143.

J. A. Pontt, J. R. Rodriguez, A. Liendo, P. Newman, J. Holtz and J. M. San Martin, "Network-Friendly Low-Switching-Frequency Multipulse High-Power Three-Level PWM Rectifier", IEEE Transactions on Industrial Electronics, vol. 56, no. 4, pp. 1254--1262, 2009.

Abstract:
High-power converters for regenerative drives and distributed generation need a network-friendly operation, low harmonic conductive electromagnetic emission for low electromagnetic interference and high electromagnetic compatibility reaching high reliability and performance. Nevertheless, the converters must be controlled with low switching frequency in order to reduce the commutation losses. These two requirements can be satisfied if an optimal modulation strategy is used. The selective harmonic elimination (SHE) is one of the low-switching-frequency strategies most used today. However, this strategy only eliminates a reduced set of harmonic components from the input current. This paper presents a novel optimal modulation strategy whose objective is to reduce the total harmonic distortion of the input current. Six- and twelve-pulse three-level neutral-pointclamped pulsewidth modulation rectifiers are used in order to implement both modulation techniques. The results confirm the advantages of the proposed strategy, namely, less input current distortion and remarkable reduction of higher order harmonics compared with the SHE method, while keeping a low-switching behavior.

142.

R. Wegener, S. Gruber and S. Soter, "Development of a low cost embedded diagnosis system for servo controlled drives including data mining technologies" in 2009 IEEE 18th International Symposium on Industrial Electronics (ISIE), 2009, pp. 373--377.

Abstract:
This paper deals with an embedded diagnosis device which improves the reliability of a machine including servo controlled drives by monitoring the system parameters and detecting abnormalities and creeping changes. The detection algorithm is based on data mining technologies, well known in business administration. The presented system consists of a low cost processor board with an SD-card slot for data storage and a field bus connection and is completely independent of the main machine control. The additional benefits are online monitoring possibilities and the storage of the process variables in a high efficient way during the complete lifetime of the machine.

141.

S. Gruber, C. Junge, F. Senicar and S. Soter, "Optimization of a high force tubular linear drive concept with discrete wound coils to fulfill safety standards in industrial applications" in 2009 IEEE Energy Conversion Congress and Exposition, 2009, pp. 2431--2435.

Abstract:
This paper deals with the next step of development of a tubular permanent magnet linear drive concept for industrial applications up to 3000 N thrust force where low cogging forces are required to fulfill safety standards. The presented linear drive concept is designed for easy production and assembly of a few hundred units per year. It can be manufactured on standard production machines because all ferromagnetic parts are made of standard not-laminated steel. This results in a very economic product. Further more the drive concept includes an internal low cost position sensor based on the hall-effect. The different steps of development are proven by measurements of thrust and cogging forces of different prototypes.

140.

C. Junge, F. Senicar, R. Wegener and S. Soter, "Pressure control of a nonlinear system with a linear-PMSM and a standard inverter" in 2009 IEEE International Electric Machines and Drives Conference, 2009, pp. 83--88.

Abstract:
This paper deals with a high dynamic hydraulic pressure control. The pressure is generated by an inverter driven linear drive which applies a force on a hydraulic cylinder. The linear drive has to generate a pressure profile into the hydraulic system and has to keep it at a constant value after reaching the demanded pressure. The controlled system, containing hydraulic oil, dissolved air and overall three spring packs, is showing a highly non-linear characteristic. The control cascade of the inverter is based on a standard position control loop, which is enhanced by a PI based pressure controller, a dynamically adapted position feed-forward and an active anti-windup of the controller in order to provide optimal control behavior of the nonlinear system.

139.

J. Holtz, "Acquisition of Position Error and Magnet Polarity for Sensorless Control of PM Synchronous Machines", IEEE Transactions on Industry Applications, vol. 44, no. 4, pp. 1172--1180, 2008.

