Ersan Kabalci

The design and analysis of a 5-level cascaded voltage source inverter with low THD

Multilevel inverters have been important devices developed in recent years, owing to their capability to increase the voltage and power delivered to the load. Researches done based on basic inverter topologies show that, multilevel inverters have many advantages such as low power dissipation on power switches, low harmonic and low electromagnetic interference (EMI) outputs. A modified Sinusoidal Pulse Width Modulation (SPWM) modulator that reduces output harmonics is presented in this paper. The proposed modulation technique can be easily applied to any multilevel inverter topology carrying out the necessary calculations. The most common multilevel inverter topologies have been studied to define the best topology for SPWM modulation strategy. It is seen that cascaded H-bridges are the most convenient solution. The cascaded H-bridge cells have been constituted by IGBT semiconductors, and switched by the proposed 24-channel SPWM modulator to obtain 5-level output at the back-end of the 3-phase voltage source inverter (VSI). The designed H-bridge cells have a strong switching bandwidth up to 40 KHz, owing to its robustly designed modulator block. The proposed VSI in this paper also has a Total Harmonic Distortion ratio of output current (THDi) around at 0.1% without requiring any filtering circuit. The harmonic analysis of proposed design has been executed under several working conditions such as various switching frequencies and modulation indexes. The detailed comparisons have been performed to determine the best working conditions of VSI and presented in this paper.

Design and analysis of a 7-level cascaded multilevel inverter with dual SDCSs

Multilevel inverters with a large number of steps can generate high quality voltage waveforms, good enough to be considered as suitable voltage source generators. A modified Sinusoidal Pulse Width Modulation (SPWM) modulator with phase disposition that increases output waveform up to 7-level while reducing output harmonics is presented in this paper. The proposed modulation technique can easily be applied to any multilevel inverter topology carrying out the necessary calculations. The modulator block is designed to control multilevel inverter that is constituted using dual H-bridge cells with IGBTs on each phase legs. The supply voltages of cells are defined at Vdc÷2Vdc ratio to obtain an asymmetrical output. The output waveform of asymmetrical topology is increased up to 7-level by using dual separate DC sources (SDCSs). The DC supply requirement of asymmetrical cascaded topology is solved using dual sources instead of 6 SDCSs. The cascaded multilevel inverter is switched by the proposed 24-channel SPWM modulator. The harmonic analysis of proposed inverter has been performed under several working conditions such as various switching frequencies and modulation indexes. The detailed comparisons are performed to determine the best working conditions of voltage source inverters (VSI) and presented in this paper.

Implementation of Energy-efficient Inverter for Renewable Energy Sources

Abstract Switching losses that occur in inverters are one of the most important issues to be considered to improve the efficiency of any inverter. High-frequency resonant DC-link inverters are proposed to reduce switching losses in regular pulse-width modulation control according to conventional voltage source inverters. On the other hand, switching losses cause deficit efficiency in solar and wind energy conversion systems. In this study, a full-bridge Class D resonant inverter is modeled with Simulink (The MathWorks, Natick, Massachusetts, USA) and controlled with unipolar sinusoidal pulse-width modulation to minimize the switching power losses. The feed-forward control of resonance circuitry is realized with zero voltage switching that detects zero crossing points of the capacitor voltage. The performed analyses have shown that the control scheme is more convenient to reduce switching power losses according to antecedent studies.

Parallel DC-AC conversion system based on separate solar farms with MPPT control

Three separate solar farms that provide 15 kW power for each farm are modelled using Matlab Simulink real-time analysis software in this study. Each solar farm models are constituted by connecting 170W photovoltaic (PV) panels and energy conversion is performed with maximum power point tracking (MPPT) algorithms in each converter. The MPPT algorithm utilized in the control step of converters is developed using Perturb and Observe (P&O) structure. The converters used in the solar farms are designed in boost converter topology while output voltages are collected in DC busbar with parallel connection of converters. The converters are connected to busbar over interphase transformers (IPT). The DC busbar voltage is applied to a full bridge inverter to generate 3-phase AC voltages at the output of inverter. The three-phase inverter is controlled with sinusoidal pulse width modulation (SPWM) scheme, which is developed with phase shifted carrier signals. The load of inverter is set to an adjustable load, which is capable to be increased up to 50 kW. The measurement points seen in the Simulink design are analysed in detail. Each measurement points definition and screen captures are also evaluated in the study.

Microgrid test-bed design with renewable energy sources

This paper is dedicated to microgrid design by using several renewable energy sources (RES) together. The generator side contains the most widely used three types of RESs that are wind energy, solar energy, and fuel cells. The wind turbine is designed according to parameters of a 6.5kW commercial permanent magnet synchronous generator (PMSG). The solar plant that has 15kW rated power is constituted with string connection of 96 solar panels that has 170Wp rated power for each. The last generator of system is modelled according to parameters of a fuel cell that generates 10.5kW peak power. All the generation units are coupled over dc bus-bar by adjusting the voltages to 48Vdc. The dc loads are directly connected to bus-bar while the ac loads are supplied by ac bus-bar that is built by a three-phase 48V/380V-50Hz inverter. An RLC load with 10kW/250VA/250VAR power is connected to the output of inverter. The proposed test-bed can be improved by adding several generator and load types, and additional controllers, breakers, and contactors. In its current state, the proposed test-bed is considered as a preliminary design.

