Master-slave control based reliable micro-Grid with back-to-back voltage source converter as master DG

Reliable and eco-friendly power demand at consumer load end leads to integration of local distributed generation (DG) based micro-grids in the electricity network. Adequate local load sharing between the DG's in the micro-grids is necessary in islanded mode under faulty grid condition. This paper presents a grid connected micro-grid system with a back-to-back voltage source converter (VSC) based DG and single VSC's based DG's. The transition from grid connected to islanded mode under faulty grid condition is presented. A master-slave load sharing control method is developed for a micro-grid in islanded mode under faulty grid condition, in which a back-to-back VSC acts as a master DG and remaining as slave DG's. This control method regulates the DC-link voltage of master DG when its DC input power is unavailable in order to overcome the micro-grid shutdown. The transient performance of the proposed micro-grid in islanded mode under load variation, failure of slave DG and unavailability of DC input power to master DG is demonstrated. The overall performance of the proposed micro-grid under both grid connected and islanded mode is verified using MATLAB simulation and OPAL-RT real time simulator.

I. Introduction

Now a days the micro-grids are gaining more importance in order to maintain reliable power supply to local loads. Microgrid is an integration of local distributed generations and local loads. Micro-grid can operate either in grid-connected mode or in islanded mode. Renewable energy sources like solar photovoltaic, wind, tidal etc. are the major sources for DG's in micro-grid [1]. The power generated from these RES's can not be directly used because the solar photovoltaic generated power is in DC form, wind generator power is in AC at variable frequency. Therefore, these RES's are interfaced through power electronic converters in order to convert input power at system frequency and system voltage level. The load sharing between DG's in micro-grid is different from conventional power system network [2].