Robust sliding mode control with five sliding surfaces of five-phase PMSG based variable speed wind energy conversion system

Abstract

The central thesis of this paper is the implementation of an optimized Sliding Mode Control to a high power multiphase permanent magnet synchronous generator based direct-driven Wind Energy Conversion System (WECS), in order to attain an optimal regime characteristic. The principle of proposed approach is to control the Rotational Speed Dynamic to follow the desired value during wind variations. Moreover, the controller is designed to ensure an effective regulation of 4 dynamic models of Direct & Quadrature axis current instead of the regular hysteresis control due to its disadvantages. In this context, the main challenge of this research with a view to ensure the system stability, is to design a controller in a way to guarantee the consistency between the input of inner loop (4 axis current regulation) and the output of outer loop (speed regulation), taking into account the risk of declined effectiveness of closed-loop due to disappearing relative changes in control periods between the cascaded loops. Furthermore, the grid supply is managed using the proposed sliding mode approach in order to guarantee a power injection with Unity Power Factor. On the other hand, a challenging matter of pure SMC can be summed up in the produced chattering phenomenon. In this work, this issue has been mitigated by implementing a new smooth continuous switching control. In order to examine the suggested approach robustness and responsiveness over other techniques, a detailed analysis has been carried out under hard and random wind speed variations. The stability of improved SMC is verified using Lyapunov stability theory by taking into account system uncertainties to guarantee more efficacy. The suggested SMC is compared to a classical PI controller. The study results exhibit the excellent performance with high robustness of the improved SMC, by improving the system efficiency to 91,14%, compared to the PI with the ratio of 86,2%.