The Essential Role and the Continuous Evolution of Modulation Techniques for Voltage-Source Inverters in the Past, Present, and Future Power Electronics

The cost reduction of power-electronic devices, the increase in their reliability, efficiency, and power capability, and lower development times, together with more demanding application requirements, has driven the development of several new inverter topologies recently introduced in the industry, particularly medium-voltage converters. New more complex inverter topologies and new application fields come along with additional control challenges, such as voltage imbalances, power-quality issues, higher efficiency needs, and fault-tolerant operation, which necessarily requires the parallel development of modulation schemes. Therefore, recently, there have been significant advances in the field of modulation of dc/ac converters, which conceptually has been dominated during the last several decades almost exclusively by classic pulse-width modulation (PWM) methods. This paper aims to concentrate and discuss the latest developments on this exciting technology, to provide insight on where the state-of-the-art stands today, and analyze the trends and challenges driving its future

Switching Frequency Effects on the Efficiency and Harmonic Distortion in a Three-Phase Five-Level CHBMI Prototype with Multicarrier PWM Schemes: Experimental Analysis

The current climatic scenario requires the use of innovative solutions to increase the production of electricity from renewable energy sources. Multilevel Power Inverters are a promising solution to improve the penetration of renewable energy sources into the electrical grid. Moreover, the performance of MPIs is a function of the modulation strategy employed and of its features (modulation index and switching frequency). This paper presents an extended and experimental analysis of three-phase five-level Cascaded H-Bridges Multilevel Inverter performance in terms of efficiency and harmonic content considering several MC PWM modulation strategies. In detail, the CHBMI performance is analyzed by varying the modulation index and the switching frequency. For control purposes, the NI System On Module sbRIO-9651 control board, a dedicated FPGA-based control board for power electronics and drive applications programmable in the LabVIEW environment, is used. The paper describes the modulation strategies implementation, the test bench set-up, and the experimental investigations carried out. The results obtained in terms of Total Harmonic Distorsion (THD) and efficiency are analyzed, compared, and discussed

FLC based adjustable speed drives for power quality enhancement

This study describes a new approach based on fuzzy algorithm to suppress the current harmonic contents in the output of an inverter. Inverter system using fuzzy controllers provide ride-through capability during voltage sags, reduces harmonics, improves power factor and high reliability, less electromagnetic interference noise, low common mode noise and extends output voltage range. A feasible test is implemented by building a model of three-phase impedance source inverter, which is designed and controlled on the basis of proposed considerations. It is verified from the practical point of view that these new approaches are more effective and acceptable to minimize the harmonic distortion and improves the quality of power. Due to the complex algorithm, their realization often calls for a compromise between cost and performance. The proposed optimizing strategies may be applied in variable-frequency dc-ac inverters, UPSs, and ac drives

