Veröffentlichungen
- 140.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. - 139.J. Holtz, M. Stamm, J. Thur and A. Linder, "High-power pulsewidth controlled current source GTO inverter for high switching frequency" in 2008 IEEE Industry Applications Society Annual Meeting, 2008, pp. 1330-1335 vol.2.
ISBN: 0197-2618
Abstract:
High-power GTO inverters require regenerative snubbers to ensure operation at predefined values of di/dt and du/dt. The use of regenerative snubbers for voltage source inverters is a well established technology. However, the proliferation of high-power PWM current source inverters is impeded by the nonavailability of an appropriate regenerative snubber scheme. The paper proposes a regenerative snubber for current source GTO inverters and reports experimental results of a 1.2 MVA prototype inverter. Energy recovery from the snubbers enables operation at extreme high switching frequency of 1 kHz and reduces the total filter kVA from 70{%} to 20{%} of the inverter power. - 138.G. Schmitt, R. Kennel and J. Holtz, "Voltage gradient limitation of IGBTS by optimised gate-current profiles" in 2008 IEEE Power Electronics Specialists Conference, 2008, pp. 3592--3596.
ISBN: 2377-6617
Abstract:
Using MOS-controlled semiconductors provide the opportunity to directly affect the voltage and currents gradients during the switching transients at the gate. An active gate driver is presented that imposes optimised gate current profiles in order to limit the dv/dt and di/dt. When limiting the dv/dt to 1 kV/mus the switching losses are be reduced by 35{%} in comparison to the common limitation method by gate resistor. The switch-off losses are improved about 10{%} by employing an optimised gate signal. - 137.J. Holtz and N. Oikonomou, "Synchronous optimal pulsewidth modulation and stator flux trajectory control for medium voltage drives" in 2008 IEEE Industry Applications Society Annual Meeting, 2008, pp. 1748-1791 Vol. 3.
ISBN: 0197-2618
Abstract:
High-power PWM inverters for medium voltage drives operate at low switching frequency to maintain the switching losses of the power semiconductor devices at an acceptable level. For these applications, synchronous optimal pulsewidth modulation methods permit a good trade-off between switching losses and harmonic distortion of the machine currents. The optimization of the pulse patterns is done off-line on the assumption of steady-state conditions. Dynamic modulation errors, and high overcurrents as a consequence, are encountered when the operating conditions change during operation. To overcome this problem, the stator flux linkage vector, including its harmonics, is subjected to closed loop control. A stator flux trajectory controller is employed for this purpose. Experimental results obtained from an industrial 1-MVA, 4.16 kV three-level inverter ac drive are presented. - 136.N. Oikonomou and J. Holtz, "Stator Flux Trajectory Tracking Control for High-Performance Drives" in 2008 IEEE Industry Applications Society Annual Meeting, 2008, pp. 1268--1275.
ISBN: 0197-2618
Abstract:
Medium voltage ac machines driven by high-power inverters operate at reduced switching frequency in order to restrain the switching losses of the power semiconductor switches. When synchronous optimal pulsewidth modulation is employed, the harmonic distortion of the machine currents is minimized under steady-state conditions. High-performance drives may be subjected to sudden changes of velocity and load. Conventional current-based closed loop control schemes cannot ensure dynamic operation without adversely affecting the preoptimized modulation patterns. To obtain high dynamic control in combination with synchronous optimal pulsewidth modulation, the estimated fundamental component of the stator flux linkage vector is used as a feedback signal. Closed loop control is established by employing a deadbeat algorithm. The harmonic component of the stator flux linkage vector is minimized in real-time, using the optimal stator flux trajectory as a reference. Experimental results obtained from a 30-kW prototype drive operated at only 200 Hz switching frequency demonstrate the effectiveness of the approach - 135.M. Wlas, H. Abu-Rub and J. Holtz, "Speed sensorless nonlinear control of induction motor in the field weakening region" in 2008 13th International Power Electronics and Motion Control Conference, 2008, pp. 1084--1089.
