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Islanding detection is of great importance for normal operation of distributed generation system. In this paper, Active Frequency Drift (AFD) method is chosen to illustrate its operation principle and concrete performance procedure in detail. On this basis, an improved method based on adaptive chopper factor is proposed to reduce the impact of the load property on AFD. The improved method can automatically change chopper factor according to different load properties to eliminate non-detected zone (NDZ)and accelerate islanding detection. Detailed analysis is included in this paper, finally simulations are carried out in Matlab to verify the proposed method.

This paper deals with the design and analysis of codebook optimization for MIMO-OFDM systems. We present a capacity based codebook construction algorithm under a specific average power and BER constraint. We also derive the close form solution of optimal transmission scheme on capacity sense. Simulation results show that the capacity based codebook construction algorithm with hybrid design of power allocation and multi-mode beamforming can achieve higher capacity than that of equal power allocation based codebook.