A Photovoltaic-Fed DC-Bus Islanded Electric Vehicles Charging System Based on a Hybrid Control Scheme

Abstract

Electric vehicle (EV) charging stations fed by photovoltaic (PV) panels allow integration of various low-carbon technologies, and are gaining increasing attention as a mean to locally manage power generation and demand. This paper presents novel control schemes to improve coordination of an islanded PV-fed DC bus EV charging system during various disturbances, including rapid changes of irradiance, EV connection and disconnection, or energy storage unit (ESU) charging and discharging. A new hybrid control scheme combining the advantages of both master–slave control and droop control is proposed for a charging station supplying 20 EVs for a total power of 890 kW. In addition, a three-level (3L) boost converter with capacitor voltage balance control is designed for PV generation, with the aim to provide high voltage gain while employing a small inductor. The control techniques are implemented in a simulation environment. Various case studies are presented and analysed, confirming the effectiveness and stability of the control strategies proposed for the islanded charging system. For all tested conditions, the operating voltage is maintained within 5% of the rated value.

Design of a PV‐fed electric vehicle charging station with a combination of droop and master‐slave control strategy

“…Such a converter provides higher efficiency and double voltage gain as compared to a conventional boost converter. 26…”

“…The buck converter (shown in Figure 6) is the EV charger, which consists of a MOSFET switch, an inductor, a diode, and a capacitor. 26 The charger's primary duties 26 F I G U R E 5 Isolated bidirectional DC-DC converter with a flyback snubber and a passive snubber 10,11 F I G U R E 6 EV buck converter 26 include connecting the DC bus to the EV battery terminals and controlling the charging current. In this work, the charging current is limited to 100A.…”

“…Figure 8 shows the flowchart to manage the changeover between the two modes. 26 There will be continuous monitoring of the reference voltage and bus voltage within the system, which enables the converter's operating scheme to be determined by the contrast between the maximum output power from PVs (P mpp ) and the maximum consumption from EVs (P EV ).…”

“…As a result, the service quality of ESU is declining over time.The key device connecting the ESU and the DC bus is the bidirectional converter requiring a stable, reliable, and efficient topology. However, the bidirectional converter used by Huang et al,26 results in significant voltage and current spikes during the connect/disconnect of the EVs to the system frequently. Moreover, the freewheeling current raises conduction losses and reduces the effective duty cycle.…”

Independent Double-Boost Interleaved Converter with Three-Level Output

“…The need for high-gain boost topology converters with a low ripple of the input current can be justified in various applications, such as bidirectional chargers for electric vehicles in smart homes [1], development of energy storage for renewable power systems [2][3][4], and DC microgrid and mobility-related concepts [5][6][7][8]. The present work focuses on the power conversion stage of low voltage DC renewable sources, such as photovoltaic panels with power optimizers and/or micro-inverter applications in AC or DC distribution microgrids [9].…”