Table of contents monday, September 9, 1: 30pm-4: 00pm modular Multi-Level Converters, hvdc, and dc grids I 3

Reliability, Diagnostic and Faults Analysis in Power Converters I

Wednesday, September 21, 1:30PM-3:10PM, Room: 102E, Chair: Jiangchao Qin, Martin Ordonez

1:30PM System-level Reliability Assessment of Power Stage in Fuel Cell Application [#1510]
Dao Zhou, Huai Wang, Frede Blaabjerg, Soeren Kundsen Kaer and Daniel Blom Hansen, Aalborg University, Denmark; Dantherm Power A/S, Denmark

High efficient and less pollutant fuel cell stacks are emerging and strong candidates of the power solution used for mobile base stations. In the application of the backup power, the availability and reliability hold the highest priority. This paper considers the reliability metrics from the component-level to the system-level for the power stage used in a fuel cell application. It starts with an estimation of the annual accumulated damage for the key power electronic components according to the real mission profile of the fuel cell system. Then, considering the parameter variations in both the lifetime model and the stress levels, the Weibull distribution of the power semiconductors lifetime can be obtained by using Monte Carlo analysis. Afterwards, the reliability block diagram can further be adopted to evaluate the reliability of the power stage based on the estimated power semiconductor reliability. In a case study of a 5 kW fuel cell power stage, the parameter variations of the lifetime model prove that the exponential factor of the junction temperature fluctuation is the most sensitive parameter. Besides, if a 5-out-of-6 redundancy is used, it is concluded both the B10 and the B1 system- level lifetime can be remarkably increased compared to when no redundancy is used.

1:55PM A Novel Online ESR and C Identification Method for Output Capacitor of Flyback Converter [#168]
Hui Li, Kai Yao, Xufeng Zhou, Fei Yang and Junfang Zhang, Nanjing university of science and technology, China; Nanjing University of Science and Technology, China

As electrolytic capacitor is apt to fail in power system, it is very important to monitor its ESR and C. A novel online monitoring method of capacitor's ESR and C for DCM Flyback converter is propose in this paper. Based on the ac component of capacitor voltage, the calculation model is founded. The method needs no current sensor and is effective for the converter operating at any switching frequency and duty cycle. This simulation results validate the effectiveness of the method.

2:20PM Fault Ride-Through Capability for Grid-Supporting Inverters [#1023]
Prasanna Piya, Masoud Karimi-Ghartemani and Ali S. Khajehoddin, Mississippi State University, United States; University of Alberta, Canada

Voltage control strategy has been observed as being more advantageous than current control strategy for microgrid applications where grid-connected and standalone operation of grid-supporting inverters are desired. Voltage control, however, limits the ability to directly control the inverter current. As a result, the fault ride-through or the low-voltage ride-through (LVRT) capability becomes more challenging to address. This paper develops a method for addressing this challenge by adding an auxiliary controller to the main voltage control system to enable the inverter to ride through the grid faults and inject a balanced current with controlled real and reactive components. Moreover, soft transition into the fault and out from the fault is achieved by the proposed controller. Derivations, partial stability analysis and detailed simulation results are presented.

2:45PM Analysis of Hybrid Energy Storage Systems with DC Link Fault Ride-Through Capability [#1145]
Ramy Georgious, Mark Sumner, Jorge Garcia and Pablo Garcia, University of Oviedo, Spain; University of Nottingham, England

In this work, a Fault Ride-Through control scheme for a non-isolated power topology for Hybrid Energy Storage Systems in a DC microgrid is presented. The Hybrid System is created from a Lithium-Ion Battery and a Supercapacitor Module coordinated to achieve a high-energy and high-power storage system; it is connected to a DC link to interface to the outer system. The power topology under consideration is based on the buck-boost bidirectional converter, and it is controlled through a bespoke modulation scheme in order to obtain low losses in nominal operation. The operation of the proposed control during a DC link short-circuit failure is shown as well as a modification to the standard control in order to achieve Fault Ride-Through once the fault is over. The operation of the converter is theoretically developed and it is verified through simulation and experimental validation.

