Research on Modified Hybrid Frequency Modulation Technology of Type-III Asymmetric CHB Multilevel Inverters

Abstract

Asymmetric Cascaded H-bridge (ACHB) level inverters can output more voltage waveforms with fewer cascaded units while ensuring the quality of output voltage waveforms, so they have attracted more and more attention. Taking the topology of Type-III asymmetric CHB multilevel inverters as the research object, a Modified Hybrid Frequency Pulse Width Modulation (MHF-PWM) strategy is proposed in this paper. This modulation strategy overcomes the local overshoot of low-voltage unit in the presence of traditional Hybrid Frequency Pulse Width Modulation (HF-PWM), thus completely eliminating the low frequency harmonics in the output voltage waveform of Type-III ACHB nine-level inverters, and the Total Harmonic Distortion (THD) of output line voltage of the modulation strategy is lower than that of PS-PWM strategy in the whole modulation degree, which effectively improves the quality waveform of the output line voltage. At the same time, the strategy can also improve the problems of current backflow and energy feedback caused by the high-voltage unit pouring current to the low-voltage unit, thereby reducing the imbalance of the output power of the high-voltage and low-voltage units. Finally, the Matlab/Simulink simulation model and experimental platform are established to verify the validity and practicality of the modulation strategy.

Reconfiguration Strategy for Fault Tolerance in a Cascaded Multilevel Inverter Using a Z-Source Converter

“…A-CMLI generates more levels in the output waveform with fewer cells compared to other multilevel topologies [15]. There are two A-CMLI structures: (a) Binary (power of 2) in which the supply voltage of each cell is doubled consecutively, and (b) Trinary (power of 3) in which the supply voltage of each cell is tripled consecutively [16] and [17].…”

Improved Cascaded H-Bridge Multilevel Inverters with Voltage-Boosting Capability

“…The cascaded H-bridge (CHB) [1] has revolutionized the dc-to-ac power conversion since its introduction. It has become a highly developed and mature technology for various industrial and renewable energy applications after a few decades of improvement [2][3][4][5][6][7]. Today, researchers are continuously improving the compactness and efficiency of cascaded multilevel inverters by establishing various topologies with reduced switch counts and fewer conversion stages [8].…”