On-line self-learning PID based PSS using self-recurrent wavelet neural network identifier and chaotic optimization
Purpose - The power system is complex multi-component dynamic system with many operational levels made up of a wide range of energy sources with many interaction points. Low frequency oscillations are observed when large power systems are interconnected by relatively weak tie lines. These oscillations may sustain and grow to cause system separation if no adequate damping is available. The present paper aims to propose an on-line self-learning PID (OLSL-PID) controller in order to damp the low frequency power system oscillations in a single-machine system. Design/methodology/approach - The proposed OLSL-PID is used as a controller in order to damp the low frequency power system oscillations. It has a local nature because of its powerful adaption process based on back-propagation (BP) algorithm that is implemented through an adaptive self-recurrent wavelet neural network identifier (ASRWNNI). In fact PID controller parameters are updated in on-line mode, using BP algorithm based on the information provided by the ASRWNNI which is a powerful fast-acting identifier because of its local nature, self-recurrent structure and stable training algorithm with ALRs based on discrete lyapunov stability theorem. Findings - The proposed control scheme is applied to a single machine infinite bus power system under different operating conditions and disturbances. The nonlinear time-domain simulation results are promising and show the effectiveness and robustness of the proposed controller and also reveal that: because of the high adaptability, the local behavior and high flexibility of the OLSL-PID controller, it can be damp the low frequency oscillations in the best possible manner and significantly improves the stability performance of the system. Originality/value - The proposed controller adaption process is done in each sampling period using a powerful adaption law based on BP algorithm. Also during the process the system sensitivity is provided by a powerful fast-acting identifier. As an alternative to multi-layer perceptron neural network, self-recurrent wavelet neural networks (SRWNNs) which combine the properties such as attractor dynamics of recurrent neural network and the fast convergence of the wavelet neural network were proposed to identify synchronous generator. Also to help the OLSL-PID stability first, PID parameters tuning problem under a wide range of operating conditions is converted to an optimization problem which solved by a chaotic optimization algorithm (COA), and afterwards PID controller is hooked up in the system and on-line tuning is done in each sampling period.
self-recurrent wavelet neural network chaotic optimization power system stabilizer intelligent pid controller adaptive learning rates neural nets programming and algorithm theory