A waveform control method of AC to DC converters with high-frequency links

Transformer isolation is a usual practice for ohmic isolation between a source and a load. The transformer designed for commercial frequency (50/60Hz) makes the converter bulky and heavy. Therefore, high-frequency link converters have been studied to make the transformer smaller and to minimize the weight, size and cost of the converters. This paper presents a new real-time control method of AC to DC converters with high-frequency links (switch mode rectifiers: SMR's). Results are as follows: (1) The new method makes the switching frequency of the SMR smaller than the conventional method. (2) The proposed method realizes sinusoidal input current, arbitrary output voltage waveform and controllable input displacement factor. The maximum output voltage ratio to the input liveto-neutral voltage is 3/2. (3) The new method is suitable for real time control and suppression of DC magnetization of the high-frequency transformer can easily be implemented. (4) Feasibility of the proposed method is confirmed by simulations and experiments. Using this method, it is easy to control the voltage waveform of the primary winding of the high-frequency tranformer by changing the output function, so that it is possible to compensate the unbalance of the source voltage and influence of the dead time.