Christian Klumpner

Bio: Christian Klumpner is an academic researcher from University of Nottingham. The author has contributed to research in topics: Voltage & Topology (electrical circuits). The author has an hindex of 29, co-authored 153 publications receiving 3399 citations. Previous affiliations of Christian Klumpner include Politehnica University of Timișoara & Aalborg University.

Evaluation of three-phase transformerless photovoltaic inverter topologies

Abstract: This paper analyzes and compares three transformerless photovoltaic inverter topologies for three-phase grid connection with the main focus on the safety issues that result from the lack of galvanic isolation. A common-mode model, valid at frequencies lower than 50 kHz, is adopted to study the leakage current paths. The model is validated by both simulation and experimental results. These will be used to compare the selected topologies, and to explain the influence of system unbalance and the neutral conductor inductance on the leakage current. It will be demonstrated that the later has a crucial influence. Finally, a comparison of the selected topologies is carried out, based on the adopted modulation, connection of the neutral and its inductance, effects of unbalance conditions, component ratings, output voltage levels, and filter size.

A new matrix converter motor (MCM) for industry applications

Abstract: The trend in electrical drives is to integrate the frequency converter, the electrical motor, and even the gear or the pump into a single unit, in order to reduce the costs, to increase the overall efficiency and the equipment reliability. This paper presents the first integrated regenerative frequency converter motor for industry applications, based on a matrix converter topology. The low volume, the sinusoidal input current, the bidirectional power flow, and the lack of the bulky and limited-lifetime electrolytic capacitors recommend this topology for this application. This paper shows how the matrix converter disadvantages-the lack of bidirectional power devices, the lower voltage transfer ratio, and the overvoltages caused by the input filter during power-up-that have delayed the industrial implementation have been overcome. In order to demonstrate the validity of the solution, a 4-kW matrix converter motor prototype is built using a standard frequency converter motor enclosure for testing the requirements for an industrial drive. The tests demonstrate the good performance of the drive.

Space-Vector Modulated Multilevel Matrix Converter

Abstract: A matrix converter is an ac-ac power converter topology that has received extensive research attention as an alternative to traditional ac-dc-ac converter. A matrix converter is able to convert energy from an ac source to an ac load without the need of a bulky and limited-lifetime energy-storage elements. The indirect three-level sparse matrix converter (I3SMC) is a new topology from this family that can synthesize three-level voltage in order to improve the output performance in terms of reduced harmonic content. This paper discusses the operating principles and a space-vector-modulation scheme for this topology. Simulation and experimental results are shown to prove the ability of this topology to generate multilevel output voltages as well as to maintain a set of sinusoidal balanced input currents. The performance of the converter is compared with the conventional matrix converter and an alternative multilevel matrix-converter topology in order to demonstrate the advantages and disadvantages of the I3SMC.

Comparison of two current modulation strategies for matrix converters under unbalanced input voltage conditions

Abstract: In this paper, the input current performance of matrix converters is analyzed, especially with reference to the operating conditions determined by unbalanced supply voltages. The space-vector modulation (SVM) technique is utilized to calculate the duty cycles of the active voltage vectors that must be applied, in each switching cycle period, in order to satisfy the input and output requirements. A detailed theoretical analysis of the input current harmonic content under unbalanced input voltage conditions is presented for two different current modulation strategies. On the basis of numerical simulations as well as measurements on a laboratory prototype setup, the strategies' performance are compared and the validity of the theoretical investigation confirmed. It is concluded that, when the input voltages are unbalanced to a significant extent, a dynamic input current modulation strategy has to be preferred, since a lower harmonic line current distortion will appear.

Using reverse blocking IGBTs in power converters for adjustable speed drives

Abstract: A new semiconductor power device that is urgently needed particularly in power converter topologies, the reverse blocking insulated gate bipolar transistor (RB-IGBT), has been realized by adding minor changes to the structure of a standard IGBT to make it capable of withstanding reverse voltage. However, the switching behavior of the device's intrinsic diode during reverse recovery is not as good as a discrete IGBT and series diode implementation. This paper analyzes the use of this device in three power converter topologies that may benefit from it, namely: 1) the matrix converter, 2) the two-stage direct power converter (DPC), and 3) the three-level voltage source rectifier. A commutation method to override the poor reverse-recovery characteristic of the RB-IGBT intrinsic diode in a two-stage DPC is proposed. A loss analysis shows that by using RB-IGBTs the efficiency of the two-stage DPC becomes similar to a two-level voltage source converter.

Overview of Control and Grid Synchronization for Distributed Power Generation Systems

Abstract: Renewable energy sources like wind, sun, and hydro are seen as a reliable alternative to the traditional energy sources such as oil, natural gas, or coal. Distributed power generation systems (DPGSs) based on renewable energy sources experience a large development worldwide, with Germany, Denmark, Japan, and USA as leaders in the development in this field. Due to the increasing number of DPGSs connected to the utility network, new and stricter standards in respect to power quality, safe running, and islanding protection are issued. As a consequence, the control of distributed generation systems should be improved to meet the requirements for grid interconnection. This paper gives an overview of the structures for the DPGS based on fuel cell, photovoltaic, and wind turbines. In addition, control structures of the grid-side converter are presented, and the possibility of compensation for low-order harmonics is also discussed. Moreover, control strategies when running on grid faults are treated. This paper ends up with an overview of synchronization methods and a discussion about their importance in the control

Recent Advances and Industrial Applications of Multilevel Converters

Abstract: 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.

Power electronics as efficient interface in dispersed power generation systems

Abstract: The global electrical energy consumption is rising and there is a steady increase of the demand on the power capacity, efficient production, distribution and utilization of energy. The traditional power systems are changing globally, a large number of dispersed generation (DG) units, including both renewable and nonrenewable energy sources such as wind turbines, photovoltaic (PV) generators, fuel cells, small hydro, wave generators, and gas/steam powered combined heat and power stations, are being integrated into power systems at the distribution level. Power electronics, the technology of efficiently processing electric power, play an essential part in the integration of the dispersed generation units for good efficiency and high performance of the power systems. This paper reviews the applications of power electronics in the integration of DG units, in particular, wind power, fuel cells and PV generators.

Power Electronics as Efficient Interface in Dispersed Power Generation Systems

Abstract: The global electrical energy consumption is rising and there is a steady increase of the demand on the power capacity, efficient production, distribution and utilization of energy. The traditional power systems are changing globally, a large number of dispersed generation (DG) units, including both renewable and nonrenewable energy sources such as wind turbines, photovoltaic (PV) generators, fuel cells, small hydro, wave generators, and gas/steam powered combined heat and power stations, are being integrated into power systems at the distribution level. Power electronics, the technology of efficiently processing electric power, play an essential part in the integration of the dispersed generation units for good efficiency and high performance of the power systems. This paper reviews the applications of power electronics in the integration of DG units, in particular, wind power, fuel cells and PV generators.

Matrix converters: a technology review

Abstract: The matrix converter is an array of controlled semiconductor switches that connects directly the three-phase source to the three-phase load. This converter has several attractive features that have been investigated in the last two decades. In the last few years, an increase in research work has been observed, bringing this topology closer to the industrial application. This paper presents the state-of-the-art view in the development of this converter, starting with a brief historical review. An important part of the paper is dedicated to a discussion of the most important modulation and control strategies developed recently. Special attention is given to present modern methods developed to solve the commutation problem. Some new arrays of power bidirectional switches integrated in a single module are also presented. Finally, this paper includes some practical issues related to the practical application of this technology, like overvoltage protection, use of filters and ride-through capability.