Power grid inertia configuration method and device considering frequency stability constraint

Abstract

The invention discloses a power grid inertia configuration method and device considering a frequency stability constraint, and relates to the field of power system inertia and frequency adjustment. The method comprises the following steps: sequentially establishing a power system frequency relational expression, a node inertia expression of power disturbance in a power system, a node inertia sensitivity expression and a power supply inertia control index model; according to the power grid structure and the inertia time constants of the power supplies, utilizing the inertia control index model of the power supplies to obtain an inertia control index of each power supply; selecting an optimal candidate power supply; establishing a target function by taking the inertia time constant lifting values of the new energy and the flexible direct current as decision variables and taking the minimum sum of the inertia time constant lifting values as a target; determining a frequency stability constraint, and determining the frequency stability constraint and the target function as an inertia lifting model; and based on the position of the optimal candidate power supply connected to the power grid, solving the inertia lifting model to obtain an inertia increment optimal configuration strategy. According to the invention, the optimal configuration of inertia improvement can be realized while the frequency safety of the system is met.

Description

Technical Field

[0001] The present application relates to the field of power system inertia and frequency regulation, and in particular to a method and device for configuring power grid inertia taking into account frequency stability constraints. Background Art

[0002] As the proportion of renewable energy and DC feed-in power increases, the power grid exhibits the "three highs" characteristics of high renewable energy penetration, high DC proportion, and high load density. Traditional renewable energy and DC do not provide inertia and do not participate in frequency regulation, resulting in low system inertia and weak frequency response capabilities. Low-inertia power systems are prone to rapid drops in system frequency and large frequency variability, which can easily lead to chain reactions such as failure of frequency control measures and disconnection of renewable energy units, resulting in major power outages. Therefore, it is necessary to develop an inertia-enhancing configuration method to improve grid frequency stability. Summary of the Invention

[0003] The purpose of this application is to provide a grid inertia configuration method and device that takes into account frequency stability constraints, which can achieve optimal inertia enhancement configuration while meeting system frequency safety.

[0004] To achieve the above objectives, this application provides the following solutions:

[0005] In the first aspect, the present application provides a grid inertia configuration method considering frequency stability constraints, including: establishing a power system frequency relationship; the power system includes a power grid and a power source connected to the power grid; both new energy and flexible direct current are used as power sources; according to the power system frequency relationship, constructing a node inertia expression for power disturbances in the power system; the node inertia expression characterizes the relationship between node inertia and the grid structure and the inertia time constant of the power source; based on the node inertia expression, establishing a node inertia sensitivity expression; based on the node inertia sensitivity expression, determining the inertia control index model of the power source; according to the grid structure and the inertia time constant of each power source, utilizing the inertia control of the power source An inertia control index model is established to obtain the inertia control index of each power source; a preset number of inertia control indexes are selected in descending order, and the power source corresponding to the selected inertia control index is determined as the optimal candidate power source; an objective function is established with the inertia time constant improvement value of new energy and flexible DC as the decision variable and the minimum sum of the inertia time constant improvement values ​​of new energy and flexible DC as the goal; a frequency stability constraint is determined and determined together with the objective function as an inertia improvement model; based on the position where the optimal candidate power source is connected to the power grid, the inertia improvement model is solved to obtain the optimal configuration strategy for inertia increment; the optimal configuration strategy for inertia increment includes the inertia time constant improvement value of each new energy and each flexible DC.

[0006] In the second aspect, the present application provides a power grid inertia configuration device that takes into account frequency stability constraints, including: a frequency relationship establishment module, a node inertia expression construction module, a sensitivity expression establishment module, an inertia control index model determination module, an inertia control index calculation module, an optimal candidate power supply selection module, an objective function establishment module, a constraint determination module and an optimal solution module.

