Harmonics overview

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    Francois
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    Why harmonics problem?    3 types of solutions!      How to make a choice ?     Any software tools ?

    Typical distorted current waveforms

    Typical distorted current waveforms

    The wide spread use of power electronic devices in power networks is due to their multiple functions: compensation, protection, adaptation and transformation of the electric energy. However, because of their switching components, power electronic converters generate current and voltage harmonics which may cause measurements, stability and control problems.

    To avoid the harmonic distortion, it is necessary to equip the installation with filtering systems.

    There are 3 types of filters: passive filters, active filters and hybrid.

    • The passive filters represent a LC circuit tuned to a harmonic order close to the order to be eliminated. Several parallel-connected branches of filters can be used if a significant reduction in the distortion of a number of harmonic orders is required.
    • The active filters represent power electronics devices, which generate and inject harmonics drawn in an opposite phase such that the line current Is remains sinusoidal.
    • The hybrid filters are a combination from active filters and passive filters.

    Before to reduce the harmonics distortion, the installation of power quality meter devices is recommended. This is the first step in gaining control over harmonic pollution!

    Measurements allow to obtain an overall idea on distribution-network status and to choose the solution for the reducing of the harmonics distortion.

    • Normally active filters are used for highly polluted networks.
    • Passive filters are usually used in less polluted networks, where limited number of harmonics are responsible for the harmonics distortion.

    In industry, very often the capacitor banks are combined with harmonic filters, as they are highly sensitive to the harmonic disturbances.

    At my knowledge, there is no tool or software that can be used for the choice of the harmonic filters, mainly measurements are used and individual solutions are proposed.

    In contrary, several software exist for sizing the capacitor banks…. Like

    Christian Petrov

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