Unified control scheme design for both the PWM rectifier and the inverter in the uninterruptible power supply (UPS) system

This paper first discusses control loop characteristics for the PWM rectifier and the inverter used in an on-line UPS system. Then a unified control scheme for both the PWM rectifier and the inverter in the UPS system is investigated using single phase control in ABC frame. Based on the unified control scheme, a generic control kernel is defined. This generic control kernel is used to realize the main performance of the UPS system, such as dynamic response, low THD and synchronism. Then the generic control kernel can be further applied to both the PWM rectifier and inverter by selecting different inputs. The unified control scheme not only significantly simplifies the UPS control software development, but also improves its maintenance. Finally, this unified control scheme is verified on a 50kVA UPS system.