[0007] A frequency relationship formula establishment module is used to establish a frequency relationship formula for a power system; the power system includes a power grid and a power source connected to the power grid; both renewable energy and flexible direct current serve as power sources;

[0008] A node inertia expression construction module is used to construct a node inertia expression for a power disturbance in the power system based on the power system frequency relationship; the node inertia expression represents the relationship between the node inertia and the inertia time constant of the grid structure and the power supply;

[0009] A sensitivity expression establishing module, used for establishing a node inertia sensitivity expression based on the node inertia expression;

[0010] An inertia control index model determination module is used to determine the inertia control index model of the power supply based on the node inertia sensitivity expression;

[0011] An inertia control index calculation module is used to obtain the inertia control index of each power supply based on the grid structure and the inertia time constant of each power supply and using the power supply inertia control index model;

[0012] An optimal candidate power source selection module is used to select a preset number of inertia control indicators in descending order, and determine the power source corresponding to the selected inertia control indicator as the optimal candidate power source;

[0013] An objective function establishment module is used to establish an objective function with the inertia time constant improvement value of new energy and flexible DC as a decision variable and the minimum sum of the inertia time constant improvement values ​​of new energy and flexible DC as the goal;

[0014] A constraint determination module, configured to determine a frequency stability constraint and determine the constraint together with the objective function as an inertia improvement model;

[0015] The optimal solution module is used to solve the inertia improvement model based on the location where the optimal candidate power source is connected to the power grid, and obtain an optimal configuration strategy for the inertia increment; the optimal configuration strategy for the inertia increment includes the inertia time constant improvement value of each new energy source and each flexible DC.

[0016] According to the specific embodiments provided in this application, this application has the following technical effects:

[0017] This application provides a grid inertia configuration method and device that considers frequency stability constraints. A node inertia sensitivity expression is established, and an inertia control index is derived based on the node inertia sensitivity, thereby determining the optimal position for inertia increase. Combined with the frequency stability constraint, the inertia increment is optimized by comprehensively considering the impact of renewable energy and flexible direct current on system frequency stability. This achieves the optimal configuration for inertia increase while ensuring system frequency safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 A flowchart of a method for configuring power grid inertia considering frequency stability constraints provided in one embodiment of the present application;

[0020] Figure 2 This is an overall framework diagram of a grid inertia configuration method considering frequency stability constraints provided in one embodiment of the present application. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0022] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0023] In an exemplary embodiment, Figure 1 As shown, a method for configuring power grid inertia considering frequency stability constraints is provided, comprising the following steps 101 to 109. In which:

[0024] Step 101: Establish a power system frequency relationship; the power system includes a power grid and power sources connected to the power grid; both renewable energy and flexible direct current serve as power sources.

[0025] Step 102: constructing a node inertia expression for power disturbances in the power system based on the power system frequency relationship; the node inertia expression represents the relationship between the node inertia and the inertia time constant of the grid structure and the power supply.

[0026] Step 103: Establish a node inertia sensitivity expression based on the node inertia expression.

[0027] Step 104: Determine the inertia control index model of the power supply according to the node inertia sensitivity expression.

[0028] Step 105: According to the grid structure and the inertia time constant of each power source, the inertia control index of each power source is obtained by using the inertia control index model of the power source.

[0029] Step 106: Select a preset number of inertia control indicators in descending order, and determine the power source corresponding to the selected inertia control indicator as the optimal candidate power source.

[0030] Step 107: Establish an objective function with the inertia time constant improvement values ​​of the new energy and flexible DC as decision variables and the minimum sum of the inertia time constant improvement values ​​of the new energy and flexible DC as the goal.

[0031] Step 108: Determine the frequency stability constraint and determine it together with the objective function as an inertia improvement model.

[0032] Step 109: Based on the location where the optimal candidate power source is connected to the power grid, the inertia improvement model is solved to obtain an optimal configuration strategy for the inertia increment; the optimal configuration strategy for the inertia increment includes an inertia time constant improvement value for each new energy source and each flexible DC current.

[0033] Figure 2 This is the overall framework diagram of a grid inertia configuration method considering frequency stability constraints of this application. Implementation of the above steps 101 to 109 achieves optimal configuration of inertia increments and improves grid frequency stability.

[0034] In another exemplary embodiment of the present application, a network equation is used to describe the frequency relationship between the network nodes of the renewable energy and flexible DC power system and the potential nodes within the generator. Then, the above step 101 can be replaced by the following steps 201 to 206:

[0035] Step 201: Nodes in the power grid are collectively referred to as network nodes, synchronous machine nodes, new energy nodes, and flexible DC nodes are collectively referred to as power supply nodes, and nodes other than power supply nodes in the power grid are collectively referred to as load nodes.

[0036] Step 202: Construct the network equations of the power system.

[0037] Step 203: Establish an equivalent parallel admittance expression of the load node.

[0038] Step 204: Based on the equivalent parallel admittance expression of the load node, simplify the network equation of the power system to obtain the equivalent network equation.

