基于多参数分岔理论的多端柔性直流并网海上风电系统电压稳定与控制

At present, the transmission topology, grid-connection mode and stability issue caused by OWPS (Offshore Wind Power System) integration have been taken as the key factors that restricting the development and utilization of offshore wind power. This project focuses on the OWPS based on MTFDC (Multi-terminal Flexible HVDC) transmission technique, and considers the multi-parameter bifurcation analysis and control for voltage stability of OWPS system in detail, the following issues will be included: ① Considering the effects caused by the wind-wave-current coupling of ocean environment, active power output features of OWPS and faults, the models of MTFDC system is given firstly basing on fractional order modeling with Caputo deifnition , then the model with limited complexity for OWPS which are available for voltage stability analysis is established. ② By using multi-parameter bifurcation method, the key bifurcation points affecting voltage stability of OWPS are traced. After the discussion of the relationship between the key bifurcation points and stability of system, then the influence on voltage instability resulting from the bifurcation points is revealed, and the typical voltage stability criteria and instability scene are developed, respectively. ③Based on the bifurcation control approaches, the control parameters of MTFDC system, wind turbine generators and reactive compensation device are optimized. Then the coordinated control methodology for OWPS is developed, thus the stability of system can be enhanced. The developed results in this project are expected to provide theory supports and technology supports for the safe and stable operation of OWPS, which can further promote the development and utilization of the offshore wind power generation.

目前，海上风电系统的输电拓扑、并网方式及并网引起的系统稳定等问题已成为制约海上风电有效开发利用的关键因素。本项目以多端柔性直流并网海上风电系统为研究对象，对该系统的分数阶建模、电压稳定分岔与控制进行研究，主要内容包括：①计及海上风-浪-流耦合环境、海上风电出力特性及故障等影响，基于Caputo定义的分数阶建模理论，构建多端柔性直流输电拓扑结构，进而建立具有有限复杂度并适合电压稳定分析的海上风电系统模型；②基于多参数分岔方法追踪影响系统电压稳定的分岔点，通过梳理关键分岔点与系统稳定间的关系，揭示系统分岔行为对电压失稳机理的作用机制，提出典型的电压稳定判据和失稳场景；③基于分岔控制理论，优化柔性直流换流器、风电机组和无功补偿设备的控制参数，实现整个系统的协调控制，以提升系统的稳定性。本项目研究成果可为海上风电系统的安全稳定运行提供重要的理论支撑和技术支持，将进一步促进海上风电的有效开发和利用。

相比陆上风电，海上风电开发的资源条件较为优越。由于海上风电并网涉及海上输电拓扑构建、并网方式选择、系统稳定、故障分析及控制等多方面关键技术，本项目以海上风电系统为研究对象，开展了其建模、潮流分析和稳定控制等相关研究。提出了基于波特图频域方法的柔性直流系统分数阶微积分建模方法，建立了基于分抗链形式的阻容分抗电路模型，提出了适用于多端柔性直流并网海上风电系统的高阶潮流算法，并基于自动微分和保留非线性进行了实用化开发；通过计算预估值和校正值两个步骤，利用具有2.414阶次收敛速率的牛拉法改进交直流系统潮流算法；基于2.414阶牛顿法和简化牛顿法的组合高阶等算法修正交直流系统的雅可比矩阵，加快程序执行调用的速度；提出了基于保留非线性和自动微分技术的交直流系统潮流高阶算法，从而了提高雅可比矩阵的计算速率。提出了基于统一迭代和交替迭代的交直流系统暂态电压分析方法，提出了基于双交错积理论的多参数分岔实现方法；在分岔点追踪和分岔控制方面，提出了一种基于自动微分和牛顿法的混合迭代方法，通过预测-校正步骤，在定雅可比矩阵迭代法的基础上，基于双交错积理论，通过对系统平衡解流形的求解，构造分岔测试函数来实现分岔点的追踪和分岔控制。本项目的研究为含柔性直流系统的交直流混合电网的建模、仿真与分析等工作提供了借鉴和思路。