CN110398630B - Dynamic tracking method for frequency of power system - Google Patents
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Abstract
A dynamic tracking method for power system frequency relates to the field of power system,the method comprises the following steps: firstly, sampling a voltage value of a single-phase power system at regular time to obtain a voltage sampling sequence u (k); then, according to the voltage sampling sequence u (k), solving a first input sequence x (i) and a second response sequence f (i); then, the identification parameter is determined as etaiIn response to 1 ≦ a ≦ cosw Δ t1≤i≤a2Identifying an estimated value of the parameter
The solution of (a) satisfies:
in response to i > a2Then solve for η(i‑1)Under the condition of keeping the initial term, adding the intermediate estimation value after the new term, and solving eta after removing the initial term(i)Is identified and estimated value
Then, solving to obtain the frequency f of the power systemiAnd displaying the change curve in real time. The invention carries out sampling processing through voltage, obtains the parameter to be identified related to the frequency of the power system through identification, obtains the frequency of the power system through solving, and realizes real-time monitoring.
Description
Technical Field
The invention relates to the field of power systems, in particular to a dynamic frequency tracking method for a power system.
Background
The electric power system is an electric energy production and consumption system which consists of links such as a power plant, a power transmission and transformation line, a power supply and distribution station, power utilization and the like. The function of the device is to convert the primary energy of the nature into electric energy through a power generation device, and then supply the electric energy to each user through power transmission, power transformation and power distribution. In order to realize the function, the power system is also provided with corresponding information and control systems at each link and different levels, and the production process of the electric energy is measured, regulated, controlled, protected, communicated and scheduled so as to ensure that users obtain safe and high-quality electric energy.
The main structures of the power system include a power source (power plants such as hydropower stations, thermal power plants, and nuclear power plants), a substation (a step-up substation, a load center substation, and the like), a power transmission and distribution line, and a load center. The power supply points are also mutually connected to realize the exchange and regulation of electric energy among different regions, thereby improving the safety and the economical efficiency of power supply. The network formed by the transmission line and the substation is usually called a power network. The information and control system of the power system consists of various detection devices, communication devices, safety protection devices, automatic control devices and automatic monitoring and dispatching systems. The structure of the power system should ensure reasonable coordination of power generation and consumption on the basis of advanced technical equipment and high economic benefit.
The state of the power system frequency is related to the safety of a power grid, and dynamic tracking of the power system frequency becomes a research hotspot.
Because the power system is a complex time-varying system, the data processing amount is larger and larger along with the operation of the system, and the required computer processing capacity for processing data is greatly increased, so that the data processing speed is reduced or the data processing cost is increased. The least square recursion is carried out by adopting the traditional forgetting factor weighting, the influence of old data cannot be completely eliminated, so that long-term fault data and the like cannot be completely eliminated, and the accuracy of the existing state data is influenced.
Disclosure of Invention
In view of some of the above drawbacks in the prior art, the present invention provides a method for dynamically tracking a frequency of an electric power system, which aims to optimize a frequency estimation solution of an electric power system network, retain only recent data, perform parameter identification, increase a solution speed of system parameter estimation, and implement dynamic tracking of the frequency of the electric power system.
In order to achieve the above object, the present invention provides a method for dynamically tracking a frequency of a power system, the method comprising:
step S1, sampling the voltage value of the single-phase power system at regular time to obtain a voltage sampling sequence u (k) of the single-phase power system; k is a sampling sequence number of a voltage sampling sequence u (k), and k is a positive integer, wherein the sampling period is delta t;
step S2, solving a first input sequence x (i) and a second response sequence f (i) according to the voltage sampling sequence u (k); the f (i) satisfies: (i) u (i +2) + u (i), said x (i) satisfying: x (i) ═ 2u (i + 1); the i is a positive integer;
step S3, determining the identification parameter as etaiCosw Δ t; the first input sequence x (i) and the second response sequence f (i) of the single-phase power system satisfy: fi＝Xiηi；
Wherein, Fi＝(f(j) f(j+1) … f(i))T，Xi＝(x(j) x(j+1) … x(i))T；
Step S4, in response to i satisfying: a is more than or equal to 11≤i≤a2Then identifying an estimated value of the identification parameter
The solution of (a) satisfies:
a is a1、a2Is a preset positive integer;
step S5, in response to i satisfying: i > a2Then solve for η(i-1)In holding leader
In case of adding a new item [ X ]i Fi]Back η(i remain_first)Intermediate estimate of (2)
Solving for η(i remain_first)Removing said leader
Back η(i)The identified estimate of
Wherein,
the above-mentioned
Satisfies the following conditions:
the above-mentioned
Satisfies the following conditions:
i is an identity matrix;
step S6, finding out from step S5
Solving to obtain the frequency f of the power systemiSaid fiSatisfies the following conditions:
step S7, according to the frequency f of the power systemiDisplaying the frequency f of the power system in real timeiThe change curve of (2).
In one embodiment, the sampling period Δ t is 5ms to 500 ms.