[0039] Step 205: Determine the voltage relationship between the network nodes and the potential nodes within the power supply according to the equivalent network equation.

[0040] Step 206: Obtain a power system frequency relationship based on a voltage relationship between the network node and the potential node within the power supply.

[0041] The detailed implementation process of steps 201 to 206 is as follows:

[0042] Nodes in the power grid are collectively referred to as network nodes, synchronous machine nodes, new energy nodes, and flexible DC nodes are collectively referred to as power supply nodes, and the remaining nodes in the power grid are referred to as load nodes. For a system with N nodes, N is the number of network nodes, n is the number of power supply nodes, g is the number of synchronous machine nodes, r is the number of new energy nodes, and h is the number of flexible DC nodes. Thus, n = g + r + h, and Nn is the number of load nodes. New energy and flexible DC use virtual synchronous machine control, and their grid connection point voltage is constant, which can be equivalent to the form of a voltage source in series with a transient reactance. Therefore, the network equation for an N-node system containing new energy and flexible DC can be expressed as:

[0043]

[0044] Where, I G , I R , I H , I L are the current column vectors of synchronous units, new energy units, flexible DC units, and network nodes injected into the system, E G 、U R 、U H is the internal potential column vector of the synchronous machine, new energy unit, and flexible DC, and the number of power supply internal potential nodes is the same as the number of power supply nodes; U L is the voltage column vector of the network node, which includes the voltage column vectors of the power node and the load node; Y is the node admittance matrix of the system, Y G,G 、Y R,R 、Y H,H 、Y L,L are the self-admittance of synchronous machine, new energy, flexible DC and network node respectively, Y G,R 、Y G,H 、Y G,L 、Y R,G 、Y R,H 、Y R,L 、Y H,G 、Y H,R 、Y H,L 、Y L,G 、Y L,R 、Y L,H is the mutual admittance between nodes.

[0045] Applying virtual synchronous machine control to renewable energy units and flexible DC systems creates inertia characteristics similar to synchronous generators, thereby increasing system inertia. Compared to traditional synchronous generators, the virtual moment of inertia of renewable energy units controlled by virtual synchronous machines, as well as the DC-side equivalent capacitance of flexible DC systems controlled by virtual synchronous machines, can be flexibly adjusted based on actual operating conditions. When potential grid frequency risks are high, increasing the virtual moment of inertia and DC-side equivalent capacitance increases the inertia time constant and the system's frequency support capability.

[0046] Considering that the injection current of the load node is smaller than that of the synchronous machine, renewable energy and flexible DC, the load is converted into the equivalent parallel admittance connected to its node. The equivalent parallel admittance of the load node is:

[0047]

[0048] Where, P L is the load active power, Q L is the load reactive power, G L is the equivalent conductance of the load in parallel, B L is the equivalent susceptance of the load in parallel.

[0049] Based on formula (3), the simplified equivalent network equation can be obtained as follows:

[0050]

[0051] Where Y′ L,L It is the self-admittance matrix of the network node after the load is converted into the equivalent parallel admittance connected to its node.

[0052] According to formula (4), the voltage relationship between the network node and the potential node in the power supply can be obtained as follows:

[0053] U L =Y L,E E (5)

[0054]

[0055] E is the voltage vector of the potential node in the power supply; Equation (6) is the amplitude and phase angle of the network node voltage and the potential node voltage in the power supply, V L 、V E is the voltage amplitude vector of network nodes and power supply internal potential nodes, δ L , δ E is the voltage phase angle vector of the network nodes and the potential nodes in the power supply; the network architecture matrix Y L,E The dimension is N×n, and its expression is shown in formula (7).

[0056] The voltage phase angle in formula (5) is derived with respect to time:

[0057]

[0058] It is the time derivative matrix of the voltage phase angle of the network nodes and the potential nodes in the power supply.

[0059] The voltage amplitude per unit value of each node in the power system is not much different, and the node phase angle difference is small, and it meets the requirements. By simplifying formula (8), we can obtain the frequency relationship between the network nodes of the power system with new energy and flexible DC access and the internal potential nodes of the power source (i.e., the power system frequency relationship formula):

[0060] f L =Y L,E f E (9)

[0061] Where, f L is the network node frequency column vector; f E is the column vector of the frequency of the potential nodes within the power supply.

[0062] In another exemplary embodiment of the present application, the above step 102 may be replaced by the following steps 301 to 306:

[0063] Step 301: Derivative the frequency with respect to time in the power system frequency relationship to obtain a frequency derivative formula.

