Power system stabilizer and implementation method thereof
Technical Field
The invention relates to an implementation method and an implementation system in the field of high-voltage operation, in particular to a power system stabilizer and an implementation method thereof.
Background
The Power System Stabilizer (PSS) is an additional excitation control technique studied for suppressing low frequency oscillation. In the excitation voltage regulator, an additional signal which is ahead of the speed of a shaft is introduced to generate a positive damping torque to overcome the action of a negative damping torque generated in the original excitation voltage regulator. The method is used for improving the damping of the power system and solving the problem of low-frequency oscillation, and is one of important measures for improving the dynamic stability of the power system. It extracts signals related to the oscillations, such as the active power, the speed or the frequency of the generator, processes them and generates additional signals which are applied to the excitation regulator, so that the generator generates additional torque which damps the low-frequency oscillations.
The existing power system stabilizer PSS has played its most role, and some oscillation modes of the system require further improvement of damping. An additional damping method is therefore required. The line overvoltage is obvious when the power of the half-wavelength line fluctuates, and rapid suppression is needed. Therefore, the wide area power system stabilizer based on the power angle difference is provided, and meanwhile, the problems of signal delay and signal loss are considered.
Disclosure of Invention
In order to solve the above-mentioned deficiencies in the prior art, the present invention provides a power system stabilizer and a method for implementing the same, which solves the problem of signal transmission time lag.
The purpose of the invention is realized by adopting the following technical scheme:
in a first aspect, the present invention provides a method for implementing a power system stabilizer, the method comprising the following steps:
inputting the power angle difference of the generator as an input signal into a power system stabilizer;
processing the power angle difference signal by using a control parameter obtained by pre-calculation;
and outputting the processed signal to an excitation regulator of the generator, and outputting the processed signal after being superposed with a voltage reference point of the excitation regulator.
Further, before the inputting the power angle difference of the generator as an input signal into the power system stabilizer, the method may further include:
determining an oscillation mode needing to be suppressed and generator sets A and B generating the oscillation mode;
measuring the power angle of the generator setAAndB;
according to the power angle of the generator setAAndBdetermining a power angle difference of a generator setAB。
Further, the power angle difference at time tABThe value of (t) can be calculated according to the following formula:
AB(t)=2AB(t-τ)-AB(t-2τ);
wherein:AB(t-tau) is a power angle difference measured value at the time of t-tau; τ is the delay of the transmitted signal.
Further, before the processing the power-angle difference signal by using the pre-calculated control parameter, the method may further include:
determining a residue R of an oscillation mode needing to be suppressed;
and calculating a control parameter according to the residue R.
Further, the calculating the control parameter according to the residue R may specifically be calculated by using the following formula:
T2=T4=αT1;
wherein,for phases requiring replenishment, T1、T2、T3、T4Is a parameter of a lead-lag element of a wide area power system stabilizer, fiIndicating the frequency of the oscillation mode that needs to be suppressed, α indicating the intermediate calculation result,
further, the processing the power-angle difference signal by using the pre-calculated control parameter may include:
according to the sampling time constant TrSampling the power angle difference signal;
amplifying the sampled power angle difference signal according to a parameter K for determining the size of damping generated by the stabilizer;
blocking the amplified signal;
according to the parameter T of the lead-lag link of the wide area power system stabilizer1、T2、T3、T4And performing phase compensation on the power angle difference signal after the direct blocking treatment.
In a second aspect, the present invention also provides a power system stabilizer, which may include:
the input module is used for inputting the power angle difference of the generator into the power system stabilizer as an input signal;
the processing module is used for processing the power angle difference signal by using the control parameter obtained by pre-calculation;
and the output module is used for outputting the processed signal to an excitation regulator of the generator, and the processed signal is superposed with a voltage reference point of the excitation regulator and then output.
Further, the power system stabilizer may further include:
a power angle difference calculation module, configured to determine an oscillation mode that needs to be suppressed and generator sets a and B that generate the oscillation mode before inputting the power angle difference of the generator as an input signal to a power system stabilizer, and measure a power angle of the generator setAAndBaccording to the power angle of the generator setAAndBdetermining a power angle difference of a generator setAB。
Further, the power system stabilizer may further include:
and the control parameter calculation module is used for determining a residue R of the oscillation mode needing to be suppressed before the power angle difference signal is processed by using the pre-calculated control parameter, and calculating the control parameter according to the residue R.
