Harmonic mitigation for inverters

WEG provides technology recommendations for VSD harmonics.

Variable speed drives (VSDs) — sometimes called inverters — are notorious for creating harmonics in electric systems. To help minimise harmful harmonics, global inverter manufacturer, WEG has released a downloadable guide on Solutions for Harmonic Mitigation in Inverter Applications. This can be downloaded from www.weg-automation.com.

Harmonics are frequency components that are higher than the fundamental frequency and can cause system voltage waveforms to distort, ultimately causing equipment to overheat or breakdown. This issue is particularly problematic with inverters and other nonlinear loads, where the harmonic currents have a non-sinusoidal shape.

WEG’s guide, Solutions for Harmonic Mitigation in Inverter Applications, provides information on how to reduce this common issue. The guide has been developed in accordance with the IEEE 519-2014 - IEEE Recommended Practice and Requirements for Harmonic Control in Electric Power Systems – the international standard which establishes goals for the design of electrical systems in both linear and nonlinear loads.

In the guide, WEG provides several practical suggestions to mitigate harmonics in inverter applications. Recommendations include using inverters with a DC inductor and using network reactance in inverters that have no DC link.

“Mitigating harmonics in inverter applications can save significant cost, time and resources,” explained MarekLukaszczyk marketing manager for WEG Europe and Middle East. “Once the level of harmonics has been identified through simulation or measurement, there are plenty of methods for minimising them to keep them within acceptable limits. Unfortunately, it is not economically feasible or possible to eliminate all harmonics.

“The IEEE 519 recommendation is to keep the total harmonic distortion (V) ≤5 per cent at the point of common coupling, or PCC, and in many applications this limit is adopted as the sole requirement. Therefore, in many cases, just using inverters with a 6-pulse rectifier and an input reactance or DC link inductor is enough to meet IEEE 519 maximum voltage distortion recommendations.”

Solutions for Harmonic Mitigation in Inverter Applications is available to download for free and contains knowledge, suggestions and diagrams created by WEG’s team of skilled engineers. Usefully, the document also contains a comparison of WEG solutions that comply with IEEE 519 – providing further reassurance.

www.weg-automation.com

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