A Two-Level Forced Oscillations Source Location Method Based on Phasor and Energy Analysis

Forced oscillations (FOs), which are caused by sustained cyclic disturbances, threaten the safe and stable operation of power system. The most effective way to eliminate FOs is to locate the oscillation source and take corresponding measures. In this paper, a two-level method for forced oscillations source location is proposed. First, the energy structure of the generator is analyzed based on Hamiltonian function. The energy injected into generator is divided into two parts, i.e., energy injected by the prime mover system and excitation system. Then, as to the energy injected into power grid, the phasor relation between the variances of branch variables is analyzed to identify the energy flow direction. Based on the former analysis, the proposed method includes two levels. The bus level location of the oscillation source is realized according to the energy flow direction obtained with phasor analysis. Furthermore, the control device level location within the generator is realized according to the injected energy of the prime mover system and excitation system of generator. This method has good robustness for the measurement of data quality issue and is able to locate multimode oscillations with multiple disturbances. The simulation results in four-machine two-area system, East China power grid and the WECC 179-bus system as well as the comparison with classic energy-based method demonstrate the effectiveness and improvement of the proposed method.