风电系统时变间谐波的解析建模与并网交互影响及危险区域研究

With the increase of wind power, the development of AC and DC hybrid system and the domination of power electronics, the influence of wind power interharmonics in new power system is getting more and more serious. Except for the inherent non-synchronous characteristics, interharmonics also present complex characteristics of time-varying, low-frequency ride-through and high-frequency transferring. A number of papers at home and abroad have reported the power quality issues like voltage fluctuations and flicker caused by interharmonics. Much attentions are also paid to the tripping risks of wind turbine generators and the damages of thermal power units induced by interharmonics. However, existing methods are almost from the perspective of stability and only for subsynchronous frequency components, which are difficult to fully reveal the above characteristics. Apart from these, the interaction mechanism between wind power and power grid, and the quantitative assessment for the damage of time-varying interharmonics are two unresolved key issues. In this project, an analytical model for time-varying wind power interharmonics will be established from the perspective of amplitude-frequency characteristics. Then the transmission law, nature characteristics and influence factors will be analyzed. With the dynamic-frequency relative gain array, the interaction between wind power and power grid and its mechanism will be investigated. Considering the comprehensive effects of multiple influence factors, a quantitative assessment method for risk intervals of time-varying wind power interharmonics will be proposed, which lays theoretical foundation for safe operation of wind power and suppression of interharmonics.

随着风电渗透率的提高、交直流混合系统的发展和电力电子化程度的加深，新一代电网中的风电系统间谐波影响越来越严重。它除了固有的非同步特性，还呈现出时变、低频穿越和高频转移的复杂特性。国内外均已报道其引起的电压波动与闪变等电能质量问题和造成的风机脱网、火电被迫切机等系统设备问题。而现有研究方法多从稳定角度出发并仅以次同步频率分量为对象，存在着难以全面揭示上述特性的瓶颈；同时，风电系统时变间谐波与电网的交互机理和间谐波危害的定量评估均是尚未解决的两大关键问题。本课题拟从幅频、相频特性角度出发，推导并建立风电系统时变间谐波的解析模型，进而研究其传变规律，揭示其特性本质和影响因素；结合动态频率相对增益原理，研究其与电网交互作用的机理与程度；基于此，考虑多影响因素综合作用，从电能质量、振荡与脱机的角度建立风电系统时变间谐波的危险区域定量评估方法，为风电安全运行控制和间谐波抑制等提供理论基础。

在我国双碳目标和建设以新能源为主体的新型电力系统背景下，风能的消费比重持续增长，大规模并网带来的时变间谐波问题贯穿电能质量领域和系统稳定领域，造成的危害越来越严峻。本项目以双馈 (DFIG)与直驱 (D-PMSG) 风电并网时变间谐波为对象，从次同步和高频段两频率范围，开展解析建模与并网交互影响及危险区域研究，揭示产生机理和时变特性，评估风险，为提升并网电能质量、提高风电系统稳定性奠定基础。.主要内容如下：.1.建立了扰动分量与转差频率耦合引起的DFIG定子间谐波电流解析模型，分析了扰动分量传变规律及间谐波电流随风速变化的幅频时变特性。.2.建立了考虑励磁的 DFIG输入阻抗频域模型，提出了3 种输入阻抗下的等效电路，阐释了输入阻抗时变特性及次同步谐振（SSR）频率随风速等交互变化的物理机制。.3.建立了D-PMSG状态空间模型与阻抗模型，量化了风速等对次同步振荡（SSO）的交互影响；将模型扩展至（多）风电场建立了阻抗网络模型，量化了不同工况下大规模风电并网SSO稳定性及相关随机变量对特性的影响。.4.基于风速/台数与谐振频率及阻尼的数学关系，结合Monte Carlo模拟和核心平滑密度估计技术，提出了双馈/直驱风电系统时变SSR/SSO概率评估方法，刻画了频率和阻尼概率分布特点及带宽变化规律。.5.计及随机时变因素，采用时序蒙特卡洛法，提出了直驱风电系统SSO风险评估方法与评估指标，建立了评估体系；计及风电场内外参数差异，对比了单机/双机/多机等值模型的风险评估性能，优化了评估方法。. 6.提出了双馈/直驱风电并网系统的临界风速定义，应用于直驱系统SSO风险评估，基此提出切入风速调整降低风险的方法；研制了宽频带次同步谐振抑制装置，实现对双馈系统4~12Hz时变间谐波电流快速响应与谐振实时抑制。.7. 建立了调制引起DFIG变流器输出谐波/间谐波电压/电流幅值与频率解析式，量化了DFIG风电系统高频间谐波发射水平；建立了高频段D-PMSG导纳模型和大规模并网系统节点导纳矩阵，提出了模态分析与电压扰动响应结合的谐振分析方法，基于电能质量限值确定了影响参数危险区域。