CN110571830A - emergency control method and device for externally-hung power system stabilizer - Google Patents
emergency control method and device for externally-hung power system stabilizer Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract
The invention relates to an emergency control method for an externally-hung power system stabilizer, which comprises the following steps that an edge computing processor obtains a sampling value of active power of a generator through a signal sampling module; the method comprises the steps that an edge computing processor identifies low-frequency oscillation frequency, damping and damping ratio of an oscillation mode of a current power system on line according to acquired active power of a generator, emergency control condition judgment is carried out through the damping and damping ratio, when the emergency control condition is met, measures are taken, namely, a control switch is driven to be switched to a PSS emergency control output channel, meanwhile, the edge computing processor reads a latest minimum interference stability scanning computing result computed and stored by a regulation cloud platform in real time to serve as an input parameter, the emergency control parameter of the PSS emergency control output channel is set in real time through edge computing, and the set emergency control parameter covers the original emergency control parameter. The invention provides damping support for the power system in an emergency state, and enhances the adaptability of the PSS and the stability of the power system.
Description
Technical Field
The invention belongs to the technical field of safety and stability control of an electric power system, particularly belongs to the technical field of dynamic safety and stability control of the electric power system, and particularly relates to an emergency control method and device for an externally-hung electric power system stabilizer.
Background
in recent years, with the large-scale construction of extra-high voltage alternating current and direct current transmission and transformation projects and the grid-connected operation of large-scale new energy power generation, the structure and trend of an original power grid are changed to a great extent, the connection of regional power grids is tighter, the dynamic characteristics of the regional power grids are also changed greatly, in addition, the development of the regional power grids, the construction of power supplies and the increase of load levels, a large number of important power transmission sections even have power flow reversal, great influence is generated on the dynamic characteristics of the power grids, a plurality of new small-interference stable oscillation modes appear among a plurality of regional power grids, and the dynamic stability characteristics of the power grids are influenced seriously. In addition, due to the adoption of the large-scale new energy power generation grid-connected converter and the flexible power transmission equipment, the power grid gradually presents the characteristic of power electronization, the rotational inertia of a power system and the capability of the system for resisting oscillation are reduced, and the dynamic stability of the power system is subjected to unprecedented tests. In the face of such a power grid operation environment, a local small disturbance or abnormal operation may cause a wide-range chain reaction of the power grid. Meanwhile, long-distance and large-capacity power transmission and the use of a large unit high-speed excitation device can deteriorate the damping of a system in a certain operation mode, so that the low-frequency oscillation phenomenon of a power system occurs, and the low-frequency oscillation phenomenon becomes one of bottlenecks limiting the transmission capability of a power grid. The effective suppression of the low-frequency oscillation of the power system not only can increase the transmission capacity of a line, but also has an important effect on improving the stability level of the whole system.
The Power System Stabilizer (PSS) is the most effective and most economical device for damping low-frequency oscillation at present, the PSS is installed on a generator set in a network, so that the local low-frequency oscillation of a power system can be damped, and the low-frequency oscillation among power networks in different areas can also be damped, however, the power system interconnection and the large operation of a quick excitation system continuously reduce the damping level and the frequency of the low-frequency oscillation, the traditional PSS2B type power system stabilizer is essentially used for inhibiting the local low-frequency oscillation of 0.2-2 Hz, once the design of a related controller is finished and the related controller is put into use, the parameters of the related controller are fixed and are limited by high-frequency-band critical gain, the PSS2B is difficult to meet the requirement of low-frequency-band gain, and the development requirement of the power networks cannot; although the novel power system stabilizer of the PSS4B type has good suppression capability in a low frequency band, the problems that the phase relation of the PSS4B is difficult to calculate, the parameters are difficult to set and the like are caused by a double-variable input and multi-branch parallel structure mode. The prior art mainly includes the following steps: firstly, an original PSS2B model power system stabilizer is improved to improve the phase compensation capability of a PSS low frequency band, but all the methods have too high requirements on models or too complex control algorithms and are difficult to popularize and apply in power systems; secondly, the novel PSS4B power system stabilizer is improved, but the problem that PSS4B parameters are difficult to adjust still exists.
the existing power system stabilizer can not adapt to the change of different operation modes of a power grid, and can not provide damping support in the emergency situation of the power grid. In addition, for safety and stability considerations and risk concerns, the power generation unit and the power system dynamic stability control supervision mechanism are relatively objected to the adoption of the novel power system stabilizer, so that a new method and a new device capable of providing damping support for the system in a power grid emergency situation are designed, and the approval of the power generation unit is firstly obtained or the normal operation of the existing power system stabilizer is not influenced.
