A Novel Double-Loop Control Strategy and Its Precise Parameters Tuning Method

With the rapid development of hardware and the improvement of control performance requirements, digital control is widely used in power electronics. And due to the mature analysis methods and convenient implantation, the traditional linear control strategies, such as PID control, are directly applied to the design of digital controllers in industrial application. However, as the control delay and the designing process approximation, most digital controllers do not achieve the desired performance indexes and its parameters need to be tested repeatedly when simply adopting traditional control strategies. In view of this above problems, taking the application in inverter systems as an example, the discrete state space model of the inverter is derived with the consideration of one beat control delay. In order to design the controller accurately, this paper proposes a double-loop control strategy in which proportional controller is used for current loop and PI plus state feedback controller is used for voltage loop. Particularly, the designing process of current loop and voltage loop is relatively independent, and the parameters of the voltage loop controller are precisely calculated according to the indexes of overshoot and bandwidth. The proposed control strategy and its parameters tuning method is verified on a platform of 30kVA 115V/400Hz inverter power.