Poor Power Quality Research Articles

Control Strategy for Resonant Inverter in High Frequency AC Power Distribution System with Harmonic Suppression and Transient Performance Improvement

In high frequency AC (HFAC) distribution system, the resonant inverter is used to improve power quality and keep the stability of the output AC voltage. Aiming at the problems of poor output power quality and slow transient performance caused by unreasonable filter parameter design and load change during inverter operation, a single-phase H-bridge LCLC resonant inverter based on analog circuit controller implement is introduced in this paper for HFAC power distribution system (PDS). In this study, to design harmonic compensator and analyze the responsiveness of the inverter, it is necessary to analyze the output voltage total harmonic distortion (THD) of LCLC resonant inverter and the performance of the open loop system in detail. On the one hand, a proportional-integral-resonant (PIR) controller is designed to maintain the zero static error of the voltage output and suppress the output voltage THD of LCLC resonant inverter. On the other hand, an integral controller combines with phase-shift modulation (PSM) method is presented to effectively improve the transient performance of resonant inverter and provide the fixed frequency of the output voltage. On the basis of the above, the experimental prototype is implemented with the output AC voltage root mean square of 28 V, and the output voltage frequency for resonant inverter is equal to switching frequency. A rated output power of 130 W experimental platform is built to verify the effectiveness of the theoretical analysis, control strategy, and modulation method.

Space Vector Rotation-Based Controlled Decaying Current Injection for Islanding Detection of Inverter-Interfaced DG

Continuous injection-based islanding detection of Inverter-Interfaced Distributed Generator (IIDG) has been a general trend. The major issues in previous islanding detection methods are large Non-Detection Zone (NDZ), poor Power Quality (PQ), high implementation cost, and lack of real-time validation. Further, the threshold in most methods is not generic and depends on the system’s rating. Hence, this paper proposes a local voltage and current measurement-based islanding detection method for IIDGs. It utilizes parameters estimated from the fundamental phasors of voltage and current at the Point of Common Coupling (PCC) of IIDG using Space Vector Rotation (SVR) and a controlled self-decaying current injection. The proposed disturbance is injected only after disturbance detection by SVR parameters to mitigate the impact on PQ. Disturbance identification is easy due to the combined PCC voltage and current effects on parameter estimation. Real-Time Digital Simulator (RTDS) and Controller Hardware In the Loop (CHIL) setup-based results from the proposed method have been obtained and compared with previous methods. These results indicate the proposed method’s real-time efficacy (low islanding detection time) with no NDZ and negligible impact on PQ for different islanding events. Also, the proposed method is independent of the microgrid’s rating and reliable for non-islanding events.

Research on variable speed constant frequency energy generation based on deep learning for disordered ocean current energy

As one of the most promising new energy sources today, ocean current energy has become an important part of energy strategies. There are short-term disorderly fluctuations in the flow rate of ocean current energy. The uncontrolled input of kinetic energy from the ocean current can lead to poor quality of power generated by current energy generators. The existing technology of current energy generation uses mechanical rigid transmission, which is prone to fatigue damage and low reliability under variable load fluctuations. In this paper, a joint simulation platform based on AMESim and Simulink is constructed based on 50kW hydraulic transmission and control power generation equipment. This paper establishes a mathematical model of the hydraulic transmission control system and proposes a constant frequency control algorithm based on a deep learning prediction model to improve the steady-state accuracy of the hydraulic motor speed. This paper proposes a deep learning prediction model based on EWT (Empirical Wavelet Transform)-LSTM (Long Short-Term Memory)-CNN(Convolutional Neural Network), which improves the prediction accuracy by 12.26% compared to short-term memory neural network. The model improves the motor speed dynamic accuracy by 90%, the standard deviation index by 78.11%, and the maximum deviation by 86.10% compared to the feed-forward Proportional Integral Derivative (PID)control algorithm. Therefore, the model can effectively improve the quality of the system’s power generation. At the same time, the time cost of the model for a single prediction is less than the sampling time of other control algorithms. In this paper, the simulation results are verified by a 50kW hydraulic transmission control experimental bench. The constant frequency control algorithm based on the deep learning prediction model can effectively improve the constant frequency dynamic accuracy of the motor of the hydraulic transmission control power generation equipment, which in turn improves the system power generation quality.

