Performance Evaluation of Pulse Width Modulation Techniques for Losses Reduction in Modular Multilevel Flying Capacitor Converter

Abstract

This paper presents the analysis and evaluation of power losses in a modular multilevel flying capacitor converter (MMFCC) controlled by three different pulse width modulation techniques. A new unipolar hybrid PWM scheme, which combines phase disposed PWM (PD-PWM) and phase shifted PWM (PS-PWM), is proposed. Detailed electrical and thermal models of the single star configured FC cells are implemented and simulated using MATLAB/SIMULINK and PLECS. The conduction and switching losses of semiconductor devices and power losses of floating capacitors in the simulated MMCC are evaluated. The results show that the proposed PWM scheme gives the lowest overall power losses and hence the highest efficiency of the three methods under different modulation index variations. Furthermore, the quality of the voltage waveform of the proposed method is as good as that obtained by using PS-PWM.

Carrier-based sinusoidal pulse-width modulation techniques for flying capacitor modular multi-level cascaded converter

“…Losses due to flying capacitor equivalent series resistance (ESR) are also included in this analysis. This method has been extensively presented in [34,38].…”

“…This is to ascertain which of the large number of possible implementations of multilevel sine-triangle PWM is the optimum for a flying-capacitor inverter. However, very few investigations have been done on the optimum type of PWM schemes for an MMCC using 5L-FC as the basic sub-module [34]. The main requirement for a suitable PWM method is that it can maintain voltages of the sub-module clamping capacitors balanced under all operating conditions [22,35,36,37,38].…”

“…Sadigh et al [39,40] presented a detailed power loss analysis for sub-modules formed by hybrid FC and NPC converters irrespective of the modulation method. Authors in [34] provided comparisons between three different sine-triangle PWM schemes for a FC-based MMCC in terms of waveform performance and power losses. The work established that the PD-PWM gives poorer waveform performance in terms of THD values and higher losses due to flying capacitor equivalent series resistance (ESR) losses resulting from high voltage fluctuation, while PS-PWM gives higher switching losses due to its high equivalent switching frequency.…”

Control of A Modular Multilevel Cascaded Converter Based Unified Power Flow Controller

“…To eliminate the disadvantages several alternative UPFC topologies have been investigated [5][6][7][8][9], but they still have drawbacks such as requiring bulky transformers on both sides. This paper proposes a novel configuration with its control schemes of UPFC based on modular multilevel cascaded converters [10][11][12][13]. The MMCC can reach to the required voltage levels without the high cost and bulky shunt interface transformer.…”

Active harmonic current elimination and reactive power compensation using modular multilevel cascaded converter

“…When unipolar scheme is used the carriers are compared with the 50 Hz sinusoidal reference and its 180°anti-phase part to decide PWM switching times [14]. The first carrier applied for phase A upper first SM has been highlighted for observation as shown in Fig.…”