Sinusoidal Output Research Articles

A single‐stage AC‐AC solid‐state transformer with ZVS operation

Solid-state transformer (SST) is an attractive concept, which provides galvanic isolation and voltage scaling by means of a medium-frequency link. In this paper, a single-stage alternative current (AC)-AC SST solution without bulky energy storage elements is presented. The front-end rectifier (FER) and rear-end inverter (REI) of the SST works at line-frequency, while the intermediate LLC series resonant converter (SRC) fulfils the tasks of galvanic isolating and regulating the output voltage. To achieve high efficiency and bidirectional power flow capability of the SST, the zero voltage switching (ZVS) condition of the LLC SRC is comprehensively analysed, and the parameters design method of the LLC SRC is developed, where the resonant currents are constructed by applying the same gating signals to the primary-side and secondary-side bridges and the dead-time is properly selected. Consequently, the presented SST has the merits of high conversion efficiency, naturally bidirectional power flow capability, potentially high power density and high reliability. The experimental results on a 1.5 kW SST prototype show that sinusoidal input and output current, ZVS operation over the full load range are achieved, and the peak efficiency is 97.63%. The experimental results verify the functionality and effectiveness of the developed methods.

Asymmetric regular sampling SPWM method based on tangent approximation algorithm

Objectives In order to improve the quality of sinusoidal waveform output by the ship's high-frequency inverter charging device and reduce the CPU occupancy rate, an asymmetric regular sampling sinusoidal pulse width modulation (SPWM) method based on tangent approximation is proposed. Methods According to the basic principle and calculation method of the asymmetric regular sampling SPWM method based on tangent approximation, a Matlab/Simulink simulation model is built, and then the software algorithm flow that can be used in the high-frequency inverter charging device is designed together with the actual output of the tangent approximation method. The effects are then compared and verified by experiments. Results The simulation results show that under pure resistive load and resistive inductive load, the total harmonic distortion (THD) of the load-end waveform based on tangent approximation method is 2.12% and 2.08%, respectively, and its waveform quality is better than symmetric regular sampling. The experimental results show that the THD of load-end waveform based on the tangent approximation method is significantly lower than the symmetric regular sampling method. When the effective value of the input line voltage is 580 V (the modulation ratio is 0.8), the quality of the output waveform is relatively optimal. Conclusions The asymmetric regular sampling SPWM method based on tangent approximation overcomes the shortcomings of the traditional symmetric regular sampling method, such as the low quality of the output waveform and the traditional asymmetric regular sampling method's high sampling frequency and high CPU occupancy rate. The research results can provide reference for the design of ship's high frequency inverter charging devices.

Modeling and Control of Grid Connected Photovoltaic System Using Sliding Mode Control

Solar PV systems are gaining attraction for energy generation in these days due to its reducing cost and efficiency. The proposed system consists of two main controllers: the DC/DC boost converter to track the maximum power from the PV panels using an application of sliding mode control because it is fast and unconditionally stable and the grid-tied threephase inverter to control the power active and reactive for achieved the unit power factor in connection point and synchronize a sinusoidal current output with a voltage grid with regulated DC bus voltage. Simulation results are provided to demonstrate the effectiveness of the proposed design and robustness under different operating conditions such as changes in atmospheric conditions.

Implementation of inductor-less 13-level inverter topology with reduced number of required component

This paper presents an inductor-less multilevel inverter (MLI) with a 13-level ac output. The proposed MLI consists of only 11 switches, 2 capacitors, and 2 input sources. Owing to the inductor-less symmetrical topology, the proposed MLI can reduce the component count in comparison of conventional MLIs. This leads to reduction of power loss and hardware cost. To clarify the effectiveness of the proposed MLI, the characteristic evaluation is given in detail. Some computer-based simulations in SPICE simulator environment as well as breadboard-based experimental tests are conducted concerning the proposed 13-level inverter. In the performed simulations, the power efficiency of the proposed MLI reaches about 85% and 88% at 1 kW in the case of a sinusoidal output and a triangular output, respectively. The proposed MLI improves power efficiency more than 2.5% comparing with the conventional K-type MLI when the output power is 1 kW. Furthermore, the experimental result proves the physical feasibility of the proposed topology by demonstrating the 13-level ac output.

