Random pulse-width modulation technique for voltage-controlled power inverters

Power Line Communication (PLC) technologies are being used in many applications and offer the advantage of utilizing existing power cables for both power and data transmission, thus minimizing cost and complexity. Nevertheless, PLC technology requires further investigation to solve possible co-existence issues. Indeed, recent studies confirmed that alternative modulation schemes such as Random Pulse Width Modulation (RPWM), applied to switching-mode power converters to minimize conducted emissions, detrimentally interfere with the PLC system. This paper presents an experimental test campaign aimed at investigating the effects of RPWM on the G3-PLC system, with the final goal of understanding the conditions under which RPWM schemes can be considered as an effective alternative to conventional Pulse Width Modulation (PWM) in applications involving PLC systems. In details, the effects of different RPWM parameters such as switching frequency, modulation index, and Random Number Update Rate (RNUR) on the G3-PLC is investigated. In addition, different RPWM schemes such as Random Frequency Modulation (RFM) and Random Pulse Position Modulation (RPPM) are compared in terms of performance so as to highlight which RPWM is best suited to assure coexistence with PLC systems. The impact of RPWM on the communication channel is evaluated in terms of Frame Error Rate (FER), Channel Capacity, and Channel Capacity Loss metrics. Experimental results confirmed that randomly modulated converters with switching frequencies near the G3-PLC bandwidth cause more significant disturbance and possible coexistence issues than the switching frequencies out of this range. Results also show that the modulation index and the RNUR of RPWM have a direct effect on the communication channel. Moreover, a trade-off between Electromagnetic Interference (EMI) reduction and coexistence issues is observed: RFM, which is very effective for EMI reduction, is found to be very disruptive for G3-PLC, compared to alternative random modulation techniques such as RPPM.

This paper proposes fuzzy based Random Pulse Width Modulation (RPWM) technique to trim down the overriding harmonic clusters in the output current's spectrum. Asynchronous Motor is fed by PWM inverter and current is controlled by Field Oriented Control (FOC) algorithm. When an inverter with constant switching frequency is used, it would result in narrow-band harmonics. These harmonic clusters can make acoustic noises and Electromagnetic Interference (EMI). In order to diminish the noises and EMI consequence of these harmonic clusters, adaptive fuzzy controller based random-switching PWM strategies have been introduced. The concept of RPWM technique is to spread the original narrow-band harmonic throughout a wide range of frequencies. Acoustic noises and EMI are reduced uniformly in output current's spectrum. Proposed switching pattern is compared with conventional switching pattern that is proposed earlier. Simulation results of conventional and proposed method are obtained by using MATLAB/Simulink Software.

Brushless dc (BLDC) motor drives have gained significant attention due to their merits such as high efficiency, high dynamic response, high reliability etc. From the literatures, it is understood that there has been remarkable developments evolved in application of the feedback controllers for both the BLDC motor drive's speed and current loops. The recent investigation and innovations in the pulse width modulation (PWM) methods are not encompassed in BLDC drives. The conventional PWM results mechanical vibration and acoustic noise, and limit the application scope the BLDC drives. This is due to the incapability of deterministic PWM in spreading the harmonic power. This paper presents random pulse width modulation (RPWM) for BLDC motor drive with better harmonic power distribution. The randomness is introduced in carrier wave by toggling between triangular wave (+fc) and its inverted form (-fc). The performance of the proposed RPWM is validated by using MATLAB software and results such as harmonic spread factor (HSF), total harmonic distortion (THD), and acoustic noise spectrum are presented. The comparison of results with the conventional PWM demonstrates the superiority of the proposed PWM.

Pulse Width Modulation (PWM) techniques are vital for voltage source inverters (VSIs) to deliver high-quality, controlled outputs. The output voltage harmonic spectrum reveals the distinct performance of different PWM algorithms. Conventional PWM methods focus on enhancing performance parameters such as increasing the fundamental component, reducing total harmonic distortion (THD), minimizing switching losses, and selectively eliminating harmonics. In modern applications, additional challenges such as harmonic power dispersion and electromagnetic interference mitigation are also critical. This paper primarily addresses the enhancement of harmonic power dispersion through random PWM (RPWM) techniques. Unlike traditional deterministic PWM strategies, RPWM generates non-deterministic harmonic profiles, effectively spreading harmonic energy across a wider frequency range and thereby reducing acoustic noise in drive applications. A set of carrier-based RPWM techniques is proposed to improve VSI performance. These are implemented on a field-programmable gate array (FPGA) platform, confirming high-speed operation, less power dissipation, and efficient hardware utilization. The effectiveness of the FPGA implementation is validated through MATLAB–Simulink co-simulation, demonstrating the proposed RPWM methods' superiority in harmonic power dispersion and system performance.

