Electric power system effective reserve capacity analysis method and system, medium and terminal

Abstract

The invention discloses an electric power system effective reserve capacity analysis method and system, a medium and a terminal, and the method comprises the steps: carrying out the anticipated fault analysis of an electric power system based on an anticipated fault set of the electric power system, and constructing a channel power flow safety constraint based on a power flow transfer relation generated through analysis; analyzing the maximum possible value and the minimum possible value of each constraint function on the basis of describing the channel active power flow as a linear function of source load injection power and direct current receiving power, and filtering out the constraint functions of which the maximum possible values and the minimum possible values are located in corresponding allowable ranges in the channel power flow security constraints so as to obtain network security constraints; a model for solving the effective reserve capacity of a power system is established by taking maximization of the active output variation of a conventional unit of each node in an extremely severe state as an optimization target and combining with network security constraints. By adopting the method, the number of free variables can be reduced, unnecessary constraints can be filtered out, and the analysis efficiency of the effective reserve capacity is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power system performance analysis, and in particular to a method, system, medium and terminal for analyzing effective spare capacity of a power system. Background Art

[0002] The reliability constraint of the safe operation of the power system requires that the power grid can withstand the impact of certain expected faults, that is, when the expected fault occurs and causes some power equipment to exit operation, the power flow of any power equipment does not exceed its short-term overload capacity, avoiding chain disconnection and leaving sufficient time for operators to deal with the fault. In order to cope with risk factors such as the output of new energy falling short of expectations, oversupply of load, reduction of external power, and failure of AC and DC power components, when arranging the operation mode of the power system, the unit needs to reserve a certain amount of spare capacity. The spare calculation generally takes the maximum possible output of the unit minus the actual output of the unit as the spare that the unit can provide. When considering grid congestion, some units cannot operate at full output due to grid safety constraints, and their spare capacity cannot be actually called upon under the condition of ensuring grid safety after the disturbance. This part of the spare capacity is not an effective spare capacity.

[0003] At present, there is still a lack of fast and practical calculation methods for effective reserve. Generally, it relies on manual experience or network constraints under specific operating modes to deduct the restricted capacity of specific units in advance. With the rapid development of AC and DC power grids, large-scale grid-connected operation of wind power and photovoltaic power, and the deepening of the reform of the spot electricity market, the scale of the network is increasing, the grid structure is becoming more complex, and the uncertainty of source and load is greatly enhanced. It is difficult to achieve fast and accurate calculation of effective reserve through manual experience, and existing technologies are difficult to accurately evaluate the effective reserve capacity under specific operating modes of the power grid. Summary of the invention

[0004] The embodiments of the present invention provide a method, system, medium and terminal for analyzing the effective reserve capacity of an electric power system, which converts the flow transfer relationship related to the branch flow into a function of the channel flow, can reduce the number of free variables and improve the sparsity of constraints, and filter out unnecessary constraints, thereby improving the analysis accuracy and efficiency of the effective reserve capacity of the electric power system.

[0005] In order to solve the above technical problems, an embodiment of the present invention provides a method for analyzing effective reserve capacity of a power system, comprising:

[0006] Based on the expected fault set of the power system, the power system is analyzed for expected faults to generate power flow transfer relations;

[0007] Using the power flow transfer relationship, constructing channel power flow safety constraints;

[0008] Based on describing the active power flow of the channel as a linear function of the source load injection power and the DC input power, the maximum possible value and the minimum possible value of each constraint function in the channel power flow security constraint are analyzed. If the maximum possible value and the minimum possible value of the current constraint function are both within the allowable range of the current constraint function, the current constraint function is filtered out from the channel power flow security constraint, and the channel power flow security constraint that has completed the constraint function filtering is used as the network security constraint;

[0009] Taking maximizing the active output variation of conventional units at each node under extremely harsh conditions as the optimization goal, and combining the network security constraints, a linear programming model is established, and then the linear programming model is solved to obtain the effective backup capacity of the power system.

[0010] In the implementation of the embodiment of the present invention, based on the expected fault set of the power system, the power system is analyzed for expected faults to generate a power flow transfer relationship, which can deeply understand the impact on the system under different fault scenarios, and then effectively identify the system weaknesses. Then, the power flow transfer relationship is used to construct the channel power flow safety constraint, and the power flow transfer relationship related to the branch power flow can be converted into a function of the channel power flow, which helps to reduce the number of free variables and improve the sparsity of the constraints, so as to facilitate the subsequent filtering of redundant constraints. Then, based on describing the channel active power flow as a linear function of the source load injection power and the DC receiving power, the possible variation range of the constraint function in the channel power flow safety constraint is analyzed, and then the constraints that meet the possible variation range are converted into the constraints that meet the possible variation range. All constraint functions are filtered out from the channel flow safety constraints, and the filtered channel flow safety constraints are used as network security constraints. By filtering redundant constraints, the number of network security constraints is reduced, which makes the optimization model more concise and reduces the calculation scale of the optimization problem. The optimization goal is to maximize the change in active output of conventional units at each node under extremely harsh conditions. Combined with network security constraints, a linear programming model is established. Finally, the linear programming model is solved to obtain the effective spare capacity of the power system, which can improve the utilization rate of spare resources and ensure that the spare capacity can be called in time in the event of a fault, effectively improve the system's response capability under extreme conditions, and reduce the uncertainty of power supply.

