Piezoelectric Energy Harvesting Improvement with Complex Conjugate Impedance Matching

One way to enhance the efficiency of energy harvesting systems is complex conjugate impedance matching of its electrical impedance. In Piezoelectric energy Harvesting systems the match is done to increment the energy flows from a vibration energy source to an energy storage electrical circuit. In this article, we compare the power generated using the modulus impedance matching with the power generated using the complex conjugate impedance matching. We present the power ratio between both types of matching methods. The novelty of this article consists of a piezoelectric transducer completely adapted with a complex conjugate impedance match. The theory developed is validated on a commercial piezoelectric transducer QP40w from Midé Technology. The transducer model is first identified by means of a system identification step based on a novel two-port Lumped-Electromechanical Model. The QP40w is complex conjugate matched at its fourth resonant mode increasing the generated power by up to 20% more compared with the modulus match.