Research On The Control Strategies Of PV Inverter In Micro Grid

In recent years, distributed generation has developed rapidly, especially for PV and wind power generation. It can reduce line loses on transmission and the pollution of environment. However, as the number of DG increasing, the high cost and grid structure limits and other issues are also increasing apparently, which limits the development of DG to a great extent.In order to eliminate the contradiction between the DG and the power system, The United States, European Union, Japan and other countries have put forward micro grid (Micro-grid) concept, its essence can be summarized as follows:micro grid make micro source, load, energy storage device, control device etc together, forming a single control unit, to provide electricity and heat for customer. Micro grid can break through the bottleneck of the development of DG, and enhance the ability the end of power grid. But, it changes the structure and performance of the system, making the system more complex management. Micro grid has a unique energy management system, PV power to integrate into one, must be in good cooperation with it.In grid connected operation, micro grid energy management system require PV power run in the form of the current source. The central manager direct each inverter transmitting electric energy with program instruction. Base on the PV inverter grid connected model, the paper put forward the space vector pulse width modulation control strategy. The simulation results and the experiment results verify the validity and effectiveness of the proposed control strategy.In the island operation, due to the loss of large power grid support,the bus voltage will fluctuate. At this time, the micro energy management system require PV power run in the form of current source, to stabilize the bus voltage, providing support for the other distributed power operation. This paper adopt master-slave droop control strategy, the simulation and experiment results verify the effectiveness of the proposed control strategy.In the switching process, sometimes it may fail, because the central manager islanding detection time is too long or transmission delay. This paper adopt the super capacitor and DC/DC chopper circuit as energy storage device, to provide energy and stabilize DC voltage of PV inverter, the simulation results verify the validity of the proposed method.