Line Impedance Stabilization Network Research Articles

Co-Reduction of Common Mode Noise and Loop Current of Three-Level Active Neutral Point Clamped Inverters

The increased switching frequency and speed of silicon carbide (SiC) MOSFETs lead to higher power density of inverters, but meanwhile resulting in weak electromagnetic interference (EMI). The impedance balance technique is a good way to reduce the common mode (CM) noise by making the voltage across the line impedance stabilization network (LISN) as small as possible. However, a side effect of this technique is the generation of relatively large loop current that circulates in the inverter. It can cause additional losses and cost, which can be a factor that stops the increase of the switching frequency by SiC MOSFET. This article, for the first time, analyzes the relationship between the CM noise and loop current of the three-level active neutral point clamped (ANPC) inverter, and proposes a co-reduction method for both. First, the CM noise and loop current are clarified for the ANPC inverter, and the analytical models for both are established. The conflict between the CM noise and loop current is introduced with a specific case by the existing design method. Then a co-reduction method is proposed and elaborated, which can both suppress the CM noise and the loop current. The extra cost and volume by the proposed method are also analyzed and are negligible. The design guideline is further shown for clarity. Finally, the analysis and proposed method is validated by the experiment.

Proposing an Improved DC LISN for Measuring Conducted EMI Noise

Switched-mode power supplies are among the sources of emitting electromagnetic interference (EMI) noise for various applications. Several standards specify limits of allowable generated EMI, where special line impedance stabilization network (LISN) has been introduced to measure both differential-mode (DM) and common-mode (CM) conducted noise. This article introduces an improved multistage LISN to measure the conducted noise for dc-dc converters. An analytical approach is suggested to decide on the number of stages. The proposed LISN has a good specification over the specified frequency bandwidth. Simulations are performed by the advanced design system to show the impedance and frequency response of the introduced LISN. Also, an implemented version of the suggested LISN has been set up for the required tests, whose practical measurements verify the performed simulations. Both simulations and experiments confirm the accuracy of the suggested LISN according to the requirements necessitated by standards compared to those of conventional LISN.

Analysis of the Influence of Measurement Circuit Asymmetries on Three-Phase CM/DM Conducted EMI Separation

Electromagnetic interference (EMI) conducted emissions (CE) are of increasing concern in power electronics due to the high switching frequency and fast switching speeds of the latest generation of wide-bandgap semiconductors. The decomposition of the total conducted EMI noise into its common-mode (CM) and differential-mode (DM) part by means of a CM/DM noise separator is a useful tool that allows for a systematic EMI filter design. Carefully designed realizations achieve a CM rejection ratio and DM rejection ratio of 50 dB at 30 MHz. However, a very high-performance CM/DM noise separator is not sufficient. It is theoretically analyzed and experimentally proven that asymmetries in the EMI test setup result in an unwanted conversion between CM and DM EMI noise, and therefore significantly influence the CM/DM EMI separation. In particular, three main influences are identified: the line impedance stabilization network (LISN), the connection cables between LISN and the equipment under test (EUT), and the converter EMI filter. The unwanted noise conversion is pronounced for frequencies in the MHz range, where parasitic resonances occur. Experimental results show a CM-to-DM conversion of up to -30 dB at 30 MHz (a degradation by 20 dB or a factor of 10 compared to a high-performance separator alone) considering a connection cable length mismatch of roughly 5 cm. Values as high as -21 dB result when standard commercial LISNs are used for the measurement. The impact of asymmetries in the EMI filter is most severe, and clearly limits the EMI noise splitting at high frequencies. A high-performance noise separator can, however, be used to investigate such filter asymmetries (component tolerances and/or layout), and therefore helps to improve the filter design process and facilitates the modeling of EMI noise sources. [COMP: Change bullet list to numbered].

Consideration to Terminating Condition of Mains Cable for Radiated Emission Measurement Caused by Different Disturbance Sources

Very high frequency (VHF)-line impedance stabilization network (VHF-LISN), which is defined as the termination device for mains cable of equipment under test to specify the input impedance of each line at the mains power supply outlet, can improve correlation between test sites that perform radiated emission measurement. Balanced and unbalanced types of VHF-LISN are currently under proposal with International Special Committee on Radio Interference (CISPR) as a device for prescribing the terminating condition of the power supply cable. Simulation analysis with common mode (CM)/differential mode (DM) signal sources was performed to investigate the emission characteristics with the two types of termination devices under several measurement arrangements that used two-wire and three-wire mains cables. Furthermore, to confirm the validity of the simulation analysis, measurement of a versatile comb-generator-operated by ac mains was performed under the same test arrangement and two types of termination devices. Quasi CM/DM signal from an ac-operated comb generator was injected back into the mains cable of the same comb generator. This article explains how we ascertained the radiated emission characteristics with each termination device, and provides guidance for their appropriate usage.

