Multilevel high voltage converter driving dielectric elastomer generators

Electro Active Polymers are highly suitable as generators to convert mechanical strain energy into electrical energy, because of the high energy density. To harvest energy, the polymer is stretched by an external force to increase the capacitance of the variable capacitor. After applying charges at the maximum stretch until a predetermined allowable field strength is reached, the external force is reduced and the polymer relaxes. During relaxation a considerable amount of the strain energy is converted into electric field energy and at the end of relaxation the charges can be harvested at a higher voltage compared to the initial voltage level. For the electrical control, a special high voltage power-electronics is necessary driving the generators at high voltages and typically low currents. This is realized with a multilevel converter topology, which provides the required bidirectional energy flow and a high efficiency. A model of the converter is derived and a high dynamic voltage controller with underlying current controller is designed. Finally measurement results are presented, demonstrating the converters' ability to drive dielectric elastomer generators for energy harvesting.