VOLTAGE STABILITY ENHANCEMENT IN CONTINGENCY CONDITIONS USING

SHUNT DEVICES

SEMINAR PRESENTATION ON

Gaurav Agarwal, VIII Sem. EE2

Content of the presentation

1) Major blackout around the globe2) Voltage Instability/collapse3) Facts devices4) Modal analysis

a) Matrix Equations5) Case study

a) IEEE 14 Bus Power Systemb) Flowchart

6) Proposed method of prevention7) Comparison with earlier installation

Gaurav Agarwal, VIII Sem. EE3

Major blackouts around the globe

1. September, 2006, a severe disturbance occurred on the National

Grid System of Pakistan which caused cascading outages of

transmission lines and generating stations that ultimately led to

system wide collapse/blackout.

2. 2006, a three phase fault and tripping of the Hassayampa- North

Gila 500 kV line under off peak conditions

3. August 2003, blackout in North -Eastern U.S.A and Canada…

4. March 1993, when a blackout took place in the Rio de Janeiro,

Brazil…

5. The 1987 Tokyo blackout…

6. The 1977 New York Blackout…

One reason reactive power problem

Gaurav Agarwal, VIII Sem. EE4

Voltage Stability

The voltage stability of a power system refers to its ability to properly maintain steady, acceptable voltage levels at all buses in the network at all times, even after being subjected to a disturbance.

Instability is caused due to insufficient supply of increased demand in reactive power

Voltage collapse can be initiated due to small changes of system conditions as well as large disturbances

Gaurav Agarwal, VIII Sem. EE5

FACTS Devices

1) The term FACTS refers to alternating current transmission systems incorporating power electronic-based and other static controllers to enhance controllability and increase power transfer capability

2) Used in parallel with electro-mechanical devices

3) Effective response in operation, frequent variation in output and smoothly adjustable output

4) Various functions are :

a) Voltage control b) Short Circuit Current Limiting

c) Transient Stability d) Dynamic Stability

e) Active and Reactive Power Flow Control

5) Commonly used FACTS devices are:

SVC STATCOM SMES

BESS TCSC SSSC

UPFC IPC

Gaurav Agarwal, VIII Sem. EE6

Modal analysis

Most effective static method which involves computation of critical eigenvalue of the reduced power system steady state Jacobian matrix and the associated participation factors

Shows how close the current operating point of power system is to the voltage collapse point

At each operating point P was kept constant and evaluate voltage stability by considering the incremental relationship between Q and V

The linearized steady state system power voltage equations are given by.

To reduce (1), let ∆P =0,

Gaurav Agarwal, VIII Sem. EE7

v = h∆V = the vector of modal voltage variationsq= h∆Q = vector of modal reactive power variations

Gaurav Agarwal, VIII Sem. EE8

Relative participation of kth bus to ith mode is expressed by bus participation factor as

where ξki and hik are kth element of the right and left eigenvectors corresponding to i th eigenvalue of JR

for the ith mode

In the proposed method, for each contingency a probabilistic index is defined which evaluates the relative participation of each bus in voltage instability caused by all of the critical eigenvalues corresponding to that contingency

Gaurav Agarwal, VIII Sem. EE9

the larger the magnitude of bus participation factor in critical modes, that bus is more effective in voltage instability. the smaller the magnitude of positive σj, that mode is more critical

the total participation in all critical modes (TPCM) for each bus

PCMi = contribution of bus i to voltage instability caused by critical modes under k th contingency state

Poutage = likelihood of kth contingency occurring corresponding to outage of line k

m = number of critical eigenvalues in kth contingency

Pij = participation factor of bus i to critical eigenvalue j

σj = critical eigenvalue j

Gaurav Agarwal, VIII Sem. EE10

Case study

IEEE 14 Bus Power System

11Gaurav Agarwal, VIII Sem. EE

Gaurav Agarwal, VIII Sem. EE12

Flowchart of the proposedmethod

Gaurav Agarwal, VIII Sem. EE13

Proposed method of prevention of voltage collapse

Assumption taken:1. σcritical=12. The smallest eigen value of the reduced Jacobian matrix is determined as σmin= 2.713. The failure probability of all lines is assumed to be 0.024. The load and generation of the system is scaled by the factor of 0.95

Choose bus with largest value of TPCM and minimum value of σ

Table 1- smallest eigen values for the three different contingencies

Table 2- The smallest eigen value associated with contingency after installation of STATCOM at Bus 12

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Gaurav Agarwal, VIII Sem. EE

Gaurav Agarwal, VIII Sem. EE

Table 5- The smallest eigen value associated with contingency after installation of STATCOM at Bus 7

Table 4- TPCM values of buses

Table 3- TPCM values of buses

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Gaurav Agarwal, VIII Sem. EE16

Comparison of proposed method from earlier installation

In earlier proposed methods, the optimal allocations are0.19pu at bus 10 0.25pu at bus 13 0.25pu at bus 14 for the outage of line 1.

On the other hand

The optimal FACTS devices allocations obtained by the proposed method are

0.2pu at bus 70.11pu at bus 12.

The number of STATCOMs to be installed is decreased as well as their reactive power capacity. The reason- the allocated FACTS devices proposed earlier are

applied only in one area of the network which causes a non-uniform reactive power supply in the network.

The method proposed here allocates FACTS devices in two separated areas of the network. Consequently, it will be effective in more contingency conditions

correspond to the outage of lines.

Gaurav Agarwal, VIII Sem. EE

THANK YOU !

QUERIES ??

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