BY

Y. SANNUTHI

New STATCOM control scheme for Power Quality improvement

in wind farm

ABSTRACT

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

and these are measured according to national/international guidelines.

This project demonstrates new control scheme for STATIC

COMPENSATOR(STATCOM) which is connected at a point of common

coupling with a battery energy storage system (BESS) to mitigate the power

quality issues.

INTRODUCTION Renewable energy resources are receiving considerable attention in the

continued growth and development of electric power systems, being the wind power production the fastest growing type of renewable energy.

During the normal operation, wind turbine produces a continuous variable output power.

These power variations are mainly caused by the effect of turbulence, wind shear, and tower-shadow and of control system in the power system.Thus, the network needs to manage for such fluctuations.

The STATCOM is shunt connected at the bus where the wind turbine is connected to the power network to provide voltage regulation and improve the short-term transient voltage stability. The STATCOM control schemes are suitably designed and coordinated.

WIND ENERGY GENERATING SYSTEM

FACTS

• STATCOM

BESS

COMPONENTS

WIND ENERGY GENERATING SYSTEM

Non linear loads

kinetic Energy

Mechanical Energy

Electrical Energy

wind Wind turbine Induction generator

Grid Non- linear load

POWER QUALITY

Power quality mainly deals with,• Continuity of power supply.• “Quality” of the voltage.

“POWER QUALITY” maintenance is an important aspect in the economic operation of a system.

Various “POWER QUALITY ”problems may leads to another undesirable problems.

POWER QUALITY ISSUES

Wind Turbine Location In Power System

Voltage variations

Harmonics

Flickers

FACTS – Flexible AC Transmission system.

Used to enhance controllability and increase power transfer capability."

FACTS

It is a regulating device used on AC transmission networks.

It acts in either capacitive or inductive mode.

It is based on a voltage-source converter.

STATCOM

Voltage-Source Converter converts voltage and currents from DC to AC while the exchange of power can be in both direction.

From AC to DC (rectifier mode). From DC to AC (inverter mode).

Mainly 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.

It is used for the purpose of voltage regulation.

It can be used to level the power fluctuation by charging and discharging operation.

It rapidly injects or absorbed reactive power to stabilize the grid system.

BATTERY ENERGY STORAGE SYSTEM(BESS)

CONTROL SCHEME

It is based on injecting the currents into the grid using “Bang-Bang controller.”

It gives correct switching signals for STATCOM operation.

BLOCK DIAGRAM

POWER NETWORK MODEL OF GRID CONNECTED SYSTEM

3PH SOURCE

V I

RL BRANCH

STATCOM BREAKER

LOADV I

WIND TURBINE

ASYN-GEN

PF CORRECTION

FILTER CONTROLLER

GAIN

UNIT VECTOR

RELAY

NOT

SIMULATION DIAGRAM

SIMULATION RESULTS

Source voltage wave form

Simulation diagram of Source voltage

Source current waveform

It is observed that the Source Current on the Grid is affected due to the effects

of Non-Linear load and Wind Generator. Thus purity of waveform may be lost on both sides in the system.

Simulation diagram of source current

Simulation diagram of STATCOM injecting current

The compensated current for the Non-Linear load and demanded Reactive Power is provided by the Inverter.

The Real Power Transfer from the Batteries is also supported by the Controller of this Inverter.

STATCOM injecting current wave form

Simulation diagram of load current

load current waveform

WITHOUT STATCOM WITH STATCOM

Supply Voltage and Current at PCC. The source current with and without STATCOM operation is shown in Fig.

The Unity Power factor is maintained for the source Power when the STATCOM is in operation.

Simulation diagram of Supply Voltage and Current at PCC

WITHOUT STATCOM WITH STATCOM

THD% at PCC with STATCOM

The Power Quality issues and its consequences are presented.

STATCOM has a capability to cancel out the Harmonic parts of

the Load Current.

STATCOM maintains the Source Voltage and Current in-Phase

and support the Reactive Power demand for the Wind Generator

and load at PCC.

CONCLUSION

ANY QUERIES?