Wind without borders – a unique solution to Indian Scenario
V.Balaji
M.Venkateshan
P.Bhaskara Rao
P.R.Raghuram
CM, SRLDC
POSOCO
Sr. Engr., SRLDC
POSOCO
AGM, SRLDC
POSOCO
GM, SRLDC
POSOCO
Abstract
Dwindling reserves of coal and oil and mandate of Intergovernmental Panel on
Climate Change and National Action Plan for Climate Change, Wind and other Renewable
energy sources are to be harnessed to the fullest extent. However, Variability, Intermittency
and Uncertainty of these renewable resources have been the biggest challenges in
Integration of wind energy the world over. These intrinsic characteristics pose problems to
system operators as they have to scramble for providing spinning reserves and vary the
generation levels to their technical limits. As the penetration levels of these green sources
increase, there is a need for enhancing the levels of reserves which is a luxury for a country
facing severe deficits.
The compulsions of system operation calls for treating these sources like any other
generator as far as planning and accountability is concerned. The Regulators have offered
various methods to fulfill the Renewable Purchase Obligation (RPO) either physically
(across the Control Area seams) or virtually by procuring Renewable Energy Certificates
(RECs).
Exposing wind generation to power market across the regions may enhance the
commercial viability of the wind projects. However, this is a challenge to the Regulators,
planners and grid operators alike. Building an optimum transmission network, designing a
suitable market pricing/commercial mechanism, implementation of robust settlement
system etc. are some of the key areas for success of this objective. In this paper, the authors
examine the issues facing the physical movement of wind power across seams, the
commercial settlement aspects, the need for forecasting and scheduling and how
surmounting such issues could help renewables participate dynamically in the power
market.
1. Introduction
Wind generation potential is limited to a few states (Control Areas) in India. The
installed capacity of wind generators has witnessed steep growth in India since the middle
of the last decade. The South-western parts of Tamilnadu, Central/North Karnataka,
Maharashtra, Gujarat and Rajasthan have major pockets of wind generation. From May
onwards, wind generation increases and help meet the summer demand. Monsoon periods
of July to September produce maximum generation which tapers down upon receding of
monsoon from October. Fig.1 shows typical (seasonal) variation patterns of wind
production in Tamilnadu. In other states also similar pattern can be seen. Similarly Fig.2
shows typical generation on a maximum wind day. Fig. 3 gives an idea how wind varied
from ~ 1000 MW to 70 MW in a typical day.
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Seasonal pattern of Wind generation in TN for 2011
July-11
June-11
2550
September-11
August-11
1550
May-11
MW
2050
1050
October-11
December-11
January-11
November-11
550
Apr-11
March-11
February-11
March-11
50
1
2
3
4
5
January-11
July-11
6
7
8
9
February-11
August-11
10
11
12
13
Hours
March-11
September-11
14
15
16
17
Apr-11
October-11
18
19
20
21
22
May-11
November-11
23
24
June-11
December-11
Fig. 1 Typical (seasonal) patterns of wind production in TN over the year. In other states
also similar pattern can be seen.
Fig 2 Maximum wind day in TN (Max wind day: Tamilnadu 11/07/2011 – 59.7Mu generated, 26.4%
of total state consumption, max: 3770 MW, min 1925MW (35% of demand met by wind @12.05 hrs)
Variation of Wind in a typical day in TN on 08-07-10
1200
1000
MW
800
600
400
23:26:00
22:49:00
22:12:00
21:35:00
20:58:00
20:21:00
19:44:00
19:07:00
18:30:00
17:53:00
17:16:00
16:39:00
16:02:00
15:25:00
14:48:00
14:11:00
13:34:00
12:57:00
12:20:00
11:43:00
11:06:00
10:29:00
09:52:00
09:15:00
08:38:00
08:01:00
07:24:00
06:47:00
06:10:00
05:33:00
04:56:00
04:19:00
03:42:00
03:05:00
02:28:00
01:51:00
01:14:00
00:37:00
0
00:00:00
200
Time
08/07/2010
Fig.3 Wind variation in a typical day.
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Such large variations in renewable power, (in the absence of sufficient
commercially viable reserves), may lead to huge load shedding or overdrawls from the
Regional grid. In case of overdrawls, there will be not only a huge financial implication on
heavy Unscheduled Interchanges (UI) charges but also threat to the security of the grid.
2.0 Problems in Sub transmission system :
Traditionally, the transmission/ sub-transmission system in the areas of wind
pockets witness low voltages due to low short circuit levels and generally high requirement
of Reactive power by the Wind Turbine generators (WTG). Therefore, the power losses
also are generally on the higher side in this system. Commercial recovery of these losses is
a major issue for the State utility. Further due to low capacity Factor, there is a tendency to
under-build the transmission system. These factors call for huge investment in evacuating
transmission system. Huge financial implication and uncertainty in recovery of the
investment could be some of the factors impeding investment in the evacuation of system.
