Core losses analysis of the LCL filter inductor for SiC-based inverter

The ability of SiC devices to switch at high speed allows increasing significantly the power density in both converters and passive components, reducing their required size. To mitigate harmonic injection form inverters into the grid, in order to comply with power quality standards, an accurate filter design is required. Given its excellent performance, an LCL filter is the configuration most suitable in grid-connected power converters. Several parameters must be considered when designing an effective LCL filter, and the inverter-side inductor assumes a special importance because of its relevance to suppress high frequency harmonic content at the inverter side. One of the most relevant issues to be considered in the process of designing the LCL filter is the evaluation of core losses in the inverter-side inductor, which will determine the final temperature of the inductor. This paper analyses the core losses of the inverter-side inductor of an LCL filter. The proposed method is based on the computation of the current harmonics generated by the inverter and on Steinmetz’s empirical equation. As a result, core losses calculated taking into account several carrier and sideband harmonics show good agreement with the experimental values. When current harmonics are estimated by simulation, as it is done in the proposed design procedure, results are less accurate, but precise enough for a design procedure

Towards High Efficiency and High Power Density Converter: System Level Design, Modulation, and Active EMI Filters

Power converter exposes strong challenges to its efficiency, power density and reliability. For the grid-connected inverter application, three-level (3-L) T-type neutral-point-clamped (TNPC) inverters has higher efficiency and lower total harmonic distortion (THD) compared to two-level inverter. Hybrid switch concept combines the benefit of both silicon carbide (SiC) MOSFET and Si IGBT. By applying hybrid switch structure in 3-L T-type inverter, the total power density of 3-L TNPC inverter will be higher while the cost will be lower than that of all-SiC 3-L T-type inverter. The hybrid switch based 3-L TNPC inverter also imposes challenge to its modulation and control, a propoer modulation and control shceme need to be chosen to enable better inverter performance in terms of efficiency, neutral point balancing and electromagnetic interference (EMI). Morever, to shrink the EMI filter size for the power converter, an active EMI filter (AEF) structure is proposed. The proposed AEF provides superior performance than any of the conventional passive EMI filter and the existing AEFs. In this work, the system level design and testing of a 30 kW grid-connected 3-L T-type inverter with hybrid switch structure is discussed. Then, an improved space vector modulation (SVM) has been proposed, which enables neutral-point balancing (NPB) control in the proposed hybrid-switch-based TNPC inverters with loss and common-mode voltage reduction. Finally, the design, modelling, and testing of the proposed AEF is demonstrated

Design and Assessment of a Grid Connected Industrial Full-SiC Converter for 690 V Grids

