Resonance Analysis of Multi-paralleled Converter Systems and Research on Optimal Virtual Resistor Damping Methods

The system network impedance and resonant characteristics change when several LCL converters are parallel connected. And it will affect the output current control effect. So quantitative analysis of the output current resonance and research of harmonic suppression methods have important practical significance. This paper developed the Norton's equivalent circuit of the multi-paralleled converter system to analyze the distribution law of the resonance frequency. Then the mathematical expression of the resonance frequency was obtained by the simplified model. The influence on the output current by different virtual resistor values was studied. And the calculation method of the optimal virtual resistance value was proposed to ensure the output current following the reference. Simulation and experimental results are provided to validate the accuracy of the quantitative analysis and effectiveness of the virtual resistor value calculation method.