Grid integration of renewable power generation

This thesis considers the use of three-phase voltage and current source inverters as interfacing units for renewable power, specifically photovoltaic (PV) into the ac grid. This thesis presented two modulation strategies that offer the possibility of operating PV inverters in grid and islanding modes, with reduced switching losses. The first modulation strategy is for the voltage source inverter (VSI), and exploits 3rd harmonic injection with selective harmonic elimination (SHE) to improve performance at low and high modulation indices, where the traditional SHE implementation experiences difficulties due to pulse dropping. The simulations and experimentation presented show that the proposed SHE allows grid PV inverters to be operated with less than a 1kHz effective switching frequency per device. This is vital in power generation, especially in medium and high power applications. Pulse dropping is avoided as the proposed modified SHE spreads the switching angles over 90°, in addition increasing the modulation index. The second proposed modulation strategy, called direct regular sampled pulse width modulation (DRSPWM), is for the current source inverter (CSI). It exploits a combination of forced and natural commutation imposed by the co-existence of an insulated gate bipolar transistor in series with a diode in a three phase current source inverter, to determine device dwell times and switching sequence selection. The DRSPWM strategy reduces switching frequency per device in a CSI by suspending each phase for 60°, similar to VSI dead-band, thus low switching losses are expected. Other benefits include simple digital platform implementation and more flexible switching sequence selection and pulse placement than with space vector modulation. The validity of the DRSPWM is confirmed using simulations and experimentation. This thesis also presents a new dc current offset compensation technique used to facilitate islanding or grid operation of inverter based distributed generation, with a reduced number of interfacing transformers. The proposed technique will enable transformerless operation of all inverters within the solar farm, and uses only one power transformer at the point of common coupling. The validity of the presented modulation strategies and dc current offset compensation technique are substantiated using simulations and experimentation.This thesis considers the use of three-phase voltage and current source inverters as interfacing units for renewable power, specifically photovoltaic (PV) into the ac grid. This thesis presented two modulation strategies that offer the possibility of operating PV inverters in grid and islanding modes, with reduced switching losses. The first modulation strategy is for the voltage source inverter (VSI), and exploits 3rd harmonic injection with selective harmonic elimination (SHE) to improve performance at low and high modulation indices, where the traditional SHE implementation experiences difficulties due to pulse dropping. The simulations and experimentation presented show that the proposed SHE allows grid PV inverters to be operated with less than a 1kHz effective switching frequency per device. This is vital in power generation, especially in medium and high power applications. Pulse dropping is avoided as the proposed modified SHE spreads the switching angles over 90°, in addition increasing the modulation index. The second proposed modulation strategy, called direct regular sampled pulse width modulation (DRSPWM), is for the current source inverter (CSI). It exploits a combination of forced and natural commutation imposed by the co-existence of an insulated gate bipolar transistor in series with a diode in a three phase current source inverter, to determine device dwell times and switching sequence selection. The DRSPWM strategy reduces switching frequency per device in a CSI by suspending each phase for 60°, similar to VSI dead-band, thus low switching losses are expected. Other benefits include simple digital platform implementation and more flexible switching sequence selection and pulse placement than with space vector modulation. The validity of the DRSPWM is confirmed using simulations and experimentation. This thesis also presents a new dc current offset compensation technique used to facilitate islanding or grid operation of inverter based distributed generation, with a reduced number of interfacing transformers. The proposed technique will enable transformerless operation of all inverters within the solar farm, and uses only one power transformer at the point of common coupling. The validity of the presented modulation strategies and dc current offset compensation technique are substantiated using simulations and experimentation

THD Analysis of a Seven, Nine, and Eleven Level Cascaded H-Bridge Multilevel Inverter for Different Loads

A multilevel inverter is implemented for generating the required staircase AC voltage of output from various steps of voltages of DC sources. The multilevel inverter gives a better harmonic spectrum and a compatible quality of output. This article delves into an analytical analysis of the total harmonic distortion (THD) of different multilevel inverters which employ a multicarrier PWM technique. This technique is implemented for operating the switches at their respective angle of conduction. This paper deals with various cascaded H-Bridge multilevel inverters (CMI) with various loads that are modelled by implementing the MATLAB/Simulink platform. The output gives a better result of the proposed model in terms that it is helpful towards reducing the THD and the losses of switching

Implementation of SHE-PWM technique for single-phase inverter based on Arduino

This paper presents design and practical implementation of single-phase inverter based on selective harmonic elimination-pulse width modulation (SHE-PWM) technique. Microcontroller mega type Arduino used as a controller for producing the gate pulses. The optimized switching angles determination results in wide range of output voltage. Depending on number of switching angles, the lower order harmonics (LOHs) can be eliminated to improve the output voltage waveform. A comparison study using MATLAB/Simulink for sinusoidal-PWM and SHE-PWM techniques, which shows for the same LOH in the output voltage waveform, the SHE-PWM has less number of pulses per half cycle than sinusoidal-PWM strategy. The reduction in number of pulses results less switching losses. The simulation done using ten switching angles to drive R-L load. A prototype of SHE-PWM inverter with R-L load is used to validate the simulation results

Application of the cascaded multilevel inverter as a shunt active power filter

Abstract unavailable please refer to PD

Development and implementation of two-stage boost converter for single-phase inverter without transformer for PV systems

