Current Total Harmonic Distortion Research Articles

Influence of reactive power compensation from PV systems on electrical grid

The rising electricity consumption, rapid fossil fuel depletion, and a higher shift to the use of renewable or green energy resources have increased the need to integrate renewable and distributed energy resources (DERs), like solar photovoltaic (PV) energy to power the utility grids. In this study, the researchers have determined the effect of PV inverters to offer reactive power to an adapted IEEE 13-node distribution network. Power flow analyses were conducted on MATLAB/Simulink for various reactive power modes of PV inverters to show the effect of the reactive power on the regulation of grid voltage, reduced the total harmonic distortion (THD), and maintain the power factor so as to improve the ability of the system to handle power. The result shows that using a 400 KW PV system in a bus (675) led to a reduction in the power generated from the generator by 11%, and the use of the reactive power capability of PV inverters on-site improved the voltage profile significantly. as well, reduced the voltage THD by 27.09% when injected with reactive power, reduce the current THD by 77.39% When absorbing reactive power, and improved the power factor on-site.

Assessment of a single-phase single-stage grid-connected photovoltaic system

A grid-connected photovoltaic (GCPV) system plays an important role in the development of green technology. However, generated photovoltaic (PV) power that is injected into the grid causes instability in the grid system. Previous studies have shown that power quality for a three-phase system is thoroughly being discussed, but not for a single-phase system. Single-phase system also contribute to instability in low-voltage grid networks during high power penetration as majority of the single-phase GCPV nowadays are installed on rooftops. Thus, in this study, the power quality of a single-phase single-stage GCPV system is investigated based on the total harmonic distortion (THD), power factor (PF), and the generated active (P) and reactive (Q) power during different solar irradiance and varying loads conditions. A model of the GCPV system was developed in MATLAB/Simulink, so that certain variables can be varied to observe their effect towards the power quality. The results show that the current and voltage of generated PV power are synchronized and having low current THD which is less than 1% for all cases. PF values are also in the acceptable range in compliance to IEC 61727 standard which is 0.9971, and the generated PQ is in accordance to the connected load.

Bidirectional Charging for BEVs with Reconfigurable Battery Systems via a Grid-Parallel Proportional-Resonant Controller

This paper investigates the potential of bidirectional charging using modular multilevel inverter-based reconfigurable battery systems via grid-parallel control. The system offers several advantages such as modularity, scalability, and fault-tolerance over conventional battery electric vehicle systems. It is designed for seamless integration with the grid, allowing bidirectional power flow and efficient energy storage. Within this study, the battery system is first simulated in Matlab/Simulink and later implemented into a hardware setup. Eventually, the simulation results and the measurements have been compared and evaluated. Thereby, startup sequences and constant current scenarios were investigated. It has been shown that the system is fully capable to charge and discharge the batteries in the grid-parallel connection, thus enabling bidirectional charging with close to full drive system power. The current total harmonic distortion complies with grid regulations and can potentially improve the grid quality. The proposed system offers significant potential for grid-integrated energy storage systems, addressing the challenges associated with renewable energy integration, grid stability, and energy management. In comparison to other publications on this topic, the proposed approach does not need additional dedicated power electronic hardware and has more degrees of freedom for current control.

Optimization of a Single-Switch Wireless Power Transfer Circuit Based on a Multi-Coil Array

In response to the issue of large input current ripple and noise, which can cause current shocks and compromise the overall stability in single-tube wireless power transmission systems, a P# type LCC-S compensation network and a multi-coil phase-shifting control method have been proposed to suppress input current ripple, improve input current waveform, reduce input current total harmonic distortion (THD), and ultimately enhance system efficiency and stability. Firstly, the working mode and waveform of the P# type LCC-S compensation network are analyzed, and the calculation method for its parameters is provided. Secondly, the analytical relationship between input current, input voltage, coil mutual inductance, and load impedance of the multi-coil array is derived. Additionally, Fourier transform is used to analyze the input current composition, and the phase shift suppression method is employed to reduce the input current ripple. Finally, a test platform is constructed to verify the relevant experiments. The experimental results demonstrate that the input current ripple is significantly suppressed at the rated transmission power, and the system efficiency is improved to 88.2%, which validates the effectiveness of the proposed method.

