Control Technique Analysis for Induction-Type Traction Motor Used in Electrical Vehicle

本論文針對電動車的感應型牽引馬達控制技術進行深入分析，感應馬達具有結構堅固與價格便宜的特點，因此已經有許多款電動車採用感應型牽引馬達做為動力源，但是感應型牽引馬達的轉子磁通由感應電流所產生，因此轉矩與轉速控制系統很複雜，尤其在低轉速工作區間，轉子磁通變動劇烈使得電磁轉矩控制更加困難，車輛也因此很容易發生推進力不順暢的現象。本論文採用改良型電壓頻率比值控制法與直接轉矩控制法分別對感應型牽引馬達做閉迴路的全域電磁轉矩控制，以四分之一車的動態模型做為馬達的負載，控制器的設計特別對電動車牽引力及再生剎車控制策略做全域轉速的性能優化，外迴路控制器則利用車輪滑差訊號來偵測車輪與路面的摩擦力變動，用模糊滑模控制法對車輪加速度命令值做修正，使電磁轉矩控制系統可以直接反應路面摩擦力的變動，當車輛急加速時可以阻止車輪空轉，當車輛減速時則可以利用再生剎車所產生的反向轉矩對車輛做剎車並且回收再生電能。本論文將感應型牽引馬達模型、四分之一車動態模型、改良型電壓頻率比值控制器、直接轉矩控制器、滑差模糊滑模控制器都建立於電腦模擬系統，並進行多項情境的模擬與分析，結果顯示在電磁轉矩響應、車輪加速度追蹤、乾濕路面穩定度以及剎車能量回收等方面，直接轉矩控制法的數據都比改良型電壓頻率比值控制法優越，車輪滑差控制系統確實可以在路面摩擦力變動下防止再生剎車造成打滑，也可以防止急加速時發生空轉。This thesis investigates the control techniques of induction-type traction motor for powering electric vehicles. The inner loop of the traction motor control system manages the electric torques delivered to the wheel, the outer loop aims at confining the wheel slip ratio to within a specified range. Induction-type traction motors are known for their firm structure. However, due to the rotor flux produced by the induced current, the torque control to an induction motor is quite complex, especially severe rotor flux fluctuations may occur during low speed drive. The enhanced V/f control technique makes use of a voltage compensation for low speed drive to elevate the torque quality, however, in terms of open-loop control. The direct torque control technique measures and manipulates the stator quantities for estimating and controlling the motor torque. The wheel slip control loop diminishes the drive torque or regenerative torque whenever the wheel tends to skid or lock up. The induction motor model and quarter car load is built in the simulation system as the controlled plant. The traction motor controller of the simulation system contains the wheel slip controller, the direct torque inverter and the enhanced V/F inverter. The performance of the traction motor control system based on the direct torque technique and on the enhanced V/F control technique have been examined and compared extensively through simulations. The results show that the direct torque control one performs better than that of the enhanced V/f control one in terms of the response of electrical torque, recovery of regenerative energy, tracking ability of wheel acceleration, drive stability either on wet or dry road