Multi-port converter with improved modulation and control strategies for PV and energy storage systems

The integration of energy storage elements to solar photovoltaic (PV) systems provide a wide range of operational flexibilities. Traditional approaches use separate converter for PV and energy storage element, i.e. battery which cause significant conversion losses. This paper presents an isolated high frequency link multi-port converter based on triple active bridge (TAB) topology for PV integrated battery systems in residential applications. The conventional dual active bridge (DAB) is extended to establish the proposed high frequency link TAB topology. Limited soft-switching capability and high circulating current are common problems in this style of converters when there is a mismatch in the dc-link voltages. This is pronounced at lower powers with the single phase shift (SPS) modulation technique. To overcome these problems, this paper proposes an improved modulation and control method based on a quintuple phase shift modulation (QPSM) strategy. The QPSM modulation method produces 3-level modulated square wave bridge voltages. A mathematical model of the proposed high frequency linked multi-port converter with QPSM modulation is developed based on a harmonic analysis approach. The simulation and experimental results show that the QPSM scheme applied to the proposed multi-port converter provides better operation and improves the efficiency compared to the traditional SPS modulation scheme. © 2019 IEEE.