Multi-resonant Controller Design for a PV-Fed Multifunctional Grid-Connected Inverter in Presence of Unbalanced and Nonlinear Load

The use of Active Power Filters (APFs) in future power grids with high penetration of nonlinear loads is unavoidable. Voltage Source Inverters (VSIs) interfacing Photovoltaic (PV) generator could play the APF role in addition to power supply. In this paper, the control of a PV-fed multifunctional grid-connected three-phase VSI is addressed with nonlinear and unbalanced load. The control objective is threefold. The first one is to deliver the maximum available power from the PV source to the grid satisfying power quality standards. The second one is the Voltage Balancing Control for DC-link capacitors to guarantee correct operation of the VSI. The last one is shunt APF control to compensate for nonlinear and unbalanced load harmonics, reactive power, and unbalanced sequences. A quasi-Proportional-Resonant (PR) controller with harmonic compensators is proposed for the current control loop. The quasi-PR controller parameters are determined through optimization algorithms such as Particle Swarm Optimization (PSO), Genetic Algorithm (GA), and a combination of both PSO and GA. The aim of the objective function is to improve static and dynamic behavior. The different gains at the fundamental resonant frequency and the selected odd harmonics are obtained for the proposed quasi-PR controller. The dynamic characteristics of the optimized quasi-PR controllers show superiority against conventional ones in terms of gain margin, phase margin, overshoot, and robustness. With the proposed control scheme, the harmonics, reactive power, and unbalanced sequences are appropriately compensated. The performance of the PV-fed VSI shunt APF under irradiance change, load change, and distorted grid voltage conditions is validated through numerical simulations performed on hbox {PSIM}^{copyright } software. The results show that the grid currents Total Harmonic Distortion for irradiance change case study are 4.57%, 4.57%, and 3.22% in phase a, b, and c with the proposed control method, while they are 9.25%, 5.65%, and 10.12% with conventional instantaneous p-q theory.

A variable step size robust normalized least mean absolute third‐based control scheme for a grid‐tied multifunctional photovoltaic system

SummaryThis paper develops a variable step size robust normalized least mean absolute third (VSSRNLMAT)‐based control scheme for a three‐phase grid‐tied multifunctional photovoltaic system (GTMPVS). The GTMPVS delivers PV power to grid‐connected loads and feeds excess power to the grid through a voltage source converter (VSC) when PV power is available. It enhances power quality (PQ) by mitigating current harmonics and compensating for an unbalanced load and reactive power simultaneously. The proposed control scheme accurately extracts the fundamental active and reactive weight components of nonlinear load current. The power exchange at the grid side occurs with balanced and sinusoidal grid currents. During the absence of PV power, the VSC continues its operation as a distribution static compensator (DSTATCOM), thus increasing the effective utilization of the power electronic switches employed in the VSC. The GTMPVS model is created in MATLAB/Simulink. The response of GTMPVS is observed under steady‐state and dynamic operating conditions while feeding power to a nonlinear load. The dynamic operating conditions are created by a change in solar irradiation and an unbalanced nonlinear load. Further, the proposed VSSRNLMAT control scheme is compared with some of the other adaptive filtering‐based control schemes, including least mean square (LMS), least mean fourth (LMF), least mean absolute third (LMAT), and normalized LMAT (NLMAT) in terms of convergence, oscillations, mean square deviation (MSD), computational complexity, and grid current total harmonic distortion (THD). It is found that the VSSRNLMAT control scheme offers THD of grid current as per IEEE‐519 standard. The proposed control scheme is implemented to operate the laboratory‐developed GTMPVS to verify the simulation results.