[0064] Step 302: Establish an expression for the frequency change rate of the potential nodes within the power supply.

[0065] Step 303: Construct an expression for the impact power allocated to the power supply when a power disturbance occurs in the network node.

[0066] Step 304: Based on the impact power expression, determine a relationship between the power supply unbalance power and the network node disturbance power.

[0067] Step 305: Combining the frequency derivative formula, the frequency change rate expression of the potential node in the power supply, and the relationship between the power supply unbalanced power and the network node disturbance power, obtain the network node initial frequency change rate expression.

[0068] Step 306: Determine the inertia expression of the node where the power disturbance occurs in the power system based on the expression of the initial frequency change rate of the network node.

[0069] The detailed implementation process of steps 301 to 306 is as follows:

[0070] The derivative of frequency with respect to time in formula (9) is:

[0071]

[0072] The frequency change rate of the potential node in the power supply can be obtained by using the unbalanced power and its inertia time constant:

[0073]

[0074] Where, T J is the n×n dimensional diagonal matrix composed of the power supply inertia time constant, ΔP E is the power unbalance column vector.

[0075] When active disturbance occurs in the system, the voltage phase angle of the network node changes, and the impact power is distributed to each power source according to the electrical distance of the potential node in the power source. When the power disturbance ΔP occurs at the network node j Lj , the impulse power allocated to power source i is:

[0076]

[0077] Where i is the potential node number in the power supply; j is the network disturbance node; ΔP Ei is the impulse power allocated to the i-th power supply; ΔP Lj is the disturbance power of network node j, ΔP when power supply trips Lj The first n row vectors are not 0, and the load is disturbed when ΔP Lj The last Nn row vectors are not 0; The electrical distance between two points, U Ei , δ i are the potential voltage and phase angle of the i-th generator respectively; U Ej , δ j are the voltage and phase angle of network node j respectively; is the equivalent admittance between power source i and network node j.

[0078] Based on equations (12) and (13), the relationship between the power supply unbalance power and the network node disturbance power satisfies:

[0079]

[0080] Where D E,L is the impact power distribution coefficient matrix, and its element in row i and column j is ΔP L is the network node disturbance power vector. When only the jth node experiences power disturbance, the impact power distribution coefficient matrix is ​​expressed as follows:

[0081]

[0082] It can be seen from the formula that when only the jth node has power disturbance, the impact power distribution coefficient matrix D E,L Only the jth column is not 0, and all other positions are 0.

[0083] Substituting equations (11) and (14) into equation (10), we obtain:

[0084]

[0085] Where, is the network node initial frequency change rate RoCoF.

[0086] When power disturbances occur at multiple network nodes, the initial frequency change rate of node j is:

[0087]

[0088] When only the jth node experiences power disturbance, the initial frequency change rate of node j is:

[0089]

[0090] The inertia of node j is the ratio of the disturbance power to the initial frequency change rate at node j after the power disturbance occurs at node j:

[0091]

[0092] Assume that the occurrence of a magnitude of ΔP at node j Lj Based on equations (17) and (18), the node initial frequency change rate RoCoF is substituted into equation (19), and the node inertia expression of power disturbance in the power system is obtained as follows:

[0093]

[0094] Where Y L,E is the network architecture matrix, (j,i) represents the connection between node j and power source i, T Ji is the inertia time constant of power source i. Equation (20) shows that node inertia is determined solely by the grid structure and the power source inertia time constant. This metric describes the weight of power source i's inertia on the frequency of node j based on electrical distance. Therefore, when the grid structure is fixed, increasing the inertia time constant of renewable energy and flexible DC systems in advance based on grid demand can increase node inertia and improve system frequency stability.

[0095] In another exemplary embodiment of the present application, the definition of node inertia shows that increasing the inertia time constant of renewable energy and flexible DC is beneficial to increasing node inertia. To study the optimal increase in inertia parameter size and location, it is necessary to calculate the node inertia sensitivity. The node inertia sensitivity expression is:

[0096]

[0097] Where, H is the inertia sensitivity of node m to the change of the inertia time constant of power supply i, m is the node inertia, T Ji is the inertia time constant of power supply i, M is the inertia control coefficient, Y L,E(m,i) The subscript (m,i) indicates the connection between node m and power source i. is the electrical distance between node j and power source i, T Ji is the inertia time constant of power source i, n is the number of power source nodes; is the electrical distance between the inertia weak node k and the power source i.

