Improved PLL Under Distorted Utility Conditions

In this paper, an improved algorithm for realizing a phase locked loop (PLL) for three phase system is reported. The reported approach results in fast dynamic response and negligible distortion in PLL output, under severely distorted utility conditions, even with appreciable DC offset in input signals. Also, the locking time obtained is independent of the level of utility distortion. So this PLL is eminently suitable for decoupled control of active and reactive power in all custom power devices, including dynamic voltage restorer (DVR). Important design details are provided which are supported with simulation results. These are experimentally verified and compared with existing methods to highlight the improvements.