Application of SMC with I/O feedback linearization to the control of the cascade controlled-rectifier/inverter-motor drive system with a small DC-link capacitor

The necessity of the compactness of the converters in many applications imposes the reduction of the size of their different components when it is possible. In this paper a control method allowing the use of a small size DC-link capacitor for the assembly voltage controlled-rectifier/inverter-motor drive system is proposed. This is achieved by adding the power balance equation in the system's model and the application of an exact I/O feedback linearization technique in a way that the rectifier controller compensates any sudden change in the inverter load, which is here an induction motor. Since the exact I/O feedback linearization technique is sensitive to the uncertainties over system parameters, a robust control strategy based on Sliding Mode Controller (SMC) is proposed. By this approach, the DC-link voltage becomes almost insensitive to the load variations. As a result, the DC-link voltage level is stabilized with a small DC-link capacitor. The robust property of the overall controlled system to the variation of the rotor time constant of the induction motor is investigated when an opened loop flux observer is used. The simulation and experimentation results can confirm the performance of the control system.