弱电网下双馈风机多机系统直流电压控制时间尺度的建模与稳定性分析
Modeling and Stability Analysis of DC Voltage Control Timescale in DFIG Multi-Machine System Under Weak Power Grid
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摘要: 研究了弱电网下双馈多机系统直流电压控制时间尺度的建模和稳定性。首先,建立了双馈多机系统直流电压控制时间尺度的小信号模型,包括直流电压控制、有功功率控制、端电压控制和锁相环,可以充分刻画风机直流电压控制时间尺度的动态特性。然后,通过特征根和主导振荡模态参与因子分析,研究影响双馈多机系统稳定性的主导风机和主导控制环路,其贡献点在于揭示不同控制带宽下影响双馈多机系统稳定性的关键因素。研究发现在双馈风机的各控制环路中,锁相环对风机稳定性的占主导地位,而直流电压环对风机稳定性的影响最小。最后,建立双馈多机系统时域仿真模型,验证了建模和稳定性分析结果的有效性。Abstract: The modeling and stability of DC voltage control timescale in doubly-fed multi-machine system under weak power grid are studied. Firstly,a small-signal model of DC voltage control timescale of doubly-fed multi-machine is established,including DC voltage control,active power control,terminal voltage control and phase-locked loop,which can fully describe the dynamic characteristics of DC voltage control timescale. Then,through the analysis of eigenvalues and dominant oscillation mode participation factors,the dominant wind turbine and the dominant control loop which affect the stability of the DFIG system are studied. The contribution of the proposed method is to reveal the key factors affecting the stability of doubly-fed multi-machine system under different control bandwidth.It is found that the PLL plays a dominant role in the stability of DFIG,while the DC voltage loop has the least influence on the stability of DFIG. Finally,detailed model based time domain simulations verifies the validity of modeling and stability analysis results.
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