Algorithmic Structure of Wind Turbines System based on an Induction Machine Directly Connected to the Grid

Department of Electrical Complexes of Self-Contained Objects and Electrical Transport, National Research University “Moscow Power Engineering Institute”, Moscow, Russia.

Abstract

One of the relatively simple (comparatively cheap) and promising solutions of the wind power plant - the wind turbine system (WTS) with variable speed on the shaft of the wind wheel - is to execute it on the basic of an induction machine - IM. Today, the problem of self-excited induction machine is solved in two ways - by using either capacitors, or electronic converters. As a generating system (based on IM), several WTS are often used, working parallel or directly connected to the grid. For induction machine: squirrel-cage induction generator (SCIG) and doubly-fed induction generator (DFIG) are used, several possible types of them are systematized, evaluated and compared on functional features and properties. Based on computer simulations, the ability of DFIG with back to back converters (in the form of two serially connected 2 level voltage source converters - converter-1 and converter-2) is determined in the rotor circuit at a variable speed of the drive shaft (in modes sub-synchronous and hyper-synchronous speeds) give to the grid only active power. For mass-scale and energy indicators, this structure is the optimum for WTS.