Flicker Mitigation in Voltage.pptx

7/30/2019 Flicker Mitigation in Voltage.pptx

1/21

Using 11-level VSC based STATCOM

FLICKER MITIGATION IN VOLTAGE


2/21

FLICKER IN VOLTAGE ?

Flicker is rapid visible changes of light level. Definition of thecharacteristics of voltage fluctuations that produce objectionable lightflicker has been the subject of ongoing research.

Flicker is addressed as random or repetitive variations in the RMS voltagebetween 90 and 110% of nominal.

This phenomenon is always caused by arc furnaces.


3/21

NEED FOR FLICKER MITIGATION

The voltage current characteristic of the arc is nonlinear, and is the causeof harmonic currents.

These harmonic currents, when circulated in the electric network cangenerate harmonic voltages which in turn can affect other users.

Blinking in incandesant bulbs is observable under voltage flicker inhousehold.

Flicker may also affect sensitive electronic equipment such as televisionreceivers or industrial processes relying on constant electrical power.

Lifetime of electrical appliances decrease.


4/21

FLICKER COMPENSATION TECHNIQUES

The most commonly used methods for compensation of voltage flicker isby regulating the EAF passive components, static VAR compensator (SVC)and DSTATCOM.

Distribution Static Compensator (DSTATCOM), which consists of an GTO-based voltage source converter, uses advanced power switches to provide

fast response and flexible voltage control at the PCC for power qualityimprovement in distribution systems.


5/21

STATCOM ?

The STATCOM has been defined as per CIGRE/IEEE with following threeoperating structural components. First component is

Static: based on solid state switching devices with no rotatingcomponents; second component is

Synchronous: analogous to an ideal synchronous machine with 3sinusoidal phase voltages at fundamental frequency; third component is

Compensator: provided with reactive compensation


6/21

TYPES OF STATCOMS

STATCOM is one of the key Converter-based Compensators which areusually based on the VSI or CSI.

VSC are often preferred over current sourced converters for FACTSapplications.

The STATCOM is composed of a VSC with a dc capacitor, couplingtransformer, and signal generator and control circuit .


7/21

Principle of operation

The STATCOM is basically a DC-ACvoltage source converter with anenergy storage unit, usually a DCcapacitor.

It operates as a controlled SVSconnected to the line through acoupling transformer. Fig. shows the

schematic configuration ofSTATCOM.

The STATCOM regulates voltage atits terminals by controlling theamount of reactive Current injectedinto or absorbed from the powersystem.


8/21

V-I & V-Q CHARACTERISTICS OF STATCOM

The STATCOM is essentially an alternating voltage source behind a couplingreactance with the corresponding V-I and V-Q characteristics shown in figbelow.

These show that STATCOM can be operated over its full output current rangeeven at very low (theoretically zero), typically about 0.2 p.u. system voltage

levels.

V-I characteristics V-q characteristics


9/21

ADVANTAGES OF STATCOM

Quicker response time (A STATCOM has a step response of 8 ms to 30ms). Thishelps with compensation of negative phase current and with the reduction ofvoltage flicker.

Active power control is possible with a STATCOM (with optional energy storageon dc circuit). This could further help with system stability control

High efficiency

High dynamic and very fast response time

Single phase control for unbalanced

Enables grid code compliance

Small footprint

Maximum reactive current over extended

Enhanced ride-through capability voltage range

High reliability and availability


10/21

APPLICATIONS OF STATCOM


11/21

H-BRIDGE VSC


12/21

CONTROL MECHANISMS OF STATCOM

types

closed loopcontrol

Fuzzy logiccontrol P-I control

open loopcontrol

D-q theory

P-Q theory


13/21

OPEN LOOP CONTROL

The schematic diagram for open loop control of STATCOM is shown in figbelow


14/21

CLOSED LOOP P-I CONTROL OF STATCOM

Closed loop d-q theory p-I control of STATCOM is as shown below.


15/21

SIMULATION S IN MATLAB

Open loop control schema :-


16/21

Output wave forms


17/21

Closed loop control schema :-


18/21

STATCOM CONTROLLER BLOCK

Statcom ocntroller block consists of the following blocks

1.) PLL block with abc/dqo converter

2.) Ac voltage regulator

3.) Current regulator

4.) steady state MI regulator & Transcient MI regulator


19/21

SIMULATION RESULTS OF CLOSED LOOP

CONTROL


20/21


21/21

Documents

Flicker Mitigation in Voltage.pptx