Minimum Total Harmonic Distortion Research Articles

Analysis of Cascaded Asymmetric Inverters using Low Frequency Technique

Multilevel inverters include a wide range of configurations and numerous benefits. Since each level switching angle is not neatly prepared, most conventional inverters cannot produce optimized waveforms. To attain an adequate voltage profile, we should indeed closely review the switching angle arrangement to attain a minimal Total Harmonic Distortion (THD). This work focuses on Cascaded H Bridge (CHB) multilevel inverters with asymmetrical configuration operating under a low frequency (LF) scheme. This work discusses various methods of harmonic mitigation techniques that comes under the LF scheme which includes the finest switching angle optimizations for generating various levels. Furthermore, the effectiveness of the topologies is investigated by minimizing lower-order harmonics and THD. THD is compared for various mitigation techniques for seven and nine-level configurations. The proposed configurations are simulated by employing MATLAB/Simulink. THD is calculated theoretically and evaluated by comparing it to simulated results for the suggested inverters. Additionally, thermal simulations of the configuration are carried out in PLECS to estimate power losses and efficiency. The suggested configurations are examined utilizing OPAL-RT (4510) test bed and the outcomes are included.

Determination of Optimal Locations and Parameters of Passive Harmonic Filters in Unbalanced Systems Using the Multiobjective Genetic Algorithm

This paper discusses the problem of optimal placement and sizing of passive harmonic filters to mitigate harmonics in unbalanced distribution systems. The problem is formulated as a nonlinear multiobjective optimisation problem and solved using the multiobjective genetic algorithm. The performance of the proposed algorithm is tested on unbalanced IEEE 13- and 37-bus three-phase systems. The optimal solutions are obtained based on the following objective functions: 1) minimisation of total harmonic distortion in voltage, 2) minimisation of costs of filters, 3) minimisation of voltage unbalances, and 4) a simultaneous minimisation of total harmonic distortion in voltage, costs of filters, and voltage unbalances. Finally, an analysis of the influence of uncertainties of load powers and changes in system frequency and filter parameters on filter efficiency was performed.

Enhancing power stability and efficiency with multilevel inverter technology based on renewable energy sources

Power conversion raises harmonics, which can cause increased losses and decreased power stability. The limitations of conventional inverters can be addressed by using the technological innovations of multilevel inverters. In recent years, there has been a growing use of multilevel inverter technologies as affordable alternatives for many industrial applications. In addition to having fewer components and switching losses, this architecture provides superior output voltage/current waveforms. The most crucial need for multilevel inverters is the minimization of total harmonic distortion that can be present at the output side of the DC/AC inverter for both voltage and current waveforms. This study proposes a system that consists of five distinct renewable energy sources with output voltages of 1E, 2E, 3E, 4E, and 21E. A new control technology is utilized to achieve 63 voltage levels at the output. Renewable energy sources include battery systems, wind turbines, PV systems, diesel generators, and hydropower plants. Different scenarios are proposed in this work to ensure proper system design and maintenance of the power supply, such as the loss of one or two of the renewable energy sources mentioned above.

A Three-Phase Multilevel Inverter Synthesized with 31 Levels and Optimal Gating Angles Based on the GA and GWO to Supply a Three-Phase Induction Motor

A three-phase multilevel inverter (MLI), synthesized with 31 levels in regard to its output voltage, is used to provide the AC supply to a three-phase, squirrel cage induction motor. The gating angles required for the 30 power switches on the MLI are optimized using both the genetic algorithm (GA) and the grey wolf optimizer (GWO), in which the optimal angles are determined through solving the trigonometric equations taken from Fourier analysis to target the minimum total harmonic distortion (THD) at the MLI output. A simulation model and an experimental prototype are developed for performance analysis and validation. The results demonstrate that the MLI is effectively able to produce 31 levels of three-phase AC output voltage, with the THD not exceeding 5% when loaded with a resistive load and a three-phase induction motor. The voltage and current are measured and recorded for different loads and operating conditions, including the amount of energy consumed by the load. The results of the frequency analysis demonstrate that most of the triple harmonics, which can harm the efficiency of the inverter, are cancelled.

