Random PWM Research Articles

Generalized N-State Random Pulse Position Discontinuous PWM for High-Frequency Harmonics Reduction and Performance Improvement at High Modulation Ratios

Generalized <i>N</i>-State Random Pulse Position Discontinuous PWM for High-Frequency Harmonics Reduction and Performance Improvement at High Modulation Ratios

Comparative harmonic elimination techniques for supraharmonic reduction in microgrid

In order to reduce voltage distortion and supraharmonic (SH) emission in microgrid (MG) systems with electric vehicle (EV) charging stations, this research compares several harmonic elimination approaches. The increasing deployment of EVs has led to the integration of EV charging stations within MG systems, presents challenges in maintaining a high power quality (PQ). Voltage distortions and SH emissions are caused due to non-linear loads and the intermittent nature of EV charging, which have an effect on the performance and dependability of the MG. In order to solve these problems, multilevel converters (MLCs) are used to produce high-quality waveforms. MLCs use harmonic elimination methods to cut down on SH emissions, which improves the PQ overall. Sinusoidal pulse width modulation (PWM), selective harmonic elimination (SHE), space vector modulation (SVM), and random-PWM (RPWM) techniques are among the harmonic elimination methods compared and analyzed. The results will enable the selection of the most appropriate strategy for minimizing voltage distortion and SH emission in MG systems, while providing valuable insights into the effectiveness of each method.

A Modified SVPWM Strategy for Reducing PWM Voltage Noise and Balancing Neutral Point Potential

PWM (pulse width modulation) is the most widely applied current conversion technology, but the high-frequency harmonics it causes have a significant negative impact on inverter system performance. This paper focuses on the three-phase T-type three-level inverter as the research object and addresses existing PWM voltage noise and midpoint potential imbalance issues by proposing an improved random SVPWM strategy, named Neutral Point Potential Balance Random Space Vector PWM (NPB–RSVPWM). The NPB–RSVPWM strategy includes three main steps: (1) introducing a midpoint potential balancing control loop to adjust the synthesis timing of the effective vectors to generate pulse signals, optimizing midpoint potential balance; (2) employing a randomly varying carrier frequency in place of the carrier used in the SVPWM strategy to generate the driving signals for switching devices; and (3) controlling the inverter through the driving pulse signals. This strategy optimizes the synthesis sequence of traditional SVPWM strategy vectors and incorporates random frequency modulation techniques. The mathematical model analyzes PWM harmonic expressions corresponding to fixed switching frequencies, and a random frequency carrier is chosen to suppress these PWM harmonics. The effective vector’s equivalent circuit is analyzed, proposing a technique for optimized vector synthesis timing. The simulation and experimental results verify that the NPB–RSVPWM technique can disperse PWM harmonic energy, reduce voltage noise, and optimize midpoint potential balance. Under the NPB–RSVPWM strategy, the line voltage spectrum becomes uniform, the maximum harmonic content is greatly reduced, and the fluctuation in the DC side midpoint potential is significantly improved. Compared with the traditional SVPWM strategy and random PWM strategy, the NPB–RSVPWM strategy has a lower voltage noise, smaller total harmonic distortion, and a more stable midpoint potential. The effectiveness and feasibility of the NPB–RSVPWM strategy are verified by simulation and experimental results.

Ripple Minimization in a Quadratic Boost Converter: Software vs. Hardware solutions

In this work, the authors have studied a quadratic boost DC-DC converter to reduce its ripple in the output voltage and the input current. This aim has been obtained by implementing two different solutions: the hardware solution consists on the use of coupled inductors and a notch output filter, the software solution is based on a random PWM and uses uncoupled inductors. The two solutions show a different impact on the output voltage and in the input current ripple. The performance of proposed solutions is evaluated and compared by simulation analysis both in time and frequency domain.

