FPGA Based Multiplex PWM Generator for Multilevel Converters Applied Wind Power Generator

Abstract

With the direct-drive wind power system, full-power converter technology has been developed and applied. However, most of wind generators operate at rated voltage of 690 V in wind field at present while direct-drive power system needs the full-scale power converter. For the high-power output, power devices must support higher current. Before the breakthrough of the present level of the current rating, multi converters can meet the low-voltage, high-current condition under the parallel operation. In full-scale power converters of direct-drive wind power system, we combine carrier phase shifted technique and parallel converters successfully, and realize the normal operation in low frequency. More and more multilevel converter used in the larger wind power plant. With the development of multilevel converter , multi-pulse generator is needed. In this paper, a twelve-pair PWM generator based on FPGA is designed for three-phase voltage source 5-level inverters. Carrier phase shifted SPWM (CPS-SPWM) is applied as switch modulation strategy. CPS- SPWM can achieve a high equivalent switching frequency effect at rather low real device switching frequency, which is very suitable for high power equipments. A three-phase voltage source 5-level cascade inverters prototype is accomplished by this twelve-pair PWM generator. The experimental results verify the correctness of the design. Other modulation strategies, such as multilevel space vector modulation and sample time staggered space vector modulation, can also be accomplished by FPGA. This is of much significance to the further application of multi-modular converters and multilevel converters.