The principle of electric vehicle wireless charging analysis of electric vehicle wireless charging technology
1. Types of non-contact charging devices
There are three types of non-contact charging devices: electromagnetic induction, magnetic resonance, and microwave.
Second, the advantages of non-contact charging devices
Compared with electric vehicles, traditional fuel vehicles are not only in the convenience of use, curb weight, driving ability There are many advantages in terms of , manufacturing and operating costs, and fuel replenishment does not consume more time.
Electric vehicles not only take a long time to charge, but also have operational inconveniences when replacing batteries or using charging piles to charge through cables, and the safety of working in rainy days is even more worrying.
In contrast, contactless charging devices do not require a cable to connect the vehicle to the power supply system, allowing it to be charged directly and quickly. In addition, non-contact fast charging can be arranged in various places such as parking lots, houses, roadsides, etc., and can provide charging services for various types of electric vehicles (including plug-in hybrid electric vehicles), making electric vehicles charging anytime, anywhere. possible. For buses, charging facilities can be arranged at terminals, hubs, transfer stations, etc., and fast charging can be completed with a short parking time.
Three, the working principle of non-contact charging device
1, electromagnetic induction method
Electromagnetic induction transmits electricity between the power transmission coil and the receiving coil, which is the most practical charging method. When there is an alternating current in the transmission coil, alternating magnetic fluxes are generated between the sending (primary) and receiving (secondary) coils, thereby generating an induced electromotive force that changes with the magnetic flux in the secondary coil, and passes through the terminals of the receiving coil. Output alternating current to the outside.
The current problem is: the power transmission distance is relatively short (about 100mm), and when there is a large deviation between the power transmission and the receiving part, the power transmission efficiency will drop significantly; The size is directly related. When high-power transmission power is required, more investment in infrastructure construction and power equipment is required.
2, magnetic resonance method
The magnetic resonance transmission method was developed by the Massachusetts Institute of Technology (MIT) in 2007 Since its success, it has been widely concerned by countries all over the world.
It is mainly composed of main parts such as power supply, power output, power receiving, rectifier, etc. The principle is basically the same as that of electromagnetic induction. When there is current passing through the power transmission part, the generated alternating magnetic beam makes the receiving part generate an electric potential, and outputs the current when charging the battery.
The difference from the electromagnetic induction charging method is that the magnetic resonance method is equipped with a high-frequency drive power supply, and uses an LC resonance circuit with both a coil and a capacitor, instead of a simple coil that constitutes both power transmission and reception. unit.
The value of the resonance frequency will change with the distance between the transmitting and receiving units. When the transmission distance changes, the transmission efficiency also decreases rapidly like electromagnetic induction. To this end, the resonant frequency can be adjusted by the control circuit, so that the circuits of the two units resonate, that is, “resonance”. Therefore, this magnetic resonance state is also called “magnetic resonance”.
By changing the frequency of transmission and reception under the action of the control loop, the power transmission distance can be increased to about several meters, and the resistance of the two-unit circuit can be minimized to improve the transmission efficiency.
Of course, the transmission efficiency is also related to the diameter of the transmitting and receiving electrical units. The larger the transmission area, the higher the transmission efficiency. The current transmission distance can reach about 400mm, and the transmission efficiency can reach 95%.
3, Microwave method
A 2.45GHz radio wave generator is used to transmit power, and the transmitter is connected to the “magnetic field” used in microwave ovens. Control” is basically the same. The transmitted microwave is also an alternating current wave, which can be received in different directions by an antenna, and converted into direct current by a rectifier circuit to charge the car battery.
In order to prevent microwave leakage during charging, the charging part is equipped with a metal shielding device. In use, the effective shielding between power transmission and reception can prevent microwave leakage.
The main problem at present is that the efficiency of the magnetron to generate microwaves is too low, causing a lot of electricity to be consumed as heat energy.
