Smart grid: variable ratio distribution transformers
Smart grid: variable ratio distribution transformers
(OP)
Smart grid currently is often regarded as a topic requiring lots of highly advanced new equipment and a lot of communication in between the different stations.
However, in Germany a quite pragmatic solution is gaining significant ground: The variable ratio distribution transformer, either using a scaled down on-load tap-changer well known from larger units or some power electronic equipment (rated at some per cent of the nominal power) to vary the secondary voltage. With both approaches the secondary voltage is controlled, mainly to allow for higher photovoltaic power beeing injected without exceeding the voltage limits.
Do you see similar solutions in other regions ?
How do you assess this approach compared to the solid-state-transformer (processing the full power with power electronics and hence operating the core at higher frequency) that is favoured by research in US ?
However, in Germany a quite pragmatic solution is gaining significant ground: The variable ratio distribution transformer, either using a scaled down on-load tap-changer well known from larger units or some power electronic equipment (rated at some per cent of the nominal power) to vary the secondary voltage. With both approaches the secondary voltage is controlled, mainly to allow for higher photovoltaic power beeing injected without exceeding the voltage limits.
Do you see similar solutions in other regions ?
How do you assess this approach compared to the solid-state-transformer (processing the full power with power electronics and hence operating the core at higher frequency) that is favoured by research in US ?






RE: Smart grid: variable ratio distribution transformers
RE: Smart grid: variable ratio distribution transformers
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Smart grid: variable ratio distribution transformers
Like the grand idea that appliances could have frequency sensors and shut down on low frequency. Great in theory, but not in practice. With low penetration they won't matter one way or another. But, in higher penetration if set in such a manner as to not trip on transient frequency events it won't trip until the system is gone, no added value. If set more sensitively, it would remove load during frequency events while the system is designed and operated with the expectation a certain load response. Almost any under frequency we see is the result of a huge dynamic break being used to arrest an over frequency event in conjunction with significant generation shedding. Last thing we need is load going away on its own.
RE: Smart grid: variable ratio distribution transformers
This problem is common to all micro-generation plants where power quite often is supplied at the end of the "arteries" and thus rises voltage above acceptable limits. There are tap changers, voltage regulators and other devices that can handle the situation. I think that Uwe wanted to know how this problem is handled in other parts of the World (outside Germany, that is).
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Smart grid: variable ratio distribution transformers
RE: Smart grid: variable ratio distribution transformers
On the other hand, LTC (either switching types, solid state or hybrid) could be useful to utilities for other conditions. If the prices could be kept low (not much more than the typical pole pig), they could be a useful tool for long line distribution systems that exhibit wide voltage swings and require line regulators, capacitors and other equipment. Think about how this technology could improve single wire earth return system performance on long rural distribution systems.
RE: Smart grid: variable ratio distribution transformers
You know if you keep your distribution feeders short, these won't be needed. Many of these gee wiz produncts only solve a few problems without them selves becomming a problem.
Our position currently is if the customer wants to ruin there own power, then OK. However if they ruin somone elses our legal people make them fix it.
RE: Smart grid: variable ratio distribution transformers
To David: Inverters that actively regulate the voltage by feeding in reactive power are already state-of-the-art in Germany . However, even this is sometimes not enough to cope with high PV-generation at the end of long feeders. Therefore the variable ratio distribution transformer is a solution to complement this approach.
Feeding in reactive power can be done with little penalty on performance if the inverter is designed properly.
RE: Smart grid: variable ratio distribution transformers
RE: Smart grid: variable ratio distribution transformers
Best regards,
Grinc
RE: Smart grid: variable ratio distribution transformers
Alot of these people are pushing solutions (voltage regulators, distribution capacitors, etc.) that any engineer worth his salt has already implemented on their distribution systems. If you have long feeders and haven't looked into reactive compensation via capactiors, shame on you as this concept is taught in basic circuits in EE school.
So really, all this "smart grid" talk on the vendor side is just re-packaging existing technology for no-experience managers who don't know any different and are too bull headed or stupid to listen to their experienced engineering staff.
A true smart grid? there are some out there probably already. Heck, given the right spin the basic recloser could be "smart grid" all by itself!
I have seen alot of systems-especially small rural electrics and small municples-that have never had an engineer on staff paying attention to load growth, system performance, etc, and those are exactly the markets the "smart grid" vendors are targeting. Large rural Coops, large municiples, and IOUs that have engineers consistently on staff over the years already know it's just a repackage. You'll never get them to bite. With the current sales pitch that is...
RE: Smart grid: variable ratio distribution transformers
RE: Smart grid: variable ratio distribution transformers
RE: Smart grid: variable ratio distribution transformers
RE: Smart grid: variable ratio distribution transformers