基于VSC-HVDC的海上风电场并网系统概率风险评估模型及应用

By subject crossing of electrical power system, optimization theory, reliability fundamentals and meteorology etc., this project started its work with studying the risk assessment theory about VSC-HVDC transmission systems for grid connection in offshore wind farms. Given the operation control features for VSC-HVDC system, intermittent wind power output, as well as the bad sea weather and so on, this project has built a reliability evaluation index framework (such as equivalent active power, reactive adjust degree, coordination degree of wind farms and VSC-HVDC, etc.) and a three-level hierarchical reliability evaluation model for VSC-HVDC transmission systems for grid connection in offshore wind farms. According to different factors involved, this model can be applied respectively to do reliability evaluation over VSC-HVDC system itself, VSC-HVDC systems for grid connection in onshore wind farms, VSC-HVDC systems for grid connection in offshore wind farms, and this means it has created a new way to do the reliability analysis on VSC-HVDC system. Combined with the contribution VSC-HVDC has done for the reliability of the large power grid, along with the cost of equipment investment, installation, operation and maintenance and so on, a unified optimization model for equipment selection and grid connection topology is built to serve VSC-HVDC systems for grid connection in offshore wind farms. This model is designed to improve the reliability of power grid, reduce the loss caused by outage, and to provide a new analysis method and quantitative decision-making foundation for VSC-HVDC system planning, operation, and improvement.

本项目通过电力系统、优化理论、可靠性理论和气象学等多学科的交叉，从探寻海上风电场的VSC-HVDC并网系统风险评估理论入手，根据VSC-HVDC的运行控制特性、风电出力的间歇性、海上恶劣天气因素等，建立海上风电场VSC-HVDC并网系统的可靠性评估指标体系（如等值有功功率、无功调节度、风电场和并网系统的协调度等）和三层递阶可靠性评估模型。根据计入因素不同，该模型可分别用于：VSC-HVDC系统本身、基于VSC-HVDC的陆上风电场并网系统、基于VSC-HVDC的海上风电场并网系统可靠性评估，开拓了VSC-HVDC系统可靠性分析的新途径。结合VSC-HVDC对大电网的可靠性贡献，计及设备的投资、安装、运行维护等费用建立海上风电场VSC-HVDC并网系统设备选型和并网拓扑的统一优化模型，提高电网可靠性、减少停电损失，为VSC-HVDC并网系统的规划、运行和改造提供新的分析方法和量化决策依据。

由于海上风电场具有不占用宝贵的土地资源、基本不受地形地貌影响、风能资源丰富以及单机容量大和利用小时数高等特点，大规模近海风电场的开发已成为国际上风能利用的大趋势。由于风电场出力的间歇性、VSC-HVDC 运行控制的灵活性，致使 VSC-HVDC 系统可靠性评估、运行控制、调度和调峰等方面都需要深入研究。本项目主要针对海上风电场的VSC-HVDC 并网系统概率风险评估模型及应用等开展研究，主要研究内容及取得的主要研究成果如下：.建立了基于解析法的风电场多状态Markov模型：首先结合风速ARMA模型和风电转换特性，确定单台风机出力序列；然后采用K-均值聚类法对风机出力进行状态划分，根据风速之间以及风机状态之间的转移关系，建立单台风机的Markov模型；最后组合多台风机并对风电场的输出功率进行聚类，基于边界墙原理确定各状态之间的转移率，建立了风电场的7状态Markov模型。.在深入研究VSC-HVDC系统主要元件及其故障后果的基础上，建立了联接变压器、换流器等元件的Markov模型。根据元件故障对系统状态转移的影响，通过模型组合建立了计及STATCOM状态和风电场出力间歇性的VSC-HVDC系统统一Markov模型。.提出了一种将Markov法和Monte Carlo法相结合的多端VSC-HVDC并网系统可靠性评估的混合法。首先根据多端VSC-HVDC系统的接线特点和各组成元件的功能将并网系统划分为不同的子系统，包括风电场子系统、整流端子系统、逆变端子系统等，分别建立各子系统的Markov模型；然后基于时序Monte Carlo法计算系统可靠性指标。另外，为了刻画风电场出力间歇性对VSC-HVDC并网系统可靠性的影响以及VSC-HVDC系统的无功补偿能力，建立了多端VSC-HVDC并网系统可靠性评估指标体系。.基于成本效益分析原理，综合VSC-HVDC系统的可靠性和经济性，研究了VSC-HVDC系统设备最优选型模型及算法。该模型属于离散非线性优化模型，基于遗传算法给出了模型的求解算法，为改善算法的收敛性和计算速度，遗传算法中采用了整数编码、自适应交叉率和变异率以及保留最优个体等技术。