Further, the processing module may include:
a sampling unit for sampling time constant TrSampling the power angle difference signal;
the amplifying unit is used for amplifying the sampled power angle difference signal according to a parameter K for determining the damping generated by the stabilizer;
the blocking unit is used for blocking the amplified signal;
a first lead-lag unit for determining a lead-lag link parameter T according to the wide area power system stabilizer1、T2Performing first phase compensation on the power angle difference signal output by the previous unit;
a second lead-lag unit for determining a lead-lag link parameter T according to the wide area power system stabilizer3、T4And performing second phase compensation on the power angle difference signal output by the last unit.
Compared with the closest prior art, the technical scheme provided by the invention has the beneficial effects that:
the power system stabilizer and the implementation method thereof provided by the invention adopt a wide-area signal of the power angle difference of the generator as an input signal of the power system stabilizer, process the power angle difference signal by utilizing a control parameter obtained by pre-calculation, and superpose the power angle difference signal on a voltage reference point of the excitation regulator of the generator after passing through the wide-area power system stabilizer and a reference voltage, thereby realizing the function of the power system stabilizer.
Drawings
Fig. 1 is a flowchart of a method for implementing a wide area power system stabilizer according to a first embodiment of the present invention;
fig. 2 is a schematic diagram of a model structure of a wide area power system stabilizer according to a second embodiment of the present invention;
fig. 3 is a schematic structural diagram of a wide area power system stabilizer according to a second embodiment of the present invention.
Detailed Description
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
The following description and the drawings sufficiently illustrate specific embodiments of the invention to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. The examples merely typify possible variations. Individual components and functions are optional unless explicitly required, and the sequence of operations may vary. Portions and features of some embodiments may be included in or substituted for those of others. The scope of embodiments of the invention encompasses the full ambit of the claims, as well as all available equivalents of the claims. Embodiments of the invention may be referred to herein, individually or collectively, by the term "invention" merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept if more than one is in fact disclosed.
The Prony algorithm is a method for fitting the equidistant sampling data by using a linear combination of a group of exponential terms so as to analyze the information of amplitude, phase, damping factor, frequency and the like of a signal.
The WAMS (Wide Area monitoring System) adopts a synchronous phase angle Measurement technology, and realizes real-time high-speed acquisition of a whole network synchronous phase angle and main data of a power grid by gradually arranging synchronous phase angle Measurement units (PMUs) of key Measurement points of the whole network.
The first embodiment,
The invention provides a method for realizing a wide area power system stabilizer by taking the power angle difference of a generator as an input signal, which solves the problem that the operation of the stabilizer is influenced by signal time lag and realizes the feasibility of engineering application of the wide area power system stabilizer.
The details will be described below.
Firstly, the embodiment of the invention can select the oscillation mode to be suppressed and install the unit of the wide area power system stabilizer through the off-line simulation calculation of the power grid. And performing disturbance test near the selected unit to obtain a unit power angle difference curve, and then combining a Prony algorithm to obtain the residue of the oscillation mode, and finally obtaining the control parameters of the wide area power system stabilizer. The time delay corresponding to the signal transmission of the WAMS system is obtained by adopting a linear interpolation algorithm, so that the real-time performance of the signal is ensured, and the working reliability of the wide area power system stabilizer is ensured.
Fig. 1 shows a flow chart of a method for implementing a power system stabilizer in an embodiment of the present invention, where the method may include the following steps:
step 101, inputting a power angle difference of a generator as an input signal into a power system stabilizer;
102, processing the power angle difference signal by using a control parameter obtained by pre-calculation;
and 103, outputting the processed signal to an excitation regulator of the generator, and outputting the processed signal after being superposed with a voltage reference point of the excitation regulator.
In order to implement a wide area power system stabilizer and solve the problem of signal transmission time lag, the embodiment of the invention provides an implementation method of the wide area power system stabilizer using the power angle difference of a generator as an input signal, the method solves the problem that the signal time lag influences the operation of the stabilizer, and the feasibility of the engineering application of the wide area power system stabilizer is realized.
In an implementation, before the inputting the power angle difference of the generator as an input signal into the power system stabilizer, the method may further include: and determining the power angle difference of the generator set.
The determining the power angle difference of the generator set specifically may include the following steps:
determining an oscillation mode needing to be suppressed and generator sets A and B generating the oscillation mode;
measuring the power angle of the generator setAAndB;
according to the power angle of the generator setAAndBdetermining a power angle difference of a generator setAB。
In implementation, the power angle difference of the two unitsABCan be as follows:AB=A-B。
since the delay τ of the WAMS system transmission signal is not a constant, in order to further solve the delay problem, the embodiment of the present invention may also be implemented in the following manner.
