Research On Building Dc Micro-Grid Control Strategy Based On Multiple-Input DC-DC Converter

Industrialization has not only boosted the rapdid development of the world economy and society but also continiously consumpted the energy and deterioated the enviroment. To ease the strain on the resources and to improve the environment, the new clean distributed way of power supply technology has become a research hotspot among Combined Power Supply System. In DC micro-grid system, distributed energy resources(DER) restricted by some enviroment factors may lead to uncertainty,randomness and etc, if these DER were accessed directly, the system would be impulsed. It will improve the reliability of power supply and will make the system more stable and sustainable to use DC micro-grid power supply network, to collect various types of DER for micro-grid energy supply network and to achieve full utilization of all energy properties.The paper specific studies include:1) In DC micro-grid power supply system, multi-input DC converter(MIC) of energy concentrator comparing to the single-input DC advantages over its simple structure and low cost. Based on the traditional Buck-Boost DC converter, the thesis proposes a new three-input DC/DC converter that has the advantages such as rising and falling voltage, simple structure and powering load individually or simultaneously;analyzes the working principle and steady-state characteristics; presents the control strategy, and builds a three-input converter simulation model in MATLAB/Simulink simulation platform to verify the correctness of theoretical analysis.2) In order to fully realize the value of new DER in micro grid, effective and reliable energy management for micro grid energy is necessary. The whole idea of energy management is taking full advantage of distributed clean energy, and micro-grid power fluctuation coordinate controlled by the storage unit and grid.In this paper, the two-input DC-DC converter is used as energy collection device for the micro-grid systems, batteries and grid connected to the DC bus. Proposed bus voltage hierarchical control method for the amount of change in the DC bus voltage, the bus voltage is divided into 6 different levels, resources converting different modes of operation based on real-time bus voltage level, coordinate control various resources output power to maintain the power balance and voltage stability. The photovoltaic unit of double input converter adopt perturbation and observation MPPT method control, output maximum power constantly, while wind power generation unit controlled by DC bus voltage, and the battery use constant current and voltage controlor voltage droop control. Finally, DC micro-grid simulation model based MIC is built in MATLAB simulation platform,and the reasonableness of the energy management strategy is verified by simulation results.