail here.

[0083] After obtaining the boundary estimation equation of the dominant stability domain, a stability criterion and judgment criteria can be further proposed, which will be applied to the high-dimensional phase trajectory point x in the system fault. ui Substitute into the following formula to determine the stability of the system at this time, i.e.

[0084]

[0085] Where, F(x|x uiLet be the defined transient synchronous stability criterion equation, satisfying:

[0086]

[0087] Furthermore, the boundary estimation equation for the dominant stable region can be derived from the corresponding limit cut-off time minimum, i.e.

[0088]

[0089] The critical resection time (CCT) calculated for each equilibrium point is:

[0090]

[0091] Specifically, for the first dynamic safety domain, based on the definition of a Type I dynamic safety domain, the first phase trajectory point after a predetermined fault clearing and the boundary equation of the dominant stability domain are calculated based on the current reference value in the initial space to determine the transient synchronization stability of the system. If stable, the current reference value at this time is located within the Type I dynamic safety domain; if unstable, the current reference value at this time is located outside the Type I dynamic safety domain.

[0092] S120: Determine the dynamic security domain of the microgrid based on the dominant stability domain boundary estimation equation.

[0093] In specific implementation, after obtaining the boundary estimation equation of the dominant stability region, it can be used to determine the dynamic security region. The dynamic security region can include a first dynamic security region and / or a second dynamic security region. The first dynamic security region is the Type-I Dynamic Security Region (DSR), which draws on the definition of the traditional synchronous machine dominant system. It is the set of all active current reference value injection points in the active current reference value space of all converter equipment (including grid-connected and grid-connected new energy, energy storage, and flexible loads) that can maintain transient synchronous stability after a predetermined fault (such as a three-phase short circuit, which is cleared after the protection action time).

[0094] Specifically, the Type I dynamic safety domain, drawing on the definition of a traditional synchronous machine-dominated system, refers to the set of all active current reference value injection points that enable the system to maintain transient synchronous stability after a predetermined fault occurs and is cleared, within the active current reference value space of all converter devices. For calculation, an initial search space for injected active current reference values ​​is first generated, typically discretized within the range of zero to three times the rated current. Based on the definition of the Type I dynamic safety domain, a predetermined fault is simulated and the phase trajectory points after fault clearing are calculated for each current reference value in the initial space. These points are then substituted into the boundary equation of the dominant stability domain determined in step S110 to determine the transient synchronous stability of the system. If stable, the current reference value lies within the Type I dynamic safety domain; if unstable, it lies outside the domain.

[0095] The second dynamic security region, also known as the Type-II Generalized Dynamic Security Region (GDSR), is an extension of the Type-I dynamic security region. It is based on the controllable elements of the actual dispatching department. It is defined as the set of all controllable parameter values ​​that allow the system to maintain transient synchronization stability after a predetermined fault occurs and is cleared, within the space of controllable synchronization element parameters of all converter equipment (such as controller proportional-integral parameters, inertia and damping parameters of the virtual synchronizer, etc.). For calculation, an initial search space for controllable parameters is first generated. This space is typically discretized within the range of zero to ten times the rated parameters to generate a set of combinations of proportional and integral control parameters. Based on the definition of the Type-II dynamic security region, for each set of controllable parameters in the initial space, a predetermined fault is simulated, and the phase trajectory points after fault clearing are calculated. These points are then substituted into the boundary equation of the dominant stability region for stability determination. If stable, the set of controllable parameters lies within the Type-II dynamic security region; if unstable, it lies outside the region.

[0096] For the first dynamic safety domain: The Class I dynamic safety domain of a fully renewable energy microgrid draws on the definition of a traditional synchronous machine-dominated system. The Class I dynamic safety domain ΩI DSR of a fully renewable energy system is defined within the active current reference value space of all converter equipment. That is, after a predetermined fault (considering the operating time of relay protection devices, generally 50 cycles after a three-phase short circuit, i.e., clearing after 0.1s), the system maintains transient synchronous stability within the injected active current reference value space.

[0097]

[0098] Among them, i dref This represents the reference value of the active current of the converter equipment, Φ(i dref B(x) represents the second phase trajectory point of the system after a predetermined fault. s (i dref)) represents the transient synchronous stability domain of the system after a fault.

[0099] Furthermore, the initial space for searching the injected active current reference value is generated, i.e.

