AC-DC Micro-grid Hybrid Modeling And Operation Control

AC-DC hybrid micro-grid combines the advantages of AC micro-grid and DC micro-grid, and it has been widespread concerned in academia and engineering fields. Microsource has the access to micro-grid by all types of converters network interface, It has a directly affect that energy converter and coordinated control issues plays on the efficient use of clean energy and AC-DC micro-grid stable operation. Grid-converter with several operating modes, whose operating modes is influenced by different weather and environmental. How to achieve the micro-source coordination control and to explore the hybrid switching control law is the main content of this paper, as follows:This paper in-depth analysis of a variety of microsource grid converter topologies and multiple operating modes, which includes wind power generation system access converter topology and its operation mode control, PV micro-source system access converter topologies and operation mode control, energy storage unit bidirectional DC-DC converter topologies and operation mode control and its operation mode control. Then, their hybrid switching model was established. A coordinated control energy control strategy based on the DC bus voltage and micro-grid power shortage was proposed. It considers the DC bus voltage deviation, micro-grid power shortage, the battery charge status and other factors.Based on this, the structure of AC/DC hybrid micro-grid with multi-AC bus and multi-DC bus is presented, and its characteristics and advantages are analyzed in detail. Then according to AC/DC micro grid structure characteristics, the blending theory, analyzes the AC/DC microgrid in the event of a switch, microgrid switching system model is established. The AC-DC micro-grid events were defined, micro-grid hybrid switching system works were analyzed and micro-grid event switch hierarchy was proposed. The AC-DC micro-grid hybrid switching system is divided into three levels, they are:topology switching layer, micro-source/load unit operating mode switching layer, power-device interfaces internal switching layer. Finally, the three-level hybrid hierarchical switching control structure with pre-evaluation and energy management aspects was designed. The pre-evaluation part include of the pre-evaluation of the economic, security and stability.Simulation results and theoretical analysis show that the improved droop control can not only maintain power balance between AC-microgrid and DC-microgrid, but also reduce the switching frequency of the bi-directional inverter operating mode, reduce unnecessary harmonics caused by power electronic devices.The hybrid hierarchical control method with pre-evaluation and design of energy management thesis is applied. Taking it into account that a variety of conditions and failure process that may arise, it can achieved AC-microgrid and DC-microgrid power balance, improve system stability and controllability. What’s more the hybrid switching model of AC-DC micro-grid operation mode and control model can adapt winds light and other uncertainties, and achieve a variety of operating mode switching control and coordination AC-DC micro-grid hybrid.