Passive automatic maximum wind energy tracking wind power generation system
This paper proposes a novel off-grid wind power generation system, comprising a double-winding permanent magnet synchronous generator, a three-phase controllable saturated reactor, two rectifiers, a battery and a load. The output power curve of the new system keeps in accordance with the maximum output power curve of the wind turbine, which makes the system track maximum wind energy automatically. A 300W prototype was manufactured. Experimental results show that the power output curve of the new system matches with the maximum output power curve of the wind turbine in a wide range of rotational speed. Compared with the traditional system, Wind energy utilization coefficient of the new system is improved greatly.
Modeling of a Converter-Connected Six-Phase Permanent Magnet Synchronous Generator
A MATLAB/Simulink model of a six-phase permanent magnet synchronous generator is established for simulation purpose. The machine is part of a microturbine generation system and is to be connected with a rectifier and a grid-connected inverter. It has two sets of three-phase windings on the stator side, which are shifted by 30 electrical degrees with each other. The internal dynamics of the machine is derived in a stationary d-q frame and then realized in MATLAB/Simulink with a user-definable S-function. The electrical interface with the converter is realized with a combination of voltage measuring units and controlled current sources provided by Simulink itself.
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.