摘要
级联H桥静止无功发生器(SVG)是改善电能质量、进行无功补偿的常用装备。然而,作为一种由控制主导动态特性的电力电子装备,必然存在振荡风险,对电力系统安全稳定运行造成威胁。针对上述问题,该文首先分析级联H桥SVG非线性、强耦合的内部动态特性,针对开关频率以下的低频段,建立考虑多控制环路作用的SVG谐波状态空间复矢量阻抗模型。然后,基于系统频率耦合关系,得到降维后的SVG阻抗模型及等效的单输入单输出阻抗模型,通过Matlab/Simulink仿真平台进行频率扫描,验证阻抗模型的正确性。在阻抗模型基础上,基于不同控制环以及其控制参数对SVG进行稳定性分析。分析发现,锁相环对系统稳定性影响显著,因此对其参数进行量化分析,为参数设计提供参考。而相间均压环对系统稳定性影响相对不显著。为解决SVG并网稳定性问题,该文针对主导控制环即锁相环引发的振荡风险,提出一种电压前馈阻抗重塑策略,有效减小锁相环带来的负阻问题,进而提高系统的并网稳定性。最后,基于RT-Lab建立SVG并网系统的硬件在环实验,验证该文所提的理论分析和振荡抑制策略的有效性。
Due to its compensation capabilities and fast dynamic response times,the cascaded H-bridge static var generator(SVG)has become widely adopted for enhancing power quality and providing reactive power in modern power systems.However,as a power electronic device predominantly governed by control-driven dynamics,the SVG faces the risk of oscillations.In addition,the mechanisms of wideband oscillations in SVG systems remain insufficiently understood,and effective stability enhancement techniques are lacking.This paper analyzes the cascaded H-bridge SVG's nonlinear and strongly coupled internal dynamic characteristics.Focusing on the low-frequency range below the switching frequency,a harmonic state-space(HSS)complex vector impedance model is developed,incorporating the influence of multiple control loops.A detailed time-domain model is constructed to simulate the system's behavior,and frequency scanning is conducted using Matlab/Simulink.Furthermore,considering the system's frequency coupling relationships,the dynamic interactions of internal currents,output voltages,and three-phase capacitor voltages and their coupling grid impedance are examined.Accordingly,an equivalent single-input single-output impedance model is constructed.A stability analysis of the SVG is performed to evaluate the impact of various control loops and their associated parameters on system stability.The phase-locked loop(PLL)is critical in determining system stability.Consequently,a quantitative analysis of the PLL parameters is conducted for parameter design and optimization.In contrast,the inter-phase voltage balancing loop has a minor influence on system stability.This paper proposes a voltage feedforward impedance reshaping strategy to mitigate the stability challenges associated with SVG grid integration.This approach targets the oscillations introduced by the dominant control loop(the PLL),which can offset its impact.However,since this method involves high-order integration,it is prone to causing system instability.Therefore,an optimized control strategy is proposed,effectively reducing the negative resistance region caused by the PLL,thereby enhancing the overall stability of the grid-connected system.A hardware-in-the-loop experiment is implemented using the RT-LAB platform.The experimental results verify the effectiveness of the proposed methods in improving system stability.The key conclusions of this study are as follows.(1)The PLL and its control parameters significantly influence the system's oscillation risk based on the developed HSS impedance model for multi-frequency weights,considering both expert experience and the actual essential indicators.(3)Based on cloud theory and the quantitative criteria of each index evaluation grade,the comprehensive evaluation model can overcome the fuzziness and randomness between the quantitative index value and the evaluation grade boundary,improving the engineering applicability.(4)The simulation results demonstrate that the proposed model and method intuitively give the comprehensive evaluation results and ranking of each location scheme,which provides a basis for the decision-making and application of dynamic adjustment topology to limit the distribution of short-circuit current fast switches.
作者
李龙灿
熊小玲
罗博晨
赵成勇
徐莹
雷添翔
Li Longcan;Xiong Xiaoling;Luo Bochen;Zhao Chengyong;Xu Ying;Lei Tianxiang(School of Electrical and Electronic Engineering North China Electric Power University,Beijing 102206 China;State Grid Economic and Technological Research Institute Co.Ltd,Beijing 102209 China)
出处
《电工技术学报》
北大核心
2025年第24期8108-8122,共15页
Transactions of China Electrotechnical Society
基金
国家自然科学基金资助项目(52277176)。
关键词
静止无功发生器
谐波状态空间
频率耦合
稳定性分析
阻抗重塑
Short-circuit current
comprehensive evaluation
fast switch location decision-making
topology adjustment
cloud model
