Current Source Strategy for Energy Injection from a CapMix Cell

Abstract

Circulation of salty and fresh water through the electrodes of a deionization cell produces a voltage between the electrodes caused by the Capacitive Donnan Potential (CDP). The voltage so generated is very low (100 mV), but this work demonstrates that it is possible to develop a power converter suitable to inject this energy into the grid or into energy storage systems; this is a relevant aspect of this paper, for most works in the literature simply dissipate this energy over a resistor. To increase the input voltage, a stack of electrodes is connected in series. A bridgeless rectifier that uses a dual buck–boost converter to operate with both the positive and negative cycles is used to extract the energy from the cell. The topology chosen, which is operated as a current source, can work at extremely low voltage levels and provide power factor correction. After this stage, an H-bridge inverter can be included to inject the energy into the AC grid. The whole system implements a hysteresis control system using the current through the inductor of the power converter as control variable. This paper investigates the influence of such current on the efficiency of the total system.