Research On The Control Mode Of Micro-grid And Engineering Application

With the aggravation of the world energy crisis, people are giving more and more attention to the use of large scale renewable energy, of which the distributed generation (DG) technology like wind power generation and photovoltaic power generation develop fast. Since most renewable energy should be processed before becoming alternating current, it is very important to research how to access DG to power system in a proper way. Micro-grid technology integrates DG and grid-on and grid-off control strategy, which makes DG more rational and effective.First, the concept of micro-grid is introduced, including the definition and projects of different countries. It’s pointed out that it’s very important for the safety and stability of micro-grid to select an appropriate control strategy. Second, the DG including wind turbine generation, photovoltaic power generation and storage battery are introduced. The control of DG inverters are modeled in MATLAB, including constant power (PQ) control, constant frequency and voltage control and droop control. Then a virtual synchronous generator inverter control method is proposed based on the synchronous generator control method in power system. The second order model of synchronous generator is included in the control system of inverter, so the inverter has the excellent characteristics of synchronous generator such like big rotary inertia, high output impedance, and current mutation restraint. The control method is modeled in MATLAB, and compared with traditional droop control. Last, the design and control strategy of a micro-grid project is introduced. The master-slave control strategy and peer-to-peer control strategy are simulated separately. The output power, frequency, and system stability are compared. The advantages and disadvantages are compared between the two control strategies to provide references for micro-grid projects. Considering the power quality of micro-grid, a harmonics restraint inverter control method with PV generation is proposed in master-slave control simulation. The inverter outputs fundamental power and restrains harmonics. The simulation results indicate that the control method is useful.