Noise Suppression Technology for DTP-PMSM Based on Dual Random Modulation Strategy

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.

Permanent magnet synchronous motors (PMSM) generate high-frequency electromagnetic vibration and noise when powered by inverters, and the cause is high-frequency electromagnetic exciting force (EMEF). In this paper, the frequencies and orders of EMEF are analyzed. The expression of EMEF acted on the stator inner surface is derived and the frequencies and orders of main components of vibration are listed. The high-frequency vibration experiments are conducted on a surface mounted 8-pole and 12-slot PMSM. The high-frequency vibrations near switch frequency and its multiples are main components of vibrations of motors when powered by inverters, and experiments are conducted to study the influence of switch frequency on the vibration acceleration. The impacts of periodic frequency PWM and random frequency PWM on the vibration acceleration and peak value of its frequency spectrum are studied by experiments. Introduction The vibration of motors is one of the most important performance indicators. The noise generated by vibration will pollute our working and living environment. A severe vibration can even destruct the machine structure. There are higher requirements for vibration in special applications. While the application of inverter improves the dynamic performance of the motor, it causes high frequency vibration and noise. Many researchers have done a lot of work about the vibration and noise of motors. The frequency of noise of inverter-fed induction machine is calculated[1,2]. The influence of inverters on the vibration of axial flux PM motors is studied by finite element method(FEM) and experiments. The impacts of random PWM and harmonic injection is studied[4-6]. The effect of pulse frequency modulation(PFM) in reducing noise of induction motor is studied[7]. When powered by inverters, the stator current has a lot of time harmonics which increases the complexity of air gap flux. The air gap flux determines the magnitude and frequency of electromagnetic exciting force (EMEF) acted on the inner surface of stator. In this paper, the flux distribution is derived by magnetic circuit method firstly. Then, the expression of radial of EMEF is obtained by Maxwell’s stress tensor. The frequency, order and sources of the main EMEF are listed. The high-frequency vibration experiments are conducted on a surface mounted 8-pole and 12-slot PMSM. The high-frequency vibrations near switch frequency and its multiples are main components of vibrations of motors when powered by inverters, and experiments are conducted to study the influence of switch frequency on the vibration acceleration. The impacts of periodic frequency PWM and random frequency PWM on the vibration acceleration and peak value of its frequency spectrum are compared by experiments. Calculation of EMEF in PMSM The vibration of stator of PMSM is mainly determined by radial EMEF acted on the inner surface of the stator. Neglecting the effect of magnetostriction and assuming 0 Fe μ μ  , the EMEF acted on the inner surface can be expressed as[8]: 2nd International Conference on Electrical, Computer Engineering and Electronics (ICECEE 2015) © 2015. The authors Published by Atlantis Press 1580 2 0 1 2 n n o F B μ = (1) where 0n B is the radial air gap flux density in the inner surface of stator. So the air gap flux distribution need to be obtained before calculating the EMEF. Neglecting the core magnetic reluctance, the air gap flux distribution can be expressed as ( ) ( ) ( ) , , , b t f t t θ θ λ θ = ⋅ (2) where θ is the mechanical angle, ( ) , f t θ is the air gap magneto-motive force(MMF) and ( ) , t λ θ is the air gap permeance. In a surface mounted PMSM (SPMSM), the air gap permeance does not change with time. It can be approximately expressed as ( ) 0 l θ λ λ = Λ +∑ (3) where 0 Λ is the constant part and l λ is the space periodic part caused by slots. l λ can be expressed as ( ) ( ) ( ) 0 ( 1) sin 1 cos cos ( 1) l l k l k k lZ lZ k l k k δ

<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>

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.

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.

PWM-VSI inverter driven AC-machines emit acoustical noise. The authors present a combined modulation strategy which uses the acoustical noise for playing a melody in combination with random modulation and stator flux oriented asynchronous vector modulation (SFAVM) in order to reduce the effect of the acoustical noise. The relationship between notes and switching frequencies is discussed as well as the duration of a note. A computer program converts notes from a melody to a modulation file which easily can be implemented in a microcontroller. The modulation strategy is tested in a high performance AC-drive system. A test shows it is possible to activate tones in a melody from an AC-machine by varying the switching frequency. The best effects are obtained at two times the switching frequency. Tests also show that tones have optimum effect at lower speed as well as they show that random modulation reduce the acoustic noise effectively. Random modulation uncovers some mechanical resonant frequencies. Finally, it is demonstrated that music modulation is easy to implement and cost a minimum of ROM and can be a new benefit in combination with random and SFAVM modulation for AC-drives in the future.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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.

