Common Mode EMI Research Articles

Common-Mode EMI Noise Reduction With Improved Balance Technique for DC–AC Converters

Common-Mode EMI Noise Reduction With Improved Balance Technique for DC–AC Converters

Common-Mode EMI Reduction Control Strategy for Interleaved Converters

Common-Mode EMI Reduction Control Strategy for Interleaved Converters

Component-Splitting and Multisegment Compensation Methods for Common-Mode and Differential-Mode EMI Suppression in High-Power SWPDT Systems

Component-Splitting and Multisegment Compensation Methods for Common-Mode and Differential-Mode EMI Suppression in High-Power SWPDT Systems

Analysis and Suppression of Common-mode EMI Using Synchronous Pulsed Compensation in Power Electronics

Analysis and Suppression of Common-mode EMI Using Synchronous Pulsed Compensation in Power Electronics

Efficient Integrated Magnetics with Winding Cancellation Technique to Reduce Common-Mode EMI Noise for A Single Phase CLLC Converter

Efficient Integrated Magnetics with Winding Cancellation Technique to Reduce Common-Mode EMI Noise for A Single Phase CLLC Converter

Conducted Common-Mode EMI Modeling of Active Magnetic Bearings Based on Multi-Axis Online Impedance Measurement

Conducted Common-Mode EMI Modeling of Active Magnetic Bearings Based on Multi-Axis Online Impedance Measurement

Dual-current-injection CSCC Active Common-mode EMI Filters with High Insertion Loss for DC-DC Converters

Dual-current-injection CSCC Active Common-mode EMI Filters with High Insertion Loss for DC-DC Converters

A Seven-Switch Current-Source Inverter Using Wide Bandgap Dual-Gate Bidirectional Switches

Conventional current-source inverters (CSIs) using silicon-based reverse-blocking (RB) switches typically suffer from high conduction loss, low switching frequency, and bulky size. New bidirectional (BD) switches (also called four-quadrant switches) built from wide bandgap semiconductor materials such as gallium nitride and silicon carbide offer both reverse-voltage-blocking capability and low conduction loss that make them appealing candidates for increasing the CSIs efficiency. This article proposes a new modulation scheme for an emerging three-phase CSI topology (H7-CSI) to enable it to operate safely with BD switches to achieve higher efficiency (as much as 3%) compared to the conventional H6-CSI topology or the emerging H7-CSI using RB switch. In addition, this modulation strategy combined with the proposed H7-CSI-BD topology is capable of significantly reducing the conducted common-mode (CM) EMI up to 20 dB⋅μV. Based on this improvement, a promising CM EMI filter network consisting of a CM choke and Y-capacitor has been designed for the H7-CSI-BD topology to meet EMI standards. The required filter component values for the H7-CSI-BD topology are significantly lower than those required in conventional CSIs. Analysis, simulation, and experimental results are provided that confirm the advantages of the proposed BD switch-enabled H7-CSI over conventional H6-CSI and emerging H7-CSI topologies using RB switches.

Balance Techniques and PCB Winding Magnetics for Common-Mode EMI Noise Reduction in Three-Phase AC–DC Converters

In this article, balance technique is applied into two-channel interleaved three-phase ac–dc converters with critical conduction mode based soft switching modulation. By adding additional inductors and coupling them with the original ones, the realization of the balance becomes possible with proper design; thus reducing the common-mode (CM) EMI noise. The balance condition is derived, and the impact of balance technique on the circuit operation especially on the switching frequency variation is quantified in order to provide the design guideline. Based on the application of balance technique, instead of the commonly used litz-wire-based inductors, PCB winding coupled inductors are adopted and designed to effectively achieve the reduction of CM EMI noise. The design methodology and process are presented, and the design tradeoff is made between the inductor loss and the inductor footprint. Finally, the effect of CM EMI noise reduction and the system efficiency with balance techniques and PCB winding magnetics are tested on a 25-kW silicon-carbide-based soft-switching three-phase ac–dc converter prototype.

Influence of System Layout on CM EMI Noise of SiC Electric Vehicle Powertrains

This paper investigates the influences of system layout on common mode (CM) EMI noise of an electric vehicle (EV) powertrain with a traction inverter using silicon carbide (SiC) MOSFETs. First, a system level conducted EMI model for the whole SiC EV powertrain is presented, which includes a battery pack, DC cables, a SiC inverter, AC cables, and a PMSM. Then, the impacts of system layout, such as the AC cable length, the AC cable type, and the DC cable type (shielded cable and unshielded cable) on CM EMI noise are analyzed through time domain simulations of the system level conducted EMI model. Next, a conducted EMI emission test-bed for a SiC EV powertrain is built. Finally, experiments on the test-bed are carried out to verify the influences of system layout on CM EMI noise in the SiC EV powertrain.