[0011] As a preferred solution, the flow transfer relationship is used to construct a channel flow safety constraint, specifically:

[0012] The parallel lines or parallel main transformers are divided into the same channel, and the sum of the active power flows flowing into the current channel is used as the channel active power flow of the current channel;

[0013] According to the base state active power flows of all branches divided into the current channel and the channel active power flow of the current channel, a function is established to describe the base state branch active power flow as the channel active power flow;

[0014] By using the method of describing the base state branch active power flow as a function of the channel active power flow, the safety constraint of the pre-constructed base state active power flow is optimized, and by using the power flow transfer relationship and the method of describing the base state branch active power flow as a function of the channel active power flow, the reliability constraint of the pre-constructed considering the N-1 safety criterion is optimized to form an initial safety constraint; wherein the power flow transfer relationship is a linear function of describing the branch active power flow after the fault as the branch active power flow before the fault;

[0015] Redundant constraints are identified for the initial safety constraints, and then the identified redundant constraints are filtered out from the initial safety constraints, and the initial safety constraints that have completed redundant constraint identification and filtering are used as channel power flow safety constraints.

[0016] The preferred solution of the embodiment of the present invention is to divide the parallel lines or parallel main transformers into the same channel, which is helpful to simplify the model of the power system, and take the sum of the active power flows flowing into the current channel as the channel active power flow of the current channel, and then establish a function that describes the base state branch active power flow as the channel active power flow according to the base state active power flow of all branches divided into the current channel and the channel active power flow of the current channel, so as to characterize the functional relationship between the base state branch active power flow and the channel active power flow, and achieve a more accurate description of the power flow, thereby improving the accuracy of the power flow calculation. In addition, by describing the base state branch active power flow as a function of the channel active power flow, the safety constraints of the pre-constructed base state active power flow are optimized, which can better meet the safety requirements of the power system operation when considering multiple branches and channels, and by using the power transfer relationship and the base state branch active power flow as a function of the channel active power flow, the reliability constraints of the pre-constructed considering the N-1 safety criterion are optimized, which can ensure reliability and robustness when a system failure occurs, and reduce the risk of large-scale power outages caused by failures.

[0017] As a preferred solution, the initial security constraints are specifically:

[0018]

[0019] In the formula, Indicates the long-term allowable current carrying capacity of branch j; K Bj represents the branch coefficient of branch j in its corresponding channel; P ∑c Indicates the active power flow of the channel numbered c; S C Represents a collection of channels; represents the set of running branches in the base state of channel c; Indicates the short-time allowable current carrying capacity of branch j; represents the set of channels that affect the power flow of branch j under fault state k; S represents the linear coefficient of the power flow of branch j under fault state k and the power flow of channel c before the fault; K represents the expected fault set; Represents the operating branch set after the expected fault k occurs.

[0020] By implementing the preferred solution of the embodiment of the present invention, in the process of realizing the constraint on the active power flow of the channel, the long-term allowable current carrying capacity of the branch is considered, which can ensure the safety of the line in the long and short term. In addition, in the fault state, by considering the channel set and linear coefficient that affect the branch flow, the impact of the N-1 fault can be accurately evaluated, ensuring that the system can still maintain stable operation when a single component fails.

[0021] As a preferred solution, the active power flow of the channel is described as obtaining a linear function of the source load injection power and the DC input power, specifically:

[0022] When the unit output changes, a sensitivity analysis is performed on the active power flow of the channel, and a sensitivity row vector is constructed based on the sensitivity analysis result and the pre-constructed linearized power flow equation; wherein the sensitivity row vector includes the sensitivity of the active power flow of the channel to the active power injection of the node;

[0023] The sensitivity row vector is derived and analyzed to obtain a linear function that describes the channel active power flow as the source load injection power and the DC input power.

[0024] By implementing the preferred solution of the embodiment of the present invention, sensitivity analysis is performed on the active power flow of the channel, which can quickly identify the impact of the change in unit output on the channel power flow, thereby improving the depth of understanding and response speed of the dynamic behavior of the system. Then, based on the sensitivity analysis results and the sensitivity row vector constructed by the linearized power flow equation, the active power flow of the channel can be accurately described as a linear function of the source load injection power and the DC input power, which helps to more accurately describe the power flow distribution of the power system. In addition, by understanding the sensitivity of the active power flow of the channel to the active power injection of the node, it is possible to make more effective scheduling decisions when the unit output changes, optimize the power flow control of the system, and ensure the stability and efficient operation of the power system.

[0025] As a preferred solution, the anticipated fault set based on the power system is used to perform anticipated fault analysis on the power system to generate a power flow transfer relationship, specifically:

[0026]

[0027] In the formula, S K represents the expected fault set; represents the active power flow of branch j after the expected fault k occurs; and Represent the base state active power flow of branch i and branch j respectively; It represents the power flow transfer coefficient of the disconnected branch i to the non-disconnected branch j after the expected fault k occurs; represents the set of branches disconnected by the expected fault k; represents the set of operating branches after the expected fault k occurs,

[0028] The preferred scheme of implementing the embodiment of the present invention considers the flow transfer coefficient of the disconnected branch to the non-disconnected branch after the expected fault occurs, as well as the base-state active flow of the branch, evaluates and analyzes the changes in the active flow of the branch before and after the expected fault occurs, and then establishes a flow transfer relationship that can accurately characterize the flow changes.

