新型無交越死點開關調變法應用於三相阻性-感性負載的模擬與分析

Abstract

本論文內容提出結合六步方波與向量空間調變方法，開發新型無交越延遲死點(dead time)調變切換。其優點: a) 新型六步正弦波調變，無上下臂同時開關切換，避開越延遲死點(dead time)，增加轉換效率。 b) 三臂6 個功率電晶體開關，瞬間只有三個功率電晶體運作，可以有效降低功率電晶體導切換損。 c) 空間向量調變可以降低直流無刷電動機漣波轉矩輸出。目前研究執行進度將上述構想經理論推導導出特定區間功率電晶體開關時間公式，以及利用電路模擬軟體PSIM建構出此調變法的架構模型，進行三相阻抗驅動模擬測試。在模擬測試上已經看見初步成果是此新型調變法與加入死區時間後的弦波調變與空間向量調變比較，可以看見其輸出能力較後兩者高，惟某些區間有特定電壓突波必須透過程式去避免。並在之後的研究中完成速度的閉迴路回授控制，期望之後的研究接著利用TI的微控制器完成實際的馬達驅動。

In this thesis, a novel modulation method which combining the concepts of six-step square wave and space vector modulation(SVM) is proposed. This novel modulation, unlike the old modulation methods which has to set dead time between every period of PWM, it’s no need to add dead time in the control signal, and has the advantages shown as below: a) This novel modulation method can avoid dead time and improve the energy efficiency by separating the enable time of two transistors in each phase. b) There are only three transistors operating in every section in a cycle of rotation, the others are unable in the same section. With this rule of modulation, it can reduce the switching loss of every transistors. c) The space vector modulation concept can reduce the ripple of output torque in brushless machine. So far the researching progress has already derivate the specified section PWM duty ratio formula of each power transistors. And by using the electrical simulation software PSIM, the simulation model of this novel modulation method has been constructed and tested by three phase inductance-resistance load. Simulation results show that compared with sine-wave modulation(SPWM) and space vector modulation(SVPWM), this novel modulation method has higher output ability. But it’s denotes that there are voltage ripple occur in certain section which has to be avoid by simulation program. For future researching it will test in close loop current and speed control, and using DSP to realize the brushless motor driving.