[0098] Based on the node inertia sensitivity expression, the influence of the inertia increase position and size on the system frequency stability can be quantified.

[0099] In another exemplary embodiment of the present application, It can reflect the inertia control capability of power source i on node m. Therefore, the inertia control coefficient can be defined as the influence of power source i on all nodes when it changes the inertia time constant. The inertia control coefficient M of power source i is: i It can be expressed as:

[0100]

[0101] Considering that not all nodes do not meet the inertia requirements, only the influence of power source i on the nodes whose inertia does not meet the requirements is considered. The nodes whose inertia does not meet the requirements are called inertia weak nodes. According to their weakness, the inertia control index model of power source i is obtained as follows:

[0102]

[0103] Where, is the inertia control index of power supply i, r m is the weight, H min is the minimum value of node inertia, and k is the inertia weak node. The larger the value, the stronger the power source i's ability to control the inertia of the weak inertia nodes in the region, and the easier it is to achieve inertia improvement. Therefore, the value of each power source is obtained by formula (23): The power supplies with the highest ranking are selected as the final candidate power supplies to identify the optimal candidate power supply.

[0104] In another exemplary embodiment of the present application, the objective function is:

[0105]

[0106] Where, ΔT R,b , ΔT H,c are the inertia time constant improvement values ​​of new energy b and flexible DC c, G m is the sum of the inertia time constant improvements of new energy and flexible DC, r is the number of new energy nodes, and h is the number of flexible DC nodes.

[0107] In another exemplary embodiment of the present application, to ensure the frequency stability of the system, the frequency stability constraints include: node initial frequency change rate constraint, node inertia constraint and frequency deviation maximum value constraint.

[0108] The node initial frequency change rate constraint is:

[0109]

[0110] 0≤ΔT R ≤ΔT Rmax (27)

[0111] 0≤ΔT H ≤ΔT Hmax (28)

[0112] Where Y L,E is the network architecture matrix, T J is the inertia time constant of the power supply, ΔT J D is the diagonal matrix composed of the inertia time constant improvement value of the power supply, E,L is the impact power distribution coefficient matrix, ΔP L is the network node disturbance power vector, RoCoF max is the maximum value of the initial frequency change rate; ΔT R , ΔT H The diagonal matrix composed of the inertia time constant improvement values ​​of new energy and flexible DC, ΔT Rmax , ΔT Hmax They are the maximum values ​​of the inertia time constant improvement of new energy and flexible DC respectively.

[0113] The node inertia constraint is:

[0114]

[0115] Where, T Ji is the inertia time constant of power source i, ΔT Ji is the inertia time constant increase value of power supply i, is the electrical distance between node j and power source i, is the electrical distance between the inertia weak node k and the power source i, n is the number of power nodes, H min is the minimum value of node inertia.

[0116] Frequency deviation maximum constraint:

[0117] The lowest frequency point is mainly affected by the overall system inertia and primary frequency modulation. To ensure frequency stability and safety, the inertia center frequency can be used as a frequency constraint.

[0118]

[0119] Where Δf(t) is the frequency deviation; P G,a P is the frequency modulation response power after the synchronous machine a disturbance occurs; R,b P is the frequency modulation response power after the disturbance of new energy b occurs; H,c is the frequency modulation response power after the flexible DC c disturbance occurs; D is the load damping; P D is the total system load before the disturbance; ΔP Lj is the disturbance power of network node j, The sum of all disturbance powers, H sys0 is the original system inertia, They are the rated power of the a-th synchronous machine, the b-th renewable energy machine, and the c-th flexible DC machine, T a 、T b 、T c is the original inertia time constant of the ath synchronous machine, the bth new energy source, and the cth flexible DC power supply, ΔH is the power supply inertia increase, ΔT R,b , ΔT H,c is the increase value of the inertia time constant of the b-th new energy and the c-th flexible DC, which are matrices ΔT R , ΔT H The b-th and c-th diagonal elements in .

[0120] Assume that the synchronous machine, new energy and flexible DC primary frequency modulation response power increases linearly with time, and at t G , t R , t H After the full response, assuming that the full response time of the same type of power supply is not much different, that is:

[0121]

[0122] Where, is the primary frequency modulation capacity of synchronous machine a, is the primary frequency regulation capacity of new energy b, is the primary frequency regulation capacity of flexible DC c.

