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:
- Utility Applications I
- Electric Machines for Transportation Electrification
- Multilevel Converter Applications
| 10:10AM Battery Storage Sizing for a Grid Tied PV System Based on Operating Cost Minimization [#1670]
Mohamed Badawy, Fatih Cingoz and Yilmaz Sozer, University of Akron, United States An optimal battery storage sizing is determined for a high power photovoltaic (PV) grid tied system. The sizing of the battery storage is chosen based on an optimal power flow management system intended to minimize the system running cost. Thus, a lower level power flow optimization problem is formulated along with the required constraints. The operating cost in this problem is formulated as a combination of electricity grid prices and the battery degradation cost. In the lower optimization level, forecasted system data is used to find the optimal power management solution for a year long operation. On the higher level, a sizing optimization problem is formulated using the outcomes of the lower level optimization while updating it with the new selected battery size. A case study is applied under various conditions to test the system performance and analyze the necessary storage sizing subjected to different circumstances. 10:35AM Dynamic Braking System of a Tidal Generator [#148]
The data used in this paper is representative of a typical river or tidal generator. The analysis is based on a generator with a power rating of 40 kW. The tidal generator under consideration is driven by two sets of helical turbines connected to each side of the generator located in between the turbines. The generator is operated in variable speed, and it is controlled to maximize the energy harvested as well as the operation of the turbine generator. The electrical system consists of a three-phase permanent magnet generator connected to a three-phase passive rectifier. The output of the rectifier is connected to a DC-DC converter to match the rectifier output to the DC bus voltage of the DC-AC inverter. The three-phase inverter is connected to the grid, and it is controlled to provide a good interface with the grid. One important aspect of river and tidal generation is the braking mechanism. In a tidal generator, the braking mechanism is important to avoid a runaway condition in case the connection to the grid is lost when there is a fault in the lines. A runaway condition may lead to an overspeed condition and cause extreme stresses on the turbine blade structure and eventual disintegration of the mechanical structure. In this paper, the concept of the dynamic braking system is developed and investigated for normal and abnormal operations. The main objective is to optimize the performance under emergency braking while designing the system to be as simple as possible to avoid overdesigning the power electronics or exceeding the target budget. Utility Applications I Tuesday, September 20, 8:30AM-11:00AM, Room: 202A, Chair: Hirofumi Akagi, Rajasekharareddy Chilipi 8:30AM Multi-frequency Power Routing for Cascaded H-Bridge Inverters in Smart Transformer Application [#655] Youngjong Ko, Markus Andresen, Giampaolo Buticchi, Luca Concari and Marco Liserre, Christian-Albrechts-University, Germany; University of Parma, Italy The smart transformer is a solid state transformer with advanced control functionalities that can efficiently manage a low-voltage micro-grid by also supporting the medium-voltage grid. Cascaded H-bridge (CHB) converters proved to be a suitable option to realize the MV stage of the smart transformer due to their modularity and multi-level output. Normally the power is equally split among the CHB cells, however, in order to delay failures of the system, certain cells can be unloaded if premature deterioration is detected. In this work, multi-frequency power transfer is used to control the power processed by the dc/dc converters that supply the dc link of the CHB. The potential is analyzed analytically and validated experimentally. 8:55AM A High Power Medium Voltage Resonant Dual Active Bridge for DC Distribution Networks [#973]
This paper presents a megawatt scale, medium voltage, medium frequency resonant dual active bridge dc-dc converter operating as a bus-tie converter in a dc distribution network. The high voltage side of the converter is designed using series connected low voltage devices in order to efficiently operate at higher switching frequencies. A combined variable frequency and phase shift control method is propsed to achieve input/output power flow and voltage control, while maintaining soft switching operation for both high voltage and low voltage bridges. A 1MW converter prototype is presented to validate the proposed topology and control. 9:20AM Mu synthesized robust controller for multi-SST islanded smart grid [#848]
