13-05-2014, 02:20 PM
MICRO WIND POWER GENERATOR WITH BATTERY ENERGY STORAGE FOR CRITICAL LOAD
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Abstract
In the micro-grid network, it is especially difficult to support the critical load without unin-
terrupted power supply. The proposed micro-wind energy conversion system with battery
energy storage is used to exchange the controllable real and reactive power in the grid and to
maintain the power quality norms as per International Electro-Technical Commission IEC-
61400-21 at the point of common coupling. The generated microwind power can be ex-
tracted under varying wind speed and can be stored in the batteries at low power demand
hours. In this scheme, inverter control is executed with hysteresis current control mode to
achieve the faster dynamic switchover for the support of critical load. The combination of
battery storage with micro-wind energy generation system (WEGS), which will synthesize
the output waveform by injecting or absorbing reactive power and enable the real power
flow required by the load. The system reduces the burden on the conventional source and
utilizes μWEGS and battery storage power under critical load constraints. The system pro-
vides rapid response to support the critical loads. The scheme can also be operated as a
stand-alone system in case of grid failure like a uninterrupted power supply.
Introduction
With high population growth and economic development in the world, there is a very
high demand for energy. Traditional fossil sources such as oil, coal are costly and have a
serious pollution to the environment. As a renewable energy, wind energy generation has
been focused as a clean and inexhaustible energy providing a feasible solution to energy
shortage. The micro wind power generation system with battery energy storage is becom-
ing more prominent with the increasing demand of power generation. It also reduces the
environment pollution. However the output power of micro wind generator is fluctuating
and will affect the operation in the distribution network. The utility system cannot accept
new generation without strict condition of voltage regulation due to real power fluctuation
and reactive power generation absorption. The industrial and commercial customers often
operate the sensitive electronic equipments or criticalload that cannot tolerate voltage sags,
voltage swells, or loss of power, which moreover cause interruption in life operating equip-
ments or stoppage in industrial production.
Control scheme of the system
The control scheme with battery storage and micro-wind generating system utilizes the
dc link to extract the energy from the wind. The micro-wind generator is connected through
a step up transformer and to the rectifier bridge so as to obtain the dc bus voltage. The
battery is used for maintaining the dc bus voltage constant; therefore the inverter is imple-
mented successfully in the distributed system. The three-leg 6-pulse inverter is interfaced
in distributed network and dual combination of battery storage with micro-wind generator
for critical load application, as shown in fig.3.1.
Conclusion
The paper proposed micro-wind energy conversion scheme with battery energy storage,
with an interface of inverter in current controlled mode for exchange of real and reactive
power support to the critical load. The hysteresis current controller is used to generate the
switching signal for inverter in such a way that it will cancel the harmonic current in the
system. The scheme maintains unity power factor and also harmonic free source current at
the point of common connection in the distributed network. The exchange of wind power
is regulated across the dc bus having energy storage and is made available under the steady
state condition. This also allows the real power flow during the instantaneous demand of
the load. The suggested control system is suited for rapid injection or absorption of re-
active/real power flow in the power system. The battery energy storage provides rapid
response and enhances the performance under the fluctuation of wind turbine output and
improves the voltage stability of the system.