[0029] As a preferred solution, the maximum change in active output of conventional units at each node under the extremely harsh state is taken as the optimization goal, and a linear programming model is established in combination with the network security constraints, specifically:

[0030] The sum of the active output of all conventional units added under extremely severe conditions is used as the effective reserve of the power system, and the first objective function is established with the maximization of the change in active output of conventional units at each node under extremely severe conditions as the optimization goal, and the second objective function is established with the minimization of the shortfall of node load power relative to the reference oversupply rate under extremely severe conditions as the optimization goal;

[0031] The network security constraint is described as a system power balance constraint under an extremely harsh state, and a linear programming model is constructed by combining the first objective function and the second objective function.

[0032] The preferred scheme for implementing the embodiment of the present invention takes into account situations such as the output of new energy falling short of expectations, oversupply of loads, and reduction of DC external power, and takes maximizing the change in active output of conventional units at each node under extremely harsh conditions as the optimization goal, and establishes a first objective function, which can motivate each unit to exert its maximum capacity under extreme conditions and improve the emergency response capability of the system. The second objective function is established with minimizing the shortfall of node load power relative to a reference oversupply rate under extremely harsh conditions as the optimization goal, and can optimize load scheduling and supply to ensure the stable operation of the power system under extreme conditions. The network security constraint is then described as a system power balance constraint under extremely harsh conditions, and the first and second objective functions are combined to construct a linear programming model for solving the effective reserve capacity of the power system, thereby enhancing the emergency response capability of the power system under extreme conditions.

[0033] In order to solve the same technical problem, an embodiment of the present invention further provides a power system effective reserve capacity analysis system, comprising:

[0034] A fault analysis module, used for performing a predicted fault analysis on the power system based on a predicted fault set of the power system to generate a power flow transfer relationship;

[0035] A constraint construction module, used to construct a channel flow safety constraint by using the flow transfer relationship;

[0036] A constraint filtering module is used to analyze the maximum possible value and the minimum possible value of each constraint function in the channel flow security constraint based on describing the channel active power flow as a linear function of the source load injection power and the DC input power. If the maximum possible value and the minimum possible value of the current constraint function are both within the allowable range of the current constraint function, the current constraint function is filtered out from the channel flow security constraint, and the channel flow security constraint that has completed the constraint function filtering is used as a network security constraint;

[0037] The modeling and solving module is used to maximize the change in active output of conventional units at each node under extremely harsh conditions as the optimization goal, and to establish a linear programming model in combination with the network security constraints, and then solve the linear programming model to obtain the effective backup capacity of the power system.

[0038] As a preferred solution, the constraint construction module specifically includes:

[0039] A constraint optimization unit is used to divide the parallel lines or parallel main transformers into the same channel, and use the sum of the active power flows flowing into the current channel as the channel active power flow of the current channel; according to the base-state active power flows of all branches divided into the current channel and the channel active power flow of the current channel, establish a function that describes the base-state branch active power flow as the channel active power flow; using the function that describes the base-state branch active power flow as the channel active power flow, optimize the safety constraint of the pre-constructed base-state active power flow, and using the power transfer relationship and the function that describes the base-state branch active power flow as the channel active power flow, optimize the reliability constraint that considers the N-1 safety criterion in advance to form an initial safety constraint; wherein, the power transfer relationship is a linear function that describes the branch active power flow after the fault as the branch active power flow before the fault;

[0040] The identification and filtering unit is used to identify redundant constraints for the initial safety constraints, then filter out the identified redundant constraints from the initial safety constraints, and use the initial safety constraints that have completed redundant constraint identification and filtering as channel flow safety constraints.

[0041] In order to solve the same technical problem, the present invention also provides a computer-readable storage medium, which includes a stored computer program; wherein, when the computer program is running, the device where the computer-readable storage medium is located is controlled to execute the method for analyzing the effective reserve capacity of an electric power system.

[0042] In order to solve the same technical problem, the present invention also provides a terminal, including a processor, a memory and a computer program stored in the memory; wherein the computer program can be executed by the processor to implement the method for analyzing the effective reserve capacity of a power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 : A flow chart of a method for analyzing effective reserve capacity of a power system provided in Embodiment 1 of the present invention;

[0044] Figure 2 : A structural diagram of a power system effective spare capacity analysis system provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Embodiment one:

[0047] Please refer to Figure 1 , is a method for analyzing effective reserve capacity of a power system provided by an embodiment of the present invention, the method comprises steps S1 to S4, each step is specifically as follows:

[0048] Step S1, based on the expected fault set of the power system, performing expected fault analysis on the power system to generate a power flow transfer relationship.

[0049] As a preferred solution, after the occurrence of the expected fault k, the fault state active power flow of branch j can be described as a linear function of its base state active power flow and the base state active power flow of each disconnected branch, that is, the base state active power flow of the branch and the linear function between the base state active power flow of each disconnected branch are used to characterize the fault state active power flow of the branch. For the specific power flow transfer relationship, please refer to formula (1).

