The invention discloses a method for calculating equivalent
load line impedance of a three-phase three-wire
system unbalanced
system. The method includes the steps that firstly, a
bus voltage phasor and a general incoming
line current phasor of a three-phase unbalanced power
system are acquired, the
voltage phasor and the current phasor are resolved according to a symmetrical component method, and therefore a
bus voltage positive-sequence component, a general incoming
line current positive-sequence component and a general incoming
line current negative-sequence component of the three-phase unbalanced power system are acquired; secondly, the
minimum phase of a general incoming line current phasor module value serves as a reference phase, and the general incoming line current negative-sequence component is rotated in the positive sequence, so that the general incoming line current negative-sequence component in the positive sequence is acquired; the general incoming line current negative-sequence component in the positive sequence is subtracted from an original general incoming line current negative-sequence component of a non-reference phase, so that a current component passing through the non-reference
interphase is acquired; thirdly, the
bus voltage positive-sequence component, the general incoming line current positive-sequence component, the general incoming line current negative-sequence component in the positive sequence and the
interphase current component are used for calculation, so that positive-sequence impedance, negative-sequence impedance in the positive sequence and
interphase impedance of the non-reference phase of a load are acquired, the positive-sequence impedance and the negative-sequence impedance in the positive sequence of the load are equivalently converted in an angle joint mode and combined with the interphase impedance together, and therefore the equivalent
load line impedance of the three-phase three-wire system unbalanced system can be calculated through a impedance parallel formula.