Total Harmonic Distortion Of Output Voltage Research Articles

Comparative evaluation of Z source / quasi Z-source direct and indirect matrix converters for PMG based WECS

The present era sees the dominance of wind energy conversion systems as a leading technology in renewable energy. Various technologies have been devised to harness wind energy, with variable speed systems emerging as particularly advantageous. Consequently, these systems are designed to operate at specified speeds using power electronic interfaces, maximizing power extraction from the wind. The integration of Permanent Magnet Generators (PMGs), directly linked to the wind turbine lacking a gearbox, allows operation at minimum speeds. To stabilize the continuously fluctuating output voltage of the PMG, power electronic converters are extensively utilized in Wind Energy Conversion Systems (WECS), ensuring a consistent voltage and frequency output. The voltage gain of Traditional matrix converters (MCs) is limited to less than 0.866. In turn, the Z-source (ZS) and discontinuous QZSDMC, as well as ZS IMCs, topologies have achieved voltage gains exceeding 0.866. However, the former provides complicated commutation issues from DMC, while the latter incorporates a Z source network in the DC link, resulting in a non-all-silicon solution. A novel continuous QZSDMC and QZSIMC are suggested, wherein a qZS network incorporates the grid-side filtering function. This design eliminates the need for an additional input filter in the proposed system. Three newly introduced topologies of ZSDMC, QZSDMC and QZSIMC are thoroughly compared across various parameters including voltage gain, current and voltage ripples, inductor current and capacitor voltage stresses, filtering capabilities, input current, and output voltage Total Harmonic Distortion (THD), finally efficiency. The paper presents their control and modulation methods to achieve the desired performance levels. Experimental comparisons validate the theoretical analysis and demonstrate the potential of the proposed QZSDMC as a promising topology.

Single Phase Sine-Wave Inverter with High DC Bus Utilization Using Natural Compensation

Abstract- In this paper, a new fixed frequency single phase sine-wave inverter topology - having high DC bus utilization - is presented. The main inverter uses six IGBT switches operating at low frequency in over-modulation mode to create a five-level voltage waveform; thus, having low switching losses with high DC bus utilization. A series active power filter (SAPF) using power MOSFETs helps to remove the major harmonic voltages. No isolated DC power supply is required across the SAPF that works on a simple feed-forward compensation (instead of feedback), based on the principle of natural compensation. The DC bus voltage needed for the SAPF is about half of the inverter, thus the SAPF has low switching loss even at the designated switching frequency. The switching frequency components of the SAPF remain in the output as they are not compensated, necessitating the use of a small filter at the output to attenuate them, to create a low total harmonic distortion output voltage with higher fundamental compared to the conventional schemes using Sinusoidal Pulse Width Modulation. The proposed inverter is suitable for fixed frequency backup power supply or other applications like renewable energy connection to the power grid.

Design a 25-level inverter topology with less switching devices fed by PV systems

<span lang="EN-US">Multilevel inverter (MLI) technology has lately emerged as one of the most popular solutions for high power and medium voltage energy management. MLIs have many benefits and require more switches for higher levels, which are considered disadvantaged. This could result in large size and extremely expensive cost for the MLI. So, in order to overcome this problem, a new MLI topology is proposed with reduced number of switches. A 25‐level inverter fed by isolated unequal photovoltaic panels as DC sources is chosen in this study. The structure of DC voltages is chosen as (1:1:5:5) Vdc. The proposed approach, which is created using twelve switches, is ideally suited for a high-power application. Multi-carrier with a sinusoidal PWM technique is programmed as a controller. According to the simulation findings, a single-phase system's output voltage and current total harmonic distortion (THD) values are 1.2% and 0.462%, respectively, while a three-phase system's values are 1.07% and 0.342%. These findings prove that the power circuit and investigation were successful.</span>

A novel control method for enhanced performance of single‐phase matrix converters

