Simple Modulation Technique Research Articles

Dual-input configuration of three-phase split-source inverter for photovoltaic systems with independent maximum power point tracking

This paper presents a dual-input configuration for the three-phase split-source inverter (SSI) to be used with photovoltaic (PV) systems, it is denoted as DSSI. Compared to using one SSI for each PV input, the proposed configuration uses a lower number of semiconductors. Thus, lower cost along with higher power density can be acquired. The proposed DSSI inherits the brilliant features of the conventional SSI. This includes continuity of input current and high voltage boosting gain. The proposed DSSI offers independent control for the power extracted from each PV source. Thus, independent maximum power point (MPP) tracking is ensured. In addition, no circulating current between the input ports is generated. Simple modulation technique is developed for the proposed configuration. In addition, the control system design to ensure independent MPP tracking along with power quality requirements is illustrated. Comparative study with other dual-input topologies is presented. Simulation, experimental as well as real-time simulation results for DSSI are presented. The results show good performance under dual- and single-input scenarios. In addition, well dynamic performance is verified. Thus, performance at steady-state and dynamic conditions is validated for the proposed DSSI. An efficiency of 92.3 % is achieved by the experimental prototype.

Single-phase dual-input split-source inverter for photovoltaic systems

This paper proposes dual-input configuration of split-source inverter (abbreviated as DSSI) to transfer the power of two photovoltaic (PV) modules simultaneously or individually. The proposed DSSI keeps the continuity of the input current and the voltage boosting capability offered by the conventional split-source inverter (SSI). Thus, independent as well as efficient tracking of the maximum power points (MPPs) is realized. In addition, low capacitance is utilized for power decoupling in single-phase circuits. Compared to using one SSI per PV source to feed a common load, the proposed DSSI uses lower number of switches at reduced total volt-ampere stresses. Therefore, decreased cost, size, and control circuitry are realized. Simple unipolar modulation technique is presented. Accordingly, the modes of operation and the Volt-ampere stresses of the switches are explained. A closed loop control system is explained to fulfill operation at MPP along with regulation of DC-link voltage and load current. Comparative study with other dual-input topologies is presented. Experimental results as well as real-time simulation results for dual- and single-input scenarios are presented. Also, the dynamic performance under step change in the radiation is investigated. Finally, the capability of operation under different power factors is verified.

Pulse Oximetry Based on Quadrature Multiplexing of the Amplitude Modulated Photoplethysmographic Signals

In this research, a pulse oximeter based on quadrature multiplexing of AM-PPG signals is proposed. The oximeter is operated by a microcontroller and employs a simple amplitude modulation technique to mitigate noise interference during SpO2 measurement. The two AM-PPG signals (RED and IR) are quadrature multiplexed using carrier signals with equal frequencies but a 90-degree phase difference. The study focused on noise interference caused by light intensity and hand movement. The experiment was conducted under three different levels of light intensity: 200 Lux, 950 Lux, and 2200 Lux. For each light intensity level, the SpO2 level was measured under three scenarios: hand still, shadow movement over the hand, and hand shaking. A comparison between the proposed technique and the conventional method reveals that the proposed technique offers a superior performance. The relative error of the measured SpO2 level using the proposed technique was less than 3.1% overall. Based on the study, the proposed technique is less affected by noise interference caused by light intensity and hand movement compared to the conventional method. In addition, the proposed technique has an advantage over contemporary methods in terms of computational complexity. Consequently, the proposed technique can be applied to wearable devices that include SpO2 measurement functionality.

A Simple SVM Technique on Three-Phase MPUC7 Inverter for Solar Photovoltaic System

