The Variable Hysteresis Band in Delta-Sigma Modulation (original) (raw)
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2004 IEEE International Symposium on Circuits and Systems (IEEE Cat. No.04CH37512), 2004
This paper proposes to suppress the harmonic spikes in asynchronous sigma delta modulation by randomizing the hysteresis window for the distribution of the switching frequency and harmonic spectrum. The proposed scheme was examined in the dc/dc buck converter. The experimental results show that the proposed technique provides improved performance in terms of low peaks of harmonic while maintaining low output voltage ripple.
Sigma-delta modulation of multi-phase high frequency converters
2010
Abstract A power conversion control architecture is proposed that merges advanced digital modulation techniques, high frequency resonant converters, and multi-phase converters. If a converter's switching frequency is high enough, the converter may be turned on and off quickly to modulate power flow. The proposed system is composed of several high frequency converters connected in parallel, only a few of which are active at a given time to regulate the output voltage.
7th IET International Conference on Power Electronics, Machines and Drives, PEMD 2014, 2014
Inverters using deterministic switching schemes produce switching noises concentrated on the harmonic frequencies. To suppress the harmonic spikes in three phase three-level voltage source inverters, a Space Vector based Dithered Sigma Delta modulation scheme is proposed in this paper. In the proposed scheme the instantaneous reference voltage space vector is synthesized by dithered sigma delta analog-to-digital converter. The spurious harmonic spikes at the output of the Sigma Delta Modulator with regular input are eliminated by introducing a dithered sequence in the Dithered Sigma Delta Modulator. The switching frequency of dithered sigma delta converter varies randomly resulting in the spreading of power spectrum of the inverter. The minimum pulse width of the output pulse train is the sampling time period, which prevents the inverter from missing switching operations. In the present work, the quantizer in the sigma delta converter uses the principle of Vector Quantization instead of conventional scalar quantizer. In this study the space vectors are represented in the 60° coordinate system to reduce the computational complexity compared to the conventional Cartesian coordinate system. Experimental results of proposed scheme are compared with Space Vector based Sigma Delta Modulator, SVPWM scheme and Random PWM scheme.
A novel random hysteresis current control for a single-phase inverter
AUSTRALIAN JOURNAL OF …, 2007
Although hysteresis current control is a simple and a reliable modulation technique in switching control systems, its harmonic spectrum around a switching side band is not distributed broadly. The Random Pulse Width Modulation (RPWM) technique presented here is an effective scheme that distributes the harmonic spectrum of the load current and can reduce the acoustic noise and mechanical vibration of an inverter-fed motor drive. This paper presents a Random-Band Hysteresis Current Control (RBHCC) to spread more harmonic spectrum of the load current. In this paper, the effects of hysteresis band variations have been analysed in order to determine the best variation range for the hysteresis bands and the results have been compared with the traditional hysteresis current control. Theoretical analysis and simulations have been performed to describe the method.
Implementation of Improved Control Strategy of DC-AC Converter using Delta-Sigma Modulator
Smart Grid as a Solution for Renewable and Efficient Energy
This Chapter presents a comparative study between two current control techniques, namely, conventional Delta Modulator and novel Delta-Sigma Modulator. The use of Delta modulator in variable speed drives poses a problem of noise while converting analog signal in to digital form; to optimize Pulse Width Modulated (PWM) inverter waveforms on-line without any optimization process. But in the Delta-Sigma Modulator the noise varies. It can be successfully applied to over-sampling digital-to-analog and analogto-digital data converters, switch mode power supplies and inverters It is easy to implement, smooth inverter operation and provides low harmonics at the inverter output. The comparative study between the above said current controllers has been verified by the MATLAB computer simulation in terms of the high frequency power spectra, average switching frequency, rms current error and total harmonic distortion of load current waveforms. The obtained theoretical results are validated with experimental platform based on TMS320F2812 digital signal processor for effectiveness of the study.
Hexagonal Sigma-Delta modulation
IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 2003
A novel application and generalization of sigma-delta (61) modulation has emerged in three-phase power-electronic converters. A conventional 61 modulator with scalar signals and binary quantizer is generalized to a 61 modulator with vector signals and a hexagonal quantizer. Indeed, power-electronic switching states may be thought of as determining the quantizer outputs. The output spectrum is a key performance measure for both communications and power electronics. This paper analytically derives the output spectrum of the hexagonal 61 modulator with a constant input using ergodic theory and Fourier series on the hexagon. The switching rate of the modulator is important for power-electronic design and formulas for the average switching rate are derived for constant and slowly varying sinusoidal inputs.
IEEE Transactions on Power Electronics, 2021
The efficiency of wide-bandgap (WBG) power converters can be greatly improved using high-frequency modulation techniques. This paper proposes using single-loop and double-loop hexagonal sigma-delta modulation (H-Σ∆ and DH-Σ∆ respectively) for voltage source converters (VSC) that use silicon carbide (SiC) semiconductors. These allow high switching frequencies to operate more efficiently than silicon devices. Thus, Σ∆ modulations are excellent candidates for taking advantage of WBG devices. The proposed modulation techniques allow working with a variable switching frequency, thus producing an extreme reduction in switching losses and mitigating the low-order harmonics in comparison with the classical space vector pulse width modulation (SVPWM) technique, and with the innovative variable switching frequency pulse width modulation (VSFPWM). The performance and losses of both Σ∆ techniques are analysed here using Matlab/Simulink and PLECS, and then compared with SVPWM and VSFPWM. Furthermore, the frequency spectrum and the total harmonic distortion (THD) are evaluated. Experimental results performed on a VSC converter that uses SiC MOSFETs show how H-Σ∆ and DH-Σ∆ greatly improve efficiency and generate fewer low-order harmonics than the SVPWM and VSFPWM strategies do.
Hexagonal$Sigma Delta$Modulators in Power Electronics
IEEE Transactions on Power Electronics, 2005
Design techniques for 61 modulators from communications are applied and adapted to improve the spectral characteristics of high frequency power electronic applications. A high frequency power electronic circuit can be regarded as a quantizer in an interpolative 61modulator.Wereviewonedimensional61 modulators and then generalize to the hexagonal sigma-delta modulators that are appropriate to three-phase converters. A range of interpolative modulator designs from communications can then be generalized and applied to power electronic circuits. White noise spectral analysis of sigma-delta modulators is generalized and applied to analyze the designs so that the noise can be shaped to design requirements. Simulation results for an inverter show significant improvements in spectral performance.
Fractal Based Sigma Delta Modulation Scheme for Multilevel Inverter
2018
This paper presents a novel vector quantization technique in Sigma Delta Modulation scheme for multilevel inverter which quantizes the instantaneous reference space vector directly by using a hexagonal quantizer with fractal features of space vector diagram of inverter in 60 coordinate system .The voronoi region for reference space vector in the proposed scheme is the triangle enclosing the reference space vector formed by its nearest three permissible switching states. The proposed scheme eliminates generation of impermissible switching states for n-level inverter compared to the existing direct space vector quantization technique in SDM. The proposed scheme is compared with existing direct vector quantization scheme in SDM for five-level and three-level inverter configurations and verified results are presented in this paper. The proposed scheme has better performance in terms of THD than the existing direct vector quantization technique in SDM. The proposed scheme is implemented ...