考虑换相过程的电网换相换流器小信号阻抗建模

Small-signal Impedance Modeling of Line-commutated Converter with Commutation Overlap

建立准确的数学模型对于判断电力系统稳定性具有重要意义,其中阻抗模型凭借简单有效的优势成为判断系统稳定性的常用工具。为完成考虑换相过程的电网换相换流器阻抗建模,在dq坐标系下采用了基于平均化的小信号建模方法。首先,将换相重叠过程中各物理量的非线性变化过程利用小信号法线性化,建立了物理量之间的传递函数;然后,加入了交流电源侧的交流网络简化模型,同时考虑了定电压控制方式和锁相环的建模,得到电网换相换流器直流侧和交流侧的等效阻抗模型;最后,通过对比PSCAD/EMTDC仿真结果和模型计算结果,证明了阻抗模型的准确性。

In order to judge the stability of a power system,it is of great significance to establish an accurate model,among which the impedance model has become a common tool for judging system stability due to its simplicity and effectiveness.In the dq coordinate system,the small-signal modeling method based on averaging is adopted to complete the impedance modeling of line-commutated converter(LCC)which considers commutation overlap.Firstly,the nonlinear change process of each physical quantity in commutation overlap process is linearized by the small-signal method,and the transfer function between physical quantities is established.And then,the equivalent impedance model of DC side and AC side of LCC is obtained by introducing simplified model of AC network in AC side and considering the modeling of constant voltage control mode and phase-locked loop.Finally,by comparing PSCAD/EMTDC simulation results and model calculation results,the accuracy of the proposed impedance model is proved.