Open loop wind turbine emulator

A new wind turbine emulator (WTE) is presented, which is able to simulate the turbine power curves without using a closed loop control system. The state of the art emulators use DC or AC motors, closed loop controlled by processors with the turbine power curves recorded. The presented emulator has a DC voltage source, a power resistor and a DC motor with independent excitation. The motor power curve has a shape similar to a wind turbine power curve for a given wind speed; the wind speed variations can be emulated by the variations of the DC voltage source. The open loop emulator is completely different and new, because it works in open loop and does not require the presence of a processor.The following elements are included: the theoretical foundations of the emulator, the emulator power curves adjustment procedure to simulate a commercial wind turbine and the experimental tests.     

Effect of SnO2 intermediate layer on performance of Ti/SnO2/MnO2 electrode during electrolytic-manganese process

SnO₂ intermediate layers were coated on the titanium (Ti) substrate by thermal decomposition. Scanning electron microscope (SEM) and X-ray diffraction (XRD) results show that uniform SnO₂ intermediate layers with rutile crystal structure were successfully achieved. According to the results of linear sweep voltammetry (LSV), oxygen evolution potential (OEP) of the Ti/SnO₂/MnO₂ electrodes decreases with increasing SnO₂ content, indicating that the electro-catalytic oxidation activity of the electrode increases. Accelerated service life tests results demonstrate that SnO₂ intermediate layer can improve the service life of the Ti/SnO₂/MnO₂ electrode. As the content of SnO₂ intermediate layer increases, the cell voltage and the energy consumption decrease apparently.     

10000 m~3/h制氧机产能下降原因分析与处理措施

分析了10000 m3/h制氧机产能和产况下降的原因,并提出相应的处理措施,对制氧机的安全稳定生产起到了一定的实际指导作用。     

Single‐Stage ZVS‐PWM AC‐AC Power Converter Using All SiC Power Module for High‐Frequency Induction Heating Applications

This paper presents a novel prototype of a single‐stage zero voltage soft‐switching pulse‐width modulation ‐controlled ac‐ac converter with a silicon carbide (SiC)‐MOSFET/SiC‐SBD power module for high‐frequency (HF) induction heating (IH) applications. The newly developed ac‐ac converter can achieve higher efficiency than a Si‐IGBT/Si‐PN diode power module‐based prototype due to a low ON‐resistance of SiC‐MOSFET and a low forward voltage of SiC‐SBD under the condition of HF switching. The performances of the new prototype converter are evaluated by experiment with a single‐phase IH utensil of ferromagnetic stainless metal, after which the high‐efficiency and low switching noise characteristics due to the all SiC power module are actually demonstrated.     

A conceptual spacecraft radioisotope thermoelectric and heating unit (RTHU)

Spacecraft venturing to the outer planets and beyond—or onto the planetary surface where available solar energy is reduced—benefit from the longevity and consistency of electrical and thermal energy derived from radioisotope energy sources. A review of likely mission requirements and concept studies of small electrical generating units (<10 W_e) reveals a potential opportunity for a unit with an electrical output of around 1 W_e that can also supply some heat to the spacecraft to aid thermal control: a radioisotope thermoelectric and heating unit. This power requirement cannot be achieved with current US space‐qualified modular radioisotope fuel assemblies. Additionally, new European programmes consider ²⁴¹Am fuel to be much more cost effective than ²³⁸Pu. Taken together, these factors provide the rationale for taking a relatively ‘clean‐sheet’ approach to design of a radioisotope thermoelectric and heating unit fuelled with ²⁴¹Am. In this paper, initial requirements and performance targets for such a unit are developed, a simple concept design and thermal model is presented and the performance and mass are estimated. The results suggest that units generating 1–2 W_e may achieve a specific power of around 0.7–0.9 W_e kg^?1 without the thermal inputs to spacecraft becoming impractically large. Such units can use a bismuth telluride thermoelectric material, which is commercially applied in terrestrial applications and is therefore likely to incur lower cost and development risk than more specialised compounds. This study may form the basis of a more detailed design effort. Copyright © 2011 John Wiley & Sons, Ltd.     

基于特高压交流变电站检修典型问题分析

本文在对于特高压交流变电站检修典型问题演技中,主要对于轮停检修感应电压问题及测量误差等问题进行分析,希望能够为其他特高压交流变电站检修工作提供一定帮助.     

Power conversion system for high altitude wind power generation with medium voltage AC transmission

High Altitude Wind Power (HAWP) generating system provides clean energy at low cost and high capacity factor due to reduced size of the turbine and high speed streamlined wind at high altitude. An air-borne wind turbine (AWT) at high altitude extracts kinetic energy from wind using buoyancy provided by the blimp/aerostat. The generated electrical power is then transmitted to the ground based station (without any power conditioning) using the transmission lines (tether). The power conversion system (PCS) for harnessing HAWP is proposed in this paper. The proposed PCS consists of a three-level neutral point clamped (NPC) rectifier, a three-level NPC DC–DC converter followed by a two-level inverter. Modelling, design and control of the PCS are presented and discussed. The PCS provides generation side maximum power-point tracking (MPPT) using sensorless optimal torque control technique. The DC–DC converter provides electrical isolation as well as voltage step-down functions. A modified proportional resonant (PR) control which can selectively eliminate lower order current harmonics of the grid-connected inverter is also presented. The proposed control scheme of the PCS is evaluated through simulation studies using software programs like PSIM and MATLAB. A scaled-down 1 kW laboratory prototype of the complete PCS is designed, built and tested. The experimental test results obtained validate the proposed control scheme for efficient power generation from high altitude wind and interface to the grid/load.     

PSO-based MPPT control of wind-driven Self-Excited Induction Generator for pumping system

In recent years, much research has been done to improve the performance of a wind energy conversion system at various wind speeds using Maximum Power Point Tracking (MPPT) algorithms to find an efficient production of peak energy.In most cases, the MPPT techniques used to maximize the turbines power coefficient neglect the effect of losses generated by the system components, which can shift the true optimal operating point of the wind turbine. Furthermore, conventional MPPT methods such as Perturbation and Observation (P&O) and Incremental of Conductance (IncCond), need to sense both the rotor speed and the power of the wind turbine. In addition, other methods such as Fuzzy Logic and neural networks based on MPPT algorithms are proposed but these methods require knowledge of the wind speed and system parameters for the training phase.In this context, a new MPPT technique is being proposed in this paper, based on Particle Swarm Optimization (PSO) for a standalone Self-Excited Induction Generator (SEIG) operating at variable wind speed and supplying an induction motor coupled to a centrifugal pump.