Key technologies of fuel cell vehicles

　　Compared with internal combustion vehicles, electric vehicles have a shorter driving range, so in order to maximize the use of on-board stored energy, a suitable energy management system must be selected. Sensors can be installed in various subsystems of the car, including temperature sensors inside and outside the car, current and voltage sensors for charging and discharging time, current and voltage sensors for electric motors, vehicle speed sensors, acceleration sensors, and external climate and environment sensors. The energy management system fulfills 9 functions:

　　1) Optimize system energy flow;

　　2) Estimating the energy generated to estimate the distance that can still be traveled;

　　3) Provide reference for effective operation;

　　4) Obtain energy directly from braking and store it in energy storage components, such as batteries;

　　5) Adjust temperature control according to the outside climate;

　　6) Adjust the light brightness according to the external environment;

　　7) Estimate the appropriate charging algorithm;

　　8) Analyze energy sources, especially battery work records;

　　9) Diagnose any inappropriate or ineffective operation of energy sources.

　　Combining the energy management system with the navigation system makes it possible to plan energy-efficient routes, locate charging stations and predict the driving range based on traffic conditions. In short, the energy management system combines the significant advantages of multi-function, flexibility and changeability, so that limited on-board energy can be rationally utilized

　　1 fuel cell

　　Compared with electrochemical cells, the significant advantage of fuel cells is that fuel cell electric vehicles can achieve the same driving range as fuel vehicles. This is because the driving range of fuel cell electric vehicles is only related to the amount of fuel in the fuel tank. Regardless of the size of the fuel cell. In reality, the size of the fuel cell is only related to the level of power requirements of the electric vehicle.

　　Advantages of fuel cells:

　　1) The reactant feeding time is much shorter than the charging time of electrochemical batteries (except for mechanical rechargeable batteries);

　　2) The service life is longer than that of electrochemical batteries and the battery maintenance workload is smaller. Compared with ordinary batteries, a fuel cell is an energy generating device and continues to generate energy until the fuel is used up. The advantages of fuel cells include: 1) converting fuel into electrical energy with high efficiency;

　　2) Work quietly;

　　3) Zero-emission or low-emission work;

　　4) The remaining heat generated can be reused;

　　5) Fuel replenishment is quick and fuel is easy to obtain;

　　6) Durable and reliable work.

　　Fuel cell electric vehicles are an integrated product of the latest achievements in engineering technologies such as automobiles, electric drive, power electronics, automatic control, chemical power sources, computers, new energy and new materials. Therefore, the development and industrialization of fuel cell electric vehicles require solving many key technologies, such as fuel cells, motor control, body and chassis design, testing technology and system optimization.

　　2 New fuel cell technologies

　　Fuel cells use the electrochemical reaction of hydrogen and oxygen to generate clean energy without producing CO2. However, due to limitations of hydrogen storage technology, current vehicle prototypes and demonstration models powered by fuel cells can only reach a maximum driving distance of 322 km. Under standard temperatures and pressures, to store enough hydrogen to reach a driving distance of 483 km requires an onboard fuel cell with a volume equivalent to a double-decker bus; other methods include compressing and storing hydrogen in cylinders or Liquefied hydrogen is stored in tanks, etc., but these methods are impractical due to quality and volume issues.

　　Researchers from the UK-SHEC project team are trying to store hydrogen at a higher density to control battery quality within an acceptable range. They use chemical adsorption methods to draw gas molecules into the crystal lattice of solid compounds and release them when needed. Now, researchers have developed a series of lithium hydride compounds that can meet these requirements well. The project coordinator, Professor Peter Edwards of the University of Oxford, UK, said that this is a long-awaited breakthrough for the fuel cell industry and the transportation sector. This key breakthrough will enable the mass production and application of fuel vehicles in the next 10 years. possible.

　　3 Drive motor technology

　　In order to enable the vehicle to travel more miles with enough fuel at once, to maximize the use of hydrogen energy and to minimize the vehicle's curb weight after modification, the electric drive system is required to have high efficiency and power-to-weight ratio. Drive motors should develop towards high power, high speed, high efficiency and miniaturization. Current drive motors mainly include induction motors (IM) and magnetic brushless motors (PMBLM). In particular, permanent magnet brushless motors have the advantages of high power density and efficiency, small size, low inertia and fast response. In terms of electric vehicles, It has broad application prospects. When designing and selecting the drive motor, it should be ensured that the torque/speed characteristics of the motor match well with the load characteristics of the vehicle, the dynamic performance of the motor torque is good, and the efficiency of constant speed, constant power and variable working conditions should be high.

　　4 Electronic control technology

　　Like traditional vehicles, electronic control will play an increasingly important role in the development of fuel cell vehicles. Various control systems of automobiles will develop in the direction of electronics and electrification, realizing wire control, that is, using wires to replace mechanical transmission mechanisms, such as wire braking and wire steering. The existing 12 V power supply can no longer meet the needs of all electrical systems in automobiles, and the implementation of the new standard for 42 V automobile electrical systems will cause major changes in the design and structure of automobile electrical components; at the same time, mechanical relays and fuse protection circuits will also be eliminated. The characteristics of fuel cells have their own characteristics:

　　1) Low voltage and high current;

　　2) The output current will increase as the temperature increases, and the output voltage will decrease as the output current increases;

　　3) From the beginning of outputting voltage and current to gradually entering a stable state, the dynamic response time staying within the transition zone is relatively long.

　　It is precisely because of the above characteristics that most electrical appliances and motors cannot adapt to their voltage characteristics, so they must be used in conjunction with DC/DC converters and DC/AC inverters. A large amount of power adjustment is required on the fuel cell system to ensure voltage stability. .

　　5 Vehicle system optimization technology

　　The entire vehicle system of a fuel cell electric vehicle is a complex system involving multi-disciplinary technologies, and its performance is affected by multi-disciplinary related factors. Therefore, the entire vehicle system must be optimized based on full consideration of various influencing factors, and the fuel cell system can be improved. Battery electric vehicle performance and reduced vehicle design and manufacturing costs.

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