An improved combined heat and power economic dispatch model for natural gas combined cycle power plants

Abstract

An increasing number of natural gas combined cycle (NGCC) plants are operated under combined heat and power mode. Therefore, a combined heat and power economic dispatch (CHPED) is the key to achieve the optimal utilization of fuel. In this paper, an improved CHPED model is developed, in which short-term loads variation process models of plants are integrated to ensure the feasibility of dispatched demands. The short-term loads variation process of NGCC plants is modelled based on the power and heat loads control logic in the field operation process. In comparison with the CHPED models in most existing researches, the improved CHPED model can be applied in the real-time field operation of plants. In addition, the influence of heat load ramp rates on CHPED results is investigated, which can offer theoretical support and guidance for field operation. Based on the data from field operation and manufacturer of an NGCC power station, case studies are performed. Results show that the errors between the short-term loads variation process model and field operational data are less than 2.6 s on power load, and less than 1 s on heat load, which proves the accuracy of the model. All the dispatched demands of the improved CHPED model can be met in the required regulation time limits. On one-hour cumulative fuel consumption, the improved CHPED model saves 171.4 kg (0.12%) over the field operational demands. The improved CHPED model not only enhances the economic performance, but also guarantees the operational reliability of plants.