The power production from renewables like wind and solar are increasing rapidly over past decade and will continue in future. As the power from these sources are not constant, it needs a large storage system that can balance the power into the grid. The pump storage hydropower plant is the best option for such a large scale storage. At present, the pump storage plants cannot dynamically change its mode from pumping to generating or vice versa because the electrical machines are directly connected to the large AC network.Also, the hydraulic and electrical machines run at almost constant speed depending upon the frequency of the grid regardless of the amount of water flow into the turbine/pump. However, it is a well-proven theory that the turbine/pump operates at optimal effi ciency only if its speed is varied according the variation in the water fl ow. This optimal efficiency operation of hydraulic machines and dynamic transition in modes of operation (pumping and generating) can be achieved only by decoupling the turbine/generator sets from the AC grid using a full power back-to-back converter between the AC machine and the grid.

The research within this PhD will involve a lab setup of 100 kW capacity with 2-level back-toback converter connected between the grid and the synchronous machine. The prime mover of the synchronous machine will be an induction machine and the variable speed operation of turbine to track the maximum effi ciency will be simulated using a motor inverter connected to the induction machine. As the converters decouple the physical inertia of the machine, emulating virtual inertia and damping in the control system will also be one of the major requirement. The decoupling will also limit the infl uence of grid dynamics on the hydraulic and civil structures.

To avoid the additional passive fi lter components or to make it very small, Multi-Modular Converter (MMC) topologies will also be tested.