Voltage Harmonic Distortion Research Articles

A kind of full bridge current type multi-input distributed generation system

A kind of full bridge current type multi-input distributed generation system (DGS) is put forward in this paper and deeply analyses the energy management control strategy (EMCS), circuit topology and steady-state principle. The suggested DGS is comprised of a full bridge current type single-stage power structure multi-winding high-frequency-link multi-input inverter (MII) and a battery bidirectional charge and discharge HF isolated converter whose outputs are parallel-connected with the AC output terminal, the EMCS can achieve precision control of DGS power flow direction and smooth conversion of three power supply modes (PSMs) by analysing the value of load power and the sum power of multiple inputs, and inhibit the magnetic saturation of the inductor and the total harmonic distortion of the output voltage. A 2.5KV prototype is designed to verify that the proposed DGS and EMCS have features of supply power simultaneously, single-stage power conversion, isolation among input, load, and battery, strong adjustable ability, strong load capacity, simple and fast-responsed control, etc.

Harmonic mitigation of AC electric railway power feeding system by using single-tuned passive filters

Harmonic is an important factor affecting the quality of the power transmission system. caused by non-linear loads and power conversion devices. In this research, several train simulation samples of the city line Airport Rail Link (ARL) electric train were used to simulate the effects of harmonics on the power electric substation (ESS) by calculating the Total Harmonic Distortion of voltage (THDv) and current (THDi). Then compared with IEEE519-2014 standards to indicate the quality of power found that THDi 35th–50th exceeds the standard. In addition, the comparison of the harmonic reduction effect of the sample train from the single tuned passive filter designs of 3rd, 5th, 7th, and 11th showed that the 11th filter was able to keep the THD within the standard.

Water Cycle Algorithm Based Parametric Tuning of Non-Negative LMMN Control of Grid Tied Renewable Energy Systems

ABSTRACT This work proposes a hydrological cycle-based optimisation technique for performance enhancement of a non-negative least mean mixed norm (NNLMMN) based voltage source control (VSC) for a three-phase grid integrated wind/photovoltaic (PV) system. Water cycle algorithm (WCA) is employed to tune the proportional–integral (PI) controller parameters of VSC to regulate voltage variations at DC link generated during dynamic load and wind conditions. This results in generation of a specific loss component (Iloss) of current to boost the performance of VSC. The NNLMMN control deals with system identification troubles with a non-negativity limitation in varied Gaussian noise conditions. It generates accurate Iloss to upgrade the ability of VSC to accurately extricate weight signals and the fundamental load current component in terms of improvement in DC link voltage (vdc) and total harmonic distortion. The proposed algorithm mitigates problems like voltage fluctuations besides performing operations like reactive power compensation, enhancement of power quality, load and power balancing at the point of coupling during steady-state and dynamic conditions. In conjunction with the NNLMMN algorithm, the proposed technique reduces the surplus mean square error iteratively, resulting in a compact expression of step size. The proposed topology stands out with an improved performance of vdc under wind gusts and the well-known bell-shaped irradiance curve. For relative evaluations, the performance of non-optimised PI and particle swarm optimised PI has been added to analyse the improved response of vdc and Iloss. Extensive simulation results obtained in MATLAB/Simulink are exhibited to corroborate the efficacy of the suggested system.

Modified W-type configuration for a single-phase reduced parts count 81-level inverter.

The technology of modern power systems is revolutionizing as renewable energy sources are being integrated with electric power grids. In the form of inverters, power electronic converters are becoming an integral part of power systems due to their massive demand for grid integration of photovoltaic (PV) systems. Existing multilevel inverter topologies either require an output filter to get a sinusoidal voltage or generate a higher number of output voltage levels at the expense of many hardware resources. This paper presents a new single-phase 81-level inverter configuration with the name given as 'Modified W-Type Multilevel Inverter'. The proposed inverter configuration uses only eighteen power switches and four DC voltage sources to generate an 81-level output voltage approaching a sinusoidal waveform without an output filter. The general design equations are developed to calculate the number of switches, the number of voltage levels, and the number of DC sources for the proposed configuration. Loss and efficiency analysis is carried out that verifies a good practical efficiency of the proposed inverter configuration during the dynamic operation. A comparative analysis with the existing MLI topologies is also carried out that validates the effectiveness and novelty in reducing parts count and higher number of voltage levels. The proposed topology offers 1.04% total harmonic distortion of the output voltage which is within the benchmarks specified for grid integration without any filter requirements. The proposed inverter configuration is simulated in MATLAB/Simulink, and the results are validated by the design and development of a hardware prototype.

