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Recent Progress and Future Research Direction of Nonlinear Dynamics and Bifurcation Analysis of Grid-Connected Power Converter circuits and systems

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ieee journal OF emerging AND selected topics IN POWER ELECTRONICS 2020年第4期8卷 3193-3203页

作者： Reza, C. M. F. S. Lu, Dylan Dah-Chuan Univ Technol Sydney Sch Elect & Data Engn Ultimo NSW 2007 Australia

Since the discovery of nonlinear dynamics and chaotic behaviors of basic power converter circuits, stability analysis has been extended to more complex converter structures, paralleled and interconnected converters, microgrids, and power systems. While the analysis has long been identifying the parameters that cause various nonlinear phenomena, some work has shown direct relevance toward practical design of power converters, and control circuits. In this article, a review is conducted to highlight the key contributions of bifurcation analysis for power converter circuits and systems, and to discuss the ongoing work in this area.

关键词： Averaged model bifurcation discrete-time mapping microgrid nonlinear dynamics power converters

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Machine-Learning-Based Microwave Sensing: A Case Study for the Food Industry

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ieee journal on emerging and selected topics in circuits and systems 2021年第3期11卷 503-514页

作者： Ricci, Marco Stitic, Bernardita Urbinati, Luca Di Guglielmo, Giuseppe Vasquez, Jorge A. Tobon Carloni, Luca P. Vipiana, Francesca Casu, Mario R. Politecn Torino Dept Elect & Telecommun I-10129 Turin Italy Pontificia Univ Catolica Chile Sch Engn Santiago 7820436 Chile Columbia Univ Dept Comp Sci New York NY 10027 USA

Despite the meticulous attention of food industries to prevent hazards in packaged goods, some contaminants may still elude the controls. Indeed, standard methods, like X-rays, metal detectors and near-infrared imaging, cannot detect low-density materials. Microwave sensing is an alternative method that, combined with machine learning classifiers, can tackle these deficiencies. In this paper we present a design methodology applied to a case study in the food sector. Specifically, we offer a complete flow from microwave dataset acquisition to deployment of the classifiers on real-time hardware and we show the effectiveness of this method in terms of detection accuracy. In the case study, we apply the machine-learning based microwave sensing approach to the case of food jars flowing at high speed on a conveyor belt. First, we collected a dataset from hazelnut-cocoa spread jars which were uncontaminated or contaminated with various intrusions, including low-density plastics. Then, we performed a design space exploration to choose the best MLPs as binary classifiers, which resulted to be exceptionally accurate. Finally, we selected the two most light-weight models for implementation on both an ARM-based CPU and an FPGA SoC, to cover a wide range of possible latency requirements, from loose to strict, to detect contaminants in real-time. The proposed design flow facilitates the design of the FPGA accelerator that might be required to meet the timing requirements by using a high-level approach, which might be suited for the microwave domain experts without specific digital hardware skills.

关键词： Sensors Microwave imaging Microwave theory and techniques Microwave circuits Microwave antennas Machine learning Production Microwave sensing microwave antenna arrays machine learning MLP classifier food safety high level synthesis food technology contactless diagnostics

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Quantitative Analysis of Harmonic Transfer for Modular Multilevel Converter

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ieee journal OF emerging AND selected topics IN POWER ELECTRONICS 2021年第4期9卷 4739-4749页

作者： Jiao, Ning Wang, Shunliang Ma, Junpeng Liu, Tianqi Sichuan Univ Coll Elect Engn Chengdu 610065 Peoples R China

The harmonic transfer of the modular multilevel converter (MMC) leads to the harmonic intersection between the ac and dc sides and introduces additional harmonics, which worsen the power quality. Especially, the low-order harmonics, which are difficult to filter out, may cause harmonic resonance and the aging of equipment. In this article, the mechanism of harmonic transfer for MMC is revealed more easily and clearly based on the relationship between arm currents and voltages. The successive approximation method (SAM) is extended for the quantitative analysis of harmonic transfer. A digital-iteration scheme (DIS) is proposed to derive the general quantitative expressions of harmonic transfer of the MMC. The DIS is appropriate for both the conditions with and without considering the effect of the control system. By the iterative calculation, the harmonics can be calculated more accurately, especially the inner harmonics. The effectiveness of the quantitative analysis is verified by comparing the calculation, simulation, and experiment results.

