Minimum Total Harmonic Distortion Research Articles

Design and Analysis of Novel Three-Phase PFC for IM Drives

Induction motor drives (IMDs) can achieve high performance levels comparable to dc motor drives. A major problem in getting high dynamic performance in an IMD is the coupling between the flux and torque producing components of stator current. This is successfully overcome in FOC (Field-Oriented Control) IM, making it to the industry standard control. The performance of an IMD with an improved power quality converter at the front end is presented in this study. In the IMD, boost converter is employed to reduce power quality difficulties at the utility interface. As the boost converter contains only one switch, it results in a low processing time and cost. To ensure sinusoidal supply currents with high PF (Power Factor) and minimal THD (Total Harmonic Distortion), a novel PFC (Power Factor Corrector) control technique is proposed. To enhance the performance of the converter and to lower distortions at the motor side, PI (Proportional Integral) controller is incorporated at the PFC side. Thus it controls the DC bus voltage. The proposed boost converter improves power quality by lowering overall harmonic distortion of AC mains current, improving power factor correction, and regulating dc-link voltage. It is designed, modelled, and simulated in the MATLAB/simulink platform. Using a DSP (Digital Signal Processor), the suggested system’s performance is experimentally validated. The system’s performance is evaluated for speed and load torque, and the power quality indices are determined to meet IEEE-519 standards under all operating conditions. From the obtained results, it is evident that the proposed system mitigates the power quality issues effectively.

THD Minimization under Low Switching Frequency for Superior Two Level Three Phase Inverter Performance

The total number of switching pulses permitted in one-quarter of the fundamental-cycle of an inverter is restricted due to the restrictions of switching losses in high-power inverter devices. The elimination of major low-order dominating harmonics using SHEPWM (Selective Harmonic Elimination) is suggested in this research paper. The positive or negative voltage transition at the instant where fundamental voltage has the greatest positive slope distinguishes the various types of waveforms. Due to the switching loss limitations, two forms of the pole voltage PWM waveforms i.e., type A, type B, were studied in this research at lower pulse number (P = 5). For a two-level three-phase inverter, an ideal Pulse Width Modulated (PWM) waveform is developed for whole modulation index range in terms of least total harmonic distortion (THD). MATLAB simulation and practical experiments are performed for a two-level inverter to support the theoretical analysis and results.

Digitally Controlled Bridgeless Totem-Pole Power Factor Corrector

This paper presents the steps of designing, controlling, and implementing a 3kW Gallium-Nitride (GaN)-based bridgeless totem-pole power factor corrector (PFC) for single-phase 230V rectifier applications. The bridgeless design of such a converter combined with zero-recovery switching loss of GaN transistors enables more efficient design operation compared to traditional Si-based solutions. Thermally efficient design with forced-air cooling for the switching devices increased the power density beyond 100W/inch3 while keeping the power switches temperatures less than the thermal limits. Continuous Conduction Mode (CCM) was adopted in this work for better converter stability and was analyzed thoroughly along with the losses breakdown for each part of the converter. The digital control model of the converter was discussed in detail accompanied by the hardware design steps for the converter. Experimental results proved a maximum efficiency of 98.9% during 2.4kW operation and 98.6% during 3kW (full load) operation with minimum Total Harmonics Distortion (THD) of AC input current of 2.78% at rated current (13A) when converting the AC input voltage (230V) to 400 VDC.

Optimal Solution for Frequency and Voltage Control of an Islanded Microgrid Using Square Root Gray Wolf Optimization

Voltage and frequency deviation in the islanded operation of a microgrid (MG), due to the uncertainty and lack of inertia in the selection of optimal proportional integral (PI) controller gain, is a challenging task. Although various optimization algorithms have been proposed to achieve this task, most of them require a large number of iterations and are time intensive, making them inefficient for real-time applications. Gray wolf optimization (GWO), a new meta-heuristic algorithm, addresses these issues and has many advantages, including simplicity due to fewer control parameters, flexibility, and globalism. This paper proposes a simple and efficient modified algorithm, called square root gray wolf optimization (SRGWO) algorithm, to realize superior hunting performance. SRGWO is verified using twenty-three benchmark test functions. The algorithm is applied for optimal voltage and frequency regulation of a photovoltaic-based microgrid system operating in the islanded mode during distributed generation insertion and load change conditions. The voltage and frequency gain parameters of the PI controller are optimized. A comparison of the simulation results of the SRGWO algorithm with those of the original gray wolf algorithm (GWO), particle swarm optimization (PSO), augmented gray wolf optimization (AGWO), enhanced gray wolf optimization (EGWO), and gravitational search algorithm (GSA) reveal that the proposed SRGWO algorithm significantly improves system performance while maintaining its simplicity and easy implementation. Furthermore, the SRGWO algorithm obtains the minimum fitness function value in fewer iterations than other algorithms. Moreover, it improves the power quality of the system with regard to minimum total harmonic distortion.

