Research On Active Power Stability In Independent Micro-grid Based On Hierarchical Control

Nowadays, the energy and environment problems have attracted many attentions of the society. The exploration of the new energy technology is constantly advancing. Micro-grid firstly put forward by American is a new way to take advantage of the new energy. Micro-grid can solve the adverse effects caused by that the large-scale distributed generations are incorporated electrified wire netting, and also can make full use of the energy of remote areas to establish an independent micro-grid system providing electric energy for the local users.The independent micro-grid usually consists of micro-turbines power generations, photovoltaic power generations, wind power generations, energy storage devices and so on. Firstly, as the main power in micro-grid, the micro-turbine has some shortcomings that its capacity is limited and its inertial is deficiency and its response is slow, so the active power vacancy of sudden loads and the new energy can’t be timely compensated. Secondly, the new energy is greatly affected by the weather and the environment. It should be effectively solve that each generation and loads are coordinated, allocated and managed, in order to ensure that the independent micro-grid operates stably and efficiently to provide users with the high-quality power energy.In this thesis, the object of research is the independent micro-grid with relatively common form. It includes a micro-turbines power generation, a wind power generation, a photovoltaics power generation, a battery pack, user loads and unloadings. Firstly, the DC inverter circuit is established. The control methods of the inverter is designed and debugged. It includes Voltage and frequency(V/f) control and the active and reactive power control(PQ). Secondly, in order to highlight the focus of the thesis, the micro-power like the micro-turbine, the Wind Turbine and the photovoltaic are simplified by V/f and PQ control methods, and then the micro-source models are established. Thirdly, the active power vacancy is estimated by current jump caused by the load mutations. This method is faster than that of the changes of the frequency, and the error is within the acceptable range, thus providing a reliable reference for the output of the battery pack and the increase or decrease of the unloading. Finally, obtaining the relevant information of each micro-power, loads and the battery pack, using dynamic programming as the upper centralized control method and combining with the micro-source local control(V/f and PQ) optimize the scheduling, allocation and management of micro-grid power generations and users. The simulation results show that the battery pack can effectively inhibit the fluctuations of the active power, and the centralized control can ef fectively ma nage the each unit of micro-gr id and make full use of new energy power generation, thus providing the load with high-quality power energy.