This document discusses small signal analysis based closed loop control of a buck converter. It first provides background on buck converters and their use. It then describes performing small signal analysis to linearize the system for control purposes. Different control design methods like bode plot analysis and Zeigler-Nichols tuning are examined. The proportional and integral gains of a PI controller are derived using these frequency domain techniques. Simulation results show the output voltage is regulated as desired with the PI controller despite input voltage and load disturbances.
Introduction
Power Quality Problems
Power Quality Measurement Devices
Power Quality Terminology
Power Quality Standards
Unbundled Power Quality Services
Power Quality Monitoring
Benefits of Power Quality
Conclusion
References
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Finally when the energy meter coming to zero user can again recharge according to the purpose used. In this proposed system, the consumer will get his energy consumption data on real time basis on a LCD display. The same data is sent through GSM modem to the electricity department via SMS. A microcontroller of 8051 family is interfaced to the energy meter to get the Watt Hour pulses.
Further this project can be enhanced by to control the electrical appliances remotely via SMS. Also, the electricity department can send the monthly bill amount over SMS to the receiving unit for consumer information.
Introduction
Power Quality Problems
Power Quality Measurement Devices
Power Quality Terminology
Power Quality Standards
Unbundled Power Quality Services
Power Quality Monitoring
Benefits of Power Quality
Conclusion
References
GSM BASED PREPAID ENERGY METER BILLING VIA SMSSRINIVAS REDDY
The project is designed for reading electrical energy consumed in units and in rupees to display on an LCD screen to the user. This data is also provided to the electrical department using GSM technology for billing purposes. Owing to high electricity cost these days it becomes necessary for the consumer to know as to how much electricity is consumed to control electricity bill within his budget by recharging the energy meter units via S.M.S .
Finally when the energy meter coming to zero user can again recharge according to the purpose used. In this proposed system, the consumer will get his energy consumption data on real time basis on a LCD display. The same data is sent through GSM modem to the electricity department via SMS. A microcontroller of 8051 family is interfaced to the energy meter to get the Watt Hour pulses.
Further this project can be enhanced by to control the electrical appliances remotely via SMS. Also, the electricity department can send the monthly bill amount over SMS to the receiving unit for consumer information.
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Power Quality Improvement Using A DVR (Dynamic Voltage Restorer)
ABSTRACT
Power quality is one of major problems in the today’s scenario. It has become important with the introduction of complex devices, whose performance is very sensitive to the quality of power supply. Power quality problem is an occurrence developed as a nonstandard voltage, current or frequency that results in a failure of end use equipment. Some of the major problems dealt here is the power sag and swell. This paper describes the effectiveness of using dynamic voltage restorer (DVR) in order to mitigate voltage sags and swells in low voltage distribution systems. Dynamic Voltage Restorer can provide the most cost effective solution to mitigate voltage sags and swells that is required by customer. The Dynamic Voltage Restorer (DVR) is a rapid, flexible and resourceful solution to power quality problems.
Practically, the capability of injection voltage by DVR system is 50% of nominal voltage. This allows DVRs to successfully provide protection against sags to 50% for durations of up to 0.1 seconds. Furthermore, most voltage sags rarely reach less than 50%.
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It will be useful for reducing requirement of manpower.
When a fault occurred a SMS will be sent to the registered mobile number detailing about type of fault and location of fault.
Soft Computing Technique for the Control of Triple-Lift Luo ConverterIJERA Editor
Positive output Luo converters are a series of new DC-DC step-up (boost) converters, which were developed from prototypes using voltage lift technique. These converters perform positive to positive DC-DC voltage increasing conversion with high power density, high efficiency and cheap topology in simple structure. They are different from other existing DC-DC step-up converters with a high output voltage and small ripples. Triple lift LUO circuit is derived from positive output elementary Luo converter by adding the lift circuit three times. Due to the time varying and switching nature of the Luo converters, their dynamic behaviour becomes highly nonlinear. The classical control methods employed to design the controllers for Luo converters depend on the operating point so that it is very difficult to select control parameters because of the presence of parasitic elements, time varying loads and variable supply voltages. Conventional controllers require a good knowledge of the system and accurate tuning in order to obtain the desired performances. A fuzzy logic controller is a soft computing technique which neither requires a precise mathematical model of the system nor complex computations. The performances of the Triple-lift Luo converter with fuzzy logic controller are evaluated under line and load disturbances using Matlab-Simulink based simulation. The results are presented and analyzed.