Indirect power control of grid-connected photovoltaic system using fuzzy control with a three-level inverter

This paper proposes an enhanced study of a photovoltaic generator (PVG) connected to the grid. A fuzzy maximum power point tracking (MPPT) is used to extract maximum power. The control strategy adopted gives the possibility to control separately the active and reactive power. the voltage control at the input of the three levels inverter allows fixing the reference currents in the DQ frame to control indirectly the power injected into the grid. The use of a three-level neutral point clamped voltage source inverter (3L-NPC-VSI) with space vector pulse width modulation (SVPWM) control and the RL filter allows to have a quality current and voltage wave with a minimum total harmonic distortion (THD). The simulation results on MATLAB/Simulink confirm the performance of this proposed strategy in the steady-state with high efficiency.

Differential Evolution Applied to a Multilevel Inverter—A Case Study

This work aims to obtain the switching angles to reduce the total harmonic distortion (THD) and compare the different sets of angles obtained by modifying the modular index (Mi) in a seven-level multilevel inverter using the differential evolution (DE) algorithm. A seven-level cascaded multilevel inverter with RL load was simulated in MATLAB Simulink. The Mi was varied (0.6 to 1.27) to check which set of switching angles is optimal to reduce the THD. These sets of angles are then experimentally validated on a test bench. A brief discussion of the results is presented, comparing the minimum THD found without considering Mi, versus the minimum THD obtained if Mi is less than 1.

Multilevel Inverter with Predictive Control for Renewable Energy Smart Grid Applications

In a world where climate changes and power management are becoming increasingly important, research work focuses on renewable energy based smart grid to meet adequate demands of energy. The smart grid is a modernized autonomous power network that can transmit electricity effectively, conserve resources and costs, and increase the local grid's stability. As a result, a smart grid connected multilevel inverter is presented in this work. The inverter is controlled using a model predictive control algorithm with increased levels with the primary goal of controlling the injected power generated by the renewable source, improving the quality of the current waveform, lowering THD, and eliminating the shift phase among the injected current and the grid voltage in effort to match the smart grid network's requirements. Therefore, this paper aims to show the performance analysis of multilevel inverters with predictive control for renewable energy smart grids application. The major concern was observed with most of the multi-level inverters are that with increased level total harmonic distortion (THD) is increased if switching control is not designed properly. Therefore, in this case predictive control is implemented on renewable energy based smart grid inverters to increase level with minimum voltage THD and current THD. The case analyzed voltage and current THD in the different levels of multilevel inverter. The result analysis was performed on 7, 11, 17, 21, 27, 31, 37 and 41 respectively. From result analysis it was observed that minimum THD was observed with level 31, i.e., 0.35% and at level 41 it was increased up to 0.55% which is still not high as compared to other existing MLI architectures. The result findings of proposed approach decreased THD with varying levels and outperforms better as compared to other works.

Minimization of total harmonic distortion in neutral point clamped multilevel inverter using grey wolf optimizer

<span lang="EN-US">The inverter has been attracting researchers for their application in renewable energy. So far, multilevel inverter is considered as low distortion class, which produces multilevel output voltage imitating a pure sine waveform. However, the needs for free distortion of output voltage have been motivating to improve multilevel pulse width modulation PWM generation method. In this paper, the modified PWM technique is proposed to reduce the voltage total harmonics distortion (THD) of multilevel inverter. This modulation technique is then applied to control a single-phase threelevel neutral point clamped multilevel inverter (NPC-MLI). Grey wolf optimizer (GWO) algorithm is utilized to generate optimal amplitude and phase shift of modified reference signal. The GWO algorithm is then compared with other optimization algorithms such as differential evolution (DE), human psychology optimization (HPO), and particle swarm optimization (PSO) to evaluate their performance in harmonic minimization. The performance of the proposed work is validated through simulation and experimentation on a prototype. The results show that the modified PWM technique optimized with GWO can reduce THD on NPC-MLI output voltage.</span>

