This document provides an overview of various pulse width modulation techniques for voltage source inverters, including naturally sampled PWM, regular sampled PWM, delta modulation, delta sigma modulation, space vector modulation, and hysteresis PWM. It describes the basic concepts and operating principles of each technique, and compares them in terms of performance metrics like harmonic distortion and switching losses. Space vector modulation techniques are ranked as providing the best performance in terms of minimizing harmonics, followed by regular sampled PWM and sine-triangle modulation.
Firing Angle Control & Constant Current ControlKaushik Naik
This document discusses firing angle control and constant current control techniques for HVDC systems. It describes two main firing angle control schemes: Individual Phase Control (IPC) and Equidistant Pulse Control (EPC). IPC determines firing pulses individually for each valve but causes harmonic instability. EPC produces pulses at equal intervals and has three methods - pulse frequency control, pulse period control, and pulse phase control. It also discusses constant current control and provides references for further reading.
The document provides information about a PowerPoint presentation on Distributed Static Compensator (D-STATCOM) given by Sheikh Mohammad Sajid. It introduces D-STATCOM as a device used to mitigate current-based power quality problems at the distributed level. It discusses various classifications, topologies, components, control strategies and objectives of D-STATCOM, including reactive power compensation, load balancing and harmonic suppression. The key principles of operation involve injecting compensating currents from a voltage source converter to regulate voltage at the point of common coupling.
Design of Speed and Current Controller for Two Quadrant DC Motor DriveKaushik Naik
This document discusses the design of a current controller for a two-quadrant DC motor drive system using a model order reduction technique. It first presents the literature on various order reduction methods. It then derives the transfer functions of the DC motor, converter, current and speed controllers. Using the symmetric optimum method, it designs the current controller as a second-order system and the speed controller as a first-order system, reduced from their original higher orders. Simulation results show the performance of the reduced order system matches the conventional system. The document concludes the motor drive control is designed and simulated successfully using the symmetric optimum method.
The document discusses different types of singular points in control systems:
1. A nodal point occurs when both eigenvalues are real and negative, causing all trajectories to converge to the origin in a stable manner.
2. A saddle point occurs when the eigenvalues are real and equal but opposite in sign, making the origin unstable with some trajectories converging and others diverging.
3. A focus point occurs when the eigenvalues are complex conjugates with negative real parts, causing the trajectories to spiral inward in a stable manner towards the origin.
4. A center or vortex point occurs when the eigenvalues are purely imaginary, causing the trajectories to travel in closed paths around the origin in a limitedly stable manner.
This document discusses multi-terminal DC (MTDC) systems. It begins with an introduction stating that MTDC systems have more than two converter stations that can operate as either rectifiers or inverters. It then describes the two types of MTDC systems - series and parallel (including radial and mesh configurations). The document outlines some applications of MTDC systems, as well as typical problems. It notes advantages like reversible power flow and lack of commutation failures, and disadvantages such as need for large smoothing reactors. Finally, it discusses future aspects like microgrids and renewable integration, and concludes that VSC-HVDC technology may help address challenges and enable more MTDC system implementation.
The document discusses converter configurations and analyzes a 12 pulse converter. It begins by explaining pulse number and valve/switch types in converters. It then discusses how converter configuration is selected based on pulse number to maximize valve and transformer utilization. It provides equations for peak inverse voltage, utilization factor, and transformer rating calculations. Finally, it analyzes a 12 pulse converter, explaining how two transformers connected in star-star and star-delta configurations produce 12 pulses of output with each pulse having a 30 degree duration.
Simulation and study of multilevel inverter (report)Arpit Kurel
The document discusses the simulation and study of a multilevel inverter. It begins with an abstract that outlines that multilevel inverters are used to convert DC power to AC power at required voltage and frequency levels for applications like motor drives and grid connections. It then discusses different multilevel inverter topologies like diode clamped, flying capacitor, and cascaded H-bridge. For this project, a three phase five level inverter is simulated using sinusoidal PWM technique in MATLAB/Simulink. The topology used is a cascaded H-bridge inverter with separate DC sources. The multilevel inverter reduces harmonic contents in the output waveform compared to a three level inverter.
The document discusses different types of compensators used in control systems including lag, lead, and lag-lead compensators. It describes the S-plane representation of each compensator and how they can be realized using electrical networks. A lag compensator provides phase lag, improving steady-state performance but slowing the response. A lead compensator increases bandwidth and response speed by providing phase lead. A lag-lead compensator combines the advantages of lag and lead compensation.
Firing Angle Control & Constant Current ControlKaushik Naik
This document discusses firing angle control and constant current control techniques for HVDC systems. It describes two main firing angle control schemes: Individual Phase Control (IPC) and Equidistant Pulse Control (EPC). IPC determines firing pulses individually for each valve but causes harmonic instability. EPC produces pulses at equal intervals and has three methods - pulse frequency control, pulse period control, and pulse phase control. It also discusses constant current control and provides references for further reading.
The document provides information about a PowerPoint presentation on Distributed Static Compensator (D-STATCOM) given by Sheikh Mohammad Sajid. It introduces D-STATCOM as a device used to mitigate current-based power quality problems at the distributed level. It discusses various classifications, topologies, components, control strategies and objectives of D-STATCOM, including reactive power compensation, load balancing and harmonic suppression. The key principles of operation involve injecting compensating currents from a voltage source converter to regulate voltage at the point of common coupling.
Design of Speed and Current Controller for Two Quadrant DC Motor DriveKaushik Naik
This document discusses the design of a current controller for a two-quadrant DC motor drive system using a model order reduction technique. It first presents the literature on various order reduction methods. It then derives the transfer functions of the DC motor, converter, current and speed controllers. Using the symmetric optimum method, it designs the current controller as a second-order system and the speed controller as a first-order system, reduced from their original higher orders. Simulation results show the performance of the reduced order system matches the conventional system. The document concludes the motor drive control is designed and simulated successfully using the symmetric optimum method.