Power angle difference at time tABThe value of (t) can be calculated according to the following formula:
AB(t)=2AB(t-τ)-AB(t-2τ);
wherein:AB(t-tau) is a power angle difference measured value at the time of t-tau; τ is the delay of the transmitted signal.
In an implementation, before the processing the power-angle difference signal by using the pre-calculated control parameter, the method may further include:
determining a residue R of an oscillation mode needing to be suppressed;
and calculating a control parameter according to the residue R.
In specific implementation, the embodiment of the invention can obtain a power angle difference change curve between two sets of modules by utilizing voltage steps at the generator terminal of off-line simulation, and confirms the residue R of the oscillation mode needing to be suppressed by combining a Prony identification method.
In an implementation, the calculating the control parameter according to the residue R may specifically be calculated by using the following formula:
T2=T4=αT1;
wherein,for phases requiring replenishment, T1、T2、T3、T4Is a parameter of a lead-lag element of a wide area power system stabilizer, fiIndicating the frequency of the oscillation mode that needs to be suppressed, α indicating the intermediate calculation result,
in an implementation, the processing the power-angle difference signal by using the pre-calculated control parameter may include:
according to the sampling time constant TrSampling the power angle difference signal;
amplifying the sampled power angle difference signal according to a parameter K for determining the size of damping generated by the stabilizer;
according to the parameter T of the lead-lag link of the wide area power system stabilizer1、T2、T3、T4And carrying out phase compensation on the amplified power angle difference signal.
In a specific implementation, the processing of the power-angle difference signal in the embodiment of the present invention may include a sampling link, an amplifying link, and two lead-lag links.
According to the implementation method of the power system stabilizer provided by the embodiment of the invention, the wide-area signal of the power angle difference of the generator is used as the input signal of the power system stabilizer, the power angle difference signal is processed by using the pre-calculated control parameter, and the power angle difference signal is superposed on the voltage reference point of the excitation regulator of the generator after passing through the wide-area power system stabilizer and superposed with the reference voltage, so that the function of the power system stabilizer is realized.
Example II,
The method provided by the embodiment of the invention can comprise the following steps:
1) determining parameters of a wide area power system stabilizer and solving a signal delay problem, and calculating a unit needing to install the wide area power system stabilizer according to an offline manner;
2) confirming the residue of the oscillation mode needing to be suppressed through an online test;
3) further, parameters of a wide area power system stabilizer are obtained;
4) constructing a model of a wide area power system stabilizer;
5) and determining control parameters of a wide area power system stabilizer model, and finally superimposing the power angle difference signal on a voltage reference point of the excitation regulator of the generator after passing through the wide area power system stabilizer, thereby realizing the function of the power system stabilizer.
Wherein: in step 1), firstly, determining an oscillation mode to be suppressed and two relative units A and B related to the oscillation mode according to off-line calculation of a power grid, and measuring power angles of the two units by using a WAMS (wide area measurement system)AAndB。
wherein: in step 2), determining the power angle difference between the two units A and BAB(t) is:
AB(t)=A(t)-B(t) (1)
applying disturbance to the generator excitation system, and utilizing the power angle change curve between the two units recorded by the WAMSA(t)、B(t), further obtaining a power angle difference curve;
wherein:AandBrespectively representing the power angles of the two units A and B measured by using a wide area monitoring system WAMS; t represents time.
Wherein: and 3) in step 3), confirming the residue R of the oscillation mode needing to be inhibited by combining a Prony identification method.
Confirming the residue R of the oscillation mode to be inhibited by combining a Prony identification method;
the input and output of a linear time-invariant system are subjected to Laplace transform, and then the model is as follows:
Y(s)=G(s)*I(s) (2)
in the formula: i(s), Y(s), G(s) are Laplace transformations of input, output and transfer functions of the power system, respectively;
the output signal Y(s) in the power system is decomposed into the sum of a plurality of modes; the traditional Prony algorithm only analyzes the output signal and does not consider the influence of the input signal, so that G(s) cannot be directly taken. Since the modality obtained by analyzing y(s) includes both the modality of the system itself and the modality caused by the input signal, and the number of modalities included in a specific input and output signal is determined, an accurate system transfer function can be obtained if the specific form of the input signal is known.
