This paper deals with modified reactive power control (RPC) for islanding detection. The RPC approach is an effective technique for detecting islanding in distributed generation (DG). However, existing RPC methods have limitations of injecting/drawing unnecessary reactive power into/from the grid. Furthermore, RPC methods may be affected by disturbances such as power system transients resulting in false islanding detection. This paper proposes a new controller’s reference reactive power based on the positive sequence voltage of the point of common coupling (PCC) and a reactive mismatch coefficient to overcome the aforementioned drawbacks. Furthermore, the Discrete Wavelet Transform (DWT) of the difference between the amplitude of actual and nominal PCC voltages is incorporated in the decision criteria. An entropy function based on DWT is defined to improve the reliability of the RPC method under disturbances. The proposed islanding detection method (IDM) is evaluated under various load and disturbance conditions to show its performance. Simulation and experimental finding indicate that the proposed IDM can detect islanding quickly and with a negligible Non-Detection Zone. Moreover, the DG and load reactive powers are nearby matched during the normal operation, and non-islanding events are effectively prevented.

本文讨论了用于孤岛检测的改进无功功率控制（RPC）。RPC方法是一种用于检测分布式发电（DG）中孤岛的有效技术。但是，现有的RPC方法具有向电网注入不必要的无功功率/从电网汲取不必要的无功功率的局限性。此外，RPC方法可能会受到干扰（例如电力系统瞬变）的影响，从而导致错误的孤岛检测。本文提出了一种基于公共耦合点（PCC）的正序电压和无功失配系数的新型控制器参考无功功率，以克服上述缺点。此外，将实际PCC电压和标称PCC电压的幅度之差的离散小波变换（DWT）纳入决策标准。定义了一种基于DWT的熵函数，以提高扰动下RPC方法的可靠性。在各种负载和干扰条件下，对提出的孤岛检测方法（IDM）进行了评估，以显示其性能。仿真和实验结果表明，提出的IDM可以快速检测出孤岛，且无检测区可以忽略不计。此外，在正常操作期间，DG和负载无功功率在附近匹配，并且有效地防止了非孤岛事件。