Improved VSG low-voltage ride-through control for asymmetric grid voltage sag problem
In response to the problem of voltage sag in asymmetric power grids and the tendency of unbalanced three-phase current to exceed the limit,which leads to low-voltage ride through failure,the mathematical model and control structure of virtual synchronous machines(VSG)in grid connected inverters are analyzed based on the mathematical model of low-voltage ride through in asymmetric grid connected voltage inverters.Based on the balanced current control method,an improved VSG control strategy is proposed to control the positive and negative sequence components of voltage and current,and to limit the current to a certain extent.The effectiveness of the improved VSG method based on balanced current is verified by constructing a simulation model of photovoltaic low-voltage crossing.
low voltage ride-throughasymmetric voltage sagvirtual synchronizerbalanced current control
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