[0100]

[0101] Among them, the minimum value of each current reference value is 0, and the maximum value is 3 times the current rating (based on the overcurrent capability of power electronic devices, the converter is generally considered to have three times the short-circuit current).

[0102] For the second dynamic safety domain: The Class II dynamic safety domain ΩII GDSR of a fully renewable energy system is defined within the controllable synchronization parameter space of all converter equipment. That is, after a given fault (considering the relay protection device's operating time, typically 50 cycles after a three-phase short circuit, i.e., clearing after 0.1s), the system maintains transient synchronization stability within a controllable parameter space.

[0103]

[0104] Where, k controlled B(x) represents the controllable parameters of the converter equipment. s (k controlled )) represents the transient synchronous stability domain of the system after a fault.

[0105] Furthermore, a search initial space for controllable parameters is generated, namely...

[0106]

[0107] The minimum value of the proportional and integral control parameters is 0, and the maximum value is 10 times the rated value. The specific values ​​can be set according to the requirements. This disclosure does not limit this. Generally, the design difference of controllers at different time scales is 10 times. The adjustable range of a single controller does not exceed 10 times the initial value. If it exceeds 10 times, the control performance of the system cannot be guaranteed.

[0108] Following this step, a transient synchronization stability margin extension strategy can also be generated based on the dynamic security domain.

[0109] Specifically, if the system includes both Type I and Type II dynamic security domains, the expansion strategy can follow a "control first, adjust later" logic: First, adjust the controllable parameters of the system's current operation based on the Type II dynamic security domain until the area increment of the adjusted second dynamic security domain is less than the preset increment (e.g., 10%). Then, based on the optimized control parameters and the calculation results of the Type I dynamic security domain, adjust the active current reference value of the converter (generally, prioritize adjusting grid-connected energy storage and flexible loads, then adjust grid-connected new energy and energy storage equipment). By simultaneously adjusting the current reference value and control parameters, the transient synchronization stability margin of the all-renewable energy microgrid can be effectively increased, reducing the risk of transient synchronization instability under common faults.

[0110] Specifically, if the aforementioned safety domain only includes Type I dynamic safety domain, then the active current reference value of the converter will be adjusted based on the calculation results of Type I dynamic safety domain. Generally, the adjustment of the active current reference value will first consider grid-connected energy storage and flexible loads, and then adjust grid-connected new energy and energy storage equipment.

[0111]

[0112] If the aforementioned security domains only include Type II dynamic security domains, then the controllable parameters of the system's current operation are adjusted according to the Type II dynamic security domains. When adjusting the controllable parameters results in a limited increase in the area of ​​the dynamic security domain, no further adjustments are made, thus satisfying the condition.

[0113]

[0114] Wherein, S(Ω) II GDSR ) represents the area of ​​the Type II dynamic security domain. That is, when the area of ​​the Type II dynamic security domain obtained by the (i+1)th adjustment is less than 10% larger than the area obtained by the ith adjustment, the control parameters will no longer be adjusted.

[0115] If the aforementioned security domain includes both Type I and Type II dynamic security domains, then first, based on the Type II dynamic security domain, the controllable parameters of the system's current operation are adjusted. When adjusting the controllable parameters results in a limited increase in the area of ​​the dynamic security domain, no further adjustments are made, thus satisfying the condition.

[0116]

[0117] Wherein, S(Ω) II GDSR ) represents the area of ​​the Type II dynamic security domain. That is, when the area of ​​the Type II dynamic security domain obtained by the (i+1)th adjustment is less than 10% larger than the area obtained by the ith adjustment, the control parameters will no longer be adjusted.

[0118] Furthermore, when the system's transient synchronization stability margin still does not meet the requirements, the active current reference value of the converter is adjusted based on the calculation results of the Class I dynamic security domain. Generally, the adjustment of the active current reference value first considers grid-connected energy storage and flexible loads, and then adjusts grid-connected new energy and energy storage equipment.

[0119]

[0120] Therefore, based on the Class I and Class II dynamic safety domains, by simultaneously adjusting the current reference value and control parameters, the transient synchronization stability margin of the all-renewable energy microgrid is increased, and the risk of transient synchronization instability of the system under common faults is reduced.