“MODELING AND ANALYSIS OF DC-DC CONVERTER FOR RENEWABLE ENERGY SYSTEM” Final...8381801685
This project portrays a comparative analysis of DC-DC Converters for Renewable Energy System. The electrolysis method which increases the hydrogen production and storage rate from wind-PV systems. It has been proved that DC-DC converter with transformer has the desirable features for electrolyser application. The converter operates in lagging PF mode for a very wide change in load and supply voltage variations, thus ensuring ZVS for all the primary switches. The peak current through the switches decreases with load current.This paper portrays a comparative analysis of DC-DC Converters for Renewable Energy System . The simulation and experimental results show that the power gain obtained by this method clearly increases the hydrogen production and storage rate from wind-PV systems. It has been proved that DC-DC converter with transformer has the desirable features for electrolyser application. Theoretical predictions of the selected configuration have been compared with the MATLAB simulation results. The simulation and experimental results indicate that the output of the inverter is nearly sinusoidal. The output of rectifier is pure DC due to the presence of LC filter at the output. It can be seen that the efficiency of DC-DC converter with transformer is 15% higher than the converter without transformer.
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It is a simulation work project done on a 5hp,440V/5A and 1440rpm Induction motor.It explains the control of induction motor using matlab-simulink algorithm by PI control as well as Fuzzy logic control.
Power Quality Improvement Using A DVR (Dynamic Voltage Restorer)
ABSTRACT
Power quality is one of major problems in the today’s scenario. It has become important with the introduction of complex devices, whose performance is very sensitive to the quality of power supply. Power quality problem is an occurrence developed as a nonstandard voltage, current or frequency that results in a failure of end use equipment. Some of the major problems dealt here is the power sag and swell. This paper describes the effectiveness of using dynamic voltage restorer (DVR) in order to mitigate voltage sags and swells in low voltage distribution systems. Dynamic Voltage Restorer can provide the most cost effective solution to mitigate voltage sags and swells that is required by customer. The Dynamic Voltage Restorer (DVR) is a rapid, flexible and resourceful solution to power quality problems.
Practically, the capability of injection voltage by DVR system is 50% of nominal voltage. This allows DVRs to successfully provide protection against sags to 50% for durations of up to 0.1 seconds. Furthermore, most voltage sags rarely reach less than 50%.
GSM Based Fault Monitoring System (Project)Aishwary Verma
This is a modern technique of Monitoring of switchyard which is used in many other countries.
It will be useful for reducing requirement of manpower.
When a fault occurred a SMS will be sent to the registered mobile number detailing about type of fault and location of fault.
Soft Computing Technique for the Control of Triple-Lift Luo ConverterIJERA Editor
Positive output Luo converters are a series of new DC-DC step-up (boost) converters, which were developed from prototypes using voltage lift technique. These converters perform positive to positive DC-DC voltage increasing conversion with high power density, high efficiency and cheap topology in simple structure. They are different from other existing DC-DC step-up converters with a high output voltage and small ripples. Triple lift LUO circuit is derived from positive output elementary Luo converter by adding the lift circuit three times. Due to the time varying and switching nature of the Luo converters, their dynamic behaviour becomes highly nonlinear. The classical control methods employed to design the controllers for Luo converters depend on the operating point so that it is very difficult to select control parameters because of the presence of parasitic elements, time varying loads and variable supply voltages. Conventional controllers require a good knowledge of the system and accurate tuning in order to obtain the desired performances. A fuzzy logic controller is a soft computing technique which neither requires a precise mathematical model of the system nor complex computations. The performances of the Triple-lift Luo converter with fuzzy logic controller are evaluated under line and load disturbances using Matlab-Simulink based simulation. The results are presented and analyzed.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
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output voltage must be kept constant, regardless of changes in the input voltage or in the effective load
resistance. Transfer function is the necessary knowledge to design a proper feedback control such as PID
control to regulate the output voltage as linear PID and PI controllers are usually designed for DC-DC
converters using standard frequency response techniques based on the small signal model of the
converter.
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pull inverter implemented here with high frequency applications like
induction heating, Fluorescent lighting, Digital signal processing sonar. This
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variations. Solar power is used as the input source for the system. Simulation
of the proposed system is carried out in PSIM software and experimentally
verified the results.
A High Step Up Hybrid Switch Converter Connected With PV Array For High Volt...ijitjournal
T
his paper
presents
a
ste
p up DC
-
to
-
DC converter with
hybrid switch capacitor technique having
high
voltage conversion ratio with small
switch voltage stress
. The converter is suitable for the applications
where high voltage conversion is required. The proposed
DC
-
DC converter
has low voltage ratted
MOSFET switch and is connected to PV array to get high output voltage at small duty ratios.
Hence it has
high efficiency.