Impact of charging infrastructure for electric vehicles on the power quality of the distribution networks

The paper studies the impact of electric vehicle charging stations on the power quality of distribution networks. The effects of the charging infrastructure on the power quality have been investigated highlighted the possible challenges these infrastructures can create. The impact of lowcharging and fast-charging stations installed in a private company parking, owned by the Milan distribution system operator Unareti, have been investigated. To identify potential network problems, the main electrical variables at the points of common coupling with the medium voltage distribution network have been examined. By installing a temporary measurement, the voltage and current rootmean-square, the voltage, and current total harmonic distortion have been recorded and analyzed over 15 consecutive days. The data point out potential criticalities and challenges that could be considered in the planning and operating future low-carbon distribution networks.

Rapid Control Prototyping of Five-Level MMC based Induction Motor Drive with different Switching Frequencies

In this paper, Rapid Control Prototyping (RCP) of five-level Modular Multilevel Converter (MMC) based Induction Motor (IM) drive performance is observed with different switching frequencies. The Semikron based MMC Stacks with two half-bridge each are tested with the switching logic generated by phase and level shifted based Sinusoidal Pulse Width Modulation (SPWM) technique. The switching logic is generated by the Typhoon Hardware in Loop (HIL) 402. The disadvantages of Multilevel Converter like not so good output quality, less modularity, not scalable and high voltage and current rating demand for the power semiconductor switches can be overcome by using MMC. In this work, the IM drive is fed by MMC and the experimentally the performance is observed. The performance of the Induction Motor in terms of speed is observed with different switching frequencies of 2.5kHz, 5kHz, 7.5kHz, 10kHz, 12.5kHz and the results are tabulated in terms of Total Harmonic Distortion (THD) of input voltage and current to the Induction Motor Drive. The complete model is developed using Typhoon HIL 2021.2 Version Real-Time Simulation Software.

Temperature rise and DC current capability tests of star-point reactor used in HVDC transmission

Star-point reactors are grounding devices installed in HVDC stations between the converter transformer secondary side and AC side of converter arms to provide a reference to ground. Such reactors are used as high-impedance grounding on the converter side of power transformers, providing high impedance path for the fundamental harmonic (i.e. 50 or 60 Hz) and a low impedance path for DC current, eliminating DC current flowing through the transformer windings. Temperature rise and DC current capability tests of 420 kV star-point reactor are presented in this paper. The purpose of temperature rise test is to verify that temperatures that can damage the insulation of star-point reactor will not be reached with the specified service conditions. The temperature rise test was carried out according to the requirements of the IEC 61869-3 standard and client’s request which included simultaneous application of fundamental, 3rd harmonic voltage and DC excitation. The inclusion of 3rd harmonic excitation of an amplitude up to 15% simulates voltage harmonic distortion which may appear in the power system at the location of star-point reactor installation. Prior to temperature rise test, DC current capability test was performed. The goal of this test is to determine the value of DC current at which the saturation point is reached. DC current is injected through star-point reactor while AC voltage is applied. Two different cases are considered regarding AC voltage: test with fundamental voltage harmonic and test with fundamental voltage harmonic with superimposed third voltage harmonic. Test circuit is proposed which is suitable for generation of complex voltages composed of fundamental harmonic and superimposed third harmonic with amplitudes up to 15% of the applied fundamental harmonic. The proposed test circuit was also used during the temperature rise test and it is applicable for testing of HV equipment with rated voltage up to 420 kV.

Modified CCF Based Shunt Active Power Filter Operation With Dead-Band Elimination for Effective Harmonic and Unbalance Compensation in 3-Phase 3-Wire System

The effect of reduction in the terminal voltage of a grid-tied inverter together with minimization in total harmonic distortion (THD) of terminal voltage and current, in the presence of dead-band in the switching remains always challenging for the researchers. With high switching frequency, this issue increases by many folds. The grid-tied inverter used for harmonic compensation acts as a shunt active power filter (SAPF). The implementation of the dead-band elimination technique is based on output current polarity detection, suffers from multiple zero-crossing due to the generation of high frequency switching harmonics during SAPF operation. This paper deals with a dead band elimination methodology together with harmonic compensation using SAPF under non-linear and unbalanced loading conditions. Here, SAPF uses a dual fundamental component extraction (DFCE) scheme with modified complex coefficient filter (MCCF) to extract fundamental components for reference current generation to implement an indirect current control PWM scheme. MCCF extracts fundamental components even in the presence of dc offset and unbalancing at the input. For incorporating dead-band elimination in control, exact polarity detection is done separately through SAPF output current estimation using sensed load current, and modified CCF computed reference source current. Since the estimated SAPF output current contains no high-frequency switching harmonics, the dead-band elimination technique can be correctly implemented. To synchronize the zero-crossing of the estimated and actual SAPF current, an adaptive delay control is used. The proposed MCCF based control logic’s performance together with the dead-band elimination technique is validated for SAPF operating under non-linear, unbalance, and dynamic load conditions. The proposed dead-band elimination scheme based SAPF model is developed and simulated using MATLAB/ SIMULINK. The simulation results show a significant reduction in source current harmonics due to the elimination of odd harmonic injection into the system by incorporating dead-band elimination in SAPF operation. The real-time simulation of the proposed method is also validated using OPAL-RT OP4510 real-time platform.

