Development Of Permanent Magnet Synchronous Motor Control Algorithm For Plug-in Hybrid Vehicle

Drive motor control system is one of the key technologies for hybrid electric vehicles(HEVs). While industrial motors is usually optimized at the optimal operating point, drivemotor for hybrid vehicles has special requirements in terms of load requirements, technicalperformance and the work environment. The paper aims at developing motor controlalgorithm for a specific vehicle configuration, specific powertrain parameters and specificvehicle control strategy to satisfy the demands of power-split plug-in hybrid vehicle (PHEV)in consideration of the limitation of electric drive system.Based on the analysis of the difference between industrial motor and hybrid electricvehicle drive motor and the performance contrast of several typical drive motors for HEV,three-phase permanent magnet synchronous motor (PMSM) is selected as the object of study.In order to develop more targeted vehicle motor control algorithm, this paper analyzes themotor control system requirements and constraints of vehicle configuration system, vehiclepowertrain parameters and vehicle control strategy, which point out the direction of theoptimization of automotive PMSM for PHEV.Three-phase permanent magnet synchronous motor is a multi-variable, strong couplingand nonlinear electromechanical energy conversion devices. In view of the structure andworking principle of permanent magnet synchronous motor, three-phase permanent magnetsynchronous motor vector control system is set up in this paper. The thought of "layereddevelopment" is applied in the algorithm design of the control system of three-phasepermanent magnet synchronous motor. Space Vector Pulse Width Modulation (SVPWM)algorithm is used and the inverter switching time is controlled to achieve the equivalent ofthree-phase sinusoidal voltage input in the bottom layer. PI regulator is used to controltwo-phase permanent magnet synchronous motor current and a decoupling control algorithmbased on model prediction is put forward to achieve fast and accurate control of the two-phasecurrent in the middle layer. PI control algorithm based on vehicle modes is adopted,feed-forward compensation algorithm based on vehicle torque distribution is put forward inhigh layer which can meet the requirement for the motor of HEV better. Several key questions for the three-phase permanent magnet synchronous motor vector control algorithmdevelopment are studied in five areas:1. On the basis of analysis of voltage and current limit circle, maximum torque/currentratio control strategy and weak magnetic control strategy are clarified，and simulation resultsverify that these strategies can make PMSM work with constant torque below base speed andconstant power above base speed. Under the premise of specific control strategies, theconcepts of the torque coefficient and the weakening coefficient are given clearly, and therelations among output external characteristics, motor parameters and motor stator currentsare expressed in the form of mathematical relationship which provides certain referencesignificance for the match of motor parameters and optimization of control algorithm.2. Three-phase permanent magnet synchronous motor is powered by DC bus voltage andvector control strategy is adopted to make the motor output characteristics meet therequirements of drive motor for HEV. The principles and its inverter technology of SVPWM,especially the basic flow of SVPWM algorithm and the related sets of mathematical formulasare derived in the paper. Simulation results show that SVPWM algorithm used in this papercan achieve three-phase permanent magnet synchronous motor vector control well.3. The working environment of drive motors for HEV is greatly different from that ofindustrial motors, so we should not select the drive motors for HEV in accordance with themethod of selecting industrial motors. Thus a new motor parameter matching method whichconsiders the strategy of PMSM is proposed and the relevant formulas are given. Theoreticalcalculations and simulation results show that this new motor parameter matching method hasreference values.4. A motor control algorithm optimization method with the goal of the requirements fordrive motors of HEV is proposed. PMSM control system parameters are initially chosen infrequency domain using transfer functions and Bode diagrams as its principal tools, and thenthese parameters are corrected by simulation in time domain. Simulation results prove that theinitially chosen parameters can achieve good property for both dynamic and steady-stateoutput characteristics and the modified parameters can meet the demands for drive motors ofHEV better under different vehicle driving modes. Decoupling control algorithm based onmodel prediction and feed-forward compensation algorithm based on vehicle torquedistribution are put forward and simulation results verify that these algorithms can greatly improve the three-phase permanent magnet synchronous motor output characteristics.5. The rationality of motor control algorithm based on vehicle driving modes is testifiedby simulation. Simulation results show that three-phase permanent magnet synchronous motorusing a control algorithm based on vehicle driving modes can output the torque steady withoutbig fluctuations and overshoot which can meet the output characteristic requirements fordrive motors of plug-in hybrid vehicles when climbing or accelerating the vehicle.