Samson Sing’oei Soshyo, Sameer Kamrudin Bachani, Julius Ng’ong’a Muga

Abstract

Renewable energy storage continues to be a significant energy system problem with the ever-increasing Renewable Energy (RE) resource harnessing. Energy storage is required if stability and reliability are to be achieved in power systems with high RE integration. Pumped-up Hydro Storage (PHS) systems are the most preferred over other systems such as Battery Energy Storage Systems (BESS). Nevertheless, the deployment of PHS systems is a great challenge, especially in their operational dynamics, cost, relief, land, and other environmental curtailments. The specific focus of this research is on the dynamic performance of direct wind-powered PHS systems. A critical examination of the effect of wind speed ramps depicted a predictable system. The primary control action within the wind turbine and generator models acted first and fast. A secondary PID controller action followed immediately albeit slowly. The control system acted to regulate power input to the PHS synchronous machine pump, in response to wind speed ramps. While the positive wind speed ramps were easy to manage by the controller’s actions, the negative wind speed ramps were more detrimental to the system. The system achieved a 5% settling time of less than 2s with positive ramps of +11.1% of the rated speed of 9m/s. Only negative wind speed ramps of less than -5% of rated speed were easily manageable by controller action. The key recommendation is that a control algorithm for managing the negative wind speed ramps is required for this system to function in all typical wind speed variations. The algorithm should be able to predict the ramps in the immediate near term while at the same time, incorporate primary controller action response. With this in place, it will be possible to control effectively the PHS system under both positive and negative wind speed ramps.

Key Words: Wind, pumped-up, hydro, storage, PID, controller, ramps