Design of the electric vehicle charging device

Hawkins S. The design of the electric vehicle charging pile [J].

SAE International Journal of Alternative Powertrains,

2015，5（3）: 213-221.

Abstract

Under the severe situation of the world shortage of oil resources and global climate warming, the construction of low-carbon vehicles will become a new development direction of the automobile industry.The global research on electric vehicles has entered white-hot, and people are trying to make them the mainstream in the 21st century.Electric vehicle charging device is an important part that cannot be ignored in the electric vehicle industry chain. While vigorously developing the electric vehicle industry, it should also fully consider the development of charging devices. Therefore, it is very necessary to study the design of electric vehicle charging device and its control methods.

Key words: electric vehicle charging device; balanced control; human-computer interaction

1 Introduction

Countries around the world are advocating energy conservation and environmental protection, among which the word "low-carbon" is familiar to everyone. Today's automobile carbon emissions are large, and the research focus of the automobile industry has gradually shifted to the low-carbon field.The auto industry is generating higher carbon emissions.In order to do a good job in the rise and development of the industry and environmental protection and emission reduction balance, the automobile industry is facing the transformation of development.Under the severe situation of world oil resource shortage and global warming, the unified standards of the global automobile industry will refer to the carbon emission standards, thus making the better development of the global automobile industry.Electric cars, show prominent advantages in environmental protection and energy saving.Electric vehicles have many advantages, such as less polluting gas emissions, high energy efficiency, low noise, low operating cost, etc., and these advantages are of great significance in alleviating air pollution and energy shortage.

2 Electric vehicle charging infrastructure

The key technologies of electric vehicles mainly include: energy system with power battery and charging device as the core, power system with drive motor and transmission system as the core; and vehicle control system to ensure the safe, efficient and comfortable operation of the vehicle.For carbon-friendly electric vehicles, the charging device is indispensable. Its function is to transform the power of the power grid into the electric vehicle battery to provide power for electric vehicles.

Charging devices are mainly charging stations and charging devices.Charging charging stations are generally equipped with a number of fast charging plugs and a few slow charging devices.Some cities plan to build charging devices in public places such as residential areas, parking lots, and supermarkets.The two charging devices have their own advantages and disadvantages, and the suitable for local devices should be selected according to the actual situation.Charging stations mainly with fast charging mode have the advantages of short charging time and high charging efficiency.The power sources selected in the service areas and large charging stations along the highway are mostly charging devices that can generate 600V / 300A DC power.Usually, factors including the use environment should be considered. The charging device can only ensure the charging efficiency of electric vehicles only when generating higher voltage and large current, and the power is large (about 100KW), which puts forward high requirements for the technical method and safety of charging.Therefore, the charging station consumes a much higher construction and management cost than the charging device, and the scale should be the same as that of the gas station.Now the car battery technology still needs to be developed, and the fast charging mode will cause great damage to the battery.Experts believe that the fast charging mode is equivalent to forcing "pouring" electricity into the battery in a relatively short period of time. After several fast charging, the life of the battery will be greatly reduced.In addition, it is worth noting that the charging demand of large-scale electric vehicles cannot be met by relying on the charging stations alone, and the charging stations will occupy the land area, which will produce a large number of management costs.Therefore, charging stations are only suitable for charging services for a small number of public transport.Charging device covers a small area and a low cost, which is very suitable for the construction of supermarkets, parking lots, residential areas and other vehicle parking areas.More importantly, the charging device is mainly slow charging mode, because it requires a very small current, which ensures its safety performance, and is good for the extended battery life.But the disadvantages of this mode are also obvious, when the vehicle has an emergency operation demand, can not be charged in time.For example, a home charging device providing an AC power supply of 220V / 16A, is a small and simple on-board charger.The charging device mainly provides charging services for private cars. The power is about 3 to 5 kilowatts, and the charging time takes 5 to 10 hours.