Disclosure of Invention
The invention aims to provide an emergency control method and device for an externally-hung power system stabilizer.
The invention adopts the following technical scheme:
An emergency control method for an externally-hung power system stabilizer comprises the following steps:
The edge calculation processor obtains a sampling value of the active power of the generator through the signal sampling module;
The edge calculation processor identifies the low-frequency oscillation frequency, the damping and the damping ratio of the oscillation mode of the current power system on line by using an improved Prony analysis method according to the acquired active power of the generator, judges the emergency control condition through the damping and the damping ratio, takes the emergency control measure when the emergency control condition is met, the emergency control measure comprises the steps of driving a selection control switch to be switched to a PSS emergency control output channel, simultaneously, the edge calculation processor reads the latest small-interference stable scanning calculation result calculated and stored by a regulation cloud platform in real time to serve as an input parameter, carries out instant setting on the emergency control parameter of the PSS emergency control output channel by adopting edge calculation, and covers the original emergency control parameter by adopting the emergency control parameter after the instant setting.
further, the improved Prony analysis method is that on the basis of the original Prony analysis method, the average value is calculated for the sampling values of the active power of the generator.
Further, the obtained sampling value of the active power of the generator is the sampling value of the active power of all generators outside the fault-free unit.
Further, the initial value of the emergency control parameter of the PSS emergency control output channel is the PSS parameter setting value in the power grid dead-large mode.
Further, the small-interference stable scanning calculation result calculated and stored by the cloud platform is regulated and controlled to include all characteristic roots, oscillation frequency, damping and damping ratio existing in the oscillation mode of the power system. The specific characteristic root and damping ratio calculation process is as follows:
The calculation process of all characteristic roots, oscillation frequencies and damping ratios existing in the current power system is as follows:
Establishing a nonlinear state equation model of the power system, and linearizing at a balance point of the power system to obtain a linearized state equation of the power system as shown in formula (1):
In the formula (1), X is a state vector in the incremental form of the power system, and A is a coefficient matrix of the power system; according to the stability theory of ordinary differential equation, the corresponding characteristic equation of the power system is shown in formula (2):
|λI-A|＝0 (2)
All the characteristic roots lambda can be obtained by solving the formula (2)1,λ2,,λNWherein, one pair of conjugate compound roots is shown as formula (3):
λi,j＝α±jω (3)
in the formula (3), α represents a real part, ω represents an angular frequency, and the oscillation frequency of the oscillation mode corresponding to the conjugate complex root is obtained from the formula (3)damping ratio of
Defining a feature root λiThe corresponding right eigenvector is uiSatisfying the following formula (4):
Aui＝λiui(i＝1,2,...N) (4)
Then, a right eigenvector matrix U corresponding to the power system characteristic root is as shown in formula (5):
U＝[u1,u2,...uN] (5)
Defining a feature root λiCorresponding left feature vector is viSatisfying the following formula (6):
In formula (6), Λ ═ diag (λ)1,λ2,...,λN) Then, the left feature vector V corresponding to the system feature root is as shown in formula (7):
V＝[v1,v2,...,vN] (7)
Calculating k state variable X of degree through left and right eigenvectorskThe same ith characteristic root lambdaiOf controllable observability, i.e. the correlation factor pkithe expression is shown as (8):
wherein v iskiIs an element of the left eigenvector matrix, ukiIs the element of the right eigenvector matrix.
