Part of Grid Network »

The Grid Professionals Group covers electric current from its transmission step down to each customer's home. 

Question

What do you think is the best way to handle harmonic distortions?

Shaun Peden's picture
Marketing Specialist Micatu

Marketing Specialist at Micatu Inc., where we manufacture innovative optical sensing solutions that measure current, voltage, harmonics, non-shifted phase angle, power factor & more, for the...

  • Member since 2021
  • 6 items added with 1,417 views
  • Dec 16, 2021
  • 306 views

Harmonic distortion is and has been becoming an issue for grid operators everywhere as more DERs are implemented on the grid. What do you think is the best way to handle these issues? I may be biased, but modernizing the grid from traditional legacy equipment and being able to have real time, accurate data, appears to be the first steps. This allows our grid operators and engineers to analyze the technical impact of DERs and find solutions much faster. What are your thoughts? 

Your access to Member Features is limited.

Best Answer

Here's the answer as I personally see it. 

 

I am guessing the the topic revolves around voltage harmonic distortion caused by inverter based DERs. There are, to my knowledge a few ways to deal with harmonic distortion on the grid due to the increased presence of inverter based DERs. These are as follows:

 

  1. Increase system strength (fault current). This is a lot easier said than done. System strength is increased by installing more rotating synchronous generators that produce fault current on the level of 4 to 5 times their rated MVA power output. The drive toward increasing renewable inverter based generation will continue to erode system strength as it is coupled with the drive to retire synchronous generators (baseload generation driven by fossil fuels).
  2. Another option that has historically been used to reduce voltage harmonics is to install passive filters tuned to integer harmonics (3rd, 5th, 7th, 11th, 13th . . . ) at the DER facility. This is problematic since today’s voltage source converters produce inter-harmonics (not multiples of the fundamental frequency of the grid). Active filters may work but they will likely be too costly.
  3. The only viable solution currently being seriously considered to increase system strength is to install strategically located synchronous condensers. These are basically synchronous generators without a prime mover (turbine). Instead they draw a small amount of power from the grid to rotate the machine. Coupled with a flywheel, synchronous condensers can produce significant fault currents and thus increase system strength, aka Short Circuit Ratio (SCR).  

 

I hope this helps. I understand that this is extremely technical, but power harmonics is a complicated subject.

Shaun Peden's picture
Shaun Peden on Dec 16, 2021

It most definitely does help, thanks David!

Most Solar Inverters check and adjust for any harmonics and help reduce them. QUOTE=Code requirements for THD specifically for solar inverters: Grid-connected PV inverters have to comply with UL1741 standard in US which refers to IEEE 1547 for harmonic limitations. IEEE 1547 defines two sets of limitations; one specific to certain harmonics itself and the second is overall harmonic distortion, which is 5%.

   So Solar is not the problem. It is normally the loads that cause and are the problem. so correct the loads and there is no problem. QUOTE=Harmonic distortions are usually caused by the use of nonlinear loads by the end users of electricity. Nonlinear loads, a vast majority of which are loads with power electronic devices, draw current in a nonsinusoidal manner.

When we first started to design SMART microgrid systems we took this problem into the forefront of every design. Two of the biggest culprits of "dirty electricity" are the inverter and the smart meter for most renewable energy projects. As part of our phase 1 build we have partnered with a company that has pioneered line harmization technology and include them as part of every project that we do. Cleaning up the grid is everyone's responsibility, whether we are making a new one or trying to piecemeal the one we have.

Tap Into The Experience of the Network

One of the great things about our industry is our willingness to share knowledge and experience.

The Energy Central Q&A platform allows you to easily tap into the experience of thousands of your colleagues in utilities.

When you need advice, have a tough problem or just need other viewpoints, post a question. Your question will go out to our network of industry professionals and experts. If it is sensitive, you can post anonymously.