Passivity-based Voltage Controller for Tidal Energy Conversion System with Permanent Magnet Synchronous Generator
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ISSN:1598-6446 eISSN:2005-4092 http://www.springer.com/12555
Passivity-based Voltage Controller for Tidal Energy Conversion System with Permanent Magnet Synchronous Generator Youcef Belkhier* and Abdelyazid Achour Abstract: Nonlinear dynamical and time varying parameters of the permanent magnet synchronous generator (PMSG), make it difficult to control. This paper presents a new passivity-based control (PBC) of tidal turbine based PMSG, connected to the grid through a back-to-back converter. The control problem is challenging for at least two reasons. First, the dynamics of the conversion system are described by a highly coupled set of nonlinear differential equations and various uncertainties of the PMSG model. Second, it is preferable to operate this kind of systems at the point of maximum power, which is a nonlinear function. To this end, two kinds of control strategies have been used. A new passivity-based voltage controller (PBVC) design applied to the machine-side, that ensures asymptotic convergence to the MPPT is presented. A proportional integral derivative (PID) is added to design a desired torque dynamic in order to guarantee a fast convergence and stability of the closed loop system, which allows to the PMSG to operate at an optimal speed. Secondly, a classical proportional integral (PI) controllers is applied to the grid-side in order to regulate the DC-Link voltage and to deliver only the active power into distribution network. Finally, the obtained simulation results under MATLAB/Simulink, show that the proposed control strategy ensures stability and fast response of the DC-link voltage and the reactive power generated is extremely minimized. Keywords: Nonlinear control, passivity-based voltage controller, permanent-magnet synchronous generator (PMSG), tidal turbine.
1.
INTRODUCTION
Tidal energy is one of the most fascinating kinds of renewable energy in recent years. Tidal power has become the focus of research and development, because of being highly predictable, compared to other forms of renewables energies [1–3]. As the most common option for extracting kinetic energy, a marine current turbine based PMSG conversion system, connected to the grid via a back-to-back converter is used in this work, due to their higher efficiency, good electricity generation, low cost and non-polluting impact [4]. However, the maximum power which can be extracted is nonlinear, due to the water flow speed, also a tidal system based PMSG can capture significantly more power than a wind system with the same characteristic due to the water density which is thousand times higher than the air density. So, it is necessary to design an appropriate controller in order to harvest the power extracted at its maximum point [5, 6]. Nonlinear controls have been largely investigated to minimize the problems resulted from the PMSG complex-
ity and instability. Reference [7], proposed a new inertial power perturb and observe based third order super twisting sliding mode control (SMC) to find the maximum power point tracking (MPPT
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