The wind farm with the electricity grid,

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.

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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 performance, DVR is the best equipment for
protecting the 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:

v  Power Factor

v  Harmonic Distortion

v  Voltage Transients

v  Voltage Sags or Dips

v  Voltage Swells