The document discusses different types of singular points in control systems:
1. A nodal point occurs when both eigenvalues are real and negative, causing all trajectories to converge to the origin in a stable manner.
2. A saddle point occurs when the eigenvalues are real and equal but opposite in sign, making the origin unstable with some trajectories converging and others diverging.
3. A focus point occurs when the eigenvalues are complex conjugates with negative real parts, causing the trajectories to spiral inward in a stable manner towards the origin.
4. A center or vortex point occurs when the eigenvalues are purely imaginary, causing the trajectories to travel in closed paths around the origin in a limitedly stable manner.
This document discusses multi-terminal DC (MTDC) systems. It begins with an introduction stating that MTDC systems have more than two converter stations that can operate as either rectifiers or inverters. It then describes the two types of MTDC systems - series and parallel (including radial and mesh configurations). The document outlines some applications of MTDC systems, as well as typical problems. It notes advantages like reversible power flow and lack of commutation failures, and disadvantages such as need for large smoothing reactors. Finally, it discusses future aspects like microgrids and renewable integration, and concludes that VSC-HVDC technology may help address challenges and enable more MTDC system implementation.
The document discusses converter configurations and analyzes a 12 pulse converter. It begins by explaining pulse number and valve/switch types in converters. It then discusses how converter configuration is selected based on pulse number to maximize valve and transformer utilization. It provides equations for peak inverse voltage, utilization factor, and transformer rating calculations. Finally, it analyzes a 12 pulse converter, explaining how two transformers connected in star-star and star-delta configurations produce 12 pulses of output with each pulse having a 30 degree duration.
Simulation and study of multilevel inverter (report)Arpit Kurel
The document discusses the simulation and study of a multilevel inverter. It begins with an abstract that outlines that multilevel inverters are used to convert DC power to AC power at required voltage and frequency levels for applications like motor drives and grid connections. It then discusses different multilevel inverter topologies like diode clamped, flying capacitor, and cascaded H-bridge. For this project, a three phase five level inverter is simulated using sinusoidal PWM technique in MATLAB/Simulink. The topology used is a cascaded H-bridge inverter with separate DC sources. The multilevel inverter reduces harmonic contents in the output waveform compared to a three level inverter.
The document discusses different types of compensators used in control systems including lag, lead, and lag-lead compensators. It describes the S-plane representation of each compensator and how they can be realized using electrical networks. A lag compensator provides phase lag, improving steady-state performance but slowing the response. A lead compensator increases bandwidth and response speed by providing phase lead. A lag-lead compensator combines the advantages of lag and lead compensation.
Different transformations and reference
frame theory, modeling of induction machines, voltage fed inverter
control-v/f control, vector control, direct torque and flux
control(DTC).
The concept of FACTS (Flexible Alternating Current Transmission System) refers to a family of power electronics-based devices able to enhance AC system controllability and stability and to increase power transfer capability.
1) The document describes different types of nonlinearities that can occur in systems. It classifies nonlinearities based on their magnitude (incidental or intentional) and frequency (limit cycles, jump resonance, etc.).
2) Some common types of nonlinearities described include saturation, dead zones, backlash, relays, harmonics, and chaotic behavior.
3) Nonlinearities can cause issues like degradation of system performance, limit cycles, and even destabilization of systems. Understanding different nonlinear effects is important for analyzing system behavior.
Series & shunt compensation and FACTs Deviceskhemraj298
Series compensation is used to improve the performance of extra high voltage transmission lines by connecting capacitors in series with the line. It allows for increased transmission capacity and improved system stability by reducing the phase angle between sending and receiving end voltages for the same power transfer. Shunt compensation controls the receiving end voltage by connecting shunt capacitors or reactors to meet reactive power demand and prevent voltage drops or rises. Flexible AC transmission systems use high-speed thyristors to switch transmission line components like capacitors and reactors to control parameters like voltages and reactances to optimize power transfer.
This document provides an overview of voltage source converters (VSC) for high voltage direct current (HVDC) transmission. It discusses the components and operation of VSC-HVDC systems, including different converter configurations like two-level, three-level, and modular multi-level converters. It also compares VSC-HVDC to conventional HVDC systems using line-commutated converters, noting advantages of VSC-HVDC like eliminating the need for reactive power compensation and reducing the risk of commutation failures.
Pulse-Width Modulation (PWM) techniques are used to control output voltages of power converters. There are three main PWM methods: Sine PWM uses a reference sine wave compared to a triangular carrier wave to generate PWM signals; Hysteresis PWM uses a feedback control loop with variable switching frequency to maintain output within a hysteresis band; Space Vector PWM approximates the reference voltage vector using combinations of the eight switching states and their durations to reduce harmonic distortion and improve voltage utilization.
This document provides an introduction to multilevel inverters. It begins by defining power electronics as the field dealing with conversion and control of electric power across a wide range of power scales. It then discusses different types of power converters including rectifiers, cycloconverters, choppers, and inverters. The document focuses on inverters, explaining that they convert DC to AC with adjustable frequency, phase and amplitude. It provides examples of two-level and multilevel inverters, describing their components and operation. The benefits of multilevel inverters for medium voltage applications are outlined. Finally, it discusses common multilevel inverter topologies including diode-clamped, flying capacitor, and cascaded H-bridge configurations.
This document provides an overview and summary of a book titled "High-Power Converters and AC Drives" by Bin Wu and Mehdi Narimani. The book covers topics related to high-power semiconductor devices, multipulse rectifiers, multilevel voltage source converters, PWM current source converters, and their applications in high-power AC drives. It includes detailed information on converter configurations, modulation schemes, harmonic analysis, and control strategies.
This chapter discusses digital control systems. It describes the components of a digital control loop including digital controllers, analog-to-digital converters (ADCs), and digital-to-analog converters (DACs). ADCs convert analog signals to digital words, while DACs convert digital words to analog signals. Proper sampling and holding is required for interfacing between analog and digital systems. The sampling frequency must be high enough to avoid aliasing, with a recommended rate of 6-25 times the bandwidth of the controlled process.