A Novel Coordinated Control System to Reactive Power Compensation of Photovoltaic Inverter Clusters

With the development of new energy, a cost-effective reactive power compensation scheme is essential to the voltage stability of the power system for small-capacity distributed generation. This paper proposes a coordinated control scheme of inverter cluster which is based on the reactive power support capability of the photovoltaic inverter. Moreover, by using power angle vectors, a reactive power distribution algorithm is proposed to solve the poor power quality of the point of common coupling connecting source and load in the distributed generation station. Simulations verify the performance of the algorithm is better than the conventional static capacity distribute algorithm and dynamic residual margin distribute algorithm. Finally, the effectiveness of the reactive power compensation scheme and distribution strategy for improving power quality and regulation ability proposed in this paper is verified by operation experiments in the actual power station.

Effect of Power Quality on Production Reliability and Stability of Water Treatment Plant at Vodovod-Osijek

Power quality issues are pervasive in most industries. The system operator and the network user are responsible for the power quality at the point of common coupling (PCC). Since a water treatment plant must operate continuously, a reliable and continuous power supply of satisfactory quality is necessary in accordance with HRN EN 50160:2012. Additionally, the electromagnetic feedback of load consumption on the power grid must be within the permitted values prescribed by the Distribution System Grid Code (Official Gazzete nos. 74/18, 52/20). The low-voltage power grid of the “Nebo Pustara” water treatment plant contains sensitive electric and electronic loads. As such, the loads require a power supply of satisfactory quality. Moreover, these loads have non-linear voltage/current characteristics and as such negatively affect power quality. In order to prevent the effects of poor power quality on the water treatment plan operation and to reduce the impermissible effect of non-linear loads on the power grid, the “Nebo Pustara” power sub-station was outfitted with a PQube3 power quality analyzer. This paper presents the results of the power quality analysis. Additionally, the paper details the actions taken in the user and distribution power grid to increase effect production reliability and stability of the water treatment plant and water supply, with the aim of reducing the negative effect on plant operation and equipment and also reducing the impermissible feedback of non-linear loads. Key words: power quality, water for human consumption, production reliability and stability of water treatment plant and water supply, Nebo Pustara, PQube3

Power impact and electromagnetic disturbances of different lighting modes from spot LED lamp

Light-emitting diode (LED) lamp has been widely used in recent years for lighting systems due to its environmental friendliness, long life, low power consumption and high efficiency. However, LED lamps are sources of harmonic pollution due to AC/DC conversion by rectifier diodes which results in poor power quality. LED lamps research focuses on improving the power factor (PF) and reducing current harmonics.In this article, we present the study of the harmonics of the current generated by two Spot-type LED lamps of the same brand and of different power. We took the following harmonics measurement cases: 6 W and 12 W lamps, the two lamps in parallel, for the different lighting modes, we need to make measurements for the three lighting modes: white lighting, colored lighting and mixed lighting between white and colored. Then, the electromagnetic disturbances conducted in common mode and in differential mode, using the Line Impedance Stabilization Network (LISN), were determined.

Evaluation of energy consumption and power qua798lity in oil mills using advanced smart meters

One of the main industries in Spain and other Mediterranean countries are oil mills. Although the specific energy consumption of oil mills depends on the capacity and other characteristics, some studies have highlighted the high energy consumption of these industries. In the case of olive mills, previous studies have shown that energy consumption is mainly supported by electricity, with low contribution from gas, diesel or biomass. Considering the importance of reducing the electricity consumption in oil mills, it is necessary to analyse the power consumption in order to take actions focused to reduce the contracted power and the energy required in its operation. Moreover, since these industries may require stable power supply, it is appropriate to analyse the power quality in order to detect possible adverse effects derived from a poor power quality. This paper presents the analysis of data collected by the Circutor MYeBOX 1500 portable meter installed in an olive oil mill. It is shown how monitoring these facilities during several weeks can provide relevant information regarding the energy assessment and policies.

A review of controllers and optimizations based scheduling operation for battery energy storage system towards decarbonization in microgrid: Challenges and future directions

The microgrid connected with the battery energy storage system is a promising solution to address carbon emission problems and achieve the global decarbonization goal by 2050. Proper integration of the battery energy storage system in the microgrid is essential to optimize the overall efficiency as well as manage the power efficiently and securely. However, battery energy storage system integrated microgrid exhibits several concerns, including intermittencies, poor power quality, high capital cost, and energy imbalance between supply and demand. To address these shortcomings, an improved scheduling controller and optimization of the battery energy storage system are required to ensure the resilient, sustainable, and economic operation of the microgrid. Several approaches have been employed to improve the performance of microgrids; however, the review studies on controllers and optimizations based scheduling operations in microgrid have not been explored yet. In light of this research gap, this review offers a comprehensive investigation of battery energy systems scheduling operation and their impacts on decarbonization in microgrid applications. The different types of optimization objectives and constraints of the battery energy storage system are discussed, focusing on cost, capacity, lifetime, and emission. Besides, this review provides a detailed discussion and classification of the various controller and optimization methods and algorithms concerning framework, executions, key findings, benefits, research gaps, along with existing issues and challenges. Additionally, the influences of battery energy storage system scheduling controllers in the decarbonizing microgrid are analyzed rigorously. Finally, this review delivers some significant recommendations that will assist the researchers, industrialists, and policymakers in developing an advanced optimized scheduling controller of battery energy storage system towards achieving sustainable management and decarbonization goals in a microgrid.

