In this thesis a control algorithm for interior permanent magnet synchronous machine (IPMSM) without position sensor is presented. In many sensorless drives the observers used only work at higher speeds. Such driver usually start with an open loop control, where a rotating magnetic field is created to accelerate the rotor. Because the rotor position is not known, the chance of machine desynchronization at higher load torque is great. For robust operation information about rotor position is needed. Rotor position estimation at low speeds or standstill is using the fact that IPMSM inductance is rotor position dependent. If inductance is being measured, position can be extracted from it. For this reason, stator is excited with high frequency signal and rotor position estimated from current response. The field oriented control (FOC) is then used to control quadrature current, which creates torque. Because rotor position is known, torque performance of the drive is also increased.
We observed two major deviations from the expected behavior of the algorithm on a real system, which degrade the rotor position estimation. The first deviation occurs due to the dead time of the inverter. We have shown how it affects the algorithm and presented some options for minimizing the error. The second factor that affects the position estimation is a phenomenon of higher harmonic distortion, which we failed to explain and eliminate. Additionally, it is shown that the algorithm works worse at lower speeds.
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