Independent Dc Sources Research Articles

Multilevel Converter Based on Series and Parallel Connections Using Floating Capacitor

The series connections of converter cells are interesting for high voltage applications, while parallel connections are for high current applications. The series/parallel is interesting for medium voltage and current applications because they present semiconductor devices with a lower rating in both voltage and current, thus, reducing the cost and size of the converters. This article investigates the configuration of a single-phase multilevel DC-AC converter based on series and parallel connections of H-bridges using floating capacitors to reduce the number of independent DC sources. The use of the floating capacitor has the limitation of working in certain operating regions. This article investigates which regions can work with floating capacitors and presents the mathematical model, general control strategy, pulse width modulation (PWM) strategies, and loss comparison with conventional series or parallel systems. Simulations and experimental results are presented to validate the control and PWM strategies used.

Design of a 21‐level multilevel inverter with minimum number of devices count

SummaryMultilevel inverters (MLIs) have attracted the attention of researchers for their needs in industrial applications, renewable energy systems, and electric vehicles. MLIs require a large number of power electronic components to synthesize higher levels at the output voltage. However, overuse of power electronic devices increases the complexity, losses, and cost of MLIs. In this study, a new MLI has been proposed with a reduced number of power switches. The basic unit of the proposed MLI comprises only three independent DC sources and 10 switches (eight unidirectional and two bidirectional) to produce 21 levels at the output voltage waveform. The nearest level control (NLC) modulation method has been used to produce gate pulses. Furthermore, three extension topologies have been proposed to generate a higher number of levels, and the extension parameters have been compared with recently introduced and conventional topologies. The comparative study shows that the proposed MLI topology requires fewer components in terms of power electronics parameters than the others. On the other hand, the presented first extension study that can be used for all non‐extendable basic units is one of the prominent values of the study. Simulation studies showing modulation methods, switching patterns, and signal outputs were performed with Matlab/Simulink. A prototype of the proposed main module has been realized and tested in the laboratory with an FPGA processing board. Experimental results have been verified with simulation results, and the performance of the proposed topology has been proven.

Some aspects of comparing the operational properties of synchronous machines with a conventional and two mutually shifted excitation windings

A comparative analysis of the operational properties of traditional and two-valve synchronous machines with a rotor, having a reciprocating axis, excited from independent regulated DC sources, is generalized. On the basis of research, it has been shown that the use of a control quadrature excitation winding significantly improves the performance of synchronous machines at low costs for its manufacture. The authors have shown a significant improvement in the performance of machines with different operating modes based on the results of theoretical and experimental studies carried out on synchronous machines with a rotating axis of magnetic saturation, attached to various designs of quadrature excitation winding. It has been recognized that neglecting magnetic saturation in performance calculations for synchronous machines leads to significant estimation errors properties of the studied machine. In addition, the advantages of synchronous machines with sine-cosine field winding are shown. With an insignificant complication of the manufacturing technology, it opens the way to solving the problem of creating energy-saving turbine generators, which have a property that is very important for the practice of operation, i.e. an almost unchanged (sinusoidal) shape of the resulting magnetic field in the air gap of the machine within the allowable range of load variation under steady-state symmetric modes.

A novel reduced switch single‐phase five‐level inverter

AbstractConventional multilevel inverters (MLI) incorporate many independent dc sources and switches, which adds to the overall system's cost and complexity. This article presents a detailed analysis of a reduced switch single‐phase five‐level inverter for medium‐ and high‐power applications. The comparison of the proposed topology with traditional and recently developed MLI topologies shows that the topology proposed has a smaller number of circuit elements, isolated dc sources, and voltage stress of half of the supply voltage on 50% of switches. Reducing the number of components and sources reduces the complexity and total cost of the inverter. These reduced switches voltage stresses increase the overall system reliability. The MATLAB/SIMULINK simulations for different load changes were carried out for analysis in software mode. The scaled‐down prototype is used for the validation of simulation analysis. The components comparison was also carried out to list the advantages of this topology over other MLI configurations.

