harish suryanarayana doctoral student energy sources and systems purdue university
TRANSCRIPT
FUZZY LOGIC BASED SUPERVISION OF DC LINK PI CONTROL IN A DSTATCOM
Harish Suryanarayana Doctoral Student
Energy Sources and SystemsPurdue University
OVERVIEW OF THE PRESENTATION
Custom Power The Distribution Static Compensator Symmetrical Component Theory Fuzzy Logic Fuzzy Logic Based Supervision Simulation Results
CUSTOM POWER
It is a concept based on the use of Power Electronic controllers in the distribution system to supply value- added, reliable, high-quality power to its customers.
Power Electronic Controller – DSTATCOM, DVR Distribution level : 1kV to 38kV High Quality Power: No
sags/swells/harmonics
THE DISTRIBUTION STATIC COMPENSATOR
An SSG or a Static Synchronous Generator is defined by the IEEE as a self-commutated switching power converter supplied from an appropriate electric energy source and operated to produce a set of adjustable multiphase voltages, which may be coupled to an AC power system for the purpose of exchanging independently controllable real and reactive Power.
STATCOM : An SSG with a capacitor as the energy source is known as a STATCOM or a Static Compensator.
DSTATCOM : When a STATCOM is used at the distribution level or the load end, it is known as a DSTATCOM or Distribution Static Compensator.
DSTATCOM
Courtesy : PSERC 2003 Seminar
DSTATCOM – MAIN GOALS
To cancel the effect of harmonics due to load so that the current drawn from the source is nearly sinusoidal .
To help maintain near unity power factor by canceling the effect of poor load power factor
To help offset the effect of unbalanced loads, such that the current drawn from the source is balanced.
DSTATCOM SCHEMATIC
scv
d cC
PCC
U n b a la n c e d lo a d
Z c
Z b
Z a
N o n lin e a r lo a d
L s R ssav
sbv
Nn
0i
fi C d ci
d cv
n lL nlR
D C L in k
S 2 a
S 3 aS 1 a
S 4 aS 2 c
S 3 cS 1 c
S 4 cS 2 b
S 3 bS 1 b
S 4 b
'n
L fR f i fa i fb i fc
i la
i lb
i lc
isa
isb
isc
A ph as eH -B rid ge
SYMMETRICAL COMPONENT THEORY
Any set of ‘n’ unbalanced polyphase quantities could be expressed as the sum of ‘n’ symmetrical sets of balanced phasors.
Three Phase: Positive Sequence, Negative Sequence and Zero Sequence
c
b
a
a
a
a
i
i
i
aa
aa
i
i
i
2
2
2
1
0
1
1
111
SYMMETRICAL COMPONENT THEORY
Source Currents are balanced.
Only the average load power is supplied by the source.
Relation between Source Currents and Source Voltages.
All equations in matrix form.
0sa sb sci i i
sa sa sb sb sc sc lavgv i v i v i P
lavgscsbsa
scsbsasbsascsascsb
sc
sb
sa
pvvv
vvvvvvvvv
i
i
i
0
0
333
1111
( 3 ) ( 3 ) ( 3 ) 0sb sc sa sa sc sa sb sb sa sb sc scv v v i v v v i v v v i
SYMMETRICAL COMPONENT THEORY
Reference Compensator Currents.
Reference Compensator Currents with loss.
*
*
*
sa sb scfa la sa la lavg
sb sc safb lb sb lb lavg
sc sa sbfc lc sc lc lavg
v v vi i i i P
v v vi i i i P
v v vi i i i P
*
*
*
sa sb scfa la sa la lavg loss
sb sc safb lb sb lb lavg loss
sc sa sbfc lc sc lc lavg loss
v v vi i i i P P
v v vi i i i P P
v v vi i i i P P
2
, ,sj
j a b c
v
tan( ) 3
FUZZY LOGIC
Concept introduced in 1965 by Lotfi. A. Zadeh
Crisp set and Fuzzy set. Ex. Set of tall people.
Diagram of a crisp set and a fuzzy set.
FUZZY LOGIC CONTROLLER
The four main components of a Fuzzy Controller. 1) The Fuzzification Interface
2) The Inference Mechanism3) The Rule Base4) The Defuzzification Interface
Fuz z ificationInference
Mechanism
R ule B ase
D efuz z ificationIn p u t O u tp u t
FUZZY CONTROLLER
Inputs:
Outputs: Calculation of Ploss
refdc dcerr(i) = v - v (i)
derr(i) = err(i) - err(i-1)
p pref pK K K
i iref iK K K
( ) ( )ref refloss p dc dc i dc dcP K v v K v v dt
FUZZIFICATION
Inputs to the Fuzzy controller: Error and change in error of the capacitor voltage.
