應用於離心式負載之小直流鏈電容高功因永磁同步馬達無感測驅動器之研製

Abstract

本文主旨為實現並分析採用小直流鏈電容高功因永磁同步馬達驅動電路的數位控制器。在交流輸入的馬達變頻系統中，需大直流鏈電容負責進行整流器的穩壓轉換，針對此電容值，本文意圖將其縮小為傳統條件下的數百分之一，並以可靠度較高的薄膜電容取代傳統所使用的電解電容，即便在輸入功率級不使用主動開關或大電抗的濾波器也能實現高輸入功因的可調速永磁同步馬達驅動器；然而所使用的小直流鏈電容將導致劇烈的直流鏈電壓漣波進而惡化了馬達控制的表現，因此於馬達電流控制中，藉由直流鏈電壓補償以及電壓解耦合控制來改善控制的表現，若功率因數並非主要考量，即便在小電容下也能在一定的直流鏈電壓漣波下執行無轉矩漣波之可調速控制；但若欲更進一步提升功因，本文將輸入電壓規格與電容之做功為考量加以分析出不同操作轉速下，滿足高輸入功因的變頻器功率方程式以及所對應的功率因數，並進一步對馬達的電流命令修正，以達到對輸入電流的功率因數校正，此條件下將導致100%以上的轉矩漣波，因此選用大慣量的離心式負載較能濾除轉矩漣波對轉速的影響作為較合適的應用條件；於馬達的驅動方式採用無感測向量控制策略，省略了位置回授硬體，以回授之電流命令及電壓命令加以估測出轉子磁通鏈向量，進而實現寬廣速控範圍的位置估測演算法，且積分之誤差可被避免。內部包含了外迴路速度控制以及內迴路的同步座標電流控制，提到的控制架構將實現在意法半導體具有單精度浮點運算器的STM32F3微控制器並進行驗證，在輸入電壓源規格為單相110Vrms及60Hz的實驗中，以輸入功率因數、轉矩漣波與效率…等加以分析並評比不同電容值下的表現。

The purpose of this thesis is to not only develop the digital controller in application to a three-phase PM synchronous motor dirver with small dc-link capacitor for high power factor but also analysis its performance. For the motor drive system fed by single-phase ac source, large DC-link capacitor is uesd to be adopted for voltage regulation between diode rectifier and 3-phase inverter. In this thesis, the capacitance is reduced to less than 1% of the capacitance in the conventional drives. The traditional electrolytic capacitor can be replaced by smaller film capacitor which has much higher reliability. Even though no switch or large reactor is installed in proposed adjustable-speed PMSM drive, superior power factor still can be achieved. However, since small DC-link capacitance leads to severe fluctuation of DC-link voltage, the control capability of motor deteriorates naturally. DC-link voltage compensation and voltage decoupling control are applied to improve the performance of current regulation. Thus, with less consideration of power factor, adjustable speed control can also be operated without large torque ripple under the condition of small dc-link capacitor. However, for higher power factor, the desired inverter power and corresponding power factor with different operating speed are derived with consideration of input voltage and capacitance. Then, input current is power factor corrected by modification of the motor current reference. Modified current may result in above 100% torque ripple. Therefore, centrifugal load with large inertia is the more appropriate application in the proposed system due to stronger capability to supress speed ripple. The control structure based on FOC consists of inner current loop and outer speed loop. Experiment verification The proposed digital control structure is implemented on STM32F3 micro-controller with floating-point unit and then verifies the results of experiment. The experimental performance of power factor, torque ripple and efficiency with different capacitance is evaluated and analyzed.