Research On Modeling Of HVDC Converter Firing Control

As more and more HVDC transmission projects have been put into operation in recent years, the interaction of HVDC transmission system with AC power system is getting more attention in China. HVDC transmission system is a highly controllable system and the controllability is realized by the converter control. Converter firing control(CFC) is the key block of converter control and realize the core function of HVDC control, therefore, the modeling study for CFC has the great significance.Based on the actual current engineering software HiDraw, the paper research on converter firing control(CFC) of ABB HVDC transmission control system, part of the independent functional modules are described in detail and the response curves of the modules are given.The paper proposed two method to improve the accuracy of PLL. When single-phase short circuit fault occurs in the power system, the voltage of converter bus will get imbalanced and this will cause the output offset of phase-locked loop(PLL) and the asymmetric operation of valves, these methods can solves the problem effectively.To overcome the shortage of simplified CFC model currently used in the electromagnetic transient simulation software, author proposed a detailed CFC model which can be successfully integrated in PSCAD/EMTDC for HVDC steady and transient simulation.Finally, the simulation results of the developed model are given with comparison of the CIGRE benchmark system as well as the field recorded curves in three different operating conditions including HVDC starting, DC line fault and inverter side AC bus single-phase ground short-circuit. The results show that the model is reasonable and can be used in the follow-up research.