International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 03 | Mar -2017
p-ISSN: 2395-0072
www.irjet.net
Changing Role of Coal-Fired Power Plants: From Base Load Operation to Flexible Operation Nitish Kumar Gupta NTPC Ltd., Rae Bareli, India ---------------------------------------------------------------------***--------------------------------------------------------------------2. CHALLENGES FOR GRID RELIABILITY
Abstract – Coal-fired power plants have been the mainstay
of Indian power sector and they will continue to hold this pivotal position even in the foreseeable future. However in recent times, particularly in this decade, there has been a paradigm shift in the operating philosophy of these plants. In contrast to their earlier base load operation, the coal-fired plants are now entering the regime of flexible operation, owing to the changing landscape of power sector. Although many of the coal-fired plants have been able to meet the moderate requirements of flexibility in generation but there is a price to pay for that. The flexible operation has considerable bearing on the performance parameters of these plants; also the plant reliability and equipment life are in question. Further, even greater degrees of flexibility requirements from coal-fired power plants are on the cusp. This paper is an attempt to briefly discuss the impact of flexible operation on the performance and reliability of coal-fired power plants.
Key Words: Synchronism, Unit heat rate, enthalpy, APC, reliability.
1. INTRODUCTION Presently, Indian power sector is undergoing through a phase of radical change in its fuel mix. Although nobody knows the ‘Optimum Fuel Mix’ for the future, but it is for sure that renewable sources of energy will constitute a major chunk of installed capacity in India as well as around the world. Even now thermal power plants are facing operational requirements, which have not been anticipated during their design, due to large scale capacity addition of conventional and non-conventional power plants & suppressed demand. Plants designed as base load plants are operating as peaking plants or as per grid demand and even some times forced to stop as per severity of the situation. All this results in performance deterioration of coal-fired power plant in terms of heat rate, auxiliary power consumption, secondary fuel oil consumption to support low load operation and carbon emission. The severity of the problem increases with frequently changing demand. The situation is going to aggravate further with increasing penetration of renewable sources of energy in the grid because of the variable nature of these sources and uncertainties associated with them. © 2017, IRJET
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Impact Factor value: 5.181
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Electric power grid is constituted of various types of generation resources and loads and the most important aspect of an electric power Grid is its reliability and maintaining the balance between Load and Generation is one important aspect of reliability. Power grid is a dynamic system which has a lot of uncertainties associated with it, e.g., step changes in load and generation, faults in the system etc. For successful operation, the power grid must ride through all these dynamics and must maintain a reliable supply at all times. These sudden changes in demand or generation in the power grid can initiate a steep fall or rise in the frequency of the power grid, can be detrimental to the power grid operation, if not contained immediately. So, power grids have to maintain their alternating current frequency within defined limits to keep the machines in synchronism with each other. The synchronous generators connected to the grid form an inertial mass which stores the kinetic energy. This inertia of the machines acts as a readily available pool of energy for the grid. Whenever there is a step change in load or generation this kinetic energy changes so as to accommodate that change and correspondingly the grid frequency also changes. Thus an electrical grid which consists of inertial masses inherently tries to maintain the grid frequency. However, the system also has to have active support to re-match supply to demand within seconds so that the system frequency can be quickly restored after it has begun to change. The immediate arrest of this fall or rise of the frequency of the power grid necessitates Real Power reserves in the grid which respond almost instantaneously with the frequency change, popularly referred to as 'Primary response from the generators'. In the absence of Primary Response, such disturbances will have to be handled by automatic load disconnection, which is not desirable. So Real Power Reserves are essential in the power grid to provide primary frequency control and to help the system to cope up with uncertainties. This primary frequency support function is provided by requiring some plants to be designed and operated in a manner to allow the supply of increased or reduced power on a very short-term reactive basis. But this scenario is changing with the integration of renewable energy sources. The reason being, many renewable sources add to the generation capacity of the grid but they lack any synchronously rotating mass which can add to the grid inertia also at present they do not have the ISO 9001:2008 Certified Journal
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