A method of measuring a link voltage, performed in a direct AC-AC power converter circuit including: a DC link; a current source converter having three input terminals (Pr, Ps, Pt) for receiving three-phase AC voltages (Vr, Vs, Vt) by phase, and commutating current supplied from said input terminals at a cycle which is divided into a first period (drt • T0) and a second period (dst • T0) to apply a link voltage (Vdc) which is a DC voltage to said DC link; and a voltage source inverter for performing switching on said link voltage with a switching pattern based on pulse width modulation to output multiphase alternating current, whereby each said switching pattern represents a particular combination of the switching states of all switches of the voltage source inverter; said first period being a period in which said DC link is supplied with current flowing into a first pair (Pr, Pt) of said three input terminals, to which a voltage of the phase with the highest voltage value and a voltage of the phase with the lowest voltage value among said three-phase AC voltages are applied, and said second period being a period in which said DC link is supplied with current flowing into a second pair (Ps, Pt) of said three input terminals, to which a voltage of the phase with the intermediate voltage and said voltage of the phase with the lowest voltage value among said three-phase AC voltages are applied, said first period being divided into multiple sections, and said method comprising the steps of: (a) measuring a first measured value (Vmax1) which is said link voltage measured at a midpoint of a first section of said multiple sections in which only a single first said switching pattern is adopted for the longest time in said first period; (b) measuring a second measured value (Vmax2) which is said link voltage measured at a midpoint of a second section of said multiple sections in which only a single switching pattern is adopted for a time as long as said first section or for the second longest time next to said first section in said first period, and (c) obtaining a representative value (Vmax) of said link voltage in one said cycle including said first period by interpolation of said first measured value and said second measured value. a DC link; a current source converter having three input terminals (Pr, Ps, Pt) for receiving three-phase AC voltages (Vr, Vs, Vt) by phase, and commutating current supplied from said input terminals at a cycle which is divided into a first period (drt • T0) and a second period (dst • T0) to apply a link voltage (Vdc) which is a DC voltage to said DC link; and a voltage source inverter for performing switching on said link voltage with a switching pattern based on pulse width modulation to output multiphase alternating current, whereby each said switching pattern represents a particular combination of the switching states of all switches of the voltage source inverter; said first period being a period in which said DC link is supplied with current flowing into a first pair (Pr, Pt) of said three input terminals, to which a voltage of the phase with the highest voltage value and a voltage of the phase with the lowest voltage value among said three-phase AC voltages are applied, and said second period being a period in which said DC link is supplied with current flowing into a second pair (Ps, Pt) of said three input terminals, to which a voltage of the phase with the intermediate voltage and said voltage of the phase with the lowest voltage value among said three-phase AC voltages are applied, said first period being divided into multiple sections, and said method comprising the steps of: (a) measuring a first measured value (Vmax1) which is said link voltage measured at a midpoint of a first section of said multiple sections in which only a single first said switching pattern is adopted for the longest time in said first period; (b) measuring a second measured value (Vmax2) which is said link voltage measured at a midpoint of a second section of said multiple sections in which only a single switching pattern is adopted for a time as long as said first section or for the second longest time next to said first section in said first period, and (c) obtaining a representative value (Vmax) of said link voltage in one said cycle including said first period by interpolation of said first measured value and said second measured value. (a) measuring a first measured value (Vmax1) which is said link voltage measured at a midpoint of a first section of said multiple sections in which only a single first said switching pattern is adopted for the longest time in said first period; (b) measuring a second measured value (Vmax2) which is said link voltage measured at a midpoint of a second section of said multiple sections in which only a single switching pattern is adopted for a time as long as said first section or for the second longest time next to said first section in said first period, and (c) obtaining a representative value (Vmax) of said link voltage in one said cycle including said first period by interpolation of said first measured value and said second measured value.