MPPT strategy based on speed control for AWS-based wave energy conversion system

Abstract

One of the attractive direct-drive wave energy conversion systems is the Archimedes Wave Swing (AWS) coupled to a Linear Permanent Magnet Synchronous Generator (LPMSG). This paper presents an integrated control strategy for the back-to-back converter interfacing the LPMSG not only to extract the maximum power from the wave, but also to ride-through the fault. The proposed maximum power tracking technique is based on speed sensorless control of the LPMSG. The unscented Kalman filter is adapted to estimate the translator velocity. The optimal velocity is obtained from the instantaneous active power at the generator terminals. Moreover, a low-voltage ride-through control is integrated to satisfy the grid-code requirements by injecting reactive current during grid disturbances. The generated active power at the fault instant is considered in determining the dynamic reactive power injection to not exceed the ratings of the grid-side converter. The superiority of the proposed strategy is the result of its ability to regulate the translator velocity that generates optimum power. Numerical simulations are conducted to evaluate the dynamic performance of the proposed integrated optimal strategy. Besides, it has been shown that the proposed methodology outdoes others by the decreased power fluctuations which leads to a reduction of the converter size.