Modelling, Simulation, And Energy Management Research For Electricity, Gas, And Heat Based Micro Energy System

With the increasing utilization of combined heat and power(CHP) plant in microgrid, heat, gas, and electrical systems become more linked to each other. However, the interactions among the three systems are not well captured and managed by traditional methods. This thesis will focus on modeling, simulaton, and energy management of micro energy system with heat, gas and electrical subsystems. The main work can be summarized as follows:1) Interactions between natural gas and electric networks are not well captured by traditional microturbine(MT) models. To address this issue, two improved models for single-shaft MT and split-shaft MT were proposed in this paper. In addition, dynamic models of hybrid natural gas and electricity system(HGES) were developed to analyze their interactions. In addition, dynamic behaviors of natural gas in pipes were described by partial differential equations(PDEs), while the electric network was described by differential algebraic equations(DAEs). A two-time scale method was then proposed to simulate the HGES. Numerical studies indicated that the proposed algorithm could capture the interactions between the two networks.2) A hierarchical framework was developed for the energy management system(EMS) of micro energy system. Traditional energy hub based scheduling method was combined with a hierarchical control structure to incorporate transient characteristics of natural gas flow and energy converters in microgrids. The EMS included a supervisory control layer, an optimal control layer(OCL), and an execution control layer. In order to efficiently accommodate multi time-scale characteristics of the system, the OCL was decomposed into three sub-layers: slow, medium and fast. Heat, gas and electrical management systems were integrated into slow, medium, and fast control layers, respectively. Potential impacts of the hierarchical EMS were investigated based on a building energy system integrating photovoltaic and microturbines. Numerical studies indicated that, by using the hierarchical EMS, micro energy system could be economically operated. Also, interactions among heat, gas, and electrical systems could be effectively managed.3) An integrated steady state analysis algorithm was developed for micro energy system, which could be considered as the ‘power flow’ tool of micro energy system. In the algorithm, energy hub was used to describe the interrelation among heat, gas and electrical systems. Multiple operating modes and component capacities of the CHP were integrated into the energy hub. Based on the proposed algorithm, an optimal powr flow(OPF) model was proposed. In order to efficiently handle the nonlinear optimization problem, a particle swarm optimization algorithm was used to set the control variables in the OPF problem. Simulation results demonstrated that the interactions between different systems could be reflected by the proposed method. Also, the proposed algorithm can be used in both microgrids and distribution systems.4) A hierarchical scheduling method for heat, gas and electrical system based micro energy system was developed considering demand response(DR). A hierarchical framework was developed for day-ahead and intro-hour scheduling. A bi-level coordination method was integrated into the intro-hour scheduling. In the upper level, the integrated OPF method was used to generate set-points for the CHP. Two types of objective functions, cost minimization and tie-line power smoothing, were integrated with the OPF tool. In addition, a group-based DR approach was proposed to take DR resource location and phase into account. In the lower level, CHP and DR regulation boundaries were calculated and transmitted to the upper level. Numerical studies indicated that by using the proposed method, micro energy system could be economically operated. Also, the tie-line power could be effectively managed by DR and CHP system coordination.