Practical approach for parameter determinations of interior permanent magnet generator

Recently, there has been a lot of researches on various methods for a sensorless control of permanent magnet generators (PMG) in wind turbines. The sensorless control of the PMG considers estimations of a rotor angle and speed which are based on the PMG parameters estimation. The parameters that have been estimated are stator resistance, rotor flux, d-axis and q-axis inductance. For more precise rotor angle and speed estimation, it is essential to determinate values of the PMG parameters in every operating point as accurately as possible. A change of the operating point (different rotor speed, shaft torque etc.) causes the change of the PMG parameters due to stator currents and temperature variation. Accordingly, the PMG parameters could be measured during a PMG commissioning. In this work, the stator resistance is measured while taking into considering a dead time compensation and voltage drop on a power switching devices. A determination of the d-axis and q-axis inductances is based on PMG voltage equations in a dq synchronous reference frame. Thus, the measurements of the rotor speed, stator currents and voltages are required. The experimental measurements are carried out on a 375 kW interior permanent magnet generator. Finally, the measured values could be saved on a digital signal processor (DSP) as look-up tables and used for the sensorless control of the PMG.