Performance and Characterization of Optimal Harmonic Dispersion Effect in Double FrequencyBand Random PWM Strategy

Performance and Characterization of Optimal Harmonic Dispersion Effect in Double FrequencyBand Random PWM Strategy

Dual Random Noise Suppression Strategy for Permanent Magnet Synchronous Motor Based on Random Pulse Width Modulation and Random High-frequency Injection Method

This study proposes an innovative dual control strategy to tackle the challenge of electromagnetic noise in the sensorless low-speed operation of Permanent Magnet Synchronous Motors (PMSM). The strategy combines random Pulse Width Modulation (PWM) technology with a stochastic high-frequency injection approach. By incorporating two distinct randomized frequency switching techniques into the high-frequency injection circuit, the method integrates two-state Markov chains into both PWM technology and the random high-frequency injection method. Subsequently, a mathematical model for signal processing is developed, and extensive simulation and experimental verification are conducted. The experimental findings affirm the effectiveness of this approach in effectively mitigating electromagnetic noise while ensuring accurate location estimation within an acceptable range.

Multiaverage Random Switching Frequency Space Vector Pulsewidth Modulation Strategy for High-Order Harmonics Dispersion

A multi-average random switching frequency space vector pulse width modulation (MARSF-SVPWM) strategy is proposed in this paper, 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 pulse width 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.

A Novel Electromagnetic Noise and Image Stripe Noise Suppression Method Between SMA-OIS Actuator and CMOS Image Sensor

In order to solve the electromagnetic compatibility (EMC) problem between shape memory alloy (SMA) optical image stabilization (OIS) actuator and CMOS image sensor (CIS), a novel electromagnetic noise and image stripe noise (ISN) suppression method is proposed in this paper. The electromagnetic interference mechanism of SMA-OIS actuator is analyzed by electromagnetic field simulation and magnetic dipole mathematical model. The CIS noise mechanism based on the readout circuit model and image signal processing (ISP) pipeline is analyzed and the ISN evaluation method of CIS is proposed. The drive frequency and ISN model is established by frequency sweep experiment through the joint experimental platform of SMA-OIS actuator and CIS. Furthermore, the random frequency modulation PWM method based on the spread spectrum principle is proposed to suppress the electromagnetic noise and ISN. The experimental results show that the state-of-the-art noise suppression method proposed in this paper can not only eliminate ISN, but also have good technical adaptability in practical applications.

A Variable Switching Frequency Space Vector Pulse Width Modulation Control Strategy of Induction Motor Drive System With Torque Ripple Prediction

The constant switching frequency space vector pulse width modulation (CSFSVPWM) generates high-frequency harmonics with integer multiples of the switching frequency, making it fail to fully exploit the potential of pulse width modulation (PWM) technique. In this paper, a variable switching frequency space vector pulse width modulation technique with the function of torque ripple prediction is proposed for induction motor drive system, which could optimize the high-frequency harmonic current distribution and torque ripple. The mathematical correlation between inverter average voltage and instantaneous voltage under the space vector pulse width modulation (SVPWM) is first analyzed, followed by the analysis of current ripple in a switching cycle using the typical seven-segment SVPWM, thus the torque ripple of induction motor during this period can be predicted. The switching period is dynamically adjusted according to the magnitude of predicted torque ripple, and the average switching frequency is maintained to be the same with that of CSFSVPWM. The effectiveness of the proposed method in suppressing high-frequency current harmonics and torque ripple is fully verified by experimenting on a 2.2 kW induction motor drive system, and a comprehensive comparison with CSFSVPWM and random PWM modulation is implemented.

Modified RPWM Strategy Based on Level-Shifted Random Carrier and Power Balance to Reduce the PWM Voltage Noise in Three-Phase CHB Inverters

Aimed at the pulse width modulation (PWM) voltage noise and power imbalance in three-phase cascaded H-Bridge (CHB) inverters, a modified random PWM (RPWM) strategy, named the power-balanced RPWM (PB-RPWM) strategy, is proposed in this paper. The PB-RPWM strategy mainly includes three steps: (1) random pulse signals are generated by compared modulation wave with level-shifted random carriers; (2) the random pulse signals are circularly distributed between CHB units by a logic operation method, and then the driving pulse signals of switching devices are produced; (3) the driving pulse signals are used to control the inverter. Under the PB-RPWM strategy, the spectra of the line voltage become uniform and continuous, that is, the PWM voltage noise of the line voltage can be effectively reduced. The output voltage of a single H-bridge unit can contain three basic voltages within 3/2 TA, that is, the power balance between CHB units can be realized. When compared with conventional non-random and random PWM strategies, the PB-RPWM strategy has a lower PWM voltage noise and smaller total harmonic distortion (THD). When compared with the level-shifted PWM (LS-PWM) strategy, the PB-RPWM strategy has a balanced power performance. The effectiveness and feasibility of the PB-RPWM strategy is verified by abundant simulations and experiments.

