Simple Modulation Technique Research Articles

A Three-Phase Symmetrical DC-Link Multilevel Inverter With Reduced Number of DC Sources

This paper presents a novel three-phase DC-link multilevel inverter topology with reduced number of input DC power supplies. The proposed inverter consists of series-connected half-bridge modules to generate the multilevel waveform and a simple H-bridge module, acting as a polarity generator. The inverter output voltage is transferred to the load through a three-phase transformer, which facilitates a galvanic isolation between the inverter and the load. The proposed topology features many advantages when compared with the conventional multilevel inverters proposed in the literatures. These features include scalability, simple control, reduced number of DC voltage sources, and less devices count. A simple sinusoidal pulse-width modulation technique is employed to control the proposed inverter. The performance of the inverter is evaluated under different loading conditions and a comparison with some existing topologies is also presented. The feasibility and effectiveness of the proposed inverter are confirmed through simulation and experimental studies using a scaled down low-voltage laboratory prototype.

Adaptive spatial modulation and thresholds optimization for MIMO systems in correlated Rayleigh channels

Spatial modulation (SM) is a simple and spectral efficient modulation technique that has received much interest recently. In this paper, an adaptive SM (ASM) scheme is presented by combining adaptive modulation with conventional SM. The performance of ASM is analyzed in spatially correlated Rayleigh fading channels. In order to reduce the computational complexity of average bit error rate (BER), an approximate expression of error probability of the antenna index estimation, which contributes one of two components of the average BER, is derived by using the fitting method and matches well with simulation results in the SNR range of interest. With the above results, the closed-form spectrum efficiency (SE) and overall average BER are obtained, respectively. Besides, the optimized switching thresholds for maximizing SE under an average BER constraint are achieved by means of the Karush Kuhn Tucker conditions, and the resultant SE performance can be improved greatly when compared to the ASM system with fixed thresholds. Simulations indicate that the theoretical SE and BER are effective and agree well with the corresponding simulations. Moreover, the SE and BER performance of ASM under spatially correlated channel are poorer than those under spatially independent channel because of the influence of spatial correlation.

Common-Ground-Type Transformerless Inverters for Single-Phase Solar Photovoltaic Systems

This paper proposes a family of novel flying capacitor transformerless inverters for single-phase photovoltaic (PV) systems. Each of the new topologies proposed is based on a flying capacitor principle and requires only four power switches and/or diodes, one capacitor, and a small filter at the output stage. A simple unipolar sinusoidal pulse width modulation technique is used to modulate the inverter to minimize the switching loss, output current ripple, and the filter requirements. In general, the main advantages of the new inverter topologies are: 1) the negative polarity of the PV is directly connected to the grid, and therefore, no leakage current; 2) reactive power compensation capability; and 3) the output ac voltage peak is equal to the input dc voltage (unlike neutral-point-clamped and derivative topologies, which requires twice the magnitude of the peak ac voltage). A complete description of the operating principle with modulation techniques, design guidelines, and comprehensive comparisons is presented to reveal the properties and limitations of each topology in detail. Finally, experimental results of 1-kVA prototypes are presented to prove the concept and theoretical analysis of the proposed inverter family for practical applications.

Power Allocation and Performance Analysis of Cooperative Spatial Modulation in Wireless Relay Networks

In this paper, the error performance analysis of an amplify-and-forward (AF) relay-aided cooperative multi-antenna system using spatial modulation (SM) over Rayleigh channels is presented. The SM is a simple and spectral efficient modulation technique that can increase the data rate by using input data bits to select a transmit antenna to send a constellation point. The relay transmission deploying SM not only can enhance the coverage and but also can improve the spectral efficiency. In the performance analysis, the overall average bit error rate (BER), which is related to the error probability of an antenna index detection ( $P_{a}$ ) and the error probability of symbol detection ( $P_{d}$ ) given transmit antenna index, is analyzed. With the derivation of the probability density function and the moment generating function of output signal-to-noise ratio (SNR), closed-form expressions of $P_{a}$ and $P_{d}$ are obtained to compute the overall BER. With the obtained BER expression, asymptotical BER expressions are derived to reveal the BER performance of the system at high SNR. By minimizing the asymptotical BER, a suboptimal power allocation (PA) scheme is developed. The diversity gain is analyzed at high SNR. The results indicate that the cooperative AF-SM can achieve full diversity order. Simulation results verify the effectiveness of the theoretical BER analysis, and the cooperative AF-SM with PA scheme outperforms upon the equal PA scheme.

