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A d15 mode piezoelectric energy harvester (PEH) with two PZT-51 elements in series connection (SC), in which the elements are arranged along the width direction, was fabricated, and it is compared with the traditional d15 mode PEH with a single PZT-51 element (SPEH) to discuss the output peak-to-peak voltage (Up−p). The energy harvesting performances of PEHSC are modeled by combining the single degree of freedom model and the electrical model with the piezoelectric constitutive equation of the d15 mode. The energy harvesting performances of PEHSC were systematically measured at various frequencies and load resistances, and Up−p and output power are 12.4 V and 8.7 μW at a load resistance of 2.2 MΩ and resonance frequency of 73 Hz. The experimental Up−p of PEHSC and SPEH are 25.4 and 15.6 V at the resonance frequencies under open circuit condition, and this indicates that the SC structure can improve the energy harvesting performance for d15 mode PEH. The experimental Up−p, output power and the transient voltage–time curve of PEHSC are in agreement with the results of finite element numerical solutions and theoretical modeling, so they are acceptable. The d15 mode and SC structure could potentially improve the energy harvesting performance of PEHs.

Considering the buffer layer and electrodes, we set up a piezoelectric multilayered cantilever model to evaluate the dynamic performance of the micro-cantilevered piezo-actuator (MCPA) based on Euler-Bernoulli beam theory without considering the residual stresses on the MCPA. Adopting the material and geometric parameters of the previous MCPAs with the different lengths, the first-mode resonance frequency-beam length, the tip deflection-voltage and harmonic response curves are simulated by using the traditional and proposed models, and the results based on the proposed model are much closer to the experimental and finite element simulation results than those based on the traditional model, indicating that the proposed model is valid for evaluating the actuation performances of the MCPA. The effect of the mechanical damping and bending stiffness on the actuation performance of the MCPA is also discussed. Using the proposed model, the dependences of the first-mode resonance frequency and tip deflection of the MCPA on non-piezoelectric layer thicknesses are analyzed at the certain driving voltage. The above-mentioned methods and conclusions can be used for the structure optimized design and performance improvement of MCPAs.

Random variation of grid-connected wind power can cause stochastic variation of the power system operating point. This paper proposes a new scheme to design an adaptive damping controller by tracking the variation of system operating points and updating the controller’s functions to achieve a robust damping control effect. Firstly, the operating space is classified into different modes according to the classification of wind power outputs. Multiple power system stabilizers (PSSs) are then designed. Secondly, the method of optimal classification and regression decision tree (CART) is utilized for classifying subspaces of system operating point and it is proposed that the on-line measurements from wide area measurement system (WAMS) are used for tracking the dynamic behaviors of stochastic drifting point and thus guide the updating of appropriate PSSs be switched on adaptively. A 16-generator-68-bus power system integrated with wind power is presented as a test system to demonstrate that the adaptive control scheme by use of the CART can damp multi-mode oscillations effectively when the wind power output changes.