Project 1&2 of Designing and Simulating full bridge controlled rectifier.

Project 1&2 of Designing and Simulating full bridge controlled rectifier.

HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGYSCHOOL OF ELECTRICAL ENGINEERING====o0o====

DESIGN REPORTPROJECT IIPROJECT NAME:DESIGNING & SIMULATING FULL BRIDGE CONTROLLED RECTIFIER CLASS :EE.CTTT. K55

1. INSTRUCTOR : DR. DO MANH CUONG STUDENTS : Nguyn c Tm CODE : 20102119

Hanoi : 07/31/2014TABLE OF CONTENTPREFACE.2

CHATER 1:GENERAL INTRODUCTION TO THYRISTOR4 1.The basic theory of thyristor ......4 2.Basic principle and state of thyristor..6 3.Basic parameters of thyristor..6 4.Control principle of thyristor...7 5.Some advantages and disadvantages of controlled thyristor with other controlled rectifier..9

CHAPTER 2: CHOOSING AND CALCULATION OF POWER STAGE..9 1.Requirement for control stage.9 2.Choosing and calculating the power stage..9CHAPTER 3: DESIGN AND SIMULATING CONTROLLED CIRCUIT AND CONCLUSION.........12 1.Block diagram of controlled state..12 2.Schematic and simulation result.17 3.Conclusion..20 4.References..20

PREFACE

In the recent years, with the very high development of our country and get many achivements and make basic premiss for our country go to the new period, the period of industrialization and modernization of the country and the power electronics of electrical engineering is the most important part of the development of the country.Especially, with the application of power electronic in all sector of national economy.In our project related to rectifier using thysistor control we concern about the method to control safety and and accurately.It is the mission of sector power electronic is needed to solve.Student of sector automation control engineering need to have more about knowledge power electronic to apply in factory, enterpriseto enhance productivity and bring atomatic control technology into manufacturing process. The project supplies for our many knowledge about power electronic, specially, in predictive control algorithm control for PWM AC chopper.To help me to reinforce the knowledge and have some experiences teacher Dr.Do Manh Cuong help our to do project about predecitve control.From searching project and some document in internet,specially with the help of my teacher we now complete the project.The main content of this assignment I concentrate 2 problems: determine,calculate,design parameter of circuit and simulating control circuit..The assignment give our many new knowledge and help me recognize, design one power electronic circuit better. Although we attempt to make the good project but with the little experiences so the project has many mistakes, please forget about it! Student group: Nguyn c Tm

Chapter 1GENERAL INTRODUCTIONI. Motivation One of the great things ever to happened to mankind in the 20nd century was the invention of a transistor by John Bardeen,Walter Brattain and Wiliam Shockley in 1947 at Bell,USA and the successful production of the first transistor in 1954.The transistor is the heart of power electronic and now has become central to our lives. As the number of transistor on intergrated circuit doubles,computing power is increasing and online control of complex and faster processes are becoming more commom.This is due to shrinking transistor size,higher operating speeds and introduction of more power efficient semiconductor.As the processor die size is decreasing , the processing speed is increasing and production costs are decreasing.Low power consumption in the devices has been largely achieved by decreasing the operating voltage,improvement and introduction of new semiconductor technology and manufacturing methods. One of the other side of semiconductor technology, is use of semiconductor in high power and high voltage electronic.To control these power semiconductors is power supply paths losses .The control should be able to compute online the medium cost with the real time measurement using complex control algorithm and be able to apply the control law immediately to achieve the desired the control object.In this research , a finite set model predictive control algorithm (FS-MPC) that is presented which can be computed by using DSP II. Background The recent developments in the few of power electronics make it possible to improve the electrical power system ultility interface.Line commutated AC controller can be replaced by PWM AC chopper controller which have better overall performance and the above problem can be improved if there controllers are designed to operate in the chopping mode.In this case ,the input supply voltage is chopped into segments and the output voltage level is decided by controlling the duty cycle of the chopping switching function.on easurement using complex control algorithm and be able to apply the control law immediately to achieve.The growth in the field of the power electronics has made it possible to improve the performance of electrical system ultilites through various mean.The solid state power switching devices are employed in source conditioning by changing either its magnitude or frequency such as inverter,converter, chopper, regulator.The advantages of using these devices are listed out by Addosweet.They are below + Fast respone + Compactness + Loss free control + Low power demands of control circuitryMedium,large motor drives and higher power supply inverter in flexible alternate current transmission system need switching element wich can bear high voltage and current.To overcome the limitation of semiconductor switches , several new techniques and topologies has been developed,such as multiple switching elements in one lag of the inverter.III. Choppers1.General about DC choppers A chopper is a static device which is used to obtain a variable dc voltage from a constant dc voltage source.A chopper is also known as dc-to-dc converter.The thyristor convert offers great efficiency,faster respone,lower maintenance,small size and smooth control.Choppers are widely used in trolley cars,control of large number of dc motor,etcThey are also used in regenative braking of dc motor to return energy back to supply and also as dc voltage regulator. Choppers are of two types + Step-down choppers + Step - up choppersa.Step down choppers

