A generalized circuit topology of multilevel voltage source inverters which is based on a direct extension of the three-level inverter to higher level is proposed. The circuit topologies up to five-level are presented. The proposed multilevel inverter can realize any multilevel pulsewidth modulation (PWM) scheme which leads to harmonic reduction and provides full utilization of semiconductor devices like GTOs, especially in the high power range where high voltage can be applied. The capacitor voltage balancing problem is discussed and a circuit remedy for such a problem is given. >

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A general circuit topology of multilevel inverter

The authors present the analysis of the neutral-point potential variation of the neutral-point-clamped voltage source PWM (pulse-width-modulation) inverter (NPC-VSI) for AC motor drives and static VAr compensators (SVC). The potential variation is analyzed with the focus on the current flowing out of or into the neutral point of the DC link. The theoretical minimum capacity of the DC link capacitors is discussed for its application to both a vector-controlled induction motor system of 2.2 kW and a SVC system of 10 MVA, 6.6 kV, 60 Hz. It is shown that the proposed control scheme makes it possible to suppress the neutral-point potential variation within a few percent, so that the total capacity of the DC link capacitors in the NPC-VSI is almost the same as that in the conventional voltage source inverter. >

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Analysis of variation of neutral point potential in neutral-point-clamped voltage source PWM inverters

In many single-phase power factor correction (PFC) applications, the power level can reach several kilowatts; and in some situations, the input voltage can be quite high too. For high power and/or high voltage applications, the major concerns of the conventional boost PFC converter are the inductor volume and weight, and losses on the power devices, which will affect converter cost, efficiency, and power density. In this paper, a three-level boost converter is adopted for single-phase PFC, which uses a much smaller inductor and lower voltage devices than the conventional boost PFC converter does, yielding high power density, high efficiency, and low cost. >

Single-phase three-level boost power factor correction converter

This paper studies the inherent relations between sine-triangle and space-vector pulsewidth modulation schemes for three-level voltage-source inverters. It is shown that the two schemes can function equivalently through proper selection of common-mode injections in the case of sine-triangle modulation, or dwell times in equivalent redundant switching states in the case of space-vector modulation. Simulation and measurement results illustrate that understanding of these relations can lead to a more efficient and flexible three-level modulator with desired or optimal performance.

Sine-triangle versus space-vector modulation for three-level PWM voltage-source inverters

The momentum toward high efficiency, high frequency, and high power density in power supplies limits wide use of conventional wire-wound magnetic components This paper gives an overview of planar magnetic technologies with respect to the development of modern power electronics The major advantages and disadvantages in the use of planar magnetics for high-frequency power converters are covered, and publications on planar magnetics are reviewed A detailed survey of winding conduction loss, leakage inductance, and winding capacitance for planar magnetics is presented so power electronics engineers and researchers can have a clear understanding of the intrinsic properties of planar magnetics

Overview of Planar Magnetic Technology—Fundamental Properties

The application of three-level pulsewidth modulation (PWM) to voltage source inverters feeding three-phase induction motors is considered. A subharmonic modulation method using two modulating waves is introduced. It is particularly well adapted to the elimination of specific harmonic bands. Systematic optimization of precalculated wave forms with respect to loss factor shows that three-level PWM is very well suited to harmonic reduction. Transient behavior is discussed. It is concluded that three-level PWM yields significant improvements compared with two-level PWM, especially in high-power (gate-turn-off) GTO applications where the high DC link voltage requires a series connection of the switches.

A novel approach to the generation and optimization of three-level PWM wave forms

New developments of 3-level PWM strategies

The application of three-level pulsewidth modulation (PWM) to voltage source inverters feeding three-phase induction motors is considered. A subharmonic modulation method using two modulating waves is introduced. It is particularly well adapted to the elimination of specific harmonic bands. Systematic optimization of precalculated waveforms with respect to loss factor, shows that three-level PWM is very well suited to harmonic reduction. Transient behavior is discussed. It is concluded that three-level PWM yields significant improvements compared with two-level PWM, especially in high-power (gate-turn-off) GTO applications where the high DC link voltage requires a series connection of the switches. >

A novel approach to the generation and optimization of three-level PWM wave forms for induction motor inverters

In design of high-frequency magnetic devices, various approaches have been used to provide calculation tools that are able to predict winding losses, including skin effect and proximity effect, in their two-dimensional (2-D) aspects. Up to now, these approaches have been mainly focused on giving quantitative results for specific cases. Because the final purpose of designers is not to perform single calculations, but to obtain optimal designs, we have looked for a complementary approach providing more general 2-D guidelines and understanding of the phenomena. In this paper, we examine the case of a foil winding undergoing edge effect, a typical situation where classical one-dimensional theories underestimate the real losses. Using a 2-D closed-form formula we developed in a previous work and the associated database of 400 2-D numerical models, we systematically analyze the dependence of the 2-D field and the corresponding extra losses with the geometrical design variables describing the dimension and position of the winding.

Bruno Velaerts

Papers

A novel approach to the generation and optimization of three-level PWM wave forms

New developments of 3-level PWM strategies

A novel approach to the generation and optimization of three-level PWM wave forms for induction motor inverters

Two-dimensional analysis of the edge effect field and losses in high-frequency transformer foils

An improved power diode model for PSPICE applied to converter simulation