An adaptive network latency compensator design for wide area damping control of power system oscillations

Use of phasor measurement units in power systems has emerged new real-time control techniques such as wide area damping control (WADC). WADC systems were shown to be very effective if the network induced time delay is handled properly. Delay compensation techniques based on constant delay assumption lack robustness and many of techniques assuming time variant delay are not suitable for real-time systems due to resulting complex structures of controllers or the strict requirements imposed on signal transmission. Handling time delay adaptively by switching among a set of lead controllers to provide required compensation based on online measurements shown to be both practical and robust. Here, frequent switching between the controllers should be avoided in order to avoid sustained oscillations. Putting a limit on switching period hinders proper delay compensation. This paper presents algorithms for adaptive selection of switching period based on the condition of network traffic in order to provide near real-time delay compensation. Network activity is observed by a metric defined as the difference of the average time delays measured in consecutive intervals. Based on this metric, switching period is decreased adaptively when time delay characteristics change fast. For slow changing dynamics of time delay, the algorithm picks longer switching periods in order to prevent sustained oscillations. Performance evaluation of the proposed algorithms are conducted by a WADC system designed for two-area, four-machine benchmark model. The algorithms are shown to be successful in tracking the fast changing dynamics of a communication network through simulations.