A Passive Impedance Matching Interface Using a PC Permalloy Coil for Practically Enhanced Piezoelectric Energy Harvester Performance at Low Frequency

Abstract

This paper presents an analytical and experimental study of a passive impedance matching interface based on a large inductive reactance but with a centimeter-scaled size for practically enhanced piezoelectric energy harvester performance at low frequency. Low frequency vibration normally leads to a large capacitive reactance value for small-sized piezoelectric energy harvesters and it is impractical to achieve the maximum power transfer condition by use of a conventional inductor as its volume would be of a few cubic meters. In this paper, PC permalloy material was used to implement a passive impedance matching interface in order to reduce the size of the inductor to a few cubic centimeters as it has a very high initial magnetic permeability of 6 × 10 4 H/m. The implemented interface is capable to practically perform the complex conjugate load matching of a macrofiber composite energy harvester at a frequency ≤10 Hz. The effects of the interface on the voltage, current, and power transferred to resistive loads were examined through comparisons of the results between configurations with and without the interface for applied strain levels and frequencies in the range between 480-1170-με peak-to-peak and 2.5-10 Hz, respectively. An increment of the power around 94.6% was obtained under an excitation of 480 με at 10 Hz in correspondence to an optimal resistive load reduced by over 70%. Compared with the stateof-the-art active impedance matching techniques, which use additional power sources to control the signal generated by piezoelectric energy harvesters, the developed interface is totally passive, easier to be implemented, and can be potentially used for the enhancement of vibration energy harvesting performance.Index Terms-Passive impedance matching, maximum power transfer, inductor circuit, low frequency strain energy harvesting.

Adaptive Maximum Power Point Finding Using Direct V OC/2 Tracking Method With Microwatt Power Consumption for Energy Harvesting

“…A M8528-P2 macro-fiber composite (MFC) piezoelectric transducer bonded on a composite material using epoxy was used as the PEH [14], as illustrated in Fig. 3.…”

“…This is because the reactive component introduced by the intrinsic capacitor of PEHs limits the transferable power to less than the maximum power that PEHs can generate [13]. To achieve absolute maximum power, inductive elements are used to complex conjugate the intrinsic capacitance of the PEHs [14]. However, the hill-climbing or FOCV methods are generally easier to implement as a standalone system because complex conjugate matching generally requires an impractically large sized inductor with inductances of hundreds to kilos of Henries [12], [14].…”

“…To achieve absolute maximum power, inductive elements are used to complex conjugate the intrinsic capacitance of the PEHs [14]. However, the hill-climbing or FOCV methods are generally easier to implement as a standalone system because complex conjugate matching generally requires an impractically large sized inductor with inductances of hundreds to kilos of Henries [12], [14]. Also, complex conjugate matching is load dependent [12], [14] which still requires a circuit to find the MPP of PEHs.…”

Single Piezoelectric Transducer as Strain Sensor and Energy Harvester Using Time-Multiplexing Operation

“…For a 31 operational mode of the MFC, the amplitude of the open-circuit voltage V OC generated can be given by (1) [6]:…”

“…Piezoelectric transducers are widely used as vibration energy harvesters due to their simple structures and high power generation capability [6], [7]. Strain induced on a structure due to vibration can be harvested using flexible patch type piezoelectric transducers such as macro fiber composite (MFC), which is directly bonded onto the host structure to convert the dynamic strain experienced by the host structure into electrical energy [5], [6].…”