The Role of Supply Conditions on the Measurement of High-Frequency Emissions

A standardized measurement procedure and source specification for laboratory high-frequency (HF, 2–150 kHz) emissions tests of low-voltage (LV) electronic equipment are still in development. To date, emissions have been measured by direct supply from the mains network or a controllable power source (PS), but both methods are known to interfere with the assessment process. A line impedance stabilization network (LISN) limits supply-load interactions but has been underevaluated until now in the HF analysis, despite being named a potential approach in IEC Standards. This article quantifies the effect of supply conditions on HF emission assessment and the role of the LISN. The effect of the supply voltage fundamental amplitude and low-frequency background distortion on the magnitude and frequency of the characteristic HF emissions is presented, and a new supply configuration combining a programmable PS with LISN is proposed. Experimental results from a case study of two LED lamps with distinct HF emissions, representative of a number of typical LV electronic devices, indicate that only the proposed programmable PS+LISN supply can guarantee the accurate and repeatable measurements under controllable voltage supply conditions and impedance separation that are needed by ongoing HF standardization and modeling activities.

A CM Filter Configuration for Grid-Tied Voltage Source Converters

Common mode (CM) filters play a crucial role in determining adherence to conducted emissions (CE) standards for grid-tied voltage source converters. Design and implementation of such filters can be challenging since they depend on several factors like identification of CM noise paths, fidelity of passive components and discerning the frequency and amplitude of CM noise sources. In this article, a CM filter has been proposed, which uses passive components along with the converter's heat sink as a circulating return path for the CM currents. Based on the presented CM circuit models with the proposed filter, a detailed design process has been delineated for selecting the passive components required to realize the CM filter. Additionally, the heat-sink potential has been shown to be touch safe during both ideal and nonideal grid conditions with the proposed CM filter. CE spectral results measured using a commercially procured line impedance stabilization network and captured time domain converter operational wave forms for a 2-level, 3π grid-tied voltage source converter validate the functionality and effectiveness of the presented design.

Modeling and Stability Analysis of Active Differential-Mode EMI Filters for AC/DC Power Converters

In this paper, the active differential-mode (DM) electromagnetic interference (EMI) filter topology for ac/dc converters is first briefly investigated. The active DM EMI filter model was developed based on the models of filter components including a current transformer, a high-pass filter, an operational amplifier, and a class AB amplifier. The system model including the active filter, ac/dc converter, and line impedance stabilization networks (LISNs) are explored. With the developed system model, the loop gain and insertion gain of the active filter are derived. Based on the loop gain, the stability of the active filter is investigated and the compensation is applied to achieve stability and good EMI reduction. Both simulations and experiments are conducted to validate the developed technique.

Characterization of AC/Coaxial Adapter for LISN Calibration Above 30 MHz Using Improved Equivalent Circuit Model

This paper improves the equivalent circuit model of an ac/coaxial adapter for line impedance stabilization network (LISN) calibration above 30 MHz using transmission line theory and evaluates the characteristics of the one-phase adapter for Japan up to 1 GHz using the improved model. Consequently, this adapter severely affects the LISN calibration above 100 MHz, and when the height between the adapter and the reference ground is more than 10 mm, the impact of the ground on its transmission coefficient can be ignored. Additionally, the requirements of a correction method to eliminate the adapter characteristics from the measured LISN characteristics up to 1 GHz are clarified. Finally, the validity of the improved model is indicated by comparison with the measured transmission characteristics of two adapters connected back to back.

Analytical Design of Passive LCL Filter for Three-Phase Two-Level Power Factor Correction Rectifiers

This paper proposes a comprehensive analytical LCL filter design method for three-phase two-level power factor correction rectifiers (PFCs). The high-frequency converter current ripple generates the high-frequency current harmonics that need to be attenuated with respect to the grid standards. Studying the high-frequency current of each element proposes a noniterative solution for designing an LCL filter. In this paper, the converter current ripple is thoroughly analyzed to generalize the current ripple behavior and find the maximum current ripple for sinusoidal pulse width modulation (PWM) and third-harmonic injection PWM. Consequently, the current ripple is used to accurately determine the required filter capacitance based on the maximum charge of the filter capacitor. To choose the grid-side inductance, two methods are investigated. First method uses the structure of the damping to express the grid-side filter inductance as a function of the converter current ripple. Reducing the power loss in the filter and optimizing the grid-side filter inductance is the main focus of the second method which is achieved by employing line impedance stabilization network (LISN). Accordingly, two LCL filters are designed for a 5 kW silicon-carbide-based three-phase PFC. Various experimental scenarios are performed to verify the filters attenuation and performance.

