Improved study on double closed-loop control of three-phase PWM rectifier based on induction heating rectifier side

Abstract

With the development of power electronics technology, induction heating power supply becomes more applicable. The three-phase PWM rectifier is widely used in induction heating system because of its advantages of better power factor and bi-directional energy transfer, and often adopts the control method of voltage outer loop and current inner loop to improve its control performance. However, the traditional rectifier control structure in the application process will appear such as poor anti-interference ability, low fault tolerance and other outstanding problems. In this paper, an improved H∞ controller is designed for the induction heating system based on the rectifier-side power regulation by combining the robust control principle, establishing a state space model of the system with an equivalent series resonant load, firstly decoupling the linearization of the model, and then designing a double-closed-loop PI controller as well as an improved current inner-loop H∞ controller based on the decoupled model. In order to facilitate the analysis, the PI controller and the H∞ controller are simulated under two kinds of starting conditions, and the comparison further confirms that the improved system has better anti-interference ability and dynamic characteristics.