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

P2302 An Adaptive Charging Control Strategy For Ultracapacitor Light Rail Vehicles [#421]
Zhou Rong, Huang Zhiwu, Li Heng, Wu Zhihui and Peng Jun, Central South University, China

In this paper, an adaptive extremum seeking control strategy with sliding mode is develop to charge the ultracapacitor light rail vehicles. Compared with existing model-based charging algorithms, the proposed extremum seeking (ES) charging control strategy is model-free, which implies that it can handle the ageing effect of ultracapacitors well. Moreover, a sliding mode mechanism is embedded into the charging controller to suppress the disturbances introduced by sensors. Simulation and experiment results are presented to show the effectiveness of the proposed design.

P2303 A High Power Density Drivetrain-Integrated Electric Vehicle Charger [#1443]
Usama Anwar, Hyeokjin Kim, Hua Chen, Robert Erickson, Dragan Maksimovic and Khurram Afridi, University of Colorado Boulder, United States

This paper presents a new architecture for an isolated level 2 on-board electric vehicle (EV) battery charger which is integrated with the EV's drivetrain dc-dc boost converter. The proposed charger leverages many of the existing stages of a highly efficient and power-dense composite- architecture-based drivetrain boost converter. This composite boost converter comprises a buck, a boost and a dc transformer (DCX) stage. In selecting the proposed charging architecture, four alternative approaches to drivetrain integration are identified, explored and compared quantitatively in terms of added weight and charging losses. Out of the considered approaches, the proposed charging architecture provides an effective tradeoff between additional weight and charging losses. This drivetrain- integrated charger adds only a bridgeless-boost-based power factor correction (PFC) ac-dc stage, plus an H-bridge and a single winding to the composite boost converter, to achieve high-power on-board charging functionality without substantial additional weight. A 6.6 kW prototype of the proposed charger has been designed and its PFC stage built and tested. The PFC stage uses a digital implementation of a current sensor-less control strategy and employs effective ways of mitigating zero crossing distortion. The proposed charger architecture reduces the additional weight required for the on-board charging functionality, while achieving greater than 97\% peak efficiency for the added charger module PFC stage.

P2304 Railway Power Conditioner Based on Delta-connected Modular Multilevel Converter [#161]
Jiao Shang, NingYi Dai, BaoAn Wang and Hao Chen, Southeast University Chengxian College, China; University of Macau, Macau; Southeast University, China; Weihai Power supply company, China

Single-phase traction loads generate negative sequence currents, reactive current and harmonics to the power grid. Modular multilevel converter (MMC) is a better alternative to implement railway power conditioner (RPC), which is connected to 25 kV supply system. A MMC with delta configuration is fit for controlling negative-sequence current because circulating currents across delta- connected clusters provide extra flexibility in unbalance control. A RPC based on delta-connected MMC is developed. Steinmetz theory is used to calculate fundamental frequency phase reference current. Since the obtained fundamental frequency phase reference current always has a 90 degree phase difference with the line voltage, the dc voltage balancing of the MMC is easy to achieve. In addition, harmonic reference current among the three phases are balanced to reduce the total rating of the converter. The design and control of the RPC based on delta-connected MMC are validated by simulation results.

P2305 Dynamic Study of Electromechanical Interaction in Marine Propulsion [#856]
Jishnu Kavil Kambrath, Aaron Alexander Ayu, Youyi Wang, Yong-Jin Yoon, Xiong Liu, Chandana Jayampathi Gajanayake and Amit Kumar Gupta, Rolls-Royce NTU Corporate Lab, Singapore; Nanyang Techonological University, Singapore; Rolls-Royce Singapore Pte. Ltd, Singapore

Electrical propulsion is gaining popularity in the marine industry, because of its good energy management and better dynamic performance. An azimuth thruster driven by an electric motor is a common configuration found in modern electric propulsion systems. In recent years failures relating to bevel gears and bearings in azimuth thruster drive train failures were reported in the marine industry. The failures are believed to be attributed to the ship operation in extreme sea state conditions, resulting in dynamic mismatch between the motor drive and the mechanical drive train systems. Hence, an analysis of the mechanical drive train system behaviour under different control modes will be an asset to the industry. The azimuth thruster is simplified as a generalised six mass system and the induction motor dynamics are both modelled in MATLAB Simulink; under extreme condition in the sea, i.e. propeller ventilation, there are torsional stresses between masses that can affect the life expectancy of drive line components.

