The double-carrier modulation method is proposed based on the inverter’s
operation mode. The duty cycle for buck switch is always one if the inverter is running in
boost mode. And the duty cycle for boost switches are always zero if the inverter is
running in buck mode. Because of this, the carrier for boost mode is stacked on the top of
iii
the carrier for buck mode, as a result, there is no need to compare the input and output
voltage to decide which mode the inverter should operate in. And the inverter operates
smoothly between these two modes. Based on similar concept, three advanced
modulation methods are proposed. One of them can help further improve the efficiency,
and one of them can help increase the bandwidth and gain, and the last one takes the
advantage of both.