Dielectric elastomer transducers (DETs) are commonly modeled by lumped-element models (LEMs), however such models do not capture the cutoff behavior that manifests at relatively low frequencies due to the high resistivity of the stretchable electrodes. Moreover, the contribution of the electrodes into the lumped series resistance is not accurately known. The aim of this work is to define the accuracy and frequency limits of the LEM and to derive the exact values of its lumped components. This is achieved by developing a detailed three-dimensional distributed-element model (DEM) of the transducer structure. Based thereon, analytical expressions are developed for the LEM components and limits are explored. Through numerical evaluation of the DEM it is found that only two-third of the single-polarity electrode resistance contributes to the lumped series resistance, which is three times lower than predicted by existing models. Comparison between the LEM and DEM further shows that the LEM is adequate for frequencies significantly below the cutoff frequency. Thereafter, capacitance and resistance fall off as a result of signal propagation limitations. This has been experimentally verified. The developed DEM and established validity range of the simple LEM allows for more accurate sensors and better optimized transducers designs, with up to three times less electrode material.

This paper presents an investigation on modulation modes for dual active bridge modules stacked in a 10-kV input parallel output series converter for energy extraction in dielectric electroactive polymer (DEAP) wave energy converters. The converter requirements for energy harvesting with DEAPs are derived, and the operating areas and limitations of each modulation mode are compared. A hybrid modulation strategy consisting of several variable frequency modulation modes is proposed, which is capable of operating over a wide voltage and current range at high-efficiency levels as required by the DEAP harvesting cycles. Through loss calculations using an experimentally validated loss model and by including both material and converter losses in the harvesting cycle, it is shown that the hybrid modulation method increases the energy output of low-strain cycles by 25%.

This paper presents a modulation strategy for wide voltage output in a bidirectional modular multilevel dc-dc power electronic converter for wave energy extraction using Electro Active Polymer Wave Energy Converters (EAPWECs). The chosen electrical power converter uses a 10 kV, low current bidirectional dc-dc modular multilevel topology with Dual Active Bridges (DABs) as a basis for each module. This paper proposes a modulation method consisting of several variable frequency DAB modulation modes and explains their operating areas and limitations. Through a simulation model it is shown how the control for the multilevel converter is implemented. Finally, loss estimation is performed using the developed loss model, which was previously validated on an experimental setup.

This paper introduces a separate control method for modules of the bidirectional modular multilevel dc-dc power converter in order to improve overall converter efficiency. The proposed multilevel power converter topology is based on a Dual Active Bridge (DAB) converter as elementary electrical building block - module. Using efficiency curves it is determined how the modules should be separately controlled in order to decrease the total power converter losses, thus optimizing the total efficiency. The bidirectional modular multilevel dc-dc converter finds its application in energy extraction from Electro Active Polymer Wave Energy Converters (EAPWECs). It is shown that achieved power converter efficiency improvements have significant impact on the produced power in EAPWEC systems. Efficiencies of the power converter are modeled and verified with experimental measurements on the DAB module to support loss model.

Dielectric elastomers used as generators have received considerable attention lately and several prototypes were built to demonstrate the process. The aim of the paper is to show how an innovative energy harvesting cycle can be realized to use the DEs as an efficient generator. It investigates the effects of (dis)charging instants, the current amplitude and how the parasitics of the material influences the energy gain and show what kind of trade-offs can be reached by selecting parameters carefully. Also an EAP emulator is introduced: it is able to implement a variable capacitor by a controllable power supply. It can be used for evaluating PTOs, tests, measurements; without the complexity, vulnerability and high price of the elastomer.

From an electrical point of view dielectric elastomers are variable capacitors, which are frequently used as generators. The focus of this paper is to show, how the maximum energy gain can be realized by realizing an innovative current waveform to charge and discharge the polymer. Several energy harvesting cycles are introduced and their energy output compared. The most promising cycle has been optimized to increase its production while taking several limiting factors into account.

Dielectric Elastomers are well known for there performance as actuators, but these materials can be used effectively as generators. Research on this field have received considerable attention lately, several prototypes were built like wavepower and human kinetic power generators. The focus of this paper is how the dielectric elastomer can be used as generator. The paper presents a dynamic model to calculate the capacitance of the electroactive polymer according to the external loading and investigates and compares several energy harvesting cycles based on the energy gain.