Power Quality in Future Electrical Power Systems
Power quality is necessary for electrical systems to operate in their intended manner without any deterioration of performance. This book highlights the new emerging challenges of power quality due to the penetration of large-scale renewable energy generation technologies, the advances in nonlinear loads, the increased electricity demands in the deregulated market, and the recent requirements of smart grids that need better hierarchical design with enhanced quality, improved controllability, higher reliability, and security. Novel research that links the past, present and future of electrical power grids from a power quality perspective is also introduced. Topics include power quality definitions; frequency-domain power theory and metering of harmonic pollution responsibility; active and passive harmonic filters; shunt flexible AC transmission; power quality improvement using series FACTS; distributed generation systems; islanding scenario generation algorithm; decentralised voltage control in smart grids; techno-economic issues of power quality; economic robust programming for energy management systems; and future trends in power quality. Power Quality in Future Electrical Power Systems is a tool for planners, designers, operators and practicing engineers of electrical power systems who are concerned with power network quality, reliability, and security. It is essential reading for postgraduate students, engineers, academics, and researchers who have some background in electrical power systems.
Inspec keywords: power supply quality; harmonic distortion; power system harmonics; power grids; power system stability; power system interconnection; power system economics
Other keywords: nonlinear loads; power system harmonics distortion; stability margins; future electrical power systems; interconnected power grids; electricity demands; transmission losses; distribution losses; power system economic operation; power quality; power conditioners; large-scale renewable energy-based generation technology; voltage quality reduction
Subjects: General electrical engineering topics; Power supply quality and harmonics; Power system control; Power system management, operation and economics
- Book DOI: 10.1049/PBPO092E
- Chapter DOI: 10.1049/PBPO092E
- ISBN: 9781785611230
- e-ISBN: 9781785611247
- Page count: 456
- Format: PDF
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Front Matter
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1 Power quality definitions
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The power quality (PQ) can take into the different behavior of the electrical signals in power systems, which supply to the loads economically with uninterrupted power supply services, and various influences arise to change the waveform characteristics in electrical signals. PQ was not considered as an important issue in the field of electrical engineering until the entry of electronic equipment. This electronic equipment is more sensitive than electrical equipment. In a human body, if there is any problem in the blood or blood circulation, it will collapse the entire organ system. Likewise, if there are any defects in the PQ, it collapses the entire high sensitive equipment. In a power system, all the equipment are connected linearly. If a problem occurs at one end, it can be felt at the other end of the power system. If a short circuit occurs, it results in the opening of the circuit breaker to run the generator on no-load condition, and after fault clearance, the generator is shifted to on load, which gives a serious impact on all the equipment connected to the power system.
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2 Frequency-domain power theory and metering of harmonic-pollution responsibility
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In non-sinusoidal and unbalanced systems, the definitions of apparent power and its power resolutions are still a topic that remained controversial in electrical engineering community. Thus, the various definitions were proposed in the literature, and different ones are encouraged by the standards focussed on power measurement. In addition, the guidelines and standards on the limitation of harmonic pollution do not include any method to determine the harmonic-producing consumers, and the conventional harmonic-pollution metering index as current total harmonic distortion is not capable of metering consumer's harmonic-pollution responsibility due to the fact that it depends on the distortion of utility side's supply voltage. Therefore, to fulfil this gap, for the harmonic-source detection and sharing harmonic responsibility between utility and consumer sides, several methods and indices are proposed in the literature. In this chapter, both frequency-domain power theory and harmonic-pollution metering approaches are summarized, and they are qualitatively and quantitatively analysed to clearly show their principles, limits, advantages and disadvantages.
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3 Passive harmonic filters [for electrical power systems]
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The current chapter presents the harmonic passive filters commonly used in the industry, their classifications, configurations, advantages and disadvantages, theoretical as well as practical design considerations and the data required for their installation. The goal of this chapter is to present the frequency characteristics variation and consequently the filtration properties of different passive filters.
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4 Active harmonic filters
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APF can reduce some types of power quality disturbances such as harmonics, reactive power, and unbalanced load currents. The APF uses fast switching solidstate devices and GTO emerging as a viable in smart grid applications, battery charging scheme battery storage system. Smart grid uses distributed-STATCOM (D-STATCOM) for energy efficiency, energy saving, loss reduction, and power factor enhancement. The chapter presents different APF topology with modified control application and case studies for smart grid and renewable energy utilization. New emerging application for APFs in campus intelligent met heuristic optimization and search algorithm for optimal PWM using symmetrical, a symmetrical, inverse sine carrier, and optimum point on wave switching strategy with online search to minimize dominating harmonic and THD at the point of interface with the AC smart grid.
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5 Shunt flexible a.c. transmission
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This chapter is intended to discuss the most general approach to harmonic studies, which can be applied to shunt FACT devices and to all devices regulated by means of power electronic switches, such as wind power plants. This approach is supported by international standards. Some specific installations may require special considerations that are not addressed in detail in this chapter; however, specific references are provided for further reading whenever these special conditions are identified.
