1
POWER QUALITY ........................................................................................ ERROR! BOOKMARK NOT DEFINED.
1.1
POWER QUALITY PROBLEMS: ................................................................................. ERROR! BOOKMARK NOT DEFINED.
1.1.1 Transients: ........................................................................................................ Error! Bookmark not defined.
1.1.2 Interruptions: .................................................................................................... Error! Bookmark not defined.
1.1.3 Voltage sag: ...................................................................................................... Error! Bookmark not defined.
1.1.4 Under voltage: .................................................................................................. Error! Bookmark not defined.
1.1.5 Voltage swell: ................................................................................................... Error! Bookmark not defined.
1.1.6 Over voltage: .................................................................................................... Error! Bookmark not defined.
1.1.7 Voltage unbalance: ........................................................................................... Error! Bookmark not defined.
1.1.8 Wave form distortion: ....................................................................................... Error! Bookmark not defined.
1.1.9 Voltage fluctuations: ......................................................................................... Error! Bookmark not defined.
1.2
POWER QUALITY PROBLEMS EXAMPLES: ............................................................... ERROR! BOOKMARK NOT DEFINED.
1.3
POWER QUALITY SOLUTIONS ............................................................................................................................... 3
1.3.1 Reduce Effects on Sensitive Equipment............................................................. Error! Bookmark not defined.
1.3.2 Interconnected power system ............................................................................ Error! Bookmark not defined.
1.3.3 Deregulation ..................................................................................................... Error! Bookmark not defined.
1.3.4 Power conditioning equipment manufacturers ................................................. Error! Bookmark not defined.
1.3.5 Utilities ............................................................................................................. Error! Bookmark not defined.
1.3.6 End users........................................................................................................... Error! Bookmark not defined.
1.3.7 End-user equipment manufacturers .................................................................. Error! Bookmark not defined.
1.3.8 Monitoring-equipment manufacturers .............................................................. Error! Bookmark not defined.
1.4
POWER QUALITY IMPROVING DEVICES .................................................................. ERROR! BOOKMARK NOT DEFINED.
1.4.1 Line voltage regulators: .................................................................................... Error! Bookmark not defined.
1.4.2 M-G sets:........................................................................................................... Error! Bookmark not defined.
1.4.3 Fly wheel energy storage systems: .................................................................... Error! Bookmark not defined.
1.4.4 SMES Devices: .................................................................................................. Error! Bookmark not defined.
1.4.5 UPS: .................................................................................................................. Error! Bookmark not defined.
1.4.6 Custom power devices: ..................................................................................... Error! Bookmark not defined.
1.5
MERIT OF DVR OVER OTHER CUSTOM POWER DEVICES........................................ ERROR! BOOKMARK NOT DEFINED.
2
DYNAMIC VOLTAGE RESTORER ............................................................ ERROR! BOOKMARK NOT DEFINED.
2.1
DVR BASICS........................................................................................................ ERROR! BOOKMARK NOT DEFINED.
2.2
BASIC CONFIGURATION OF DVR ........................................................................... ERROR! BOOKMARK NOT DEFINED.
2.2.1 Energy Storage Unit: ........................................................................................ Error! Bookmark not defined.
2.2.2 VSC: .................................................................................................................. Error! Bookmark not defined.
2.2.3 Harmonic Filters: ............................................................................................. Error! Bookmark not defined.
2.2.4 Injection transformer: ....................................................................................... Error! Bookmark not defined.
2.2.5 Control Strategies ............................................................................................. Error! Bookmark not defined.
2.2.6 Operating Modes: ............................................................................................. Error! Bookmark not defined.
2.3
SAG/SWELL DETECTION TECHNIQUES: .................................................................. ERROR! BOOKMARK NOT DEFINED.
2.3.1 Fourier Transform (FT) method ....................................................................... Error! Bookmark not defined.
2.3.2 Phase Locked Loop (PLL) method .................................................................... Error! Bookmark not defined.
2.3.3 Peak value detection method............................................................................. Error! Bookmark not defined.
2.3.4 Root mean square (RMS) method ..................................................................... Error! Bookmark not defined.
2.3.5 Space Vector control ......................................................................................... Error! Bookmark not defined.
2.3.6 Wavelet Transform (WT) method ...................................................................... Error! Bookmark not defined.
2.4
VOLTAGE INJECTION METHODS: ............................................................................. ERROR! BOOKMARK NOT DEFINED.
