摘要
光伏电站并网时需要具备一定的无功支撑能力,通常需要配备无功补偿装置,二者之间的相互作用增加了静态同步稳定问题的分析难度。该文首先提出一种含静止同步补偿器(STATCOM)的光伏并网系统静态同步稳定分析方法;然后考虑不同并网变换器dq坐标系间的变换,构建多并网变换器并联系统的等效小信号模型,在阻抗分析方法基础上改进稳定判据,并利用衰减系数指标定量刻画系统的静态同步稳定性能,构建静态同步稳定量化评估指标体系;最后结合改进的判据和量化指标,详细地分析了STATCOM对光伏并网系统静态同步稳定性能的影响,总结了各控制参数对于系统运行零极点分布的影响规律。
PV systems are typically equipped with reactive power compensation devices when connected to the grid,and static synchronous compensator(STATCOM)devices are widely employed due to their flexible control capabilities.The increasing utilization of power electronic devices in the power grid has resulted in a shift from physical synchronization to control synchronization as the dominant mode of system operation.Analyzing static synchronization stability problem is more challenging for these systems compared to conventional power systems,as converter output characteristics are influenced by control strategies.Therefore,it is imperative to urgently address the problem of static synchronization stabilization under control strategy dominance.First,this paper establishes the static synchronous stability analysis model of the grid-connected converter based on the control loop and circuit structure of each converter in a parallel system under the respective dq reference frame.The dq reference frame of the converter is determined by the phase information provided by the control loop in a multiple converter parallel system,thus enabling a unified coordinate system for static synchronization stability analysis.Subsequently,an equivalent small signal model is developed for analyzing multiple grid-connected converters.In comparison with existing coordinate conversion methods,Kirchhoff's current law is incorporated to enhance accuracy and reduce errors.Then,the stability criterion for impedance analysis is enhance,and the static grid-synchronization performance indices are created.The small perturbation oscillation characteristics are measured using overshooting and regulation time,while the participation factor is employed to analyze the impact of each pole of the system.Finally,the attenuation coefficient is utilized to assess static synchronization stability performance.The model is developed in Matlab/Simulink for simulation verification.Subsequently,an analysis is conducted on the impact of parameters such as the control loop parameters and STATCOM capacity on static synchronization stability.The main conclusions are summarized as follows:(1)Optimizing the reactive power output of the grid-connected converter based on known control parameters can significantly enhance static synchronization stability performance,with the dominant influence of small perturbations after oscillation mode being attributed to poles generated by phase-locked loop control.(2)The attenuation coefficient of the system exhibits a rapid increase in proximity to the critical stability region.Hence,it is imperative for the system to possess a certain margin of attenuation coefficient during operation.Based on the simulation analysis results presented in this study,static synchronous instability phenomena occur when the attenuation coefficient of the PV system exceeds 300.Conversely,when the attenuation coefficient falls below 250,the system remains in a state of static synchronous stability.These findings establish a criterion for analyzing and assessing static synchronization stability within such systems.(3)The addition of STATCOM to the PV system primarily impacts the conductance matrix transfer function of the q-coupled channel.The phase-locked-loop coupling oscillations between the grid-connected converters do not affect the dd channel.Within the stable operating region,an increase in bandwidth for the DC voltage control loop,active current control loop,and reactive current control loop results in an amplification of both attenuation coefficient and system oscillation amplitude.(4)When the phase-locked loop parameters of the STATCOM are the same as the PV system,the stability performance of the system is mainly affected by the grid impedance and the equivalent conductance transfer function of each grid-connected converter.And each grid-connected converter can independently connect to the grid and achieve stable operation to ensure that the system achieves static synchronous stability in this case.(5)In cases where the active output of the PV system is low,STATCOM typically adjusts its capacitive or inductive reactive power provision to improve static synchronization stability performance.Conversely,when compensating for capacitive reactive power,utilizing STATCOM may yield superior results compared to using the PV grid-connected converter alone.Hence,allocating an optimal capacity for STATCOM can significantly enhance static synchronization stability performance.
作者
马睿聪
曹永吉
张恒旭
李常刚
Ma Ruicong;Cao Yongji;Zhang Hengxu;Li Changgang(School of Electrical Engineering,Shandong University,Jinan 250061,China;Academy of Intelligent Innovation,Shandong University,Jinan 250101,China)
出处
《电工技术学报》
北大核心
2025年第11期3410-3426,共17页
Transactions of China Electrotechnical Society
基金
国家自然科学基金智能电网联合基金集成项目(U22B6008)
山东省自然科学基金项目(ZR2021QE133)资助。