This document discusses using a phase-locked loop (PLL) to control the speed of a DC motor. A PLL synchronizes the frequency of a voltage-controlled oscillator (VCO) to the frequency of an input reference signal. For motor speed control, the VCO is replaced by the combination of the DC motor and speed encoder, which generates a feedback signal proportional to motor speed. A phase detector compares this feedback signal to the reference frequency, and the output filters and converts the phase difference into control pulses for the motor driver. This allows the motor speed to be precisely synchronized to a multiple of the reference frequency, enabling accurate digital speed control.
This document summarizes different types of stepper motors, including variable reluctance, permanent magnet, and hybrid stepper motors. It describes their construction, working principles, modes of operation like single phase ON, two phase ON, and half step modes. It also discusses static characteristics like torque vs step angle/current and dynamic characteristics like pull in and pull out. Finally, it lists some common industrial applications of stepper motors such as in printers, disk drives, machine tools, robotics, and tape drives.
This document discusses transmission lines and HVDC transmission. It defines a transmission line as consisting of two or more parallel conductors used to connect a source to a load. The key parameters of transmission lines are resistance, inductance, capacitance, and conductance per unit length. Transmission lines are used to transfer energy, signals, or power from a transmitter to a receiver. Common types include parallel wires, twisted pair wires, ribbon cables, coaxial cables, and waveguides. HVDC transmission has advantages over HVAC like improved controllability of power flow and ability to transmit power over long distances. HVDC systems convert AC to DC using rectifiers, transmit DC power, and then convert it back to AC using in
This ppt gives the basic idea about multilevel inverter.this ppt includes
1.Introduction
2.Advantages of multilevel inverters
3.Types of multilevel inverters
4.Working of multilevel inverters
5.Applications.
This document discusses auto-reclosing, which is a protective relay scheme used on overhead transmission lines. It aims to quickly reclose circuit breakers after faults to restore power supply while avoiding permanent faults. The document describes the different types of faults, steps for auto-reclosing installation and operation, schemes of operation including live bus/dead line charging. It also discusses factors to consider like protection characteristics, circuit breaker characteristics and types of auto-reclosing like medium voltage and high voltage auto-reclosing. Benefits of auto-reclosing include minimizing power interruptions and maintaining system stability and integrity.
This document discusses power control and power flow analysis for high voltage direct current (HVDC) transmission. It describes various methods of power control, including using a current order derived from reference power divided by DC voltage. It also discusses power flow analysis techniques like Newton's method and fast decoupled load flow method that are used to simulate power systems and design optimal power flow models. The document concludes that key concepts of power control systems were covered, including current order, VDCOL control, and supervisory control methods.
This document provides an overview of power system stability, including various types of stability issues like rotor angle stability, voltage stability, and small signal stability. It defines key concepts, classifies stability into different categories, and describes factors that affect stability issues like voltage stability. Analysis techniques for different stability problems are discussed, like transient stability analysis, PV curves for voltage stability assessment, and eigenvalue analysis for small signal stability. The role of controls like power system stabilizers is also mentioned.
Torque Production & Control of Speed in Synchronous Motor.
Speed of synchronous motors can be controlled using two methods called open loop and close loop control.
Open loop contol is the simplest scalar control method where motor speed is controlled by independent frequency control of the converter.
In case of close loop self control mode, instead of controlling the inverter frequency independentaly, the frequency and the phase of the output waveform are controlled by an absolute position encoder mounted on the machine shaft giving an account of position of the rotor.
Digital signal processing based on motor control pptboga manisha
This document discusses digital signal processing (DSP) based motor control using the TMS320C240 DSP controller. It provides an overview of DSP and motor control trends, describes the TMS320 family and TMS320C240 controller, and discusses AC induction motors and different control methods like scalar and vector control. Vector control methods like field oriented control are highlighted as providing faster response, four quadrant speed control, and reduced motor size and power consumption. The conclusion states that the TMS320C240 DSP controller allows for intelligent control approaches to reduce system costs and improve drive system reliability.
This document outlines the design of a 200 Watt, 150 Vrms PWM bipolar inverter with the following key points:
1. The design process includes calculating component values based on design requirements, building the circuit in Multisim software, and analyzing the simulation results.
2. Key calculations include determining the required DC bus voltage to achieve the 150Vrms AC output voltage despite voltage drops, as well as component sizing based on the given power, modulation index, and carrier frequency specifications.
3. Simulation results show the generated PWM switching signals and the final inverter output voltage matching the desired 150Vrms sinusoidal waveform.
Different transformations and reference
frame theory, modeling of induction machines, voltage fed inverter
control-v/f control, vector control, direct torque and flux
control(DTC).
The concept of FACTS (Flexible Alternating Current Transmission System) refers to a family of power electronics-based devices able to enhance AC system controllability and stability and to increase power transfer capability.
1) The document describes different types of nonlinearities that can occur in systems. It classifies nonlinearities based on their magnitude (incidental or intentional) and frequency (limit cycles, jump resonance, etc.).
2) Some common types of nonlinearities described include saturation, dead zones, backlash, relays, harmonics, and chaotic behavior.
3) Nonlinearities can cause issues like degradation of system performance, limit cycles, and even destabilization of systems. Understanding different nonlinear effects is important for analyzing system behavior.
Series & shunt compensation and FACTs Deviceskhemraj298
Series compensation is used to improve the performance of extra high voltage transmission lines by connecting capacitors in series with the line. It allows for increased transmission capacity and improved system stability by reducing the phase angle between sending and receiving end voltages for the same power transfer. Shunt compensation controls the receiving end voltage by connecting shunt capacitors or reactors to meet reactive power demand and prevent voltage drops or rises. Flexible AC transmission systems use high-speed thyristors to switch transmission line components like capacitors and reactors to control parameters like voltages and reactances to optimize power transfer.
