Addressing the critical technical challenge of mitigating voltage and frequency oscillations during the transition between grid-connected operation and islanding operation modes in microgrid systems with a master-slave control structure is imperative.Focusing on the dynamic characteristics of voltage and frequency during microgrid grid-connected operation and islanding operation mode,a smooth switching control strategy is proposed based on parallel operation and numerical soft starter.Through the synchronized PQ control and V/F control,the parallel operation effectively suppresses current fluctuations during mode transitions.And the numerical soft starter plays a crucial role in smoothing the input reference values for current inner loop,and reducing the impact of transient impulse current on current inner loop during switching process,which suppresses the oscillations of bus voltage and frequency during microgrid mode switching.Finally,a model of photovoltaic-storage micro-grid system is constructed using Matlab/Simulink,and the simulation experiments,covering scenarios such as grid-connected/islan-ding mode transitions and load variations,verify the effectiveness of the proposed smooth switching control strategy.
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