Electromagnetic design and optimization of dual‐stator brushless doubly‐fed wind power generator with cage‐barrier rotor

Abstract

This paper explores the feasibility of an intuitive solution torque density for the existing brushless doubly-fed generator by dual-stator and cage-barrier rotor structure, so as to better adapt to the offshore wind power generation. The torque density of electrical machine is related to the key design parameters, such as the machine main dimensions, slot-pole combinations, coupling between stator and rotor, and nonmagnetic ring thickness. According to working principles and design requirements of electrical machine, the dual-stator brushless doubly-fed wind power generator (DSBDFWPG) with cage-barrier rotor is designed, and the key parameters relating to torque density are analyzed and discussed. Meanwhile, the main parameters of electrical machine are optimized by Taguchi method, such as air-gap length and nonmagnetic ring thickness. On this basis, the performance parameters of DSBDFWPG are analyzed by finite element method, which is verified by experimental tests. Through analysis of the results, not only the design requirements are satisfied by the DSBDFWPG, but also the correctness and rationality of machine design method can also be verified. Finally, the torque density and other aspects of designed DSBDFWPG are compared with dual-stator brushless doubly-fed induction generator, doubly-fed induction generator, asynchronous machine, and brushless doublyfed generator; it demonstrates the torque density improvement of the studied machine with its significance and value. KEYWORDS brushless doubly-fed machine, dual stator, electromagnetic design, optimization, torque density, wind power generator 1 | INTRODUCTION Because of the rapid development of wind energy in recent years, wind power becomes one of the main new energy powers. According to thelatest data from the Global Wind Energy Council, the global installed capacity is 486.7 GW, and the new installed capacity 1 is more than 54.6 GW in 2016. It is also observed that wind-generated electricity is valued by all countries. So far, the wind-generated electricity is mainly based on land, which has the disadvantages of regional limitation and wind speed instability. Thus, people began to seek from the land to offshore wind power. The wind energy resource developed by offshore wind farm is three times of that by the land wind energy resource. Meanwhile, the offshore generating capacity is 20% to 40% higher than that of the land. Compared with the land wind energy, the offshore wind energy has advantages with rich reserves, good stability, high wind speed, and easy prediction. 2,3 Therefore, the offshore wind power generation has become

A dual-stator brushless doubly-fed generator for wind power application

“…Brushless doubly-fed machines (BDFMs) have strengths of high reliability, low maintenance costs and improved low-voltage crossing capability because of the elimination of brushes and slip-ring parts [9][10][11][12][13]. Meanwhile, the BDFMs are suitable for slow running because the number of electric machine pole-pairs is about two times greater than traditional doubly-fed induction machines (DFIMs) under the same armature diameter in [14,15].…”

“…Meanwhile, the BDFMs are suitable for slow running because the number of electric machine pole-pairs is about two times greater than traditional doubly-fed induction machines (DFIMs) under the same armature diameter in [14,15]. Therefore, the BDFMs have attracted a lot of attention in various areas, for instance, the wind power generator in [16], pump in [17], ship in [18], rotary transformer in [19], and electric vehicle [20]. However, the prominent problem of BDFMs is low torque density in [21].…”