Grid Interconnection of Wind Turbines Presentation to GERC Ahmedabad 07.02.09 M.P.RAMESH, former Executive Director Centre for Wind Energy Technology.

Grid Interconnection of Wind Turbines

Presentation to GERC Ahmedabad

07.02.09

M.P.RAMESH, former Executive DirectorCentre for Wind Energy Technology

GERC posers

• GERC has put up the following questions:– Intra-state grids– Interstate regional grid– Bulk quantity of wind/solar inputs in ‘low load

areas’ impact assessment – Increasing wind/solar inputs - need for backing

down ?– Limits?

GERC Posers

• What are problems associated with wind power & commercial implications?

• Technologies for scheduling/dispatch• On-line monitoring • Solar power generation• Relevance of intra-state grid connectivity for

major wind & solar energy inputs• Some insight into the wind potential in GUJRAT

Some history• Gujarat is THE FIRST STATE which experimented

with grid connected wind turbines.• The state also was the first state to have

‘commercial wind farm’ at Mandvi.• The state’s wind map shows second highest

potential nearly everywhere adding up to 10645 MW (installed) based on certain assumptions.

• CWET/MNRE would be getting the atlas prepared for India shortly. We would then have a more comprehensive idea about the possibilities.

Installable Wind Power potential in India (2006 estimate)

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An area requirement of 12 hectares/MW assumed.4.There can be differences due to terrain related changes in WPDs.WPD range

Potential (MW)

200-250 (red)

7216

250-300 (violet)

2842

300-400 (green)

587

Total 10645

Wind farming areas

Gujarat wind Potential• It is seen that a large part of

Gujarat has moderate wind potential.

• But for a few pockets, the wind turbines would have good steady winds during monsoon months.

• A well defined May to August SW high wind season & a moderate NE wind season during December-January.

• Year on year variations are well with in reasonable limits

• Wind power quite evenly distributed across the State.

Some time scales in grid management• There are four levels in

grid management.– Unit commitment – which works

on a scale of days– Scheduling needed on a day

upon day basis– Load following which has a time

scale of minutes to hours– Regulation which happen over

seconds to minutes

• We need to understand that it is a complex issue and needs detailed analysis either to accept or reject an idea.

SR

WR

NR

ER

NER

Freq - 1

Freq - 2

INDIA CURRENTLY OPERATING AT

“TWO” FREQUENCIES – NORTH & SOUTH

- 5 Regional Networks in the Country

- Currently 4 Regional Networks merged

Evacuation – The big picture – Northern & Southern GridsEvacuation – The big picture – Northern & Southern Grids

INTER-REGIONAL EXISTING CAPACITIESINTER-REGIONAL EXISTING CAPACITIES

SOUTHERN REGION

WESTERN REGION

NORTHERN REGION

NORTH-EASTERN REGION

13450 MW

1000 MW6450 MW

4600 MW

1300 MW3700 MW

30,000 MW OF INTER-REGIONAL POWER BY 2011 -12

EASTERN REGION

ER

“NO Augmentation” proposed between “Southern & Northern” Grids

INTER-REGIONAL PROPOSED CAPACITIES BY 2011-12INTER-REGIONAL PROPOSED CAPACITIES BY 2011-12

SOURCE : CEA

Weak link

Impact on grid and associated equipment

• As such, wind turbines and associated equipments are designed to take care of each and every eventualities that the installations would be subjected over their service life.

• Double redundant safety systems including electrical equipments are a ‘type certification’ requirement.

• In India it is not possible to grid connect wind turbines which do not have a valid type certificate.

• Therefore a wind farm would work much like a standard power plant in all respects.

• The problems of first generation wind turbines have been very largely addressed in the modern wind turbines.

• MODERN WIND TURBINES MEET THE MOST STRINGENT GRID REQUIREMENTS FOR SAFE OPERATION.