3 Present situation of charging system

In recent years, charging system has made good progress in terms of both product and technology: with the development of advanced technology such as control technology and artificial intelligence, charging products have developed in the direction of multifunctional and safer intelligence; field industrial bus technology, such as CAN, RS485 and LIN bus makes the communication means of monitoring system diversified, high speed and secure.France uses nuclear power and hydropower, with sufficient power generation capacity. According to statistics, three quarters of its total power generation comes from nuclear power plants and one sixth from hydropower stations, so its power supply is clean, cheap electricity price and developed automobile industry, so it is one of the first countries in the world to develop and promote electric vehicles.(Go to Baidu Library) The French government cooperates with EDF (EDF), and cooperates with PSA Company, Renault (Renault) Automobile Company and many other companies to develop electric vehicles.The investment of 50 small four electric vehicles in LaRocheHe (La Rochelli) and 12 (including three fast and nine ordinary) charging stations have been in service and tested for more than two years.Japan's new energy vehicles have also been at the world's lead level, and Tokyo Electric Power has announced its successful development of a large fast charger, which greatly reduces the charging time, providing a greater possibility for the popularity of electric vehicles in Japan.On the construction of the design of charging devices and control charging devices, First Solar in the United States first built five fast charging devices at high speed in California, capable of charging electric vehicles within 3.5 hours at 240V / 70A.

4 Charging pile of functional requirements

With electric passenger cars promote gradually, people to its corresponding charging infrastructure also gave high attention. If the charging station, charging pile, can carry on the security and intelligence to the electric vehicle charging, so the popularity of electric cars, progress will be accelerated. In order to realize intelligent charging pile in the management and application, you need to understand the function of charging pile demand. Electric vehicle charging piles need to have the following several main functions: to guarantee the normal work of the system, monitoring and protection measures necessary, charging posts must have electrical protection device, when the system failure occurs, the system of charging power supply is cut off quickly, within the stipulated time to ensure the personal safety of users. Charging pile must be reliable operation, charging pile equipment adopts modular structure; local fault cannot threaten the normal operation of the whole system, charging pile must also be able to parallel processing more than one event. All logins, control, exit the important operations, such as charging pile should have corresponding records, but also allows to query and statistic of operating records, charging pile have ensure data and system security protection of information is not theft and destruction. Charging pile should use the graphical interface in Chinese, the user according to the screen display can realize self-help charging; provide convenience for people intuitively clear charging operation. Users can query on charging pile to the charging time, place, and the historical data of the basic information such as rechargeable battery, charging pile should also install with embedded printers, convenient charging print statements. Charging pile should be according to the electricity information deriving from watt-hour meter, and calculate the user charge the amount spent, and can save data backup, convenient send to background monitoring system. Charging pile system should be able to practice the trapezoidal pricing mechanism.

5 The integral design of charging pile system

The electric car is ac charging pile used in ac, dc power supply, ac working voltage is 220 v or 380 v, can according to different types of electric vehicles, adopts the corresponding charging voltage grade, ordinary pure electric car charging pile to charge need 4 ~ 5 hours. The input voltage of dc charging pile using three phase four wire AC380V, frequency 50HZ can provide enough power, and the output of adjustable dc, therefore can meet the requirement of quick charge. Electric vehicle charging pile, concentrator, battery management system, charging management platform, such as complementary to each other, constitute the charging system. Battery management system (BMS) real-time information interaction with charging posts controller, the purpose is to monitor the battery voltage, current and temperature state parameters, forecast capacity (SOC) of batteries, batteries in to avoid bad phenomenon (over discharge, overcharge, overheating and battery voltage imbalance between monomer), it can maximize battery storage capacity and cycle life of assurance. The service management platform is mainly to the electric car battery charge information, IC and piles these data for centralized management of information. In general, the service management platform is important function for charging management and operation, as well as integrated query. To intuitively clear communication with the customers, charging pile has important information can be shown on LCD display convenient man-machine interaction. Electric vehicle charging, the screen will display the charging time, charging power, the main information such as the amount payable.

Charging, the battery charging or owe electricity will damage to the battery inside, accelerate cell aging, will affect battery performance. According to the analysis, the inappropriate way of charging is the main cause of battery life cut short. Therefore, how to guarantee quickly and does not affect the battery life, has become an important research topic in recent years. Charging mode choice determines the length of the battery life, among them, the constant current, constant voltage charging and charging in stages of these methods is a common way of charging. Is the advantage of constant current charging control method is simple, but by the law of mass we know: rechargeable batteries can accept current capacity with the charging process is a trend of gradual decline. Late to charge, the charging current is much used for electrolysis of water, can produce gas, so that to get nothing. Constant voltage charging way early in the process of charging current is too large, the impact on battery life is great, and constant voltage charging mode battery plate bending easily, causing the battery scrap. Phase charging method is actually a constant current, constant voltage charging the method of combining more commonly used phase charging method includes two stages and three phase charging method.