Optimal PWM in Three-Level Inverter for THD Minimization with Quarter Wave Symmetry Relaxed

Background: Previous works on total harmonic distortion (THD) minimization for multilevel inverters (MLI’s) has made a symmetrical approach that imposes Quarter Wave Symmetry (QWS) and Half Wave Symmetry (HWS) with the aim to restrict the computational difficulties to solve the finalized non-linear expressions. Objective: However, QWS constraint can be abolished, which leads to more generalized formulations and multiple solutions corresponding to minimum THD for complete modulation index-range. Methods: A systematic search approach using MATLAB in-build function is adopted to investigate ideal angles of switching related to three-level, three-phase inverter restricted to only HWS as a constraint for two and three (i.e., N= 2 and 3) switching transitions per quarter cycle. Results: On account of the effective minimization of the dominant low-order odd line voltage harmonics, the proposed pulse-width-modulation (PWM) scheme proved its superiority based on minimum THD% performance compared to the previously reported PWM techniques with both HWS and QWS being retained. Conclusion: The simulation, as well as experimental results to confirm the efficacy of the proposed non-symmetrical PWM scheme over the traditional PWM method restricted to QWS and HWS symmetries over the entire modulation-index range with added advantage of general formulation and multiple solutions.

Optimization and Design of a Sustainable Industrial Grid System

Electricity is a multifaceted form of energy and is used globally, with a continuously growing demand. Electrical power grids are there for more than 150 years. The generated electrical power is delivered to different industrial, commercial, and residential sectors, thereby fulfilling the ever-growing demand. In this research paper, the design and optimization of an industrial grid for various electrical loads is discussed. The electrical grid ensures a stable power supply to the loads by providing quality power with the minimum total harmonic distortion (THD) possible. A complete study of the short circuit current has been done in two different electrical grid systems, as it is seen that the short circuit current depends on the impedance of the transformer which feeds the load. These two designs of a single diagram will be simulated by using a power system analyzer, the Electrical Transient Analyzer Program (ETAP) software. The different electrical parameters, like choosing the optimised rated generator, cables, and transformers, are done. Load flow analysis is performed on both the design to evaluate the THD, short circuit fault, as well as to choose the right protection circuit for the system.

Predictive Current Control of Six-Phase IM-Based Nonisolated Integrated On-Board Battery Charger Under Different Winding Configurations

Integrated on-board battery charging (IOBC) constitutes one of the future trends and the potential state-of-the-art technologies proposed for high-power chargers of electric vehicles. Model predictive control has recently been favored in different applications due to its simplicity in defining new control objectives and the straightforward handling of nonlinear constraints. In this article, the predictive current control (PCC) is applied to a six-phase induction-machine-based IOBC with three different winding configurations. From the grid perspective, this article introduces the required winding connections that maximize the charging grid current. Under PCC, different stator phases are controlled to draw balanced three-phase grid currents through controlling the machine nontorque-producing <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>xy</i></b> current components while ensuring zero average/ripple torque production. This article also discusses the effect of winding configuration on the mapping of the 64 available voltage vectors to the <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>αβ</i></b> , <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <i>xy</i></b> , and <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0⁺ 0⁻</b> subspaces. The optimal subset voltage vectors of each configuration that achieve the highest possible dc-link utilization, zero torque production, minimum total harmonic distortion (THD), and unity power factor are then introduced. The feasibility to employ the concept of virtual voltage vectors to improve the current quality is also investigated. The three six-phase configurations are obtained from an externally reconfigured 1 kW 12-phase induction motor, which has been used to experimentally validate the theoretical findings.

New direct reactive power control based fuzzy and modulated hysteresis method for micro-grid applications under real wind speed

