Performance Characteristics Analysis For HVDC System Based On CCC

The capacitor commutated converter, that is CCC, can overcome the inherent drawbacks of conventional converters. The CCC topology includes capacitors in series with the valve side transformer windings. The reactive power consumption of converters is supplemented by the serial capacitors. The capacity of allocated filters can be smaller. The voltages on these capacitors aid in the commutation process thus resulting in a more robust converter, which is potentially less dependent on the AC network strength and more robust against network disturbances. This thesis is studied aiming at guizhou-guangdong HVDC system.In the thesis, the mathematical model of CCC is presented firstly. The stability characteristics of CCC are analyzed. Furthermore, a comparison is made between the characteristics of conventional converters and CCC.PSCAD/EMTDC simulation package is used to model the conventional converter system as well as the CCC-HVDC system. Through applying varying faults at a fixed time to the two system models respectively, including close-in AC faults, remote AC faults, AC asymmetric faults, inverter side DC faults, converter faults, load rejection faults, etc, I observe their performance regularity and record the waveforms, involving in rectifier and inverter AC voltage and current, DC voltage and current, firing angle and power, and so on. Furthermore, the performance characteristics is analyzed and compared. Finally, Subsynchronous oscillation (SSO) in the two converter systems is analyzed.By means of studying the steady state characteristics and transient characteristics, I can draw conclusions as follows:(1) Chances of commutation failure can be reduced as a result of using CCC;...