In This paper, a simple single-dimension Space Vector Modulation (SVM) technique is introduced to implement on three-phase thirteen-level Modified Packed U-Cell (MPUC) inverter for photovoltaic system in which many DC sources are available. The three-phase thirteen-level converter consists of three single-phase seven-level MPUCs that each phase has six switches and two isolated DC sources. One major advantage of proposed method is to produce an output voltage with nearly constant amplitude in desired range in case of input DC voltage fluctuations, which is common in renewable sources like Photovoltaic Systems (PV). On the other hand, the conventional Pulse Width Modulation (PWM) strategies do not have such capability. Thus, the converter behavior is investigated for the proposed control method and Level Shift PWM (LS-PWM) and it is shown that the LS-PWM method does not function properly when the DC voltage varies. In order to produce an output voltage with seven equal levels, which results in reduction of the switching losses and Total Harmonic Distortion (THD), it is necessary to trigger switches in proper way. Consequently, two switching patterns are introduced and the significant decrease in power loss due to the second switching pattern is shown. Furthermore, it is investigated that in three-phase mode, the 3rd order line-voltage harmonics are eliminated well and the voltage and current THD are further improved by the proposed method. To validate the proposed SVM technique, MATLAB Simulink simulation results are presented and a comparative analysis is done between the proposed method and LS-PWM.

A novel self-boosting 5-level inverter for grid-connected photovoltaic system

Renewable energy systems are presently recognized as the primary alternative power source due to increased electricity demand and the depletion of fossil resources. The photovoltaic (PV) system is a rapidly growing renewable energy system. Inverters are used to integrate PV systems to the utility grid. Multilevel inverters are the most popular option for PV application due to reduced total harmonic distortion (THD), switching stress, and electromagnetic interference. This work presents a 5-Level grid-connected inverter while minimizing the cost. The proposed inverter uses six unidirectional switches and one diode with a single switched capacitor. Furthermore, it removes the requirement of multiple isolated DC sources. A simple modulation technique generates a suitable switching pulse for the inverter. Additionally, the comparison of the proposed inverter with the other topologies existing in the literature shows that it has reduced power devices, total standing voltage (TSV), and cost function. The PV connected grid system is investigated with specified controlling and implemented in MATLAB/Simulink and validated through hardware-in-the-loop (HIL) real-time simulation in OPAL-RT. In addition, the laboratory setup of the proposed structure is built and tested to verify its effectiveness.

A Precise Switching Frequency Formulation of Hysteresis-Controlled Grid-Connected Inverters Considering Nonlinear Ripple Current

Hysteresis current control (HCC) is one of the most simple and rapid modulation techniques for multilevel grid-connected inverters (MGCIs). It controls the output current by limiting its ripple within fixed hysteresis limits. This results in a varying switching frequency, which is not known implicitly. The knowledge of switching frequency is essential for filter design, device selection, and loss calculations of the MGCI. The existing frequency estimations for HCC assume linear ripple current considering high-frequency operation. This assumption is invalid for the range of low frequencies. This leads to inaccurate estimation of switching frequency, which can have a considerable effect on system design. In this article, a more precise and generalized expression to estimate the switching frequency of the MGCI is obtained. The improvement in accuracy is demonstrated with an example of second-order filter design. The effect of change in hysteresis limits and input voltage on the switching frequency is analyzed to determine the operating point for accurate system design. Simulation and experimental results are found to be in good agreement with the theoretical claims.

Comparative study on minimization of conduction and switching losses in cascaded multilevel inverter via reduced switches and equal voltage source-sharing

PurposeMultilevel inverters play a major role in the development of high-power industrial applications. In traditional low-level inverters (e.g. 2-level), the switching frequency is restricted and the harmonic spectrum of the system is hard to meet power requirements. Similarly, high-level inverters consist of a large number of switches, complex modulation techniques and complex hardware architecture, which results in high power loss and a significant amount of harmonic distortion. Furthermore, it is a must to ensure that every switch experiences the same stress of voltage and current. The purpose of this paper is to present an inverter topology with lower conduction and switching losses via reduced number of switches and equal voltage source-sharing technique.Design/methodology/approachHerein, the authors present a cascaded multilevel inverter having less power switches, a simple modulation technique and an equal voltage source-sharing phenomenon implementation.FindingsThe modulation technique becomes more complex when equal voltage source-sharing is to be implemented. In this study, a novel topology for the multilevel inverter with fewer switches, novel modulation technique, equal voltage source-sharing and Inductor-Capacitor-Inductor filter implementation is demonstrated to the reduce harmonic spectrum and power losses of the proposed system.Originality/valueThe nine-level inverter design is validated using software simulations and hardware prototype testing; the power losses of the proposed inverter design are elaborated and compared with the traditional approach.