Die Bedeutung von Leistungshalbleitern mit großem Bandabstand (Wide Band Gap, WBG) nahm in den letzten drei Jahrzehnten kontinuierlich zu. Diese Bauelemente haben das Potenzial, Silizium (Si) - Bauelemente in bestimmten Anwendungen sowie Leistungs- und Frequenzbereichen zu ersetzen. Siliziumkarbid (SiC)-Leistungshalbleiter sind die gegenwärtig am Weitesten entwickelten WBG-Leistungshalbleiter. Dank besonderer Materialeigenschaften zeichnen sich SiC-Leistungshalbleiter im Vergleich zu Si-Bauelementen durch einen geringeren spezifischen Widerstand, eine höhere Schaltgeschwindigkeit, geringere schaltverluste sowie eine höhere maximale Sperrschichttemperatur aus. Die deutlich erhöhten Herstellungskosten limitieren den Einsatz von SiC-Leistungshalbleitern auf Anwendungen, in denen die Vorteile dieser Bauelemente die höheren Kosten überkompensieren und Systemvorteile ermöglichen. Heute werden SiC-Leistungshalbleiter z.B. in Solarwechselrichtern oder in Elektrofahrzeugen verwendet. Für Stromrichter industrieller elektrischer Antriebe ist die Kosten-Nutzen-Bilanz des Einsatzes von SiC-Leistungshalbleitern gegenwärtig nicht bekannt. Diese Fragestellung motiviert diese Arbeit. Die Auslegung sowie die daraus resultierenden Vor- und Nachteile eines Stromrichters mit SiC-Leistungshalbleitern für elektrische Industrieantriebe ist der Untersuchungsgegenstand dieser Arbeit. Zu diesem Zweck wurde unter Einhaltung industrieller Auslegungskriterien ein 240 kVA SiC-basierter Stromrichterdemonstrator als aktiver Gleichrichter am dreiphasigen 690 V Niederspannungsnetz untersucht. Auf der Basis einer Stromrichterauslegung für SiC- und Si-Leistungshalbleiter wurde ein theoretischer Vergleich von Kosten, Effizienz, Größe und Gewicht durchgeführt. Die Arbeit stellt zunächst den Stand der Technik für SiC-Leistungshalbleiter dar. Anschließend wird ein geeignetes SiC-MOSFET Module für den industriellen Stromrichter ausgewählt und bezüglich des Schaltverhaltens sowie der Parallelschaltung charakterisiert. Der Auslegung des Stromrichterleistungsteils liegen industrielle Anforderungen zu Grunde. Ein realisierter Demonstrator für einen netzseitigen Stromrichter (Active Front End) ist durch eine symmetrische Parallelschaltung von zwei SiC-Modulen, geeignete Ansteuerschaltungen (Gate Drive Units), eine niedrige Streuinduktivität im Kommutierungskreis sowie ein LCL-Filter mit Standard-Kernmaterialien gekennzeichnet. Der Stromrichtervergleich zeigt, dass der betrachtete Stromrichter mit SiC-Leistungshalbleitern im gesamten Betriebsbereich geringere Verluste verursacht als ein vergleichbarer Stromrichter mit Si-Leistungshalbleitern. Der SiC - basierte Stromichter ermöglicht auch eine deutliche Gewichtsreduktion bei ca. 89% der Systemkosten. Somit stellen SiC-Leistungshalbleiter eine attraktive technische Lösung für die untersuchte Anwendung eines aktiven Gleichrichters für industrielle elektrische Antriebe dar.Wide bandgap (WBG) power semiconductors have drawn steadily increasing interest in power electronics in the last three decades. These devices have shown the potential of replacing silicon as the default semiconductor solution for several applications in determined power and frequency ranges. Among them the most mature WBG semiconductor material is silicon carbide (SiC), which presents several characteristics at the crystal level that translate in the potential of presenting lower resistivity, be able to switch faster with lower switching loss, and present both higher characteristics to tolerate and dissipate heat when com pared with silicon. However, the same characteristics that make it great also present a different set of drawbacks to be considered, which aligned with its increased cost make it challenging to assess if its advantages are justified for a particular application. Applications that highly value efficiency and/or power density are the most benefited, and converter solutions featuring the technology have already breached into these application markets. However in other applica tions, the line from which silicon carbide starts making sense in the cost/benefits/drawbacks balance is not clear. This is typically the case of industrial applications, which were the main focus and motivation of this work. Hence, in this work the main goal has been to determine the basic characteristics, advantages and limitations that SiC technology designs for industrial low voltage high power grid connected converters present. To that end, a 690 V, 240 kVA SiC-based grid-tied converter demonstrator following industrial design criteria has been developed. Then, based on this design procedure a theoretical comparison between a 690 V, 190 kVA SiC-based converter against a silicon-based converter designed for the same power output has been performed to compare them regarding cost, efficiency, size and weight. This work also comprises a thorough revision of the state of art of SiC devices, which led to the selection of the switching device. Additionally, a characterization of both single and parallel-connected operation of the semiconductor modules was performed, to determine the module characteristics and its suitability to build the SiC converter demonstrator. Results show that the converter demonstrator operates as designed, proving that is possible with the corresponding precautions to achieve: a low inductive power loop, balanced parallel connection of SiC modules, adequate driving circuits for the parallel-connected modules and an adequate filtering solution in compliance with grid-codes based on standard core materials for the selected switching frequency. Finally, the theoretical comparison between the two designed power converters shows that, attained to the conditions of the comparison, the SiC converter solution presents efficiency gains over the whole operating range, while presenting substantial weight savings at 89% of the costs of the Si-IGBT design, presenting itself as the cost-effective solution for the presented application requirements under the given design constraints

