Active Interface for Piezoelectric Harvesters Based on Multi-Variable Maximum Power Point Tracking

An active electronic interface for maximizing the power extracted from a resonant piezoelectric vibration harvester by means of a multi-variable Maximum Power Point Tracking (MPPT) technique is presented. The input voltage of the electronic interface is dynamically adapted in order to ensure that the maximum power is extracted even if the vibration characteristics change with time. The digital control unit updates the amplitude, the phase and the frequency of such an input voltage without requiring the high-frequency sampling and elaboration of the harvester current or voltage. The unit exploits only the information on the vibration frequency kept from a small piezo accelerometer and a low-frequency sampling of the DC current. The implemented algorithm is as simple as the widespread Perturb & Observe algorithm, but it allows the extraction of significantly more power from the harvester. The power increase for a piezoelectric harvester with the proposed electronic interface is investigated both theoretically and experimentally. By using a commercially available piezoelectric harvester, the maximum power tracking performance of the proposed active interface is experimentally compared with that of a usual AC/DC converter with Perturb & Observe MPPT control.