Research On The Suppression Of Low Frequency Oscillation In Power System By SVC

With the access to a large number of rapid excitation systems and the interconnection of power systems between various regions,the grid has grown in size.When the power system fails,the electromechanical oscillation mode has a crisis of reduced damping and the probability of low-frequency oscillation of the system becomes larger due to insufficient system damping.With the appearance of the FACTS additional damping controllers,the suppression of the low-frequency oscillation of the system combined with the additional damping control the PSS and the FACT becomes the current hot spot.In this paper,SVC is taken as an example to analyze the restraining mechanism of its additional damping control low-frequency oscillation and combined with PSS to suppress the low-frequency oscillation of the system.Parameters of the PSS and SVC damping controllers are optimized from both the frequency domain and the intelligent algorithm,Designing the SVC damping controller is completed under the time delay and the SVC put into the large grid test.Firstly,this paper introduces the classification and basic structure of SVC and the TSC-TCR SVC control strategy.In order to better explain the control principle of SVC,a single machine system is built in matlab/simulink to simulate TSC-TCR SVC.Taking the Phillips-Heffron model of the single machine infinite bus system as an example,this paper expounds the principle of PSS and SVC for restraining the low frequency oscillation of the power system,showing SVC's additional damping controller and PSS can suppress the low frequency oscillation.For stand-alone systems,the damping torque method is used to design the parameters of PSS and SVC damping controllers for a single machine infinite bus system,a single machine infinite bus system is built in matlab/simulink to verify it for time domain simulation.For the multi machine system,in order to overcome the difficulties of modeling and calculate system eigenvalue problem,the proposed BP-PSO algorithm for coordinating design of PSS and SVC damping controller parameters,selecting the line active power fluctuation ITEA standard as the objective function,and compared with the traditional PSO algorithm optimization results in matlab/simulink to build four machine two area power system the validity,the time-domain simulation and the verification algorithm.The results show that: the transient stability and small signal time domain simulation for the multi machine power system,the controller parameters optimization of BP-PSO algorithm is extremly lower than the traditional PSO controller parameters online optimization algorithm,used in the low frequency oscillation damping system,the time of adjusting and overshoot was significantly reduced,inhibition of low frequency oscillation can be better.Finally,in the grid background,designing SVC wide area damping controller,the main mode of Prony fitting and ratio index method are combined for wide area measurement;according to the proposed BP-PSO algorithm,combined with Prony fitting line active power fluctuation of the damping ratio,as well as the objective function has been optimized and obtain the results;Basing on PSASP and ADPSS in consideration of the feedback signal delay time,completing the design of the SVC input large power grid to test.The test results show that the SVC damping controller optimized by the BP-PSO algorithm is larger than the SVC without input into the SVC.Compared with two cases of above all,the active power damping ratio of the nine line can be increased by 2% to 3%.