Understanding the unbalanced-voltage problem in wind turbine generation

Abstract

-Most wind turbines are equipped with line-connected induction generators. Induction generators are very attractive as wind turbine generators due to their low cost, ruggedness, and the need for little or no maintenance. At constant frequency, the induction generator operates in a small range of speeds and, therefore, it operates with a small range of slips with respect to synchronous speed. Compared to a synchronous generator, an induction generator provides lower stiffness, thus alleviating the mechanical stress.In a weak power system network, an unbalanced load at the distribution lines can cause unbalanced voltage conditions. If an induction generator is connected to an unbalanced voltage, the resulting stator current will be unbalanced. The unbalanced current creates unequal heating (hot spots) on the stator winding. The heat may increase the winding temperature, which degrades the insulation of the winding, i.e., the life expectancy of the winding. Unbalanced currents also create torque pulsation on the shaft resulting in audible noise and extra mechanical stress. This paper explores the unbalanced voltage problem in induction generator. The levels of unbalance and the loads are varied. Experimental and predicted results are presented in this paper. INDEX TERMSUnbalanced-voltages, induction generators, wind energy.

Sliding-Mode Control for a DFIG-Based Wind-Power Generation System with Series Grid-Side Converter under Unbalanced Grid Voltage Conditions

“…The first converter is the Grid-Side Converter (GSC) and the other one is the Rotor-Side Converter (RSC). Wind farms are mainly located in rural areas where nonlinear, asymmetric loads and grid faults can lead to such more frequently disturbances [1][2][3]. As a consequence, unbalanced and harmonic disturbances are inevitable in the wind power systems.…”

Adverse Peculiarity Arising with Overhead Power Lines

“…Unbalanced voltages are highly unwanted for the loads, especially for electrical motors as well as for other loads [3], [4], [5].…”

Improved Control of DFIG during Grid Voltage Distortion for Reduction of Current Harmonic Using PI-Fuzzy

“…In detail, both positive and negative sequence components are used in this scheme. Referring in [5], [6], dynamic programming power control plus which applies the Bellman theory for optimal control of discrete time systems is suggested to obtain correctly the converter switching sequence for controlling the decoupled active and reactive powers under the network unbalance condition. The optimum policy is determined from the pre-defined quadratic time-domain performance criterion and cost function for any operating point [7].…”