Total Harmonic Distortion Rate Research Articles

Harmonic characteristics analysis and power quality requirements of Light-Emitting Diode lamps used in nuclear power plant lighting system

Abstract This article conducts an in-depth study of the application of LED (Light-Emitting Diode) lamps in nuclear power plant lighting systems and conducts a comprehensive analysis of its impact on the power quality of the plant’s low-voltage AC power system. First of all, through a detailed discussion of the harmonic characteristics of LED lamps and the power quality requirements of nuclear power plants, it is pointed out that the harmonics of LED lamp drivers will inevitably have an impact on the power quality of low-voltage AC power systems. Therefore, the harmonic characteristics of LED lamps must comply with certain constraints. Subsequently, the application of LED lamps under different capacity transformers was analyzed and combined with relevant standards and specifications, and application suggestions for LED lamps in nuclear power plant lighting systems were put forward. Finally, measures to improve the total harmonic distortion rate of LED lamp current were discussed, emphasizing the importance of power factor correction technology. In summary, this article provides important reference and guidance for the application of LED lamps in nuclear power plants, helping to ensure the safe and stable operation of nuclear power plants.

Los vehículos eléctricos y su impacto en el sistema eléctrico de distribución: Caso de estudio “Alimentador urbano de la ciudad de Portoviejo”

In Portoviejo, the current use of electric vehicles (EVs) is limited compared to conventional vehicles. However, due to the implementation of laws, regulations, and policies promoting electric mobility in Ecuador, a significant increase in the integration of EVs into the city's electrical system is anticipated in the coming years. To anticipate the impact on the electrical infrastructure, a simulation is conducted using CYMDIST software on an electrical distribution feeder operated by the Public Company Corporación Nacional de Electricidad (CNEL EP), Manabí Business Unit (Portoviejo). The simulation considers three scenarios projected for 2030: 1. Baseline scenario without EV integration, 2. Unrestrained EV integration, and 3. Managed EV integration. This research aims to simulate the integration of up to 230 EVs into the network to provide benchmark data for understanding the potential impacts on the feeder as EV adoption increases, with vehicles being charged over extended periods. The investigation will highlight the importance of demand management with EV integration, demonstratingsignificant effects on the demand curve, voltage profile, and total harmonic distortion rate (THD%) of a 13.8 kV distribution feeder.

Research on the prediction method of porcelain insulator pollution degree based on electric field monitoring

The online monitoring of insulator surface pollution states is crucial for predicting/preventing pollution flashover accidents. This paper conducts artificial pollution tests on porcelain insulators at five pollution levels to obtain the electric field signal during the flashover process. Subsequently, the time-frequency performance of the electric field signal waveform at various discharge stages is discussed in detail. Finally, a method for predicting pollution degrees by combining back propagation (BP) neural networks and non-contact electric field signal monitoring is proposed and validated. Research results indicate that during the pollution flashover process of the porcelain insulator, the peak value of the electric field signal shows an upward trend in sections. As the equivalent salt deposit density (ESDD) increases, the curves of electric field values rise. The development of dry-band arcing clearly distorts the electric field signal waveform at its crest and trough parts, increasing the total harmonic distortion (THD) rate. The THD can reach 100–130 % when closing to flashover, with the third harmonic acting as the main component. By taking kmax (the rising rate of the E-field signal amplitude), g (the ratio of Emax to Erms), K3 (the third harmonic coefficient), and THD as inputs to the BP neural network model, an ESDD prediction with a relative error lower than 10.63 % is realized. This research can offer novel technical support for predicting pollution degrees.

Performance and harmonic detection algorithm of phase locked Loop for parallel APF

