Current Total Harmonic Distortion Research Articles

Bi-directional Battery Charging/Discharging Converter for Grid Integration: A Step Towards Power Quality and Efficient Energy Management in Electric Vehicles

This paper presents the design and simulation of a bi-directional battery charging and discharging converter capable of interacting with the grid. The proposed converter enables Electric Vehicles (EVs) not only to charge their batteries from the grid but also to discharge excess energy back into the grid through the Vehicle-to-Grid (V2G) operating mode. The work discusses charger design considerations, including control strategies, and examines its potential contribution to efficient energy management and grid stability. Furthermore, a simulation study using MATLAB/Simulink validates the performance, efficiency, and dynamic response of the bi-directional converter, demonstrating its viability for real-world grid integration. The simulation shows better performance in various performance aspects, including high-power factor correction (PFC), minimized steady-state oscillations, reduced DC link voltage overshoot, increased overall efficiency, and both voltage and current Total Harmonic Distortions (THD maintained below 5%).

Novel Integrated NLC-SHE Control Applied in Cascaded Nine-Level H-Bridge Multilevel Inverter and Its Experimental Validation

In this paper, a novel integrated SHE - NLC control is proposed for the mitigation of unwanted lower-order harmonics in the cascaded H-bridge multilevel inverter. The proposed algorithm has been developed by hybridizing the NLC and SHE methods, in an attempt to keep the merits of both the individual control. The switching angles and nearest levels are calculated by applying the Genetic Algorithm (GA). The proposed technique reduces the calculation time and implementation complexity, thus can be a viable alternative to the real time implementation for SHE. Integrated NLC-SHE control is tested by varying the modulation index and load dynamics. This technique resulted in the reduction in Total Harmonic Distortion (THDs) in load voltage and current. Comparative analysis of NLC, SHE and Integrated NLC-SHE technique is also performed on the CHB nine-level inverter. There is significant reduction in voltage and current THD values and power losses. Efficiency of the inverter is increased. The efficacy of the proposed control CHB nine-level is tested on MATLAB Simulink environment and further validated by experimental results.

Single-Phase Hybrid Switched-Capacitor PFC Boost Rectifier With Low Voltage Gain

Power factor correction (PFC) rectifiers based on the classic boost topology have become widespread owing to their current input features, and can obtain optimal results in terms of power quality. However, several applications require an output dc voltage lower than the ac input voltage. In such cases, two-stage topologies provide lower voltage values at the output, which increases the number of components. Moreover, such topologies tend to incur higher losses and are costly. Therefore, a unidirectional hybrid single-stage single-phase PFC boost rectifier with a switched-capacitor cell and low voltage gain is proposed. Furthermore, the proposed topology has two active switches, and natural balance exists between the voltages of the capacitors. Therefore, an additional control system is not required. The proposed topology was theoretically analyzed and experimentally validated using a 1 kW prototype with two different operational situations: (A) 127 V ac and 100 Vdc; (B) 220 Vac and 200 Vdc, input and output voltages, respectively. The experimental results essentially reveal that the power factor is approximately one, and the total harmonic distortion of the input current is 4.6%. The maximum efficiency achieved was 96.5% in the operational situation (B).

Optimized Power Factor Correction for High Speed Switched Reluctance Motor

The Power Factor Correction (PFC) in Switched Reluctance (SR) motor is discussed in this article. The SR motors are applicable for multiple applications like electric vehicles, wind mills, machineries etc. The doubly salient structure of SR motor causes the occurrence of torque ripples, which affects the power factor of the motor. To improve the power quality, the power factor has to be corrected and the ripples have to be minimized. In order to achieve these objectives, a novel power factor correction (PFC) method is proposed in this work. Here, the conventional Diode Bridge Rectifier (DBR) is replaced by a Bridgeless Hybrid Resonant (HR) converter, which assists in improvising the output in a wider range. The converter is chosen because of having variety of beneficial measures including high gain. The converter’s output is fed to the SR motor by means of an asymmetric Bridge Resonant (BR) converter. The proposed converter operates in continuous mode of conduction with the switching frequency of 10 KHz. A hysteresis current controller and Proportional Integral (PI) controller are utilized for reducing the harmonics in the source current along with the regulation of output voltage. In addition, the speed control of SR motor is accomplished by means of the Whale Optimization Algorithm (WOA) assisted PI controller. The proposed methodology is effective for the control of unity power factor, torque and current ripples. The Total Harmonic Distortion (THD) of the source current is also minimized, which suits the standard of International Electrotechnical Comission IEC 61000-3-2. By this methodology, the power factor of 0.99 is achieved with 97% efficiency and 3.92% THD. The proposed methodology is validated in simulation by MATLAB and in hardware by FPGA Spartan 6E.