This document provides an overview of voltage source converters (VSC) for high voltage direct current (HVDC) transmission. It discusses the components and operation of VSC-HVDC systems, including different converter configurations like two-level, three-level, and modular multi-level converters. It also compares VSC-HVDC to conventional HVDC systems using line-commutated converters, noting advantages of VSC-HVDC like eliminating the need for reactive power compensation and reducing the risk of commutation failures.
Pulse-Width Modulation (PWM) techniques are used to control output voltages of power converters. There are three main PWM methods: Sine PWM uses a reference sine wave compared to a triangular carrier wave to generate PWM signals; Hysteresis PWM uses a feedback control loop with variable switching frequency to maintain output within a hysteresis band; Space Vector PWM approximates the reference voltage vector using combinations of the eight switching states and their durations to reduce harmonic distortion and improve voltage utilization.
This document provides an introduction to multilevel inverters. It begins by defining power electronics as the field dealing with conversion and control of electric power across a wide range of power scales. It then discusses different types of power converters including rectifiers, cycloconverters, choppers, and inverters. The document focuses on inverters, explaining that they convert DC to AC with adjustable frequency, phase and amplitude. It provides examples of two-level and multilevel inverters, describing their components and operation. The benefits of multilevel inverters for medium voltage applications are outlined. Finally, it discusses common multilevel inverter topologies including diode-clamped, flying capacitor, and cascaded H-bridge configurations.
This document provides an overview and summary of a book titled "High-Power Converters and AC Drives" by Bin Wu and Mehdi Narimani. The book covers topics related to high-power semiconductor devices, multipulse rectifiers, multilevel voltage source converters, PWM current source converters, and their applications in high-power AC drives. It includes detailed information on converter configurations, modulation schemes, harmonic analysis, and control strategies.
This chapter discusses digital control systems. It describes the components of a digital control loop including digital controllers, analog-to-digital converters (ADCs), and digital-to-analog converters (DACs). ADCs convert analog signals to digital words, while DACs convert digital words to analog signals. Proper sampling and holding is required for interfacing between analog and digital systems. The sampling frequency must be high enough to avoid aliasing, with a recommended rate of 6-25 times the bandwidth of the controlled process.
This document discusses using a phase-locked loop (PLL) to control the speed of a DC motor. A PLL synchronizes the frequency of a voltage-controlled oscillator (VCO) to the frequency of an input reference signal. For motor speed control, the VCO is replaced by the combination of the DC motor and speed encoder, which generates a feedback signal proportional to motor speed. A phase detector compares this feedback signal to the reference frequency, and the output filters and converts the phase difference into control pulses for the motor driver. This allows the motor speed to be precisely synchronized to a multiple of the reference frequency, enabling accurate digital speed control.
This document summarizes different types of stepper motors, including variable reluctance, permanent magnet, and hybrid stepper motors. It describes their construction, working principles, modes of operation like single phase ON, two phase ON, and half step modes. It also discusses static characteristics like torque vs step angle/current and dynamic characteristics like pull in and pull out. Finally, it lists some common industrial applications of stepper motors such as in printers, disk drives, machine tools, robotics, and tape drives.
This document discusses transmission lines and HVDC transmission. It defines a transmission line as consisting of two or more parallel conductors used to connect a source to a load. The key parameters of transmission lines are resistance, inductance, capacitance, and conductance per unit length. Transmission lines are used to transfer energy, signals, or power from a transmitter to a receiver. Common types include parallel wires, twisted pair wires, ribbon cables, coaxial cables, and waveguides. HVDC transmission has advantages over HVAC like improved controllability of power flow and ability to transmit power over long distances. HVDC systems convert AC to DC using rectifiers, transmit DC power, and then convert it back to AC using in
This ppt gives the basic idea about multilevel inverter.this ppt includes
1.Introduction
2.Advantages of multilevel inverters
3.Types of multilevel inverters
4.Working of multilevel inverters
5.Applications.
This document discusses auto-reclosing, which is a protective relay scheme used on overhead transmission lines. It aims to quickly reclose circuit breakers after faults to restore power supply while avoiding permanent faults. The document describes the different types of faults, steps for auto-reclosing installation and operation, schemes of operation including live bus/dead line charging. It also discusses factors to consider like protection characteristics, circuit breaker characteristics and types of auto-reclosing like medium voltage and high voltage auto-reclosing. Benefits of auto-reclosing include minimizing power interruptions and maintaining system stability and integrity.
This document discusses power control and power flow analysis for high voltage direct current (HVDC) transmission. It describes various methods of power control, including using a current order derived from reference power divided by DC voltage. It also discusses power flow analysis techniques like Newton's method and fast decoupled load flow method that are used to simulate power systems and design optimal power flow models. The document concludes that key concepts of power control systems were covered, including current order, VDCOL control, and supervisory control methods.
This document provides an overview of power system stability, including various types of stability issues like rotor angle stability, voltage stability, and small signal stability. It defines key concepts, classifies stability into different categories, and describes factors that affect stability issues like voltage stability. Analysis techniques for different stability problems are discussed, like transient stability analysis, PV curves for voltage stability assessment, and eigenvalue analysis for small signal stability. The role of controls like power system stabilizers is also mentioned.
Torque Production & Control of Speed in Synchronous Motor.
Speed of synchronous motors can be controlled using two methods called open loop and close loop control.
Open loop contol is the simplest scalar control method where motor speed is controlled by independent frequency control of the converter.
In case of close loop self control mode, instead of controlling the inverter frequency independentaly, the frequency and the phase of the output waveform are controlled by an absolute position encoder mounted on the machine shaft giving an account of position of the rotor.
Digital signal processing based on motor control pptboga manisha
This document discusses digital signal processing (DSP) based motor control using the TMS320C240 DSP controller. It provides an overview of DSP and motor control trends, describes the TMS320 family and TMS320C240 controller, and discusses AC induction motors and different control methods like scalar and vector control. Vector control methods like field oriented control are highlighted as providing faster response, four quadrant speed control, and reduced motor size and power consumption. The conclusion states that the TMS320C240 DSP controller allows for intelligent control approaches to reduce system costs and improve drive system reliability.