Impact on grid and associated equipment

• After the area and capacity of a given wind farm are decided, Wind farm design preceded by detailed load flow analysis, impacts of voltage & frequency excursions, harmonics, seamless power factor controls and optimised.

• There are wind turbines which have facility to provide leading pfs if required.

• Wind farm Substations are built to meet strict standards laid down by the TRANSCos.

Backing down Thermal ?• The question of backing down of thermal power stations due

to presence of large wind is open ended. It is a combination of many factors.

• In a surplus power supply system there could be a need to back-down some flexible generation facility (Hydro/gas based system for example).

• In our context, when grid frequency is < 50 hz, there will be some margins that takes care of the so-called infirm power.

• Therefore in all likely hood there may be no need to back down thermal stations.

• If we integrate different regions effectively, flexibility would improve so that resources could be utilized far more efficiently.

Is there any limit?• In Denmark presently about 21 % of energy

consumed is supplied by wind turbines alone.• Penetrations of wind power into local grids have at

times gone upto 60 % in good windy season. • In Tamilnadu we have over 4000 MW against 12000

MW of the so called firm power. That is about 33% on installed power basis. If we consider a 50% plf in high wind season, we are looking at a penetration level of18% on an average.

• As such there is no limit. It essentially depends on resources and grid management strategies.

Infirm power? • EB Comments from a state that has topped the Wind

Power deployment for decades has this to say:“….. while occasionally the wind slows down in one location leading to decreased output in a particular location (also within the particular pass itself, the wind mills are installed over a radius of 30 to 40 KM), locations with high penetration of wind energy would compensate for the same. As a result, it typically takes much time or even hours for the total wind energy output of a region to change significantly. This makes it relatively easy for the utility system operators to accommodate these changes without relying on the reserves i.e. slowly taking the tag of ‘infirm power’ out of wind energy”.

Effect of aggregation• Just to illustrate the observations of the EB

engineers some sample wind farms in Karnataka were chosen.

• A total capacity of about 300 MW from three areas within a radius of 50 km were considered.

• Real time data from these wind farms have been collected and the outputs summed up to on a 24 hour basis during high wind month and a moderate wind month.

Though there is much variation, the ramp-up & ramp down happens over several hours

Some observations

• With more and more wind farms coming on stream from different geographical locations, the averaging effect will be even more pronounced.

• The changes in delivered power are not drastic and sudden.

• It provides time to the system manager to take corrective measures

Technologies available for scheduling/dispatching

• A system manager has to continuously monitor both the supplies and loads.

• While supplies could be controlled to some extent, loads can only be anticipated and corrective measures taken.

• In this dynamic situation it is important to note that it is a balancing act with or without wind/solar power on the grid.

• With wind having its variability, the management would have to be only slightly more innovative.

• There are emerging technologies to forecast in short term (horizon of 60 hours).

• Validation and implementation is some distance away.

It may be seen that the general trends are predicted with some degree of uncertainty.

There are issues of input data for such exercises such as outputs of Global Circulation Models. Accuracies of input data for GCMs etc. are again sources of errors.It is a well known fact that the model outputs will come with uncertainties and validation takes some time, funds and effort.

Some forecast results

On-line monitoring• Online monitoring of wind turbines is a reality

of the day. It is not uncommon in new wind farms. They are specifically designed SCADA systems used to centrally monitor and control wind farms in a given area.

• It is possible to obtain near – online info from wind farms in a limited way.

• Though theoretically it is possible to have GSM connectivity, V-SAT terminals etc.., bandwidth related issues still exist.

Intra-grid• Studies have shown that it is most desirable to have

these connectivity's in place. • In the context of RE technologies, it would add some

more flexibility to the local grid management to have conduits to bigger networks.

• Inter-regional exchange of power has larger and generally positive ramifications.

• It is much like the ‘golden quadrilateral’ which has virtually revolutionized connectivity to rural India.

• Thank You for your attention.