Veröffentlichungen
- 190.A. Uphues, K. Nötzold, R. Wegener and S. Soter, "Crowbar-less ride through of asymmetrical gric faults with DFIG based WECS" in 2017 IEEE AFRICON, 2017, pp. 1026--1031.
Abstract:
Due to the increased renewable power penetration level renewable power plants have to provide low-voltage ride-through (LVRT) capability with simultaneous dynamic voltage support, to ensure the grid stability during grid faults. Concerning doubly fed induction generator (DFIG) based wind energy conversion systems (WECS) large electromotive forces and rotor currents, which may damage the rotor-side converter, or adversely affect the DFIG's controllability are induced into the rotor circuit in case of voltage dips. To handle and limit the rotor currents in case of asymmetrical voltage dips without crowbar triggering, a virtual resistance control approach based on the standard dq-control in the synchronous reference frame is discussed. The theoretical results are compared with those of more demanding virtual inductance control. The LVRT capability is verified with measurement results, recorded during a certification campaign at a 2.1 MW WECS concerning the Indian grid code. - 189.A. Uphues, K. Nötzold, R. Wegener and S. Soter, "DFIG's virtual resistance demagnetization for crowbar less LVRT" in 2017 IEEE 12th International Conference on Power Electronics and Drive Systems (PEDS), 2017, pp. 265--270.
ISBN: 2164-5264
Abstract:
Due to the increased renewable power penetration level renewable power plants have to provide low-voltage ride-through (LVRT) capability with simultaneous dynamic voltage support, to ensure the grid stability during grid faults. Concerning doubly fed induction generator (DFIG) based wind energy conversion systems (WECS) large transient electromotive forces (EMF) and rotor currents, which may damage the rotor-side converter (RSC), or adversely affect the controllability of the DFIG are induced into the rotor circuit in case of voltage dips. To limit the rotor currents and to accelerate the transient flux component's or transient electromotive force's damping respectively, a virtual resistance demagnetization approach based on the standard dq-control in the synchronous reference frame is discussed. The theoretical results are compared with those of more demanding virtual inductance and virtual impedance approaches. Additionally, to increase the IGBT's current conductivity, a reduction of switching losses due to a simple pulse pattern optimization is provided. The LVRT-capability is verified with measurement results, recorded during a certification campaign at a 2.1 MW WECS in India, concerning the Indian grid code. - 188.J. Holtz, "Advanced PWM and Predictive Control---An Overview", IEEE Transactions on Industrial Electronics, vol. 63, no. 6, pp. 3837--3844, 2016.
Abstract:
Synchronous optimal modulation and predictive current control and their preferred applications in drive control systems are described. Operation at low switching frequency is required to minimize harmonic distortion and switching losses, thus increasing the utilization of medium-voltage inverters and drive motors. Maximum fundamental output voltage is achieved by predictive overmodulation. Predictive torque control offers less attractions. - 187.A. Uphues, K. Nötzold, R. Wegener and S. Soter, "Comparison of parameter identification approaches with linearised process models based on RLS for induction machines with P {\textgreater} 100 kW" in 2016 IEEE International Conference on Industrial Technology (ICIT), 2016, pp. 134--140.
Abstract:
This paper presents a comparison between a continuous time domain approach (CTD) and a discrete time domain approach (DTD) for parameter identification of induction machines P{\textgreater}100 kW fed with a voltage source inverter (VSI). The machine parameters are identified off-line, based on the reference voltage and the measured current at standstill and single-axis excitation by the VSI. The quality of the identified parameters is verified with the comparison of measured and estimated torque for the whole operating range, exclusively the field weakening region. - 186.S. Gruber, "Analyse und Optimierung eines tubularen Linearmotors in Sonderbauform für hydraulisch betätigte Kupplungs-Brems-Kombinationen", {Bergische Universität Wuppertal}, 2016.
- 185.A. Uphues, K. Nötzold, R. Griessel, R. Wegener and S. Soter, "Overview of LVRT-capability pre-evaluation with an inverter based test bench" in 2015 IEEE 24th International Symposium on Industrial Electronics (ISIE), 2015, pp. 748--753.