In one embodiment, in the step S7, the abscissa of the variation curve is time t, and the ordinate is the frequency f of the power systemiAdjacent said power system frequency fiThe time difference between them is the sampling period deltat.
In one embodiment, in the step S5, the initial value is set
Satisfies the following conditions:
the invention has the beneficial effects that: in the invention, the upper limit of data is kept as a by limiting the number of data items of the power system2And items, when the data volume is less than the upper limit, directly solving the estimated value of the parameter, and when the data volume exceeds the upper limit, adding a new item and deleting the first item to keep the data length. AIn addition, because the power system is a gradual change system, the data which is farther from the current time node is lower in accuracy, the farther from the current time node is removed, and the system precision is effectively improved. In addition, the two-step solution is carried out through the formula, the higher the obtained parameter estimation precision is, and the parameter estimation accuracy is enhanced. The invention carries out sampling processing through voltage, obtains the parameter to be identified related to the frequency of the power system through identification, obtains the frequency of the power system through solving, and realizes real-time monitoring. Compared with the recursion of the least square method by adopting the traditional forgetting factor weighting, the method can clear the long-term fault data, clear the influence of the old data, reduce the influence of the old data on the existing state data and improve the accuracy.
Drawings
Fig. 1 is a schematic flow chart of a method for dynamically tracking a frequency of a power system according to an embodiment of the present invention.
Detailed Description
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
the sampling model of the voltage signal of the single-phase power system can be expressed as follows:
wherein u iskA voltage sampling signal value of the single-phase power system, V is a voltage amplitude,
the phase is an initial phase, w is the power fundamental wave angular frequency, delta t is a sampling time interval, and xi (k) is random noise;
from the sum and difference, one can obtain:
thus, it is possible to obtain:
vk+2+vk＝2vk+1cos(wΔt) (3)
let f (i) u (i +2) + u (i), x (i) 2u (i +1), η cos (w Δ t), then formula (3) can be:
namely: fi＝Xiηi (5)
Wherein, Fi＝(f(j) f(j+1) … f(i))T，Xi＝(x(j) x(j+1) … x(i))T；
At this time, w can be solved reversely by only obtaining the estimation value of the above formula, and the power system frequency can be further obtained.
Conventionally, by the least squares method, one can obtain:
in the recursive calculation process of the invention, in order to maintain the data length, a new line is added to the data on one hand, and meanwhile, the original data is reduced by a first line on the other hand so as to maintain the data length.
When [ X ]i-1,Fi-1]TAdding a new set of data [ x ]i,fi]TAnd then, the added data meet the following conditions:
further reduction of top line [ x ] for the above dataj,fj]TI.e. also data [ X ]i-1,Fi-1]TFirst line, modified data [ X ]i,Fi]TSatisfies the following conditions:
wherein, assume a data retention length of a2Then data [ Xi-1,Fi-1]TFirst serial number j ═ i-a2；
The following formulae (7) to (8) can be substituted for the formula (6), respectively:
the calculation of equation (9) can be solved:
the calculation of equation (10) can be solved:
the following can be obtained through continuous simplification:
according to
w ═ 2 π f can be found:
i is an identity matrix;
in the invention, the upper limit of data is kept as a by limiting the number of data items of the power system2Term, when the data amount is less than the upper limit, the estimated value of the parameter is directly solvedAnd when the data volume exceeds the upper limit, adding a new item and deleting the first item to keep the data length.
On one hand, the previous data are removed, so that the calculation processing amount is reduced, and meanwhile, as the power system is a gradual change system, the data accuracy is lower when the power system is farther from the current time node, the data farther from the current time are removed, and the system precision is effectively improved. In addition, the two-step solution is carried out through the formula, the higher the obtained parameter estimation precision is, and the parameter estimation accuracy is enhanced.
Specifically, as shown in fig. 1, in a first example of the present invention, there is provided a power system frequency dynamic tracking method, including:
step S1, sampling the voltage value of the single-phase power system at regular time to obtain a voltage sampling sequence u (k) of the single-phase power system; k is a sampling sequence number of a voltage sampling sequence u (k), and k is a positive integer, wherein the sampling period is delta t;
step S2, solving a first input sequence x (i) and a second response sequence f (i) according to the voltage sampling sequence u (k); the f (i) satisfies: (i) u (i +2) + u (i), said x (i) satisfying: x (i) ═ 2u (i + 1); the i is a positive integer;
step S3, determining the identification parameter as etaiCosw Δ t; the first input sequence x (i) and the second response sequence f (i) of the single-phase power system satisfy: fi＝Xiηi；
Wherein, Fi＝(f(j) f(j+1) … f(i))T，Xi＝(x(j) x(j+1) … x(i))T；
Step S4, in response to i satisfying: a is more than or equal to 11≤i≤a2Then identifying an estimated value of the identification parameter
The solution of (a) satisfies:
a is a1、a2Is a preset positive integer;
step S5, in response to i satisfying: i > a2Then solve for η(i-1)In holding leader
In case of adding a new item [ X ]i Fi]Back η(i remain_first)Intermediate estimate of (2)
Solving for η(i remain_first)Removing said leader
Back η(i)The identified estimate of
Wherein,
the above-mentioned
Satisfies the following conditions:
the above-mentioned
Satisfies the following conditions:
i is an identity matrix;
step S6, finding out from step S5
Solving to obtain the frequency f of the power systemiSaid fiSatisfies the following conditions:
step S7, according to the frequency f of the power systemiDisplay in real timeIndicating the frequency f of the power systemiThe change curve of (2).