Experimental evaluation of mutual coupling influence on the isolation characteristics of a dual-port v-type line impedance stabilization network

This research investigates the influence of parasitic coupling on the dual-port V-type line impedance stabilization network (LISN) characteristics. The measurement results demonstrate that the mutual interaction between two lines in a dual-port LISN could affect the isolation characteristics between the AC power line ports, receiver ports, equipment under test ports.

Modelling and measurement of high‐frequency conducted electromagnetic interference in DC–DC converters

Conducted electromagnetic compatibility (EMC) noise qualification tests are normally carried out after a prototype has been designed, built and tested and the process is repeated in the event of non-compliance. The ability to determine compliance with electromagnetic interference (EMI) standards at the design stage is therefore desirable. This study will present conducted EMC noise modelling and measurement techniques, yielding simulated and measurement noise results accurate enough to serve as a prequalification test at the design and prototyping stages, respectively. Accurate models of the power feed line connecting the line impedance stabilisation network to the device under test (converter), including the load are developed. Predictive conducted EMC modelling is accomplished using detailed active level 3 SPICE-based models, creating a real-time circuit model consisting of a complete converter in its operational state, without the need to separate into equivalent models. Effects of the power feed-line length on EMI noise measurements are investigated as currently available literature has not dealt adequately with this issue. The modelling and measurements are performed using software and instruments available in a development laboratory..

A Noise Source Impedance Extraction Method for Operating SMPS Using Modified LISN and Simplified Calibration Procedure

A noise source impedance extraction method for switched-mode power supply (SMPS) under operating condition is proposed and validated in this letter. First, a simplified precalibration method using several known impedances is introduced to eliminate the influence of measurement instruments and other parasitic effects. Second, the configuration of the proposed method is presented and the calculation methods of common-mode and differential-mode noise source impedances using microwave transmission analysis are described, respectively. The experimental results show that the proposed method can extract the noise source impedance of SMPS in wide frequency band with sufficient accuracy. Compared with traditional methods, the complex calibration process can be simplified, and no more additional equipment is required. Moreover, a novel multiple-function line impedance stabilization network (MF-LISN) with the function of electromagnetic interference measurement and noise source impedance extraction is designed according to the proposed method. Since only MF-LISN is used, it can be more convenient to extract the noise source impedance of SMPS for electromagnetic compatibility pretest.

Evaluation of Conducted Emission Test Methods for Charge Pump DC/DC Converters

This paper presents conducted emission measurements for a group of commercially available capacitive step-up dc/dc converters. A comparison of the traditional line impedance stabilization network conducted emission method with integrated circuit test methods including $1\,\Omega$ , direct and transverse electromagnetic cell methods is presented. The frequency performance and systematic offsets of each method are examined. Relative electromagnetic compatibility of these devices is compared and correlation of results of different methods explored. Improved understanding of the electromagnetic environment improves the potential reliability of electronic systems.

Impact Analysis of Conducted Emission Measurement Without LISN

Common-mode (CM) and differential-mode (DM) conducted emissions without the line impedance stabilization network (LISN) is investigated. Using a switched-mode power supply (SMPS) as an equipment under test (EUT), the in-circuit CM and DM impedances of the actual measurement setup with and without LISN are extracted so that the impact on conducted emission measurement without LISN can be better understood.

Improvement of LISN Measurement Accuracy Based on Calculable Adapters

The line impedance stabilization network (LISN) is mostly used in electromagnetic compatibility (EMC) for conducted and radiated radio frequency emission and susceptibility tests. The input impedance is one of the most important parameters in LISN calibration. To measure the input impedance, an adapter is required to connect the vector network analyzer to the equipment under test port of the LISN. For EMC test laboratories, it is of best interest to perform this calibration with high accuracy. Until now, the impact of the adapter used has not been clearly demonstrated theoretically. This paper explains the magnitude and phase impedance errors caused by the adapter. Theoretical and practical methods for the elimination of generated error are given. We present the design of two sets of adapters and their associated modeling, a method for removing their impact from the measurement, the theoretical error on magnitude and phase input impedance, and the uncertainties related to the impedance measurement.

