This paper aims to explore the history and development of eight types of reaction water turbines, namely Hero’s turbine, Barker’s mill, Pupil’s turbine, Whitlaw’s mill, Quek’s turbine, the cross pipe turbine, the split reaction turbine and the Z-Blade turbine. These water turbines are discussed in terms of the complexity of the designs, the manufacturing processes involved, and the applications. It has been observed that even though most reaction type water turbines, except for the split reaction turbine and Z-blade turbine, have undergone different levels of design-related modifications and manufacturing processes, they are considered as being unsuitable for low-head and low-flow water resources in pico-hydro systems.

This paper analyzed a single phase nine level cascaded h-bridge multilevel inverter (CHMLI) topology in which requires lesser number of components and easier to control if compared to other methods. The inverter of different voltage levels (up to 9-Levels) are designed and simulated using MATLAB Simulink. A Level Shifted Multi-Carrier PWM control scheme is used to control the operation of the power switches for CHMLI topology. The results are compared in terms of THD.  The value of THD is found to be reduced as the number of voltage level of CHMLI is increased.

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