A New single phase double-conversion UPS using PWAM method

With the increase in the use of advanced digital information devices that are sensitive to power failure, the demand of UPS (Uninterruptible Power Supply) is increased. This paper proposes a new modulation method for double-conversion single-phase UPS system. The proposed modulation method is the incorporation of PWM (Pulse Width Modulation) and PAM (Pulse Amplitude Modulation) methods. We call the new method as a PWAM (Pulse Width/Amplitude Modulation) method. If the PWAM method is used, switching is done at the lower voltage than that of existing methods and the times of switching is reduced. As a result, the switching loss and the size of heat sink for switching elements are reduced. In addition, the size of the input and output filters can also be reduced by decreasing the EMI (ElectroMagnetic Interference). Also, this method can decrease the THD (Total Harmonics Distortion) of output voltage.