The increase in renewable energy sources such as wind, solar, tidal andhydropower will levitate as much as possible in the current configuration. Theprofitable, sustainable and clean nature of the wind explains why it is thefastest growing energy source in the world. The wind farms were built withfixed speed wind turbines and induction generators in the olden days for windpower development. Energy efficiency is literally low for most wind speeds assuch generators because it always prefers constant speed operation. In order toachieve better efficiency, today the development of large modern windgenerators with variable speed operation has increased.Wind energy isfast becoming one of the world’s leading sources of renewable energy. Most windfarms use fixed speed wind turbines, their performance depends on thecharacteristics of the mechanical sub circuits, every time a gust of wind hitsthe turbine, you can observe a fast and strong variation of the electric outputpower, as the response time of the mechanical sub-circuits is of the order of10 milliseconds. These load variations require a rigid electrical network and arobust mechanical design to absorb the high mechanical stresses.
In this sense, the Doubly Fed Induction Generator (DFIG) is mostly usedbecause of its variable speed action, its independent control of active andreactive power and its partially evaluated power converter. To increase energyproduction, the wind farm is connected to the electricity grid. Byinterconnecting the wind farm with the electricity grid, the wind farm emitsfluctuating electrical energy due to the arbitrary nature of the windresources.These fluctuations have a pessimistic impact on stability and PQ onelectrical systems. In addition, the integration of large wind farms into theelectricity 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 ofthe most serious disturbances caused by three-phase earth faults or thestarting of large motors, the shutdown of domestic and industrial equipment andthe malfunction of the drive systems. Most of the industrial and commercial loads are non-linear, causingharmonics.
The utility that powers these non-linear loads must provide largeVARs as well for mitigation of voltage sag and current harmonics; custom powerdevice technology enters into the picture. The custom power device widely usedby many researchers to mitigate voltage issues is the Dynamic Voltage Restorer(DVR). Due to its excellent dynamic performance, DVR is the best equipment forprotecting the sensitive loads from short-term voltage sags or swells. But theDVR does not handle the harmonics of the load current which, when leftuntreated, produces a low power factor, causes a voltage notch and reduces thepower consumption of the distribution system.STATCOM is widely used for the eradication of load current harmonics inaddition to the contribution of reactive power control, but does not addressvoltage related problems. UPQC is the only widely used device for harmonicattenuation of voltage sag and harmonics of load current, thus replacing thefunctions of two devices, DVR and STATCOM. The choice of the suitablecontroller plays a key role in improving UPQC’s performance.
In the conventional PI controller, proportional and integral gains areheuristically selected and also require a precise linear mathematical model ofthe system, which is difficult to obtain with parameter variations andnonlinear load disturbances. To overcome this problem, the Artificial Neural Networkcontroller is proposed, which is most suitable for nonlinear loads, and doesnot need a mathematical model. In the proposed work, PQ problems, voltage sagand current harmonics are simulated and analyzed in the wind power systemconnected to the grid.To improve the PQ, the proposed UPQC based on ANN is implemented foreffective and efficient attenuation of voltage sag and current harmonics. Theperformance of the proposed system is validated by comparing the results of thesimulation with UPQC controlled by conventional PI. POWER QUALITY The contemporary container crane industry, like manyother segments of the industry, is often fascinated by the bells, the colorfuldiagnostic screens, the high-speed performance and the levels of automationthat can be achieved. Although these features and their indirectly relatedenhancements are key elements to the effective operation of the terminal, wemust not forget the basis on which we work.
Power quality also affects theterminal’s operating economics, crane reliability, our environment and theinitial investment in power distribution systems to support new craneinstallations. To quote the electricity company bulletin thataccompanied the last monthly issue of my electricity bill: “The judicious useof electricity is a good environmental and commercial practice that saves youmoney, reduces emissions from power plants and conserves our natural resources”.The next-generation container cranes, which are already under submission, willneed an average power of 1500 to 2000 kW, almost twice the total average demandof three years ago, with rapidly rising energy demand levels, an increase inthe population of container cranes, modifications to the SCR crane converter,and the large AC and DC drives needed to power and control these cranes willincrease awareness of the energy quality problem in the very near future. POWERQUALITY PROBLEMS For the purpose of this article, we will definepower quality problems as follows: “Any power problem that results in afailure or malfunction of the customer’s equipment is an economic burden to theuser, produces negative effects on the environment’. For the container craneindustry, energy problems that degrade the quality of energy include:v Power Factorv Harmonic Distortionv Voltage Transientsv Voltage Sags or Dipsv Voltage Swells