Since the advent of power electronic devices, Inverters have become an integral part in applications like UPS, AC drives, HVDC transmission. These applications mainly use voltage source inverters. Voltage source inverters are classified based on the no. of levels in output voltage as two-level inverter and multilevel inverters (diode clamped, flying capacitor and cascaded H-bridge). This paper enlightens the performance comparison of two-level inverter using space vector PWM and all three classical multilevel inverters (5-level) using phase disposition multi-carrier modulation. This comparison is based on factors like total harmonic distortion, EMI, switching frequency, switching losses and the no. of switching devices. The simulation of all these inverters is done in MATLAB/Simulink and the simulation results are used as a source of comparison.

Performance Comparison of Two Level Inverter with Classical Multilevel Inverter Topologies

The paper proposes a generalized circuit configuration of a new multilevel current-source inverter (CSI) with no-isolated switching devices. In this new multilevel inverter topology, all of the power-switches in the inverter are connected on a common-potential level. Hence, all of the power switches only need a single gate drive power supply without using isolated power supplies or conventional bootstrap techniques. This key feature is still valid even if the number of the power switches increases due to the higher number of the output current waveform levels. As a result, complexity of the gate drive circuit can be remarkably moderated. In addition, the multilevel CSI circuit is capable to operate at high switching frequency if required, because all of the power switches are connected on the common potential level. Five-level PWM inverter configuration, including its chopper circuit as DC current-power source circuits using small input inductors, is verified through computer simulations and experimental tests. The results show feasibility of the proposed topology with reducing the circuit complexity and physical size of the multilevel CSIs.

Generalized Multilevel Current-Source PWM Inverter with No-Isolated Switching Devices

The advent of high power and medium power appliances has given substantial importance to Multilevel Inverters (MLI) in recent times. The MLI is widely used in driving AC loads which requires to be operated with low harmonics. In this paper, the various MLI topologies and the modulation techniques implemented on MLIs are reviewed. While reviewing the various MLI topologies, they are categorized into symmetrical type and asymmetrical type. All the existing MLIs topologies and those that are developed in future can be categorized into one of these two categories. A comprehensive review is done of these topologies to examine the various performance parameters. The modulation techniques are also classified into fundamental switching frequency (FSF) modulation techniques and high switching frequency (HSF) modulation techniques. This classification provides an easy understanding of the concepts that are conveyed by MLI. This paper also gives a broad understanding of the various features of each modulation technique.

Multilevel Inverters: A Review of Recent Topologies and New Modulation Techniques

An efficient pulse width modulation scheme for Cascaded H-Bridge inverter (CHBI) is proposed in this paper. The proposed modulation scheme is a low switching frequency modulation scheme termed as modified Nearest Level Modulation (mNLM) scheme. Compared to the conventional nearest level modulation (NLM) scheme, the proposed modulation scheme reduces the total harmonic distortion (THD) at the ac output of the inverter. The mNLM follows an algorithm presented in the paper in order to arrive at a set of switching angles for MLI which offers reduced THD. Simulation is carried out using MATLAB/Simulink 2015b software and hardware is presented which validates the simulation results. Results show that there is a notable reduction in the THD content with the use of proposed modulation scheme. Because of the improved THD content, improvement in the other inverter parameters such as rms voltage, rms current and increased output power is also observed.

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A Modified Nearest Level Modulation Scheme for a Symmetric Cascaded H-Bridge Inverter

In this paper, a novel single phase multilevel inverter with reduced number of switches is presented which is named as Half-height neutral point clamped (NPC) inverter. The proposed inverter consists of a single DC voltage source, a full bridge cell, switching devices, and power diodes which are half in number as compared to conventional topology. Unipolar modulation technique is used to generate switching signals for the proposed inverter, that provides optimum total harmonic distortion (THD) performance in both output voltage and current. The offered inverter topology is described with the help of a single-phase eleven-level inverter. The simulation of the topology is carried out through MATLAB/ Simulink. A comparison of the proposed topology with conventional one is also presented.

A Novel Single Phase Multilevel Inverter Topology with Reduced Number of Switching Elements and Optimum THD Performance

Multilevel inverters have been deliberated for an increasing number of application due to their high power capability. This paper discusses about a multilevel inverter topology with reduced number of switches, where sinusoidal pulse width modulation (SPWM) is used to produce a seven level output voltage. Also an L-C Filter is used at the output of the inverter to suppress the ripples in the output and produce the pure sinusoidal output voltage. Harmonics and switching losses can be reduced by this topology. And reduction of switches also reduces the cost. Multilevel inverters are used in industry for medium and high voltage application. The main disadvantage of this multilevel inverter is that it require complex gate driving circuit.

L. Bhattar

Papers

Multilevel inverter with reduced number of switches