Simplified selective harmonic elimination PWM for three‐level five‐phase T‐NPC inverter

SummaryThis paper presents a selective harmonic PWM strategy (HSE‐PWM) to control a five‐phase three‐level T‐NPC inverter. The proposed method aims to reduce switching losses and directly eliminate specific orders of harmonics, while also controlling the fundamental magnitude. MATLAB/Simulink simulations are conducted using an RL load, and the implementation is tested using a simplified method on an STM32F4 controller board. Experimental tests are then carried out to validate the simulation results. Additionally, power losses and efficiency are studied using Plecs software. The paper explores four different cases of switching angles number and proposes three SHE methods: a simple SHE based on Newton Raphson's method, SHE with current THD optimization, and SHE with common mode voltage (CMV) optimization using the PSO algorithm. The proposed methods provide complete control over the fundamental of the output voltage and the selected harmonics while reducing switching losses. A comparison is carried out in terms of voltage waveform, maximum CMV, fundamental magnitude, total harmonic distortion (THD), and power efficiency for the three methods. The paper concludes that the proposed modulation can be useful in high‐power applications.

Multi-Converter UPQC Optimization for Power Quality Improvement Using Beetle Swarm-Based Butterfly Optimization Algorithm

The primary goal of this paper is to design a Multi-Converter Unified Power Quality Conditioner (MC-UPQC). The proposed method is solved based on the Synchronous Reference Frame (SRF) theory. The MC-UPQC involves two series Voltage Source Converters (VSCs) for power transfer between feeders to eliminate voltage sag, swell, interruption, and transient response in the system. The proposed model adopts control strategies based on an optimized Fuzzy Logic Controller (FLC) in SRF, utilizing a hybrid metaheuristic algorithm called Beetle Swarm-based Butterfly Optimization Algorithm (BS-BOA), which combines Beetle Swarm Optimization (BSO) and Butterfly Optimization Algorithm (BOA) for membership limit optimization and control rule generation. The major benefit of the optimized FLC-based MC-UPQC is its quick behavior in minimizing Total Harmonic Distortion (THD) in source and load side voltages and currents. Simulation and MATLAB environment are used for the entire system implementation. The comparative analysis of the proposed controller for MC-UPQC is performed against conventional controllers to validate its effectiveness. Quantitative data related to the main research outcomes, such as THD of source voltage and current, and dynamic behavior of the system, are included. The main benefit of the study is the significant reduction in THD and improved dynamic performance of the system.

Analysis and Experimental Validation of an Integrated Current-Source Power Supply With High Power Factor for DBD Applications

An integrated current-source high-frequency pulse excitation power supply with high power factor (PF), low total harmonic distortion (THD) of the input current, and high efficiency for dielectric barrier discharge (DBD) loads is proposed in this article. The proposed power supply consists of a current source unit and a bipolar pulse excitation voltage generation unit. The current source unit is used to generate a current source for the excitation voltage generation unit and achieve a high PF and a low current harmonic distortion in the ac side of the proposed power supply. By planning the modes of the excitation voltage generation unit, not only a bipolar pulse excitation voltage with high rising and falling rates on the DBD loads is generated, but also the soft-switching of all power switches is achieved. The experimental results show that not only a unity PF ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$</tex-math> </inline-formula> 0.99) and a low THD ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&lt;$</tex-math> </inline-formula> 10%) are achieved, but also a bipolar high-frequency (hundreds of kilohertz) pulse excitation voltage with high average rising and falling rates (7.227 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 109 V/s) for a DBD excimer lamp is generated. Finally, in comparison with different power supplies, the proposed power supply can not only fully take advantage of the potential of the DBD excimer lamp but also has many advantages of high efficiency (92%), integrated structure, and simple driver.

