Passive Electromagnetic Interference Filter Research Articles

Simulation and optimization of EMI filter of conducted emission for high voltage gain DC-DC converter

In the continuity of the work on design of high voltage gain DC-DC converter, used for feeding the CubeSat electrospray thrusters with a variable output voltage according to the maneuver size, this paper introduces a simulation of the converter model with MATLAB/Simulink to determine its conducted emission level. By referring to the MIL-STD-461 standard, a required passive electromagnetic interference (EMI) filter parameters are calculated to reduce, under thresholds, the converter noise. With consideration of the available volume and power constraints in this kind of satellite, the design of common-mode (CM) choke is optimized with proposed procedure optimization, so as to reduce its volume and electrical losses. Also, this optimization procedure can be generalized and applied for any passive EMI filter design.

A Review of EMI Research of High Power Density Motor Drive Systems for Electric Actuator

With the global attention given to energy issues, the electrification of aviation and the development of more electric aircraft (MEA) have become important trends in the modern aviation industry. The electric actuator plays multiple roles in aircraft such as flight control, making it a crucial technology for MEA. Given the limited space available inside an aircraft, the power density of electric actuators has become a critical design factor. However, the pursuit of high power density results in the need for larger rated power and higher switching frequency, which can lead to severe electromagnetic interference (EMI) issues. This, in turn, poses significant challenges to the overall reliability of the electric actuator. This paper provides a comprehensive review of EMI in high power density motor drive systems for electric actuator systems. Firstly, the state of the art of electric actuator systems are surveyed, pointing out the contradictory relationship between high power density and EMI. Subsequently, various EMI modeling approaches of motor control systems are reviewed. Additionally, the main EMI suppression methods are summarized. Active EMI mitigation methods are emphasized in this paper due to their advantages of higher power density compared with passive EMI filters. Finally, the paper concludes by summarizing the EMI research in motor drive systems and offering the prospects of electric actuators.

A Virtual Impedance Enhancement Based Transformer-Less Active EMI Filter for Conducted EMI Suppression in Power Converters

Due to the successive switching actions in a power electronic system, considerable conducted electromagnetic interference (EMI) is generated. This has been a major concern in designing power converters, which requires additional EMI filtering efforts. Passive EMI filters are the most common solutions to EMI reduction but usually consume a large portion of the volume as well as weight in power converters. Active EMI filters (AEFs) or hybrid EMI filters (HEFs) are considered best candidates over traditional passive EMI filters to achieve higher power density in power converters. The utilization of current transformer to sense or to compensate the EMI noise can increase the volume of an AEF. In this article, a transformer-less AEF, sprung from the concept of virtual impedance enhancement, is proposed. The proposed design features feedforward control with current-sensing-voltage-compensating. The operation principle of the proposed AEF is thoroughly introduced, and its performance is evaluated through simulations and experiments. Experimental results with an ac–dc power converter and a dc–ac inverter show that the proposed AEF can be generally applied to reduce conducted EMI on either ac or dc power lines.

Considerations for Gain Selection of Feedforward Active EMI Filters

The reduction of the electromagnetic interference (EMI) is an important issue in the design of switching power converters. The passive EMI filter has been widely used for the reduction of the conducted EMI. The active EMI filter (AEF) has recently been considered as a useful alternate for the small sized implementation. This paper deals with an optimal design of a voltage sensing and voltage cancellation (VSVC) type feedforward AEF. The ideal feedforward AEF is theoretically stable because it does not have any feedback loop. However, some non-ideal factors such as the source and load impedances cause the unstable operation of the AEF for certain AEF gains, which limits the magnitude of the gain and degrades the performance of the AEF. In order to overcome this problem, the method of selecting the optimum AEF gain is studied with considering both the stability and AEF performance using the concept of the symmetry. The characteristics of the cancellation loop for the AEF including the source and load impedances is first investigated in view of the stability. The boundary of the maximum AEF gain to ensure the stable operation is then discussed based on the theoretic analysis and experimental works for the actual AEF. The results can be used for implementing the AEF with the optimum EMI reduction performance.