further, according to the obtained active power of the generator, a modified Prony analysis method is used for identifying the low-frequency oscillation frequency and the damping ratio of the current power system on line, and the specific process is as follows:
Selecting sampling values of active power signals of all generators except for the fault unit to carry out average value calculation, and recording the nth sampling point of the active power signal of the kth group of generators as xk(N), where N is 1,2, …, N-1, the sampled signal of the genset can be fitted using a linear combination of P exponential functions:
in the formula (9), m represents the number of the exponential function; a. themRepresenting the amplitude of the generator active power signal; thetamrepresenting the phase of the generator active power signal; a ismAn attenuation factor representing the generator active power signal; f. ofmAn oscillation frequency representing an active power signal of the generator; Δ t represents a sampling time interval for obtaining the active power of the generator;
after sampling signals of M groups of generator sets are obtained, calculating the average value of the sampling signals as follows:
Constructing a sample function matrix as follows:
In the formula (11), the reaction mixture is,representing a sample function; pmIs an estimate of the order of the algorithm and has Pm＞P,1≤i≤Pm,0≤j≤Pm；
Determining the effective rank P and parameter a of a sample function matrix using singular value decomposition and least squaresiThe method comprises the following steps:
root the equation (12) and recur the approximate value of the kth genset signal
And is provided with
The parameter b is obtained by the formula (14)k，bkis a column vector:
wherein, bkiFor the ith of the kth group of genset signalsa component;
Then, the amplitude A of each signal is calculatedkiPhase thetakiAttenuation factor aiAnd frequency fiThe following formula (15):
And obtaining the low-frequency oscillation frequency of the current electric power system oscillation mode, so that corresponding damping and damping ratio can be identified according to the small-interference stable calculation result of the dispatching cloud platform.
An emergency control device for an external power system stabilizer comprises a PSS emergency control output channel, an edge calculation processor, a memory, a selection control switch and a signal sampling module, wherein the PSS emergency control output channel is arranged in parallel with an original PSS output channel in operation; the PSS emergency control output channel has the same structure as the original PSS output channel; the edge computing processor is provided with a port which is in real-time communication with the regulation cloud platform; the edge calculation processor is in communication connection with a corresponding port of the signal sampling module, and the memory is respectively and electrically connected with the edge calculation processor and the signal sampling module; and the controlled end of the selection control switch is in communication connection with the output end of the edge calculation processor, and the output port of the selection control switch is respectively connected with the PSS emergency control output channel and the original PSS output channel.
Further, the signal sampling module comprises an A/D converter connected with the edge calculation processor through a bus, and the A/D converter is used for carrying out signal sampling on the active power of the generator.
Further, the edge calculation processor is used for controlling the signal sampling module to sample the active power of the generator according to the sampling period.
Further, the edge calculation processor is used for identifying the low-frequency oscillation frequency, the damping and the damping ratio of the oscillation mode of the current power system on line according to the active power of the generator by using a modified Prony analysis method.
because the Prony analysis method is used for identifying the low-frequency oscillation frequency on line and the requirement of the damping ratio on noise is higher, the active power signal of the generator needs to be preprocessed, and therefore, the signal sampling module further comprises a digital filter which is used for filtering high-frequency stray signals in the active power signal of the generator. Similarly, the Prony analysis method is sensitive to noise signals, and when the low-frequency oscillation frequency and the damping ratio of the current power system are identified on line, a large error is generated if a single input signal is used for oscillation mode identification, so that the Prony analysis method is improved in that after a digital filter is adopted to filter high-frequency stray signals, a direct-current component is removed by using an averaging method, namely, the signals of the same type are averaged, so that the signals complement each other, and the identification accuracy is improved.
meanwhile, the accuracy of the algorithm can be improved by selecting the sample function matrix order of a proper Prony analysis method.
further, the edge computing processor judges whether an emergency control condition is met according to the damping and the damping ratio of the current power system oscillation mode, if so, an emergency control measure is taken, the emergency control measure comprises that the edge computing processor drives a selection control switch to switch between a PSS emergency control output channel and an original PSS output channel, the edge computing processor reads a latest small-interference stable scanning calculation result of a regulation cloud platform in real time to serve as an input parameter, the edge computing is adopted to carry out instant setting on the emergency control parameter of the PSS emergency control output channel, and the instant-set emergency control parameter is adopted to cover the original emergency control parameter.
further, the two emergency control measures are performed simultaneously.
Furthermore, the memory is used for storing a sampling value of the signal sampling module, a PSS parameter setting program, a PSS parameter setting result and a regulation cloud platform small-interference stable scanning calculation result.
furthermore, the output port of the selection control switch is divided into a main port and a standby port, the original PSS output channel is accessed to the main port of the selection control switch, and the PSS emergency control output channel is accessed to the standby port of the selection control switch.