IMPROVED ACTIVE FILTER PERFORMANCE IN SINGLE-PHASE CONTROLLED RECTIFIERS WITH PULSE WIDTH MODULATION (PWM) CONTROL

Various commutation techniques, such as forced commutation, ignition angle control, and symmetrical angle control, have been developed to improve the input power factor and harmonic level. However, all of these techniques will produce only one pulse per half cycle of the converter input current, and consequently, the lowest order harmonic is the third harmonic. A comparative study of active filter converters between single pulse and PWM control has been investigated. Both converters are given identical R and RL loads to compare power factor (PF) and Total Harmonic Distortion (THD). The method used is a simulation with the PSPICE program. The performance of both rectifiers is evaluated based on the input current waveform, THD, and PF. At RL load, the input current distortion decreases drastically, with a THD of 100.67%. In PWM control, harmonics are reduced with a THD of 25.48%. The rectifier power factor in the active filter obtained PF of 0.25, whereas in PWM control, PF increased by 0.65.

A modulation strategy for eliminating zero-crossing distortion of dual buck high-precision resonant converter

Due to no current distortion caused by blanking time, the resonant pole dual buck soft-switching power converter (RPDBSPC) can be applied to ultra-precision motor drive. The soft-switching operation can expand the switching frequency and improve the current response. Based on the resonant pole soft-switching topology, this paper proposes an in-phase modulation strategy. By analyzing the output voltage characteristics of switching nodes under different inductance current states, it reveals the mechanism of in-phase modulation to achieve nonlinear voltage suppression by adjusting the common conduction region. According to the correlation of modulated signals, the mathematical model of modulation algorithm is established, then the strategy feasibility and system stability are researched. Finally, the total harmonic distortion of output current can reach to 0.134% by applying the in-phase modulation when the bus voltage is 500V and the switching frequency is 100 kHz.

ELECTRIC VEHICLE ONBOARD CHARGING VIA HARRIS HAWKS OPTIMIZATION-BASED FRACTIONAL-ORDER SLIDING MODE CONTROLLER

Electric vehicles (EVs) have become more popular due to their excellent efficiency and pollution-free benefits. The technology requirements for onboard chargers are increasing as the number of electric vehicles increases. This research proposes a fractional-order sliding mode controller (FOSMC) for power converters to improve the efficiency of the onboard battery charger. The Harris Hawks optimization (HHO) algorithm chooses the FOSMC parameters. Independent controllers are used in a two-stage charging scheme. The grid-side ac–dc converter helps to smooth the current and voltage in the dc bus while reducing the harmonic frequency in the grid. A dc-dc converter with a constant current–constant voltage curve regulates the charging parameters of the battery on the battery side. Experiments show that HHO-based FOSMC improves the overall dynamic response of the onboard battery charger. Moreover, the proposed method performs with a current total harmonic distortion (THD) of less than 2 %. The proposed method improves 98% efficiency than existing methods such as SSA-PID and SSA- FOAFPIDF controllers.

A Series-Connected 24-Pulse AC–DC Converter With Double-Diode Harmonic Suppression Circuit

A series-connected 24-pulse ac–dc converter with a double-diode harmonic suppression circuit (DDHSC) is presented in this article. The DDHSC is installed at the dc side of the ac–dc converter, and it consists of several passive devices. The DDHSC generates a specific current at the dc link to modulate and increase the operating modes of this ac–dc converter. Then, the series-connected 12-pulse ac–dc converter is extended to a novel 24-pulse ac–dc converter, and total harmonic distortion of the input line current is reduced to the acceptable levels (less than 5%). The maximum current through the auxiliary diodes in the DDHSC is only 6.8% of the load current, which means the current rating and conduction losses of the auxiliary diodes are low. The proposed DDHSC scheme is more suitable for high-current occasions. Given that only a low capacity (2.06% of the output power) DDHSC is sufficient to double the number of pulse of the 12-pulse ac–dc converter, the proposed scheme is simple and cost effective. The detailed theoretical analysis is provided, and an experimental prototype is established to demonstrate the performance of the proposed converter.

