Conducted EMI Mitigation in Power Converters using Active EMI Filters

Wide bandgap devices enable high power density power converters. Despite the advantages of increased switching frequency, the passive components are still a major bottleneck towards enabling high power density. Among the passive components in the converter, the passive EMI filters are unavoidable to ensure compliance with conducted EMI standards. Active EMI filters help reduce the volume of the passive components and have been around for three decades now. Firstly, this work presents a summary of all the different active EMI filters based on the type of noise-sensing, noise-processing, the type of active circuits used and the type of control methods. This is followed by modeling, design and stability analysis of three different active EMI filters for DM noise attenuation. The first active EMI filter is a conventional active EMI filter. The key bottlenecks to improving performance of the conventional active EMI filter are identified while still achieving volume reduction of passive components. Following this two novel active EMI filters are presented that overcome the bottlenecks of conventional active EMI filter. The second active EMI filter is based on a analog twin-circuit. This novel filter uses a twin-circuit which enables the use of low-voltage surface-mount components for compensation. The third active EMI filter uses zero-phase filtering implemented in an FPGA. While all the filters are demonstrated for differential-mode noise, their use can be extended for common-mode noise attenuation

EMC in Power Electronics and PCB Design

This dissertation consists of two parts. Part I is about Electromagnetic Compatibility (EMC) in power electronics and part II is about the Maximum Radiated Electromagnetic Emissions Calculator (MREMC), which is a software tool for EMC in printed circuit board (PCB) design. Switched-mode power converters can be significant sources of electromagnetic fields that interfere with the proper operation of nearby circuits or distant radio receivers. Part I of this dissertation provides comprehensive and organized information on the latest EMC developments in power converters. It describes and evaluates different technologies to ensure that power converters meet electromagnetic compatibility requirements. Chapters 2 and 3 describe EMC noise sources and coupling mechanisms in power converters. Chapter 4 reviews the measurements used to characterize and troubleshoot EMC problems. Chapters 5 - 8 cover passive filter solutions, active filter solutions, noise cancellation methods and reduced-noise driving schemes. Part II describes the methods used, calculations made, and implementation details of the MREMC, which is a software tool that allows the user to calculate the maximum possible radiated emissions that could occur due to specific source geometries on a PCB. Chapters 9 - 13 covers the I/O coupling EMI algorithm, Common-mode EMI algorithm, Power Bus EMI algorithm and Differential-Mode EMI algorithm used in the MREMC

POWER QUALITY CONTROL AND COMMON-MODE NOISE MITIGATION FOR INVERTERS IN ELECTRIC VEHICLES

Inverters are widely utilized in electric vehicle (EV) applications as a major voltage/current source for onboard battery chargers (OBC) and motor drive systems. The inverter performance is critical to the efficiency of EV system energy conversion and electronics system electro-magnetic interference (EMI) design. However, for AC systems, the bandwidth requirement is usually low compared with DC systems, and the control impact on the inverter differential-mode (DM) and common-mode (CM) performance are not well investigated. With the wide-band gap (WBG) device era, the switching capability of power electronics devices drastically improved. The DM/CM impact that was brought by the WBG device-based inverter becomes more serious and has not been completely understood. This thesis provides an in-depth analysis of on-board inverter control strategies and the corresponding DM/CM impact on the EV system. The OBC inverter control under vehicle-to-load (V2L) mode will be documented first. A virtual resistance damping method minimizes the nonlinear load harmonics, and a neutral balancing method regulates the unbalanced load impact through the fourth leg. In the motor drive system, a generalized CM voltage analytical model and a current ripple prediction model are built for understanding the system CM and DM stress with respect to different modulation methods, covering both 2-level and 3-level topologies. A novel CM EMI damping modulation scheme is proposed for 6-phase inverter applications. The performance comparison between the proposed methods and the conventional solution is carried out. Each topic is supported by the corresponding hardware platform and experimental validation

Circuit configurations and performance of the active common-noise canceler for reduction of common-mode voltage generated by voltage-source PWM inverters

This paper discusses two different circuit configurations of the active common-noise canceler (ACC) which has been proposed by the authors. One is characterized by its DC power supply isolated from the DC link of a PWM inverter. The configuration makes it possible to integrate the ACC with a medium-voltage PWM inverter. The other compensates a partial frequency component of the common-mode voltage. The purpose is not to achieve complete cancellation, but to restrict only a slope in a change of the common-mode voltage applied to an AC motor. As a result, the core size of the common-mode transformer used in the ACC becomes considerably small. Experimental results show good effects of the proposed active circuits on both ground current and conducted EMI</p

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

Performance optimization aspects of common mode chokes

Optimization aspects of common mode chokes are presented. These are based on a behavioral model for common mode chokes and its sensitivity study. Results are used to show the influence of the designable parameters on the final performance of the choke placed in a circuit

Measurements, Models, Systems and Design

531 s.

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