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CN115117883B - Long-term voltage calculation method for power systems involving discrete actions - Google Patents

Long-term voltage calculation method for power systems involving discrete actions Download PDF

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CN115117883B
CN115117883B CN202210877969.1A CN202210877969A CN115117883B CN 115117883 B CN115117883 B CN 115117883B CN 202210877969 A CN202210877969 A CN 202210877969A CN 115117883 B CN115117883 B CN 115117883B
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陈浩
李慧星
黄志龙
曹路
李建华
周毅
史济全
时艳强
张怡静
黄志光
丁浩寅
刘毅
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East China Branch of State Grid Corp of China
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Abstract

本发明提供了一种包含离散动作的电力系统中长期电压计算方法，包括：建立电力系统的中长期准稳态模型；从模型中采用配点法逼近可变参数影响的模型曲线，得到逼近电压轨迹；选取任意相邻的第一离散动作和第二离散动作，获取第一离散动作前一时刻在中长期准稳态模型中对应的第一电压以及第一电压导数，获取第二离散动作下一时刻在中长期准稳态模型中对应的第二电压以及第二电压导数；根据第一电压、第二电压、第一电压导数和第二电压导数获取电压多项式函数，作为第一离散动作和第二离散动作之间的电压轨迹；将逼近电压轨迹按照离散动作发生的最早时间分为前后两段，第一离散动作和第二离散动作之间的电压轨迹替换后段逼近电压轨迹。

The present invention provides a method for calculating medium- and long-term voltage of an electric power system including discrete actions, comprising: establishing a medium- and long-term quasi-steady-state model of the electric power system; using a collocation method to approximate a model curve affected by a variable parameter in the model to obtain an approximated voltage trajectory; selecting any adjacent first discrete action and second discrete action, obtaining a first voltage and a first voltage derivative corresponding to the first discrete action in the medium- and long-term quasi-steady-state model at a moment before the first discrete action, and obtaining a second voltage and a second voltage derivative corresponding to the second discrete action in the medium- and long-term quasi-steady-state model at a moment after the second discrete action; obtaining a voltage polynomial function according to the first voltage, the second voltage, the first voltage derivative and the second voltage derivative as the voltage trajectory between the first discrete action and the second discrete action; dividing the approximated voltage trajectory into two sections, a front section and a back section, according to the earliest time when the discrete action occurs, and replacing the rear section of the approximated voltage trajectory with the voltage trajectory between the first discrete action and the second discrete action.

Description

Method for calculating medium-long-term voltage of power system comprising discrete actions
Technical Field
The invention relates to the technical field of power systems, in particular to a method for calculating a medium-term voltage of a power system with discrete actions.
Background
In recent years, the transmission power of the power grid is increasing, the power system is running near the limit point more and more frequently, and the problem of unstable voltage is threatening the safe operation of the power grid increasingly. The voltage instability is classified into transient voltage instability and medium-to-long-term voltage instability of the order of minutes according to its time frame.
In an electrical power system, variations in certain parameters, such as, for example, the output of a generator, the amount of reactive compensation, the amount of interruption of a load, etc., may affect the system operating state. With the increase of the operating pressure of the power system and the increase of variable parameters in the power system, the problem of medium-long-term voltage instability of the power system is increasingly prominent. In the calculation process of the medium-long-term voltage track, the polynomial approximation method directly approximates the medium-long-term dynamic process due to the generation of discrete action events, so that the approximation accuracy of the medium-long-term voltage track is reduced, the approximation error of the voltage track is large, and the analysis of the medium-long-term voltage stability problem is more challenging.
Disclosure of Invention
The invention aims to provide a medium-long term voltage calculation method of an electric power system comprising discrete actions, which can acquire a medium-long term voltage track with higher accuracy, reduce approximation errors of the voltage track and reduce the difficulty of analysis of the medium-long term voltage stability problem.
