Starting Techniques for Doubly Fed Induction Machines in Pumped Hydro Storage Plants

Pumped hydro storage plants are an essential asset in modern power systems. Big-scale hydro-power storage solutions provide the required stability and flexibility to renewable energy-dominated grids in a clean and efficient way. The evolution of power electronics has enabled to place variable speed solutions at the heart of pumped hydro storage plants, allowing on the one hand to assume large seasonal water head variations under turbine mode, and on the other hand to take on part-load operation under pump mode. Among variable speed solutions, doubly fed induction machines (DFIM) are the most widespread systems owing to two main advantages with respect to other solutions, one of them being their versatility in terms of active and reactive power management, and the other their reduced rating requirement for the back-to-back voltage source converter connected to the rotor winding. The starting-up of DFIM, yet being a frequent operation in pumped hydro storage plants, requires a large number of maneuvers and additional elements, such as auxiliary power converters and switches, that make the process costly and technically challenging. Different starting-up techniques for DFIM have been proposed over the years both in academia and in industry. In this chapter, the starting-up possibilities of DFIM for pumped-storage hydro-power plants are described in depth, providing the theoretical foundations, the normalized electrical diagrams and the step-by-step practical implementation of each of the techniques.