Photovoltaic systems are often connected to the main grid through multiple paralleled inverters to support and to reinforce the power generation into the grid. This interconnection can be affected by resonance phenomena that may be introduced by the excitation of passive filters and lead either to small oscillations that can deteriorate the power quality or large oscillations that can affect the whole system reliability. Therefore, early detection of such oscillations is essential to keep a resilient operation. This paper proposes a novel algorithm for an online resonance frequency monitoring based on wavelet transform (RFM-WT) that can perform fast detection of undesired resonance frequencies. The RFM-WT is performed through two steps. The first step consists in decomposing each inverter output current into different signals using the wavelet transform. This allows separating the different frequencies that exist in the inverter output current. The second step allows estimating the frequencies from the signals obtained in the first step. Accordingly, a comprehensive approach describing the design of the proposed monitoring algorithm is presented. Its effectiveness is compared to the classical PLL algorithm. Unlike the PLL algorithm, the proposed technique is easy to implement and doesn't require regulators’ parameters design and configuration. The simulations and experiments proved that the algorithm can accurately locate the resonance frequencies in inverters output currents. Thus, its robustness was validated through load variation and transition from grid- connected to islanded mode.

光伏系统通常通过多个并联逆变器连接到主电网，以支持和加强发电并入电网。这种互连可能会受到谐振现象的影响，谐振现象可能由无源滤波器的激励引起，并导致可能导致电能质量恶化的小振荡或可能影响整个系统可靠性的大振荡。因此，早期检测此类振荡对于保持弹性操作至关重要。本文提出了一种基于小波变换 (RFM-WT) 的在线共振频率监测新算法，该算法可以快速检测不需要的共振频率。RFM-WT 通过两个步骤执行。第一步包括使用小波变换将每个逆变器输出电流分解为不同的信号。这允许分离逆变器输出电流中存在的不同频率。第二步允许从第一步中获得的信号估计频率。因此，提出了描述所提出的监测算法的设计的综合方法。其有效性与经典的 PLL 算法相比较。与 PLL 算法不同，所提出的技术易于实现并且不需要调节器的参数设计和配置。仿真和实验证明，该算法能够准确定位逆变器输出电流中的谐振频率。因此，