Table of contents monday, September 9, 1: 30pm-4: 00pm modular Multi-Level Converters, hvdc, and dc grids I 3
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- Bu səhifədəki naviqasiya:
- Control of Electric Drives I
- Medium Voltage Drives and High Power Drives
- Power Modules
| 2:20PM Influence of Blade Pass Frequency Vibrations on MCSA-based Rotor Fault Detection of Induction Motors [#128]
Yonghyun Park, Sang Bin Lee, Myung Jeong, Jose Antonino-Daviu and Mike Teska, Korea University, Korea, Republic of; UNIVERSITAT POLITECNICA DE VALENCIA, Spain; SKF Condition Monitoring Center, United States Motor current signature analysis (MCSA) has recently become widespread in industry for on-line detection of rotor cage faults in induction motors for preventing forced outages. Although it can provide low cost, remote monitoring of rotor faults, cases of false indications have been reported, where the causes of some false indications are still unknown. It is shown for the first time in this work that high-amplitude blade pass frequency (BPF) vibrations produced in pumps, fans, or compressors can cause false rotor fault indications, if the number of motor poles is an integer multiple of the number of blades. The influence of BPF vibration on MCSA based rotor fault detection is analyzed, and it is shown that the interaction between BPF vibration and rotor faults can produce false positive and negative fault indications. Alternative test methods capable of separating the influence of the BPF vibration and rotor faults are suggested for avoiding false MCSA alarms. The claims made in the paper are verified experimentally on a custom-built 380 V induction motor-centrifugal pump system setup. 2:45PM Stator Insulation Quality Assurance Testing for Appliance Motors with Aluminum Windings [#127]
A number of appliance manufacturers have recently replaced the motor stator winding material from copper (Cu) to aluminum (Al) to reduce the product cost in the competitive global appliance market. Although reduction in the motor cost could be achieved, a noticeable increase in the failure rate due to stator insulation breakdown was observed. In this paper, increased failures in Al winding stator insulation is investigated for 230 V, 50 W single phase induction fan motors used in the outdoor unit of air conditioners (A/C). Since the motors with defects or failures could not be screened out with the quality assurance tests (QA) that were applied to Cu winding motors, new QA test methods are evaluated for screening out the units with high risk of failure. The investigation shows that partial discharge (PD) measurement under surge excitation can serve as an effective means of screening out the units that are likely to fail. The claims made in the paper are verified through comparative experimental surge PD testing on Al and Cu winding motors before and after accelerated degradation. 3:10PM Robust detection of rotor winding asymmetries in wound rotor induction motors via integral current analysis [#50]
Current analysis has been widely employed in academy and industry for the diagnosis of rotor damages in cage induction motors. The conventional approach based on the FFT analysis of steady-state current (MCSA) has been recently complemented with the development of alternative techniques that rely on the time-frequency analysis of transient quantities of the machine. However, the application of current-based methodologies to wound rotor induction motors (WRIM) has been much less studied. The present work proposes the application of an integral methodology based on the analysis of both stationary and transient currents for the diagnosis of winding asymmetries in WRIM. The method, based on up to five different fault evidences, is validated in laboratory motors and it is subsequently applied to a large field motor (1,500 kW) that was showing signs of abnormal rotor functioning. The results prove that the method is of interest for the field since it helps to ratify without ambiguity the existence of eventual asymmetries in the rotor windings. 3:35PM Asynchronous Motors Fault Detection Using ANN and Fuzzy Logic Methods [#1444]
Detection of stator faults in their early stage is of great importance since they propagate rapidly and may cause further damage to the motor. Some variations in induction motors such as torque load anomalies must be considered in order to reliably detect stator faults. This paper presents robust artificial intelligence (AI) techniques for interturn short circuit (ITSC) fault detection of stator in three phase induction motors. In this work, the focus is first on the application of artificial neural networks and then fuzzy logic systems to reduce significantly the effect of load variations on fault detection procedure. The proposed ANN methodology has the merit to detect and locate ITSC fault, while the Fuzzy approach is capable of detecting and diagnosing the severity of ITSC fault. The simulation and experimental results are also given to verify the efficiency of both approaches under ITSC fault and load change. Control of Electric Drives I Monday, September 19, 1:30PM-4:00PM, Room: 101CD, Chair: Radu Bojoi, Roberto Petrella 1:30PM Minimizing Torque Ripple of Highly Saturated Salient Pole Synchronous Machines by Applying DB-DTFC [#748] Michael Saur, Daniel Gaona, Jelena Zdravkovic, Bastian Lehner, Robert Lorenz and Dieter Gerling, Universitaet der Bundeswehr, Germany; University of Oviedo, EMMC STEPS Consortium, Spain; University of Wisconsin-Madison, United States DB-DTFC is a flux-observer-based high bandwidth digital, closed-loop torque control law that achieves the commanded torque at the end of each switching period. When flux estimation is accurate, instantaneous torque is fed back and unwanted pulsating torque is inherently minimized. This research presents real time flux-observer-based torque ripple estimation of a highly nonlinear synchronous reluctance machine (SynRM). Saturation and cross-saturation are incorporated directly into the control law and considered in each switching period. Deadbeat torque response and torque ripple reduction is demonstrated experimentally. FEM-simulations validate the torque ripple minimization. 