Mitigation of Power Quality Problems Using Custom Power Devices: A Review

Electrical power quality (EPQ) in distribution systems is a critical issue for commercial, industrial and residential applications. The new concept of advanced power electronic based Custom Power Devices (CPDs) mainly distributed static synchronous compensator (D-STATCOM), dynamic voltage restorer (DVR) and unified power quality conditioner (UPQC) have been developed due to lacking the performance of traditional compensating devices to minimize power quality disturbances. This paper presents a comprehensive review on D-STATCOM, DVR and UPQC to solve the electrical power quality problems of the distribution networks. This is intended to present a broad overview of the various possible DSTATCOM, DVR and UPQC configurations for single-phase (two wire) and three-phase (three-wire and four-wire) networks and control strategies for the compensation of various power quality disturbances. Apart from this, comprehensive explanation, comparison, and discussion on D-STATCOM, DVR, and UPQC are presented. This paper is aimed to explore a broad prospective on the status of D-STATCOMs, DVRs, and UPQCs to researchers, engineers and the community dealing with the power quality enhancement. A classified list of some latest research publications on the topic is also appended for a quick reference

Regulatori struje aktivnih filtara snage za poboljšanje kvalitete snage: Tehnička analiza

Non-linear load deteriorates the quality of current waveforms at the point of common coupling of various consumers. Active power filter (APFs) is used to mitigate the most concern harmonic pollution in an electrical network. The controller part is the nucleus of an active power filter configuration. Active power filter performance is affected significantly by the selection of current control techniques. The active filter and its current control must have the capability to track sudden slope variations in the current reference to compensate the distorted current drawn by the voltage source inverter. Therefore, the choice and implementation of the current regulator is more important for the achievement of a satisfactory performance level. In this survey, technical reviews of various types of controllers covering a wide range have been presented. This work also reveals the advantages and disadvantages of the practiced control strategies. The effectiveness of the study will help the researchers to choose the proper control methods for various applicationsof active power filter.Nelinearni tereti pogoršavaju kvalitetu strujnih valova u točki u kojoj se spaja više potrošača. Aktivni filtar snage se koristi za ublažavanje najvažnijeg harmoničkog onečišćenja strujne mreže. Jezgra aktivnog filtra snage je regulator. Na performanse aktivnog filtra snage značajno utječe odabir upravljačke tehnike. Aktivni filtar i njegova tehnika upravljanja strujom moraju imati mogućnost pratiti nagle skokove u referentnoj vrijednosti struje kako bi mogli kompenzirati izobličenja struje koju vuče inverter naponskog izvora. Zato su izbor i implementacija regulatora struje iznimno važni za postizanje zadovoljavajuće razine performansi. U ovom pregledu su predstavljene tehničke recenzije koje pokrivaju širok raspon regulatora. Ovaj rad također otkriva prednosti i mane korištenih strategija upravljanja. Efektivnost ovog pregleda pomoći će istraživačima da izaberu ispravnu metodu upravljanja za različite aplikacije aktivnog filtra snage

Regulatori struje aktivnih filtara snage za poboljšanje kvalitete snage: Tehnička analiza

Non-linear load deteriorates the quality of current waveforms at the point of common coupling of various consumers. Active power filter (APFs) is used to mitigate the most concern harmonic pollution in an electrical network. The controller part is the nucleus of an active power filter configuration. Active power filter performance is affected significantly by the selection of current control techniques. The active filter and its current control must have the capability to track sudden slope variations in the current reference to compensate the distorted current drawn by the voltage source inverter. Therefore, the choice and implementation of the current regulator is more important for the achievement of a satisfactory performance level. In this survey, technical reviews of various types of controllers covering a wide range have been presented. This work also reveals the advantages and disadvantages of the practiced control strategies. The effectiveness of the study will help the researchers to choose the proper control methods for various applicationsof active power filter.Nelinearni tereti pogoršavaju kvalitetu strujnih valova u točki u kojoj se spaja više potrošača. Aktivni filtar snage se koristi za ublažavanje najvažnijeg harmoničkog onečišćenja strujne mreže. Jezgra aktivnog filtra snage je regulator. Na performanse aktivnog filtra snage značajno utječe odabir upravljačke tehnike. Aktivni filtar i njegova tehnika upravljanja strujom moraju imati mogućnost pratiti nagle skokove u referentnoj vrijednosti struje kako bi mogli kompenzirati izobličenja struje koju vuče inverter naponskog izvora. Zato su izbor i implementacija regulatora struje iznimno važni za postizanje zadovoljavajuće razine performansi. U ovom pregledu su predstavljene tehničke recenzije koje pokrivaju širok raspon regulatora. Ovaj rad također otkriva prednosti i mane korištenih strategija upravljanja. Efektivnost ovog pregleda pomoći će istraživačima da izaberu ispravnu metodu upravljanja za različite aplikacije aktivnog filtra snage