As the boost of power electronics technology, the harmonic problem in the power system is becoming increasingly prominent. Fourier decomposition is performed on the load current in the power system, and components with a frequency that is an integer multiple of the fundamental wave are referred to as harmonic components. Harmonic control is essential to establish a safe and reliable power grid environment and provide high-quality and clean electricity to power users. The study focused on parallel active power filters, proposed a specific harmonic detection method on the grounds of synchronous harmonic rotating coordinate system, and developed a phase-locked loop design on the grounds of order generalized integrator. Meanwhile, a compensation current control method on the grounds of space vector pulse width modulation was introduced. The results showed that in the full compensation simulation experiment, the compensated A-phase grid side current waveform was significantly improved and presented a sinusoidal shape. After 0.05 s, the actual output compensation current closely followed the command current. Meanwhile, after compensation, the total harmonic distortion rate decreased from 26.58 to 3.06%. In specific harmonic compensation simulation experiments, when the sum of 5th, 7th, and 11th harmonic components was used as the command current for compensation, the distortion of the current waveform was improved after the load undergoes a sudden change. After compensation, the 5th, 7th, and 11th harmonic content significantly decreased, and the total harmonic distortion rate decreased to 4.08%. This indicated that the proposed phase-locked loop design and harmonic detection method for active power filters had high stability and effectiveness. The study’s primary contribution is to enhance the utilization efficiency of DC voltage and improve the dynamic response ability of current. Additionally, it offers a new method for reducing the impact of harmonics on the power grid and improving power quality. It provided an effective method reference for technological progress in related fields such as power electronics and control engineering.

Estimation of the total current harmonic distortion using an ELF magnetometer

The conventional operation of the grid and electrical devices can be disturbed by harmonics, so standards impose strict limits on harmonic current. The entire grid is essential for today’s society, but electromagnetic fields are radiated at their fundamental frequency and harmonics. This paper investigates a methodology to estimate the total current harmonic distortion of the grid by analyzing the magnetic flux density obtained from an extremely low-frequency magnetometer in the 0–2.2 kHz range. A Fast Fourier transform algorithm was applied to determine the magnetic flux density in the frequency domain. By evaluating the ratio of the fundamental component of the magnetic flux density to the harmonics, its total harmonic distortion rate could be deduced. Finally, the data were compared with measurements obtained by two power quality analyzers.

Parallel active power filter based on single-phase independent control

With the rapid development of high-voltage power grids and power electronics technology, the integration of numerous power electronic devices has led to a significant increase in harmonic pollution in power grids. Consequently, the demand for high-voltage and large-capacity active power filters has become increasingly urgent. This article introduces a novel approach using single-phase independent control and proposes a parallel active power filter based on magnetic flux compensation. This filter not only enhances power quality but also achieves three-phase decoupling control. It is specifically designed for medium and high-voltage three-phase three-wire power systems. Simulation experiments were conducted to validate the efficacy of the proposed active power filter, demonstrating its ability to effectively reduce the total harmonic distortion rate at the grid connection point and subsequently improve power quality.

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.

Research on Multi-carrier PWM Technology Based on Modular Multilevel Inverter

The modular multilevel inverter circuit structure is introduced, three traditional multi-carrier PWM modulation strategies for modular multilevel inverter circuits are studied and analyzed, and the inverter-side output voltage spectrum is analyzed by simulation. Based on the traditional multi-carrier PWM modulation strategy, this paper uses the PWM technology combining multi-reference wave and multi-carrier to analyze and simulate, and builds a modulation model and a circuit model of the modular multilevel inverter circuit in the Matlab/Simulink environment. Compared with the simulation results of the traditional multi-carrier PWM strategy, the multi-carrier modulation algorithm of the multi-reference wave can slightly reduce the total harmonic distortion rate. At the same time, the multi-carrier modulation algorithm of multiple reference waves can ensure that the capacitor voltage values of each submodule of the modular multilevel inverter circuit are equal so that there is no circulation phenomenon between each phase. Finally, a physical platform is built to verify the authenticity of the simulation experiment.

Harmonic Suppression Strategy of LCL Grid-Connected PV Inverter Based on Adaptive QPR_PC Control

To reduce the influence of voltage harmonics on the grid current, a control strategy based on adaptive quasi-proportional phase compensated resonance (QPR_PC) is proposed. Firstly, the LCL grid-connected photovoltaic inverter system model is established, and the stability performance of the three-level inverter system under double closed-loop control is analyzed using the output impedance model of the inverter. Then, a QPR regulator for the zero steady-state error tracking of AC signals is studied. To solve the problem that the system has poor robustness against frequency changes when the traditional QPR regulator is used in the static coordinate system, this paper improves the traditional QPR regulator to optimize the response characteristics of the closed-loop system. Based on the QPR regulator, a phase margin compensation structure is introduced to form QPR_PC control. Then adaptive frequency design is added to ensure good control even when the power grid frequency drifts, which is the control strategy proposed in this paper. Verification shows that the proposed method improves the phase margin of output impedance at a specific frequency, restrains the interference of the 3rd, 5th, and 7th harmonics of grid voltage, and improves the dynamic performance of the system and the quality of grid-connected current. Finally, the simulation results show that the total harmonic distortion rate of grid-connected current is reduced by 1.03% after adopting this strategy, which verifies the effectiveness and correctness of the proposed method.

