alizadeh bidgoli - K. N. Toosi University of Technology Tehran, Iran
soori - K. N. Toosi University of Technology Tehran, Iran
tavakoli bina - K. N. Toosi University of Technology Tehran, Iran

Automated load balancers can swap output phases of feeders in a distribution substation by the use of matrix converters. In addition, the rotational three phase loads operate clockwise if three phase system has positive sequence. In order to complete the proposed method for balancers, in this paper three different methods is proposed for recognizing phase sequence in power systems. The first evaluated method detects phase sequence by measuring of instantaneous symmetrical components. This method has drawbacks of complexity and low speed in detecting. The second method detects phase sequence by using a phase lock loop (PLL) for metering the power system frequency. The second technique is fast, but PLL that is used in this technique operates incorrectly under unbalanced condition. Finally, the third method is a new technique that is proposed for the first time in this paper which is very fast. This innovative method detects phase swapping by the zero crossing times. The whole methods are simulated by SIMULINK to verify and compare the suggested method with other techniques.

power system balancer, phase sequence, phase lock loop, zero crossing detection