Method and device for constructing optimal dispatching model of power system considering frequency safety

Abstract

The application provides a kind of optimization scheduling model construction method and device of power system considering frequency safety, in the optimization scheduling model construction method of power system considering frequency safety, the system inertia of power system and the power disturbance amount faced by power system are acquired;Based on system inertia and power disturbance amount, the frequency curve approximation equation of system frequency deviation of power system is constructed;Determine the frequency safety constraint based on the frequency curve approximation equation;Frequency safety constraint includes: quasi-steady frequency constraint, frequency change rate constraint and frequency minimum point constraint;Linearization is carried out based on frequency minimum point constraint, and linear frequency minimum point constraint is obtained;Quasi-steady frequency constraint, frequency change rate constraint and linear frequency minimum point constraint are used to construct optimization scheduling model.The highly nonlinear frequency safety constraint is converted into linear constraint by the above method, the analytical complexity of the constructed optimization scheduling model is reduced, and the calculation error of analysis is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power systems, in particular to a method and device for constructing an optimal scheduling model of a power system considering frequency safety. BACKGROUND

[0002] With the high proportion of new energy access, conventional thermal power units are gradually replaced, and the inertia and damping characteristics of the power system are further deteriorated. When the power system faces a large power disturbance, such as unit tripping, DC blocking and other faults, the system frequency will decrease rapidly, which may lead to low-frequency load shedding or even power grid splitting, causing huge economic losses. In recent years, some scholars have embedded frequency safety related constraints into the optimal scheduling model to ensure that the system operates stably while minimizing operating costs when facing power shortages.

[0003] Embedding frequency safety constraints in the scheduling model can minimize operating costs while ensuring frequency safety and reducing operating costs without low-frequency load shedding. Currently, the commonly used method for constructing an optimal scheduling model considering frequency safety is to construct a nonlinear optimal scheduling model, which has high computational complexity in the solving process, or to aggregate all units into one unit, which has a large error. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a method and device for constructing an optimal scheduling model of a power system considering frequency safety, which can reduce the analytical complexity of the constructed optimal scheduling model of the power system and reduce the calculation error of the analysis.

[0005] In a first aspect, the present application provides a method for constructing an optimal scheduling model of a power system considering frequency safety, comprising:

[0006] obtaining the system inertia of the power system and the power disturbance amount faced by the power system;

[0007] based on the system inertia and the power disturbance amount, constructing a frequency curve approximation equation of the system frequency deviation of the power system;

[0008] determining a frequency safety constraint based on the frequency curve approximation equation; the frequency safety constraint includes a quasi-steady state frequency constraint, a frequency change rate constraint, and a frequency minimum point constraint;

[0009] linearizing the frequency minimum point constraint to obtain a linear frequency minimum point constraint;

[0010] constructing the optimal scheduling model based on the quasi-steady state frequency constraint, the frequency change rate constraint, and the linear frequency minimum point constraint.

[0011] Optionally, the method further comprises: obtaining unit power increment information;

[0012] Based on the system inertia and the power disturbance, a frequency curve approximation equation of a system frequency deviation of the power system is constructed, comprising:

[0013] According to the inertia center principle, based on the system inertia, the unit power increment information and the power disturbance, the frequency curve approximation equation is constructed.

[0014] Optionally, based on the frequency minimum point constraint, linearization processing is performed to obtain a linear frequency minimum point constraint, comprising:

[0015] According to the convolution theorem of Laplace transform, a first time domain function of the unit power increment information is determined;

[0016] Based on the first time domain function, a first function based on a first product is constructed, the first product being a product of the system inertia and the system frequency deviation;

[0017] The first function is subjected to linearization processing to obtain a second function of the first product in a first scheduling time period;

[0018] Based on the second function, a first linear constraint of the second function, a second linear constraint of the first product in the first scheduling time period and a third linear constraint of a second product are determined, the second product being a product of the unit power increment information in the first scheduling time period and the system inertia in the first scheduling time period;

[0019] The linear frequency minimum point constraint is determined according to the first linear constraint, the second linear constraint and the third linear constraint.

[0020] Optionally, the linearization processing of the first function comprises: adopting a piecewise linearization method to perform linearization processing on the first function.

[0021] Optionally, the method further comprises: obtaining a step response of the unit;

[0022] Based on the step response, a static gain of the unit is determined;

[0023] Then, based on the frequency curve approximation equation, the quasi-steady state frequency constraint is determined, comprising:

[0024] The quasi-steady state frequency constraint is determined based on the static gain and the frequency curve approximation equation.

[0025] Optionally, the optimization scheduling model is to minimize the unit operation cost as an objective.

[0026] Optionally, the method further comprises:

[0027] determining basic constraints based on the optimization scheduling model; the basic constraints comprise: unit capacity constraints, unit minimum start-up constraints, unit minimum shut-down constraints, unit ramping constraints, system reserve constraints, system power balance constraints, and line power flow constraints;

[0028] The constructing the optimization scheduling model based on the quasi-steady-state frequency constraint, the frequency change rate constraint, and the linear frequency minimum point constraint comprises:

[0029] The constructing the optimization scheduling model based on the quasi-steady-state frequency constraint, the frequency change rate constraint, the linear frequency minimum point constraint, and the basic constraints.

