多端柔性直流输电系统的阻抗建模及稳定性分析

与两端柔性直流输电(VSC-HVDC)系统相比,多端柔性直流输电(VSC-MTDC)系统更具灵活性和经济性,且有助于电力系统接纳新能源,在VSC-MTDC系统中,换流器需兼备整流器和逆变器的功能,其控制器参数会对系统的稳定性造成较大的影响,阻抗分析法可直接用于指导控制器的参数整定。为此,以一个三端系统为例,提出了适用于VSC-MTDC系统的阻抗稳定性分析方法,建立了系统的等效小信号阻抗模型,根据Nyquist判据判稳,并结合时域仿真,对直流电压控制器参数进行了分析和整定。仿真分析结果验证了所提阻抗模型和判稳方法有效、精确。

Impedance Modeling and Stability Analysis of VSC-MTDC

Compared with double-terminal Voltage Source Converter Based High Voltage DC (VSC-HVDC) transmission systems, the Voltage Source Converter in Multi-terminal High Voltage DC (VSC-MTDC) transmission systems is more flexible and economical, and is beneficial for the power system to accept more renewable energy. In the VSC-MTDC transmission systems, voltage-source converters (VSCs) are required to operate both as an inverter and a rectifier. Their controller parameters will have a greater impact on the stability of the system. The impedance-based analysis method can be used to guidance the parameter tuning of the controller directly. Taking a three terminal HVDC transmission system as an example, this paper proposed an impedance-based stability analysis method suitable for VSC-MTDC. The equivalent small signal impedance model of the system was established. Combined with time domain simulation, the Nyquist stability criteria was used to determine the DC voltage controller. The simulation result verifies the effectiveness and accuracy of the impedance model and stability determination method proposed in this paper.