Reiko Raute

Analysis and Compensation of Inverter Nonlinearity Effect on a Sensorless PMSM Drive at Very Low and Zero Speed Operation

It has been well established in the literature that inverter nonlinearity effects afflict saliency-based sensorless drives. The inverter nonlinearity leads to the generation of signals that corrupt the useful position information. The resulting effect differs depending on the injection approach utilized in the drive. Various compensation techniques to overcome this effect have been published in the literature. This paper is concerned with the zero-vector current-derivative technique. The effect of the varying ON-state resistance of the inverter power devices on the position signal is investigated in detail. Knowledge of the source of the corrupting signals facilitates compensation and determines its applicability. Two approaches for inverter nonlinearity compensation are compared. The first approach utilizes a lookup table from offline-processed data, while the second one is a simpler approach based on the current-dependent resistance characteristic of the inverter switching devices. Experimental performance under sensorless condition is shown for both approaches.

A zero speed operation sensorless PMSM drive without additional test signal injection

The inherent back EMF and the saliency of AC machines can be utilized to identify the rotor/flux position. A novel technique, which takes both of these effects into account is proposed in this paper. No additional test signals are injected into the machine and the difficulties in sensing the machine terminal voltage at low speed is eased. Only three standard current transducers are used in the drive system. For the position/speed estimator only the machine current derivative during the relatively long (at low speed) zero voltage vectors is used as feedback. Practical results show the operation of the drive at several torque and speed conditions including stand still.

Sensorless Control of Induction Machines at Low and Zero Speed by Using PWM Harmonics for Rotor-Bar Slotting Detection

This paper presents the use of the inherent high-frequency pulsewidth modulation (PWM) harmonics for sensorless control of ac machines. The amplitude and position of the PWM voltage harmonics cannot be controlled independently and are determined by the fundamental machine operation. However, they do form a high-frequency excitation and can provide information on saliencies within ac machines. This paper examines the feasibility of sensorless control based on extracting the rotor-bar slot position information for a cage induction machine using PWM harmonics. The position-signal demodulation and compensation schemes used are derived. Experimental results are provided for an off-the-shelf induction motor operating under sensorless current, speed, and position control, including zero excitation and zero speed.

Sensorless Control of Induction Machines by Using PWM Harmonics for Rotor Bar Slotting Detection

The paper presents the use of the inherent high frequency PWM harmonics for sensorless control of AC machines. The amplitude and position of the PWM voltage harmonics cannot be controlled and depends on the fundamental machine operation. The paper examines the feasibility of sensorless control based on the extracted rotor bar slot position information in the case of a cage induction machine. The position signal demodulation and compensation schemes used are discussed. Experimental results of sensorless torque, speed and position control at loaded conditions including zero excitation and zero speed are given for an off-the-shelf induction machine.

Sensorless position control of a PMSM for steer-by-wire applications

This paper shall present the design and implementation of a MATLAB/Simulink Model for the sensorless control of a PMSM in a steer-by-wire application. Simulation results for position, speed and current loops in both open-loop and closed-loop sensorless modes are shown. The sensorless method is based on the tracking of saliencies by high frequency injection.

Inverter non-linearity effects on a sensorless PMSM drive without additional test signal injection and zero speed operation

It has been well established in the literature that inverter non-linearity effects afflict saliency based sensorless drives operating in the low and zero speed region. The inverter non-linearity leads to the generation of signals that corrupt the useful position signals. In certain cases, the magnitude of the former signals is comparable if not higher to the latter. Various compensation techniques to overcome this effect have been published in the literature. This paper is concerned with the sensorless technique utilizing the current derivatives during the zero voltage vector states without additional test signal injection, as proposed in. This paper incorporates the varying on-state resistance of the inverter power devices in the system model to explain the corrupting signal experienced in. Knowledge of the source of the corrupting signals facilitates compensation and determines its applicability. The same effect will also be present in sensorless techniques utilizing signal injection although its influence might be less significant due to the magnitude of the injected signal.

Design of a periphery control FPGA board for electric drive systems

The paper describes the setup of an experimental microprocessor control system for electric drive systems. Particular the design of a customised designed periphery control FPGA board is described in detail. The setup has been used for research on sensorless drive control algorithms.

Sensorless position tracking for steer-by-wire applications

This paper shall present the design, simulation and implementation of a sensorless observer for three-phase permanent magnet synchronous machines which can be used for automotive steer-by-wire applications. The observer tracks steering transients enabling the sensorless speed/position estimates to be used for backup in case of encoder failure. The sensorless method is based on a high frequency injection approach which estimates speed/position from machine saliencies. The simulation/experimental test scenarios were designed so as to emulate actual steering conditions studied as part of this research project.

Torque feedback for steer-by-wire systems with rotor flux oriented PMSM

This paper presents the design and implementation of a current controlled Rotor Flux Oriented PMSM for automotive steer-by-wire applications. The development of a realistic torque feedback reference is carried out by monitoring the steering torque while driving a commercial vehicle. The paper shall discuss the torque dynamics of the PMSM drive with respect to position demands replicating a driver at the handwheel.