[0050]

[0051] In the formula, S K represents the expected fault set; represents the active power flow of branch j after the expected fault k occurs; and Represent the base state active power flow of branch i and branch j respectively; It represents the power flow transfer coefficient of the disconnected branch i to the non-disconnected branch j after the expected fault k occurs; represents the set of branches disconnected by the expected fault k; represents the set of operating branches after the expected fault k occurs,

[0052] In this embodiment, the AC power flow method or the DC power flow method is used to calculate the power flow transfer relationship, wherein the power flow transfer relationship is to describe the active power flow of the branch after the fault as a linear function of the active power flow of the branch before the fault according to the power flow transfer ratio.

[0053] Step S2, using the power flow transfer relationship to construct channel power flow safety constraints.

[0054] As a preferred solution, step S2 includes step S21 to step S24, and each step is specifically as follows:

[0055] Step S21, divide the parallel lines or parallel main transformers into the same channel, and take the sum of the active power flows flowing into the current channel as the channel active power flow of the current channel. At the same time, define the ratio of the branch active power flow to the channel active power flow as the branch coefficient, and the relationship of this definition is specifically referred to in formula (2).

[0056]

[0057] In the formula, K Bj represents the branching coefficient of branch j in its corresponding channel; represents the base state active power flow of branch j; c represents the channel number; P ∑c represents the total active power flow of channel c; S C Represents a collection of channels; Represents the set of operating branches in the base state of channel c.

[0058] It should be noted that, whether in the base state or fault state, for parallel lines or parallel main transformers, the distribution ratio of the active power flow is approximately constant. For parallel lines, the active power flow distribution ratio of each line is mainly determined by its impedance. When two lines with the same parameters are connected in parallel, the active power flow flowing through each line must be the same. Since the branch coefficient is approximately a constant and has little to do with the specific operating state, it can be determined based on the base state active power flow.

[0059] Step S22, based on the base state active power flows of all branches divided into the current channel and the channel active power flow of the current channel, establish a function that describes the base state branch active power flow as the channel active power flow. For details of this function, please refer to formula (3).

[0060]

[0061] In the formula, K Bj represents the branching coefficient of branch j in its corresponding channel; represents the base state active power flow of branch j; c represents the channel number; P ∑c represents the total active power flow of channel c; S C Represents a collection of channels; Represents the set of operating branches in the base state of channel c.

[0062] Step S23, by describing the base state branch active power flow as a function of the channel active power flow, the pre-constructed safety constraint of the base state active power flow is optimized, and by using the power transfer relationship and describing the base state branch active power flow as a function of the channel active power flow, the pre-constructed reliability constraint considering the N-1 safety criterion is optimized to form an initial safety constraint.

[0063] In this embodiment, equation (4) is derived from equations (1) and (3). For details of the pre-constructed safety constraint of the base-state active power flow, please refer to equation (5). For details of the pre-constructed reliability constraint considering the N-1 safety criterion, please refer to equation (6).

[0064]

[0065] In the formula, represents the set of channels that affect the power flow of branch j under fault state k, which includes the channel where the breaking element of fault k is located and the channel where branch j is located; It represents the linear coefficient of the power flow of branch j under fault state k and the power flow of channel c before the fault.

[0066]

[0067] In the formula, represents the set of running branches j in the base state; Indicates the long-term allowable current carrying capacity of branch j; Represents the base state active power flow of branch j.

[0068]

[0069] In the formula, Indicates the long-term allowable current carrying capacity of branch j; Indicates the short-time allowable current carrying capacity of branch j; S Krepresents the expected fault set; Represents the operating branch set after the expected fault k occurs.

[0070] As a preferred solution, the initial safety constraint, please refer to formula (7) (8) for details.

[0071]

[0072] In the formula, Indicates the long-term allowable current carrying capacity of branch j; K Bj represents the branch coefficient of branch j in its corresponding channel; P c Indicates the active power flow of the channel numbered c; S C Represents a collection of channels; represents the set of running branches in the base state of channel c; Indicates the short-time allowable current carrying capacity of branch j; represents the set of channels that affect the power flow of branch j under fault state k; S represents the linear coefficient of the power flow of branch j under fault state k and the power flow of channel c before the fault; K represents the expected fault set; Represents the operating branch set after the expected fault k occurs.

[0073] Step S24, redundant constraint identification is performed on the initial safety constraint, and then the identified redundant constraints are filtered out from the initial safety constraint, and the initial safety constraint after redundant constraint identification and filtering is used as the channel power flow safety constraint.

[0074] It should be noted that the number of fault state constraints in the system's effective spare capacity configuration is very considerable, which brings great difficulties to its numerical solution. How to reduce the fault state constraints is the key to whether the system's effective spare capacity configuration can be practical. The initial safety constraints formed by equations (7) and (8) are all linear constraints, and the feasible domain space they constitute is a convex space. There are a large number of safety constraints formed by equations (7) and (8), and a large number of these constraints are redundant. Eliminating redundant constraints has no effect on the feasible domain space. Identifying and filtering redundant constraints helps to discover key constraints, reduce the number of constraints describing the feasible domain space, and greatly improve the efficiency of solving optimization problems. Describing branch flow as a function of channel flow helps to reduce the number of free variables, improve the sparsity of constraints in equation (8), and help filter redundant constraints.

