Applying PR Controller to Improve the Islanding Detection Time of the Distribution Generation
A Distribution generation (DG) test system includes a software phase-locked loop, a power controller and islanding detection technology, which is implemented in this paper. Two types of power controllers, proportional-integral (PI) and proportional-resonant (PR), are compared in terms of the transient response. The PI controller is only used when there is a DC signal. The abc frame uses a Park transformation to the synchronized reference frame to produce the DC signals, which requires much calculation time, but the DC control signal is more stable than AC. The PR controller can operate in the AC mode, which saves the time that is taken for the transformation. The PR controller includes a two-order filter, but the output signal is slightly more unstable than that for a PI. The islanding detection time is affected by the transient response of the power controller. An islanding detection method that uses the rate of change of frequency is used in the DG test system. The experimental results show that the PR controller has a faster transient response and that it detects islanding events faster than a PI controller.
Keywords - Proportion-integral controller, Proportion-resonance controller, Distribution generation, Anti-islanding operation.