The principles of operations and the theoretical analysis are presented in this paper.
All the
simulations are
done in MATLAB
-
SIMULINK Environment and
results were obtained with voltage
conversion ratio of 4.
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Research Inventy : International Journal of Engineering and Scienceinventy
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This paper presents a step up DC-to-DC converter with hybrid switch capacitor technique having high voltage conversion ratio with small switch voltage stress . The converter is suitable for the applications where high voltage conversion is required. The proposed DC-DC converter has low voltage ratted MOSFET switch and is connected to PV array to get high output voltage at small duty ratios. Hence it has high efficiency. The principles of operations and the theoretical analysis are presented in this paper. All the simulations are done in MATLAB- SIMULINK Environment and results were obtained with voltage conversion ratio of 4.9.
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LCC resonant converter it is associated with a disadvantage that, though it has two resonant frequencies, the
lower resonant frequency is in ZCS region [5]. For this application, we are not able to design the converter
working at this resonant frequency. LLC resonant converter existed for a very long time but because of
unknown characteristic of this converter it was used as a series resonant converter with basically a passive
(resistive) load. . Here, it was designed to operate in switching frequency higher than resonant frequency of the
series resonant tank of Lr and Cr converter acts very similar to Series Resonant Converter. The benefit of LLC
resonant converter is narrow switching frequency range with light load[6] . Basically, the control ckt plays a
very imp. role and hence 555 Timer used here provides a perfect square wave as the control ckt provides no
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converter in continuous conduction mode (CCM). To verify the design and modeling at
primary stage, study of the converter is practiced in CCM operation for input AC voltage
230V at 50Hz and output DC voltage of 5V and 50W output power rating using PSIM 6.0
software. Simulation result shows a little ripple in output of the converter in open loop. Finally
in order to evaluate the system as well as response of the controller, flyback converter is
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bridge and the due to presence of two semiconductor switches in the current
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conduction losses and improved thermal management compared to the
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detail. Performance of the proposed SEPIC PFC rectifier is carried out using
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Small signal analysis based closed loop control of buck converter
1. Small signal analysis based closed loop control of buck converter
K.V.V.S.R.Chowdary*, S Devi Prasad†
* Assistant Professor, School of Electrical Engineering, KIIT University Bhubaneswar, India, E-mail: rchowdaryfel@kiit.ac.in,
†
M.Tech Research Scholar, School of Electrical Engineering KIIT University Bhubaneswar,
Email:sdeviprasad555@gmail.com.
Keywords: Buck converter, PI controller,bode plot, Zeighler
Nicholes method.
Abstract
From the past several years with the advent of renewable
sources prognosis of DC-DC converter had a remarkable
growth in the fields of power electronic application. Buck
converter closed loop control is popular because it is easy to
get feedback. In this paper we have implemented the control
technique based on small signal analysis of Dc buck
converter. The implementation of control technique with the
DC-DC buck converter is analyzed using tuning methods like
frequency domain and Ziegler Nichols for better performance
and transient response. The perturbation of input voltage
source and load has applied to the model and obtained the
desired output.
1 Introduction
The Buck converter are mostly used in electronic
circuit design and low power rated supplies. According to
the study there are more than 450 model of DC-DC converter.
For development of DC-DC converters technique this
research is vital important. Experts, scientist, researcher from
different parts of the world has spend more than 25 years in
this research area[8].
The closed loop control of DC-DC converter ensures
not only the desired output response but also maintain input
power quality control [6]. In embedded technology
applications like DSP, FPGA requires fast and better response
[12].In closed loop control of Buck converter two important
attributes are regulating the out-put voltage and output
voltage is insensitive to the disturbances[3]. This paper
constitutes small signal mode representation of buck
converter. Then estimated PI controller design parameters
from bode plot and also used ZN-Method. These methods are
explained in the following sections. The controller parameters
are verified by considering the changes in the input voltage
and load resistances. All the above mentioned statements are
provided with the simulation results.
2 Buck Converter
Dc converters in functionality resembles transformer for
DC Circuits. This is also known as voltage step-down DC-
DC converter because the output voltage is less than the input
voltage. It constitutes input DC voltage source(V) , High
switching frequency switch(S), diode(D), inductor(L), filter
capacitor(C), and output resistance(R). The power circuit
diagram is shown figure 2.1.
Buck converter operates in two modes of
configurations. In mode 1 at time t=0 the switch 'S' is switch
is turn ON. There will be the rise of input current which flows
through inductor (L), filter capacitor(C), and resistor(R). In
mode 2 at time t=t1 the switch 'S' is switched off. The energy
stacked in the inductor delivers to the resistor with the help of
conducting freewheeling diode (D). The current which is
flowing from the inductor continually go through L, C, load
and diode D. The inductor current continues to fall until the
switch 'S' ON again in the next cycle.