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6 Power-quality improvement using series FACTS
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The chapter has developed simple modeling for the series FACTS (SSSC and IPFC) into NR-RCIM load flow method that can be used to analyze and improve the power quality. The developed models are based on current injection approach. In this modeling, the series controllers are represented as injected currents at the terminals of their impedances. These currents are calculated in terms of the specified power flow and buses voltage. The injected currents can easily be implemented in load-flow algorithm without any change in the Jacobian matrix. The parameters of series FACTS can be updated during the iterative process using simple equations based on their basic equivalent circuits. In these developed series controllers, the real and/or reactive power flow in single- or multiline transmission system can be controlled; the selection of appropriate initial values of FACTS devices is not required; the problem that happens when the series FACTS device is the only link between two areas has been solved; the structure of the admittance and Jacobian matrices has been kept without change. Consequentially, the complexity of load-flow algorithm with series FACTS has been reduced.
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7 Distributed generation systems
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Power electronics continues to penetrate into more power applications and plays a main part in energy transformation and consuming. It is anticipated in power industry that power electronics will become more involved in energy generation and distribution. The high efficiency and compactness of power converters are the main momentum behind power electronic technologies. It is therefore considered an enabling technology. The earth, wind, sun and plants are the main resources for all renewable energy technologies which provide environmental friendly, numerous, clean energy. In our modern life, energy has a vital role in future economic growth and well-being. While handling climate change problem and guaranteeing the energy supply security, numerous challenges should be taken into account. As part of addressing such challenges is to study to what extent distributed generation (DG) could supplement, or in the longer term potentially provide an alternative to, a centralised system. There are different incentives and barriers that impact on distributed electricity generation that should be taken into account.
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8 Backward-forward sweep-based islanding scenario generation algorithm for defensive splitting of radial distribution systems
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This chapter proposes a novel two-stage scenario generation strategy for controlled or defensive islanding of smart distribution systems. In the first step, the primary line and bus data matrices have been determined with respect to deterministic and probabilistic nodes and branches for each island. In the second stage, line and bus information matrices can be updated for all islands in each generated scenario using node elimination matrices (NEMs). Backward-forward power flow is then solved in each island according to modified line and bus information matrices. In this study, binary imperialistic competitive algorithm (BICA) is used to find the best splitting points with the aim of minimizing total active power losses and nodal voltage deviations considering voltage limits and feeder capacity constraints. The proposed strategy is evaluated through an extensive test conducted on 12.66 kV, 33-bus radial distribution system with three DG units to validate the speed and the effectiveness of the developed algorithm.
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9 Decentralised voltage control in smart grids
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The conventional electric power grid features on a vertical hierarchical up-down design approach consisting of the generation, transmission and the distribution systems. The new forms of markets with diverse consumers, integration and high penetration of renewable energy resources and the distributed generation call for evolutions of the conventional power grid. The next-generation power grid, namely smart grid, is meant to overcome the existing challenges and to improve the quality of the energy service and generation. Enhanced quality, improved controllability, higher reliability and security, demand-side management (DSM), smart appliances and technologies are some motives for the smart grid. Disassembling and reorganising the conventional grid hierarchy, communication, real-time advanced metering infrastructure, grid optimisation and computational intelligence are the main aspects of the smart grid development to achieve the targeted environmental and the economic benefits.
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10 Techno-economic issues of power quality
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The power quality issue is as old as the electrical invention. The complexity in the system and day-by-day increasing size forces supply company to pay attention to power quality with new dimensions. With the implementation of new Electricity Act in India, consumers have become more aware of power quality and hence the power supply companies. The chapter focuses on the tariff-related issues correlation with power quality and need of revenue for improving the condition. It is observed that all developing countries have moreover same condition and policies to address power quality. It needs to change and should become more consumer-friendly as well as it should reduce burden from power supply or distribution companies so that it can encourage use of quality power.
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11 An economic robust programing approach for the design of energy management systems
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Energy management systems have a key role in the operation of microgrid applications. Due to their importance, several approaches have been reported in the specialized literature. In this chapter, a novel formulation for robust optimizationbased EMS for microgrid applications. The novelty recast in the introduction of transmission constraints and in the avoidance of the use of prediction models for the uncertain variables. In this formulation, a time-variant uncertainty set is used to include the uncertainty in the optimization process. Unlike in the approaches reported in the specialized literature, the sets are previously defined based on the empirical statistics of historical data available. Thus, at each sampling time, the boundaries for the uncertain variables are obtained without using a prediction model. This reduces the complexity of the EMS making possible to compute the solution of the associated optimization problem in the range of the seconds. A modified version of the IEEE 9-bus system benchmark was used as test bench. In the modified version, the hydraulic generation unit (the largest unit in the system) was changed by an equivalent wind power station. The EMS was in charge of assigning the real power and the voltage level of the remaining two generation units.
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12 Future trends in power quality
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The chapter presents a review of power quality issues, measurements, monitoring, performance indices, impacts and standards associated with established PQ indices, impacts, emerging limitations and PQ future trends and challenges. The case study presented at the chapter-end presents three new designs of FACTS-based low-cost switched filter compensation devices acting as dynamic Modulated/PWM switched filters to reduce power quality THD of voltages and currents at point of common coupling. The three FACTS devices include hybrid switched power filter, switched/ MPFC and series-shunt FACTS switched power filter. The chapter is intended as a short guide and a review of power quality issues, limitations and emerging challenges due to the increasing use of renewable Energy AC-DC FACTS devices and compensating systems, mushrooming use of non-linear loads and new smart metering and interface issues with the smart grid.
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Back Matter
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