Static reactive power compensator design, based on three-phase voltage converter

At present, electrical network stability is of the utmost importance because of the increase in electric demand and the integration of distributed generation deriving from renewable energy. In this paper, we proposed a static reactive power compensator model with common direct current voltage sources. Converter parameters were calculated and designed to fulfill specifications. In order to ascertain the device response for different operating modes as reactive power consumer and generator, we developed the model’s power and control circuits in Matlab Simulink. Simulations were performed for different conditions, and as a result, the current and voltage waveforms and the circular power chart were obtained. This paper has theoretically proven it is possible to achieve the consumption or generation of purely active or reactive power by implementing a static reactive power compensator with common DC voltage sources. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

A new method for power quality improvement

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.A new control method for active power filters in conjunction with a passive filter circuit are presented and analysed in this thesis. A new technique for load modelling is introduced in order to enable the design of compensators to improve the power factor and to reduce harmonic levels in electrical power systems. The principles of analysis, design, operation and control of the new circuit equipped with IGBTs are presented. This enables the compensation of rapidly changing loads and reactive power. A special circuit equipped with IGBTs is able to compensate for the reactive power and harmonic currents of different orders. The important aspect of the present work is based on the compensator control circuit for power factor correction and harmonic elimination, and its application. This new configuration improves the rating of the active power filter, reducing power losses in the switches compared to existing and newly developed active filters. Furthermore, it is very stable in operation and much faster by a factor of 20. The thesis also presents a detailed mathematical modelling of the proposed system with frequency and time domain equations. The frequency response of the proposed system is also discussed. This new proposal has been checked using a dedicated software simulation program, which was specifically developed for this purpose. An experimental set-up has been designed and implemented in order to apply the new method using IGBTs as well as some other devices. This thesis also presents a critical literature survey, which provides a critical overview of previous work relevant to the power quality improvement reactive power compensation and active filtering

Power system reliability enhancement with reactive power compensation and operational risk assessment with smart maintenance for power generators

Modern power systems incorporate advanced contingency measures with the aim of enhancing system performance. Among them, the strategical installation of reactive power compensators into a power system is commonly practised to minimize power losses and improve system reliability. Such a practice requires a robust optimization technique that could reduce the computational burden and provide optimal planning and operation of the compensators. This thesis proposes an advanced optimization technique, named as Accelerated Quantum Particle Swarm Optimization (AQPSO) to determine the optimal placement, sizing and dispatch strategy of the reactive power compensators with the aim of improving the system level reliability. The uniqueness of the technique is the incorporation of the concept ‘best observation’, which accelerates the search towards the optimal solution. The implementation of advanced maintenance strategies is another common contingency measure used to enhance system performance. In this context, this thesis proposes a novel Smart Maintenance (SM) strategy for power generators that maximize the generation adequacy and provide increased economic benefits in a framework of system reliability. The uniqueness of the SM approach is the incorporation of the ‘obsolescence’ state through the stages of the bathtub curve and half-arch shape to model the aging process and then quantify the operational risk of the generators using fuzzy logic theory. Further, SM combines the proposed AQPSO and Sequential Median Latin Hypercube to obtain a comprehensive maintenance schedule. The investigation presented in this thesis contributes with novel AQPSO-based algorithms to enhance power system reliability with the operation of reactive power compensation; a more realistic and accurate aging reliability model of power generators; a detailed SM mathematical framework and an algorithm for the scheduling of proactive maintenance of generators of small and large-power systems. The proposed models are significant in the journey to the smart operation of a power system with diverse levels of applications

Design of future distribution grids

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e de ComputadoresThis work presents the concept of voltage control in power distribution systems with distributed generation and electric vehicles penetration. The impact of DG and EV in the voltage supply is investigated. DG provides more power into the system, which can cause the inversion of the load flow and an increase in the voltage supply when the demand is low. EVs on the other hand are additional load in distribution systems, increasing power demand and voltage drop. Both might be a cause of voltage problems in the power supply, when no voltage control is applied. Devices such as the tap-changer transformer or the voltage regulator which were not essential in the past are now important solutions to solve voltage variation issues. In this work, several different solutions for voltage control are analyzed, both technically and economically. Overall, the results show that different strategies have different outcomes, and some solutions provide better voltage control than others. In order to have a proper solution for a system, when choosing a control strategy, it is necessary to always take into account the cable ampacity, the technical limits of each device and the costs associated with it

Impact of distributed generation on protection and voltage regulation of distribution systems : a review

During recent decades with the power system restructuring process, centralized energy sources are being replaced with decentralized ones. This phenomenon has resulted in a novel concept in electric power systems, particularly in distribution systems, known as Distributed Generation (DG). On one hand, utilizing DG is important for secure power generation and reducing power losses. On the other hand, widespread use of such technologies introduces new challenges to power systems such as their optimal location, protection devices' settings, voltage regulation, and Power Quality (PQ) issues. Another key point which needs to be considered relates to specific DG technologies based on Renewable Energy Sources (RESs), such as wind and solar, due to their uncertain power generation. In this regard, this paper provides a comprehensive review of different types of DG and investigates the newly emerging challenges arising in the presence of DG in electrical grids.fi=vertaisarvioitu|en=peerReviewed

Improve the Flexibility of Power Distribution Network by Using Back-to-back Voltage Source Converter

