Improving Flexibility and Economic Efficiency of CCGT Units’ Operation in the Conditions of the Wholesale Electricity Market

Abstract

The issues of improving flexibility and operation modes of combined-cycle plants with three-pressure heat-recovery steam generators (CCGT with HRSG) are considered in the conditions of the wholesale electricity market. Operation modes of high-performance CCGT units, which were designed mainly for the basic operation mode with a minimum number of starts and load variations are significantly different from it due to the lack of regulatory capacities in power systems. The increasing CCGT unit fractional load running time, emerging role of ramping to the minimal possible load, and expediency of involving the CCGT unit to adjust the frequency and power in the power system make it necessary to extend their adjustment load range limits. The article analyzes the possibilities and the need for maximum CCGT ramping during the night-time valley from a technical and economic point of view. The factors limiting the CCGT load range are obtained computationally and experimentally. The ways to reduce the technological minimum CCGT load are considered by heating the compressor inlet air, bypassing part of the compressed air to its inlet, and enhancing its flow control using inlet guide vanes (IGV) as well as combining these methods. The influence of the electricity price in the day-ahead market on the optimal generating capacity load is analyzed. The optimization of the CCGT operating modes in the conditions of the wholesale electricity market is carried out with allowance for the developed load range extension methods.