Design of a multi-level inverter for applications in distributed generation

At present, the use of electricity generation systems through alternative sources of energy is continuously increasing, due to the increase in global energy demand, and a trend in which CO2 emissions are being reduced. As a result of these trends, the implementation of these energy sources has increased steadily in the last quarter of a century. For the integration of these alternative forms of electricity generation to be adequate, especially in the use of solar energy and wind energy, because it is necessary to condition them, it has become latent the need to implement electronic power devices such as inverters (continuous current - alternating current), which currently seek to have small, medium and high power sources of electricity, which meet the requirements of efficiency, quality and safety established by the Commission Federal de Electrician (CFE). In the present work, the design and the implementation of a DC/AC converter (direct current - alternating current) using a topology for the inverter of cascaded H - bridges with independent DC sources in a multilevel configuration of 11 voltage levels of control. Applying the technique of the Selective Harmonic Elimination modulation, technique that allows it by Fourier series analysis appropriately chooses the switching angles for the elimination of harmonics of the most significant low frequency.

A Single-Stage Multi-Port Buck-Boost Inverter

This article presents a novel inverter topology with a multi-port structure, which aims to connect two independent dc sources to a three-phase load by using single-stage power conversion. The proposed inverter has been developed to be used in hybrid renewable energy applications such as photovoltaic (PV), fuel cell (FC), and battery energy storage systems. Compared to the conventional hybrid dual-source inverters that use a multi-input dc-dc converter to provide a dc-link voltage at the input of the inverter stage, the proposed dual-source inverter uses an integrated dc-ac power conversion stage. The conventional topologies use bulky electrolytic capacitors at the input of the inverter stage, which leads to lower voltage gain and reliability due to high parasitic ESR/ESL and short lifetime of these capacitors. Moreover, compared to existing multi-port voltage source inverters, the proposed topology uses lower semiconductors, cost, and weight and has higher voltage gain. Besides, the proposed topology draws continuous current from both input ports and there is magnetic isolation between the input sources, which makes it suitable for hybrid PV and FC systems. In the proposed topology, two interlocked impedance networks are used, which are connected by coupled inductors, diodes, and capacitors. The proposed topology uses a simple switching method that is implemented with low-cost microcontrollers. The analysis and performance of the proposed inverter are verified through both computer simulations and experimental results of a 600 W-50 Hz laboratory prototype using the simple boost-SPWM modulation method.

Calculation of Optimal Switching Angles for a Multilevel Inverter Using NR, PSO, and GA- a Comparison

Currently, multilevel inverters have been increased the number of applications in the industrial sector and renewable energy sources. Among its characteristics, the most remarkable are modular design, high performance, and low harmonic distortion in the output voltage waveform. For this paper, a single-phase Cascade H-Bridge Multilevel Inverters (CHB-MLI or CMLI) topology with independent DC sources, has been selected for the case study. Analyzing three scenarios: 5-level, 7-level, and 9-level applying the concept of the Optimized Harmonic Stepped-Waveform (OHSW) and comparing the results between the Selective Harmonic Eliminated-Pulse Width Modulation (SHE-PWM) and the Optimal Minimization of the Total Harmonic Distortion (OMTHD) are also presented. To compare the results obtained with classical and nature-inspired optimization methods, three techniques are used to solve transcendental nonlinear equations for the problem of Total Harmonic Distortion (THD) minimization: Newton Raphson (NR), Genetic Algorithm (GA), and Particle Swarm Optimization (PSO), which have been widely used for the problems of THD minimization in multilevel inverters.

Modelling of DVR with Artificial Intelligence for Compensate the Voltage Sag, Swell and Flickers by Using SVPWM Switching Techniques in Distribution Lines

In this research proposes FLC and Artificial Neural Network (ANN) based on Dyanamic Voltage Controller (DVR) along with d q o transformation for power qulity improvement in a distribution system. Design a 9levels CHMLI based on Custom Power device with SVPWM techniques. Distribution needs to protect against the harmonics such as sag, swell and flickers are affect on standard pure power supply at the end of the load. These power quality issues are minimised with voltage injection using DVR.The designed inveter to reduced the voltage switching losses and stresses of semiconductor devices. Here used single DC voltage source with a series connection of 4 capacitors for self balancing purpose, 3 diodes,output voltage levels and Cascaded H-bridge cell. the proposed 9 level CHMLI inverter citcuit to helps reducing the number of independent voltage dc sources and IGBTS. The harmonics are less in the output voltage proposed work (new topologies)compared to conventional topology. A comparision of FLC and ANN with THD and Power Factor results and study. It has been carried out to analyse through MATLAB / SIMULINK Software.

