In piezoelectric energy harvesting (PEH), with the use of the technique named synchronized switch harvesting on inductor (SSHI), the harvesting efficiency can be greatly enhanced. Furthermore, the introduction of its self-powered feature makes this technique more applicable for stand-alone systems. In this paper, a modified circuit and an improved analysis for the self-powered SSHI (SP-SSHI) are proposed. With the modified circuit, direct peak detection and better isolation among different units within the circuit are achieved, both of which result in the further removal on the dissipative components. In the improved analysis, details in the open circuit voltage, switching phase lag, and intermediate voltages among different phases are discussed, all of which lead to a better understanding on the working principle of SP-SSHI. The total power dissipation from the piezoelectric source is also investigated. It is of concern but has not been considered in the previous literatures. Both analyses and experiments show that, in terms of the harvested power, the higher the excitation level, the closer between SP-SSHI and ideal (externally powered) SSHI; at the same time, the more beneficial the adoption of SP-SSHI treatment in PEH, compared to the standard energy harvesting (SEH) technique. Under the four excitation levels investigated, the SP-SSHI can harvest up to 200% more power than the SEH interface circuit.

Improved Design and Analysis of Self-Powered Synchronized Switch Interface Circuit for Piezoelectric Energy Harvesting Systems

In a piezoelectric energy harvesting (PEH) system, the dynamics and harvested power vary with different interface circuits connected. The impedance matching theory was regarded as the theoretical base for the harvested power optimization in the harmonically excited PEH systems. The previous literature started the impedance analyses based on the proposition that the harvested power is maximized when the output impedance of the piezoelectric transducer is matched by the input impedance of the harvesting circuit. Yet, retrospecting to the origin of the impedance matching theory, a philosophical problem is found with this proposition. Moreover, the definition, constraint, and composition of the equivalent impedance in the real (nonlinear) harvesting circuits were not clear as well. This paper clarifies these concepts and provides the impedance modeling and analysis for the PEH systems with different interface circuits, including standard energy harvesting, parallel synchronized switch harvesting on inductor, and series synchronized switch harvesting on inductor. The equivalent impedance network and corresponding mechanical schematics of a general PEH system are proposed. The difference between the PEH equivalent impedance network and the conventional impedance network is discussed. The harvested power is investigated based on this impedance analysis. The analytical results show good agreement with the experiments carried out on a base excited PEH device.

Impedance Modeling and Analysis for Piezoelectric Energy Harvesting Systems

Scavenging energy from ultra-low frequency mechanical excitations through a bi-directional hybrid energy harvester

Conventional vibration energy harvesters have been usually studied as single-degree-of-freedom models. The fact that such harvesters are only efficient near sole resonance limits their applicabilit...

/pdf/a-multiple-degree-of-freedom-piezoelectric-energy-harvesting-1ptiqyx5rv.pdf

A multiple-degree-of-freedom piezoelectric energy harvesting model:

This article presents a novel nonlinear energy extraction technique for piezoelectric vibration energy harvesting. The proposed approach is an improvement of the previous technique, “synchronous el...

Piezoelectric vibration energy harvesting by optimized synchronous electric charge extraction

SSHI (synchronized switch harvesting on inductor) techniques have been demonstrated to be capable of boosting power in vibration-based piezoelectric energy harvesters. However, the effect of frequency deviation from resonance on the electrical response of an SSHI system has not been taken into account from the original analysis. Here an improved analysis accounting for such an effect is proposed to investigate the electrical behavior of a series-SSHI system. The analytic expression of harvested power is proposed and validated numerically. Its performance evaluation is carried out and compared with the piezoelectric systems using either the standard or parallel-SSHI electronic interfaces. The result shows that the electrical response of an ideal series-SSHI system is in sharp contrast to that of an ideal parallel-SSHI system. The former is similar to a strongly coupled electromechanical standard system operated at the open circuit resonance, while the latter is analogous to that operated at the short circuit resonance with different magnitudes of matching impedance. In addition, the performance degradation due to non-ideal voltage inversion is also discussed. It shows that a series-SSHI system avails against the standard technique in the case of medium coupling, since its peak power is close to the ideal optimal power and the reduction in power is less sensitive to frequency deviation. However, the consideration of inevitable diode loss in practical devices favors the parallel-SSHI technique, since the frequency-insensitive feature is much more pronounced in parallel-SSHI systems than in series-SSHI systems.

/pdf/revisit-of-series-sshi-with-comparisons-to-other-interfacing-1owgz95iyw.pdf

Revisit of series-SSHI with comparisons to other interfacing circuits in piezoelectric energy harvesting

This paper investigates the electrical response of a series connection of piezoelectric energy harvesters (PEHs) attached to various interface electronics, including standard and parallel-/series-SSHI (synchronized switch harvesting on inductor) circuits. In contrast to the case of parallel connection of multiple oscillators, the system response is determined by the matrix formulation of charging on a capacitance. In addition, the adoption of an equivalent impedance approach shows that the capacitance matrix can be explicitly expressed in terms of the relevant load impedance. A model problem is proposed for performance evaluation of harvested power under different choices of interface circuits. The result demonstrates that the parallel-SSHI array system exhibits higher power output with moderate bandwidth improvement, while the series-SSHI system delivers a pronounced wideband at the cost of peak harvested power. The standard array system shows a mild ability in power harvesting between these two SSHI systems. Finally, comparisons between the series and parallel connection of oscillators are made, showing the striking contrast of these two cases.

/pdf/analysis-of-an-array-of-piezoelectric-energy-harvesters-3lzxx3zuq7.pdf

Analysis of an array of piezoelectric energy harvesters connected in series

This article investigates the electrical response of piezoelectric energy harvesters (PEHs) connected in series. Analytic estimates of harvested power output are proposed for a series PEH array system attached to various energy harvesting circuits, including standard and parallel-/series-SSHI (synchronized switch harvesting on inductor) interfaces. In contrast to the case of parallel connection of multiple oscillators, the results are presented through the matrix formulation of charging on capacitance. Besides, they are validated numerically by standard circuit simulations.Copyright © 2012 by ASME

H C Lin

Papers

Revisit of series-SSHI with comparisons to other interfacing circuits in piezoelectric energy harvesting

Analysis of an array of piezoelectric energy harvesters connected in series

Series Connection of Multiple Piezoelectric Oscillators