1:55PM Using Volt-sec. Sensing to Directly Improve Torque Accuracy and Self-Sensing at Very Low Speeds [#1260]
As a result of dead-time, device on-state voltage drop, DC bus voltage error and fluctuation, etc., Volt-sec. errors degrade precise control of torque and flux linkage, particularly at low speeds. This is true for deadbeat-direct torque and flux control (DB-DTFC) which directly manipulates the Volt-sec. vector sourced by inverters as well as for indirect field oriented control (IFOC) drives. This paper introduces a real-time sensing scheme to measure the terminal Volt-sec. vector for each switching period with negligible phase delay. Based on Volt-sec. sensing, a model reference adaptive system (MRAS)- based approach is developed to decouple Volt-sec. errors from inverter nonlinearity and DC bus voltage. By delivering accurate Volt-sec. for each switching period, torque and flux control accuracy, self-sensing performance and parameter estimation accuracy are significantly enhanced. 2:20PM Torque Ripple Reduction for 6-stator/4-rotor-pole Variable Flux Reluctance Machines by Using Harmonic Field Current Injection [#88]
The variable flux reluctance machines (VFRMs) are electrically field excited synchronous machines having both field and armature windings on the stator. In order to investigate the torque production of the 6/4 VFRM, an instantaneous torque equation is derived for the first time considering the inductance harmonics by using Fourier series. According to the equation, the undesirable torque ripples having multiples of third harmonic exist due to the inductance harmonics of the field and armature windings. Hence, the harmonic field current injection methods are proposed for the torque ripple reduction. The torque waveforms calculated by 2D-finite element analysis (FEA) are compared with the predicted results from the derived torque equation. Although the methods are proposed at which the magnetic saturation does not occur, the torque ripple can be also reduced in saturation region. Since the proposed method utilizes the machine parameters the influence of the parameter mismatch is investigated. It shows that the torque ripple reduction performance is not affected much unless the fundamental component of nominal inductance is underestimated. The experimental results verify that the proposed approach can effectively reduce the torque ripple in the VFRM. 2:45PM Novel On-Line Optimal Bandwidth Search and Auto Tuning Techniques for Servo Motor Drives [#250]
The main theme of this paper is to propose fast on-line optimal bandwidth search and controller tuning techniques for servo motor drives. The proposed controller tuning method derives the controller gains by searching the optimal bandwidth and identifying the inertia. The optimal bandwidth can be achieved before oscillation occurs. It will be shown the gains of speed controller of servo drives are tuned automatically to reflect the variation of load inertia. Experimental results derived from DSP-controlled PMSM servo drives will be shown. The results demonstrate on-line optimal bandwidth and auto gain tuning can be achieved without motor and load information in prior. These results fully support the developed techniques and claims. 3:10PM Open-loop Control for Permanent Magnet Synchronous Motor Driven by Square-wave Voltage and Stabilization Control [#319]
In this paper, the open-loop control for permanent magnet synchronous motor (PMSM) driven by a square-wave voltage is proposed. The proposed control is able to transit from the PWM region to the square-wave voltage region via the over modulation region seamlessly. When the PMSM is driven by the square-wave voltage using the proposed control, the low-frequency torque vibration except 6th or 12th order harmonics occurs due to the transition to the square-wave voltage region. Therefore, a variable band pass filter (BPF) is introduced as the reduction method of the low- frequency torque vibration. The low-frequency component in the active current for the stabilization control is extracted by the filter. As an experimental result, the proposed method reduces the low- frequency vibration which can be represented for the torque by over 40%. 3:35PM A Robust Current Control Based on Proportional-Integral Observers for Permanent Magnet Synchronous Machines [#1120]