Optimisation of Model Predictive Torque Control Strategy with Standard and Multi-Objective Genetic Algorithms

Abstract In this paper, the flux error-related weighting factor (WF) of the predictive torque control (PTC) strategy for induction motor (IM) control is optimised by a standard genetic algorithm (SGA) through speed errors only and multi-objective genetic algorithm (MOGA) through torque and flux errors. This paper compares the performances of both optimisation methods. Compared to MOGA, SGA offers a straightforward way to select WF and does not need a decision-making method to choose a final solution. But MOGA considers the given problem in a multi-objective way and directly optimises the control objectives of the PTC strate-gy. Comparisons are made over the flux and torque ripples, total harmonic distortion of stator phase current, and average switching frequency for different operating conditions. Simulation results show that both methods choose a close WF value. Consequently, SGA stands out in the optimisation of the PTC strategy with its simple structure.

A Fractional Order Fast Repetitive Control Paradigm of Vienna Rectifier for Power Quality Improvement

Due to attractive features, including high efficiency, low device stress, and ability to boost voltage, a Vienna rectifier is commonly employed as a battery charger in an electric vehicle (EV). However, the 6k ± 1 harmonics in the acside current of the Vienna rectifier deteriorate the THD of the ac current, thus lowering the power factor. Therefore, the current closed-loop for suppressing 6k ± 1 harmonics is essential to meet the desired total harmonic distortion (THD). Fast repetitive control (FRC) is generally adopted; however, the deviation of power grid frequency causes delay link in the six frequency fast repetitive control to become non-integer and the tracking performance to deteriorate. This paper presents the detailed parameter design and calculation of fractional order fast repetitive controller (FOFRC) for the non-integer delay link. The finite polynomial approximates the non-integer delay link through the Lagrange interpolation method. By comparing the frequency characteristics of traditional repetitive control, the effectiveness of the FOFRC strategy is verified. Finally, simulation and experiment validate the steadystate performance and harmonics suppression ability of FOFRC.

PSO Trained Feed Forward Neural Network Based SAPF for Power Quality Enhancement in Distribution Networks

Power distribution infrastructure is being harmed by the advent of nonlinear devices, which cause harmonics to enter into the power system networks and distort the voltage and current signals. Shunt Active Power Filter (SAPF) is a new power electronics-based technology that can reduce harmonics and improve the power quality in distribution networks. This research provides an efficient and inexpensive strategy to minimizing harmonics and improving the power quality in power distribution networks by employing Shunt Active Power Filter’s (SAPF), which uses the Particle Swarm Optimized Artificial Neural Network Controller (PSO-ANN). The goal of the PSO-ANN algorithms have been developed for SAPF is to improve system performance by lowering the amount of Total Harmonic Distortion (THD). In this work, the standard PI controller is initially tuned using the PSO algorithm to obtain the optimal gain values (Ki, Kp) for the PI controller. After that, these values of the PSO-PI controller's input and output will serve as a dataset for the ANN controller. Now, the PSO algorithm is being used to tune this ANN controller in order to acquire the optimal values for the weight and bias. Using the MATLAB/SIMULINK tool, the proposed algorithm's performance is evaluated and compared to that of a PSO-PI based SAPF and the conventional PI based SAPF. The results of the simulation demonstrate that a SAPF which is based on a PSO-ANN controller is capable of achieving superior THD in the drawing source current while maintaining minimum levels and which are acceptable in accordance with the IEEE-519 standard for harmonics.