This paper introduces a robust controller design method for maintaining microgrid operation under grid islanded mode by solid state transformers (SST) using master-slave control strategy. In the grid islanded mode, the grid voltage controller of the master SST, designed using Mu synthesis, ensures stable control of the microgrid voltage. This paper extends the uncertainty modeling to general grid impedance uncertainties, slave SST current command uncertainties and master SST DC link voltage uncertainties. Also, the proposed design method is general and flexible enough to be readily scaled for applications in larger power systems. A three-SST system is used to demonstrate the design method with twelve uncertainties modeled. The designed system stability and performance robustness are validated in Mu analysis, PLECS simulation, and a controller-hardware-in-the-loop (CHIL) test bed with a Real-Time Digital Simulator (RTDS). 9:45AM Cascaded Open-End Winding Transformer based DVR [#767]
This paper introduces and generalizes a class of multilevel dynamic voltage restorer (DVR) for voltage sags/swells compensation of high-power sensitive loads. Two DClinks can provide either symmetrical (i.e., equal DC-link voltages) or asymmetrical (i.e., different DC-link voltages) operation of the DVR converters. Generalization for K-stages is presented as well. The proposed configuration is named as DVR-COEW (i.e., cascaded open-end winding). The topology permits to generate a maximized number of voltage levels per converter leg. The multilevel waveforms at the output voltages of the converter are generated by using a suitable PWM strategy associated with both: i) DC-link voltages ratio and ii) transformers turns ratio. The model and PWM control are addressed in this paper. Simulation and experimental results are presented. 10:10AM Modeling and Control of Gan Based Multiport Power Converter [#1488]
This paper presents the small-signal modeling and controller design of a single phase multilevel, three-port based on gallium nitride (GaN) devices for renewable energy and UPS applications. The system has two ac-port with five-level waveforms and one DC port. A small-signal model of the converter is derived by the method of state-space averaging. It is controlled with two loops, an outer voltage controller is designed to regulate the DC link voltage and inner control loop compensates the grid current to track the step change in the load current. Comparison of the close-loop simulation from the derived small-signal model and a detailed circuit model showcases the effectiveness of the small signal model. Closed loop simulation results from both the small-signal model and the detail circuit model are presented and experimental results are provided. 10:35AM Economic Feasibility Analysis and Operational Testing of a Community Energy Storage System [#402]
A study of the impact of utility rates on the economic viability of Community Energy Storage (CES) is presented in this paper. Using the U.S. Utility Rate Database, the residential rate structures available at each available zip code in the continental United States were analyzed to see how viable CES is for that zip code. An operational CES hardware system was also tested to verify the results from economic analysis for the specific regions. Electric Machines for Transportation Electrification Tuesday, September 20, 8:30AM-11:00AM, Room: 102D, Chair: Akira Chiba, Emmanuel Agamloh 8:30AM Electrical machine acoustic noise reduction based on rotor surface modifications [#120] Andreas Andersson and Torbjorn Thiringer, Volvo Car Group, Sweden; Chalmers Univeristy of Technology, Sweden Electromagnetic acoustic noise from electrical machines has increasingly become an area of attention for both academia and industry. In electric propulsion systems, this is a main contributor to the total acoustic noise and it is usually perceived as annoying due to its tonal appearance. This paper presents an alternative rotor design for a permanent magnet synchronous machine with the objective to decrease prominent machine orders in the acoustic noise by force density harmonics minimization. Apart from this, torque characteristics and core losses are included in the study as well, in order to investigate possible adverse effects. In the proposed design, irregularities are introduced in the rotor surface to suppress harmonics in the flux density by locally altering the airgap permeance. The analysis is based on finite element modeling, using a sequentially solved, weak coupled, multi-physics approach which enables separation of the electromagnetic-, structural dynamical- and acoustic problems. The results show that the most prominent harmonics in the acoustic noise can be reduced without significantly deteriorating the dynamic performance. It is also demonstrated that the core losses of the machine is positively affected by the obtained harmonic magnitude reduction in the flux density. Although the paper focuses on minimization of radial force density harmonics, the results indicate that the approach and the methodology may also be used for torque harmonics minimization. 8:55AM Integrated Control of an IPM Motor Drive and Hybrid Energy Storage System for Electric Vehicles [#1663]
