Power Performance Of Plug-in Hybrid Electric Vehicles Based On Motor Current Decoupling Control

Vehicle industry’s sustainable development faces three big challenges: energy supply and energy safety, air pollution and global warming. To solve the three problems, the development of new energy vehicles industry is the best solution. At present, the hybrid electric vehicle in our country is a better transitional scheme, and the plug-in hybrid electric vehicle is a transitory technique from hybrid to pure electric.Plug-in hybrid electric vehicle(PHEV) mainly focuses on the energy management and the dynamic control. For the energy management, there are many literatures, which are mainly based on steady-state characteristics of power supply to control overall system. The literatures about the dynamic control is concentrated on the state switch, which is involved the engine’s dynamic characteristics. This paper analyses Plug-in hybrid electric vehicle’s power performance from the point of dynamic control, namely the problems of torque fluctuations, the speed stably following the expectations, and motor torque accuracy under various mode switch.For the torque accuracy problems of Permanent Magnet Synchronous Motor(PMSM) for HEV, namely the coupling problems of d-axis and q-axis currents in the synchronous rotating frame, the diagonal matrix decoupling control method is proposed in this paper. The field current id and torque current iq are decoupled into each other by increasing a decoupling compensator in the motor current loop, so as to ensure the accuracy of PMSM’s output torque. What’s more, this method is compared with the feedforward decoupling control method and the feedback decoupling control method. This method has better robustness and solves the torque inaccuracy problems of PMSM for HEV when the motor speed is higher or the motor parameters change.For torque fluctuations and the speed unstably following the expectation under the mode switch in HEV, in this paper, a control method of the motor torque compensation is put forward, which is based on PID controller of the wheel angular velocity difference. When a vehicle is running from the EV mode to the HEV mode, the speed(or acceleration) don’t stably follow the expectation because the engine’s steady-state characteristics are different from its dynamic characteristics. So this overall system increases a dynamic regulator to compensate the engine torque and keep the speed stably following the expectations. The proposed control method can effectively dampen torque fluctuations and keep the speed stably following the expectations, which ensures power transfer smoothly under various mode switch.