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:
- Grid Synchronization
- Thursday, September 22, 10:30AM-12:10PM Electric Machines for Wind Power Systems
- Converter Topologies for Energy Storage Systems
- AC Microgrids II: Sharing and Coordination
| 9:20AM Impact of Poly-Crystalline Diamond within Power Semiconductor Device Modules in a Converter [#1560]
Mark Robert Sweet, Kalyani Menon and Ekkanath Madathil Sankar Narayanan, University of Sheffield, United Kingdom; Rolls-Royce, United Kingdom This paper presents the finding of thermal characterization of polycrystalline diamond for power semiconductor device modules in a converter. Comparisons of measured thermal performance of two diamond demonstrators, consisting of metalized diamond tiles attached to aluminum and copper forced air cooled heat sinks; show that power dissipation can be increased from 278W to 535W when compared to commercial products operating at a case temperature of 100oC and a maximum junction temperature of 175oC. Detailed converter simulations of a two level three-phase inverter driving a 15kW permanent magnet machine shows that using diamond can increase active power density from 13kW/kg to 17kW/kg at a coolant temperature of 100oC and a flowrate of 6 liters per minute. 9:45AM A Novel 3D Structure for Synchronous Buck Converter Based on Nitride Gallium Transistors [#1034]
In this paper a novel power loop structure design is proposed and analyzed for converters based on Nitride Gallium transistors. Thanks to its innovative way to place the decoupling capacitors and the GaN devices, the proposed structure shows better results in terms of parasitic loop inductance than a classical 2-D power loop structure, leading to lower voltage stress over the GaN transistors (1,46 nH for the 3-D structure against 5,82 nH for the 2-D one). Moreover, this design generates lower common mode disturbances, which is experimentally demonstrated with EMC tests. Eventually, efficiency is investigated making comparison for the same experimental conditions. Magnetics I Thursday, September 22, 8:30AM-10:10AM, Room: 102A, Chair: John Siefken, Charles Sullivan 8:30AM NiCuZn Ferrite Cores by Gelcasting: Processing and Properties [#565] Lanbing Liu, Yi Yan, Khai Ngo and Guo-Quan Lu, Virginia Tech, United States We used gelcasting, a processing technology for fabricating ceramic parts without pressure, to make NiCuZn ferrite cores, which are traditionally made by a process that requires high hydrostatic pressure. A commercial NiCuZn ferrite powder was mixed with water, dispersant, and organic monomers to form a slurry, and then cast into a mold of toroid shape followed by sintering at 900, 950, and 1000oC respectively for two hours. The sintered core mass density was found to increase with sintering temperature. The magnetic properties of the cores, i.e. complex permeability and core- loss density, were measured. We found that the real part of the permeability increased with sintering temperature from about 44 at 900oC to 77 at 1000oC. The core-loss density data at 5 MHz showed that the cores sintered at 950oC had the lowest core-loss density, about 50% lower than that of a commercial NiZn ferrite (4F1) core. Since gelcasting does not require pressure and is scalable and low cost, it has the potential to make magnetic cores with intricate shapes and sizes for desired coupling of magnetic fluxes to improve efficiency and power-density of power electronics converters. 8:55AM Low-Capacitance Planar Spiral Windings Employing Inverse Track-Width-Ratio [#1092]
Planar spiral windings have garnered a significant amount of attention recently due to the popularity of slim consumer electronics combined with their low-profile, high reproducibility, and simple manufacturing. Unfortunately they still suffer from high internal capacitance which limits their use at high frequencies. This work presents the novel inverse Track- Width-Ratio (TWR) planar structure, which greatly reduces the undesired capacitance of multi-layer planar spiral windings by changing the turn widths. The amount of overlapping copper is ultimately reduced with the proposed technique, especially in the areas where the capacitance is the highest, resulting in significantly improved performance. Analytical models for the resistance of planar spiral windings with inverse TWR employed are presented and used as inputs into Finite Element Analysis to predict the capacitive behaviour of the structure. These results are compared to experimental results obtained from an impedance analyzer and a capacitance reduction up to 50% is exhibited, with a reduction in ac resistance by 20%. 9:20AM On-Chip Transformers with Shielding Structures for High dV/dt Immunity Isolated Gate Drive [#1385]