This document outlines the design of a 200 Watt, 150 Vrms PWM bipolar inverter with the following key points:
1. The design process includes calculating component values based on design requirements, building the circuit in Multisim software, and analyzing the simulation results.
2. Key calculations include determining the required DC bus voltage to achieve the 150Vrms AC output voltage despite voltage drops, as well as component sizing based on the given power, modulation index, and carrier frequency specifications.
3. Simulation results show the generated PWM switching signals and the final inverter output voltage matching the desired 150Vrms sinusoidal waveform.
This document describes a 1Ф PWM sine wave inverter project. It focuses on converting DC to pure AC sine wave output. The methodology uses low voltage DC to low voltage AC conversion followed by step up to high voltage AC. The key blocks include a sine wave generator, triangle wave generator, MOSFET bridge, driver and filter to generate a pure sine wave output. Inverters are useful for powering devices from batteries or solar panels through AC power.
This document summarizes a MATLAB simulation of an SPWM inverter using bipolar and unipolar switching strategies. The objective is to analyze the output voltage using FFT. It describes how the SPWM technique works by comparing a reference sine wave to a high frequency triangular carrier wave to generate PWM signals. Circuit diagrams and output waveforms are shown for both bipolar and unipolar inverters, and FFT analysis is performed. The conclusion is that a unipolar inverter with a filter provides a more sinusoidal output waveform than a bipolar inverter.
Sinusoidal PWM has been a very popular technique used in AC motor control. This is a method that employs a triangular carrier wave modulated by a sine wave and the points of intersection determining the switching points of the power devices in the inverter.
The document discusses pulse width modulation (PWM) variable speed drives that are increasingly used in industrial applications. It describes how PWM is used to generate variable voltage and frequency for AC drives from a three-phase voltage source inverter. Space vector PWM (SVPWM) is highlighted as it provides superior harmonic quality and larger modulation range compared to sinusoidal PWM. SVPWM represents the inverter states as voltage space vectors to calculate duty cycles for adjacent vectors and zero vectors to synthesize the desired output voltage vector. The document outlines the theory of SVPWM and compares different sequencing methods. It also discusses simulations and advantages of PWM including proportional average value, fast switching, noise resistance and less heat.
PWM adalah teknik modulasi lebar pulsa yang digunakan untuk mentransfer data telekomunikasi atau mengatur tegangan sumber konstan dengan menghasilkan tegangan rata-rata yang berbeda. PWM bekerja dengan memanipulasi lebar pulsa sinyal atau tegangan dalam periode tertentu. Ada dua jenis PWM, analog dan digital, dengan digital memiliki resolusi berdasarkan bitnya. Aplikasi PWM meliputi keluaran perangkat, masukan kendali perangkat,
The chapter discusses various types of pulse modulation techniques including pulse amplitude modulation (PAM), pulse width modulation (PWM), pulse position modulation (PPM), and pulse code modulation (PCM). PAM varies the amplitude of pulses based on the analog signal, PWM varies the width of pulses, PPM varies the position of pulses, and PCM converts the analog signal to a digital code using sampling and quantization. Digital communication through pulse modulation offers advantages like easier reception, less signal corruption over distance, ability to clean up noise and amplify signals, security through coding, and ability to store signals.
Pulse modulation techniques can encode an analog signal for transmission. This document discusses several techniques including:
- Pulse-amplitude modulation (PAM) which varies pulse amplitudes based on sample values of the message signal.
- Pulse code modulation (PCM) which assigns a binary code to each analog sample. PCM is commonly used in digital communications systems.
- Delta modulation which transmits one bit per sample indicating if the current sample is more positive or negative than the previous. It requires higher sampling rates than PCM for equal quality.
Pulse width modulation (PWM) is a more efficient technique than linear control for driving solenoids. PWM works by turning the signal on for part of its period and off for the rest, varying the duty cycle. If the duty cycle is shorter than the solenoid's rise time, the current will be discontinuous and not reach its maximum; if longer, the current will be continuous but have ripple. At high frequencies, the current becomes essentially constant by adjusting the duty cycle. Dither can also be added to counter stiction and hysteresis in hydraulic valves, producing small vibrations in the solenoid current. High frequency PWM allows independent control of current level and dither properties.
The document analyzes and compares three research reports related to MBA programs. It examines the structure, content, and organization of each report. The reports are evaluated based on their inclusion of sections like introduction, literature review, methodology, findings, and conclusion. Their language, tone, literature review components, and data analysis approaches are also assessed. Tables are included to summarize the presence or absence of key elements in each report. The analysis provides a framework for understanding the structure and components of effective research reports.
PWM is used to control motor speed and light dimming by varying the duty cycle of an output waveform. It can be generated using a timer, comparator, and waveform generator. The timer increments at a set rate while the comparator monitors the timer value and outputs a pulse while the timer is less than the compare value set by the output compare register. Different PWM modes and registers control aspects like waveform, frequency, and output compare functionality.
This document compares 1-phase cascaded and multilevel diode clamped leg inverters (MLDCLI) using pulse width modulation (PWM) control methods. It discusses that MLDCLI can significantly reduce switch count compared to cascaded H-bridge inverters as the number of voltage levels increases. The document presents performance analysis of a seven level MLDCLI based on sine and space vector PWM control techniques using MATLAB/SIMULINK simulations. Key performance parameters like waveform pattern, harmonic spectrum, fundamental value, and total harmonic distortion are analyzed.
Kevin Power Solutions Ltd. was established in 2004 and manufactures inverters, solar charge controllers, and UPS systems in India. It is recognized as a prominent manufacturer of sine wave inverters. The company's IGBT-based UPS systems provide pure sine wave output which is safer for electronics than distorted output from other brands. Kevin also produces DSP sine wave inverters for industrial applications from 2.5 to 60 KVA. The document further describes the features and specifications of Kevin's product lines and lead-acid batteries.
