电动汽车用异步电动机低速转矩最大化

电动汽车用异步电动机经常会遇到爬坡等低速重载运行工况,特别对于低压大电流的交流异步电动机,在逆变器电流限制条件下实现转矩最大化非常重要。以电机稳态电路为基础,建立电流约束条件下基于非线性励磁电感的低速转矩最大化模型。模型分析表明该最优问题可以简化为一维搜索问题,并采用经典的搜索算法在低速范围进行求解。实际电机计算结果和理论分析表明,整个低速范围内最大转矩值工作点的转矩值、齿部磁通密度、转差率几乎保持恒值,相当饱和的磁场导致严重的非线性。非线性励磁电感应用于改进的空间矢量控制系统,实现大电流约束条件下低速转矩最大化运行,仿真结果表明控制方法的正确性。实验结果也验证了转矩优化模型、模型分析结论及改进的空间矢量控制方法的正确性。

Torque Maximization about Electric Vehicle Induction Motor at Low Speed

Induction motor for electric vehicle (EV) often encounters low speed and heavy load conditions such as climbing slope. In such cases, the maximum torque constrained by inverter current is very important, especially for low voltage and large current induction motor. From steady circuit of induction motor a current constrained torque maximization model was constructed based on a nonlinear magnetizing inductance. Analysis of this model indicates that the optimization problem can be simplified into a one-dimension searching problem. A classical searching method was used to get the solutions in low speed range. The calculation results of an actual induction motor and theoretical analysis show that the torque, teeth flux density and slip frequency of all the torque maximization points nearly keep constant, and the fairly saturated magnetic field results in severe nonlinearity. When the nonlinear magnetizing inductance is applied to an improved space vector pulse width modulation(SVPWM) control system, the maximum torque under large current constrained condition can be implemented. The simulation and experimental results verify the optimization model, analysis results and the improved SVPWM.