Electric Machines for Automotive Applications II

Wednesday, September 21, 1:30PM-3:10PM, Room: 102B, Chair: Heath Hofmann, Jing Xue

1:30PM Optimisation of the Torque Quality of a Combined Phase Transverse Flux Machine for Traction Applications [#398]
Jamie Washington, Cristofaro Pompermaier and Glynn Atkinson, Hoganas Great Britian Ltd., United Kingdom; Hoganas AB, Sweden; Newcastle University, United Kingdom

Transverse flux machines can be a torque dense solution for applications requiring a relatively low speed such as electrically assisted bicycles or scooters. Common drawbacks include a high torque ripple caused by a high cogging torque and high back electromotive force harmonics. Cogging torque is of particular importance as it can be felt even when the system is disengaged and the bicycle is being pushed. This paper uses an optimisation procedure to reduce the cogging torque and overall torque ripple of a recently introduced type of transverse flux machine. This machine topology has been shown to have a 10% increase in torque compared to more conventional TFM designs but at the cost of an increased cogging torque and therefore torque ripple. During the optimisation there is a trade-off between reductions in cogging torque and the overall torque production of the machine, this will be analysed and compared to a more conventional TFM design to ensure the benefits of the newer design continue.

1:55PM An Examination for Improvement of Constant Output Characteristics at High-Speed Region in a Spoke-Type IPMSM using Ferrite Permanent Magnet by Changing the Shape of Rotor Surface [#1496]
Shoya Nagano, Masatsugu Takemoto and Satoshi Ogasawara, Hokkaido University, Japan

In recent years, interior permanent magnet synchronous motors (IPMSMs) using ferrite permanent magnet are being studied for high power density motor application, such as electric vehicles. However, the residual flux density of ferrite magnet is lower than that of rare-earth permanent magnet. Thus, in general, it is difficult for IPMSMs using ferrite magnet to maintain constant high output power in high-speed region. Accordingly, a spoke-type IPMSM using ferrite magnet with specification similar to the currently commercially available IPMSM using rare-earth magnet is examined in this research. Owing to increasing constant output power in high-speed region, analysis with 3D-FEA was conducted and the analysis results show that the constant output characteristics in high-speed region are improved by contriving the shape of the rotor surface. Moreover, experimental results of a prototype of the examined spoke-type IPMSM using ferrite magnet will be presented in this paper.

2:20PM Variable Flux Permanent Magnet Synchronous Machine (VF-PMSM) Design to Meet Electric Vehicle Traction Requirements with Reduced Losses [#710]
Apoorva Athavale, Kensuke Sasaki, Brent Gagas, Takashi Kato and Robert Lorenz, University of Wisconsin-Madison, WEMPEC, United States; Nissan Motor Co., Ltd, Japan

Variable flux permanent magnet synchronous machines (VF-PMSMs) in which the magnetization state (MS) of low coercive force (low-Hc) permanent magnets can be actively controlled to reduce losses in applications that require wide-speed operation have been proposed recently. While prior focus has been on achieving MS manipulation without over-sizing the inverter and obtaining higher torque capability, this paper extends the design objectives to include the power requirements of an electric vehicle traction motor over its entire speed range. Finite element methods are used to study the effect of combinations of low-Hc and high-Hc permanent magnets arranged in either series or parallel on the performance of VF-PMSMs. It is shown that while both configurations help improve the torque density, only the series configuration can help improve the high speed power capability. Experimental results showing the variable MS property, torque-speed capability and loss reduction capability of a series magnet configuration VF-PMSM test machine are presented.

2:45PM Comparison of Traction Motors that Reduce or Eliminate Rare-Earth Materials [#1668]
Ayman El-Refaie, Tsarafidy Raminosoa, Patel Reddy, Steven Galioto, Di Pan, Kevin Grace, James Alexander and Kum-Kang Huh, GE Global Research, United States; GE Global research, United States

Important global efforts are underway toward lowering the cost of electric machines for electric and hybrid vehicles by reducing or eliminating the use of rare earth materials which have been experiencing significant price increases and volatility. This paper will present several designs that reduce or eliminate rare-earth materials. All these designs are targeting the same set of specifications of 55kW peak at 2800 rpm and 30kW continuous over a speed range going from 2800 rpm to 14000 rpm. This provides a fair basis of comparison of various machine topologies. The paper will provide a quantitative comparison of the performance of various machine topologies as well as highlight the key tradeoffs.