AbstractThe conventional topology of direct single‐to‐single‐phase matrix converter (SSMC) is widely adopted in industrial and power system‐related applications owing to its desired features. Current control methods in the literature either limit the voltage transfer ratio (VTR) or prohibit their utilization to drive inductive (RL) loads. In this study, we propose a novel control method that overcomes these limitations by enabling the SSMC to achieve relatively high VTRs while driving RL loads with negligible output voltage spikes and without current commutation problems. Further, the proposed control method improves the overall performance by reducing output voltage and source input current total harmonic distortion (THD) and offering soft‐switching at the commutation instances. The rigidity of the proposed control method over the counterpart methods in the literature is verified through simulation and experimental case studies over a wide range of synthesized output frequencies and modulation indexes. A 530‐W laboratory prototype is built for the experimental study. Results demonstrated the ability of the proposed method in enabling the SSMC to drive an RL load without current commutation issues and with mitigated output voltage spikes while achieving relatively high VTRs and suppressing the output voltage and source input current THD.

Neutral-point-clamped inverter based synchronous reluctance motor drive for solar pump application

PurposeIndustrial drives require appropriate control systems for reliable and efficient performance. With synchronous reluctance machines (SynRMs) slowly replacing the most commonly used induction, switched reluctance and permanent magnet machines, it is essential that the drive and its control be properly selected for enhanced performance. But the major drawback of synchronous reluctance motor is the presence of high torque ripple as its design is characterized by large number of variables. The solutions to reduce torque ripple include design modifications, choice of proper power electronic inverter and PWM strategy. But little has been explored about the power electronic inverters suited for synchronous reluctance motor drive to minimize torque ripple inherently by obtaining a more sinusoidal voltage. The purpose of this paper is to elaborate on the potential multilevel inverter topologies applicable to SynRM drives used in solar pumping applications.Design/methodology/approachThe most significant field-oriented control using maximum torque per ampere algorithm for maximizing the torque production is used for the control of SynRM. Simulation results carried out using Matlab/Simulink are presented to justify the choice of inverter and its control technique for SynRM.FindingsThe five-level inverter drive gives lesser core or iron losses in the SynRMin comparison to the three- and two-level inverters due to lower Id current ripple. The five-level inverter reduces the torque ripple of the SynRM significantly in comparison to the three- and two-level inverter fed SynRM drives. The phase disposition-PWM control method used for the inverter shows the least total harmonic distortion (THD) levels in output voltage compared with the other level shifted PWM techniques.Originality/valueAmong the available topologies, a fitting topology is proposed for use for the SynRM drive to have minimal THD, minimal current and torque ripple. Additionally, this paper presents various modulation techniques available for the selected drive system and reports on a suitable technique based on minimal THD of output voltage and hence minimal torque ripple.

A Reduced Switch Count Multilevel Inverter for PV Standalone System using Modified JAYA Algorithm

ABSTRACT This paper introduces a hybrid multilevel inverter (MLI) with reduced switch count, which can generate higher output voltage level with minimum number of DC input sources. The operation of this proposed MLI is carried out with unequal DC sources to achieve the desired output voltage level. The reduced MLI output voltage is set to minimal total harmonic distortion (THD) with the help of modified JAYA (MJAYA) algorithm. A JAYA algorithm with improved steps by adopting an accelerating parameter has been proposed in this research work to obtain a faster convergence of the objective function. The MJAYA algorithm has provided the suitable switching angles for the proposed three-phase 15-level MLI and reduced the output voltage THD to 2.23%, which satisfies the standard set by IEEE-519. To prove the efficiency of this proposed modified algorithm, the comparative analysis is carried out through MATLAB program and Simulink tool using common JAYA and modified particle swarm optimisation algorithms. The performance and productivity of the proposed MLI have been investigated through simulation and experimental setups.