The document describes the Van de Graff generator, which uses a moving belt to generate very high voltages. It was invented in 1929 and can now produce voltages up to 5 megavolts. It works by using combs to impart negative charges to a moving belt from a grounded lower electrode and transfer those charges to an upper electrode and metal sphere at high voltage. Applications include accelerating subatomic particles for nuclear reactions and medical cancer treatments. However, it produces very low current, is costly to maintain due to its large size, and has limitations in the maximum voltage it can generate due to air ionization.
The document describes two types of electrostatic generators: the Wimshurst machine and the Van der Graaf generator. The Wimshurst machine uses two plastic discs that generate static electricity through friction as they spin, storing opposite charges in two Leyden jars. The Van der Graaf generator uses a motorized rubber belt to continuously charge a hollow metal sphere to very high voltages through induction, causing sparks to form when objects touch the sphere.
Goals of a well designed inverter,Application,Types of power conveter,Introduction to inverters,Properties of an ideal inverter, Block diagram of an inverter ,Pulse Width Modulation,Inverter operation
This document summarizes research on pulse width modulation (PWM) techniques for three-phase inverters. It describes sinusoidal PWM switching schemes that allow control of output voltage magnitude and frequency. Simulation models of three-phase inverters using sawtooth and triangular carrier waveforms are presented and analyzed. The results show that a sawtooth carrier waveform produces a more appropriate three-phase voltage waveform compared to a triangular carrier waveform. In conclusion, sinusoidal PWM inverters can generate clean sinusoidal output voltages through comparison of reference and carrier signals to control switching.
Analysis and Implementation of Unipolar PWM Strategies for Three Phase Cascad...IJAAS Team
This paper presents unipolar pulse width modulation technique with sinusoidal sampling pulse width modulation are analyzed for three-phase five-level, seven-level, nine-level and eleven-level cascaded multi-level inverter. The unipolar PWM method offers a good opportunity for the realization of the Three-phase inverter control, it is better to use the unipolar PWM method with single carrier wave compared to two reference waves. In such case the motor harmonic losses will be considerably lower.The necessary calculations for generation of unipolar pulse width modulation strategies have presented in detail. The unipolar SPWM voltage switching scheme is selected in this paper because this method offers the advantages of effectively doubling the switching frequency of the inverter voltage. The cascaded multi level inverter fed induction motor is simulated and compared the total harmonic distroction for all level (five-level, seven-level, nine-level and elevel-level)of the inverter. Theoretical investigations were confirmed by the digital simulations using MATLAB/SIMULINK software.
PWM control techniques for three phase three level inverter drivesTELKOMNIKA JOURNAL
In this paper two very efficient pulse width modulation techniques were discussed named Sin pulse width modulation and space vector pulse width modulation. The basic structure of the three-level inverter neutral-point clamped is introduced and the basic idea about space vector pulse width modulation for three-level voltage source inverter has been discussed in detail. Nearest three vectors space vector pulse width modulation control algorithm is adopted as the control strategy for the three phase three level NPC inverter in order to compensate the neutral-point shifting. Mathematical formulation for calculating switching sequence has determined. Comparative analysis proving superiority of the space vector pulse width modulation technique over the conventional pulse width modulation, and the results of the simulations of inverter confirm the feasibility and advantage of the space vector pulse width modulation strategy over sin pulse width modulation in terms of good utilization of dc-bus voltage, low current ripple and reduced switching frequency. Space vector pulse width modulation provides advantages better fundamental output voltage and useful in improving harmonic performance and reducing total harmonic distortion.
The power electronics device which converts DC power to AC power at required output voltage and frequency level is known as inverter. Multilevel inverter is to synthesize a near sinusoidal voltage from several levels of dc voltages. In order to maintain the different voltage levels at appropriate intervals, the conduction time intervals of MOSFETS have been maintained by controlling the pulse width of gating pulses. In this paper single phase to three phase power conversion using PWM technique. The simulation is carried out in MATLAB/Simulink environment which demonstrate the feasibility of proposed scheme.
This paper presents investigation and performance analysis of novel down sampling based clamping SV PWM technique for diode and cascaded Multi-level Invereter fed to Induction motor drive. A novel down sampling based clamping SVPWM has developed by adding triangular off set to sinusoidal fundamental waveform is modified by down sampling the reference wave by order of 10 so this technique is called clamping space vector pulse width modulation techniques such as PD, POD and APOD. so as to shift the lower order harmonics to higher order side. This novel carrier is compared with the offset injected space vector reference waveform to generate the required PWM pulses to the inverter. To analyze the performance of the proposed PWM technique it is implemented on seven level diode and cascaded Multi-level Inverter using Matlab/Simulink software tool for output line, phase voltage, currents, speed, torque and Total harmonic distortion analysis.
Multilevel inverters have become more popular over the years in electric high power application
with the promise of less disturbances and the possibility to function at lower switching frequencies than
ordinary two-level inverters. This paper presents information about several multilevel inverter topologies,
such as the Neutral-Point Clamped Inverter and the Cascaded Multi cell Inverter. These multilevel
inverters will also be compared with two-level inverters in simulations to investigate the advantages of
using multilevel inverters. Modulation strategies, component comparison and solutions to the multilevel
voltage source balancing problem will also be presented in this work.
Keywords — multilevel, Neutral-clamped, PWM.
Investigation of THD for Cascaded Multi-Level Inverter Using Multicarrier Mod...IJERA Editor
This document summarizes an investigation into the total harmonic distortion (THD) of cascaded multi-level inverters using different multicarrier modulation techniques. It describes three modulation techniques - phase shifted multicarrier modulation (PSHM), level shifted multicarrier modulation (LSHM), and wave level shifted multicarrier modulation (WLSHM). Simulation results for 7-level, 9-level, 11-level, and 13-level inverters show that WLSHM achieves the lowest THD compared to the other techniques. The document concludes that WLSHM is the best modulation method for reducing THD in cascaded multi-level inverters.
