Power sharing control strategy for a no-storage hydrokinetic-diesel system in an isolated AC mini-grid

Abstract

The operation of diesel engine generator sets (gensets) with light loading leads to deterioration in the engine performance and efficiency. This problem is intensified in no-storage hydrokinetic-diesel systems since the genset is usually oversized to make-up for the potential shortage of renewable energy. In this paper, a new power sharing control strategy has been developed which minimizes this issue using a hydrokinetic energy conversion system (HKECS) that employs a diode AC-DC converter and voltage source inverter. The genset works with a frequency vs. power droop control. The HKECS is controlled with maximum power point tracking unless the grid frequency rises above a limit that indicates the underloading of the genset. At this point, a controlled DC load is activated so as to decrease the power injected by the HKECS thus regulating the grid frequency at this operating point. The proposed strategy is verified with a set-up with rotating machines and power electronic converters controlled via a dSPACE® system. The dynamic and steady-state operation of the system including power balancing, voltage and frequency control are presented.