This paper offers a two-stage boost converter for a single-phase inverter without transformer for PV systems. Each stage of the converter is separately controlled by a pulse width modulated signal. A Simulink model of the converter using efficient voltage control topology is developed. The proposed circuit performance characteristics are explained and the obtained simulation results are confirmed through the applied experiments. Moreover, this paper has examined the control circuit of a single-phase inverter that delivers a pure sine wave with an output voltage that has the identical value and frequency as a grid voltage. A microcontroller supported an innovative technology is utilized to come up with a sine wave with fewer harmonics, much less price and an easier outline. A sinusoidal pulse width modulation (SPWM) technique is used by a microcontroller. The developed inverter integrated with the two-stage boost converter has improved the output waveform quality and controlled the dead time as it decreased to 63 µs compared to 180 µs in conventional methods. The system design is reproduced in Proteus and PSIM Software to analyze its operation principle that is confirmed practically

Interleaved Buck Converter Based Shunt Active Power Filter with Shoot-through Elimination for Power Quality Improvement

The “shoot-through” phenomenon defined as the rush of current that occurs while both the devices are ON at the same time of a particular limb is one of the most perilous failure modes encountered in conventional inverter circuits of active power filter (APF). Shoot-through phenomenon has few distinct disadvantages like; it introduces typical ringing, increases temperature rise in power switches, causes higher Electromagnetic Interference (EMI) and reduces the efficiency of the circuit. To avert the “shoot-through”, dead time control could be added, but it deteriorates the harmonic compensation level. This dissertation presents active power filters (APFs) based on interleaved buck (IB) converter. Compared to traditional shunt active power filters, the presented IB APFs have enhanced reliability with no shoot-through phenomenon. The instantaneous active and reactive power (p-q) scheme and instantaneous active and reactive current component (id-iq) control scheme has been implemented to mitigate the source current harmonics. Type-1 and Type-2 fuzzy logic controller with different membership functions (MFs) viz. Triangular, Trapezoidal and Gaussian have been implemented for the optimal harmonic compensation by controlling the dc-link voltage and minimizing the undesirable losses occurred inside the APF. Additionally, the adaptive hysteresis band current controller (AHBCC) is being implemented to get the nearly constant switching frequency. The performance of the control strategies and controllers for the presented IB APF topologies has been evaluated in terms of harmonic mitigation and dc-link voltage regulation under sinusoidal, unbalanced sinusoidal and non-sinusoidal voltage source condition. This dissertation is concerned with the different topologies of 3-phase 4-wire IB APFs viz. split capacitor (2C) topology, 4-leg (4L) topology, transformer based full-bridge IB APF or single capacitor based FB IB APF (1C 3 FB IB APF) and full-bridge IB APF (FB IB APF) for low to medium power application. Moreover, APF topology is now being expanded to multilevel VSIs for high power application. Thanks to flexible modular design, transformerless connection, extended voltage and power output, less maintenance and higher fault tolerance, the cascade inverters are good candidates for active power filters with the utility of high power application. The cascaded FB IB APF is modelled with no shoot-through phenomenon by using multicarrier phase shifted PWM scheme. Extensive simulations have been carried out in the MATLAB / Simulink environment and also verified in the OPAL-RT LAB using OP5142-Spartan 3 FPGA to support the feasibility of presented IB APF topologies, control strategies and controllers during steady and dynamic condition. The performance shows that IB-APF topologies bring the THD of the source current well below 5% adhering to IEEE-519 standard. A comparison has also been made, based on SDP (switch device power) between the IB-APF topologies

Bipolar and unipolar schemes for confined band variable switching frequency PWM based inverter

The single phase inverter performance through the unipolar and bipolar strategies has been previously analyzed based on the constant switching frequency pulse width modulation (CSFPWM). However, the confined band variable switching frequency PWM (CB-VSFPWM) is currently proposed as a new variable switching frequency PWM technique through unipolar strategy to facilitate the design of high order filter, to reduce the switching losses, and to reduce the current total harmonics distortion (THD) as well. To evaluate the performance of a single phase inverter based on the CBVSFPWM through bipolar strategy, this paper presents a comparative study of the CB-VSFPWM based inverter performance using the unipolar PWM and the bipolar PWM strategies. The study adopts MATLAB/Simulink to simulate the inverter and to analyze the simulation results in terms of harmonics spectrum, total harmonic distortion (THD), and fundamental components. The analysis of the study results gives an indication about the appropriate type of CB-VSFPWM strategy (unipolar PWM or bipolar PWM) to guarantee the desired performance of the connected inverter in terms of the electrical grid standards like THD, and harmonics spectrum of the inverter current