This document presents research on a cascaded nine-level inverter using pulse width modulation (PWM) and hybrid PWM techniques. It describes the topology and operation of a cascaded multilevel inverter using H-bridge cells. Phase shifted PWM and a hybrid modulation strategy are analyzed for controlling the inverter. Simulation results show the line voltage, phase voltage, and load current waveforms for both modulation methods. Total harmonic distortion is calculated, showing 17.44% for phase shifted PWM and 9.92% for hybrid PWM modulation. The hybrid method achieves lower distortion by operating higher voltage cells at lower switching frequencies.
This document summarizes a research paper on fuzzy control of a multicell converter. It begins with an introduction to stacked multicell converters, which allow sharing of voltage and current stresses across switches. It then discusses the topology and operation of the multicell converter. Sinusoidal pulse width modulation is used to control the output voltage. Fuzzy logic control is then proposed to control the RMS voltage value using MATLAB. Simulation results show that total harmonic distortion is reduced with increasing voltage levels in the multicell converter output waveform. Open and closed loop control of a 6x2 multicell converter are analyzed through MATLAB simulation.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology.
Matlab Simulink Model of Sinusoidal PWM For Three-Phase Voltage Source Inverterijtsrd
This paper concentrates on modeling and simulation of single phase inverter as a frequency changer modulated by sinusoidal Pulse Width Modulation PWM technique. An inverter is a circuit that converts DC sources to AC sources. To judge the quality of voltage produced by a PWM inverter, a detailed harmonic analysis of the voltage waveform is done. Pulse width modulated PWM inverters are among the most used power-electronic circuits in practical applications. These inverters are capable of producing ac voltages of variable magnitude as well as variable frequency with less harmonic distortion. The model is executed utilizing MATLAB Simulink software with the SimPower System Block Set using PC simulation. MATLAB Simulink is a successful instrument to examine a PWM inverter. Major reasons for using MATLAB are Faster reaction, accessibility of different simulation devices and the nonappearance of joining issues. In this paper, Insulated Gate Bipolar Transistor IGBT is used as switching power device. IGBT is ideal since it high switching speed and also high input impedance. Finally a MATLAB SIMULINK model for the SPWM is presented. Various simulation results are also included. Asha Durafe "Matlab/Simulink Model of Sinusoidal PWM For Three-Phase Voltage Source Inverter" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-6 , October 2018, URL: http://www.ijtsrd.com/papers/ijtsrd18614.pdf
Harmonic comparisons of various pwm techniques... A reportSaquib Maqsood
Abstract: Cascaded inverters are ideal for connecting renewable energy sources with an AC grid, because of the need for separate dc sources, which is the case in applications such as photovoltaic or fuel cells. The inverter could be controlled to either regulate the power factor of the current drawn from the source or the bus voltage of the electrical system where the inverter was connected. The modulation techniques are crucial in operating any inverter at desired conditions. In this work different PWM techniques are implemented for five level cascaded multilevel inverter and THD variation is analyzed.
IRJET- Analysis of Sine Pulse Width Modulation (SPWM) and Third Harmonic Puls...IRJET Journal
This document analyzes and compares sine pulse width modulation (SPWM) and third harmonic pulse width modulation (THPWM) techniques for a three-phase voltage source inverter (VSI). It discusses how these modulation techniques work, their effect on harmonic content in the output waves, and simulations conducted in MATLAB. The key findings are:
1) THPWM allows for 15.5% greater utilization of the DC bus voltage compared to SPWM, leading to higher fundamental output voltage.
2) Simulation results show THPWM achieves lower total harmonic distortion (THD) in both the output voltages and currents compared to SPWM.
3) The minimum current THD for both techniques occurred at a carrier frequency
The document describes pulse width modulation (PWM) and pulse position modulation (PPM) circuits. It discusses using an op-amp comparator circuit and 555 timer in monostable mode to generate PWM signals. For PPM, the document proposes using the PWM output from the first 555 timer to trigger a second 555 timer in monostable mode, producing a pulse position modulated output. The aim is to study these modulation techniques experimentally by building the circuits and observing the output waveforms on an oscilloscope while varying modulation parameters.
Optimized Hybrid Phase Disposition PWM Control Method for Multilevel InverterIDES Editor
This paper presents a new variation of hybrid
phase disposition pulse width modulation technique suitable
for cascaded multilevel inverter. A hybrid PDPWM is
developed based on low frequency PWM and high
frequency Sinusoidal PWM. An optimized sequential
switching scheme introduced in this proposed method to
equalize electro static and electro magnetic stress among the
power devices. It is confirmed that the proposed technique
offers significantly lower switching losses and switching
transitions. Furthermore, the proposed hybrid PDPWM
offers better harmonic performance compared to its
conventional PWM counterpart. Simulation results are
included in this paper in order to confirm the effectiveness
of the proposed technique.
This document presents space vector based generalized discontinuous pulse width modulation (GDPWM) algorithms for voltage source inverter (VSI) fed induction motor drives. The proposed algorithms aim to reduce the complexity of sector identification and angle calculation involved in conventional space vector PWM (CSVPWM). GDPWM uses the concept of imaginary switching times and variables like modulation phase angle δ and constant μ to generate modulation waveforms. Simulation results in MATLAB/Simulink show that the proposed GDPWM algorithms reduce current ripple compared to CSVPWM and different GDPWM sequences produce different total harmonic distortion levels in the motor current.
Simulation of 3-phase matrix converter using space vector modulationIJECEIAES
This paper illustrates the simulation of 3-phase matrix converter using Space Vector Modulation (SVM). Variable AC output voltage engendered using matrix converter with bidirectional power switches controlled by appropriate switching pulse. The conventional PWM converter engenders switching common mode voltage across the load system terminals, which cause to common mode current and its leads to bearing failure in load drive. These problems can be rectified using SVM and which minimize the effect on the harmonic fluctuation in AC output voltage and stress on the power switch is reduced using bidirectional switch for proposed 3-phase matrix converter. The simulation results have been presented to validate the proposed system using matlab / simulink.
