Wide area signal based optimal neurocontroller for a UPFC

The design and implementation of an optimal neurocontroller for a flexible AC transmission device - the unified power flow controller (UPFC) is presented in this paper. Wide area signals in a power system are used to provide auxiliary control to a UPFC in order to achieve enhanced damping of system oscillations. The neurocontroller provides auxiliary signals to the real and reactive power references of a UPFC series inverter. The design of the optimal neurocontroller is based on an adaptive critic design (ACD) approach - the Heuristic dynamic programming (HDP). A system identifier, referred to as the wide area monitor (WAM), and a critic network (performance evaluator) are designed for optimizing the neurocontroller. Real-time implementation of the optimal UPFC neurocontroller for a multi-machine power system is carried out successfully on a digital signal processor (DSP). The power system is simulated on a real-time digital simulator (RTDS). The performance of this neurocontroller is compared with a conventional linear damping controller. Results show enhanced damping of both inter-area and intra-area modes in the power system under different operating conditions and disturbances with the neurocontroller. The improvement in the damping is also quantified using the Prony method.