Under weak grid conditions, there is a strong nonlinear coupling between phase-locked loops (PLLs) and the doubly-fed induction generators (DFIGs), and the influence of its dynamic characteristics on system stability cannot be ignored. For a system to be stable, the dynamic properties must be considered. First, based on instantaneous power theory, the sub-synchronous frequency component of power oscillation in a three-phase symmetrical system with the participation of a PLL is deduced. Second, the PLL transient stability is studied under two power grid structures. Third, to connect with the power grid model, a DFIG with a PLL structure is established, and the phase disturbance of the PLL is used as the excitation signal. In the rotor current inner loop and the voltage outer loop transfer processes, the PLL phase disturbance component plays a role. A d-axis structure block diagram of the current loop with the PLL phase disturbance component is constructed, and the disturbance transfer function is deduced. The influence mechanism of the PLL control parameters on system power oscillation is investigated. Finally, the modeling simulation verifies the validity of the theoretical analysis.

在弱电网条件下，锁相环（PLL）与双馈感应发电机（DFIG）之间存在强非线性耦合，其动态特性对系统稳定性的影响不容忽视。为了使系统稳定，必须考虑动态特性。首先，基于瞬时功率理论，推导了有锁相环参与的三相对称系统中功率振荡的次同步频率分量。其次，研究了两种电网结构下的锁相环暂态稳定性。第三，为了与电网模型相连接，建立了一个带锁相环结构的双馈电机，以锁相环的相位扰动作为激励信号。在转子电流内环和电压外环传递过程中，PLL相位扰动分量起作用。构建了带锁相环相位扰动分量的电流环d轴结构框图，推导了扰动传递函数。研究了锁相环控制参数对系统功率振荡的影响机理。最后通过建模仿真验证了理论分析的有效性。