A Stand Alone Building Integrated PV Tied Bidirectional Capability Direct DC Electric Vehicle Charging System through Z-Source Inverter Impedance Network Capacitors

Abstract

Due to declining fossil fuel resources and rising gasoline prices, Electric Vehicles (EVs) have recently regained popularity. Meanwhile, due to the expensive initial cost of the battery, range anxiety or limited travel distance, a lack of charging infrastructure, and poor recharging rates, widespread adoption of EVs is not occurring at a rapid pace. There is a lot of attention in the building-integrated PV (BIPV) for the past few years around the world and they have been designed and integrated in different ways to meet out the building load requirements. The PV design experts and architectural consultants are exploring ingenious techniques, and they have delivered the innovative building elevation design with wall mounted PV structure. Even though these BIPVs are supplying the local building loads, due to the increase in the electrical vehicles (EVs) users in the commercial buildings, there is need to provide sufficient power requirement for their fast charging.  Due to the consideration of EVs with respect to the environmental sustainability, high progression is expected in the near future, and it will because extreme surges in the claim while charging them during rush hours (particularly during daytime). Hence similar to rooftop PV system, BIPV is a trustful system to provide the electricity to the EVs.  Nevertheless, numerous challenges are still addressed in the fast charging with PV and utility grid power. Hence, the proposal motivates to design high-efficient and low-cost wall mounted BIPV integrated electric vehicle DC fast charging system to meet out the EV power requirement for their quick charging [1,2].

       A single stage inverter called Z-source inverter (ZsI) can buck or boost as well as reverse the input dc voltage. In PV-grid-connected/ Stand Alone applications, it has sparked a lot of attention in current era. The ZsI able to boosts the input dc voltage to match the inverter-side ac output voltage requirements with impedance network two capacitors and two inductors. The passive components are crucial to the operation of a ZsI [3]. It opens up the possibility of incorporating energy storage devices into such a system. The capacitor voltage of impedance network of the ZsI can be tapped and from there DC supply can be taken. Hence in this papers a modified ZsI with split capacitors to provide the DC supply to the EV charging side pulsating transformer. The conventional X- network type ZsI C₁ and C₂ capacitors are splitted into two namely C₁ as C₁₁ and C₁₁ besides C₂ as C₂₁ and C₂₂. This capacitors are connected with the primary widening of the isolated full-bridge converter (IFBC). Hence the isolated full-bridge converter receive the two cycle pulsating DC from the both primary winding of IFBC. The secondary side of the IFBC connected with EV Battery. This topology also proves a bidirectional capability to get the power from the battery and charges the impedance network capacitors.  

     The simulation and experimentation is conducted for the proposed BIPV EV charging ZsI standalone system. The Test set is built for established values of 1.2-kWp roof-top PV panels (15 tin film panels, each 90W) attached single-phase ZsI standalone system. The 24V/20Ah li-iron battery is used for the EV battery

The proposed method is capable of any EV charging architecture anfd it can be used in a centralised charging setup in semi-commercial venues such as a supermarket car park. This approach can be extended to wall and rooftop PV inverters for grid connected and domestic applications. This research presented an energy storage topology based on the symmetrical operation of a Z-source converter's impedance network