Averaged modeling and control of a single-phase grid-connected two-stage inverter for battery application

This paper proposes a small-signal averaged model and control design of a single-phase grid-connected two-stage inverter to comprehend its dynamic characteristics for battery application. However, when the circuit analysis of two-stage inverter is attempted at the same time, mathematical procedure for deriving its dynamic equation is very complex and difficult. The main idea of modeling for two-stage inverter is that bi-directional DC-DC converter or single-phase full-bridge DC-AC inverter is replaced with an equivalent current source, and then the dynamic equations for the separated converter and inverter are derived by using state-space averaging technique. The procedures for building the small-signal model of two-stage inverter is described in detail. Based on the derived small-signal model, the individual controllers are designed in a frequency-domain analysis. The input current and DC-link voltage controllers are used for converter, while the grid current controller is used for inverter. The simulation results illustrate that the validity of the proposed modeling approach and the controller design is well verified.