Simulation of Power Electronics Circuits using SIMULINK

      


                         

                    

  

             

               

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Simulation of Power Electronics Circuits using SIMULINK

by

Hadeed Ahmed Sher Department of Electrical Engineering, King Saud University, Riyadh, Kingdom of Saudi Arabia

Dedicated to my Wife and my family

Preface Power electronics is a core field in automation and industrial world. It forms the life lines of industrial revolution in the present era. A lot of books on power electronics are available in market. These books, in general, cover the theoretical aspects of power electronics. Presently software based simulation has gained a lot of attention and is considered most effective tool for research and development in engineering. MATLAB is one of the most powerful tools for analyzing the hypothesis and ideas of engineers. Within MATLAB is SIMULINK, that provides us a modular approach to solve problems. The prime aim of this book is to facilitate students in an elegant manner about using SIMULINK in general and SIM POWER SYSTEMS in particular. A very basic approach is adopted as each and every step is depicted to facilitate the students in getting grip of this powerful tool. The book has six chapters. First chapter explains the importance of modeling and simulation and i have tried my best to explain the very basics of modeling a physical system and above all why simulation is required. This section also highlights the choice of using SIMULINK mainly when a variety of powerful softwares are available. Chapter two and three covers the rectifiers with a difference that chapter three is about the SCR based controlled rectifiers. Inverters are discussed in chapter 4. Variety of different inverters including single phase, quasi wave and three phase with induction motor as load are presented in it. AC-AC conversion is covered in chapter 5 with a title of cycloconverters. Here only single phase to single phase and three phase to single phase step down cycloconverter are simulated. Chapter 6 covers basic types of DC-DC converters and along with them full bridge converters are simulated using unipolar and bipolar PWM switching. The focus of this book is simulating power electronics circuits using SIMULINK, therefore detailed theory is not presented. Readers are advised to consult the standard text books for theoretical explanation of these circuits. The simulation results in this book are verified using the famous power electronic books by renowned authors. The experiments in this book are written keeping in view the undergraduate course of power / industrial electronics in almost all universities and technological institutes of region, however it can be considered as a useful quick reference guide for the students of graduate classes. I am greatly thankful to my family, colleagues and friends for providing support in accomplishing this task. Any comments and suggestions regarding this book are greatly welcomed and should be sent to the hadeedsher[at]gmail[dot]com. Hadeed Ahmed Sher KSU, Riyadh, Saudi Arabia

Page II

Contents 1 Introduction to Modeling and Simulation 1.1 Importance of Simulation . . . . . . . 1.2 Why Simulink . . . . . . . . . . . . . . 1.3 SIMPOWER SYSTEM . . . . . . . . 1.4 Architecture of book . . . . . . . . . .

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1 1 3 4 5

2 Uncontrolled Rectifiers 2.1 Introduction . . . . . . . . . . . . . . . . . 2.2 Single phase half wave rectifier . . . . . . 2.2.1 Without freewheeling diode . . . . 2.2.2 With freewheeling diode . . . . . . 2.3 Single phase full wave center tap rectifier 2.3.1 Without freewheeling diode . . . . 2.3.2 With freewheeling diode . . . . . . 2.4 Single phase full wave bridge rectifier . . . 2.4.1 Without free wheeling diode . . . . 2.4.2 With free wheeling diode . . . . . 2.5 Three phase full wave rectifier . . . . . . . 2.5.1 Without freewheeling diode . . . . 2.6 Twelve pulse rectifier . . . . . . . . . . . . 2.6.1 Simulation Procedure . . . . . . . 2.6.2 Results . . . . . . . . . . . . . . .

