Energy Optimization And Management Of CCHP Microgrid

Energy shortage, environment pollution and climate change are main factors that restraint the economic and social sustainable development of the world, while energy and environment problem have become the major strategic issues, which have been paid high attention at home and abroad. Combined cooling heating and power (CCHP) microgrid follows the principle of appropriate allocation, each taking what he needs,corresponding temperature, and cascade utilization, integrating power generation with cooling and heating.Its high energy utilization efficiency, flexible and reliable energy supply mode make the CCHP an important mean to realize the transformation of energy production and consumption, improve energy utilization efficiency and solve the problem of energy and environment. Compared with the traditional electric power system, the load and renewable energy inside the CCHP microgrid are susceptible to the influence of many uncertain factors such as climate, environment etc, which bring great challenges to the energy management and optimization of CCHP microgrid. What's worse, the high randomness, the coupling characteristics among the cooling, heating, power load and the renewable energy, the diversity of equipment operation condition, and the features of energy complementary make the energy management a hard work.Therefore, considering the structure and operation requirements of CCHP microgrid, this dissertation study the energy optimization management of the CCHP microgrid from the following four aspects: modeling of the CCHP microgrid units, modeling of day-ahead uncertainty, multi-time scale coordinated optimal dispatchin and performance analysis of the combined operation of interconnected-BCCHP microgrids. The main work of this paper is as follows:(1) Modeling of the CCHP Microgrid UnitsModeling of the CCHP microgrid units is the basis of optimization operation of CCHP microgrid. In this part, the structure of CCHP microgrid has been analyzed and discussed in detail. The model of gas turbine has been built, which includes the nonlinear relation between the thermal power output efficiency, the load rate and its piecewise linearization. In addition, the models of distributed generator including wind power generation systems and photovoltaic power generation systems, energy storage battery, heat storage tank, gas boiler and device of waste heat recovery have also been studied.(2) Optimal Operation of a CCHP Microgrid Using Interval Mixed-Integer Linear ProgrammingAn interval optimization based CCHP microgrid interval dispatch strategy is proposed, considering interval distribution of cooling, heating and net electricity (including renewable energy output), and operational parameter uncertainties such as efficiency of equipment. In this part, the interval of the system operation cost are optimized, and the constraints such as the power balance and operation constraints of various devices are formulated as interval constraints, thus reflecting the problems such as lack of data and inaccurate parameters. The interval dispatch problem is transformed into two deterministic dispatch problems and the optimization problem is solved by the Mixed Integer Linear Programming (MILP).The test cases have verified the proposed dispatching method.(3) A Robust Optimization Method for Energy Management of the CCHP MicrogridIn order to consider both safety and economy under uncertain environment, a robust optimization method for energy management of the CCHP Microgrid is proposed, which considers the interval distribution of cooling, heating, electricity and distributed renewable energy. In this approach, the system operation cost are optimized, the nonlinear constraints of equipment are converted into manageable linear constraints by piecewise linearization method, and the conservative parameters are introduced to unify regulation system uncertainty. By introducing the dual variables,this robust optimization problem is transformed into a deterministic dispatching problem. The proposed optimal dispatching strategy is verified on numerical cases.(4) Multi-time Scale Coordinated Optimal Dispatching of the CCHP MicrogridConsidering the situation that the day-ahead optimal scheduling cannot meet the need of real-time operation, multi-time scale coordinated optimal dispatching model of the CCHP microgrid is proposed, which contains three parts: day-ahead optimal scheduling, intra-day predictive control and real-time adjustment. In the day-ahead optimal scheduling stage, an interval linear programming and robust optimization based joint decision system is proposed, and optimal operation state of each distributed unit during each time interval of whole day is arranged. In the intra-day predictive control stage, the result of day-ahead scheduling is adjusted by model predictive control, according to the latest data, and the output power of the equipment in this system.In real-time adjustment stage, according to the real-time data of cooling, heating, electricity and distributed renewable energy, the output power of the equipment in this system are adjusted to smooth the power fluctuation in the internal CCHP microgrid network. Finally, the cases studies verified the rationality and validity of the proposed method.(5) Performance Analysis of the Combined Operation of Interconnected-BCCHP microgridsThe combined operation of interconnected-BCCHP microgrids is based on the optimal operation of the system model with the year load, and the goal is to minimize the annual primary energy consumption, the annual CO2 emissions and the annual operation cost. The performance of the interconnected system and its operation modes is studied in this part. Reference buildings are used for case analysis, and the optimization results under different operating modes are discussed. The impacts of the prices of electricity and natural gas on operation of interconnected-BCCHP microgrids are analyzed.