In this embodiment, the sampling period Δ t is 5ms to 500 ms.
In this embodiment, in the step S7, the abscissa of the variation curve is the time t, and the ordinate is the frequency f of the power systemiAdjacent said power system frequency fiThe time difference between them is the sampling period deltat.
In the present embodiment, in the step S5, the initial value
Satisfies the following conditions:
the foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.
Claims (4)
1. A method for dynamically tracking a frequency of a power system, the method comprising:
step S1, sampling the voltage value of the single-phase power system at regular time to obtain a voltage sampling sequence u (k) of the single-phase power system; k is a sampling sequence number of a voltage sampling sequence u (k), and k is a positive integer, wherein the sampling period is delta t;
step S2, solving a first input sequence x (i) and a second response sequence f (i) according to the voltage sampling sequence u (k); the f (i) satisfies: (i) u (i +2) + u (i), said x (i) satisfying: x (i) ═ 2u (i + 1); the i is a positive integer;
step S3, determining the identification parameter as etaiCos w Δ t; the first input sequence x (i) and the second response sequence f (i) of the single-phase power system satisfy: fi＝Xiηi；
Wherein, Fi＝(f(j) f(j+1)…f(i))T，Xi＝(x(j) x(j+1)…x(i))T；
Step S4, in response to i satisfying: a is more than or equal to 11≤i≤a2Then identifying an estimated value of the identification parameter
The solution of (a) satisfies:
a is a1、a2Is a preset positive integer;
step S5, in response to i satisfying: i > a2Then solve for η(i-1)In holding leader
In case of adding a new item [ X ]i Fi]Back η(i remain_first)Intermediate estimate of (2)
Solving for η(i remain_first)Removing said leader
Back η(i)The identified estimate of
Wherein,
the above-mentioned
Satisfies the following conditions:
the above-mentioned
Satisfies the following conditions:
i is an identity matrix;
step S6, finding out from step S5
Solving to obtain the frequency f of the power systemiSaid fiSatisfies the following conditions:
step S7, according to the frequency f of the power systemiDisplaying the frequency f of the power system in real timeiThe change curve of (2).
2. The dynamic tracking method for the frequency of the power system as claimed in claim 1, wherein the sampling period Δ t is 5ms-500 ms.
3. The method as claimed in claim 1, wherein in step S7, the abscissa of the variation curve is time t, and the ordinate is the frequency f of the power systemiAdjacent said power system frequency fiThe time difference between them is the sampling period deltat.
4. The method as claimed in claim 1, wherein in step S5, the initial value is set
Satisfies the following conditions:
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| EP2226639A1 (en) * | 2009-03-03 | 2010-09-08 | Mitsubishi Electric R&D Centre Europe B.V. | Spectral analysis and FMCW automotive radar utilizing the same |
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| CN103777083A (en) * | 2014-01-24 | 2014-05-07 | 武汉大学 | Capacitive equipment dielectric loss online monitoring system and method based on Kalman frequency tracking |
| CN106980775A (en) * | 2017-03-27 | 2017-07-25 | 华南师范大学 | Temporal gene chip data method for digging based on the consistent Evolution Type of whole continuation columns |
| CN108051702A (en) * | 2017-11-29 | 2018-05-18 | 西安理工大学 | Faulty line calculation method of parameters based on singlephase earth fault recorder data |
| US20200270069A1 (en) * | 2019-02-27 | 2020-08-27 | Walmart Apollo, Llc | Flexible automated sorting and transport arrangement (fast) robotic arm |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2226639A1 (en) * | 2009-03-03 | 2010-09-08 | Mitsubishi Electric R&D Centre Europe B.V. | Spectral analysis and FMCW automotive radar utilizing the same |
| CN103281033A (en) * | 2013-05-21 | 2013-09-04 | 常州联力自动化科技有限公司 | Asynchronous motor parameter identification method |
| CN103777083A (en) * | 2014-01-24 | 2014-05-07 | 武汉大学 | Capacitive equipment dielectric loss online monitoring system and method based on Kalman frequency tracking |
| CN106980775A (en) * | 2017-03-27 | 2017-07-25 | 华南师范大学 | Temporal gene chip data method for digging based on the consistent Evolution Type of whole continuation columns |
| CN108051702A (en) * | 2017-11-29 | 2018-05-18 | 西安理工大学 | Faulty line calculation method of parameters based on singlephase earth fault recorder data |
| US20200270069A1 (en) * | 2019-02-27 | 2020-08-27 | Walmart Apollo, Llc | Flexible automated sorting and transport arrangement (fast) robotic arm |
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