Fuzzy - Based Representative Quality Power Factor for Unbalanced Three - Phase Sy
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Fuzzy - Based Representative Quality Power Factor for Unbalanced Three - Phase Systems
S7 Electrical and Electronics
College Of Engineering, Trivandrum
Fuzzy - Based Representative Quality Power Factor for Unbalanced Three - Phase Systems.pptx (Size: 633.95 KB / Downloads: 94)
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Power factor definitions
Fuzzy logic – Introduction
Fuzzy based RQPF module
Application and simulation results
Under ideal sinusoidal operating conditions, the definition of power factor for single phase and balanced three-phase systems is unique and meaningful
In non sinusoidal situations and unbalanced three-phase system operation, different power factors have been proposed
Three recommended power factors
1) Fundamental positive-sequence power factor (FPSPF);
2) Transmission efficiency power factor (TEPF)
3) Oscillation power factor (OSCPF)
A new fuzzy-based representative quality power factor (RQPF) is introduced to represent three recommended power factors.
The RQPF is applied to different cases: balanced, unbalanced, linear, nonlinear, sinusoidal, and non sinusoidal.
The FPSPF indicates how much active power is being transmitted out of the maximum power when considering the fundamental frequency component only
The TEPF indicates how much active power, including the fundamental plus the non fundamental components, is being transmitted from the source to the load.
The OSCPF is an indication of how much oscillation is being superimposed on the transmitted power
Why existing sytems are inadequate?
Power factor definitions
For a sinusoidal single-phase system, there is a unique definition for the power factor that is given by the ratio
Where P is the transmitted active power and is the S maximum active power or the apparent power
The FPSPF is defined PF as the ratio
where are the fundamental positive-sequence active power and apparent power respectively, such that
The TEPF is defined as the ratio
The oscillation power factor will be the ratio
For single-phase system, the maximum value of the OSCPF is 0.816 while for three-phase system, the maximum value is 1
Fuzzy Inference Systems (FIS)
Fuzzification: Transforms any crisp value to the corresponding (fuzzy value)
Knowledge base: Contains membership functions definitions and the necessary IF-THEN rules.
Inference engine: Simulates the human decision-making process.
Defuzzification: Transforms the fuzzy output into a crisp numerical value.
FUZZY-BASED RQPF MODULE
The value of the RQPF represents an amalgamation of the existing power factors—FPSPF, TEPF, and OSCPF
Fuzzy IF-THEN Rules:-Examples
1) If (FPSPF is L) and (TEPF is L) and (OSCPF is L), then (RQPF is L).
2) If (FPSPF is L) and (TEPF is L) and (OSCPF is M), then (RQPF is ML).
3) If (FPSPF is L) and (TEPF is L) and (OSCPF is H), then (RQPF is SL).
low (L), moderately low (ML), somewhat low (SL), medium (M), somewhat high (SH), moderately high (MH), and high (H).
Application and simulation results
RQPF module is applied to different test cases with different situations: linear, nonlinear, balanced, unbalanced, sinusoidal, and nonsinusoidal
Linear Load Supplied From the Balanced Sinusoidal Source
Linear Load Supplied From Unbalanced Sinusoidal Source
In all cases, the OSCPF is less than one which indicates more oscillations in the transmitted power in this situation.
In all cases, the RQPFs have values less than that for the balanced sinusoidal source which indicates that the RQPF is very expressive and sensitive in all situations to any change in the OSCPF
Linear Load Supplied From the Balanced Nonsinusoidal Source
For case 1, the FPSPF and the TEPF have the same value of one while they have different values in the other cases which indicate that the transmitted power is not only due to the fundamental positive-sequence component.
In almost all cases, the FPSPF is greater than or equal to the TEPF which indicates that there is some amount of power that is not transferred as active power to the load.
Nonlinear Load Supplied From the Balanced Sinusoidal Source
For all cases, the FPSPF and TEPF have different values since for the nonlinear load, the current may contain some harmonics.
For the balanced cases 1, 2, and 3, the OSCPF values are close but not equal to one.
For cases 4, 5, and 6 unbalanced cases, the OSCPF values are less than one since the load imbalance contributes to the oscillation
Nonlinear Load Supplied From the Nonsinusoidal Source
In cases 1, 3, 4, and 5, the OSCPF has been reduced than in sinusoidal condition, which means more oscillation in the transmitted power.
The RQPF tracks the increase and decrease of the OSCPF in this situation and takes into account the deviations between the FPSPF and the TEPF.
The RQPF represents an amalgamation of the three recommended power factors by representing them with a single value.
In order to test its validity, accuracy, and sensitivity, it has been applied to different cases and simulation results are analysed.
RQPF developed is very expressive, accurately represents the three recommended power factor values, and is very sensitive to any changes in them.
The use of fuzzy logic for developing that module has many advantages, such as being simple, easy to apply, altered, adjusted, and self contained.
RQPF can be useful in many applications, such as customer billing, setting up tariffs, evaluating the power quality especially in unbalanced non sinusoidal situations.
Walid G. Morsi and M. E. El-Hawary,” A new fuzzy-based representative quality power factor for unbalanced three-phase systems with nonsinusoidal situations,” IEEE Trans. Power Del., vol.23, no. 4, pp.2426-2438, Jul.2008.
P. S. Filipski, “Polyphase apparent power and power factor under distorted waveform conditions,” IEEE Trans. Power Del., vol. 6, no. 3, pp.1161–1165, Jul. 1991.
 Y. Jin, Advanced Fuzzy Systems Design and Applications. New York: Physica-Verlag Heidelberg, 2003.
S. A. Farghal, M. S. Kandil, and A. Elmitwally, “Quantifying electric power quality via fuzzy modeling and analytic hierarchy processing,” Proc. Inst. Elect. Eng., Gen. Transm. Distrib., vol. 149, no. 1, pp. 44–49, Jan. 2002.
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