Control Strategy for Resonant Inverter in High Frequency AC Power Distribution System with Harmonic Suppression and Transient Performance Improvement

In high frequency AC (HFAC) distribution system, the resonant inverter is used to improve power quality and keep the stability of the output AC voltage. Aiming at the problems of poor output power quality and slow transient performance caused by unreasonable filter parameter design and load change during inverter operation, a single-phase H-bridge LCLC resonant inverter based on analog circuit controller implement is introduced in this paper for HFAC power distribution system (PDS). In this study, to design harmonic compensator and analyze the responsiveness of the inverter, it is necessary to analyze the output voltage total harmonic distortion (THD) of LCLC resonant inverter and the performance of the open loop system in detail. On the one hand, a proportional-integral-resonant (PIR) controller is designed to maintain the zero static error of the voltage output and suppress the output voltage THD of LCLC resonant inverter. On the other hand, an integral controller combines with phase-shift modulation (PSM) method is presented to effectively improve the transient performance of resonant inverter and provide the fixed frequency of the output voltage. On the basis of the above, the experimental prototype is implemented with the output AC voltage root mean square of 28 V, and the output voltage frequency for resonant inverter is equal to switching frequency. A rated output power of 130 W experimental platform is built to verify the effectiveness of the theoretical analysis, control strategy, and modulation method.

A New Transformer-Less Single-Phase Photovoltaic Inverter to Improve the Performance of Grid-Connected Solar Photovoltaic Systems

Photovoltaic (PV) energy systems have found diverse applications in fulfilling the increasing energy demand worldwide. Transformer-less PV inverters convert the DC energy from PV systems to AC energy and deliver it to the grid through a non-isolated connection. This paper proposes a new transformer-less grid-connected PV inverter. A closed-loop control scheme is presented for the proposed transformer-less inverter to connect it with the power grid. The proposed transformer-less inverter reduces extra leakage current and holds the common-mode voltage at a constant point. To eliminate extra leakage current, as well as achieve constant common-mode voltage, a midpoint clamping method is utilized to operate the inverter. The proposed transformer-less inverter is formed of seven insulated gate bipolar transistors (IGBTs) employing a unipolar sinusoidal pulse width modulation (SPWM) technique for switching purposes. An LCL filter is employed to reshape the two-level inverter output voltage and current to obtain closer sinusoidal waveforms. The output voltage and current total harmonic distortion (THD) of the proposed transformer-less inverter were found to be 1.25% and 0.94%, respectively, in the grid-connected mode. The leakage current elimination mechanism with the proposed transformer-less inverter is deeply analyzed in this paper. The performances of the proposed transformer-less inverter were evaluated with MATLAB/Simulink simulation and validated in a laboratory scale experiment.

Adaptive SMC based cascaded control of the grid-forming inverter

ABSTRACT The grid-forming inverter (GFI) plays an indispensable role in the microgrid (MG). Thus, it is critical for a microgrid to control the GFI flexibly and accurately, because of its voltage-forming and frequency regulation capabilities. The conventional proportional integral (PI) control strategy is usually used to control the GFI. However, the conventional PI control strategy has a high output voltage total harmonic distortion (THD) and deteriorative performance under external disturbances, which results in several problems in system flexibility, reliability and stability. This paper proposed a novel adaptive sliding mode control (ASMC) based cascaded control of the GFI system, which involves an ASMC-based inner current loop and outer voltage loop, and shows some superior performances of low THD, fast dynamic tracking performance and good robustness. Both the MATLAB/SIMULINK-based simulation and StarSim Modelling Tech-based semi-physical experimental results were presented to validate a perspective: the control strategy proposed by this paper has a better performance than the conventional PI control strategy under transient and steady-state condition.

Integrated Damper Cage for THD Improvements of Variable Speed Salient-Pole Synchronous Generators for the More Electric Aircraft

Wound field synchronous generators (WFSGs) have been implemented as aircraft main ac power generation for decades. The trend of moving toward more electric aircraft (MEA) made dc and variable-frequency ac buses favorable for the next-generation power systems in aircraft, as opposed to constant frequency ac grid systems. The minimization of the generators’ output voltage total harmonic distortion (THD) is an ever-more critical objective, especially for variable-frequency power systems where this target has to be met within the whole range of operating speeds. In conventional, constant speed, and WFSGs, a number of consolidated techniques are implemented to meet this requirement. In variable-speed SGs intended for the MEA, these techniques are no longer fully effective and new methodologies are thus necessary. This article replaces the conventional squirrel-type damper cage with a new integrated damper cage (IDC) located at the interpole regions. The proposed IDC, while acting as a mechanical structure to retain the field windings at high operating speeds, also achieves very low-voltage THD values at different speeds, thus complying with the power quality requirement. A 250-kVA prototype is designed, analyzed, built, and tested to prove the proposed concepts and methodologies.