The optimal design and research of interior permanent magnet synchronous motors for electric vehicle applications

AbstractAn interior permanent magnet synchronous motor (IPMSM) with “VV—” shape rotor topology structure is proposed, and its performances are compared with “V” shape and “V—” shape rotor topology structure. The results show that the performances including output average torque, reluctance torque, torque ripple, cogging torque, iron loss of the IPMSM with “VV—” shape is better than the other two rotors. Firstly, the parameters which have great influence on the torque and the efficiency of the IPMSM are analyzed and optimized. The no‐load back electromotive force (EMF) of three different optimized rotor topology structures are analyzed and compared, the results show that the no‐load back EMF of the IPMSM with “VV—” shape topology structure has the lowest total harmonic distortion rate (THD). Secondly, the torque of the IPMSM with “VV—” shape under different current angles, current densities and speeds are analyzed and compared with the other two rotors. The results show that the torque performance of the IPMSM with “VV—” shape rotor topology structure is better than that of the other two. Finally, aiming at the problems that the torque ripple and cogging torque of the IPMSM with “VV—” shape rotor topology structure are greatly increased when the iron loss is reduced, This paper proposes to add a set of circular flux isolation holes between the second layer and the third layer of permanent magnets, and the position and diameter of this set of circular flux isolation holes are optimized and adjusted. The results show that the torque ripple and cogging torque of the IPMSM with the further optimized “VV—” shape rotor topology structure are greatly reduced, and the THD of no‐load back EMF is also further reduced, which has great significance to reduce vibration and noise, improve the control accuracy of the IPMSM.

CONTROL OF DOUBLY FED INDUCTION GENERATOR USING ARTIFICIAL NEURAL NETWORK CONTROLLER

In this paper, we propose a direct power control (DPC) based on an artificial neural network (ANN-DPC) for the doubly-fed induction generator (DFIG), which is applied to the wind turbine system. The main objective of this intelligent technique is to replace the switching table and the hysteresis comparators with a neural control to reduce the ripple to the level of current and power. Field-oriented control (FOC) is traditionally achieved using a conventional proportional-integral controller (PI). The power ripples are reduced, and a reasonable total harmonic distortion rate is ensured by using an ANN-DPC.

Extended state observer-based predictive control for soft open point

This paper proposes an extended state observer-based ultra-local model-free three-vector predictive control method for Soft Open Point (SOP). First, the Ultra-Local Model-Free Predictive Control (ULMFPC) method is proposed to improve the robustness of the system, which only uses the input and output of the outer-loop, and any other parameters are not involved. Second, considering parameter perturbations and external disturbances in the SOP system, an expansion state observer (ESO) is established to observe the SOP system’s total perturbations and the perturbations are compensated in real-time to improve the system. Third, to solve the problem of significant current harmonics in traditional model predictive control (MPC), a three-vector MPC method (TV-MPC) is adopted to reduce the total harmonic distortion rate (THD) of the current. Finally, it is verified by simulation that the proposed method can effectively reduce the current harmonics of the SOP system, rate value setting time, and improve the dynamic performance effectively. When perturbations occur in the system, the proposed method can improve the anti-interference and robustness of the system.

Smooth Switching Method for Multi-Mode Synchronous Space Vector Modulation of NPC Three-Level Inverter

To meet the requirements of output harmonic distortion of neutral point clamped (NPC) three-level inverter under low switching frequency conditions, multi-mode synchronous space vector modulation is usually adopted. When switching between different pulse patterns, there will be oscillation in the output current. This paper proposes a smooth switching method for synchronous space vector modulation. This method compensates the phase angle of the reference voltage vector, in order to make the flux trajectories continuous before and after switching. Multi-position smooth switching can be realized in the fundamental period, and there is no delay in switching. Compared with direct switching, the total harmonic distortion rate of current during switching is reduced. The calculation of the phase angle compensation value of the reference voltage vector is not affected by the specific parameters and operating conditions of the motor, and can be carried out offline. Finally, experiments are carried out on a 7.5 kW induction motor fed by NPC three level inverter to verify the feasibility and effectiveness of the proposed method.

