Wide-area Damping Control For Complex Power System Using Goal Representation Heuristic Dynamic Programming

With the increasing amount of renewable energy,the interconnection among large power grids and the remote distrbution of electric power,the power grids become more and more complicated and interarea oscillation challenges the secure and stable operation of power grids.The power system stabilizer(PSS)commonly uses the local signal as input signal,so that its damping performance in interarea oscillation is not very satisfying.Wide-area signals have higher observability for interarea oscillation modes than local signals,thus wide-area damping control(WADC)has gained popularity.However,there exist the problems of communication time delay and communication failure in WADC.Consequently,it is necessary and meaningful to design a WADC considering communication delay and communication failure.Adaptive dynamic programming(ADP)is a model-free designing method,which contains the approximate dynamic programming,neural network and reinforcement learning.Goal representation heuristic dynamic programming(Gr HDP),which developed from ADP,has stronger learning ability and adaptivity,and its effectiveness and astringency have been strictly proved in mathmatics.Currently,Gr HDP has been employed in many fields,such as power,transportation,and logistics.Accodingly,Gr HDP can be utilized to design WADC,to adapt to the change of power system operation conditions,the communication delay and communication failure.In this paper,Gr HDP is used in a complicated AC/DC interconnected power system,the Gr HDP-WADC can adapt to different operation conditions of power system,and can deal with a wide range of communication time delay and communication failure.The main progresses are as follows:(1)In order to adapt to the operation conditions change of power system better,a parallel phase shift channel is added in the input channel of Gr HDP,so that it can compensate phase shift between the output and input signals of a complex AC/DC power system and achieve better damping performance.(2)Aiming at the problem of communication time delay,an adaptive delay compensator is added in the input channel of Gr HDP,which consists of a weighted combination of several pre-designed sub-compensators and their weights can be adjusted online according to the instant measured value of the communication delay.With the adaptive delay compensator,Gr HDP-WADC can handle a wide range of time delay of wide-area input signal.(3)In order to deal with the communication failure,the Gr HDP-WADC employs local signal and wide-area signal as input signals to tolerate communication failure.If communication failure occurs,the Gr HDP-WADC can maintain a good damping performance with the remaining normal local signal and its strong online learning ability.(4)Similarly,to handle the problem of communication failure,three wide-area signals are used as input signals of Gr HDP-WADC.Besides,a supervisory fuzzy logic module(FLM)is also proposed in the Gr HDP-WADC,which can adjust the learning rate of Gr HDP online when encountering communication failure.With redundant input signals and FLM,Gr HDPWADC can deal with the situations when one or two communication channels failure.