Abstract:
In the paper it is presented speed sensorless nonlinear control system using multiscalar model based MMB operating in the lower field weakening speed region. Nonlinear control methods can improve the performance of induction motor drives in transients. The maximum available output torque, which guarantees satisfactory motor dynamics in field weakening region, is calculated using the steady state dependencies of induction motor model. Full dynamic reaction to commanded changes or to disturbances that occur during operation at the voltage limit is enabled by reducing the excitation level in a fastest possible way. Experimental results are presented to demonstrate reliability of proposed controller. In the experimental implementation a 22 kW induction motor is used. The whole control scheme (including multiscalar control, speed computation and space vector PWM) are implemented on a DSP and FPGA. - 134.H. Abu-Rub, H. Schmirgel and J. Holtz, "Sensorless Control of Induction Motors for Maximum Steady-State Torque and Fast Dynamics at Field Weakening" in 2008 IEEE Industry Applications Society Annual Meeting, 2008, pp. 96--103.
ISBN: 0197-2618
Abstract:
A method is described that fully utilizes both the maximum inverter voltage and current for steady-state torque production at field weakening. The control algorithm thus provides the maximum possible torque in the entire field weakening region. Dynamic requirements when operating at maximum voltage are met by creating a temporary voltage margin to enable a fast reaction of the current controller. The control algorithm is insensitive to changes of the machine parameters and to variations of the dc link voltage. The approach is based on a stator flux oriented scheme and permits operation without using a speed sensor - 133.J. Juliet and J. Holtz, "Sensorless acquisition of the rotor position angle for induction motors with arbitrary stator windings" in 2008 IEEE Industry Applications Society Annual Meeting, 2008, pp. 1321-1328 vol.2.
ISBN: 0197-2618
Abstract:
The anisotropy of a cage rotor is utilized to determine the angular position of the rotor in an induction machine. The switching transients generated by a pulsewidth-controlled inverter serve as test signals. The response of the three-inverter terminal currents is exploited to derive a quasi-instantaneous rotor position signal. The position is sensed at the inverter through the 3-phase motor cable by measuring the current derivatives. The method does not require additional wire connections. It is applicable to induction motors having the stator windings connected either in wye or in delta. The results are supported by measurements from an experimental setup. - 132.T. Rösmann and S. Soter, "Regenerative Operation of DC-Series Machines in Pitchsystems for Multimegawatt Windturbines" in 2008 IEEE Industry Applications Society Annual Meeting, 2008, pp. 1--7.
ISBN: 0197-2618
Abstract:
Modern windmills and multimegawatt turbines are nearly exclusively equipped with electrical pitchsystems.The pitchsystem itself has to fulfill the following functions: In the case of strong wind conditions during normal operation, the system is responsible to limit the generator torque. On the other hand, the feathering position of the blades is needed to brake down the turbine in stop or emergency situations. In modern windturbines this aerodynamical brake is necessary, because the mechanical brake is designed as a holding brake and is not able to prevent overspeed conditions. The last function described is safety relevant. Because of this, pitch systems are equipped with an backup energy storage. So the blade can be put into feathering position in any case. DC-machines are preferred in pitch systems because of their capability to be supplied directly by the DC-storage unit without any control or powerelectronics. The motor must be designed especially for this battery driven operation because current and speed during emergency battery drive are depending on the mechatronical behaviour of the machine. Actually two different DC machine types are used in pitch systems: DC-series and DC-compound machines. DC- compound machines were introduced because of their natural 4Q operation area. But an actual development allows the regenerative operation also for DC-series machines and makes them very cost attractive for multimegawatt pitchsystems. - 131.R. Wegener, S. Gruber, K. Nötzold and S. Soter, "Optimization of a Low-Cost Position Sensor for a Permanent Magnet Linear Drive" in PCIM Asia 2008, 2008.
