Dynamic non-detection zones of positive feedback anti-islanding methods for inverter-based distributed generators

Positive feedback anti-islanding methods have been widely applied to inverter-based distributed generators recently due to their high cost-performance ratio. The effectiveness of these anti-islanding methods is usually demonstrated by means of steady-state non-detection zones (NDZs) represented in a load parameter space (LPS). However, these NDZs cannot accurately describe the impact of the inverter interface controls on the anti-islanding methods' detection performance, especially in multi-inverter systems. In addition, the intrinsic destabilization characteristic of the positive feedback anti-islanding scheme cannot be exhibited by these NDZs. This paper proposes an improved dynamic NDZ in the LPS to evaluate the islanding detection effectiveness of the positive feedback anti-islanding methods. The modal analysis approach is employed to determine the critical RLC load quality factor which is defined as the small-signal stability limit index of the islanded distributed generation (DG) systems for the dynamic NDZs. The sensitivity analysis of the dynamic NDZs for different DG system parameters is conducted in this paper. The applications of the proposed dynamic NDZs in multi-DG systems are also presented

Small-signal model of multiple inverter-based DG system with positive feedback anti-islanding protection

This paper presents a small-signal model suitable to analyze the stability and dynamic characteristics of multiple inverter-based distributed generation (DG) systems and the associated positive feedback anti-islanding scheme. The developed model is validated by comparing its results against those obtained by detailed, non-linear electromagnetic transient simulations. With the developed model, the sensitivity analysis can be conducted to study the small-signal stability of the multiple inverter-based DG systems

A systematic gain setting method of the positive feedback anti-islanding scheme for inverter-based distributed generators

This paper proposes a systematic gain setting method for the positive feedback anti-islanding scheme which is designed to protect the interconnected inverter-based distributed generators (DGs) from islanding operation. Two main factors affecting the performance of the anti-islanding scheme are investigated when the positive feedback gain is tuned. One is the stability impact of the anti-islanding control on distributed generation (DG) systems and the other is the islanding detection time of the anti-islanding scheme. The small-signal model and the electromagnetic transient simulation model of an inverter-based DG system are developed to facilitate the realization of the proposed gain setting method. This method provides a practical and reliable tool for DG planning engineers