Research On Parallel Operation System Of Active Power Filters

With the acceleration of country's industrialization process, a large number of non-linear and impact loads have appeared. Harmonic current and reactive current which generated by these loads on the public grid pollution is also becoming increasingly serious. To suppress harmonic pollution caused by non-linear devices, there were many ways to solve harmonic problems. Active power filter (APF) is a promising device for harmonic suppression. From the eighties, active power filter theory and applications have achieved great progress. As the"instantaneous reactive power theory in three-phase circuits"in the success of active power filter's applications, active power filter device has entered a phase of industrial and practical.However, with the increasing capacity of system, the allowed switching frequency of the power electronic devices is getting lower and lower. The lower switching frequency has a direct impact on the compensation effect of active power filter. When active power filter is used for large-capacity harmonic compensation, there is contradiction between device switching frequency and capacity of the device. Therefore, in order to obtain a larger compensation capacity, research on the use of parallel operation system of multiple APFs is great significance.Based on the research of the single active power filter, this paper researches parallel operation strategy to achieve the parallel operation of multiple APFs .This parallel operation solves the issue of compensation for large-capacity harmonic.Firstly, the development status and work principle of active power filter is introduced in this paper. The harmonic detection methods, control methods of shunt active power filter and DC side capacitor's voltage control is researched in detail.Secondly, various parallel control strategies of multiple APFs are introduced and researched. Advantages and disadvantages of these control strategy are compared in detail. On this basis, this paper presents a new control strategy based on current sharing. The new control strategy overcomes the shortcomings of the used methods of the APFs parallel operation. The new parallel operation system has high reliability and good dynamic performance. This paper has analyzed the performance characteristics of parallel operating system. Its validity and feasibility is validated by MATLAB simulation. Finally, based on the theoretical analysis and simulation, the experimental platform is build. Experimental prototype based on DSP is designed. The hardware design and software design of experimental prototype have carried out a detailed study and conducted a series of experimental studies to verify the theoretical analysis is correct.