A Harmonic Damping Method for a Loop Power System

Increasing demand for electric power reliability in industrial consumers, such as high-tech science parks, has led to the development of a loop power system. The harmonic resonance, due to power factor correction capacitors and line inductors or transformer leakage inductance, may cause significant voltage distortion along the feeder. A discrete frequency tuning active filter is proposed in this paper to suppress the harmonic resonance of a loop power system. The active filter is installed at the middle point of the line to operate as various conductance for each harmonic frequency. This algorithm allows the damping conductance of individual harmonic frequency is adjusted according to voltage distortion at the active filter installation point in response to increase or decrease of nonlinear loads. The harmonic conductance also can be tuned with resonant capacitor variation to accomplish effective suppression functionality, which is the significant advantage of the proposed approach. Therefore, the voltage distortion of each harmonic frequency at the active filter installation point can be definitely maintained below an allowable level, and the voltage throughout the feeder can receive uniform and quality waveform. Operation principles are explained in detail, and computer simulations and experimental results are provided to validate the effectiveness of the proposed approach.