Power Sharing Control for a Microgrid with PV Power Plants, Batteries and Quasi-Z-source Cascaded H-bridge Multilevel Inverter

Abstract

In recent years, Quasi-Z-source cascaded H-bridge multilevel inverters (qZS-CHBMLIs) have become an interesting solution for integrating renewable energy into the utility grid. The possibility of performing power conversion in a single stage, without an additional DC/DC converter, and a higher voltage gain, are their main advantages over traditional inverters. In addition, individual control of the maximum power point tracking (MPPT) can be achieved for each PV plant. Owing to the intermittent nature of PV power plants, battery energy storage systems (BESS) are commonly used to smooth out PV power fluctuations. This paper presents a control system for the active and reactive power delivered to the grid according to the system operator references and an EMS for an ES-qZS-CHBMLI. The BESS is coordinated through an energy management system (EMS) based on the state of charge (SOC) The system is evaluated under two different operation modes. One of them, where the PV power plants operate according to their MPP and the other in which the MPPT faults and thus, the PV power is decreased. A MATLAB-Simulink simulation is used to validate the proposed control system for a grid-connected single-phase configuration based on a qZSCHBMLI with three cascade qZSI, each connected to a 4.8 kW PV power plant and a BESS.