26-04-2011, 12:00 PM
Presented by
Chiranjibi Prasad Behera
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introduction
Micro-grid
Micro-grid is a localized grouping of electricity generation, energy storage, supply loads that normally operate along with the main grid but can disconnect and operate autonomously.
How it came into existence?
In august 2003, 10 million people in Canada and 45 million people in US suffered from blackout for three days. Research shows that despite the enhanced regulation designed to prevent such event, it can’t eliminated totally.
Reducing the impact of large scale blackouts, micro-grids have been promoted by researchers as a way to improve grid reliability and reduce dependence on the long distance transmission grid.
differences between a Micro-grid and a conventional power plant
(1)Micro sources are of much smaller capacity with respect to the large generators in conventional power plants.
(2) Power generated at distribution voltage can be directly fed to the utility distribution network.
(3) Micro sources are normally installed close to the customers’ premises so that the electrical/heat loads can be efficiently supplied with satisfactory voltage and frequency profile and negligible line losses.
A typical Micro grid configuration
Continue
Micro-grid operates in two modes:-
-grid connected mode
-stand alone mode
The operation and management of Micro-grid in different modes is controlled and coordinated through:-
-micro source controller(MC)
-central controller(CC)
micro source controller
The main function of MC is to independently control the power flow and load-end voltage profile of the micro source in response to any disturbance and load changes.
MC also participates in economic generation scheduling, load management by controlling the storage devices.
The most significant aspect of MC is its quickness in responding to the locally monitored voltages and currents irrespective of the data from the neighboring MCs.
Central controller
The CC executes the overall control of Micro-grid operation and protection through the MCs.
Its objectives are:-
(i) to maintain specified voltage and frequency at the load end .
(ii) to ensure energy optimization for the Micro-grid.
Energy Management Module (EMM)
EMM provides the set points for active and reactive power output, voltage and frequency to each MC.
The EMM must see that:-
Micro sources supply heat and electrical loads to customer satisfaction
Micro-grids operate satisfactorily in synchronization with main grid.
Micro sources operate at their highest possible efficiencies.
Protection Co-ordination Module (PCM)
Its main function is to protect the micro-grid from any fault i.e. occurring in the main grid.
For achieving this, there is proper commu-nication between the PCM and the MCs.
For main grid fault, PCM immediately switches over the Micro-grid to stand-alone mode for supplying power to the priority loads at a significantly lower incremental cost
PCM also helps to re-synchronize the Micro-grid to the main grid
Interconnection of Micro-grids
According to IEEE recommendation: maximum capacity of micro-grid is 10MVA.So a no of micro-grids can be interconnected to form a larger power pool for meeting bulk power demand. For interconnected micro-grids, each CC executes its control in close co-ordination with neighboring CCs.
advantages of Micro-grid
Reduction of T&D feeder congestion.
Reduction of T&D losses to about 3%.
Reduce the effect of blackouts as it can operate independently.
micro-grids may sell power back into the main-grid during periods of peak demand.
Micro-grid is the best option for the places where main grid is unreachable.
Challenges in Micro-grid development
High installation cost for Micro-grids is a great disadvantage
Since micro-grid is a comparatively new area, standards are not yet available for addressing operation and protection issues.
No standard legislation and regulations are available to regulate the operation of micro-grids.
Market monopoly.
conclusion
Micro-grid, a new area in the power sector, has immense potential to reduce the effect of blackouts, power deficiencies and its autonomy helps to supply power uninteruptly to the customers.
Its implementation requires restructuring of electrical standards, market rules and govt. grants, which are not a big issue but need some time.
This revolution has a great effect, because still there are some places where electricity has not been reached yet and for them micro-grid is the only affordable, sustainable and reliable option.