2.4.1 Pre-sag/dip compensation method:................................................................... Error! Bookmark not defined.
2.4.2 In-phase compensation method: ....................................................................... Error! Bookmark not defined.
2.4.3 In-phase advanced compensation method: ....................................................... Error! Bookmark not defined.
2.4.4 Voltage tolerance method with minimum energy injection: .............................. Error! Bookmark not defined.
3
DVR CONTROL STRATEGIES ................................................................... ERROR! BOOKMARK NOT DEFINED.
3.1
SRF THEORY: ........................................................................................................ ERROR! BOOKMARK NOT DEFINED.
BASICALLY, THE THREE REFERENCE FRAMES CONSIDERED IN THIS IMPLEMENTATION ARE:
................................................................................................................................. ERROR! BOOKMARK NOT DEFINED.
1. THREE-PHASE REFERENCE FRAME, IN WHICH VA, VB, AND VC ARE CO-PLANAR THREE-PHASE
QUANTITIES AT AN ANGLE OF 120 DEGREES TO EACH OTHER. ............ ERROR! BOOKMARK NOT DEFINED.
2. ORTHOGONAL STATIONARY REFERENCE FRAME, IN WHICH VΑ (ALONG Α AXIS) AND VΒ
(ALONG Β AXIS) ARE PERPENDICULAR TO EACH OTHER, BUT IN THE SAME PLANE AS THE
THREE-PHASE REFERENCE FRAME. .............................................................. ERROR! BOOKMARK NOT DEFINED.
3. ORTHOGONAL ROTATING REFERENCE FRAME, IN WHICH VD IS AT AN ANGLE Θ (ROTATION
ANGLE) TO THE Α AXIS AND VQ IS PERPENDICULAR TO VD ALONG THE Q AXIS. ..... ERROR! BOOKMARK
NOT DEFINED.
3.1.1
Clarke Transformation.................................................................................................................................... 6
THE THREE-PHASE QUANTITIES ARE TRANSLATED FROM THE THREE-PHASE REFERENCE
FRAME TO THE TWO-AXIS ORTHOGONAL STATIONARY REFERENCE FRAME USING CLARKE
TRANSFORMATION. THE CLARKE TRANSFORMATION IS EXPRESSED BY THE FOLLOWING
EQUATIONS: ..............................................................................................................................................................6
3.1.2
3.1.3
Inverse Clarke Transformation ....................................................................................................................... 6
Park Transformation ....................................................................................................................................... 6
𝐕𝐝 = 𝐕𝛂𝐬𝐢𝐧𝛉 + 𝐕𝛃𝐜𝐨𝐬𝛉
𝐕𝐪 = 𝐕𝛃𝐜𝐨𝐬𝛉 − 𝐕𝛂𝐬𝐢𝐧𝛉...............................................................................................................................................6
3.1.4
Inverse Park Transformation .......................................................................................................................... 6
𝐕𝛂 = 𝐕𝐝𝐜𝐨𝐬𝛉 − 𝐕𝐪𝐬𝐢𝐧𝛉
𝐕𝛃 =
𝐕𝐪𝐜𝐨𝐬𝛉 + 𝐕𝐝𝐬𝐢𝐧𝛉 ........................................................................................................................................................7
3.2
PROPORTIONAL-INTEGRAL CONTROLLER ....................................................................................................................... 7
THE FUNCTION OF THE PROPORTIONAL ACTION IS TO RESPOND QUICKLY TO THE CHANGES IN
THE ERROR DEVIATION. INTEGRAL ACTION IS SLOWER THAN THE PROPORTIONAL RESPONSE
BUT USED TO REMOVE THE OFFSETS BETWEEN THE INPUT AND THE REFERENCE AT STEADY
STATE. BEFORE THE DVR STARTS INJECTING VOLTAGE TO THE SYSTEM, A CONSIDERABLE TIME
PERIOD WAS ALLOWED FOR THE SYNCHRONIZATION. THE SYNCHRONIZATION PROCESS WAS
MADE ACCORDING TO THE POSSIBLE SYSTEM FREQUENCY DEVIATION. AS THE SYSTEM
FREQUENCY IS NOT MUCH DEVIATE FROM 50 HZ THE FAST SYNCHRONIZATION IS NOT A
NECESSITY. HENCE IT HELPS THE LOAD VOLTAGE WITHOUT PHASE JUMP. THEREFORE, THE
DERIVATIVE ACTION IS NOT NEEDED AND THE NEED OF PID CONTROLLER WAS OMITTED. ..........7
3.3
