A Stability Enhancement Method Based on a Novel Orthogonal Signal Generator for Railway Electrification Train-Grid System

The low-frequency oscillation (LFO) threatens the safe and stable operation of the railway electrification train-grid (RETG) system, and high-performance stability enhancement methods are desirable. However, many methods neglect the dynamic of the orthogonal signal generator (OSG), resulting in suboptimal performance. To address this, a stability enhancement method based on a novel and simple OSG is proposed in this article, which can suppress the LFO while providing fast dynamic performance. In this scheme, an impedance model of the RETG system is initially constructed. Then, with the impedance-based stability criterion, the impact of current OSG method on stability of the RETG system is analyzed. Accordingly, a current reference values-based OSG (CRV-OSG) is proposed. Through stability comparison and robustness analysis, it is revealed that the proposed CRV-OSG method is helpful for system stability enhancement, and meanwhile has satisfactory adaptability to variations in traction grid parameters. Eventually, extensive simulations and experimental tests are implemented to verify the steady state and dynamic performances of the proposed method.