New Nine-Level Cascade Multilevel Inverter with a Minimum Number of Switches for PV Systems

To support the grid system with high power quality from photovoltaics (PVs) and reduce the partial shading condition (PSC) effect of the PV system, as well as the mismatch power issue, in this study, we present a simple single-phase, nine-level cascade inverter architecture for photovoltaic (PV) systems with a minimum number of power components and passive parts. This reduction in the number of switches decreases the switching losses and the number of driving circuits, which causes a reduction in the complexity of the control circuit and hence reduces the cost and size. The suggested inverter shows a lower output voltage total harmonic distortion (THD) and unity power factor. In addition, this inverter’s control and switching techniques are far simpler than those of recently published designs. To evaluate the performance of the proposed inverter, we performed a comparison of the cascaded multilevel inverter (CMLI) topology, which required recent cascade topologies with the same nine voltage levels. The comparison depends on parameters such as the number of components (diode and capacitors) and the number of active switches in the inverter, in addition to total harmonic distortion. MATLAB/Simulink models for a grid-tied solar system PV application driven by the proposed nine-level inverter were built for design and validation.

Robustness of Model-Predictive and Passivity-Based Control in the Three-Phase DC/AC Converter Application

In modern controller design, various solutions for controlling power converter systems can be found depending on their applications, speed of working, pulse width modulation (PWM) techniques, switching frequencies—fc, and different load types. The need to manipulate control parameters can be often observed in classical structures, e.g., well-known PID, repetitive, or deadbeat control particularly sensitive to distinct parameters uncertainties. The purpose of this paper is to present an improved version of controllers designated for a UPS that will be considerably resistant to model changes. Proposed control techniques are independent of unexpected output filter changes: Lf—filter coil inductance and Cf—filter capacitor conductance. The second aspect of this paper is to compare effectiveness of modified predictive MPC (model-predictive control) and feedback PBC (passivity-based control) controllers in reducing output voltage total harmonic distortion (THD) for various load values. The biggest distortions of output voltage were observed during experiments with nonlinear RC load. Both simulation and experimental verification of mismatching parameters were performed and examined. Thanks to the proposed solution, the output voltage THDv quality factor was reduced below 8% in an efficient way for all the applied loads and stayed at the level of 1% when well-matched filter parameters were provided.

Open Circuit Fault Diagnosis in Five-Level Cascaded H-Bridge Inverter

The development of power electronic converter, especially multilevel converter, is remarkable for several decades. The complex switching and increased power of semiconductor devices are prime reasons for faults in multilevel inverters and have raised question about reliability. To improve the reliability, a cost-effective solution in terms of fault diagnosis is essential. In this context, this study proposed an open circuit fault (OCF) diagnosis technique for a switching device in a five-level cascaded H-bridge multilevel inverter using fuzzy logic control. The OCF features like output voltage total harmonic distortion (THD) and normalized average output voltage are fuzzed as input variables of the fuzzy logic controller. These input variables are divided into various triangular antecedent membership function (MF). The output produced by the fuzzy controller as consequent MFs is divided into different levels to identify the faulty switch. In order to make a complete fault-tolerant structure, a reduced modulation index-based postfault control is suggested to get a balanced output voltage. The MATLAB/Simulink results and prototype results are the evidence to support the proposed fault diagnosis technique.

