A novel control strategy of direct current control is proposed to improve the performances of electric springs (ESs) based on current-source inverters (CSIs). The proposed control can realize the functions of voltage regulation, harmonic suppression, and power factor correction (PFC) at the same time. The topology of the ES with CSI is described firstly, then its operating principles are analyzed in detail. A cascade generalized integrator (CGI) is used to construct the quadrature signal generator (QSG). Compared with the QSG based on second-order generalized integrator (SOGI), the proposed CGI-QSG can construct quadrature signals with completely consistent waveforms, and can extract the fundamental component of critical load (CL) current more quickly and effectively. The active and reactive power of ES are decoupled by dq0 transformation to realize multiple functions simultaneously. Finally, the effectiveness of the proposed control is verified by simulation and experimental results in the case of over-voltage and under-voltage respectively.