According to the different configuration forms of prime mover, electric hybrid power can be divided into series type, parallel type and mixed type. The capacitance and battery in the hybrid power system can be used as energy storage elements, which can maintain the engine working in the high efficiency zone, improve the utilization rate of fuel and reduce exhaust emissions. On the basis of considering the factors of energy saving, emission, layout and cost of the system, there are two main modes used in construction machinery: parallel hybrid driving mode and series hybrid driving mode.
1.Parallel hybrid drive mode
In parallel hybrid drive mode, the output energy of diesel engine is mainly used to drive external load, and the excess or insufficient part of energy is converted by engine or motor. The motor as auxiliary power meets the requirement of peak load power together with diesel engine. The system transfer table is driven directly by the motor, saving the energy consumed on the hydraulic control valve. When the arm hydraulic cylinder is down, the gravitational potential energy is converted into hydraulic energy, the engine is driven by hydraulic motor to generate electricity, and stored in the battery after inverter to provide power for the motor.
2.Series hybrid drive mode
Series hybrid power, engine output power is used to drive generator power generation, power storage in batteries and capacitors.
3.Advantages and Disadvantages
Advantages of electric hybrid power: it can not only balance the output torque of internal combustion engine, make the working point of internal combustion engine always in the economic working area, but also adopt closed transmission scheme for each hydraulic cylinder by using motor control technology.
Disadvantages: on the one hand, because the energy conversion has experienced many links, such as diesel engine, generator, battery, motor, hydraulic pump, hydraulic cylinder, hydraulic motor and so on, each link has energy loss, which leads to a large energy loss in the whole conversion process, thus offsetting the energy saving effect achieved by adopting this technology to some extent. On the other hand, because of the many links of energy conversion, the system tends to be complex and the technical requirements are improved accordingly. In addition, the electric hybrid power technology makes the excavation power system change fundamentally from the structure, which has a great impact on the whole excavator manufacturing system, resulting in the increase of production cost.