Vehicle-Grid System Modeling and Stability Analysis With Forbidden Region-Based Criterion

The voltage low frequency oscillation (LFO), between traction network and electric locomotives or electric multiple units in high speed railway, is a typical phenomenon happening in cascade systems with power electronic converters accessed, which is regarded as the stability problem of a vehicle-grid (V2G) system in general. To address the problem, the mathematical model of the V2G system is deduced in detail first, and a generalized dq-decoupled small-signal model of a single-phase pulse width modulation rectifier is established in this process. Then, a novel stability criterion based on forbidden region for dq-decoupled multi-input multi-output cascade systems is proposed to analyze the stability of the V2G system. The proposed criterion has less conservatism than singular-value criteria and norm criteria, and can be applied for systems with either high or low power factor. The comparison with other criteria and simulation results verifies that the proposed forbidden region-based criterion performs well in the analysis of the critical condition of LFO. Moreover, the impact factors of LFO, both grid parameters and vehicle parameters, are researched based on the proposed stability analysis criterion and the simulation verification, which provides design guidance for the V2G system to restrain LFO.