Multilevel Converters: An Enabling Technology for High-Power Applications

| Multilevel converters are considered today as the state-of-the-art power-conversion systems for high-power and power-quality demanding applications. This paper presents a tutorial on this technology, covering the operating principle and the different power circuit topologies, modulation methods, technical issues and industry applications. Special attention is given to established technology already found in industry with more in-depth and self-contained information, while recent advances and state-of-the-art contributions are addressed with useful references. This paper serves as an introduction to the subject for the not-familiarized reader, as well as an update or reference for academics and practicing engineers working in the field of industrial and power electronics.Ministerio de Ciencia y Tecnología DPI2001-3089Ministerio de Eduación y Ciencia d TEC2006-0386

Improving the Power Electronics Laboratory teaching/learning process: an interactive web tool

European Higher Education Area; Power Electronics Laboratory; educational methods Resumen: The forthcoming European Higher Education Area implies an important change in the teaching/learning process: it is necessary to get students more involved as well as to promote their independence and active participation. To achieve this objective, the new teaching methodologies aimed at more effective and appropriate learning for professional practice involve the use of audiovisual, computer and multimedia tools on the part of lecturers. Therefore, a web tool, based on a content management system, has been developed for the teaching in Power Electronics Laboratory. Moreover, the use of these multimedia tools makes possible to promote the students independence. Finally, the use of this web tool results in a very significant increase in the motivation students.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Power conversion for a modular lightweight direct-drive wind turbine generator

A power conversion system for a modular lightweight direct-drive wind turbine generator has been proposed, based on a modular cascaded multilevel voltage-source inverter. Each module of the inverter is connected to two generator coils, which eliminates the problem of DC-link voltage balancing found in multilevel inverters with a large number of levels.The slotless design of the generator, and modular inverter, means that a high output voltage can be achieved from the inverter, while using standard components in the modules. Analysis of the high voltage issues shows that isolating the modules to a high voltage is easily possible, but insulating the generator coils could result in a signicant increase in the airgap size, reducing the generator effciency. A boost rectier input to the modules was calculated to have the highest electrical effciency of all the rectier systems tested, as well as the highest annual power extraction, while having a competitive cost. A rectier control system, based on estimating the generator EMF from the coil current and drawing a sinusoidal current in phase with the EMF, was developed. The control system can mitigate the problem of airgap eccentricity, likely to be present in a lightweight generator. A laboratory test rig was developed, based on two 2.5kW generators, with 12 coils each. A single phase of the inverter, with 12 power modules, was implemented, with each module featuring it's own microcontroller. The system is able to produce a good quality AC voltage waveform, and is able to tolerate the fault of a single module during operation. A decentralised inverter control system was developed, based on all modules estimating the grid voltage position and synchronising their estimates. Distributed output current limiting was also implemented, and the system is capable of riding through grid faults

Distributed control of a fault tolerant modular multilevel inverter for direct-drive wind turbine grid interfacing

Modular generator and converter topologies are being pursued for large offshore wind turbines to achieve fault tolerance and high reliability. A centralized controller presents a single critical point of failure which has prevented a truly modular and fault tolerant system from being obtained. This study analyses the inverter circuit control requirements during normal operation and grid fault ride-through, and proposes a distributed controller design to allow inverter modules to operate independently of each other. All the modules independently estimate the grid voltage magnitude and position, and the modules are synchronised together over a CAN bus. The CAN bus is also used to interleave the PWM switching of the modules and synchronise the ADC sampling. The controller structure and algorithms are tested by laboratory experiments with respect to normal operation, initial synchronization to the grid, module fault tolerance and grid fault ride-through

Housing equilibrium price framework for Malaysian middle Class group in affordable housing market