Variable Pulse Density Modulation for a Buck-Type Three-Switch Current Source Rectifier

With flexible voltage adjustment without an intermediate DC/DC converter, short-circuit protection, self-starting, high reliability, and three-phase current source rectifiers (CSRs) are being widely used in high-power medium-voltage applications and low-power low-voltage applications. Modulation methods significantly affect the performance of CSRs and can be categorized into offline modulation methods, such as selective harmonic elimination/compensation pulse width modulation (SHE/SHC-PWM), and online modulation methods, such as space vector pulse width modulation (SV-PWM) and carrier-based pulse width modulation (CB-PWM). The SHE/SHC-PWM is popular in high-power medium-voltage applications that do not require a fast dynamic response and have a low switching frequency. Online modulations considerably improve the dynamic response and performance of the CSR; however, high computational power, such as digital signal processors (DSPs), is required at higher switching frequencies, leading to greater system complexity and cost. In this paper, an offline method based on variable pulse density modulation (VPDM) of power switches to synthesize sinusoidal input currents and control power transfer with pulse width modulation (PWM) is proposed. The proposed modulation is applicable to the three-switch buck-type VIENNA rectifier, showing the capability of improving the input current total harmonic distortion (THD) with respect to the SHE-PWM and is comparable to online modulations at a sufficiently high switching frequency. The simulation and experimental results basically prove the feasibility of the proposed modulation.

Data Driven Model Predictive Control for Modular Multilevel Converters With Reduced Computational Complexity

Model predictive control (MPC) has become increasingly popular among researchers for modular multilevel converters (MMCs) due to its ability to incorporate multiobjective control and provide superior dynamic response. However, it is computationally challenging to implement it on MMCs when the number of submodules is increased. This paper proposes a finite control set (FCS) model predictive control (MPC) with reduced computational complexity for modular multilevel converters (MMCs). To accomplish this goal, a reduced order data-driven model is obtained using sparse identification of nonlinear systems (SINDy) by incorporating the input terms in the load current and circulating current dynamics. As a result, the need to use the arm voltages or the submodule capacitor voltages dynamic equations as in the case of a conventional FCS-MPC is eliminated. To improve the output current total harmonic distortion (THD) and reduce the effect of higher switching frequencies caused by the FCS-MPC, an updated cost function is proposed. The effectiveness of the proposed technique is validated by simulation and experimental results.

Soft-Switched Integrated AC–DC Bidirectional Converter With Natural Grid Harmonic Elimination

Two-stage ac–dc converters have hard-switched ac–dc stage followed by soft-switched dc–dc stage. Since devices in the ac–dc stage are switched at low frequency (typically 10–20 kHz), bandwidth of current control loop of this stage is limited (typically less than 2 kHz). This low bandwidth current loop fails to reject current harmonic disturbances arising due to distorted grid voltages, thus necessitating multiple harmonic compensation loops or complex control algorithms for meeting IEEE Std 519-2014. Lack of soft-switching prohibits devices of the ac–dc stage from being switched at a frequency above 100 kHz and thereby attain a bandwidth of around 10 kHz for natural rejection of grid current harmonics. This article proposes an integrated three-phase bidirectional isolated ac–dc converter, where soft-switching operation is extended to devices in ac–dc stage as well. Thus, high bandwidth current loop can be achieved without reduction in efficiency. The proposed modulation scheme decouples ac–dc and dc–dc operations using <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xor</small> logic. An iterative procedure for design of resonant tank is provided. The integration also leads to 25% fewer devices. Experiments carried out on a 5-kW prototype demonstrate that a low current total harmonic distortion, complying with IEEE standard, can be achieved with good efficiency, even under distorted grid voltages.