P2306 Model-based Control Design for a Battery/Ultracapacitor DC-DC Converter System [#1326]
Anantharaghavan Sridhar, Phil Kollmeyer and Thomas Jahns, University of Wisconsin-Madison, United States

For battery and ultracapacitor hybrid energy storage systems, the design and control of the DC-DC converter is an important stage of the system design process. The design approach for a model-based controller for a half-bridge DC-DC converter is presented with experimental results from a scaled test configuration. The contribution of this paper lies in presenting a well- behaved discrete-time system model, a controller tuning methodology, and an effective technique to address the nonlinear system response caused by discontinuous conduction. The results show that the controller bandwidth and command tracking that is achieved with the proposed techniques meet application requirements, and that reduced design effort is required for the presented tuning methodology, combined with helpful physical insights. The presented approach can also be generalized to other DC-DC converter systems.

P2307 Sliding Model Control Based On Estimation Of Optimal Slip Ratio For Railway Wheel Slide Protection Using Extremum Seeking [#382]
Qing Peng, Jianfeng Liu, Zhiwu Huang, Weirong Liu and Heng Li, Central South University, China

It is very important for railway vehicles to have a good braking performance to avoid the phenomenon of idling and skidding, which can be implemented by looking for and keeping an optimal slip ratio. The optimal slip ratio is a value existing in the creep zone of functions between friction coefficient and slip ratio corresponding to the maximum adhesion. Controller based on the sliding mode control needs to be entered an reference slip ratio which can be used to find out the optimal control by the designer and can be tracked by actual slip ratio by the controller. Moreover, as an indispensable factor for calculating slip ratio, vehicle velocity is estimated by the proposed algorithm based on locomotive dynamic model. Then the optimal control ensures the actual slip ratio is equal to or close to the best reference slip ratio generated by extremum seeking algorithm dynamically. According to those functions, the optimal slip ratio changes dynamically once the pavement behavior changes. The simulation result demonstrates that compared with constant reference slip ratios, the proposed dynamical seeking algorithm for optimal reference slip ratio achieves the effect of real-time adjustment for braking torque, which prevents the brake torque from being too large or small and guarantees the braking performance.

P2308 Evaluation of Negative-Sequence-Current Compensators for High-Speed Electric Railways [#503]
Antonios Antonopoulos and Jan Svensson, ABB Corporate Research, Sweden

This paper evaluates three alternative topologies for a static compensator (StatCom), suitable to eliminate the negative-sequence currents in a railway system. The compensator is placed in a transformer substation, which feeds two separate sections of the catenary. The major requirements of this converter is to: (i) symmetrize the railway load as seen from the high-voltage side, (ii) control the catenary voltage to a defined level, and (iii) compensate for the harmonics generated by the rolling stock. The topologies investigated here are: (a) a 2-level converter with a common dc-bus capacitor, (b) a delta-connected modular multilevel converter (MMC) based on full-bridge submodules, and (c) a double-star MMC based on half-bridge submodules. The evaluation is based on the minimum device-rating requirements of each converter that fulfill the application requirements in the steady-state. Simulation results are provided to support the conclusions of this evaluation.

Poster Session: Power Converter Topologies

Tuesday, September 20, 11:00AM-12:30PM, Room: Exhibit Hall, Chair: Pradeep S. Shenoy, Leon M Tolbert

P2501 A ZVS Integrated Single-Input-Dual-Output DC/DC Converter for High Step-up Applications [#905]
Ming Shang and Wang Haoyu, ShanghaiTech University, China

This paper presents a novel integrated dc/dc topology with a step-up output and a step-down output. A new control scheme is developed to regulate both outputs simultaneously. Compared with discrete configurations, the proposed integrated converter utilizes a lower number of switches due to the reuse of components. The converter characteristics are studied comprehensively. It is demonstrated that all MOSFETs are turned on at zero voltage with reduced switching losses. For the step-up stage, the converter provides a high boost ratio and is able to clamp the switch voltage spikes. For the step-down stage, the steady-state characteristics and the dynamic performances are similar to that of the conventional buck converter. Moreover, the step-down output port can be extended to multiple ports, where the single-input-multiple-output (SIMO) version of converter can be derived. A 250 W, 42 V to 390 V and 15 V converter prototype is designed, analyzed and tested. The experimental results are presented to verify the feasibility of the topology.

