When distributed renewable energy is connected to the remote end of the distribution network, the grid-connected inverter system may be affected by the large internal impedance and background harmonics of the weak grid at the same time. However, the optimization of the control design of the grid-connected inverter is not easy to achieve effectively. A novel resonance suppression method for distributed power grid-connected systems with a weak power grid and harmonic distortion is proposed. In this method, the grid voltage feedforward control of the grid-connected inverter is combined with the active damper connected in parallel. The former is used to suppress the influence of harmonic voltage distortion, and the latter is used to reshape the output admittance of the grid-connected system to suppress the resonance between that system and the weak grid. The design method of the virtual resistance value of the active damper and the method of increasing the cut-off frequency of the grid-connected system are given. The time-domain simulation results based on Matlab/Simulink show that the designed grid-connected system can not only effectively suppress the grid-connected current distortion caused by harmonic voltage distortion, but also suppress harmonic resonance caused by the presence of net side admittance.

This work is supported by the National Key Research and Development Program of China (No. 2021YFB2400900).