An Active EMI Filter in Grounding Circuit for DC Side CM EMI Suppression in Motor Drive System

In this article, an active electromagnetic interference (EMI) filter is designed to reduce the dc side common mode (CM) EMI in motor drive system. Different from the traditional passive EMI filter which is added in the main circuit, the designed active EMI filter (AEF) in this article is added in the grounding circuit which is connected between motor frame and the ground and it can be decoupled from the main circuit. By properly setting the components value, the dc side CM EMI can be suppressed while maintaining a low motor frame voltage. The structure of the AEF is simple and the volume of the AEF can be kept small. The operation principle of the AEF is introduced first and the performance of this AEF is evaluated through simulation. Experiment results verified the effect of this AEF that it can suppress the dc side CM EMI and the motor frame voltage can be kept low.

A Compact EMI Filter Design by Reducing the Common-Mode Inductance With Chaotic PWM Technique

Passive electromagnetic interference filters (PEFs) are the most common way to solve electromagnetic interference (EMI) problems in power converters. However, PEFs bring additional volume, weight, and cost for power converters, especially common-mode (CM) inductors in PEFs, and it is a tricky issue for the high-power-density converters that must meet the electromagnetic compatibility specification. In order to design compact PEFs for power converters with pulsewidth modulation (PWM), a volume reduction method of CM inductors with chaotic PWM (CPWM) is proposed in this article. First, the mechanism that CPWM reduces the CM inductance by increasing the corner frequency is analyzed. Second, the relationship between the reduction of EMI spectrum magnitude by CPWM and the decrease of the CM inductance is quantitatively calculated. Third, utilization rate of the magnetic core <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">η</i> is defined to reasonably compare the size of the different inductors under traditional PWM and CPWM. Finally, the proposed design method of CM EMI filters is applied into a dc–dc converter and a dc–ac inverter, respectively, to verify its effectiveness and feasibility. In a dc–dc converter with the switching frequency 100 kHz, 275 W, the volume of the CM inductor and the volume of CM EMI filters are reduced by 63.5% and 48.3%, respectively, by using the proposed compact EMI filter.

A Customized Integrated Circuit for Active EMI Filter With High Reliability and Scalability

This article proposes an active electromagnetic interference (EMI) filter (AEF) realized by a customized integrated circuit (IC) to reduce conducted emission noises. A fully transformer-isolated feedforward current-sense current-compensation structure is selected as a base topology of the AEF. To achieve the high reliability of the proposed AEF by using low-voltage IC devices, the injection transformer is added to protect IC devices from high-voltage hazards. The operation of the proposed AEF is theoretically demonstrated, and practical design guidelines for the IC part and nearby components are developed. The designed IC was fabricated by a 0.18 μm bipolar-CMOS-DMOS process. The fabricated IC is implemented in a compact printed circuit board for application to a three-phase inverter motor system. The performance, stability, and surge immunity of the AEF are experimentally demonstrated. A designed 1stage AEF achieves better noise-attenuation performance than 2stage passive EMI filters (PEFs) over 6 dB at 150 kHz without critical resonance peak at the high-frequency range. Weak points of the conventional PEFs in both low and high frequencies are effectively improved by using the proposed 1stage AEF. In addition, the surge immunity of the designed IC within the AEF is validated under numerous 5 kV surge tests.

Design of EMI filter based on impedance matching

ABSTRACT Electromagnetic interference (EMI) filters play an important role in restraining conducted EMI, affected by the impedance of the noise source, and the load, the performance of the EMI filter is often poor. In order to resolve the mismatch problem of passive filter, this paper proposes an EMI filter based on impedance matching. Based on the fundamental design principle of the passive filter, the design of passive EMI filter is analysed and discussed at first.Then, on the basis of the theoretical foundation, more detailed and practical design is given further. By using the method of the matching network, the design of passive EMI filter under the worst circuit stances is emphasised. Finally, the design result is emulated and analysed, the proposed EMI filter idea is verified by the simulation result.