A Low-Complexity Endurance Modulation for Flash Memory

The repeated program/erase (P/E) cycles wear out flash memory cells which limits the device’s lifetime. The larger the injected/erased charge, the faster the wear out rate and thus there is interest in reducing the percentage of cells programmed to high voltage levels. Conventional data shaping techniques often introduce a nonnegligible overhead as well as incurring additional complexity to encode the input data into shaped codewords and decode the read data. We propose a novel lossless yet simple endurance modulation technique that relies solely on the error-correction code (ECC) to retrieve the original data. This idea is motivated by the fact that ECCs are usually designed to correct channel errors towards the end of the device’s lifetime and hence at early age, the ECC can be jointly used for channel error correction and endurance demodulation. The proposed scheme consists of data shaping by flipping bits in a controlled manner and simple max-log demodulation to recover those flipped bits. The simulation results show that the proposed scheme does not undermine the device’s ability to recover the original data if the shaping gain is adjusted as the device ages. Once the channel errors exceed a prescribed threshold, the controller disables the endurance modulation and operates in normal mode.

Hybrid Output Voltage Modulation (PWM-FSHE) for a Modular Battery System Based on a Cascaded H-Bridge Inverter for Electric Vehicles Reducing Drivetrain Losses and Current Ripple

This paper shows a preliminary study about the output voltage modulation of a modular battery system based on a seven-level cascaded H-bridge inverter used for vehicle propulsion. Two generally known modulation techniques, pulse width modulation (PWM) and fundamental selective harmonic elimination (FSHE), are extensively compared for such an innovative modular battery system inverter considering EVs’ broad torque-speed range. The inverter and the battery losses, as well as the inverter-induced current THD, are modeled and quantified using simulations. At low speeds, if the modulation index M is below 0.3, FSHE induces a high current THD (>>5%) and, thus, cannot be used. At medium speeds, FSHE reduces the drivetrain losses (including the battery losses), while operating at higher speeds, it even reduces the current THD. Thus, an individual boundary between multilevel PWM and FSHE can be determined using weightings for efficiency and current quality. Based on this, a simple hybrid modulation technique is suggested for modular battery system inverters, improving the simulated drive cycle efficiency by a maximum of 0.29% to 0.42% for a modeled small passenger vehicle. Furthermore, FSHE’s high speed dominance is demonstrated using a simple experimental setup with an inductive load.

Multi-user High Data Rate Indoor VLC Systems

In this paper, we propose, design and evaluate the performance of an angle diversity transmitter (ADT) to achieve high data rate multi-user indoor visible light communication (VLC) systems. Our proposed systems are examined with three different receivers: a wide-field of view (W-FOV) receiver, an angle diversity receiver (ADR) and an imaging diversity receiver (IMDR). A novel algorithm is introduced also to eliminate the multi-user interference that is caused by line of sight (LOS) components, since these have a great impact on VLC systems performance. The effect of multi-user interference, mobility and diffuse reflections are considered in this work. We also investigate the effect of an increase in the number of the users on our proposed systems while achieving a high data rate for each user. Our proposed systems achieve 1 Gb/s for ADT with W-FOV receiver, 2 Gb/s for ADT with ADR and 4 Gb/s for ADT with IMDR with a simple modulation technique (on–off-keying, OOK).

A Novel Multilevel DC-Link Three-Phase T-Type Inverter

This research proposes a four-level T-type inverter that is suitable for low-power applications. The presented topology outranks other types of inverters in terms of a smaller number of semiconductor devices, absence of passive components such as clamping diodes and flying capacitors, low switching and conduction losses, and high efficiency. The proposed topology is free from voltage deviation and unbalanced voltage occurrences that are present in other multilevel converters having clamping diodes or flying capacitors. The proposed inverter can extend to N levels using unequal dc-link voltage sources for medium-voltage application. The inverter employs the simple fundamental frequency staircase modulation technique. Moreover, this paper presents a current commutation strategy to prevent the occurrences of short circuit and minimizing the number of required switching devices and switching transitions, resulting in improving the efficiency of the inverter. This paper also analyses the theoretical converter losses showing lower switching and conduction losses when compared to existing four-level inverters. The experimental validation of the proposed inverter shows its operating feasibility and a low output voltage THD.