P2502 A Survey on Voltage Boosting Techniques for Step-Up DC-DC Converters [#1041]
Mojtaba Forouzesh, Yam P. Siwakoti, Saman A. Gorji, Frede Blaabjerg and Brad Lehman, Aalborg University, Denmark; Swinburne University of Technology, Australia; Northeastern University, United States

Step-up dc-dc converters are used to boost the voltage level of the input to a higher output level. Despite of its features such as simplicity of implementation, the fundamental boost dc-dc converter has shortcomings such as low boost ability and low power density. With these limitations, researches on new voltage boosting techniques are inevitable for various power converter applications. This can be achieved either by additional magnetic or by electric field storage elements with switching elements (switch and/or diode) in different configurations. Such combination of primary voltage boosting techniques and topologies are large, which at times may be confusing and difficult to follow/adapt for different applications. Considering these aspects and in order to make a clear sketch of the general law and framework of various voltage boosting techniques, this paper comprehensively reviews different voltage boosting techniques and categorizes them according to their circuit performance.

P2503 Analysis and Design of a Current fed Non-isolated Buck-Boost DC-DC Converter [#1152]
Ashok Kumar, Roja Peri and Parthasarathi Sensarma, Indian Institute of Technology, Kanpur, India

This paper presents the analysis and design of a non-isolated, current-fed buck-boost DC-DC converter. The converter is capable of performing both buck and boost operations with zero-ripple input current. An active-clamp circuit is used to recycle the energy stored in the leakage inductance, which minimizes the voltage stress of main switch and provides zero voltage switching at turn-on. The circuit configuration, operation principle and design considerations of the converter in boost mode are discussed in detail. Experimental results for a 300 W hardware prototype with an input voltage range of 40-50 V and regulated output voltage of 400 V are obtained for validation of the converter topology.

P2504 Impulse Commutated Current-fed Three-phase Modular DC/DC Converter for Low Voltage High Current Applications [#753]
Akshay Rathore and Radha Sree Krishna Moorthy, Concordia University, Montreal, Canada; National University of Singapore, Singapore

Current-fed converters with their innate boost nature, short circuit protection etc. offer enormous potential for high current and high gain applications. To resolve the issue of turn-off spike severe in current-fed converters, this paper proposes a commutation strategy termed as impulse commutation in a three-phase current-fed full bridge converter. This simple and cost-effective technique employing high frequency (HF) parallel capacitors achieves load adaptive zero current switching (ZCS) of the primary semiconductor devices. Variable frequency modulation ensures output voltage regulation and power transfer with source voltage variations. Modularity and scalability of the full bridge converter improves the converter reliability and a compact light-weight system can be easily realized.

P2505 Comparative evaluation of capacitor-coupled and transformer-coupled dual active bridge converters [#1052]
Parikshith Channegowda and Giri Venkataramanan, University of Wisconsin-Madison, United States

Dual Active Bridge (DAB) converters are emerging to become the preferred high power DC-DC conversion topology to satisfy the requirements of modularity, high voltage transfer ratio, high efficiency and bidirectional power transfer capability. However transformer design for DAB converters remains a challenging problem, especially for high voltage conversion ratio and higher switching frequencies. Capacitor-coupled transformer-less DC-DC converters capable of arbitrary high voltage transfer ratio with reasonable efficiency have been recently introduced. The voltage gain in this case is achieved by series combination of capacitor coupled active bridge modules. This paper introduces the capacitor-coupled dual active bridge converter and compares it with the traditional transformer-coupled dual active bridge converter. A brief overview of the analytical models of both transformer- coupled and capacitor-coupled DAB converters is presented and the important design factors of both topologies are identified, followed by a comparative evaluation of a published benchmark design with details of all the power circuit components.