A Motor CM Impedance Based Transformerless Active EMI Filter for DC-Side Common-Mode EMI Suppression in Motor Drive System

Due to the continuous switching action of the inverter in the motor drive system, an electromagnetic interference (EMI) is generated in the system. Active EMI filter has a smaller volume and higher power density compared with the widely used passive EMI filter. However, for the conventional voltage-sensing voltage-compensating active filter and the current-sensing current-compensating active EMI filter, the active EMI filter itself needs a transformer to compensate or to sense the EMI noise and this will increase the volume of the active EMI filter. In order to save the sensing or the compensating transformer required by the active EMI filter itself, a voltage-sensing current-compensating active EMI filter for the motor drive system is designed. Combining the sensed common-mode (CM) voltage with the artificially fitted ac-side CM impedance network, the adverse CM current can be generated that can be used to suppress the dc-side CM EMI. This active EMI filter itself does not need any transformer in principle. Experimental results have validated the effectiveness of the proposed active EMI filter. It is shown that using this active EMI filter can simplify the structure of the active EMI filter and effectively suppress the dc-side EMI.

The Conducted Emission Attenuation of Micro-Inverters for Nanogrid Systems

Road lighting systems require a significant amount of electric energy. To compensate for the utilized energy, the concept of a nanogrid road lighting system is presented. A solar panel is installed on the top of a lighting pole to generate electric power. In this research, a photovoltaic simulator (PV simulator), which is used to simulate solar behavior such as current, voltage, and power based on temperature and solar irradiance levels, is employed to replace a solar panel. In the nanogrid system, grid-connected and stand-alone micro-inverters are employed to convert the electric power. The inverters comprise switching devices that can generate electromagnetic interference (EMI) when operating, which is harmful to the grid system and the electrical equipment. In general, EMI has been studied and reduced in electrical appliances, which only receive electric power. However, for the nanogrid system, which supplies electricity to the grid system, there is less study on the EMI topic because the usage is still not widespread. In the future, the nanogrid system will be widely used delivering high power directly into the electrical grid system. Therefore, the study and attenuation of EMI in the nanogrid system are very promising. Conducted emission (CE) is one form of EMI that flows through a cable connecting several appliances in the frequency range of 150 kHz to 30 MHz. CE of grid-connected and stand-alone micro-inverters have high levels in the low-frequency range between 150 kHz–5 MHz and then decreases steadily. CE attenuation is important for this inverter in a solar power system. This research studies the effect of CE mitigation on the nanogrid system. The result is compared with the Comité International Spécial des Perturbations Radio (CISPR) 14-1 standard. Finally, the passive EMI filter can reduce CE and meets the CISPR 14-1 standard.

Perancangan Filter EMI Pasif dalam Rangka Mitigasi Conducted emission pada Lampu LED

Lampu light emitting diode (LED) populer digunakan dalam berbagai macam aplikasi, karena penggunaan daya yang rendah, efisiensi yang tinggi dan perawatan yang rendah. Keuntungan LED lainnya adalah awet dan ramah lingkungan karena lebih sedikit mengandung komposisi zat beracun jika dibandingkan dengan jenis lampu lain. Untuk mencapai efisiensi yang tinggi dalam transfer energi pada catu daya LED, diterapkan topologi switched mode power supply (SMPS). SMPS diimplementasikan dengan pulse width modulation (PWM) yang beroperasi pada frekuensi konstan, menghasilkan emisi yang signifikan disejumlah frekuensi melalui mekanisme conducted dan radiated, emisi ini dinamakan electromagnetic interference (EMI). Sebagai akibatnya, banyak lampu LED berpotensi tidak bisa memenuhi standar electromagnetic compatibility (EMC). Pada penelitian ini dilakukan perancangan dan implementasi filter EMI pasif untuk meredam conducted emission pada lampu LED yang ada dipasaran. Filter EMI pasif berupa low pass filter (LPF). Sebelum lampu LED diterapkan filter pasif EMI, conducted emission yang terukur melebihi standar regulasi CISPR 22 class B, nilai emisi tertinggi mencapai 82,5 dBµV pada frekuensi 299,25 kHz atau melebihi standar CISPR sebesar 30,9 dBµV. Saat filter pasif EMI dipasang lampu LED terjadi reduksi conducted emission pada rentang frekuensi 150kHz – 1,65MHz dengan nilai rata–rata sebesar 23,3 dBµV dan nilai reduksi maksimal sebesar 34,7 dBµV.

