Virtual synchronous machine-controlled grid-connected power electronic converter as a ROCOF control device for power system applications

Rate of change of frequency (ROCOF) is an indicator of frequency stability of a power system network. Maintaining the ROCOF value within the acceptable limit is a major challenge with increasing penetration of converter-based renewable energy generation technologies. A virtual synchronous machine (VSM) is proposed in this paper as a ROCOF control device with a novel battery power management algorithm to extend the lifetime of the batteries. The VSM unit consists of a DC storage connected through a three-phase voltage source converter with a harmonic filter to the grid and the corresponding local control system. The Kundur two-area system is used as a test case to analyse the performance of the VSM. A hardware prototype of the VSM with 1 kW, 200 V and 50 Hz rating is developed in the laboratory environment. The modified Kundur two-area system and the control strategies are implemented in OPAL-RT real-time simulator. The effect of VSM on the modified Kundur two-area system is analysed using the power hardware-in-the-loop concept. The experimental results indicate that the VSM is effective in reducing the ROCOF values in power system networks during rapid fluctuations in frequency caused due to the load switching events. The hardware implementation of a VSM interfaced with the modified Kundur two-area system, the novel battery power management algorithm and the application of VSM as a ROCOF control device for power system applications are the unique contributions in this paper.