Abstract
Harmonic pollution of double fed induction generators (DFIGs) has become a vital concern for its undesirable effects on power quality issues of wind generation systems and grid-connected system, and the double pulse width modulation (PWM)converter is one of the main harmonic sources in DFIGs. Thus the harmonic analysis of the converter in DFIGs is a necessary step to evaluate their harmonic pollution of DFIGs. This paper proposes a detailed harmonic modeling method to discuss the main harmonic components in a converter. In general the harmonic modeling could be divided into the low-order harmonic part (up to 30th order) and the high-order harmonic part (greater than order 30) parts in general. The low-order harmonics are produced by the circuit topology and control algorithm, and the harmonic component will be different if the control strategy changes. The high-order harmonics are produced by the modulation of the switching function to the dc variable. In this paper, the low-order harmonic modeling is established according to the directions of power flow under the vector control (VC), and the high-order harmonic modeling is established by the switching function of space vector PWM and dc currents. Meanwhile, the simulations of harmonic a components in a converter are accomplished in a real time digital simulation system. The results indicate that the proposed modeling could effectively show the harmonics distribution of the converter in DFIGs.
Highlights
The installation rate of renewable energy sources is increasing rapidly in large power plants [1,2], and the fastest growing source of renewable energy in the power industry is wind energy [3].Many studies have been done to analyze the different kinds of problems in wind turbines after connecting to the grid [4,5,6,7,8]
These advantages are realized on the basis of the pulse width modulation (PWM) converter, which is widely used in the double fed induction generators (DFIGs) systems for its ability to realize a bidirectional flowing of energy
Based on the circuit topology of DFIG, a detailed modeling of double PWM converter can be established in real time simulator CAD (RSCAD)
Summary
The installation rate of renewable energy sources is increasing rapidly in large power plants [1,2], and the fastest growing source of renewable energy in the power industry is wind energy [3]. As a variable speed wind generator, DFIG has many advantages compared with other types, such as its good stability after connecting to the grid, and decoupled control of active and reactive power [9,10,11] These advantages are realized on the basis of the pulse width modulation (PWM) converter, which is widely used in the DFIG systems for its ability to realize a bidirectional flowing of energy. The harmonic modeling established in this article focuses on the converter of the DFIG, considering the influence of the different control methods and the different operation states, and is relatively complete for the study of the harmonics. The results of the whole harmonic modeling are summarized
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