[0030] In a second aspect, the present application provides an optimization scheduling model construction device for a power system considering frequency safety, comprising:

[0031] An acquisition unit is configured to acquire system inertia of a power system and a power disturbance amount faced by the power system;

[0032] A construction unit is configured to construct a frequency curve approximation equation of a system frequency deviation of the power system based on the system inertia and the power disturbance amount;

[0033] A determination unit is configured to determine frequency safety constraints based on the frequency curve approximation equation; the frequency safety constraints comprise: quasi-steady-state frequency constraints, frequency change rate constraints, and frequency minimum point constraints;

[0034] A linearization processing unit is configured to perform linearization processing based on the frequency minimum point constraints to obtain linear frequency minimum point constraints;

[0035] The construction unit is further configured to construct the optimization scheduling model based on the quasi-steady-state frequency constraints, the frequency change rate constraints, and the linear frequency minimum point constraints.

[0036] In a third aspect, the present application provides an optimization scheduling model construction device for a power system, comprising:

[0037] A memory is configured to store a computer program;

[0038] A processor is configured to execute the computer program stored in the memory to implement the steps of the optimization scheduling model construction method for a power system considering frequency safety according to the first aspect.

[0039] In a fourth aspect, the present application provides a computer readable storage medium, wherein the computer readable storage medium stores a computer program, and the computer program is executed by a processor to implement the steps of the optimization scheduling model construction method for a power system considering frequency safety according to the first aspect.

[0040] It can be seen that the method and device for constructing an optimal scheduling model of a power system considering frequency safety are provided in the embodiments of the present application. In the method for constructing an optimal scheduling model of a power system considering frequency safety, the system inertia of a power system and the power disturbance faced by the power system are obtained. Based on the system inertia and the power disturbance, a frequency curve approximation equation of the system frequency deviation of the power system is constructed. The frequency safety constraint is determined based on the frequency curve approximation equation. The frequency safety constraint includes a quasi-steady frequency constraint, a frequency change rate constraint, and a frequency minimum point constraint. The linearization processing is performed based on the frequency minimum point constraint to obtain a linear frequency minimum point constraint. The optimal scheduling model is constructed based on the quasi-steady frequency constraint, the frequency change rate constraint, and the linear frequency minimum point constraint. Through the above method, the highly nonlinear frequency safety constraint is converted into a linear constraint, the analytical complexity of the constructed optimal scheduling model is reduced, and the calculation error of the analysis is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art based on these drawings.

[0042] Figure 1 is a frequency curve diagram of a power system provided by the embodiments of the present application;

[0043] Figure 2 is a flowchart of a method for constructing an optimal scheduling model of a power system considering frequency safety provided by the embodiments of the present application;

[0044] Figure 3 is a diagram of an increment of total power of a unit provided by the embodiments of the present application;

[0045] Figure 4 is a control block diagram provided by the embodiments of the present application;

[0046] Figure 5 is a diagram of a first function provided by the embodiments of the present application;

[0047] Figure 6 is a diagram of linearization processing of the first function provided by the embodiments of the present application;

[0048] Figure 7 is a flowchart of another method for constructing an optimal scheduling model of a power system considering frequency safety provided by the embodiments of the present application;

[0049] Figure 8A structural schematic diagram of an optimization scheduling model construction device for a power system considering frequency safety is provided in the embodiments of the present application. DETAILED DESCRIPTION

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some, but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art belong to the scope of protection of the present application.

[0051] To facilitate the understanding of the technical solutions of the present application, the technical solutions of the present application will be explained below in conjunction with the background art.

[0052] As shown in Figure 1 , Figure 1 A frequency curve diagram of a power system is provided in the embodiments of the present application. When a high-power disturbance occurs in the power system, the power system will experience a frequency regulation process: the system frequency decreases, the unit increases the output power, and the frequency rises to the quasi-steady frequency after passing through the lowest point. Therefore, it is necessary to construct an optimization scheduling model of the related power system to ensure the stable operation of the frequency safety and the minimum operation cost.

[0053] In the prior art, the optimization scheduling model of the power system is a low-order response model of the unit, all units are aggregated into one or several units by an aggregation method, and a simplified frequency response equation is derived. The frequency response equation is generally nonlinear, and therefore a piecewise linearization or iteration method is further used for optimization calculation. For the first scheme, due to the need for analysis of the frequency minimum point, this scheme can only consider the low-order model of the unit, the error of the frequency regulation capability evaluation of the unit is large, and therefore the calculation error of the frequency minimum point is large, and the scheduling result may not be the optimal solution. In addition, the frequency minimum point derived by this scheme is still highly nonlinear, and the use of a nonlinear optimization method for calculation will lead to high calculation complexity, and the use of a linearization method will introduce a large calculation error.