In order to achieve the above object, the present invention provides a method for calculating a long-term voltage in an electric power system including discrete actions, including:
establishing a medium-long-term quasi-steady state model of the power system according to the state variable of the fast dynamic element, the algebraic variable of the power system, the state variable of the slow dynamic element, the state variable of discrete action and the variable parameter;
approximating a model curve influenced by variable parameters from the medium-and-long-term quasi-steady-state model by adopting a point matching method so as to obtain an approximated voltage track;
Selecting any adjacent first discrete action and second discrete action, acquiring a first voltage corresponding to the first discrete action in the medium-and-long-term quasi-steady-state model at the previous moment and a first voltage derivative of the first voltage with respect to time, and acquiring a second voltage corresponding to the second discrete action at the next moment and a second voltage derivative of the second voltage with respect to time;
Obtaining a voltage polynomial function based on the first voltage, the second voltage, the first voltage derivative and the second voltage derivative to represent a voltage trace between the first discrete action and the second discrete action, and
Dividing the approximation voltage track into a front section and a rear section according to the earliest time of the discrete actions, replacing the rear section approximation voltage track with the voltage track between the first discrete action and the second discrete action, and forming the middle-long-term voltage track by the front section approximation voltage track and the voltage track between the first discrete action and the second discrete action.
Optionally, in the method for calculating the medium-long term voltage in the power system, the medium-long term quasi-steady state model is as follows:
Wherein x is a state variable of a fast dynamic element in the power system, y is an algebraic variable in the power system, z c is a state variable of a slow dynamic element in the power system, z d is a state variable of discrete action in the power system, p is a medium-long variable parameter of the power system, f represents a balanced form of a differential equation describing the fast dynamic element, g represents an algebraic equation mainly describing a network equation of the power system, h c represents a differential equation describing the slow dynamic element, h d represents a discrete equation describing a discrete action occurrence process, x - is a state variable of the fast dynamic element in the power system at a moment before discrete action occurs, and y - is an algebraic variable in the power system at a moment before discrete action occurs; a state variable of a slow dynamic element in the power system that is the previous moment in time when the discrete action occurred; Is a state variable of a discrete action in the power system at a time immediately before the discrete action occurs.
Optionally, in the method for calculating the long-term voltage in the electric power system, the state variables of the fast dynamic element comprise the rotating speed of the generator, the flux linkage of the exciting winding and the power angle.
Optionally, in the method for calculating the long-term voltage in the power system, algebraic variables of the power system comprise node voltage of the power system, node current of the power system, input power of a generator set and output power of the generator set.
Optionally, in the method for calculating the long-term voltage in the power system, the state variables of the slow dynamic element comprise a recovery amount of the self-recovery load and a reactive limiting amount of the over-excitation limiter.
Optionally, in the method for calculating the long-term voltage in the power system, the state variables of the discrete actions comprise an on-load voltage regulating transformer action and an over-excitation limiter action.
Optionally, in the method for calculating the long-term voltage in the power system, the variable parameters include load shedding time and load shedding amount.
Optionally, in the method for calculating the long-term voltage in the power system, the method for approximating the model curve affected by the variable parameter by using a point matching method to obtain the approximated voltage track includes:
Wherein v (t; p) represents the simulated voltage trace in compact form of the variables x and y, v (t; p) and To approximate the voltage trace.
Optionally, in the method for calculating the long-term voltage in the power system, the method for obtaining the first voltage derivative includes:
Wherein: At the time of the first voltage level, As a derivative of the first voltage,For the voltage at the delta t time after the occurrence time point t i,j (p) of the medium-long discrete action event, delta t is the step size of the numerical simulation.
Optionally, in the method for calculating the long-term voltage in the power system, the method for obtaining the second voltage derivative includes:
Wherein: at the time of the second voltage level, As a result of the second derivative of the voltage,For the voltage at the time deltat before the occurrence time point t i,j (p) of the medium-long discrete action event, deltat is the step size of the numerical simulation.