Design of new structure of multilevel inverter based on modified absolute sinusoidal PWM technique

The advantage of multilevel inverters is to produce high output voltage values with distortion as minimum as possible. To reduce total harmonic distortion (THD) and get an output voltage with different step levels using less power electronics switching devices, 15-level inverter is designed in this paper. Single-phase 11-switches with zero-level (ZL) and none-zero-level (NZL) inverter based on modified absolute sinusoidal pulse width modulation (MASPWM) technique is designed, modelled and built by MATLAB/Simulink. Simulation results explained that, multilevel inverter with NZL gives distortion percent less than that with ZL voltage. The THD of the inverter output voltage and current of ZL are 4% and 1%, while with NZL is 3.6% and 0.84%, respectively. These results explain the effectiveness of the suggested power circuit and MASPWM controller to get the required voltage with low THD.

An enhancement approach of Reboost converter for unification of disparate WECS with the utility grid system

The WECS is an important phenomenon to reduce green house gas emission. The power generated from wind energy is clean, zero emission and volatility. The generation of Wind energy is stochastic due to the variation of velocity of wind. The Unification of WECS with the utility grid is a major formidable area of research. The integration of grid with WECS is done by means of Rotor side converter and Grid side inverter. These two converters are linked by using a DC link capacitor in a conventional system. In this paper, a novel topology had been proposed. The conventional system DC link element is replaced by Reboost converter. A Reboost converter is a DC–DC converter which bestows boosting or increased output voltage. It comprises a power MOSFET switch, hence the switching stress is minimized and efficiency of the proposed converter is predominant. The Reboost converter dispenses a continuous input current that lessen the voltage stress. The output ripple voltage and total harmonic distortion factor are minimized. A comparative analysis on different types of wind generators are performed by implementing the Reboost converter. The input voltage total harmonic distortion, output voltage, output power and output voltage total harmonic distortion factor are determined. The MATLAB Simulation on different types of wind generators are analyzed and the results prove that Doubly fed induction generators are expedient. • The Wind energy conversion system is a blooming technology in the field of research area to meet the energy demands in the world. • The article focuses on performance study of the proposed Reboost converter on the different wind energy conversion systems. • According to the literature survey and the simulation results attained, it had been concluded in the article the proposed converter with Doubly fed Induction Generator bestows the better performance on comparison with Permanent Magnet Synchronous Generator and Squirrel Cage Induction Generator. • The circuit description of the proposed converter along with its modal circuit had been elaborated in the article. • The Simulation Circuit Schematic of Reboost Converter with Utility Grid for PMSG, SCIG and DFIG based WECS are embraced with its performance study and its values are verified experimentally.

A Novel Dual Slope Delta Modulation Technique for a Current Source Inverter Based Dynamic Voltage Restorer for Mitigation of Voltage Sags

This article investigates the use of a dual-slope delta modulation (DSDM) technique to control a dynamic voltage restorer (DVR) that can mitigate the voltage sag problems in power systems. Traditionally, the DVR uses a pulsewidth modulation technique to control the power electronic switches in a voltage source inverter (VSI). However, the VSI suffers from several disadvantages, such as ripples in the output voltage, high dv/dt, and high total harmonic distortion. To overcome these problems, this article proposes a novel DSDM technique for a current source inverter (CSI) based DVR. The proposed DSDM technique generates the switching pulses for the power electronic switches in the CSI to produce the required missing voltage waveforms with the necessary phase angle jump to restore the load voltage to its nominal value following power systems faults. The DVR usually requires an energy storage device to support the system voltage during voltage sag, which is referred to as a storage-energy-supplied (SES) DVR. However, the energy storage device makes the DVR bulkier and costlier. A line-energy-supplied (LES) DVR scheme has been proposed in the literature that can eliminate the need for the energy storage device and hence has the potential to reduce the cost of the DVR. To validate the proposed DSDM technique, different types of fault-induced voltage sags are simulated in a radial distribution system. The proposed DSDM technique is tested to control the CSI-based SES-DVR and LES-DVR to mitigate the voltage sag. The simulation results show that the proposed DSDM technique is effective to mitigate the voltage sags by accurately injecting the required missing voltage both in magnitude and phase angle.