Abstract:
With increased renewable power penetration level the system operators of power grids require low-voltage ride-through (LVRT) capability of renewable power plants. The LVRT-capability has to be verified during the process of certification with precisely defined short circuit tests on a reactance based test bench. For the development of the fault ride through (FRT) capability the cost intensive reactance based test configuration is replaced by an inverter based voltage sag generator (VSG). This paper deals with an overview of the whole inverter based test configuration including the control structure of the grid emulator and the adjustment of the grid side converter's control structure to reach LVRT-capability as well as measurement results for the pre-evaluation. - 184.S. Gruber, R. Wegener and S. Soter, "Design Process for High Force Tubular Linear Drive with DiscreteWound Coils" in The 10th International Symposium on Linear Drives for Industry Applications, 2015.
- 183.J. Holtz, G. da Cunha, N. Petry and P. J. Torri, "Control of Large Salient-Pole Synchronous Machines Using Synchronous Optimal Pulsewidth Modulation", IEEE Transactions on Industrial Electronics, vol. 62, no. 6, pp. 3372--3379, 2015.
Abstract:
High-power grinding mills are used in the cement and mining industries to crush clinker or copper ore and grind these materials to fine powder. The multimegawatt speed-controlled mill drives operate at a very low angular speed. Synchronous motors with a high number of pole pairs are used as the prime movers. They are traditionally fed by load-commutated thyristorized cycloconverters. These are prone to failure modes that can lead to excessive torque pulsations and high overcurrents. The huge stator, which was built as a separate ring-shaped structure around the tubular mill, may then get mechanically displaced, and the operation of the plant is interrupted. A novel and reliable direct drive uses a voltage source inverter that operates at the unity power factor for increased efficiency. Synchronous optimal pulsewidth modulation ensures a low harmonic current distortion and reduced switching losses at a very low switching frequency. The optimization of the pulse patterns takes the anisotropic magnetic properties of a separately excited synchronous motor into account. The implementation in a 23-MW semiautonomous grinding mill installed in a Zambian copper mine is intended. - 182.J. Holtz, M. Höltgen and J. O. Krah, "A Space Vector Modulator for the High-Switching Frequency Control of Three-Level SiC Inverters", IEEE Transactions on Power Electronics, vol. 29, no. 5, pp. 2618--2626, 2014.
Abstract:
Operating three-level inverters at very high switching frequency improves the dynamics of servo drives. It reduces the cost and size of harmonic filters that lessen the dv/dt stress of drive motor windings and bearings. Low harmonic current distortion is a further benefit. Other applications are line-side front end converters, uninterruptable power supplies (UPS), and photovoltaic installations. The requirements of very high-switching frequency control are beyond the computing power of modern microcontrollers and digital signal processors. The problem is overcome by a three-level space vector modulation scheme that defines the switching sequence by taking a sequence of logic decisions instead of doing time-consuming arithmetic operations. The control of the inverter neutral point potential is an inherent part of the scheme and does not need additional algorithms. Implementation in an FPGA permits operating at switching frequencies up to 100 kHz. Experimental results are presented. - 181.T. Boller, J. Holtz and A. K. Rathore, "Neutral-Point Potential Balancing Using Synchronous Optimal Pulsewidth Modulation of Multilevel Inverters in Medium-Voltage High-Power AC Drives", IEEE Transactions on Industry Applications, vol. 50, no. 1, pp. 549--557, 2014.
Abstract:
This paper presents neutral-point potential (NPP) balancing while maintaining low harmonic distortion using optimal pulsewidth modulation (PWM) of a multilevel inverter for medium-voltage high-power industrial ac drives. This method is applicable for five-level inverters or higher. A high performance of the machine is observed experimentally at low-switching-frequency operation employing the proposed technique. In the past, low distortion and optimal common-mode voltage at low-switching-frequency control have been reported using proposed synchronous optimal PWM.