IEEE Access Special Section Editorial: Index Modulation Techniques for Next-Generation Wireless Networks

Index modulation (IM) techniques appear as competitive candidates for next-generation (5G and beyond) wireless networks due to the attractive advantages they offer in terms of spectral and energy efficiency as well as hardware simplicity. IM is a highly spectrum- and energy-efficient yet simple digital modulation technique, which utilizes the indices of the building blocks of the corresponding communication systems to convey additional information bits. IM systems provide alternative ways to transmit information in contrast to traditional digital modulation schemes that rely on the modulation of the amplitude/phase/frequency of a sinusoidal carrier signal for transmission, as widely considered in the field of communications over the past 50 years. Radically, IM schemes have the ability to map information bits by altering the on/off status of their transmission entities such as transmit antennas, subcarriers, radio frequency (RF) mirrors, transmit light emitting diodes, relays, modulation types, time slots, precoder matrices, dispersion matrices, spreading codes, signal powers, loads and so on. In other words, IM creates completely new dimensions for data transmission. Since the initial skepticism of both academia and industry on the potential and applicability of IM technologies has now gone away, we strongly believe that IM is not another simple digital modulation alternative, but rather can be a game-changing communication paradigm whose time has come!

Analysis of Harmonics and Ripple Current in Multi-module Converters with Increasing Number of Modules for High Power Applications

Controlled rectifiers are considered as the most important hardware part in the field of HVDC systems in transmission lines and can be used for a number of power electronics based system operation, control and utility applications. In this paper, a brief design of a 12-pulse, 24-pulse, 36-pulse and a 48-pulse converter connected to the grid is presented along with the harmonic and ripple current analysis with its comparison statistics and thus providing a justification for the suitable ones. The performance of the 12, 24, 36 and 48-pulse converters are compared for their effectiveness in both quantitatively as well as qualitatively. Further, comparison of the 48-pulse converter on its THD and current ripple which is connected towards the grid with simple pulse width modulation technique is also proposed. It combines all features of the low switching concepts and DC current re-injection techniques. Some basic topological explanation of the controlled rectifiers and simulation results using MATLAB are also presented in this paper in order to justify the harmonic analysis. The simulation results along with the quantitative results shows the effectiveness of the proposed scheme for the cancelation or the elimination of the harmonics result in maximum harmonic mitigation, for high power utility applications, the 48-pulse converter is most fitting to improve the conversion efficiency, low di/dt and dv/dtand active and reactive power controllability.

Sliding-Mode Control of PWM Dual Inverter-Based Grid-Connected PV System: Modeling and Performance Analysis

This paper proposes a novel robust and adaptive sliding-mode (SM) control for a cascaded two-level inverter (CTLI)-based grid-connected photovoltaic (PV) system. The modeling and design of the control scheme for the CTLI-based grid-connected PV system is developed to supply active power and reactive power with variable solar irradiance. A vector controller is developed, keeping the maximum power delivery of the PV in consideration. Two different switching schemes have been considered to design SM controllers and studied under similar operating situations. Instead of the referred space vector pulsewidth modulation (PWM) technique, a simple PWM modulation technique is used for the operation of the proposed SM controller. The performance of the SM controller is improved by using an adaptive hysteresis band calculation. The controller performance is found to be satisfactory for both the schemes at considered load and solar irradiance level variations in simulation environment. The laboratory prototype, operated with the proposed controller, is found to be capable of implementing the control algorithm successfully in the considered situation.

