A Novel RPV (Reactive-Power-Variation) Antiislanding Method Based on Adapted Reactive Power Perturbation

In this paper, a novel intermittent reactive-power-variation (RPV) method based on loads´ resonance frequency detection is proposed to reduce the injected reactive power. The RPV method detects the frequency of point of common coupling (PCC) and outputs the minimum reactive variation, which perturbs the frequency of PCC to the frequency thresholds decided by the utility standards when the islanding condition happens. Furthermore, the islanding detecting control strategy under unbalanced loads condition is discussed. Compared with the traditional bilateral RPV method, the proposed method only output unilateral RPV in each variation period and the variation amplitude of each period is less than 5% of the output active power (P), thus the perturbation of reactive power can be reduced significantly. In addition, experimental results of a three-phase 30-kW inverter are given to verify the proposed method. The proposed method is proved to be capable of islanding detection with balanced loads, motor loads within standard permissible detection times. The application of the proposed method to unbalanced loads is also discussed.