Comparison of Strategies for Operational Flexibility Enhancement of Combined Heat and Power Plants

This paper compares the strategies for improving the operational flexibility of combined heat and power (CHP) plants to support wind power integration. Four commonly used strategies, namely cutting off low pressure cylinder, installing heat accumulator, installing electric boiler, and utilizing by-pass device are discussed. An integrated model is proposed to quantify the performance of various strategies in improving the flexibility of CHP plants. A 350 MW subcritical extraction condensing turbine in China is used as an example, to compare the performance of the four strategies from the viewpoint of the operating cost of flexibility enhancement. The maximum flexibility and the scope of applicability can be enhanced.

I. Introduction

The curtailment of wind power is significantly increasing in the three-north area (northwest China, north China, and northeast China), particularly in winter when there is a high demand of heat supply from CHP plants [1]. Due to the coupling of heat and power supplies in CHP plants, the electricity generation is also at a high level when the heat demand is high [2]. As a result, the electricity generated from coal with high emissions is used instead of wind power, which should be avoided.