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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