A New Control Method of a Current Balancer in Single-Phase Three-Wire Secondary Distribution Systems Using the Correlation and Cross-Correlation Coefficients

This paper proposes a new control method of a current balancer for single-phase three-wire secondary distribution systems using the correlation and cross-correlation coefficients to reduce the capacity of the three-leg PWM inverter, which performs the current balancer. The components correlative and cross-correlative to the primary side voltage waveform, which correspond to the active and reactive currents, are calculated from the detected load currents on each feeder. Then the reactive and unbalanced-active currents are compensated on the source side. The balanced source currents with the power factor of 0.9 are obtained in each feeder. This imperfect compensation of the reactive power reduces the capacity of both the three-leg PWM inverter and do capacitor. The basic principle of the proposed method is discussed in detail, and then confirmed by digital computer simulation. A proto-type experimental system is constructed and tested. Experimental results demonstrate that the balanced source currents with the power factor of 0.9 are obtained in spite of unbalanced load currents reducing the capacity of the three-leg PWM inverter.