Power Conditioning with a Switched Series-Resonant Circuit Operating at a High Internal Frequency

Electronic power converters operating with a high-frequency link are receiving an increasing amount of attention. A forced interruption in current in the semiconductor switches will lead to excessive momentary values of the power compared to the conduction losses for the current conduction interval, which must be dissipated in these switching elements. The switching losses are the fundamental reason for the increase in the total losses in the semiconductor switches for an increased repetition frequency of the switches. The development of the theory presented here and the technology of electronic power converters with high internal frequencies is based on the special properties of resonant circuits in switching networks. In general, such a converter consists of a series-resonant circuit. excited by a number of electronically controlled (semiconductor) switches. This resonant circuit is inserted in the direct path of the energy transfer of the power converter. The (quasi) sinusoidal currents in the semiconductor switches allow the current conducted through the switch to be interrupted at the zero crossing and, when combined with the limited value for the rate of rise of the current after turn-on and before turn-off, the switching losses can be reduced to a minimum. It is then possible to increase the above-mentioned barrier for the maximum pulse frequency up to hundreds of kHz. The energy can be emanated from a source (single or polyphase voltage source generating unipolar or bipolar waveforms) and is transmitted to a network (load) in a specific form (unipolar or bipolar, single or polyphase voltage waveforms).