Steady state performance analysis for load sharing in DC distributed generation system

DC microgrids are gaining popularity over ac microgrids, because of high efficiency and reliability with low installation cost. To achieve equal load sharing (in per unit) among sources, droop based controllers are used. However, equal sharing of load is achieved in ideal system. This paper investigates the deviation in load currents from their ideal values. Steady state mathematical model of the system is developed. This model is applicable to any interconnecting structure of sources and loads. Deviation of source currents from their ideal values is expressed in terms of load distribution pattern and differences in nominal voltages. Sensitivity of source currents to load currents and nominal voltages is derived. Effects of branch resistances and droop constants on the sensitivity of source currents are examined. Results obtained by analysis are verified by detailed simulation study. Viability of the model is confirmed by experimental results from a scaled-down laboratory prototype of dc microgrid.