Operation of the DC Link in the Conditions of Poor Quality of Grid Power

Operation of the DC Link in the Conditions of Poor Quality of Grid Power

An Optimized PI Controller-Based SEPIC Converter for Microgrid-Interactive Hybrid Renewable Power Sources

With the use of hybrid renewable sources for example solar and wind turbines, an autonomous electric power generation system based on self-sufficient electric power generation is built in order to promote a smart and ecologically friendly environment. The three-phase inverter that links this scattered generating unit to the grid is in charge of ensuring that it is properly connected to the grid. While the energy produced by the hybrid unit is being utilized, it is also being stored in the batteries so that it may be used to transport power when other sources of power are not available, such as when the grid is down. This stand-alone power conversion and storage system is being built with the aid of power electronic converters and controllers, among other components, in order to ensure balanced power flow operation. To produce PWM pulses for the generator side converter, a PI controller is utilized. On the PV side, an improved PI controller is used to drive the SEPIC converter, which increases the transient responsiveness of the converter while it is being controlled by the controller. In order to communicate with the grid, the generated electricity is routed via a three-phase inverter that is controlled according to the DQ theory. The challenges connected with poor power quality are substantially resolved by the converters that have been presented. For simplicity of use, an automated control function has been introduced; in addition, an interactive MATLAB model of the system is being developed for minor and medium-scale microgrid applications; also, a prototype is being created to verify the simulation results.

Review and design of modular multilevel inverter with modified multicarrier PWM techniques for solar PV applications

PurposeThese implementations not only generate excessive voltage levels to enhance the quality of power but also include a detailed investigating of the various modulation methods and control schemes for multilevel inverter (MLI) topologies. Reduced harmonic modulation technology is used to produce 11-level output voltage with the production of renewable energy applications. The simulation is done in the MATLAB/Simulink for 11-level symmetric MLI and is correlated with the conventional inverter design.Design/methodology/approachThis paper is focused on investigating the different types of asymmetric, symmetric and hybrid topologies and control methods used for the modular multilevel inverter (MMI) operation. Classical MLI configurations are affected by performance issues such as poor power quality, uneconomic structure and low efficiency.FindingsThe variations in both carrier and reference signals and their performance are analyzed for the proposed inverter topologies. The simulation result compares unipolar and bipolar pulse-width modulation (PWM) techniques with total harmonic distortion (THD) results. The solar-fed 11-level MMI is controlled using various modulation strategies, which are connected to marine emergency lighting loads. Various modulation techniques are used to control the solar-fed 11-level MMI, which is connected to marine emergency lighting loads. The entire hardware system is controlled by using SPARTAN 3A field programmable gate array (FPGA) board and the least harmonics are obtained by improving the power quality.Originality/valueThe simulation result compares unipolar and bipolar PWM techniques with THD results. Various modulation techniques are used to control the solar-fed 11-level MMI, which is connected to marine emergency lighting loads. The entire hardware system is controlled by a SPARTAN 3A field programmable gate array (FPGA) board, and the power quality is improved to achieve the lowest harmonics possible.

Electrical Submersible Pumps: A System Modeling Approach for Power Quality Analysis With Variable Frequency Drives

This article proposes a high-level engineering guide to develop an integrated system model for power quality analysis in electrical submersible pump (ESP) applications with variable frequency drives (VFDs). Such analyses are troublesome in the industry due to the complexity of these systems. In this article, simple steps to perform system integration analyses of such arrangements, including torsional analysis, are developed. A simplified VFD-ESP model suitable for coupled electrical and mechanical analysis in steady state is proposed in all their configurations of practical interest. Such a model can be easily implemented in common simulation software, significantly reducing engineering efforts for implementation and analysis. The focus of the proposed model is the prediction of ESP failures that might result from a poor power quality caused by VFDs. Analytical expressions of different types of harmonics in these systems, as well as their accurate locations in the frequency domain, including their interharmonics and common-mode harmonics, are derived for this purpose. The effectiveness of the proposed model is verified through offline and real-time hybrid simulation results. Finally, a comparison between simulation results obtained using the proposed model and measurements collected on a down-scale laboratory prototype is carried out to demonstrate the accuracy of the suggested modeling approach.