[0054] Therefore, the application provides a method and device for constructing an optimal scheduling model of a power system considering frequency safety. In the method for constructing an optimal scheduling model of a power system considering frequency safety, the system inertia of the power system and the power disturbance faced by the power system are obtained. Based on the system inertia and the power disturbance, a frequency curve approximation equation of the system frequency deviation of the power system is constructed. The frequency safety constraint is determined based on the frequency curve approximation equation. The frequency safety constraint includes a quasi-steady frequency constraint, a frequency change rate constraint, and a frequency minimum point constraint. The linear frequency minimum point constraint is obtained by linearizing the frequency minimum point constraint. The optimal scheduling model is constructed based on the quasi-steady frequency constraint, the frequency change rate constraint, and the linear frequency minimum point constraint. Through the above method, the highly nonlinear frequency safety constraint is converted into a linear constraint, the analytical complexity of the constructed optimal scheduling model is reduced, and the calculation error of the analysis can be effectively reduced.

[0055] To facilitate understanding of the technical solutions provided by the application, a method for constructing an optimal scheduling model of a power system considering frequency safety provided by the application will be described below with reference to the accompanying drawings. Referring to Figure 2 , the figure is a flowchart of a method for constructing an optimal scheduling model of a power system considering frequency safety provided by an embodiment of the application, as Figure 2 indicated, the method includes S101-S105.

[0056] S101: Obtain the system inertia of the power system and the power disturbance faced by the power system.

[0057] It can be understood that the system inertia refers to the degree of swing of the system in the dynamic process of the power system. The greater the degree of swing, the greater the inertia, and vice versa. The degree of swing is smaller, the smaller the inertia. The power disturbance can be understood as the power fluctuation caused by the fluctuation of the load, the fluctuation of the generator output, and the sudden change of the system parameters.

[0058] The application does not limit the specific way of obtaining the system inertia. As an example, the application determines the system inertia based on the system power base value and the unit inertia by obtaining the system power base value and the unit inertia. As an example, the system inertia can be obtained by the following formula:

[0059]

[0060] In the formula, represents the system inertia at time T, represents the system power base value, represents the identification of the unit, i.e., the i-th unit; represents the set of units, represents the inertia level of the i-th unit, The power base value of the unit The power base value of the unit The unit on-off state, which can be 0 or 1.

[0061] S102: Based on the system inertia and the power disturbance, a frequency curve approximation equation of the system frequency deviation of the power system is constructed.

[0062] The application does not limit the specific way of constructing the frequency curve approximation equation of the system frequency deviation of the power system based on the system inertia and the power disturbance.

[0063] As an example, the application can also obtain unit power increment information, and then S102 constructs the frequency curve approximation equation of the system frequency deviation of the power system based on the system inertia and the power disturbance, including: based on the inertia center principle, constructing the frequency curve approximation equation based on the system inertia, the unit power increment information and the power disturbance.

[0064] It can be understood that when the power system faces a large power disturbance, the system frequency follows the following swing equation based on the inertia center principle:

[0065] ;

[0066] In the formula: is the system inertia, is the system frequency deviation, is the unit power increment, is the power disturbance faced by the power system.

[0067] It can be understood that the unit power increment information obtained by the application is a function of time t, which increases linearly with time. As shown in Figure 3 , the total unit power increment provided by an embodiment of the application is shown in Figure 3 . The specific function form of the total unit power increment can be as follows:

[0068] ;

[0069] In the formula, is the unit power increment, is the power disturbance faced by the power system, is the frequency minimum point, and t represents time.

[0070] Suppose at , the frequency minimum point is , the system frequency deviation reaches the minimum point at this time , so , the system frequency deviation reaches the lowest point can be determined by the unit power increment at the moment of the lowest frequency point.

[0071] The function of the unit power increment information is substituted into the swing equation, and , the approximate frequency curve is obtained by solving the first-order linear homogeneous differential equation:

[0072]

[0073] wherein the moment of the lowest frequency point is expressed as: , The approximate equation of the frequency curve about the system frequency deviation is is the system inertia, is the power disturbance faced by the power system, and t represents time, represents the lowest system frequency deviation.

[0074] S103: determining a frequency safety constraint based on the approximate equation of the frequency curve; the frequency safety constraint includes: a quasi-steady-state frequency constraint, a frequency change rate constraint, and a lowest frequency point constraint.

[0075] In the embodiments of the present application, after the approximate equation of the frequency curve is constructed, the frequency modulation capability of the unit is evaluated based on the approximate equation of the frequency curve, so that the frequency safety constraint is determined based on the principle that the frequency modulation capability of the unit should cover the power disturbance.

[0076] The present application does not limit the specific way of determining the lowest frequency point constraint, as an example, the present application can first determine that the complex frequency domain form of the approximate equation of the frequency curve is

[0077] ;

[0078] In the formula, represents the approximate equation of the frequency curve in the complex frequency domain, is the system inertia, and s is a complex number of Laplace transform, which is a variable; represents the Laplace transform.