A review on intelligence algorithms for THD minimization in multi-level inverter

ABSTRACT The multi-level inverter (MLI) is advantageous for DC to AC voltage conversion in power distribution networks. The low-power applications require square and quasi-square waveforms, whereas the sinusoidal waveform is required in high-power applications. The pure sinusoidal waveform of an inverter is obtained by improving the number of levels in the inverter. Hence, more switches and DC sources are used in the inverters to produce multi-levels at the output. The large number of switches and DC sources increases harmonics in the system. The modulation techniques are used with the MLI topologies to alleviate these issues. Recently, modulation techniques based on optimization algorithms have been used to minimize Total Harmonic Distortion (THD). This paper reviews optimization algorithm-based modulation techniques in the recent literature. This review aims to provide an effective solution for enhancing THD in MLI. Different MLI types are initially explained, and then the recent algorithms are explained for THD minimization.

Harmonic elimination of a fifteen‐level inverter with reduced number of switches using genetic algorithm

AbstractMultilevel inverters play a crucial role in high‐power renewable energy applications and medium voltage drives. However, existing solutions such as capacitor‐clamped and diode‐clamped multilevel inverters are not suitable for these applications due to their dependence on isolated DC sources, complex control techniques, and potential reliability issues. Here, a novel fifteen‐level inverter topology is proposed which addresses these limitations. The proposed multilevel inverters utilize a topology with reduced number of switches, which can effectively accommodate isolated DC sources. It consists of eight switches for level generation and four switches for polarity generation (H‐bridge). One of the key advantages of this topology is that it significantly reduces the Total Harmonic Distortion (THD) in accordance with the IEEE 519 standards. Genetic algorithm‐based selective harmonic elimination technique was employed for THD minimization. A detailed switching loss calculation and harmonic analysis were performed to support the effectiveness of the proposed topology and the control used. The implementation of the proposed topology is simple and straightforward. Furthermore, to validate the results, insulated gate bipolar transistor based hardware model was developed. The optimized firing pulses were generated using the dSPACE 1104 controller. The results were compared with the existing recent literature and was found to address the limitations of existing topology.

Multiobjective Optimization Design of a Brushless Excitation Synchronous Motor Based on the Taguchi Method

Considering the issue of significant total harmonic distortion in the no-load back electromotive force (EMF) and torque ripple of a brushless excitation synchronous motor (BESM) used in a compressor, a multiobjective optimization design method of a BESM based on the Taguchi method was proposed. By selecting the polar arc coefficient, stator slot width, damping winding pitch, and air gap length as the optimization parameters, the maximum no-load back EMF, minimum back EMF total harmonic distortion rate, and minimum torque ripple are selected as the optimization objectives. Then, the Taguchi method was employed to construct an orthogonal table to enhance the performance of the optimization objectives. This approach facilitated the determination of the optimal parameter combination for optimization. Finally, the simulation results indicate significant enhancements in each optimized aspect of the motor’s performance following the optimization process. This outcome serves as validation for the efficacy of the Taguchi method in achieving an optimal design for the BESM.

Phase noise suppression technique based on an improved reference interferometer scheme.

The reference interferometer scheme is an effective noise reduction method, but the optical path length difference (OPD) of the two interferometers must be strictly equal, which limits its application in practical environments. In this paper, an improved reference interferometer demodulation technique without strictly equal OPDs is proposed to suppress phase noise. By introducing a reference interferometer, the phase noise can be removed from the demodulation results. The combination of the differential self-multiplication algorithm and the fitted phase modulation depth calculation formula can evaluate the phase modulation depth of both interferometers in real time and simultaneously eliminate the nonlinear distortion caused by phase modulation depth drift and the effect of different OPDs on the reference interferometer scheme. The experimental results show that the technique can obtain highly stable and accurate demodulation results even if the OPDs of the two reference interferometers are different. The phase modulation depth calculation error is less than 0.57%, the maximum phase noise reduction is 15 dB, the average reduction is 9 dB, the minimum total harmonic distortion is 0.17%, and the SINAD reaches 35.90 dB.

Exact THD Calculations Applied to Minimize Space Harmonic Content of Winding and Rotor Magnetic Fields

As a metric for measuring the combined space harmonic content of electric machine winding magnetomotive force (MMF), the winding total harmonic distortion (THD) is defined with an infinite series. Without truncation, the exact THD can be evaluated via a “family grouping” facilitated by a “family sum” over the fewest possible winding factors. Uniformly applicable to distributed windings and fractional-slot concentrated windings (FSCWs), this procedure also explains the inherent difference in harmonic content between both winding categories. Furthermore, the minimal THD (mTHD) that can be achieved by optimizing a winding is revealed with a closed-form expression. While intended for windings, the mTHD concept also benefits the design of low harmonic content rotor magnetic fields. Examples of both winding and rotor mTHD designs are provided.

