Capability curves of a VSC-HVDC connected to a weak AC grid considering stability and power limits

The connection point of a VSC-HVDC for the transmission of RES electricity, can be located far from the large generation plants, leading to a weak grid connection. This paper analyses the limitations on the power flow transfer through a VSC-HVDC system connected to a weak grid. First, the impact of the angle and voltage stability limits and the VSC rating are examined. Then, the power transfer capability curves of a VSC connected to a weak grid of an SCR of 1.1 pu by means of an L-interface are calculated. Finally, the impact of providing additional reactive power (Q) support is investigated through utilising a capacitor at the connection point. It has been shown that an additional Q-support of 0.2 pu can maintain the transfer of full power without the need for oversizing the VSC.