5 10 15-5-10-15 0
1
err(t) in Volts
PLZ PS PMNLNM
NS
5 10 15-5-10-15 0
1
PLZ PS PMNL NS
derr(t) in Vo lts
NM
INFERENCE MECHANISM
The two main functions of the inference mechanism are:
a) Based on the active membership functions in error and the change in error inputs, the rules which apply for the current situation are determined.
b) Once the rules which are on are determined, the certainty of the control action is ascertained from the membership values. This is known as premise quantification. ( Minimum Operation used )
" " is (positive large)
" " is (positive medium)
" " is ( Large Kp )
" "
IF
error PL
change in error PM
THEN
Kp L
Ki
is ( Small Ki )SKi
RULE BASECapacitor Voltage Waveform during a load change
t im e ( s )Z
N S
N L
P S
P M
P L
err < 0
Vo lts
N M
derr>0 derr<0derr>0derr<0
err > 0
derrerr NL NM NS Z PS PM PL
NL L L L M S S Z
NM L L M S S Z S
NS L M S S Z Z Z
Z M Z Z Z Z Z M
PS Z Z Z S S M L
PM S Z S S M L L
PL Z S S M L L L
derrerr NL NM NS Z PS PM PL
NL SKi SKi SKi Z Z Z Z
NM SKi SKi SKi Z Z Z Z
NS LKi LKi LKi Z Z Z Z
Z LKi LKi LKi Z LKi LKi LKi
PS Z Z Z Z LKi LKi LKi
PM Z Z Z Z SKi SKi SKi
PL Z Z Z Z SKi SKi SKi
Rule base for Kp Rule base for Ki
FUZZY CONTROLLER
Inputs:
Outputs: Calculation of Ploss
refdc dcerr(i) = v - v (i)
derr(i) = err(i) - err(i-1)
p pref pK K K
i iref iK K K
( ) ( )ref refloss p dc dc i dc dcP K v v K v v dt
DSTATCOM SCHEMATIC
scv
d cC
PCC
U n b a la n c e d lo a d
Z c
Z b
Z a
N o n lin e a r lo a d
L s R ssav
sbv
Nn
0i
fi C d ci
d cv
n lL nlR
D C L in k
S 2 a
S 3 aS 1 a
S 4 aS 2 c
S 3 cS 1 c
S 4 cS 2 b
S 3 bS 1 b
S 4 b
'n
L fR f i fa i fb i fc
i la
i lb
i lc
isa
isb
isc
A ph as eH -B rid ge
SIMULATION VALUESSystem Parameters Values
Supply voltage 220V (phase-rms), 50 Hz
Unbalanced loadRla = 50 , Lla = 20 mHRlb = 35 , Llb = 40 mHRla = 70 , Lla = 20 mH
Non-linear load Three-phase full wave rectifier drawing a dc current of 5 A
DC capacitor 2200 µF
Interface inductor Lf = 20 mH, R f = 5
Reference dc link voltage 500 V
Hysteresis band 0.6 A
Gains tuned using the Energy concept Kp= 110, Ki= 55
SIMULATION RESULTS
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1-15
-10
-5
0
5
10
15Nonlinear Unbalanc ed Load Currents
Time in s ec onds
Cu
rre
nt
in A
mp
ere
s
p h a s e -a p h a s e -b p h a s e -c
SIMULATION RESULTS
Filter Current - Reference and Actual
0.1 0.102 0.104 0.106 0.108 0.11 0.112 0.114 0.116 0.118 0.12
-4
-3
-2
-1
0
1
2
3
4
5
Time in s ec onds
Cu
rre
nt
in A
mp
ere
s
Ref erenc e and A c tual Filter Currents in Phas e A
R e fe re n c e c o m p e n s a to r c u rre n t a c tu a l c u rre n t
SIMULATION RESULTS
Source Currents – Balanced and Sinusoidal
0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05-25
-20
-15
-10
-5
0
5
10
15
20
25A c tual Sourc e Current Wav ef orms
Time in s ec onds
Cu
rre
nt
in A
mp
ere
s
p h a s e -a p h a s e -b p h a s e -c
SIMULATION RESULTS
Normally tuned PI and Fuzzy Supervised waveforms
0 0.1 0.2 0.3 0.4 0.5 0.6460
470
480
490
500
510
520
530
540DC link Voltages - Normally tuned and Fuzzy tuned
Time inseconds
DC
Lin
k V
olta
ge
in
Vo
lts
Normally tuned PI
Fuzzy supervised PI
SUMMARY – TAKE HOME POINTS
The DSTATCOM can be used to ensure balanced and sinusoidal source currents even if the load is unbalanced and non-linear.
Fuzzy supervision of the DC link PI controller can be used to reduce the error in DC Capacitor voltage during load change.