A new multilevel inverter with reduced switch count for renewable power applications

This paper proposes a new technique for a voltage source multilevel inverter (MLI) with reduced switch count, and it creates a smoother sinusoidal output waveform with reduced total harmonic distortion (THD). Therefore, the proposed technique identifies a better position in the list of multilevel converters used for power quality conditioners. Semiconducting devices are added to it if the number of levels increases. In this work, the topology of MLI with reduced number of switches is presented. A new MLI is proposed with lower number of switches and sources in order to achieve higher level. The proposed topology is framed out with the combination of three half bridge and a single H-bridge configuration. Detailed simulation results for 15-level inverter of single and three phase inverters are presented in this paper. Three phase 15-level inverter is developed by employing three isolated different renewable sources and 21 switches.

A Simple Sinusoidal Buck Converter Working as A Single-Phase Grid-Connected Inverter

The need for a simple grid-connected inverter is increasing. The integration of a simple buck converter and a push-pull converter to be a grid-connected inverter is presented in this paper. The buck converter is controlled by a sinusoidal duty ratio to produce a series positive half-cycle of a sine wave. Then, the push-pull converter solves it to generate the complete sinusoidal output voltage and current. Moreover, grid synchronization works properly by sensing the grid voltage, which is then used as a reference voltage to connect the inverter to the grid successfully. The grid sees the inverter as a resistive load with a unity power factor. The total harmonic distortion (THD) of the grid current is 4.87% for the THD grid voltage of 2.07%.

Independent switching technique to remove abnormal output voltage in hybrid active NPC inverters

This paper proposes the independent switching technique to remove abnormal output voltage in hybrid active neutral-point clamped (ANPC) inverters. The hybrid ANPC inverter is composed by mixing silicon (Si) devices and silicon carbide (SiC) devices, unlike the conventional ANPC inverter which is generally composed of Si devices only. SiC devices provide low switching losses under a high switching frequency and a high withstand ability under high temperature compared with Si devices. Therefore, the hybrid ANPC inverter using SiC devices provides low power losses, high efficiency, and high reliability compared with the conventional ANPC inverters. In this hybrid ANPC inverter, abnormal output voltages are generated when the sinusoidal output current crosses the zero point. The abnormal output voltages are momentary pulses that must not be generated, and these pulses distort the output current and degrade the power quality. These pulses have two typical causes: one is from the switching operation time difference between switches, and the other is from deadtime. This paper proposes the independent switching technique to remove the abnormal voltages caused by the two reasons and verifies the proposed technique by simulation and experiment.

Modified LUT-based DTC of NPC 3-Level Inverter fed Sensorless IPMSM Drive with DC Link Voltage Balance

In the proposed work, a modified look-up table-based direct torque control (DTC) scheme is reported for a neutral point-clamped three-level inverter-fed interior permanent magnet synchronous motor drive. In the classical DTC scheme, there are significant torque and flux ripples in the drive due to low number of available switching states. To reduce the oscillations in torque and flux, a three-level inverter-operated IPMSM drive is discussed. In a three-level inverter, the increased count of active voltage vectors is results in more sinusoidal output waveforms. Moreover, stator flux plane has 12 sectors in the proposed work unlike classical DTC. Besides, the higher level of flux and torque hysteresis comparators is implemented. DC link capacitor voltage balancing scheme is also instigated to minimize voltage stress on semiconductor devices, improve stator current THD and increased capacitor life. Based on the sector information, flux and torque hysteresis output and capacitor voltage balance logic, an improved LUT is established and explained for a three-level DTC scheme. Consequently, improved stator current (THD) and decrement in torque and flux ripples are observed. To make the system robust, model reference adaptive control (MRAC) based sensorless speed estimation algorithm is realized. The proposed DTC scheme is compared with a two-level inverter-fed and a three-level-inverter-fed DTC scheme without DC link voltage balance strategy. To carry out the analysis, MATLAB/Simulink environment is utilized. Moreover, to validate the simulation results, experimental analysis of the proposed technique is carried out using dSPACE1104.