PM Machines III

Wednesday, September 21, 1:30PM-3:10PM, Room: 101A, Chair: Hamid A. Toliyat, Jie Shen

1:30PM Active Voltage Regulation of Partitioned Stator Switched Flux Permanent Magnet Generator Supplying Isolated Passive Load [#444]
Hanlin Zhan, Z.Q. Zhu and Zhongze Wu, The University of Sheffield, United Kingdom

In this paper, an active voltage regulation strategy of the partitioned stator switched flux permanent magnet (PM) (PS-SFPM) generator is proposed to enable the PS- SFPM generator supplying isolated passive load to obtain a stable output voltage at different load conditions. The target is achieved through mechanically varying the relative inner stator position and adjusting the PM flux-linkage. Over the designed working range, zero output voltage regulation ratio can be obtained when compared to the non-adjusted one. The proposed method provides a solution for generator system supplying isolated passive loads to overcome the uncontrolled characteristics of the passive components. Both the field-circuit coupled finite element analysis and experiment results verify the effectiveness of the proposed method.

1:55PM Coupled and Simplified Model of the Symmetrical and Asymmetrical Triple Star Nine-Phase Interior Permanant Magnet Machines [#1051]
Olorunfemi Ojo, Tennessee Tech University, United States

In this paper triple-star nine phase symmetrical and asymmetrical wound IPM machines are modeled by means of a full order coupled modeling approach. A simplified model which predicts the average fundamental behavior is also proposed. Comparative computer simulations of these two models are provided with experimental results.

2:20PM Design and Analysis of a Novel Three-phase Flux Reversal Machine [#268]
Yuting Gao, Ronghai Qu, Dawei Li, Jian Li and Yongsheng Huo, Huazhong University of Science and Technology, China

In this paper, a novel flux reversal machine (FRM) is proposed to achieve a larger torque density and a smoother torque waveform than the conventional FRM. The proposed FRM have the same combinations of stator and rotor slots, winding pole pair and PM usage, but different PM arrangement with the conventional FRM, i.e. in the conventional FRM, a pair of PMs is mounted on the surface of each stator teeth, while the PMs of the proposed FRM are uniformly attached to the entire inner surface of the stator. First, the origination from the conventional FRM to the proposed FRM is introduced. Then, the effects of the rotor slot number, split ratio, stator/rotor slot opening ratio, PM thickness and pole arc on average torque and cogging torque are investigated and analyzed, which give a reasonable prediction for maximum achievable power density and minimum possible cogging torque of the proposed FRM. Moreover, the proposed FRM is compared to a conventional FRM in terms of back-EMF, cogging torque, rated torque, torque ripple and overload capabilities. Finally, a 12-stator-slot/17-rotor-slot FRM prototype is built to verify the theoretical analyses.

2:45PM Design, Control and Implementation of a Non-Rare-Earth Flux Switching Permanent Magnet Machine [#1635]
Chandan Sikder, Iqbal Husain and Wen Ouyang, NC State University, United States; ABB US Corporate Research Center, United States

This paper presents the control and performance of the Flux-Switching Permanent Magnet (FSPM) machine designed and built with non-rare-earth magnets. The design objective has been minimization of volume and cost, and reduction of cogging torque, noise and vibrations. A comprehensive methodology has been adopted for the design of a 12/10 segmented stator structure FSPM. Machine parameters have been identified with a nonlinear model taking mutual coupling and saturation into account. Stator flux oriented vector controller has been implemented using the machine parameters. Experimental results for the designed and fabricated are included for performance validation.

