次同步振荡实际系统分层次建模理论与方法研究

As for China, due to the converse distribution of primary energy and power load, high-capacity and long-distance power transmission has been the important approach optimally distributing primary energy nationwidely. To enhance the transmission capability of the corridors, the transmission technologies of series capacitor compensation and HVDC have been widely used in the Chinese power grid, which readily cause the increasing problems of subsynchronous oscillation (SSO). Yimin and many other power plants such as Suizhong, Shangdu, and Baorixile have all the severe problems for SSO. The problems for SSO have been placed on the Major Technical attack project of the generator-network coordination for smart grid. To ensure the safe and stable operation of the Chinese power grid, there is an urgent problem that must be resolved in suppressing SSO..So far the traditional modeling method (TMM) is the unique way to obtain the practical SSO model for an actual system, and it is the basis for the SSO analysis and suppression-technology study. However, the details of the SSO local propagation mechanism (LPM) remain unknown so that they cannot theoretically support the TMM. Thus, the TMM has three limits: identification of the internal zone boundary is subjective by means of researchers' significant familiarity with the network as well as engineering judgment because there is no clear definition about the boundary; the partition of modeling zones is unreasonable due to a larger dynamic zone in the actual systems; only adopting the detailed dynamic models has no ability to represent a larger dynamic zone due to the practicability constraints. These limits result in inaccurate results for SSO analysis and suppression-technology study, and they become a severe bottleneck inhibiting the practical application of the TMM..The project aims to reveal the details of SSO LPM, and develop the theory and method of SSO hierarchical modeling for the actual system by using the detailed LPM. It includes four parts of the work: I. The continuum model for SSO LPM is established and the quantitative laws of SSO LPM in space and time are developed; II. The natural physical quantities for the zone partition is defined by using the details of LPM, and the partition methods for the internal, external and marginal zones are established; III. By means of nonlinear TPWL reduced-order method, the dynamic equivalent model for the external zone is established in the subsynchronous time scale; IV. In the cases of small and large disturbances, the assessment indexes are developed to assess the model credibility. This project study can provide new theories and technologies for modeling the actual systems and it can also contribute to SSO analysis and suppression-technology study of the actual systems.

次同步振荡抑制是确保我国电网安全稳定运行亟待解决的问题。传统建模方法是获得实用模型的唯一途径，是次同步振荡分析及抑制技术研究的基础。但次同步振荡详细局部传播机制尚不明确，无法在理论上支持传统建模方法，造成该方法存在3个问题：内部区域边界识别具有主观性，单一详细动态模型不能建模较大区域，建模区域划分不合理。这些问题导致次同步振荡分析及抑制技术研究结果不准确，成为制约实际系统抑制技术研究的瓶颈。本项目旨在揭示次同步振荡详细局部传播机制，发展实际系统分层次建模理论与方法，包括四方面工作：（1）建立连续体模型，提出次同步振荡局部传播时空定量规律；（2）基于该规律定义分区特征物理量，提出内部、外部及边际区域划分方法；（3）应用TPWL非线性降阶方法，建立外部区域次同步时间尺度的动态等值模型；（4）针对大、小扰动，提出可信度评估指标，评估模型可信度。本项目研究将为次同步振荡分析及抑制技术研究做出贡献。

随着我国电网发展，传统次同步振荡和新型次同步振荡频繁发生。特别是自2014年6月起，我国新疆某大型风电基地发生了信心次同步振荡100多次，次同步振荡是危及我国电网安全稳定运行亟待解决的关键问题之一。而传统建模方法是获得实用模型的唯一途径，是次同步振荡分析及抑制技术研究的基础。但次同步振荡详细局部传播机制尚不明确，无法在理论上支持传统建模方法，造成传统建模方法存在诸多问题。这些问题导致次同步振荡分析及抑制技术研究结果不准确，成为制约实际系统抑制技术研究的瓶颈。本项目针对这些问题进行研究，主要取得了以下研究成果：.（1）揭示了传统次同步振荡机理和振荡传播机制.提出了随电阻参数变大，互补次同步模态电气负阻尼减小，而非互补次同步模态电气负阻尼则增加；次同步阻性电流产生负阻尼转矩，次同步感性电流产生同步转矩的详细机理；提出由于电网谐振约束了次同步振荡的传播，次同步振荡主要在串补线路及其附近的线路的局部电网中传播；.（2）提出了多种基于次同步振荡局部传播机制的建模方法.提出了基于迭代逼近、基于节点重要度指标、基于元件参数灵敏度、基于次同步振荡功率传播区域等多种次同步振荡建模方法；同时，也提出了次同步振荡研究中火电厂同型机组等值方法；.（3）研究了双馈风电场的次同步振荡机理、风险评估方法及抑制措施.揭示了双馈风电场等效电阻随着双馈风力发电机转速和系统自然谐振频率变化的规律，提出了应用等效电阻分析双馈风电场感应发电机效应危险区域的一种新方法；定义了次同步振荡风险矩阵及风险指数，并结合概率配点法发展了一种次同步谐振风险评估方法；结合单纯形算法(Simplex)与电磁暂态仿真程序，提出非线性参数优化方法引入到抑制双馈风电场次同步振荡的TCSC参数的优化。.本项目研究为传统次同步振荡分析及抑制技术研究做出贡献，为新型次同步振荡分析及抑制提供了新思路。