by Fred Steinhauser, OMICRON electronics GmbH, Austria
If you want to bring something forward, you cannot always think it through until the end. But consequences which are too obvious must not be neglected from the outset.
The inevitable transformation of our electrical energy is already going on for a while and now we start to feel the consequences.
A topic that soon attracted my interest was the loss of rotating masses and its influence on the stability of the grid. One countermeasure is the controlled use of battery storage to supply energy when required. There are already battery storage and generation stations with large capacities in operation. Even some distribution utilities offer incentives for prosumers that also install battery storage in addition to their photovoltaic systems.
I sometimes asked the question if a suited control concept for the battery powered generators would be to mimic the dynamic behavior of rotating machines. With a bit of research, I found that there are experts out there looking into this. And no, the best control strategy is most probably not to mimic rotating machines. There seem to be other options with better ride-through behavior.
There is quite some work going on, which is good. Smart people are looking into this and they will come up with the right measures to deal with it. What is not good is that this happens mostly unnoticed by the public. The public should at least get the idea that maintaining grid stability is not a piece of cake.
But while it is understandable why these problems were neglected beforehand; it was not wise to do so.
These stability problems were foreseeable. More than this, we had a role model already before photovoltaics became essential. When wind power made just a low single digit percentage of the total installed generation power, the grid codes just forced these windmills to go offline in the case of a problem. When the figures rose to double digit percentages, this was not sustainable anymore.
The stability will be even more endangered by shedding generation in this order of magnitude. The grid codes were changed so that wind power also had to contribute to grid stability. And suddenly it became important what types of generators were used and how these contribute in a ride-through scenario. What a surprise!
From the beginning, it would have been advisable to make it mandatory to balance photovoltaic generation, either by building battery storage on site or by participating in a battery storage facility.
Although this would have avoided some problems, the stability issue remains an exciting topic. Cybernetics tells us that the proven stability of individual subsystems does not guarantee the overall stability of the interconnected system. The combined behavior of the rotating machines proved to be benign. The combined behavior of the battery powered generators with new control characteristics may come with surprises. One way to tackle this is with simulation. These simulations then need a high granularity to model these effects in sufficient detail. This will require lots of computing power.
Electricity is the most noble form of energy and a precious resource. We will have to accept this quickly and need to value it as such. This must be expressed by an adequate price.
Hopefully, the times will soon be over when electricity is cheap enough to dissipate it by mining crypto currencies and make a profit with that.
Fred Steinhauser studied Electrical Engineering at the Vienna University of Technology, where he obtained his diploma in 1986 and received a Dr. of Technical Sciences in 1991. He joined OMICRON and worked on several aspects of testing power system protection. Since 2000 he worked as a product manager with a focus on power utility communication. Since 2014 he is active within the Power Utility Communication business of OMICRON, focusing on Digital Substations and serving as an IEC 61850 expert. Fred is a member of WG10 in the TC57 of the IEC and contributes to IEC 61850. He is one of the main authors of the UCA Implementation Guideline for Sampled Values (9-2LE). Within TC95, he contributes to IEC 61850 related topics. As a member of CIGRÉ he is active within the scope of SC D2 and SC B5. He also contributed to the synchrophasor standard IEEE C37.118.