Physical Model-Based VDCM Control to Enhance the Inertia of DC Bus for PV-BESS Supported Off-Board Charging Station

In renewable-based charging stations (CSs), the inherent inertia of dc bus from linked capacitors is very low. The dc-link voltage stability is vulnerable to power oscillations caused by step load changes (constant current (CC) mode) at CS by connecting and unplugging electric vehicle (EV) and intermittent renewable power. An inertia and damping control is proposed in this article based on the physical model of a virtual dc machine (VDCM) for a dc microgrid (DCMG) formed for CS. The proposed control technique was developed using the capacitors’ conversion forms for charging and discharging as the generation and motoring mode of VDCM. It intends to regulate the exterior characteristics of converters connected to the battery energy storage system (BESS) to enhance the damping and inertia properties of the dc grid. The small-signal model of the presented control method is built to analyze the system dynamics response, stability, and parameter range of VDCM. Furthermore, decentralized power-sharing control is also tested for the multiple parallel operations of storage, photovoltaic (PV), and CS extension. The simulation results demonstrate that BESS with VDCM control enhances the voltage characteristics and stability of DCMG with or without the grid. Finally, the proposed system is validated through detailed experimental studies.

I. Introduction

Environmental issues are the leading force toward revolutionizing energy generation sources and consumption methods. The share of renewable-based clean energy generation is increasing rapidly to tackle these problems. At the same time, the transportation sector is speedily moving toward clean energy-based vehicles. The increasing popularity of RESs and the expansion of EVs have been acknowledged as successful strategies to reduce the reliance on fossil fuels and achieve sustainable development [1].