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6 6 6 6 19 20 20 23 23 24 25 27 27 29 29 32

3 Controlled Rectifiers/Converters 3.1 Introduction . . . . . . . . . . . . . . . . . . . . 3.2 Single phase half wave controlled converter . . 3.2.1 Simulation Procedure . . . . . . . . . . 3.2.2 Results . . . . . . . . . . . . . . . . . . 3.3 Single phase full wave half controlled converter 3.3.1 Simulation Procedure . . . . . . . . . . 3.3.2 Results . . . . . . . . . . . . . . . . . . 3.4 Single phase full wave full controlled converter 3.4.1 Simulation Procedure . . . . . . . . . . 3.4.2 Results . . . . . . . . . . . . . . . . . . 3.5 Three phase full controlled bridge converter . . 3.5.1 Simulation Procedure . . . . . . . . . .

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Page III

Contents 3.5.2

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4 DC-AC Inverters 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Pulse Width Modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Simulation Procedure . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Single phase half bridge inverter . . . . . . . . . . . . . . . . . . . . . . . 4.3.1 Simulation procedure . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Single phase PWM inverter with bipolar voltage switching . . . . . . . . . 4.4.1 Simulation Procedure . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Single phase PWM inverter with Unipolar voltage switching . . . . . . . . 4.5.1 Simulation procedure . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Quasi square wave single phase Inverter . . . . . . . . . . . . . . . . . . . 4.6.1 Simulation Procedure . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 Single phase inverter with hysteresis band current controlled PWM . . . . 4.7.1 Simulation Procedure for PWM . . . . . . . . . . . . . . . . . . . . 4.7.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8 PWM based DC-AC 3 phase Inverter . . . . . . . . . . . . . . . . . . . . . 4.8.1 Simulation Procedure . . . . . . . . . . . . . . . . . . . . . . . . . 4.8.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9 SPWM based 3 phase inverter with 3 phase Asynchronous motor as load . 4.9.1 Simulation Procedure . . . . . . . . . . . . . . . . . . . . . . . . . 4.9.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

46 46 47 50 52 52 54 54 54 55 58 58 58 60 60 61 63 64 65 67 67 68 72 72 73 76

5 Cycloconverters 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Single phase to Single phase Step down Cycloconverter 5.2.1 Simulation Procedure . . . . . . . . . . . . . . 5.2.2 Results . . . . . . . . . . . . . . . . . . . . . . 5.3 Three phase to Single phase Step down Cycloconverter 5.3.1 Simulation Procedure . . . . . . . . . . . . . . 5.3.2 Results . . . . . . . . . . . . . . . . . . . . . .

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6 DC-DC Converters 6.1 Introduction . . . . . . . . . . 6.2 DC-DC Buck Converter . . . 6.2.1 Simulation Procedure 6.2.2 Results . . . . . . . .

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Page IV

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Contents 6.3

6.4

6.5

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DC-DC Boost Converter . . . . . . . . . . 6.3.1 Simulation Procedure . . . . . . . 6.3.2 Results . . . . . . . . . . . . . . . DC-DC Buck / Boost Converter . . . . . 6.4.1 Simulation Procedure . . . . . . . 6.4.2 Results . . . . . . . . . . . . . . . ` K DC-DC Converter . . . . . . . . . . CU 6.5.1 Simulation procedure . . . . . . . 6.5.2 Results . . . . . . . . . . . . . . . Full Bridge DC DC Converter . . . . . . . 6.6.1 Full Bridge DC DC Converter with 6.6.2 Full Bridge DC DC Converter with

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93 94 95 95 95 97 99 100 101 101 102 105

Page V

List of Figures 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 2.21 2.22 2.23 2.24 2.25 2.26 2.27 2.28 2.29 2.30 2.31 2.32 2.33 2.34 2.35