关键词： Harmonic analysis Power harmonic filters Capacitors Statistical analysis Power electronics Equivalent circuits Average-value model harmonic transfer interharmonics iteration modular multilevel converter (MMC)

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Control of Active Power Decoupling Circuit Based on Parametric Oscillator

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ieee journal OF emerging AND selected topics IN POWER ELECTRONICS 2021年第6期9卷 6837-6845页

作者： Lin, Jyun Tech Univ Denmark Sch Elect Engn DK-2800 Lyngby Denmark

In this article, we tested the buck-plus-unfolder bidirectional converter as the active power decoupling circuit to suppress the unknown low-frequency ripples on the dc bus. Due to its bipolar operation, the buffering capacitor voltage needs to be half of the frequency of the disturbance. We exploit the parametric resonance phenomenon to build a virtual oscillator controller for the converter. Unlike direct resonance, the parametric one occurs when the parameter of the reactive element of the oscillator varies around twice of the resonance frequency. The dc bus voltage ripple is chosen as the modulation signal for the oscillator. A frequency adaptive mechanism is further embedded in the controller to update the resonance frequency. With the references constructed from the states of the oscillator, a proportional-feedforward controller is designed to track the reference for the buffering capacitor voltage. The proposed control algorithm has been verified by both simulation and experiments.

关键词： Oscillators Avalanche photodiodes Capacitors Resonant frequency Frequency conversion Frequency control RLC circuits AC power decoupling active power decoupling (APD) buck-plus-unfolder decentralized control frequency dividing parametric resonance virtual oscillator control (VOC)

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Transient Analysis of ZCS PWM Converter Based on Equivalent Small Parameter Method

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ieee journal OF emerging AND selected topics IN POWER ELECTRONICS 2021年第4期9卷 4188-4199页

作者： Wen, Darong Chen, Yanfeng Zhang, Bo Qiu, Dongyuan Xie, Fan South China Univ Technol Sch Elect Power Guangzhou 510640 Guangdong Peoples R China

This letter proposes a nonlinear mathematical model for a zero-current-switching (ZCS) pulse width modulation (PWM) Buck converter and obtains the approximate analytical solutions of state variables using the equivalent small parameter method (ESPM). First, the operating modes of the converter are analyzed, and the equivalent circuit model together with a unified nonlinear mathematical description can be derived. Then, ESPM is adopted to solve this model, and approximate analytical solutions of state variables in both transient process and steady-state operation are obtained. The acquired results are verified by simulations and experiments finally. Since the ESPM combines the peculiarity of the perturbation method and harmonic balance method, the results obtained by ESPM are accurate and have obvious advantages compared with other methods.

关键词： Integrated circuit modeling Equivalent circuits Zero current switching Mathematical model Transient analysis Pulse width modulation Power electronics Equivalent small parameter modeling transient analysis zero-current-switching pulse width modulation (ZCS PWM) converter

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An Optimized Hybrid Modulation Scheme for Reducing Conduction Losses in Dual Active Bridge Converters

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ieee journal OF emerging AND selected topics IN POWER ELECTRONICS 2021年第1期9卷 921-936页

作者： Liu, Bochen Davari, Pooya Blaabjerg, Frede Aalborg Univ Dept Energy Technol DK-9220 Aalborg Denmark

A linearized hybrid modulation scheme for the dual active bridge (DAB) converter is proposed in this article. For the purpose of minimizing the conduction losses dissipated on the transformer and the power transistors, an optimal relationship function between the two control variables employed in extended phase shift (EPS) modulation can be derived. However, the obtained relationship function is a complex expression, which is not good for simple on-line control. Hence, a linearized modulation scheme is proposed in this article. This modulation scheme can achieve a quasi-minimum root-mean-square (rms) value of the leakage inductance current for the same output power. Meanwhile, the zero-voltage switching (ZVS) of the power transistors can be achieved over the whole power range. The power transfer capability is also kept the same as the optimal EPS scheme. Finally, experiments are conducted on a laboratory prototype to validate the effect of the linearized modulation scheme on the reduction of conduction losses. The experimental results present an improved converter efficiency and the realization of ZVS.

关键词： Inductance Zero voltage switching Phase modulation Bridge circuits Power electronics Optimization Dual active bridge (DAB) hybrid phase shift linearization

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Reliability-Centered Maintenance for Modular Multilevel Converter in HVDC Transmission Application

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ieee journal OF emerging AND selected topics IN POWER ELECTRONICS 2021年第3期9卷 3166-3176页

作者： Yu, Pengfei Fu, Wei Wang, Longjun Zhou, Zhenwei Wang, Gang Zhang, Zheng South China Univ Technol Sch Power Elect Engn Guangzhou 510640 Peoples R China Minist Ind & Informat Technol Sci & Technol Reliabil Phys & Applicat Elect Comp Elect Res Inst 5 Guangzhou 510610 Peoples R China Guangdong Prov Key Lab Elect Informat Prod Reliab Guangzhou 510610 Peoples R China

Due to its high modularity and scalability, the modular multilevel converter (MMC) has extensively been used in the modern industry. The low reliability of MMCs, which are consisted of tens or hundreds of vulnerable submodules (SMs), directly impacts the power supply continuity of the access systems. Redundancy and preventive maintenance are two significant measures to improve MMC reliability in operation. Therefore, this article presents a reliability model of MMCs with numerous SMs, whose lifetime follows arbitrary distribution, in redundancy strategies, such as active mode and standby mode. The lifetime of SMs is the minimum of component lifetime, which is estimated by a physics-of-failure-based lifetime estimation approach. Employing this reliability model, a reliability-centered maintenance (RCM) scheme with a minimum annual maintenance cost, is proposed to implement the dynamic decision of the maintenance intervals, quantitatively considering multistate of MMC operation. The relationship among redundancy, maintenance, and cost is further discussed in case studies. The proposed reliability model and RCM scheme provide a guideline for MMC redundancy strategy selection and maintenance decision.

