A Comparative Analysis of a Three Phase Neutral Point Clamped Multilevel Inverter

Currently, induction motors are widely used in industry because have a high potential for the efficiency improvement. Therefore, a topic of interest to the industry is to reduce the energy consumption of induction motors, as they represent almost half of the total electrical energy consumption in the world. The energy consumption of electric motors can be reduced by using motors that are more efficient and by using power converters to feed the motors, thereby enabling accurate control according to the load. The function of the power converter is to modify the intrinsic characteristics of the induction motor (speed and torque). There are different topologies of the power converter commonly called inverter for induction motors. An inverter requires a modulation strategy for its operation, there are several modulation strategies that are used in the induction converter-motor assembly. This paper presents the comparative analysis of the influence of the phase disposition modulation (PD-PWM) strategy with different modulation indices, on parameters related to the output signal of a seven-level cascaded multilevel inverter as well as on the nominal working conditions of a three-phase induction motor.

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Grid-Connected PEM Fuel Cell with Multi-Pulse Multilevel Inverter

International Journal of Engineering Research in Africa ◽

10.4028/www.scientific.net/jera.49.54 ◽

2020 ◽

Vol 49 ◽

pp. 54-67

Author(s):

Akshay Kumar Saha

Keyword(s):

Fuel Cell ◽

Proton Exchange Membrane ◽

Cell Model ◽

Research Work ◽

Proton Exchange ◽

Neutral Point ◽

Multilevel Inverter ◽

Generation Model ◽

Load Following ◽

Three Phase

Application of multi-pulse multilevel inverters is considered in this paper for distributed generation. A five-level twelve-pulse neutral point clamped inverter has been combined with a proton exchange membrane fuel cell in order to investigate load following characteristics of the fuel cell. The fuel cell implemented with a three-phase multi-pulse multilevel inverter is adept of delivering single-phase and three-phase loads both in islanded and grid-connected approach. Changes in power demand from no-load to full-load (120 kW) have been applied to study the characteristics of the system from the perspective of how it can follow the load changes in load demand. It has been observed that the fuel cell model is adept of following power request as per requirement; however, there is a response time of few seconds, because the reformer for the fuel cell requires time to generate fuel and the fuel cell requires time for chemical reactions to take place in it. Implementations of six-pulse and twelve-pulse five-level neutral point clamped and flying capacitor inverters show that total harmonic distortions for six-pulse and twelve-pulse five-level neutral point clamped inverters to be 1.066219% and 0.406149% respectively as compared to 2.466889% and 1.5104075% for flying capacitor inverters. It has been observed that with twelve-pulse neutral point clamped inverter, the output voltage waveform is smoother and close to sinewave. The results of the research work is presented with analyses to validate that multi-pulse multilevel neutral point clamped inverter is a better way out for the fuel cell power generation model as this type of inverters produces smoother waveforms to improve power quality with lower harmonics.

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