Let the transfer function of the power system be:
in the formula: lambda [ alpha ]iIs a pole, RiIs the residue;
let I(s) be a delay factor c of finite termi(i-0, 1,2,3 … k) and the same number of characteristic values Dj(j ═ 0,1,2,3 … k) and is expressed as:
when considering the contribution of the input signal i(s), the output y(s) of the system contains the mode caused by the input signal and the inherent mode of the system:
the formula (5) can be converted into:
in the formula:
performing inverse laplace transform on y(s), then:
if t ≧ DkThen the formula (8) is changed to
In the formula D0=0。
Prony analysis cannot be performed directly on formula (9) since t must be greater than the maximum delay factor DKThus, let τ be t-DkThen, it becomes:
substituting equation (11) into (7) yields the residue of the transfer function as:
b in the formula (12)jAnd λjCan be obtained by performing Prony analysis on (9), ci,DiAnd λn+1May be derived from the input. Therefore, if the input in the form of the formula (4) is applied to an excitation system, the transfer function of the system can be obtained by analyzing the power angle difference curve Prony of the unit. And selecting a characteristic value needing attention in the transfer function, and designing a model parameter according to a residue corresponding to the characteristic value.
Fig. 2 is a schematic diagram illustrating a model structure of a power system stabilizer in an embodiment of the present invention, and as shown in fig. 2, a signal processing process may include: a sampling link, an amplifying link, a blocking link and two lead-lag links. The letter s in fig. 2 denotes a complex parameter, and Tw denotes an amplification element time constant.
The control parameters of the model can be calculated by the residue R of the dominant pattern identified:
T2=T4=αT1(16)
the value of K determines the amount of damping generated by the wide area power system stabilizer, and ideally this gain is set at a value corresponding to the maximum damping, typically determined by field testing. T isrThe time constant of the sampling element is usually 0.02 s.
For phases that need to be supplemented α is the intermediate calculation result, T1、T2、T3、T4Is a parameter of a lead-lag element of a wide area power system stabilizer, fiIndicating the frequency of the oscillation mode that needs to be suppressed. R is the residue of the oscillation mode to be suppressed;
wherein: and 5) determining control parameters of a wide area power system stabilizer model, and determining a power angle difference corresponding to the time delay of the WAMS transmission signal of the wide area monitoring system.
Because the time delay tau of the WAMS system transmission signal is not a constant, a linear interpolation method can be adopted to solve the time delay problem.
Using Kalman filtering to correct power angle difference signalAB(t) processing the processed value as an input to a wide area power system stabilizer. Therefore, the problems of time delay and measurement errors of the WAMS transmission signals of the wide area monitoring system can be solved.
The kalman filtering rationale is as follows:
the system equation: x (k) ═ X (k-1) + B ═ u (k) + w (k) (17)
And adding the measured value equation of the system:
Z(k)=H*X(k)+V(k) (18)
in the above two equations, x (k) is the system state at time k, and u (k) is the control amount of the system at time k. A and B are system parameters, and for multi-model systems, they are matrices. Z (k) is the measured value at time k, H is a parameter of the measurement system, and H is a matrix for a multi-measurement system. W (k) and v (k) represent process and measured Noise, respectively, and embodiments of the present invention assume that the Noise is White Gaussian Noise (White Gaussian Noise) and their covariances (covariance) are Q, R, respectively (embodiments of the present invention assume Q, R does not change with system state changes).
Assuming that the present system state is k, according to the model of the system, the present state can be predicted based on the last state of the system:
X(k|k-1)=A*X(k-1|k-1)+B*U(k) (19)
in the equation (19), X (k | k-1) is the result predicted by the previous state, X (k-1| k-1) is the optimum result of the previous state, and U (k) is the control amount of the current state, which may be 0 if there is no control amount.
Covariance (covariance) is denoted by P:
P(k|k-1)=A*P(k-1|k-1)*A‘+Q (20)
p (k | k-1) is the covariance of X (k | k-1), P (k-1| k-1) is the covariance of X (k-1| k-1), A' represents the transpose of A, and Q is the covariance of the system process. Equations (19) and (20) are the first two of the 5 equations of the kalman filter, i.e., the prediction of the system.