Page VI

1 φ half wave rectifier with RL load . . . . . . . . . . . . . . . . . . . . Reaching simulink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Creating a new model . . . . . . . . . . . . . . . . . . . . . . . . . . . . Adding a block in the model . . . . . . . . . . . . . . . . . . . . . . . . . Construction of a model . . . . . . . . . . . . . . . . . . . . . . . . . . . Voltage block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Load selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Adjusting the oscilloscope . . . . . . . . . . . . . . . . . . . . . . . . . . Adjusting the oscilloscope parameters . . . . . . . . . . . . . . . . . . . Getting towards the simulation parameters . . . . . . . . . . . . . . . . Adjusting the simulation parameters . . . . . . . . . . . . . . . . . . . . Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FFT analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Half wave rectifier with free wheeling diode . . . . . . . . . . . . . . . . Output waveforms with free wheeling diode . . . . . . . . . . . . . . . . FFT of the rectifier with free wheeling diode . . . . . . . . . . . . . . . Circuit arrangement for single phase full wave center tap rectifier . . . . Adjusting the transformer parameters . . . . . . . . . . . . . . . . . . . Output waveform of center tapped full wave rectifier . . . . . . . . . . . Center tapped full wave rectifier with free wheeling diode . . . . . . . . Output waveform of center tapped full wave rectifier with free wheeling diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Full wave bridge rectifier . . . . . . . . . . . . . . . . . . . . . . . . . . . Full wave bridge rectifier without freewheeling diode . . . . . . . . . . . Output of full wave bridge rectifier without freewheeling diode . . . . . Full wave bridge rectifier with freewheeling diode . . . . . . . . . . . . . Full wave bridge rectifier with freewheeling diode . . . . . . . . . . . . . Three phase full wave bridge rectifier . . . . . . . . . . . . . . . . . . . . Simulation setup for three phase full wave rectifier . . . . . . . . . . . . Three phase balanced input . . . . . . . . . . . . . . . . . . . . . . . . . Three phase balanced input . . . . . . . . . . . . . . . . . . . . . . . . . Output of three phase full wave bridge rectifier . . . . . . . . . . . . . . Simulation setup for twelve pulse rectifier . . . . . . . . . . . . . . . . . Three phase three winding transformer block parameters . . . . . . . . . Waveforms for twelve pulse rectifier . . . . . . . . . . . . . . . . . . . . . FFT of primary current of transformer for phase A . . . . . . . . . . . .

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23 24 24 25 25 26 27 28 29 30 30 31 32 33 33

List of Figures 3.1 3.2 3.3 3.4 3.5 3.6

35 36 36 37 37

3.14 3.15

Single phase half wave controlled rectifier . . . . . . . . . . . . . . . . . . Simulation setup for single phase half wave controlled rectifier . . . . . . . Waveforms for single phase half wave controlled rectifier . . . . . . . . . . Single phase full wave semi-controlled rectifier . . . . . . . . . . . . . . . . Single phase full wave semi-controlled rectifier with improved configuration Simulation setup for two topologies of single phase full bridge half controlled converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Simulation results for two topologies of single phase full bridge half controlled converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Single phase full wave Full-controlled converter . . . . . . . . . . . . . . . Simulation setup for 1Φ full wave full-controlled converter . . . . . . . . . Simulation results for 1Φ full wave full-controlled converter . . . . . . . . Input parameters waveforms for single phase full bridge full controlled converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Three phase SCR based full wave full controlled converter . . . . . . . . . Simulation setup for three phase SCR based full wave full controlled converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Output voltage of 3Φ full wave full-controlled converter . . . . . . . . . . Input current analysis of 3Φ full wave full-controlled converter . . . . . .

