微网安全风险评估研究

Taking into account the fact that power system fault may lead to a local or even large-scale blackout of power grid, which might have bad impacts on economy, society and environment, the risk assessment has become one of the most challenging and essential tasks in the power industry. As a rising power system technology in recent years, microgrid can take full advantages of distributed generations in economy, energy and environment. Meanwhile, the risk assessment technology of microgrid is different from that of utility grid due to the differences of power supply structure, operation mode as well as protection and control system between them, thus it will face new problems and challenges. Considering the inherent characteristics of the microgrid and the charateristics of its risk assessment, which is different from that of the traditional power system, this project made an intensive study of the theoretical methods and techniques of the risk assessment in microgrid based on the basic theory of the risk assessment. The main contents of this project are as follows: the reliability model of microgrid components; the security risk assessment of the microgrid in an isolated mode; the security risk assessment of grid-connected microgrid; identifying and tracking the weak parts of the system during risk assessment of the microgrid; the calculation of severity of the risk of microgrid considering consumer's economic losses. An optimal technical system of microgrid security risk assessment is proposed, what's more, a theoretical basis for a larger scale and a higher proportion of microgrid integration into the power system will be established through this research project.

电力系统故障可能导致局部直至大面积的停电，对经济、社会、环境等造成影响，风险评估已成为电力工业具有挑战性的一项基本任务。微网是近年来新兴的电力系统技术，能够最大发挥分布式发电在经济、能源和环境中的优势。同时，由于与大电网电源结构、运行方式及保护控制体系的不同，使得微网的风险评估技术也有所不同，面临新的问题和挑战。本项目针对微网自身固有的特性及其区别于传统电力系统风险评估的特点，以风险评估的基本理论为基础，深入研究微网风险评估的理论方法和技术体系，量化微网对电力系统带来的风险行为。本项目主要研究内容包括：微网元件的可靠性模型、孤岛运行模式下的微网安全风险评估、并网运行模式下的微网安全风险评估、微网风险评估中系统薄弱环节的识别与跟踪、计及用户经济损失的微网风险严重度计算。通过本项目研究，能够建立完善的微网安全风险评估技术体系，为电力系统更大规模、更高比例的接入微网奠定理论基础。

微电网技术由于能够提升分布式电源消纳率，有效解决偏远地区或海岛的供电问题，自提出以来就得到了长足的发展。然而在微网内，由于清洁能源出力具有波动性和不确定性，储能设备和柴油机供电存在约束，以及微网设备的随机故障无法完全确定等问题，微网运行存在一定的风险，对其进行风险评估是保障微网安全稳定运行的一项基本任务。本项目从微网元件的可靠性模型、孤岛运行模式下的微网安全风险评估、并网运行模式下的微网安全风险评估、微网风险评估中系统薄弱环节的识别与跟踪、计及用户经济损失的微网风险严重度计算展开研究工作，主要内容有：.（1）采用马尔科夫链蒙特卡洛法建立了风力发电可靠性模型。考虑晴空指数和波动特性的相关性，采用马尔科夫链蒙特卡洛法建立了光伏出力的可靠性模型。综合考虑储能放电深度和充放电次数对储能容量衰减的影响以及储能运行策略，建立了储能系统可靠性模型。结合柴油发电机两状态模型和出力模型建立了柴油发电机可靠性模型。.（2）针对电源出力无法满足负荷需求时易引起负荷削减现象，当电源出力远超负荷需求时，又会造成弃风、弃光等问题，为此提出了一组适用于微网的风险指标，并采用蒙特卡洛模拟法对风险指标进行计算。.（3）为了得到并网型微网最优孤岛划分方案，评估微网接入对提升配电网可靠性的有益效果，提出了基于混合整数线性规划的多时段动态孤岛划分模型，并基于序贯蒙特卡洛模拟提出了考虑故障状态下动态孤岛的风险评估流程。.（4）采用故障树蒙特卡洛法对孤岛微网的薄弱环节进行识别。建立微网各用户的故障树模型，通过蒙特卡洛法随机抽样建立微网的两状态模型。从元件重要度和网络风险重要度两个方面，建立微网薄弱环节重要度指标体系。通过算例研究，验证模型的准确性，寻找系统的薄弱环节，评估微网的可靠运行能力。.（5）针对微网内不同重要程度负荷停电造成的经济损失，采用条件风险价值方法定义了经济风险严重度指标，为解决严重度指标计算公式中停电损失概率密度函数难以求取的情况，采用蒙特卡洛模拟法对其进行求解。