Optionally, in the method for calculating a long-term voltage in a power system, the method for obtaining a voltage polynomial function according to the first voltage, the second voltage, the first voltage derivative and the second voltage derivative includes:
Wherein G θ (t; p) is a voltage trace polynomial between the first discrete action and the second discrete action, and θ 0(p)、θ1(p)、θ2(p)、θ3 (p) is a coefficient term of the polynomial.
In the method for calculating the medium-long-term voltage of the power system comprising the discrete action, the discrete action is taken into consideration when the medium-long-term voltage is calculated, so that the approximation error of the voltage track is reduced, and the more accurate medium-long-term voltage track is obtained.
Drawings
FIG. 1 is a flow chart of a method of long-term voltage calculation in a power system including discrete actions in accordance with an embodiment of the present invention;
FIG. 2 is a schematic diagram of the voltage and the first derivative of the voltage with respect to time at the point of time when the medium-long discrete action occurs according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a comparison of a third-order approximated voltage trace and a mid-to-long-term actual voltage curve according to an embodiment of the present invention.
Detailed Description
Specific embodiments of the present invention will be described in more detail below with reference to the drawings. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are in a very simplified form and are all to a non-precise scale, merely for convenience and clarity in aiding in the description of embodiments of the invention.
In the following, the terms "first," "second," and the like are used to distinguish between similar elements and are not necessarily used to describe a particular order or chronological order. It is to be understood that such terms so used are interchangeable under appropriate circumstances. Similarly, if a method described herein comprises a series of steps, and the order of the steps presented herein is not necessarily the only order in which the steps may be performed, and some of the described steps may be omitted and/or some other steps not described herein may be added to the method.
Referring to fig. 1, the present invention provides a method for calculating a long-term voltage in an electric power system including discrete actions, including:
S11, establishing a medium-and-long-term quasi-steady state model of the power system according to the state variable of the fast dynamic element, the algebraic variable of the power system, the state variable of the slow dynamic element and the state variable of discrete action and variable parameters;
s12, approximating a model curve influenced by variable parameters by adopting a point matching method from the middle-long-term quasi-steady-state model to obtain an approximated voltage track;
S13, selecting any adjacent first discrete action and second discrete action, acquiring a first voltage corresponding to the first discrete action in the middle-long-term quasi-steady state model at the previous moment and a first voltage derivative of the first voltage with respect to time, and acquiring a second voltage corresponding to the second discrete action at the next moment and a second voltage derivative of the second voltage with respect to time;
s14, obtaining a voltage polynomial function according to the first voltage, the second voltage, the first voltage derivative and the second voltage derivative to represent the voltage track between the first discrete action and the second discrete action, and
S15, dividing the approximation voltage track into a front section and a rear section according to the earliest time of the discrete actions, replacing the approximation voltage track of the rear section by the voltage track between the first discrete action and the second discrete action, and forming the middle-long-term voltage track by the approximation voltage track of the front section and the voltage track between the first discrete action and the second discrete action.
The mid-to-long term quasi-steady state model of a known power system consists of a set of differential-algebraic-discrete equations, combined with the effect of variable parameters on the mid-to-long term process of the power system, and thus the mid-to-long term quasi-steady state model can be expressed as follows:
Wherein x is a state variable of a fast dynamic element in the power system, y is an algebraic variable in the power system, z c is a state variable of a slow dynamic element in the power system, z d is a state variable of discrete actions in the power system, p is a medium-long variable parameter of the power system, f represents a balanced form of differential equations describing the fast dynamic element, g represents an algebraic equation mainly based on a network equation of the power system, h c represents a differential equation describing the slow dynamic element, h d represents a discrete equation describing a discrete action occurrence process, and x - is a discrete action occurrence process
-A state variable of a fast dynamic element in the power system at a previous moment; y is an algebraic variable in the power system at the previous time when the discrete action occurred; a state variable of a slow dynamic element in the power system that is the previous moment in time when the discrete action occurred; Is a state variable of a discrete action in the power system at a time immediately before the discrete action occurs.