This paper deals with a novel robust current control scheme for Permanent Magnet Synchronous Machine based on the conventional cascade structure. The main idea is to substitute the commonly used decoupling network, which requires the precise knowledge of the system parameters in any working condition, with a more flexible and robust scheme. In particular, the traditional configuration is improved by mean of two proportional-integral observers which allow the preservation of the drive performances under the effects of disturbance. The improved robustness is achieved maintaining the reliable basic scheme with a pure proportional controller in the forward path with advantages in terms of design and tuning. A genetic algorithm is used to optimize the controller and the observer parameters. This multi-objective optimization leads to a good stability and an overall improved performance of the drive above all the operative range. The choice of the optimal solution is based on a novel fitness function which takes into account both dynamical features and disturbance rejection capabilities of the system. The effectiveness of the proposed control scheme is verified by mean of numerical simulations and experiments as well. Medium Voltage Drives and High Power Drives Monday, September 19, 1:30PM-4:00PM, Room: 101B, Chair: Shih-Chin Yang, Uday Deshpande 1:30PM A Pumpback Test Bench for IGCT-based 11MW/595Hz Variable-Frequency-Drives with 1.25MW Grid Capability [#1323] Jie Shen, Stefan Schroeder, Fan Zhang, Kunlun Chen and Richard Zhang, GE Global Research, China; GE Global Research, Germany; GE Power Conversion, China This paper presents a pumpback test bench for high-frequency high-power Variable-Frequency Drives with 11 MW power rating and up to 595 Hz load frequency. A Voltage Combiner concept is applied to allow a high-frequency output from the two IGCT bridges with minimum switching losses. The accordingly developed pumpback test bench applies a dc power coupling concept combined with a virtual grid that can achieve 11 MW test capability with only 1.25 MW facility transformer. By applying a virtual machine concept, the pumpback test can be conducted without the need of high-frequency machines, while the circulating power losses are minimized as well. The details about the virtual grid including the concept tradeoff, filter parameters and modulation schemes are presented. Moreover, design and installation guidelines for high-frequency components, especially the cables, are presented. The high-frequency high-power VFD and its pumpback test bench are both successfully built and experimentally validated at their rated operation points. 1:55PM Grounding Concept and Common-Mode Filter Design Methodology for Transformerless MV Drives [#1160]
Recently, the transformerless design of medium-voltage (MV) drives is an emerging design concept of variable-speed drives (VSD). Here, no dedicated feed transformer is used. The VSD is directly connected to the on-site facility transformer, where multiple other loads are connected as well. The benefits of such a transformerless VSD are the reduced total volume, weight, losses and system costs. In this publication, a suitable grounding concept and a generalized CM filter design methodology for transformerless MV drives is presented for the first time. Both the CM voltage injection to the grid and the CM voltage applied to the three machine terminals is considered. At the Point-of-Common-Coupling (PCC), the CM part of the grid harmonic standards can be met through a proper filter design. Since the converter-generated CM voltage could also cause issues on the machine-side, a novel design reference for the mitigation of bearing currents is applied. The introduced CM filter design methodology provides a suitable CM filter design for transformerless high-power medium- voltage converters. By this, the reliable transformerless operation of general purpose drives and retrofit applications is feasible. 2:20PM Utilisation of Series Connected Transformers for Multiple Active Rectifier Units [#802]
In many industrial systems the bulk of the power required for the process is being processed by medium-voltage (MV) high power variable speed drive systems. As the installed power of such MV drive systems increase, as a ratio of the available short circuit power, the relative power quality properties of these systems' AC-DC front ends become more critical. In high power drives several combinations of active rectifier units (ARUs) are possible, here the benefits of using several ARUs connected in parallel on the dc-side while utilizing a series connection of transformer primaries on the ac side are discussed. 2:45PM Common-Mode Voltage Limits for the Transformerless Design of MV Drives to Prevent Bearing Current Issues [#1153]
Recently, the transformerless design of medium-voltage (MV) drives is an emerging design concept of variable-speed drives (VSD). Here, no dedicated feed transformer is used. The VSD is directly connected to the on-site facility transformer, where multiple other loads are connected as well. The benefits of such a transformerless VSD are the reduced total volume, weight, losses and system costs. However, without a dedicated feed transformer the converter-generated common-mode (CM) voltage may generate harmful bearing currents that could yield serious bearing failures within a short time. For this reason, the suppression of bearing currents is a fundamental design aspect of VSD systems. In this publication, a comprehensive bearing current study highlights the two dominating bearing current mechanisms in VSD systems. Both mechanisms are caused by the converter- generated CM voltage applied to the machine terminals. Their physical understanding is used to define thresholds for the peak CM voltage and the maximum CM voltage slope to ensure the sufficient mitigation of bearing currents. The newly introduced CM voltage limits allow the development of a generalized CM filter design for transformerless VSDs which is the scope of another publication. By this, a reliable transformerless operation of general purpose drives and retrofit applications is feasible. 3:10PM A Robust Sensorless Start-up Method using Four Step Sequence for LCI system [#428]