Drive Applications

Wednesday, September 21, 1:30PM-3:10PM, Room: 101B, Chair: Davide Barater, Uday Deshpande

1:30PM A New Normal Mode dv/dt Filter With Resistor Failure Detection Circuit [#56]
Mark Baumgardner and Mahesh Swamy, Yaskawa America, Inc., United States

Insulated Gate Bipolar Transistors (IGBTs) will soon be replaced by wide band gap devices (SiC and GaN) as the choice for power semi-conductor switch in Voltage Source Inverters. These devices have extremely fast rise time and fall time compared to IGBT devices. The high dv/dt of PWM outputs create excessive voltage stress in the insulation system of AC motors due to voltage reflection issues associated with motors at large distances from the drive. In many oil field applications, the distance between the motor and the Variable Frequency Drive (VFD) approaches 300m. In walking rig applications, it is common to use multiple smaller sized conductors per phase, bunched together, to achieve the desired ampacity. This practice results in higher than usual value of the cable parasitic capacitance. Traditional dv/dt filters used for mitigating over-voltage at motor terminals, have been found to be inadequate in reducing the over voltage at the motor terminals in such oil field installations. The damping resistor often experiences high voltage and gets damaged. A new dv/dt filter suitable for use with high power AC motors at distances nearing 300m with a built-in resistor failure detection circuit is proposed here. Test results are given to demonstrate its efficacy.

1:55PM Simulation of Cable Charging Current and Its Effects on Operation of Low Power AC Drives [#510]
Helen Lewis-Rzeszutek, Ripunjoy Phukan, Rangarajan Tallam, Mark Solveson and Timothy Clancy, Rockwell Automation, United States; Georgia Institute of Technology, United States; Ansys, United States; General Cable, United States

In Variable Frequency Drive (VFD) systems, long motor leads can have many detrimental effects, including cable charging current, overvoltage at the motor terminals, and voltage stress on power modules. Different types of AC system grounding can also interact with long motor leads to yield undesirable effects on drive operation. Analyzing models of various components of a drive system is useful to determine any potential issues prior to installation and to recommend any needed filter solutions to mitigate these issues. However, prior cable models have several shortcomings and are inadequate for fully understanding long cable effects prior to VFD system installation. In this paper, a commercially available finite element analysis (FEA) tool is applied to generate a wide frequency range model for a multi-conductor VFD cable. It is shown that this cable model can be used in a system level simulation to determine application issues for low power AC drives. The method is validated using experimental tests on selected cable, motor and drive combinations.

2:20PM Systematic Modeling for a Three Phase Inverter with Motor and Long Cable using Optimization Method [#1645]
Hui Zhao, Shuo Wang, Jianjun Min and Zhi Yongjian, University of Florida, United States; China South Railway, China

A systematic behavior model based on time domain simulation to predict the EMI performance of a motor drive system is analyzed. Optimization algorithm is used to improve the accuracy of modeling of the impedances of the conduction path.

2:45PM Performance Evaluation of SiC MOSFETs with Long Power Cable and Induction Motor [#1587]
Peizhong Yi, Puneeth Kumar Srikanta Murthy and Lixiang Wei, Rockwell Automation, United States

Silicon Carbide (SiC) MOSFETs, as wide-bandgap semiconductor device, has capability to switch at much higher frequency in comparison with their silicon (Si) counterparts. Industrial motor drive is usually connected to induction motor with long shielded cable. This long shielded cable introduces parasitics such as stray inductance and capacitance to the system, which affects SiC MOSFETs performance for inverter side and reflected wave transient overvoltage on motor terminals. In this paper, switching performance of SiC MOSFETs is systematically studied under different length of cables with both inductor load and induction motor load. Compared with standard DPT, turn on and turn off current ringing decays slower with longer cable which leads to 20% higher switching loss. Long cable also contributes to longer turn off time at low current. Furthermore, a theoretical reflected wave model with SiC MOSFETs based inverter is presented to estimate motor terminal voltage. A much higher dv/dt caused by SiC MOSFETs fast switching results in more strict requirements for both motor and cable selection. The test shows motor transient voltage achieved twice DC bus voltage with 100ft cable under single pulse condition. If pulse width modulation (PWM) is not adjusted properly, motor voltage may shoot up to 3-4 times DC bus voltage. The potential solutions for switching performance improvement and reflected wave are also discussed and provided in this paper.