In the embodiment of the invention, the state variables of the fast dynamic element comprise the rotating speed of the generator, the flux linkage of the exciting winding and the power angle. Algebraic variables of the power system include node voltage of the power system, node current of the power system, input power of the generator set, and output power of the generator set. The state variables of the slow dynamic element include the amount of recovery of the self-recovered load and the amount of reactive limiting of the over-excited limiter. The state variables of the discrete actions include on-load tap changer actions and over-excitation limiter actions. The variable parameters include cut load time and cut load amount.
In the embodiment of the invention, a method for approximating a model curve affected by variable parameters by adopting a point matching method to obtain an approximated voltage track comprises the following steps:
Wherein v (t; p) represents the simulated voltage trace in compact form of the variables x and y, v (t; p) and In order to approximate the voltage trace, phi k (p) is the basis function of polynomial approximation, consisting of a set of orthogonal polynomials, satisfying:
Wherein k is the number of the basis functions, k1 and k2 represent arbitrary values in the k range, and < DEG, > represents inner product calculation; The method comprises the steps of respectively obtaining coefficients of corresponding base functions, wherein N b represents the number of the base functions approximated by a polynomial, and when c k (t) is obtained by using a point matching method, time domain simulation is needed to be carried out at M parameter point matching positions to obtain M voltage tracks (note: part of point matching is counted for a plurality of times), and the calculation mode of M is as follows:
Wherein d represents the number of variable variables, l represents the approximation order, M is the total number of the distribution points; representing the combination number calculation, and then calculating the coefficient of the basis function according to the following formula:
Wherein m represents the count of the matching points, p m represents the m-th parameter matching point, and q m is the integral coefficient corresponding to p m; e is calculated as the desired value.
Preferably, the method of the first voltage derivative comprises:
Wherein: At the time of the first voltage level, As a derivative of the first voltage,For the voltage at the delta t time after the occurrence time point t i,j (p) of the medium-long discrete action event, delta t is the step size of the numerical simulation.
Preferably, the method of deriving the second voltage derivative comprises:
Wherein: at the time of the second voltage level, As a result of the second derivative of the voltage,For the voltage at the time deltat before the occurrence time point t i,j (p) of the medium-long discrete action event, deltat is the step size of the numerical simulation.
Preferably, the method for obtaining the voltage polynomial function from the first voltage, the second voltage, the first voltage derivative and the second voltage derivative using hermite interpolation comprises:
Wherein G θ (t; p) is a voltage trace polynomial between the first discrete action and the second discrete action, and θ 0(p)、θ1(p)、θ2(p)、θ3 (p) is a coefficient term of the polynomial.
In step S15, the approximated voltage trajectory is knownAnd the calculated voltage trace G θ (t; p), which can be replaced by G θ (t; p)The latter part of the power system is combined into a new medium-long term voltage track F U (t; p) influenced by variable parameters, and the new medium-long term voltage track F U (t; p) is used as the medium-long term voltage of the power system obtained by the embodiment of the invention. The method can indirectly acquire the medium-long-term voltage track after discrete actions occur, and the approximation track F U (t; p) and the transient simulation track v (t; p) under the method have higher overlapping degree, so that the approximation accuracy of the voltage track is improved.
The functional relationship is shown in the following formula:
Wherein t i,j (p) is the discrete action occurrence time, The voltage track obtained by the middle-long period process is directly approximated by a point matching method, and can be divided into two sections before and after the discrete action occurrence time t i,j (p), namely, t < t i,j (p) and t i,j(p)≤t≤ti,j+1 (p), G θ (t; p) is a voltage track calculated according to the voltages of the adjacent two middle-long period discrete action occurrence time points and the corresponding voltage derivatives, and F U (t; p) is G θ (t; p) to replaceThe medium-long voltage track obtained by the part after the occurrence of the medium-discrete action event, namely G θ (t; p) is used for replacing the interval t i,j(p)≤t≤ti,j+1 (p)Alpha 0(t)、α1(t)、α2(t)、α3 (t) is a coefficient term in the approximation voltage track polynomial, and can be calculated by a point matching method.