HYSTERESIS VOLTAGE CONTROLLER .................................................................................................................. 7
FIG. 2: PRINCIPLE OF OPERATION OF HYSTERESIS VOLTAGE CONTROLLER ........................................8
3.4
FUZZY LOGIC CONTROLLER:................................................................................................................................. 8
3.4.1 Block diagram of fuzzy logic controller .......................................................................................................... 8
3.4.2 Membership function: ..................................................................................................................................... 9
4
SIMULATION: ......................................................................................................................................................15
4.1
4.2
4.3
4.4
SRFT WITH PI BASED DVR CONTROLLER.......................................................................................................... 15
PEAK DETECTION METHOD WITH HYSTERESIS CONTROLLER BASED DVR ............................................................................. 20
PHASE SEQUENCE ANALYZER WITH PI AND FUZZY CONTROLLER BASED DVR ....................................................................... 23
THD ANALYSIS:...................................................................................................................................................... 26
1.1 Power Quality Solutions
There are four ways to solve and prevent power quality problems:
Three-phase reference frame
Two-phase reference frame
Vb
120 o
Vq
Vβ
o
120
Rotating reference frame
Vd
Va
120o
Vα
θ
Vc
Va
α-axis
Vb
Vc
Vβ
Vα
Vq
Vd
Figure 3.1 Reference Frames
The combined representation of the quantities in all reference frames is shown in Figure 2. 5
Vb
Vq
Vβ
Vd
θ
Va
Vα
I
Vc
Figure 3.2 Combined vector representation transformation theory
1.1.1
Clarke Transformation
The three-phase quantities are translated from the three-phase reference frame to the two-axis orthogonal
stationary reference frame using Clarke transformation. The Clarke transformation is expressed by the following
equations:
𝟐
𝟏
𝐕𝐚 − (𝐕𝐛 − 𝐕𝐜 )
𝟑
𝟑
𝟐
(𝐕
𝐕𝛃 = 𝟑 𝐛 − 𝐕𝐜 )
𝐕𝛂 =
1.1.2
Inverse Clarke Transformation
The transformation from a two-axis orthogonal stationary reference frame to a three-phase stationary
reference frame is accomplished using Inverse Clarke transformation. The Inverse Clarke transformation is
expressed by the following equations:
𝐕𝐚 = 𝐕𝛂
𝟏
√𝟑
𝐕
𝟐 𝛃
𝟏
√𝟑
𝐕 − 𝟐 𝐕𝛃
𝟐 𝛂
𝐕𝐛 = − 𝟐 𝐕𝛂 +
𝐕𝐜= −
1.1.3
Park Transformation
The two-axis orthogonal stationary reference frame quantities are transformed into rotating reference frame
quantities using Park transformation. The Park transformation is expressed by the following equations:
𝐕𝐝 = 𝐕𝛂 𝐬𝐢𝐧 𝛉 + 𝐕𝛃 𝐜𝐨𝐬 𝛉
𝐕𝐪 = 𝐕𝛃 𝐜𝐨𝐬 𝛉 − 𝐕𝛂 𝐬𝐢𝐧 𝛉
1.1.4
Inverse Park Transformation
𝐕𝛂 = 𝐕𝐝 𝐜𝐨𝐬 𝛉 − 𝐕𝐪 𝐬𝐢𝐧 𝛉
𝐕𝛃 = 𝐕𝐪 𝐜𝐨𝐬 𝛉 + 𝐕𝐝 𝐬𝐢𝐧 𝛉
Va, Vb, and Vc are three-phase quantities.
Vα and Vβ are stationary orthogonal reference frame quantities.
Vd, Vq are rotating reference frame quantities, θ is the rotation angle.
1.2 Proportional-Integral Controller
PI Controller is a feedback controller which drives the plant to be controlled with a weighted sum of the error
and the integral of that value. The proportional response can be adjusted by multiplying the error by constant
KP, called proportional gain. The contribution from integral term is proportional to both the magnitude of error
and duration of error. The error is first multiplied by the integral Gain, Ki and then was integrated to give an
accumulated offset that have been corrected previously.
PI CONTROLLER
Kp
Vref
KI / S
PWM
VSI
Vin
Fig 3.3 Block diagram of PI controller control circuit
Proportional Integrate controller was used to regulate the error between the measured (supply) and the
reference phase angle to zero.
a) Proportion controller:
1) Accelerates the process response with increase in gain.
