Power Quality In Electrical Power System - Coursework Example

Power Quality in Electrical Power System Student’s Name: Institution: Table of Contents Table of Contents 2 Abstract 2 Power Quality in Electrical Power System 4 Components of Power Quality 4 Importance of Maintaining High Power Quality 6 Factors Impacting on Power Quality 8 Means of Controlling and Improving Power Quality 9 Description and Explanation of Working of the Power Quality Improving Subsystems 10 Conclusion 12 References 13 Abstract In this research essay, power quality is the combination of current and voltage quality which is applied to quantify the current and/or the voltage deviations from the perfect waveforms. These perfect waveforms are typified by sinusoidal shape of wave with fixed amplitude and frequency that is equivalent to the nominal or rated values. This paper discusses power quality in the electrical power system where the components associated with power quality are described in this instance components such as capacitors, filters, convertors among other are described. Importance of maintaining high power quality is given, where cost reduction is mentioned as the major importance. Factors impacting on power quality are mentioned where load nonlinearity, and disturbances among others are mentioned. The means of controlling and improving power quality are also discussed where improving on the system components are identified as the best method. The paper also describes the workability of two subsystems; a wind farm power quality subsystem and multifunctional AC/DC boost converter subsystem designed to improve the power quality. Power Quality in Electrical Power System Components of Power Quality There are a number of component associated with power quality. These components are similar to others electrical and electronic related components but they are more improved to ensure high quality power is received by the end users. These components include, power generator: this is a component used to produce electric power through mechanical- electrical reaction. In most cases generator contains turbines which are circulated at a high speed by water from a higher level, steam or wind. The generated electric power is trapped by use of electric cable and passed to a step up transformer. Transformer; it is a component that positively or negatively amplifies the electric power (Schipman & Delince, n.d). It contains wire windings in two phases: input and output. For step up transformer the output windings are more than the input, while step down transformer, output windings are less than input windings. Converter; this is a device that takes in dc input voltage and output a dc output amplified dc voltage (DC/DC converter), or that receives an ac current and output a dc current (AC/DC converter) (Tolbert et al., 2000). Capacitors; components used in charge storage. Linear load; in most cases, load refers to components that draw power from the power quality system for instance resistors, and lamps among others. Other components found in a quality power system include fuses to break the circuit in case the drawn power is beyond the recommended level for the load. This protects the load from blowing off. Circuit breakers works like a fuse but controls a much higher voltage. Filters they get rid of distortions acquired during transmission and try to rebuild the initial sinusoidal wave. Figure 1: A Connection Showing Components Connection in a Power Quality System Figure 2: Diagram Showing Connection of Active filters in a Quality Power System Importance of Maintaining High Power Quality According to Schipman and Delince (n.d) the most excellent electrical supply should be a constant frequency and magnitude sinusoidal power waveform. However, due to the supply system non-zero impedance of variety of large loads that might be encountered as well as of other phenomena such as outages and transients, the ideal situation is always unattainable. Therefore, the system power quality expresses extent in which a practical supply system bear a resemblance to the ideal supply scheme. According to Ferror (2008) the network power quality is termed as good if any load linked to it runs efficiently and satisfactorily. Additionally, the installation operation cost as well as carbon trace is minimal. On the contrary, loads connected to a poor network power quality will always experience failure or will contain a reduced efficiency and lifetime. In addition, the carbon trace and installation operation costs of a poor power quality system will be elevated or/and operation may be impossible (Schipman & Delince, n.d.). A system with high power quality minimizes on operation costs. According to Bollen (2003), maintaining a high power quality system will cut on the costs associated with poor systems. A high power quality system is free from problems such as unexpected failures of power supply, equipment malfunctioning or failure, overheating of equipment resulting to lifetime reduction, system losses increase, sensitive equipment damage as well as interferences in electronic communication. In addition, a poor power quality system demands oversize installations in order to cope with extra electrical stress. This kind of system also destabilizes the supply network causing a number of pollution to it. Additionally, it drives new sites connect away so as to avoid more stress. Its users may experience health problems due to light stimulus induced visual sensation unsteadiness, since its spectral distribution or luminance fluctuates frequently. Therefore, maintaining a high power quality will eliminate all the above stated problems, giving its users efficient and reliable services. Additionally it ensures clean and health services that would not result into extra problem related to user health and financial needs. Figure 3: Use of Reactors to improve Polluted Network Factors Impacting on Power Quality Classically, the objective of the system of electric power is to produce electrical energy and to distribute it to the equipment of the end-user at suitable voltage. The traditionally mentioned constraint is that, the technical objective needs to be attained for suitable costs. Therefore, the service reliability is traded off with the cost (Bollen, 2003). Although the ideal case calls for suitable cost, the cost has highly been affected by the level of power quality, which is highly influenced by a number of factors. These factors include linearity of the load, load time variation, as well as power quality disturbances for instance interruptions, transients, swells and dips (Ferrero, 2008). The named factors influence the