4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 4.22 4.23 4.24

Typical three phase inverter [4] . . . . . . . . . . . . . . . . . . . . . Pulse Width Modulation . . . . . . . . . . . . . . . . . . . . . . . . . Three phase sinusoidal PWM [5] . . . . . . . . . . . . . . . . . . . . Generation of triangular waveform . . . . . . . . . . . . . . . . . . . Triangular waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . PWM generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Results of PWM with different value of constant. . . . . . . . . . . . Single phase SinePWM . . . . . . . . . . . . . . . . . . . . . . . . . . Results of three phase SPWM. . . . . . . . . . . . . . . . . . . . . . Simulation setup of single phase half bridge inverter . . . . . . . . . Subsystem for PWM generation of single phase half bridge inverter . Results of Half bridge Inverter with Resistive load. . . . . . . . . . . Results of Half bridge Inverter with Inductive load. . . . . . . . . . . Simulation setup of single phase inverter with bipolar switching . . . Single phase asynchronous motor . . . . . . . . . . . . . . . . . . . . Waveforms for Single phase inverter with bipolar switching . . . . . Simulation setup of single phase inverter with unipolar switching . . Output waveforms of single phase inverter with unipolar switching . FFT of output of single phase inverter with unipolar switching . . . Simulation setup for quasi square wave single phase inverter . . . . . Subsystem for quasi square wave single phase inverter . . . . . . . . Results of quasi square wave inverter. . . . . . . . . . . . . . . . . . Block diagram for simulation of hysteresis band 3 phase inverter [6] . Conceptual explanation of hysteresis band single phase inverter [6] .

47 48 49 50 51 51 52 53 53 55 55 57 57 58 59 60 61 62 63 64 64 65 65 66

3.7 3.8 3.9 3.10 3.11 3.12 3.13

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Page VII

List of Figures 4.25 4.26 4.27 4.28 4.29 4.30 4.31 4.32 4.33 4.34 4.35 4.36 4.37 4.38

Simulation setup of hysteresis band inverter . . . . . . . . . . . . . . . . Results of PWM inverter using hysteresis band method. . . . . . . . . . Modeling of leg of an inverter [1] . . . . . . . . . . . . . . . . . . . . . . Modeling of output voltages of inverter [1] . . . . . . . . . . . . . . . . . Complete model of an inverter [1] . . . . . . . . . . . . . . . . . . . . . . Results three phase Inverter. . . . . . . . . . . . . . . . . . . . . . . . . FFT of inverter waveform . . . . . . . . . . . . . . . . . . . . . . . . . . Simulation setup for 3 phase inverter with 3 phase asynchronous motor as load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parameter adjustment of universal bridge . . . . . . . . . . . . . . . . . Asynchronous motor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Measurement selection of bus selector . . . . . . . . . . . . . . . . . . . Parameter adjustment of STEP input . . . . . . . . . . . . . . . . . . . Output of motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Terminal voltages and three phase stator currents . . . . . . . . . . . . .

5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12 5.13

General diagram of a cycloconverter [3] . . . . . . . . . . . General diagram of a cycloconverter [6] . . . . . . . . . . . Output waveform of a cycloconverter [3] . . . . . . . . . . . Simulation setup of a single phase to single phase step down Selection of measurements . . . . . . . . . . . . . . . . . . . Plotting of measurements . . . . . . . . . . . . . . . . . . . Plotting of measurements . . . . . . . . . . . . . . . . . . . Plotting of measurements . . . . . . . . . . . . . . . . . . . Three phase to single phase cycloconverter [3] . . . . . . . Simulation setup for 3 phase to 1 phase cycloconverter . . . Timing diagram of pulses . . . . . . . . . . . . . . . . . . . Output without filter . . . . . . . . . . . . . . . . . . . . . . Output with filter . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . cycloconverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.11 6.12 6.13 6.14

DC-DC buck converter . . . . . . . . . . . . . . . DC-DC buck converter simulation setup . . . . . DC-DC buck converter simulation results . . . . DC-DC boost converter . . . . . . . . . . . . . . DC-DC boost converter simulation setup . . . . DC-DC boost converter output current . . . . . DC-DC boost converter simulation results . . . DC-DC buck / boost converter . . . . . . . . . . DC-DC buck / boost converter simulation setup Simulation results with 25% duty cycle . . . . . Simulation results with 50% duty cycle . . . . . Simulation results with 75% duty cycle . . . . . . ` K DC-DC converter . . . . . . . . . . . . . . CU ` K DC-DC converter . . . Simulation setup of CU