Combining the predicted values and the measured values, an optimized estimated value X (k | k) of the current state (k) can be obtained:
X(k|k)=X(k|k-1)+Kg(k)*(Z(k)-H*X(k|k-1)) (21)
where Kg is Kalman Gain (Kalman Gain):
Kg(k)=P(k|k-1)H’/(H*P(k|k-1)H’+R) (22)
in order to make the kalman filter continuously operate until the system process is finished, the embodiment of the present invention may further update the covariance of X (k | k) at time k:
P(k|k)=(I-Kg(k)*H)*P(k|k-1) (23)
equations (19) - (23) are basic equations of kalman filtering, which can be used for prediction at the next time while reducing the measurement noise effect.
For application in the present application, when a wide area power system stabilizer is launched, the flag k may be 1, and the input for stabilizing the power system may be X (0|0), and X (0|0) ═ may be X (0|0)AB(0) P (0|0) ═ 0, a ═ 1, B ═ 0, and H ═ 1, and since there is no control amount, u (k) ═ 0. Z (k) ═ zAB(k) Q and R can be obtained through field test and check. Therefore, the Kalman filtering equation can start to circulate, and the input signal of the wide area power system stabilizer is ensured.
Example III,
Based on the same inventive concept, the invention also provides a power system stabilizer, and as the principle of solving the problems of the equipment is similar to the implementation method of the power system stabilizer, the implementation of the equipment can refer to the implementation of the method, and repeated parts are not described again.
Fig. 3 shows a schematic structural diagram of a power system stabilizer in an embodiment of the present invention, and as shown in fig. 3, the power system stabilizer may include:
an input module 301, configured to input a power angle difference of a generator as an input signal to a power system stabilizer;
a processing module 302, configured to process the power-angle difference signal by using a pre-calculated control parameter;
the output module 303 is configured to output the processed signal to an excitation regulator of the generator, where the processed signal is output after being superimposed with a voltage reference point of the excitation regulator.
In an implementation, the power system stabilizer may further include:
a power angle difference calculation module, configured to determine an oscillation mode that needs to be suppressed and generator sets a and B that generate the oscillation mode before inputting the power angle difference of the generator as an input signal to a power system stabilizer, and measure a power angle of the generator setAAndBaccording to the power angle of the generator setAAndBdetermining a power angle difference of a generator setAB。
In an implementation, the power system stabilizer may further include:
and the control parameter calculation module is used for determining a residue R of the oscillation mode needing to be suppressed before the power angle difference signal is processed by using the pre-calculated control parameter, and calculating the control parameter according to the residue R.
In an implementation, the processing module may include:
a sampling unit for sampling time constant TrSampling the power angle difference signal;
the amplifying unit is used for amplifying the sampled power angle difference signal according to a parameter K for determining the damping generated by the stabilizer;
the blocking unit is used for blocking the amplified signal;
a first lead-lag unit for determining a lead-lag link parameter T according to the wide area power system stabilizer1、T2Performing first phase compensation on the power angle difference signal output by the previous unit;
a second lead-lag unit for determining a lead-lag link parameter T according to the wide area power system stabilizer3、T4And performing second phase compensation on the power angle difference signal output by the last unit.
For convenience of description, each part of the above-described apparatus is separately described as being functionally divided into various modules or units. Of course, the functionality of the various modules or units may be implemented in the same one or more pieces of software or hardware when implementing the present application.
1. The current generator sets in the system are widely deployed with PSS, but as the ac grid size increases, the oscillation modes in certain cases require further improved damping, for example: the oscillation damping needs to be further enhanced for the half-wave line due to the shorter equivalent length of the line. Therefore, the invention provides a power system stabilizer based on a wide-area measurement signal and an implementation method thereof, which increase the system damping, combine the characteristic of slow change of a power angle difference signal and take the power angle difference signal as input; meanwhile, by utilizing the characteristics that Kalman filtering can not only filter but also predict, the problems of wide area measurement signal delay and measurement error are solved, and the normal work of a wide area power system stabilizer is ensured.
2. Because the Kalman filtering algorithm adopts a recursion mode, the method is particularly convenient for program realization, has high calculation speed and is suitable for engineering application.
3. According to the implementation method of the power system stabilizer and the power system stabilizer, the wide area signal is used as the input signal, so that oscillation can be effectively inhibited, the problems of determination of parameters of the wide area power system stabilizer, signal delay and loss are solved, and the feasibility of engineering application of the wide area power system stabilizer is realized.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can make modifications and equivalents to the embodiments of the present invention without departing from the spirit and scope of the present invention, which is set forth in the claims of the present application.