An Isolated Standalone Photovoltaic-Battery System for Remote Areas Applications

Abstract

A standalone photovoltaic-battery system (SBPS) for remote areas must be reliable, cost-effective, safe, and designed to extend battery life. A typical configuration of SPBS is non-isolated and uses a dc–dc bidirectional converter for charging and discharging the batteries connected to the dc link. This configuration needs a high-gain dc–dc converter, usually inefficient, to integrate the batteries to the dc link or stack batteries in series to obtain high voltage. This paper proposes connecting the batteries, through a bidirectional low ripple current converter (Cuk), to the terminals of the photovoltaic (PV) panel to solve the problems mentioned above. The Cuk bidirectional converter controls the dc-link voltage by charging/discharging the battery using simple cascade control. In addition to managing the power battery, the continuous currents at the input and output of the converter avoid excessive current oscillations at the PV panels and battery terminals, improving the maximum power point tracking (MPPT) performance and the battery lifetime. The proposed SBPS is composed of a combination of an isolated interleaved boost (IIB) converter, a Cuk bidirectional converter, and a 3-Level T-type (3LT2) Neutral-Point Clamped (NPC) inverter to reduce the number of switches and assure power quality. This configuration provides grounding and isolation between PV panels, battery, and the load. The analysis of power converters that compose the SBPS, the dynamic behavior, and the design procedures are introduced and verified by simulations and experimental results obtained from a Hardware-in-the-Loop (HIL) testing platform.