And further, the port which is communicated with the regulation cloud platform in real time is used for receiving the small-interference stable scanning calculation result of the regulation cloud platform in real time.
the invention has the following beneficial effects:
the invention is suitable for the influence of various factors such as load change of a power grid, structural change, variable operation modes, reduction of rotational inertia caused by power electronization and the like on phase-frequency characteristics and system disturbance under the background of extra-high voltage alternating current and direct current networking and large-scale new energy grid connection, and the situation that the dynamic characteristics of the power grid are deteriorated can cause low-frequency oscillation of the power grid. By designing the emergency control method and device for the externally-hung type power system stabilizer, the damping support in an emergency state is provided for the power system under the condition that the normal operation of the PSS of the conventional unit is not influenced, and the adaptability of the PSS and the stability of the power system are enhanced.
In the invention, the parallel bypass control channel is designed on the basis of normal operation of the original PSS device, so that the externally-hung design of the PSS emergency control device is realized, and the PSS output channel switching under the emergency condition of a power grid is realized by using the selection switch.
The selection switch adopts an edge processor to perform on-line calculation and identification of the oscillation mode, and automatic selection and switching are performed by judging the characteristic root and the damping ratio.
The automatic selection switch is arranged at the front end of the original output channel, the original channel is connected to a main port of the selection switch, and the emergency control channel is connected to a standby port.
The PSS initial parameter of the emergency control output channel is set to be a PSS parameter setting value in a power grid withering mode. In the invention, the edge processor is adopted to carry out the Prony analysis and the oscillation mode identification of the generator power curve, and the strong calculation capability of the edge processor is utilized to realize the real-time edge setting of the PSS parameter and provide damping for the emergency control under the emergency condition of the power grid.
When the edge processor judges that the power grid is in an emergency state, the selection switch is synchronously driven to switch and the PSS parameter is set in real time, and the PSS initial value is refreshed by adopting the PSS real-time setting value.
In the invention, cloud and mist cooperative computing of an edge processor and a regulation cloud platform is adopted, wherein power grid small-interference stable computing which needs a large amount of computing is put on the regulation cloud platform for rapid scanning computing, and a characteristic root and a damping ratio in a scanning result are used as input parameters of an emergency control channel to carry out real-time PSS parameter setting of the local machine through the edge processor. The regulation and control cloud platform is responsible for the timed small-interference stable calculation of the regional power grid; wherein the small interference stability calculation is performed every 15 minutes.
The edge processor can read the small-interference stable calculation result of the regulation cloud platform in real time.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a control diagram of an emergency control type power system stabilizer according to the present invention.
Fig. 2 is a flowchart of an emergency control method according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail and fully with reference to the accompanying drawings 1-2 and the following detailed description.
As shown in fig. 1-2, the present embodiment relates to an emergency control method and device for an external power system stabilizer, and the inventive concept thereof is as follows:
The embodiment has a control method for providing emergency damping support for a power system in an emergency and an externally-hung portable installation control device. The low-frequency oscillation damping device can meet the low-frequency oscillation damping of the full frequency band of 0-2 Hz under the background of extra-high voltage alternating current-direct current networking and large-scale new energy access, can be installed and used in parallel under the condition that the normal operation of the existing PSS of a unit is not influenced, and is simple in structure and easy to popularize in engineering. The characteristics are as follows:
The emergency control method and device design of the externally-hung power system stabilizer are realized on a regional power grid under the background of extra-high voltage alternating current and direct current networking and large-scale new energy grid connection, and comprise an edge computing processor, a memory, a signal sampling module, a selection control switch, a real-time communication port of a regulation cloud platform and an output channel of an original PSS (power system stabilizer) in parallel operation.
the signal sampling module is provided with an A/D converter connected through a bus, and the A/D converter is used for sampling the active power of the generator.
The edge calculation processor controls the A/D converter to sample the active power of the generator in a certain sampling period, the sampled values are stored in a memory, and then the frequency and the damping ratio of the generator power are identified on line by using the improved Prony analysis by using the latest N sampled values. And the edge calculation processor judges the emergency control condition through the damping and the damping ratio of the current oscillation mode of the power system, takes emergency control measures when the emergency control condition is met, and performs instant edge setting of the PSS parameters by receiving the online small-interference stable scanning calculation result of the power dispatching cloud platform in real time.
The real-time communication with the regulation cloud platform adopts a special communication port, and the small-interference stable scanning calculation result of the regulation cloud platform can be received in real time.
the memory is used for storing a sampling value of the signal sampling module, a PSS parameter setting program, a PSS parameter setting result and a regulation cloud platform small-interference stable scanning calculation result.
