| Capacitor commutation technology is a new converter technology which can effectively overcome the technical defects of line commuted converter technology. Firstly, based on the theory and converter valve’s commutation process in a complete power cycle of the capacitor commuted convertor (CCC), the paper establishes the CCC’s state mathematical model to analyze the impact of capacitor commutation technology to configuration and parameters of the primary device in HVDC system, and then proposes device optimization scheme. Second, the characteristic of automatically tuned AC filters (ATF) which is applicable to capacitor commutation technology is studied. Based on the model of magnetic valve controllable reactor, ATF’s model is established and the parameter optimization design is also given.Relying on the electromagnetic transient simulation software PSCAD/EMTDC, the simulation model of HVDC with capacitor commutated converter (CCC-HVDC) is built, and then the ATF model is introduced into it. Then the reactive power and harmonic characteristics is separately simulated. The simulation results show that the reactive power consumed by CCC is less than that of the conventional convertor but the harmonics produced by CCC which are injected to AC and DC system is much larger than that of the conventional inverter; ATF can not only give a continuous reactive power compensation to CCC-HVDC system within a certain range, but also give a good harmonic inhibition by achieving its tuning frequency being consistent with harmonics.For the real-time control feature of ATF, two control strategies are proposed in CCC-HVDC system, and then the transient characteristics under the two control strategies are simulated and comparatively analyzed. It shows that the CCC-HVDC system with ATF can do a little help on improving the CCC-HVDC system’s steady and transient characteristics by reducing the variable amplitude and shortening the recovery time. |
