Parameters tuning of HVDC small signal modulation controllers based on test signal

In this paper, a new method is put forward to tune the parameters of an HVDC small signal modulation controller. First, small signal stability of an AC/DC power system is analyzed using the test signal method. Then the frequency of the test signal is scanned at the HVDC rectifier current set point, and the oscillated active power flow in the parallel AC tie line is obtained. Thus, the open-loop transfer function between the current reference signal of the HVDC constant current regulator and the active power flow in the parallel AC inter-tie is identified by Fourier decomposition and curve fitting with time domain simulations using electromechanical transient programs. Finally, parameters of the HVDC small signal modulator are tuned based on the root locus method of the classical control theory. Simulation results show that the proposed parameter tuning method is effective and convenient, and it can be used in a practical large AC/DC power system.