High dV/dt immunity is desired for isolated gate driving of next generation fast switching power devices. This requires the on-chip isolation transformer to have a small capacitive coupling between the coils. Therefore, in this paper, on-chip transformers with solid ground shield (SGS) and patterned ground shield (PGS) structures are proposed and studied. Simulation results show that the SGS achieves perfect capacitive shielding and therefore excellent dV/dt immunity at the cost of 23% to 31% lower inductances and a 16% lower voltage gain, while the PGS reduces the capacitive coupling by 10 times and therefore achieves a 10 times better dV/dt immunity without notably sacrificing the inductances and the voltage gain. 9:45AM Additive Manufacturing of Toroid Inductor for Power Electronics Applications [#472]
A commercial multi-extruder paste-extrusion 3D printer was used to process both metal and magnetic pastes into 3D structures of magnetic components for power electronics circuits. For the magnetic core, we formulated a permalloy powder filled benzocyclobutene composite in the form of paste, termed poly-mag paste, as a feed stock for the printer; while for the conductive winding feed stock, we used a commercial nanosilver paste. A toroid inductor was 3D-printed by using the metal and magnetic pastes, and it was cured at 250 degree C for a half hour without any external pressure to form the structure. The inductance of the 3D printed toroid inductor was measured to be about 110.3nH. The DC resistance of the winding was 0.28 Ohm. Both the winding and core magnetic properties can be improved by adjusting the feed paste formulations and their flow characteristics and fine-tuning the printer parameters, such as motor speeds, extrusion rate, and nozzle sizes. Grid Synchronization Thursday, September 22, 8:30AM-10:10AM, Room: 202E, Chair: Behrooz Mirafzal, Tsorng-Juu Liang 8:30AM A New Phase-Locked Loop Method for Three-Phase System [#124] Hongyan Zhao, Trillion Q. Zheng, Yan Li, Hong Li and Shi Pu, Beijing Jiaotong University, China Stability and rapidity of phase angle detection in grid synchronization system is very important, especially when grid voltage is under adverse conditions. This paper presented a fast direct calculation phase-locked loop (FDC-PLL) method which can detect phase angle directly from the corresponding relationship between the absolute value of grid voltage and the phase angle. And the d-q conversion is not needed in FDC-PLL. Moreover, when gird voltage is unbalanced or distorted, the positive-sequence fundamental component (PSFC) of grid voltage is extracted through double second order generalized integrator (DSOGI), and phase angle is calculated by using PSFC. As a consequence, the effectiveness and feasibility of the presented PLL algorithm is verified by simulations and experiments. 8:55AM A New Second-Order Generalized Integrator Based Quadrature Signal Generator With Enhanced Performance [#1069]
Due to the simplicity and flexibility of the structure of the Second-Order Generalized Integrator based Quadrature Signal Generator (SOGI-QSG), it has been widely used over the past decade for many applications such as frequency estimation, grid synchronization, and harmonic extraction. However, the SOGI-QSG will produce errors when its input signal contains a dc component or harmonic components with unknown frequencies. The accuracy of the signal detection methods using it may hence be compromised. To overcome the drawback, the First-Order System (FOS) concept is first used to illustrate the principle of the SOGI-QSG, based on which, an improved Second- Order SOGI-QSG (SO-SOGI-QSG) is then proposed by referring the relationship of the standard FOS and the second-order system. The proposed SO-SOGI-QSG inherits the simplicity of the SOGI-QSG, while it has much stronger attenuation ability for both low- and high-frequency components. A detailed parameter design procedure for the SO- SOGI-QSG is provided in this paper as well. The effectiveness of the proposed SO-SOGI- QSG is finally validated by experimental results. 9:20AM A Modified SRF-PLL for Phase and Frequency Measurement of Single-Phase Systems [#104]