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Page VIII

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List of Figures 6.15 6.16 6.17 6.18 6.19 6.20 6.21 6.22 6.23

` K converter. . . . . . . . . . . . . . . . . . . Simulation results of CU Full Bridge DC DC converter [6] . . . . . . . . . . . . . . . . . . . . Bipolar voltage switching [6] . . . . . . . . . . . . . . . . . . . . . . . Simulation setup for bridge converter with bipolar voltage switching Subsystem for bipolar voltage switching . . . . . . . . . . . . . . . . Simulation results of bridge converter with bipolar voltage switching Voltage waveforms for unipolar voltage switching [6] . . . . . . . . . Subsystem for unipolar voltage switching . . . . . . . . . . . . . . . Simulation results for unipolar voltage switching . . . . . . . . . . .

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1 Introduction to Modeling and Simulation 1.1 Importance of Simulation Circuit performance is a key factor in designing a system in electrical engineering. Each and every component contributes towards the overall performance of a system. In high power electronics known as power electronics we need to be very focused towards the evaluation of system. Not only the components but the junction capacitances and noise also affect the output waveforms. In this modern world power electronics engineers are assisted by control engineers that providing them very useful control chips for signal generation and circuit operation. But these control ICs are also very complex and therefore it is desired to analyze them using software based tools. Circuit simulation is fast becoming an alternative to prototyping. Software based simulation is now considered as an optional aid in learning power electronics. Simulation is an art of converting a circuit design into a software model and then testing it using input stimuli and output monitoring. It can be used to evaluate the performance of new circuits for enhancement of knowledge. The flaws in any circuit can be corrected at early design stage with the help of simulation. Novel techniques can be tested using simulation based packages that saves cost, time and any potential hazard that can arise from short circuit across power components. Apart from its wide use in academia, industrial users gains benefit from simulation by verifying their process performance. Simulation in the past received critics as it adds another step in design cycle but with on going work based on simulation it has been now proved that, as a product progresses through the design cycle, errors become more and more costly to correct. It is best for conducting studies for destructive nature of tests of electric machines. Simulation is an excellent way to reveal logic and/or timing errors in a circuit before continuing for the prototyping. With simulation we can do a variety of operations including the following [3, 6] ˆ Waveforms at various points of circuit ˆ Circuit performance in transient and steady state condition that may be very difficult in hardware prototype. ˆ Assessment of performance improvement / degradations ˆ Measurement of noise and distortion at any node / point of circuit without using expensive network signal analyzers ˆ Voltage and current ratings by examining the waveforms ˆ Calculation of tolerance level for various components that leads to sensitivity analysis.

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1.1 Importance of Simulation ˆ Harmonics analysis without using any expensive equipment ˆ Evaluate the effects of non linear elements on circuit performance ˆ Optimize the design of electronic circuits in terms of circuit parameters ˆ Measurement of power losses for various components including the power switches and diodes. ˆ Development of temperature versus losses curves for circuit elements

Simulation in the field of power electronics is somewhat different then other fields of electrical engineering due to its interdisciplinary nature. Almost every circuit of power electronics exhibits an extremely non linear behavior that makes it difficult to accurately model circuit elements. The simulation time is not constant i.e it may be possible that an inverter with some electrical load at the output may require less time for simulation then an inverter driving a motor. It is because the inverter has a time constant in microseconds whereas a motor can not respond so quick so it has a response time in seconds. So for accurate simulation it is mandatory to keep the step size much smaller that has a side effect of longer simulation time. Further in power electronics we have to essentially deal with power switches like MOSFETs, IGBTs, SCRs and diodes. Unfortunately no accurate model is available therefore that makes it difficult to model them. Specific requirements can be met only with careful objective based simulation. Since, power electronics needs a controller therefore sophisticated controllers are modeled along with to verify the exact system response. Inductors and capacitors used in power electronics circuits may have some initial states that can hamper the swiftness of simulation. Therefore what we need is to carefully analyze what to achieve from a simulation.Sometimes we may not need all the responses from a circuit. A good simulation can be defined as following [6] “The best simulation is the simplest possible simulation that meets the immediate objective” Therefore we need to specify the system objectives before simulation. For a detailed system design following steps are followed [6] ˆ Low level simulation or large signal simulation ˆ Small signal model and controller design ˆ High level simulation or large signal system behavior

