中文摘要：

由于高压直流输电HVDC（high voltage direct current）系统的动态特性以及交直流接口方程的非线性，交直流输电系统将具有非常复杂的动态环节与非线性环节，传统的线性分析方法无法准确分析系统的非线性特性。为此，应用分岔理论分析了一个典型交直流输电系统的电压稳定性，将负荷端有功功率、无功功率，原动机功率、HVDC控制参数等作为分岔参数，对整个系统进行了单参数和双参数分岔研究，特别是对HVDC控制系统所引起的分岔变化进行了详细分析。研究表明，在不同运行条件下，系统将出现多种复杂的分岔现象，直流输电系统的控制方式、控制参数及传输功率对系统电压稳定性有显著影响。

英文摘要：

AC/DC system has more complicated dynamic and nonlinear components for the dynamic features of HVDC controllers and the nonlinear AC/DC interface equation, so traditional linear method can not analyze the nonlinear dynamics. In this paper, bifurcation theory is applied in the analysis of voltage stability for an AC/ DC paralleled system. The load power, generation power and HVDC control parameters are selected as the bifurcation parameters for one-parameter bifurcation analysis and two-parameter bifurcation analysis, and the influence of HVDC control on the bifurcation characteristic is especially studied in detail. Results show that various complicated bifurcations appear in different operation conditions, and HVDC control parameters, control modes and transfered power of HVDC have obvious influence on voltage stability.