An Asymmetrical Step-Up Multilevel Inverter Based on Switched-Capacitor Network

Abstract

This paper presents a transformerless step-up multilevel inverter based on a switched-capacitor structure. One of the main contributions of the proposed topology is replacing the separated DC voltage source with capacitors which are charged at predetermined time intervals. Therefore, a high-level staircase voltage waveform can be achieved by discharging some of these capacitors on the load. The other contribution of the proposed structure is to eliminate the magnetic elements which traditionally boost the input DC voltage. In addition, asymmetrical or unequal amounts of capacitor voltages create more voltage levels, which enable voltage level increments without increasing the number of semiconductor devices. This paper introduces a self-balanced boost Switched-Capacitors Multilevel Inverter (SCMLI) which is able to create a nearly sinusoidal voltage waveform with a maximum voltage of up to 45 times that of the input voltage DC source. Higher level output voltage levels are also achievable by extending the circuit topology. After determination of the switching angles and selecting the proper switching states for each level, an offline NLC method is used for modulation, which eases the control implementation. Analysis, simulation and experiments are carried out for a 91-level inverter (45 levels for positive and negative voltages and one for zero voltage) are presented.

A Diamond Shaped Multilevel Inverter With Dual Mode of Operation

“…Therefore, the voltage ripples created by switched capacitor units need to be small (i.e., <5%). The voltage ripples of both capacitors (C1 and C2) can be approximated by equation [9];…”

“…The MLI topologies which have been utilized the switched capacitor units are only compared [8][9][10][11][12][13][14][15][16]. The detailed comparison in terms of power electric components is given in Table III.…”

“…It is worth mentioning that the switched capacitors can generate higher output voltage regardless of the supply voltage. Various switched capacitor based MLIs with voltage boost abilities are discussed in [7][8][9][10]. One of the topologies proposed switched capacitor units by sustaining a series/parallel connection with the DC-DC converter [8].…”

“…It employs switching devices that require voltage ratings equal to the maximum voltage of the entire device and makes the MLI unsuitable for high voltage applications. Switched capacitor units based MLI also proposed [9]. Although this topology employs less number of power equipment where it requires M an additional H-bridge circuit to generate the output voltage and thus leads to the higher total standing voltage of switches similar to the previous topology [8].…”