基于移频理论的交直流混联电网多尺度暂态模型与多速率仿真方法研究

As an increasing integration of HVDC in ac power grid, ac-dc hybrid power grid in China presents the trends of large-scale dc transmission and dominated power electronics. The requirement of high accuracy, efficiency, flexibility of simulating electromagnetic and electromechanical transients needs to be met to ensure the operation safety and stability of ac-dc power grid. With an aim at the simulation of diverse transients over large time-scale and within different network positions, this proposal will firstly explore adaptive shifting of multiple-frequency carriers, and then develop novel shifted-frequency theory-based multi-scale model of ac-dc power grid. Based on the multi-scale numerical model, time-domain analysis of eigenvalues will be performed. Based on quantitative analysis of multi-scale transients, ac-dc power grid will be automatic partitioned, and then novel multi-rate simulation methods of the transients will be proposed. With the help of frequency shifting and eigenvalue analysis, multi-scale transient model of ac-dc power grid is decoupled along the frequency axis and grid-spatial axis, thereby improving the multi-rate simulation grid-scale, accuracy and computational speed. This proposal will deepen multiple-frequency shifting-based multi-scale transient modeling theory, and also provide theoretical and experiment guidance for the multi-scale simulation and analysis of diverse transients. Furthermore, related research contributions will provide theoretical and technical basis for an exploration of the interaction and stability between ac and dc grid, and also the guarantee of safe and stable operation in future large-scale ac-dc power system.

随着高压直流输电大量接入交流电网，我国交直流混联电网的直流规模化与电力电子化特征日趋明显，其安全稳定运行对电力系统电磁-机电暂态建模仿真技术，在准确性、快速性、灵活性等方面提出了更高要求。本项目为满足交直流混联电网对多时间尺度/多区域复杂暂态特性仿真的需求，重点研究交直流电网暂态多频率载波移动原理及其移频多尺度暂态模型，并研究暂态模型状态空间特征值分析方法，在此基础上，面向暂态量化特性研究交直流电网的动态分区与多速率仿真方法。通过多频率载波移动与时域特征值分析，实现交直流电网多尺度暂态模型的频率解耦和空间解耦，从而同时提高了多速率仿真的电网规模、速度和精度。本项目研究成果将深化移频多尺度暂态建模理论，为交直流混联电网多尺度暂态分析，及其预期特性和效果提供理论验证与实验指导；为揭示交直流互联相互作用及稳定机理，进而保障新形势下交直流电力系统安全稳定运行，奠定部分理论及技术基础。

本项目针对大型交直流混联电网面临的暂态建模与仿真难题，紧密围绕电力电子化交直流系统建模理论与仿真方法等基础科学问题，取得了以下三方面贡献：1）提出了波过程描述函数建模方法，破解了具有高频电力电子开关特性的换流器及多端柔性直流的多尺度暂态建模难题；2）提出了基于数值模型的时域特征值分析方法，能够在仿真进程中量化交直流电网的各项振荡与稳定等指标，并通过特征值分析开展大型交直流系统并行多速率自适应暂态仿真；3）将移频多尺度暂态建模技术，应用于RTLab实时仿真器，搭建了大型交直流系统仿真平台，解决了RTLab实时仿真平台电磁-机电暂态多速率多区域并行计算难题。通过上述研究构建了交直流混联电网建模仿真理论与方法体系，建设了新能源交直流系统离线与在线仿真平台，并获得中国仿真学会技术发明一等奖。该项目成果可为交直流电力系统甚至多能源互联系统在规划设计、试验运行等方面提供相关仿真基础理论与实验支持。