[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Multilevel converters have been under research and development for more than three decades and have found successful industrial application. However, this is still a technology under development, and many new contributions and new commercial topologies have been reported in the last few years. The aim of this paper is to group and review these recent contributions, in order to establish the current state of the art and trends of the technology, to provide readers with a comprehensive and insightful review of where multilevel converter technology stands and is heading. This paper first presents a brief overview of well-established multilevel converters strongly oriented to their current state in industrial applications to then center the discussion on the new converters that have made their way into the industry. In addition, new promising topologies are discussed. Recent advances made in modulation and control of multilevel converters are also addressed. A great part of this paper is devoted to show nontraditional applications powered by multilevel converters and how multilevel converters are becoming an enabling technology in many industrial sectors. Finally, some future trends and challenges in the further development of this technology are discussed to motivate future contributions that address open problems and explore new possibilities.

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Recent Advances and Industrial Applications of Multilevel Converters

This paper presents a technology review of voltage-source-converter topologies for industrial medium-voltage drives. In this highly active area, different converter topologies and circuits have found their application in the market. This paper covers the high-power voltage-source inverter and the most used multilevel-inverter topologies, including the neutral-point-clamped, cascaded H-bridge, and flying-capacitor converters. This paper presents the operating principle of each topology and a review of the most relevant modulation methods, focused mainly on those used by industry. In addition, the latest advances and future trends of the technology are discussed. It is concluded that the topology and modulation-method selection are closely related to each particular application, leaving a space on the market for all the different solutions, depending on their unique features and limitations like power or voltage level, dynamic performance, reliability, costs, and other technical specifications.

Multilevel Voltage-Source-Converter Topologies for Industrial Medium-Voltage Drives

http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

Cascaded multilevel inverters synthesize a medium-voltage output based on a series connection of power cells which use standard low-voltage component configurations. This characteristic allows one to achieve high-quality output voltages and input currents and also outstanding availability due to their intrinsic component redundancy. Due to these features, the cascaded multilevel inverter has been recognized as an important alternative in the medium-voltage inverter market. This paper presents a survey of different topologies, control strategies and modulation techniques used by these inverters. Regenerative and advanced topologies are also discussed. Applications where the mentioned features play a key role are shown. Finally, future developments are addressed.

A Survey on Cascaded Multilevel Inverters

A generalization of the PWM (pulse width modulation) subharmonic method for controlling single-phase or three-phase multilevel voltage source inverters (VSIs) is considered. Three multilevel PWM techniques for VSI inverters are presented. An analytical expression of the spectral components of the output waveforms covering all the operating conditions is derived. The analysis is based on an extension of Bennet's method. The improvements in harmonic spectrum are pointed out, and several examples are presented which prove the validity of the multilevel modulation. Improvements in the harmonic contents were achieved due to the increased number of levels. >

A new multilevel PWM method: a theoretical analysis

The converter topologies identified as diode-clamped multilevel (DCM) or, equivalently, as multipoint clamped (MPC), are rarely used in industrial applications, owing to some serious drawbacks involving mainly the stacked bank of capacitors that constitutes their multilevel DC link. The balance of the capacitor voltages is not possible in all operating conditions when the MPC converter possesses a passive front end. On the other hand, in AC/DC/AC power conversion, the back-to-back connection of a multilevel rectifier with a multilevel inverter allows the balance of the DC-link capacitor voltages and, at the same time, it offers the power-factor-correction capability at the mains AC input. An effective balancing strategy suitable for MPC conversion systems with any number of DC-link capacitors is presented here. The strategy has been carefully studied to optimize the converter efficiency. The simulation results related to a high-power conversion system (up to 10 MW) characterized by four intermediate DC-link capacitors are shown.

Diode-clamped multilevel converters: a practicable way to balance DC-link voltages

The use of energy storage devices such as batteries or supercapacitors is almost mandatory in fuel cell hybrid electric vehicles, in order to guarantee load leveling, assuring braking energy recovery and good performances in transient operations. To this end, converters with bidirectional power flows are needed to connect the accumulators to the dc-link of the motor drive system. In this paper, a new conversion structure for the bidirectional interfacing of two dc voltage sources with a higher voltage dc-link is presented, where only three controllable power electronic switches are needed and where the only limit is that the sum of the two dc voltages must be lower or equal than the motor drive dc-link voltage. The analysis of the converter structure, the control and modulation systems that have been developed, and simulations and experimental results are reported

New DC–DC Converter for Energy Storage System Interfacing in Fuel Cell Hybrid Electric Vehicles

The theory of variable structure systems with sliding mode control has been used to develop a power conditioning system. An experimental system has been developed, and digital simulation of both the power and control systems has been performed. The good agreement between the analytical study and the experimental and simulation results confirms the validity of the proposed control system.

Experimental study of a power conditioning system using sliding mode control

A balancing control strategy that allows the voltage differences among the DC link capacitors of the generalized n-level power converter to be minimized is presented. The case n=3 is treated, but the technique can be generalized to larger n values. The balancing algorithm does not achieve correct voltage sharing of the capacitors under all operating conditions, but it provides a great improvement. This strategy appears to be very promising in single-phase applications, for which nonredundant switching configurations do not affect the capacitor voltage balance. >

Mario Marchesoni

Papers

A new multilevel PWM method: a theoretical analysis

Diode-clamped multilevel converters: a practicable way to balance DC-link voltages

New DC–DC Converter for Energy Storage System Interfacing in Fuel Cell Hybrid Electric Vehicles

Experimental study of a power conditioning system using sliding mode control

Optimized modulation techniques for the generalized N-level converter