Research On Techniques Of Shunt Hybrid Active Power Filter

Power harmonics is one of the main products of industrial modernization, and one of the urgent problems of the industrial sector. In order to compensate the deficiencies of the passive filtering system, cost-effective active power filter will play an important role in the future and become the primary mean of harmonic filtering. This paper mainly focus on one shunt hybrid active power filter, consisted of series active and passive power filter. For different applications, different appropriate hybrid filtering system was analyzed and designed, and digital control parameters were deeply studied.Firstly, the basic operation principle of the hybrid filtering system was analyzed, as well as the filtering characteristics. The mutual relationship between the main circuit parameters was revealed. Then, based on the quantitative electrical relationships, a time-domain parameter design method was proposed to reduce the capacity of the APF.In the application when load harmonic is low-frequency and high-capacity, the active power filter is in series with the passive filter through a coupling transformer to suppress resonance and improve the filtering effect. The three-phase three-wire active power filter model was established firstly, and the control objects of APF output, grid current and DC-voltage control loop in s-domain was derived. Under the influence of digital control, design of control parameters was specifically discussed. Simulation and experimental results verify the correctness of controller design and the effectiveness of this filtering system.In the application with low frequency passive filter, only the high frequency harmonics and resonance need to be solved, the active power filter is in series with the passive filter directly without coupling transformer, then connect to grid in parallel with existing passive power filter to compensate the high frequency harmonics. APF capacity is small in this system. Based on the system model, the effectiveness of high frequency suppression under digital control was verified by theoretical analysis, the effect of active gain in harmonic distribution between active and passive branch was token and the choose principle was given. Simulation analysis is consistent with the theory.