Power Electronics Controls-Battery life Extension Method (GR-18-05)

Principal Investigators: Dr. Andrea Benigni, Dr. Herb Ginn, Dr. Michelle Hunt

Energy storage is an enabling technology for both the integration of renewables and for the painless adoption of time or peak based pricing for energy. Unfortunately, batteries are damaged by many of the loading patterns that come from the variability of renewable resources and from the variability of the energy consumption patterns. Super capacitors do not take damage from that type of high frequency, high C rate usage pattern but are unfortunately much more expensive per kWh.

Batteries can also be damaged by slower load patterns that come with the need to time shift or reduce the peak usage. However, absorbing that damage can be economically efficient depending on the price signals. Minimizing the damage to the battery to only what is necessary for the bulk storage of energy for dealing with the cyclical nature of the availability of the renewable resources and what is economically necessary for time shifting loads and minimizing the peak will make energy storage less expensive.

The idea for this project is design battery life extension method made of two parts. The first part is a DC/DC converter controlling power flow into and out of a super capacitor that will parallel to a battery without a power electronics converter. This part is to limit two factors in battery aging: rapid changes in current and extremely high charge and discharge currents. The second part is control of a slow changing power source. This allows the battery to be controlled to near its optimal state of charge. A pictorial representation of the envisioned system is reported in figure 1.

Figure 1 Envisioned Scenario

This project would then, both in simulation and in hardware test the difference in cycle life and total kWh charged with and without the battery life extension method.

For the end use, the method would be controlling the DC/DC converter that acts with the super capacitor, the inverter that acts with the generator as well as the generator control.