A DC bus voltage control for a motor drive is proposed in this paper using a hybrid energy storage system (HESS) composed of a battery and an ultra- capacitor for electric vehicle applications. The motor drive of an interior permanent magnet (IPM) motor is typically developed based on a fixed DC bus voltage. However, with the voltage controllability of HESS, it is possible to optimize the energy system by selecting the optimum DC bus voltage. Unlike the conventional designs, the proposed HESS processes only a portion of the vehicle power through interfacing a DC/DC converter. The new concept reduces the converter losses, enables the full usage of stored energy in the storage units and provides a boosting capability of the DC bus voltage. This capability allows the motor drive to operate with maximum torque per ampere control for longer time intervals. An EV with HESS and an IPM drive is simulated under different driving conditions to demonstrate the concept. Experimental results of a scaled down system are provided. 9:20AM Investigation and Analysis of Temperature Effects on Interior Permanent Magnet Machines [#1333]
The purpose of this paper is to analyze and investigate the influence of temperature variation on the characteristics and performance of interior permanent magnet (IPM) machines. The impact of temperature variation on the materials of IPM machines is discussed to show the sources of performance variation. The flux linkages and torque output capability variation as functions of the temperature of are analyzed and discussed. The paper also shows the influence of temperature variation on key IPM machines performance including constant torque curves, voltage limit ellipses, maximum torque per ampere and maximum torque per volt trajectories and torque-speed curves. The results and trends shown in this paper set a foundation for developing control algorithm which takes the temperature effects into consideration, especially in the applications where operating temperature varies significantly. 9:45AM A Novel Flux-Switching Permanent Magnet Motor-Compressor with Integrated Airfoil-Shaped Rotor Design [#1320]
The purpose of this paper is to propose a novel fluxswitching permanent magnet motor with an integrated airfoilshaped rotor. Some of the conventional axial-flow compressor systems need an electric motor to provide mechanical energy input to the compressor. The proposed novel flux-switching motor-compressor can integrate both an electric motor and an axial-flow compressor into a single entity and perform axialflow compression using the airfoil-shaped rotor. This integrated motor-compressor design eliminates the connection between the electric motor and compressor and makes the entire system more compact. Due to the high-speed nature of the integrated motor, no gearbox is needed in the proposed design so that reliability is improved. The principle of design for the proposed integrated motor-compressor is discussed. Analytical studies for the thermodynamics and electromagnetics are elaborated in this paper. A case study design is done to investigate the effect of rotor airfoil curvature to the torque production capability, and the results are demonstrated by finite element analysis. 10:10AM Novel 6-Slot 4-Pole Dual-Stator Flux-Switching Permanent Magnet Machine Comparison Studies for High-Speed Applications [#1336]
This paper presents the study on a novel dual-stator 6/4 flux-switching permanent magnet (FSPM) machine for highspeed applications. Three different alternative topologies of dualstator 6/4 FSPM machines are proposed and their performances regarding flux linkage, back electromotive force (back-EMF), torque density, and manufacturability are compared to the same specification of 10 kW and 15,000 rpm condition. Design considerations for each of the proposed topology are elaborated. The proposed dual-stator 6/4 FSPM machine is compared with the conventional 12/10 FSPM machine designed at the same power and speed rating. Results show that the proposed low-pole dual-stator 6/4 FSPM machine achieves a significant reduction of high-frequency losses including iron loss and magnet eddy current loss than the high-pole 12/10 FSPM machine. Thus the dual-stator 6/4 FSPM machine is more amenable for high-speed operation than the 12/10 FSPM machine because of less fundamental frequency required, less total loss, and more energy savings. 10:35AM High-Specific-Power Electric Machines for Electrified Transportation Applications - Technology Options [#1072]
Specific power of an electric machine is defined as the ratio of output power to total weight. High-specific-power (HSP) electric machines are in high demand in electrified transportation systems such as more electric aircraft (MEA) and electric vehicles (EV), because they help reduce the fuel consumption and extend the traveling range. However, electromagnetic, thermal, mechanical and manufacturing issues put limits on the machines' specific power and represent major technological challenges in their design and fabrication. This paper provides a survey of actual HSP machines and discusses design considerations and technology options for HSP machine development. An HSP permanent magnet synchronous machine architecture is proposed based on the survey and discussions. Multilevel Converter Applications Tuesday, September 20, 8:30AM-11:00AM, Room: 202E, Chair: Giri Venkataramanan, Qin Lei 8:30AM A Fully FPGA-Based Real-time Simulator for the Cascaded STATCOM [#947] Jianxin Zhu, Guodong Teng, Yang Qin, Daorong Lu, Haibing Hu and Yan Xing, Nanjing Univ. of Aeronautics and Astronautics, China A real-time simulation for the Cascaded STATCOM fully implemented on field-programmable-gatearrays(FPGA) is proposed in this paper. The switchingfunction model for the STATCOM is