Enhancement of Power Quality in Domestic Loads Using Harmonic Filters

This study deals with the mitigation of current harmonics, which is primarily important to alleviate power quality problems in modern times. Current harmonics produced by different widely used loads have been evaluated and related parameters have been tabled. Using the data obtained, a non-linear load was modelled to serve as the test load. Different mitigation solutions and techniques were studied to select an appropriate filter design for domestic single-phase application. The Active Power Filter (APF)'s steady-state and dynamic output was evaluated with reference current extraction techniques like PQ and SRF theories in Simulink. For a fair comparison, various parameters related to the filter design were kept identical between the tests conducted; and to test the dynamic performance, a highly inductive load was connected halfway through simulation. The reactive power compensation offered by the filter was studied by using various waveforms and parameters are investigated and tabulated. The study was carried out to identify a reference current extraction technique that yields the best performance and understand the implementation of the same to identify inherent issues that can sometimes be overlooked because of their simplicity and ease of implementation. The performance of two commonly used reference current extraction techniques were analyzed by subjecting it to highly non-linear and highly inductive loads that were modelled based on various loads that were analyzed

Design and Control of Electrical Motor Drives

Dear Colleagues, I am very happy to have this Special Issue of the journal Energies on the topic of Design and Control of Electrical Motor Drives published. Electrical motor drives are widely used in the industry, automation, transportation, and home appliances. Indeed, rolling mills, machine tools, high-speed trains, subway systems, elevators, electric vehicles, air conditioners, all depend on electrical motor drives.However, the production of effective and practical motors and drives requires flexibility in the regulation of current, torque, flux, acceleration, position, and speed. Without proper modeling, drive, and control, these motor drive systems cannot function effectively.To address these issues, we need to focus on the design, modeling, drive, and control of different types of motors, such as induction motors, permanent magnet synchronous motors, brushless DC motors, DC motors, synchronous reluctance motors, switched reluctance motors, flux-switching motors, linear motors, and step motors.Therefore, relevant research topics in this field of study include modeling electrical motor drives, both in transient and in steady-state, and designing control methods based on novel control strategies (e.g., PI controllers, fuzzy logic controllers, neural network controllers, predictive controllers, adaptive controllers, nonlinear controllers, etc.), with particular attention to transient responses, load disturbances, fault tolerance, and multi-motor drive techniques. This Special Issue include original contributions regarding recent developments and ideas in motor design, motor drive, and motor control. The topics include motor design, field-oriented control, torque control, reliability improvement, advanced controllers for motor drive systems, DSP-based sensorless motor drive systems, high-performance motor drive systems, high-efficiency motor drive systems, and practical applications of motor drive systems. I want to sincerely thank authors, reviewers, and staff members for their time and efforts. Prof. Dr. Tian-Hua Liu Guest Edito

Performance Enhancement of Shunt APFs Using Various Topologies, Control Schemes and Optimization Techniques

Following the advent of solid-state power electronics technology, extensive usage of nonlinear loads has lead to severe disturbances like harmonics, unbalanced currents, excessive neutral current and reactive power burden in three-phase power systems. Harmonics lower down the efficiency and power factor, increase losses, and result in electromagnetic interference with neighbouring communication lines and other harmful consequences. Over the years, active power filter (APF) has been proven to be a brilliant solution among researchers and application engineers dealing with power quality issues. Selection of proper reference compensation current extraction scheme plays the most crucial role in APF performance. This thesis describes three time-domain schemes viz. Instantaneous active and reactive power (p-q), modified p-q, and Instantaneous active and reactive current component (i_d-i_q) schemes. The objective is to bring down the source current THD below 5%, to satisfy the IEEE-519 Standard recommendations on harmonic limits. Comparative evaluation shows that, i_d-i_q is the best APF control scheme irrespective of supply and load conditions. Results are validated with simulations, followed by real-time analysis in RT-Lab.In view of the fact that APFs are generally comprised of voltage source inverter (VSI) based on PWM, undesirable power loss takes place inside it due to the inductors and switching devices. This is effectively minimized with inverter DC-link voltage regulation using PI controller. The controller gains are determined using optimization technique, as the conventional linearized tuning of PI controller yield inadequate results for a range of operating conditions due to the complex, nonlinear and time-varying nature of power system networks. Developed by hybridization of Particle swarm optimization (PSO) and Bacterial foraging optimization (BFO), an Enhanced BFO technique is proposed here so as to overcome the drawbacks of both PSO and BFO, and accelerate the convergence of optimization problem. Extensive simulation studies and RT-Lab real-time investigations are performed for comparative assessment of proposed implementation of PSO, BFO and Enhanced BFO on APF. This validates that, the APF employing Enhanced BFO offers superior harmonic compensation compared to other alternatives, by lowering down the source current THD to drastically small values.Another indispensable aspect of APF is its topology, which plays an essential role in meeting harmonic current requirement of nonlinear loads. APFs are generally developed with current-source or voltage-source inverters. The latter is more convenient as it is lighter, cheaper, and expandable to multilevel and multistep versions for improved performance at high power ratings with lower switching frequencies. There can be different topologies of VSI depending on the type of supply system. With each topology, constraints related to DC-link voltage regulation change. For effective compensation, irrespective of the number and rating of DC-link capacitors used in any particular topology, voltages across them must be maintained constant with optimal regulation of DC-link voltage. Various topologies for three-phase three-wire systems (conventional two-level and multilevel VSIs) and four-wire systems (split-capacitor (2C), four-leg (4L), three H-bridges (3HB) and three-level H-bridge (3L-HB) VSIs) are analyzed and compared based on component requirements, effectiveness in harmonic compensation, cost and area of application

