Digital control of three phase active rectifier for power conditioning with pole placement technique

A simple digital control scheme for three phase active rectifier is described in this paper. With this control scheme, the three phase rectifier is able to draw nearly sinusoidal current at unity power factor from the AC lines and provide constant DC voltage at a load. For the AC current control, this algorithm is designed to control in real time such that pulse pattern is determined at every sampling instant by solving the discrete control equations. This control configuration consists of state feedback, command feedforward and integral control. The pole placement technique is used in order to determine the control gain matrices. In this algorithm, line to line voltages are used as the control voltages instead of line to neutral voltages. A switching pattern generation method is also presented which minimizes the switching action by allowing only one switch change from one switching state to another. It was verified through computer simulations that the proposed control algorithm produced low DF in the AC line currents and has fast response for load change.