Analysis & Design of Active Inductor

Power conditioning topologies such as adjustable speed drives (ASDs) have a growing demand in industry for improving efficiency and reducing energy costs. Apart from efficiency improvement, the power density of these converters has increased considerably and a smaller form factor is preferred by modern industrial plants. Power converters produce unwanted harmonics which deteriorate the grid current quality. To mitigate the adverse effects of such harmonics, filtering techniques such as active/passive filters and harmonic traps are employed. Passive inductors play an important role in these filtering topologies. However, in higher power/utility scale power conversion systems, due to lower switching frequency, the size and weight of passive inductor is large and they occupy considerable space. In industries such as offshore oil drilling and maritime transportation, size and weight requirements are strict and such bulky solutions are not desirable. For such applications, an effective way to make passive components compact is to emulate using active devices. In this thesis, design of an Active Inductor for high power applications using an H-bridge topology is proposed. The performance of common filtering topologies such as LC and LCL with Active Inductor replacing a passive inductor is analyzed. The proposed topology emulates an inductance value which is linear for a wide range of operation, devoid of saturation issues and is compact in size and weight. Weight and volume analysis is done for an active topology and compared with equivalent passive inductors. It is shown that the emulated inductor is about 8 times lighter than a passive inductor of similar rating. Also, loss analysis proves that the topology has a high Q factor. A Zero Voltage Switching (ZVS) switching method is proposed to reduce switching losses further. In addition, the dynamic behavior of the Active Inductor improves system performance during faults and disturbances. The value of inductance can be tuned to suit the requirements of the overall power conditioning circuit. The Active Inductor is shown to limit the current and voltage overshoots occurring due to faults. Simulation and experimental results from a laboratory prototype confirm the validity and utility of the proposed topology

Isolated Wired and Wireless Battery Charger with Integrated Boost Converter for PHEV and EV Applications

Vehicle charging and vehicle traction drive components can be integrated for multi-functional operations, as these functions are currently operating independently. While the vehicle is parked, the hardware that is available from the traction drive can be used for charging. The only exception to this would be the dynamic vehicle-charging concept on roadways. WPT can be viewed as a revolutionary step in PEV charging because it fits the paradigm of vehicle to infrastructure (V2I) wirelessly. WPT charging is convenient and flexible not only because it has no cables and connectors that are necessary, but due more to the fact that charging becomes fully independent. This is possibly the most convenient attribute of WPT as PEV charging can be fully autonomous and may eventually eclipse conductive charging. This technology also provides an opportunity to develop an integrated charger technology that will allow for both wired and wireless charging methods. Also the integrated approach allows for higher charging power while reducing the weight and volume of the charger components in the vehicle. The main objective of this work is to design, develop, and demonstrate integrated wired and wireless chargers with boost functionality for traction drive to provide flexibility to the EV customers

The integration of input filters in electrical drives

PhD ThesisThe integration of passive components such as inductors and capacitors has gained significant popularity in integrated drive research, and future power electronics systems will require more integrated and standardised packages. These give rise to better power density and improved performance. However, packaging techniques and passive components have been considered a technological barrier which is limiting advances in power electronics. The focus on size reduction should be turned towards the passive components, such as converter chokes, DC-link capacitors and electromagnetic interference (EMI) filters, and achieving greater power density depends on innovative integration concepts, flexibility in structures and extended operating temperature ranges while system integration and modularity are not mutually exclusive. This research considers the possibility of integrating input power filter components into electric machines. Particular attention is paid to the integration of electromagnetic line filter inductors to give better utilisation of the motor volume and envelope. This can be achieved by sharing the machine’s magnetic circuit. An LCL line filter has been chosen to be integrated with a gridconnected permanent magnet synchronous machine. Machines have been proposed in this study for low speed (3000 RPM) and high speed (25000 RPM) operation. The two machines have similar dimensions, but the low-speed machine is less challenging in terms of losses and filter integration, so attention is directed more to the high-speed machine. Both are supplied with low- and high-power drives at power ratings of 4.5 kW and 38 kW respectively. Several novel techniques have been investigated to integrate filter inductors into the electrical machines to produce a single mechanically packaged unit without significant increases in size and losses. Different approaches have been simulated using finite element analysis (FEA) to assess the effectiveness of the integration of passives within the machine structure. Each design has been iteratively optimised to determine the best mass of copper and core for the integrated filter inductors, targeting parity in power density when compared to traditional separate packages. The research demonstrates that an approach utilising a double-slot stator machine (named the integrated double slot (IDS) machine) with input filters wound into the outermost slots is the most appropriate choice in terms of achieving higher power density. The integrated filter inductors mimic the electromagnetic behaviour of the discrete industrially packaged inductors but with a volume reduction of 87.6%. A prototype of the IDS machine design of a 38 kW, 25000 RPM, including filter inductors was manufactured and testedthe General Electricity Company of Libya (GECOL), the Engineering and Physical Sciences Research Council (EPSRC), and the Engineering Doctorate scheme at Newcastle University

