A. Kirubakaran

A multilevel inverter with reduced number of switches

A multilevel inverter is a power electronic device that is used for high voltage and high power applications, with the added advantages of low switching stress and lower total harmonic distortion (THD), hence reducing the size and bulk of the passive filters. This paper proposes a new topology of a cascaded multilevel inverter that utilizes less number of switches than the conventional topology. Therefore with less number of switches in the circuit, there will be a reduction in the gate driver circuits and also in effect fewer switches will be conducting for specific intervals of time. The circuitry consists of smaller multilevel inverter blocks connected in series to achieve its characteristic output waveform. A seven level inverter will be simulated with the implementation of PWM techniques and its effect on the harmonic spectrum will be analyzed. The system will be modelled with the help of MATLAB/SIMULINK.

A two-stage power electronic interface for fuel cell-based power supply system

The increasing energy demands, insufficient availability of power generation and increasing global environmental problems, need alternate/green power sources. Among the different green power technologies such as wind power, photovoltaic, gas turbine and fuel cell, the fuel cell-based distributed generation is considered as one of the most promising solutions for stand-alone/grid applications due to its cleanliness, modularity and higher potential capability. The selection of a power conditioning unit plays an important role to maintain the stability of the system and to improve the performance of fuel cell system. While using a single-stage DC/AC inverter with step up transformer for stand-alone/gird applications, the major issue is high current flow through the inverter and primary side of the transformer. This paper presents a two-stage power conditioning unit, a DC/DC boost converter combined with a DC/AC inverter for fuel cell system to reduce the current level at the DC/AC inverter.

Development of LabVIEW-based multilevel inverter with reduced number of switches

In the present scenario, the development of multilevel inverter is becoming popular for industrial applications and higher scale renewable green power technologies such as fuel cell, PV cell and wind turbine systems connected to the load. But the traditional multilevel topologies have large components and complex Pulse Width Modulation (PWM) controller leading to reduced harmonics and voltage stress on the load. Therefore, a new topology of a cascaded multilevel inverter employing less number of switches with reduced gate driver circuits and simple control scheme is presented in this paper. A comprehensive MATLAB/Simulink model of a seven-level inverter and the generation of control pulses using multi-carrier-based PWM is evolved and discussed. With the aid of LabVIEW, an experimental prototype is developed and their results are compared with simulation results.

A new multilevel DC-DC boost converter for fuel cell based power system

This paper presents a system model of fuel cell based distributed generation systems (DGS) in a standalone AC power supply system. Non-isolated high step-up DC-DC converters are required widely in the industrial applications. Many of these conventional DC-DC converters have the disadvantages of operating at high duty-cycle, high switch voltage stress and high diode peak current. A three-level step-up converter is implemented to boost the fuel cell stack voltage of 90V to 340V. This high DC link voltage is fed to the voltage source inverter and interfaced with the load. Two feedback control loops are designed to make the system operate in stable conditions. This system configuration is suitable for low-power applications. The Performance of the developed system is analyzed in MATLAB/Simulink environment under steady state and transient conditions.

DSP controlled DC/DC boost converter for renewable/green power applications

Increasing energy demands and global rising pollution awareness resulted much of the research work to focus on green power technologies. Fuel cell based distributed generation is considered as one of the most promising devices due to their major advantages of higher efficiency, cleanliness, modularity and eco friendly nature. In multi stage power electronic interface, common DC distribution and hybrid systems the deployment of boost converter plays a vital role to reduce the operating current level with increased DC link voltage. The development of control scheme using analog circuits is more complex due to more component counts and their performance totally depends on the accuracy of each component. However, in the present scenario development of digital technology plays a significant role due to their advantages of higher fast and compactness. Therefore, in this work a low cost TMS320F2812 DSP controller is used to generate the firing pulse interfaced with MATLAB/Simulink model in Real Time Workshop to regulate the boost converter output voltage for varying load.

Simulation and performance evaluation of 10 kW two stage power electronic interface for fuel cell based power supply system

In recent years, fuel cell is gaining more popularity for residential/grid connected applications due to its higher efficiency, cleanliness, modularity and quick startup over other renewable energy sources. But the performance of the fuel cell is affected by its slow response characteristics for sudden changes in load. Therefore, a suitable power conditioning unit is very important for better voltage regulation and to reduce the overall system cost. Moreover the current flowing through the single stage DC-AC inverter followed by a step up transformer is very high, which increases the inverter current rating and losses. In this paper, a simple DC-DC boost converter connected in series with DC-AC inverter is presented. The proposed power electronic interface is designed for 10 kW proton exchange membrane fuel cell. The performance of the proposed converter is analyzed in MATLAB/Simulink environment and is compared with single stage.

Distributed Generation by Solid Oxide Fuel Cell: A Review

The private power producers are increasing rapidly to meet rising load demand in domestic, commercial and Industrial sector. In this scenario distribution generation system (DGs) plays increasingly important role over fossil fuel generation. A review is therefore carried out in this area of distributed generation system (DGs) with emphasis on Solid Oxide Fuel Cells (SOFCs). The study is performed to review the impact of SOFCs characteristics and associated control strategies on system dynamic behavior in standalone/grid connected applications with the constraint of providing good quality supply to the customers. The main aim of this review is to support researchers in the above field to carry out further research work so as to evolve/design an effective dynamic model/power conditioning unit with overall reduced system cost and increased life span & efficiency of generating system.

A new 3-Phase Hybrid Matrix multilevel inverter

This paper presents a new topology of 3-Phase Hybrid Matrix multilevel inverter with reduced number switches and electrical isolation. Each phase consists of two cascaded units; the first unit is used for level generation whereas the second one doubles the number of levels and provides electrical isolation and step up the voltage to required range. The proposed topology show significance in design, reduced components, simplicity compared to conventional topologies for more than five level productions. Therefore, in this paper, operation and switching control scheme for the proposed topology is presented for five level output. Moreover, the performance of the proposed model is analyzed in MATLAB-SIMULINK environment and their results are presented.

A front end boost asymmetrical multi level inverter with single input source

This paper presents a new front end boost switched capacitors based asymmetrical seven level DC-AC converter with single input DC source. It has potential applications for low voltage fuel cell, PV cell inverters, electric vehicles, energy devices etc. with front end multilevel output boost (MOB) switched-capacitors and uses a single input DC source for generating multilevel output voltage waveform. The proposed MOB converter generates asymmetrical DC link output voltage that is converted into AC using one H-bride inverter and auxiliary switches. Operation of the proposed topology is explained with the use of a single seven-level boost inverter and the appropriate control scheme is also presented. Simulation results using MATLAB are given to verify the proposed topology.

A novel four level cascaded Z-source inverter

This paper presents a novel four-level cascaded Z-source inverter based on space vector pulse width modulation (SVPWM) technique. The proposed model provides high gain output voltage compared to the conventional four-level inverter and wide range of control using SVPWM. This effectively utilizes the DC sources for varying modulation index while synthesizing output voltage with lower harmonic distortion and high gain. Besides, it alleviates the voltage balancing problem and lower components count compared to NPC and cascaded multilevel inverters. The proposed model finds application in industrial, domestic and automobile sectors. To validate the theoretical concept, the proposed model is developed in MATLAB/Simulink environment and the results are presented and compared with the conventional four level inverter.