Modeling and MPPT Control in DFIG-Based Variable-Speed Wind Energy Conversion Systems by Using RTDS

Abstract

-The generating systems use Doubly-Fed Induction Generators (DFIGs) to achieve high conversion efficiency and to reduce the installation cost. This paper presents a modeling and Maximum Power Point Tracking (MPPT) control method of DFIG-based variable-speed wind energy conversion system. The generator considered is a wound rotor induction machine whose stator is connected directly to the grid and the rotor is fed through back-to-back Pulse-Width Modulation (PWM) converters. Stator flux-oriented vector control is applied to control the active and reactive current loops independently. The MPPT control method in a Wind Energy Conversion System (WECS) is proposed. The proposed control solution aims at driving the position of the operating point near to optimality. This is a very important aspect to maintain DFIGs efficiently in a variable wind speed. The wind generator is modeled in RSCAD program which is interfaced with the Real Time Digital Simulator (RTDS).

A state-space model and control of a full-range PMSG wind turbine for real-time simulations

“…In a fixed-speed wind turbine, the generator, normally a conventional squirrel-cage induction machine is directly connected to the grid through a transformer [1][2][3]. Variable speed wind turbines are controlled by power electronic equipment, and depending on the arrangement, both induction and synchronous machines can be employed [4][5][6][7].…”

“…To overcome this problem, models in the dq reference frame have been developed; these models consider the most suitable scheme of the test system according to the topology under study and the control necessities [1,6,14]. In the case of real-time simulations the complexity of the model and the computational effort are two aspects to take into account in the modeling [4,15]. In this contribution a state-space model in the dq reference frame was developed based on these considerations, that is, the model needs to be simpler compared with models obtained in the phase domain and preserve the dynamic behavior of the test system.…”