Exploration of special feedback signals for VSC-HVDC based damping controller

This paper explores some special feedback signals for implementing damping controllers in embedded voltage source converter (VSC) based HVDC links. While a variety of feedback signals are feasible, a few signals stand out due to their favourable properties. The paper recognizes the voltage angle/frequency difference between the rectifier and inverter side ac buses as one such local signal. This signal has good residue properties which can lead to improvement in the damping of all controllable swing modes. The large gain behaviour may be improved by modifying this signal. The paper proposes a nonlocal equivalent of this modified signal. This non-local signal may overcome the restriction on the controller gain due to the need to ensure stability of local non-swing modes. The synthesis of the signal is eigen-solution free and computationally easy.