Design and Comparison of Controller for the Reduction of Conducted Electromagnetic Interference in an Inverter

This paper presents the design of a controller for the measurement and reduction of conducted Electro Magnetic Interference (EMI) caused in the power electronic circuits. The conducted EMI is also separating the Common Mode (CM) and Differential Mode (DM) simultaneously using Line Impedance Stabilization Network (LISN). EMI is mitigated by the fuzzy controller. By comparing common mode voltage with the standard reference value, the generated error can be minimized by using fuzzy controller. Fuzzy controller is varying the PWM signal of the power electronic switching devices for reducing the electromagnetic interference. In this paper, comparison of PI and fuzzy controller of the open loop and closed loop models are implemented using MATLABr and also simulation results of the PI controller and fuzzy controller analysis are presented in this paper. The fuzzy controller is provided to achieve the EMI level of the inverter within the standard limit.

Electromagnetic interference frequencies prediction model of flyback converter for snubber design

Snubber design for flyback converters usually requires experimental prototype measurements or simulation based on accurate and complex models. In this study simplified circuit modelling of a flyback converter has been described to dimension snubbers in early stage of design process. Simulation based prediction of the transistor and diode ringing frequencies has been validated by measurements in a prototype setup. In that way obtained simulation data enabled fast and precise snubbers dimensioning. Application example has illustrated effectiveness of the proposed methodology by line impedance stabilisation network (LISN) spectra evaluation of the experimental flyback converter resulting from snubbers dimensioning.

Design and characterization of a step-down switched-mode power converter based on the regulator MC34063A

This paper presents the winning design of the 2015 Student EMC Hardware Design Competition at the EMC 2015, Joint IEEE International Symposium on Electromagnetic Compatibility and EMC Europe. A step-down switched-mode power converter based on the regulator MC34063A is designed. Special attention is given to the minimization of its conducted emissions and output voltage ripple. The selection of the components and the design of the printed circuit board (PCB) layout are discussed. The output voltage ripple and conducted emissions of the designed converter are measured. A line impedance stabilization network (LISN) designed on a separate PCB is used for the conducted emission measurements.

Modeling of a Buck Converter With a SiC JFET to Predict EMC Conducted Emissions

The reduced switching times of silicon carbide (SiC) components compared to Si components in similar conditions are a great advantage from the point of view of efficiency, but, due to the high dv/dt and di/dt, conducted electromagnetic emissions are increased. Therefore, the availability of a method which can predict these emissions is increasingly necessary. To the best of the authors' knowledge, a model that can predict differential mode as well as common mode for a converter including sic devices has not yet been published. the novelty of the work presented here is the integration of different modeling approaches to form a circuit model of a SiC-based buck dc-dc converter working in frequency range from 40 Hz to 30 MHz. A modeling approach of the passive parts of the converter is presented. Then, the model obtained is used in simulations to predict the drain-to-source voltage and the drain current for the JFET. Conducted emissions received by the line impedance stabilization network are also computed. Simulation results are compared to measurements for different duty cycles and different gate resistors in the time and frequency domains. A good agreement is obtained. In the frequency domain, in all cases, differences are less than 5 dBμV up to 30 MHz excepted in the JFET source current.

The Influence of Network Impedance on Conducted Disturbances Within the High-Voltage Traction Harness of Electric Vehicles

Currently, automotive traction systems are increasingly being revised from combustion engine drives to electric propulsion. The high power cables of electric vehicles are routed close to various communication, sensor, or control units. This circumstance results in a tightened challenge for the developing engineers, who need to ensure the electromagnetic compatibility of these miscellaneous and adjacent systems. A trial-and-error approach in the development process of electromagnetic interference filters can only be avoided if the influence of the network impedances within the high voltage traction harness on conducted RF disturbances is known. This contribution presents the current methodology of determining the conducted emissions of power inverters for electric driven cars. It highlights the differences between the traditional low-voltage cable wiring and novel high-voltage traction harnesses, and their impact on the network impedances. An adaption of the line impedance stabilization networks used recently to the characteristic impedance of the high-voltage cables applied shows the influence of termination mismatch on conducted emissions within the traction harness. High-voltage components employed in a car are usually supplied by a traction accumulator battery, which acts as transmission line termination. The influence of a battery's input impedances on disturbances within a component level EMC test setup is shown.