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.

The existing random carrier pulse‐width modulation (RCPWM) schemes result in poor non‐deterministic characteristics. They basically use a single‐frequency triangular carrier and its inverted version to synthesise the random carrier by a pseudo‐random binary sequence (PRBS) bit selector. Even though the bits are highly random in nature with large pattern repetition rate, the resulting random carrier does not possess required level of randomness. Rather it can make slight positional variation in the resulting PWM pulses. Moreover, the harmonic spreading effects of these randomness may not be sufficient to meet the expectations of modern drives. Hence, this study proposes a multiple carriers based RCPWM (MCBRCPWM) scheme for the voltage‐source inverter fed induction motor drive to enhance the harmonic power spreading ability of the modulator. The proposed MCBRCPWM scheme utilises the non‐deterministic characteristics of both the PRBS and hopping action between the MCs involved. The simulation results using MATLAB 7.1.0 (2010a)‐Simulink software and the experimental results with hardware implemented using XC6SLX45 field programmable gate array for a 3Ø squirrel cage induction motor load prove the excellent harmonic spectra spreading capability of the proposed scheme as compared with existing non‐deterministic methods.

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.

The experiences of stress are common to all living things. Noise is one of the most widespread sources of environmental stress. Noise is a pervasive aspect of many modern community and work environments. So, it is important to consider noise when we design human-oriented products. This study investigates the responses of electrocardiogram (ECG) and eye tracker data in order to evaluate the direct effects of low, middle, and high frequency noise on the two main physiological stress axes: the autonomic nervous system, and cognitive responses for a human-oriented product design. A subject was exposed to low (100 Hz), middle (1000 Hz), and high frequency (100000 Hz) noise while awake. ECG and eye tracker data were collected during noise exposure. Sympathetic nervous system (SNS) activity was less in the low and high frequency noise ranges compared to the no sound. On the other hand, parasympathetic nervous system (PNS) activity was greater in the low and high frequency noise ranges than the SNS activity in the no sound. The cognitive responses or latency saccadic eye movement (LSEM), in low or high frequency noise was greater than that in the no sound. And results of EEG and eye movement were statistically significant in low and high frequency noise (r > 0.93, p < 0.05). The findings of this study indicate that the stress induced by low frequency noise is as stressful as the stress induced by high frequency noise. Additionally, utilizing eye tracker data and acquiring the LSEM is useful in the analysis of human stress responses during various stressful situations in addition to the analysis of human stress responses during noise exposure.

As an alternative to the existing deterministic pulse-width modulation methods, a random pulse-width modulation technique for voltage-controlled power inverters is proposed. Advantages of the technique include non-repetitiveness of the switching pattern, simplicity of the hardware, and uncommonly high limits of switching frequency. A prototype random pulse-width modulator is described and experimental results are presented.

In the system of permanent magnet synchronous motor (PMSM) driven by indirect matrix converter (IMC), SVPWM technology is used in the inverter stage, which causes that the output current generates high-frequency harmonics around the integral multiples carrier frequency, thus generating high-frequency noise and electromagnetic interference. In order to suppress the high-frequency harmonics of output current in IMC-PMSM, a Markov chain random asymmetrical SVPWM (MRA-SVPWM) method is proposed in this paper. Although random PWM (RPWM) technology have some effect to reduce the harmonic amplitude. There are still some inherent defects. Markov chain with non-aftereffect is applied to random switching frequency PWM in order to improve the performance of RPWM. Meanwhile, MRA-SVPWM changes the switching state by adjusting the vectors order and thus changes the coefficient of the harmonic. A better suppression performance around the integer multiples carrier frequency is achieved. Meanwhile, the principle of harmonic suppression is analyzed by using three-dimensional Fourier. Finally, the effectiveness of the proposed algorithm is verified by experiments.

The use of a bi-directional buck-boost cascade converter in electric vehicles allows the suitable control of both motoring and regenerative braking operations. Based on the bidirectional buck-boost cascade converter, the random pulse width modulation (RPWM) scheme is implemented to reduce the conducted electromagnetic interference (EMI). Compared with the fixed frequency PWM (FPWM), the proposed RPWM scheme can suppress the peaky EMI as well as provide the bidirectional power transfer capability. Simulation and experimental results are given to support the validity.