Research On Hierarchical Control Of Microgrid Based On Large Scale Systems Theory

The vigorous development of new energy generation plays an important rol e in promoting China's energy production and consumption revolution.New energy generation is of great significance both in terms of sustainable development and improvement of China's energy structure.In this thesis,a high proportion of new energy micro grid as the research object.The new energy power generation systems are combined to form a joint power generation system composed of wind power generation,photovoltaic power generation,solar-thermal power generation and diesel generator.The comprehensi ve economy of microgrid is the optimization target.The comprehensive economy includes the economic index of operation cost,renewable energy utilization index and environmental protection index.The coordination and control of the microgrid system are researched by using the large system theory.The core idea of large scale systems theory is to transform a large scale system into several subsystems through decomposition,coordination and decentralized control.By means of decomposition and coordination,a multi-level hierarchical control structure is established.It consists of coordination layer,local decision unit and scheduling layer.Firstly,the coordination layer of the micro grid system is constructed.Then comprehensive economic model of the micro grid is established and comprehensive economy is the goal of optimization.At the same time,the global constraint model of the micro grid is established,and the Lagrange function of the objective function is established by introducing the Lagrange multiplier and global constraint conditions.The coordination layer updates the Lagrange multiplier by receiving feedback from the lower layer,and sends the updated Lagrange multiplier to the lower layer local decision unit.In order to prevent the oscillation phenomenon in the traditional sub-gradient method,the adaptive sub-gradient method and the aggregation projection sub-gradient method are used to update the Lagrange multiplier.The improved sub-gradient shows good optimization effect.Secondly,the local decision unit of micro grid is constructed.By means of the decomposition and coordination idea of large system theory,the overall objective function of microgrid is decomposed into sub-problems in several subsystems.Considering the constraints of each generation system,the sub-problems are optimized in the local decision unit and the optimization results are fed back to the upper coordination layer.Through theoretical analysis and algorithm test comparison,the improved quantum particle swarm optimization algorithm has faster convergence speed and better global optimization performance.Thirdly,the dispatching layer of micro grid is constructed.A prediction model is created for wind power generation system,photovoltaic power generation system and so lar-thermal power generation system.The model prediction controller is constructed to deal with the uncertainty of wind and solar energy.The stability of diesel generator set is better,and the fuzzy PID controller is used to control the output of the di esel generator sets.Through the tracking control of each subsystem,the comprehensive economy of hybrid power generation system is minimizedFinally,the simulation study of the theory is carried out to obtain the output of different types of units when the comprehensive economy is optimized..The feasibility and effectiveness of the proposed method are proved by the comparison between the decomposed coordinated scheduling based on the large system theory and the integrated scheduling based on the quantum particle swarm optimization.This study provides a certain reference for the large-scale generation of high proportion of new energy.