PV‐fed DVR for simultaneous real power injection and sag/swell mitigation in a wind farm

Generally, a dynamic voltage restorer (DVR) installed in a grid-connected wind farm, is utilised for mitigating sag/swell in grid voltage and hence stays idle under nominal grid voltage. To enhance the utility of such a DVR, this study proposes to install a solar photovoltaic (PV) plant in the DVR, so that in addition to addressing sag/swell in grid voltage, energy can be harvested and injected into the grid from the PV plant using the same DVR. Various modes of operations of the proposed PV-assisted DVR (PVDVR) are described, underlining the logically set priorities. Comprehensive mathematical and graphical analyses are developed to explore the boundaries of the operating region of each mode of PVDVR considering fluctuations in grid voltage and available PV power. Investigations are carried out in a 50 MW wind farm and a 0.75 kW laboratory induction machine (both grid connected) each with a suitable DVR. Results of simulations in power systems computer-aided design/electro-magnetic transient design and control and laboratory tests demonstrate improved utilisation of DVR when fed from PV plant.