Search Results (8)

On the basis of the space voltage vector pulse width modulation (SVPWM) technique, the random pulse width modulation (RPWM) technique, which can reduce harmonics, is investigated based on the vector control system of permanent magnet synchronous motor (PMSM) to address the problem of generating a large number of high-amplitude harmonics at the carrier frequency and its multiplier frequency. Firstly, the root causes of the large number of high-amplitude harmonics at the carrier frequency and its multiplier frequency are analyzed in depth, and the RPWM technique is explained in detail on how to reduce the amplitude of these harmonics effectively. Secondly, to address the problem of insufficient random performance in the traditional RPWM technique, an innovative optimization scheme is proposed, i.e., the introduction of a two-state Markov chain and, based on the immune algorithm for transition probability and random gain, the optimization of two key parameters. Ultimately, through experimental verification, the proposed method significantly improves the spectral distribution of the current waveform compared with the traditional RPWM, which makes the distribution more uniform and effectively reduces the high-amplitude harmonics concentrated near the carrier frequency and its octave frequency, thus enhancing the overall performance of the system. Full article

This study investigates the efficiency and noise, vibration, and harshness (NVH) characteristics of electric vehicle (EV) powertrains based on three key Pulse Width Modulation (PWM) techniques: Space Vector PWM (SVPWM), Discontinuous PWM (DPWM), and Random PWM (RPWM). The objective is to evaluate the impact of these PWM techniques on inverter and motor efficiency, as well as their effects on NVH performance, particularly in relation to noise and vibration. Experiments were conducted across various speed and torque levels using a motor dynamo. The study reveals that DPWM provides the highest efficiency, outperforming SVPWM by up to 2.23%. However, DPWM introduces more noise due to increased total harmonic distortion (THD), negatively affecting NVH performance. SVPWM, on the other hand, offers a balanced trade-off between efficiency and NVH, while RPWM demonstrates comparable noise characteristics to SVPWM, with potential for broader harmonic distribution. The findings suggest that each PWM technique offers distinct advantages, and their selection should depend on the required balance between efficiency and NVH. Full article

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 T_A, 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. Full article

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. Full article

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. Full article

Random Pulse Width Modulation (RPWM) allows controlling the switching signal of power converters in order to reduce the harmonic peaks by spreading the noise spectrum. Currently, many manufacturers of power converters are deploying this modulation scheme in order to comply with Electromagnetic Compatibility (EMC) test requirements. However, when the converters coexist with Power Line Communication (PLC) systems, such as in Smart Grid (SG) applications, resorting to RPWM needs further investigations since it potentially affects the communication channel by increasing the bit error rate. This possible detrimental effect is investigated in this work, by considering a PLC system for automatic meter reading (AMR) implemented in a SG application. To this end, the model of a complete PLC system is implemented in SIMULINK, and Quadrature Phase Shift Keying (QPSK) modulation is used to model the PLC modems in the communication channel. Results show that, even if the deployment of RPWM techniques may lead to an appreciable reduction/spreading of the peaks in the noise spectrum, it may also lead to an increase of the bit error rate on the PLC system. Full article

The pulse width modulation (PWM) inverter is an obvious choice for any industrial and power sector application. Particularly, industrial drives benefit from the higher DC-link utilization, acoustic noise, and vibration industrial standards. Many PWM techniques have been proposed to meet the drives’ demand for higher DC-link utilization and lower harmonics suppression and noise reductions. Still, random PWM (RPWM) is the best candidate for reducing the acoustic noises. Few RPWM (RPWM) methods have been developed and investigated for the AC drive’s PWM inverter. However, due to the lower randomness of the multiple frequency harmonics spectrum, reducing the drive noise is still challenging. These PWMs dealt with the spreading harmonics, thereby decreasing the harmonic effects on the system. However, these techniques are unsuccessful at maintaining the higher DC-link utilizations. Existing RPWM methods have less randomness and need complex digital circuitry. Therefore, this paper mainly deals with a combined RPWM principle in space vector PWM (SVPWM) to generate random PWM generation using an asymmetric frequency multicarrier called multicarrier random space vector PWM (MCRSVPWM). he SVPWM switching vectors with different frequency carrier are chosen with the aid of a random bi-nary bit generator. The proposed MCRSVPWM generates the pulses with a randomized triangular carrier (1 to 4 kHz), while the conventional RPWM method contains a random pulse position with a fixed frequency triangular carrier. The proposed PWM is capable of eradicating the high-frequency unpleasant acoustic noise more effectually than conventional RPWM with a shorter random frequency range. The simulation study is performed through MATLAB/Simulink for a 2 kW asynchronous induction motor drive. Experimental validation of the proposed MCRSVPWM is tested with a 2 kW six-switch (Power MOSFET–SCH2080KE) inverter power module-fed induction motor drive. Full article

In the existing random pule width modulation (RPWM) selective harmonic elimination methods, the formula of switching cycle T_N+1 is complex, and the duty ratio D_N+1 of the next switching cycle needs to be calculated in advance. However, in the case of unknown T_N+1, D_N+1 is also difficult to calculate accurately, and the two parameters are based on each other. A novel selective harmonic elimination method in RPWM is proposed in this paper. The PWM voltage pulse is placed at the back of the switch cycle, which simplifies the formula of the switch cycle T_N+1 and eliminates the need to calculate the duty ratio D_N+1. Two kinds of RPWM selective harmonic elimination ideas are summarized. The general formulas of the switch cycle, the effective random number k, and the upper and lower limits of switch frequency corresponding to k are derived. The spectrum shaping of inverter output voltage can be realized without using digital filter in this method. Simple algorithm, small calculation and easy implementation are characteristics of the proposed method. The simulation and experimental results confirm the ability of the proposed method for reducing harmonics at the specific frequency in power spectral density (PSD). Full article