Frankfurt (Germany), 6-9 June 2011 Ying Wang – China – Session2– Paper 0587 Voltage Sag Frequency Assessment Considering Customer Satisfaction Degree Ying

Frankfurt (Germany), 6-9 June 2011

Ying Wang – China – Session2– Paper 0587

Voltage Sag Frequency Assessment Considering Customer Satisfaction Degree

Ying Wang

Sichuan University ,China

E-mail:[email protected]


Contents

1. Introduction 1. Introduction

2. Customer Satisfaction degree and its Interval Characteristic2. Customer Satisfaction degree and its Interval Characteristic

3. Voltage Sag Assessment Under Interval Measure 3. Voltage Sag Assessment Under Interval Measure

4. Proposed Analytical Method 4. Proposed Analytical Method

5. Case Studies5. Case Studies

6. Conclusions 6. Conclusions


What is purpose of

the utilities?

For money? Supply light or heat?

Power the machines?


To meet customer satisfaction is the main concern for the utilities and customers

Especially, when smart grid becomes a household name

What is customer satisfaction degree (CSD) ?


Voltage sag classical assessment methods

1

2

Statistic methodStatistic method

Modeling methodModeling method

reliabledirect

Long monitoring Costly installation

Analytical method

Fuzzy method

Probabillity method

Other uncertainty method


2. Customer Satisfaction degree (CSD)and its Interval Characteristic


% 100% 100%s s

s c t

T TS

T T T

Sets the total operation time is Tt;the normal operation time as Ts; the abnormal operation time as Tc; Tt= Ts + Tc,

The CSD presented by S % is:




Satisfaction area

Satisfaction degree uncertainty area

Un-satisfaction area

Curve 2

Curve 1

U/p.u.

Umax

Umin

Tmax Tmin T/ms

presented by an interval data

based on the upper and lower thresholds of equipment voltage tolerance.

CSD varies in a range

outside the curve 1--- operates normally

inside curve 2 ---un-satisfaction area

between the curve 1 and 2 is the uncertainty area.


Equipment types

Umin

(%)

Umax

(%)

Tmin

(ms)

Tmax

(ms)

PLC 30 90 20 400

ASD 59 71 15 175

PC 46 63 40 205



Tab. 1 the uncertain ranges of sensitive equipments

B. Description of the contents

satisfaction area

S%=100

unsatisfaction area

S%=0

uncertainty area

S%=[0,100 ]


3. Voltage Sag Assessment Under Interval Measure 3. Voltage Sag Assessment Under Interval Measure

1-x

m

Power supply system

nf

i

x

(1 )k k kif im inZ x Z xZ

2(1 ) 2 (1 ) (1 )k k k k kff mm nn mn mnZ x Z xZ x x Z x x z

( )pf pf pf pff m n mV V V V x

pfmV pf

nVwhere, and are pre-fault voltage at bus m and n. 0 1 2

0 1 2

if if ifpf pfi i f

ff ff ff

Z Z ZV V V

Z Z Z

The voltage sag frequency is an interval range depending on CSD. The interval number of voltage sag is:

[ , ]i c c uN N N N


4. Proposed Analytical Method 4. Proposed Analytical Method

A. Critical fault

location

B. Un-satisfaction

area

C. Assessment of Voltage Sag

Frequency

Proposed Analytical Method


4-A. Critical fault location

( ) 0crit th if x V V

Vth is the limit voltage , The fault position xcrit is the critical fault point

Using Newton iteration method, the iteration equation is:

1

( )nn n

n

f xx x

f x

（）( 0,1,2 )n

where the xn , xn+1 are iteration values

11

11

( )3 ( ) 4 ( ) ( )

2

n nn n n

n nn n

x xx x f x

x xf x f f x


4-B. Un-satisfaction areaVL is short for “voltage limit ”,VSM is short for “voltage sag magnitude ”

SA is short for “satisfaction area”, U-SA is short for“ un-satisfaction area”

Step I

Step IIStep II

Step IIIStep III

Step IVStep IV

if the VL is less than the VSM both in the fault line beginning and the end, the bus is in the SA.

if the VL is more than the VSM in all the point , the bus is in the U-SA.

the VL is between the VSM in the bus beginning and the end, there is a critical fault point and the line is partly in the U-SA.

if the VL is less than the maximum in all the point, and more than the VSM both in the beginning and the end, there are two critical fault points and the line have two parts in the U-SA.


4-C. Assessment of Voltage Sag Frequency Based on Un-satisfaction area Uniform distribution of fault position along the transmission line was assumed, the sag frequency is:

1

n

i j jj

N l

where δj and lj are the fault rate and fault line length in customer un-satisfaction area; n is the bus number.


5. Case StudiesA five-bus power system shown in the Figure

j0.025

j0.025

j0.01

j0.10 j0.05

j0.02 j0.045

2

1 5 4 3

Tab.2 Voltage sags per year at various busses

BussNumber

Proposed

Method

Fault Positions Method

P=10 P=100 P=1000

2 22.23 24.4 22.52 22.252

4 4.115 5.6 4.28 4.116

5 6.676 8.4 6.92 6.7

Buss Number

Proposed Method

Secant Iteration Method

2 9 18

4 8 12

5 8 11

Tab.3 The numbers of iteration at various busses


5. Case StudiesThe simulated system shown in Figure. It consists of 6 generator units, 30 buses interconnected by 37 lines and 4 transformers.


5. Case Studies

Buss

Number

PC PLC ASD

Monte Carlo

Simulation

Proposed Method

Monte Carlo

Simulation

Proposed Method

Monte Carlo

Simulation

Proposed Method

7[5.2848,

9.4808]

[5.2767, 9.4815]

[2.6157, 27.568]

[2.5829, 27.591]

[8.4264, 11.880]

[8.4242, 11.882]

15[1.6674,

8.2391]

[1.6521, 8.2443]

[0.9309, 32.217]

[0.9107, 32.225]

[5.5859, 14.150]

[5.5851, 14.155]

21[3.4316,

10.545]

[3.4297, 10.548]

[1.5520, 34.203]

[1.5481, 34.207]

[8.2879, 16.052]

[8.2822, 16.054]

26[6.5614,

14.086]

[6.5612, 14.075]

[1.6654, 36.070]

[1.6478, 36.081]

[12.367, 19.909]

[12.358, 19.933]

30[8.5904,

14.284]

[8.5902, 14.288]

[4.9952, 36.111]

[4.9606, 36.118]

[12.408, 18.510]

[12.400, 18.511]

Tab.4 Voltage sags per year for different assessment methods


6. Conclusions

interval data of CSD

CSD &

customers

correct and suitable

Interval data of CSD identifies the customer un-satisfaction area by an analytic method.

It is adaptive for radical network and meshed networks.

Simulation results have proved that the proposed method is correct and suitable for practical applications.

CSD can reflect how much the customers are influenced by the voltage sag.


Documents

Frankfurt (Germany), 6-9 June 2011 Ying Wang – China – Session2– Paper 0587 Voltage Sag Frequency Assessment Considering Customer Satisfaction Degree Ying