[0075] As a preferred solution, before executing step S3, it also includes an acquisition process of "describing the channel active power flow as a linear function of the source load injection power and the DC input power", including steps S01 to S02, and each step is specifically as follows:

[0076] Step S01, when the unit output changes, a sensitivity analysis is performed on the active power flow of the channel, and a sensitivity row vector is constructed based on the sensitivity analysis result and the pre-constructed linearized power flow equation.

[0077] Among them, the sensitivity row vector A c Includes the sensitivity of channel active power flow to node active power injection.

[0078] In this embodiment, the linearized power flow equation of formula (9) is first established, and then formula (10) is derived from formula (9). When the unit output changes, the active power flow of the channel will change. At this time, a sensitivity analysis is performed on the active power flow of channel c near the base state power flow solution to obtain the sensitivity analysis result of formula (11), and then formula (11) is substituted into formula (10) to obtain formula (12). Next, let Then the sensitivity row vector A c The elements corresponding to the node active power injection are the sensitivity of the active power flow of channel c to the node active power injection.

[0079]

[0080] In the formula, represents the power flow Jacobian matrix; ΔP=[ΔP1,ΔP2…ΔP n ] represents the node active power injection change vector; ΔQ=[ΔQ1,ΔQ2…ΔQ n ] represents the node reactive power injection change vector; Δe=[Δe1,Δe2…Δe n ] represents the voltage real part change vector; Δf=[Δf1,Δf2…Δf n ] represents the change vector of the imaginary part of voltage; ΔP ∑c Indicates the change in the active power flow of channel c.

[0081] Step S02, deriving and analyzing the sensitivity row vector, and obtaining a linear function that describes the channel active power flow as the source load injection power and the DC input power.

[0082] In this embodiment, assuming that the node reactive power injection remains unchanged, ΔQ = 0, then It can be simplified to the expression of formula (13). Then, based on formula (13), the branch active power flow P ∑c It is described as a linear function of unit output, load power and DC feed-in power. For details of this linear function, please refer to formula (14).

[0083]

[0084] In the formula, SG represents the set of terminal nodes of conventional units; S WDRepresents the set of wind turbine terminal nodes; S PV Represents the terminal node set of the photovoltaic system; S DC represents the set of AC nodes of the DC transmission converter; S LD represents the load node set; ΔP Gi Indicates the change in active output of the unit at node i; ΔP WDi Indicates the change in active output of wind turbine at node i; ΔP PVi Indicates the change in active output of the photovoltaic unit at node i; ΔP DCi It represents the change in active power fed into the grid from the AC side of the converter at node i; ΔP LDi Represents the change in active power of the load at node i.

[0085]

[0086] In the formula, represents the constant term of the active power flow function of channel c; P Gi represents the active output of the unit at node i; P WDi represents the active output of wind turbine at node i; P PVi represents the active output of the photovoltaic unit at node i; P DCi P represents the active power fed into the grid from the AC side of the converter at node i; LDi Represents the active power of the load at node i.

[0087] It should be noted that, in actual situations, nodes with very small sensitivity can be ignored, and only units, loads and DC input points with absolute sensitivity values ​​greater than a certain threshold (such as 0.02) are retained. Therefore, formula (14) has good sparsity.

[0088] Step S3, based on describing the channel active power flow as a linear function of the source load injection power and the DC receiving power, analyze the maximum possible value and the minimum possible value of each constraint function in the channel power flow safety constraint. If the maximum possible value and the minimum possible value of the current constraint function are both within the allowable range of the current constraint function, the current constraint function is filtered out from the channel power flow safety constraint, and the channel power flow safety constraint that completes the constraint function filtering is used as the network security constraint.

[0089] In this embodiment, in the effective reserve calculation problem, since the output of each conventional unit, load power and DC input power are all subject to upper and lower limits, the maximum possible value and minimum possible value of the active power flow of each channel can be obtained according to formula (14), and then the maximum possible value and minimum possible value of each constraint function in formula (7) and formula (8) can be obtained. If the maximum possible value and the minimum possible value of the constraint function are both within the allowable range of the corresponding constraint, it means that the security constraints will be satisfied. Filtering such constraints has no effect on the optimization results, but it helps to further reduce the number of network security constraints and improve the calculation speed.

[0090] Step S4, taking maximizing the active output change of conventional units at each node under extremely severe conditions as the optimization goal, and combining network security constraints, a linear programming model is established, and then the linear programming model is solved to obtain the effective backup capacity of the power system.

[0091] As a preferred solution, step S4 includes step S41 to step S43, and each step is specifically as follows:

[0092] Step S41, taking the sum of the active outputs of all conventional units increased under extremely severe conditions as the effective reserve of the power system, and taking maximizing the change in active output of conventional units at each node under extremely severe conditions as the optimization goal, a first objective function is established, and then the network security constraint is described as the system power balance constraint under extremely severe conditions, and taking minimizing the shortfall of node load power relative to the reference oversupply rate under extremely severe conditions as the optimization goal, a second objective function is established.

