25-08-2017, 09:32 PM
An Efficient Experimental Method for High Power Direct Drive Wind Energy Conversion Systems
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INTRODUCTION:
Because of energy shortage and environment pollution, the renewable energy, especially wind energy has become more and more considerable all over the world . Direct drive wind energy conversion systems based on multi pole permanent magnet synchronous generator (PMSG) have some advantages such as no gearbox, high power density, high precision and easy to control . In three different schemes for generator are given in order to
obtain an optimum rating of a PMSG and its power converter.
A detailed comparison of voltage-controlled VSI and current-controlled VSI for distributed generation systems (DGS) applications is presented in [5].In our research project, a 2MW direct drive wind energy conversion system is developed. The traditional way to test the converter is using resistance loads. An efficient experimental method can collect the energy which is wasting on the loads. A large circulating current flows in the converter, but only a small part of the current caused by the losses of the converter flows into the grid. The method can save a lot of energy when the converter is tested and the experiment can be done in the micro grid. The method can test the main stage, drive circuit, protect circuit and some parts of control circuit.
The method has some advantages, such as low power losses and easy to control. Modeling and control scheme of the efficient experimental method are introduced in this paper, as well as the control scheme of the grid side converter. Some differences caused by sinusoidal pulse width modulation (SPWM) and space vector modulation (SVM) in the method have been analyzed. The configurations of the direct drive wind energy conversion systems will be presented in section II. Then the control scheme will be introduced in section III. The comparison between SPWM and SVM using in the method will be introduced in section IV. Simulation and experimental results will be given in section V. The conclusion will be given in section VI.
SYSTEM CONFIGURATIONS:
The structure of direct drive wind energy conversion system is shown in Fig. 1. The system comprises wind turbine, 6 phases PMSG, generator side converter, grids ide converter and LC filter. In this system, the wind turbine captures the wind energy and the generator converts it to the electrical power. Then the power electronics equipment converts it to the high quality power and controls the rotor speed of the generator. (1700 V, 2400 A) form EUPEC corporation is chosen as experimental switch in this system. Two multiple converters which are connected in parallel in the both sides are used in this high power situation. Multiple techniques can reduce the current of each converter. So it can increase the reliability of the converter. At the same time, it can reduce the ripple of the output current. So the output filter inductor L and capacitor C can be reduced observably.
CONTROL SCHEMES:
When the converter is tested, both generator side converter and grid side converter are connected to the same grid, which is shown in Fig. 2. A large circulating current is controlled to flow through each full bridge, but only a small part of the current caused by the losses of the converter flows into the grid The circulating current between each bridge
. CONCLUSION:
This work shows the performance of an efficientexperimental method for high power converter which isused in direct drive wind energy conversion systems. Alarge circulating current flows in the converter, but only asmall part of the current caused by the losses of the
converter flows into the grid. The method can save a lot ofenergy when the converter is tested and the experimentcan be done in the micro grid. The method can test themain stage, drive circuit, protect circuit and some parts ofcontrol circuit. Modeling and control scheme of the
efficient experimental method are introduced in this paper,as well as the control scheme of the grid side converter.Some differences caused by SPWM and SVM in the
method have been analyzed. Simulation and experimentalresults verify the analysis and the conclusion.