New Energy Vehicle Technology Research


Nowadays, the shortage of oil and fossil energy and pollution problems are getting more and more serious. Due to its low energy consumption and non-polluting characteristics, electric vehicles are developing rapidly. Electric vehicles are a new type of environmentally friendly vehicles powered by on-board batteries, which is an important solution to solve the problem of high consumption of non-renewable fossil energy, environmental pollution and reduce operating costs. There are two types of charging methods for electric vehicles: wired charging and wireless charging. Wired charging technology has defects such as complicated operation, unsafe plugging and unplugging, and poor environmental adaptability, which creates obstacles for the development of the electric vehicle industry; whereas wireless charging technology has the advantages of convenient operation, no contact dissipation, no high-voltage danger, and high automation, which is the mainstream trend in the current market.


Pure electric vehicle wireless charging has a small footprint unit can be charged vehicles more convenient operation static that is stopped that is charged, dynamic that is open that is charged, low damage rate mechanical connection less advantages, and can even solve the current electric vehicle range anxiety. Why over the years, wireless charging technology, still has not been popularized in large numbers? The basic principle of cell phone wireless charging device is the principle of electromagnetic induction, electric vehicle wireless charging technology is also used by the principle of electromagnetic induction. Electric vehicle wireless charging technology popularization difficulties in which?

Basic Principles of Wireless Charging Technology for Electric Vehicles

Wireless charging is a technology for wireless energy transfer, usually using the principle of electromagnetic induction. Electromagnetic induction is the phenomenon of induced electromotive force due to a change in magnetic flux. An electric current is generated in a conductor when a portion of a closed circuit moves in a magnetic field cutting through the magnetic inductance. Electromagnetic induction generally performs low power wireless charging and uses resonance for high power wireless charging. The power supply (charger) transmits energy to the device, which uses the energy it receives to charge the battery and operate itself at the same time.

Wireless charging technology utilizes wireless energy transmission technology to allow devices such as electronics and automobiles to be charged without the need to connect to a power cord. Currently, there are four main types of wireless charging technology: electromagnetic induction, magnetic resonance, radio wave and electric field coupling. With the progress of science and technology and market demand, wireless charging technology has a broad development prospect, but also faces some technical difficulties. The realization of wireless charging is divided into

(1) Electromagnetic induction type wireless energy transmission system is based on the principle of magnetic field coupling, which establishes an alternating magnetic field between the primary and secondary coils by means of a separable transformer structure, thus inducing a current in the secondary coil. Since the magnetic field can penetrate non-metallic materials, the system can realize the transmission of electric energy at a certain distance without electrical contact.

(2) Magnetic field resonance wireless charging technology is a method of realizing energy transmission based on the principle of magnetic field resonance, which is based on the principle of forming a changing magnetic field at the transmitting end, and then converting the magnetic field energy into current energy by resonating with the coil at the receiving end. This technology is suitable for low-power wireless charging applications, and the key is to make the electromagnetic frequency of the receiving antenna and the transmitting field reach the same.

(3) Radio-wave wireless charging This method uses microwaves as a carrier for transmitting energy in free space and has the advantages of directionality and penetration of the ionosphere. It consists of a microwave transmitting device and a microwave receiving device that captures the radio wave energy bouncing back from the wall and maintains a stable DC voltage level as the load changes.

(4) The electric field coupling wireless charging technology utilizes two sets of asymmetric dipoles to generate an induced electric field along the vertical direction and coupled to each other, thus realizing the power transmission in a way called electric field coupling.

EV Car Home Charger Application

Types of Wireless Charging Methods for Electric Vehicles

Slow charging

AC charging technology is based on the principle of utilizing an AC charging interface to transmit AC power from the AC grid directly to the energy storage device and converting it to DC power through a built-in inverter and performing a charge/discharge cycle. This technology takes a long time to achieve a high percentage of replenishment, typically reaching 100% in 6 to 8 hours.

Fast Charge Charging

High-power DC charging technology is characterized by the use of DC charging interfaces to convert AC power from the AC grid into DC power through inverters, and carry out high-efficiency charging and discharging cycles to the energy storage device through fast charging interfaces. This technology can achieve a high percentage of replenishment in a short period of time, typically up to 80% within 30 minutes.

Energy exchange mode

The energy exchange mode for new energy vehicles is characterized by the rapid replacement of the power system of new energy vehicles in dedicated energy exchange stations, instead of the traditional charging method. This mode is characterized by storing, charging, discharging, circulating and distributing large quantities of power systems through centralized charging stations, and realizing rapid matching and replacement between power systems and new energy vehicles in the energy exchange stations, thus realizing the integrated operation of charging, discharging, circulating, logistic scheduling and energy exchange services.