Abstract:
Sensorless control of a permanent-magnet synchronous machine at low and zero speed is based on the injection of an oscillating high-frequency carrier signal. A particular demodulation technique serves to eliminate the estimation error introduced by pulsewidth modulation delay and the nonlinear characteristics of the inverter. Before the drive is started, the initial rotor position and the magnet polarity are detected. The initialization is performed by injecting an AC carrier and two short current pulses in a sequence.

138.

N. Oikonomou and J. Holtz, "Closed-Loop Control of Medium-Voltage Drives Operated With Synchronous Optimal Pulsewidth Modulation", IEEE Transactions on Industry Applications, vol. 44, no. 1, pp. 115--123, 2008.

Abstract:
Inverters for medium voltage drives operate at reduced switching frequency so as to restrain the dynamic losses of the power semiconductor devices. The resulting current harmonics can be reduced by synchronous optimal pulsewidth modulation (PWM), provided that steady-state conditions prevail. Transient conditions, however, interfere adversely with the optimal modulation patterns. Such conditions necessarily occur when the modulator forms part of a conventional closed-loop control scheme. Trajectory tracking control is employed to achieve high dynamic control in conjunction with synchronous optimal PWM. An optimal trajectory of the stator flux linkage vector is derived from the pulse pattern in actual use. The stator flux linkage vector is forced to follow this target trajectory. Modifying the target trajectory in transient conditions enables closed-loop torque control in a deadbeat fashion while conserving optimal modulation. Experimental results obtained from a 30-kW prototype drive operated at only 200 Hz switching frequency demonstrate the effectiveness of the approach.

137.

J. Holtz and N. Oikonomou, "Estimation of the Fundamental Current in Low-Switching-Frequency High Dynamic Medium-Voltage Drives", IEEE Transactions on Industry Applications, vol. 44, no. 5, pp. 1597--1605, 2008.

Abstract:
The switching frequency of medium-voltage ac drives is limited to low values to restrain the dynamic losses of the power devices. This favors the use of synchronous optimal pulsewidth-modulation schemes that minimize the harmonic current. It is a drawback, though, that optimal algorithms do not have a means to extract the fundamental component of the load current. High-performance torque control is therefore difficult to obtain. This paper proposes a method to identify the instantaneous fundamental component of the stator currents. A novel observer is developed for this purpose. The approach enables fast torque control at very low switching frequency. Experimental results from a 30-kW induction motor drive are presented.

136.

J. Holtz and N. Oikonomou, "Fast Dynamic Control of Medium Voltage Drives Operating at Very Low Switching Frequency---An Overview", IEEE Transactions on Industrial Electronics, vol. 55, no. 3, pp. 1005--1013, 2008.

Abstract:
Medium voltage AC machines fed by high-power inverters operate at a low switching frequency to restrain the switching losses of power semiconductor devices. Particular care is thus required in the design of the drive control system. The signal delay caused by low switching frequency operation increases undesired cross-coupling effects in vector-controlled schemes. These are not sufficiently compensated by established methods like feedforward control. Improvements are achieved by a more accurate modeling of the machine and the inverter. An adequate controller is introduced, having a transfer function with complex coefficients. The high harmonic distortion due to the low switching frequency is a tradeoff. Using synchronous optimal pulsewidth as an alternative permits reducing the switching frequency without increasing the harmonics. The detrimental effects of conventional control methods are eliminated by forcing the harmonic components on an optimal spatial trajectory. Deadbeat behavior and complete decoupling are thus achieved. The performance of the aforementioned schemes is compared based on mathematical analyses and experimental results.

135.

S. Soter, "Wind Converters and Farms -- Technologies and Control", Electrical Energy Systems -- University Enterprise Training Partnership, vol. 2008, no. 4, 2008.

134.

R. Wegener,Zylindrischer Linearmotor mit konzentrierten Wicklungen für hohe Kräfte: Dortmund, Techn. Univ., Diss., 2008. Norderstedt: {Books on Demand}, 2008.