Usually for initial testing of new system and for choosing the circuit topology controller is not included in initial level simulation. Predefined signals are given to the system to observe the response. The observations from such low level simulation is then tested with analytical calculations. This gives an idea about the component ratings and circuit topology. Normally we need not to use detailed models for devices used at such low level simulation. Ideal components are used to get a bird eye view of system performance.

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1 Introduction to Modeling and Simulation After deciding the type of circuit the next step is to include the design of controller. Component values are also specified to create a linear model. Controller design may include Proportional (P), Proportional Integral (PI) or Proportional Integral Derivative (PID) control and may be strengthened by use of Fuzzy Logic (FL), or Artificial Neural Network (ANN). The complete design of controller makes it sure to proceed for the high level simulation where it is combined with the circuit to verify the performance of the designed system. At this stage the power losses, heat curves and non linear behavior is also studied in detail. The details of voltage stress on switching devices, the effect of stray capacitances and leakage inductances are also incorporated in this stage to get a response closer to the real world. At this stage ideal models are not used , rather we use detailed models to show the system nonlinearities explicitly. The bottom line here is “Simulation makes it easier to find design problems early in the design cycle.”

1.2 Why Simulink SIMULINK is available with MATLAB installation and unlike MATLAB it is a model based software, i.e. it models the system with the help of building blocks and small elements and then simulates for the analysis of the model. It is so simple that making a system is not more than plug and play. You put your desired building blocks on the blank model page, fix their values and connect the output to a scope to see the effect. Various kinds of building blocks are available within SIMULINK ranging from the simple to advanced one based on artificial intelligence techniques. Both linear and non linear systems can be modeled in it with the same ease. The analysis could be of dynamic system and can be of any level. The main idea behind every simulation is to model the system. It can perform mathematical modeling as well as real component based modeling. The ongoing research in the field of engineering has proved that the SIMULINK results are very promising and resembles too close with the real system provided that the modeling is accurately accomplished. The models can be made in accordance with the simulation guidelines given in section 1.1. The model once made can be modified with real values of components. It can be used for the simulation of following systems ˆ Continuous timed model ˆ Sampled timed model ˆ Hybrid system with both continuous and sample time modeling ˆ Linear system ˆ Non-linear system

With the time, SIMULINK has become so mature in its work that now a very large portion of research work is based on the simulation results of SIMULINK. Since the main computational engine used is MATLAB therefore SIMULINK allows you to use the

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1.3 SIMPOWER SYSTEM MATLAB functions to work in parallel with the SIMULINK model. Even the MATLAB function can be made as part of the SIMULINK model. Engineers and scientists are using this to testify their theoretical hypothesis and novel techniques and its outcome is saving a lot of time and money. SIMULINK is widely used in the following areas [2] ˆ Aerospace and defense ˆ Automotive ˆ Power system analysis ˆ Power electronics and renewable energy system simulation ˆ Artificial intelligence based systems ˆ Communications ˆ Electronics and signal processing ˆ Medical instrumentation

As this book is on the simulation of power electronics therefore we will focus on one of the functionaries of SIMULINK known as SIMPOWER system.