[0079] As an example, the present application further includes: obtaining a transfer function corresponding to a control block diagram of the unit. It can be understood that the corresponding transfer function is obtained through the control block diagram of the unit, which is well known to those skilled in the art, and will not be repeated here. As shown in Figure 4 , Figure 4 is a control block diagram schematic diagram provided by an embodiment of the present application. Figure 4 The input is a step power disturbance , which generally refers to sudden decrease of generated power or sudden increase of load power, so the input is negative and the output is system frequency deviation , initial system frequency deviation = 0. Wherein, the first row represents the transfer function of the system response, is the equivalent inertia of the system, is the load droop coefficient, is a complex number of Laplace transform, which is a variable. The second row and the third row represent the transfer function of the frequency modulation of the new energy unit, wherein is the power increment of the first unit, is the sum of the power increments of all units, (t) is the frequency deviation, represents the speed regulator adjustment coefficient of the first unit, represents the speed regulator time constant of the first unit, represents the heater time constant of the first unit, represents the high-pressure turbine power proportionality coefficient of the first unit, represents the mechanical power gain coefficient of the first unit. The third row represents a unit different from the second row, which will not be described herein. The present application obtains the transfer function corresponding to the control block diagram as , and the complex frequency domain form of the power increment information of the i-th unit can be obtained by taking the frequency approximate curve as the input:

[0080] ;

[0081] In the formula, represents the complex frequency domain form of the power increment information of the i-th unit, represents the transfer function corresponding to the control block diagram, represents the frequency curve approximate equation in the complex frequency domain form.

[0082] By performing the Laplace inverse transform on the complex frequency domain form of the unit power increment information, the time domain form of the power increment information of the i-th unit can be obtained as:

[0083]

[0084] In the formula, represents the time domain form of the power increment information of the i-th unit, represents the frequency curve approximate equation in the complex frequency domain form, represents the transfer function corresponding to the control block diagram, represents the Laplace inverse transform.

[0085] According to the above formula, the power increment information of the i-th unit at the moment of the lowest frequency point can be obtained as:

[0086] ;​

[0087] Therefore, in combination with the above formula, the frequency minimum point constraint can include the following equation:

[0088] ;

[0089] In the formula, represents the minimum point of the frequency deviation, represents the minimum system frequency deviation, represents a set of units, represents the i-th unit, represents the power increment information of the i-th unit at the minimum point of the frequency, represents the time domain form of the power increment information of the i-th unit at the minimum point of the frequency. The frequency minimum point constraint is still highly nonlinear and has no analytical form, and the present application will linearize it in S104. The present application does not limit the specific way of determining the frequency change rate constraint, and as an example, for the frequency change rate constraint, in the swing equation,

[0090] the initial frequency change rate is:

[0091]

[0092] ;

[0093] In the formula, represents the initial frequency change rate.

[0094] Therefore, the frequency change rate constraint is:

[0095]

[0096] In the formula, is the maximum allowed frequency change rate.

[0097] Or written as:

[0098] ;

[0099] The present application does not limit the specific way of determining the quasi-steady state frequency constraint, and as an example, the power system optimization scheduling model construction method considering frequency safety provided by the present application further includes the following steps A1-A2:

[0100] A1: Obtain the step response of the unit.

[0101] The present application does not limit the specific way of obtaining the step response, and the step response can be obtained by experiment, simulation or calculation.​​​

[0102] A2: determining a static gain of the unit based on the step response.

[0103] S103 determines the quasi-steady frequency constraint based on the frequency curve approximation equation, including: determining the quasi-steady frequency constraint based on the static gain and the frequency curve approximation equation.

[0104] It can be understood that the static gain is the final value of the step response, which can be determined by the following formula:

[0105] In the formula, denotes the static gain of the i-th unit, denotes the transfer function corresponding to the control block diagram, denotes the step response of the unit.

[0106] Therefore, the quasi-steady frequency is:

[0107] ;

[0108] In the formula, denotes the quasi-steady frequency of the power system, denotes the droop coefficient of the load, denotes the sum of the static gains of all units.

[0109] The quasi-steady frequency constraint is:

[0110]

[0111] In the formula, is the maximum quasi-steady frequency deviation allowed by the power system.

[0112] S104: linearizing the frequency nadir constraint to obtain a linear frequency nadir constraint.

[0113] The present application does not limit the specific way of linearizing the frequency nadir constraint to obtain a linear frequency nadir constraint. As an example, linearizing the frequency nadir constraint to obtain a linear frequency nadir constraint can include the following steps: B1-B5.

[0114] B1: determining a first time-domain function of the unit power increment information according to the convolution theorem of Laplace transform.

[0115] According to the above description, the complex frequency domain form of the unit power increment is:

[0116] ;

[0117] It is known that:

[0118] ,

[0119] According to the convolution theorem of Laplace transform, the time-domain form of the power increment of the unit is:

[0120] In the formula, represents the time-domain form of the step response of the unit, represents the variable inside the integral, and the remaining parameters are the same as described above, which will not be repeated here. Therefore, at the moment when the frequency is the lowest , the power increment of the unit is:

[0121] ;

[0122] It can be understood that, at the moment when the frequency is the lowest , the equation of the power increment of the unit is the first time-domain function to be determined.

