With isolation transformers, the output voltage polarity reversal does not become a design restriction. In addition, transformers are used in switching mode converters for electrical isolation between the input and output reduction of stresses in switching devices and provision multi-output connections. Unlike line-frequency transformers, these transformers are high frequency and much smaller in size and weight.

As a result, transformers must be added between the power stage and the output for the purpose of voltage scaling. However, for many applications, the input voltage is normally derived from an off-line half- or full-wave rectifier, and the output voltage is normally a very small fraction of the rectified dc input voltage. For applications in which the output voltage does not differ from the input voltage by a large factor, those topologies can be used. 4 showed that the four basic converter topologies have their output conversions determined by the duty ratio, D, and that they consist of a single input and a single output with a common reference point. The performance of the PMSM drive system with varying loads is compared and analyzed for the improvement in power quality.The discussion in Chap. Experimental results obtained from different topologies of high frequency isolated converters are presented to examine their effectiveness in power quality improvement. Their hardware developments include use of buck–boost converter in discontinuous conduction mode of operation with reduced sensor requirement and improved power quality features.

The modeling and simulation is presented for investigating the suitability of isolated converter topologies in improving the power quality at AC mains. This chapter relates to the design and modeling of isolated active waveshaping buck–boost AC-DC converter topologies.

The use of high frequency transformer in isolated topologies of AC-DC converters in discontinuous conduction mode requires only the DC-link voltage feedback for improving the power quality at the AC mains. While using topologies with active waveshaping techniques the isolation between AC and DC is not possible which is desired in a number of applications, and also they require voltage and current sensors for their control.

The isolated cuk converter waveforms