1.3 SIMPOWER SYSTEM SimPower Systems software is a very useful tool for the analysis of power system problems. It has produced a lot of ease for engineers and researchers for in depth analysis of power system using its user friendly interface. As discussed above the work of SIMULINK is merely a plug and play operation therefore SimPower Systems is easy to use and models can be developed using simple click and drag procedures. SIMULINK is used for variety of systems and SimPower Systems being an integral part of SIMULINK provides and opportunity to develop a whole industrial environment with thermal, mechanical and control blocks connected with the electrical system. In SimPower Systems software the electrical components are present that can be adjusted to model a specific device. For example transformer has built in data that can be modified for the input and output values by simple clicking and editing the value. Besides the transformer SimPower Systems has other components like transmission lines, electrical machines, wind generation, HVDC and electric drives. For simulation of power electronics systems a semiconductor based library lies within the SimPower Systems. Measurement library allows the researcher to measure various parameters like current, voltages, power, THD, RMS, and impedance for single and three phase systems. Input can be selected by a mix library of input sources that includes the AC and DC voltage and current sources. Very interestingly the POWERGUI block makes it fun calculating the FFT of the waveform at any instant and any particular point. By selecting the fundamental frequency and the limit for harmonic analysis one can see details of harmonic pollution within a model in both graphical and tabular form. People have spent years on the research and development

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1 Introduction to Modeling and Simulation of these components therefore, these models are proven and are tested in reputed laboratories including Power Systems Testing and Simulation Laboratory of Hydro-Qubec, a large North American utility located in Canada, and also on the experience of cole de Technologie Suprieure and Universit Laval [2]. The capabilities of SimPower Systems software for modeling a power electronics system are presented in this book with a lot of graphical illustrations.

1.4 Architecture of book Power electronic is a science of power conversion. There are four types of power conversion within the domain of power electronic conversion. These include ˆ AC-DC conversion (Rectifiers) ˆ AC-AC conversion (Cycloconverter) ˆ DC-AC conversion (Inverter) ˆ DC-DC conversion (Switch Mode Power Supplies)

In this book the topic of rectifiers has been divided into two parts with simulation of controlled and uncontrolled rectifiers. Different topologies for single and three phase rectifiers are simulated using free wheeling diode and without using freewheeling diode. A little theory has also been given for each circuit assuming that the reader know well about the working of these circuits. Chapter on cycloconverter has two simulations for single phase to single phase and single phase to three phase cycloconverter with step down feature. We have tried to cover inverters with detail especially the single phase, three phase, quasi square wave and SPWM inverters. Last chapter is about DC -DC converters. All the basic types are simulated and in addition to them the concept of unipolar and bipolar output has been elaborated using simulation of full bridge DC-DC converter.

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2 Uncontrolled Rectifiers 2.1 Introduction Most of the power electronic devices converts the incoming AC voltage of fixed frequency and fixed voltage into DC of fixed value. The objective here is to obtain useful DC supply from grid side. Diode based rectifiers are used commonly for such purpose. They are also known as uncontrolled rectifiers. In these type of rectifiers the power can only flow from AC side to the DC side hence, we do not have any control on the power flow. The output is entirely dependent on circuit topology and the biasing condition of diodes. As soon as the applied voltage exceeds the diode depletion layer potential (typically 1-2 V for a power diode and 0.7V for ordinary Si diode and 0.3V for ordinary Ge diode) it starts conducting and keeps on conducting unless and until the voltages becomes less then the required threshold voltage. Since, everything that happens in this entire process is automatic and no external parameter can control the power flow therefore such rectifiers are called uncontrolled rectifiers. These kind of power electronic devices are also known as linear power supply and suffer from their large size and low efficiency. However, these type of rectifiers are widely used in single and three phase domestic applications. In this chapter we are presenting the simulation for both single phase and three phase rectifiers with various configurations.

2.2 Single phase half wave rectifier Single phase half wave rectifiers are the most basic form of rectifier. A rectifier without having any control on power flow is based on diodes. These diodes turn on and off according to the voltages available on their terminals. They cannot be controlled through some external signal. The term half wave is originated from the fact that these rectifiers only allow half wave to appear across the load. Half of the cycle always drops across the diode. They have the least number of diodes in their topology that results in poor power quality, increased voltage drop and less power utilization. They typically have an efficiency of 41 % and a ripple factor of 121 %, therefore such type of rectifiers are not used in practical applications. Since this kind of rectifier is a basic building block for the theoretical advancement in diode based rectifiers it is simulated for RL load.

