A Soft-Switched Multiport Converter for Distributed PV Application With Energy Storage
Sivakrishna Karpana, Suman Maiti, Chandan Chakraborty
Abstract
A stand-alone dc/ac micro-grid often requires multiple dc–dc converters to integrate distributed generators and an energy storage (ES) unit. The challenge lies in balancing cost, efficiency, power density, and system reliability. The presence of photovoltaic (PV) systems adds complexity, especially in situations of uneven shading among PV strings. This often leads to reduced PV generation, either due to misleading of the maximum power point tracking (MPPT) algorithm or due to dip in PV voltage. To tackle this issue, a solution is proposed using a nonisolated multiport converter. This design allows seamless integration of two individual PV strings and an ES unit in series, offering advantages like distributed MPPT, soft switching, and differential power processing. These features significantly enhance the overall system performance. A novel control scheme is proposed for this configuration that allows independent control of each source. Notably, the converter's structural simplicity, utilizing only two half bridge modules, makes it highly practical for industrial applications. The concept's feasibility has been substantiated through experimental validation using a 760 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{W}_\text{p}$</tex-math></inline-formula> lab-developed prototype, complemented by thorough theoretical analysis.