Passive and active filters, compared with the following differences:
First, the working principle: the LC passive filters and other passive components, it is designed for low impedance at a certain frequency, the frequency of the corresponding harmonic current shunt, their behavior pattern to provide passive harmonic current bypass channel; and Active filter power conversion apparatus constructed by the power electronics and DSP, etc., to detect the load harmonic current and the initiative to provide corresponding compensation current, source current compensation of almost pure sine wave, its behavior is an active current source output .
Second, the harmonic processing: Passive harmonic filters can filter out a certain frequency range; but it can solve the system harmonic problems, solve practical problems in the process of electricity, and can meet the state's power sector standards; active filter can dynamically filter out a certain number of harmonics.
Third, the impedance effect: passive filter system impedance seriously affected by the presence of harmonics and resonance amplification of danger; and active filtering unaffected.
Fourth, the frequency effect: passive filter resonance point offset, the effect is reduced; active filter is not affected.
Five load Impact: passive filter may be damaged due to overload; no danger of damage to the APF, harmonic is greater than the ability to compensate the effect occurs only compensate for the lack of it. Load change on harmonic compensation effect. Passive filter compensation effect change as the load changes; active filter without load change impacts.
Sixth, the equipment cost: low passive filters; active filter is too high.
VII Application comparison:
1. Active filtering capacity of a single set of no more than 100KVA, passive filter does not have this limitation.
2. Active Filter provides filtering at the time, can not or rarely provide reactive power compensation, due to the accounting capacity; the passive filter is at the same time providing reactive power compensation.
3. Active Filter highest applicable grid voltage not exceeding 450V, low-voltage passive filtering and the highest applicable grid voltage up to 3000V.
The passive filter because of its price advantage, and hardware-independent, widely used in electricity, oil, steel, metallurgy, coal, petrochemicals, shipbuilding, automobile, electric railway, new energy and other industries; active filter due to inability to solve hardware problems that can not be used in large-capacity situation for telecommunications, hospitals and other electrical power smaller and higher harmonic frequency units, better than passive filtering.