Ground Fault Analysis and Grounding Method of Static Power Converters in Flexible AC Traction Power Supply Systems

Flexible traction power supply system (FTPSS) can eliminate neutral sections of all catenaries and improve the poor power quality of railway substations. The static power converter (SPC) is the key equipment of FTPSS and its internal faults must be quickly identified and cleared with minimal impact on catenaries to ensure the safety and reliability. This article investigates the two-stage fault characteristics in FTPSS. Before blocking, overcurrent and voltage distortion may result in a wide range of abnormal power supply. After blocking, capacitor overvoltage becomes the primary problem threatening the safety of faulty SPC because of the energy feeding from other SPCs. Equivalent circuits are established and applied to various fault conditions. The most serious fault case can be found through the comparison, so the complicated large-scale simulation scanning can be avoided. A T-shaped grounding method is proposed to solve the problem of fault current and capacitor overvoltage. Based on the calculation and simulation results of several typical fault cases, the dimensioning criterion of grounding circuit is provided for reference. Moreover, a comprehensive scheme of grounding protection is designed to detect and isolate serious faults. The theoretical fault analysis and the proposed grounding method are verified by simulations and experiments.

Poor power quality is a major barrier to providing optimal care in special neonatal care units (SNCU) in Central India.

Background:Approximately 25% of all neonatal deaths worldwide occur in India. The Indian Government has established Special Neonatal Care Units (SNCUs) in district and sub-district level hospitals to reduce neonatal mortality, but mortality rates have stagnated. Reasons include lack of personnel and training and sub-optimal quality of care. The role of medical equipment is critical for the care of babies, but its role in improving neonatal outcomes has not been well studied. Methods:In a qualitative study, we conducted seven focus group discussions with SNCU nurses and pediatric residents and thirty-five key informant interviews and with pediatricians, residents, nurses, annual equipment maintenance contractors, equipment manufacturers, and Ministry of Health personnel in Maharashtra between December 2019 and November 2020. The goal of the study was to understand challenges to SNCU care. In this paper, we focus on current gaps and future needs for SNCU equipment, quality of the power supply, and use of SNCU equipment. Results:Respondents described a range of issues but highlighted poor power quality as an important cause of equipment malfunction. Other concerns were lack of timely repair that resulted in needed equipment being unavailable for neonatal care. Participants recommended procuring uninterrupted power supply (UPS) to protect equipment, improving quality/durability of equipment to withstand constant use, ensuring regular proactive maintenance for SNCU equipment, and conducting local power audits to discern and address the causes of power fluctuations. Conclusions:Poor power quality and its negative impact on equipment function are major unaddressed concerns of those responsible for the care and safety of babies in SNCUs in Central India. Further research on the power supply and protection of neonatal equipment is needed to determine a cost-effective way to improve access to supportive care in SNCUs and desired improvements in neonatal mortality rates.

Enhanced dynamic performance of grid feeding distributed generation under variable grid inductance

<p>Controlling weak grid-connected systems is very challenging. In transient, frequency and voltage oscillations may lead to voltage and/or frequency stability problems and finally lead to system collapse. During steady-state operation and at the point of common coupling (PCC), voltage degradation and grid voltage background harmonics restrict the inverter's functionality, reduce the power flow capability and cause poor power quality. With weak grid connection, grid impedance variance will contaminate the voltage waveform by harmonics and augment the resonance, destabilizing the inverter operation. In this paper, complete mathematical modeling is carried out and state feedback-plus-integral control is implemented to support the stabilization of the system. The proposed controller is adopted to provide a smooth transient under sudden load change by controlling the injected grid current under different grid inductance values. Furthermore, the proposed control is used to reduce the order and size of the inverter output filter while maintaining system stability. The proposed control has been compared with the conventional proportional integral (PI) controller under different scenarios to validate its effectiveness and to strengthen its implementation as a simple controller for distributed generator applications.</p>

Voltage-Sourced Converter Fed High-Speed Switched Reluctance Motor Drive System With Energy Feedback and Near-Unity Power Factor

The diode bridge rectifier fed asymmetric half-bridge converter (AHBC) is conventionally employed to drive switched reluctance motors (SRMs), which leads to poor grid-side power quality. In the proposed system, a topology made up of a voltage-sourced converter and an AHBC is employed to drive the high-speed SRM. Stable SRM operation can be obtained by manipulating the active power flowing to motor side, and on the basis of that, the grid-side power quality is enhanced by directly manipulating input reactive power. Predictive deadbeat control with disturbance observer is employed to follow the power references, thereby achieving controllable speed, energy feedback, near-unity grid-side power factor, and low grid-side current distortion simultaneously. Additionally, an improved asymmetric modulation method is developed for switching frequency reduction. Experiments are carried out to test the proposed drive system in steady and dynamic conditions. Performance comparisons validate the improvement of the proposed high-speed SRM drive system.

