Static Wireless Charging of Electrical Vehicles

The invention of Electric Vehicles is a revolutionary step in the field of electrified transportation. Electric vehicles are increasingly purchased worldwide, however, several issues, such as the limited driving range, battery deterioration, unavailability of charging stations etc, present barriers

Project Title

Static Wireless Charging of Electrical Vehicles

Project Area of Specialization

Electrical/Electronic Engineering

Project Summary

The invention of Electric Vehicles is a revolutionary step in the field of electrified transportation. Electric vehicles are increasingly purchased worldwide, however, several issues, such as the limited driving range, battery deterioration, unavailability of charging stations etc, present barriers for advancement of EVs. To overcome the range anxiety of EVs, it’s crucial to develop its advanced charging infrastructure. Charging of Electric Vehicles is done through plug in chargers which are inconvenient as the user needs to
manually plug in and plug out the charger. To provide safe and flexible power transfer, wireless charging systems are introduced. Wireless charging systems can be implemented by many methods which include CPT, IPT, CIPT, RIPT etc. Resonant Inductive Power Transfer (RIPT) is gaining in popularity for wireless charging applications of future electric transportation. The methodology used in this project is
RIPT due to its wide adoption and better efficiency. The working phenomena of RIPT wireless charging system is that a transmitting pad is located on the ground and a receiving pad is mounted underneath the vehicle. A 240V ac input is taken and is rectified in order to get a dc output which is then fed into a high frequency inverter. The high frequency ac voltage is then fed into the transmitting pad. Transmitting and
receiving pads are made up of coils. The power from transmitting end is transferred to receiving pad through the phenomena of mutual induction. Voltage induced in receiving pad is then given to a rectifier which converts the ac into dc which is used to charge the battery of Electric vehicle. RIPT system basically differs from conventional inductive power transfer (IPT) system in that the system operates at a
resonance. The main advantage of RIPT methodology is that at resonance the reactive component of inductor and the capacitor cancel out each other and the system behave as purely resistive due to which maximum current flows. A fundamental impediment to the efficient operation of an RIPT system is the existence of bifurcation phenomenon in a doubly tuned circuit. We will be using proper design
techniques to avoid bifurcation in our system. Wireless charging is not only safe but also minimizes the number of charging cables eventually reducing the cost of EV charging and achieves an efficiency of 90% - 92%.

Project Objectives

With the growing world and advancement of technology we have selected this project to study the advanced methods of charging the electric vehicles and make a product which can be used in parking lots, house garages, public stations, etc. to charge the vehicle. It is a product which is user friendly, the electric vehicle owner does not have to manually plugin the charger instead the car is parked on the slot and the charging begins automatically. The second most important objective of project is to make a safer method of charging EVs as the manual charging includes direct human interaction with electricity and any mishap can cause swear damage to human health of the vehicle. Wireless charging does not have direct contact with electricity (only linked magnetically) isolated by an air gap which provides a safer environment for the charging process. In previous wireless topologies there are too many power losses which doesn’t make them suitable for charging process. But our objective is to minimize the power losses by using different topologies which are operating system at higher frequencies ranging between 40k Hz to 90 Hz, using special design of transmitting and receiving pads, use of  ferrite bars across both transmitting and receiving pads, use of resonant operating circuit to minimize the internal losses  across the components.

Main objective also includes:

• Deign of  regulated dc supply
• A high frequency inverter of 80k to 90k Hz
• Resonant operating circuit at both sides of transmitter and receiver
• Special design of transmitter and receiver pads to maximize linkage
• Secondary side rectifier and filter to smooth the output dc which will be fed to the battery.

Project Implementation Method

The circuitry of the system includes AC source at the start, the AC supply is converted to DC which is then inverted to high frequency AC supply at the transmitting pads through switches and through this power is transfer wirelessly to the receiving pad. After the receiving AC supply at the receiving pad, the AC supply is converted to DC and through which the battery in the vehicle is charged. The methodology used for transferring the power wirelessly from transmitting pad to secondary pad is called resonance inductive power transfer(RIPT). For resonance case, series configuration of L and C is used at the both transmitting and receiving pads. The efficient power transferring is achieved at the point when the resonance frequency at the transmitting and receiving pad is matched together. At resonance frequency the inductor and capacitor each other effect on both the transmitting and receiving pads, showing resistive behavior thus maximizing the output efficiency. The resonance frequency ranges from 10 kilohertz to 100 kilohertz, in our case it is 40 kilohertz. As the resonance frequency increases the flux generated at pads increases, effecting the mutual induction process and causes the reduction of coupling coefficient. The coupling coefficient ranges between 0.2 and 0.3 due to the minimum height clearance requirement of the electric vehicles. For this scenario, magnetic ferrite cores in a variety of structures are utilized in order to improve the coupling coefficient in the wireless power transfer topology.

Benefits of the Project

• Wireless charging is a convenient topology of charging where the electrical contacts are not acceptable or battery is embedded in the product.
• Wireless charging also reduces the amount of cables and power adapters for charging of the electrical vehicles increasing convenience and aesthetic quality of charging. 
• Wireless charging enables the safe usage of maximum charging power and thus makes charging much faster as compared to traditional charging through adapters.
• Wireless charging of EV's is a safer and user friendly way of charging as driver just need to park the vehicle on the pad and charging starts automatically.
• This method of charging reduces the wear and tear of electrical sockets and cable. It provides higher reliability as the charging system automatically operates without the dependence on user to plug and unplug the cable, thus providing higher durability.
• There is less chances to electrical faults, protection against danger of corrosion as circuits and devices are enclosed.

Technical Details of Final Deliverable

Our final deliverable is prototype of a static wireless charger for EVs which includes all the technical details of the charging process. It includes the primary rectifier which rectifies the ac input signal into dc signal which then filtered using LC combinations. Then we are using a high frequency inverter which will convert that dc into high frequency ac. To achieve high frequency with minimum internal loses we are using Mosfets in our switching techniques. The main purpose of this ac into dc and then dc into ac conversions is to achieve high frequency for our transmitter circuit. We need high frequency to maximize our flux linkage between transmitter and receiver. After achieving high frequency we have used resonant operating circuitry across the transmitter (which is basically an inductor coil).we used resonant circuits to minimize the internal losses because we know at resonance internal impedances of capacitors and inductors becomes zero and only resistive losses are left. Our main goal is to lower leakage flux as we are using air as core so to get maximum flux linkage we have used a special design of transmitter pads which is known as DD pads. It is designed in such a way that it will maximize the flux linkage. Furthermore we have added ferrite bars in transmitter and receiver coils. Then after receiver the signal is converted into dc using a rectifier and this dc is filtered out using LC combination and fed ti the battery.

Path of power flow:

Ac input ? rectifier ?filter ? HF inverter ? primary resonant compensation circuit? transmitting pad? receiving pad ? secondary resonant compensation circuit ? rectifier ? filter ? battery.

Final Deliverable of the Project

Hardware System

Core Industry

Manufacturing

Other Industries

Core Technology

Others

Other Technologies

Sustainable Development Goals

Industry, Innovation and Infrastructure

Required Resources

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