Principles, implementation, and application of permanent magnet machine sensorless technology

The technology of power electronics and of microprocessors (DSPs) dedicated to industrial applications has progressed rapidly and thus many advanced variable-speed motor drives with AC machines and reluctance machines have been developed and are widely used in industry. The performances of these drives depend heavily on elaborate torque control which can be realized only if the rotor position and speed of the machine is known. The new generation microprocessors, e.g. DSPs, provide powerful tools to implement advanced algorithms and derive the rotor position of the machine by measurement of motor voltages and currents only.; The permanent-magnet (PM) machine is a member of the family of synchronous AC machines. The existing sensorless control schemes of PM machines have been implemented by back-EMF measurement, back-EMF related flux observer, or in terms of the geometric or saturation saliency of the rotor. When using the back-EMF measurement or observer, low speed operation is problematic. In schemes utilizing the inherent saliency of PM machines, a special probing signal injection or a modified PWM modulation is needed to detect speed-independent rotor position information which causes undesirable side effects in the performance of the drives.; In an attempt to solve the problems of existing sensorless control methods of PM machines, a novel general purpose rotor-position estimation approach has been proposed based on conventional sin-Δ or space vector PWM modulation without any signal injection. In this approach, the current ripples at each cycle of PWM modulation are measured, and the rotor position is derived through either inductance calculation or back-EMF computation. The proposed position estimation approach does not need any machine parameters or any specified signal injection. Since the current ripples rather than the fundamental currents or voltages are measured, the approach works well at standstill and low speed as well as at high speed. The proposal has been investigated by computer simulation. (Abstract shortened by UMI.)...