The Ripple Correlation Optimal Point Determination in a Medium Power Wind Conversion System and Performance Evaluation with Respect to Conventional Algorithms

Abstract

This paper deals with the application of the method called ripple correlation speed (RCS) in a power wind conversion system (PWCS) based a permanent magnet synchronous generator (PMSG). This method is widely used in photovoltaic systems for optimal maximum power point determination. The contribution of this work is the use of two electrical sensors instead of mechanical sensors in order to find the maximum power point (MPP). This method is justified by a ratio of proportionality between the mechanical speed of the (PMSG) generator and the output voltage of the three-phase rectifier. The reading of the power curve as a function of the output voltage of the three-phase rectifier showed that the optimum point has a maximum according to the wind speed. The desired point is characterized by a determined voltage. This observation allows to apply the ripple correlation between power and voltage at the output of the three-phase rectifier. The (PMSG) generator associated with the three-phase diode rectifier is considered as a continuous source whose voltage is dependent on the wind speed and hence the mechanical speed of the generator. This paper uses a power conversion structure based on a synchronous generator, a three-phase rectifier and a boost converter. The choice of this structure is justified by the reliability, simplicity of implementation and control. The boost converter ensures maximum power point tracking. The control duty cycle of the boost converter is determined by the ripple correlation of the input voltage and power of the Boost converter. This paper discusses the performance evaluation of a MPPT method called RCS (ripple correlation speed) in comparison with the conventional methods. To achieve this objective, four criteria are chosen: speed convergence, need of mechanical sensors, accuracy and dependence of the previous position. The main features presented in this paper are as follows: (a) modeling the power wind conversion system, (b) presenting and detailing the conventional MPPT method (c) detailing the proposed (MPPT), (d) presenting simulation results, (e) conducting a discussion and evaluation performance of the proposed method and comparison with conventional methods.