Design of Supplementary subsynchronous damping controller for HVDC transmission based on improved matrix beam algorithm and projective theorem

HVDC transmission can effectively improve the power transmission capacity, but the rapid controllability of dc may cause subsynchronous oscillation phenomenon of the thermal power unit at the end of the transmission, thus causing damage to the shaft system of the unit. Supplementary subsynchronous damping controller is widely used in practical engineering as an economical and effective measure to suppress subsynchronous oscillating vibration. In this paper, based on the improved matrix beam algorithm, the oscillation modal parameters are identified and an Supplementary subsynchronous damping controller is designed. First, the system function under the natural torsional vibration frequency of the generator shafting is obtained through the improved matrix beam algorithm, and then the Supplementary subsynchronous damping controller is designed based on the projective theorem, and finally the subsynchronous oscillation is suppressed. Taking a practical power grid model as an example, the simulation results show that the Supplementary subsynchronous damping controller based on improved matrix beam algorithm and projective theorem can effectively suppress the subsynchronous oscillation caused by DC transmission, and the designed controller has the advantage of low order, which is beneficial to engineering implementation.