A new H-bridge NNPC converter for 10kV class motor drives

This paper presents a new seven-level voltage source converter (VSC) for high-power medium-voltage (MV) motor drives. The proposed topology is composed of H-bridge connection of two nested neutral-point-clamped (NNPC) converters called 7L-HNNPC converter. This converter has interesting features such as operating over a wide-range of output voltages particularly for a range of (10kV-15kV) without the need for connecting power semiconductor in series, high quality output voltage, less number of components in compare to other classical seven-level topologies. A novel SPWM technique has been developed for the proposed 7L-HNNPC converter to control and balance of the flying capacitors. The outstanding property of the control strategy is that the control can be applied independently to each leg of the converter that reduces the complexity of the controller significantly. The performance of the proposed converter is studied under different operating conditions in the MATLAB/Simulink environment. The feasibility of the proposed converter is evaluated experimentally on a scale-down prototype.