Multilevel high power converters for reversible power flow between utilities and power pool transmission corridor

Abstract: Multilevel converters have emerged as the state of the art high power conversion for applications in reversible power flow. Electric power could be tapped from or injected to the grid regardless of the discrepancies in voltage levels, frequency, phase number and different modes of operation of the grid and the system. This paper presents an overview of different topologies of multilevel converters and modulation strategies with a verification of back-to-back neutral point converter for bidirectional power flow applicatio

High-performance motor drives

This article reviews the present state and trends in the development of key parts of controlled induction motor drive systems: converter topologies, modulation methods, as well as control and estimation techniques. Two- and multilevel voltage-source converters, current-source converters, and direct converters are described. The main part of all the produced electric energy is used to feed electric motors, and the conversion of electrical power into mechanical power involves motors ranges from less than 1 W up to several dozen megawatts

Review on power quality solution technology

This paper presents a comprehensive study of various possible solutions for power quality improvement in common applications and supply system. This includes improved power quality converters (IPQC), multi-pulse converters, active compensation, passive compensation and their hybrid configurations. Various configurations and topologies of custom power devices such as DSTATCOM (Distribution Static Compensator), DVR (Dynamic Voltage Restorer) and UPQC (Unified Power Quality Compensator) are also described in detail. Main applications of these devices are for reactive power compensation, harmonic elimination, voltage sag/swell mitigation, voltage regulation, load balancing, neutral current reduction etc. Many such cases of power quality problems have been taken up and suitable solutions have been identified for those cases. As an example, a model of DSTATCOM is developed and its performance is presented for a distribution system feeding nonlinear loads

Multilevel inverters for renewable energy systems

Voltage source inverters have become widely used in the last decade primarily due to the fact that the dangers and limitations of relying on fossil fuel based power generation have been seen and the long term effects felt especially with regards to climate change. Policies and targets have been implemented such as from the United Nations climate change conference (COPxx) concerning human activities that contribute to global warming from individual countries. The most effective way of reducing these greenhouse gases is to turn to renewable energy sources such as the solar, wind etc instead of coal. Converters play the crucial role of converting the renewable source dc power to ac single phase or multiphase. The advancement in research in renewable energy sources and energy storage has made it possible to do things more efficiently than ever before. Regular or 2 level inverters are adequate for low power low voltage applications but have drawbacks when being used in high power high voltage applications as switching components have to be rated upwards and also switch between very high potential differences. To lessen the constraints on the switching components and to reduce the filtering requirements, multilevel inverters (MLI's) are preferred over two level voltage source inverters (VSI's). This thesis discusses the implementation of various types of MLI's and compares four different pulse width modulation (pwm) techniques that are often used in MLI under consideration: three, five, seven and nine level inverters. Harmonic content of the output voltage is recorded across a range of modulation indices for each of the three popular topologies in literature. Output from the inverter is filtered using an L only and an LC filter whose design techniques are presented. A generalized prediction algorithm using machine learning techniques to give the value of the expected THD as the modulation index is varied for a specific topology and PWM switching method is proposed in this study. Simulation and experimental results are produced in five level form to verify and validate the proposed algorithm

MLI Power Topologies and Voltage Eminence: an Exploratory Review

Due to their performances and inherent edges, particularly in medium-voltage and dynamic applications, multilevel inverters have received associate degree increasing attention in universe industrial applications. This paper deals with a review of the most structure electrical converter topologies additionally their commonest derived and hybrid structures quoted in previous analysis works. It additionally encompasses associate degree investigation on voltage harmonic elimination and THD estimation. For that reason, the paper summarizes the foremost relevant modulation techniques used to date to boost the output voltage quality. Theoretical formulas elicited within the literature, for calculating the output voltage THD higher and lower bounds area unit reportable and verified by adequate simulations

Active Harmonic Elimination in Multilevel Converters

The modulation technique for multilevel converters is a key issue for multilevel converter control. The traditional pulse width modulation (PWM), space vector PWM, and space vector control methods do not completely eliminate specified harmonics. In addition, space vector PWM and space vector control method cannot be applied to multilevel converters with unequal DC voltages. The carrier phase shifting method for traditional PWM method also requires equal DC voltages. The number of harmonics that can be eliminated by the selective harmonic elimination method is restricted by the number of unknowns in the harmonic equations and available solutions. For these reasons, this thesis develops a new modulation control method which is referred to as the active harmonic elimination method to conquer some disadvantages for the existing methods. The active harmonic elimination method contributes to the existing methods because it not only generates the desired fundamental frequency voltage, but also completely eliminates any number of harmonics without the restriction of the number of unknowns in the harmonic equations and available solutions for the harmonic equations. Also the active harmonic elimination method can be applied to both equal DC voltage cases and unequal DC voltage cases. Another contribution of the active harmonic elimination method is that it simplifies the optimal system performance searching by making a tradeoff between switching frequency and harmonic distortion. Experiments on an 11-level multilevel converter validate the active harmonic elimination method for multilevel converters

