Optimal load management of a microgrid with an electric boiler and renewable generation

  • Siran LU

Student thesis: Master's Thesis

Abstract

Renewable energy penetration into power grid keeps on increasing due to environment issues and fossil fuel shortage in the past several years. The scale of wind power generation has grown significantly in the past 30 years. However, power curtailment of renewable generations happens frequently due to the limitations of existing power transmission infrastructure amongst other reasons such as load fluctuations. This brings a great challenge to the development of renewable energy and the penetration levels of renewable energy.To deal with renewable power curtailment problem in a microgrid equipped with renewable generation, an electric boiler and a thermal energy storage (TES) tank, this thesis proposes a model to control the power flows within the microgrid so that the electric boiler, together with the TES tank, can absorb surplus renewable generation. The microgrid can also make power exchange with the external power grid. That is, if the renewable generation cannot meet the energy demand, it will purchase electricity from the external power grid; if there is surplus renewable energy, the redundant renewable generation can be sold or converted to heat to be stored in the TES. Power flows between the grid, renewable sources, boiler, and the remaining electric load of the microgrid will be controlled. The eventual target of the control model is to minimize the electricity cost of the user while at the same time maintain necessary thermal comfort.For the electric boiler and TES, temperature control is used to regulate the outlet water temperature by changing the electric power supply. The electric boiler under consideration can operate on different taps, and each tap position corresponds to a specific rated power. If renewable energy is larger than the electric load other than the boiler in the microgrid, the electric boiler may operate on high tap and produce redundant heat energy stored in TES for delayed thermal load.The electric boiler may also operate on low tap or OFF position and the TES tank provides further heat flux if the renewable energy is lower. The exact operation schedule of the electric boiler depends on the solution of the optimal control model which can operate differently from the above observations due to the time-dependent load, renewable generation, electricity tariff and feed-in tariff.In order to verify the efficiency of the proposed model and control schemes, simulation studies have been worked out using MATLAB. The operational cost and the customers' discomfort level are considered in the mathematical model. Genetic algorithm (GA) is applied to find the optimal solution of case studies. Simulation results demonstrate that the proposed model can deal with renewable energy curtailment problem effectively with lower operational cost, so as to improve the penetration levels of renewables.
Date of Award1 Jul 2016
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorHong Yue (Supervisor) & Jiangfeng Zhang (Supervisor)

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