The Research Of Grid-connected Inverter In Microgrid

With the continued increase of the global economic, it was found that the shortage ofenergy and the conservation of environment had became the main problem of the globaleconomy. Although there are a variety of the advantages of distributed generation, it will havegreater impact on power grid if distributed generation systems access to the power griddirectly. To lower the influence of the distributed generation, and improve the consistency ofpower grid. Microgrid technology comes into being. For users, microgrid shows acustomizable power. For power system, microgrid shows a single controlled unit.Microgrid is a novel network presence, it can realize switchover between grid-connectedform and isolated form. Therefore, the access standard of microgrid only aims at the accesspoint of grid-connected network without aims at specific distributed generation. It not onlysolves the access problem of large-scale distributed generation, but also better develops thepotential of distributed generation. Grid-connected inverter is a very important part inmicrogrid, so it is very important to study the grid-connected inverter of microgrid.In this paper, it researches the grid-connected inverter in microgrid detailly. UsingSVPWM to control the output voltage. The whole island detection module adopts theOVP/OUP and OFP/UFP with improved active power perturbation method to finish. Toaccomplish the seamless transitions with the improved droop control. Research works in thispaper are summarized as follows:1. We point out the basic conception and utilization of microgrid. And introduce thecategory, control, the type of the output filter and topological structure of the grid-connectedinverter.2. We research the output voltage of the grid-connected inverter to increase the steadyand dynamic character. The PWM modulation technology is widely adopted to realize thecontrol of output voltage. PWM, SPWM, SVPWM are proposed respectively. In this paper,we use SVPWM technology to manage the output voltage. To realize grid connection withpower system hopefully.3. We research the island detection technology of the grid-connected system in microgrid.Microgrid can not only grid-connected run, but also isolated run. It is imperative to detect thegrid-connect and isolate. It describes the definition of the island detection, and involves withcommonly used detection methods. We improves the traditional detection methods. The wholeisland detection module adopts the OVP/OUP and OFP/UFP with improved active powerperturbation method to finish, and designs the hardware circuit of the island detection.4. We research the seamless transition technology between grid-connected network andisolated network. The concept of seamless transition, require, voltage leap during theswitching process and the traditional droop control are given. It studies the handoff process between grid-connected network to isolated network and isolated network to grid-connectednetwork, and designs the hardware circuit. Based on the seamless transition of improveddroop control is given. Using Matlab/Simunlink to simulate the seamless transitions whichfrom isolated network to grid-connected network, and solves the power sharing of invertereffectively.