Low-order controller design using remotely measured time delayed signals for stabilisation of equivalent power grid

This study discusses the use of time-delayed remote signals available through phasor measuring units (PMUs) for low-order controller design in order to stabilise the power oscillations in the range of 0.3-0.42 Hz between two areas. In the proposed approach, first synchronisation measures are determined among the group of generators located in two areas. Then, an index that characterises the joint observability and controllability property in terms of Hankel singular values is defined as a criterion to preselect the remote feedback signal. Following this, a low-order controller design based on minimisation of H^∞ norm is considered. The measurement redundancy is taken into account in controller design using rotor angle, power flow or speed deviation as feedback signal from one of the generators. Additionally, if some specific PMU fails to provide measurements from a chosen generator, then controller effectiveness is guaranteed using signal from other generator in the same area. The performance of controller is verified considering single-step and multi-step disturbances applied to the reference voltage of exciter system. The comparison with design functions such as H² norm, complex stability radius and spectral abscissa are also presented. The analytical results confirm using H^∞ design algorithm provides better dynamic performance.