DC-Link Capacitance Reduction in PFC Rectifiers Employing PI+Notch Voltage Controllers

It is well-known that adding a notch filter in series with the typically employed type-II (or PI) regulator allows improving the tradeoff between dc-link voltage dynamics and grid-side current total harmonic distortion (THD) in practical single-phase power factor correction rectifiers. The article demonstrates that notch filter utilization alternatively allows reducing the value of dc-link capacitance in case hold-up time requirement is absent. The revealed value of minimum capacitance is expressed by explicit function of possible mains frequency values range, maximum expected grid voltage magnitude, rated system power, dc-link voltage set point, maximum tolerable grid-side current THD, and the desired phase margin (PM) of dc-link voltage loop. It is demonstrated that the proposed approach yields fourfold reduction of dc-link capacitance for typical values of 5% tolerable grid-side current THD under 40° PM constraint. Experimental results exhibit close-fitting resemblance to corresponding analytical predictions, verifying the proposed methodology.

A Hybrid PWM Technique to Improve the Performance of Voltage Source Inverters

Due to the rapid advancement of power semiconductor devices, the use of voltage source inverters (VSIs) has gained widespread acceptance. As a consequence, the performance of the voltage source inverter has emerged as a critical aspect that is highly reliant on the modulation strategy. The pulse width modulation (PWM) technique is the most widely utilized method of controlling power semiconductor switches of VSI. Power quality is always considered as an industrial concern for VSI-based power system such as grid-connected renewable energy systems and industrial motor drives which largely depends on the PWM technique used for switching. However, the existing PWM schemes for VSIs suffer from high total harmonic distortion (THD) and power loss problems. To mitigate the THD and power loss of VSI, a hybrid PWM technique has been proposed in this paper. The proposed hybrid PWM technique introduces a modified modulating signal along with newly shaped carrier signal. A two-level VSI is used to evaluate the performance of the proposed hybrid PWM technique both for with and without filter conditions against RL load. The proposed hybrid PWM technique offers 0.89% filtered voltage THD and 0.69% filtered current THD which are lower than that of existing PWM techniques. On the contrary, at without filter condition, the proposed hybrid PWM technique shows THDs of 45.77% and 12.50% for inverter output voltage and current, respectively which are also lower than those of existing PWM techniques. Apart from these, the proposed hybrid PWM technique reduces the switching and conduction power losses of the VSI as compared to existing PWM techniques. The simulation works are carried out in MATLAB/Simulink environment and a reduced scale experiment is conducted in laboratory to evaluate the performance of the proposed hybrid PWM technique.

Design of the inverter in high accuracy and development of work therein by using compound ligation

A ligation (CL) system with a very high frequency in an inverter was used, it is a novelty in this study. We also employed a three-phase dynamic load (positive sequence voltage) to correct the power factor and account for active and reactive power in the output system this work is a novelty. The technique through compound ligation (CL) can improve inverter output waveform by reducing losses caused by ingrained agents in voltage source inverters (VSI), such as dead time caused by overload or voltage drop in an inverter's output, or abnormal load current conditions such as a short circuit current occur in the output stage of the inverter, and so on. The invention relates to the conversion of D.C. to A.C. power inverters, it is preferable to use compound ligation to achieve high efficiency, the device is lightweight, and has low losses and good precision. In addition, the present invention relates to improving an inverter load request sensation circuit, smoothing operational current, inverter response, and inverter spontaneous power factor improvement, as well as correction of the reactive power of passive components. In addition, an inverter with high active power (P) equal to (2.6×106 Watt), reactive power (Q) (5.4×107 VAR), was designed, and used positive sequence voltage (1.6×108 Watt ), as well as the switching period (10µs), The system's total harmonic distortion (THD) in voltage and current was 0.11 percent, while the system's accuracy was 99 percent. This is developed by using FPGA and oscillator circuit and programmable peripheral interface 8255 A as well as, ultrasonic PWM with a high-frequency range of (20–500 kHz) as demonstrated evidenced by the results obtained

Implementation of an ADALINE-Based Adaptive Control Strategy for an LCLC-PV-DSTATCOM in Distribution System for Power Quality Improvement