New EV Battery Charger PFC Rectifier Front-End Allowing Full Power Delivery in 3-Phase and 1-Phase Operation

A new universal front-end PFC rectifier topology of a battery charger for Electric Vehicles (EVs) is proposed, which allows fast charging at rated and/or full power level in case of 3-phase (Europe) as well as 1-phase (USA) mains supply. In this regard, a conventional 3-phase PFC rectifier would facilitate only one-third of the rated power in case of 1-phase operation. The new topology is based on a two-level six-switch (2LB6) 3-phase boost-type PFC rectifier, which is extended with a diode bridge-leg and additional windings of the Common-Mode (CM) chokes of the EMI filter. Besides this extension of the power circuit, the general design of the new converter is explained, and the generated Differential Mode (DM) and Common Mode (CM) EMI disturbances are investigated for 3-phase and 1-phase operation, resulting in guidelines for the EMI filter design. The EMI performance (CISPR 11 class-B QP) is experimentally verified for 1-phase and 3-phase operation at an output power of 4.5 kW, using a full-scale hardware prototype that implements the proposed extensions for a 2LB6 3-phase boost-type PFC rectifier and that is designed for output power levels of 22 kW and 19 kW in case of 3-phase and 1-phase operation, respectively. Compared to a conventional 2LB6 PFC rectifier, the volume of the extended system increases from 2.7 dm3 to 3.4 dm3, of which 0.5 dm3 is due to the additional dc-link capacitance for buffering the power pulsation with twice the mains frequency occurring for 1-phase operation.

Characteristics of SiC inverter powertrains on common-mode EMI noise

This paper studies the characteristics of SiC inverter powertrains on common-mode (CM) EMI emission. First, a CM noise source model of an EV powertrain is built. Then, the factors of switching frequency, switching speed, and switching ringing on the CM noise source are analyzed. Finally, experiments on a conducted EMI test-bed are carried out to verify the influence of SiC inverters on conducted CM EMI emission in EV powertrains.

Reduced Common-Mode Voltage PWM Scheme for Full-SiC Three-Level Uninterruptible Power Supply With Small DC-Link Capacitors

In this article, a pulsewidth modulation (PWM) scheme for three-level full-SiC uninterruptible power supplies is developed to achieve a high power density. Two key passive components are selected for size reduction of the ac–ac stage: common-mode (CM) EMI filter, and dc-link capacitors. To reduce the CM noise, a new vector combination is proposed based on synchronous switching among three-phases. The proposed combinations align CM voltage (CMV) to be a single pulse per switching period. Owing to the simple shape, CMV cancellation between a three-level rectifier and inverter can be maximally utilized. A transition between the three combinations can control the drift of neutral point voltage. An equivalent carrier-based implementation is developed. Second, a simple algorithm to compensate neutral point voltage fluctuation is proposed both for differential mode (DM) and CM output voltage. Low-order harmonics on three-phase currents and an additional high-frequency CM noise by misaligned switching instant can be eliminated. The proposed compensation can be implemented by a simple correction on carrier slopes and injected zero-sequence voltage. The proposed PWM scheme is verified with 20-kW full-SiC UPS switching at 60 kHz with 140 μ F dc-link capacitors.

Common-Mode EMI Noise Analysis and Reduction for AC–DC–AC Systems With Paralleled Power Modules

In this article, the common-mode (CM) noise model is developed for an ac–dc–ac system with paralleled power modules. The CM noise contributions from both rectifiers and motor drives are analyzed. The interaction between the ac/dc rectifiers and dc/ac motor drives is explored. The CM noise reduction techniques which include a decoupling inductor technique and a CM noise balance technique are proposed to reduce the CM noise on the ac input side. Experiments and simulations were conducted to validate the developed CM noise model, rectifier and inverter interaction theory and CM noise reduction techniques.

Common mode EMI reduction through PWM methods for three-phase motor controller

Pulse-width sequences are identified as the determining factor for common-mode (CM) voltage, which together with CM path generate CM current. This paper introduces a series of pulse-width modulation (PWM) methods, which are focusing on reducing CM noise of three-phase inverters as motor controller. Firstly, theoretic analysis and PWM reduction methods of CM voltage for general three-phase two-level inverters are introduced. Analysis results indicate that the realization of CM noise reduction should take switching frequency and loop impedance into consideration together to avoid CM resonant phenomenon. The regular three-phase two-level inverter is incapable of eliminating CM voltage because of the limitation of topology. Then, optimal PWM methods applied to for advanced topologies can be utilized to eliminate the CM voltage theoretically. Two typical typologies presented in this paper are three-level inverters and paralleled inverters. Three-level inverters can achieve zero-CM output voltage by selecting zero-CM voltage vectors at the expense of power quality. However, for paralleled inverters, zero-CM PWM method is able to achieve zero CM voltage output, as well as the improved output current harmonics and voltage balancing.

