Analytical investigation of interleaved input/output parallel DAB converter for grid scale battery storage

Abstract

With the surge of integration of intermittent renewable energy sources into the grid the installation of large scale battery energy storage is rising at a rapid rate to support the power system. The grid scale battery storage needs to be scalable with varying power system requirements. Parallel connected modular dual active bridge (DAB) converter with high frequency transformers interface can facilitate adjustable large power flow for grid scale battery storage. The high gain between LV and HV side can be achieved using isolated high frequency transformers and parallelism of the DAB converter with efficient and smooth bidirectional power transfer capability. In this paper, a generalized interleaving operation (ILO) on both input and output parallel connected DAB (IOPDAB) converter has been proposed for large energy storage capability and to enable improved quality of power flow. The generalized expressions of peak currents, average circulating current and active power flow, has been developed for the IOPDAB converter with n-parallel connected DAB modules. A detailed analytical investigation has been carried out to show the improved currents profile in both input and output sides in the interleaved mode. The operating performance of the IOPDAB converter has been shown using PSCAD/EMTDC software based simulation. The results are verified through laboratory experimental setup with two interleaved I/O parallel DAB using Spartan 3AN FPGA processor as controller. A performance comparison has been done with the non-interleaving operation (NILO) and interleaving operation (ILO) modes, and it is shown that the ILO mode has better performance in terms of efficiency, Input/output ripple current reduction, increased ripple frequency and circulating current minimization.