Electric car is a kind of electric vehicle. It refers to the car which is provided with full or partial power by on-board power supply and driven by electric motor to drive the wheel, meeting various requirements of road traffic and safety laws and regulations.
This paper focuses on the composition, basic parameters and functions of several key components of pure electric vehicles, and briefly introduces the driving mode and classification of hybrid electric vehicles and fuel cell electric vehicles, striving to be easy to understand.
Definition of battery electric vehicle
Battery electric vehicle refers to the vehicle fully powered by on-board power supply and driven by electric motor to drive the wheels.
Battery electric vehicle basic composition
Battery electric vehicle mainly consists of three parts: power supply system, electric drive system and auxiliary system.
When the car is running, the electric energy (current) output by the power battery drives the motor to run with the comand of the controller, and the torque output by the motor drives the wheel forward or backward through the driveline.
1. Power supply system
Including power battery, battery management system and charger.
The function of the power battery pack is to drive the electric motor to provide the drive electric energy. The power battery pack of battery electric vehicles commonly used has lead-acid battery, nickel-cadmium battery, nickel-hydrogen battery, lithium ion battery and so on.
Battery management system, its main function is to conduct real-time monitoring of the power battery pack and monomer, monitoring the use of the battery and control the charger to charge the battery pack.
The purpose of the charger is to receive and execute the instructions of the battery management system to convert the alternating current of the grid to direct current to supplement the power of the battery pack.
2. Electric drive system
Electric drive system mainly includes motor controller, power converter, drive motor, mechanical transmission device and wheel, etc.Its function is to transform the electric energy in the power battery pack efficiently into the kinetic energy of the wheel, and can collect be the wheel's kinetic energy into the electric energy into the power battery pack in the car deceleration braking process .
3. Auxiliary system
It mainly includes auxiliary power source, air conditioner, power steering system, navigation system, wiper, radio and lighting and defrosting device.
Auxiliary power source mainly consists of auxiliary power supply and DC/DC power converter.Its function is to power steering system, air conditioner and other auxiliary equipment to provide power.
Introduction to hybrid electric vehicles
1. Hybrid electric vehicles
Hybrid electric vehicle refer to the car equipped with two or more power sources, including motor driven, in line with the road traffic and safety rules and regulations of car. Car power source has a variety of: battery, fuel cells, solar battery, diesel engine generator set. The current hybrid electric vehicle is usually refers to the diesel engine generator and battery electric vehicles.
2. Advantages of hybrid electric vehicles:
(1) after the use of hybrid power, it can choose the maximum power of the combustion engine by the average power needed. At this time the fuel consumption is low , pollution is less and engine work under the optimal conditions.When need high power which combustion engine is short, the battery will supplement;When the load is low, the extra power can be generated to charge the battery.
(2) because of the battery,it is very convenient to recycle the energy while braking, downhill, idle.
(3) in the downtown area, can shut down the combustion engine, and driven by the battery alone, to achieve "zero" emissions.
(4) with the combustion engine,it is very convenient to solve the energy consumption of air conditioning, heating, defrost and other problems battery electric vehicles encountered.
(5) you can use the existing gas stations to fill up, no need anothter invest.
(6) can keep the battery in good working condition, do not happen overcharge, overdischarge, extend its service life, reduce the cost.
3. Classification of hybrid electric vehicles
Hybrid electric vehicle can be classified into plug-in hybrid and ordinary hybrid two kinds according to whether the car can be charged from outside (whether there is charging interface).And according to connection mode of the combustion engine and electric power, it can be divided into series hybrid (engine and electric power connect by series), parallel hybrid (engine and electric power are arranged in parallel), mixed type (both series and parallel).
The following takes plug-in Hybrid Vehicle (PHV) as an example to introduce the classification of Hybrid electric vehicles according to the driving mode:
(1) Series Hybrid Electric Vehicle-SHEV
This type of plug-in hybrid is still technically an electric vehicle.The car has only one set of electric drive system, including motor, control circuit, battery.Extended-range plug-in hybrids have electric motors that drive the wheels directly, and engines that drive generators to charge the batteries.Because the engine does not drive the wheels directly, no gearbox is needed.This is the equivalent of loading a petrol/diesel generator into an ordinary electric car.
SHEV advantages:
It has the advantages of quiet electric vehicle and large starting torque, so it can be used as a pure electric vehicle. Under the condition of convenient charging, only charging and no refueling can be done, and the use cost is low.