Analysis of Input Voltage Switching Ripple in Three-Phase Four-Wire Split Capacitor PWM Inverters

Three-phase, four-wire split capacitor inverters are currently employed in many applications, such as photovoltaic systems, battery chargers for electric vehicles, active power filters, and, in general, in all grid-tied applications that deal with possible grid voltage and/or current unbalances. This paper provides a comprehensive evaluation of the capacitor-switching voltage ripple and dc-link switching voltage ripple for the three-phase, four-wire, split capacitor inverters. Specifically, analytical formulations of the peak-to-peak and rms values of the voltage ripples are originally pointed out in this paper and determined in the case of balanced three-phase and unbalanced (two-phase and single-phase) output (ac) currents. The obtained results can help in designing the considered inverter and sizing of the dc-link capacitors. Reference is made to the sinusoidal PWM modulation and sinusoidal three-phase output currents with an almost unity power factor, representing a grid-connected application. Extensive numerical simulations have been carried out to thoroughly verify all the analytical developments presented in this paper. Furthermore, some experimental tests, having balanced output currents on the ac side, have been accomplished, validating numerical simulations and analytical developments.

INFLUENCE OF CHARACTERISTICS OF A NONLINEAR TRANSFORMER TO WORK THE INVERTER

The article deals with the modes of switching on an inverter with a sinusoidal output voltage when working with a nonlinear transformer. The study is implemented by simulation modeling in Simulink Matlab. Simulation is carried out using the SPS model of a nonlinear transformer with various core magnetization curves. It is shown that a soft start of the inverter, performed by a gradual increase in the sinusoidal modulating voltage, eliminates in-rushes of the primary current and the magnetization current, regardless of the modulation voltage switching angle. The process of forming a hysteresis loop for a given magnetic flux is considered. The time diagrams of the direct starting-up the converter are given at various values of the modulation voltage initial phase for a core with a hysteresis loop. It is shown that the statistical characteristics of the inverter do not depend on the type of the transformer’s core magnetization curve.

A Transformer-Less High-Gain Inverter With Step-Up/Down and Single Energy-Processing Features

Many transformer-less pseudo dc-link inverters with step-up/down feature have been proposed to simplify circuit complexity and improve efficiency. Among them, the traditional boost converter is usually used to step up output voltage. In actuality, however, voltage gain will be limited by both the parasitic resistance of the power components and the reverse-recovery problems exhibited by the power diodes under a high duty ratio. Therefore, in order to develop grid-tied photovoltaic (PV) power systems with 220- V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> voltage, this article proposes a transformer-less high-gain step-up/down inverter. The proposed inverter is composed of a high-gain boost converter and a full-bridge unfolder. The input current is equally shared by the two boost inductors, so the conduction losses can be reduced to improve efficiency. A partial sinusoidal pulsewidth modulation (P-SPWM) controls the full-bridge unfolder to implement the step-down function. The proposed inverter requires only a single stage of energy processing to generate 220- V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> sinusoidal output voltage. Finally, a 1-kW laboratory prototype is built using careful analysis and design procedures. The experimental results are provided to verify the validity and feasibility of the proposed inverter.

Performance comparison of field oriented control based permanent magnet synchronous motor fed by matrix converter using PI and IP speed controllers

This paper focuses on modeling and closed-loop speed control of a three-phase Permanent Magnet Synchronous Motor (PMSM) fed by a Matrix Converter (MC) based on Field-Oriented Control (FOC). The model considers a set of a small input filter with supply impedance or cable effect, to improve the quality of the input current. A simplified form of the Venturini modulation algorithm is used for switching the matrix converter and a comparative study of two types of speed controllers is presented, namely a proportional integral (PI) and a proportional integral (PI) to improve performances of the drive system in transient and stable conditions. The overall drive system is simulated using Matlab/Simulink environment. The motor performance is evaluated under different operating conditions such as sudden changes in the load or changes in the angular speed reference. The results of the converter MC gives unlimited output frequency, sinusoidal input current and output voltage waveforms and unity input displacement factor. The IP controller is shown to achieve better performance of the speed control loop, with or without the load torque as compared to the PI classic controller.

