Frequency-Coupled Impedance Modeling and Stability Analysis of Multiple Grid-Connected Voltage-Source Converters

This paper focus on stability of grid-connected voltage-source converters (VSCs) in subsynchronization / supsynchronization frequency bands. Linearized models are built in synchronous (dq) frame, thus transformed to models in stationary (αβ) frame. Analysis is made on frequency coupling brought by asymmetrical control of d/q axis. Based on theoretical derivation, methods are proposed for identification of VSC model parameters by simulations or tests. Furthermore, complicated networks within multiple VSCs are modeled as node voltage equations, thus stability criterions are discussed, and methods of oscillation-source location are proposed. for complicated networks with VSCs. Results of impedance analysis are verified by simulations and eigenvalues calculations.