AC-DC Fuzzy Linear Active Disturbance Rejection Control Strategy of Front Stage of Bidirectional Converter Based on V2G

Aiming at the problems of output voltage fluctuation and current total harmonic distortion (THD) in the front stage totem-pole bridgeless PFC of two-stage V2G (Vehicle to Grid) vehicle-mounted bi-directional converter, a fuzzy linear active disturbance rejection control strategy for V2G front-stage AC-DC power conversion system is proposed. Firstly, the topological working mode of the totem-pole bridgeless PFC is analyzed, and the mathematical model is established. Combined with the system model and the linear active disturbance rejection theory, a double closed-loop controller is designed with the second-order linear active disturbance rejection control as the voltage outer loop and PI control as the current inner loop. The controller can realize self-adaptive tuning of the proportional gain coefficient of the active disturbance rejection controller through fuzzy reasoning and realize self-adaptive control. Simulation and experimental results show that this method can better solve the problems of slow system response and high total harmonic distortion rate of input current and effectively improve the system’s robustness.

Multi-objective model predictive control method for T-type three-level grid-connected

Based on the mathematical model of T-type three-level topology, a T-type three-level inverter model is proposed to predict the multi-objective control method, which mainly includes DC neutral voltage (NP-V), switching state, inverter voltage vector, and multi-objective cost function. Different emphases can be selected according to the application requirements, and coordinated control of different control objectives can be realized by giving different weight values to different control objectives. An extended observer (ESO) is added to observe the error part of the grid-connected inverter system, and the observed results are compensated to the grid-connected reference voltage. The simulation results show that the total harmonic distortion rate of the output current of the inverter is lower than that of the traditional finite control set model predictive control strategy. In addition, the proposed method can realize the balance control of the midpoint potential, and the principle is simple.

Constrained Multi-Objective Optimization for Double-Sided Tubular Machine With Hybrid Segmented PM

Double-sided tubular machines (DSTM) have greatly improved space utilization and power density, and are widely used in tidal power generation and high-power electric drives, while the thrust force ripple is also significant. To get the minimum cogging force with the maximum thrust force, hybrid segmented PM array topology is introduced to the DSTM and used as research object for multi-objective optimization. Due to the constraints among the parameters to be optimized, this paper proposes a new constrained multi-parameter multi-objective optimization method. In this method, a new optimal Latin hypercube(OLH) is put forward to solve the constrained parameter sampling problem. RReliefF is used to distinguish the importance of multi-parameter and divide them into three layers: strong, medium and weak, and surrogate models are established hierarchically to simplify the optimization complexity. In addition, an improved Gaussian process regression(GPR) algorithm is proposed to improve the optimization accuracy of strong significance parameters. The optimization results show that the average thrust force is increased by 4.7%, the cogging force is reduced by 28%, and total harmonic distortion rate of the voltage is reduced by 30.5% without loss of efficiency, which significantly improves the performance of the machine, and verifies the effectiveness of the proposed method, which is suitable for constrained multi-parameter multi-objective optimization.

Sensorless DTC-SVM applied to an induction motor controlled by a three-level inverter using SMSFO

