Electromagnetic torque analysis-based method for performance evaluation and optimisation of closed-loop CPS regarding small signal stability

摘要

Low frequency oscillation occurs frequently in the smart grid, which threatens the security and stability of the physical system. Wide-area damping controller (WADC), which belongs to cyber system, can effectively suppress inter-area low frequency oscillations and improve the small signal stability of the closed-loop cyber-physical system (CPS). However, with the introduction of global signals, time delays of communication are inevitable. Considering that, this paper deduces the general mathematics expression among electromagnetic torque coefficients, WADC control parameters and time delays, which makes it possible to analyse the influence mechanism of time delay on small signal stability. Based on these analysis, on the one hand, the time-delay small signal stability region is established to evaluate the operation state of closed-loop CPS, on the other hand, if small signal stability is not achieved due to the measured time delays, optimisation scheme is proposed to carry out WADC control parameters coordination to optimise small signal stability of the closed-loop system. Finally, taking two time delays as example, this study verifies the effectiveness and advantages of the proposed method by comparing the closed-loop system performance considering two time delays with the cases of considering singe time delay and without time delay.