Step down chopper with Resistive loadThe thyristor in the circuit acts as a switch.When the thyristor is ON ,supply voltage aprear across the load and when thyristor is OFF, the voltage across the load will be zero.The output voltage and current waveform are shown in below

Step down choppers output voltage and current wavform Vdc = average value of the output or load voltage Idc = average value of output or load current tOFF = time interval for which SCR conducts tON = time interval for which SCR is OFF T= tOFF + tON is period of switching or chopping period Average output voltage

b.Step up choppers

Step up chopper A step up chopper obtain a load voltage Vo higher than input voltage V.When the choppe is ONN the inductor L is connected across the supply and when the chooper is OFF the inductor current I is forced to flow through the diode D and load for a period.Therefore the voltage across load is given by When chopper is ON - Voltage across inductor L=V Therefore energy store in inductor = V.I.tON Where TON = ON period of chopperWhen chopper is OFF Energy supplied by inductor L=(V0-V)ItOFF , where tOFF = OFF period of chopper. Voltage across L = V0 - V2. The method of control Pulse Width Modulation is one method of control.The pulse width (tON) of the output waveform is varied keeping chopping frequency f varied by varying the ON time.The output voltage is varied and by varying hence chopping period T constant.Therefore out voltage waveform for different ON time.

Pulse Width Modulation Control.

3.General about AC choppers. AC chopper is a static converter which convert AC to AC without changing the frequency and AC chopper have been widely used to control average load power from a fixed ac source.The common applictions are industrial heating and ac speed control. The advantages of AC chopper over DC chopper + Simplicity + Ability of controlling large amount of power + High efficiency The disadvantages of AC chopper over DC chopper + Protection against detrimental switching voltage transients + Negative Temperature coefficienta. Single phase topology By the supply mode , PWM AC chopper are classified in differential and non-differential .Both structure are made by two inverter commuanication cells with IGBTs bydirectional in current and unidirectional in voltage.

Basic single phase PWM AC choppers Both converter have the same control,depending on the voltage source

b.Three phase topologyIn the three phase topology the PWM AC chopper operate like unidirectional voltage chopper.In the second control depending on the voltage source sign the three phase structure operate like two independent unidirectional voltage chopper.

In the buck PWM AC chopper for three phase systems the switches with the smallest voltage source among three voltage source are fully turned on.

Chapter 2MODEL PRIDECTIVE CONTROL ALGORITHM.

I. History of model predictive controlThe earliest algorithm of Model predictive control was proposed by a French engineer Richalet in 1978 but the receding horizon principle was proposed as early as 1963 by Propoi in open loop optimal feedback control In 1968,Rafal and Stevens presented a control system with a quadratic cost,linear constraints and moving horizon of one.This was essentially an MPC formulation.MPC later become popular in the chemical and other slow process industries due to simplicity of the algorithm and the advent of the computer and the introduction of online optimization.The MPC control systems was ideal in industrial because of its capability handlding multivariable systems and constraints II. Branches of predictive controlMany control schemes has been proposed and are used power electronics the most common controller being the linear controller with pulse width modulation.