[0121] This disclosure uses an equivalent three-phase short-circuit fault in a power grid to detect the effectiveness of the method described herein. The accuracy of the method is verified by comparing the simulation results of the Type I and Type II dynamic security domains with those of the time domain obtained by the method described herein.

[0122] Considering a three-phase short-circuit fault in the system and the operating time of the relay protection device, which is generally 5 cycles after the three-phase short circuit occurs, i.e., clearing the fault after 0.1s, leaving a certain margin, we examine 0.08s (4 cycles), 0.1s (5 cycles), and 0.12s (6 cycles). Taking the 0.1s fault clearing as an example, the numerical simulation calculation result of the Class I dynamic safety domain (maximum value of active current reference value) for grid-connected equipment (new energy, energy storage, flexible loads) is 0.89 pu, while the result obtained using the proposed method is 0.98 pu, with an absolute error of 0.09 pu and a relative error of 10.11%. Therefore, combining the three sets of data, we can conclude that the method described in this disclosure has a small error in estimating the Class I dynamic safety domain and can effectively guide the improvement of transient synchronization stability margin.

[0123] The table below shows the Class I dynamic safety domain (maximum reference value of active current) for grid-connected equipment (new energy, energy storage, flexible loads) under different fault clearing times.

[0124] Resection time (s) Numerical simulation (pu) Proposed method (pu) Absolute error (pu) Relative error (%) 0.08 (4 cycles) 0.95 1.03 0.08 8.42 0.10 (5 cycles) 0.89 0.98 0.091 0.11 0.12 (6 cycles) 0.85 0.93 0.08 9.41 surface

[0125] The table below shows the Class I dynamic safety domain (maximum reference value of active current) for grid-connected equipment (new energy, energy storage, flexible loads) under different fault clearing times.

[0126] Resection time (s) Numerical simulation (pu) Proposed method (pu) Absolute error (pu) Relative error (%) 0.08 (4 cycles) 0.91 0.98 0.07 7.70% 0.10 (5 cycles) 0.85 0.92 0.07 8.24% 0.12 (6 cycles) 0.80 0.86 0.06 7.50% surface

[0127] For the Type II dynamic safety domain, the system also considers the occurrence of a three-phase short-circuit fault and the operating time of the relay protection device, which is generally 5 cycles after the three-phase short circuit occurs, i.e., 0.1s after disconnection, leaving a certain margin. The operating times of 0.08s (4 cycles), 0.1s (5 cycles), and 0.12s (6 cycles) are examined respectively. The Type II dynamic safety domain obtained by the proposed method and numerical simulation is shown in Figure 4, where the dashed line represents the Type II dynamic safety domain calculated by the proposed method, and the gray area represents the Type II dynamic safety domain obtained by simulation calculation. It can be seen that the method described in this disclosure has a very small error in estimating the Type II dynamic safety domain.

[0128] In summary, the method disclosed herein can accurately calculate the Type I and Type II dynamic security domains of fully renewable energy microgrids, enabling the quantitative calculation and evaluation of the transient synchronization stability margin of the microgrid. It can also quantitatively analyze the impact of system operating conditions, control parameters, and other factors on the system stability margin. The calculation method described in this invention is novel and highly practical, with a simple and clear process, facilitating its field application in existing heavy industrial microgrids with a high proportion of new energy or fully renewable energy, such as those in heavy chemical, electrolytic aluminum, and metallurgical industries. It has advantages in the dynamic security domain evaluation and stability margin improvement of fully renewable energy microgrids.

[0129] Figure 5 is a structural block diagram of a microgrid dynamic security domain determination method device provided in an embodiment of this application. As shown in Figure 5, the device includes:

[0130] Module 501 is used to determine the boundary estimation equation of the dominant stability domain based on the transient synchronization model of the microgrid.

[0131] Processing module 502 is used to determine the dynamic security domain of the microgrid based on the dominant stability domain boundary estimation equation.

[0132] In one possible implementation, the determining module 501 is specifically used for:

[0133] Calculate all equilibrium points in the transient synchronization model and the corresponding stable manifolds of the equilibrium points;

[0134] Based on the stable manifold at the equilibrium point, the boundary estimation equation of the dominant stable domain corresponding to the equilibrium point is determined by comparing the limit cut-off time. The limit cut-off time is the shortest time taken for the system state trajectory point to change from satisfying the transient synchronous stability discrimination equation to being less than zero or equal to zero in a given fault simulation.

