Study On Application Of Active Power Filter In Distribution Network Of Metallurgical Enterprises

In recent years,with more and more non-linear load connected to the utility grid,harmonic pollution of the power system is becoming more and more serious,which seriously affected the safe and economical operation of the enterprise distribution network.As the national strategic strategy of Energy-saving Emission Reduction steadily pushed forward,harmonic suppression has become an important part of green energy management.Aiming at the problem of power quality of the distribution network in a certain domestic steel metallurgy enterprise,this paper focuses on the harmonic domain modeling of the enterprise distribution network,the optimal design of the harmonic detection and the current control method of the active filter.(1)By explaining the mechanism of harmonic excitation and its harm in distribution network,the background and significance of active power filter are described.In this paper,the harmonic suppression methods and research status of distribution network are described and the corresponding technology and research status of high voltage system and low voltage system in distribution network are summarized respectively.Furthermore,the topology,access type and current research status of active power filter commonly used for harmonic suppression are discussed in detail.(2)The compensation performance of the harmonic management device is closely related to the topology of the distribution network and the load characteristics of the network.For this reason,taking a domestic iron and steel metallurgy enterprise as an example,the power supply system and the load type and its harmonic characteristics are analyzed in detail,and the analytic expression of harmonic content and frequency is obtained.Through the modeling and simulation and field data measurement,the main power quality problems of the metallurgical field are studied,and the problem of the characteristic harmonic current exceeding the distribution of the distribution network in the metallurgical enterprise is analyzed in detail.Focusing on the harmonic compensation,the active power filter solution is proposed.(3)The harmonic current detection of active power filter directly affects the response speed and harmonic compensation effect of the whole system.With the comparison of instantaneous reactive harmonic current detection method and Fourier harmonic current detection method,the optimized harmonic detection method suitable for engineering practice is proposed with the improved low-pass filter in harmonic detection loop.The simulation results show that the proposed method can improve the dynamic response and steady-state accuracy,and provide accurate and reliable instruction signal for the active power filter.(4)Aiming at the rapid change of harmonic current in metallurgical enterprises,a fast repetitive control strategy based on single synchronous rotating frame is proposed.With the s domain model of active power filter in synchronous rotating coordinate system established,the feasibility of T1/6 delay repetitive control strategy is analyzed and the fast compound harmonic current control strategy is obtained by introducing fast repetitive control to the traditional proportional integral control strategy.The theoretical analysis and simulation results show that the proposed method can improve the compensation accuracy of the charac-teristic harmonic current,adapt to the changes of the load quickly,and has satisfactory dynamic perfor-mance.