Converter control method Predective control further be broken into several control schemes Deadbeat control and MPC with a continuous control set require modulators such as pulse width modulation which results in fixed switching frequency while hysteresis, trajectory and MPC with finite set control Moded predictive control is further divided into two kind: MPC with a continuous control set MPC with a finite set control + MPC with continuous control set requires a modulator.

In an MPC with a finite set control ,the switches position form part of the optimization process

III. Model predictive control theory Predective thinking is nautral for people for example during driving the car ,the driver look ahead and observer the shape of the road and possible obstacles.The discrete time model of the system can be given by the following equation

Which describe the future state vector as a function of the current state vector and the current input vectorModel predictive control refer to a class of control algorithm in which a plant or process dynamic model is used to control a process or plant by minimizing an objective function.MPC uses mathematical function model of system to predict the future behavior.MPC process can be summarized as follow To take a measurement of a system state and output Compute a finite horizon sequence Carry out on-line optimization using a cost function Apply the vector control variable with the least cos on the controlled plant A model of plant is necessary for the controller The success of the controller depend on the accuracy of the model State and process measurement provide feedback for the system Acorrding to the component of model predictive control are1.Influence of predictions on actions MPC in constrast computer the affect of the current actions over a finite horizon2.Prediction are based on model3.Selecting input The advantages of MPC rding to the Volt-Ampere characteristic of Thyristor, the width of control pulse is required that current through Thyristor increase from 0 to Ith_max . Normally, the width of control pulse is not smaller than 5ms. If we increase the width if control pulse, the amplitude of control pulse will be decreased.3. The raising and falling edge of control pulseThe raising and falling time smaller is better. It will decrease the loss power by heating of Thyristor especially using many Thyristor in circuit. We try to decrease the value of them to 0, then the control pulse is look like rectangular pulse.4. Confidence of circuitThe circuit have to operate exactly in condition having increase of temperature, appear some noise. The Thyristors are not allow to open when the leakage current appear. The control pulse is little denpend on heating, oscilation of input voltage, noise , IV. Choosing and calculating the power stage.1. Calculation and choosing ThyristorWe are consider one phase bridge rectifier using Thyristor, so we have: The maximum reverse voltage of Thyristor is :URe_max = .U2 = 220 = 311(V) The needed reverse voltage of Thyristor is:

URe_needed = 1.8 UNg_max = 1.8311 = 560(V) The working current of Thyristor following rated current:Iv =1/Irated = 0.577 166 = 95.8(A) The needed current of Thyristor is:Ineeded = 3.2 Iv = 3.295.8 = 306.56(A)From all above parameters, we check in Thyristor parameter table and we choose TF440-06X with parameters:

- The rated current: Irated = 400(A)- The maximum reverse voltage: URe_max = 600(V)- The peak current:Ipeak = 4000(A)- The drop voltage on Thyristor:Vdrop = 2(V)- The gate current: Ig = 200(mA)- The gate voltageVg = 5(V)- The leakage current:Ileak = 25(mA)- The maximum working temperature:Tmax = 125(oC)- The maintain current:Imaintain = 70(mA)2. Calculation and choosing transformer2.1. Choosing cross section of iron core S0S0 = (0.9 0.93) S (mm2)With S = ab . Choose a= 3mm, 5mm.We have S = 35=15 (mm2)So we get S0 = 0.915 = 13.5 (mm2)The estimation power with cross section wounding S0 :Pestimate = U2I2where U1 = 220(V), f = 50(Hz)U2 = 24(V),I2 = 1(A)Pestimate = U2I2 = 241 = 24(V)2.2. Choosing the number of winding per volt WWe choose B = 0.7 ( Tesla), so K = 64.So W = 64/13.5 = 4.74 ( round per volt)So we choose W = 5.2.3. Choosing the number of winding in primary W1 and secondary W2,W3- The number of primary winding :W1 = WU1 = 5 220 = 1100 ( round)- The number of secondary winding :W2 = W3 = U2 / 2 = 24 / 2 = 12 ( round)Determine the cross section for winding:- The cross section of primary winding :S1 = (mm2) is the effiency of transformer: = 0.850.9J is the current density of winding.