THD analysis for symmetrical five level and seven level cascaded multilevel inverter

Total Harmonic Distortion (THD) is one of the problems in the multilevel inverter. This paper discussed a brief review of THD in different cascaded H-bridge multilevel inverter topologies of five levels and seven levels at the output waveforms. The five levels inverter contains eight switches while seven levels inverter used twelve switches. Each single H-bridge inverter circuit is fed by equally independent DC source for both inverters. The inverter uses MOSFET as the switching point and acts as the controller for a fundamental switching operation. The switching value has been set at the gating block to control the operation of the MOSFET switching. Several waveforms and simulation findings are provided to validate the quality of the proposed topology.

Advanced Single-Phase Nine-Level Converter for the Integration of Multiterminal DC Supplies

This paper presents a new symmetrical single-phase nine-level dc–ac converter for the applications of distributed generation systems. The proposed multilevel inverter (MLI) utilizes four independent dc sources to generate the nine output voltage levels considering a reduced number of switching devices. The proposed inverter consists of main and auxiliary circuits. The main circuit is a single H-bridge circuit, which is responsible for output voltage polarity. The auxiliary circuit consists of a special combination of switching devices, which are used to synthesize the multilevel output voltage. The merits of the proposed MLI are: increased output voltage levels at reduced number of switching devices, low switching loss, low total harmonic distortion, low dv/dt stress on the switches, and hence, low ratings of the switching devices, and low cost. The effectiveness of the proposed MLI and its pulsewidth modulation switching pattern has been verified experimentally by using a laboratory prototype controlled by DSPACE-1103.

A Single-Stage Buck-Boost Three-Level Neutral-Point-Clamped Inverter with Two Input Sources for the Grid-Tied Photovoltaic Power Generation

This paper proposes a novel single-stage buck-boost three-Level neutral-point-clamped (NPC) inverter with two independent dc sources coupled for the grid-tied photovoltaic (PV) application, which can effectively solve the unbalanced operational conditions generally appearing between two independent PV sources. The proposed control scheme can simultaneously guarantee the maximum power point (MPP) operation of both PV sources and maintain the output waveform quality. Compared to the traditional two-stage PV inverter, the proposed NPC inverter could reduce the PV array voltage requirement and the voltage rating of dc-link capacitors; also it shows advantages in operational efficiency. MATLAB simulations and experimental results are presented to examine the performance of the proposed three-level NPC inverter.

On the Concept of the Multi-Source Inverter for Hybrid Electric Vehicle Powertrains

This paper presents an inverter topology named the multi-source inverter that aims to connect several independent DC sources to the same AC output using a single stage of conversion. This power converter has been developed for applications, such as electrified powertrains. Compared to the conventional hybrid powertrains that use a DC/DC converter to provide an adaptable voltage to the load, the multi-source inverter can drive a traction motor from variable DC voltages without the use of an additional power converter. Hence, the high power DC/DC converter can be dissociated from the traction mode and its use will be restricted to the engine $^{\prime }$ s start-up and regenerative braking, allowing a significant reduction of its power rating from tens of kWatts to a few kWatts. The overall efficiency of the electrified traction drive can also be improved due to the single conversion stage between the battery and the motor. In this paper, the multi-source inverter topology is introduced and its different operating modes are determined through the study of the inverter circuit. Closed-loop control simulations and experiments with a scaled-down prototype and an induction motor were performed to validate the effectiveness of the proposed topology and concept.