This paper proposes a new senseless start-up method using a closed loop current control and a flux estimator without position sensor, and it is composed of four step sequence. Step 1 is applied for detection of the initial rotor position, and an initial rotor position is estimated around 1% of accuracy within 150ms. Step 2 is applied for a stable start-up state from the standstill through a closed loop current control, and is up to 3% of the rated speed of synchronous machine. Step 3 and 4 are used in the range generating a sufficient back-emf, and employ a flux estimator. The flux estimator consists of field flux model and flux voltage model, and rotor position/speed are estimated by using a phase locked loop. Field flux model is applied up to 5% of the rated speed. Performance of the proposed start-up method is evaluated by Simpower/Matlab simulation at overall speed range. To verify a feasibility of the proposed method, a 5kVA prototype of load commutated inverter (LCI) system is implemented. Experimental results show the proposed sensorless start-up method works well in the overall sequence region. 3:35PM Virtual Voltage Source Control for 2x27 MVA Machine Test Bench [#1367]
In this paper, a special control solution called Virtual Voltage Source is developed for no-load tests of induction machines. This concept is applied to a 2x27 MVA high-power machine test bench, where the test bench is requested to precisely characterize e.g. 3 MW machines at no-load currents. The developed Virtual Voltage Source thoroughly solves the stability issue of induction machines at low speed ranges. A set of optimizations is presented here that systematically improves the voltage precision of the test bench. Experimental results prove that the proposed concept achieves extremely low voltage and current unbalance, and low Harmonic-Voltage-Factor, verified by more than 100 induction machines. Power Modules Monday, September 19, 1:30PM-4:00PM, Room: 202C, Chair: Muhammad Nawaz, Douglas C Hopkins 1:30PM Performance Comparison of 10 kV-15 kV High Voltage SiC Modules and High Voltage Switch using Series Connected LV SiC MOSFET devices [#1703] Kasunaidu Vechalapu and Subhashish Bhattacharya, NC State University, United States The 10 kV to 15 kV SiC MOSFET and 15 kV SiC IGBT are state of the art high voltage (HV) devices designed by Cree Inc. These devices are expected to increases the power density of converters and are expected to replace 4.5 kV/6.5 kV Si IGBTs. However these are not commercially available. On the other hand low voltage (LV) 1.7 kV SiC MOSFET is commercially available and it is replacing existing 1.7 kV Si IGBT and it can meet immediate need of medium or high voltage (MV or HV) converter applications with series connection of these devices and can replace existing 4.5 kV/6.5 kV Silicon (Si) IGBT. Therefore, 10 kV-15 kV SiC modules and series connected 1.7 kV SiC MOSFET will be competing with each other for MV and HV converter applications. Hence, to explore the capability of low voltage SiC devices for MV or HV applications, a HV switch (10 kV-15 kV) using series connection of 1.7 kV/300 A SiC MOSFET modules has been investigated. For making HV switch using series connected 1.7 kV SiC MOSFET, a simple RC snubber method has been used for dynamic voltage sharing to offset the turn-off delays due to mismatch of device characteristics and/or gate signals. Experimental switching characterization with different values of RC snubbers has been carried out and a methodology has been outlined to find the optimal RC snubber which gives minimum voltage sharing difference, snubber losses and total semiconductor losses. In addition, experimental switching characterization of 10 kV-15 kV SiC modules is presented. Furthermore, performance comparison of HV 10 kV-15 kV SiC modules and HV switch using series connected 1.7 kV SiC MOSFETs is presented in this paper 1:55PM Development of an Ultra-high Density Power Chip on Bus (PCoB) Module [#1005]
A traditional power module uses metal clad ceramic (e.g. DBC or DBA) bonded to a baseplate that creates a highly thermally resistive path, and wire bond interconnect that introduces substantial inductance and limits thermal management to single-sided cooling. This paper introduces a Power Chip on Bus (PCoB) power module approach that reduces parasitic inductance through an integrated power interconnect structure. The PCoB maximizes thermal performance by direct attaching power chips to the busbar, integrating the heatsink and busbar as one, and uses a dielectric fluid, such as air, for electrical isolation. This new power module topology features all planar interconnects and double-sided air cooling. Performance evaluations are carried out through comprehensive electrical and multi-physics simulation and thermal testing for a 1200V, 100A rated single-switch PCoB design. Fabrication and assembly processes are included. For the developed double- sided air-cooled module, 0.5 C/w thermal resistance and 8nH power loop parasitic inductance are achieved.
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