Combined use of double-band hysteresis current and proportional resonant control methods for single-phase UPS inverters

A double-band hysteresis current-control (DBHCC) strategy for single-phase UPS inverters with the use of proportional resonant (PR) controller is introduced. The PR controller eliminates the steady-state error in the output voltage. The output of PR controller serves as reference inductor current which is compared with the measured inductor current. The current error is then fed to the DBHCC block whose outputs are the control signals of the inverter switching devices. The use of double band hysteresis function is very effective in reducing the switching frequency of the inverter switching devices. It is shown that the output voltage can track its reference with zero steady-state error regardless of the hysteresis width. The performance of the proposed control method has been tested by simulations and experiments under resistive and diode bridge rectifier loads. The results demonstrate that the proposed method not only maintains the advantages of DBHCC method such as fast dynamic response, reduced switching frequency and simplicity in implementation, but also achieves zero steady-state error in the output voltage regardless of the hysteresis width.