Figure2.1 Buck Converter
Small Signal Analysis:
Buck converter is a non linear system to make the system
linear; we are using small signal analysis. Small-signal
simulation is most frequently used technique in the branch of
electrical engineering. This is used to estimate the behavior
of non linear device with linear equation [1]. Small signal
analysis will give the better perception about the inherent
features of the system for closed loop control of output
voltage.
In this model we considered both voltage and duty ratio are
inputs and the output is desire output voltage. The small-
signal ac inductor loop equivalent circuit equation and the
small signal ac capacitance loop equivalent circuit is shown in
figure 2.2 and figure 2.3 respectively. The analysis of a small-
signal ac model at a quiescent operating point (I, V) of buck
converter is very important to make the system linear [12].
2. The small signal equivalent circuit of buck converter is shown
in the figure 2.4.
Figure 2.2 Small signal ac inductor loop equivalentcircuit
Figure 2.3 Small Signal ac capacitance loop equivalent circuit
Figure 2.4 Small signal equivalent circuit of buck converter
L {di͂(t)/dt} = D. Ṽg(t) + d(t).Vg - Ṽ(t) (1)
C{dV͂ (t)/dt} = i͂(t) - {dV͂ (t)/R} (2)
The Equation 1 and Equation 2 are came from the small
signal ac inductor loop equivalent circuit and small signal ac
capacitance loop equivalent circuit which is show in figure
2.3 and figure 2.4 .
Transfer function:
The capacitor C and the output resistor R in figure are
referred to the primary side of 1:1 transformer. Now, we need
to find out the transfer function of the buck converter. Since,
there are two independent ac inputs (Vg(s),d(s)),the voltage
at the output ac variations v(s), can be formulated in term of
arising from these two input are So, the transfer function can
be defined as
Gvd(s)=VgR /(LCR S2
+LS + R) (3)
Gvg(s) = D.R /(LCR S2
+LS + R) (4)
Figure 2.5Block Diagram of controller with buck converter
Design of transfer function of buck converter
Design vales: Vg=12 volt, R=5Ω, L= 145.8 µH , C
= 200 μF Frequency = 25 kHz saw tooth signal carrier varies
from 0 to 1[16]. So, according to the given parameters open
loop system function of the buck converter is given by
GOL(s)= Gvd(s)H(s)(1/Vm)
= VgR /(LCR S2
+LS + R)
The step response of the transfer function is shown in the
figure 2.6.and values are given below
Rise Time : 9.2475e-05
Settling Time : 0.0015
Settling Min : 8.4763
Settling Max : 18.4834
Overshoot : 54.0284
Undershoot : 0
Peak : 18.4834
Peak Time : 2.5180e-4
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
x 10
-3
0
2
4
6
8
10
12
14
Open loop Step Response
Time (seconds)
Magnitude(V)
Figure2.6 . Step response of the transfer function
3. 3 CONTROLLER DESIGN
The PI is one of the families of PI controller which is most
flexible and simple method. For turning up of PI controller,
the value of proportional (KP) and integral (KI) needs to be
estimated. The PI controller depends upon the past and
present value. The proportional constant depends on existing
error; the integral constant depends on the aggregation of past
error.
There are numerous types of methods available in literature to
select proportional gain (KP) and Integral gain (KI) for the PI
controller [13]. They are like Ziegler-Nichols, Time domain
design, Frequency domain design. To apply any of these
methods, the common requirement is to have the open loop
transfer function of the system. Out of these methods,
frequency response method is quite popular because of its
ease and effectiveness. The transfer function of the buck
converter is extracted from the small signal model. So by
assigning the values to the transfer function, we can design
the PI controller by frequency domain or bode plot. From
bode plot we can determine the magnitude and the phase
margin Determining these values we can easily determine the
value of proportional gain (KP) and Integral gain (KI)[10].
Bode plot
From bode plot we observe phase margin at the cross
over frequency gain (7º). It may cause the closed loop system
to be unstable as the integral controller adds an additional
phase lag. It is recommended to have a phase margin above
for the stable closed loop system. So, it is prefer to take the
cross over frequency gain more than 45º .If we take the new
cross over frequency gain at 130º then we will get amagnitude
26.2 and the new gain cross over frequency which is denoted
as jω.The proportional constant and Integral constant found
from the figure3.1. As follows
KP = 10-(|G(jω)|/20)
KP = 10-(26.2/20)
= 0.049
KI = (ω/10) KP
KI = 15.4 X 100 X 0.049 = 75.4259.
