Discrete Sliding Mode Repetitive Controller Design And Implementation In An Inverter

Many industrial plants are required to perform repeatable tasks, where exogenous disturbance may include periodic components. Repetitive control is an effective method, which can achieve complete rejection of the periodic signals. In the power electronic devices, CVCF PWM inverters are widely used. The output waveforms of inverters contain a large number of harmonic. Repetitive control can achieve perfect tracking of periodic signals and effectively eliminate the periodic disturbances in inverters.This thesis focuses on the design of discrete sliding mode repetitive controller and its implementation in an inverter. The main work and contributions of this thesis are as follows:1. This thesis uses reaching law method and ideal switching dynamics to design the discrete sliding mode repetitive controller for uncertain systems with periodic disturbances.2. In order to design the sliding mode repetitive controller, this thesis uses the method of ideal switching dynamics. Disturbance rejection measure is embedded into the power reaching law to design ideal switching dynamics. For characterizing the convergent performance of the system, this thesis derives the three kinds of convergence layers in the system. The layers include the band of absolute attractive layer, the band of monotone descending region, and the band of quasi-sliding mode.3. When the initial state of the system is away from the switching surface, the convergence rate of the power reaching law is slow. This thesis uses the double-power reaching law which can improve the convergence rate of the system. The discrete sliding mode repetitive controller is designed based on the ideal switching dynamics in this thesis.4. Due to the chatting problem of exponential reaching law, this thesis presents an improved reaching law to reduce the chatting. The repetitive sliding mode controller is designed based on the improved reaching law, which can eliminate the periodic disturbances and improve the control performance.5. Through designing the hardware of the inverter and programming in the DSP, the discrete sliding mode repetitive controllers are implemented. Experiment results show that the proposed controllers can effectively eliminate the harmonic and reduce the THD.