| With the development of society,the demand for power system is increasing.In terms of the stability of power supply,the cleanness of energy,the wide-area of energy transmission and the development of high voltage and ultra-high voltage,the main problem affecting the stable operation of power system is the low-frequency oscillation caused by the low damping of widearea power system.The precondition to realize the stability control of wide-area power system is to analyze control signals in wide-area measurement system(WAMS).There are many types of signals which include valid,invalid and noise signals in WAMS.Because these signals have communication time-delays to some extent,the system state cannot be reflected in time and system protection measures cannot be taken,which brings serious harm to the damping control of wide-area power system.At the same time,considering the wide-area damping controller will also be affected by time-delays and other factors.The equipment around the world needs to be optimized.Therefore,three current research hot issues are discussed in this paper.They are time-delay compensation in wide area power system,optimal selection of WAMS control signal and optimal design of wide area damping controller(PSS),respectively.The effectiveness of WAMS control signal in system,which focuses on the optimization of excitation signal selection of PMU input controller is studied in this paper.Firstly,the closedloop model of wide-area power system is established(KPCAK).Secondly,a signal selection algorithm based on kernel matrix and Kalman filter optimization is proposed.This method could reduce the dimension by kernel matrix,select the signal by kernel function and optimize the selected effective signals.The optimization analysis of current,voltage and frequency signals are mainly considered.Finally,taking the four-machine two-area system model as an example,simulations are carried out to compare the optimized signal with the original signal without optimization.The optimized signal can effectively suppress the low-frequency oscillation and ensure the stability of the power system.Secondly,based on the previous chapter,we continue to consider the random communication time-delay in the actual operation of the wide area power system.To solve the problem of time-delay compensation,firstly,the time-delay model of wide area system is established.A method of prediction compensation is proposed based on the mathematical model of t-distribution and an improved Prony method,and the whole process of realization of the method is given.The method combines the time-delay segmentation with prediction compensation.The time-delay can be obtained through the standard compensation effect evaluation index and the compensation data could transfer to the controller.Finally,by using the traditional four-machine two-area model,the control effect is improved about 20% compared with the traditional Smith compensation method.Thirdly,based on the optimal selection of signal and time delay compensation,the optimal design of PSS is considered.Firstly,the wide-area time-delay system model is established.Secondly,a design method based on ? trade-off parameters of damping controller is proposed,which can comprehensively coordinate the influence of damping and time-delay on the controller.Finally,Simulations are carried out by the four-machine two-area model.Simulation results show that the controller designed by ? trade-off algorithm can provide higher damping ratio compared with the same conditions so as to better achieve the control effect of the initial damping controller,and the stable operation time of the power system is increased by about 30%.Finally,the method is verified by using "Yunnan-Guangzhou" practical model on the RTDS experimental platform.Results of real-time online simulation are basically the same as those by MATLAB offline simulations.Experimental results show that the proposed method can effectively improve the damping control of wide-area power system from the control signal aspect and improve the stability control of power system from the wide-area power system equipment aspect. |
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