控制功率因數角度之永磁同步風扇馬達高效率無感測V/f控制

Abstract

本文針對永磁同步馬達提出一種弦波無感測V/f控制方法，藉由馬達電壓與電流的相角差偵測與修正，以閉迴路控制方式達到最佳效率的控制效果。此方法無須複雜之座標轉換計算，亦不受馬達參數變化的影響，惟動態響應較為緩慢，適用於單相與三相永磁同步馬達在風扇、幫浦領域之應用。針對永磁同步馬達之無感測控制IC設計，本文提出具有低成本、低噪音、高效率、低參數靈敏度特色的控制架構，並完成設計與系統驗證。本文從同步旋轉 座標軸下之馬達數學模型，以及負載-轉矩特性曲線兩種觀點，配合上線性化小訊號分析，進行開迴路V/f控制下的穩定性分析。另外為了改善系統效率，本文利用空間向量圖提出效率最佳化原理，並配合實驗數據證實其正確性。藉由偵測並回授電壓電流相角差，控制器產生一電壓修正量修正相角差誤差使系統達到效率最佳化之操作點。全轉速範圍內的最佳電壓命令以及最佳功率因數角度命令可利用馬達數學模型計算獲得，藉由此高效率控制迴路將使系統在穩態達到高效率操作，且在暫態響應上也可獲得改善。基於推導得到之小訊號模型，可分析並模擬控制器設計流程和補償效果。本文在單晶片微控器DSP-2407A上實現提出之控制架構，並且可應用於市售單相無刷直流馬達冷卻風扇和市售18W之三相永磁同步馬達涼風扇。將實驗結果與市售風扇原配控制器、零交越點偵測無感測控制架構兩種方法，分別在穩態效率以及暫態加減速上做一比較。實驗結果證明在暫態響應上提出之架構對單相、三相風扇均能達到與零交越點無感測控制架構相似的加速時間，且由最低轉速至最高轉速不同操作點均可維持穩定操作。穩態下本文提出的架構在單相風扇比起市售有感測IC其相電流有效值至少改善12%，其相電流峰對峰值至少改善35%；本文架構在三相風扇比起市售風扇原配控制器其相電流有效值至少改善30%，其相電流峰對峰值改善35%，其DC電流平均值至少改善17%也就是效率至少改善17%，與零交越點無感測控制架構相較下相電流有效值至少改善7%，其相電流峰對峰值改善20%，其DC電流平均值至少改善13%也就是效率至少改善13%。

This thesis proposes a sensorless V/f control method drives with sinusoidal current control for permanent magnet synchronous motor. The control loop achieves optimal efficiency control by detecting and correcting phase angle between motor voltage and current. The method does not need complex calculations for coordinate transformation and model based estimator such as in FOC based sensorless control schemes, and it also has advantage of insensitive to motor parameters variation. The proposed method can be realized on both single-phase and three-phase PMSM in applications like fans or pumps. For sensorless control IC implementation of PM fan motors, this thesis proposes a control strategy have advantages such as low cost, low noise, low sensitive of parameter variation and high efficiency. This thesis uses the model of synchronous rotating (g -d ) reference frame and torque speed characteristic curve with small signal analysis to analyze the stability of V/f control method. This thesis uses space vector diagram to illustrate the relation between efficiency and phase angle between voltage and current. With the detection of phase angle between voltage and current, the controller will generate a correcting incremental voltage to minimize this phase angle error to reach to the optimal efficiency operating point. Based on the derived small-signal model, the controller has been designed and analyzed with simulation. The proposed control scheme has been realized with a single-chip DSP controller 2407A, and be applied to the control of a 18W 3-phase PMSM cooling fan. The experiment results show that the proposed method has similar acceleration time compared with ZCPs detection method. At steady state, the proposed method can maintain stable operation at different operation points. It can improve phase current RMS value at least 12% than original controller on single-phase fan motor. For three-phase fan motor, it can improve RMS value of phase current at least 35% and improve average value of DC current at least 17% than original controller. Compared with ZCPs detection method, it can improve RMS value of phase current at least 4% and improve average value of DC current at least 13%.