15-10-2010, 11:40 AM
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INTRODUCTION
AGC Of An Interconnected Hydro-Thermal System
INTRODUCTION
Generation in large interconnected power system comprises of thermal, hydro, nuclear and gas power generation. Nuclear units owing to their high efficiency are usually kept at base load close to their maximum output with no participation in system automatic generation control (AGC). Gas power generation is ideal for meeting varying load demand. However, such plants do not play very significant role in AGC of a large power system, since these plants form a very small percentage of total system generation. Gas plants are used to meet peak demands only. Thus the natural choice for AGC falls on either thermal or hydro units.
The characteristics of hydro turbine differ from steam turbine in many:
In a hydro-turbine relatively large inertia of water, used as the source of energy, causes a greater time lag in the response of the change in prime mover torque to a change in gate position. Moreover, there is an initial tendency for the torque to change in a direction opposite to that finally produced .Modem hydro units are normally equipped with electric governors in which the electronic apparatus is used to perform low power functions associated with speed sensing and droop compensation.
The model uses continuous mode strategy, where both system and controllers are assumed to work in the continuous mode. It is to be appreciated that in realistic situation, the system works in the continuous mode whereas the controllers work in the discrete mode. PerhapsNanda, Kothari and Satsangi are the first to present comprehensive analysis of AGC of an interconnected hydrothermal system in continuous-discrete mode with classical controllers. In the interconnected hydro-thermal system used by them, the thermal system uses reheat turbine and the hydro system uses a mechanical governor.
In modern hydro thermal system, reheat type turbine and electric governor [4] are used. To the best of authors’ knowledge, no work seems to have been reported for AGC of an interconnected hydro-thermal system in the continuous-discrete mode strategy with reheat turbine and electric governor. A few investigations have been carried out using Fuzzy Logic Controllers (FLC) for AGC of thermal systems surprisingly, till date, no attempt has been made to examine the effect of FLC in an interconnected hydro-thermal system.
The characteristics of hydro turbine differ from steam turbine in many:
In a hydro-turbine relatively large inertia of water, used as the source of energy, causes a greater time lag in the response of the change in prime mover torque to a change in gate position. Moreover, there is an initial tendency for the torque to change in a direction opposite to that finally produced .Modem hydro units are normally equipped with electric governors in which the electronic apparatus is used to perform low power functions associated with speed sensing and droop compensation.
The model uses continuous mode strategy, where both system and controllers are assumed to work in the continuous mode. It is to be appreciated that in realistic situation, the system works in the continuous mode whereas the controllers work in the discrete mode. PerhapsNanda, Kothari and Satsangi are the first to present comprehensive analysis of AGC of an interconnected hydrothermal system in continuous-discrete mode with classical controllers. In the interconnected hydro-thermal system used by them, the thermal system uses reheat turbine and the hydro system uses a mechanical governor.
In modern hydro thermal system, reheat type turbine and electric governor [4] are used. To the best of authors’ knowledge, no work seems to have been reported for AGC of an interconnected hydro-thermal system in the continuous-discrete mode strategy with reheat turbine and electric governor. A few investigations have been carried out using Fuzzy Logic Controllers (FLC) for AGC of thermal systems surprisingly, till date, no attempt has been made to examine the effect of FLC in an interconnected hydro-thermal system.