employed, where the IGBTs and diodes are taken as ideal switches, to reduce the amount of calculation. With the help of external circuit calculation, the operation in dead-time period is taken into consideration, which makes all of the operation modes covered. To eliminate the reverse current of diode in discretized simulation, a simple measure and approximation is taken by setting the negative calculated current zero. Full parallelism and deep pipelining are employed in FPGA implementation to minimize the latency. To make a full comparison, a Simulink-based STATCOM model and a 30A 380V scale-down STATCOM prototype were built respectively. The simulation and experiment show that the results from real-time simulator match those from Simulink model and the prototype pretty well, which demonstrate the effectiveness of the proposed real-time simulator for the Cascaded STATCOM. 8:55AM A Broad Range of Speed Control of a Permanent Magnet Synchronous Motor Driven by a Modular Multilevel TSBC Converter [#1319]
This paper provides a theoretical and experimental discussion on a modular multilevel triple-star bridge-cell (TSBC) converters. This paper also proposes a new control method for mitigating ac voltage fluctuation of the dc capacitor of each bridge cell. The proposed method is characterized by properly injecting both common-mode voltage and circulating currents to each cluster in the whole speed range. Moreover, this paper attempts to optimize the amplitude and frequency of the sinusoidal common-mode voltage with help of numerical analysis. This makes the ac voltage fluctuation the smallest. The new method can reduce both voltage fluctuation and cluster current more effectively than existing methods. Experimental waveforms using 370-V, 75-Hz, 15-kW interior-permanent magnet synchronous motor loaded at the rated torque show good start-up performance from a standstill to the rated speed, keeping both capacitor-voltage and cluster current within acceptable levels. 9:20AM Comparison of SiC and GaN Devices for Front-End Isolation of Quasi-Z-Source Cascaded Multilevel Photovoltaic Inverter [#1065]
The wide band-gap Silicon Carbide (SiC) and gallium nitride (GaN) materials based semiconductor devices have attracted tremendous attentions in modern power electronics applications. They provide much higher switching frequency and higher junction temperature than silicon power devices, thus to significantly decrease the system volume and weight, especially on passive components. In this paper, the characteristics of the SiC and GaN materials and devices are overviewed. A front-end isolated quasi-Z-source cascade multilevel inverter (qZS-CMI) based Photovoltaic (PV) power system is proposed to insulate the PV array from high voltage grid and make possible of PV grounding, thus to enhance the system reliability and safety. The SiC and GaN devices applied to the front-end isolation of qZS inverter module are compared. Experimental results verify the proposed front-end isolated qZS-CMI and comparison results, demonstrating a competitive solution for the future development of such inverters. 9:45AM Which is more suitable to a Modular Multilevel SDBC Inverter for Utility-Scale PV Applications, Phase-Shifted PWM or Level-Shifted PWM? [#887]
This paper discusses and compares phase-shifted pulsewidth modulation (PS-PWM) and level-shifted PWM (LSPWM) in a modular multilevel single-delta bridge-cells (SDBC) inverter for utility-scale grid-tied photovoltaic (PV) applications. A unique characteristic of this inverter application is the capability to operate even under imbalanced power distribution among its bridge cells. An imbalanced energy distribution may degrade harmonic performance and limit the inverter operating range. The focus of this research lies in analyzing the following two fundamental properties; waveform quality and energy balancing capability when either PS-PWM or LS-PWM is applied. This paper highlights the benefits of LS-PWM over PS-PWM in this particular application, and demonstrates that the SDBC inverter is suitable for applications with imbalanced power distribution. Experimental results obtained from a three-phase 10-kW downscaled SDBC inverter with six bridge cells per cluster show good agreement with those from theoretical analysis. 10:10AM A Symmetrical Hybrid Nine-Level Inverter for High Speed Open-Winding Motor Drive System [#1271]
In order to reduce output voltage harmonics and improve efficiency, a symmetrical hybrid nine-level inverter for high speed open-winding motor drive system is presented in this paper. Each phase of this inverter is composed of a five-level DC/DC converter and an H-bridge. The DC/DC converter is operated at high frequency with low voltage MOSFETs and the H-bridge is operated at fundamental frequency with high voltage IGBTs. The three phases are connected to a common DC-link and each drives an isolated winding of an open-winding motor. The operating principles and modulation method is introduced. A detailed analysis of the average currents through the flying capacitor and neutral point of the DC-link is presented and a capacitor voltage balancing method is proposed. Experimental results are presented to demonstrate the feasibility of this inverter.
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