effectiveness of current and voltage in a power system negatively and consequently lowering its level of quality and thus increasing on the cost. Other factors affecting the level of power quality include power factor of transmission efficiency, power factor of positive sequence of node zero, power factor of oscillation, overall demand distortion, and overall harmonic distortion of equivalent voltage. The stated factors also affect the voltage and current efficiency in the system and they are inversely proportional to the power quality level (Morsi & El-Hawary, 2011). Means of Controlling and Improving Power Quality According to Brenna et al. (2009) energy storage plays an increasing vital role in the system of electrical power and therefore, its maintenance would consequentially result to maintenance of high quality power. In this regard, Brenna et al. developed two dc/dc converters that maintain the duty cycle at average value throughout the switching frequency, so as to decrease the ripple factor while the switching frequency is increased. This high switching frequency improves energy storage power quality. The two converters; Buck and boost, work to reduce the ripple factor that affects the switching frequency negatively while high. Buck converter accomplish this by varying the duty cycle while Boost converter works more efficiently since it receives boost operation from the in-built capacitor and thus more recommended in maintain high quality power in a system (Svelto, 2000) Figure 4: DC/DC converter block diagram The use of Unified power quality conditioners (UPQCs) is another means used in maintaining high quality power. UPQCs permit mitigation of current and voltage disturbances, which could influence susceptible electrical loads when compensating the reactive power of the load (Moreno et al., n.d.). More improved digital UPQCs controller are currently used to allow compensation of reactive power and harmonics of load current at the grid part while shunning the voltage harmonics, over-voltage, and voltage dips effects on the local loads (Forghani & Afsharnia , 2007). Figure 5: UPQCs Controller General Structure Description and Explanation of Working of the Power Quality Improving Subsystems A wind farm power quality subsystem: in this power subsystem, the power is created from a wind farm of 3-turbine, which also supply the generated power to an elevated power quality grid. Various control techniques are employed to all subsystems that include grid connection, aggregation, and generation. The control objective in the generation subsystem is to mine maximum power of wind below rated spend of wind, and to bound the power beyond the rated speed of wind. The aggregation subsystem applies three fuzzy bi-directional logic-controlled DC/DC single ended induced converters (SEPIC) for collection of fixed voltage DC power. The subsystem linking the grid to the wind farm is managed to improve the system power quality. Improvement of power quality is done through a current-regulated power controlled PWM inverter for grid synchronization containing a power factor of one while minimizing harmonics of current (Eskander et al., 2005). Multifunctional AC/DC boost converter subsystem: the convertor is designed to be applied in a subsystem of an industry in power transfer from AC to DC and also in improving the power quality. The converter receives alternating current and using full rectification technology, it converts the full received AC current into DC current. The converter is also equipped with passive components, transformer impedance and input filters, which together with other important criteria are evaluated and the best fit of the converter is created so as to produce maximum current from the input AC current, and thus improving on the power quality (Schiavo et al., 1999). Figure 6: AC/DC Boost Converter Conclusion Power quality is a current and voltage quality combination applied to quantify the current and/or the voltage deviations from the perfect waveforms. There are a number of component associated with power quality. These components are similar to others electrical and electronic related components but they are more improved to ensure high quality power is received by the end users. The network power quality is termed as good if any load linked to it runs efficiently and satisfactorily. A system with high power quality minimizes on operation costs. The chief objective of the system of electric power is to produce electrical energy and to distribute it to the equipment of the end-user at suitable voltage. It has also been realized that energy storage plays an increasing vital role in the system of electrical power and therefore its maintenance would consequentially result to maintenance of high quality power. References Brenna, M., Lazaroiu, G. C., Rotaru, R., & Tironi, E. (2009). Interconnection of electrical energy storage systems for power quality improvement. The Preparation of Bucharest Tech Conference. Bucharest, Romania: IEEE. Bollen, M. H. J. (2003). What is power quality? Electric Power Systems Research, 66, 5-14. Eskander, M. N., Ibrahim, W. M., Abdel-Aziz, M. M., & Ibrahim, A. M. (2005). Generation control of a wind farm with variable speed wind turbines for high power quality. INTELEC ’05. Proceedings of 27th International Conference on the Telecommunication, Berlin: IEEE. Ferrero, A. (2008). Measuring electric power quality: problems and perspectives. Measurements, 41, 121-129. Forghani, M., & Afsharnia, S. (2007). Online wavelet transform-based control strategy for UPQC control System. IEEE Transactions on Power Delivery, 22 (1), 481-491. Moreno, V. M., Pigazo, A., Liserre, M., & Dell’Aquila, A. (n.d.). Unified power quality conditioner (UPQC) with dips and over-voltages compensation capacity. Morsi, W. G., & El-Hawary, M. E. (2011). Power quality evaluation in smart grids considering modern distortion in electric power systems. Electric Power Systems Research, 81, 1117-1123. Schiavo, L., Marino, A., & Testa, A. (1999). Design criteria for a multifunctional AC/DC boost converter. Proceeding of the International Conference on Electric Power Engineering. Budapest: IEEE Schipman, K., & Delince, F. (n.d.). The importance of good power quality. ABB Power Quality Products. Belgium, 1-20 Svelto, C., Ottoboni, R., & Ferrero, A. (2000). Optically supplied voltage transducer for distorted signals in high-voltage systems. IEEE Transactions on Instrument Measurement, 49 (2), 550–554. Tolbert, L. M., Peng, F. Z., & Habetler, T. G. (2000). A multilevel converter-based universal power conditioner. IEEE Transactions on Industry Applications, 36 (2), 596- 603. Read More