Experimental investigation of off-grid organic Rankine cycle control system adapting sliding pressure strategy under proportional integral with feed-forward and compensator

Highlights: • Control system of an off-grid organic Rankine cycle was investigated. • Sliding pressure control was implemented to meet the load requirements. • Proportional Integral scheme was tested to track expander speed set-point. • Proportional integral, feed-forward and compensator was proposed as improvement. - Abstract: This article presents an experimental investigation of an organic Rankine cycle control system in off-grid island mode. A robust control system is required for a reliable autonomous operation of the system without human intervention to manage the fluctuations in demand and produce. Sliding pressure control strategy is used to meet the varying demand in load by changing evaporation pressure using a proportional-integral algorithm. The system was subjected to load disturbance and its performance was tested on an off-grid organic Rankine cycle test bed system. An improved scheme based on proportional-integral, feed-forward and lead-lag compensator was proposed and tested for same operating conditions and same load disturbance. It was found that the new scheme was able to track the expander rotational speed in a better way and system recovers to set point speed in nearly half the time compared to proportional-integral based scheme.