Correction of the Photovoltaic System Control by the Addition of a Voltage Regulator in the Electrical Conversion Chain

The objective of this work is to meet the variations of the electrical energy needs by modifying the conventional topology of the conversion chain, at the same time to improve the operation of the photovoltaic system. This article focuses on improving the performance and efficiency of photovoltaic systems connected to the AC grid, through the use of advanced control algorithms (Sliding Mode control SMC and Fuzzy Logic Control FLC) for the control of DC/DC and DC/AC power conditioners. The control of the DC/DC converter allows the pursuit of the maximum power point MPPT of the photovoltaic generator with a view to a better utilization of the photovoltaic generator. The inverter control system is used to inject synchronized sinusoidal output current to the power grid and to improve the quality of energy injected into the grid. The original idea of this work is based on the insertion of a DC/DC BOOST voltage regulator in the conversion chain (between the battery and the inverter) to adjust the voltage transfer of the DC bus. This technique allows the provision of AC voltage for the sufficiency of the energy required by the control according to the need of the load.

A cost‐effective single‐phase semi flipped gamma type magnetically coupled impedance source inverters

SummaryThis paper presents a new two winding coupled inductor architecture for a semi magnetically coupled impedance source (SMCIS) inverter by connecting the coupled inductor windings in flipped gamma fashion. The proposed topology is derived from the conventional MCIS inverters. It can produce sinusoidal output voltage/current without using any shoot‐through operation and output LC filter, which improves the system reliability. Further, a doubly grounded feature, no start‐up inrush current, reduced component count, low input current ripple, continuous output currents, and small leakage currents are the major advantages of the proposed inverter. However, the proposed semi flipped gamma MCIS inverters still suffer from limited output voltage gain problem. The voltage‐boosting feature is added to the proposed inverter by connecting two converter modules in differential boost configuration through the embedded structure. The voltage‐boosting ability is the major advantage of this differential boost embedded configuration. It has flexibility in choosing a wide range of duty cycle operation from zero to one (whereas, the duty cycle was limited to 0.666 in case of semi‐Z‐source inverter [ZSI]). The modes of operation, design procedure, and feature comparisons of proposed inverters are discussed in this paper. Finally, the effectiveness of proposed inverters is validated through simulation and experimental results in terms of component count, voltage gain, and feature comparison.

Generation of energy from Solar and its protections

In this article, a seven-level inverter powered by solar has been proposed to achieve a sinusoidal output voltage with high efficiency and enhanced power quality. This system consists of active inverter and flipped condenser clamping. It gives output voltage level of 2/3. By connecting the switched condenser branch in the front or back end series to the inverter output a seven-level output voltage wave shape can be obtained with ample non-work switching states to match the voltage of switching condensers. The consequence of the proposed method is validated using MATLAB SIMULINK for simulation. Comparing with conventional seven-level inverter topology, the proposed design used a minimal number of switches using a basic modulation process. The demand for electricity that is so high in India might be a key driver for the use of renewable power as an option for energy requirements. To satisfy this need, this article introduces a solar smart flower layout and then modeled using the resources provided in the solid function system. And use a set Photovoltaic panels harvest additional power mostly during 12 pm to 2:00 Pm in Nigeria which resulted in less renewable energy. Consequently, there is a need to increase the energy consumption of PV solar panel by developing a solar tracker cannot be overlooked. Photovoltaic cells must be aligned with the sun in order to just get optimum energy.The microcontroller is being used to power the motor dependent on information gathered from the LDRs. The findings of this research have clearly demonstrated that the monitoring solar panel generates more electricity compared to a conventional panel. The location of solar panel including voltage was going to monitor by using IoT. Light Dependent Resistors LDRs are being used to detect the strength of lighting and thus the PV solar panel is appropriately addressed to control maximum energy. The system uses motors to regulate the amount of the solar panel. The microcontroller is being used to power the motor centered on signals obtained from the LDRs. The outcome of this work has demonstrated clearly that the monitoring solar panel generates more power compared to a conventional panel. The location of solar panel and volts was going to monitor through using IoT.