The Development and Packaging of a High-Density, Three-Phase, Silicon Carbide (SiC) Motor Drive

Technology advances within the power electronics field are resulting in systems characterized by higher operating efficiencies, reduced footprint, minimal form factor, and decreasing mass. In particular, these attributes and characteristics are being inserted into numerous consumer applications, such as light-emitting diode lighting, compact fluorescent lighting, smart phones, and tablet PCs, to industrial applications that include hybrid, electric, and plug-in electric vehicles and more electric aircraft. To achieve the increase in energy efficiency and significant reduction in size and mass of these systems, power semiconductor device manufacturers are developing silicon carbide (SiC) semiconductor technology. In this dissertation, the author discusses the design, development, packaging, and fabrication of the world\u27s first multichip power module (MCPM) that integrates SiC power transistors with silicon-on-insulator (SOI) integrated circuits. The fabricated MCPM prototype is a 4 kW, three-phase inverter that operates at temperatures in excess of 250 °C. The integration of high-temperature metal-oxide semiconductor (HTMOS) SOI bare die control components with SiC power JFET bare die into a single compact module are presented in this work. The high-temperature operation of SiC switches allows for increased power density over silicon electronics by an order of magnitude, leading to highly miniaturized power converters. This dissertation is organized into a compilation of publications written by the author over the course of his Ph.D. work. The work presented throughout these publications covers the challenges associated with power electronics miniaturization and packaging including high-power density, high-temperature, and high-efficiency operation of the power electronic system under study

Design and Control of Power Converters for High Power-Quality Interface with Utility and Aviation Grids

Power electronics as a subject integrating power devices, electric and electronic circuits, control, and thermal and mechanic design, requires not only knowledge and engineering insight for each subarea, but also understanding of interface issues when incorporating these different areas into high performance converter design.Addressing these fundamental questions, the dissertation studies design and control issues in three types of power converters applied in low-frequency high-power transmission, medium-frequency converter emulated grid, and high-frequency high-density aviation grid, respectively, with the focus on discovering, understanding, and mitigating interface issues to improve power quality and converter performance, and to reduce the noise emission.For hybrid ac/dc power transmission,• Analyze the interface transformer saturation issue between ac and dc power flow under line unbalances.• Proposed both passive transformer design and active hybrid-line-impedance-conditioner to suppress this issue.For transmission line emulator,• Propose general transmission line emulation schemes with extension capability.• Analyze and actively suppress the effects of sensing/sampling bias and PWM ripple on emulation considering interfaced grid impedance.• Analyze the stability issue caused by interaction of the emulator and its interfaced impedance. A criterion that determines the stability and impedance boundary of the emulator is proposed.For aircraft battery charger,• Investigate architectures for dual-input and dual-output battery charger, and a three-level integrated topology using GaN devices is proposed to achieve high density.• Identify and analyze the mechanisms and impacts of high switching frequency, di/dt, dv/dt on sensing and power quality control; mitigate solutions are proposed.• Model and compensate the distortion due to charging transition of device junction capacitances in three-level converters.• Find the previously overlooked device junction capacitance of the nonactive devices in three-level converters, and analyze the impacts on switching loss, device stress, and current distortion. A loss calculation method is proposed using the data from the conventional double pulse tester.• Establish fundamental knowledge on performance degradation of EMI filters. The impacts and mechanisms of both inductive and capacitive coupling on different filter structures are understood. Characterization methodology including measuring, modeling, and prediction of filter insertion loss is proposed. Mitigation solutions are proposed to reduce inter-component coupling and self-parasitics