2) Produces a steady state deviation in the absence of integrator in the transfer function. This
offset decrease with increase in proportional gain.
b) Integral Controller
1) Eliminates the steady state deviation.
2) Response is sluggish with long oscillations.
3) Increase of gain makes the system more oscillatory and leads to instabilities.
Reasons for selecting a PI controller
The function of the proportional action is to respond quickly to the changes in the error deviation. Integral action
is slower than the proportional response but used to remove the offsets between the input and the reference
at steady state. Before the DVR starts injecting voltage to the system, a considerable time period was
allowed for the synchronization. The synchronization process was made according to the possible system
frequency deviation. As the system frequency is not much deviate from 50 Hz the fast synchronization is
not a necessity. Hence it helps the load voltage without phase jump. Therefore, the derivative action is not
needed and the need of PID controller was omitted.
1.3
Hysteresis Voltage Controller
Here we are using a conventional hysteresis voltage control technique which is one type of nonlinear voltage
control based on voltage error. Hysteresis controller is easy to implement, has simple operation and very fast
response. Hysteresis controller work on the error signal between injection voltage and reference voltage of DVR
and produces proper gate pulses for converter. Fig.2 shows the principles of hysteresis voltage control. It
consists of a comparison between the output voltage Vo and the tolerance limits (VH, VL) around the reference
voltage Vref. While the output voltage Vo is between upper limit VH and lower limit VL. When the error is going
from lower to upper limit switch 1 is ‘on’ for that duration and switch 2 is ‘off’. And when the error is going
from upper to lower limit switch 2 is ‘on, and switch 1 is ‘off’.
Fig. 2: principle of operation of hysteresis voltage controller
1.4
Fuzzy logic controller:
The concept of Fuzzy Logic (FL) was conceived by Lotfi Zadeh, a professor at the University of California at
Berkley, and presented not as a control methodology, but as a way of processing data by allowing partial set
membership rather than crisp set membership or non-membership. This approach to set theory was not applied
to control systems until the 70's due to insufficient small-computer capability prior to that time. Professor
Zadeh reasoned that people do not require precise, numerical information input, and yet they are capable of
highly adaptive control. If feedback controllers could be programmed to accept noisy, imprecise input, they
would be much more effective and perhaps easier to implement. The performance of Fuzzy Logic Controllers
is well documented in the field of control theory since it provides robustness to dynamic system parameter
variations as well as improved transient and steady state performances
The drawbacks of PI controller are improper tuning of Kp and Ki values which will lead to increase in settling
time of the system stability and the continuous usage of controller with fixed PI parameters leads to reduce the
life time of DVR. These drawbacks can be overcome by using Fuzzy Logic controller.
In the Boolean logic, there are two existing states i.e. 0 and 1 or true or false. There are no other states are
available in the Boolean logic other than these two values.
On the other hand, fuzzy logic, unlike the Boolean logic can have number of different states (membership
values) between 0 and 1. One of the most important features of the fuzzy logic is the, use of linguistic variables
instead of numerical variables. In linguistic variables, variables are defined in natural languages sentence e.g.
Big, small, High, low etc. These linguistic variables are represented by fuzzy sets
1.4.1
Block diagram of fuzzy logic controller
It consists of 4 main blocks
1.
2.
3.
4.
Fuzzification
Knowledge base
Inference mechanism
De fuzzification
Data base
input
Fuzzification
output
Interface
system
De fuzzification
Rule base
Fig 3.4 Block diagram of FLC
In FLC, a basic control action through a set of linguistic rules to finding by the system, since the mathematical
modeling of system variables is not required in FLC because of numerical variables are transferred into
linguistic variables.
Fuzzification converts a crisp input signals error, and change in error into fuzzified signals that can be identified
by level of memberships in the fuzzy sets
The knowledge base is composed of data base and rule base.
Data base consists of input and output membership functions and provides information for appropriate
fuzzification and De fuzzification operations. The rule-base consists of a set of linguistic rules relating the
fuzzified input variables to the desired control actions.
The inference mechanism uses the collection of linguistic rules to convert the input conditions to fuzzified
output. Finally, the De fuzzification converts the fuzzified outputs to crisp control signals using the output
membership function.
The output generated by fuzzy logic controller must be crisp which is used to control the PWM generation
unit.