THD Minimization in a Seven-Level Multilevel Inverter Using the TLBO Algorithm

This paper presents the minimization of total harmonic distortion in a seven-level cascaded H-bridge multilevel inverter with resistive load using the teaching–learning-based optimization algorithm. The minimization of Total Harmonic Distortion (THD)is a challenging optimization problem due to the fact that nonlinear equations are involved. Recently, bio-inspired algorithms have become very popular approaches to solving various optimization problems in different areas of engineering. For this reason, the results obtained with the Teaching–Learning-Based Optimization (TLBO)algorithm were compared with three other popular bio-inspired algorithms, the genetic algorithm, differential evolution, and particle swarm optimization. The comparative analysis, conducted by sweeping the modulation index, made it possible to obtain graphs and data on the behavior of the four analyzed algorithms. Finally, it was concluded that the TLBO algorithm is very effective and is able to solve the THD-minimization problem. Its main advantage over the other algorithms is the fact that it does not require control parameters for its correct operation in the solution of the problem.

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.

Üç Fazlı Bir Asenkron Motorun Çeşitli Bobin Adım Biçimi ile Performans ve Harmonik Analizi

In this work, analyses of the effect of full-, under-, and over-pitched stator winding configurations on the efficiency, output power, torque characteristics, and current and voltage harmonic components are carried out on a three-phase, squirrel cage induction motor. Performance analyses have been performed both via Ansys/RMxprt and Maxwell/2D software by modelling the stator winding with coil pitches of 100°, 120°, 140°, 160°, 180°, 200°, 220°, 240°, and 260°. Current and voltage harmonics analyses have been performed in Matlab using the data obtained from Maxwell/2D simulations. Maxwell/2D results showed that the maximum efficiency is attained at 200° over-pitched configuration, which is 0.73% higher than the efficiency when the motor is full-pitched. The maximum output power and torque are attained at 240° over-pitched configuration, which is 7.96% and 7.45% more than the power and torque obtained when the motor is full-pitched, respectively. Harmonic analysis results showed that both under-pitched and over-pitched coils can be used to eliminate harmonics in the current and voltage waveforms. However, over-pitched coils performed better in eliminating the phase current harmonics. The minimum total harmonic distortion (THD) of the phase current and induced voltage are reached at 260° over-pitched and 120° under-pitched configurations, which is 52.39% and 74.36% lower than the THD when the motor is full-pitched, respectively. Over-pitched coils provide slightly higher efficiency, output power, and torque than the under-pitched coils. There is no unique coil pitch configuration to eliminate all harmonic components. Therefore, in order to eliminate a specific harmonic component, a specific coil-pitch must be applied.

Ameliorated PGC demodulation technique based on the ODR algorithm with insensitivity to phase modulation depth.

For the optical fiber sensing system using phase generated carrier (PGC) technology, it is very important to eliminate the nonlinear effect of phase modulation depth (C) fluctuation on the demodulation results in the actual environment. In this paper, an ameliorated phase generated carrier demodulation technique is presented to calculate the C value and suppress its nonlinear influence on the demodulation results. The value of C is calculated out by the fundamental and third harmonic components with the equation fitted by the orthogonal distance regression algorithm. Then the Bessel recursive formula is used to convert the coefficients of each order of Bessel function contained in demodulation result into C values. Finally, the coefficients in demodulation result are removed by the calculated C values. In the experiment, when the C ranges from 1.0 rad to 3.5 rad, the minimum total harmonic distortion and maximum phase amplitude fluctuation of the ameliorated algorithm are 0.09% and 3.58%, which are far superior to the demodulation results of the traditional arctangent algorithm. The experimental results demonstrate that the proposed method can effectively eliminate the error caused by the fluctuation of the C value, which provides a reference for signal processing in practical applications of fiber-optic interferometric sensors.