[0123] B2: based on the first time-domain function, a first function based on a first product is constructed, the first product being a product of the system inertia and the system frequency deviation.

[0124] In the formula, the first function of the first product is a first function expression corresponding to the first product.

[0125] In the embodiments of the present application, the first product W can be constructed, and , so that:

[0126] ;

[0127] In the formula, represents the system inertia, represents the power increment information of the i th unit at the moment when the frequency is the lowest .

[0128] After the given power disturbance amount , there is only the variable on the right side of the above formula, so there is:

[0129]

[0130] Thus, the first function based on the first product is:

[0131] ;

[0132] For , by taking different and get , the scatter points line, you can. and The selection is as follows:

[0133]

[0134]

[0135] In the formula, is the possible minimum system inertia, is the possible maximum system inertia, is the possible maximum frequency deviation, is the number of selected system inertia, is the number of selected system frequency deviation, are all coefficients.

[0136] As an example, the first function As shown in Figure 5 , Figure 5 is a schematic diagram of a first function provided by an embodiment of the application.

[0137] The application proposes a first function, so that the frequency modulation capability of the unit can be described concisely by variables and curve This provides great convenience for embedding the optimization scheduling model at the lowest point of the frequency deviation.

[0138] B3: linearizing the first function to obtain a second function of the first product in the first scheduling period.

[0139] In the embodiment of the application, after the first function is determined, the first function can be linearized. The application does not limit the specific way of linearizing the first function. As an example, the application can use a piecewise linearization method to linearize the first function. As shown in Figure 6 , Figure 6 is a schematic diagram of linearizing the first function provided by an embodiment of the application.

[0140] As shown in Figure 6 , by linearizing , from small to large, is divided into segments, the segment points are , and the slope of each segment is .

[0141] In the first scheduling period , an indication variable Indicates the first product of the first scheduling period Located in segment, based on integer variable modeling, determine the second function of the first product in the first scheduling period It is understandable that the It is a continuous nonlinear function that is smooth when plotted. From here, we approximate this smooth nonlinear function to a piecewise linear function, but with almost no error, and it can be considered to replace the original function.

[0142] It can be understood that the present application uses a piecewise linearization method with segmented intervals from small to large to convert The curve is linearized into 5 segments, which linearizes the nonlinear function while introducing almost no error.

[0143] B4: Based on the second function, determine the first linear constraint of the second function, the second linear constraint of the first product in the first scheduling period, and the third linear constraint of the second product, where the second product is the product of the unit power increment information in the first scheduling period and the system inertia in the first scheduling period.

[0144] After determining the second function , we can introduce the following first linear constraint:

[0145]

[0146]

[0147]

[0148]

[0149] In the formula, represents the first product of the first scheduling period, Represents the first product of the first scheduling period Located in part, Represents the first product of the first scheduling period Located in part, Indicates the The horizontal coordinate of the segment point, Indicates the +1 The horizontal coordinate of the segment point, Indicates the The vertical coordinate of the segment point, Refers to the amount used in the dth segment, such as When taking When , ,

[0150] For the first product, the system inertia in the first dispatch period is:

[0151] ;

[0152] wherein, is the system power base value, is the power base value of the i-th unit, is the inertia level of the i-th unit, is the on-off state of the i-th unit, with value 0 or 1. The expression of the first product can be written as:

[0153] ;

[0154] wherein

[0155] The first intermediate number is constructed, and let

[0156] , then the first product The second linear constraint introduced by the first intermediate number is: ;

[0157] ;

[0158] ;

[0159] ;

[0160] wherein, is the minimum system frequency deviation after power disturbance in the i-th dispatch period,

[0161] denotes the maximum possible system frequency deviation. In addition, the application also constructs the product of the unit power increment information of the first dispatch period and the system inertia of the first dispatch period as the second product, i.e. , and constructs the second intermediate number , then

[0162]

[0163] ;

[0164] wherein, ​​​​Indicates the on or off status of the j-th unit, j is a natural number, and the remaining parameters are the same as those recorded above and will not be repeated here.

[0165] So the second product The third linear constraint introduced is:

[0166]

[0167]

[0168]

[0169]

[0170] The parameters in the formula are the same as those recorded above and will not be repeated here.

[0171] It is understandable that if is a continuous variable, then the two bilinear terms are in the form of continuous variable × continuous variable, and the constraints introduced are nonlinear constraints. However, the present invention points out that due to A special form of Actually, it is about the operating status of the unit The bilinear term of discrete variable × continuous variable can be completely linearized.

[0172] B5: Determine the linear frequency lowest point constraint according to the first linear constraint, the second linear constraint, and the third linear constraint.

[0173] In an embodiment of the present application, after determining the first linear constraint, the second linear constraint, and the third linear constraint, the three can be combined to determine the linear frequency minimum point constraint. The linear frequency minimum point constraint is the constraint obtained by combining the first linear constraint, the second linear constraint, and the third linear constraint.