In this work, a single phase phase-lockedloop (PLL) that uses a low-pass notch filter is proposed. The new PLL was derived from the synchronous reference frame PLL (SRF-PLL) in which the dq axis components were generated using the alpha-beta reference signals. The single-phase grid voltage was used as the alpha component, whereas the beta component was derived by delaying the grid voltage by 90 degrees in phase. The dynamics of the proposed PLL were compared to those of the SRF-PLL. The frequency measurement using the new PLL showed better performance over the SRF-PLL and a second-order generalized integrator (SOGI) PLL. The proposed PLL displayed better performance under both variable frequency and distorted grid voltage conditions. Experimental results were used to validate the dynamics obtained from the simulation results. The proposed method adds very little complexity to the conventional SRF-PLL. 9:45AM Influence Of Double-Line Frequency Power Oscillation In Photovoltaic Generator Efficiency And H-Bridge VSI Performance [#622]
In this work it is presented a theoretical and experimental investigation of the influence of the low power oscillation due to the pulsating single-phase energy flow in a H-bridge voltage source inverter that operates connected to the grid and is fed by photovoltaic (PV) panels. That oscillation can be responsible for efficiency reduction of PV generators connected to the DC-bus of the inverter, as well as degrades its AC output voltage quality. Experimental results are provided to validate the theoretical approach and to evaluate the performance and quantify energy gain by proposing a method to improve the amount of energy extracted from a PV generator even with low frequency oscillation. Thursday, September 22, 10:30AM-12:10PM Electric Machines for Wind Power Systems Thursday, September 22, 10:30AM-12:10PM, Room: 203AB, Chair: Ion Boldea, Pragasen Pillay
10:30AM Comparison Analysis of PM Transverse Flux Outer Rotor Machines with and without Magnetic Shunts [#475] Oleksandr Dobzhanskyi, Gouws Rupert and Amiri Ebrahim, Doctor, Ukraine; Professor, South Africa; Ass. Professor, United States This paper presents electromagnetic analysis of two permanent magnet transverse flux outer rotor machines with and without magnetic shunts. The research started with designing and analysing a permanent magnet transverse flux machine with inner rotor, previously patented by J. Giearas in 2010. 10:55AM A Generator-Converter Design for Direct Drive Wind Turbines [#1057]
In this paper, a new generator-converter system for direct drive wind turbines in order to decrease the capital cost and improve the system reliability is presented. The grid-side Voltage Source Inverter (VSI) is replaced by a single-stage boost inverter. This provides flexibility to design a low-voltage generator and thus decreasing the number poles required in the generator. A 1.5MW generator for the proposed system is designed using Finite Element (FE) computations. This design is compared with an existing 1.5MW permanent magnet generator for direct drive wind turbine. The proposed system is supported with set of finite element computations and MATLAB/Simulink simulations. 11:20AM Gearbox Fault Diagnosis Using Vibration and Current Information Fusion [#1685]
This paper proposes a novel vibration and current information fusion-based fault diagnostic method for drivetrain gearboxes. First, two multiclass support vector machines (SVMs) are designed to output the probabilities of different fault (or health condition) classes according to the input features extracted from a vibration signal and a current signal collected from the condition monitoring system, respectively. The Dempster-Shafer (D-S) theory is then applied to fuse the probabilistic outputs of two SVMs to get the final fault diagnostic result. Experiments are conducted for a gearbox with different types of fault, where a gearbox vibration signal and a generator current signal are collected to prove the effectiveness of the proposed method. Results show that the proposed method is more robust and reliable than the traditional methods of using a single sensor or a single type of sensor for gearbox fault diagnosis. 11:45AM Bearing Fault Diagnosis of Direct-Drive Wind Turbines Using Multiscale Filtering Spectrum [#1097]