[0093] In this embodiment, referring to formula (15), compared with the base state power flow, the sum of the active output of the conventional units increased in the extremely bad state is the effective reserve P of the system. RES .

[0094]

[0095] Where P RES Indicates the effective reserve of the power system; Represents the base state active output of the node i unit.

[0096] It should be noted that effective reserve is to evaluate the maximum power supply capacity of the power supply in the grid when the output of new energy is lower than expected, the load is higher than expected, and the external power is reduced, that is, the most unfavorable new energy forecast error, load forecast error and external power forecast deviation that can be tolerated under a specific grid operation mode and startup mode. Here, the worst operating conditions that can be tolerated under the current grid operation mode and unit startup mode are defined as extremely bad conditions, mainly considering the situation where the output of new energy is lower than expected, the load is oversupplied, and the DC external power is reduced.

[0097] In this embodiment, the first objective function is first established as shown in formula (16), and then the system power balance constraint under the extremely harsh state is established as shown in formula (17). Furthermore, formula (17) can be replaced by formula (18).

[0098]

[0099]

[0100] In the formula, ΔP Gi Indicates the change in active output of conventional units at node i under extremely severe conditions; ΔP PVi Indicates the change in active output of wind turbine at node i under extremely severe conditions; ΔP PVi Indicates the change in active output of the photovoltaic unit at node i under extremely severe conditions; ΔP DCi represents the change in DC input power at node i; ΔP LDi represents the load power change of node i; The superscript BASE indicates the base state power flow; represents the active output of the conventional unit at node i in the base state; represents the active output of wind turbine at node i in the base state; represents the active output of the photovoltaic unit at node i in the base state; represents the DC input power of node i in the base state; represents the load power of node i in the base state.

[0101] In this embodiment, the effective reserve calculation mainly evaluates the maximum safe output of conventional units when the output of new energy is lower than expected, the load is oversupplied, and the DC external power is reduced. Therefore, the parameters in formula (18) are subject to constraints as shown in formulas (19)(20)(21)(22)(23).

[0102]

[0103] In practical applications, it is generally believed that the load grows approximately in proportion. However, considering that the system effective reserve calculation mainly focuses on the problem of unit output limitation caused by network security constraints, and does not care about the problem of local load growth limitation caused by network security constraints, the second objective function of formula (24) can be added, and the constraints of formula (25) can be added.

[0104]

[0105]

[0106] In the formula, λ LD Indicates the load reference oversupply rate; P L ' DiIt represents the shortfall of node i load power relative to the reference oversupply rate under extremely severe conditions.

[0107] Step S42, constructing a linear programming model by combining the system power balance constraint under an extremely bad state, the first objective function and the second objective function.

[0108] In this embodiment, equation (16) and equation (24) are weighted to obtain the objective function of the linear programming model shown in equation (26).

[0109]

[0110] Step S43, solving the linear programming model to obtain the effective reserve capacity of the power system.

[0111] In this embodiment, by solving the linear programming model composed of equations (15) to (18) and equations (24) to (26), the effective standby of each unit can be obtained. The linear programming model is a linear programming problem in mathematics, which can be solved by the simplex method and the interior point method, or by commercial optimization software (such as CPLEX).

[0112] Please refer to Figure 2 , is a schematic diagram of the structure of a power system effective reserve capacity analysis system provided by an embodiment of the present invention, the system includes a fault analysis module M1, a constraint construction module M2, a constraint filtering module M3 and a modeling and solving module M4, and each module is specifically as follows:

[0113] The fault analysis module M1 is used to perform a predicted fault analysis on the power system based on the predicted fault set of the power system to generate a power flow transfer relationship;

[0114] The constraint construction module M2 is used to construct the channel flow safety constraint by using the flow transfer relationship;

[0115] The constraint filtering module M3 is used to analyze the maximum possible value and the minimum possible value of each constraint function in the channel flow security constraint based on describing the channel active power flow as a linear function of the source load injection power and the DC input power. If the maximum possible value and the minimum possible value of the current constraint function are both within the allowable range of the current constraint function, the current constraint function is filtered out from the channel flow security constraint, and the channel flow security constraint that has completed the constraint function filtering is used as the network security constraint;

[0116] The modeling and solving module M4 is used to maximize the change in active output of conventional units at each node under extremely harsh conditions as the optimization goal, and to establish a linear programming model in combination with network security constraints, and then solve the linear programming model to obtain the effective backup capacity of the power system.

[0117] As a preferred solution, the constraint construction module M2 specifically includes a constraint optimization unit 21 and an identification filtering unit 22, and the specific details of each unit are as follows:

[0118] The constraint optimization unit 21 is used to divide the parallel lines or parallel main transformers into the same channel, and use the sum of the active power flows flowing into the current channel as the channel active power flow of the current channel; according to the base-state active power flows of all branches divided into the current channel and the channel active power flow of the current channel, establish a function that describes the base-state branch active power flow as the channel active power flow; use the function that describes the base-state branch active power flow as the channel active power flow to optimize the pre-constructed safety constraint of the base-state active power flow, and use the power transfer relationship and the function that describes the base-state branch active power flow as the channel active power flow to optimize the pre-constructed reliability constraint considering the N-1 safety criterion to form an initial safety constraint; wherein the power transfer relationship is a linear function that describes the branch active power flow after the fault as the branch active power flow before the fault;

[0119] The identification and filtering unit 22 is used to identify redundant constraints for the initial safety constraints, and then filter out the identified redundant constraints from the initial safety constraints, and use the initial safety constraints that have completed redundant constraint identification and filtering as the channel flow safety constraints.

