According to the characteristics of harmonic frequency filtered by passive filter, it can be divided into single-tuned filter, double-tuned filter, three-tuned filters and high-pass tuned filter and detuned filter

Single-tuned filter, mainly filter a particular frequency harmonic currents, form series resonant circuit in a particular frequency, that is, XCn-XLn = 0. Double-tuned filter, has two resonant frequencies, absorbing the two frequencies harmonic, it is equivalent of two single-tuned filter in parallel. High-pass filter, also known as damped filter, above a particular frequency it present low impedance, high impedance is presented below. High-pass filter on the structure divide into first, second, third, and C type, commonly used for the second-order high-pass tuning filter.

The resonant frequency of the detuning filter is usually lower than the lowest harmonic frequency of power grid, frequency is usually set to 3.8 to 4.2 times of fundamental frequency, can only absorb a small amount of harmonics, the main purpose is to prevent harmonic amplification, its structure and impedance characteristics similar to the single-tuned filters, but have different resonant frequencies.

Two-tuned three-tuned filter as its small footprint, low loss, commonly used in HVDC transmission systems, but the structure complex, tuning difficulties, rarely used in low pressure systems. Low-pressure systems often use a single tuning, detuning and second-order high-pass filter.

High-pass filter, also known as reduction amplitude filters, including first-order high-pass filter, second-order high-pass filter, third-order high-pass filter, and c-type filter to attenuate the harmonics whose frequency higher than a certain frequency. The frequency is called the high-pass filter cutoff frequency.