[0135] In one possible implementation, the processing module 502 is specifically used for:

[0136] The initial dynamic security domain is determined based on the transient synchronization model of the microgrid;

[0137] Set up the initial space for searching the initial dynamic security domain;

[0138] Substituting the points in the initial space into the dominant stability domain boundary estimation equation, the boundary of the initial dynamic security domain is determined, and the dynamic security domain is obtained.

[0139] In one possible implementation, the processing module 502 is specifically used for:

[0140] For each point in the initial space, a predetermined fault is simulated, and the points are substituted into the boundary estimation equation of the dominant stability domain to obtain the phase trajectory points after the predetermined fault is removed.

[0141] In one possible implementation, the dynamic security domain includes a first dynamic security domain and / or a second dynamic security domain, and the initial space includes a first initial space and a second initial space. Then, the processing module 502 is specifically used for:

[0142] Generate a first initial space for the first dynamic security domain; and / or

[0143] A second initial space is generated for the second dynamic security domain, wherein the first initial space is used to characterize the search space for the injected active current reference value for the first dynamic security domain, and the second initial space is used to characterize the search space for the controllable parameters for the second dynamic security domain.

[0144] In one possible implementation, the processing module 502 is specifically used for:

[0145] The first phase trajectory point after a predetermined fault clearance is determined based on the current reference value in the first initial space; and / or

[0146] The second phase trajectory point after the predetermined fault is cleared is determined based on the controllable parameters in the second initial space.

[0147] In one possible implementation, the processing module 502 is specifically used for:

[0148] A transient synchronization stability margin extension strategy is generated based on dynamic security domains.

[0149] In one possible implementation, when the dynamic security domain includes a first dynamic security domain and a second dynamic security domain, the processing module 502 is specifically used for:

[0150] Adjust the controllable parameters based on the second dynamic security domain until the area increment of the adjusted second dynamic security domain is less than the preset increment.

[0151] Adjust the active current reference value of the converter based on the first dynamic safety domain.

[0152] In one possible implementation, if the preset increment is 10%, then processing module 502 is specifically used for:

[0153] If the area of ​​the second dynamic safety domain obtained after the previous adjustment is less than 110% of the area of ​​the second dynamic safety domain obtained after the next adjustment, the adjustment of the controllable parameters shall be stopped.

[0154] In one possible implementation, module 501 specifically constructs the transient synchronization model using the following method.

[0155] Acquire microgrid information, including at least the microgrid system topology, operating mode, equipment control strategy, and microgrid parameters;

[0156] A transient synchronization model of the microgrid is established based on the microgrid information.

[0157] As shown in Figure 6, this embodiment of the application provides an electronic device, including a processor 111, a communication interface 112, a memory 113, and a communication bus 114, wherein the processor 111, the communication interface 112, and the memory 113 communicate with each other through the communication bus 114.

[0158] Memory 113 is used to store computer programs;

[0159] In one embodiment of this application, when the processor 111 executes a program stored in the memory 113, it implements the method provided in any of the foregoing method embodiments, including:

[0160] Based on the transient synchronization model of the microgrid, the dynamic security domain of the microgrid is determined;

[0161] The transient synchronization stability of the microgrid is evaluated based on the dynamic security domain.

[0162] This application also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the method provided in any of the foregoing method embodiments.

[0163] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0164] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented using software plus a general-purpose hardware platform, or of course, using hardware. Based on this understanding, the above technical solutions, in essence or the parts that contribute to the related technology, 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 ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0165] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A method for determining the dynamic security domain of a microgrid, characterized in that, include: Based on the transient synchronization model of microgrids, the boundary estimation equation of the dominant stability domain is determined; Based on the dominant stability domain boundary estimation equation, the dynamic security domain of the microgrid is determined.

2. The method according to claim 1, characterized in that, The microgrid-based transient synchronization model determines the dominant stability domain boundary estimation equation by: calculating all equilibrium points in the transient synchronization model and the stable manifolds corresponding to the equilibrium points; and determining the dominant stability domain boundary estimation equations corresponding to the equilibrium points by comparing the limit cut-off times, wherein the limit cut-off time is the shortest time taken for the system state trajectory point to change from satisfying the transient synchronization stability discrimination equation (greater than zero) to less than zero or equal to zero in a given fault simulation.

