Optimal regulator-based control of electronic power transformer for distribution systems

This paper presents the design of a linear-quadratic-regulator (LQR) with integral action to improve dynamic performance of an electronic power transformer for distribution systems (DEPT). The integral action is added to cancel the steady-state errors knowing that the standard LQR provides only proportional gains. This controller is designed to achieve the following four control objectives: (1) to keep the input currents sinusoidal and in phase with the input voltages to achieve unity input power factor, (2) to maintain the dc-link voltage at a reference value, (3) to maintain the output voltages at a constant value and (4) to keep the output voltages sinusoidal and symmetric. The DEPT model which includes the integral action in the d–q rotating frame is built and linearized around a set point. The system is tested for dc-link reference voltage, load and input voltages variations, respectively. The validity of the built model and the proposed control strategy is demonstrated by simulation results based on MATLAB/SIMULINK.