This study presents a comprehensive detailed analysis of the effect of five different random modulation switching schemes and their randomness levels on the elector magnetic interference (EMI) of designed simple and interleaved DC-DC buck converters for smartphone applications. The analyzed switching schemes are pulse width modulation (PWM), random pulse width modulation (RPWM), random pulse position modulation (RPPM), random carrier frequency modulation various duty (RCFMVD), and random carrier frequency modulation fixed duty (RCFMFD). The experimental analysis is performed for all aforementioned switching modulation schemes at the switching frequency of 20 kHz and different randomness levels (RL) (30% to 85%). For a fixed RL of 40%, the switching current harmonics/conducted emission (CE) levels are 5–10 dB/11 dBμV and 17 dB/14 dBμV lower for the RCFMVD case when compared to conventional PWM for both simple and interleaved buck-converters, respectively. The observed switching current harmonics and CE levels for interleaved schemes are around 23 dB and 12 dBμV lower when compared to the conventional simple buck converter scheme for the analyzed circuit configurations. The EMI levels decrease with the increase in the randomness levels from 30% to 85% with less variations in the output voltage level. The findings suggest that a interleaved buck converter circuit with the least-independent switching mechanisms and higher randomness is more appropriate for the reduction of both current spikes and CE levels with RCFMFD as the switching modulation scheme.

This paper presents an electromagnetic interference analysis of the random modulation switching schemes based on the switching current harmonics and conducted emission (CE) levels of a buck converter. The analyzed switching schemes are pulse width modulation (PWM), random pulse width modulation (RPWM), random pulse position modulation (RPPM), random carrier frequency modulation various duty (RCFMVD), and random carrier frequency modulation fixed duty (RCFMFD). The conducted experimental analysis suggests that the utilization of the RCFMFD did not only reduces the harmonics and CE levels but also produces the desired output voltage value of the buck converter.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper proposes a new hybrid random pulsewidth modulation (PWM) scheme based on a TMS320LF2407 DSP, in order to disperse the acoustic switching noise spectra of an induction motor drive. The proposed random PWM pulses are produced through the logical comparison of a pseudorandom binary sequence (PRBS) bits with the PWM pulses corresponding to two random triangular carriers. For this reason, the PWM pulses of the proposed scheme possess the hybrid characteristics of the random pulse position PWM and the random carrier frequency PWM. In order to verify the validity of the proposed method, the simulations and experiments were conducted with a 1.5-kW three-phase induction motor under the 2.5-A load condition. The DSP generates the random numbers, the PRBS bits with a lead-lag random bit (8 bit) and the three-phase reference signals. Also, a frequency modulator MAX038 makes the randomized frequency triangular carrier (3 <formula formulatype="inline"><tex Notation="TeX">$\pm$</tex></formula> 1 kHz). From the results, the proposed scheme shows good randomization effects of the voltage, current, and acoustic noise of the motor as compared with conventional scheme (3 kHz). </para>

High amounts of harmonics cause noise and electromagnetic interference to nearby systems. Pulsewidth modulation (PWM) techniques are used to reduce the amount of harmonics near the multiples of switching frequencies. To trim down the noise and electromagnetic interference and improve the quality of the output voltages, different types of constant and variable switching frequency random PWM techniques for dual inverter-fed open-end winding induction motor drive configuration are discussed in this study. Moreover, the vector control technique is used along with random PWM techniques to improve the transient response of the dual inverter.

Randomized modulation technology can effectively suppress high frequency noise in motor drive application. This paper is devoted to issues in synthesis of randomized modulation schemes and proposes a dual random PWM technology based on two-state Markov chain and pseudo-random binary sequence (PRBS). This combined type of randomized modulation can make the switching cycle more evenly distributed and significantly suppress the high frequency noise focused on the switching frequency and its integer multiples. We focus on the power spectra of certain associated waveforms. Furthermore, the DTP-PMSM model with random PWM has been built to evaluate the effect with random PWM modulations based on four methods including conventional method, Markov chains, PRBS and the method combining Markov chain with PRBS. The simulation results prove that proposed PWM strategy possesses excellent harmonic power spreading ability and high frequency noise suppression capability.

