Veröffentlichungen
- 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.
- 133.J. Jiang and J. Holtz, "An efficient braking method for controlled AC drives with a diode rectifier front end" in 2008 IEEE Industry Applications Society Annual Meeting, 2008, pp. 1446-1453 vol.3.
ISBN: 0197-2618
Abstract:
Standard PWM inverter fed induction motor drives employ a diode rectifier bridge to supply AC power from the utility to the DC link. Although a diode rectifier is the most cost-effective solution, it does not permit reversing the power flow. This prohibits operating the machine in the regenerative braking mode for active deceleration. An innovative control method substitutes conventional hardware, such as an active front-end rectifier or a chopper controlled braking resistor in the DC link circuit, by additional software that is implemented in the standard microprocessor control. The control algorithm maximizes the power losses in the machine and in the inverter. It enables regenerative braking operation of the induction motor at high torque. The algorithm conserves the high dynamic performance of a vector controlled drive system. - 132.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. - 131.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.