PurposeThe direct torque control (DTC) of induction motor (IM) drive is featured by high ripples in the electromagnetic torque and stator flux profiles because they are controlled by two hysteresis regulators. Furthermore, the machine flux is not directly measurable. Hence, it is better to reconstitute it from the instantaneous electrical equations of the machine. Once the stator flux is estimated, we can guarantee a reliable sensorless DTC control. Thus, the purpose of this research work is to ensure fast response and full reference tracking of the IM under sensorless DTC strategy with desired dynamic behavior and low ripple levels.Design/methodology/approachIn this work, an improved DTC strategy, which is DTC_SVM_3L, is suggested. The first step of the designed approach is to substitute the conventional inverter feeding the motor with a three-level inverter because it guarantees reduced switching losses, improved quality of voltage waveform and low-current total harmonic distortion rate. The second aim of this paper is to make the IM operate at a constant switching frequency by using the nearest three vectors-based space vector modulation (SVM) technique rather than hysteresis controllers. The third objective of this study is to conceive a sliding-mode stator flux observer, which can improve the control performances by using a sensorless algorithm to get an accurate estimation, and consequently, increase the reliability of the system and decrease the cost of using sensors. The stability of the proposed observer is demonstrated based on the Lyapunov theory. To overcome the load change disturbance in the proposed DTC control strategy, this paper exhibits a comparative assessment of four speed regulation methods: classical proportional and integral (PI) regulator, fuzzy logic PI controller, particle swarm optimization PI controller and backstepping regulator. The entire control algorithm was tested under different disturbances such as stator resistance and load torque variations.FindingsIt was ascertained that the IM, controlled with three-level inverter, exhibits good performances under the proposed DTC-SVM strategy based on a sliding-mode observer. The robustness of the suggested approach against parameter variations is also proved.Originality/valueThe theoretical development of the proposed control strategy is thoroughly described. Then, simulations using Matlab/Simulink software are launched to investigate the merits of the sensorless DTC-SVM command of three-level inverter-fed IM drive with different speed regulators.

Wide Frequency PWM Rectifier Control System Based on Improved Deadbeat Direct Power Control

The precision of deadbeat direct power control depends on the parameters of the system model. In wide frequency applications, such as multi- electric aircraft and electric vehicles, variations in frequency and resistive parameters will affect the control effect. The AC side voltage frequency of the generator rectifier varies widely, which will lead to a steady-state reactive power error in the deadbeat direct power control. In addition, the large temperature variation range during the operation of the multi-electric aircraft and electric vehicles leads to large changes in the filter inductance and line resistance of the AC side, and the model parameters do not match the actual parameters, which will further deteriorate the control accuracy. In this paper, a PWM rectifier control method is proposed for the occasions when the frequency and temperature change are in a wide range. Using repetitive control and power compensation, it solves the problems of steady-state reactive power error and control accuracy degradation caused by the mismatch of model parameters under severe operating conditions. The control method can precisely adjust the output DC voltage of PWM rectifier, and it also can maintain unity power factor and reduce the total harmonic distortion rate of the input current. The effectiveness of the proposed control method is verified by the experimental results.

Multi-Objective Optimization of an Axial Flux Permanent Magnet Brushless DC Motor with Arc-Shaped Magnets

To get a better electromagnetic performance of an axial flux permanent magnet brushless DC motor (AFPMBLDC), an AFPMBLDC with arc-shaped magnets and its multi-objective optimization design are researched. Firstly, the main design parameters of the AFPMBLDC are proposed, and the initial designs are carried out according to the given requirements. Furthermore, the pole arc coefficient, permanent magnet thickness, permanent magnet arc radius, and air-gap length are selected as optimization factors. Then, an orthogonal experiment table is established, in which the flux density, no-load back EMF, harmonic distortion rate, and output torque ripple are selected as optimization targets. The Taguchi optimization method is adopted to optimize the performance indexes and the optimal parameters are obtained. Finally, the optimized model is constructed, and some simulations are carried out to verify the optimal design. The research results have shown that the air-gap flux density of the optimized AFPMBLDC is reduced to 31.8%, the total harmonic distortion rate of no-load back EMF is less than 7.5%, and the torque ripple is reduced to 4.3%.

An improved PGC demodulation algorithm for optical fiber interferometers with insensitive to carrier phase delay and modulation depth

Phase generated carrier (PGC) demodulation is widely used in optical fiber interferometers due to its high sensitivity, large dynamic range and high signal fidelity. Based on the traditional PGC DCM demodulation scheme, we propose a algorithm to eliminate the carrier phase delay and compensate the modulation depth of PGC phase demodulation. The proposed algorithm provides real-time compensation for carrier phase delay and modulation depth without additional compensators. Through theoretical analysis and simulation, the performance of the improved demodulation scheme is compared with the traditional PGC-DCM demodulation algorithm. A complete demodulation system hardware is built, and the improved algorithm, the traditional PGC-DCM scheme and the traditional PGC-Arctan algorithm are tested respectively based on the Michelson interferometer. Experimental results show that the proposed algorithm is insensitive to carrier phase delay and modulation depth, its signal-to-noise ratio and distortion rate can reach 56.15 dB, and the total harmonic distortion rate is 0.13 %.