The selection control switch is used for the PSS to calculate an analysis result according to the sampling signal to automatically select an output channel, and when the judgment result meets an emergency control condition, the selection control switch is switched to the PSS to emergently control the output channel path;
The selection control switch is connected in series with the front end of the original output channel, the original output channel is set as a main channel, and the selection switch is switched to the emergency control channel only when the edge calculation result meets the emergency control condition.
The PSS emergency control output channel structure is the same as the original output channel, a standby port of a selective control switch is accessed, a transfer function internal system can receive a regulation cloud platform small-interference stable scanning calculation result through an edge calculation processor, and edge real-time PSS parameter setting can be carried out.
the implementation process of this embodiment is described in detail as follows:
1. by utilizing the D5000 online safety and stability calculation function of the regulation and control cloud platform, small-interference stability calculation in a real-time mode is performed every 15 minutes, calculated results such as characteristic roots, damping ratios and the like are stored in the cloud, and the original calculation result is covered by a new calculation result every time.
The specific process is as follows: establishing a nonlinear state equation model of the power system, and performing linearization at a balance point of the power system to obtain a linearized state equation of the system, wherein the linearized state equation of the system is as follows:
in the formula (1), X is a state vector in the form of system increment, A is a coefficient matrix of the system, and the corresponding characteristic equation of the system is known from the stability theory of ordinary differential equation
|λI-A|＝0 (2)
all the characteristic roots lambda can be obtained by solving the formula (2)1,λ2,...,λNWherein a pair of conjugated complex roots is
λi,j＝α±jω (3)
The oscillation frequency of the oscillation mode corresponding to the conjugate complex root is obtained from the formula (3)Damping ratio of
defining a feature root λithe corresponding right eigenvector is uiAnd satisfies the following conditions:
Aui＝λiui(i＝1,2,...N) (4)
Then the right eigenvector matrix corresponding to the system eigenroot is
U＝[u1,u2,...uN] (5)
Defining a feature root λicorresponding left feature vector is viAnd satisfies the following conditions:
In formula (6), Λ ═ diag (λ)1,λ2,...,λN) If the left feature vector corresponding to the system feature root is:
V＝[v1,v2,...,vN] (7)
The k state variable X of the degree can be obtained through the left and right eigenvectorskThe same ith characteristic root lambdaiis a controllable observability geometric measure of (i.e. correlation factor p)ki：
2. The edge calculation processor controls the A/D converter to sample the active power of the generator at a certain sampling frequency, then the active power of the generator is analyzed by using improved Prony, the low-frequency oscillation frequency and the damping ratio of the current power system are identified on line, when the emergency control condition is met, the selection control switch is driven to be switched to an emergency control channel, meanwhile, the edge calculation processor reads the latest minimum interference stable calculation result of the regulation cloud platform in real time as an input parameter, and the edge calculation is adopted to carry out real-time setting of the PSS emergency control parameter.
The method comprises the following specific steps:
When the edge calculation processor controls the A/D converter to sample the active power of the generator, the sampling theorem needs to be satisfied, the sampling frequency needs to be more than twice of the highest frequency of a signal, a considerable margin needs to be reserved in practical application, the frequency band of interest is 0-2 Hz in the low-frequency oscillation process, and 10Hz is selected in the embodiment of the inventionsampling frequency, sampling period TsAt 0.1 second, a higher sampling frequency may result in a poor fit. In addition, the sampling time length tlGenerally, the oscillation with the lowest frequency of two cycles is included, in the low-frequency oscillation analysis, the improved Prony analysis is carried out in a time length of 10-20 seconds, and the too long time can make the fast-decaying component unrecognizable, so that the result loses important information.
After the sampling data are obtained, because a Prony analysis method used for online identification of low-frequency oscillation frequency and damping ratio has higher requirements on noise, the active power signal of the generator needs to be preprocessed. Meanwhile, the accuracy of the algorithm can be improved by selecting the proper sample function matrix order of the Prony algorithm.
when the low-frequency oscillation frequency and the damping ratio of the current power system are identified on line, the Prony algorithm is sensitive to noise signals, and a large error is generated when a single input signal is used for identifying an oscillation mode, so that the improved Prony algorithm is used, the similar signals are used for averaging, the signals are mutually supplemented, and the identification accuracy is improved.