[0123] When the frequency reaches its lowest point, the frequency deviation is the largest, and the frequency deviation change rate is 0. The response speed of renewable energy and flexible DC is usually in the millisecond level, while that of synchronous generator is usually in the second level. Therefore, the lowest frequency point of the system will occur when renewable energy and flexible DC fully respond, but the synchronous generator has not yet fully responded. According to formula (30), the time to reach the lowest point is:

[0124]

[0125] Where,

[0126] Integrating the frequency change rate in equation (30) from the moment the disturbance occurs to the lowest frequency point yields:

[0127]

[0128] Substituting equation (36) into equation (37) yields the maximum frequency deviation expression:

[0129]

[0130] Where Δf nadir is the maximum frequency deviation value. f0 is the frequency reference value.

[0131] Maximum frequency deviation constraint:

[0132] |Δf nadir |≤Δf max (39)

[0133] Where Δf max is the maximum frequency deviation of the system.

[0134] In another exemplary embodiment of the present application, based on the determined inertia-enhanced renewable energy and flexible DC positions, the YALMIP toolbox and CPLEX solver are used to minimize the inertia increase as the objective function to plan the optimal configuration strategy of inertia increment considering the frequency stability constraint, thereby improving the system frequency stability. The optimal configuration strategy is composed of the ΔT of all renewable energy and DC controlled by virtual synchronous machines. R,b and ΔT H,c composition.

[0135] The beneficial effects of this application are as follows:

[0136] 1. This application comprehensively considers the impact of new energy and flexible direct current on system frequency stability, and proposes an inertia increment configuration method based on sensitivity analysis and frequency stability constraints. It can achieve optimal inertia configuration while ensuring system frequency safety, and solve the low inertia problem of the "three highs" power system.

[0137] 2. When solving the inertia configuration model of the three high power grid considering frequency stability constraints, it is necessary to select the site for inertia increase and optimize the increment. This makes the model difficult to solve and the solution efficiency is low. This application obtains the inertia control index based on inertia sensitivity, quickly and accurately determines the optimal location for inertia increase based on the inertia control index, and then optimizes the inertia increment. The model is solved step by step, which reduces the difficulty of solving the model and improves the solution efficiency.

[0138] Based on the same inventive concept, embodiments of the present application further provide a device for configuring a power grid inertia with frequency stability constraints, for implementing the aforementioned method for configuring a power grid inertia with frequency stability constraints. The solution provided by this device is similar to the solution described in the aforementioned method. Therefore, the specific limitations of one or more embodiments of the device for configuring a power grid inertia with frequency stability constraints provided below can be found in the aforementioned limitations of the method for configuring a power grid inertia with frequency stability constraints, and are not further elaborated here.

[0139] In an exemplary embodiment, a power grid inertia configuration device considering frequency stability constraints is provided, including: a frequency relationship establishment module, a node inertia expression construction module, a sensitivity expression establishment module, an inertia control index model determination module, an inertia control index calculation module, an optimal candidate power selection module, an objective function establishment module, a constraint determination module and an optimal solution module.

[0140] The frequency relationship establishment module is used to establish the frequency relationship of the power system; the power system includes a power grid and a power source connected to the power grid; both new energy and flexible direct current are used as power sources.

[0141] A node inertia expression construction module is used to construct a node inertia expression for power disturbances in the power system based on the power system frequency relationship; the node inertia expression represents the relationship between the node inertia and the inertia time constant of the grid structure and the power supply.

[0142] The sensitivity expression establishing module is used to establish a node inertia sensitivity expression based on the node inertia expression.

[0143] The inertia control index model determination module is used to determine the inertia control index model of the power supply according to the node inertia sensitivity expression.

[0144] The inertia control index calculation module is used to obtain the inertia control index of each power supply based on the power grid structure and the inertia time constant of each power supply and using the power supply inertia control index model.

[0145] The optimal candidate power source selection module is used to select a preset number of inertia control indicators in descending order, and determine the power source corresponding to the selected inertia control indicators as the optimal candidate power source.

[0146] The objective function establishment module is used to establish an objective function with the inertia time constant improvement value of new energy and flexible DC as the decision variable and the minimum sum of the inertia time constant improvement values ​​of new energy and flexible DC as the goal.

[0147] The constraint determination module is used to determine the frequency stability constraint and determine the inertia improvement model together with the objective function.

