A DC-AC Power Conversion Technique Using Twin Resonant High-Frequency Links

The advantages of load commUtated high-frequency (HF) sinusoidal inverters as link stiiges in power conversion are well-known. An inverter configuration that employs parallel connection of the load to the resonating capacitor can be employed to realize the high- frequency link. A technique of dc to low-frequency ac power conversion using two, such high-fre4uency links is presented. The frequencies of the two links differ by twice the required output frequency. The difference between the two link voltages is then a high- frequency ac voltage whose envelope is a low-frequency ac wave at the required output frequency. The frequency of the envelope wave is decided by the difference between the two link frequencies while the amplitude depends on the amplitude of the individual voltages. Thus the output voltage can be regulated by varying the link frequencies, and so long as the frequency difference remains constant, the output (envelope) frequency is not affected. The output voltage can be obtained from the difference of the two link voltages by appropriate rectification/inversion. This process can be regarded as a form of cycloconversion in which the modulation process is incorporated in the input voltage instead of the switching.