Cascaded H-bridge multilevel inverter (CHBMI) is able to generate a staircase AC output voltage with low switching losses. The switching angles applied to the CHBMI have to be calculated and arranged properly in order to minimize the total harmonic distortion (THD) of the output voltage waveform. In this paper, two non-iterative switching-angle calculation techniques applied for a 15-level binary asymmetric CHBMI are proposed. Both techniques employ a geometric approach to estimate the switching angles, and therefore, the generated equations can be solved directly without iterations, which are usually time-consuming and challenging to be implemented in real-time. Apart from this, both techniques are also able to calculate the switching angles for a wide range of modulation index. The proposed calculation techniques have been validated via MATLAB simulation and experiment.
Keyword:Asymmetric multilevel inverter Binary multilevel inverter Cascaded H-Bridge Multilevel inverter Non-Iterative
This paper presents a single-phase multilevel inverter (MLI) with simpler basic unit cells. The proposed MLI is able to operate in two modes, i.e. charge mode to charge the batteries, and inverter mode to supply AC power to load, and therefore, it is inherently suitable for photovoltaic (PV) power generation applications. The proposed MLI requires lower number of power MOSFETs and gate driver units, which will translate into higher cost saving and better system reliability. The power MOSFETs in the basic unit cells and H-bridge module are switched at near fundamental frequency, i.e. 100 Hz and 50 Hz, respectively, resulting in lower switching losses. For low total harmonic distortion (THD) operation, a deep scanning method is employed to calculate the switching angles of the MLI. The lowest THD obtained is 8.91% at modulation index of 0.82. The performance of the proposed MLI (9-level) has been simulated and evaluated experimentally. The simulation and experimental results are in good agreement and this confirms that the proposed MLI is able to produce an AC output voltage with low THD.
Keyword:CHBMI DSM MLI PV THD
Cascaded H-bridge multilevel inverter is among the most preferred topology in solar systems. While traditional asymmetric cascaded H-bridge multilevel inverter is easy to achieve higher number of output voltage levels compared to traditional symmetric cascaded H-bridge multilevel inverter, charge balancing between the voltage sources remains a challenge for asymmetric cascaded H-bridge multilevel inverter. This drawback results in unsteady DC voltage levels due to unbalanced power drawn from each voltage sources. Besides that, in battery powered applications, unbalanced power drawn results in unequal discharged in the batteries. In this paper, two three-phase asymmetric cascaded H-bridge multilevel inverter topologies are proposed which offer easier in terms of modularity while maintaining the ease in charge balancing control. The performance of these two proposed topologies with charge balance control has been evaluated using PSIM software.
Cascaded H-Bridge (CHB) multilevel inverter (MLI) is among the most preferred topology in solar PV systems. While traditional asymmetric CHB MLI is easy to achieve higher number of output voltage levels compared to traditional symmetric CHB MLI, charge balancing between the voltage sources remains a challenge for asymmetric CHB MLI. This drawback results in unsteady DC voltage levels due to unbalanced power drawn from each voltage sources. Besides that, in battery powered applications, unbalanced power drawn results in unequal discharged among the batteries. In this paper, an asymmetric half H-bridge (HHB) MLI topology is presented which is easy to modularize as for symmetric CHB MLI while maintaining the ease in charge balancing control. The performance of this proposed asymmetric HHB MLI with charge balance control has been evaluated using PSIM software.
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