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Acoustic Noise and Its Control in SRMs
Published in R. Krishnan, Switched Reluctance Motor Drives, 2017
Modulation of phase voltages while varying switching frequency or the pulse position randomly is referred to as random pulse width modulation (RPWM). A number of publications have established that RPWM causes the power spectrum of the output voltage to acquire a continuous part, while the harmonic part is significantly reduced, which in turn reduces very marginally acoustic noise and vibrations while the sound pressure is not affected.22 This strategy has been applied to induction motor drives, and a few attempts have been made to adapt it to SRM drives.21,23,24
Suppression of EMI Using Cost-Effective FPGA-Based Digital Communication Modulation Techniques in Power Converters
Published in IETE Journal of Research, 2023
Different types of random modulation schemes were proposed for a synchronous dc–dc converter [24] for the suppression of EMI. After investigation, it is found that Random CFM with fixed duty cycle (RCFMFD) and random pulse width modulation (RPWM) are found to be the effective methods to produce minimum low-frequency harmonic spectrum. An extension of the above paper is done with a few more random modulation techniques [25] in DC–DC converter through field programmable gate array (FPGA) and it is found that 10.8 dBµV reductions are obtained by the random pulse position modulation (RPPM) method when compared with the PWM technique in the converter to comply with the CISPR 22 class B standards. A Direct-sequence spread-spectrum technique is used [26] in DC–DC buck converter for harmonic reduction and communication. A 12 dBmV reduction is obtained by implementing the proposed modulation method when compared with the constant PWM technique. In all the works mentioned above, although the methodology of the proposed modulation was explained clearly with the suppression of EMI, they failed to address the parameters from the grid side, such as power factor (PF), THD, and harmonic spectrum. Hence, an effort is made in this paper to measure the essential power quality parameters by using DSSS and frequency-hopping spread-spectrum (FHSS) modulation techniques.
A novel measurement approach based on wideband excitation for frequency-coupling admittances of train converter
Published in International Journal of Rail Transportation, 2022
Haidong Tao, Xiaojuan Zhu, Haitao Hu, Jiameng Yu, Zhengyou He
Secondly, the rapid measurement of SFCAs faces difficulties to extract target coupling harmonics from multiple coupling relationships in 4QC control system. The impedance measurement methods mainly include three categories: passive test without disturbance injection [25], frequency-scan test [22], and wideband-excitation test. The last test greatly shortens the measurement time and improves the efficiency. It realizes the simultaneous measurement at multiple frequency points by injecting broadband harmonic disturbance. The broadband signals mainly include binary sequence [26], ternary sequence, chirp signal [23], and multi-frequency signal (i.e. multi-tone signal) [27]. Wherein the binary sequence signal mainly contains random pulse-width-modulation (RPWM) [28], square wave, pseudo-random binary sequence (PRBS), maximum length binary sequence (MLBS) [29], and discrete interval binary sequence (DIBS) [30]. The binary sequence, ternary sequence, and chirp signal can emit harmonic perturbations over a wide frequency band at one time [26]. Yet, it is arduous to control the harmonic perturbations at specific frequencies. There are abundant harmonic signals outside the frequency band of interest, which reduces the signal-to-noise ratio (SNR) of measurement [31]. These signals are widely applied to measure the network impedance [26], but may not be suitable for measuring coupling admittances of VSC. The multi-tone signal consisting of multiple sine signals has strong controllability, where the amplitude and phase of each harmonic component are flexibly designed [31,32]. However, there are multiple frequency-coupling relationships in the 4QC control system [7]. The response may overlap when injecting the broadband signal, making the measurement inaccurate [33]. It is essential to avoid the interferences from other frequency-coupling relationships while measuring SFCAs of 4QC. More research is required for the detailed design of broadband signals.
Supraharmonics reduction in LED drivers via random pulse-position modulation
Published in International Journal of Electronics, 2018
Joaquin Garrido-Zafra, Antonio Moreno-Munoz, Aurora Gil-De-Castro, Manuel A. Ortiz-López, Tomás Morales
The organisation of the rest of the paper is as follows. Section 2 is devoted to Power Quality (PQ), mainly in the supraharmonic topic. Section 3 presents a survey of LED drivers. Section 4 addresses the Random Pulse-width modulation techniques while Section 5 is devoted to results. And finally, Section 6 contains the conclusions.