本論文旨在建構適用於海潮流發電系統之直交流電源轉換變流器，並採用改良型正弦波寬調變控制策略，針對變動之輸入電壓進行對應補償，俾以降低輸出電壓之低頻諧波含量。海潮流發電機所產生之交流電能，係經由整流濾波電路轉換為穩定直流電壓，再藉變流器轉換為適當規格之交流電輸出。在整流濾波電路中，使用大容值電容作為濾波器，雖可使濾波電壓準位較為平穩，然亦造成整流器之導通角度變小，致使再生電能無法持續饋入；惟若使用小容值電容作為濾波器，雖可提高導通角度，但會導致變流器直流鏈電壓為變動值。針對直流鏈浮動電壓，變流器若採標準型正弦波寬調變，其輸出交流電壓將具大量諧波成分，影響輸出電壓品質。本文係就直流鏈為浮動電壓時，提出改良型調變控制策略，配合直流鏈電壓之變動，調整脈波寬度，以降低輸出電壓之低頻諧波含量。經由理論分析與模擬驗證，並實際建構具改良型調變控制策略之海潮流發電系統用SPWM變流器，實驗結果顯示，所提改良型正弦波寬調變控制策略，得有效降低輸出電壓之低頻諧波含量。

This thesis proposes a control method for sinusoidal pulsewidth modulation (SPWM) single-phase inverters for the tidal current generating system. The AC power from the generator is changed to DC power by a rectifier and filter, and then the DC power is changed to AC power by an inverter to provide a stable voltage for the electronic product. However, the current is discontinuous and has the higher peak current because of the filter composed of capacitors. But it will cause the fluctuating voltage if the filter is removed. So that the output voltage of the inverter will have large low-order harmonics when the classical SPWM is used. It is verified by simulation and experiment and that the proposed modified SPWM could make total harmonic distortion (THD) of the output voltage lower when the input voltage of the inverter is not constant. The results of simulation and experiment demonstrate that the low-order harmonics of output voltage is reduced effectively and its THD is less than 2.5%.

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