The increase in renewable energy sources such as wind solar tidal and hydropower will levitate as much as possible in the current configuration The profitable sustainable and clean nature of the wind explains why it is the fastest growing energy source in the world The wind farms were built with fixed speed wind turbines and induction generators in the olden days for wind power development Energy efficiency is literally low for most wind speeds as such generators because it always prefers constant speed operation In order to achieve better efficiency today the development of large modern wind generators with variable speed operation has increased Wind energy is fast becoming one of the world's leading sources of renewable energy Most wind farms use fixed speed wind turbines their performance depends on the characteristics of the mechanical sub circuits every time a gust of wind hits the turbine you can observe a fast and strong variation of the electric output power as the response time of the mechanical sub circuits is of the order of 10 milliseconds
These load variations require a rigid electrical network and a robust mechanical design to absorb the high mechanical stresses In this sense the Doubly Fed Induction Generator DFIG is mostly used because of its variable speed action its independent control of active and reactive power and its partially evaluated power converter To increase energy production the wind farm is connected to the electricity grid By interconnecting the wind farm with the electricity grid the wind farm emits fluctuating electrical energy due to the arbitrary nature of the wind resources These fluctuations have a pessimistic impact on stability and PQ on electrical systems In addition the integration of large wind farms into the electricity grid produces service power quality problems such as voltage sag swell harmonics flicker and so on The results of PQ problems are data errors automatic resets and equipment failures The voltage sag is considered one of the most serious disturbances caused by three phase earth faults or the starting of large motors the shutdown of domestic and industrial equipment and the malfunction of the drive systems Most of the industrial and commercial loads are non linear causing harmonics The utility that powers these non linear loads must provide large VARs as well for mitigation of voltage sag and current harmonics custom power device technology enters into the picture
The custom power device widely used by many researchers to mitigate voltage issues is the Dynamic Voltage Restorer DVR Due to its excellent dynamic capabilities the DVR is well suited for protecting sensitive loads from short term voltage sags or swells But the DVR does not handle the harmonics of the load current which when left untreated produces a low power factor causes a voltage notch and reduces the power consumption of the distribution system STATCOM is widely used for the eradication of load current harmonics in addition to the contribution of reactive power control but does not address voltage related problems UPQC is the only widely used device for harmonic attenuation of voltage sag and harmonics of load current thus replacing the functions of two devices DVR and STATCOM The choice of the suitable controller plays a key role in improving UPQC s performance In the conventional PI controller proportional and integral gains are heuristically selected and also require a precise linear mathematical model of the system which is difficult to obtain with parameter variations and nonlinear load disturbances To overcome this problem the Artificial Neural Network controller is proposed which is most suitable for nonlinear loads and does not need a mathematical model In the proposed work PQ problems voltage sag and current harmonics are simulated and analyzed in the wind power system connected to the grid To improve the PQ the proposed UPQC based on ANN is implemented for effective and efficient attenuation of voltage sag and current harmonics
The performance of the proposed system is validated by comparing the results of the simulation with UPQC controlled by conventional PI POWER QUALITY The contemporary container crane industry like many other segments of the industry is often fascinated by the bells the colorful diagnostic screens the high speed performance and the levels of automation that can be achieved Although these features and their indirectly related enhancements are key elements to the effective operation of the terminal we must not forget the basis on which we work Power quality also affects the terminal s operating economics crane reliability our environment and the initial investment in power distribution systems to support new crane installations To quote the electricity company bulletin that accompanied the last monthly issue of my electricity bill The judicious use of electricity is a good environmental and commercial practice that saves you money reduces emissions from power plants and conserves our natural resources The next generation container cranes which are already under submission will need an average power of 1500 to 2000 kW almost twice the total average demand of three years ago with rapidly rising energy demand levels an increase in the population of container cranes modifications to the SCR crane converter and the large AC and DC drives needed to power and control these cranes will increase awareness of the energy quality problem in the very near future POWER QUALITY PROBLEMS For the purpose of this article we will define power quality problems as follows Any power problem that results in a failure or malfunction of the customer s equipment is an economic burden to the user produces negative effects on the environment For the container crane industry energy problems that degrade the quality of energy include Power Factor Harmonic Distortion Voltage Transients Voltage Sags or Dips Voltage Swells
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