An improved random SVPWM for zero voltage switching three phase inverter

This paper addresses improved electromagnetic compatibility (EMC) in switched-mode power converters (SMPCs), without using electromagnetic interference (EMI) filters. A practical solution is proposed for minimizing conductive EMI in a pulsewidth modulated (PWM), and random PWM dc-dc power converters. A comparative investigation is performed into the use of different random modulation schemes (driven by the DSP-2 board with the TMS320C32) as against the normal PWM. The effectiveness of randomization on spreading those dominating frequencies that normally exist in constant frequency PWM schemes is evaluated by power spectral density (PSD) estimations in the low-frequency range. Some parasitical- and topology-based EMI sources in devices are presented and frequency analysis is shown by using the discrete Fourier transform (DFT). SPICE simulations are also used to verify practical solutions for eliminating negative EMI sources and achieving EMC improvements. Finally, levels of conductive EMI are estimated with DFT, and experimentally verified to comply with the CISPR 25 (or EN 55025) regulations. Moreover, it is clearly shown, that limited speed PWM driving of the power switches with appropriate snubber circuits guarantees reduced conductive EMI. When considering the price and high EMC, in the final solution the power converter is driven by the mu-controller PIC16F876 with limited numerical and peripheral capabilities, where only normal PWM and randomized PWM can be implemented

FPGA based Random Pulse width modulation (RPWM) technique is adopted to trigger the Single Input Dual Output (SIDO) DC Chopper configuration. Comparison between conventional Pulse width Modulation (PWM) and proposed switching technique is made through simulation results. The configuration and switching techniques proposed can suppress the conducted Electromagnetic Interference (EMI) better than the conventional switching schemes. Experimental results obtained validate the proposed configuration.

A novel random switching technique for high performance inverter control is presented in this paper. Since the switches of power devices are randomized, the acoustic noise generated by the voltage and current harmonics of inverter control can be significantly reduced. It will also be shown that the technique has been developed without changing the sampling and modulation schemes, Asymmetric Regular-Sampling and double edge modulation schemes respectively, which have been widely used in practical inverter control systems. Therefore, the modifications necessary to upgrade the performance of inverters using the proposed random switching technique can be easily incorporated into existing digitalized inverter control systems, e.g. vector control systems. Furthermore, in comparison with the conventional randomized pulse position technique [10] which may result in single edge modulation and thereby causes greater mean value of flux error for drive control, the proposed random switching technique provides less mean value of flux error due to double edge modulation. In comparison with conventional inverter control techniques based purely upon the Asymmetric Regular-Sampling technique, e.g. space vector modulation [17], which results in fixed voltage and current harmonic spectra and therefore generates annoyed acoustic noise, the proposed random switching technique can reduce this kind of noise by randomizing the switches. Once the switches are randomized, the first dominant harmonic which dominates the generation of acoustic noise can be dramatically reduced. A novel Random Space Vector Modulation (RSVM) technique will be presented based upon the novel random switching technique. The RSVM technique is realized using a Digital Signal Processor (DSP) and the experimental results will be shown to confirm the theoretical analysis.

A multiaverage random switching frequency space vector pulsewidth modulation (MARSF-SVPWM) strategy is proposed in this article, in order to further disperse the high-order harmonics concentrated at the switching frequency and its integer multiplies in the output voltage of the inverter. The proposed strategy divides the fundamental period equally, with different stages corresponding to different average switching frequencies and spread-spectrum ranges, in contrast with the conventional random switching frequency space vector pulsewidth modulation (RSF-SVPWM), under the premise of maintaining the same overall average switching frequency and spread-spectrum range. The simulation and experimental results demonstrate that, even in the case of a narrow spread-spectrum range, the proposed MARSF-SVPWM strategy can obtain a better effect of high-order harmonic dispersion.

Random pulse width modulation (RPWM) is a switching technique used to spread voltage and current harmonics over a wide frequency range. By using a randomly changing inverter switching frequency, the power spectrum of the electromagnetic acoustic noise can be spread to the wideband area. Wideband noise is much more comfortable and less annoying than narrowband noise. Thus, RPWM has been attracting interest as an excellent method for the reduction of acoustic noise in inverter drive systems. A new RPPWM (random position space vector PWM) is proposed and implemented. Each of three phase pulses is located randomly in each switching interval. Along with randomisation of the PWM pulses, space vector modulation is also executed in a C167 microcontroller. Simulation and experimental results show that the voltage and current harmonics are spread to the wideband area and that the audible switching noise is reduced by using the proposed RPPWM method.