Parallel control strategy of single-phase inverter based on virtual impedance

In the conventional single-phase inverter parallel system, because of the inconsistent line impedance and frequency characteristic of the inverter output equivalent impedance, the load harmonic power can not be well-distributed by the inverters in the system. By analyzing the equivalent impedance of the single-phase inverter, this paper proposed a virtual impedance design method in the dual close loop feedback control inverter. This method can improve the frequency response performance of the inverter impedance and the equivalent output impedance appears as pure resistance on a large scale. Therefore, the inverter parallel system adopted this control method can share the harmonic power symmetrically, and lead to better load-sharing performance. The parallel system model based on the control method is built, and the experiment platform is constructed. Finally, experimental results show the effectiveness and the engineering practicability of the method.