Right of way is also an issue in these areas.
As the wind generators are located in areas with considerable vegetation, the connecting
lines upto the pooling stations are prone to earth faults created by low clearances etc. Any
large scale trippings of Wind Turbines in large Wind farms has the potential danger of
cascading to disturbances in the sub transmission system. Therefore it essential that the
wind mills have the ability to stay connected to the grid during voltage dips caused by
short-circuit one or all phase of its terminal current upto a specified voltage level. This
capability is called Fault Ride Through (FRT) /Low Voltage ride-through (LVRT).
Therefore, it is better if regulatory provisions mandate enforcement of these capabilities.
3.0 Efforts of Regulators and policy makers
Since the introduction of imbalance pricing mechanism with introduction of Availability
Based Tariff in 2003 and Open access in Inter-State and intra-state transmission system in
2004 formal Power Market is established in India. After reforms by way of Electricity
Act2003, unbundling of state electricity boards in phases and introduction of power
Exchange platform in 2008 way was paved for strengthening the Power Market in a big
way. It got matured under the regulatory supervision of the Central Commission and active
participation from the Captive Power Plants, Independent Power Plants, bulk consumers,
Extra High Tension consumers and state generators and power procurement utilities.
3.1 Measures already implemented :
All the regulators have facilitated sale of power from all the Renewable Energy
generators at a preferential tariff or Feed In Tariff (FIT) which ensures a ‘cost-plus’ return
on investment to the developer.
Solar power is exempted from sharing transmission charges and losses. Further to bring
grid parity, solar power is bundled with unallocated share of the state owned National
Thermal Power Corporation and given to the host state, so that the average cost of solar
power would come down to an affordable level.
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With a view to give fillip to these generators, the Central Government had given sops like
Accelerated Depreciation (AD) , Generation Based Incentive (GBI) etc. The Regulators on
their part had implemented Renewable Energy Certificate (REC) In the REC mechanism,
each State utility is obligated to fulfill Renewable Purchase Obligation (RPO) as specified
by its Regulators by purchasing either Renewable Energy directly or equivalent Certificates
(RECs) as an indirect means of supporting the Renewable Energy generators. The price of
these certificates are discovered in a national platform of the Power Exchanges. Fig. 4
shows the modus operandi of REC
Under this mechanism, the RE generator can opt for selling the energy part of the power to
host State at a Weighted Average Power Purchase cost specified by the concerned SERC
and sell the RE Certificates at rates discovered in the Power exchange platform.
Alternately, the power can be sold to a third party at any mutually negotiated price, and sell
the RECs in power exchange.
Accreditation of RE by
State Agency
Generation of
Power
RE Generator to Apply
for Registration of RE
by Central Agency
Confirmation of
Generation by
Issue of REC
Central Agency
Apply for REC
By RE generator
Apply for REC
By RE generator
Redeeming of REC
in Px
. Fig. 4 Modus operandi of REC
The REC mechanism received enthusiastic response from all the stake holders. Since the
implementation, over 6,70,000 RECs were issued out of which over 6,09,000 were
redeemed involving a trade amount of over Rs.1650 millions.
3.2 Measures under implementation stage :
To enable the concerned Control Area to plan the reserves and load-generation
balance, Forecasting and Scheduling of Grid connected wind and Solar generators is
envisaged under Indian Electricity Grid Code. The same is expected to be implemented
shortly. Eligible generators would be required to forecast their generation with a minimum
accuracy of + 30%. Any deviation upto + 30% will not have any cost implication to the
Renewable Energy generator. The RE generator can enter in to contract to supply power to
any entity located any where in the country under Short Term Open Access at a price
negotiated bilaterally. Such power will be scheduled by the concerned SLDC/ RLDCs and
can be revised based on the Forecasted generation data, to minimize the impact of
Unscheduled Interchanges from Regional Grid. Through this scheme, the wind generator is
made accountable to forecast the production.
The cost of Unscheduled Interchange by
the host State due to this variation would be reimbursed from/to a nationally operated Fund
called Renewable Regulatory Fund (RRF) which is operated by National Load Despatch
Centre (NLDC). The burden of the Fund is expected to be socialized among all the States
in the country.
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4.0 International Experience :
A study of European countries shows that, in most of the countries, though a matured
Electricity Market is in place, in most of the countries the wind generators sell power under
Feed-In-Tariff, which ensures a minimum guarantee price to the developer. The wind
generator is generally not penalized for the imbalances, except in Belgium, Denmark,
Spain, Sweden Netherlands, UK and Poland. In such cases, they are compensated with
Green Certificates, which can be sold to the obligated entities in the market. In France
they even participate in Auctions or spot markets also. In all these countries, they have to
invariably forecast and schedule the generation with Gate closure time varying from
½hour to 24 hours. Table 1 summarizes the above. Fig 6 gives a glimpse of Venn diagram
of countries following various incentive schemes.