P2506 Planar Transformer Winding Technique for Reduced Capacitance in LLC Power Converters [#1372]
Mohammad Ali Saket Tokaldani, Navid Shafiei and Martin Ordonez, University of British Columbia, Canada

Planar transformers (PTs) offer advantages over traditional wire-wound transformers including low-height, low leakage inductance, excellent thermal characteristics, Exceptional reproducibility and manufacturing simplicity. Despite these features, PTs have very high parasitic capacitance due to the large overlapping area and the small distance between consecutive layers. These parasitic capacitances can severely affect the performance of power converters and limit the application of PTs in high frequencies. In this paper, a new PT with very low parasitic capacitance is introduced to mitigate the problems that arise from the parasitic capacitances. The the superiority of the proposed PT is confirmed through finite element analysis (FEA) and the experimental measurements and it is shown that the proposed transformer has 21:2 times less intra and 16:6 times less inter-winding capacitance than traditional spiral PT. This significant capacitance reduction has a tangible effect on the performance of power converter and the experimental results of employing the proposed transformer in 1:2 kW LLC resonant converter shows considerable performance improvement of the converter in terms of common mode (CM) noise and light-loading voltage regulation.

P2507 Topology and Controller of an Isolated Bi-Directional AC-DC Converter for Electric Vehicle [#720]
Beham Koushki, Praveen Jain and Alireza Bekhshai, Queen's University, Canada

An isolated, single-stage bidirectional AC-DC converter for electric vehicle battery charger is proposed. The topology utilizes two half-bridge circuits and a series resonant LC circuit in between. The proposed topology uses only six switches. Low component count in the circuit results in lower cost and volume. Control methods using variable phase-shift and duty-cycles of the half-bridge circuits are proposed. They transfer the desired power and obtain ZVS for all the switching instants while minimizing the RMS current through the resonant circuit and switches. ZVS operation of the circuit enables the switching frequency to increase, without increasing the switching losses. This will result in smaller reactive components and transformer. The proposed controllers also obtains the best performance out of the circuit. Simulation results with PSIM and experimental results to verify the theory have been done.

P2508 High Efficiency LLC DCX Battery Chargers with Sinusoidal Power Decoupling Control [#722]
Dong-Jie Gu, Zhiliang Zhang, Yaqi Wu, Dong Wang, Handong Gui and Li Wang, Nanjing Univ. of Aeronautics and Astronautics, China; The University of Tennessee, United States

With the sinusoidal charging scheme, the large dc link capacitance of the onboard battery charger can be reduced significantly. However, the variable charging current together with the wide battery voltage range imposes serious challenge to maintain high efficiency throughout the whole charging procedure. This paper proposes a LLC dc to dc transformer (DCX) battery charger topology solution to improve the efficiency over the full battery voltage range. Furthermore, on the basis of the topology, a sinusoidal power decoupling control scheme is proposed to realize the front end PFC and sinusoidal output current at the battery side. A 1kW battery charger prototype was built to verify the benefits. For a battery voltage range from 64 V to 84 V, the efficiency of the proposed charger maintains above 95.8% and the peak efficiency is 96%. The dc link voltage ripple is only 12 V with a 22uF film bus capacitor, which is reduced by 97% compared with the conventional dc charging scheme.

P2509 PWM Strategies with Duality between Current and Voltage Source AC/DC Converters for Suppressing AC Harmonics or DC Ripples [#175]
Junpei Isozaki, Kazuma Suzuki, Wataru Kitagawa and Takaharu Takeshita, Nagoya Institute of Technology, Japan

This paper presents duality of PWM (Pulse Width Modulation) strategies between current and voltage source AC/DC converters and the relation between PWM strategies for suppressing either AC harmonics or DC ripples. In addition, the authors propose the PWM strategies of a voltage source AC/DC converter which have the duality of the PWM strategies of a current source AC/DC converter without extra logic circuit. The validity of the PWM strategies is verified by experiments.

P2510 Analytical Expression for Harmonic Spectrum of Regular Sampled Space Vector Modulated Rectifier Connected to IPM Generator [#455]
Jian Zhang, XuHui Wen, JinLong Li, Youlong Wang and WenShan Li, Institute of Electrical Engineering, CAS, China

The harmonic issue of generator rectifier system is discussed in this paper. A general method for determining the theoretical harmonic components of the regular sampled symmetrical SVPWM is presented. The analytical expression for SVPWM was validated by comparing the analytical calculated results with experimental measurements.

