Modeling and Control of Two-Stage Inverter for Battery Energy Storage System

This paper proposes a small-signal model and control design of two-stage inverter for battery energy storage system (BESS) to comprehend its dynamic characteristics. However, when the circuit analysis of two-stage inverter is attempted simultaneously, 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 controller is used for bi-directional DC-DC converter, while the dc-link voltage controller and grid current controller are used for single-phase full-bridge DC-AC inverter. The simulation results illustrate the validity of the small-signal model and the controller design.