Active EMI Filter Design With a Modified LCL-LC Filter for Single-Phase Grid-Connected Inverter in Vehicle-to-Grid Application

More and more attention has been gained in the vehicle-to-grid (V2G) system due to its attractive features, such as transferring bidirectional power between electric vehicles and grid, regulating grid voltage/frequency. This paper develops the active electromagnetic interference (EMI) filter (AEF) with significant system volume and weight reduction compared to the traditional passive EMI filter (PEF). While the high-frequency parasitic parameters of the AEF and the restricted loop gain result in limited AEF EMI noise attenuation in the high-frequency range. Thus, an additional passive EMI filter is commonly needed to suppress the EMI noise. For avoiding external passive filter components, the active EMI filter is designed and integrated with a modified LCL-LC filter as a hybrid filter to guarantee EMI noise attenuation. The modified LCL-LC filter can maintain satisfactory harmonic suppression with a higher EMI reduction ability compared to other types of harmonic filters. Based on a single-phase grid-connected inverter, the total harmonic distortion (THD) and the conducted EMI measurement results are compared with the results of traditional LCL, LLCL, LCL-LC filters. The effectiveness of the proposed circuit is verified by simulation and experimental results. The proposed circuit successfully improves the filter design of the inverter in the suppression of harmonics and EMI noise.

Design of Passive Common-Mode Attenuation Methods for Inverter-Fed Induction Motor Drive With Reduced Common-Mode Voltage PWM Technique

This paper investigates the influence of active zero vector pulsewidth modulation (AZPWM-1) and space vector pulsewidth modulation (SVPWM) on the design of passive common-mode (CM) attenuation methods to reduce CM current and shaft voltage in inverter-fed V/f-controlled induction motor drives. The passive CM attenuation methods examined here are the CM choke, the CM electromagnetic interference (EMI) filter, and the CM transformer. The attenuation requirement of AZPWM-1 and SVPWM is identified to design the passive CM choke and EMI filter. Based on the attenuation requirement, the design guidelines are revisited for SVPWM, and design rules are proposed for AZPWM-1. However, the CM transformer is designed based on the step change in magnitude of CM voltage of both the pulsewidth modulations (PWMs). The limitations in design, regarding switching frequency and component size for each case, are also established. It is shown that to have a similar attenuation in the considered two PWM cases, AZPWM-1 requires smaller passive components compared to SVPWM. The proposed design guidelines are substantiated with experimental results on a 1.1-kW induction motor drive.

Modeling and Design of the Magnetic Integration of Single- and Multi-Stage EMI Filters

A magnetic integration method of single- and multi-stage electromagnetic interference (EMI) filters is presented. Common-mode and differential-mode inductors are integrated into a single magnetic core unit to significantly reduce the filter volume. A 500-W silicon carbon (SiC) single-phase inverter is used as an experimental platform. The magnetic integration model is designed, and the magnetic circuit analysis is conducted in a simulation to ensure that the core will not reach magnetic saturation under full-load conditions. The feasibility of the proposed method is verified by an EMI test in a simulation and an experiment. Compared with a traditional discrete passive EMI filter, the proposed integrated EMI filters can reduce 40% of the total volume and 69% of the inductor volume in an integrated single-stage EMI filter with satisfactory EMI suppression ability. Although the weight of integrated inductor of integrated multi-stage EMI filter (IMSEF) has 23.8% increment, the IMSEF shows a better EMI suppression ability and 4.6% inductor volume reduction.

Modeling and Stability Analysis of Active/Hybrid Common-Mode EMI Filters for DC/DC Power Converters

Hybrid electromagnetic interference (EMI) filters (HEFs), which are composed of an active filter and a passive filter, have been proposed to reduce the size and weight of conventional passive EMI filters in literatures. However, accurate models that can be used to predict the stability and performance of HEFs have not been developed. To cope with this, this paper presents a modeling technique for a hybrid common-mode (CM) filter. The technique can be applied to the modeling of other HEFs. Critical component models were first developed for the HEF. HEF's overall model was further developed based on these individual component models. Experimental results validated that the developed model can successfully predict the stability and performance of active/hybrid CM filters.

