Modified deadbeat digital controller for UPS with 3-phase PWM inverter

In this paper, a modified deadbeat control scheme is proposed for 3-phase PWM inverter control such as uninterruptible power supply (UPS). The deadbeat controller, which is generally constructed with voltage and current controller in UPS, is used for fast transient response, but this might have an instability due to the same pole placement of the double controller. To solve this instability problem, separation of pole placement can be considered, and it is performed by the proposed deadbeat control scheme. In this paper, this control scheme is called the modified deadbeat, which produces a first-order exponential response during one input step. As the overall controller is constructed by deadbeat control, the response of the proposed control system is fast and the structure of the controller is simple. In addition, the disturbance observer with full-order state is constructed, which can cancel the disturbances by adding a feedforward compensating loop in the controller and hence it can compensate the disturbances caused by a sudden load change in the UPS system.