Sensorless Drives I

Wednesday, September 21, 1:30PM-3:10PM, Room: 101CD, Chair: Giacomo Scelba, Ramakrishnan Raja

1:30PM Design consideration of interior permanent magnet machine position sensorless drive using square-wave voltage injection [#285]
Shih-Chin Yang, Sheng-Ming Yang and Jing-Hui Hu, National Taiwan University, Taiwan; National Taipei University of Technology, Taiwan

Although it is widely known that the saliency-based position sensorless drive is able to achieve the closed-loop control at zero and low speed, there is little literature addressing the consideration on the selection of injection voltage frequency. This paper evaluates the square-wave injection voltage at different frequencies for the design of interior permanent magnet (PM) machine saliency-based sensorless drive. It is shown that more flux saturation on high frequency (HF) d-axis inductance occurs than the saturation on q-axis inductance due to the magnetic relaxation. The performance of saliency-based sensorless drive can be enhanced by properly designing the frequency of injection voltage. An IPM machine with a saliency ratio (Lq/Ld) of 1.41 is tested for the experimental evaluation.

1:55PM A Synchro-Perspective-Based High-Frequency Signal Injection Method for Position-Sensorless Vector Control of Doubly-Fed Induction Machines [#654]
Anuwat Srivorakul and Surapong Suwankawin, Chulalongkorn University, Thailand

In this paper, a novel high-frequency (HF) injection method of sensorless drive for doubly-fed induction machines (DFIM) is proposed. The high-frequency voltage is injected into the rotor winding and according to the concept of synchro, the rotor position can be simply extracted from the phase difference among the stator current and the rotor current regardless of machine and grid parameters. In addition, the proposed scheme is robust against the disturbance of high-frequency stator voltage propagated from the grid. The vector phase- locked loop (PLL) technique is employed to calculate rotor position and rotor speed simultaneously and the global stability of the PLL is validated. The feasibility of the proposed concept is verified by the experimental results with 4-kW DFIM drive.

2:20PM Enhancing Estimation Accuracy by Applying Cross-Correlation Image Tracking to Self-Sensing Including Evaluation on a Low Saliency Ratio Machine [#1100]
Timothy Slininger, Yinghan Xu and Robert Lorenz, University of Wisconsin, Madison, United States

Image tracking self-sensing, which utilizes cross-correlation to detect the rotor position by evaluating the orientation of the current image across a full injection cycle can enhance estimated accuracy and improve tolerance to noise. Cross-correlation over a full injection cycle replaces the classical heterodyning demodulation used in traditional point-tracking methods and is known to produce significant harmonic content. Image tracking mitigates dynamic degradation since there is no longer a need for low pass filtering of the harmonic content. Cross-correlation also handles complex images well. This paper will document how by the careful consideration of the machine properties at an operating point, details of the current response can be used to generate a complex image over the full injection cycle. This paper will also show how cross-correlation of the sampled image over each full injection cycle with this detailed model, allows for a more accurate estimate of position when compared to traditional point-tracking methods. These methods are evaluated experimentally on a low saliency ratio SPM and compared to classical rotating and pulsating point-tracking HFI methods.

2:45PM The Crowded Axis of the Frequency: Optimal Pole/Zero Allocation for a Full Speed Sensorless Synchronous Motor Drives [#637]
Virginia Manzolini, Mattia Morandin and Silverio Bolognani, University of Padova, Italy

Full speed sensorless Interior Permanent Magnet Synchronous Motor (IPM-SM) drives estimate the rotor speed and position by means of a HF voltage injection at standstill or low speed operation and by some form of back-electromotive force or PM flux estimator at the medium and high speed range. Both the estimation strategies include an inner loop closed by a PI+I regulator for extracting speed and position, as well as high-pass, low-pass filters devoted to the separation of the injected HF voltages from the fundamental power voltages. Gains and time constant of the regulator, together with filter bandwidths interfere with PWM and injected frequency as well as with current control and speed control bandwidths. In order to design a high performance drive, all these frequencies have to be appropriately allocated. The paper gives a deep theoretical insight of the subject, supported by simulations and experimental validations, aimed to propose a complete set of guidelines for the optimal design of the sensorless control of IPM-SM drives.