Bearing fault diagnosis of direct-drive (i.e., no gearbox) wind turbines is a challenging issue due to the varying shaft rotating frequency (SRF) caused by the erratic wind environment. To solve the spectrum smearing problem of the SRF- related components and remove the disturbances of the SRF-unrelated components in a measured signal, this paper proposes a novel method, called multiscale filtering spectrum (MFS), to obtain the weighted energy distribution of the mono-component signals within a local order range based on the Vold-Kalman filter (VKF). First, the instantaneous SRF of the wind turbine is estimated from a generator current signal. Then, a VKF-based multiscale filter bank is designed according to the center frequencies corresponding to the SRF at different scales. The mono-component signals whose frequencies are continuous multipliers of the SRF are subsequently extracted from the envelope of the measured current or vibration signal. Finally, a weighted energy spectrum is constructed within the selected order range, from which possible bearing fault characteristic orders can be identified. Simulation and experiment results show that the proposed new MFS method can enhance the characteristic orders and suppress the noise and, therefore, has better performance than the traditional angular resampling method for bearing fault diagnosis of direct-drive wind turbines under varying speed conditions. Converter Topologies for Energy Storage Systems Thursday, September 22, 10:30AM-12:10PM, Room: 203C, Chair: Behrooz Mirafzal, Ion Boldea 10:30AM Design Considerations of an Isolated GaN Bidirectional DC-DC Converter [#233] Fei Xue, Ruiyang Yu and Alex Q. Huang, North Carolina State University, United States This paper investigates three design considerations of a novel bidirectional dc-dc converter for distributed energy storage device. They are the layout for minimum loop inductance and heat dissipation, gate drive power supply for high side Gallium-Nitride (GaN) device and high resolution digital PWM control methodology. The special package of the available GaN devices requires a PCB layout method that takes into account the thermal design as well as the switching loop inductance. Besides, the high dv/dt will introduce a circulating current in the high-side gate drivers and power supplies. This current should be minimized. Furthermore, conventional digital PWM modules is not precise enough for high frequency (usually >50kHz) converter modulation and will cause limited cycle oscillation. A high resolution digital phase-shift modulation scheme is utilized to improve the resolution of the phase-shift control for the 150 kHz converter. In the end, an optimized engineering design method is proposed. The experimental results are analyzed on a 1kW bidirectional dc-dc converter to verify the concepts. 10:55AM Flexbattery - Merging Multilevel Power Conversion and Energy Storage [#397]
This paper describes a ``flexbattery'' modular battery pack concept that integrates the function of energy storage, active cell balancing, and bidirectional multilevel power conversion. As a result, the flexbattery pack does not have a positive or negative terminal, but terminals that can operate at arbitrary voltage levels, both positive or negative. Since each connection terminal can generate a variable voltage within a certain range, the system can also supply ac voltage. Therefore, with appropriate control this innovative flexbattery could be directly applied to an electrical motor. Also, the flexbattery pack can be charged from any voltage level within the nominal output range of the pack, both dc or ac. The elementary flexbattery unit is introduced and analyzed together with the operation of a pack. Additionally, the concept has been experimentally verified with a 120 W three-unit, nine- level prototype under both ac and dc operation. 11:20AM A Novel Modular Dual Active Bridge (DAB) DC-DC Converter with DC Fault Ride-Through Capability for Battery Energy Storage Systems [#957]
This paper proposes a novel modular dual-active-bridge (DAB) dc-dc converter for spilt-battery energy storage system (BESS) in medium-voltage dc (MVDC) grid application. Compared to modular cascaded DAB converter, the proposed topology has current-fed DAB characteristics, with directly dc current control to achieve dc fault ride-through capability. In addition, the proposed converter exhibits favorite features of DAB converter such as galvanic isolation, soft-switching condition and small passive components. The operating principle is described in details, and the corresponding control system is developed to realize the power flow and balancing control. A case study of 500 kW, 20 kHz BESS based on proposed converter is simulated for validation. 11:45AM A High Current Bidirectional DC-DC Converter for Concept Demonstration of Grid-Scale SMES Systems [#1457]
