Three-port converter with decoupled power control strategies for residential PV-battery system

Abstract

The traditional method for interconnecting PV and a battery energy storage system (BESS) to a household load uses at least two separate converters. In this paper, a fully-isolated three-port converter (TPC) which is based on a dual active bridge (DAB) configuration is proposed for integrating the PV and BESS with the household loads to avoid multistage power conversion. A converter with more than two ports is normally designed to have multimode operations which requires multiple control loops. Due to these multiple cross-coupled power control loops, designing closed loop power control strategies for the TPC becomes a complex issue. This paper presents the small signal modeling of the isolated TPC with proper decoupled networks to eliminate the interaction between multiple power control loops. The decoupled network allows a closed loop power control system design for the TPC to control the port powers independently. As two degrees of freedom (DOFs) are available, the control system can control the PV port power and the ac load port power. The battery port must then provide the balancing power. The power flows between the ports are managed by phase shift modulation (PSM). The responses of the power control system of the proposed TPC with decoupled networks are verified by simulation studies.