A grid-interfaced test system for modeling of NiMH batteries in a battery-buffered smart load application

Testing and modeling of batteries are essential to evaluate the performance and effectiveness of battery energy storage systems (BESS) in power system applications. The procedure of extraction and experimental verification of any battery model require a reliable and efficient testing system. In this paper, a programmable grid-interfaced battery test system for battery modeling in a frequency-controlled battery-buffered smart load application is proposed. The testbed is based on the same smart load experimental system which consists of a single phase bidirectional AC-DC converter, a DC-link, and a bidirectional DC-DC converter. The AC-DC converter is designed to control a bidirectional power flow between the AC-line and the DC-link. Therefore, the energy can be controlled effectively flowing between the battery and the power line during charge and discharge without significant power losses. This design realizes an energy-conserving electronic load by supplying the battery energy to the grid instead of dissipating it during discharge. To verify the functionality of the developed test system, 3Ah, 1.2V NiMH batteries were tested for a Thevenin-based model identification. Then, a simulation of the identified model was implemented in MATLAB/Simulink to validate the model under the smart load charging and discharging conditions.