[0120] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0121] An embodiment of the present invention also provides a computer-readable storage medium, which includes a stored computer program; wherein, when the computer program is running, the device where the computer-readable storage medium is located is controlled to execute a method for analyzing effective reserve capacity of a power system as described in Embodiment 1.

[0122] An embodiment of the present invention further provides a terminal, comprising a processor, a memory, and a computer program stored in the memory; wherein the computer program can be executed by the processor to implement a method for analyzing effective reserve capacity of a power system as described in Embodiment 1.

[0123] Preferably, the computer program can be divided into one or more modules / units (such as computer program, computer program), one or more modules / units are stored in the memory and executed by the processor to complete the present invention. One or more modules / units can be a series of computer program instruction segments that can complete specific functions, and the instruction segments are used to describe the execution process of the computer program in the terminal.

[0124] The processor can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor, or the processor can also be any conventional processor. The processor is the control center of the terminal, and various parts of the terminal are connected using various interfaces and lines.

[0125] The memory mainly includes a program storage area and a data storage area, wherein the program storage area can store an operating system, an application required for at least one function, etc., and the data storage area can store related data, etc. In addition, the memory can be a high-speed random access memory, or a non-volatile memory, such as a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, and a flash card (Flash Card), etc., or the memory can also be other volatile solid-state storage devices.

[0126] It should be noted that the above-mentioned terminal may include, but is not limited to, a processor and a memory. Those skilled in the art will understand that the above-mentioned terminal is merely an example and does not constitute a limitation on the terminal. It may include more or fewer components, or a combination of certain components, or different components.

[0127] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0128] The present invention provides an effective reserve capacity analysis method, system, medium and terminal for an electric power system. Based on the expected fault set of the electric power system, the expected fault analysis is performed on the electric power system to generate a power flow transfer relationship, which can deeply understand the impact on the system under different fault scenarios, and then effectively identify the system weaknesses. Then, the power flow transfer relationship is used to construct a channel power flow safety constraint, and the power flow transfer relationship related to the branch power flow can be converted into a function of the channel power flow, which helps to reduce the number of free variables and improve the sparsity of the constraints, so as to facilitate the subsequent filtering of redundant constraints. Then, based on describing the channel active power flow as a linear function of the source load injection power and the DC receiving power, the possible variation range of the constraint function in the channel power flow safety constraint is analyzed. Then all constraint functions that satisfy the possible variation range are filtered out from the channel flow safety constraints, and the filtered channel flow safety constraints are used as network security constraints. By filtering redundant constraints, the number of network security constraints is reduced, which makes the optimization model more concise and reduces the calculation scale of the optimization problem. Then, the optimization goal is to maximize the change in active output of conventional units at each node under extremely harsh conditions, and a linear programming model is established in combination with network security constraints. Finally, the linear programming model is solved to obtain the effective backup capacity of the power system, which can improve the utilization rate of backup resources, ensure that the backup capacity can be called in time in the event of a fault, effectively improve the system's response capability under extreme conditions, and reduce the uncertainty of power supply.

[0129] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for analyzing effective reserve capacity of a power system, characterized in that: include: Based on the expected fault set of the power system, the power system is analyzed for expected faults to generate power flow transfer relations; Using the power flow transfer relationship, constructing channel power flow safety constraints; Based on describing the active power flow of the channel as a linear function of the source load injection power and the DC input power, the maximum possible value and the minimum possible value of each constraint function in the channel power flow security constraint are analyzed. If the maximum possible value and the minimum possible value of the current constraint function are both within the allowable range of the current constraint function, the current constraint function is filtered out from the channel power flow security constraint, and the channel power flow security constraint that has completed the constraint function filtering is used as the network security constraint; Taking maximizing the active output variation of conventional units at each node under extremely harsh conditions as the optimization goal, and combining the network security constraints, a linear programming model is established, and then the linear programming model is solved to obtain the effective backup capacity of the power system.

2. A method for analyzing effective reserve capacity of a power system according to claim 1, characterized in that: The flow transfer relationship is used to construct the channel flow safety constraint, which is specifically: The parallel lines or parallel main transformers are divided into the same channel, and the sum of the active power flows flowing into the current channel is used as the channel active power flow of the current channel; According to the base state active power flows of all branches divided into the current channel and the channel active power flow of the current channel, a function is established to describe the base state branch active power flow as the channel active power flow; By using the method of describing the base state branch active power flow as a function of the channel active power flow, the safety constraint of the pre-constructed base state active power flow is optimized, and by using the power flow transfer relationship and the method of describing the base state branch active power flow as a function of the channel active power flow, the reliability constraint of the pre-constructed considering the N-1 safety criterion is optimized to form an initial safety constraint; wherein the power flow transfer relationship is a linear function of describing the branch active power flow after the fault as the branch active power flow before the fault; Redundant constraints are identified for the initial safety constraints, and then the identified redundant constraints are filtered out from the initial safety constraints, and the initial safety constraints that have completed redundant constraint identification and filtering are used as channel power flow safety constraints.

