The interface impedance can filter out harmonics, but interface impedance and voltage sensors increase the size, power loss, and complexity of the system. To solve these problems, a virtual impedance-based voltage sensor-free control scheme is proposed to have the inverter grid-connected. The inverter model and the principle of virtual impedance implementation are elaborated, and a virtual impedance-based control method is proposed to achieve interface impedance-free and AC voltage-sensor-free control. In addition, a method is proposed to use current sensor synchronization at startup. To reduce the complexity of the system, only virtual resistors are used for self-synchronization. The stability and dynamic characteristics of the proposed methods were verified by comparing Matlab/simulink simulations with experimental results.
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