This paper presents the development and testing results of the high current bidirectional DC-DC converter system for concept demonstration of the next generation high current superconducting magnetic energy storage (SMES) system under a program funded by ARPA-E. The grid-scale SMES system could be enabled by new superconductor materials and manufacturing technologies and targets MWh level energy storage applications. In the SMES power conversion system, interleaving of three-level NPC DC-DC converters with voltage reversal for bidirectional power flow is proposed to meet the requirements of new SMES coil systems, such as high current and voltage ratings, low current and voltage ripples, wide operation range, and modularity. To demonstrate the concept, a 700A/12V SMES lab coil prototype and a 6-channel interleaved bidirectional DC- DC converter with three-level NPC modules have been developed and tested. The paper focuses on the detail design and implementation of the high current DC-DC converter system including the power stage, passive components and control electronics, and the testing results for the proposed converter solution for SMES applications. AC Microgrids II: Sharing and Coordination Thursday, September 22, 10:30AM-12:10PM, Room: 203DE, Chair: Pedro Rodriguez, Hui Li 10:30AM Harmonic power sharing with Voltage Distortion Compensation of Droop Controlled Islanded Microgrids [#605] Hassan Moussa, Jean-Philippe Martin, Serge Pierfederici and Nazih Moubayed, Lorraine University, France; Lebanese University, Lebanon Harmonics are found to have deleterious effects on power system equipment including transformers, capacitor banks, rotating machines etc. This paper describes the voltage distortion generated by nonlinear loads and proposes a new Harmonic Droop Control to reduce the voltage harmonic distortion at the point of common coupling (PCC) and to share the harmonic power between parallel islanded Inverters controlled by classical frequency droop method. Simulation and experimental results are presented to show the competence of the proposed algorithm in achieving harmonic power sharing and in improving the voltage harmonic distortion at the PCC. 10:55AM Novel Active Synchronization Strategy for Multi-Bus Microgrid with Distributed Cooperation Control [#355]
This paper presents a novel active synchronization control strategy of multi-bus microgrid based on distributed cooperation technology. The method can reconnect microgrid back to utility grid (UG) seamlessly with sparse communication channels. Through the cross product of voltage vectors in the synchronizer, the frequency and phase of microgrid can track the main grid simultaneously. The voltage differences of UG and point of common coupling (PCC) are fed back to subsequent PI controllers to generate synchronization correction signals, which are only sent to the leader distributed generators (DG). Meanwhile, each DG exchanges information with its neighbors. The voltage of PCC can follow and synchronize with the main grid for a seamless transition and all DGs achieve the consensus behavior. Compared with traditional synchronization methods, the proposed method obviates complex communication network and improves flexibility and redundancy. Simulation results are presented to verify the effectiveness of the proposed method. 11:20AM An Inverter-Current-Feedback based Reactive Power Sharing Method for Parallel Inverters in Microgrid [#627]
This paper proposes a method to improve the reactive power sharing performance of parallel inverters in a low-voltage islanded microgrid. The proposed method utilizes only the output capacitor voltage and the inverter side current to implement the droop control loop, virtual impedance loop and inner voltage control loop for inverter control. This eliminates the need for extra grid side current sensors and therefore reduces implementation costs. A frequency adaptive reactive power compensation module is added to the reactive power droop loop to improve the accuracy of reactive power sharing. The system stability with the proposed method is analyzed based on the Thevenin equivalent model of the voltage source inverters (VSIs). Moreover, a second- order general integrator (SOGI) filter is introduced into the inverter current based virtual impedance loop to improve the stability. Simulation and experimental results are presented to verify the effectiveness of the method.
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