02-10-2012, 04:53 PM
A BESS-STATCOM Based Control Scheme for Grid Connected Wind Energy System for Power Quality Improvement
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Abstract
Injection of the wind power into an electric grid affects the power quality. The influence of the wind turbine in the grid system concerning the power quality measurements are-the active power, reactive power, variation of voltage, flicker, harmonics, and electrical behavior of switching operation. In this proposed scheme BESS-STATCOM is connected at a point of common coupling to mitigate the power quality issues. It is integrated to sustain the real power source under fluctuating wind power. The effectiveness of BESS-STATCOM scheme relives the main supply source from the reactive power demand of the load and the induction generator. The paper study demonstrates the power quality problem due to installation of wind turbine with the grid. The experimental setup for the grid connected WEGS for power quality improvement is simulated using MATLAB/SIMULINK. Index Terms - Power quality, Wind energy generating system (WEGS). Battery Energy Storage System (BESS), Static Compensator (STATCOM).
INTRODUCTION
To have sustainable growth and social progress, it is necessary to meet the energy need by utilizing the renewable energy sources like wind, biomass, hydro, co-generation etc. The need to integrate the renewable energy like wind energy into power system is to make it possible to minimize the environmental impact on conventional plant [1].The integration of wind energy into existing power system presents a technical challenges and that requires consideration of voltage regulation, stability, power quality problems. The issue of power quality is of great importance to the wind turbine [2]. There has been an extensive growth and quick development in the exploitation of wind energy in recent years. The individual units can be of large capacity up to 2 MW, feeding into distribution network, particularly with customers connected in close proximity [3]. In the fixed-speed wind turbine operation, all the fluctuation in the wind speed are transmitted as fluctuations in the mechanical torque, electrical power on the grid and leads to large voltage fluctuations. The power quality issues can be viewed with respect to the wind generation, transmission and distribution network, such as voltage sag, swells, flickers, harmonics etc.
TOPOLOGY FOR POWER QUALITY IMPROVEMENT
The STATCOM based current control voltage source inverter injects the current into the grid in such a way that the source current are harmonic free and their phase angle with respect to source voltage has a desired value. The injected current will cancel out the reactive part and harmonic part of the load and induction generator current, thus it improves the power factor and the power quality.
BESS- STATCOM
The BESS is used as an energy storage element for the purpose of voltage regulation. It will naturally maintain dc capacitor voltage constant and is best suited in STATCOM since it rapidly injects or absorbed reactive power to stabilize the grid system. It also controls the distribution and transmission system in a very fast rate. When power fluctuation occurs in the system, the BESS can be used to level the power fluctuation by charging and discharging operation. The battery is connected in parallel to the dc capacitor of STATCOM [10]–[14]. The STATCOM is a three-phase voltage source inverter having the capacitance on its DC link and connected at the point of common coupling. The STATCOM injects a compensating current of variable magnitude and frequency component at the bus of common coupling.
CONCLUSION
The paper presents the BESS-STATCOM based control
scheme for Power quality improvement in grid connected
wind generating system and with non linear load. The power
quality issues and its consequences on the consumer and
electric utility are presented. The operation of the control
system developed for the BESS-STATCOM in
MATLAB/SIMULINK for maintaining the power quality is
simulated. It has a capability to cancel out the harmonic parts
of the load current. It maintains the source voltage and current
in-phase and support the reactive power demand for the wind
generator and load at PCC in the grid system, thus it gives an
opportunity to enhance the utilization factor of transmission
line. The proposed scheme has not only for power quality
improvement feature but it also has sustained capability to
support the load with the energy storage through the batteries.