1.4.2
Membership function:
The membership function is a graphical representation of the magnitude of participation of each input. It
associates a weighting with each of the inputs that are processed, define functional overlap between inputs, and
ultimately determines an output response.
There are different membership functions associated with each input and output response. Some features to
note are:
Triangular MF.
Gaussian MF.
Trapezoidal MF.
Z-shaped MF.
S-shaped MF.
Generalized bell MF.
SHAPE - triangular is common. More complex
functions are possible but require greater computing
overhead to implement. HEIGHT or magnitude (usually
normalized to 1). WIDTH (of the base of function),
SHOULDERING (locks height at maximum if an outer
function. Shouldered functions evaluate as 1.0 past their
center) CENTER points (center of the member function
shape) OVERLAP (N&Z, Z&P, typically about 50% of
width but can be less).
Fig 3.5 Triangular membership function
The input membership functions for error and change in error are shown in Fig 5&6 respectively,
f6
Error
mamdani
(
)
Actuating-signal
Error-Rate
Fig 3.6 Fuzzy inference systems for 2 input and 1 output variable
Membership function
plots
zero
FIS Variables
neg
pos
1
Error
Actuating-signal
0.5
Error-Rate
0
-15
-10
-5
0
5
10
input variable "Error"
Fig 3.7 Membership Function for Input Variable Error
Fig 3.8 Membership Function for Input Variable Error rate
15
Membership function
plots
zero
FIS Variables
negbig
negsmall
possmall
1
Error
Actuating-signal
0.5
Error-Rate
0
-0.3
-0.2
-0.1
0
0.1
0.2
output variable "Actuating-signal"
0.3
Fig 3.9 output membership function for change in control input
Table 3.1 fuzzy control linguistic rules set
Error/Error rate
Error
neg
zero
pos
neg
negbig
negsmall
zero
zero
negsmall
zero
possmall
pos
zero
possmall
posbig
posbig
8
Control strategy of DVR
Voltage
Reference
Vinput
Va,Vb,Vc
Convert to dqo
Convert to dqo
Coordinate system
Coordinate system
Compare
PLL
Convert to Vabc
Coordinate system
Generate signal for
PWM
2
SIMULATION:
2.1 SRFT with PI based DVR controller
In this simulation SRFT based PI controller is used:
In this SIMULINK model, the system consists of 13Kv 3-phase source is stepped using 3-winding T/F,
and it is feeding to two parallel lines of same parameters but one is compensated, and other kept as it is
this control topology mitigates all balanced and unbalanced types of faults (sags & swells) at a reduced
harmonic distortion. It will compensate up to 80% of sag and swells and in the control circuit I am used
a fault detection algorithm if the faults is greater than 2 cycles then only DVR injects/absorbs power
and if the faults duration is greater than 10 cycles then DVR stops (and you can use your own standby
generator if the fault is sustained), in practical implementation DVR injection cycles must be greater
than (2-10 cycles). But due to simulation times very large so I take limed number of cycles.
Fault duration: 1st cycle – 15th cycle (sag).
DVR working times: 3rd cycle – 11th cycle.
Fig 2.9 Main Simulink block of SRFT based DVR
Fig 3.0 DVR control circuit
Fig 3.1 2 cycle sag detector
Fig 3.3 10 cycle sag detector
Fig 3.4 Open loop error generator
Fig 3.5 Measurements
Ideal Source Voltage
1.5
Voltage in p.u
1
0.5
0
-0.5
-1
-1.5
0
0.05
0.1
0.15
0.2
0.25
0.3
0.25
0.3
Un Compensated Load Voltage
Voltage in p.u
2
1
0
-1
-2
0
0.05
0.1
0.15
0.2
Time in secs
Fig 1.2 Waveforms of Ideal source voltage and uncompensated load voltage
x 10
Voltage in volts
1
Converter Output Voltage
4
0.5
0
-0.5
-1
0
0.05
0.1
0.15
0.2
0.25
0.3
0.25
0.3
Voltage in volts
Converter Output Voltage After LPF
4000
2000
0
-2000
-4000
0
0.05
0.1
0.15
0.2
Time in secs
Fig 1.3 Waveforms of Converter output voltage
Compensated Load Voltage(PI)
Voltage in p.u
2
1
0
-1
-2
0
0.05
0.1
0.15
0.2
0.25
0.3
0.25
0.3
Compensated Load Voltage after APF(PI)
Voltage in p.u
2
1
0
-1
-2
0
0.05
0.1
0.15
0.2
Time in secs
Fig 1.4 Waveforms of Compensated load voltage
System patameters:
Table 4.1 System parameters for SRFT with PI based DVR
S.No
System parameters
1
3-phase source
2
Dc Battery
3
Load1
Values
13KV, 50Hz
7e3
11KV, 10e3KW,4e3KVAR
4
Load2
11Kv, 10e3Kw, 4e3Kvar
5
Step up (Υ/Δ/Δ)
6
Step down-1 (Δ/Υ)
132/11 Kv
7
Step down-2 (Δ/Υ)
132/11 Kv
8
Line length
50Km
9
Carrier frequency
1080Hz
10
Kp, Ki
10, 1
13/132/132 Kv
2.2 Peak detection method with hysteresis controller based DVR
In this simulation, peak detection method with hysteresis controller based DVR is used:
In this Simulink model, the system consists of 380V is connected to nonlinear load in series with
DVR, I am created sag and swell at different instances and DVR compensates sag and swell and
harmonics present in the Load voltage.
