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Friday, 3 February 2017

Ancillary services for Indian electric market

In a vertically integrated power system, one organization carried out all the work of electricity generation, transmission and distribution. Example is the erstwhile State Electricity Boards in India. Power industry throughout the world is undergoing the restructuring process and is adopting the deregulated structure for better utilization of resources and for providing quality services to its consumers at an economical price. 

The introduction of deregulation has brought in several new entities and some form of competitive electricity market. The vertical integrated utilities were separated into Generating companies (Gencos), Transmission Companies (Transco’s) and Distribution Companies (Discos). Apart from these three entities,  entities such as System Operators, Market Operators, Regulators etc were also formed. 

Central Electricity Regulatory Commission (CERC) Regulations 2010 defines Ancillary services as those services that are necessary to support the power system operation in maintaining power quality, reliability and security of the system or the grid. Examples are active power support for real time load following, reactive power support, black start, voltage control support etc.

In the deregulated environment, ancillary services are no longer treated as integral part of the electric supply. The system operators have to purchase these services from ancillary service providers. The CERC Regulation, 2010 made operation of ancillary services as an exclusive function of Regional Load Despatch Centre (RLDC). In the Central Advisory Committee meeting of CERC, held on 14th March 2012, there was a general consensus on the need for introducing ancillary services to enhance the secure and reliable operation of Indian power system.     

Main ancillary services under consideration in India:

Currently three main types of ancillary services are under consideration in India and they are:
1.      Real power support service or Frequency support ancillary service or Load following,
2.      Voltage or Reactive power support services, and
3.      Black Start support service.

Real power support service or Frequency support ancillary service or Load following:

In India, the real power support or the frequency support services are to be provided by generating station or any other authorized entity on behalf of the generating station. The services/capacity of the said station should be available for despatch as required by the nodal agency i.e. RLDC to support the system frequency. 

Considering the Indian power system as a whole there are cases when certain surplus energy, particularly from Captive power plants, lie un-utilized at some point of time at some location. At the same time some portion of the system is facing power shortage and carrying out load shedding to cope up with the situation. 

Therefore, there is an urgent need for service mechanism such as Frequency Support to properly utilize these unused capacities to enhance the Grid security. Initially generators having surplus generation, either because of un-requisitioned quantum by the beneficiaries or quantum of generation which could not find buyers or captive generation capacity, may bid for the frequency support when their services are sought upon by the system operator. 

Frequency support services can also help to mitigate the intermittent nature of renewable energy sources such as wind and solar farms. At this juncture it is worth mentioning that Indian government has set some very ambitious targets towards renewable energy generation particularly from wind and solar.     

Eligibility Criterion and Implementation
All the producers and the regional entities which are members of the scheduling and deviation settlement mechanism for real and reactive power are entitled to participate in the ancillary market, but the condition is that they must have relevant telemetry facilities. 

No other No Objection Certificate (NOC) or clearance, other than that issued by the respective RLDC/SLDC for participation in the Day-ahead Market (DAM), is required. The Frequency Support Ancillary Services (FSAS) are to be implemented through bidding in the power exchange. The participants are free to bid in any of the Power Exchanges of the country for ancillary services. The bids for FSAS to be dispatched on next day are to be opened up after the closure and clearance of the day-ahead market. Time-block-wise bids with the quantum, price and the location (where services are to be given) are to be submitted for the next day despatch.  

Reactive Power Ancillary Services

Unlike the frequency, voltage is a local phenomenon, and hence the requirement for reactive power support from capacitors or reactors at the different sub-stations or generating stations may vary. Thus, reactive power ancillary services are also in the list of ancillary services in India. Although there is a provision in the IEGC regulations and according to which proper voltage profile is to be maintained at all interchange points between the control areas in the Indian power grid.

However this is not sufficient and there is an urgent need for reactive power support to be added in the ancillary services list. Whenever there is persistent low voltage profile at one or more points in the system (this may be frequent during agricultural season), the system operator should have the voltage support ancillary tool in his armory. 

The voltage support ancillary service provider may also bid through the power exchange. Since the reactive power and hence the voltage support is a local phenomenon and their requirement are different at different locations, therefore mobile reactive power supports on trailers etc. can be very useful in the Indian power system. It is supposed that initially the government transmission companies will provide the mobile reactive power support and further opening up of the scenario will depend on their outcome.      

Black Start Ancillary Services

Black start is the process of restoring a power station to operation without relying on the external electric power from the transmission network. Normally the electric power required by a plant for its operation is provided by its own generators. If all the generators of a generating plant are out of service then to restore the generation, the station requires the electric supply externally, drawn from the transmission line connected to the station. In the event of power outage in a wide area, the transmission lines are also out of supply. In the absence of transmission line or grid, the so called Black Start facility is required.   

The Central Electricity Authority (CEA) Regulations 2007 mandates the Hydel power stations in the country to provide the Black Start facility. There is a provision of incentives to such service providers who offer their services (black start services) when asked by the system operator. Black Start Ancillary Services (BSAS) are to be paid when it is required by the SLDC i.e. the nodal agency. The generators capable of providing the start up power are to be paid for one day capacity charges for their services. The quantum of energy supplied during the restoration process is paid (energy prices are paid the BSAS provider) at twice the energy charges as determined by the Commission.  

Ref.: “Introduction of Ancillary services in Indian Electricity Market”, Central Electricity Regulatory Commission, New Delhi, April 2013