A control method for integrating hybrid power source into an islanded microgrid through CHB multilevel inverter

This paper proposes a control strategy for an islanded microgrid to effectively coordinate hybrid power source (HPS) units and to robustly control individual interfaced inverters under unbalanced and nonlinear load conditions. Cascaded H-bridge (CHB) multilevel inverters are flexibly deployed in order to enhance the power quality and redundancy. The HPS employs fuel cell (FC) as the main and supercapacitors (SC) as complementary power sources. Fast transient response; high performance; and high power density are the main characteristics of the proposed HPS system. The presented control strategy consists of a power management strategy for the HPS units and a voltage control strategy for the CHB multilevel inverter. A multi proportional resonant (multi-PR) controller is employed to regulate the load voltage at unbalanced and nonlinear load conditions. The proposed multi-PR controller includes a fundamental voltage controller with harmonic compensators. Digital time-domain simulation studies in the PSCAD/EMTDC environment are given to verify the overall proposed system performance.