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.

Conducted EMI Suppression in Plasma Cutting Power Supply

A systematic approach to the design of the conducted electromagnetic interference （EMI） filter of high-density plasma cutting power supply has been developed. Converter components have been accurately modeled, with parasitic elements extracted to reveal their impacts on the EMI noises. Circuit simulations have been used to analyze and minimize the EMI noises. Conducted EMI noise measurement and filter design of this power supply have been achieved which successfully satisfy the FCC class B limits in the frequency range from 150 kHz to 30 MHz. The analyses and experimental results show that the designed filter guarantees that the required attenuation will be achieved.

SUPPRESSING CONDUCTED EMI FROM A DC/DC HIGH POWER CONVERTER BASED ON MIXED-MODE FILTER

Conducted electromagnetic interference (EMI) from a 7.5kVA DC/DC high power converter is investigated to agree with EN class A. Here in some passive methods of suppressing conducted EM Noise, such as mixed-mode (MM) EMI filters, snubbing circuits and other means, are used. Based on measurement, the sources of noise are detected with the characteristics analyzed in detail. The MM EMI filters is valuable means with which low-frequency part and some of the high frequency part of conducted EM Noise can be efficiently reduced. How to lay out the MM filters on both sides of the converter is outlined in detail. In addition, multiple grounding and RDC snubbing circuits are employed to improve the performance in high frequency. The experimental results confirm the methods adopted.

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 MATLAB® SIMULINK for measurement and reduction of the EMI level;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.

Prediction of the conducted EMI in PWM converter system with parasitic parameters considered

This paper presents a new approach for modeling of the conducted electromagnetic interference(EMI) prediction for widely used converter systems.Coupling paths and mechanism of differential mode(DM) interference and common mode(CM) interference have been analyzed.Models to predict the high-frequency noise of PWM converter system are created.A direct calculation method in frequency domain is proposed for the deduction of frequency spectrum.A method is given for obtaining the parasitic parameters and topological structure of the model.An experimental investigation of the conducted emission from an actual high-power rectifier system is described.The validity of the models is confirmed by comparison to laboratory measurements.

Uniform Distribution Spread-spectrum Modulation Strategy for MMC to Reduce Conducted EMI and Switching Loss

Modular multilevel converters(MMCs)have been widely used owing to their superior performance.However,the rapid switching of power electronics devices causes serious electromagnetic interference(EMI).There are a large number of obvious EMI peaks in the frequency spectrum of the carrier phase-shifted constant-switching-frequency pulse-width modulation(CSFPWM).Spreading the EMI across a wider frequency range can help to reduce the EMI peaks.In this study,we designed a uniform distribution(UD)spread-spectrum modulation technology using the principle of uniform switching frequency distribution and minimum switching loss for MMC.Its feasibility is verified by theoretical derivation and simulation.Then,the effectiveness of UDPWM in reducing the EMI is verified in experiments with a prototype MMC testbed in the lab.Compared with traditional CSFPWM,UDPWM can reduce conducted EMI by 10-20 dB.Also,compared with random PWM(RPWM),UDPWM can improve efficiency and reduce total harmonic distortion(THD)of output voltage and current in MMC.