A self-coordinating adaptive control scheme for HVDC transmission systems

The transients in a HVDC system can temporarily change line currents, voltages, and power substantially from the reference steady state values and the behavior of the system depends greatly upon the parameters of the converter controller. The DC system performances are affected by the AC system characteristics such as the short circuit ratio, and the AC system inertia. A controller which has good performance for a particular operating condition may not have sufficiently good performance under another operating condition or vice versa. Performance of the controller also depends on the impedance at the rectifier and the inverter bus, which may vary according to the operating conditions of the AC network. A controller with self-coordinating adaptive capability can perform better in various situations. The proposed controller is tested at a very low SCR, the most critical value for system performance evaluation, and at the low inertia of the AC system. Simulation results are compared between proposed controller, fuzzy tuned controller, gain scheduling controller, and fixed-parameter controller. All simulations are conducted using MATLAB/SIMULINK software package.