New Random PWM Method at Constant Switching Frequency and Maximum Harmonic Reduction Created With a Flexible FPGA-Based Test Bench

It has been shown that the converters that integrate random PWM produce a spread spectrum in their harmonic emission, shortening the emission peaks. On the converter’s input side, the reduction minimizes electromagnetic interference EMI. On the output side of the converter, the reduction manages to smooth the voltage and current ripple in the load. We have built a flexible test bench (FTB) developed with FPGA to generate most of the proposed random PWM modes for converters. The conducted harmonic voltage emission of these modes, both on the input side of the converter and on the load side, has been measured and compared in a DC-DC Buck converter. FTB also has the ability to create new random PWM modes. Of the random modes, the ones that produce the greatest peak reductions are those with variable switching frequency. However, variable frequency modes lead to load feedback problems. A new random PWM method has been developed that significantly reduces the amplitude of the emission peaks but keeps the switching frequency constant.

Error Self-Calibration of Phase Current Reconstruction Based on Random Pulsewidth Modulation

Three-phase current is the cornerstone parameter in vector control. Restricted by minimum sampling time of the traditional space vector pulsewidth modulation (PWM), the problem of immeasurable areas (IAs) exists in one dc bus current sensor (ODBCS) three-phase current reconstruction. In addition, affected by actual conditions such as temperature drift, aging, and noise, the problem of offset error (OE) in the three-phase current sampling path is the essential factor that restricts the sampling accuracy. This article is the first to investigate the influence of IAs and OE of ODBCS on the reconstructed current. An error self-calibration (ESC) random PWM reconstruction strategy is proposed, which is self-detection and self-calibration of current OE accomplished by dual sampling of the complementary nonzero vector dynamic current. The proposed ESC of phase current reconstruction based on random PWM does not require the insertion of redundant voltage vectors and major computation and is not limited to a particular PWM technology. The experimental results verify the accuracy and practicability of the proposed method.

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.

Performance and Analysis of N-State Random Pulse Position SVPWM With Constant Sampling Frequency

Random pulsewidth modulation (RPWM) with variable carrier frequency generally disperses the dominant PWM harmonics more effectively than the RPWM with constant carrier frequency. But variable carrier frequency results in variable sampling frequency, which changes controller parameters and makes RPWM difficult to use in closed-loop applications. To significantly disperse dominant harmonic clusters located nearby the PWM frequency and its multiples, while maintaining constant sampling frequency, in this article, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> -state random pulse position space vector pulsewidth modulation is proposed. This method randomly selects one of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> selected carrier patterns with equal probability in each carrier period, resulting in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> different pulse position states. By applying two-dimensional Fourier analysis, the additional multiplication factor in the derivation results, named harmonic dispersion coefficient in this article, can intuitively explain the principle from the perspective of mutual cancellation of complex vectors in different directions. All dominant PWM harmonics are significantly dispersed except those located nearby the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> th PWM frequency and its multiples when using the proposed method. Besides, power losses and switching counts are detailed discussed. Both simulation and experimental results verify the effectiveness of the method at last.

DSPACE-based dual randomized pulse width modulation for acoustic noise mitigation in induction motor

dSPACE-based dual randomized pulse width modulation for acoustic noise mitigation in induction motor

Development of performance characterization in VSI fed induction motor drives using random PWM

Any industrial or power sector application requires a pulse width modulation (PWM) inverter. Industrial drives in particular are highly concerned with industrial standards. To satisfy the voltage source inverter (VSI) drives objects, a variety of PWM approaches are used, including inverter DC input voltage utilizations, suppression of higher and lower order of harmonics, as well as spreading harmonics, acoustic noise reduction, among others PWMs. One of the better approaches for minimizing noise on voltage source threephase inverter fed drives is random pulse width modulation PWM random palse width modulation (RPWM). Despite the fact that these described RPWM approaches are superior in terms of harmonic spreading and mitigation, these methods are unable to achieve the target DC-link utilizations. As a result, the focus of this paper is on combining multicarrier RPWM principles with space vector PWM space vector pulse width modulation (SVPWM) to produce multi-carrier random SVPWM (MCRSVPWM). The suggested PWM generates random unsystematic triangle carrier (5 kHz, 2.5 kHz, 1.25 kHz, 1 kHz) based pulses, whereas the traditional random PWM techniques are uses a fixed frequency triangular carrier to generate random pulse positions. Asynchronous induction motor driving simulation is carried out using MATLAB/Simulink. The proposed MCRSVPWM is put to the test with a 2kW six-switch VSI-fed induction motor drive system.