This study investigated the problem of controlling a three-phase three-wire photovoltaic (PV)-type distribution static compensator (DSTATCOM). In order to model, simulate, and control the system, the MATLAB/SIMULINK tool was used. Different controllers were applied to create switching pulses for the IGBT-based voltage source converter (VSC) for the mitigation of various power quality issues in the PV-DSTATCOM. Traditional control algorithms guarantee faultless execution or outcomes only for a restricted range of operating situations due to their present design. Alternative regulators depend on more resilient neural network and fuzzy logic algorithms that may be programmed to operate in a variety of settings. In this study, an adaptive linear neural network (ADALINE) was proposed to solve the control problem more efficiently than the existing methods. The ADALINE method was simulated and the results were compared with the results of the synchronous reference frame theory (SRFT), improved linear sinusoidal tracer (ILST), and backpropagation (BP) algorithms. The simulation results showed that the proposed ADALINE method outperformed the compared algorithms. In addition, the total harmonic distortions (THDs) of the source current were estimated under ideal grid voltage conditions based on IEEE-929 and IEEE-519 guidelines.

Harmonic mitigation in a hybrid system using intelligent control methods

The demand for electrical energy is increasing day by day. Therefore, renewable energy systems are used in the power system. Due to the intermittent nature of renewable sources, hybrid systems are developed. This paper presents a cascaded multilevel inverter fed with hybrid DC (Direct Current) sources. The pulses to the switches of the proposed inverter are obtained using the sinusoidal pulse width modulation method. An intelligent control method for the regulation of the output voltage of the inverter is implemented. The performance of the intelligent control strategy is compared with that of the conventional PI (Proportional Integral) controller. Furthermore, the proposed system is compared with the existing works. The simulation and experimental results show that the proposed controller outperforms well by providing a voltage and current THD (Total Harmonic Distortion) of 4.13% and 0.93%, respectively, which are within the IEEE (Institute of Electrical and Electronics Engineers) 519-2014 standard.

Artificial intelligence based active and reactive power control method for single-phase grid connected hydrogen fuel cell systems

In grid-connected power generation systems, power factor fluctuations caused by non-linear power circuits used between the grid and source should be controlled with the help of voltage source inverters (VSI). In addition, in order to improve the quality of the electrical energy injected into the grid and to prevent possible electrical faults, the total harmonic distortion (THD) in the grid current should be controlled in accordance with IEEE-519 standards. In other respects, uncontrolled injected energy may causes losses, excessive electrical energy demand and overloading. In this study, an artificial neural network based active and reactive power control method is proposed for grid-connected single-phase Proton Exchange Membrane Hydrogen Fuel Cell (PEMFC). The aim of the proposed control structure is to have low harmonic distortion, high power factor performance as well as an easy and understandable structure. The proposed method was applied to a 6 kW prototype. Five different scenarios and nine different activation function were tried to verify the performance of the proposed control method. As a result of these processes, the power factor was measured as unity (>0.99) and the total harmonic distortion (THD) of the grid current, under all operation states, is <2%. In addition, it has been observed that the success rate of artificial neural networks is >97%.

Control of distribution static compensator with active damped inductor‐capacitor‐inductor filter using dual loop αβ‐frame current controllers for power quality improvement

AbstractA distribution system is connected with many non‐linear loads, and generated harmonies are mitigated by using distribution static compensator (DSTATCOM) which is coupled at the point of common coupling through a voltage source inverter (VSI) and filter circuit. High‐frequency switching ripples are generated along with the output of the VSI during pulse width modulation switching. Inductor‐capacitor‐inductor (LCL) filter is used to suppress the high frequency switching noises. Still, the primary concern about the LCL filter is generation of resonance peak at the resonance frequency. The conventional synchronous reference frame current controller with LCL filter has a complex coupling between and axis; hence decoupling is very difficult. This research article presents a new technique based on active damped dual loop ‐frame current controllers to control the DSTATCOM with LCL filter for achieving improved load compensation. The dual loop controller is enhanced by using capacitor current in the inside loop and grid current at the outside loop with proportional resonant (PR) regulator parallel with harmonic compensator (HC). The proposed method effectively dampens the resonance peak under stationary reference frame The PR controller offers unlimited gain at the fundamental frequency and HC can offer more gain at the specific harmonic frequencies. Hence, characteristics of the PR and HC controllers used together to achieve minimum steady‐state error and the problematic decoupling are ignored. The complete DSTATCOM model with proposed control scheme is discussed with PR and (PR + HC) controllers separately under balanced, unbalanced source voltage. Stability analysis is carried out through Bode and pole‐zero plots to judge the performance of the proposed current controllers. The obtained results, including total harmonic distortion of the source current, are compared with conventional passive damped ‐frame current controller.

