The utility model discloses a there is not broad width alternating voltage grade modulated circuit who keeps apart, including first converter, second converter and power frequency isolation transformer, the input of second converter is inserted respectively at input voltage's both ends, the output of second converter and power frequency isolation transformer's high -pressure side winding are connected, power frequency isolation transformer's low tension side winding and first converter are connected, the output and the voltage output end of first converter are connected, input voltage US and second, the offset voltage UC that first converter produced carries out the vector stack, produce output voltage U0. The utility model discloses contactless, stepless, the sinusoidal wave power electronic voltage regulator of broad width, the stabiliser that have that frequency transformer keeps apart, be applicable to single, the three -phase system of different capacity grades, high performance -price ratio, etc.