空間向量調變演算法於多階多相電壓源反流器

Abstract

空間向量調變方法具有高電壓源使用率與實現簡易之優點，因此，空間向量調變演算法被廣泛應用於三相二階與多相多階電壓源電路，然而，空間向量調變演算法存在有些議題，如相電流諧波失真與開關切換損失之抉擇、運算複雜度隨著更高相數與階數而增加與無系統化方法決定開關切換周期。這抉擇為三相二階電壓源電路之重要議題，而運算複雜度與系統化方法為多相多階電壓源電路之關鍵議題。本論文分別針對三相二階與多相多階電壓源電路提出一創新空間向量調變演算法，以解決以往空間向量調變演算法之議題。 本論文提出一電壓誤差補償脈波寬度調變演算法，以有限脈波寬度所產生之累積電壓誤差用來調整參考電壓向量，此機制可以補償前一載波周期所產生之電壓誤差，由模擬結果可知，藉由半載波周期之誤差補償機制，所提演算法可降低相電流基頻諧波失真而只使用一半載波頻率。所降低之開關切換損失可提高系統效率、減少開關散熱系統體積與延長開關壽命 本論文提出一abc框架之非連續空間向量調變演算法於多相多階電壓源電路，所提演算法可系統化地應用於各種多相多階電壓源電路，模擬結果驗證所提演算法可應用於三相五階串接全橋式、五相三階飛馳電容式與七相三階二極體箝位式電壓源電路。實驗結果驗證所提演算法具有高電壓源使用率、低運算量與簡易實現之優點於三相五階串接全橋式電壓源電路，因此所提演算法適合即時實現於微控器。

Space vector pulse-width modulation (SVPWM) algorithms have the advantages including good dc-link voltage utilization and easy implementation. Therefore, SVPWM algorithms are widely applied to two-level three-phase and multilevel multiphase voltage source inverters (VSIs). However, SVPWM has some issues such as the tradeoff between the current harmonic distortion and the switching loss, the increased computational complexity with higher level and phase number, and no systematic approach to determine switching pulse durations of switches. The tradeoff is an important issue for two-level three-phase VSIs, and the computational complexity and systematic approach are critical issues for multilevel multiphase VSIs. In this dissertation, novel SVPWM algorithms are proposed for two-level three-phase and multilevel multiphase VSIs respectively in order to resolve the issues in previous SVPWM algorithms. This dissertation proposes an error compensated pulse-width modulation (ECPWM) algorithm for two-level three-phase VSIs. The ECPWM uses the accumulated voltage error induced by finite pulse-width resolution to adjust the reference voltage vector. This mechanism can compensate the voltage error produced in the previous carrier period. From the simulation and experimental results, with the error compensation every half-carrier period, the proposed ECPWM can reduce the phase current harmonic distortion in the baseband frequency by only using half of carrier frequency. The reduced switching loss can enhance the system efficiency, reduce the heat sink requirement, and prolong the lifetime of switches. In this dissertation, a discontinuous SVPWM algorithm in the abc reference frame is proposed for multilevel multiphase VSIs. The proposed discontinuous SVPWM algorithm can be systematically applied to different multilevel multiphase VSIs. The simulation results confirm that the proposed DSVPWM can be applied to five-level three-phase cascaded H-bridge, three-level five-phase flying-capacitor, and three-level seven-phase diode-clamped VSIs. The experiment results demonstrate that the proposed DSVPWM has good dc-link voltage utilization, low computational complexity, and easy implementation for a five-level three-phase cascaded H-bridge VSI. Therefore, it is suitable for real-time implementation on microcontrollers.