Approach of optimal tuning frequency in single tuned harmonic filter

Filter detuning strongly affects the filter´s size and operating performance. Partial resonance is recommended to raise the filtering efficiency of a single-tuned filter at the worst point in the detuning range. This paper presents a new way to obtain the optimal tuning frequency of a single-tuned harmonic filter in order to control harmonic currents to the allowable value with a minimum filter capacity or a given capacity. By scanning the partial resonant ratio and filter resistance within their possible range, when the filter harmonic currents at the two points of maximum negative detuning and positive detuning are equal to the allowable value, the optimal tuning frequency and the minimum capacitance satisfying the harmonic control are obtained. On condition that power factor improving predetermines the filter capacity, the optimal tuning frequency can be searched to obtain either the maximum safety margin or the maximum filtering efficiency. A PC-based filter design procedure accompanied by a simulation code to verify the effectiveness of the filter was developed based on MATLAB. An industrial system was selected to demonstrate the application of the proposed procedure.