Head variation adaptive control of small-scale doubly-fed pumped storage units

Compared to conventional hydropower units, small-scale pumped storage units have smaller reservoir capacities, and the water heads are sensitive to seasons, climate, and loads, thereby prejudice control performance of the pumped storage system. Conventional control strategies, e.g. PID controllers, of pumped storage units are usually deployed with fixed parameters, thus is likely to encounter control performance degeneration in the form of rotor speed fluctuations with varying water head from time to time. This paper proposes a water head variation adaptive control of small-scale doubly fed pumped storage units. Firstly, linearized models of the pump-turbine, doubly-fed induction motor, excitation control system alongside related control systems are established for deriving feasible stable regions of PI controller parameters via root locus analysis. A hyper-heuristic algorithm is then utilized to optimize the controller's PI parameters within the derived stable regions besides converter speed limitations entailed by a doubly-fed system. The objective of the optimization model is set to be maximization of speed regulation capability under varying water head conditions. Matlab/Simulink simulation analysis demonstrates the superior performance of the proposed method applied to small-scale pumped storage units, on suppressing speed oscillations and expediting speed recovery under varying water head conditions.