Table 1 International practices w.r.t incentives to Wind
(Source: Wind Generation in Day-Ahead Energy Markets in Italy: Imbalances Penalties C. Brunetto, M. Nicita and G. Tina, Member, IEEE http://www.labplan.ufsc.br/congressos/
powertech07/papers/297.pdf)
All US Power Pools like MISO, NYISO, CAISO, PJM and ERCOT use forecasting of
Wind. In Europe RTE, France, Canada and Brazil also have Wind Forecasting capabilities.
In Spain, a dedicated control centre for Renewables is operational for forecasting,
scheduling, assessing the reliability of the grid under various scenarios.
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Fig 6 Venn diagram of countries following various incentive schemes.
(AT- Austria, CY-Cyprus
CZ-Checkoslovakia, DK, Denmark, EE- Estonia, ES-Spain,
Fr-France, BG- Bulgaria, DE-Germany, GR-Greece, HU-Hungary, IE-Ireland, LTLithuania, LU-Luxemberg, PT-Portugal, NL-Netherland, SI- Slovania, SK-Slovakia, BEBelgium, SE-Sweden, PL-Poland, FI-Finland, MT-Malta, IT-Italy, LA-Laos)
5.0 Unique Solution to Indian scenario :
Although, in the states with high wind potential, the control area-wise the maximum
penetration is about 30-40%, on an all India basis, it is only 3-5%. Therefore, problems of
intermittency and variability can be better handled on an All India basis. As the penetration
levels are increasing, the problems of host state brought by variability, uncertainty etc. also
increase exponentially. Therefore, the Renewable Energy generator has to be made more
accountable for the deviations and there is a need to treat him like any other type of
generator yet giving due consideration to the variability aspect. Commercial responsibility
for variations beyond a certain limit as specified by the regulator shall rest with the RE
generator. This calls for Forecasting and scheduling the wind generation.
A good short term wind forecast is a pre-requisite for successful market participation by
wind generator. The forecast can facilitate the RE generator to reduce the adverse impact
of deviations. It will also help the system operator to assess the Reliability and carry out
operational planning.
With a slew of incentives enumerated in the preceding paragraphs, the wind generators
have enhanced the prospects of higher returns and in turn are encouraged to enter the power
market which enhance their profitability. With market entry of the Renewable Energy
generator will enable physical transport of wind power across the seams, so that the burden
on the host state reduces. Further, in a larger grid issues related to wind integration can be
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alleviated to a considerable extent. It is expected to induce a sense of accountability,
enhance the profitability and viability of projects, attract investment, address grid parity
issues.
However, for a successful market participation, a strong backbone of transmission network
free of congestion is a pre-requisite. Though the regulators are trying to facilitate trade
across the boundaries, it is not happening due to lack of dedicated evacuation system. As
can be seen in Fig. 7, the wind packets in the rural Western part of the country should get
robust connectivity to the load centres spread around the major cities and industrial hubs.
It is a known fact that sources of generation like Coal, Nuclear fuel, Oil etc can be
transported to wherever generating stations are located. Whereas Renewable sources like
wind, solar, micro hydro etc can not be transported. This calls for building of strong
transmission network for evacuation. It is prudent to provide pooling stations and
transmission network near to these areas with high potential after assessing the expected
capacity addition.
SOURCES OF RESOURCES
HYDRO RESOURCES
RESOURCES ARE FAR
AWAY FROM LOAD
CENTERS.
NECESSITATES LONG
TRANSMISSION
LINKS FOR
EVACUATION
DELHI
Source:
Powerline
(Siemens Ad),
Oct-2006
KOLKATTA
MUMBAI
COAL
BELT
BANGALORE
CHENNAI
AREAS SHOWN ARE APPROXIMATE AND
INDICATIVE
Fig 7 Wind potential pockets vis-a-vis of Load centres
6.0 Building an evacuation – a challenge
Traditionally there has been a time lag in building wind projects vis-à-vis matching
evacuation system due to multiple reasons range from such as concerns of optimal
utilization of transmission network by a generating system with low Capacity utilization
factor , lack of funds; uncertainty of project realization etc. Often the cost of transmission
is recovered based on the energy transmitted in terms of per unit rates.. Due to low
Capacity utilization Factor, the recovery is at a very low rate on a long periods, thus there
could be some amount of reluctance to develop transmission/sub-transmission system.