in the specific implementation process, sampling values of active power signals of all generators except a fault unit are selected to be averaged, and the nth sampling point of the active power signal of the kth group of generators is recorded as xk(N), where N is 1,2, …, N-1, the sampled signal of the genset can be fitted using a linear combination of P exponential functions:
in the formula (9), m represents the number of the exponential function; a. themRepresenting the amplitude of the generator active power signal; thetamrepresenting the phase of the generator active power signal; a isman attenuation factor representing the generator active power signal; f. ofmAn oscillation frequency representing an active power signal of the generator; Δ t represents a sample taken of the active power of the generatora time interval;
After sampling signals of M groups of generator sets are obtained, calculating the average value of the sampling signals as follows:
Constructing a sample function matrix as follows:
In the formula (11), the reaction mixture is,representing a sample function; pmIs an estimate of the order of the algorithm and has Pm＞P,1≤i≤Pm,0≤j≤Pm；
Determining the effective rank P and parameter a of a sample function matrix using singular value decomposition and least squaresithe method comprises the following steps:
Root the equation (12) and recur the approximate value of the kth genset signal
And is provided with
The parameter b is obtained by the formula (14)k：
wherein, bkiis the kth group generatorThe ith component of the group signal;
Then, the amplitude A of each signal is calculatedkiPhase thetakiattenuation factor aiand frequency fiThe following formula (15):
and obtaining the low-frequency oscillation frequency of the current electric power system oscillation mode, so that corresponding damping and damping ratio can be identified according to the small-interference stable calculation result of the dispatching cloud platform. If the low-frequency oscillation with the damping ratio meeting the emergency control condition (less than 5 percent of the threshold value) exists, the emergency control is selected, the real-time setting of the PSS parameter is realized through edge calculation, and the setting parameter covers the original emergency control channel parameter.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. An emergency control method for an externally-hung power system stabilizer is characterized by comprising the following steps:
The edge calculation processor obtains a sampling value of the active power of the generator through the signal sampling module;
the edge calculation processor identifies the low-frequency oscillation frequency, the damping and the damping ratio of the oscillation mode of the current power system on line by using an improved Prony analysis method according to the acquired active power of the generator, judges the emergency control condition through the damping and the damping ratio, takes the emergency control measure when the emergency control condition is met, the emergency control measure comprises the steps of driving a selection control switch to be switched to a PSS emergency control output channel, simultaneously, the edge calculation processor reads the latest minimum interference stable scanning calculation result calculated and stored by a regulation cloud platform in real time to serve as an input parameter, carries out instant setting on the emergency control parameter of the PSS emergency control output channel by adopting edge calculation, and covers the original emergency control parameter by adopting the emergency control parameter after the instant setting.
2. The emergency control method for the external hanging type power system stabilizer according to claim 1, characterized in that the improved Prony analysis method is based on the original Prony analysis method, and the average value of the obtained sampling values of the generator active power is obtained.
3. the emergency control method of an external power system stabilizer according to claim 1, wherein the initial value of the emergency control parameter of the PSS emergency control output channel is the PSS parameter setting value in a dead-large format of the power grid.
4. The emergency control method of the externally-hung power system stabilizer according to claim 1, wherein the calculation result of the small interference stability scanning calculated and stored by the regulation cloud platform comprises all characteristic roots, oscillation frequencies, damping and damping ratios existing in the oscillation mode of the power system.
5. The emergency control method for the externally-hung power system stabilizer according to any one of claims 1 to 4, wherein the calculation process of all characteristic roots, oscillation frequencies and damping ratios existing in the current power system is as follows: establishing a nonlinear state equation model of the power system, and linearizing at a balance point of the power system to obtain a linearized state equation of the power system as shown in formula (1):
In the formula (1), X is a state vector in the incremental form of the power system, and A is a coefficient matrix of the power system; according to the stability theory of ordinary differential equation, the corresponding characteristic equation of the power system is shown in formula (2):
|λI-A|＝0 (2)
All the characteristic roots lambda can be obtained by solving the formula (2)1,λ2,...,λNWherein, one pair of conjugate compound roots is shown as formula (3):
λi,j＝α±jω (3)
In the formula (3), α represents a real part, ω represents an angular frequency, and the oscillation frequency of the oscillation mode corresponding to the conjugate complex root is obtained from the formula (3)Damping ratio of
Defining a feature root λiThe corresponding right eigenvector is uisatisfying the following formula (4):
Aui＝λiui(i＝1,2,...N) (4)
Then, a right eigenvector matrix U corresponding to the power system characteristic root is as shown in formula (5):
U＝[u1,u2,...uN] (5)
Defining a feature root λiCorresponding left feature vector is viSatisfying the following formula (6):
in formula (6), Λ ═ diag (λ)1,λ2,...,λN) Then, the left feature vector V corresponding to the system feature root is as shown in formula (7):
V＝[v1,v2,...,vN] (7)
calculating k state variable X of degree through left and right eigenvectorskThe same ith characteristic root lambdaiOf controllable observability, i.e. the correlation factor pkiThe expression is shown as (8):
wherein v iskiIs an element of the left eigenvector matrix, ukiIs the element of the right eigenvector matrix.
