Comparative study of multilevel inverters under unbalanced voltage in a single DC link

Abstract

This study explores the feasibility of an AC/DC/AC drive with near unity power factor front-end rectifier and five-level rear-end multilevel inverter topology with a focus on achieving lower voltage total harmonic distortion and higher energy efficiency. The unity PF front-end rectifier in this AC/DC/AC drive may cause unbalanced voltage in the DC bus capacitors leading to high voltage distortion on the output AC voltage of a rear-end multilevel inverter. Based on the analysis, modelling and experimental results, rear-end multilevel flying-capacitor inverter with unity PF front-end rectifier in an AC/DC/AC power drive is proposed which is able to provide better DC voltage balancing when compared to diode-clamped topology. Having no diode components being used in this multilevel inverter, the flying-capacitor topology produces lesser commutation losses. Furthermore, rear-end multilevel flying-capacitor topology offers better efficiency and good quality output voltage without any bulky and expensive LC filter and even without any additional DC voltage balancing circuitry. The analytical performance of the drive is verified on a 1.3 kW laboratory prototype.

Five-Level PWM Inverter Using Series and Parallel Alternative Connection of Batteries

“…When a circuit employs series-connected capacitive components, sometimes it has a voltage unbalance problem because of different charging and discharging periods. Thus, voltage balancing control is required to maintain voltage in a constant value [20][21][22][23]. Although the proposed 5-level PWM inverter also uses series-connected batteries, it does not need to consider on voltage unbalancing problem since both batteries have the same time for charging and discharging.…”

Performance Evaluation and Comparison of Two Cascaded Configurations of PV Generators-Five Levels Inverter for a Stand-Alone Application in South Algeria

“…It is shown that the total harmonic distortion is less than 5% (Figure 14(c)). Then, the PV cascade with separate PV sources is the best solution seeing that we do not need to use another algorithms such as application of redundant states of vectors [12], or introduce a resistive clamping bridge [14] or the use of four DC/DC converters [15] to balance the capacitor voltage DC bus. …”

“…The Simplified Space Vector Pulse Width Modulation Technique (SSVPWM) is used in this paper in order to get the best voltage waveform. For the configuration with only one PV source, we introduce in the control loops another algorithm which uses the redundant vector of Space Vector Diagram (SVD) of five levels inverter to stabilise the DC bus capacitor voltages [12]. A real data of solar irradiation and temperature obtained by radiometric station in Ghardaïa city in south Algeria are used to test the performance of proposed controls.…”

Cascaded Symmetric Multilevel Inverter with Reduced Number of Controlled Switches

“…Every topology has its own limitations and advantages. For example, flying capacitor topology was ignored due to unequal charging of capacitors [6][7]. Similarly, the clamped diode topology lost the importance due to the unequal losses across semiconductor devices and requirement of a large number of components for higher number of output levels [8].…”