Hybrid microgrid testbed involving wind/solar/fuel cell plants: A desing and analysis testbed

This study introduces design, integration, control, and analysis of a hybrid microgrid (MG) testbed including a 300 kW wind energy plant of three 100-kW permanent magnet synchronous generators (PMSGs), 50 kW solar energy plant of 200 solar panels, and a 50 kW fuel cell stack. Generation side of the hybrid plant coupled on 120V dc bus where wind energy plant consists of uncontrolled diode rectifier and dc-dc buck converter rail while the solar and fuel cell plants are just controlled by dc-dc buck converters. The energy conversion of solar energy plant is operated by using proportional-integral (PI) controller assisted perturb and observe (P&O) maximum power point tracking (MPPT) algorithm. The dc-dc converters of the left generators are operated with PI controllers. All the dc-dc converters are constituted with mosfets that are switched at 30 kHz. The islanded AC grid of the plant is built by three-phase inverter that generates 480 V 60 Hz industrial voltages of the U.S. The inverter is operated by a sinusoidal pulse width (SPWM) modulator where the modulation index is set to 0.8 and switching frequency to 5 kHz. The proposed testbed is assumed essential to test and validate several case studies in terms of MG and renewable energy source integration issues. The most recent power control methods (PQ) and amplitude controls (V-f) can also be implemented by using the presented testbed.

A modified harmonic mitigation analysis using Third Harmonic Injection PWM in a multilevel inverter control

A modified Third Harmonic Injection PWM (THI-PWM) modulator that reduces output harmonics has been presented in this paper. The modulator is combined with harmonic injection and phase shifting parts in Simulink design. The harmonic injection ratios have been analysed according to harmonic amplitude ratio of third harmonic to fundamental amplitude. The designed modulator is capable to minimize the injected harmonic ratio in order to increase the modulation index over 1.15 limit of regular THI-PWM control scheme. The proposed VSI in this paper supplies 7-level line voltages and 0.25% THDi ratio at 5 kHz while the modulation index is 1.2.

Microgrid facility at European union

The global microgrid market is promptly flourishing as government and private sector willingly to support actively. Todays, many countries and government have encouraged installing renewable energy farms for example wind farms and solar farms etc., and huge research has started in various aspect of it at the university level. The energy market in the United States is the largest market which has already taken a clear lead and they have mainly focused on remote microgrid and military microgrid. In European Union region, microgrids have reached in mature technology to participate in utility grid. However, in Asia-Pacific and Far East region has huge potential to grow up renewable energy market in future due to emerging economies to overcome power shortages/power outages and low grid connectivity. This paper presents several distributed generation around the European Union region and we have tabled testbeds information together. It helps the researcher to visualize todays microgrid and insight perceiving the possible evolvement of future grid. The study has concluded emphasizing the remarkable findings and potential research areas that would enhance for microgrid facilities.

Control Methods Applied in Renewable Energy Systems

This chapter is dedicated to introducing the control methods used in renewable energy sources. The conventional and innovative energy generation methods are explained according to their historical background in the initial section. The power electronic circuits that are widely known by most of the readers are briefly analysed in Sect. 2 where the circuit topologies and design criteria are also addressed. The control methods of power electronics used in renewable energy sources such as solar, wind, and fuel cells are comprehensively explained in the following sections. The maximum power point tracking (MPPT) that is the essential part of solar power systems is introduced by means of software and hardware. On the other hand, the required circuit topologies of current control method are explained with grid-connected and island-mode operations of a solar energy system. The rest of the chapter consists of renewable energy systems based on wind turbine and fuel cells. The wind turbine dynamics are initially introduced to create a link through the power electronics and control methods. The control methods of fixed and variable wind turbines are explained regarding to current and voltage control requirements. The fuel cell-based renewable energy systems and control methods are also explained in the last section of the chapter.

Design and implementation of a remote laboratory platform using MATLAB builder for NE

In this study, a highly instructive and novel remote laboratory platform using up to date software and hardware units is designed to teach main concepts of Electrical Engineering with the help of web‐based simulations and remote accessible experiments in real time. Interactive experimental applications for direct current (DC) motors and several electrical circuits are carried out in this study to test the efficiency of the system. First, mathematical model of each simulation is developed in MATLAB and then all models are transferred into .NET platform by means of MATLAB Builder for NE toolbox. A dynamic library for each model is also created using NE toolbox. Then, all libraries are embedded into an interactive web page designed in ASP.NET platform. Data transmission between the server and the real experimental set is established by a microprocessor via the USB port to achieve the experimental studies over the Internet in real time. While remote experiments are being performed, data obtained by the experimental set are simultaneously transferred to the MATLAB. Then, the system generates both graphical and numerical results about the current experiment and all results are sent to a user‐friendly web interface to give users some feedback on the experiment.© 2011 Wiley Periodicals, Inc. Comput Appl Eng Educ 22:617–629, 2014; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.21553