Case Study: Active Harmonic Filtration

Avoiding Wasted Produce with Filtration

Egg Hatchery Losing Produce

An interesting case emerged from a Hatchery which relies on generators to provide emergency backup for when power is lost. At least once per month, it was essential for the site to carry out generator tests – but there was no choice but to carry out the tests during regular production time as there was no opportunity to have “down time”.

What caused the harmonics in the first place?

Whilst this site does operate lots of non-linear loads, the main issue was… testing the bugs. The site requires updates. We will complete this article in due course.

12:50 – Making Changes

13:26 – Changed Theme to test

13:28 Put Theme back

13:44 – deactivated Cloudflare – made no difference

13:49 – re-installed wordpress. Made no difference

13:52 – cleared browser cache again

16:13 – installed a plugin called busted – still need to force refresh to see changes

16:45 – in discussion with GoDaddy

18:07 This is apparently fixed… let’s see

18:25 Lets see again…

Modern problems mean modern solutions

Traditional strategies for filtration included passive harmonic filters; a tuned LC circuit which provides very low impedance to specified harmonics.  A number of these tuned circuits can be connected in parallel (each tuned to a different harmonic), providing a low impedance path for them. The harmonic currents then flow into these filters in preference to the supply, effectively isolating these harmonics from the supply.

The major drawback with this form of filtration is that it relies on there being a sufficient amount of lagging reactive power before they can be effective. They are basically parallel connected capacitors which produce leading reactive power; and with the modern non-linear loads operating at a unity power factor, there’s just not enough reactive power on the system to absorb this.

The “modern” solution (which has been available for many years now) is the Active Harmonic Filter, which as stated above, can target a multitude of harmonics at the same time and can vary its effectiveness automatically as and when the load requires.

An active filter is basically an inverter-based harmonic current source that measures the magnitude and phase of the load current harmonics.  The active filter control synthesises the load harmonic currents but phase shifts them by 180°.  This harmonic anti-phase current is injected into the system and combines with the load current to create a supply current that has a much-reduced level of harmonic distortion.  The principal of operation is shown graphically in Figure 1.

How we can help

PureSine offer a full harmonic analysis, design and installation service for active harmonic filtration systems, drawing on 25 years of power quality experience to provide an optimal harmonic filtering solution tailored to the sites specific needs.

The first step is to get in touch with us, typically by completing the form below. We’ll then schedule a call with you to discuss any problems you’re experiencing and make recommendations on what the best way to proceed.

The most likely outcome will be the suggestion that a week-long study is conducted, as this will provide a full and thorough evaluation of the electrical system. We’ll also make use of the time on site to discuss your processes and paint an overall picture of what’s causing the issues.

If active harmonic filters are required, we’ll provide a competitive, no obligation quotation for the system and will provide consultation services afterwards to ensure that the filter has had the desired effect.

Already know what you need?

That’s great, we’ll be happy to provide a competitive price for the tender based on your specification. Please contact us below with your requirements and will be in touch to discuss the application and provide a quotation accordingly.

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