2.2.1 Without freewheeling diode The single phase half wave rectifier is shown in Fig.2.1. It has only one diode that allows to pass only one half cycle of input AC voltage and blocks the other half. The part of cycle it blocks depends on the connectivity of diode with input supply. These kind of

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2 Uncontrolled Rectifiers converters have a fixed output and a low efficiency due to the wastage of half the supply voltage.

Figure 2.1: 1 φ half wave rectifier with RL load

Simulation Procedure We will now simulate this circuit using the following values of circuit components ˆ Resistance = 0.5 Ω ˆ Inductance = 6.5 mH ˆ Vin =220 Vrms at 50Hz (312Vp )

Open MATLAB and click on the icon for SIMULINK as shown in fig.2.2. Alternatively you can open SIMULINK by writing SIMULINK in the command window. Another way is to adopt the way through START icon of MATLAB Start ⇒ Simulink ⇒ Librarybrowser. Click on NEW MODEL or go to F ILE ⇒ N EW ⇒ M ODEL and a new blank model is created as shown in Fig.2.3. You can also reach this point directly by adopting this route M AT LAB ⇒ F ile ⇒ N ew ⇒ M odel. However, after creating a blank model you need to open the SIMULINK component storeroom by going to V iew ⇒ LibraryBrowser. Select SIMPOWER SYSTEMS then select Power Electronics library and by right clicking on diode and click on add to untitled will add the diode in the blank model. Alternatively you can drag the component directly in the model page as shown in Fig.2.4. Similarly go to ELECTRICAL SOU RCES ⇒ AC Voltage Source and add it to untitled. Select Elements and select SERIES RLC BRANCH and add it to untitled. Simulink do not perform simulation unless and until a measurement block is present in a system. Since we need to measure the instantaneous input and output voltages and the load current we need to have 3 instruments (2 voltmeters and 1 ammeter). To add them select Measurement in SIMPOWER SYSTEMS and then

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2.2 Single phase half wave rectifier

Figure 2.2: Reaching simulink

add current measurement and voltage measurement blocks to untitled. Oscilloscope is not included in SIMPOWER SYSTEMS and is present in the top most block of the left column that is SIM U LIN K ⇒ Sinks ⇒ Scope. We can join various blocks by clicking on their edges and then drag the wire till the other connection terminal. Construct the circuit by joining them together in the form as given in Fig. 2.5

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2 Uncontrolled Rectifiers

Figure 2.3: Creating a new model

Figure 2.4: Adding a block in the model

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2.2 Single phase half wave rectifier

Figure 2.5: Construction of a model

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2 Uncontrolled Rectifiers

Figure 2.6: Voltage block

Now double click the voltage block to set the values of voltage and frequency. A dialog box will appear as shown in Fig.2.6. Inside it various parameters can be set that are ˆ Peak amplitude of the generated voltage, in volts (V)

Set it to 312 V (Default is 100V)(. ˆ Phase in degrees (deg).

Set it to zero (0) degrees. ˆ Frequency in hertz (Hz).

Set it to 50Hz (Default is 60Hz) ˆ Sample time in seconds (s). The default is 0, corresponding to a continuous source.

Let it remain as it is ˆ Measurements

Set it to none because we are not using multi meter (Use of multi meter is discussed in comming simulations). Double click on diode and you can set various parameters for DIODE according to the specific data sheet. Double click on series RLC branch and set the values for R and L

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2.2 Single phase half wave rectifier as given in the start of the problem. Select the Branch type as RL as shown in Fig.2.7. It should be noted that for writing the values of L we have to use e-6 for micro and e-3 for milli etc. In the Scope menu “>” is shown which can only be connected to the inverse icon “