Figure 3.1. Bode plot of GOL(s) showing frequency and magnitude (dB) at
50o phase margin
Now whatever process we are establishing is to ensure the
desired response at the output. For verifying the desired
response we constituted the model with the above design
values. Following figure 3.2 indicates Simulink based Model
of buck converter with PI controller
Figure 3.2. Simulink based Model of converter with PI controller
The output voltage of the DC buck converter is maintained to
be constant. In the above figure input, reference and output
measured voltages are shown. So for that we need compare to
the reference voltage. After comparing with the reference
voltage, we will get the error signal. This error signal is fed to
the PI controller. From the bode plot we obtain the PI
controller parameters i.e. Value of Kp and KI. The response
signal from the PI controller is given to the saturation which
is later compared with the repeated sequence. So, finally the
pulse is generated and given to the gate terminal of the switch
(MOSFET). Simulation result for the model shown in the
figure3.3.
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014
0
2
4
6
8
10
12
Time(sec)
OUTPUTVOLTAGE(v)
Figure 3.3. Response of buck converter output voltage using bode plot
Ziegler Nichole method
Assume KI and Kd is zero. And we have to ascertain
the value of ultimate gain (Ku) and ultimate period (Tu). By
substituting Ku and Tu we can find the value of Kp and KI as
per the given table. From the transfer function we will take
the characteristic equation .Using the characteristic equation
and applying to the Routh-Hurwitz criterion, the value of the
Ku and Tu .After getting the ultimate gain and ultimate period
values and putting in the table, the proportional constant and
integral constant are determined.
4. Table 1 Determination of Kp,Ki, Values
Table 2 Representation of Characteristic Equation
The characteristic equation from the transfer function is
According to the Routh Hurwitz criterion by using
characteristic equation, the value of ultimate gain(Ku) and
ultimate period (Tu) are determined.
Taking the even equation
2.916 X 10-8
S2
+ 5 + Kcr = 0 (5)
Put S = jω
So, the equation (5) will be
2.916 X 1.458 X 10-4
(jω)2
+ 5 + Kcr = 0
Since 5 + Kcr >0 , So the value of Kp lies between 0 to 5 i.e
0< Kcr <5. If the maximum value Kcr =5 then the value of ω =
5.85606 X 103
Since ω = 2Πf =2Π/ Tu , So Tu = 1.071 X 10-3
.
Substituting the value in the table2,
we will get the value of the Kp = 2.5 and the value of KI =
2521.Putting the value of Kp and the value of KI the transient
response is observed .The output voltage is shown in the
figure 3.4.
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014
0
1
2
3
4
5
6
7
8
9
10
Time(sec)
OUTPUTVOLTAGE(V)
Figure3.4. Response of buck converter output voltage using ZN method
By the visual inspection from the figure 3.3, 3.4 we can
understand that the transfer function which we considered
from small signal analysis can be validated. Also it is clear
that the response is fairly smooth incase of ZN method (figure
3.3).
4 PERTURBATION OF INPUT VOLTAGE
For the model shown in the figure7 if there is perturbation in
input voltage. This consideration is quite realistic. For
observing the output response of the model we have
considered controlled source. Hence from the figure4.1 it is
clear that the constant voltage is maintained even though
input voltage or reference value is varied. This response
plotted by considering the parameters obtained from the
bode plot & Z- N method.
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1
0
2
4
6
8
10
12
14
Time
Figure 4.1.Response of output voltage for Perturbation in the input voltage
using
Now for the same model perturbation in load is applied
response was plot in the figure 4.2. Variation in the load has
been attained with the help of variable resistance. Figure 4.2
clearly depicts that even though load resistance is varied then
also fairly flexible control obtained.
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1
0
2
4
6
8
10
12
14
Time
Figure4.2.Response of output voltage for Perturbation in the load
Conclusion
In this paper we have implemented the control technique
based on small signal analysis of DC-DC buck converter. The
output voltage is steady at 5V even though the input varies
from 5V to 12V.That means ,one can apply any voltage
between 5V to 12V as input, the output will be certainly reach
to 5V in steady state. The variation of input voltage source
and load has applied to the model and the obtained desired
output. It is also observed that ZN method provides optimum
settling time and nearly minimum rise time with fairly smooth
response. From the results obtained in disturbance rejection
mode the ZN step response method provides smooth response
than Frequency domain method.
5. Acknowledgements
I would be greatly Thankful to KIIT University,
School of Electrical Engineering for allowing to me
carry out this work. .
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