P2511 A Systematic Topology Generation Method for Dual-Buck Inverters [#415]
Li Zhang, Tao Zhu, Lin Chen and Kai Sun, Hohai University, China; Tsinghua University, China

This paper proposes a systematic method of the topology generation rules to generate dual-buck inverter topologies based on the concept of power flowing routes splitting and reconstruction. By using these topology generation rules, not only the existing dual-buck inverter topologies, but also a family of new transformerless DBFBI topologies with high reliability are derived from conventional H-bridge inverter topologies. A dual-buck H6-type transformerless topology is analyzed in detail with operational modes given. A prototype of this topology is built to verify the operation principle, experimental results verify the effectiveness of the improved modulation strategy.

P2512 Analysis and Control of Decentralized PV Cascaded Multilevel Modular Integrated Converters [#712]
David Scholten, Nesimi Ertugrul and Wen Soong, The University of Adelaide, Australia

Multilevel cascaded photovoltaic (PV) inverters can create interleaved voltage waveforms, allowing for reduced filter sizes and higher efficiencies, whilst still allowing for the maximum power point tracking (MPPT) of individual PV modules. However, unlike the micro inverter, a high gain boost converter is not required due to the series nature of the PV modules. To reduce wiring and installation costs in small scale applications, the compromise is a decentralised approach utilising a restrictive low bandwidth and intermittent communications link between the modular integrated converters (MICs), which limits MPPT. In this paper, a simplified decentralised control algorithm for the MPPT of multilevel cascaded MICs is proposed that covers both individual and global control of the prototype system. The limits of multilevel power sharing distributions are analysed and verified, exploring the fundamental limits of the cascaded topology. Additionally, the necessary communications update rate of the algorithm is analysed as the MPPT speed is varied, focussing on the repercussions that this has on the harmonic current and required global/local operational balance.

P2513 Experimental Study of a SiC MOSFET based Single Phase Inverter in UPS Applications [#741]
Cheng Luo, Xinyu Wang, Tianyang Jiang, Richard Feng, Huiting Xin and Han Li, Eaton Corporate Research and Technology, China

Single phase uninterruptible power supply (UPS) has been widely used for a variety of critical load to overcome the disruption in utility power supplies. Wide band gap (WBG) power semiconductor devices, such as Silicon Carbide (SiC) finds its application in UPS systems due to its higher switching frequency, lower losses, and higher power density compared to Si devices. In this paper, a full SiC-based 2-level single phase inverter was simulated and tested for single phase UPS applications. The performance is compared with a Si-based 3-level single phase inverter. The simulation and experimental results show that SiC-based 2-level inverter can achieve better efficiency than Si-based 3-level inverter with reduced component counts and system complexity. The impact of switching frequency and filter inductor size on the SiC inverter efficiency is also investigated.

P2514 Performance Analysis of a flexible multi-level converter for high voltage photovoltaic grid-connected power system [#232]
Lu Zhou, Li Wuhua, Hu Senjun, Luo Haoze, He Xiangning, Cao Fengwen, Zhang Chaoshan and Du Jiyuan, Zhejiang University, China; Aalborg University, Denmark; Suzhou Vocational University, China; XiAn Kai Tian Power Electronics Technical Co, China

Multi-level converters are widely employed in medium voltage grid-connected PV systems, since they feature better power quality and higher conversion efficiency compared with two-level converters. The conventional two-stage PV converter configuration with additional high step-up elements can satisfy the wide input voltage requirements, but results in reduced conversion efficiency and increased cost. In this paper, a flexible multilevel converter is proposed and its topology derivation process is introduced. The proposed flexible multilevel converter can adaptively work as a single-stage three-level NPC converter under high PV voltage and as a two-stage five-level converter under low PV voltage. Therefore, it realizes high conversion efficiency during a wide PV voltage variation. Furthermore, the modulation scheme of the presented converter is analyzed in detail. Moreover, the power losses with MATLAB/PLECS simulation and fault-tolerant performance of this converter is explored. Finally, a test bench is built to validate the theoretical analysis of the proposed flexible multilevel converter.