The transient response of the single-phase enhanced PLL (EPLL) under the step change of amplitude, phase angle, and frequency is derived. It is revealed that there are transient periodic ripples in the estimation results of the standard EPLL. Furthermore, a virtual quadrature-coordinate EPLL combining a second-order generalised integrator with a quadrature-coordinate EPLL is proposed and the transient response is derived. The proposed EPLL possesses a better dynamic performance than the standard EPLL. The detailed experimental results are shown and compared with each other to validate the theoretical analysis and the advantages of the proposed EPLL.