直驱式永磁风力发电机软并网与功率调节的控制集成

为实现直驱式永磁同步风力发电机无冲击并网与风能最大跟踪控制, 设计了一种软并网与功率调节一体化的控制集成装置. 基于广义功角特性, 提出了一种对逆变器输出功率进行直接控制, 从而实现最大风能跟踪的控制策略. 新的控制策略可使发电机的转速按所期待的动态运动, 因而具有良好的静态与动态性能. 另外, 该控制律中对电机参数具有很强的鲁棒性, 因而该控制器能适应各种不同参数的同步风力发电机, 成为同步风力发电并网与功率调节的独立装置.     

An electromagnetic, vibration-powered generator for intelligent sensor systems

This paper describes the design of miniature generators capable of converting ambient vibration energy into electrical energy for use in powering intelligent sensor systems. Such a device acts as the power supply of a microsystem which can be used in inaccessible areas where wires can not be practically attached to provide power or transmit sensor data. Two prototypes of miniature generator are described and experimental results presented. Prototype A is based around two magnets coupled to a coil attached to a cantilever; prototype B is based around four magnets.

For prototype A, experimental results are given for its resonant frequency and its open circuit and loaded output as a function of vibration amplitude. For prototype B, experimental results are given for the generator’s Q factor in air and vacuum, its output voltage as a function of vibration amplitude as well as its magnetic field strength. This generator has been tested on a car engine and shown to produce a peak power of 3.9 mW with an average power of 157 μW.     

Electromagnetic generator for harvesting energy from human motion

This paper presents an electromagnetic based generator which is suitable for supplying generating power from human body motion and has application in providing energy for body worn sensors or electronics devices. A prototype generator has been built and tested both by a shaker at resonance condition and also by human body motion during walking and slow running. The experimental results will show that the prototype could generate 300 μW to 2.5 mW power from human body motion. The measured results are analyzed and compared with the theoretical model.     

Micromachined PZT cantilever based on SOI structure for low frequency vibration energy harvesting

A PZT piezoelectric cantilever with a micromachined Si proof mass is designed and fabricated for a low frequency vibration energy harvesting application. The SiO₂ layer in the SOI wafer promotes accurate control of the silicon thickness that is used as a supporting layer in the cantilever beam structure. The entire effective volume of the fabricated device is about 0.7690 mm³. When excited at 0.75g (g = 9.81 m/s²) acceleration amplitude at its resonant frequency of 183.8 Hz, the AC output measured across a resistive load of 16 kΩ connecting to the device in parallel has an amplitude of 101 mV. The average power and power density determined by the same measurement conditions are, respectively, 0.32 μW and 416 μW/cm³.     

An efficient electromagnetic power harvesting device for low-frequency applications

Mechanical energy in the form of low frequency vibrations (1-100 Hz) can be commonly available and this energy type can be advantageously converted to electrical one by exploiting energy harvesting techniques. At the same time, in many applications, the devices that convert low frequency mechanical energy to electrical one should have a small size. An electromechanical power generator is proposed for converting mechanical energy in the form of low-frequency vibrations, available in the measurement environment, into electrical energy. The intended applications for the proposed electromechanical power generator, described in this paper, are for examples mechanical systems with low frequency vibrations (1-100 Hz). The operating principle is based on the relative movement of a planar inductor with respect to permanent magnets. The generator implements a novel configuration of magnets that is proposed and analyzed with the aim to improve the conversion efficiency, increasing the spatial variation of magnetic flux. Furthermore, the generator uses polymeric material as resonators, which have low-frequency mechanical resonances due to the low Young's modulus of the materials by which they are made. The different materials, with which the suspensions for the planar inductor were made, have allowed to compare different behaviors of the resonators: linear and nonlinear. The experimental results have shown, for a linear resonator, a vibration frequency of about 100 Hz with generated powers of about 290 μW and a harvesting effectiveness of 0.5%, while, for the polymeric resonator made by Latex, the vibration frequency is around 40 Hz with a maximum power of 153 μW and a harvesting effectiveness of 3.3%. The proposed configuration can be adopted for its low profile, modularity and low-frequency vibrations in many applications from industrial to medical.     

Synchronized switch harvesting applied to self-powered smart systems: Piezoactive microgenerators for autonomous wireless receivers

This paper introduces the conceptual architecture of a fully integrated, truly self-powered structural health monitoring (SHM) scheme. The challenge here is to power an array of numerous distributed actuators and sensors as well as wireless data transmission modules without recurring to heavy and costly wiring. Based on microgenerators which directly convert ambient mechanical energy into electrical energy, using the synchronized switch harvesting (SSH) method, the proposed solution allows avoiding the periodic replacement or reloading of batteries. This addresses environmental and economic issues at the same time, knowing that such elements are heavy, polluting and might be installed in rather inaccessible locations. Indeed, especially in airborne structures saving weight and maintenance cost is of priority importance.Previous work showed that such microgenerators provide a stand-alone power source, whose performances meet the requirements of autonomous wireless transmitters (AWTs) that comprise an acoustic Lamb wave's actuator and a radio frequency (RF) emitter (D. Guyomar, Y. Jayet, L. Petit, E. Lefeuvre, T. Monnier, C. Richard, M. Lallart, Synchronized switch harvesting applied to self-powered smart systems: Piezoactive microgenerators for autonomous wireless transmitters, Sens Actuators A: Phys. 138 (1) (2007) 151–160, doi:10.1016/j.sna.2007.04.009). Following this work, the present contribution presents a further step towards the integration of the SHM technique. It shows the ability of our microgenerators to provide enough energy to give logical autonomy to each self-powered sensing node, named autonomous wireless receiver (AWR), and thus to provide some local (decentralized) pre-processing ability to the SHM system.A preliminary design of the device using off-the-shelf electronics and surface mounted piezoelectric patches will be presented. Since the existence of a positive energy balance between the harvesting capabilities of the SSH technique and the energy requirements of the proposed device will be proved, the system formed by the combination of the AWR with the previously developed AWT, is a proof of concept of truly self-powered smart systems for damage detection in simple structures, setting apart application-specific optimization or miniaturization concerns that will be addressed in future works.     

A hierarchical optimization model for energy data flow in smart grid power systems

Environmental concerns and high prices of fossil fuels increase the feasibility of using renewable energy sources in smart grid. Smart grid technologies are currently being developed to provide efficient and clean power systems. Communication in smart grid allows different components to collaborate and exchange information. Traditionally, the utility company uses a central management unit to schedule energy generation, distribution, and consumption. Using centralized management in a very large scale smart grid forms a single point of failure and leads to serious scalability issues in terms of information delivery and processing. In this paper, a three-level hierarchical optimization approach is proposed to solve scalability, computational overhead, and minimize daily electricity cost through maximizing the used percentage of renewable energy. At level one, a single home or a group of homes are combined to form an optimized power entity (OPE) that satisfies its load demand from its own renewable energy sources (RESs). At level two, a group of OPEs satisfies energy requirements of all OPEs within the group. At level three, excess in renewable energy from different groups along with the energy from the grid is used to fulfill unsatisfied demands and the remaining energy are sent to storage devices.