Development of performance characterization in VSI-fed induction motor drives using random PWM

Any industrial or power sector application requires a pulse width modulation (PWM) inverter. Industrial drives, in particular, are highly concerned with industrial standards. To satisfy the voltage source inverter (VSI) drives objects, a variety of PWM approaches are used, including inverter DC input voltage utilizations, suppression of higher and lower order of harmonics, as well as spreading harmonics acoustic noise reduction, among others PWMs. One of the better approaches for minimizing noise on voltage source three-phase inverter fed drives is random pulse width modulation (RPWM). Despite the fact that these described RPWM approaches are superior in terms of harmonic spreading and mitigation, these methods are unable to achieve the target DC-link utilizations. As a result, the focus of this paper is on combining multicarrier RPWM principles with space vector PWM (SVPWM) to produce multi-carrier random SVPWM (MCRSVPWM). The suggested PWM generates random unsystematic triangle carrier (5 kHz, 2.5 kHz, 1.25 kHz, 1 kHz) based pulses, whereas the traditional random PWM techniques are uses a fixed frequency triangular carrier to generate random pulse positions. Asynchronous induction motor driving simulation is carried out using MATLAB/Simulink. The proposed MCRSVPWM is put to the test with a 2-kW six-switch VSI-fed induction motor drive system.

36-5-4] 전력전자변환기에 적용된 Chaos PWM 기법의 스펙트럼 확산에 관한 연구

In this study, the power spectrum of the random PWM technique using the Linear Congruential Generator (LCG) and the PWM technique with chaotic logistic, tent and double tent map characteristics were compared with the fixed frequency switching PWM technique. The random technique generates random numbers using LCG, and the chaos number is generated using each chaos map, and a bifurcation tree with a=4.0 and λ=0.99 conditions in which a complete chaos state exists in the ranges of 0 and 1 is used. In order to prove the validity of this study, a DSP-based power electronics converter for driving a three-phase induction motor was manufactured. As a result, the chaos logistic map and tent map were limited in the spread of broadband in the spectrum of power electronics converters. However, the advanced chaos double tent map was similar to the excellent spectrum spread performance of the Random PWM technique by LCG. Harmonic Spread Factor(HSF) of the output voltages of each technique were measured according to the increase in the modulation index, and the chaos double tent map and random technique were very advantageous from the viewpoint of HSF.

Influence of Random Modulated Power Converter on G3 Power Line Communication

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.

Analysis of output voltage ripple for dual randomized PWM buck converter operating in continuous and discontinuous conduction modes

Dual Randomized Pulse Width Modulation (DRPWM) is renowned for its better effectiveness than Simple Randomized Pulse Width Modulation (SRPWM) in reducing conducted Electro-Magnetic Interferences (EMI) in power converters. However, the introduction of low-frequency ripples into the output voltage by dual randomization has not yet been addressed; this effect is investigated in this paper for a buck converter operating in both the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM). First, the modulating principle is presented. Then, a general analytical expression for power spectral density (PSD) of the input current is derived and validated for the proposed DRPWM scheme for both the CCM and DCM. A comparison of the PSDs of the input current for all RPWM schemes in both the CCM and DCM shows the PSD spreading effectiveness of the dual scheme as compared to simple schemes. Finally, the low-frequency output ripple is analysed using the PSD of output voltage. The results reveal that the output voltage ripple is affected by all the randomized schemes in both the CCM and the DCM. Also, the dual scheme (RCFM-RPPM) introduces the highest low-frequency voltage ripple, especially in the CCM and for low duty cycles. In DCM, the RPPM scheme gives the lowest voltage ripple, while the RCFM scheme gives the lowest voltage ripple in the CCM. The results are confirmed by both theory and simulations.