Investigating channel frequency selectivity in indoor visible‐light communication systems

Channel characterisation for indoor visible-light communication systems is revisited. The purpose of this study is to evaluate the channel frequency selectivity, or in other words, the significance of inter-symbol interference (ISI) at the receiver and the necessity of channel equalisation to recover the transmitted data. The authors focus on the effect of the indoor channel by assuming no bandwidth constraint on the light-emitting-diodes and by considering a simple intensity modulation technique, excluding discrete multi-tone modulation. The channel impulse response (CIR) is first simulated using the iterative site-based method. Then, conventional metrics for evaluating channel frequency selectivity, that is, the root-mean-square delay spread and channel frequency response are investigated and their practical interest is discussed. The authors also consider the signal-to-ISI ratio (SIR), which they define based on the sampled (i.e. discrete-time) signal at the receiver, and demonstrate its usefulness in determining the necessity of channel equalisation at the receiver. They consider several link scenarios in a medium-size and a large room, and show the significance of the LOS components of CIR in determining the channel frequency selectivity. They also discuss the choice of the receiver filter and explain how it affects the SIR.

Chemical doping modulation of nonlinear photoluminescence properties in monolayer MoS2

We demonstrate a simple modulation technique of nonlinear optical properties in monolayer (1L) MoS2 via chemical doping. The strong nonlinear behavior of the exciton photoluminescence (PL) intensity is observed with increasing excitation power density for low-electron-density 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ)-doped 1L-MoS2, whereas the exciton PL intensity of as-prepared, heavily electron-doped 1L-MoS2 exhibits weak sublinear behavior. These results are attributable to an enhanced exciton–exciton annihilation rate for the excitons in F4TCNQ-doped 1L-MoS2 as the dominant decay pathway under strong optical excitation conditions.

Modeling, control and analysis of cascaded inverter based grid-connected photovoltaic system

Abstract This paper proposes a vector controlled isolated source cascaded two-level inverter (CTLI), for grid connected photovoltaic (PV) system. The system is controlled to operate with variable solar irradiance, supplying different levels of active power. The PV systems are designed, modeled and tested with the proposed controller, to provide maximum power output. Additional operation as a reactive power supplier, in the absence of solar radiation, is also tested. A simple sinusoidal pulse width modulation (PWM) technique is used, instead of referred space vector PWM (SVPWM) technique, for the operation. Two different schemes have been considered to operate the inverter with equal and unequal DC-link voltages. The control scheme has been found working, for both active and reactive power supply in steady state and transient conditions. The power supplies of both the schemes are analyzed. The controller performance is found to be satisfactory for both the schemes to extract maximum power at the considered working conditions.

Analysis of Impedance Source Inverter Topologies for Grid integration of PV inverters

In this paper, the performance of different Impedance Source Inverter (ZSI) topologies in implementing single stage power conversion for grid ingetertion of PV power converters <del cite="mailto:QP%20Council" datetime="2015-08-11T09:53"> </del>is discussed.Unlike the traditional inverters, ZSI employs a distinctive impedance network, thereby making shoot-through state is possible. The independent control variables are shoot-through duty ratio and modulation index. Simple Boost Control pulse width modulation technique was used in this work to vary the modulation index. Here the basic operation, simple boost control method, characteristics, requirements and harmonic analysis of the classical Z-Source Inverter (ZSI), TZ-Source Inverter (TZSI), Trans-Z-Source Inverter (Trans-ZSI) and Improved ZSI (IMZSI) topologies were compared for interfacing the wide range <del cite="mailto:QP%20Council" datetime="2015-08-11T09:54"> </del>variable input energy to utility supply system. The performances were compared based on its MATLAB/SIMULINK simulation model and featured results are shown to confirm its validity.