ABSTRACT This paper presents a fixed-switching frequency of direct reactive power control, called modulated hysteresis-direct reactive power control (MH-DRPC), for a variable speed wind turbine-based doubly fed induction generator (DFIG). Combination of two techniques, i.e. reactive power control-based fuzzy logic control and modulated hysteresis (MH) direct torque control, is the principle of the proposed strategy. The main advantage of this methodology is that the switching frequency of the converter switches is constant, where the major drawback of the classical DRPC is eliminated (the variable switching frequency). This new methodology aims to achieve sinusoidal forms of generated AC current with a constant frequency, ensure minimal current total harmonic distortion (THD), and minimum output voltage ripple irrespective of the wind speed fluctuations. This research work is aimed primarily at analyzing the performances of the new MH-DRPC, taking into account certain constraints that reflect the true working of wind turbine generators, such as the random wind speed behavior and variable reactive power demand. This allows analyzing all operation modes of DFIG, with an emphasis on synchronous and over-speed modes. A comparison with a classical DRPC is made to underline the effectiveness of the suggested approach. The MPPT algorithm and the pitch angle control are invested to optimize the captured wind power. Simulations of the proposed method are made under Matlab/Simulink. The simulation results revealed significant improvements over the classical DRPC in the following characteristics: a significant reduction in current THD supplying the AC grid (98.29%) and a good dynamic response with a significant reduction of ripples of electromagnetic torque (66.67%), rotor flux (42.67%), generated current frequency (96.70%), local reactive power compensation (50.23%), and generated active power (26.34%). In addition, the suggested MH-DRPC technique is extremely robust to machine parametric changes and random variations in references command.

A Simple 18-Pulse Star Rectifier Using Two Passive Auxiliary Circuits at DC Link

In this article, a simple 18-pulse star rectifier using two new passive auxiliary circuits at dc link is proposed for reducing the harmonics content in ac line current. The proposed rectifier combines a double-star rectifier and four-tapped interphase reactor (FTIPR) with four diodes. Passive auxiliary circuits increase the state of the output voltage and current of the double-star rectifier, thereby increasing the pulse number of the load voltage and step number of the input line current. When FTIPR is optimally designed, passive auxiliary circuits convert double-star rectifier to 18-pulse star rectifier. Tap ratios of the FTIPR are determined based on minimum total harmonic distortion (THD) of the input line current and minimum ripple of the output voltage. The proposed rectifier simultaneously reduces ripple of the output voltage and THD of the input line current. A prototype is developed to verify the theoretical analysis through experimental results. Theoretical THD of the input line current is about 10.1%, whereas experimental THD is about 5.44%.

Design and experimental investigation on VL-MLI intended for half height (H-H) method to improve power quality using modified particle swarm optimization (MPSO) algorithm

A Voltage lift performance is an excellent role to DC/DC conversion topology. The Voltage Lift Multilevel Inverter (VL-MLI) topology is suggested with minimal number of components compared to the conventional multilevel inverter (MLI). In this method, the Modified Particle Swarm Optimization (MPSO) conveys a primary task for the VL-MLI using Half Height (H-H) method, it determine the required optimum switching angles to eliminate desired value of harmonics. The simulation circuit for fifteen level output uses single switch voltage-lift inverter fed with resistive and inductive loads (R &amp; L load). The power quality is developed by voltage-lift multilevel inverter with minimized harmonics under the various Modulation Index (MI) while varied from 0.1 up to 1. The circuit is designed in a Field Programmable Gate Array (FPGA), which includes the MPSO rules for fast convergence to reduce the lower order harmonics and finds the best optimum switching angle values. To report this problem the H-H has implemented with MPSO to reduce minimum Total Harmonic Distortion (THD) for simulation circuit using Proteus 7.7 simulink tool. Due to the absence of multiple switches, filter and inductor element exposes for novelty of the proposed system. The comparative analysis has been carried-out with existing optimization and modulation methods.

Improved modified a multi-level inverter with a minimum total harmonic distortion

Renewable energy sources are developed as a result of the increased demand for electrical power. The nature of the solar energy source is DC. The DC source for many applications needs to be converted to AC. The inverter is used to convert the power from DC to AC. Total harmonic distortion (THD) is a significant concern with inverters. Multi-level inverters are used to reduce the THD. The stair output voltage of the multi-level inverter not only reduces the THD but also reduces the switches' stresses, so a low voltage rating can be used for the switches. In this paper, a modified inverter topology is introduced in which the number of switches is reduced for the same number of output voltage levels, which leads to reducing the losses and the cost. To reduce the THD, different amplitudes for the carrier signals that control the switches in each level are suggested. Another method to reduce the THD by using different capacitor values across the input DC source is presented. The MATLAB/Simulink is used to show the validity of the suggested modified topology and the modifications.