Wireless Charging

The principle of wireless charging technology is to utilize the inductive effect generated by the high-frequency AC magnetic field to wirelessly transmit the electric energy in the guide rail buried underground to the vehicle traveling on the ground and equipped with a receiver, and to carry out charging and discharging cycles for its energy storage device. This technology reduces the dependence of electric vehicles on power system capacity, improves their range performance, and enhances the safety and convenience of replenishment services.

Analyze and Compare

At present, the most mainstream charging efficiency in China is 7Kw for slow charging and 15Kw-360Kw for fast charging. slow charging does not consider the power transmission loss, while radio charging is more "wasteful" than wired charging. Fast charging, in terms of power, wired fast charging is more advantageous in the high-frequency band. Power exchange mode represented by Azera, directly replace the battery pack, only 3-5 minutes to complete the replenishment; while the wireless charging time is related to the charging power, even if the full power charging, such as 70Kwh power battery, full 22Kw of power needs 3 hours. But the car has static wireless charging and dynamic wireless charging. Under the low frequency band power wireless fast charging of dynamic wireless charging, there will be the phenomenon that power is still decreasing even if it is charging. The power input is not as good as the power output.

Compared with the charging mode, the power exchange mode has the following advantages:

Fast speed of energy exchange: in general, a single exchange can be completed in only 1-5 minutes, while charging takes half an hour or even more than an hour This can effectively alleviate the user's mileage anxiety and improve the driver's earnings.

Low cost of purchase: adopting the mode of "separating vehicle and power system", users only need to purchase the vehicle itself, and lease or purchase the power system according to the usage. This reduces the upfront cost of purchasing a vehicle and enjoys policy subsidies.

Ensure safety: As all power systems are managed and monitored by professional operators, charging and discharging cycles are carried out under constant temperature conditions, and regular testing and maintenance is performed. This avoids factors such as over-discharge/charging, excessive temperature, etc., which may affect safety and lifespan.

Enhanced utilization: Since all power systems can be used and shared among different vehicles, they can be deployed and utilized during idle time. This increases resource efficiency and reduces operating costs.

Key issues that make wireless charging for electric vehicles difficult to penetrate

While a gasoline vehicle typically takes only a few minutes to fill up a tank of fuel at a gas station, the fastest wireless charging technology takes much longer to fully charge a depleted vehicle than it does to fill it up. Long charging times are one of the main factors limiting the widespread use of electric vehicles. Therefore, in order to further expand the application prospects of wireless charging technology in the field of electric vehicles, it is necessary to continuously increase the research on fast charging. At the same time, the battery life of the vehicle should be extended in order to significantly reduce the charging interval and improve the efficiency of the vehicle. Supercapacitors are one of the effective ways to solve this problem and can be used for wireless charging.

Compared with the traditional wired charging technology, wireless charging technology adds two coils and utilizes the coupling effect to achieve energy transfer, and it is difficult to avoid energy loss because the whole charging process is completed without contact. In addition, with the addition of the coils, the internal resistance of the coils themselves causes a certain amount of power consumption, which increases the complexity of the wireless charging system model. In view of this, the following should be the focus of research in the coming period.

Cost problem: As far as economy is concerned, the difficulty of wireless charging for electric vehicles lies in the charging equipment. The path of a car is different from that of a railed moving car, subway, or tram, which is dispersive and random. Therefore, in terms of access to charging equipment, it is easier to arrange the equipment under a fixed line; for electric vehicles with unpredictable trajectories, the accessibility of static wireless charging and dynamic wireless charging is different. In the case of static charging, i.e., wireless charging when the vehicle is stationary, it is a fixed route, except that this type of fixation is stationary. Similar to a cell phone, it is sufficient to be equipped with a wireless charging socket. Let's take the BMW 530e as an example. Its earlier wall box charging post costs $1,000 per unit, and wireless charging devices can be even more expensive. Dynamic charging is wireless charging while the vehicle is in motion. Dynamic wireless charging uses the most efficient magnetic field resonance method of wireless charging. The highway becomes the charging device, the electric vehicle is the appliance, and the magnetic field is the transmission medium. The difficulty lies in the construction of infrastructure such as highways.

EV Home Charger Application

Wireless charging technology solution direction for electric vehicles

A new type of wireless charging infrastructure for roadways

Rechargeable roads are a new type of charging infrastructure that can provide continuous power to moving electric vehicles, alleviating the range problem of electric vehicles and reducing users' reliance on batteries. The current e-Road is contactless driven, i.e., powered by wireless charging technology for EVs, and is suitable for different locations such as parking lots, garages, and roads. One of the most mature inductive charging pavement technologies is represented by dynamic inductive charging. Compared with other types of charging pavements, inductive charging pavements based on IPT systems offer potential advantages such as safe operation, ease of use, low maintenance costs, and good user experience, because the charging device is buried in a shallow part of the pavement structure, which does not take up space above the pavement, and there are no exposed physical interfaces.

