LQR with Integral Action for Phase Current Control of Constant Switching Frequency Vienna Rectifier

This paper deals with the design of a linear quadratic regulator (LQR) with integral action (LQIR) to improve dynamic performance of a three-phase Vienna rectifier. The integral action is added to cancel the steady state errors knowing that the standard LQR controller provides only proportional gains. The controller is designed to achieve overall output voltage regulation, DC load unbalance compensation and unity power factor. The converter small-signal model is in the dq rotating reference frame augmented with the integral of the q-component of input currents; overall output voltage and DC load unbalance. The performance of the controller depends on the weightening matrix which is chosen to guaranty satisfactory responses. The converter is controlled as a whole which provides the input current references and a fixed PWM at 2.04 kHz is used to generate the gating signals of the power semiconductors. Simulation results obtained using Matlabreg/Simulink are presented to confirm the validity of the proposed controller design. The system is tested for a balanced load at rated power, in case of unbalanced load and for mains voltages perturbations and shows good performance in terms of the overall DC output voltage regulation, DC load unbalance compensation (small overshoot and very fast time response) and small total harmonic distortion (THD) of line currents