Modeling and Simulation of AC-DC-AC Converter System for MW-Level Direct-Drive Wind Turbine grid Interface

As global energy crisis increases, especially in the electricity energy market. It is quite necessary to exploit new ways of capturing energy. Wind turbines are more and more welcomed as a new method of obtaining electricity for it is clear energy and technology for it has been greatly developed. The electricity obtained from wind generator must be compatible with the grid. Thus there must be electromechanical converter unit to accomplish the transformation. The wind turbine directly connected to a generator is referred to as the direct-drive concept. One advantage of the direct-drive concept is the removal of the losses associated to the gearbox. Power AC-DC-AC converter system is preferred to transform the energy compatible to the grid in direct-drive wind turbines application. This paper is about modeling and simulation of power AC-DC-AC converter including its control strategy for MW wind turbine grid interface, which can be separated into two units: a diode bridge rectifier with a multiple boost DC-DC converter and a dual IGBT inverter (VSI). Basic principle of wind turbine power converter is that the rectifier transforms the variable frequency and variable voltage electricity into DC power, then the multiple boost DC-DC converter arises the DC voltage level and keeps it nearly constant over whole wind speed to satisfy the following dual VSI. According to modeling and simulation of power AC-DC-AC converter for MW wind turbine grid interface, with analysis of several important waveforms, it is verified that the power AC-DC-AC converter with its control strategy works well and can efficiently convert electricity generated by wind generator and transform it to grid successfully