Showing papers by "Yehui Han published in 2015"

Integrated Modular Motor Drive Design With GaN Power FETs

Abstract: This paper explores the use of GaN power FETs to realize an integrated modular motor drive (IMMD) with an induction motor. A structure in which inverter modules are connected in series is proposed to reduce the module maximum voltages and to offer an opportunity to utilize low-voltage wide-band-gap GaN devices. With the superb switching performance of GaN power FETs, a reduction in IMMD size is achieved by eliminating inverter heat sink and optimizing dc-link capacitors. Gate signals of the IMMD modules are interleaved to suppress the total voltage ripple of dc-link capacitors and to further reduce the capacitor size. Motor winding configurations and their coupling effect are also investigated as a part of the IMMD design. The proposed structure and design methods are verified by experimental results.

Parallel Architecture for Battery Charge Equalization

Abstract: One limitation of many battery charge equalizers is their slow equalization speed, especially when there are a large number of batteries in the series-string in high-voltage and high-power applications. This paper presents a new architecture for battery charge equalization. In this architecture, independent equalizers are placed in different layers and all the layers can equalize the corresponding batteries simultaneously, thus reducing equalization time by 50%. We explore the operation, performance characteristics, and the design of the architecture. Both simulation and experimental results are presented to validate the analysis in this paper.

PV Balancers: Concept, Architectures, and Realization

Abstract: This paper presents a new concept of module-integrated converters called PV balancers for photovoltaic applications. The proposed concept enables independent maximum power point tracking for each module, and dramatically decreases the requirements in terms of electrical rating, size, and manufacturing cost for power converters. The power rating of a PV balancer is less than 20% of its counterparts, and the manufacturing cost is thus significantly reduced. In this paper, two architectures of PV balancers are proposed, analyzed, realized, and verified through simulation and experimental results. It is anticipated that the proposed approach will be a low-cost solution for future photovoltaic power systems.

System-Theoretic Analysis of a Class of Battery Equalization Systems: Mathematical Modeling and Performance Evaluation

Abstract: Battery equalizers are widely used in multibattery systems to maintain balanced charge among individual battery cells. While the research on the hardware realization of battery equalizers has received significant attention, rigorous analysis of the battery equalization process at the system level remains largely unexplored. In this paper, we study three types of battery equalization system structures: series-based, layer-based, and module-based. Specifically, we derive mathematical models that describe the system-level behavior of the battery equalization processes under these equalization structures. Then, based on the mathematical models, analytical methods are developed to evaluate the performance of the equalization processes. In addition, we carry out statistical analysis to compare the performance of the three equalization structures considered.

Control of input-series and output-independent power converter building block system based on buck converter topology

Abstract: A modularized battery system made up of integrated battery building blocks has been brought into sight recently. The battery building block system has advantages such as no external equalizers, no centralized converters, reduced power and voltage stresses, easy reconfiguration and customization, control of thermal distribution, etc. However, the control of charging the building block system faces challenges in stabilizing the system while distributing different power to different modules. This paper recognizes the battery building block system as a single-input and multiple-output system (SIMO). The system features an input-series and output-independent (ISOI) architecture, where the inputs of the converters are connected in series while the output of each converter is independently supplying different load. The modeling and control of the ISOI system are demonstrated. A two-level supervised distributed control method is proposed and analyzed to achieve the stable power distribution control with simulation and experiment validation.

Used-battery management with integrated battery building block system

Abstract: This paper utilizes an integrated building block system to manage battery packs made up of battery cells retired from transportation applications. These used batteries could have different brands, capacities, chemistries, aging conditions, etc. The importance of the second use of the retired batteries is addressed and an integrated building block system is introduced in this paper. The control strategy for handling used batteries is also proposed. A prototype is built and the concept is verified by experimental results.

Evaluation of a module-integrated distributed battery energy storage system

Abstract: This paper presents an evaluation of a module-integrated distributed battery energy storage system (BESS). Compared with the conventional centralized BESS, this paper provides a detailed evaluation of the module-integrated system merits and evaluates the charging, discharging and module balancing performance. A case study of a three-module system is used to demonstrate the functional performance of the module-integrated distributed BESS. It is verified through experiments that the module-integrated distributed BESS provides satisfied functional performance with additional advantages such as no extra equalizers or additional power converters, reduced power and voltage stresses of power electronic components, etc.

A novel switched-capacitor based partial power architecture for a 20 MHz resonant SEPIC

Abstract: This paper presents a new switched-capacitor (SC) based partial power architecture which enhances the performance of resonant dc-dc converters operating at high frequency (HF, 3 MHz–30 MHz) and very high frequency (VHF, above 30 MHz). A wider input and output range, larger voltage conversion ratio, smaller size and excellent transient performance are expected. The prototype comprises of a 20MHz resonant single-ended-primary-inductor-converter (SEPIC) as a regulated stage and a high-efficiency (96.5 %) 200 kHz SC as an unregulated stage. The resonant SEPIC handles 30 % of total the input power while regulates the output using a high bandwidth (170 kHz) ON/OFF PWM control scheme, which enables fast transient responses. The high-efficiency SC processes 70 % of the input power and provides a large voltage conversion ratio. The low energy storage requirements of the proposed converters allow the use of air-core inductors and ceramic capacitors, thereby eliminating magnetic core loss, and short-lived electrolytic capacitors. The power stage of the prototype achieves a peak efficiency of 93.7 % and a power density of 705.86 W/in3 at 93.88 W.

Modelling and control of single-input and multiple-output modular converter systems

Abstract: This paper introduces a modular single-input and multiple-output (SIMO) converter system achieved by an input-series and output-independent (ISOI) architecture, where the input of each modular converter is connected in series while the output is independent. The system can generate multiple outputs at different power and voltage levels. The system modelling and analysis are presented. The cooperative control scheme is proposed to achieve the independent power and voltage control among different outputs. Under this control strategy, the system features a modular distributed control architecture. Each modular converter is controlled by its own on-board controller without any global information. There is no cross-regulation or communication in the system. At last, the proposed control scheme is verified through simulation and experiment on a modular SIMO system consisted of three buck converter modules.

A class of modular multilevel motor drives with design flexibility and reduced components number

Abstract: This paper extends the work of multilevel converter motor drives with modular design and split windings machine. A class of multilevel motor drive topologies is introduced. The proposed topologies can reduce the component quantity by using the machine itself to synthesize converter outputs. Mature multilevel topologies can be also incorporated to achieve more voltage levels with great design flexibility. In this paper, two examples including neutral point clamped and flying capacitor topologies are discussed. Furthermore, the winding patterns and winding models of the proposed split windings machine are presented. Both simulation and experimental results are provided to validate the proposed concept.

High step-down ratio DC-DC converter with multi-leg transformer

Abstract: In this paper, a multi-leg transformer structure is proposed to realize high effective turns ratio for high step-down ratio dc-dc converters. By adding an extra degree of freedom, the proposed transformer structure can reduce the number of winding layers and the cost of a planar transformer. The proposed core and winding structures effectively reduce the number of primary turns, which results in balanced core loss and winding loss, reduced dc winding loss, and reduced fringing effect loss. To meet the core height and volume requirements, different structures are compared and high efficiency and high power density are achieved. Several design considerations are discussed, and extra trace copper loss is minimized by careful layout design. A 200 kHz 400 V-to-2 V 120 W forward converter prototype is built to verify the proposed transformer design.