电力电子化配电网背景谐波振荡机理及治理研究

Compared to the traditional distribution network, the background harmonic of the distribution network with power electronic has the following features. The principle of background harmonic propagation is different owing to the impedance of the grid-tied inverters; due to the resonance of grid-tied inverters, there are two main background harmonic sources instead of the single background harmonic source; and the traditional schemes for damping out harmonic propagation could not work well. From the viewpoint of eliminating the background harmonic source, more attention of the distributed parameters of distribution network has not been paid in the resonance study of grid-tied inverters. According to the aforementioned, the project will mainly focus on the following aspects: 1) Study the impedance characteristics of the grid-tied inverters controlled under different schemes and the principle of background harmonic propagation. 2) Study the characteristics and the influence of the distributed parameters of distribution network as well as the resonance mechanism of the grid-tied inverters which are controlled in a centralized mode or decentralized mode. 3) Study and apply the innovative power electronic converters to regulate the site and magnitude of harmonic resonance of background harmonic on a transmission line and adjust the equal impedances of the distribution network and grid-tied inverters, to combine the mitigation of background harmonic and elimination of inverters resonance in distribution network with power electronics. Ultimately, the research will be helpful to increase the power quality of distribution network with high penetration of new source generation, increase the reliability of power source, and facilitate the development of technology for new power source interfaced to the grid.

末端接入高渗透新能源并网逆变器群组的电力电子化配电网中，逆变器并网阻抗改变了背景谐波传播规律，逆变器群组谐振导致配电网由单背景谐波源系统变为双谐波源系统，因此传统配电网背景谐波治理方案不能有效发挥作用。从消除背景谐波源的角度看，现有并网逆变器群组的谐振研究对配电网分布参数关注不足。针对以上问题，本申请重点研究：1)研究采用不同控制方案的规模化并网逆变器群组的阻抗特性，分析电力电子化配电网的背景谐波的传播规律；2)研究传输线分布参数特性与影响，分析集中式和分散式等并网控制模式下逆变器组谐振机理；3)研究并协调应用新型电力电子变换器，调整背景谐波谐振点在配电网的位置及谐振幅值，调整逆变器接入点配电网等效阻抗及逆变器等效阻抗，解决以高渗透率电力电子并网装置为特征的配电网逆变器群组谐振和背景谐波振荡问题。研究成果将提高新能源高渗透率的电力电子化配电网电能质量，保障用电安全，促进新能源并网技术发展。

末端接入高渗透新能源并网逆变器群组的电力电子化配电网中，逆变器并网阻抗改变了背景谐波传播规律，逆变器群组谐振导致配电网由单背景谐波源系统变为双谐波源系统，因此传统配电网背景谐波治理方案不能有效发挥作用。本项目结合线缆分布参数模型、多机不同控制方案对阻抗的影响，研究多环路控制阻抗模型，研究多机谐振问题。结合微电网多源背景谐波特性，研究微网多种并网模式下背景谐波的振荡放大规律。研究两种双功能复合型变流器，兼顾抑制网内多源背景谐波的振荡放大和新能源并网多机变流器群组的振荡。利用复合型背景谐波APF变换器，结合微网新能源变换装置研究、不平衡坐标系控制方案、频率电压双重优化等方案的综合协调控制解决电力电子化配电网背景谐波振荡。本项目研究发现并网逆变器的高频谐振会引起系统次生的低频谐振，这为系统多机谐振治理的谐振源分析提供了新的思路。传输线线性化模型及下垂型并网系统的阻抗模型，为系统多机谐振的线性判据使用提供了技术支持，可以提高原线性判据的应用范围。提出的一种等效一定长度长传输线的变换器用以抑制背景谐波放大，其原理完全不同于RAPF，通过对谐波在传输线上的传播规律，根据无限长线上不存在反射波的原理提出，而等效复阻抗变换器则是结合了谐波在传输线上传播的波腹位置特点的一种电力电子新装置。本项目谐振分析的场景特性，涵盖了并网稳态，低电压穿越，下垂孤岛，黑启动重合闸电压频率预调节，柴油同步发电机并逆变器等工况。谐波特性及抑制的研究同时兼顾了电力电子化系统继电保护的需求。利用谐波分析对地短路等工况的发生。研究的谐波振荡频率宽，考虑了功率环、锁相环、电压控制、LCL滤波器、电流环影响，从几赫兹到几千赫兹。本项目研究成果将提高新能源高渗透率的电力电子化配电网电能质量，保障用电安全，促进新能源并网技术发展。