LVRT control strategy of VSC-HVDC connected large PV plant

This paper investigates a low voltage ride through control strategy of a large scale PV plant that integrated onto the grid via a single terminal VSC-HVDC line. An improved VSC-control scheme, coordinated with the super-capacitor battery controls at the PV plant, is proposed to provide the grid reactive power boost, and to absorb the unbalancing power in the DC grid, to ensure stability of the integrated DC/AC grid. A PSCAD/EMTDC model, which includes a PV plant, a single terminal VSC-HVDC line, an inverter station connected to a transformer, an AC line and then to an infinite source, is created to verify the proposed control strategy. A three phase to ground fault at the inverter station is given as an example, to demonstrate the proposed LVRT control strategy. Extensive simulation tests have provided that the PV plant is able to ride through the fault scenarios while supplying reactive power to the AC grid, and observing no over-voltage over the DC grid and the VSC-HVDC line, providing the proposed LVRT control strategy is feasible and reliable.