Coupled-Inductor-Based Aalborg Inverter With Input DC Energy Regulation

Due to the global environmental issues and energy crisis, the injection of renewable energy sources (RESs) into the power system is continuously increasing. As the interface between RESs and power grid, grid-tied inverters using MOSFET switches, without traditional line frequency transformers, show some potential advantages, in terms of low cost, high efficiency, and lightweight and small size. Among several proposed configurations, the Aalborg inverter was proposed as a new family of high efficiency MOSFET-switch-based hybrid source inverters. For a conventional “half bridge” type Aalborg inverter, due to the imbalance of two independent dc sources, the input dc energies may not be fully utilized, which may reduce the efficiency of whole system. In order to extract the maximum energy from two independent dc sources, a coupled-inductor-based “half bridge” type Aalborg inverter is proposed in this paper. The principle of operation is presented and demonstrated through equivalent circuits. The effectiveness of a new energy balancing technique has been validated through simulations and experiments on a 110 V/ 500 W prototype.

Cascaded H-Bridge with Single DC Source and Regulated Capacitor Voltage

Multilevel power electronic converter has wide range of applications. In multilevel power electronic converters the output can be synthesized by combining several DC voltage sources. Cascade H-Bridge multilevel inverter generally requires more number of DC sources. An alternative option is to replace all the DC sources feeding H-Bridge cells with capacitors, leaving only one H-Bridge cell with a real DC sources. But balancing the capacitor voltage is challenging. In this paper a new control method for cascade H-bridge multi level inverter fed with only one independent DC source is presented. Simulation results support the proposed control method.

Capacitor Voltage Regulation in Single-DC-Source Cascaded H-Bridge Multilevel Converters Using Phase-Shift Modulation

Cascaded H-bridge multilevel power electronic converters generally require several dc sources. An alternative option is to replace all the separate dc sources feeding the H-bridge cells with capacitors, leaving only one H-bridge cell with a real dc voltage source. This will yield a cost-effective converter. However, the required capacitor voltage balancing is challenging. In this paper, using the phase-shift modulation approach, a new control method for cascaded H-bridge multilevel converters fed with only one independent dc source is presented. The proposed method has a wide voltage regulation range for the replacement capacitors in the H-bridge cells. Experimental and simulation results support the proposed control method.

Research of Mining STATCOM Based on Hybrid Multilevel H-bridge Inverter

The paper presents a new STATCOM system based on H-bridge inverter. It can be used in mine power network. It has been commonly verified for the positive effects of SVG on the reactive power compensation and voltage fluctuation suppression. This paper focuses on a generalized structure of multilevel power converter where individual voltage sources are not necessarily the same. The cascade H-bridge consists of two cells, high-voltage cell and low-voltage cell. The high-voltage cell is responsible for voltage lifting, while the low-voltage cell is responsible for PWM modulation. If two cells are cascaded with DC voltages in a ratio of 2:1, the single-phase output voltage can reach 7 levels. Increasing voltage levels of output waveform can bring up AC current quality, optimize harmonic spectrum and enhance converter efficiency. The hybrid multilevel is characterized by per-phase series connection of a high-voltage H-bridge converter and a low-voltage H-bridge converter. Due to the different capacitor voltage, it is a key problem as to how to maintain the capacitor’s voltage at a reference level. Independent DC source can effectively ensure the DC voltage. Through the reactive power compensation technology, the three-phase voltage and current can remain at the same phase.

MAGY: An innovative high voltage–low current power supply for gyrotron

From the electrical point of view, the body and the anode of high power gyrotrons behave as capacitive loads. A highly dynamic power supply is, therefore, hard to achieve. The MAGY concept (Modulator for the Anode of a triode type GYrotron) embodies an innovative solution to manage the capacitive current ensuring a very low ripple on the output voltage. It consists of a series of independent, bi-directional and regulated DC sources. Compared to existing topologies, this solution requires a smaller number of power modules. It avoids internal high frequency modulation and simultaneously offers high resolution of the output voltage and a wide range of operating scenarios.

Polyphase converter for induction motor control using the stator core saturation

This paper presents a new polyphase converter using saturation of the stator core of the induction motor. In this case, the commutation is performed by the saturation of the stator core even if the magnetic characteristic of the stator core is not of a sharp saturation. In order to compensate the effect of the slow saturation of the stator core, the base currents of the main transistors are supplied by independent dc sources. By changing the voltage of the dc sources, the ratio of the output voltage to the oscillation frequency can be arbitrarily controlled. The oscillation frequency is derived theoretically by idealizing each element of the converter. The phase rotation of the output voltages is determined by a simple R-C network with an auxiliary transistor.