Design and Implementation of an Active EMI Filter for Common-Mode Noise Reduction

This paper presents the analysis and design of an active electromagnetic interference (EMI) filter (AEF) for the common-mode (CM) noise reduction of switching power converters. The features of the several types of AEFs are discussed and compared in terms of implementation. The feed-forward AEF with a voltage-sensing and voltage-cancellation (VSVC) structure is implemented for an LLC resonant converter to replace a multiple-stage passive EMI filter and thereby reduce CM noise. The characteristics and performance of the VSVC-type AEF are investigated through theoretical and experimental works.

Scattering Parameter-based Measurement of Planar EMI filter

Planar electromagnetic interference (EMI) filters are widely used to restrain the conducted EMI of switching power supplies. Such filters are characterized by small size, low parasitic parameters, and better high-frequency performance than the passive discrete EMI filter. However, EMI filter performance cannot be exactly predicted by using existing methods. Therefore, this paper proposes a method to use scattering parameters (S-parameters) for the measurement of EMI filter performance. A planar EMI filter sample is established. From this sample, the relationship between S-parameters and insertion gain (IG) of EMI filter is derived. To determine the IG under different impedances, the EMI filter is theoretically calculated and practically measured. The differential structure of the near-field coupling model is also deduced, and the IG is calculated under standard impedance conditions. The calculated results and actual measurements are compared to verify the feasibility of the theory.

Application and Stability Analysis of a Novel Digital Active EMI Filter Used in a Grid-Tied PV Microinverter Module

This paper presents a novel technique to suppress common-mode electromagnetic interference (EMI) using a digital active EMI filter (DAEF). The DAEF control technique is concurrently implemented with a digital controller of a grid-tied photovoltaic microinverter. A brief description of the microinverter architecture and its inverter circuit is illustrated. The inverter stability is investigated using the overall transfer function. Accordingly, the system compensation is designed based on the direct quadrant (DQ) reference frame control technique. Finally, the proposed digital controller is tested on a grid-connected 200-W dc-ac microinverter. The experiment results validate the effectiveness of the proposed technique. Compared with the conventional passive EMI filter, the proposed digital controller can achieve an equivalent or better performance in terms of EMI suppression and maintain stability within the operation bandwidth. Therefore, the embedded DAEF can significantly reduce the size, cost, and space of the overall power inverter printed circuit board without the need of a conventional passive EMI filter.

Digital Active EMI Control Technique for Switch Mode Power Converters

A novel electromagnetic interference (EMI) suppression technique based on field programmable logic array technology is proposed to provide a significant EMI noise attenuation for switch-mode power converters. This technique uses noise acquisition at very high-sampling rate. The noise signal is processed to invert its phase angle and reconstructed with high fidelity to counteract the noise signal before reaching the line impedance stabilization network. Thus, high noise attenuation is achieved. The new technique is validated through simulation and experimental results of a single-phase ac-dc converter. The proposed technique can be extended to dc/dc converters to replace the conventional passive EMI filter where the PCB space is restricted. This technique can be a desired contingent in industrial applications where space is a major design constraint.

Suppression of common-mode input electromagnetic interference noise in DC–DC converters using the active filtering method

This study introduces a technique that combines passive and active electromagnetic interference (EMI) filtering methods to attenuate the common mode conducted noise in the input bus of the DC/DC converter and to minimise the size and the cost of the existing passive EMI filters. The technique presented can be implemented in all DC/DC converters topologies to provide a level of compliance with the electromagnetic directives. The circuit analysis and the attenuation curves showing the performance and the viability of this technique is provided. The filter input/output impedance criterion is verified to ensure the stability of the converter, by measuring the gain and the phase margins of the open-loop frequency response of the converter. The proposed technique provides a valuable design solution for compliance engineers where the Printed Circuit Board real-estate is an issue. Experimental results reveal more than 30 dB attenuation across the electromagnetic compatibility spectrum. This method contributes to the reduction of the size and weight of the input passive EMI filter. The proportion of the passive filter as compared to the DC/DC converter device can vary from 5 to 3%, depending on the converter specifications. Experimental results to demonstrate the performance and the effectiveness of the input active EMI filter in DC/DC converters are presented.