753 International Journal of Research and Reviews in Computer Science (IJRRCS) Vol. 2, No. 3, June 2011 An Isolated Boost PMSG-Wind-Turbine System Based on Direct Torque Control Drive Scheme Noureddine Hidouri 1 , Samah Hammadi 2 , Lassâad Sbita 3 1 Preparatory Engineering Institute of Gafsa, Department of Preparatory Technological Engineering studies, Campus Universitaire Sidi Ahmed Zarrouk - 2112 Gafsa, Tunisia 2 Higher Institute of Technological Studies of Gafsa, Department of Electrical Engineering, Campus Universitaire Sidi Ahmed Zarrouk - 2112 Gafsa, Tunisia 3 National Engineering School of Gabes, Department of Electrical and Control engineering, Zrig, Gabes 6029, Tunisia Abstract: In this paper, the Authors present a Direct Torque Control scheme of a Salient Permanent Magnet Synchronous Generator (PMSG) associated with a wind turbine system. The turbine is used to drive the PMSG in order to feed an isolated DC load. It receives the required active power from the generator through a rectifier and a DC bus and a boost converter. A rectifier, a DC bus and a boost converter models are developed and used in the system control scheme. The main contribution is to compute the flux level from the torque command which is developed on the basis of direct current clamped to zero and regulate the voltage load by a boost converter when the wind varies. Mathematical relations treating the system components are presented and studied. The boost converter, the generator and the turbine dynamic performances are analyzed. The simulation results of the system entire control have shown that the proposed methodology is an efficient and promising control procedure. Keywords: DTC, PMSG, Wind turbine system, Boost converter, DC Bus, DC load. 1. Introduction During the last decades, the renewable energy system has witnessed a real evolution worldwide. The generation of electric power from renewable energy sources such as wind is very efficient in reducing environmental pollution by proving an alternative for the insufficiency of the traditional sources. The wind energy source is rapidly growing and has the highest percentage in terms of installation compared to other energy sources [1], [2], [18]. The wind turbines are constructed in different power ranges according to the energy needs. In isolated areas where no grids are available such as mountains and remote islands, micro turbines are used. In wind energy systems, the power depends on many factors such as weather conditions and geographic location and this varies with time. These considerations are carried out to figure out the adequate way to drive the associated converters, in order to adopt the system automatically. Wind turbine is equipped with an electric generator allowing the energy conversion between rotor turbine and the local load or an electric grid. Currently, for the power conditioning, the wind generator is followed by a DC-DC converter. Many types are used such as boost, buck and boost-buck converters. Many researches are developed in order to prove the most compatible type in terms of power optimization [16], [17], [27]. Several types of electric generator are being associated with wind turbines such as Squired-cage Induction generator [1], Doubly-fed Induction generator [14], [15], [21], Synchronous Generator with external field excitation. Recently, permanent magnet synchronous generator (PMSG) is used for wind power generating system [2], [4], [16], [17], [19]. The absence of the external excitation and the coils in the rotor reduce the maintenance cost and increase the efficiency of the PMSG as a power generating system. The main inconvenience of PMSG is the important non linearity of the developed torque that can introduce undesirable transient torque oscillations for heavy load operating points. According to the motor operating mode and in terms of available drive strategy of rotating electrical machines, Direct Torque Control (DTC) method [5], [10] and the most DTC- based approaches [6], [9], [11], [12], [13] have shown that excellent fast torque response can be obtained by controlling accurately stator flux vector. Recently, DTC was applied to wind turbine control systems based on DFIG [12], [21], [25] and PMSG [22], [23], [26]. In this paper a Direct Torque Control (DTC) strategy is synthesized for a pitched wind turbine permanent magnet synchronous generator to produce the load required power. A boost converter is used in the control scheme to adapt the DC voltage required by the load when the wind varies. This control scheme has also shown a very fast torque response and a good power control. 2. The Wind turbine System Model Figure 1 shows the wind turbine system considered in this work. The rotor of pitch controlled wind turbine is coupled to a permanent magnet synchronous generator in order to convert the mechanical power to electric power. The DTC controlled FCR (force commutated rectifier) which is connected to the PMSG stator is used to control the PMSG torque by establishing the optimum relation between the three phases AC supply and the DC voltage. The PWM controlled Boost converter, linked to the force commutated rectifier through a DC Bus link, regulates the DC voltage needed by the load against wind variation.