Influence evaluation of integrated energy system on the unit commitment in power system

Abstract

This article presents a research on unit commitment(UC), which consider the interaction between conventional power system and district-level integrated energy system(IES). The increasing number and scale of IES projects at distribution network bring incremental effect to the whole energy system. Their influence on power system transmission level unit commitment becomes one of the notable topics. Within these IES projects, gas-power and cooling-heating-power are two main types of 'integrated' forms. In this article, a model system is built for UC analysis in which several district-level IESs are connected to a conventional power system. Heating, cooling and electrical forms of energy are integrated in these IESs. The UC problem is modeled and solved by mixed integer linear programming(MILP), the partial load characteristics of these power plants are handled by piecewise linearization. The common piecewise linearization method used in power and gas system is modified to reduce binary variables and constraints. The purpose of this modification is to increase the MILP solving speed. Case studies are carried out to evaluate the influence of IESs on two different time scales. The simulation result shows that the application of IESs can reduce the whole energy system service cost. As the number of applied district-level IESs increases, the cost reduction becomes more significant. The reduction relies on preventing high-cost small capacity plants go into operation, reducing the number of generator startup, and choosing an economical power output level. These benefits are owing to the reinforcement from gas network via CCHPs (Combine cooling, heating and power) and the buffer from multiple forms of energy storage devices (thermal and cooling).