Enhanced DTC induction motor drives for THD minimization performance improvement with multilevel inverter

Direct torque control (DTC) is a method applied in induction motor (IM) drives to control the speed and torque of IM accurately and independently without feedback signal. However, in fast fourier transform (FFT) analysis, the total harmonic distortion (THD) of the IM drives is high in DTC method with conventional inverter (CI). Therefore, the purpose of this study is to minimize the THD without affecting the drive’s performance. A DTC IM drive with multilevel inverter (MLI) is proposed in this study to reduce THD and preserve good speed and torque response of IM simultaneously. DTC IM drive with proposed MLI based THD minimization has several advantages over the DTC IM drive with CI, including higher generated output voltage with low distortion, operate under low switching frequency, and work with renewable energy. In order to prove the effectiveness of the proposed MLI based THD minimization in DTC IM drive, MATLAB Simulink is used to investigate the response of the IM drive and THD under different operating condition. From this study, proposed MLI based THD minimization DTC IM drive is able to reduce THD with a maximum of 13% in low speed operation as compared to DTC IM drive with CI.

Power quality improvement of distribution systems asymmetry caused by power disturbances based on particle swarm optimization-artificial neural network

With an increase of non-linear load in today’s electrical power systems, the rate of power quality drops and the voltage source and frequency deteriorate if not properly compensated with an appropriate device. Filters are most common techniques that employed to overcome this problem and improving power quality. In this paper an improved optimization technique of filter applies to the power system is based on a particle swarm optimization with using artificial neural network technique applied to the unified power flow quality conditioner (PSO-ANN UPQC). Design particle swarm optimization and artificial neural network together result in a very high performance of flexible AC transmission lines (FACTs) controller and it implements to the system to compensate all types of power quality disturbances. This technique is very powerful for minimization of total harmonic distortion of source voltages and currents as a limit permitted by IEEE-519. The work creates a power system model in MATLAB/Simulink program to investigate our proposed optimization technique for improving control circuit of filters. The work also has measured all power quality disturbances of the electrical arc furnace of steel factory and suggests this technique of filter to improve the power quality.

Frequency spectra based approach to analytical formulation and minimization of voltage THD in staircase modulated multilevel inverters

Staircase Modulation (SCM) is a popular switching strategy for multilevel inverters (MLI), which is often a preferable alternative to Pulse Width Modulation (PWM) due to its reduced switching losses, especially for MLIs with a relatively high number of voltage levels (N). In some applications, such as motor drives, or when output filters are applicable, SCM may also suit MLIs with moderate N values. While MLIs with Equal DC Sources (EDCS) are more common, MLIs with Unequal DC Sources (UDCS), such as asymmetric Cascaded H-Bridge (CHB) MLIs are known to further reduce the waveforms’ Total Harmonic Distortion (THD). The main objective of SCM is to adjust the waveform’s fundamental component, while employing some harmonic mitigation strategy, such as THD minimization. Such an optimization approach relies on an accurate THD formulation, which eliminates underestimation errors associated with numerical THD approximations. This paper reveals novel generic analytical formulations of both Phase-voltage THD (PTHD) for single-phase MLIs and Line-voltage THD (LTHD) for three-phase MLIs. The revealed exact formulation approach is derived from Fourier series representation of THD, resulting in simple closed-form PTHD and LTHD expressions, applicable to any MLI topology, with either EDCS or UDCS configurations, and arbitrary value of N (odd and even). Given an arbitrary N value, the proposed formulations can be used to generate symbolic N-level PTHD or LTHD expressions, which are symbolic functions of the Phase Switching Angles (PSA) and (optionally) the DC source Ratios (DCR). The revealed THD formulations are verified and compared against recently introduced time-domain-based THD formulations. It is shown that when both time and frequency-based formulations are employed in THD minimizations to form a novel Hybrid Temporal-Spectral (HTS) Optimal Minimization of THD (OMTHD) approach, even better results can be achieved. The novel OMTHD is deeply explored and verified by both digital simulations and Controller + Hardware in Loop (C-HIL) based real-time experiments using 7- and 8-level three-phase MLI configurations. A downloadable supplemental file containing Maple and MATLAB functions of the proposed THD expressions, as well as pre-calculated sets of optimum variables for different values of N is provided for readers' convenience.

Evaluation and Minimization of Total Harmonic Distortion in Three-Phase Two-Level Voltage Source Inverter with Low Switching Frequency

Evaluation and Minimization of Total Harmonic Distortion in Three-Phase Two-Level Voltage Source Inverter with Low Switching Frequency

Evaluation and minimisation of total harmonic distortion in three-phase two-level voltage source inverter with low switching frequency

Evaluation and minimisation of total harmonic distortion in three-phase two-level voltage source inverter with low switching frequency