ISLANDING DETECTION APPARATUS FOR PARALLEL DISTRIBUTED GENERATION SYSTEM

摘要

An islanding detection apparatus minimizes a reduction in power quality and detects islanding when distributed generations are operated in parallel. Also, another islanding detection apparatus for parallel distributed generations synchronizes parallel distributed generations by periodically applying a reactive current at a half cycle. Further, another islanding detection apparatus for parallel distributed generations easily synchronizes parallel distributed generations even when inverters installed in the respective distributed generations are fabricated through different makers.

主权项

1. An islanding detection apparatus for parallel distributed generations, comprising:
an inverter configured to convert a DC voltage supplied from a renewable energy source into an AC voltage; a three-phase/two-phase converter configured to convert an output of the inverter into a three-phase/two-phase stationary reference frame; a phase locked loop (PLL) configured to calculate the phase and frequency of a grid voltage of a grid connected to the inverter using a two-phase voltage outputted from the three-phase/two-phase converter; a filter configured to pass a half cycle of one cycle of a signal outputted from the three-phase/two-phase converter or the PLL; a phase controller configured to generate a current phase reference value for controlling an output phase of the inverter, using the frequency of the output voltage of the PLL and a current amplitude reference value applied from outside; a half cycle passer configured to perform an AND operation on the current phase reference value outputted from the phase controller and an output of the filter and output a current phase reference value for islanding detection; a current reference frame converter configured to convert the current amplitude reference value of a synchronous reference frame and the current phase reference value of the synchronous reference frame, outputted from the half cycle passer, into a current amplitude reference value and a current phase reference value of a two-phase stationary reference frame, using a phase angle outputted from the PLL; a current phase calculator configured to subtract the phase of the inverter output current outputted from the current two-phase converter from the current phase reference value of the two-phase stationary reference frame, outputted from the current reference frame converter, and output a current phase control value; a current amplitude calculator configured to subtract the amplitude of the inverter output current, outputted from the current two-phase converter, from the current amplitude reference value of the two-phase stationary reference frame, outputted from the current reference frame converter, and output a current amplitude control value; a current controller configured to generate a current control signal using the calculated current phase and the calculated current amplitude; an output three-phase converter configured to convert the current control signal of the two-phase stationary reference frame, outputted from the current controller, frame into a current control signal of a three-phase stationary reference frame; and a PWM controller configured to output a PWM control signal to the inverter using the current control signal of the three-phase stationary reference frame, outputted from the output three-phase converter.