Quattrocchi Antonino, Montanini Roberto, De Caro Salvatore, Panarello Saverio, Scimone Tommaso, Foti Salvatore, Testa Antonio
Department of Engineering, University of Messina, 98166 Messina, Italy.
Sensors (Basel). 2020 Oct 16;20(20):5862. doi: 10.3390/s20205862.
Piezoelectric energy harvesters (PEHs) are a reduced, but fundamental, source of power for embedded, remote, and no-grid connected electrical systems. Some key limits, such as low power density, poor conversion efficiency, high internal impedance, and AC output, can be partially overcome by matching their internal electrical impedance to that of the applied resistance load. However, the applied resistance load can vary significantly in time, since it depends on the vibration frequency and the working temperature. Hence, a real-time tracking of the applied impedance load should be done to always harvest the maximum energy from the PEH. This paper faces the above problem by presenting an active control able to track and follow in time the optimal working point of a PEH. It exploits a non-conventional AC-DC converter, which integrates a single-stage DC-DC Zeta converter and a full-bridge active rectifier, controlled by a dedicated algorithm based on pulse-width modulation (PWM) with maximum power point tracking (MPPT). A prototype of the proposed converter, based on discrete components, was created and experimentally tested by applying a sudden variation of the resistance load, aimed to emulate a change in the excitation frequency from 30 to 70 Hz and a change in the operating temperature from 25 to 50 °C. Results showed the effectiveness of the proposed approach, which allowed to match the optimal load after 0.38 s for a ΔR of 47 kΩ and after 0.15 s for a ΔR of 18 kΩ.
压电能量采集器（PEH）是嵌入式、远程和无电网连接电气系统的一种功率较低但至关重要的电源。一些关键限制，如低功率密度、低转换效率、高内阻和交流输出，可以通过使它们的内部电阻抗与所施加的电阻负载的电阻抗匹配来部分克服。然而，所施加的电阻负载会随时间显著变化，因为它取决于振动频率和工作温度。因此，应该实时跟踪所施加的阻抗负载，以便始终从PEH采集到最大能量。本文通过提出一种能够实时跟踪和跟随PEH最佳工作点的有源控制来解决上述问题。它采用了一种非常规的AC-DC转换器，该转换器集成了一个单级DC-DC Zeta转换器和一个全桥有源整流器，并由基于脉宽调制（PWM）和最大功率点跟踪（MPPT）的专用算法控制。基于分立元件创建了所提出转换器的原型，并通过施加电阻负载的突然变化进行了实验测试，旨在模拟激励频率从30 Hz变化到70 Hz以及工作温度从25°C变化到50°C的情况。结果表明了所提出方法的有效性，对于47 kΩ的ΔR，在0.38 s后能够匹配最佳负载；对于18 kΩ的ΔR，在0.15 s后能够匹配最佳负载。