Compared with other plug-in hybrid models, the extended-range plug-in hybrid can be used without a gearbox, slightly reducing the cost.With an engine to generate electricity, as long as there is a gas station, it can run forever. It will not be forced to tow vehicles in places where it is not convenient to charge.
Because the engine does not directly drive the wheel, the engine speed and wheel speed has no direct relationship, through the optimization of control system , the engine can always work at the best speed. Even when charging inconvenient and the city traffic jam condition, fuel consumption is relatively low, engine noise can also be controlled very small.
SHEV faults:
Since the engine and generator do not drive the wheels directly, this waste of power is caused, and the weight of the engine and generator is not reduced.For example, an incremental plug-in hybrid vehicle has an engine power of 50KW, a generator power of 50KW, and a motor power of 100KW. The vehicle carries a total power of 200KW engine and motor, but the power to drive the wheel is only 100KW.On the highway, fuel consumption is on the high side.
Typical models in this category include the BMW i3 (optional range-extending module) and the Chevrolet volt (with hidden direct-drive mode)
(2) Parallel Hybrid Electric Vehicle-PHEV
This type of plug-in hybrid car has two sets of drive systems, most of which are based on the traditional fuel cars by adding electric motors, batteries and electric controls, which drive the wheels together with the engine.There is only one motor in the car, which acts as an electric motor when driving the wheels and a generator when not driving the wheels to recharge the batteries.
(3) parallel-series Hybrid Electric Vehicle-PSHEV
Like a parallel plug-in hybrid, this model has two drive systems, but the difference is that this type of hybrid has two motors.One motor is only used to drive the wheels directly, and another motor has dual roles: when the ultimate performance is required, it acts as the motor to drive the wheels directly, and the whole vehicle power is the sum of the power of the engine and two motors;When the power is low, it act acts a generator to recharge the batteries.
PSHEV advantages:
Therefore, the hybrid type has the advantages of both series hybrid and parallel hybrid: in pure electric mode, it has the advantages of quiet electric vehicle and low use cost;In extended range mode, there is no "range anxiety", and the engine can always be controlled at the optimal speed, low fuel consumption, low noise and vibration;In parallel mode, two motors and one engine can work together, and the power of the three together has very good starting and acceleration performance, which is a relatively perfect combination.
PSHEV faults:
On the other hand, the two motors, engine and gearbox all be needed, and the control circuit, battery, transmission system and oil circuit all be needed. The overall cost is higher than other types of plug-in hybrid, and the total weight of the car will be larger.However, the control system is relatively complicated because it has to control two motors and one engine and different working modes, which will increase the cost.
Definition of fuel cell electric vehicle
Fuel cell electric vehicle (FCV) is a vehicle powered by electricity generated by on-board fuel cell devices.The fuel used in the vehicle fuel cell device is high purity hydrogen or high hydrogen content fuel.The difference in power, compared with conventional electric vehicles, is that the FCV uses electricity from on-board fuel cell devices, while the electricity used in electric vehicles comes from batteries charged by the grid.So the key to FCV is the fuel cell.
The advantages of fuel cell electric cars
Compared with traditional vehicles, the engine and transmission powertrain no longer exist in fuel cell vehicles, replaced by fuel cell reactor, battery, hydrogen tank, motor, DC /DC converter and other equipment, fuel cell electric vehicles have the following advantages:
(1) zero or nearly zero emissions.
(2) reduce water pollution caused by oil leakage.
(3) reducing greenhouse gas emissions.
(4) improved fuel economy.
(5) improve engine combustion efficiency.
(6) smooth operation and no noise.
Fuel cell electric vehicle components
(1)Fuel cell engine (FCE) : mainly composed of fuel cell reactor, air intake system, drainage system, hydrogen supply system, cooling system, reactor control unit and monitoring system.This is the main power source.
(2) power battery: auxiliary power source.
(3) current converter: ac-dc conversion.
(4) power train: transfer power, shift.
(5)Hydrogen system: provide hydrogen.
(6)Power control unit: power control, fault diagnosis.
Fuel cell electric vehicles
In addition to the body, controller and drive system, fuel cell electric vehicles is facing the same problem with the electric car, in terms of its energy storage sources---- fuel cells still have many problems need to solve. For hydrogen fuel cells, in such aspects as production, storage and carrying of hydrogen fuel, and efficiency, volume, quality and response speed of fuel cell system, it still need to be further improved.
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