Forced oscillation (FO) has posed a significant threat to the power system stability. Accurate and fast FO source location (FOSL) plays an essential role in mitigating FOs. However, most existing FOSL methods fail in dealing with non-stationary FOs and exciter-induced FOs. To overcome the above issues, a multi-synchrosqueezing transform (MSST)-based data-driven approach is developed in this paper to locate the FO source in bulk power systems by using measurement data. Firstly, MSST matrices of multi-channel measurements are formed by MSST. Then, the bus time-frequency representation (BTFR) defined and calculated from the MSST matrices is employed to extract the multi-channel FO components via the ridge detection technology. Furthermore, the MSST-based dissipating energy flow (DEF) model in the time-frequency domain and the dissipating energy spectrum (DES) model in the frequency domain are derived from the conventional time-domain DEF model, and their corresponding FOSL criteria are established. Moreover, an auxiliary criterion of the proposed approach has been developed to overcome the malfunction of the conventional DEF in interactions between generators. The performance of the proposed FOSL method is evaluated with simulation data from the WECC 240-bus and WECC 179-bus test systems, as well as field measurements from ISO New England. The results demonstrate the efficiency and accuracy of the proposed method in locating FO sources.

A voltage security region (VSR) is a powerful tool for monitoring the voltage security in bulk power grids with high penetration of renewables. It can prevent cascading failures in wind power integration areas caused by serious over or low voltage problems. The bottlenecks of a VSR for practical applications are computational efficiency and accuracy. To bridge these gaps, a general optimization model for tracking a voltage security region boundary (VSRB) in bulk power grids is developed in this paper in accordance with the topological characteristics of the VSRB. First, the initial VSRB point on the VSRB is examined with the traditional OPF by using the base case parameters as initial values. Then, the rest of the VSRB points on the VSRB are tracked one after another, with the proposed optimization model, by using the parameters of the tracked VSRB point as the initial value to explore its adjacent VSRB point. The proposed approach can significantly improve the computational efficiency of the VSRB tracking over the existing algorithms, and case studies, in the WECC 9-bus and the Polish 2736-bus test systems, demonstrate the high accuracy and efficiency of the proposed approach on exploring the VSRB.