Driving system of permanent magnet synchronous motor

A synchronous motor driving system including a synchronous motor, a PWM signal controller for conducting pulse width modulation on three-phase voltage command signals by using a carrier signal, and a power converter driven by a gate signal subjected to pulse width modulation,

• the synchronous motor driving system comprising:
• command voltage generation means for generating three-phase voltage command signals to apply a high frequency voltage to the synchronous motor;
• current detection means for detecting a current which flows through the synchronous motor when the high frequency voltage is applied to the synchronous motor;
• and
• magnetic pole position estimation means for estimating a magnetic pole position of the synchronous motor on the basis of a result of the current detection,
• the command voltage generation means generating the three-phase voltage command signals by conducting successive switching among a first applied voltage mode for applying a positive-negative alternating high frequency voltage having arbitrary voltage amplitude to an arbitrary phase θ, a second applied voltage mode for applying a high frequency voltage having similar amplitude to a phase shifted in electric angle from the phase θ by 120 degrees, and a third applied voltage mode for applying a high frequency voltage having similar amplitude to a phase shifted in electric angle from the phase θ by 240 degrees,
• the current detection means detecting positive side values and negative side values of a pulsating current generated by applying the high frequency voltage in the first, second and third applied voltage modes at a rate of one phase in each of the modes, and obtaining information of a positive side U-phase detected current value, a negative side U-phase detected current value, a positive side V-phase detected current value, a negative side V-phase detected current value, a positive side W-phase detected current value, and a negative side W-phase detected current value, and
• the magnetic pole position estimation means calculating an estimated magnetic pole position of the synchronous motor by using detected current values of respective phases of the positive side and detected current values of respective phases of the negative side.