6. An emergency control method for an on-board power system stabilizer according to any one of claims 1-3, characterized in that, based on the obtained generator active power, a modified Prony analysis method is used to identify on-line the low-frequency oscillation frequency and its damping ratio existing in the current power system oscillation mode, which comprises the following steps:
selecting sampling values of active power signals of all generators except for the fault unit to carry out average value calculation, and recording the nth sampling point of the active power signal of the kth group of generators as xk(N), where N is 1,2, …, N-1, the sampled signal of the genset can be fitted using a linear combination of P exponential functions:
In the formula (9), m represents the number of the exponential function; a. themrepresenting the amplitude of the generator active power signal; thetamRepresenting the phase of the generator active power signal; a ismAn attenuation factor representing the generator active power signal; f. ofmAn oscillation frequency representing an active power signal of the generator; Δ t represents a sampling time interval for obtaining the active power of the generator;
After sampling signals of M groups of generator sets are obtained, calculating the average value of the sampling signals as follows:
Constructing a sample function matrix as follows:
In the formula (11), the reaction mixture is,Representing a sample function; pmIs an estimate of the order of the algorithm and has Pm＞P,1≤i≤Pm,0≤j≤Pm；
Determining the effective rank P and parameter a of a sample function matrix using singular value decomposition and least squaresiThe method comprises the following steps:
Root the equation (12) and recur the approximate value of the kth genset signalThe calculation formula (13) is as follows:
And is provided with
the parameter b is obtained by the formula (14)k，bkis a column vector:
Wherein, bkiIs the ith component of the kth set of genset signals;
then, the amplitude A of each signal is calculatedkiphase thetakiAttenuation factor aiAnd frequency fiThe following formula (15):
And obtaining the low-frequency oscillation frequency of the current electric power system oscillation mode, and identifying corresponding damping and damping ratio according to the small-interference stable calculation result of the dispatching cloud platform.
7. An emergency control device of an external power system stabilizer is characterized by comprising a PSS emergency control output channel, an edge calculation processor, a memory, a selection control switch and a signal sampling module, wherein the PSS emergency control output channel is arranged in parallel with an original PSS output channel in operation; the PSS emergency control output channel has the same structure as the original PSS output channel; the edge computing processor is provided with a port which is in real-time communication with the regulation cloud platform; the edge calculation processor is in communication connection with a corresponding port of the signal sampling module, and the memory is respectively and electrically connected with the edge calculation processor and the signal sampling module; and the controlled end of the selection control switch is in communication connection with the output end of the edge calculation processor, and the output port of the selection control switch is respectively connected with the PSS emergency control output channel and the original PSS output channel.
8. The on-hook power system stabilizer emergency control device according to claim 7, characterized in that the signal sampling module comprises an A/D converter connected with the edge computing processor through a bus, and the A/D converter is used for signal sampling of generator active power.
9. the on-hook power system stabilizer emergency control device according to claim 7, wherein the edge calculation processor is configured to identify the low frequency oscillation frequency, damping and damping ratio of the current power system oscillation mode on-line according to the generator active power using a modified Prony analysis method.
10. the emergency control device of an externally-hung power system stabilizer according to claim 7, wherein the edge computing processor is configured to determine whether damping and damping ratio in the current power system oscillation mode satisfy emergency control conditions, and if so, take emergency control measures, the emergency control measures including the edge computing processor driving the selection control switch to switch between the PSS emergency control output channel and the original PSS output channel, and the edge computing processor reading the latest small interference stabilization scan calculation result of the regulation cloud platform in real time as an input parameter, performing instant setting on the emergency control parameter of the PSS emergency control output channel by using edge computing, and covering the original emergency control parameter with the instant-set emergency control parameter.
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