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INTRODUCTION

While non-renewable energy resources are mostly used for the power generation they are becoming exhausted due to continuous utilization and global warming. To overcome this the utilization of renewable energy sources like wind, biomass, hydro etc., are used to maintain sustainable growth of power generation. By using special collectors, we store some energy which can be used as a source of power supply in future generation and the energy is produced until we preserve our natural renewable sources of energy like wind flow, daylight and trees grow.

CITATION Vid12 l 16393 [1]When the wind energy generation unit is connected to the grid causes several issues such as the generated voltage and the frequency from the wind energy generation unit must match with the grid influencing the quality of power that leads to poor performance of the systemCITATION Int14 l 16393 [2]. As the nature of wind stream is of not constant speed that leads to frequency fluctuations, the presence of harmonics and the desired voltage cannot be obtained.

The power quality gets affected that leads to dynamic over responsive power, voltage variations harmonics and the electrical behavior of the switching operations while interconnecting the wind energy generation unit into the grid CITATION DSr12 l 16393 [3]. For the power generation and performance, the voltage and frequency of the individual units remain the same. Due to the fluctuations in wind speed, the frequency in both units changes as speed is directly proportional to the frequency of the generation unit results in changes in voltage, frequency, and grid failure.

The desired reactive power is to be produced by asynchronous generators which can absorb energy produced by a wind turbine CITATION Abd10 l 16393 [4].Due to the high utilization of power electronics converter in various applications. The non-direct loads produce genuine symphonious flows and responsive capacity to the dispersion and transmission framework, which results in a low energy factor, prompts voltage source and diminishes the use of the distributing systems. Generally, current harmonics caused by non-linear loads have been managed by using channels comprising of capacitors, inductors and damping resistors with basic arrangements such as vast size and weight.Hence this research involves the generation and storage of Electricity with good power factor by interconnecting the power grid with renewable sources of energy generation using STATCOM which helps in power quality enhancement thereby improving the unity control factor and reactive power support at the source side ,eliminates various losses associated with the increment of power loads such as the presence of harmonics and a non-pure sinusoidal waveforms can be overcome and a simple controller for STATCOM to accomplish fast unique reaction CITATION Ahm12 l 16393 [5] .The proposed research is carried out in the MATLAB/SIMULINK software to carry out the simulation of a proposed model to STATCOM control plot for the grid associated wind energy for power quality enhancement.THEORYGeneration of Wind Energy and Interconnecting to the Power GridDepending on the nature of the wind stream the vane makes the wind turbine blades to rotate in its own axis. These blades are of maximum resistance and the energy obtained is absorbed by kinetic energy produced in cutting edges and these blades of a wind turbine are usually very light, High resistance for flexible movement in such a way they are capable to generate energy even with the low stream. For safety purposes, we can control turbines as the blades are coupled to the shaft with the help of the hub. CITATION Wei101 l 16393 [6]left132842000As the low-speed shaft and the wind turbines pivot at same speed parallelly.in order to get greater power high range of speed is required which can be obtained with gearbox used to get higher increasing speed over a hundred times and exchanges it to the fast shaft results in more electricity generation CITATION Con18 l 16393 [7]. The high-speed shaft turns with a vast number of revolutions. The resultant energy is input to generators changes” mechanical energy to electrical energy”6435092449779Fig 1: Interconnection of Wind energy system to Power Grid CITATION Tan18 l 16393 [20]00Fig 1: Interconnection of Wind energy system to Power Grid CITATION Tan18 l 16393 [20], acts as a source of direct current. The direct flow is led in transformers changing over the immediate flow into the alternating flow with high voltage. The substituting flow from individual turbines is offered to the underground cables and then fed to a power grid. CITATION Mea16 l 16393 [8] CITATION Ahm12 l 16393 [5] CITATION Wei101 l 16393 [6]However, there are a few restrictions for the voltage and speed characteristics for a rotor to work. The power gets disturbed due to passive mechanisms like damaged equipment and braking failures which causes the improper cutting-edge angle. The limitations of speed characteristics will be affected with low rating .Generally when a high-quality standard values for electricity generation unit is needed, the controlling component should be dynamic .the wind turbine acceleration control is possible with pitching method .by doing this we can guarantee the safety working increasing execution and less damage .a random examination is to be done on the weather , grid activity simultaneously using monitoring devices . CITATION Man081 l 16393 [9]Problems Associated with the Interconnection of wind energy to Power GridThe efficient working of the energy generation unit depends mainly on the quality of power and free from harmonics, which are explained below CITATION HIb11 l 16393 [10] CITATION Ani14 l 16393 [11]Power quality: The power nature of intensity supply of a perfect power framework intends to supply electric energy with an ideal sinusoidal waveform at a consistent recurrence of a predetermined voltage with the slightest measure of unsettling influences. Power quality is an issue that is winding up progressively critical to power purchasers at all dimensions of use. The apparatus and non-straight loads are presently increasingly a regular place in different divisions. Because of this, uplifted attention to the quality of power is creating among power users. Events influencing the power supply that was once viewed as adequate by power organizations anyway the symphonious is crucial because of which none of the condition is satisfied. The harmonics in the system, disturbs the waveform state of voltage and current, and expands the present dimension and changes the power factor of supply and which thus makes such a significant number of issues. CITATION Zob13 l 16393 [12] CITATION RDH94 l 16393 [13] CITATION SRa13 l 16393 [14] Harmonics: When a non-linear current obtained from the sinusoidal voltage by injecting the nonlinear device with the grid causes harmonics. The presence of harmonics leads to adding of the unwanted frequency results in larger voltage variations and quality control issues damaging the entire unit of power generation unit. The generated electromotive force from an alternator is usually a non-sinusoidal waveform. The output voltage is not a pure sinusoidal waveform due to the presence of some impurities and makes it appear distorted. Due to the armature in the grid, an EMF is induced in the armature winding produces a current, but if the nonlinear devices are connected the current drawn will not be a sinusoidal creating periodical waveform. The distorted waveforms are known as harmonics. CITATION Edv12 l 16393 [15]Methodology of STATCOM :Most of the wind turbines are located at remote place or offshore where the power grid is usually at long distance and under voltage condition. Because of the limited reactive power capability, Doubly Fed Induction Generator (DFIG) cannot always supply required reactive power, as a result its terminal voltage fluctuates. The problem of voltage fluctuation can be solved by using dynamic reactive power compensation. CITATION And14 l 16393 [16]361950133731000A STATCOM (or Static Synchronous Compensator) is a voltage controlling device. It is designed with the help of IGBT/diode power electronics devices. STATCOM relates to the grid connected wind energy system. The STATCOM controlled scheme is used for improving the power factor and power quality. CITATION And14 l 16393 [16]49530084455Fig 2: STATCOM based on voltage source inverter (VSI) CITATION Stu18 l 16393 [21]00Fig 2: STATCOM based on voltage source inverter (VSI) CITATION Stu18 l 16393 [21]The methodology followed by adjustment of phase and magnitude of these voltages at the output of the STATCOM allows to effectively controlling of active and reactive power between the STATCOM and the grid. C is the capacitor where the energy is stored. It is better to connect the STATCOM near to the load.