Improved control scheme for simultaneous reduction of common-mode voltage and current harmonic distortion of the Vienna-type rectifier with balanced and unbalanced neutral-point voltages

As a non-generative-boost rectifier, the Vienna-type rectifier has been proposed and applied in several applications, such as wind power generation systems, battery charging system, etc. This paper further proposes an improved control scheme for reducing common-mode voltage (CMV) and input current harmonic distortions under balanced and unbalanced neutral-point (NP) voltages. At first, the operating fundamentals of the Vienna-type rectifier are presented. The zero-sequence voltage and its corresponding ranges are carefully derived to control the dc-link capacitor voltages separately. Considering the specific constraint of this rectifier, the zero-sequence voltage is further revised to reduce the current harmonic distortions around the zero-crossing points. Doing so, the simultaneous reduction of CMV and input current harmonic distortions can be realized, which is applicable to balanced and unbalanced NP voltages. The comparisons of the proposed scheme, the conventional zero-sequence voltage injection scheme, and the CMV reduction method under balanced NP voltage condition are conducted, which demonstrate the salient advantages of the presented scheme.

Grid-Forming Operation of Energy-Router Based on Model Predictive Control with Improved Dynamic Performance

The focus of this study is on the grid-forming operation of the Energy Router (ER) based on Model Predictive Control (MPC). ER is regarded as a key component of microgrids. It is a converter that interfaces the microgrid (s) with the utility grid. The ER has a multiport structure and bidirectional energy flow control. The ER concept can be implemented in Nearly Zero-Energy Buildings (NZEB) to provide flexible energy control. A concept is proposed where the ER works as a single grid-forming converter. The challenge is to keep the predefined reference voltage and frequency inside the NZEB in all possible modes, including the idle operation mode, current sources, and nonlinear load control. To gain stability and output voltage quality, the MPC is proposed. The design of the modified MPC algorithm with improved dynamics performance is explained. PLECS software is utilized to verify the proposed algorithm. The results demonstrate the suitable performance of the proposed control method in terms of total harmonic distortion of the output voltage. The influence of weighting coefficiencies is evaluated, showing the higher impact of the capacitor filter voltage on lowering the total harmonics distortion of the output voltage. Finally, the capability of the control system toward step change in the reference value is evaluated.

A novel design of fourth-order harmonic passive filters for total demand distortion minimization using crow spiral-based search algorithm

Mathematical design of a new fourth-order harmonic passive filter is presented and its optimal strategy is proposed with regards to various design scenarios. The considered objective function is total demand distortion minimization of the supply current. The crow spiral-based search algorithm (CSSA) is applied to solve the design problem formulated. This CSSA relies on a spiral search mechanism that improves the convergence and balances the exploration and exploitation abilities of the conventional crow search algorithm. Various power quality indices are taken into consideration like the individual and total harmonic voltage distortion values, individual and total current harmonic distortion values, active power loss, actual and displacement power factor percentages, and resonance damping capabilities. These indices were handled as non-linear constraints in the design. Additionally, a comparative investigation of the different damped filters is presented to assess the planned filter performance. The results obtained confirm the success of the filter design proposed in this paper.

Intelligent transformer tap controller for harmonic elimination in photovoltaic interfaced micro-grid network

The photovoltaic (PV) system is interfaced to the microgrid through an on-load tap changer (OLTC) transformer. Pulse width modulation (PWM) AC choppers are used to control these OLTC but create harmonics owing to their non-optimal firing angles. In this paper, Differential Evolution (DE) and Grey Wolf Optimizer (GWO) techniques are used for optimal control of an AC chopper to keep the harmonic distortion of voltage and current within limits. An IEEE-13 node network is adapted as a micro-grid with PV integration through transformers. The simulated results are validated by a laboratory set-up. A dSPACE experimental set-up is used for the real-time implementation of optimization algorithms. The results show that the DE gives firing angles that improve power quality, particularly a reduction in total harmonic distortion and improvement in the root mean square voltage profile. The research is particularly useful for the on-line power quality improvement in PV interfaced microgrid networks.