[0174] As a possible implementation, the linear frequency minimum point constraint of the present application may further include a fourth linear constraint, specifically as follows:

[0175] ;

[0176] ;

[0177] In the formula, For the The lowest system frequency deviation after a power disturbance occurs within a scheduling period. is the maximum permissible system frequency deviation, Indicates the number of units, that is Indicates a unit collection The number of elements contained;

[0178] S105: constructing the optimization scheduling model based on the quasi-steady frequency constraint, the frequency change rate constraint, and the linear frequency minimum point constraint.

[0179] The quasi-steady frequency constraint, the frequency change rate constraint, and the linear frequency minimum point constraint are determined, and the constraints are embedded into an optimization scheduling model of a power system, so that the construction of the optimization scheduling model is realized.

[0180] By the above method, the highly nonlinear frequency safety constraint is converted into a linear constraint, the analytical complexity of the constructed optimization scheduling model is reduced, and the calculation error of the analysis of the optimization scheduling model is reduced.

[0181] The application does not limit the specific content of the optimization scheduling model. As a possible implementation manner, the optimization scheduling model is to minimize the unit operation cost. It can be understood that the optimization scheduling model in the application is to minimize the unit operation cost under the premise of considering frequency safety, so that the optimization result can guarantee the system frequency safety while minimizing the operation cost. In addition, the frequency minimum point of the system when facing frequency shortage can be directly obtained by solving the optimization model. The objective formula of the optimization scheduling model is as follows:

[0182] ;

[0183] In the formula, is a scheduling period, is a maximum scheduling period, and is taken as ; represents the i-th unit, is the number of units; is the T scheduling period unit output state, is the T scheduling period unit operation state. The unit cost function takes a quadratic cost function, which can be handled by piecewise linearization. The unit start-up cost and the unit shutdown cost are as follows,

[0184]

[0185] wherein, is the cost of a single start-up of a unit, is the cost of a single shutdown of a unit, represents the state of the i-th unit start-up and shutdown, represents that the unit is on, =0 represents that the unit is off, is a 0-1 variable indicating the start-up of the unit, ​is a 0-1 variable indicating the unit is shut down, Indicates the situation of the unit switching from off to on. Represents unit i in the The scheduled period changes from shutdown to startup. It means that the unit i is in the A scheduled period changes from on to off.

[0186] As a possible implementation method, the present application provides a method for constructing an optimal dispatching model for an electric power system taking into account frequency safety, which also includes the following steps: determining basic constraints based on the optimal dispatching model; the basic constraints include: unit capacity constraints, unit minimum startup constraints, unit minimum shutdown constraints, unit climbing constraints, system standby constraints, system power balance constraints and line flow constraints.

[0187] It is understandable that the optimization model will also include basic constraints, such as unit capacity constraints, unit minimum startup / shutdown constraints, unit ramp constraints, system backup constraints, system power balance constraints, and line flow constraints.

[0188] This application does not limit the specific content of the unit capacity constraint. As an example, the unit capacity constraint is as follows:

[0189] ;

[0190] Where: is the minimum output of the unit, The maximum output of the unit.

[0191] This application does not limit the specific content of the minimum startup constraint and the minimum shutdown constraint of the unit. As an example, the minimum startup constraint and the minimum shutdown constraint of the unit are as follows:

[0192] ;

[0193] Where: Minimum startup time, is the minimum shutdown time, The remaining running time of the unit, The length of time the unit must remain shut down after being shut down, defined as:

[0194]

[0195]

[0196] in: The initial operating state of the unit. It is the initial operation and shutdown time of the unit.

[0197] The application does not limit the specific content of the unit ramping constraint. As an example, the unit ramping constraint is as follows:

[0198]

[0199] In the formula: is the maximum upward ramping rate, is the maximum downward ramping rate, is the output level of the i th unit at the T th scheduling period, is the output level of the i th unit at the T-1 th scheduling period.

[0200] The application does not limit the specific content of the system reserve constraint. As an example, the system reserve constraint is as follows:

[0201]

[0202] In the formula: is the maximum output of the unit, is the total load, is the reserve demand.

[0203] The application does not limit the specific content of the system power balance constraint. As an example, the system power balance constraint is as follows:

[0204]

[0205] In the formula, is the output level of the i th unit at the T th scheduling period, in megawatts (MW).

[0206] The application does not limit the specific content of the system line flow constraint. As an example, the line flow constraint is as follows:

[0207]

[0208] In the formula: is the line flow, is the maximum value of the line flow, is the power transfer distribution factor, is the unit output vector, is the unit load vector, is the node-unit association matrix, is the node-load association matrix, and ● represents multiplication operation.

[0209] The application does not limit the specific content of the frequency change rate constraint. As an example, the frequency change rate constraint is as follows:

[0210]

[0211]

[0212] In the formula: is the system inertia at time T, is the system power base value, is the unit inertia level, is the unit power base value, is the power disturbance amount, is the maximum allowable frequency change rate.