Fault duration: 1st cycle – 3rd cycle (sag) and 5th cycle – 8th cycle (swell).
Fig 2.9 Main Simulink block of Peak detection with hysteresis controller based DVR
Fig 3.3 DVR control circuit
Fig 3.8 VSC circuit
Grid Voltage
Volts
500
0
-500
0
0.05
0.1
0.15
0.2
0.15
0.2
0.15
0.2
Load Voltage
Volts
500
0
-500
0
0.05
0.1
Injected Voltage
Volts
200
0
-200
0
0.05
0.1
Time in secs
Fig 4.9 Waveforms of Grid voltage, load voltage and injected voltage
Table 4.2 peak detection method with hysteresis controller based DVR
S.No
System Parameters
Values
1
3-Phase source
380V, 50Hz
2
Load (non-linear)
3
Dc Battery
60ohm, .15e-3H
400V
2.3 Phase sequence analyzer with PI and Fuzzy controller based DVR
In this simulation, phase sequence analyzer with PI and Fuzzy controller based DVR used:
In this Simulink model, the system consists of 13Kv 3-phase source is stepped up to 66Kv feeding to
11Kv load through Pi line of 30kms and stepped down to 11kv in series with DVR. In this model, PI
and fuzzy logic controller comparative study is to be analyzed. But this type of controller is used for
balanced type of faults only. Because the phase sequence analyzer produces only positive sequence
signals produced because for the generation of gate pulses to the converter reference 3 phase
sinusoidal signal is required otherwise under unbalanced condition it produces 9 signals so after
processing the converting of these positive, negative and zero sequence signals into 3 – phase signal
requires additional circuit then we go for balanced faults only.
Fault duration: 5nd cycle – 10th cycle (sag).
Fig 4.0 phase sequence analyzer with PI controller based DVR
Fig 4.1 phase sequence analyzer with Fuzzy controller based DVR
Fig 4.2 Converting of per unit error signal 3-phase error signal
Table 4.3 phase sequence analyzer with PI and Fuzzy controller based DVR
S.No
System parameters
Values
1
3-Phase source
11KV, 50Hz
2
Step up (Υ/Δ)
11/66 KV
3
Step down (Δ/Υ)
66/11 KV
4
Load
5
11KV, 1e3KW,1e3KVAR
Line length (Pi model)
30KM
Compensated Load Voltage (PI)
1.5
Voltage in p.u
1
0.5
0
-0.5
-1
-1.5
0
0.05
0.1
0.15
0.2
0.25
0.3
0.2
0.25
0.3
Grid Voltage
1.5
Voltage in p.u
1
0.5
0
-0.5
-1
-1.5
0
0.05
0.1
0.15
Time in secs
Fig 4.5 Waveforms of Compensated load voltage (PI), grid voltage
Compensated Load Voltage(Fuzzy)
1.5
1
Voltage in p.u
0.5
0
-0.5
-1
-1.5
0
0.05
0.1
0.15
0.2
0.25
0.3
Time in secs
Fig 4.6 Waveforms of Compensated load volatge (Fuzzy)
2.4 THD analysis:
Table 4.4 THD analysis
S.No
1
Type of Controller
SRFT (PI)
2
Peak value detection method
(Hysteresis)
3
Phase sequence analyzer
1) (PI)
2) (Fuzzy)
1)
2)
%THD
%THD (Without
controller)
1.88
25.56
0.26
3.30
0.623
0.578
1) 2.98
2) 2.98