Harmonic Mitigation in VFD Controlled Chiller Compressor Using AC Line Reactor and DC Link Choke Combination

With the goals of a better power factor and reduction in energy use, variable frequency drives (VFDs) have been standardized in various industrial applications including Heating, Ventilation, and Air-conditioning (HVAC) systems. However, key issues related to the deterioration in the power quality associated parameters (voltage harmonic distortion and current harmonic distortion) due to the growing number of VFDs demand a wholesome analysis of the problems faced by the users. In this present work, an analysis has been performed to investigate the potential impact of using alternating current (AC) line reactor and direct current (DC) link choke combination on harmonic mitigation in a VFD driven water-cooled centrifugal chiller compressor. Using a combination of AC line reactor and DC link choke as one of the low cost solutions in harmonic mitigation of a VFD driven load in HVAC systems can be decided based on the investigation done in this research work.

Electrical and Mechanical Characteristics Assessment of Wind Turbine System Employing Acoustic Sensors and Matrix Converter

Permanent magnet synchronous generator (PMSG)-based wind turbine systems have a wide range of applications, notably, for higher-rated wind energy conversion systems (WECS). A WECS involves integrating several components to generate electrical power effectively on a large scale due to the advanced wind turbine model. However, it offers several glitches during operation due to various factors, notably, mechanical and electrical stresses. This work focuses on evaluating the mechanical and electrical characteristics of the WECS using two individual schemes. Firstly, wind turbines were examined to assess the vibrational signatures of the drive train components for different wind speed profiles. To apply this need, acoustic sensors were employed that record the vibration signals. However, due to substantial environmental impacts, several noises are logged with the observed signal from sensors. Therefore, this work adapted the acoustic signal and empirical wavelet transform (EWT) to assess the vibration frequency and magnitude to avoid mechanical failures. Further, a matrix converter (MC) with input filters was employed to enhance the efficiency of the system with reduced harmonic contents injected into the grid. The simulated results reveal that the efficiency of the matrix converter with input filter attained a significant scale of about 95.75% and outperformed the other existing converting techniques. Moreover, the total harmonic distortion (THD) for voltage and current were examined and found to be at least about 8.24% and 3.16%, respectively. Furthermore, the frequency and magnitude of the vibration signals show a minimum scale for low wind speed profile and higher range for medium wind profile rather than higher wind profile. Consolidating these results from both mechanical and electrical characteristics, it can be perceived that the combination of these schemes improves the efficiency and quality of generated power with pre-estimation of mechanical failures using acoustic signal and EWT.

Impacts of Harmonic Voltage Distortions on the Dynamic Behavior and the PRPD Patterns of Partial Discharges in an Air Cavity Inside a Solid Dielectric Material

The monitoring of partial discharges (PDs) is one of the main methods used worldwide for evaluation and diagnosis of the insulation conditions in equipment powered by medium and high voltages. The occurrence of PDs is usually an indication of the appearance of insulation defects, which over time can compromise the dielectric withstand of the material used, increasing the probability of complete breakdown. In general, laboratory tests for detecting and registering PDs are carried out using purely sinusoidal voltages. However, it is very common for an electrical asset to be subjected at some point in its operating life to voltages distorted by harmonic components. Some studies reported in the literature reveal that harmonic distortions can affect the PDs’ characteristics, nevertheless, the effects of individual harmonic components on PDs still need to be analyzed. In this context, this paper proposes to evaluate the impacts of harmonic voltage distortions on the dynamic behavior and the phase-resolved partial discharge (PRPD) patterns of PDs in an air cavity within a solid dielectric material. For this, a simulation model was implemented, which was used to analyze the effects of applying distorted voltages composed of different harmonic orders (third, fifth, and seventh) and distinct levels of distortion (1%, 3%, 5%, 10%, 15%, and 20%). In addition, the influence of the third harmonic phase angle on PDs is also analyzed. The results extracted from the simulations revealed that the harmonic distortions caused changes in the numbers of PDs per cycle, in the mean apparent charges of the PDs per cycle, and in the PRPD patterns’ characteristics. These changes were very significant for higher distortion levels, which in practice may impair the interpretation of PD measurement records for the diagnosis of the condition of the insulation system.