[0213] As Figure 7 shown, Figure 7 is another flowchart of a method for constructing an optimal dispatching model of a power system considering frequency safety provided by the embodiments of the present application. As Figure 7 shown, the present application will construct an optimal dispatching model (Security-Constrained Unit Commitment, SCUC) of a power system considering security constraints. The present application needs to perform frequency modulation resource step response test and gain evaluation to obtain the step response of the unit and the static gain, so as to determine the quasi-steady frequency constraint in combination with the static gain. The present application will perform linearization processing based on the frequency minimum point constraint to obtain the linear frequency minimum point constraint, so as to construct the optimal dispatching model of the power system considering security constraints based on the quasi-steady frequency constraint, the frequency change rate constraint and the linear frequency minimum point constraint. When solving the actual model, the power grid and fault parameters need to be input. Solving the model is a mixed integer linear programming (MILP) problem in the optimization field, and the optimal solution of the unit state, output and frequency minimum point can be obtained by inputting the model into a commercial solver.

[0214] Next, a device for constructing an optimal dispatching model of a power system provided by the embodiments of the present application is introduced. The device described in the following description can be correspondingly referred to the method for constructing an optimal dispatching model of a power system considering frequency safety described in the foregoing description.

[0215] Referring to Figure 8 , Figure 8 is a structural schematic diagram of a device for constructing an optimal dispatching model of a power system considering frequency safety provided by the embodiments of the present application. The device comprises an acquisition unit 201, a construction unit 202, a determination unit 203 and a linearization processing unit 204.

[0216] The acquisition unit 201 is configured to acquire the system inertia of the power system and the power disturbance amount faced by the power system.

[0217] The constructing unit 202 is configured to construct a frequency curve approximation equation of a system frequency deviation of the power system based on the system inertia and the power disturbance amount.

[0218] The determining unit 203 is configured to determine a frequency safety constraint based on the frequency curve approximation equation; the frequency safety constraint comprises a quasi-steady frequency constraint, a frequency change rate constraint, and a frequency nadir constraint.

[0219] The linearization processing unit 204 is configured to perform linearization processing based on the frequency nadir constraint to obtain a linear frequency nadir constraint.

[0220] The constructing unit 202 is further configured to construct the optimal dispatching model based on the quasi-steady frequency constraint, the frequency change rate constraint, and the linear frequency nadir constraint.

[0221] As a possible implementation manner, the obtaining unit 201 is further configured to obtain unit power increment information.

[0222] The constructing unit 202 is specifically configured to construct the frequency curve approximation equation based on the system inertia, the unit power increment information, and the power disturbance amount according to an inertia center principle.

[0223] As a possible implementation manner, the linearization processing unit 204 is specifically configured to:

[0224] determine a first time domain function of the unit power increment information according to a convolution theorem of Laplace transform;

[0225] construct a first function based on a first product based on the first time domain function, the first product being a product of the system inertia and the system frequency deviation;

[0226] perform linearization processing on the first function to obtain a second function of the first product in a first dispatching time period;

[0227] determine, based on the second function, a first linear constraint of the second function, a second linear constraint of the first product in the first dispatching time period, and a third linear constraint of a second product, the second product being a product of the unit power increment information in the first dispatching time period and the system inertia in the first dispatching time period;

[0228] determine the linear frequency nadir constraint according to the first linear constraint, the second linear constraint, and the third linear constraint.

[0229] As a possible implementation manner, the linearization processing unit 204 is specifically configured to:

[0230] The linearization processing on the first function comprises: performing linearization processing on the first function by using a piecewise linearization method.

[0231] As a possible implementation, the obtaining unit is further configured to obtain a step response of the generating unit, and the apparatus further comprises:

[0232] The determining unit 203 is further configured to determine a static gain of the generating unit based on the step response.

[0233] The determining unit 203 is specifically configured to determine the quasi-steady-state frequency constraint based on the static gain and the frequency curve approximation equation.

[0234] As a possible implementation, the optimization scheduling model is configured to minimize a generating unit operation cost.

[0235] As a possible implementation, the apparatus further comprises:

[0236] The determining unit 203 is further configured to determine a basic constraint based on the optimization scheduling model, and the basic constraint comprises: a generating unit capacity constraint, a generating unit minimum start constraint, a generating unit minimum stop constraint, a generating unit ramp constraint, a system reserve constraint, a system power balance constraint, and a line power flow constraint.

[0237] The constructing unit 202 is further configured to construct the optimization scheduling model based on the quasi-steady-state frequency constraint, the frequency change rate constraint, the linear frequency minimum point constraint, and the basic constraint.

[0238] It should be noted that the apparatus for constructing an optimization scheduling model of a power system provided by the embodiments of the present application has the technical effects of any one of the above embodiments, and the embodiments of the present application will not be repeated here.

[0239] The present application further provides an apparatus for constructing an optimization scheduling model of a power system, which can include a memory and a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the computer program, the method for constructing an optimization scheduling model of a power system considering frequency safety is realized.

[0240] It should be noted that the apparatus provided by the embodiments of the present application has the technical effects of any one of the above embodiments, and the embodiments of the present application will not be repeated here.

[0241] The application further provides a computer readable storage medium, which has a computer program stored thereon, the computer program can implement the steps provided by the above embodiments when executed. The storage medium can include a U disk, a mobile hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk and various storage medium capable of storing program codes.