Examples
In the electric power system provided by the embodiment of the invention, the delay time of the on-load voltage regulating transformer is 30s, the mechanical action time is 6s, all generator sets except the generator G1 are additionally provided with the over-excitation limiter, the load adopts a static ZIP load, ZIP parameters of the load are listed in a table 1, and the table 1 is a static load ZIP coefficient table.
TABLE 1
Constant impedance coefficient Constant current coefficient Constant power coefficient
Load L1 0.0 0.0 1.0
Load L2 1.0 0.0 0.0
The fault is that one high-voltage transmission line between the nodes 4 and 5 is cut off after three-phase short circuit occurs, the discrete action event is low-voltage load shedding action, when the voltage at the node 10 is lower than 0.9p.u., the first round of cut load is triggered after 6 seconds of time delay, and when the voltage at the node 10 continuously drops and is lower than 0.87p.u., the second round of cut load is triggered after 2 seconds of time delay. The load L2 at the node 10 is selected as the interrupt load, and the variable parameter is the cut-off amount of the load L2.
Firstly, establishing a long-term quasi-steady state model in a power system considering variable parameters:
Where x (t) is a state variable of a fast dynamic element in the electric power system, y (t) is an algebraic variable in the electric power system, z c (t) is a state variable of a slow dynamic element in the electric power system, z d(t+) is a state variable of a discrete motion in the electric power system, p is a medium-long-term variable parameter of the electric power system, f is a balanced form of a differential equation describing the fast dynamic element, g is an algebraic equation mainly describing a network equation of the electric power system, h c is a differential equation describing the slow dynamic element, h d is a discrete equation describing a discrete motion generation process, x (t -) is a state variable of the fast dynamic element in the electric power system at a time before the discrete motion occurs, y (t -) is a state variable of the slow dynamic element in the electric power system at a time before the discrete motion occurs, z d(t-) is a state variable of the discrete motion in the electric power system at a time before the discrete motion occurs, p is a state variable of the discrete motion in the electric power system at a time when p is taken as a low-voltage load shedding L2 of two-round load shedding, and p is 3435. The variation range of the two is p 1∈[0,5]％,p2 epsilon [0,5]%.
Next, the voltage trace of the node 10 is approximated based on the fitting method:
to quantify the effect of the variable parameter on the voltage trace of the node 10, a polynomial relationship of the variable parameter and the voltage of the node 10 is established to obtain an approximated voltage trace of the node 10 Can be expressed as:
The approximation order is 3, v (t; p) represents the simulated voltage trace in compact form of variables x and y, v (t; p) and To approximate the voltage trace, phi k (p) is the basis function of the polynomial approximation.
Next, approximating the voltage at the moment when the long-term discrete action occurs in the system and the derivative of the voltage at the moment with respect to time by using a point matching method:
As shown in fig. 2, the voltage at the time point when the long-term discrete action occurs in the system and the first derivative of the voltage at that time point with respect to time are approximated using a point-by-point method. Comprising the point in time t i,j (p) at which the discrete action occurs and the voltages at the time before and the time after the discrete action occurs AndAndAndFirst order voltage derivative over timeAndThe two voltage derivatives obtained are as follows:
In the formula, At the time of the first voltage level,As a derivative of the first voltage,For the voltage at a delta t time after the occurrence time point t i,j (p) of the medium-long discrete action event, delta t is the step length of the numerical simulation; at the time of the second voltage level, As a result of the second derivative of the voltage,For the voltage at the time deltat before the occurrence time point t i,j (p) of the medium-long discrete action event, deltat is the step size of the numerical simulation. In the view of figure 2,AndAndAndAndThe first derivative of the voltage and the voltage at the point 0, the point 1', the point 2 with respect to time are respectively shown, wherein the point 0 and the point 1 are the voltages at the points of discrete action moments in the first low-voltage load shedding process, the point 1 is the voltage before the abrupt change in the first low-voltage load shedding process, the point 1 is the voltage after the abrupt change, the point 1', the point 2 are the voltages at the points of discrete action moments in the second low-voltage load shedding process, the point 1' is the voltage before the abrupt change, and the point 2 is the voltage after the abrupt change.
