Current Total Harmonic Distortion Research Articles

Modeling and Performance Analysis of a Grid-Connected Photovoltaic System with Advanced Controller considering Varying Environmental Conditions

This paper presents a mathematical model of 255 kW grid-connected solar photovoltaic (SPV) system. To study the performance characteristics of the grid-connected SPV system, a new hybrid adaptive grasshopper optimization algorithm with the recurrent neural network (AGO-RNN) control technique was implemented. Furthermore, the power quality at the point of common coupling (PCC) has been studied using the conventional (PSO) and proposed AGO-RNN controllers. The characteristics of the PV system were analyzed under varying environmental (variable irradiance and temperature) conditions considering 3 different cases such as (i) standard test conditions (STC), (ii) variable radiation with constant temperature, and (iii) variable radiation with variable temperature. For each case, the total harmonic distortion (THD) has been calculated using the proposed AGO-RNN control technique, and the results were compared with particle swarm optimization (PSO) technique. The 255 kW PV model is initially developed and connected to a three-level NPC inverter, an MPPT-based perturbation and observation algorithm. Later, the PV model is controlled by an AGO-RNN pulse width modulation (PWM) controller and is then integrated to the main grid at PCC. The main advantage of this technique is exploiting the separate DC-DC converter between the SPV module and the inverter. Finally, the proposed grid-connected SPV system was simulated on MATLAB for analyzing the performance of the system based on its I-V and P-V characteristics, inverter voltage, grid power, gird voltage, grid current, power factor, and THD under different environmental conditions. The simulation results demonstrate that the current magnitude and THD of the SPVGC system are improved with the cutting-edge AGO-RNN controller compared to PSO in all three different scenarios, and this value is less than 1.6%, which is within the permitted limits of IEC 61727 standards.

Observer based model predictive current control of distorted grid connected single phase rectifier without AC voltage sensor

In this research, a grid voltage sensorless control scheme under the distorted grid voltage condition for a single-phase rectifier was proposed. For eliminating the grid voltage sensor, a time-varying state observer was designed, which provided direct, accurate, and fast estimation of the grid voltage without subsequent complex calculations, even for the presence of harmonics, a DC component, and frequency fluctuations, and it was implemented in the digital processor through Forward Euler discretization. In addition, the aforementioned observer would be partially reused in another observer to modify the input of the PI controller and then reduce the total harmonic distortion of the input current. To warrant robustness for the real world, the proposed observers were investigated in detail for load resistance variations and grid voltage fluctuations. Several simulations and experimentation tests were conducted to verify the effectiveness of proposed scheme. The obtained results indicated that the proposed observers had fast dynamic responses and low estimation errors. The proposed scheme decreased the THD of the input current.

Modulated Model-Free Predictive Current Control for Voltage Source Inverters With Stagnation Elimination and Sampling Disturbance Suppression

Model-free predictive current control (MFPCC) has been widely used in voltage source inverters (VSIs). The output current performance of look-up-table-based MFPCC is affected by the number of the applied voltage vectors (VVs), the current gradient updating and the sampling disturbance. To improve the current performance, a novel modulated MFPCC is proposed for VSI, while real-time current gradient updating and sampling disturbance suppression can be achieved. First, three basic VVs are picked, whose duration time are computed according to the current gradients. Second, an advanced current gradient updating method is presented by establishing the equations of different current gradients under different VVs. Furthermore, the sampling disturbance effect on MFPCC is analyzed and an extended state observer is designed to suppress such effect. Simulation model and experimental platform of the VSI system are structured to verify the preponderance of the proposed MFPCC in reducing the total harmonic distortion of output current.

