具可調變直流鏈電壓之馬達驅動系統擾動解耦策略

Abstract

本論文提出一應用於可調變直流鏈電壓馬達驅動器之電流擾動解耦策略。在常見的馬達驅動器中，一般使用固定直流鏈電壓之電壓源變頻器以驅動馬達。然而，當馬達操作在低轉速區間時，對直流鏈電壓的需求沒那麼高，而越高的直流鏈電壓將導致變頻器之相電壓諧波越高。這些電壓諧波成分會在馬達上產生更高的功率損耗。因此，為了降低馬達相電壓之總諧波失真，本論文採用電壓源變頻器串聯前級電源轉換器之雙級馬達驅動架構，以調控直流鏈電壓。 然而，控制整合之雙級系統並不似分別控制轉換器與變頻器那樣簡單。兩級之間的交叉耦合物理量將影響直流鏈電壓之控制，直流鏈電壓又將限制馬達之轉速控制。本論文將針對交叉耦合之現象加以介紹並分析其對直流鏈電壓控制穩定度之影響。根據這些分析，本論文提出之電流擾動解耦策略將可改善直流鏈電壓之動態響應，並簡化前級轉換器之電壓補償器設計。由於此電流擾動解耦策略在硬體上不需要額外的元件，在提升雙級馬達驅動器表現的同時，幾乎不需做額外的取捨。最後，電壓總諧波失真之降低與電流解耦策略的效果都將透過電腦模擬與實際硬體實作來驗證。

A current disturbance decoupling strategy (CDDS) on motor drive with variable DC-link voltage is proposed in this thesis. In general motor drive, voltage source inverter (VSI) with a constant DC-link voltage is normally adopted. However, operating in low-speed region does not require the high DC-link voltage and higher DC-link voltage causes higher harmonics on VSI phase voltage, which results in higher power loss on the motor. Hence, for the purpose of reducing the Total Harmonic Distortion (THD) on phase voltage, dual-level motor drive topology which is a VSI in conjunction with a front-end converter is adopted in this thesis to manipulate the DC-link voltage. Nevertheless, controlling the integrated system is not as simple as controlling the converter and the VSI separately. The cross-coupling quantities between the two stages would affect the DC-link voltage control that the speed control of the motor may get further influenced. The cross-coupling phenomenon will be analyzed in this thesis, as well as its effect on DC-link voltage control stability. On the basis of the analysis, the proposed CDDS can improve the dynamics of the DC-link voltage control and simplify the compensator design of the front-end converter. Since there is no extra hardware components required for the CDDS, a better performance of the dual-level motor drive can be achieved while hardly any trade-off. Computer simulation and hardware experimental results are presented to verify the performance of voltage THD reduction and the effectiveness of the proposed CDDS.