Research on the Partition Method Based on the Observation Points of Voltage Distortion in Harmonic Optimization

With the use of a large number of power electronic equipment, the harmonics in the power grid are becoming more and more serious. There are many methods for harmonic mitigation and optimization such as Global network Optimization. When there are many nodes, the global network optimization method is more complicated. Considering the problem of large numbers of harmonic injection nodes in the power grid, this paper proposes a method of clustering the voltage distortion nodes according to correlation, and using the characteristic nodes to describe the harmonic voltage distortion in the region to mitigate harmonic voltage. This method is based on the observation data of the voltage distortion of the nodes for dynamic selection and grouping. The results show that this method meets the needs of Global network Optimization. The data processing methods used in this paper such as feature extraction methods and time series interpolation optimization can effectively reduce the data dimension, and get better optimization effect.

Grid integration of three phase solar powered fault‐tolerant cascaded H‐bridge inverter

AbstractGrid integration of solar photovoltaic (PV) systems is becoming popular recently due to the merits of stable support to conventional grid, limiting global warming and reduced emissions. However, maintaining capacitor voltage balancing, unity power factor, sinusoidal grid current, and harmonic profile improvement are challenging tasks owing to change in irradiation conditions. Multilevel inverters (MLI) in grid‐connected systems will enhance the system's power quality in terms of voltage and current total harmonic distortion (THD). One of the most promising multilevel topologies for renewable energy applications is the cascaded H‐bridge (CHB) inverter. Since CHB inverters include many components, they have a higher risk of failure, lowering system reliability. Due to the change in irradiation condition, the voltage across the corresponding DC link capacitor may vary. Therefore, the DC‐link capacitor balancing is mandatory and done by an individual control scheme. This paper presents a highly reliable, robust, and modular solar PV‐fed fault‐tolerant CHB inverter with an individual voltage/current control strategy for grid integration. Higher reliability and modularity, power factor correction, and harmonic profile improvement are the main objectives of the proposed system. The proposed system has been simulated in MATLAB/Simulink and validated with experimental results on the developed prototype for different irradiation conditions.

Active and reactive power control of grid‐connected single‐phase asymmetrical eleven‐level inverter

In recent times, multilevel inverters (MLIs) have become very popular for commercial and industrial applications. Here, an eleven-level inverter and its power flow control are presented. The presented topology has a lesser component count than other existing topologies, thus reducing the devices and overall cost of the inverter. This inverter comprises six bidirectional switches, two DC sources, one four-quadrant switch, and two capacitors for the voltage divider circuit. The conduction modes and corresponding switching states of the presented eleven-level inverter are shown in detail. Further, the apparent power control of the presented inverter under grid-connected operation is discussed, which provides simultaneous active and reactive power control over the power injected into the grid. Switching and conduction losses are calculated for 3 and 6 kVA grid injected power at 0.8 power factor lagging. The obtained results show that the total harmonic distortion (THD) of the inverter output voltage and grid current is 12.10% and 0.23%, respectively, under 6 kVA power transfer conditions. The real-time analysis is also carried out for 3 and 6 kVA power transfer conditions for the presented eleven-level inverter to validate the active and reactive power flow control.

Performance analysis of grid interactive single-phase solar powered fault tolerant cascaded inverter

Abstract Grid integration of solar photovoltaic (PV) systems is becoming popular recently due to the merits of stable support to conventional grid, limiting global warming and reduced emissions. However, maintaining capacitor voltage balancing, unity power factor, sinusoidal grid current and harmonic profile improvement are the challenging tasks owing to change in irradiation conditions. Multi-level inverters in grid connected systems will enhance the power quality of the system in terms of voltage and current total harmonic distortion. This paper proposes a highly reliable, robust and modular single phase solar PV fed fault tolerant hybrid cascaded H-bridge inverter with individual voltage/current control strategy for grid integration. Higher reliability and modularity, power factor correction, able to with stand without degrading the performance of the topology even under faulted conditions and harmonic profile improvement are the main objectives of the proposed system. The proposed system has been simulated and validated with experimental results on the developed prototype for different irradiation conditions and tested the performance of the topology with creation of faults on different modules at different times.

Conservative Power Theory for Harmonic Voltage Responsibility Assignment

Discussions on the different methods for sharing responsibilities regarding harmonic distortions in power grids have received wide attention in the area of power quality. This paper proposes a methodology based on Conservative Power Theory (CPT) for responsibility assignment due to the harmonic voltage distortions present at the point of common coupling. First, a theoretical basis for analyzing the orthogonal current decomposition of CPT under non-sinusoidal conditions is presented. Next, using the frequency domain, a methodology is introduced to separate the contributions of the harmonic voltage distortions in the CPT's orthogonal currents. To illustrate the application of the proposed methodology, it is simulated a real large-scale electrical system composed of an energy utility and three industrial plants connected to the same common coupling point. Finally, the results obtained are compared to other method showing the effectiveness of the proposed approach.