Employing increasing distributed generations (DGs) into existing distribution networks is an inevitable trend of the development of modern electric power systems because of the benefits including the environmentally friendly generation, higher efficiency and improved flexibility and reliability. However, high DG penetration level could pose various issues among which the voltage violation and fault level increase are the most concerned. According to the current situation of UK distribution networks, voltage violation is likely to be the first constraint to be met when DG penetration level is increased to certain level. Therefore, compensators are considered to be implemented to regulate the voltage. The reactive power compensators that widely used in transmission systems appear less effective in distribution networks thus active power compensation is desired. Soft-open points (SOPs) are power-electronic devices used replacing the normally-open points which can control active power transfer between two feeders and/or provide reactive power compensation. The back-to-back voltage source converter (B2B-VSC) is preferred as the SOP because of its capability of restricting fault current despite that it has higher power loss and associated capital cost. Two types of controller are developed for the B2B-VSC-based SOP: one is based on the PI control theory and the other is based on the concept of synchronverters. For the former type, the controller design is introduced comprehensively including system modelling and parameters selection. The precise selection of the damping ratio for nonstandard second-order system is derived, and a technique of resetting integrator in output voltage controller loop to achieve fast and smooth islanding transition is proposed. For the latter type, modifications are made to adapt the synchronverter idea to the application of an SOP. Simulations and experiments are carried out to validate the controller designs and both the controllers are verified to be able to provide sufficient performance on voltage regulation, fault current restriction and independent load supply in island mode. In general, the controller based on PI control theory has better performance in fault condition thanks to the current control loop, and the controller based on synchronverter owns better reliability because it does not require additional detections and signal switches inside the controller. At last, the use of an SOP in a dynamic load dominated network after the loss of mains is further investigated. Torque-speed characteristic is used to analyse the influence of the VSC’s filter impedance on the stability margin of an induction motor. Though the filter impedance can significantly decrease the stability margin, the output impedance of the VSC can be mitigated by properly designing the output voltage controller. Simulation and experiment are carried out to validate the analyses and controller design. The results show that the VSC is capable of supplying an induction motor in island mode

Optimal Allocation of STATCOMs and Wind-Based Distributed Generators using a Stochastic Mathematical Program

In the last two decades, large economies worldwide have been relying increasingly on renewable energy sources to reduce greenhouse emissions and dependence on fossil fuels. This has changed the topology of distribution systems adding complexity to their planning and operation. In this study, a new planning model is proposed to allocate static synchronous compensators (STATCOMs) and wind-based distributed generators (W-DGs), considering the stochastic nature of wind velocities and load demands. The proposed optimization model is a mixed-integer nonlinear program (MINLP), which simultaneously allocates STATCOMs and W-DGs. It minimizes the costs of power losses, investment, operation, and maintenance while maximizing the CO2 reduction rewards and power generation revenues. The Canadian 41-bus network with loads following the IEEE-RTS generic load model is used to test and validate the proposed planning approach. The achieved results demonstrate the effectiveness of such a planning approach in the allocation of STATCOMs and W-DGs. The installation of wind-based distributed generators (W-DGs) in the form of individual units to supply a few loads or in bulk to supply larger loads have increased. High penetration levels of W-DGs have altered the topology of distribution networks (DNs) from being unidirectional to multi-directional, i.e., active direction networks (ADNs). The government’s commitments to clean energy has led to an increase in the investments toward more use of renewable resources to generate clean energy with less environmental impacts. A case study is presented based on actual wind data obtained from Windsor Ontario region. The data is modeled using a Gamma distribution function to model the probabilities of wind speed. Genetic algorithm (GA) is utilized to solve the developed model to allocate and size the W-DGs and the STATCOMs

Assessing the areas of concern regarding decarbonisation of industrial microgrids based on a novel classification framework

This thesis is made for a technology company in Vaasa, Finland which has the focus on decarbonisation of microgrids through optimisation with different aspects in mind, such as, reducing emissions, decreasing fuel consumption, increasing grid reliability and asset availability, and lowering operation costs. The aim of the thesis is to investigate the fundamental areas of concern, when making an early assessment of the potential for decarbonisation through optimisation in industrial microgrids. This is done through a qualitative study based on semi-structured interviews with experts with different areas of expertise in the company. The interviews are then analysed and compared to relevant literature in the field. The outcome is a proposed classification framework grouped into three different sections: generation, network & control, and load. These sections are further divided into different sub-sections with own themes, where categories are listed. Additionally, some suggestions on further utilisation are also proposed in the work, for example, in customer conversations or as an aid for experts.Detta diplomarbete är gjort åt ett teknologiföretag beläget i Vasa, Finland, vilket fokuserar på utfasning av fossila bränslen (eng. decarbonisation) i mikronätverk genom optimering inom olika fokusområden. Exempel på dessa är minskning av utsläpp och bränsleförbrukning, ökning av nätverksstabilitet och tillgänglighet av elproduktionsanläggningar samt optimering av driftskostnader. Målet med diplomarbetet är att utreda inom vilka områden det kan uppstå utmaningar när man i ett tidigt skede kartlägger möjligheterna för utfasning av fossila bränslen genom optimering i industriella mikronätverk. Det här är gjort genom en kvalitativ studie baserad på semistrukturerade intervjuer med sakkunniga med olika expertisområden inom företaget i fråga. Intervjuerna är sedan analyserade och jämförda med relevant litteratur inom ämnet. Resultatet av studien är ett klassificeringssystem indelat i tre olika huvudområden: generering, nätverk & kontroll och last. Dessa är vidare uppdelade i underområden med egna teman i vilka olika kategorier är listade. Därtill i arbetet ges även förslag på användningsområden för detta klassificeringssystem, exempelvis i kundsamtal eller som hjälpmedel för experter