Operation of the STATCOM

In STATCOM the voltage source inverter switches as IGBT which require triggering pulses to operate (Alpha).If the alpha greater than 90o used for rectifiers ,alpha less than 90o for inverters and alpha equal to 90o STATCOM. Because we know that the reactive power is equal to product of voltage, current and the sine of angle between voltage and current, as If we provide the alpha 90o, the output reactive power is maximum from the STATCOM. The energy stored is converted into reactive power and supplied to the load.6165853063240Fig 3: Overview of Plant and Control UnitFig 3: Overview of Plant and Control Unit center

Control Strategy

The control scheme implemented uses two tuned PI controllers with supply voltage control for the Voltage Source inverter (VSI) of the STATCOM. The supply voltage is controlled by pulse width modulation technique (PWM).The aim of the PWM control scheme is to maintain constant voltage magnitude CITATION Raj14 l 16393 [17]. With these converters the AC output voltage can be controlled by varying the pulse width. With PWM technique the output of each switch in the converter is switched several times during a fundamental cycle between the positive and negative terminals6762752004060Fig 4: Control system Scheme CITATION Rak15 l 16393 [19]0Fig 4: Control system Scheme CITATION Rak15 l 16393 [19]5429250of the DC source. To get the better reactive power injection in to the system with less ripple, we will use filter at the output. STATCOM uses closed loop approach and Pulse width of converter is controlled to maintain the voltage .We will sense the load voltage and take reference voltage from the grid. The error of the reference and the load voltage is fed to PI controller CITATION TEs17 l 16393 [18] .The output of the PI controller is given to the PWM generator to control the Converter. If the error is high the width of pulses given to the converter also increases. This implies more voltage out from the converter which is converted into the reactive power. When load requires Q power STATCOM takes active part in delivering the Q power to the load. STATCOM connected in parallel with the system and injects current in it to compensate for reactive power. STATCOM is faster and having better performance in maintain the power quality and power factor. With this the power quality problems on integrating wind energy into the grid can be reduced. CITATION Rak15 l 16393 [19]

SIMULATION MODELS

right37528500sIMULATION MODEL WITHOUT STATCOMFig 5: Proposed Simulink Block Diagram without STATCOMAbove Simulink model represents the grid connected wind generating system with non -Linear load without STATCOMcenter643890000Output Waveform without STATCOM3898903073400Fig 6: Power Factor at source side with-out STATCOM020000Fig 6: Power Factor at source side with-out STATCOMThe above graph shows the power factor at source side without STATCOM is not unity. As if we observe the voltage and current wave forms are in phase. 2266952837815Fig 7: Simulation Block Diagram With STATCOM00Fig 7: Simulation Block Diagram With STATCOM-19050046037500SIMULATION MODEL WITHOUT STATCOMAbove Simulink model represents the grid connected wind generating system with non -Linear load with STATCOM. It maintains the unity power factor at the load end.Output Waveform with STATCOMleft519320800center2548839Fig 8: Power Factor at source side with STATCOM020000Fig 8: Power Factor at source side with STATCOMObserving the above graph the voltage and current wave forms are in phase implies unity power factor.

REFERENCES BIBLIOGRAPHY

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