Fault ride-through capability improvement in a DFIG-based wind turbine using modified ADRC

In this paper, an overview of several strategies for fault ride-through (FRT) capability improvement of a doubly-fed induction generator (DFIG)-based wind turbine is presented. Uncertainties and parameter variations have adverse effects on the performance of these strategies. It is desirable to use a control method that is robust to such disturbances. Auto disturbance rejection control (ADRC) is one of the most common methods for eliminating the effects of disturbances. To improve the performance of the conventional ADRC, a modified ADRC is introduced that is more robust to disturbances and offers better responses. The non-derivability of the fal function used in the conventional ADRC degrades its efficiency, so the modified ADRC uses alternative functions that are derivable at all points, i.e., the odd trigonometric and hyperbolic functions (arcsinh, arctan, and tanh). To improve the efficiency of the proposed ADRC, fuzzy logic and fractional-order functions are used simultaneously. In fuzzy fractional-order ADRC (FFOADRC), all disturbances are evaluated using a nonlinear fractional-order extended state observer (NFESO). The performance of the suggested structure is investigated in MATLAB/Simulink. The simulation results show that during disturbances such as network voltage sag/swell, using the modified ADRCs leads to smaller fluctuations in stator flux amplitude and DC-link voltage, lower variations in DFIG velocity, and lower total harmonic distortion (THD) of the stator current. This demonstrates the superiority over conventional ADRC and a proportional-integral (PI) controller. Also, by changing the crowbar resistance and using the modified ADRCs, the peak values of the waveforms (torque and currents) can be controlled at the moment of fault occurrence with no significant distortion.

An Adaptive DC-Link Voltage Control of a Multifunctional SPV Grid-Connected VSI for Switching Loss Reduction

In the proposed method in this article, to minimize the burden on the switches of the multifunctional grid-connected voltage-source inverter (MFGCVSI), the voltages of dc-link split capacitors are adjusted according to power injection from the MFGCVSI. The MFGCVSI is used to control the active power injection from solar photovoltaic (SPV) power generation to the main grid and loads, load reactive power compensation, harmonic mitigation, and main grid current total harmonic distortion within 5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> . In such a case, the voltages of split capacitors depend on the rated power injection from the MFGCVSI. The power generated from the SPV system and the loads that are connected at the point of common coupling vary with respect to time. It is observed that the selection of rated dc-link voltages during low power injection from the MFGCVSI leads to additional switching stress and higher switching losses. Therefore, to reduce the burden on inverter switches and switching losses, the reference dc voltage is reduced under low power injection from the MFGCVSI. A model predictive controller with a multiconstraint technique is used in the proposed method for balancing the dc-link capacitor voltages and average switching frequency reduction. The proposed method is validated through simulation and hardware setup.

Fault-Tolerant Model-Free Predictive Controller for Multilevel Cascaded H-Bridge Inverters With Faulty Cells

In this article, a fault-tolerant model-free predictive controller (FT-MFPC) for cascaded H-bridge multilevel inverters (CHMLIs) is proposed. FT-MFPC is based on an association of model-free predictive controller (MFPC) and a proportional--integral (PI) like structure known as current variation controller (CVC). As in MFPC, the dynamic structure (DS) that is used for the prediction of the system output is obtained from past measurements of current variations, but CVC modifies the dynamics before they are stored for prediction. As a consequence, even if the converter operates with bypassed modules, FT-MFPC adapts its DS to represent the real dynamics of the system and enables a closed-loop response with balanced load currents in unbalanced CHMLIs. Simulation and experimental results validate the adaptability of the proposed strategy to operate a seven-level inverter under various configurations of bypassed H-bridge modules. The experimental results show that, for different postfault operations, the maximal current total harmonic distortion and imbalance factor at steady state in the worst case scenario are below 5% and 2%, respectively.