Coordination and optimization of small signal modulators in multi-infeed HVDC systems

There may exist negative interactions among HVDC small signal modulation controllers in multi-infeed HVDC systems, so it is necessary to tune the parameters of the HVDC modulators coordinately. The problem is equivalent to solving a non-linear programming problem provided that the structures of the HVDC modulators are known. In this paper the objective function consists of the active power in the AC inter-ties and the rotor angles of all the generators. The parameters of the HVDC modulators can be optimized simultaneously with an inherent non-linear optimization module of NETOMAC. The presented parameter tuning procedure has itself included the non-linear nature of the AC/DC system and does not need to manually derive the explicit mathematical model of the whole system, so system simplification and linearization are not needed. A dual- infeed HVDC system with two lightly damped inter-regional oscillation modes is constructed to demonstrate the effectiveness of the presented parameter tuning procedure. Simulation results show that the optimized HVDC modulators can improve the damping of overall power oscillations in the dual-infeed HVDC system. Furthermore, the optimized modulators are robust to changes in system configurations, operating conditions and fault modes.