Peter Mutschler

Fault-Tolerant Voltage Source Inverter for Permanent Magnet Drives

In this paper, a two-level fault-tolerant voltage source inverter (VSI) for permanent magnet drives is systematically designed and tested. A standard two-level inverter consists of three legs. In this case of fault-tolerant inverter, a redundant leg is added that replaces the faulted leg. Faulted leg isolation and redundant leg insertion are done by using independent back-to-back-connected thyristors. The proposed inverter provides tolerance to both short-circuit and open-circuit faults of the switching devices. The postfault performance is the same as the normal prefault operation and fault compensation is fast enough such that there is negligible disturbance in the drive operation. The fault tolerance of the inverter is verified using field-oriented control of a permanent magnet synchronous motor.

A direct control method for matrix converters

Until now, direct control methods have been mainly investigated and used in conjunction with voltage source converters. In this paper, the authors develop a direct current control method for matrix converters. There are two objectives for the direct current control: the desired current has to be impressed into the load, and the current, drawn from the mains, should be in phase with the voltage and should be (nearly) sinusoidal. This implies active damping of the 400 Hz resonance or the line filter. The method is implemented on a DSP and tested on a 10 kVA matrix converter.

Permanent magnet drives with reduced dc-link capacitor for home appliances

This paper proposes a control strategy for drives in home appliances with small energy storage in dc-link. The examined system consists of a single-phase diode rectifier, a small dc-link film-capacitor, a three-phase inverter and a permanent magnet synchronous motor (PM). With a small dc-link capacitor (less than 11 μF/kW) an approximately trapezoidal torque is generated by the PM in each half-cycle of the mains. For home appliances motor-torque variation with twice the line frequency is widely accepted. The method is based on the field-oriented control and uses the modulation of the d-q-axis currents of the PM. Simulations and experimental results in this paper demonstrates the feasibility of this method.

Improved method for higher dynamics in sensorless position detection

Numerous methods have been published for sensorless detection of the rotor position in PM synchronous motors (PMSM) by evaluating the magnetic anisotropy. In this paper, the one based on the injection of an alternating voltage carrier is considered. It is able to detect the anisotropy, and by its means the rotorpsilas position, without any additional hardware or modifications on the samplings times. It will be shown that the observerpsilas dynamics is bounded by the carrier frequency. The carrier is usually sinusoidal and with a frequency of about 1/4 of the switching frequency or lower. As a measure to improve the dynamics of the position observation, a square wave carrier with the highest possible frequency, namely the switching frequency, will be used. In addition, the carrier response will be decoupled from the controlled q-current in order to avoid the usual bandpass filter. This filter would introduce a significant delay in the observer loop. The frequency increase, together with the removal of the filter allows a faster time response in the position estimation. Experimental results showing the improvements in the estimationpsilas dynamics are presented.

Speed Sensorless Control of a Long-Stator Linear Synchronous Motor Arranged in Multiple Segments

In the case of long-stator linear drives, unlike rotative drives for which speed or position sensors are a single unit attached to the shaft, these sensors extend along the carriage way, becoming a costly part of the system. Therefore, sensorless methods are of higher concern in linear motors than in rotative ones. For long carriage ways, the stator is usually divided in several independently fed segments in order to reduce the reactive power and to allow more than one vehicle to move on the same carriage way. This arrangement presents additional challenges in the implementation of sensorless methods because the position-dependent variables [as the electromotive force (EMF)] of each segment are nonperiodic signals. Moreover, the acquired speed and position information from one segment must be synchronized with the adjacent one when the mover passes over a segment transition. In this paper, a method to get a continuous estimation of the speed and position, even during the transition between segments, is proposed. This method uses an EMF observer for each active segment (i.e., where the mover is currently located, and the subsequent segment). Then, based on the addition of the observed EMF, a single speed and position observer is implemented for the mover. Using an experimental setup, validation results are attained and presented.

Comparison of wind turbines regarding their energy generation

The energy capture of wind turbines depends not only on the specific wind conditions found at the site where the turbine is installed, but it depends also on the control strategy used for the turbine. As differences in the site conditions make the influence of the control strategy difficult to measure, very different results have been reported. In this paper the results of a simulation-based approach are presented, which are valid for a broad range of sites. It is shown how a lot of the different results found in the literature can be explained by different site conditions.

Controlling a System of Linear Drives

A system of linear drives is proposed for process integrated material handling. On a carriage way several vehicles (work piece carriers) should be able to travel with a high degree of independency. The carriage way must allow for curves and for closed paths. A permanent magnet synchronous long stator linear motor with passive, lightweight vehicles is proposed, which does not need any energy or information transferred to the vehicles. The long stator is divided into several sections, each section is fed by an inverter providing individual control of several vehicles. Multiple inverters exchange information with the vehicle controllers via a time triggered inverter bus. A standard PC with additional interface cards is used to control vehicles. During transition between stator segments, the position dependent force is produced by controlling two inverters simultaneously. EMF and thrust force are measured and compared to FEM -calculation results

Speed sensorless control of a long-stator linear synchronous-motor arranged by multiple sections

Linear permanent magnet (PM) motors have become a viable alternative for material handling and processing systems in the industry, mainly because of its higher dynamic response, robustness and accuracy. For long stators, the position sensor, which extents along the carriageway, becomes a costly part of the system. In addition, for long carriageways, the stator is divided in several sections increasing sensing complexity. Therefore, sensorless methods are of higher concern than in rotative motors. In this paper, a speed sensorless control of a long-stator linear synchronous motor arranged by multiple sections is presented. This method uses an EMF observer for each active section (i.e. where the mover is and the subsequent). Then, based on the addition of the observed EMF a single speed and position observer is implemented for the mover. Finally, using an experimental setup, validation results are attained and presented.

Sensorless position-control method based on magnetic saliencies for a Long-Stator Linear Synchronous-Motor

A sensorless method based on evaluating magnetic saliencies by HF signal injection is investigated for long-stator linear synchronous-motors. For long carriageways, the stator is divided into several independently fed segments, in order to reduce the reactive power and to allow more than one vehicle to move on the same carriageway. This kind of linear motors present difficulties, not found in rotative ones, in order to implement the sensorless methods. For instance, due to the end-effect of the stator, stationary saliencies arise which interfere with the position detection. In addition, the position dependent inductance of each segment is non-periodic. Therefore the position information from one segment must be synchronized with the adjacent one when the mover passes over a segment transition. In this paper, a sensorless position-control method providing means to overcome the stationary saliencies and the segment transition is proposed. It was tested in an experimental setup and performance results are shown

Sensorless position estimation by using the high frequency zero-sequence generated by the inverter

A method for sensorless position estimation in PM synchronous motors is proposed. The high frequency zero sequence voltage generated by the PWM is used as carrier source. It is applied to the motor by closing the neutral point to the DC-link through a filter. The anisotropy information, and consequently the position of the rotor, is evaluated from the resulting non-zero sequence current. When compared with the usual methods that inject the carrier in non-zero sequence, the proposed method provides a resulting anisotropy dependent signal four times higher for equal applied voltage. This advantage is useful in motors with weak saliencies as is the case of long-primary linear motors. An analysis of the method and experimental results, using a long-primary linear motor, are presented.