Industrial and Technological Applications of Power Electronics Systems

The Special Issue "Industrial and Technological Applications of Power Electronics Systems" focuses on: - new strategies of control for electric machines, including sensorless control and fault diagnosis; - existing and emerging industrial applications of GaN and SiC-based converters; - modern methods for electromagnetic compatibility. The book covers topics such as control systems, fault diagnosis, converters, inverters, and electromagnetic interference in power electronics systems. The Special Issue includes 19 scientific papers by industry experts and worldwide professors in the area of electrical engineering

Design and Application of Hybrid Multilevel Inverter for Voltage Boost

Today many efforts are made to research and use new energy sources because the potential for an energy crisis is increasing. Multilevel converters have gained much attention in the area of energy distribution and control due to its advantages in high power applications with low harmonics. They not only achieve high power ratings, but also enable the use of renewable energy sources. The general function of the multilevel converter is to synthesize a desired high voltage from several levels of dc voltages that can be batteries, fuel cells, etc. This dissertation presents a new hybrid multilevel inverter for voltage boost. The inverter consists of a standard 3-leg inverter (one leg for each phase) and H-bridge in series with each inverter leg. It can use only a single DC power source to supply a standard 3-leg inverter along with three full H-bridges supplied by capacitors or batteries. The proposed inverter could be applied in hybrid electric vehicles (HEVs) and fuel cell based hybrid electric vehicles (FCVs). It is of voltage boosting capability and eliminates the magnetics. This feature makes it suitable for the motor running from low to high power mode. In addition to hybrid electric vehicle applications, this paper also presents an application where the hybrid multilevel inverter acts as a renewable energy utility interface. In this dissertation, the structure, operation principle, and modulation control schemes of the proposed hybrid multilevel inverter are introduced. Simulation models and results are described and analyzed. An experimental 5 kW prototype inverter is built and tested

Modified Cascaded H-Bridge Multilevel Inverter Using Particle Swarm Optimization

For more than two decades,multilevel inverters in different topologies and control strategies have been involved in many applications.In contrast to conventional three-level inverters,they are more efficient and better suited for applications requiring high power and high voltage levels.The current multilevel inverter topologies available in the market include diode clamped or neutral point clamped (NPC),capacitor clamped or flying capacitor (FC), and cascaded H-bridge (CHB).It is essential to produce an effective power converter from the perspective of cost,efficiency and output quality.These factors have lead to develop a new family of multilevel inverters known as modified CHB-MLIs of a single and three phases for five,nine and thirteen levels.This topology of the modified inverters requires fewer components compared to existing inverters (particularly in the higher levels) and requires fewer carrier signals and gate drives. Therefore,the overall cost and complexity are greatly reduced,particularly for higher output voltage levels.An important issue in the power electronic converters is the modulation control method in order to produce high quality output with a minimum distortion.As there exist many strategies for modulation, still the low-switching frequency technique is widely accepted in higher power applications.There are different optimization aims for different applications utilizing the low-switching frequency technique it is possible to increase the number of output voltage levels and produce a better sinusoidal output waveform and efficiency.The modified CHB-MLIs for five, nine and thirteen levels have a reduced number of DC power supplies and switches when compared to the conventional CHB topologies designed for the same number of voltage levels.The aim of this thesis is to investigate the performance of modified CHB-MLIs of a single and three phases for five,nine and thirteen levels based on cascaded multilevel inverter using low-switching frequency modulation scheme.The modulation method for obtaining the optimum switching angles based on Newton Raphson (NR) and Particle Swarm Optimization (PSO)control techniques have been proposed.A NR and PSO control techniques were presented for selective harmonics elimination (SHE) solution in a modified CHB-MLIs.These control techniques have been implemented through closed-loop control system using DSP TMS320F2812.In this thesis, the complete switching angles of the SHE has been developed by using a heuristic optimization technique namely PSO by solving the non-linear equation of the output voltage waveform and later validated with the conventional method NR.To validity of a low power prototype of the modified CHB-MLIs have been designed and implemented;analytical,simulation,and experimental results have been provided.The relative merits of the proposed modulation scheme based on the NR and PSO have been assessed based on modified inverters output quality and efficiency.Investigations of the proposed modulation scheme based on PSO have been revealed that the switching pattern of the adopted inverters has the capability of producing output voltage with minimal THD and high efficiency of the modified inverters.The results acquired from the simulation results the superiority of PSO over the conventional methods NR,where the THD reduction values in the three developed CHB-MLI namely five-level, nine level,and thirteen level are 15%,7.8%,and 5.2%, respectively