Choosing J = 4 ( A/mm2)So the cross section of primary core is:S1 = = 0.03 (mm2)The cross section of secondary windings: S2 = S3 = I2 / J = 1 / 4 = 0.25 (mm2)The diameter of a primary winding:d1 = 1.13 = 1.13 0.03 = 0.2 ( mm)The diameter of secondary windings:d2 = d3 = 1.13 = 1.13 0.25 = 0.6 ( mm)

Chapter 3DESIGN AND SIMULATING THE CONTROL CIRCUIT AND CONCULSION

I. Block diagram of control stage.

SynchronousComparatorPWMIsolationControl voltage

Source

Figure 3.1: Block diagram of control satge (Source: From internet)1. Source blockThe main function of source block is provide the AC supply power for control stage with AC current 50Hz. The wave form of source is sinusoidal wave.2. Synchronous blockThe main function of synchronous block is synchonization the width pulse with the period of AC supply power 50Hz. Firstly, we use 2 diodes to have full-wave rectifier circuit to obtain DC supply power. Then we use capacitor which can charge and discharge energy to generate the sawtooth waveform. We have many sample can be choosed to implement this function, but we choose sample that using transistor to control charge and discharge of capacitor.

Figure 3.2: The synchronous block( Source: from simulation circuit)This sample is very useful. We can control the openning and closing of transisor at voltage approximately to 0 that most other sample can not be performed. So we can easy to control the charging and discharging of capacitor at region very small value of voltage. This sample control transistor depending on working principle of Operation Amplifier (OPAM).

Figure 3.3: Control transistor depending on OPAM(Source : From result simulating)3. Comparator blockTo simplize, we choose OPAM comparator to compare the value of sawtooth wave voltage and control voltage and then generate the pulse.

Figure 3.4: Comparator block(Source: From simulation circuit)In this figure, U1 and U2 are control voltage and sawtooth voltage corresponding. If sawtooth voltage greater than control voltage, the output voltage will be high level at 5V. Reverstly, the output voltage of OPAM will be low level at 0V. The advantage of this sample is that it can generate the control pule very exactly.

Figure 3.5: The voltage control by the comparator block(Source: Simulation result)

1. Pulse Width Modulation (PWM) block

When circuit operate in reality, the loss power is a big problem. So we have to find how to reduce the loss power for circuit, how to reduce the raising heat for circuit, We will using pulse width modulation methods to get it. We devide the control pulse at high level (5V) into many small period pulse, that mean the frequency of pulse is very big. It is approximately 10KHz.

Figure 3.6:Pulse width modulation block(Source: From simulation circuit)This block create the pulse with high frequency.

Figure 3.7:The pulse with high frequency(Source: result simulating)Because we consider about bridge rectifier, full-wave rectifier, we have to rectifier at 2-half period of AC sinusoidal input voltage. We using NOT logical gate to generate invert pulse serving for negative period.

Figure 3.8: The NOT logical gate(Source: From simulation circuit)Finally, we use AND logical gate with 3 inputs to combine and create the openning pulse for 4 Thyristor.5. Isolation blockThe control stage has low power, but power stage has high power. To ensure security, we have isolate control stage and power stage. Nowday, OPTO coupler is usually used to isolate control stage and power stage. Moreover, the structure of circuit is not difficult.

Figure 3.9: Isolation block(Source: From simulating circuit)Eventually, we connect the output to the input of thyristor corresponding. II. Schematic and simulation result 1. Schematic

Figure 3.10: The schematic(Source:From internet)2. Simulation result

Figure 3.11: The simulation result III. ConclusionThe our project using thyristor to control current and voltage.It are mainly used where high current and voltage are involved,and often used to control alternating current, where the change of polarity of the current causes to devices to switch off , automatically.This can be said to operate synchronously as, once the device is open,it conduct current in phase with the voltage applied over its cathode to anode junction with no further gate modulation being requires to repliable.

IV. Refereces 1. Trn Trng Minh Gio trnh in t cng sut.NXB Gio Dc2.Nguyn Bnh in t cng sut v ng dng thyristor.NXB i hc v gio dc chuyn nghip3.Controlled in power electronic Marian P.Kazmierkowski and Frede Blaabjerg.

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