Then, a voltage polynomial function is calculated based on the voltages at the occurrence time points of the adjacent two medium-long discrete actions and the corresponding derivatives:
According to voltage AndDerivative of voltageAndA cubic polynomial function can be calculated as follows:
G θ (t; p) is a voltage trace polynomial between the first discrete action and the second discrete action, and θ 0(p)、θ1(p)、θ2(p)、θ3 (p) is a coefficient term of the polynomial. Next, replacing a part of the tracks after the discrete action event occurs in the approximated voltage tracks with the calculated voltage tracks between the adjacent two medium-long discrete action occurrence time points:
after the calculated voltage track G θ (t; p) between two rounds of low-voltage load shedding is obtained, the approximate voltage track is replaced The part of the medium and G θ (t; p) with the same time interval, namely the part of the track after the discrete action event occurs in the replacement approximation voltage track, is combined into a new medium and long-term voltage F U (t; p) of the power system influenced by the variable parameters. The functional relationship is as follows:
Gθ(t;p)＝θ0(p)+θ1(p)t+θ2(p)t2+θ3(p)t3,(ti,j(p)≤t≤ti,j+1(p))
finally, t i,j (p) is the discrete action occurrence time, The voltage track obtained by the middle-long period process is directly approximated by a point matching method, and can be divided into two sections before and after the discrete action occurrence time t i,j (p), namely, t < t i,j (p) and t i,j(p)≤t≤ti,j+1 (p), G θ (t; p) is a voltage track calculated according to the voltages of the adjacent two middle-long period discrete action occurrence time points and the corresponding voltage derivatives, and F U (t; p) is G θ (t; p) to replaceThe medium-long voltage track obtained by the part after the occurrence of the medium-discrete action event, namely G θ (t; p) is used for replacing the interval t i,j(p)≤t≤ti,j+1 (p)Alpha 0(t)、α1(t)、α2(t)、α3 (t) is a coefficient term in the approximation voltage trace polynomial. A set of parameter values are selected and plotted, an approximation voltage trace v (t; p) at a node 10 and a long-term voltage F U (t; p) in a power system are shown in fig. 3, wherein a point 0 and a point 1 are voltages at discrete action time points in a first-round low-voltage load shedding process, a point 1 is a voltage before mutation in the first-round low-voltage load shedding process, a point 1 is a voltage after mutation, a point 1 'and a point 2 are voltages at discrete action time points in a second-round low-voltage load shedding process, a point 1' is a voltage before mutation, and a point 2 is a voltage after mutation.
In summary, in the method for calculating the medium-long voltage in the power system including the discrete action provided by the embodiment of the invention, the discrete action is taken into consideration when the medium-long voltage is calculated, so that the approximation error of the voltage track is reduced, and the more accurate medium-long voltage track is obtained.
The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art will make any equivalent substitution or modification to the technical solution and technical content disclosed in the invention without departing from the scope of the technical solution of the invention, and the technical solution of the invention is not departing from the scope of the invention.

