Load Sharing Techniques in Hybrid Power Systems for DC Micro-Grids

DC micro-grids is an advanced electric delivery infrastructure candidate for future Smart Grid. By interactively integrating a wide selection of renewable sources, energy storages as well as traditional utility grid within a local power network, DC micro-grids can achieve economical system operation, and bing local survivability to critical zones. As important supplement to conventional generation means, properly used renewable sources and energy storages can minimize the operational costs and maximize the system performance. Power converter system with multi-input and integrated structure is capable of processing and managing multiple sources and storages simultaneously, which is being considered as the prospective building blocks of future DC and AC micro-grids. This paper presents two new load sharing methods in dc-dc conversion for multiple inputs. First, a detailed survey will be conducted to show the status of load sharing methods in dc-dc power conversion; new requirements for load sharing operation in a DC micro-grid environment will be proposed; a cascade and a parallel organized load sharing control system proposed by the authors are presented and discussed for a multi-source/storage hybrid power system; both simulation and experimental results will be presented in the last section to prove the effectiveness of the new load sharing methods.