Quasi-Resonant Switched-Capacitor-Based Seven-Level Inverter With Reduced Capacitor Spike Current

This article proposes a novel seven-level multilevel inverter (MLI) with integrated output voltage boosting functions. The inverter uses switched capacitors (SCs), a key component of a voltage-boosting approach, to achieve the goal of increasing the output voltage at the load end. Additionally, the MLI has the ability to automatically balance the capacitor voltages. The proposed inverter is more cost-effective and has lower conduction losses than those of its rivals since it has fewer components than competing designs. An inductor is used in the capacitor charging loop to both minimize dc source current spikes and enable quicker charging of the capacitor, thereby increasing the capacitor’s lifespan. This article provides a number of waveforms, including output voltage and current, under various loading conditions and modulation indices. A laboratory model is also employed to support the viability of the proposed topology. The performance of the system is verified using MATLAB/Simulink. At long last, the maximum achievable experimental efficiency of 98.77% and total harmonic distortion (THD) for output voltage and current were 20.44% and 0.54%, respectively, at 300 V and 1.2 kW load.

Full Grid Voltage Feedforward for Critical Mode LCL-Type Single-Phase Grid-Tied Inverters With Physical Interpretations

Full grid voltage feedforward (GVF) is an effective strategy to suppress the current distortion caused by grid voltage harmonics. However, for critical conduction mode (CRM) grid-tied inverters, the time-varying parts of its control scheme make it impossible to derive its full GVF strategy from the point of view of the transfer function. Hence, this study first analyzes the physical interpretation of the full GVF of conventional LCL-type grid-tied inverters, and then reveals the role of each term from the perspective of the circuit. Then, a full GVF strategy for CRM grid-tied inverters is proposed. The design guidelines, parameter sensitivity, and application limitations of the proposed scheme are analyzed in detail. Finally, a 1-kW single-phase three-level grid-tied inverter was built. Experimental results show that the proposed full GVF can significantly suppress the current distortion caused by the grid voltage harmonics and lower the current total harmonic distortion value by 55% within the full power range.

Assessment and Exploitation of the Minimum Current Harmonic Distortion Under Overmodulation in Five-Phase Induction Motor Drives

This paper compares the most prominent overmodulation (OVM) techniques for five-phase induction motor drives with respect to the minimum current distortion (MCD) achievable. To attain a benchmark of the latter, two MCD OVM approaches are devised. Contrarily to previous strategies aimed at voltage distortion reduction/minimization, these MCD methods are focused on minimizing the harmonic stator copper loss (HSCL), thus minimizing the current total harmonic distortion (THD). One of these MCD strategies minimizes the HSCL while injecting only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$x$</tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$y$</tex-math></inline-formula> harmonics. The other MCD method exploits <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\alpha$</tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\beta$</tex-math></inline-formula> harmonic injection to further decrease the HSCL and to cover the whole OVM region. Moreover, the dual-mode OVM, which is one of the three-phase methods with the lowest distortion, is extended here for five-phase drives. The findings provide insight into how close the OVM methods are to the benchmark imposed by the MCD strategies. Notably, these MCD techniques yield a significant reduction of current THD, HSCL and peak current, especially for machines with negligible third-order space harmonic. The average switching losses are also decreased. Indications for real-time implementation of the MCD solutions are also given.

A High-Efficiency Bidirectional Single-Stage AC-DC Converter Under Wide Voltage Range for Fast Chargers

In this article, a single-stage four-phase interleaved totem-pole AC–DC converter for fast charger applications that require high power, wide battery voltage range, and bidirectional operation capabilities is proposed. Due to the four-phase interleaving effect, the grid side switches can operate at duty cycle of 0.25 or 0.5 so that the grid current always achieves ripple-free. A method for secondary side duty cycle generation is proposed for reducing the circulating power and input current total harmonic distortion (THD) under a wide voltage range. The control system is shown to be simple and reliable. An integrated four-phase transformer is designed using one core. Experimental results from a 7.5 kW prototype with an output voltage range of 150 to 750 V are provided to validate the proposed concept.