[0242] It should be noted that the computer readable storage medium provided by the embodiments of the application has the technical effects of any one of the above embodiments, which will not be repeated here.

[0243] It should be understood that, in the present application, "at least one" refers to one or more, and "multiple" refers to two or more. "And / or" is used to describe the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, "A and / or B" can represent three cases: only A exists, only B exists, and A and B exist at the same time, wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it. "At least one of the following" or the like means any combination of these items, including single item or any combination of multiple items. For example, at least one of a, b or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", wherein a, b and c can be single or multiple.

[0244] It should be further noted that, in this document, relationship terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement "including a…" does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0245] The principles and implementations of the present application are described in detail with specific examples in this paper, and the above examples are only used to help understand the method of the present application and its core idea. It should be pointed out that for ordinary skilled persons in the technical field, some improvements and modifications can be made without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A method for constructing an optimization dispatch model for a power system taking frequency security into account, characterized in that: include: Obtaining system inertia of the power system and power disturbance faced by the power system, and obtaining power increment information of the generating units; Constructing a frequency curve approximation equation of the system frequency deviation of the power system based on the system inertia and the power disturbance, comprising: constructing the frequency curve approximation equation based on the system inertia, the unit power increment information, and the power disturbance according to the inertia center principle; Determining frequency safety constraints based on the frequency curve approximation equation; the frequency safety constraints include: quasi-steady-state frequency constraints, frequency change rate constraints, and frequency minimum point constraints; Performing linearization based on the frequency minimum point constraint to obtain a linear frequency minimum point constraint, including: determining a first time domain function of the unit power increment information according to the convolution theorem of Laplace transform; constructing a first function based on a first product based on the first time domain function, where the first product is the product of the system inertia and the system frequency deviation; performing linearization on the first function to obtain a second function of the first product in a first scheduling period; determining a first linear constraint of the second function, a second linear constraint of the first product in the first scheduling period, and a third linear constraint of the second product based on the second function, where the second product is the product of the unit power increment information in the first scheduling period and the system inertia in the first scheduling period; and determining the linear frequency minimum point constraint according to the first linear constraint, the second linear constraint, and the third linear constraint; The optimization scheduling model is constructed based on the quasi-steady-state frequency constraint, the frequency change rate constraint, and the linear frequency minimum point constraint.

2. The method according to claim 1, characterized in that The linearizing the first function includes: linearizing the first function using a piecewise linearization method.

3. The method according to claim 1, characterized in that The method further includes: obtaining a step response of the unit; determining a static gain of the unit based on the step response; Then, determining the quasi-steady-state frequency constraint based on the frequency curve approximation equation includes: The quasi-steady-state frequency constraint is determined based on the static gain and the frequency curve approximation equation.

4. The method according to claim 1, wherein The objective function of the optimization scheduling model is to minimize the unit operating cost.

5. The method according to claim 1, characterized in that The method further comprises: Determining basic constraints based on the optimization scheduling model; the basic constraints include: unit capacity constraints, unit minimum startup constraints, unit minimum shutdown constraints, unit ramp constraints, system backup constraints, system power balance constraints, and line power flow constraints; The constructing of the optimization scheduling model based on the quasi-steady-state frequency constraint, the frequency change rate constraint, and the linear frequency minimum point constraint includes: The optimization scheduling model is constructed based on the quasi-steady-state frequency constraint, the frequency change rate constraint, the linear frequency lowest point constraint and the basic constraint.

6. A device for constructing an optimization dispatch model for a power system taking frequency security into account, characterized in that: include: an acquisition unit, configured to acquire a system inertia of a power system and a power disturbance faced by the power system; A construction unit, configured to construct a frequency curve approximation equation of the system frequency deviation of the power system based on the system inertia and the power disturbance; a determining unit, configured to determine a frequency safety constraint based on the frequency curve approximation equation; The frequency safety constraints include: quasi-steady-state frequency constraints, frequency change rate constraints, and frequency minimum point constraints; a linearization processing unit, configured to perform linearization processing based on the frequency minimum point constraint to obtain a linear frequency minimum point constraint; The construction unit is further configured to construct the optimization scheduling model based on the quasi-steady-state frequency constraint, the frequency change rate constraint, and the linear frequency minimum point constraint; The acquisition unit is further configured to acquire the power increment information of the generator set; The construction unit is specifically configured to construct an approximate equation of the frequency curve according to the inertia center principle, based on the system inertia, the unit power increment information, and the power disturbance; The linearization processing unit is specifically used to: According to the convolution theorem of Laplace transform, the first time domain function of the unit power increment information is determined; constructing, based on the first time-domain function, a first function based on a first product, the first product being a product of the system inertia and the system frequency deviation; Linearize the first function to obtain a second function of the first product in the first scheduling period; Determining, based on the second function, a first linear constraint of the second function, a second linear constraint of the first product in the first scheduling period, and a third linear constraint of the second product, where the second product is the product of the unit power increment information in the first scheduling period and the system inertia in the first scheduling period; The linear frequency lowest point constraint is determined according to the first linear constraint, the second linear constraint, and the third linear constraint.

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