In a tandem configuration, the output shaft of the engine is connected to the generator. The electrical energy generated by the generator is used to charge the battery or drive the motor to run. In the tandem structure, the electric motor is the only power device that drives the wheels, which can be either an induction motor or a permanent magnet motor. The electric motor installation of a series PHEV is the same as that of a conventional hybrid, and a transmission is usually not required, with the option to install an in-wheel motor. The electric motor in the tandem structure needs to meet the demand for driving torque under all operating conditions. In parallel and compound configurations, the size of the motor is smaller than that of the tandem configuration because both the engine and the motor can drive the wheels.
The driving principle and drive unit of an extended-range PHEV are the same as those of an electric vehicle. The reason why it is called a hybrid is because this type of vehicle is equipped with an engine that charges the battery. In daily use, the extended-range PHEV can be used as a pure electric vehicle. As long as the single driving distance does not exceed the cruising range provided by the battery (usually 50km), it can achieve zero emissions and zero fuel consumption. The range extension module can start the generator to generate electricity when the battery power is almost exhausted, and then drive the main motor with the generated electricity. The advantage is that the engine can always work in the best working condition, so it is very economical in urban areas, but Its efficiency in high-speed working conditions is poor, but it is not as good as ordinary fuel vehicles, because if the engine is directly driven at high speed, it is in the best working condition, and power generation increases the loss. Representatives of this type of hybrid models are the Chevrolet Volt and BMW i3 with optional range extension modules.
The parallel plug-in hybrid vehicle is composed of a battery and a motor on the basis of ordinary fuel vehicles. It can be used as an electric vehicle in daily use. The motor in the long-distance hybrid mode is responsible for both power generation and driving tasks. The advantages of this type of vehicle are simple structure, high power Strong (the motor and the engine can drive the vehicle at the same time), the disadvantage is that the engine cannot be completely prevented from working when the battery is in a low state, and the vehicle completely relies on the internal combustion engine to drive in the low battery range. The representative model is BYD Qin.
3. Series-parallel hybrid
The hybrid plug-in hybrid power system can be regarded as increasing the motor and battery on the basis of the traditional hybrid power system, or it can be regarded as the combination of the extended-range hybrid power system and the parallel hybrid power system. All the advantages can not only achieve good fuel economy after the battery is exhausted, but also realize the superposition of engine and motor power. The disadvantage is that the structure and control system are complicated. Representative models include Roewe 550 Plug-in, Toyota Prius plug-in hybrid version, BYD F3DM and BYD Tang (the engine and motor are located at the front of the vehicle, and another motor drives the rear wheels).
PHEV mainly includes two stages of energy consumption (CD) and energy maintenance (CS) during driving. In the energy consumption stage, in addition to regenerative braking, the state of charge (SOC) of the battery continues to decrease, and the operation of the engine and the motor is related to the parameter matching. When the motor power matching is large, this stage is usually pure electric operation; When the power of the motor is relatively small, and it is in a working condition with high power requirements such as rapid acceleration and climbing, or when the cooling and lubrication of the power system requires the engine to be turned on, the engine still needs to work in the CD stage; The big difference in driving range is mainly related to the capacity of the battery pack. For example, the pure electric driving range of the Toyota Prius with a battery pack capacity of 4.4kWh is only 26km, and the pure electric driving range of the Volanda with a battery pack capacity of 16kWh is 64km. , BYD Qin with a battery pack capacity of 13kWh has a pure electric driving range of up to 70km. The new national standard requires that the pure electric driving range of passenger cars at a constant speed of 60km/h and commercial vehicles at a constant speed of 40km/h is more than 50km in order to obtain preferential policies such as purchase tax exemption. The CS stage is mainly to maintain the SOC balance. Similar to the strong mix control, the SOC control target point should not be too high (such as 30%, and the strong mix target point is usually about 50%). The SOC control target point should be taken into account when selecting The charging and discharging efficiency of the battery.
PHEV involves different working modes of CD mode and CS mode. Generally, when the battery is fully charged, the vehicle runs in CD mode, and when the state of charge of the battery reaches a certain lower limit, the vehicle switches to run in CS mode. In CD mode, the car will maximize the use of battery power. In CS mode, the vehicle is mainly driven by the internal combustion engine, and the SOC of the battery is always maintained at a certain value. During operation in CD mode, the vehicle's energy management goal is to minimize total energy consumption by splitting energy between the battery and the gasoline engine/generator for a given driving condition.