A Novel Transformerless Single-Stage Grid-Connected Solar Inverter

A novel tranformerless single-stage grid-connected solar inverter with a combination of a bidirectional dc/dc boost converter followed by a flyback inductor inverter is proposed. The inverter shares a common ground with the photovoltaic (PV) panel and the grid, which realizes a zero leakage current and it is the most desired feature in transformerless inverters. Further, the proposed inverter provides the boost voltage operation, hence it does not require a second stage which decreases the system cost and increases the system reliability. The other advantage of the proposed inverter is that it provides both the symmetrical positive voltage gain and negative voltage gain, which allows to use simple sinusoidal pulsewidth modulation technique for realizing the ac sinusoidal output voltage. The proposed inverter steady-state operation and the design equations are presented in detail. The converter dynamic model is developed using state-space averaging approach, and a proportional resonant current controller is designed for inverter closed-loop operation with the grid. The presented analysis and the design are verified with both the simulation and experimental results.

Switched Capacitor Integrated (2n + 1)-Level Step-Up Single-Phase Inverter

This article presents a novel switched capacitor (SC) based (2 n + 1)-level single-phase inverter with a reduced number of components and input dc voltage supply. This inverter is designed in a way that just one dc source is required to generate different voltage levels. The circuit consists of three major parts, i.e., front-end boost stage, active SC cell(s) in the middle, and H-bridge inverter at the end. The total number of output voltage levels is up to (2 n + 1) levels, where n ≥ 2 is the number of switching cells, which consists of three active switches and two capacitors. Compared with conventional SC-based multilevel inverter topologies, the proposed topology features many advantages, such as low number of semiconductor devices, quasi-resonant charging of capacitors that reduce the inrush current and current stress on the devices, self-balancing of capacitor, and reduced voltage stress on the switches. Moreover, a simple sinusoidal pulsewidth modulation technique is employed here to generate the modulation signals for the proposed inverter. The operating principle is presented in detail followed by comparative analysis, thermal modeling, and design guidelines. Finally, computer simulation and laboratory test results are carried out for a five-level inverter with one SC cells as well as a seven-level inverter with two SC cells as two examples to verify the performance of the proposed (2 n + 1)-level inverter. Measurement results show that the proposed inverter has the 96.5 ± 1% efficiency over a wide range of load with a peak efficiency of 98.56%.

Research on the Simplified SVPWM for Three-Phase/Switches Y-Type Two-Level Rectifier

The three-phase/switch Y-type two-level rectifier is widely used in the unidirectional power-flowing applications such as LED illumination, communication and uninterruptible power supply. This paper presents the working principle of three-phase/switch Y-type two-level rectifier, and proposes two simple and fast modulation techniques (12-sector SVPWM and simplified equivalent SVPWM) based on the virtual vectors. The reference vectors of the 12-sector SVPWM are synthesized by utilizing real basic vectors and virtual vectors linearly combined from these real vectors in a switching period. So the created virtual vectors can reduce the error of reference voltage synthesis, contributing to better input current performance, this paper proposes a simplified 12-sector equivalent SVPWM, and shows the novel three-phase modulation wave expressions and waveforms. The proposed simplified 12-sector equivalent SVPWM does not need the process of sector determination with reducing computational processing time which is attractive for digital implementation. Finally, performance of the proposed modulation methods for a Y-type two-level rectifier using a 5kW prototype is experimentally verified.

An Instantaneous Power Balancing Technique for an Open-End IM Drive Using Carrier-Based Modulation for Vehicular Application

A multilevel drive can be realized by using an open-ended machine, fed from dual two-level inverters. The topology supplied from isolated dc sources is suitable for transportation electrification. In vehicular systems, it is essential that the isolated dc sources, comprising of battery packs, should discharge uniformly and maintain balanced dc voltage at the dc-link terminal. A simple carrier-based pulsewidth modulation (PWM) technique is presented in this paper, which can effectively regulate the power drawn between the two two-level inverters while maintaining the multilevel operation of the drive. The modulation technique can balance the instantaneous state of charge of independent battery packs and dynamically equalize the power flow from the two inverters, based on drive requirement. This will enhance the reliability of the propulsion system in electric vehicles. The operation of the proposed PWM technique has been validated through detailed simulation and experimental tests.