[0148] The optimal solution module is used to solve the inertia improvement model based on the location where the optimal candidate power source is connected to the power grid, and obtain an optimal configuration strategy for the inertia increment; the optimal configuration strategy for the inertia increment includes the inertia time constant improvement value of each new energy source and each flexible DC.

[0149] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0150] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for configuring power grid inertia considering frequency stability constraints, characterized in that: include: Establishing a frequency relationship of a power system; the power system includes a power grid and a power source connected to the power grid; Both new energy and flexible DC are used as power sources; Based on the power system frequency relationship, constructing a node inertia expression for power disturbances in the power system; the node inertia expression represents the relationship between the node inertia and the inertia time constant of the power grid structure and the power supply; According to the node inertia expression, a node inertia sensitivity expression is established; Determine the inertia control index model of the power supply based on the node inertia sensitivity expression; According to the grid structure and the inertia time constant of each power source, the inertia control index of each power source is obtained by using the power source inertia control index model; Selecting a preset number of inertia control indicators in descending order, and determining power supplies corresponding to the selected inertia control indicators as optimal candidate power supplies; The objective function is established with the improvement value of the inertia time constant of new energy and flexible DC as the decision variable and the minimum sum of the improvement values ​​of the inertia time constant of new energy and flexible DC as the goal; Determine a frequency stability constraint and determine it together with the objective function as an inertia improvement model; Based on the location where the optimal candidate power source is connected to the power grid, the inertia improvement model is solved to obtain an optimal configuration strategy for inertia increment; the optimal configuration strategy for inertia increment includes an inertia time constant improvement value for each new energy source and each flexible DC power source.

2. The method for configuring power grid inertia considering frequency stability constraints according to claim 1, characterized in that: Establish the power system frequency relationship, including: The nodes in the power grid are collectively referred to as network nodes, synchronous machine nodes, new energy nodes, and flexible DC nodes are collectively referred to as power nodes, and nodes other than power nodes in the power grid are collectively referred to as load nodes. Construct network equations for power systems; Establish the equivalent parallel admittance expression of the load node; Based on the equivalent parallel admittance expression of the load node, the network equation of the power system is simplified to obtain the equivalent network equation; According to the equivalent network equation, determine the voltage relationship between the network nodes and the potential nodes in the power supply; The frequency relationship of the power system is obtained based on the voltage relationship between the network nodes and the potential nodes within the power supply.

3. The grid inertia configuration method considering frequency stability constraints according to claim 1 or 2, characterized in that: The power system frequency relationship is: f L =Y L,E f E ; Where, f L is the network node frequency column vector, f E is the column vector of the frequency of the potential nodes in the power supply, Y L,E is the network architecture matrix.

4. The grid inertia configuration method considering frequency stability constraints according to claim 1, characterized in that: According to the power system frequency relationship, an expression for the node inertia of a power disturbance in the power system is constructed, specifically including: Derivative the frequency with respect to time in the power system frequency relationship to obtain a frequency derivative formula; Establish the frequency change rate expression of the potential node in the power supply; Construct an expression for the impact power allocated to the power supply when a power disturbance occurs at a network node; Based on the impact power expression, determining a relationship between the power supply unbalance power and the network node disturbance power; Combining the frequency derivative formula, the frequency change rate expression of the potential node in the power supply, and the relationship between the unbalanced power of the power supply and the disturbance power of the network node, the expression of the initial frequency change rate of the network node is obtained; According to the expression of the initial frequency change rate of the network node, the inertia expression of the node where power disturbance occurs in the power system is determined.

5. The grid inertia configuration method considering frequency stability constraints according to claim 1 or 4, characterized in that: The node inertia expression of power disturbance in the power system is: Where H j is the inertia of node j, Y L,E is the network architecture matrix, (j,i) represents the connection between node j and power source i, T Ji is the inertia time constant of power source i, is the electrical distance between node j and power source i, is the electrical distance between the inertia weak node k and the power source i, and n is the number of power source nodes.

6. The method for configuring power grid inertia considering frequency stability constraints according to claim 1, characterized in that: The node inertia sensitivity expression is: Where, H is the inertia sensitivity of node m to the change of the inertia time constant of power supply i, m is the node inertia, T Ji is the inertia time constant of power supply i, M is the inertia control coefficient, Y L,E is the network architecture matrix, (m,i) represents the connection between node m and power source i, is the electrical distance between node j and power source i, T Ji is the inertia time constant of power source i, n is the number of power source nodes; is the electrical distance between the inertia weak node k and the power source i.