Pressure-induced Semimetal-to-Semiconductor Transition in Bismuth

Semimetallic bismuth possesses an unusual electronic structure and an extremely small Fermi surface, which it is predicted can be suppressed to zero size by the application of hydrostatic pressure. We report evidence for a such a semimetal-to-semiconductor transition in single crystal bismuth as measured by transport measurements under pressure, finding that the lowtemperature conductivity (a measure of the carrier density) tends to zero at a pressure of around 25 kbar. We further describe a simple modulation technique for measuring quantum oscillations in low fields without compromising the ability to measure conventional resistivity, applicable to piston cylinder cells.

1064-nm DFB laser diode modules applicable to seeder for pulse-on-demand fiber laser systems

Semiconductor DFB (Distributed feedback) laser diodes with an operating wavelength of 1064nm, which is suitable for pulse-on-demand fiber laser, have been developed. The stable performance of CW and nanosecond/picosecond pulsed operation is reviewed. By applying gain-switching operation with a simple direct modulation technique, 50-ps pulse generation with a stable spectral single-mode property was obtained. For the efficient amplification of the obtained 50-ps pulse, a monolithic semiconductor optical amplifier (SOA) was integrated into the DFB lasers. An improved peak power of 300mW at 50-ps pulse was observed with limited optical noise injection when the synchronous modulation technique of the DFB and the SOA was employed. Short cavity lasers showed a high-frequency response compared to the original DFB lasers and achieved a short pulse width of 13ps by standard gain-switched operation.

Comparative Analysis of PWM Techniques for Three Level Diode Clamped Voltage Source Inverter

Multilevel inverters are increasingly being used in high-power medium voltage industrial drive applications due to their superior performance compared to conventional two-level inverters. Thre are a number of Pulse width modulation (PWM) techniques applied in recent years. The most widely applied PWM techniques are Sine Pulse Width Modulation (SPWM) and Space Vector Pulse Width Modulation (SVPWM). SPWM is the most simple modulation technique that can realize easily in analog circuit. However, it has some drawbacks such as higher total harmonic distortion (THD), lower effective DC utilization and lower switching frequency. Space vector pulse width modulation (SVPWM) is widely used because of their easier digital realization and better DC bus utilization and lower THD. The complexity is due to the difficulty in determining the reference vector location, on times calculation, and switching states selection. This paper presents a simple SVPWM algorithm for diode clamped three level inverters based on standard two-level SVPWM which can easily determine the location of reference vector, calculate the on-times, the selection of switching states. Three level diode clamped inverter (3LDCI) using space vector modulation technique has been modeled and simulated using MATLAB/SIMULINK and Origin 6.1 with a passive R-L load that can be extended to any level. Simulation results are presented to verify the proposed SVPWM control in terms of THD. The results are compared with conventional sinusoidal pulse width modulation (SPWM) where SVPWM shows better performance than SPWM in terms of THD. DOI: http://dx.doi.org/10.11591/ijpeds.v5i1.6038

The Control Technology of the Z-Source Three-Phase Four-Leg Inverter Based on Computer Simulation

Z-source inverter can boost the voltage of the DC-side, allow the two switches of the same leg conducting at the same time and it has some other advantages. The zero-sequence current flows through the fourth leg of the three-phase four-leg inverter so the three-phase four-leg inverter can work with unbalanced load. This paper presents a Z-source three-phase four-leg inverter which combines a Z-source network with three-phase four-leg inverter. The circuit uses simple SPWM modulation technique and the fourth leg uses fully compensated control method. The inverter can maintain a symmetrical output voltage when the proposed scheme under the unbalanced load.

