Harmonics and Notches in Dynamic Test Load

Active Harmonic Filters Improve Dynamic Test-Bed

A major pioneer in the manufacturing industry caused problems on the power supply network with their dynamic test bed. Here, an installation of the right combination of active harmonic filters now compensates harmonics up to the 100th order with great results. Both harmonics and voltage notches are reduced to enable top performance of the equipment.

Case Background

Dynamic test load before harmonics compensation

Before Compensation:
– Very high distortion on current
– Note the severe voltage notches

The test benches, owned by the development department of a major European production plant, are used to test components in the development phase. Varying test conditions can be programmed, which gives the test bench very dynamic properties.

Harmonics Compensation Challenge

The same transformer is connected to two parts of the test bench. With a very dynamic load whose load current amplitude can change from zero to maximum in approximately 100 ms, it was impossible to run both parts of the test bench simultaneously. The voltage notches of up to 25% in combination with very high harmonic disturbances prevented this. This caused serious delay in the testing facility as well as exceeding the limits in EN61000-2-4.

Active Harmonic Filters – the Solution

To solve the power quality issues, several active harmonic filters were installed to compensate the disturbances. Two 200/480V filters were installed together with one 100/480V filter that in combination compensate all frequencies up to the 100th harmonic order. The first two filters can be used to compensate lower harmonics while the third compensates for higher order harmonics and interharmonics. The three units were configured to share the

load with the 100/480V filter working on higher orders only. This resulted in extremely short response times and considerably lowered load disturbances.

Dynamic load after harmonics compensation

After Compensation:
– Very low distortion on both voltage and current
– Note the reduced notches

Harmonics Compensation – the Result

Thanks to the active harmonic filter installation, voltage notches could be reduced to 10%. In addition, harmonics were lowered to the required level stipulated in EN61000-2-4. Now, both test benches can be run simultaneously without any of the problems caused by poor power quality.

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