一种适用于不同参数逆变器的统一虚拟阻抗重塑方法

Multi-parallel inverters (MPI) have become a common structure in distributed power generation systems. The prevalent parameter differences lead to different output impedances of each inverter and affect the overall parallel impedance of inverters, which may cause instability of both the common current and the interactive current. To solve the instability problem in systems consisting of inverters with different parameters, this paper analyzes the reasons for resonance in different frequency bands and proposes the objectives of frequency-division impedance reshaping. According to the reshaping objectives, a resonance suppression method based on unified virtual impedance reshaping is proposed. The essence of the proposed method is to uniformly reshape the output impedance of inverters with different parameters by modifying the voltage feedforward function. With the proposed method, the MPI system can have strong adaptability to a wide range of grid impedances and suppression ability to the grid voltage harmonics, while effectively suppressing the common current resonance and interactive current resonance. Theoretical analyses and experimental results validate the effectiveness of the proposed method.