Claims (11)

1.一种包含离散动作的电力系统中长期电压计算方法，其特征在于，包括：1. A method for calculating medium- and long-term voltage in an electric power system including discrete actions, characterized in that it comprises: 根据快动态元件的状态变量、电力系统的代数变量、慢动态元件的状态变量、离散动作的状态变量以及可变参数建立电力系统的中长期准稳态模型；A medium- and long-term quasi-steady-state model of the power system is established based on the state variables of fast dynamic elements, algebraic variables of the power system, state variables of slow dynamic elements, state variables of discrete actions, and variable parameters; 从所述中长期准稳态模型中，采用配点法逼近可变参数影响的模型曲线，以得到逼近电压轨迹；From the medium- and long-term quasi-steady-state model, a collocation method is used to approximate a model curve affected by variable parameters to obtain an approximate voltage trajectory; 选取任意相邻的第一离散动作和第二离散动作，获取所述第一离散动作前一时刻在所述中长期准稳态模型中对应的第一电压以及所述第一电压对时间的第一电压导数，获取所述第二离散动作下一时刻在所述中长期准稳态模型中对应的第二电压以及所述第二电压对时间的第二电压导数；Select any adjacent first discrete action and second discrete action, obtain a first voltage corresponding to the first discrete action in the medium- and long-term quasi-steady-state model at a moment before the first discrete action and a first voltage derivative of the first voltage with respect to time, and obtain a second voltage corresponding to the second discrete action in the medium- and long-term quasi-steady-state model at a moment after the second discrete action and a second voltage derivative of the second voltage with respect to time; 根据所述第一电压、第二电压、第一电压导数和第二电压导数获取电压多项式函数，用以表示第一离散动作和第二离散动作之间的电压轨迹；以及Obtaining a voltage polynomial function according to the first voltage, the second voltage, the first voltage derivative and the second voltage derivative to represent a voltage trajectory between a first discrete action and a second discrete action; and 将所述逼近电压轨迹按照离散动作发生的最早时间分为前后两段，使用所述第一离散动作和第二离散动作之间的电压轨迹替换后段逼近电压轨迹，前段逼近电压轨迹和第一离散动作和第二离散动作之间的电压轨迹组成中长期电压轨迹。The approximate voltage trajectory is divided into two sections according to the earliest time when the discrete action occurs, and the voltage trajectory between the first discrete action and the second discrete action is used to replace the latter section of the approximate voltage trajectory. The front section of the approximate voltage trajectory and the voltage trajectory between the first discrete action and the second discrete action constitute a medium- and long-term voltage trajectory. 2.如权利要求1所述的电力系统中长期电压计算方法，其特征在于，所述中长期准稳态模型如下：2. The method for calculating medium- and long-term voltage in an electric power system according to claim 1, wherein the medium- and long-term quasi-steady-state model is as follows: 其中，x为电力系统中快动态元件的状态变量，y为电力系统中的代数变量，zc为电力系统中慢动态元件的状态变量，zd为电力系统中离散动作的状态变量，p为电力系统的中长期可变参数，f表示描述快动态元件的微分方程的平衡形式；g表示以电力系统网络方程为主的代数方程；hc表示描述慢动态元件的微分方程；hd表示描述离散动作发生过程的离散方程；x-为离散动作发生的前一个时刻的电力系统中快动态元件的状态变量；y-为离散动作发生的前一个时刻的电力系统中的代数变量；为离散动作发生的前一个时刻的电力系统中慢动态元件的状态变量；为离散动作发生的前一个时刻的电力系统中离散动作的状态变量。Among them, x is the state variable of the fast dynamic element in the power system, y is the algebraic variable in the power system, zc is the state variable of the slow dynamic element in the power system, zd is the state variable of the discrete action in the power system, p is the medium- and long-term variable parameter of the power system, f represents the equilibrium form of the differential equation describing the fast dynamic element; g represents the algebraic equation based on the power system network equation; hc represents the differential equation describing the slow dynamic element; hd represents the discrete equation describing the process of discrete action; x - is the state variable of the fast dynamic element in the power system at the moment before the discrete action occurs; y - is the algebraic variable in the power system at the moment before the discrete action occurs; is the state variable of the slow dynamic element in the power system at the moment before the discrete action occurs; It is the state variable of the discrete action in the power system at the moment before the discrete action occurs. 3.