Power System Wide-area Damping Control With Time Delay Considered

The blend of the electric power industries and information-based industries has enabled the application of the digital communication network technologies to power system control,which has become a prevailing trend in power systems.The implementations of wide area measurement system have offered a novel solution to damp inter-area oscillation and improve the dynamic performance of inter-area power system.Meanwhile,time-varying transmission delays are introduced into the closed-loop control in WAMS.As the latency may exacerbate the control performance and degrade power system stability,it has been suggested that the transmission latency should be seriously considered in control design for wide-area power system security.Firstly,a power system model with multiple time delays is built.By using Pade approximation,the state space equation of power system with multiple controllers and delays is formulated.The impact of multiplicity and time-varying nature of time delay on power system stability is discussed through eigenvalue analysis and simulation results.Secondly,to overcome the complexity of procedures by using robust control theory,a novel design strategy for wide area power system damping control with multiple time delay considered is proposed,with which the parameters can be solved directly in a convenient and simple way.The problem is solved by using the multiple time delay system stability criterion which is based on Lyapunov-Krasovskii theory.Instead of the complicated iterative process by using intelligent algorithm,control parameters can be easily solved by solving linear matrix inequalities(LMI)feasibility problems.Lastly,based on networked control system,wide-area data is uniformly processed estimated online with time-varying delay and packet dropout considered.An adaptive Smith predictor is introduced to reduce the impact of variable time delay and packet loss.The proposed methods are verified on a test power system.This study shed light on the effect of variable time delays on power system,and has great theoretical significance and applicable value on wide area power system damping control with the presence of multiple and variable time delays.