A Transformer-Isolated Common-Mode Active EMI Filter Without Additional Components on Power Lines

This paper proposes a new structure of transformer-isolated active EMI filter (AEF) without additional components on power lines for the reduction of common-mode (CM) conducted emissions (CE). The noise attenuation performance and loop gain are rigorously analyzed, and the design guides for the proposed AEF are developed. The AEF is designed in a compact package for the application to a switching mode power supply. The performance, stability, and leakage currents of the AEF are experimentally validated by various measurements. The CM EMI filter, including the AEF, achieves the additional CE reduction by 10 to 20 dB at a frequency range lower than 1 MHz. Also, the noise peaks due to the resonances at several MHz are reduced by 7 dB. The weak points of the conventional CM EMI filter at both low and high frequencies are effectively improved by employing the proposed AEF.

Operating principles and practical design aspects of all SiC DC/AC/DC converter for MPPT in grid-connected PV supplies

A 20 kW, 20 kHz high frequency (HF) link maximum power point tracking (MPPT) converter for a grid-connected PV supply, based on all silicon carbide (SiC) power semiconductors, is presented. In the developed converter, SiC power MOSFETs are used in the low-voltage PV panel side and SiC Schottky diodes on the high-voltage DC output, in order to maximize the power conversion efficiency and the power density. Operating principles of the resulting dual H-bridge MPPT converter and the practical aspects of the converter design and its circuit layout, are described in detail. The implemented converter performance is compared with that of a classical Si-IGBT and hybrid-IGBT based MPPT converter in terms of efficiency. This configuration can compete with the non-isolated MPPT converter topologies, such as the boost converter commonly used in grid-connected PV systems, since it allows the possibility of using a conventional two-level, three-phase grid-connected inverter. This is due to the enhanced common-mode EMI performance as compared to non-isolated MPPT topologies, resulting in a competitive high efficiency PV converter design with galvanic isolation. It has been shown that the converter size can be shrinked up to a power density of 1.6 kW/lt, with a DC-DC converter full-load efficiency of 98%. The resulting compact and highly efficient SiC power MOSFET based HF link MPPT converter is suggested to be a part of grid-connected, multi-string PV supplies with simple inverter topologies in the future.

Shielding Technique for Planar Matrix Transformers to Suppress Common-Mode EMI Noise and Improve Efficiency

Isolated high output current dc/dc converters are critical for power supplies in information technology industries. LLC converters with a matrix transformer are suitable for these applications due to their high efficiency and high power density. By pushing switching frequency up to MHz with GaN devices, planar matrix transformers with printed circuit board (PCB) windings are advantageous over conventional transformer designs, but the large interwinding capacitance of the PCB windings provides a critical coupling path for common-mode (CM) noise. In order to analyze the CM noise, the interwinding capacitance of the PCB windings is analyzed, and a related CM noise model is provided in this paper. To suppress the CM noise, shielding layers can automatically be inserted into the PCB windings between the primary and secondary windings in the fabrication process. This paper proposes a novel shielding technique, in which half of the shielding serve as the primary winding. The proposed shielding technique not only suppresses CM noise but improves the efficiency as well. The proposed shielding is verified by experiments on 1-MHz 400 V/12 V 800-W LLC converters with a peak efficiency of 97.7% and a power density of 900 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The proposed shielding reduces CM noise by 30 dB and improves full-load efficiency by 0.2%.

Common-Mode EMI Noise Modeling and Reduction With Balance Technique for Three-Level Neutral Point Clamped Topology

This paper develops a common-mode (CM) electromagnetic interference noise model for a three-level neutral point clamped topology. Compared with existing modeling techniques with only one CM noise source, two extra important CM noise sources and their characteristics are identified and derived for an accurate CM noise model. The impedances of CM noise path are also extracted. Based on the developed CM noise model, the CM noise spectrum can be well predicted. The effect of CM noise paths on CM noise is discussed based on two different LCL filters. A CM noise reduction technique with a balance bridge at a large impedance ratio is proposed based on the developed model. The technique can be easily implemented at low cost. Both simulations and experiments validate the developed theory and technique.

Common-mode EMI evaluation of forward converter with various core-reset schemes

Abstract: In switching power converters, electromagnetic emissions can interfere with the normal operation of the converter or other adjacent systems. Among various power converters, forward converters are widely used at low and medium powers that need a transformer core-reset scheme. In this paper, a prediction procedure for conducted commonmode EMI of a single-switch forward converter is presented, and common-mode EMI levels are predicted considering heat-sink parasitic capacitors and main PCB parasitic elements. The accuracy of prediction results is examined via experimental results. In addition, effects of conventional passive core-reset schemes on the conducted EMI are evaluated via experimental results. Along with the passive reset scheme, common-mode EMI of the low-side and high-side active clamps are evaluated. Finally, the EMI comparison between various core-reset techniques is presented.