Wind without borders a unique solution to Indian Scenario

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1 Wind without borders a unique solution to Indian Scenario V.Balaji CM, SRLDC POSOCO M.Venkateshan Sr. Engr., SRLDC POSOCO P.Bhaskara Rao AGM, SRLDC POSOCO P.R.Raghuram 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. Page 1 of 9

2 Seasonal pattern of Wind generation in TN for 2011 July June-11 September August May-11 MW 1050 January-11 December-11 October-11 November March-11 Apr March-11 February Hours January-11 February-11 March-11 Apr-11 May-11 June-11 July-11 August-11 September-11 October-11 November-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/ Mu generated, 26.4% of total state consumption, max: 3770 MW, min 1925MW (35% of demand met by hrs) Variation of Wind in a typical day in TN on MW :00:00 00:37:00 01:14:00 01:51:00 02:28:00 03:05:00 03:42:00 04:19:00 04:56:00 05:33:00 06:10:00 06:47:00 07:24:00 08:01:00 08:38:00 09:15:00 09:52:00 10:29:00 11:06:00 11:43:00 12:20:00 12:57:00 13:34:00 14:11:00 14:48:00 15:25:00 16:02:00 16:39:00 17:16:00 17:53:00 18:30:00 19:07:00 19:44:00 20:21:00 20:58:00 21:35:00 22:12:00 22:49:00 23:26:00 Time Fig.3 Wind variation in a typical day. 08/07/2010 Page 2 of 9

3 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. Page 3 of 9

4 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 RE Generator to Apply for Registration of RE Apply for REC By RE generator Generation of Power Confirmation of Generation by Apply for REC By RE generator Issue of REC Central Agency. Fig. 4 Modus operandi of REC Redeeming of REC in Px 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. Page 4 of 9

5 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 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. Page 5 of 9

6 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, LT- Lithuania, LU-Luxemberg, PT-Portugal, NL-Netherland, SI- Slovania, SK-Slovakia, BE- Belgium, 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 Page 6 of 9

7 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. Page 7 of 9

8 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 Inter- Regional 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, CERC (Indian Electricity Grid Code) Regulations, NLDC Procedure for implementation of the mechanism of Renewable Regulatory Fund 4. CERC(Terms and Conditions for Tariff determination from Renewable Energy Sources) Regulations, Page 8 of 9

9 5. CIGRE 293 report of Working Group C1.3 on Electric Power System Planning with the Uncertainty of Wind generation April 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 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 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. Page 9 of 9