Dietmar Krug

Comparison of 2.3-kV Medium-Voltage Multilevel Converters for Industrial Medium-Voltage Drives

This paper compares the expense of power semiconductors and passive components of a (2.3 kV, 2.4 MVA) two-level, three-level neutral-point-clamped, three-level flying-capacitor, four-level flying-capacitor, and five-level series-connected H-bridge voltage source converter on the basis of the state-of-the-art 6.5-, 3.3-, 2.5-, and 1.7-kV insulated gate bipolar transistors for industrial medium-voltage drives. The power semiconductor losses, the loss distribution, the installed switch power, the design of flying capacitors, and the components of an sine filter for retrofit applications are considered.

Design and Comparison of 4-kV Neutral-Point-Clamped, Flying-Capacitor, and Series-Connected H-Bridge Multilevel Converters

This paper describes the design of a (4-kV, 4.16-MVA) three-level neutral-point-clamped-, three-level flying-capacitor-, four-level flying-capacitor-, and nine-level seriesconnected H-bridge voltage-source converter on the basis of state-of-the-art 6.5-, 4.5-, 3.3- and 1.7-kV insulated gate bipolar transistors. The semiconductor loss distribution and the design of semiconductors and passive components are compared for a medium switching frequency assuming a constant converter efficiency of about 99%. To evaluate the converter characteristics in high switching frequency applications, a second comparison is realized for the maximum switching frequencies assuming a constant expense of semiconductors in all converters.

Power loss-oriented evaluation of high voltage IGBTs and multilevel converters in transformerless traction applications

The low-frequency line transformer in todays ac rail vehicles suffers from poor efficiency and a substantial weight. Future traction drives may operate directly from the mains without this transformer. A feasible concept for a transformerless drive system consists of series connected medium voltage converters applying modern high-voltage insulated gate bipolar transistors (HV-IGBTs). In a first design step, the switching characteristics and losses of 6.5-kV IGBTs are compared to 3.3-kV and 4.5-kV IGBTs which are already commercially used in traction applications. Based on the considered HV-IGBTs, the properties of multilevel converters are analyzed and their applicability to the transformerless system is evaluated. The paper focusses on a loss analysis of the converters. Reliability aspects and harmonic spectra are briefly discussed. Taking these design aspects into account, the three-level neutral point clamped converter turns out to be a reasonable solution to realize line and motor converter modules in a transformerless traction system.

Design and comparison of medium voltage multi-level converters for industry applications

This paper describes the design of a (2.3 kV, 2.4 MVA) two-level -, three-level - neutral point clamped -, three-level - flying capacitor - and four-level - flying capacitor - voltage source converter on the basis of state-of-the-art 6.5 kV, 3.3 kV and 2.5 kV IGBTs. The semiconductor loss distribution, design, and costs of semiconductors and passive components are compared for a constant converter efficiency of 99 %. Assuming a constant installed switch power the converters are also compared at the maximum switching frequency of each converter resulting in the minimum expense of passive components.

Comparison of power semiconductor utilization, losses and harmonic spectra of state-of-the-art 4.16 kV multi-level voltage source converters

This paper compares a three-level neutral point clamped voltage source converter (3L-NPC VSC), a three-level flying capacitor voltage source converter (3L-FLC VSC), a four-level flying capacitor voltage source converter (4L-FLC VSC) and nine-level-series connected H-bridge voltage source converter (9L-SCHB VSC) on the basis of state-of-the-art 6.5 kV, 4.5 kV and 1.7 kV IGBTs for a 4.16 kV medium voltage converter. The design of the power semiconductors, the installed switch power, converter losses, the semiconductor loss distribution, modulation strategies and the harmonic spectra are compared in detail

A new modular multilevel converter for medium voltage high power oil & gas motor drive applications

This paper presents the first commercially available water-cooled MV motor drive based on the Modular Multilevel Topology (M2C). The motor drive specific features and HW are described. Measurement results from a 12 MW back-to-back test is included, e.g. operation at low motor frequencies down to zero speed at high torque.

Design and Characteristics of a Rotor Flux Controlled High Speed Induction Motor Drive Applying Two-Level and Three-Level NPC Voltage Source Converters

This paper describes the field oriented control of a high speed induction motor (HSIM) and the design of a two-level voltage source converter (2L-VSC) and a three-level neutral point clamped voltage source converter (3L-NPC VSC) for a 420 V low voltage high speed drive. The proposed control system and both converters are simulated to determine the drive performance under two different operating conditions. Finally, current harmonics, torque ripples, and inverter losses for two different carrier frequencies of the considered converters are presented and compared in detail

Complete performance test of MV drive with modular multilevel topology for high power oil & gas applications

More than ever Oil & Gas companies are looking for ways to increase their productivity and energy efficiency. To realize these goals electrification of the drive trains is essential. These solutions make use of variable speed drives to control speed and torque of the gas compressors and pumps which leads to a higher degree of process optimization. For loads with power requirements higher than 1 MW, Medium Voltage (MV) drives become the most utilized drive solution. Depending on the output power, several different topologies of MV drives are available on the market. The modular multilevel converter (M2C) topology is the latest topology to enter the high power medium voltage drive market. To ensure that the performance of the whole drive system meets the performance data as specified by the customer, a system tests with a 12 MW motor in a back to back arrangement has been executed. The measurements of the output performance, the start-up behavior and more will be presented.