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Under these circumstances, not only generation potential may get stranded up, but also
congestion may occur in the downstream network. Therefore there is an urgent need of
providing a dedicated corridor for export of wind generation to outside the region. But the
question is who will pay for the evacuation system and how to recover the investment
within a reasonable time period; how to ensure capacity utilization in the lean seasons. It
is required to understand that gestation periods for developing a wind farm is between 6-8
months, whereas that for evacuating transmission system is over 2 years. This may result
in bottling up for wind potential. To avoid this, ‘Plug and Play’ concept of infrastructure
may be thought off on similar lines as Special Economic Zones (SEZs) for boosting the
trade. In this concept, all necessary infrastructure like distribution network, pooling
stations, augmentation/addition of substations
and transmission both within the
State/Region and across the inter-Regional borders may be readily built so that RE
generators will be able to erect a farm and connect to grid without any time lag. It is
preferable to have some common agency to execute the evacuation system in a coordinated
manner.
7.0 Harnessing the Reactive compensation available in WTG mill.
Inherently, all the WTG are provided with Capacitive compensation to avoid penalties for
reactive power drawl from the grid. During low wind seasons, such pockets of the grid
generally witness low voltages and low short circuit levels. During such periods, the
capacitive compensation can be utilized to supply reactive power to the grid. A suitable
monetary compensation mechanism can be thought of under ancillary services concept.
Conclusion :
As the penetration of wind energy increases in the Indian grid, participation of wind
generators in the market will help alleviate the problems of integration. It is opined that the
wind generator has to adopt the mantra of “Predict-Plan-Participate” as a means to address
for the challenges brought in Integration of Renewable to Grid. The congestion issues in
wind evacuation in the sub transmission system are to be solved and a strong backbone of
Inter-Regional corridor is to be provided for enabling a seamless trade across the InterRegional Borders. The wind generators have to participate in the scheduling and RRF
mechanism mandated by the Central Regulator.
Acknowledgement: Authors acknowledge the support given by Power System Operation
Corporation Ltd. (POSOCO) to publish this paper.
The views expressed in the article are that of the authors and not necessarily that of
POSOCO.
References :
1. CERC((Terms and Conditions for recognition and issuance of Renewable Energy Certificate
for Renewable Energy Generation) Regulations, 2010.
2. CERC (Indian Electricity Grid Code) Regulations, 2010
3. NLDC “Procedure for implementation of the mechanism of Renewable Regulatory
Fund”
4. CERC(Terms and Conditions for Tariff determination from Renewable Energy Sources)
Regulations, 2012.
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5. CIGRE 293 report of Working Group C1.3 on Electric Power System Planning with
the Uncertainty of Wind generation April 2006
6. High capacity power transmission corridor - project inception report of Power Grid
Corporation of India Limited
7. Wind Generation in Day-Ahead Energy Markets in Italy: Imbalances Penalties - C.
Brunetto, M. Nicita and G. Tina, Member, IEEE http://www.labplan.ufsc.br/congressos/
powertech07/papers/297.pdf)
Biography:P.R.Raghuram is presently working as General Manager at SRLDC and is responsible
for operation of the power system grid in Southern Region and for maintaining its safety
and security. He has done his graduation in Electronics and Communications Engineering
in 1978 from Malnad College of Engineering. He is a senior member of IEEE. His
interests are Power system Economics and Protection
P.Bhaskara Rao is presently working as Additional General Manager and is in-charge of
Commercial & Contracts activities at SRLDC. He has done his graduation in Electrical
Engineering in 1975 from JNTU Engineering College, Anantpur followed by M.Tech. in
Power Systems Engineering from IIT, Kharagpur. He worked in Jyothi R&D Centre for
two years and in Central Electricity Authority upto 1995. His fields of interest are Power
System Engineering , operational and real time studies, and commercial aspects of Grid
Management.
V.Balaji is presently working as Chief Manager at SRLDC and is responsible for the
commercial functions related to Regional Energy computations, operation of various pool
accounts , Open Access, transmission pricing, integration of Renewables, and Regulatory
affairs and Legal matters. He has done his graduation in Electrical & Electronics
Engineering in 1986 from JNTU College of Engineering, Kakinada followed by M.Tech. in
Power Systems from REC, Warangal. His field of interests are Reactive Power
Compensation and Power System Economics, Tariff matters, Regulatory affairs,
Power Market economics etc.
M.Venkateshan is presently working as Senior Engineer at SRLDC and is responsible for
the Operational Services function, development and maintenance of various programs like
Web Scheduling, MIS etc. He has done his graduation in Electrical & Electronics
Engineering in 2002 from BMS Evening College of Engineering, Bangalore. He earlier
worked in operation of Chamera Hydro Electric Project of National Hydro Power
Corporation. His field of interest are Power System Operation, SCADA and IT.
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