Two Double-tuned Filter Design And Protection

HVDC system receives great importance of the power engineering sector, because of its advantages of long distance and high-capacity transmission. But with the introduction of non-linear power electronic components, it generated a large number of harmonics. Usually it mostly used single-tuned filter and high- pass filter to suppress the power system harmonics, but in the HVDC system, using double-tuned filter is a better choice. In this paper, it proposed two-type structures of double-tuned filter based on traditional double-tuned filter from the structure and protection, they are two-inductor parallel type of double-tuned filter and two-capacitor parallel type of double-tuned filter. There are two resonant frequencies of double-tuned filter, which can absorb two frequencies' harmonics, so double-tuned filter is increasingly being used in practical engineering.In this paper, it analyzed the characteristic and calculated the parameters of double-tuned filter, designed the parameters of two-type structures of double-tuned filter with the equivalent method and the parametric method, simulated by PSCAD software, and analyzed filter components' transient performance. On the basic of the above, it studied the principle of two double-tuned filters' DC protection, of which high-voltage capacitor imbalance protection and the reactor's inter-turn fault protection were the focus study of the filter's protection. This paper used C8051F005 singlechip to detect the DC double-tuned filter's fault, giving the warning information. The CIP-51 Core of C8051F005 singlechip adopted pipelining structure, compared with the original 8051 singlechip, C8051F005 has greatly increased speed. The filter's protection has three parts, there are signal sampling procedure, fault calculation procedure and liquid crystal display, and the display part displayed the filter's operation state so that reminded staff of dealing with it accordingly.