An Optimized dq-Frame Admittance Modeling Method for Single-Phase Railway Vehicle-Grid System Considering the Impact of Asymmetric αβ Control

To tackle the small-signal instability in the single-phase railway vehicle-grid system, the dq admittance modeling method has received great attention. However, the orthogonal β components created by the asymmetric quadrature signal generators (QSGs) for dq control inevitably suffer from amplitude or phase errors at nonfundamental frequencies, which are not fully considered in the traditional dq modeling method. As revealed in this letter, due to the inherent signal dimensionality reduction process from the actual control output (2-D scalar) to the single-phase power stage input (1-D scalar), the nonideal β components can introduce nonnegligible errors to the traditional dq model. Thus, as a solution, an optimized dq admittance modeling method for the single-phase converter in vehicles is proposed, which involves the impact of the asymmetric QSGs by capturing the signal dimensionality reduction process, based on the existing dq models. Furthermore, the stability analysis and hardware-in-the-loop (HIL) simulations are achieved, which verify the effectiveness of the proposed optimization methodology.