| Summary: | 碩士 === 國立臺北科技大學 === 電機工程系所 === 97 === The objective of this thesis is to design a digital control single phase AC power source, which equipped with output isolation transformer. The power source consists of a full-bridge DC-AC inverter and a transformer which is installed between inverter and user side to avoid feeding DC voltage into user’s equipments. Generally, it is difficult to design an AC inverter without DC voltage component in output. And the DC voltage will let the connected transformer be saturated, which may increase output voltage harmonics and power loss of transformer. An improved voltage control approach with transformer output voltage feedback is developed to reduce the effects of DC input current and voltage drop for transformer. In the improved method, a DC current canceller, a voltage controller, and a rms voltage compensator are proposed to enhance voltage performance of the AC power source. The DC current canceller detects DC current of transformer through a lower pass filter, and mitigates the DC current using PI controller with zero DC current command. As for the latter two control modules, they are utilized to further control the transformer output voltage such that voltage command tracking performances during loaded cases, transient period, and high frequency can be improved.
To facilitate the studies performed in this thesis, a DSP-based controller is constructed and all the control algorithms are performed by software. Some experimental results show that good command tracking and load regulation in wide output frequency range can be achieved by the proposed control method.
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