Veröffentlichungen
- 124.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 - 123.R. Wegener, S. Gruber, K. Nötzold, F. Senicar, C. Junge and S. Soter, "Development and Test of a High Force Tubular Linear Drive Concept with Discrete Wound Coils for Industrial Applications" in 2008 IEEE Industry Applications Society Annual Meeting, 2008, pp. 1--5.
ISBN: 0197-2618
Abstract:
This paper deals with the development of a tubular permanent magnet linear drive with radial magnetized armature and discrete wound coils mounted on a star-shaped stator part. The rated force of the developed machine is 500 N per segment. This presented particular design results in a very economic product because all primary parts, except of the permanent magnets and coils, are made of standard non-laminated steel and are optimized for easy production and assembly. The control of this machine with a specially built low cost linear sensor based on the Hall-effect is also presented. The suitability of the design is proven by the demonstration of a prototype with measurements of thrust and cogging force. - 122.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. - 121.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 - 120.R. Wegener,Zylindrischer Linearmotor mit konzentrierten Wicklungen für hohe Kräfte: Dortmund, Techn. Univ., Diss., 2008. Norderstedt: {Books on Demand}, 2008.
- 119.J. Holtz and J. Quan, "Drift and parameter compensated flux estimator for persistent zero stator frequency operation of sensorless controlled induction motors" in 2008 IEEE Industry Applications Society Annual Meeting, 2008, pp. 1687-1694 vol.3.
ISBN: 0197-2618
Abstract:
The performance of sensorless controlled induction motors is poor at very low speed. The reasons are the limited accuracy of stator voltage acquisition and the presence of offset and drift components in the acquired signals. To overcome these problems, a pure integrator is employed for stator flux estimation. The time-variable DC offset voltage is estimated from the flux drift in a parallel stator model and used to eliminate the offset by feedforward control. Residual high-frequency disturbances are compensated by feedback flux amplitude control. A linearization of the PWM inverter transfer function and an improved stator resistance estimation scheme further enhance the system performance. Experiments demonstrate high dynamic performance of sensorless control at extreme low speed and zero stator frequency. - 118.J. Holtz and N. Oikonomou, "Optimal Control of a Dual Three-Level Inverter System for Medium-Voltage Drives" in 2008 IEEE Industry Applications Society Annual Meeting, 2008, pp. 1--8.
ISBN: 0197-2618
Abstract:
Actual developments in medium-voltage drives aim at increasing the power capability of the PWM inverter. Parallel connection of power semiconductor devices permits increasing the output current, while series connected devices increase the output voltage. In either case are additional means required for balancing the current or voltage stress of the devices. The three-level neutral-point clamped (NPC) inverter topology offers an inherent means to ensure dynamic voltage balancing of a maximum of two series connected devices. Higher operating voltages can be achieved by series connection of entire inverter topologies. Two circuit topologies are considered that behave as five-level units. Synchronous optimal pulsewidth modulation is applied for their control. This permits reducing the switching frequency to the 100-Hz region without sacrificing on harmonic distortion. - 117.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. - 116.J. O. Krah and J. Holtz, "High-performance current regulation for low inductance servo motors" in 2008 IEEE Industry Applications Society Annual Meeting, 2008, pp. 490-499 vol.1.
ISBN: 0197-2618
Abstract:
The paper reports on a standard microcontroller implementation of a pulsewidth modulator and near-deadbeat current regulator for high switching frequency. The application is in high-performance positioning systems. The control strategy relies on a simplified machine model without incurring performance degradations. Changes between different modulation strategies are programmed depending on the modulation index. The values of switching time durations are obtained exclusively by decision making, thus minimizing computational load. Features like overmodulation, dynamic overmodulation, anti-windup, and reduction of switching frequency at thermal overload are included. - 115.J. Holtz and H. Pan, "Elimination of saturation effects in sensorless position controlled induction motors" in 2008 IEEE Industry Applications Society Annual Meeting, 2008, pp. 1695-1702 vol.3.
ISBN: 0197-2618
Abstract:
Owing to the variable magnetic coupling between the stator windings and the discrete rotor bars of an induction motor, a quasi-continuous rotor position signal can be acquired by instantaneous measurement of the total leakage inductance of the three stator phases. The signals are sampled in synchronism with the regular commutations of the PWM process, thus making the injection of additional high-frequency carriers obsolete. The acquired position signal exhibits high spatial resolution and high dynamic bandwidth. Magnetic saturation also influences upon the total leakage inductances and hence constitutes a disturbance for position identification. The paper presents a detailed analysis of the saturation effects and proposes methods to eliminate their undesired impact on the position signal. Experimental results of closed loop sensorless position control at full load and high dynamic performance are presented.
