A Novel Single-Phase UPS Inverter by Error-Tracking Mode PWM Scheme

Abstract

This paper proposes a novel single-phase UPS inverter modulated by Error-Tracking Mode PWM scheme. An ac voltage regulation scheme which matches the PWM scheme is newly developed in a theoretical way. Since Error-tracking Mode PWM is based on constantly-sampled data, the controller is suited to be digitally implemented. The equivalent circuit of the UPS inverter controlled by the schemes is derived. The output impedence is found to be composed mainly of resistance differently from general ac apparatus.According to the newly-developed schemes, a 3kVA, 100V, 50Hz UPS inverter is experimentally fabricated in which the sample period is 10μs and the average switching frequency is 6kHz. No load, linear load and non-linear load characteristics are measured. The output voltage remains almost sinusoidal even for the rated non-linear load. The output impedences are also measured and well agreed with the intended values.