The Analysis Of Multi-Infeed HVDC Transmission System Model And Fault

With the development of HVDC technology in China, the next decade, the new patter of a multi-infeed HVDC systems will display in China power grid. In the traditional fault analysis method of power system, the effect of DC system on the fault analysis is rarely considered. So the relevant research of fault analysis is done based on HVDC transmission system in this paper, and the concrete contents are shown as follows:(1)The development history of HVDC is introduced and the specific problems of the multi-infeed HVDC system is analyzed in part 1. Besides, the research status of multi-infeed HVDC transmission system control strategy and the fault analysis methods of the power system is also elabortated.(2)In part 2, the main function, hierarchical structure and working process of the HVDC system control device is described detailedly. And then, the interaction between subsystems and the response of DC control system is considered comprehensively when the voltage fault occurs at the conversion current bus. At last, the pattern conversion of the DC control system is described in details when the faults occur on rectifier side and inverter side bus, respectively. Besides, the corresponding control equations are established based on the control characteristics of DC power system. So the fault analysis model of DC control system is obtained. The control system model of CIGRE HVDC standard test system is simulated and verified by use of the PSCAD/EMTDC.(3)The switching function of the voltage and current of the converter are obtained respectively based on the theory of the improved switching function. Besides, the influence of the offset angle on the converter is considered under the condition of asymmetric fault. And the fault analysis model of the converter is formulated based on the theory of switching function. Due to the effect of the second harmonic component on the fault analysis of DC power system is considered, so the computing precise of the converter model is improved.(4)The relevant elements of the DC power system is listed in this part, and the computing methods of the multi-infeed DC power system is proposed on the basis of the converter and control system model. Finally, by use of the PSCAD/EMTDC, the three infeed HVDC transmission system model is established according the CIGRE standard test system, and the simulation verify the validity and accuracy of the method proposed in the paper.