Design of a Novel Topology of Transformer-Less Cuk Inverter for Isolated Load Applications

This paper presents a new topology of single-stage inverter to generate quality sinusoidal output waveform without any additional boosting components. The proposed inverter is a combination of back-to-back two Cuk converters and hence, it is named as a cuk inverter. As per the inductor value, it can operate in continuous and discontinuous current mode. The sinusoidal output voltage can be raised or lowered with different duty ratio based on the load requirement. This Cuk inverter reduces the filter requirement in the output circuit. Further, to show the advantage of the proposed topology, a comparative study is carried out with conventional and recent converters in terms of number of switches, LC components and applications. The performance of the proposed topology is analyzed with MATLAB/Simulink tool and implemented as hardware to validate the simulated results.

Model Predictive Control of LC-Filtered Voltage Source Inverters With Optimal Switching Sequence

Voltage source inverters with output LC filter enable a sinusoidal output voltage with low harmonics, suitable for islanded ac microgrid or uninterruptible power supply applications. Conventional finite-set model predictive voltage control (MPVC) applies only a single switching vector per control period, leading to a variable switching frequency and significant output ripple. This article resolves these issues by proposing an improved MPVC with optimal switching sequence (OSS-MPVC). First, an improved vector switching sequence is defined, aiming to reduce the output-voltage ripple with a constant switching frequency. Then, to tackle the difficulty in extending the OSS to high-order systems due to the coupling effect of the output filter, a generalized “one-step estimation” solution is proposed, which directly associates the control-variable gradients with the vector switching sequence. To further enhance the output-voltage tracking accuracy, intersample dynamics are taken into account in the cost function. The control delay and dead-time compensation are also considered. Simulations and experimental results verify the feasibility of the proposed method.

Solar powered highly efficient Seven-level inverter with switched capacitors

In this article, a seven-level inverter powered by solar has been proposed to achieve a sinusoidal output voltage with high efficiency and enhanced power quality. This system consists of active inverter and flipped condenser clamping. It gives output voltage level of 2/3. By connecting the switched condenser branch in the front or back end series to the inverter output a seven-level output voltage wave shape can be obtained with ample non-work switching states to match the voltage of switching condensers. The consequence of the proposed method is validated using MATLAB SIMULINK for simulation. Comparing with conventional seven-level inverter topology, the proposed design used a minimal number of switches using a basic modulation process.

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.

Evolutionary algorithm based selective harmonic elimination for three-phase cascaded H-bridge multilevel inverters with optimized input sources

Multilevel inverters are finding wide application in electric drives, traction, flexible AC transmission systems (FACTS) and renewable energy systems. A cascaded H-bridge type multilevel inverter (CHBMLI) produces a near sinusoidal output voltage with lower switching stress and a higher conversion efficiency than the other types of MLIs. The Selective Harmonic Elimination (SHE) strategy is used to eliminate lower-order harmonic profiles and to regulate the fundamental component in the output voltage. SHE has the advantages of low switching frequency, low switching losses and low stress. In this paper, the modulation index and input voltage values are also considered as optimization variables along with the conventional switching angles to analyze the performance improvement in selective harmonic elimination. Heterogeneous Comprehensive Learning Particle Swarm Optimization (HCLPSO) and Gravitational Search Algorithm (GSA) algorithms are used to find the optimal switching angles, modulation index and input voltage source values for minimizing the lower-order harmonics present in the output voltage of seven-level and eleven-level CHBMLIs, while maintaining the fundamental component of the output voltage. The results obtained from MATLAB simulations and an experimental setup clearly indicate that the proposed HCLPSO-based multilevel inverter provides better performance when compared with GSA, firefly and Differential Search Algorithm (DSA)-based MLIs.