A　circuit　configuration　and　circuit　topological　family　of　voltage　mode　ac-ac　converters　with　high　frequency　ac　links,　which　are　based　on　forward　converters,　and　a　uni-polarity　phase-shifted　control　strategy　are　proposed　and　deeply　investigated.　These　kinds　of　converters　consist　of　a　input　cycloconveter,　a　high　frequency　transformer,　an　output　cycloconverter,　input　and　output　filters,　and　can　transfer　an　unsteady　ac　voltage　with　a　high　harmonic　into　steady　same-frequency　ac　sinusoidal　voltage　with　a　low　harmonic.　By　using　uni-polarity　phase-shifted　control　strategy,　output　filtering　inductance　current　is　naturally　commutated,　and　zero　voltage　switching　of　the　output　cycloconverter　is　realized.　The　converters＇　averaging　model,　the　output　characteristic　curve,　and　design　criteria　for　the　key　circuit　parameters　are　given.　The　theoretical　analysis　and　test　result　of　1kVA　220V　±　10%　50　Hz　ac/110V　50Hz　ac　prototype　have　shown　that　the　converters　have　such　advantages　as　high　frequency　electrical　isolation,　simple　topology,　two-stage　power　conversion　(LFAC/HFAC/LFAC),　bidirectional　power　flow,　uni-polarity　synchronized　pulsewidth　modulation　waveform,　high　efficiency,　high　power　density,　high　steady　precision,　low　total　harmonic　distortion　of　the　output　voltage,　strong　adaptability　to　various　loads,　high　line　power　factor,　and　low　audio　noise　etc.　©　2006　IEEE.