According to the connection mode of drive system, hybrid hydraulic excavator can be divided into series type, parallel type and hybrid type.
Parallel hybrid power system has internal combustion engine drive system and motor drive system. The two systems can work simultaneously or separately. It is suitable for many different working conditions, especially for complex road conditions. The connection mode has the advantages of simple structure and low cost.
The principle of the parallel type is that the engine and the generator / motor drive the hydraulic pump in parallel. The energy output by the engine is mainly used to drive the external load. The excess mechanical energy is converted into electric energy through the motor and generator, and stored in the capacitor through the rectifier / inverter. When the required torque of the hydraulic pump is less than that of the engine, the generator / motor connected with the engine is in the state of power generation, and the excess torque is converted into electric energy and stored in the capacitor. When the torque required by the hydraulic pump is greater than that of the engine, the generator / motor connected with the engine is in the electric state, and the capacitor discharges to supplement the insufficient torque. The installed power of the engine is reduced and the working point of the engine is stabilized. Compared with the series type, the installed power of generator and engine is smaller, the capacitance capacity is lower, the power is larger and the fuel consumption is lower, but the layout and control system are more complex.
