Small-Signal Modelling and Analysis of Converter Interactivity in Low-Voltage DC Grid

Due to easy amalgamation with sustainable energy sources, storage units and electric loads, DC grid system is getting more research attention in current times. With the aim of achieving a reliable as well as flexible DC common bus system, it is preferred to operate multiple DC-DC converters in parallel connected architecture. However, due to the parallel connection among converters, coupling effect is observed during the operation. For a smooth controlling of overall system, proper modelling needs to be done. This paper analyses a detailed small signal based model approach for parallel connected DC converters operating with droop control algorithm. An approximation of small ripple in inductor current is considered for modelling. Effect of coupling is taken in to account during modelling process. The presence of cable resistance has direct effect on location of zero in the right-half-plane for derived control to individual converter output voltage transfer function. The controller is designed using the coupled model to achieve suitable stability margin. The correctness of designed model and controller is verified using simulation studies.