Harmonic Distortion Reduction of Transformer-Less Grid-Connected Converters by Ellipsoidal-Based Robust Control

A photovoltaic generator connected to a large network and supplying a nonlinear load (source of harmonics) injects distorted current into the grid. This manuscript presents an invariant-ellipsoid set design of a robust controlled active power filter to inject current into the large grid with minimum total harmonic distortion (THD). The nonlinear load current is considered an external disturbance to minimize its effect on the injected grid current. Moreover, the large grid is modeled as a fixed voltage source in a series with a Thevenin impedance whose value changes within an interval. Using the invariant-ellipsoid technique, the problem is cast as a robust disturbance-rejection tracking control. The volume of the ellipsoid is minimized, which results in minimizing the effect of disturbance on system performance and keeping the trajectories as close as possible to the origin. The design is cast into a set of nonlinear matrix inequalities that are linearized by fixing a scalar. The resulting convex optimization is solved iteratively by linear matrix inequalities (LMIs). The simulation and experimental findings show that the proposed design is successful in reducing THD injected into the grid when grid impedance is uncertain and variable loads are applied (balanced and unbalanced cases).

THD Minimization and Reliability Analysis of Cascaded Multilevel Inverter

Inverters are DC to AC power converters that are widely used in AC motor drives and distributed energy generation systems. Multi-Level Inverters (MLIs) have emerged as the preferred inverter technology because of their advantages of reduced switching losses and better harmonic profile. This paper deals with the Minimization of Total Harmonic Distortion (MTHD) of Symmetric Cascaded H-bridge Multi-Level Inverter (SCMLI) and Asymmetric Cascaded H-bridge Multi-Level Inverter (ACMLI). A hybrid memetic algorithm composed of heuristic PSO (Particle Swarm Optimization) algorithm and traditional MAS (Mesh Adaptive direct Search) is proposed to optimize the switching angles. In Photo Voltaic (PV) system, the input DC voltage generally varies from its nominal value due to the change in temperature and irradiance. Thus, the sensitivity analysis of THD and harmonics is also carried out considering the variations with non-integer magnitudes of input DC sources. The experimental prototype of SCMLI and ACMLI topology is developed and validated with simulation results. The reliability and Mean Time to Failure (MTTF) of SCMLI and ACMLI are investigated based on power losses of the MOSFET and thermal parameters.

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.

Kriging-Assisted Multiobjective Optimization of Embedded Magnetic Encoder in PM Synchronous Machines

The embedded magnetic encoder (EME), located in stator slot of permanent magnet (PM) synchronous machines (PMSMs), monitors the PM flux-density in the cavity and feedback the rotor angle for vector control. To reduce the total harmonic distortion (THD) of flux-density and improve the angle estimation accuracy, the topology optimization of PMSMs can be carried out. However, as THD is set as the only objective during optimization, the other characteristics, e.g., back electromotive-force (back-EMF) due to PMs, and winding inductance of PMSMs will uncontrollably change. Hence, a systemic design optimization of PMSM combined with EME is necessary. Different from the traditional multi-objective optimization of electric machines based on the time-consuming finite element analysis (FEA), in this paper a Kriging-assisted surrogate model is proposed to replace FEA during optimization, achieving time saving and high prediction accuracy simultaneously. The decision variables are carefully selected. e.g., a Cosine function reshaping method is proposed and proper linear Hall installation position is analyzed. In the preliminary optimization, the Pareto front with minimum THD and maximum rotor saliency is obtained. Further, by modifying the THD objective with retaining the third harmonic component, the THD becomes lower and rotor saliency is increased in the optimal case. Finally, three different rotors are manufactured to verify the effectiveness of proposed reshaping method and improved optimization strategy.

A Lyapunov-Based Model Predictive Control Approach for Photovoltaic Microgrid Integration via Multilevel Flying Capacitor Inverter

In this study, we introduce a Model Predictive Control (MPC) approach based on a Lyapunov energy function, ensuring global asymptotic stability for a single-phase multilevel flying capacitor inverter (FCI) that interfaces with photovoltaic systems and microgrids. The defined cost function is derived from the Lyapunov energy function, harnessing the stored energy within the capacitor and inductor. This choice is rooted in the principle that as long as total energy is continuously dissipated, the system’s states will eventually reach the equilibrium point. Moreover, this cost function eliminates the need for tuning the weighting factors, a process that can be cumbersome and time-consuming due to the lack of clear guidelines. To assess the efficacy of the proposed control strategy, we conducted simulations using MATLAB/Simulink under varying weather conditions. The results obtained demonstrate that the MPC strategy not only ensures overall stability but also delivers high-quality sinusoidal current with minimal total harmonic distortion (THD), practical low steady-state error in the grid current, and rapid dynamic response, even in the face of changing weather conditions.

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.