Harmonic filter

This article deals with the term 'harmonic filter' used in electrical power engineering. In communications technology, filters for suppressing unwanted harmonics in electrical signals are predominantly referred to as harmonic filters .

Circuit diagram of the harmonic filters of the former GKK in Etzenricht

Course of the reactive power Q on the AC voltage side as a function of the transferred active power P in the case of an HVDC transmission system . The filters are switched on selectively, which results in the abrupt course

Harmonic filters are filters that suppress undesired harmonics in electrical energy engineering in the current or voltage of electrical energy supply systems.

The filters can be of passive construction and can be interconnected elements from capacitors and coils , which are designed either as a low-pass or suction circuit .

With systems for high-voltage direct current transmission , complex series resonance circuits ( suction circuits ) for the 5th, 7th, 11th, 13th, 17th, 19th, are applied to the corresponding frequencies (12 and 24 times the mains frequency for systems in twelve-pulse circuit ) 23rd and 25th harmonic for six-pulse circuit ). The fundamental frequency component of the load current does not flow through the components of the filter.

Low-pass filters and, if necessary, matched filters are used for transmitter output stages.

There is also the option of actively building harmonic filters. For this it is necessary to impress the harmonic components to be canceled in the current by means of power electronic actuators (e.g. inverters ) with opposite polarity.

Harmonic filters are often used in high-voltage direct current transmission and in thyristor controls.

See also

• Power factor correction filter (PFC)

Individual evidence

1. ↑ Valentin Crastan, Dirk Westermann, Electrical Energy Supply 3: Dynamics, Control and Stability ..., Volume 3