A Comparison of Modulation Techniques for Modular Multilevel Converters

Abstract

This work presents a comparison of three different modulation techniques applied to modular multilevel converters (MMCs). The three modulation strategies studied in this paper are the phase-shifted sinusoidal pulse width modulation (PS-SPWM), the space-vector modulation (SVM) and the nearest level modulation (NLM). This paper focuses on analysing the particularities and implementation of each modulation technique. The modulation technique largely defines the generated harmonic content, making this is a key point that must be studied in depth. The paper briefly describes the three modulation techniques and analyses the harmonics generated by each one of the methods. In addition, the paper presents and compares the digital implementation of the three modulation methods in a Field Programmable Gate Array (FPGA). The proposed approaches are validated using a real processing platform and experimentally evaluated in a real high-power six-level MMC.

Modular Multilevel Converters: Control and Applications

“…In the first case, the semiconductor switching losses are high. In all cases, the goal is to eliminate or greatly reduce low frequency harmonics to facilitate the filtering of the AC voltage, taking into account the fact that the type of modulation used determines, in part, the harmonics of the generated voltage [22]. First, three voltage modulators using high frequency modulation, phase disposition-sinusoidal PWM, multilevel PWM, and multilevel space vector modulation (SVM) are presented.…”

Energy balancing in modular multilevel converter systems

“…As a result, stabilization of the average value of voltages of cell capacitors in the branch is achieved. For the C-level, a converter energy balancing responsible for keeping nominal energy at Energy balancing in modular multilevel converter systems strategy for such structure is PS-SPWM [20], where carriers between the cells are phase shifted by the certain value, which depends on the number of cells in the branch. Another common technique is called the nearest level modulation (NLM).…”

“…Therefore, references are scaled by u b 2 and i b 2 coefficients respectively, which gives: (20) (13) and (14) …”

A Switching Frequency Optimized Space Vector Pulse Width Modulation (SVPWM) Scheme for Cascaded Multilevel Inverters

“…Several topologies for multilevel inverters have been proposed in the past decades, including diode-clamped [9], flying capacitor [1], cascaded H-bridge [10] and modular multilevel [11]. For a given multilevel converter topology, modulation scheme is a key factor [12][13][14][15][16][17]. Among various modulation schemes, space vector pulse width modulation (SVPWM) scheme is an attractive candidate due to its flexibility to optimize switching waveforms and its convenience to be implemented in digital signal processors [1,[12][13][14].…”

“…For a given multilevel converter topology, modulation scheme is a key factor [12][13][14][15][16][17]. Among various modulation schemes, space vector pulse width modulation (SVPWM) scheme is an attractive candidate due to its flexibility to optimize switching waveforms and its convenience to be implemented in digital signal processors [1,[12][13][14]. Generally, most SVPWM schemes can be implemented with the following three steps:…”