Method for controlling power factor of three-phase converter, method for controlling reactive power of three-phase converter, and controller of three-phase converter

A method for controlling reactive power of a three-phase converter when power is converted by the three-phase converter which subjects three-phase AC to PWM conversion for outputting DC, comprising,

• a symmetrical component calculation step for calculating symmetrical component voltage values of a three-phase balanced system, from wye-phase voltages of three-phase AC input of the three-phase converter,
• an average active power operation step for calculating an average active power value by using an output voltage value and an output current value of DC output of the three-phase converter,
• a reactive power control step for calculating an average reactive power value, from the average active power value calculated in the average active power operation step and a set power factor, on the basis of a relationship among the average active power value, the average reactive power value, and a power factor, the average reactive power value being associated with the set power factor,
• a current command value generation step for calculating a current command value, from the average active power value calculated in the average active power operation step, the average reactive power value calculated in the reactive power control step, and the symmetrical component voltage values of the three-phase AC voltages calculated in the symmetrical component calculation step, and
• a constant current control step for calculating a constant current control value by subjecting a positive-phase-sequence voltage value of the three-phase AC voltages to constant current control, based on the current command value and an input current value of the three-phase converter, wherein,
• a compensation signal for compensating for unbalanced voltages of the three-phase AC voltages and a control signal for controlling the power factor are generated, based on the constant current control value calculated in the constant current control step,
• wye-phase voltages being 120° out of phase with each other for controlling the unbalanced voltages and the reactive power are obtained based on the compensation signal and the control signal, and
• a PWM control signal for subjecting the three-phase AC to the PWM conversion for outputting DC is generated based on the wye-phase voltages thus obtained.

A controller for controlling a three-phase converter which subjects three-phase AC to PWM conversion for outputting DC, comprising,

• a symmetrical component calculation unit for calculating symmetrical component voltage values of a three-phase balanced system, from wye-phase voltages of three-phase AC input of the three-phase converter,
• an average active power operation unit for calculating an average active power value by using an output voltage value and an output current value of DC output of the three-phase converter,
• a power factor and reactive power control unit for calculating an average reactive power value, from the average active power value calculated in the average active power operation unit and a set power factor, on the basis of a relationship among the average active power value, the average reactive power value, and a power factor, the average reactive power value being associated with the set power factor,
• a current command value generator for calculating a current command value, from the average active power value calculated in the average active power operation unit, the average reactive power value calculated in the power factor and reactive power control unit, and the symmetrical component voltage values of the three-phase AC voltages calculated in the symmetrical component calculation unit, and
• a constant current control unit for calculating a constant current control value by subjecting a positive-phase-sequence voltage value of the three-phase AC voltages to constant current control, based on the current command value and an input current value of the three-phase converter, wherein,
• a compensation signal for compensating for unbalanced voltages of the three-phase AC voltages and a control signal for controlling the power factor are generated, based on the constant current control value calculated in the constant current control unit,
• wye-phase voltages being 120° out of phase with each other for controlling the unbalanced voltages and the power factor are obtained based on the compensation signal and the control signal, and
• a PWM control signal for subjecting the three-phase AC to the PWM conversion for outputting DC is generated based on the wye-phase voltages thus obtained.