A Local Measurement-Based Phase Sequence Exchange Emergency Control Approach

Phase sequence exchange (PSE) is a recently developed emergency control technology in which power electronic devices are used to switch the three-phase sequence, thereby reducing the power angle of the generator by 120° and preventing the system from losing stability. This article proposes the installation of the PSE device in the fragile cut-set line of the power grid, and to use the local measurement information for control. This method can restore the stability of the system when the power grid oscillates, thereby avoiding the collapse of the island power grid after splitting due to oscillation. First, an improved real-time power angle calculation method is proposed. When a system loses synchronization and the power angle of a line reaches the threshold, the PSE device on the same cut-set line acts simultaneously to prevent the system from falling out-of-step and “splitting” from the cut set. A PSE prototype is used for experimental verification on the real-time digital simulator platform. The results demonstrate that the proposed power angle calculation method greatly reduces the error, and the proposed PSE control method can achieve online monitoring and real-time control, which achieves better control effects than conventional methods.