| Summary: | 博士 === 國立清華大學 === 電機工程學系 === 95 === This dissertation proposes a distributed active filter system (DAFS) for alleviating harmonic voltage distortion in the power system. The proposed DAFS consists of multiple active filter units (AFUs) installed on the same location or various locations along the power line. A droop relationship between the harmonic conductance command and the volt-ampere consumption is developed and programmed into the controller of each unit so that each individual AFU operates as a harmonic conductance with droop characteristic. The slope of the droop is determined by the volt-ampere rating of the AFU to assure even distribution of filtering workload in proportion to the rated capacity of each unit without any communications. Test results based on computer simulations and experiments validate the effectiveness of the proposed approach. In addition, the filtering performance is discussed based on harmonic voltage standing waves to determine suitable AFU
installation location. Breaking the feeder into several segments smaller than half wavelength of dominant harmonic
frequencies is a key strategy to deploy AFUs whether in a radial line or a loop line. Therefore, distributed installation active filters provide effective filtering approach compared with termination installation or concentration installation active filters.
The proposed droop control algorithm is also effective for harmonic suppression applications in distributed generation systems. Together with real power-frequency droop and reactive power-voltage droop, each distributed generation units can provide the real power, the reactive power, and the harmonic volt-ampere reactive (var) based on their rated capacity. Furthermore, to maintain voltage quality at a desired level, the DAFS with dynamic tuning method is presented. In this algorithm, the volt-ampere capacity of the AFU is dynamically adjusted according to the voltage THD at the installation point, so that the voltage waveforms throughout the feeder are kept at a uniform level
in response to increasing or decreasing of nonlinear loads.
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