General-Purpose Computation of Two-Axis Frequency Characteristics of Power Converter Circuit for Stability Analysis Controlled in αβ Frame

Abstract

Frequency characteristics for a converter are necessary to design circuit and control parameters and they are utilized, for example, for stability analysis by the impedance method. This paper proposes an automatic formulation and analysis method, which are based on a general-purpose simulation algorithm for the frequency analysis of an averaged power converter, based on node-connection and model characteristic information of circuit and control elements. The general equation formulation method is extended to be able to include circuits controlled in αβ frame and characteristic expressions with αβ or dq frame. As the first application example, a three-phase grid-following inverter with a digital sinusoidal controller based on the complex vector theory in αβ frame is analyzed for the frequency characteristics of the output admittances. The characteristics are utilized for stability analysis by the impedance method and the inverter is assured to have passive characteristics and to be stable. As the second example, a three-phase inverter is analyzed for its αβ and dq impedances. The proposed method is investigated for the computed results and it is validated.