Manipulation of Electronic Devices and Data in Dispensing Pumps

The sale of fuel through electronics controlled based Dispensing units in the retail outlets are the source of manipulation. The stake holders are customers and are directly affected by the unauthorized manipulation by the petroleum product selling units. The electronic devices are more prone for changing the original encrypted data or stored data as a program. The program stored in this device can be altered unauthenticated by external device attached to the original circuit’s boarders. The circuits board is build with the microcontroller based hardware that controls the outlet pipe by setting the control signal by the selling unit. This can be alter by changing the pulse which are used to modulate the information bits so that cheating the customer by alter the set control bit by deliver less or more through the dispensing unit. This research article focus on explore the possibilities to make the encryption method of control bits more robust than the present simple pulse modulation techniques.

Generation of light beams with custom orbital angular momentum and tunable transverse intensity symmetries.

We introduce a novel and simple modulation technique to tailor optical beams with a customized amount of orbital angular momentum (OAM). The technique is based on the modulation of the angular spectrum of a seed beam, which allows us to specify in an independent manner the value of OAM and the shape of the resulting beam transverse intensity. We experimentally demonstrate our method by arbitrarily shaping the radial and angular intensity distributions of Bessel and Laguerre-Gauss beams, while their OAM value remains constant. Our experimental results agree with the numerical and theoretical predictions.

A Novel Seven-Level Active Neutral-Point-Clamped Converter With Reduced Active Switching Devices and DC-Link Voltage

This paper presents a novel seven-level inverter topology for medium-voltage high-power applications. It consists of eight active switches and two inner flying capacitor (FC) units forming a similar structure as in a conventional active neutral-point-clamped (ANPC) inverter. This unique arrangement reduces the number of active and passive components. A simple modulation technique reduces cost and complexity in the control system design without compromising reactive power capability. In addition, compared to major conventional seven-level inverter topologies, such as the neutral point clamped, FC, cascaded H-bridge, and ANPC topologies, the new topology reduces the dc-link voltage requirement by 50%. This recued dc-link voltage makes the new topology appealing for various industrial applications. Experimental results from a 2.2-kVA prototype are presented to support the theoretical analysis presented in this paper. The prototype demonstrates a conversion efficiency of around 97.2% ± 1% for a wide load range.

Highly flat optical frequency comb generation based on pulse carving and sinusoidal phase modulation

We investigate the relationship between an optical pulse shape and a time lens implemented by means of sinusoidal phase modulation. Based on this investigation, two schemes are proposed to obtain an optical frequency comb (OFC) with exceptionally high flatness and a large number of spectral lines by carving an optical pulse shape to result in a quasilinear chirp via a simple sinusoidal phase modulation technique. The first scheme utilizes an intensity modulator with a single-drive port or with dual-drive ports to carve a narrow pulse. The experimental results show very good spectral profiles with 38 OFC lines at 1.2-dB flatness and 53 lines at 1.5-dB flatness when the intensity modulator is combined with two and three phase modulators for sinusoidal phase modulation, respectively. The second scheme is implemented by replacing the intensity modulator by a dual-parallel Mach–Zehnder modulator (DP-MZM). In this case, we obtain 35 OFC lines at nearly perfect flatness of less than 1 dB and 53 lines at 1.5-dB flatness after combining the DP-MZM with two and three phase modulators, respectively.

Inter-symbol interference reduction channel codes based on time gap in diffusion-based molecular communications

In diffusion-based molecular communication simple modulation techniques based on the concentration, type, or released time of molecules are commonly used. However, random delay of the diffused molecules in environment can cause some strong inter-symbol interference (ISI) among consecutive symbols. Due to the limited computational capabilities of nano-machines, sophisticated modulation and coding schemes cannot be used to resolve this issue . In this paper, we propose several new, yet simple, ISI-resistant coding schemes for diffusion-based communications over a one-dimensional noiseless channel. These schemes map the information bits into variable length codewords and place time-gaps between the consecutive codewords to mitigate ISI issue. Our analytical and simulation results indicate that the proposed schemes provide superior performances in terms of probability of error and throughput compared to the existing schemes.