关键词： Maintenance engineering Insulated gate bipolar transistors Redundancy Capacitors Bridge circuits Integrated circuit modeling Lifetime estimation maintenance interval modular multilevel converter (MMC) redundancy strategy reliability model reliability-centered maintenance (RCM)

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Improved MVDC Breaker Operation by Active Fault Current Sharing (FCS) of Existing Power Converters for Shipboard Applications

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ieee journal OF emerging AND selected topics IN POWER ELECTRONICS 2021年第3期9卷 2620-2631页

作者： Xie, Ren Li, Hui Florida State Univ Ctr Adv Power Syst Tallahassee FL 32310 USA

In this article, an active fault current sharing (FCS) strategy is proposed to improve the dc circuit breaker (CB) operation in a breaker-based medium-voltage dc (MVdc) system. The peak turn-off current of CBs can be decreased by controlling the existing converters located in parallel with activated CBs to share the fault current. This reduction effect can be amplified from the systematic perspective since one single converter with the proposed FCS can benefit different CBs in various fault scenarios. The short-circuit fault scenarios of a shipboard breaker-based MVdc system are analyzed and the corresponding fault equivalent circuits, including power converters adjacent to CBs, are developed. The device stress of voltage-fed (VF) and current-fed (CF) converters applying the proposed active FCS strategies during short-circuit faults is derived and compared with those of passively shutdown counterparts. Finally, a downscaled experimental test bed was built to emulate a 6-kV/6-MW MVdc system fault scenarios. The experimental results are provided to verify the proposed FCS.

关键词： Circuit faults Circuit breakers Phase change materials Fault currents Power electronics Switches Equivalent circuits Circuit breakers (CBs) dc-dc power converters hybrid circuit breaker (HCB) medium-voltage dc (MVdc) power distribution faults power electronics shipboard power system (SPS) solid-state circuit breaker (SSCB)

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A Repetitive High-Current Pulse Generator Circuit Based on Multistage Pulse Transformers

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ieee journal OF emerging AND selected topics IN POWER ELECTRONICS 2021年第3期9卷 3189-3200页

作者： Li, Haitao Zhang, Cunshan Wang, Liwei Li, Zhenmei An, Yunzhu Liu, Xiaohui Liang, Xiaoyu Shandong Univ Technol Sch Elect & Elect Engn Zibo 255000 Peoples R China Univ British Columbia Sch Engn Kelowna BC V1V 1V7 Canada

The application of inductive energy storage in the generation of high-current pulses has attracted considerable attention during recent years. In this article, a new inductive high-current pulse generator circuit is proposed based on XRAM (MARX spelled backword) current multiplier converter concept and multistage pulse transformers by using power electronic switches. This circuit is capable to recover the residual energy and generate repetitive high-current pulses with a flexible output pattern. To verify the circuit operation, simulation and experimental results of a two-stage laboratory prototype are presented. The results confirm the theoretical analysis and show the validity of the converter scheme.

关键词： Inductors Pulse transformers Pulse generation Capacitors Discharges (electric) Inductance Circuit topology Electromagnetic launching power supplies power semiconductor switches pulse circuits pulse transformers pulsed power supplies

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Curvature-Based Average Modeling of Switched-Capacitor Converters

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ieee journal OF emerging AND selected topics IN POWER ELECTRONICS 2021年第5期9卷 5929-5940页

作者： Krstic, Marko Eren, Suzan Jain, Praveen Queens Univ Kingston ON K7L 3N6 Canada Genoptic LED Inc Calgary AB T2C 5C3 Canada Queens Univ Dept Elect & Comp Engn Kingston ON K7L 3N6 Canada

A precise, curvature-based, average modeling technique for switched-capacitor (SC) dc-dc converters is proposed. The generalized modeling technique provides a comprehensive characterization of the converter at steady-state, across the full range of practical operating conditions. An expression for the equivalent output impedance is obtained, which relates the slow- and fast-switching limit impedances to the total output impedance. This expression can be used to accurately compute the output voltage without deriving the converter's state equations and precisely weighs the contribution of each floating capacitor and parasitic resistance on the output impedance. The modeling technique is applied to a unity-gain SC converter, a multiphase binary converter, and a nonsymmetrical parallel-series converter, and the results are compared with existing steady-state models. The accuracy of the model is validated through simulations and experimental measurements.

关键词： Capacitors Switches Impedance Steady-state Mathematical model Resistance Power electronics DC-DC power converters modeling switched capacitor (SC) circuits

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