Failure in getting housing equilibrium price for affordable housing market has become a hot topic that is often discussed in the press due to the imbalance between housing demanded and supplied. The basic purpose of the research was to investigate the relationship between macroeconomic housing demand and supply detenninant factors and affordable housing needs in Malaysia, and to dete1111ine the equilibrium house price for middle-class income in the affordable housing market. The research involved the development of theoretical framework by synthesising the models and framework developed by past researchers on the housing equilibrium price framework. It also uses time series analysis together with regression analysis to collect and analyse data. As initial, 371 respondents from household's side and 32 respondents from developer's side in Melaka Tengah were selected as samples as case study in Melaka. During data analysed, around 200 questionnaires from households and 32 questionnaires from developers can be used. The data was analysed using SPSS software to investigate the relationship between macroeconomic housing demand and supply determinant factors towards the needs f and supply of afordable housing market. From the investigation, current house price, monetary status and population changes are the most critical factors that lead to the needs of affordable housing supplies. Meanwhile, developers put the interest rate, government interventions and population changes as the catalyst to develop the affordable housing projects. On the other hand, the empirical data of housing prices are collected from NAPIC from 2006 to 2015. The equilibrium price calculated from the sales perfonnance within four quarter reported by NAPIC is examined using linear regression method. Based on these themes, the research contended that the housing equilibrium price can be achieved using empirical data from demand and supply with supported from current house price, monetary status and population changes the interest rate, government interventions and population changes. Hence, government is the key player and be a pulling effect in controlling the housing price by using the housing demand and supply determinant factor to create a win-win situation between middle-class income and housing developers

Coordinated Control Of A Back-ToBack HVDC Link

This thesis will present the mathematical model, controller design, simulation, and analysis of a complete back-to-back VSC HVDC system. There will be two stations of Voltage Source Converter (VSC) located back-to-back. One station shall act as a rectifier and another one will be the inverter. This will allow power transfer from one station (rectifier) to other (inverter) through a DC link. A back-to-back VSC HVDC has the advantages compare to the AC transmission because it can allow power transfer without having to synchronize both of the station or networks. In order to complete a back-to-back VSC HVDC system, it will require a d-q current controller, DC voltage controller, active/reactive power controller and DC power (DC current controller). A simulation and analysis shall be executed for each of the controller and response of voltage and current for a complete system. The simulation result will show the dynamic control of the rectifier and inverter is achieved with fast response

Design and Comparison of Feasible Control Systems for VSC-HVDC Transmission System

This Paper presents the modeling and control of two-terminal Voltage Source Converter Based High Voltage Direct Current (VSC-HVDC) transmission system which are achieved using the software of PSCAD/EMTDC. There are two control designs for VSC-HVDC system in this project: 1. Phase and magnitude control design, 2. Control design under d-q frame. The VSC-HVDC system is operated successfully by using these two control methods respectively. Finally, this paper illustrates the analysis of steady state tests and dynamic load tests of VSC-HVDC system, as well as the comparison of the two control methods

A PWM current source-based DC transmission system for multiple wind turbine interfacing

A pulsewidth modulation (PWM) current source wind energy conversion system based on a parallel configuration for high voltage direct current application is proposed. A comparison between the parallel and series configurations for current source-based systems is investigated, which shows the merits of the proposed system. A new control technique for the PWM current source inverter is proposed. It can effectively control the average dc-link voltage with a feed-forward loop, while independently controlling reactive power according to grid code requirements. The system simulation confirms the performance of the proposed system with no interaction between wind turbine modules and satisfying performance with grid integration. Practical implementation further verifies the proposed inverter control. Finally, a brief comparison between conventional line-commutated converter-based systems and the proposed PWM current source converter-based system is presented

Model predictive control of a single-phase five-level VIENNA rectifier

Power converters and control strategies are very vital for the increasing sustainability of the power grid targeting smart grids. In these circumstances, it is proposed a novel single-phase five-level (SP5L) VIENNA rectifier digitally controlled by a model predictive control (MPC) with fixed switching frequency, which can be useful for a variety of applications with a robust current tracking. The proposed SP5L VIENNA rectifier is an advancement of the classical three-level VIENNA rectifier, also contributing to preserve power quality, and exhibiting the advantage of operating with more voltage levels at the expense of few additional switching devices. The proposed topology is introduced and correlated with the classical solutions of active rectifiers. The operation principle is introduced and used to describe the MPC, which is given in detail, as well as the necessary modulation strategy. The results were obtained for a set of various operating conditions, both in terms of reference of current and grid-side voltage, as well as in steady-state and transient-state, proving the benefits of the proposed SP5L VIENNA rectifier and the accurate and precise use of the MPC to control the grid-side current.This work has been supported by FCT -Fundacao para a Ciencia e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020. This work has been supported by the FCT Project newERA4GRIDs PTDC/EEI-EEE/30283/2017, and by the FCT Project DAIPESEV PTDC/EEI-EEE/30382/2017. Tiago Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by FCT