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This paper introduces a new iterative design procedure of L and LCL filters for low-voltage active-front-end PWM two-level voltage source converters. The analytical expression of the converter harmonic voltages by Bessel functions is applied to design the filter parameters for defined maximum grid current harmonics. Different filter designs are derived for various resonance frequencies and inductance split factors of LCL filter. The minimum amount of stored energy of passive components is used to select a final filter design. A voltage-oriented control scheme, including active damping, is applied in the (400 V and 50 kVA) experimental setup. Both simulation and experimental investigations are presented to verify the accuracy of the filter design procedure. Finally, the steady state and transient performance of the active front end with different LCL filters are depicted. Index Terms--Active damping, active front end, LCL filter.

The application of a particular medium-voltage converter in a certain application depends on numerous criteria. However, in completely new installations, the choice of the system voltage is very often uninhibited of external constraints. Then, the voltage level shall be selected to enable the most efficient power conversion at the lowest cost. This paper is dedicated to help in finding the best voltage level for three-level neutral-point-clamped voltage source converters (3L-NPC VSCs) with respect to the power semiconductor devices. Three insulated-gate-bipolar-transistor-based 3L-NPC VSCs of different voltage levels (2.3, 3.3, and 4.16 kV) are investigated and compared regarding their maximum output power, semiconductor efficiency, and semiconductor cost per MVA output power. The effects of thermal cycling, the loss distribution within the converter, and switching frequencies from 300 to 1050 Hz are considered in the evaluation. Index Terms--Insulated gate bipolar transistor (IGBT) converters, medium-voltage (MV) converters, three-level converters.

This paper, along with an earlier published paper as Part 1, provides a comprehensive review of the state of the art of high-power converters (above 1 MW) for adjustable-speed ac drives. In this highly active area, different converter topologies have been developed for various drive applications in the industry. Due to its extensive coverage, the subject is divided into two parts: multilevel voltage source and current source converter topologies. This paper is focused on the second part and covers the current source converter technologies, including pulsewidth-modulated current-source inverters (CSIs) and load-commutated inverters. In addition, this paper also addresses the present status of the direct converter, which is also known as cycloconverter (CCV). This paper focuses on the latest CSI and CCV technologies and an overview of the commonly used modulation schemes. It also provides the latest technological advances and future trends in CSI- and CCV-fed large drives. This paper serves as a useful reference for academic researchers and practicing engineers in the field of power converters and adjustable-speed drives. Index Terms--Current-source inverter (CSI), cycloconverter (CCV), high-power drives, load-commutated inverter (LCI).

This paper investigates the effects of grid voltage distortions caused by thyristor converters on the steady-state performance of a pulsewidth modulation (PWM) rectifier with dc voltage link for low-voltage applications. The disturbance transfer function of the current control loop is used to analyze the effects of grid distortions. Influences of the current controller, the phase-locked loop parameters, and the filter inductance on the generated current harmonics are presented. For existing grid voltage harmonics, the amplitude of the corresponding current harmonics are determined and compared to measured current harmonics using a 400-V 40-kW test bench consisting of a PWM rectifier with voltage dc link parallel to a 40-kW thyristor converter. Index Terms--Harmonic distortion, pulsewidth modulation (PWM) active front ends, thyristor 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-pointclamped, 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. Index Terms--High-power applications, multilevel converters, voltage-source inverters (VSIs).

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 LC sine filter for retrofit applications are considered. Index Terms--Filter design, medium voltage, multilevel converters, power electronics.

The three-level neutral-point-clamped voltage-source converter (NPC VSC) is widely used in high-power medium-voltage applications. The unequal loss distribution among the semiconductors is one major disadvantage of this popular topology. This paper studies the loss distribution problem of the NPC VSC and proposes the active NPC VSC to overcome this drawback. The switch states and commutations of the converter are analyzed. A loss-balancing scheme is introduced, enabling a substantially increased output power and an improved performance at zero speed, compared to the conventional NPC VSC. Index Terms--Medium voltage, power losses, three-level converter, voltage-source converter (VSC).

This paper evaluates the benefits of three-level topologies as alternatives to two-level topologies in low-voltage converters primarily operated in rectifier mode. The main evaluation aspects are input filter size, semiconductor losses, maximum switching frequency, part count, initial cost, and life cycle cost. Semiconductor loss characteristics of various three-level topologies are discussed. A detailed converter comparison is based on a 100-kW 400-[V.sub.rms] rectifier using commercially available Si insulated gate bipolar transistor modules. Index Terms--Filter, losses, multilevel converter, rectifier.

This paper compares a matrix converter (MC) and a dc-voltage link converter with an active front end for a 7.5-kW, 460-V induction motor drive. Part count, semiconductor losses, input filter design, and protection aspects are discussed. It is shown that the matrix converter's semiconductor losses are smaller only at full load operation for the same silicon area in both converters. A 33 % reduction of the device current rating of the MC is possible, resulting in comparable thermal device stress. The overall passive component count and rating is only slightly better for the MC. Index Terms--AC motor drives, input filter design, matrix converter, semiconductor losses, voltage-source converter.

This paper describes the operation of modular multilevel converter, an emerging and highly attractive topology for medium- and high-voltage applications. A new pulsewidth-modulation (PWM) scheme for an arbitrary number of voltage levels is introduced and evaluated. On the basis of this PWM scheme, the semiconductor losses are calculated, and the loss distribution is illustrated. [ABSTRACT FROM AUTHOR]

This paper, along with an earlier published paper as Part 1, provides a comprehensive review of the state of the art of high-power converters (above 1 MW) for adjustable-speed ac drives. In this highly active area, different converter topologies have been developed for various drive applications in the industry. Due to its extensive coverage, the subject is divided into two parts: multilevel voltage source and current source converter topologies. This paper is focused on the second part and covers the current source converter technologies, including pulsewidth-modulated current-source inverters (CSIs) and load-commutated inverters. In addition, this paper also addresses the present status of the direct converter, which is also known as cycloconverter (CCV). This paper focuses on the latest CSI and CCV technologies and an overview of the commonly used modulation schemes. It also provides the latest technological advances and future trends in CSI- and CCV-fed large drives. This paper serves as a useful reference for academic researchers and practicing engineers in the field of power converters and adjustable-speed drives. [ABSTRACT FROM AUTHOR]

Active three-phase pulsewidth-modulated rectifiers are connected to the grid by an inductance or an LCL filter. Although an LCL filter is more effective since it more efficiently attenuates the switching harmonics, it causes stability problems. To enable a stable operation, either a damping resistor or an active damping (AD) algorithm has to be used. However, while a damping resistor causes additional losses, an AD algorithm usually requires extra sensors. To avoid these disadvantages, this paper shows simulation and experimental results of a simple ac voltage sensorless AD solution that is suitable for industrial applications. [ABSTRACT FROM AUTHOR]