Simulation Investigation of SPWM, THIPWM and SVPWM Techniques for Three Phase Voltage Source Inverter

Pulse width modulation (PWM) technique is one of the vital issues for power electronic circuit control. A number of Pulse width modulation (PWM) techniques are increasingly applied in many new industrial applications that require superior performance. The most widely applied PWM technique for three-phase voltage source inverters are Sine Pulse Width Modulation (SPWM), Third Harmonic Injection Pulse Width Modulation (THIPWM) and Space Vector Pulse Width Modulation (SVPWM). SPWM is the most simple modulation technique that can realize easily in analog circuit. However, it has some drawbacks such as higher total harmonic distortion (THD), lower switching frequency and not capable in over modulation region. THIPWM and SVPWM both provide better THD compared to SPWM. SVPWM shows lower THD in over modulation region and in high frequency application compared to THIPWM. These three techniques are discussed, analyzed and compared in terms of modulation index, switching frequency and inverter input voltage in this paper. The modeling and simulation for all PWM techniques have been done by using MATLAB/SIMULINK and Origin 6.1. From the simulation results, SVPWM shows the best performance and meet IEEE 519 standard of current harmonics level. DOI: http://dx.doi.org/10.11591/ijpeds.v4i2.5833

Linear Pulsewidth Modulation Under Fluctuating Power Supply

Heavy fluctuations in the dc power supply cause large distortions, when the simple pulsewidth modulation technique is employed in inverters. The ripples in the dc supply may even be synchronous with the converted ac signal. To overcome this nonlinear distortion, a new carrier signal is generated by multiplying the triangular dither signal with the dc supply voltage, without changing the basic dither frequency. The modulator-demodulator characteristic becomes linear, thereby removing the distortion.

Speed Control Analysis of Brushless DC Motor Based on Maximum Amplitude DC Current Feedback

This paper describes an approach to develop accurate and simple current controlled modulation technique for brushless DC (BLDC) motor drive. The approach is applied to control phase current based on generation of quasi-square wave current by using only one current controller for the three phases. Unlike the vector control method which is complicated to be implemented, this simple current modulation technique presents advantages such as phase currents are kept in balance and the current is controlled through only one dc signal which represent maximum amplitude value of trapezoidal current (Imax). This technique is performed with Proportional Integral (PI) control algorithm and triangular carrier comparison method to generate Pulse Width Modulation (PWM) signal. In addition, the PI speed controller is incorporated with the current controller to perform desirable speed operation of non-overshoot response. The performance and functionality of the BLDC motor driver are verified via simulation by using MATLAB/SIMULINK. The simulation results show the developed control system performs desirable speed operation of non-overshoot and good current waveforms.

The Control Technology Research of the Z-source Three-phase Four-bridge Arm Inverter

Z-source inverter can boost the voltage of the DC-side, allow the two switches of the same bridge arm conducting at the same time and it has some other advantages. The zero-sequence current flows through the fourth leg of the three-phase four-leg inverter so the three-phase four-leg inverter can work with unbalanced load. This paper presents a Z-source three-phase four-leg inverter which combines a Z-source network with three-phase four-leg inverter. The circuit uses simple SPWM modulation technique and the fourth bridge arm uses fully compensated control method. The inverter can maintain a symmetrical output voltage when the proposed scheme under the unbalanced load.

A Simple Sector Independent Space Vector Modulation Technique Implemented using a DSP Processor

This paper presents the software implementation of a simple sector independent Space Vector Modulation (SVPWM) technique for simple motor drive applications using DSP processor. The closed loop control scheme with Volts/Hz principle, suitably regulates the switching period and operates with a fixed set of compare register values. The Space Vector Pulse Width Modulation hardware module on the TI TMS320LF2407A is used to produce the Pulse Width Modulated (PWM) pulses with four switching states in one PWM period. In contrast to the conventional scheme, the algorithm developed here, eliminates the computational burden involved in determining the magnitude and phase of the voltage vector, the corresponding sector and the decomposition matrices for calculating the switching time segments. A 1hp, 3 phase induction motor fed from an IGBT based inverter module is tested with the control pulses generated from the DSP processor and the performance is found to be satisfactory. DOI: http://dx.doi.org/10.11591/ijpeds.v2i3.348