Harmonic Circulating Current Control of Parallel Inverter Considering Voltage Bus Quality

The parallel connection of inverters will produce large harmonic circulation, which can be divided into two types according to different causes: load end and power end. For the harmonic circulation generated at the load end, it combines the negative virtual harmonic impedance and adaptive harmonic impedance. For other virtual harmonic impedance, this strategy can minimize the increase of bus voltage drop and harmonic distortion rate caused by adding virtual impedance, and suppress the harmonic circulation without affecting the system stability; For the circulating current generated by different dead time, Linear active disturbance rejection control is used to estimate and compensate the dead time voltage, and the circulating current is suppressed by observer bandwidth and controller bandwidth. Finally, simulation results verify the correctness and effectiveness of the proposed improved control strategy.