Design and Simulation of a Boost-Microinverter for Optimized Photovoltaic System Performancec

Renewable energy sources are the most important type of energy since they are clean and do not affect the environment. Solar energy is a kind of renewable energy that is more popular than other sources. Photovoltaic (PV) systems use solar energy as a source of electricity. The main parts of any PV system are: PV panel, DC-DC converter with maximum power point tracking and a DC-AC inverter with an adequate control. The Photovoltaic system for this study comprises a boost converter, a full-bridge inverter and an LCL filter. The boost converter is controlled using the Maximum power point Tracking (MPPT) algorithm, while the inverter is controlled through a Sinusoidal Pulse Width Modulator (SPWM).This paper provides a comparison performance between perturbation and observation [P&O] and particle swarm optimization [PSO] algorithms to get MPP for PV system. When the irradiance changes, the micro-inverter adapts under partial conditions. The micro-inverter is designed by MATLAB / Simulink/2020a software. The input maximum voltage from the PV is 80V direct current (DC) while alternating current [Ac] output voltage is 110 Vrms. The output voltage and current total harmonic distortion (THD) ratios are 2.58% and 2.76% respectively when the P&O algorithm is used , while that when using the PSO algorithm are 2.45% and 2.58%.The PV system efficiency achieved by using P&O, PSO are 95.7%, 96.8%.

Seven-Level Inverter with Reduced Switches for PV System Supporting Home-Grid and EV Charger

This paper proposes a simple single-phase new pulse-width modulated seven-level inverter architecture for photovoltaic (PV) systems supporting home-grid with electric vehicle (EV) charging port. The proposed inverter includes a reduced number of power components and passive elements size, while showing less output-voltage total harmonic distortion (THD), and unity power factor operation. In addition, the proposed inverter requires simple control and switching strategies compared to recently published topologies. A comparative study was performed to compare the proposed inverter structure with the recent inverter topologies based on the number of components in the inverter circuit, number of components per output-voltage level, average number of active switches, THD, and operating efficiency as effective parameters for inverter performance evaluation. For design and validation purposes, numerical and analytical models for a grid-tied solar PV system driven by the proposed seven-level inverter were developed in MATLAB/Simulink environment. The inverter performance was evaluated considering grid-integration and stand-alone home with level-2 AC EV charger (3–6 kW). Compared with recently published topologies, the proposed inverter utilizes a reduced number of power components (7 switches) for seven-level terminal voltage synthesis. An experimental prototype for proposed inverter with the associated controller was built and tested for a stand-alone and grid-integrated system. Due to the lower number of ON-switches, the inverter operating efficiency was enhanced to 92.86% with load current THD of 3.43% that follows the IEEE standards for DER applications.

Analysis and Simulation of a Single Phase Nine Level Inverter with Reduction in Power Switching Devices

This paper present analysis and modelling of single phase nine level inverter, a Wide range of Modulation index (M) varied between 0.05-1.05 is achieved by two switching strategies (Optimized harmonic stepped waveform (OHSW), (Optimal minimization of total harmonic distortion (OTHD)) the first strategy focusses on harmonic elimination and the other on reducing output voltage total harmonic distortion (THD). Calculation of switching angles for both equal and unequal dc sources is done by Genetic Algorithm (GA). simulation in Matlab, PSpice and PSIM is presented in this work.

Predictive Nearest-Level Control Algorithm for Modular Multilevel Converters With Reduced Harmonic Distortion

Owing to the low number of submodules (SMs) in modular multilevel converters (MMCs), especially in medium-voltage applications, the output current and voltage generated by conventional nearest-level control (NLC) methods contain evident distortions. Previously, various hybrid and level-increased NLC methods have been proposed to improve the output voltage quality, but such measures wither increased the complexity or did not regulate all the control objectives simultaneously. To further enhance the output performances of MMCs containing low numbers of SMs, an improved predictive NLC (I-PNLC) method combining NLC and model predictive control (MPC) is proposed, where the output and circulating currents are regulated with the corresponding predicted references, and the output voltage is controlled by the added voltage correction. The proposed I-PNLC not only reduces the output current and voltage total harmonic distortion (THD) considerably but also avoids additional complexity in the control system design. The results of simulations and an experiment are presented to verify the proposed approach, in addition to a comparison of the evaluations of conventional NLC methods.