3. A method for analyzing effective reserve capacity of a power system according to claim 2, characterized in that: The initial security constraints are specifically: In the formula, Indicates the long-term allowable current carrying capacity of branch j; K Bj represents the branch coefficient of branch j in its corresponding channel; P ∑c Indicates the active power flow of the channel numbered c; S C Represents a collection of channels; represents the set of operating branches in the base state of channel c; Indicates the short-time allowable current carrying capacity of branch j; represents the set of channels that affect the power flow of branch j under fault state k; S represents the linear coefficient of the power flow of branch j under fault state k and the power flow of channel c before the fault; K represents the expected fault set; Represents the operating branch set after the expected fault k occurs.

4. A method for analyzing effective reserve capacity of a power system according to claim 1, characterized in that: The active power flow of the channel is described as the acquisition of a linear function of the source load injection power and the DC input power, specifically: When the unit output changes, a sensitivity analysis is performed on the active power flow of the channel, and a sensitivity row vector is constructed based on the sensitivity analysis result and the pre-constructed linearized power flow equation; wherein the sensitivity row vector includes the sensitivity of the active power flow of the channel to the active power injection of the node; The sensitivity row vector is derived and analyzed to obtain a linear function that describes the channel active power flow as the source load injection power and the DC input power.

5. A method for analyzing effective reserve capacity of a power system according to claim 1, characterized in that: The anticipated fault set based on the power system is used to analyze the anticipated faults of the power system to generate a power flow transfer relationship, which is specifically: In the formula, S K represents the expected fault set; represents the active power flow of branch j after the expected fault k occurs; and Represent the base state active power flow of branch i and branch j respectively; It represents the power flow transfer coefficient of the disconnected branch i to the non-disconnected branch j after the expected fault k occurs; represents the set of branches disconnected by the expected fault k; represents the set of operating branches after the expected fault k occurs, 6. A method for analyzing effective reserve capacity of a power system according to claim 1, characterized in that: The optimization goal is to maximize the change in active output of conventional units at each node under extremely harsh conditions, and in combination with the network security constraints, a linear programming model is established, specifically: The sum of the active output of all conventional units added under extremely severe conditions is used as the effective reserve of the power system, and the first objective function is established with the maximization of the change in active output of conventional units at each node under extremely severe conditions as the optimization goal, and then the network security constraint is described as a system power balance constraint under extremely severe conditions, and the second objective function is established with the minimization of the shortfall of node load power relative to the reference oversupply rate under extremely severe conditions as the optimization goal; A linear programming model is constructed by combining the system power balance constraint under the extremely harsh state, the first objective function and the second objective function.

7. A power system effective reserve capacity analysis system, characterized in that: include: A fault analysis module, used for performing a predicted fault analysis on the power system based on a predicted fault set of the power system to generate a power flow transfer relationship; A constraint construction module, used to construct a channel flow safety constraint by using the flow transfer relationship; A constraint filtering module is used to analyze the maximum possible value and the minimum possible value of each constraint function in the channel flow security constraint based on describing the channel active power flow as a linear function of the source load injection power and the DC input power. If the maximum possible value and the minimum possible value of the current constraint function are both within the allowable range of the current constraint function, the current constraint function is filtered out from the channel flow security constraint, and the channel flow security constraint that has completed the constraint function filtering is used as a network security constraint; The modeling and solving module is used to maximize the change in active output of conventional units at each node under extremely harsh conditions as the optimization goal, and to establish a linear programming model in combination with the network security constraints, and then solve the linear programming model to obtain the effective backup capacity of the power system.

8. The power system effective reserve capacity analysis system according to claim 7, characterized in that: The constraint building module specifically includes: A constraint optimization unit is used to divide the parallel lines or parallel main transformers into the same channel, and use the sum of the active power flows flowing into the current channel as the channel active power flow of the current channel; according to the base-state active power flows of all branches divided into the current channel and the channel active power flow of the current channel, establish a function that describes the base-state branch active power flow as the channel active power flow; using the function that describes the base-state branch active power flow as the channel active power flow, optimize the safety constraint of the pre-constructed base-state active power flow, and using the power transfer relationship and the function that describes the base-state branch active power flow as the channel active power flow, optimize the reliability constraint that considers the N-1 safety criterion in advance to form an initial safety constraint; wherein, the power transfer relationship is a linear function that describes the branch active power flow after the fault as the branch active power flow before the fault; The identification and filtering unit is used to identify redundant constraints for the initial safety constraints, then filter out the identified redundant constraints from the initial safety constraints, and use the initial safety constraints that have completed redundant constraint identification and filtering as channel flow safety constraints.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored computer program; wherein, when the computer program is running, the device where the computer-readable storage medium is located is controlled to execute a method for analyzing effective reserve capacity of a power system as described in any one of claims 1 to 6.

10. A terminal, characterized in that: It comprises a processor, a memory and a computer program stored in the memory; wherein the computer program can be executed by the processor to implement a method for analyzing effective reserve capacity of a power system as described in any one of claims 1 to 6.

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