弱电网下电压控制型并网变流器分层控制关键技术研究

The variation of weak grid impedance deteriorates the stability of grid-connected converter system, thus additional control of converter is required, causing the whole system to be more complex. Under this background, a hierarchical control structure with power regulation was presented in our previous studies where the mechanism of dynamic parameter identification for grid impedance and remodeling of converter inner equivalent impedance was clarified. On this basis, control margin of converter system will be improved after solving the key theoretical problems above in this project. Specifically, the induction and influencing factors of low-order harmonic oscillation of grid-connected system will be further researched, so that converter can accommodate weak grid initiatively with power quality of weak grid improved as well. The development of voltage-controlled grid-connected converter in complex power grid has firm theoretical and technical support.

针对弱电网下电网阻抗变化对变流器以及并网系统稳定性影响大，导致变流器控制功能增加和系统日趋复杂的问题，该课题在前期研究工作的基础上，提出多层次架构和功率调控相结合的电压控制型并网变流器分层控制方法:阐明基于变流器的电网阻抗参数动态辨识和内部等效阻抗重塑工作机理；在此基础上，逐步完善弱电网下变流器功率调控理论和优化效果，这些关键理论问题的解决，有助于提高变流器控制系统稳定裕度的精度分析，探明并网系统低次谐波振荡的诱发机理及影响因素，进而实现变流器对弱电网的主动适应，并有效改善弱电网电能质量，为电压控制型并网变流器在复杂电网环境下更好、更快的发展提供重要的理论依据和技术支撑。

针对弱电网下电网阻抗变化对变流器以及并网系统稳定性影响大，导致变流器控制功能增加和系统日趋复杂等问题。主要从以下几方面做了深入研究：提出了具有三层（基础层、稳定层、优化层）结构的分层控制系统和功率调控相结合的电压控制型并网变流器分层控制方法；选取电压谐波注入法，搭建电网阻抗参数动态辨识控制模块；基于阻抗模型定量分析变流器稳定性问题并推广至多变流器交/直流系统，搭建等效阻抗重塑控制模块；研究了电压控制型变流器并网功率对配电网优化运行的影响。这些关键理论问题的解决，有助于提高变流器控制系统稳定裕度的精度分析，探明并网系统低次谐波振荡的诱发机理及影响因素，进而实现变流器对弱电网的主动适应，并有效改善弱电网电能质量，为电压控制型并网变流器在复杂电网环境下更好、更快的发展提供重要的理论依据和技术支撑。