Concurrently attuned design of a WADC-based UPFC PSDC and multiinput PSS for improving power system dynamic performance


Abstract: A new controller design for a unified power flow controller (UPFC) for damping of power system swings, focusing on interarea modes, is described in this paper. The proposed controller is a dual-layer controller, where the first layer is derived from local signals and the second layer is supplied by global signals, as additional measuring information from suitable remote network locations, where swings are well observable. For damping of low-frequency swing in wide-area operation, since there is little system information in the active power as input of the conventional power system stabilizer (CPSS), the effectiveness of the CPSS is low. For solving this problem, a multiinput power system stabilizer (MPSS) is used for the damping of low-frequency swings, where the choice of the MPSS location is based on modal analysis. Since an uncoordinated controller for the UPFC and MPSS may cause unwanted interactions, the concurrently attuned design of the controller parameters is necessary. The attuned design is presented as an optimization problem, where the particle swarm optimization algorithm is applied to search for the optimal controller parameters. The introduced time delay by remote signal transmission and processing in a wide-area damping controller (WADC) may be problematic for system stability and may decrease system robustness. The Lyapunov theory and model reduction technique are used to investigate the delay-dependent stability of a power system equipped with a WADC. The designed controller's effectiveness and robustness are investigated on a typical 2-area 4-machine benchmark power system.

Keywords: UPFC, power swing damping controller, wide-area damping controller, dual-layer UPFC damping controller, concurrently attuned

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