| With the development of our country’s energy Internet and the transition to clean and low-carbon energy,large-scale new energy sources,mainly wind power,are connected to the grid.While bringing higher efficiency and better performance to people,it also brings a lot of harmonic pollution to the power grid.As an important theoretical basis for harmonic control,the division of harmonic responsibilities needs to meet the requirements of fairness,reasonableness and accuracy.However,because wind power integration has brought new harmonic characteristics to the grid,the accurate division of harmonic responsibilities has become a difficult problem.Therefore,it is necessary to analyze the harmonic characteristics of wind power.Focusing on the harmonic characteristics exhibited by wind power,a targeted treatment of the problem is carried out.This article has carried out research work on two aspects of wind power harmonic current characteristics and harmonic impedance characteristics,mainly including the following contents:1)On the basis of traditional harmonic liability,the concept of weighted average harmonic liability index is proposed.Through the method of probability statistics,a more stable mode can be found,which can effectively avoid the interference of random over-values or under-values.Make the division of harmonic responsibilities of harmonic sources more objective and fair.2)The harmonic current injected by wind power has strong randomness,volatility and intermittent characteristics.In addition,the probability density function of the main subharmonic current amplitude and phase angle is different,which has an impact on the accurate division of harmonic responsibilities.Aiming at the volatility and randomness of the harmonic current injected by wind power,this paper firstly adopts the improved sparse k-means clustering method to classify the harmonic current data.Then,after analyzing the characteristics of various independent component analysis methods,a robust independent component analysis method is established to estimate the harmonic impedance.On the IEEE13-node system,simulation verification was carried out based on the actual measured data of wind power.The results show that compared with other methods,the method in this paper is more accurate and more adaptable.3)Wind farms exhibit low harmonic impedance characteristics at low frequencies,so that the wind power(consumer)side does not meet the prerequisites that are far greater than the harmonic impedance of the system side,leading to inaccuracy in the previous simplified method of harmonic liability calculation.On this basis,this paper firstly analyzes the error of ignoring the harmonic impedance of wind power,and derives the maximum relative error range,and then establishes the selection criteria.In this way,when calculating the harmonic liability of wind power,the calculation method can be selected according to the actual situation of the harmonic impedance.Perform simulation verification on Norton equivalent circuit.The results show that the method proposed in this paper is effective. |
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