| In recent years, due to the factors of energy and environmental issues as well as national policies, as an important form of making use of renewable energy, microgrid has drawn people’s more and more attentions. At present, microgrid has been widely and deeply studied in the domestic and overseas. As a part of the microgrid, energy storage plays an important role in islanding mode, grid-connected mode and the transformation between two models of microgrid. In islanding mode, the inverter with energy storage can provide voltage support for microgrid, and the power distribution in microgrid can be balanced; In grid-connected mode, the inverter with energy storage can stabilize a variety of power fluctuations caused by distributed power supply and system load switching, storage system excess power to be used as backup power supply, adjust frequency and voltage of microgrid. In this paper, the inverter with energy storage is named as Microgrid Stability Controller. The efficiency of Microgrid Stability Controller is analyzed and the measures to improve efficiency are studied.In this paper, the loss model for a complete set of Microgrid Stability Controller is built at first, including the energy storage battery loss model, the inverter loss model, the LCL filter loss model, the DC bus capacitor loss model, and the transformer loss model. Then, the influence of the driving mode of the inverter switches on losses is studied. The influence of different driving resistance on the losses of IGBT switches is analyzed by double pulse experiments. The correctness of the conclusion is verified by simulation analysis and experiments. Then the efficiency of multiple parallel Microgrid Stability Controllers is overall optimized. Based on the obtaining of global information, a method of adaptive adjustment of the droop characteristic is proposed. Some Microgrid Stability Controllers are allocated in the system and output power to microgrid. The work quantity of Microgrid Stability Controllers is adjusted according to the efficiency characteristic curve, to make them work near the maximum efficiency point in order to improve the overall efficiency. And the effectiveness and stability of the method is verified by simulation and experiments. In the end, the application of Zero Current Transform soft switching technology in the Microgrid Stability Controller is analyzed. The feasibility of efficiency improvement the soft switching technology is analyzed by comparing with the hard switching system. The correctness of the theory is verified by simulation analysis. |
PDF Full Text Request