A Simplified Virtual-Vector-Based Model Predictive Control Technique With a Control Factor for Three-Phase SPMSM Drives

Compared with the single vector-based model predictive control (MPC) technique, the multiple vector-based MPC technique gains interests in improving the total harmonic distortion (THD) of the stator currents and reducing electromagnetic torque and stator flux ripples for a three-phase surface permanent magnet synchronous motor (SPMSM). However, the complicated enumeration and operation in vector selection and duty cycle calculation increase the computational burden and limit its peneration. Hence, in this paper, a simplified virtual vector-based MPC with a control factor for a three-phase SPMSM is proposed. Without sector identification and enumeration operations, the proposed technique utilizes the control factor to automatically generate a large number of virtual vectors to achieve equivalent performance effectiveness with multiple vector-based MPC technique with lower sampling frequency. Subsequently, regardless of the number of virtual vectors, the candidate virtual vectors are directly identified in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$x-y$</tex-math></inline-formula> coordinate system to greatly reduce the computational burden. In addition, the duration of the selected optimal virtual vector and the resultant switching sequences are easily obtained and arranged to even the switching losses among the switching devices and further optimize the THD of the stator current. The proposed technique is simplified and flexible. Its control effectiveness is verified by experimental results.

A novel pulse multiplication circuit for reducing harmonic distortion of 12 pulse rectifiers in aircraft electrical power systems

AbstractTo improve the performance and reduce the total harmonic distortion (THD) of the autotransformer 12‐pulse rectifier, a novel pulse multiplication circuit (PMC) based on two tapped inter‐phase reactors (TIPRs) is proposed to improve performance and reduce the THD of the autotransformer 12‐pulse rectifier. The proposed rectifier includes a phase‐shifting autotransformer based on a polygon connection, two 6‐pulse diode bridge rectifiers (DBRs), and a PMC. The novel PMC consists of two TIPRs (TIPR1 and TIPR2), an auxiliary single‐phase diode bridge (including four diodes D1 to D4), and two auxiliary diodes D21 and D22, which are connected directly to the output terminal of the DBRs (DBR1 and DBR2). The simulation and experimental results confirm the high capability of the proposed PMC to reduce the harmonic distortion of the input current, so that by using the proposed PMC, the input current is almost sinusoidal and the THD of the input current is less than 3%. Also, the results show that the proposed 12‐pulse rectifier meets the standard requirements of aircraft electrical systems (DO‐160G) without the need for any input and output filters.

A Novel Double-Voltage-Vector Model-Free Predictive Current Control Method for Two-Level Voltage Source Inverters

An improved model-free predictive current control (MFPCC) scheme based on double-voltage-vector for two-level voltage source inverters (2L-VSIs) is proposed in this paper. First, two basic voltage vectors are chosen in each control period, whose durations are calculated based on the cost function. Then, a novel current gradient updating method is developed by using the applied two voltage vectors to calculate the current gradients of the remaining six voltage vectors. As a result, the stagnation effect can be eliminated and current ripples and total harmonic distortion can be reduced effectively. In addition, due to the nature of vector diagram symmetry, the processing of current gradient updating is simplified and the calculation speed is increased. The effectiveness of the proposed scheme is verified by simulation and experimental results from the 2L-VSI system.

Parameter Robust Deadbeat Predictive Current Control for Open-Winding Surface Permanent Magnet Synchronous Motor Drives

Deadbeat predictive current control (DPCC) of open-winding surface permanent magnet synchronous motor (OW-SPMSM) has excellent dynamic and steady-state performance, but it depends heavily on the accuracy of motor model parameters (resistance, inductance, and flux linkage). To eliminate the influence of parameter mismatch and retain the fast dynamic performance of the traditional DPCC, a parameter robust DPCC for OW-SPMSM drives is proposed in this paper. Firstly, the incremental prediction model of OW-SPMSM is introduced which eliminates the flux linkage parameters in traditional DPCC. Secondly, the parameter sensitivity analysis shows that the mismatch of resistance parameter hardly affects the current prediction errors of incremental prediction model, which are mainly caused by the mismatch of inductance parameters. Finally, to extract the actual inductance information, an inductance extraction strategy is proposed. Experimental results show that the current control performance of the proposed robust DPCC is not influenced by any motor parameter mismatch, which always has smaller current tracking errors and total harmonic distortion (THD) than traditional DPCC. Moreover, compared with the existing robust DPCC with observers, the proposed DPCC has better dynamic response performance.

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.