高渗透率并网发电系统的柔性统一阻抗适配器研究

With the increase in the renewable energy power generation system penetration, the change of grid impedance leads to the more and more serious coupling between grid and power generation system based on grid-connected inverter, and even seriously affect the stable operation of the system. A method of paralleling the impedance adapter in the point of common coupling of power generation system to achieve the remodel of grid impedance, and increasing the resonance suppression of system damping has received the attention of academia. However, the parallel impedance adapter cannot effectively suppress the resonance caused by the voltage-type harmonic source and achieve the complete decoupling of the grid impedance and the power generation system. For this reason, this project put forward an impedance adapter based on a series-parallel combination and with a flexible topology at the same time, that is, a flexible unified impedance adapter, which can overcome the above shortcomings and increase the effective capacity of the adapter through the flexible switching of the adapter structure. The main studies include: Studying the impedance coupling modeling of high permeability grid-connected power generation system to reveal the mechanism of resonance instability and harmonic amplification; Proposing a topology and its control strategy of the unified impedance adapter with flexible structure to realize the suppression of system resonance and harmonic amplification; Building a laboratory simulation program of high permeability grid-connected system to verify the effectiveness of the proposed mechanism and the suppression strategy.

随着可再生能源并网发电渗透率的提高，电网阻抗的变化导致基于逆变器的并网发电系统与电网之间的耦合越来越严重，甚至严重影响可再生能源并网发电系统的稳定运行。在发电系统并网点并联阻抗适配器实现电网阻抗的重塑，增加系统阻尼的谐振抑制方式得到了学术界的关注，但并联式的阻抗适配器无法有效抑制电压型谐波源引起的谐振，同时无法实现电网阻抗与可再生能源发电系统的解耦。为此，本课题提出基于串并联组合且具有柔性拓扑的阻抗适配器，即柔性统一阻抗适配器，克服上述缺点的同时还能通过适配器结构的柔性切换，增加适配器的有效容量和输出带宽。主要研究包括：研究高渗透率并网发电系统阻抗耦合建模，揭示系统产生谐振失稳和谐波放大的机理；提出柔性结构统一阻抗适配器拓扑及其控制策略，实现系统谐振和谐波放大的抑制；构建高渗透率并网系统实验室模拟方案，验证所提机理和抑制策略的有效性。

随着可再生能源的逐步发展，并网系统的短路容量比逐步降低，使得并网逆变器系统与电网之间的耦合问题越来越严重，不仅极大地影响并网电流的质量，严重时可致使可再生能源并网发电系统不稳定。在发电系统并网点并联阻抗适配器实现电网阻抗的重塑，增加系统阻尼的谐振抑制方式得到了学术界的关注，但并联式的阻抗适配器无法有效实现电网阻抗与可再生能源发电系统的解耦，进而抑制背景噪声引起的谐波放大。本课题针对高渗透并网发电系统的自身稳定性和谐波放大问题，从并网点阻抗这一系统耦合的关键因素出发，提出采用串联和并联相结合的统一阻抗适配器对并网点阻抗的进行适配的创新思路，实现高渗透并网发电系统与电网阻抗之间的完全解耦，抑制系统的谐波。并在统一阻抗适配器的基础上又提出具有柔性结构的统一阻抗适配器拓扑，来增加适配器的有效容量和输出带宽。基于资助项目，本课题完成了多逆变器系统的谐振机理分析，并使该方法可以应用于扫频得到的阻抗模型上，适合应用于工程分析；构建了自动扫频平台，实现了多逆变器并联系统与阻抗适配器装置的自动扫频；开发了一端口网络的RLC等效电路对谐振问题进行分析，指导阻抗适配器虚拟输出阻抗的设计；成功搭建了柔性统一阻抗适配器实验样机、高渗透并网发电系统的数字/物理混合仿真实验室模拟平台和物理模型实验室模拟平台，并利用上述两种实验平台验证了所提阻抗适配器对高渗透率并网发电系统失稳谐振和谐波放大的抑制效果的有效性。