Abstract
Energy transmission in cooling/heating and gas pipelines has time-delay, which impacts the power balance between various sources and loads in the optimal dispatch of an integrated energy campus microgrid (IECM). This article proposed an optimal dispatch model for IECMs, which considered the time-delay of energy transmission in cooling/heating and gas pipelines. In this model, the electricity and natural gas purchase cost of the IECM was made into an objective function. Partial differential equations (PDEs) were used to describe the time-delay in pipelines, and the discrete variables that described the switching number of absorption chillers and heat exchange units were included in the constraints. The proposed model was essentially a mixed-integer nonlinear programming (MINLP) model with PDE constraints. Orthogonal collocation on finite elements (OCFE) in the two-dimensional domain was used to transform PDEs into algebraic equations (AEs). Several linearization methods, including piecewise linearization and the big M method, were used to transform the initial MINLP model into a mixed-integer linear programming (MILP) model to reduce computational complexity. OCFE was compared with the first-order finite difference method, and simulation results were used to demonstrate the accuracy and efficiency of the proposed algorithm. The impact of the time-delay of pipelines on IECM was analyzed through comparison with a steady-state model.
Highlights
The coupled operation of electricity, gas, cooling, and heating in integrated energy campus microgrids (IECMs) realizes a cascaded utilization and complementary operation of different forms of energy
The IECM optimal dispatch models in [18]–[20] did not obtain numerical solutions to Partial differential equations (PDEs), and the node method was used to model the time-delay of the heating networks
The differential state variables, algebraic state variables, and control variables were fully discretized using OCFE, and the PDEs of the dynamic optimal dispatch model were transformed into algebraic equations
Summary
The coupled operation of electricity, gas, cooling, and heating in integrated energy campus microgrids (IECMs) realizes a cascaded utilization and complementary operation of different forms of energy. Huang et al [19] proposed an optimal dispatch model for integrated electrical and heating systems, which considered the temperature dynamics of pipelines using the node method. The IECM optimal dispatch models in [18]–[20] did not obtain numerical solutions to PDEs, and the node method was used to model the time-delay of the heating networks. This approach cannot obtain a solution to the temperature distribution along each pipeline, which is helpful in identifying locations for metering, monitoring, and energy storage [21].
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