Charging Device Selection

The selection of charging devices is a key link in the design of EV wireless charging system and an important factor affecting battery charging. The choice of charging pile should be based on the actual situation of the electric vehicle, under the premise of ensuring safety, reducing costs as much as possible, and also taking into account the scalability and maintainability of the electric vehicle. At present, there are mainly the following types of charging equipment on the market:

Lithium-ion batteries. (1) Lithium-ion batteries are characterized by small size, light weight, long life, no memory effect, and are not easily over-discharged, but due to their low energy density, they are used in harsh environments, and it is difficult to make improvements to them.

(2) Nickel-cadmium lead-zinc battery. It has the advantages of high power density, large capacity, light weight, good corrosion resistance, low price, but low storage capacity, low discharge voltage, narrow temperature range, the damage to the battery, and need to be replaced periodically. In the practical application of electric vehicles, the choice of charging equipment is directly related to the power, safety and economy of electric vehicles.

Therefore, when charging electric vehicles, the following aspects must be considered:

(1) the capacity and size of the charging station. In order to ensure that the demand for electric vehicles can be met under different loads; at the same time, the need to increase the capacity of the charging station should also be determined according to the load of the power grid.

(2) Charging speed and efficiency. Due to the current level of technology, most of the electric vehicles in China use the charging method of constant-current coil, so the control of its power is highly required. If the output voltage of the battery is increased, it will lead to waste of energy and loss of power. On the contrary, if the rated current of the constant current coil is not reduced, it will not reach the expected peak value, which will result in unnecessary energy consumption.

Charging coil optimization

Parametric design and characterization of the coil's shape, size, and the current flowing through it can help regulate the system's output power and transmission efficiency, which is related to the coil's mutual inductance coefficient. Current conventional coil configurations include three-dimensional helical coils, planar circular coils, and planar square coils. Due to the limited vertical mounting space of automobiles, planar coils are more suitable, which needs to be considered when selecting mutual inductance coils for electric vehicles. In practice, the rechargeable batteries of electric vehicles usually have low input resistance and high charging current.

The compensation network of the wireless charging coil refers to the fact that in order to realize more efficient power transmission in the wireless charging system, it is necessary to design the compensation network at the transmitter and receiver ends separately to compensate for the energy loss and noise interference in the wireless transmission process. The compensation network at the transmitter side mainly plays the role of matching and filtering, which can match the output impedance of the signal source with the input impedance of the wireless charging coil and filter out high-frequency noise and interference signals. The compensation network at the receiving end mainly plays the role of inverter and amplifier, which can convert the received wireless signal into DC power and amplify the output. The design of the compensation network needs to take into account a variety of factors, such as the operating frequency of the wireless charging system, the parameters of the coil, the transmission distance, etc., in order to achieve the best power transmission efficiency and system performance.

Future Outlook of Wireless Charging Technology for Electric Vehicles

The wireless charging technology industry will develop rapidly from 2020 to 2035, and the market for wireless charging will further expand after 2035 when the intelligent automobile industry matures. Wireless charging technology for electric vehicles has a great development prospect in the future. Wireless charging technology for electric vehicles is of great significance in realizing carbon peak by 2030 and carbon neutrality by 2060, alleviating environmental pollution and energy crisis. The goal of carbon neutrality has been achieved. The proposal of the "double carbon" goal will make China's green development road to a new level and become one of the main keynotes of social and economic development in the next few decades. The development of wireless charging technology for electric vehicles should consider "one-to-many" simultaneous charging for multiple vehicles to improve transmission efficiency. Wireless charging technology has been widely used in the field of electronic products, and with the transformation of energy structure, the automotive industry will also become one of the important markets for this technology, bringing new opportunities and challenges for its development. The improvement of the power grid system, the progress of electric energy technology and the increase of people's demand for wireless charging will promote the prospect of wireless charging technology. Of course, this also requires advanced scientific technology as a guarantee.


The reason why wireless charging technology is not popular is because the efficiency is too low at this stage, the economy is poor, resulting in low penetration rate, but the future development potential is very large. Wireless charging technology for electric vehicles has the convenience and safety that cannot be compared with wired charging. Existing wireless charging technology relative to wired charging, charging efficiency has not a small gap, and its expensive infrastructure is more discouraging. Wireless charging coil research, compensation network optimization, the development of electric vehicle wireless charging system, electric vehicle wireless charging popularity is not far away. Positively respond to the national policy of carbon peak by 2030, carbon neutral by 2060, to alleviate environmental pollution, energy crisis In addition, based on the current energy scarcity, it is too early to industrialize electric vehicles with high-power wireless charging technology, but as a flexible charging method in the future, it is necessary to explore in advance. With the continuous progress of technology, combined with the construction of China's smart grid, its application in the electric vehicle intelligent charging and switching service network will greatly promote the large-scale popularization of electric vehicle wireless charging.