Scalable-flexible architecture and power management strategy for a rural standalone DC community grid

Abstract

Roof-top solar PV and battery systems at individual homes form standalone DC nanogrids to electrify off-grid remote locations. To improve the reliability and sustainability of these installations, interconnections are required, forming a DC Community Grid (DCCG). A novel 380 V DCCG with 72 V nanogrid (home) members is proposed for this low voltage standalone DCCG. It is also proposed to adopt a decentralized power management strategy which utilizes the concepts of DC bus signaling and adaptive droop control. Power flow algorithm based on adaptive droop equations are developed for individual converter interfaces so that each of the subsystems operate independently but in coordination. Only local measurements of input/output currents and voltages of the particular interface are required. Therefore, these are applicable to any of the converter topologies used as an interface for the renewable sources, batteries and nanogrid interconnections. The decentralized approach will mitigate the dependencies of DCCG on the communication network. With the proposed architecture and power management strategy, addition or removal of loads, sources, or storage units at nanogrid level or community level can be done as plug-and- play without modifying the existing system. The system has been extensively simulated and analyzed using MATLAB/Simulink R2021b and further experimentally verified with closed loop operation using Spartan – 6 XC6SLX25 FPGA in FTG256 package. The experimental verification proves that the bus voltage variation is within the limits set by the power management algorithm while desired power sharing is achieved.