Analysis of Non Detection Zone for multiple distributed PCS based on Equivalent Single PCS using reactive power approach

In this paper, the methodology to analyze Non-Detection Zone (NDZ) of islanding detection algorithm for multiple Power Conditioning Systems (PCSs) connected to grid is proposed. The PCSs with renewable energy source or battery energy storage system are equipped with anti-islanding functionality and the method using frequency positive-feedback is one of the most popular methods to detect islanding condition. Because it is figured out that the positive feedback of grid frequency is only valid on reactive current, not the phase of current or active current, the reactive power according to the frequency drift algorithm is only considered for NDZ analysis in the proposed analysis. Additionally, the reactive power component by frequency drift anti-islanding can be linearized in normal operation range of grid frequency. By incorporated with this concept, Equivalent Single PCS (ESPCS), which equivalently supplies whole reactive current of multiple PCSs, is proposed and this could emulate the operation of multiple parallel PCSs without loss of the detection capability. The NDZ is analyzed by ESPCS and is compared to the NDZ of parallel PCSs. Through the computer simulation and hardware experiments, it is confirmed that NDZ based on ESPCS and operation dynamics is well matched to those of multiple PCSs.