7. The method for configuring power grid inertia considering frequency stability constraints according to claim 1, characterized in that: The inertia control index model of the power supply is: Where, is the inertia control index of power supply i, r m is the weight, H is the inertia sensitivity of node m to the change of the inertia time constant of power supply i, m is the node inertia, T Ji is the inertia time constant of power supply i, H j is the inertia of node j, H min is the minimum value of node inertia, and k is the inertia weak node.

8. The method for configuring power grid inertia considering frequency stability constraints according to claim 1, characterized in that: The objective function is: Where, ΔT R,b , ΔT H,c are the inertia time constant improvement values ​​of new energy b and flexible DC c, G m is the sum of the inertia time constant improvements of new energy and flexible DC, r is the number of new energy nodes, and h is the number of flexible DC nodes.

9. The method for configuring power grid inertia considering frequency stability constraints according to claim 1, characterized in that: The frequency stability constraints include: node initial frequency change rate constraint, node inertia constraint and frequency deviation maximum value constraint; The node initial frequency change rate constraint is: Y L,E (2T J +ΔT J ) -1 D E,L ΔP L ≤RoCoF max ; 0≤ΔT R ≤ΔT Rmax ; 0≤ΔT H ≤ΔT Hmax ; Where Y L,E is the network architecture matrix, T J is the inertia time constant of the power supply, ΔT J D is the diagonal matrix composed of the inertia time constant improvement value of the power supply, E,L is the impact power distribution coefficient matrix, ΔP L is the network node disturbance power vector, RoCoF max is the maximum value of the initial frequency change rate; ΔT R , ΔT H The diagonal matrix composed of the inertia time constant improvement values ​​of new energy and flexible DC, ΔT Rmax , ΔT Hmax are the maximum values ​​of the inertia time constant improvement of new energy and flexible DC respectively; The nodal inertia constraint is: Where Y L,E is the network architecture matrix, (m,i) represents the connection between node m and power source i, T Ji is the inertia time constant of power source i, ΔT Ji is the inertia time constant increase value of power supply i, is the electrical distance between node j and power source i, is the electrical distance between the inertia weak node k and the power source i, n is the number of power nodes, H min is the minimum value of node inertia; The maximum frequency deviation constraint is: |Δf nadir |≤Δf max ; Where Δf nadir is the maximum frequency deviation, Δf max is the maximum frequency deviation of the system, f0 is the frequency reference value, H sys is the system inertia, ΔH is the power inertia increase, ΔP Lj is the disturbance power of network node j, F R is the total primary frequency regulation capacity of new energy, F H is the total primary frequency regulation capacity of the flexible DC system, F G is the total primary frequency modulation capacity of the synchronous machine, t R is the complete response time of the new energy, t H is the full response time of flexible DC, t G is the complete response time of the synchronous machine.

10. A power grid inertia configuration device considering frequency stability constraints, characterized in that: include: A frequency relationship formula establishment module is used to establish a frequency relationship formula for a power system; the power system includes a power grid and a power source connected to the power grid; both renewable energy and flexible direct current serve as power sources; A node inertia expression construction module is used to construct a node inertia expression for a power disturbance in the power system based on the power system frequency relationship; the node inertia expression represents the relationship between the node inertia and the inertia time constant of the grid structure and the power supply; A sensitivity expression establishing module, used for establishing a node inertia sensitivity expression based on the node inertia expression; An inertia control index model determination module is used to determine the inertia control index model of the power supply based on the node inertia sensitivity expression; An inertia control index calculation module is used to obtain the inertia control index of each power supply based on the grid structure and the inertia time constant of each power supply and using the power supply inertia control index model; An optimal candidate power source selection module is used to select a preset number of inertia control indicators in descending order, and determine the power source corresponding to the selected inertia control indicator as the optimal candidate power source; An objective function establishment module is used to establish an objective function with the inertia time constant improvement value of new energy and flexible DC as a decision variable and the minimum sum of the inertia time constant improvement values ​​of new energy and flexible DC as the goal; A constraint determination module, configured to determine a frequency stability constraint and determine the constraint together with the objective function as an inertia improvement model; The optimal solution module is used to solve the inertia improvement model based on the location where the optimal candidate power source is connected to the power grid, and obtain an optimal configuration strategy for the inertia increment; the optimal configuration strategy for the inertia increment includes the inertia time constant improvement value of each new energy source and each flexible DC.

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