摘要
随着新能源装备占比不断增加,其内在同步稳定机理逐步发生改变。为此,该文对转子转速尺度双馈风机单机无穷大系统的小扰动同步稳定机理进行研究。首先,构建该转子转速尺度下双馈风机的暂态模型,仿真验证了降阶模型的合理性。通过分岔分析,发现随着电网变弱,系统将出现小扰动失稳现象。采用主导模态分析法,确定转子转速尺度下双馈风机小扰动失稳的主导环节为功率平衡环节(转子动态与有功外环)。因此,以功率平衡环节为核心,构建了类Heffron-Phillips模型,并揭示了储能元件状态量与同步环节相位之间的关系。进一步地,基于复转矩系数法,发现锁相环环节对系统同步/阻尼特性影响很小,而端电压环节是引入负阻尼的主要因素。最后,针对有功外环、端电压环节的参数影响进行了分析,为参数优化提供相应指导。上述理论分析均通过了Matlab/Simulink仿真验证和硬件在环实验。
As the penetration rate of renewable energy sources increases,the stability mechanisms of the power system are constantly changing.The double-fed induction generator(DFIG),as a mainstream renewable energy equipment,its stability is of great significance to the safe operation of the power system.The phase-locked loop(PLL)plays an important role in synchronization,but there has been less research on simultaneously considering the dynamics of the phase-locked loop and the power balance loop.Moreover,the small-signal synchronization mechanism of DFIG within rotor speed timescale needs to be further analyzed.Firstly,the transient model of single-DFIG infinite-bus system is constructed within the rotor speed scale.The simplified model is compared with the full-order model by Matlab/Simulink,and the results show that they match very well.Then,through bifurcation analysis,it is found that the system would experience small disturbance instability under weak grid condition.And it manifests itself in the form of low-frequency oscillatory instability.Furthermore,through the dominant modal analysis,it is found that the dominant unstable loop is the power balance loop.In order to analyze the small-signal synchronous instability mechanism of the system,the model is linearized around the operating point.The linearized model and the full-order model are compared using Matlab under small disturbance,and the results validate the rationality of linearization.The power balance loop dominates the instability,making it considered as the core loop.Therefore,the Heffron-Philips model of the system is established for analyzing the small-signal synchronous stability mechanism.Based on the complex torque coefficient method,the terminal voltage control loop plays a dominant role by introducing negative damping.And by studying the transfer function of the PLL,it is found that the PLL with typical parameters has a negligible impact on the system in the rotor speed scale,and can be approximately regarded as a constant.Finally,the parameters of the active outer loop and the reactive outer loop are analyzed.With the changing of the grid strength,the damping torque and synchronizing torque of each branch are quantitatively calculated.It is found that increasing the proportional coefficient of active outer loop and decreasing the integral coefficient will improve the stability of the system,and increasing the proportional/integral coefficient of the terminal voltage control loop will benefit the stability of the system.These analyses have been verified through simulations and experiments.The conclusions of this paper are as follows:(1)In the rotor speed scale,the small-signal synchronous instability of the single-DFIG infinite-bus system is dominated by the power balance loop(active outer loop and rotor dynamic),rather than the PLL.(2)By constructing the Heffron-Philips model,it is found that the synchronous phase∆θpll is approximately represented by an algebraic expression of the state variable∆ωr/∆θrof the rotor.The essence of synchronous instability lies in the instability caused by the state variable of the energy storage element.3)Using complex torque coefficient method,it is found that the terminal voltage control loop is the main factor that introduces negative damping.Through the analysis of the influence of parameters,it is found that increasing the proportional coefficient of the active power outer loop and decreasing the integral coefficient will improve system stability,and increasing the proportional/integral coefficient of the terminal voltage control loop will be beneficial to system stability.
作者
许洪胜
占萌
付聪
张水平
苗璐
包博
李顺
Xu Hongsheng;Zhan Meng;Fu Cong;Zhang Shuiping;Miao Lu;Bao Bo;Li Shun(State Key Laboratory of Advanced Electromagnetic Engineering and Technology,School of Electrical and Electronic Engineering,Huazhong University of Science and Technology,Wuhan 430074,China;Hubei Electric Power Security and High Efficiency Key Laboratory,Huazhong University of Science and Technology,Wuhan 430074,China;Power Dispatching Control Center of Guangdong Power Grid,Guangzhou 510000,China)
出处
《电工技术学报》
北大核心
2025年第11期3395-3409,共15页
Transactions of China Electrotechnical Society
基金
南方电网公司科技项目资助036000KC23090004(GDKJXM20231026)。
关键词
双馈风机
转子转速
时间尺度
主导模态分析
复转矩系数法
Double fed induction generator
rotor speed time scale
dominant mode analysis
complex torque coefficient method
