Generalized Modeling Method And Characteristic Analysis Of LCC-HVDC And VSC-HVDC Transmission System

With the development of power system and power electronic technology, HVDC is widely used in the long-distance power transmission, submarine cable transmission and non-synchronous interconnection. The current HVDC mainly includes two types: LCC-HVDC and VSC-HVDC. The large scale AC-DC hybrid power system is formed with the widely used of HVDC, which presents the complex the operation characteristics. Therefore, the researches on the control characteristics of LCC-HVDC and VSC-HVDC are necessary. Proper mathematical model should be established for analyzing the transient stability and fault characteristics, which lay a foundation for power system analysis.The aim of this paper is to analyze and improve continuation method related problems in HVDC. The specific research works are as follows:(1) The general modeling method is given for LCC-HVDC, which improve the model of main circuit, control system and direct-current transmission line. Based on the platform of PSCAD/EMTDC, the equivalent method and parameters are proposed. The proposed general modeling method of typical LCC-HVDC is valid for establishing the mathematical model, which is proper for practical system. The work provides a standard modeling method for current hybrid system.(2) The general modeling method is proposed for VSC-HVDC, which improve the model of main circuit, control system and direct-current transmission line. The VSC-HVDC model on PSCAD/EMTDC is also given, which illustrate the model of specific modules. The proposed modeling method presents a general method and standard for VSC-HVDC system model. And the analysis based on the model is valuable for traditional power system analysis, such as power flow, transient stability.(3) According to the unified modeling method of LCC-HVDC and VSC-HVDC transmission system, the electromagnetic transient models of Yindong LCC-HVDC and America Trans Bay Cable VSC-HVDC transmission system are established. Based on electromagnetic transient simulation, the Yindong LCC-HVDC model is used for analyzing operation characteristics of normal operation-state, DC fault and commutation failure; the operation characteristics of Trans Bay Cable VSC-HVDC is analyzing on three states, which including normal startup, the active power instruction value step and the reactive power instruction value step. The two cases are conducted with united modeling method, which supplies a simple, reliable and unified method for analyzing engineering characteristic of LCC-HVDC and VSC-HVDC transmission systems.