Research On The Interface Techniques Of Piezoelectric Energy Harvesting System

In order to replace the lithium battery-powered methods currently used in wireless systems andportable electronic devices, energy harvesting technology has been developing rapidly in the recentyears. Piezoelectric energy harvesting system has received widespread attention by scholars bothhome and abroad for its small size, high output powers, no electromagnetic interference and easilyminiaturized. This paper focus on the interface circuits of piezoelectric energy harvesting system. Themain contents and results are as follows:1. The electromechanical model is developed from the second class piezoelectric equation and"quality+spring+damping” vibration model. The mechanism of energy harvesting system and thesystem parameters which influence the harvested power are analyzed in principle.2. A new efficient energy harvesting interface circuit, named SCEI (Synchronous ChargeExtraction and Inversion) is designed. Then its control process is detailed and the theoreticalharvested power is derived considering the constant displacement amplitude and force amplituderespectively. The harvesting power as a function of switch on-time is analyzed. The entire workprocess of SCEI interface is simulated in electronic simulation software Multisim.3. The theoretical harvested powers as a function of the load and electromechanical couplingcoefficient of Standard, SECE, Parallel-SSHI and Series-SSHI interfaces are derived considering theconstant displacement amplitude and force amplitude respectively. Then a comparison between theSCEI and four classical interfaces are given. The comparison results show that the harvested power ofSCEI technique, which is not influenced by load, is larger than the maximum harvested power ofParallel-SSHI when ignoring the buck-boost converter’s efficiency under the circumstance of constantdisplacement amplitude. In the circumstance of constant driving force amplitude, the harvested powerfirst increases and then decreases with the increase of the system electromechanical couplingcoefficients, showing similar performance with SECE Interface.4. A piezoelectric circuit simulation model is established depending on the nature ofpiezoelectric material. The control process and harvested power of Standard, SECE, Parallel-SSHI,Series-SSHI and SCEI are simulated in Multisim.5. The experimental measurements are carried out to validate the harvested powers of Standard,SECE, Parallel-SSHI, Series-SSHI and SCEI techniques when the generator is driven with constantdisplacement amplitude. Then a comparison of these five circuits is illustrated. The results show thatthe harvested power of SCEI interface is slightly less than the maximum harvested power ofParallel-SSHI interface when buck-boost converter conversion efficiency is0.65. The change of theload has little effect on its harvested power.