The penetration of RE systems is increasing day by day. The implementation of net metering policies is encouraging the grid interconnection of RE systems at distribution level. But for weak distribution grids, is it possible to interconnect microgrids at single phase?
I'm not completely sure whether I got your question right:
It is clearly possible to connect single-phase grids. Though you have to be aware that the strategy of grid-connected inverters is basically different from the strategy of 'island' inverters (that might be attributed 'micro grid inverters'):
Island inverters define the voltage and frequency of their little 'island'. Their control strategy is driven by voltage/frequency.
Grid-connected inverters - in contrast - synchronize to the grid frequency and have a current-control strategy.
Thus, (inter-) connecting islands will not work. Connecting requires at least one source of voltage/frequency while all other contributors synchronize their output to that reference.
If you have a single phase in mind that is connected to a 'regular' 3-phase grid: this requires some careful planning as not to disturb 3-phase grid symmetry too much. But it is doable: all over the world, the number of single-phase connected devices is much higher than the number of symmetrical loads. (Absolutely sure about the numbers - no idea about the ratio in terms of power consumed.)
'Balancing' the loads on the 3-phase grid requires some planning (mostly statistics about activity distriobution). And there will always be some asymmetry. But it works.
Prasad,
I feel they can be connected, but the grid operation rules and grid discipline need to undergo modification accordingly !
And I would even claim that the modifications will be substantial from the present state.
-Sanjay
Dear Mr. Joshi,
That is possible. However, if the connection of those non inertial Distributed Generators (DGs) is planned to be extensive or in high scale, the penetration level might be an issue. The stability of the Grid might be compromised.
There is always an option to counter those problems by the calculated implementation of Virtual Synchronous Motor (VSM) such that the DGs are connected in grid and stability is kept in balance too.
Regards.
Hello Mr. Joshi,
the first question you asked. I would answer with yes.
The second question is more complex. Connecting decentralized systems as microgrid being able to operate in grid connected and in island mode is possible but expensive. Therefore you will have a higher security of supply. It depends on what customers want.
Regards
Thanks for the answers.
In case of grid connected converters, can we have facility that will enable its operation in islanded mode?
Dear Prasad,
I could understand your question.
as everybody else has suggested, technically the answer is YES!! With all sorts of planning on paper. Now knowing our local systems well, and the grid discipline issues, the feasibility of implementation is a question.
For grid connected RE systems, many countries are putting some restrictions on the proportion of grid connected RE power to conventional power, say up to 15% only; considering the infirm nature of the RE power. Because the stability of the grid is at question.
Hello
This is possible to integrate the Renewable energy systems in Distribution level in India.
The second one is quite difficult . Connecting decentralized systems as Microgrid being able to operate in grid connected and in island mode is possible, this was already implemented in Pondicherry in Tamil Nadu.
Dear Prasad,
Answer for first question is YES as already explained by others.
Second question about single phase integration of microgrid is more interesting. It is also possible but need to consider with system constraints like synchronous issues.
Your next question is "In case of grid connected converters, can we have facility that will enable its operation in islanded mode?"
Yes, Off-course.
Hello,
it is possible to integrate RE systems to the grid. Maybe there is a demand for special operation conditions or requirements (like possibility to run with islanding mode) but this is a question for the system operator.
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