Impedance Modeling and Stability Analysis of Electric Springs in Weak Grid

Electric springs can be associated with non-critical loads, forming a new generation of smart loads, which can be applied in microgrid to suppress voltage fluctuations caused by renewable energy entering the network and provide stable power quality for critical loads. However, under weak grid, the interaction between the impedance of the power grid and the output impedance of the electric spring complicates the stability issue of the system. To address this issue, firstly, an impedance stability criterion applicable to power springs is provided, and an output impedance model of a single-phase power spring system based on dual closed-loop control is established; Then, based on the impedance stability criterion, the influences of non-critical load fluctuations, controller parameters, digital control delay, grid impedance, and other factors on the stability of the power spring system are analyzed. Finally, the simulation verified the correctness of the theoretical analysis.