Second-Order Sliding-Mode Control for Three-Level H-Bridge-Based Unified Power Quality Conditioner With Vanilla Feedforward Neural Network

This article proposes a modified three-wire three-level H-bridge-based unified power quality conditioner (UPQC) without any transformer in the shunt part and controlled by using second-order sliding-mode control (SOSMC). Thus, this topology has less component count than that in the flying-capacitor- and neutral-point-clamped-based UPQC. The isolated operation of the series part of the UPQC leads to distortion in the mitigated load voltage. An SOSMC based on the supertwisting algorithm is proposed to defeat this problem. The SOSMC eliminates the differentiation requirement, thereby suppressing noise amplification compared to the first-order sliding-mode control (FOSMC). In addition to these advantages, the chattering problems are also minimized compared to FOSMC. Thus, this technique provides robustness and dynamic response during systems' external and parameters' perturbation. Furthermore, in the SOSMC controller, the compensation voltage and current references are predicted by using an artificial neural network (ANN). The ANN model uses a vanilla feedforward neural network with only two hidden layers. The proposed ANN is developed by considering the instantaneous and delayed components. Consequently, it allows for a simpler model by reducing the number of hidden layers. The total harmonic distortion (THD) of the mitigated voltage is reduced to 0.65% and the mitigated current THD is 1.22%.

Power Quality Improvement by Using Discrete Wavelet Transform Based DSTATCOM

Abstract: The discrete wavelet transform-based control technique for the distribution static compensator (DSTATCOM) is utilized in this paper to improve power quality at common points of interconnection (CPI). The discrete wavelet transform, the time frequency analysis technique, is used here to split distorted load current of each phase in order to recover the line frequency of harmonic components for estimating the respective active power components. The difference between the estimated reference active component and the detected load currents is utilized to create reference currents for DSTATCOM's voltage source converter (VSC) management. The performance of DSTATCOM is presented using MATLAB software under varied linear and non-linear load circumstances. Under various load situations, total harmonic distortion (THD) of the source current is less than 5% with a power factor of unity.

The novel algorithm-based hysteresis current control technique (HCCT) to eliminate sub and inter harmonics (SIH) in load current

PurposeThis study aims to propose a unique algorithm-based hysteresis current control technique (HCCT) for induction motor using a single-phase voltage source inverter (SPVSI) to eliminate both sub and inter harmonics (SIH) and electromagnetic interference (EMI). The total harmonic distortion (THD) of the load current also reduces in comparison to standard HCCT and modified technique-based existing HCCT.Design/methodology/approachMatlab simulation has been carried out to develop an SPVSI model and the unique algorithm-based HCCT. The same platform has also been used to develop a few existing HCCTs such as standard, dual-band and modified. The switching frequency and harmonic analysis of load currents for all the HCCTs have been compared in the paper. The hardware implementation of the proposed algorithm-based HCCT was also verified and compared with the simulation results.FindingsThe proposed unique algorithm-based HCCT provides the benefits of both unipolar and bipolar switching techniques. It reduces the switching frequency as unipolar switching scheme and eliminates the EMI. It also reduces THD and nullifies SIH of the load current. This enables an improvement in the overall performance and efficiency of the motor.Practical implicationsThis proposed HCCT eliminates the SIH and improves the overall efficiency of the motor, hence can prevent overheating, vibration, acoustic noise, pulsating torque and braking of the rotor shaft of the motor and increasing the reliability of the system.Social implicationsIt can be implemented for the motors that are used in household applications and electric vehicles through one-phase inverter.Originality/valueThis proposed HCCT has detected the zero crossing point of reference current, allowed samples and shifted the necessary amount of hysteresis band at zero crossing region to eliminate SIH and THD.