3. The method according to claim 1, characterized in that, The step of determining the dynamic security domain of the microgrid based on the dominant stability domain boundary estimation equation includes: determining an initial dynamic security domain according to the transient synchronization model of the microgrid; setting an initial space for searching the initial dynamic security domain; substituting the points in the initial space into the dominant stability domain boundary estimation equation to determine the boundary of the initial dynamic security domain, thereby obtaining the dynamic security domain.

4. The method according to claim 3, characterized in that, The step of substituting points in the initial space into the dominant stability domain boundary estimation equation to determine the boundary of the initial dynamic safety domain and obtain the dynamic safety domain includes: simulating a predetermined fault for each point in the initial space and substituting it into the dominant stability domain boundary estimation equation to obtain the phase trajectory points after the predetermined fault is cleared.

5. The method according to claim 4, characterized in that, The dynamic safety domain includes a first dynamic safety domain and / or a second dynamic safety domain, and the initial space includes a first initial space and a second initial space. Therefore, setting the initial space for searching the initial dynamic safety domain includes: generating the first initial space for the first dynamic safety domain; and / or generating the second initial space for the second dynamic safety domain, wherein the first initial space is used to characterize the search space for the injected active current reference value for the first dynamic safety domain, and the second initial space is used to characterize the search space for controllable parameters for the second dynamic safety domain.

6. The method according to claim 5, characterized in that, The first dynamic safety domain consists of all active current reference values ​​that satisfy the following condition: the system operating at the active current reference value, after a predetermined fault occurs and is cleared, has its state trajectory point located within the transient synchronous stability domain defined by the dominant stability domain boundary estimation equation; the first initial space is a set of active current reference values ​​discretized in the range of zero to three times the rated current.

7. The method according to claim 5, characterized in that, The second dynamic safety domain consists of all controllable parameters that satisfy the following conditions: the system operating with this set of controllable parameters, after a predetermined fault occurs and is cleared, has its state trajectory point located within the transient synchronous stability domain defined by the dominant stability domain boundary estimation equation; the second initial space is a combination set of proportional control parameters and integral control parameters discretized within the range of zero to ten times the rated parameters.

8. The method according to claim 5, characterized in that, The step of simulating a predetermined fault for each point in the initial space and substituting it into the dominant stability domain boundary estimation equation to obtain the phase trajectory point after the predetermined fault is cleared includes: determining the first phase trajectory point after the predetermined fault is cleared based on the current reference value in the first initial space; and / or determining the second phase trajectory point after the predetermined fault is cleared based on the controllable parameters in the second initial space.

9. The method according to claim 8, characterized in that, The method further includes: generating a transient synchronization stability margin extension strategy based on the dynamic security domain.

10. The method according to claim 9, characterized in that, When the dynamic safety domain includes the first dynamic safety domain and the second dynamic safety domain, the generation of transient synchronization stability margin expansion strategy based on the dynamic safety domain includes: adjusting controllable parameters based on the second dynamic safety domain until the area increment of the adjusted second dynamic safety domain is less than a preset increment; and adjusting the active current reference value of the converter based on the first dynamic safety domain.

11. The method according to claim 10, characterized in that, If the preset increment is 10%, then the controllable parameters are adjusted based on the second dynamic security domain until the adjusted area increment of the second dynamic security domain is less than the preset increment, including: when the area of ​​the second dynamic security domain obtained after the current adjustment is less than 110% of the area of ​​the second dynamic security domain obtained after the next adjustment, the adjustment of the controllable parameters is stopped.

12. The method according to claim 1, characterized in that, The transient synchronization model is constructed by: acquiring microgrid information including at least the microgrid system topology, operating mode, equipment control strategy, and microgrid parameters; and establishing a transient synchronization model of the microgrid based on the microgrid information.

13. A method and apparatus for determining the dynamic security domain of a microgrid, characterized in that, include: The module is used to determine the boundary estimation equations of the dominant stability domain based on the transient synchronization model of the microgrid; The processing module is used to determine the dynamic security domain of the microgrid based on the dominant stability domain boundary estimation equation.

14. An electronic device, characterized in that, It includes a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the method as described in any one of claims 1-12.

15. A non-transitory 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 method as described in any one of claims 1-12.

16. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1-12.

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