Abstract
Distributed generation is a flexible and effective way to utilize renewable energy. The dispersed generators are quite close to the load, and pose some power quality problems such as harmonic current emissions. This paper focuses on the harmonic propagation and interaction between a small-scale wind farm and nonlinear loads in the distribution grid. Firstly, by setting the wind turbines as P – Q(V) nodes, the paper discusses the expanding Newton-Raphson power flow method for the wind farm. Then the generalized gamma mixture models are proposed to study the non-characteristic harmonic propagation of the wind farm, which are based on Gaussian mixture models, improved phasor clustering and generalized Gamma models. After the integration of the small-scale wind farm, harmonic emissions of nonlinear loads will become random and fluctuating due to the non-stationary wind power. Furthermore, in this paper the harmonic coupled admittance matrix model of nonlinear loads combined with a wind farm is deduced by rigorous formulas. Then the harmonic propagation and interaction between a real wind farm and nonlinear loads are analyzed by the harmonic coupled admittance matrix and generalized gamma mixture models. Finally, the proposed models and methods are verified through the corresponding simulation models in MATLAB/SIMULINK and PSCAD/EMTDC.
Highlights
Following the depletion of fossil energy, renewable energy generation is a fast growing area nowadays
This paper focuses on the evaluation of the non-characteristic and switching harmonic emissions of a small-scale wind farm
High order switching harmonics of doubly-fed induction generators (DFIGs) with Pulse Width Modulation (PWM) controllers consist of two parts: the harmonic emission of the grid-side converter is directly injected into the grid system; the harmonic produced by the rotor-side converter intertwine through the electromagnetic coupling between the stator and rotor, and is injected into the power grid through the stator
Summary
Following the depletion of fossil energy, renewable energy generation is a fast growing area nowadays. Small-scale wind farms usually consist of several dispersed wind generators, which are directly connected to a medium or low voltage distribution grid [3]. The small-scale wind farm is quite close to the load, which can pose some power quality problems such as voltage fluctuation and harmonic current emissions. The fluctuating fundamental power can affect the controller of conversion systems and induce harmonics, so the harmonic current emissions of wind generators are analyzed by stochastic assessment. In order to analyze the complex harmonic current emissions, Generalized Gamma Mixture Models (GGMM) are proposed in this paper. This paper focuses on the harmonic propagation and interaction between a small-scale wind farm and nonlinear loads in the distribution grid. The harmonic admittance matrix models of nonlinear loads combined with the wind farm are established to analyze the harmonic propagation and interactions. The proposed models and methods are verified through a simulation model in MATLAB/SIMULINK and PSCAD/EMTDC
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