Research On The Change Control Between Dual Modes Of Microgrid Inverter

The use of new energy has brought new hope to the development and utilization of energy. However, traditional energy sources still account for a large proportion in the use of energy. With the development of each country, pollution and global warming causing in the utilization of the traditional energy attract more and more people’s attention, and humans need more channels to obtain cleaner energy. In this case, how to strengthen the utilization of the solar energy, nuclear energy, wind power and other clean energy sources attracts more and more attention each country. To solve distributed power supply problems occurring in the use of new energy process, researchers have proposed a series of control methods to improve energy efficiency.Firstly, the define and research status of microgrid in each country are introduced, and the value of microgrid research to the utilization of energy is analyzed. Some distributed power is combined to obtain micro-grid, and distributed power relys on inverter to convert their own power to meet the power requirements of the electrical energy. Therefore, the micro-grid control is just each inverter control. Thereafter, the paper established the control model of the microgrid and mathematical model of the inverter, and micro-power control method and control strategy of micro-grid level is briefly described.The control of the microgrid under the network and island operation status was studied. And the microgrid under network operation state can be modeled as a current source to large power grid, then the system controller uses PQ control, distributed power based on the voltage and frequency of the power grid to the output power. When the power grid power quality deteriorates, or out of necessity, the microgrid is disconnected from the power grid and it is under islanding operation state. In this case, the system inverter use the droop control. To solve the power uneven problem between parallel inverters in islanding operation state, this paper presents an improved droop control. In network and islanding state, micro-grid simulation is got, and the simulation results shows:under the network state, output power of the micro-grid can be controlled; and compared with the traditional droop control, improved droop control are better able to complete the task of power sharing.Finally, switching of the micro-grid inverter between the two operating modes were studied. Through researching and analysising the controlling method of the two modes, PQ control is used under the network mode, and the improved droop control is used in island operation mode. The simulation results shows:the used control method can complete the smooth switching between the two modes.