Research On Modeling And Control Strategy Of Microgrid

With the rapid development of economy, the situation of relying solely on traditional power generation modes cannot meet the ever-increasing electricity demand of people. Furthermore, the traditional power generation modes are facing new crisis, because of the extreme shortage of natural resources and serious damage to natural environment. Under such severe situation, many a distributed power generation mode using all kinds of clean energy as raw materials emerges in response to the proper time and conditions. In order to effectively manage the scattered distributed power to reduce the impact to distribution network resulted from the abuse of distributed power generation technology, ensure the efficient, stable energy supply, and improve the electricity quality of local users and the whole electricity system, the thoughts of micro-grid technology come into being, which takes regions or interconnections among distributed powers as a link. The thesis mainly starts with the composition and controllable operation of micro-grid, and proceeds with the modeling of micro-source followed by the control design of voltage source inverter, ends with the design of micro-grid cases. All of these steps contribute to testing and verifying the operational performance of micro-grid.First of all, the paper chooses PV System as the object of micro-grid modeling, and sets up the simulation model of PV cell by using Matlab software on the basis of engineering PV mathematical model. After analyzing and comparing the merits and demerits of all kinds of MPPT techniques, superadding the consideration of economical efficiency, the paper offers a Changeable-step and Weak-oscillation P&O method. Then, the paper forms the whole model of PV system by combining the model of PV cell and the MPPT part. After the test under different environmental conditions, the paper proves that a PV with the new P&O method owns better operating performance.Afterwards, the author selects the control of micro-source as research subject, and studies the principles and control thoughts of three kinds of the currently mainstream control modes, namely Droop control, V/f control and PQ control, from the perspective of voltage source inverter. Simulation models for each control mode are constructed employing software Matlab, and the reference parameters are also proposed from different angles. The result reveals that the designed models possess relatively nice control performance.Finally, taking the control strategy of micro-grid from the aspect of management as an entry point, based on the principle of peer to peer control strategy, the paper takes advantage of software Matlab to build a micro-grid system composed of two micro-sources running in the mode of Droop control. The circuit simulation validates the merits and deficiencies of Droop control strategy. Taking master-slave control strategy into account, the thesis designs a micro-gird under the mixed control strategy combining peer to peer control (in the present study, Droop control) with master-slave control (in the present study, V/f control). Through complicating the system structure gradually, the paper verifies the operational performance of the whole mixed control system under the situations of transferring operation mode, switching public load and micro-source.