Parameter-Independent Control for Battery Chargers Based on Virtual Impedance Emulation

Effective battery voltage regulation is fundamental to extend battery lifetime and to avoid overvoltage. However, the design of this regulation is complicated due to the wide battery impedance range, which, when dealing with universal chargers, is dependent not only on the operating point but also on the battery type and size. This paper first shows how the voltage response becomes highly variable when designing the controller as described in the literature. Then, it proposes to emulate virtual impedance in parallel with the battery, making it possible to achieve a voltage control which is independent of battery characteristics. Experimental results are carried out for a new lithium-ion battery with 25 mΩ impedance and an overused lead-acid battery with 400 mΩ impedance. For this large impedance variation, the results evidence the problems of the conventional control and validate the superior performance of the proposed control.