如权利要求1所述的电力系统中长期电压计算方法，其特征在于，所述快动态元件的状态变量包括：发电机转速、励磁绕组磁链和功角。3. The method for calculating medium- and long-term voltage in an electric power system according to claim 1, wherein the state variables of the fast dynamic element include: generator speed, field winding flux and power angle. 4.如权利要求1所述的电力系统中长期电压计算方法，其特征在于，所述电力系统的代数变量包括：电力系统的节点电压、电力系统的节点电流、发电机组的输入功率和发电机组的输出功率。4. The method for calculating medium- and long-term voltage in an electric power system as claimed in claim 1, wherein the algebraic variables of the electric power system include: node voltages of the electric power system, node currents of the electric power system, input power of the generator set and output power of the generator set. 5.如权利要求1所述的电力系统中长期电压计算方法，其特征在于，所述慢动态元件的状态变量包括：自恢复负荷的恢复量和过励限制器的无功限制量。5. The method for calculating medium- and long-term voltage in an electric power system according to claim 1, wherein the state variables of the slow dynamic element include: the recovery amount of the self-recovering load and the reactive power limit amount of the overexcitation limiter. 6.如权利要求1所述的电力系统中长期电压计算方法，其特征在于，所述离散动作的状态变量包括：有载调压变压器动作和过励限制器动作。6. The method for calculating medium- and long-term voltage in an electric power system according to claim 1, wherein the state variables of the discrete actions include: on-load tap-changing transformer action and overexcitation limiter action. 7.如权利要求1所述的电力系统中长期电压计算方法，其特征在于，所述可变参数包括：切负荷时间和切负荷量。7 . The method for calculating long-term voltage in an electric power system according to claim 1 , wherein the variable parameters include: load shedding time and load shedding amount. 8.如权利要求2所述的电力系统中长期电压计算方法，其特征在于，采用配点法逼近可变参数影响的模型曲线，以得到逼近电压轨迹的方法包括：8. The method for calculating medium- and long-term voltage in an electric power system according to claim 2, wherein the method of using the collocation method to approximate the model curve affected by the variable parameters to obtain the approximate voltage trajectory comprises: 其中：v(t；p)代表变量x和y紧凑形式下的仿真电压轨迹；为逼近电压轨迹，φk(p)为多项式逼近的基函数，Nb为多项式逼近的基函数的个数，为基函数的系数，t为时间。Where: v(t; p) represents the simulated voltage trajectory in compact form of variables x and y; is the approximation voltage trajectory, φ k (p) is the basis function of the polynomial approximation, N b is the number of basis functions of the polynomial approximation, are the coefficients of the basis function and t is the time. 9.如权利要求2所述的电力系统中长期电压计算方法，其特征在于，得到第一电压导数的方法包括：9. The method for calculating medium- and long-term voltage in a power system according to claim 2, wherein the method for obtaining the first voltage derivative comprises: 其中：为第一电压，为第一电压导数，为中长期离散动作事件发生时刻点后一个Δt时刻的电压，Δt为数值仿真的步长。in: is the first voltage, is the first voltage derivative, The time point at which medium- to long-term discrete action events occur The voltage at the next moment Δt, where Δt is the step size of the numerical simulation. 10.如权利要求9所述的电力系统中长期电压计算方法，其特征在于，得到第二电压导数的方法包括：10. The method for calculating medium- and long-term voltage in a power system according to claim 9, wherein the method for obtaining the second voltage derivative comprises: 其中：为第二电压，为第二电压导数，为中长期离散动作事件发生时刻点前一个Δt时刻的电压，Δt为数值仿真的步长。in: is the second voltage, is the second voltage derivative, The time point at which medium- to long-term discrete action events occur The voltage at the previous time Δt, where Δt is the step size of the numerical simulation. 11.如权利要求10所述的电力系统中长期电压计算方法，其特征在于，根据所述第一电压、第二电压、第一电压导数和第二电压导数获取电压多项式函数的方法包括：11. The method for calculating medium- and long-term voltage in an electric power system according to claim 10, wherein the method for obtaining a voltage polynomial function according to the first voltage, the second voltage, the first voltage derivative and the second voltage derivative comprises: 其中：Gθ(t；p)为第一离散动作和第二离散动作之间的电压轨迹多项式；θ0(p)、θ1(p)、θ2(p)和θ3(p)为多项式的系数项。Wherein: G θ (t; p) is the voltage trajectory polynomial between the first discrete action and the second discrete action; θ 0 (p), θ 1 (p), θ 2 (p) and θ 3 (p) are the coefficients of the polynomial.
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