Solar Energy Integration and Potential Challenges in Distribution Network: A Comprehensive Review

Solar photovoltaic (PV) power generation has emerged as a viable option among all other available energy options. The solar energy is unpredictable and variable in nature. Moreover, the distribution grids are not designed to accommodate high penetration of these sources. Therefore, such penetration poses the technical challenge like reverse power flow, voltage variation, harmonic distortion, poor power quality, malfunctioning of protective devices, overloading and underloading of feeders. Such challenges need to be addressed when solar PVs are added to the conventional grid system. The grid must have capacity to withstand and simultaneously take the corrective action against these occurrences. Therefore, there is a serious need to study these issues and further to develop control strategies to eliminate them. This paper presents various issues and challenges associated with high level PV integration in the distribution network and discussed the remedies to obtain the clean power supply.

Modulated Predictive Control to Improve the Steady-State Performance of NSI-Based Electrification Systems

This paper presents a modulated model predictive control (M2PC) strategy for a nine-switch inverter (NSI) based electrification system to improve the steady-state performance. The model predictive control method has gained significant interest due to its straightforward structure. However, the traditional finite control set model predictive control (FCS-MPC) imposes a high computational burden that is problematic in practical applications. This prevents reaching the high sampling frequencies due to an excessive increase in algorithm run-time. Selecting a low sampling frequency causes an unpleasant distortion in the control variable or poor power quality. An M2PC method for the NSI is proposed in this work to remove this trade-off. One zero vector and two active vectors are selected by evaluating a cost function for each allowed switching state of the NSI. The duty cycles of these vectors are calculated by assessing the cost function employing current error terms. An optimized sequence of these vectors is applied to the system that operates with the fixed-modulation frequency. Thus, an improvement in power quality (reduced harmonics with a better spectral content) with a lower sampling frequency is achieved. The computational burden rate (CBR) on the processor is reduced. These enhancements were proved by simulation and experimental studies. The comparison work was conducted to highlight the advantages of the proposed method over the other techniques reported in the literature. The proposed M2PC method was verified on a lab-scale NSI prototype driving two induction machines. The machine torques and speeds are well regulated, and the quality of the stator current is improved.

Design of a Supraharmonic Monitoring System Based on an FPGA Device.

During the last few decades, the poor quality of produced electric power is a key factor that has affected the operation of critical electrical infrastructure such as high-voltage equipment. This type of equipment exhibits multiple different failures, which originate from the poor electric power quality. This phenomenon is basically due to the utilization of high-frequency switching devices that operate over modern electrical generation systems, such as PV inverters. The conduction of significant values of electric currents at high frequencies in the range of 2 to 150 kHz can be destructive for electrical and electronic equipment and should be measured. However, the measuring devices that have the ability of analyzing a signal in the frequency domain present the ability of analyzing up to 2.5 kHz–3 kHz, which are frequencies too low in comparison to the high switching frequencies that inverters, for example, work. Electric currents at 16 kHz were successfully measured on an 8 kWp roof PV generator. This paper presents a fast-developed modern measuring system, using a field programmable gate array, aiming to detect electric currents at high frequencies, with a capability for working up to 150 kHz. The system was tested in the laboratory, and the results are satisfactory.

Electrical Power System Harmonics Elimination Using ETAP

Because of the fast advancement in the creation of power electronics equipment such as automatic Machines, adjustable speed drives, personal computers and other non-linear loads which are the main sources of harmonics. Due to the presence of these nonlinear loads, it is necessary to reduce the level of harmonics created in the power networks. Hence, harmonic analysis of distribution networks is important. The analysis of power systems is an important part of power system engineering. Any electrical utility company's principal goal is to provide the best quality of power. The power system harmonics is one of the major reasons of poor power quality. Harmonics and harmonic analysis must be investigated in filters in order to minimize harmonic current and voltage. This paper aims to build a simulation model of nine bus ring system to evaluate characteristics of harmonics in different cases of study using Electrical Transient and Analysis Program (ETAP). Using ETAP harmonic distortion is analyzed and mitigation techniques are used represented bysingle tuned filters which should be installed for worst case and the best-case condition. And the simulation results of ETAP shows that some of THDv,i% results are within the limit value as per IEEE 519 -1992 standard.