An integrated system configuration for electric springs to enhance the stability in future smart grid

Electric spring (ES) has been reported recently as an alternative device for achieving the grid voltage stability in distribution system using demand side management. ES comprises of six switches in total and injects the voltage in quadrature with the non-critical load current for regulating the PCC voltage to a predefined value. The voltage across the non-critical load decreases/increases as a result of ES action. Since the ES can only perform reactive compensation it faces many operational limitations. Moreover, due to quadrature injection the injected voltage requirement becomes quite high even for a small variation in the PCC voltage. This also limits the compensation range of ES. To overcome these limitations this paper proposes a new configuration for ES comprising of nine switches in total. The proposed configuration allows the complete control over the phase angle of the injected voltage thereby controlling both active and reactive power exchanged between ES and grid. Various operating modes of the proposed nine-switch based ES configuration are analyzed. An appropriate control algorithm is developed and the validity of the proposed configuration is verified through extensive simulation under different operating conditions.