Proposta de modelos individual e agregado no domínio do tempo para estimação de correntes harmônicas em usinas eólicas e fotovoltaicas

Tese (doutorado) — Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2021.Nas análises das distorções harmônicas causadas por fontes renováveis de energia, modelos computacionais são frequentemente empregados para a reprodução de impactos que emergem da interação entre a operação do conversor, as distorções pré-existentes na rede e a impedância harmônica do sistema. De acordo com a literatura atinente, poucos modelos individuais simplificados desenvolvidos no domínio do tempo são capazes de ao mesmo tempo i) estimar com precisão as distorções harmônicas e ii) reduzir o tempo de simulação demandado por modelos detalhados. Além disso, é possível observar na literatura uma lacuna no tocante a modelos equivalentes capazes de representar o comportamento harmônico de múltiplos inversores em usinas renováveis de grande porte. Nesse contexto, este trabalho apresenta uma proposta de modelo average harmônico (HM – do inglês harmonic average model) para a reprodução de unidades inversoras, e uma proposta de modelo harmônico agregado (AHM – do inglês aggregated harmonic model) para a estimação de correntes harmônicas geradas por múltiplos inversores em plantas eólicas e fotovoltaicas. No processo de concepção do HM, o princípio da superposição é aplicado em um modelo médio para a inclusão dos efeitos do tempo morto e do chaveamento dos conversores. No processo de montagem do AHM, emprega-se o HM para a representação da usina por meio de um único gerador e, em seguida, aplica-se o método de agregação de circuitos coletores desenvolvido pelo National Renewable Energy Laboratory (NREL). Da análise dos resultados das simulações computacionais executadas, é possível constatar que as formas de onda e os espectros harmônicos produzidos pelo HM e pelo AHM são aderentes àqueles proporcionados por modelos detalhados e medições reais. Cabe ressaltar que os métodos propostos são modelos genéricos rápidos e relativamente simples de serem implementados. Com isso, conclui-se que estes modelos podem ser empregados por operadores de sistemas elétricos para estimar as correntes harmônicas produzidas por inversores e, paralelamente, para analisar os impactos das fontes renováveis na qualidade e estabilidade da energia elétrica.In the analyses of harmonic distortions caused by renewable energy sources, computational models are required to reproduce the impacts that emerge from the interaction between the converter operation, background distortions, and harmonic grid impedance. According to the literature, few simplified time-domain individual models can simultaneously i) estimate harmonic currents and ii) reduce the computation time demanded by detailed models. Further, it is possible to observe a gap in the literature regarding equivalent models used to represent the harmonic behavior of multiple inverters in large-scale power plants. This work proposes a harmonic average model (HM) to represent individual inverters and an aggregated harmonic model (AHM) to estimate the harmonic currents generated by multiple converters in wind power plants and photovoltaic systems. For the HM, we apply the superposition principle in an average model to include dead time and switching effects. For the AHM, we use the HM to reproduce the entire plant as a single-machine topology and employ the National Renewable Energy Laboratory (NREL) method for equivalencing the collector system. Based on the simulation results, we verify that the waveforms and harmonic spectra produced by the HM and AHM are in accordance to those generated by detailed models and real-world measurements. It is worth mentioning that the proposed method provides generic models that are fast and relatively simple to deploy. These results show that the HM and AHM are suitable to predict harmonic currents of inverters. Further, these models investigate the impacts of renewable energy sources on power quality and system stability