Simulation Investigation of SPWM, THIPWM and SVPWM Techniques for Three Phase...IJPEDS-IAES
This document summarizes and compares three pulse width modulation techniques - sinusoidal PWM (SPWM), third harmonic injection PWM (THIPWM), and space vector PWM (SVPWM) - for a three-phase voltage source inverter. SPWM is the simplest technique but has drawbacks like higher total harmonic distortion and lower switching frequency. THIPWM provides better THD than SPWM. SVPWM shows lower THD than both SPWM and THIPWM, especially in overmodulation regions and at high frequencies. The document presents the theoretical principles, simulation models, and results of the three techniques, showing that SVPWM achieves the best performance and meets current harmonic standards.
Two leg three-phase inverters (FSTPIs) have been proposed to be used in low-power; low-cost applications because of the reduced number of semiconductor devices, and space vector pulse width modulation (SVPWM) techniques have also been introduced to control FSTPIs. However, high-performance controllers are needed to implement complicated SVPWM algorithms, which limit their low-cost applications. To simplify algorithms and reduce the cost of implementation, an equivalent scalar method for SVPWM of FSTPIs is proposed. SVPWM for FSTPIs is actually a sine PWM by modulating two sine waves of 600 phase difference with a triangle wave, but in this method third harmonics doesn’t eliminated. So as to eliminate the third harmonics we have to compose a high frequency sine wave to on existing sine waves. So such a special sine PWM can be used to control FSTPIs. The Mathematical and simulation results demonstrate the validity of the proposed method.
http://www.mathworks.com/matlabcentral/fileexchange/authors/126814
Report On diode clamp three level inverterVinay Singh
three level diode clamp inverter. that converts any type of DC ( rectified, PV cell, battery etc.) to AC supply. we made by mosfet and ardiuno . in this ppt we present the Simulink model of a three-level inverter and the hardware reort of the inverter.
also discuss about other level inverter and there THD analysis, simulink model and detail. compression between another inverter.
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1. Pulse Width Modulated Inverter Techniques
Saurabh kumar, M.Tech (Electric Drives & Power Electronics, IIT ROORKEE)
Abstract-This paper presents review of different
modulation techniques for voltage source inverter. A
variety of techniques, different in concept as naturally
sampled PWM, regular sampled PWM, delta modulation
techniques, delta sigma modulation techniques state
vector modulation and Hysteresis PWM are described
with corresponding waveform.
I. Introduction
One of the most widely utilized strategy for controlling the
A.C. output of power electronics converters is the pulse width
modulation (PWM), which varies the duty cycle (or mark
space ratio) of converter switches at a high switching
frequency to achieve target average low frequency output
voltage or current. Modulation theory has been a major
research area in power electronics for over three decades and
continues to attract considerable attention and interest. This is
not surprising since modulation is at the heart of nearly every
modern power electronic converter. There have been clear
trend in the development of PWM concept and strategies since
1970s, addressing the main objective of reduced harmonic
distortion and increased output magnitude for a given
switching frequency and development of modulation strategies
to suit different converter topology. While there have been
wealth of research investigating the modulation of DC/DC
converters the actual PWM process for these converters is
usually a simple comparison between reference waveform and
a sawtooth or triangular carrier waveform.
II. Scope of the Paper
The work presented in this paper primarily relates to medium
and high power level hard switched inverters (i.e. above 1 kW
power level). This paper considers only modulation strategies
which are appropriate for voltage source converter (VSI).
Topics covered in this paper are
1. Naturally Sampled Pulse Width Modulation
2 Regular Sampled Pulse Width Modulation
3 Delta modulation techniques
4. Delta Sigma modulation techniques
5. Space vector modulation
6. Hysteresis Pulse Width Modulation
1. Naturally Sampled Pulse Width Modulation
A. Sine-Sawtooth Modulation
The earliest and most straightforward modulation strategies is
termed as naturally sampled PWM, which compares a low
frequency target reference waveform (normally sinusoid)
against high frequency carrier waveform. In this process the
phase leg switched to upper DC rail when the reference
waveform is greater than the sawtooth carrier wave. To obtain
a sinusoidal output using this modulation strategy, the
reference waveform has the form
Where
M= modulation index with range 0<M<1
= target output frequency
= arbitrary output phase
With this type of sawtooth carrier, only the trailing edge of the
pulse varies as M varies, and hence this type of modulation is
termed trailing edge naturally sampled PWM For natural
charge of capacitors in FCMIs, this method is specially
used. A typical waveform for five level fling capacitor
inverter is shown For using PSCPWM in a flying
capacitor N -level inverter, N -1 carrier waveform is
needed which phase shifted by 2 / (N -I).
B. Sine triangle Modulation
This is more common form of naturally sampled PWM uses a
triangular carrier instead of sawtooth carrier to compare
against refrence waveform. With this type of carrier, both side
of the switched output pulse from the phase leg are modulated,
which considerably improves the harmonic performance of the
pulse train. This type of modulation is termed double-edge
naturally sampled modulation.
2. Regular Sampled Pulse Width Modulation
Regular sampled PWM control technique significantly
reduces the number of calculations required to generate
2. PWM control in real-time. It also greatly simplifies the
microprocessor software implementation, thereby
considerably reducing the on-line computing
requirements, and thus allows significantly higher
switching frequency PWM to be generated using
microprocessor techniques. In these strategies the low
frequency reference waveforms are sampled and then
held constant during each carrier interval. These sampled
values are compared against the triangular carrier
waveform to control the switching process of each phase
leg. The sampled reference waveform must change
values at either the positive or positive/negative peaks of
carrier waveform, depending on the sampling strategies.
A typical practical implementation of regular sampled
PWM is illustrated in Fig. 2. As shown in the Figure, the
sinusoidal modulating wave a is sampled at regular
intervals tl, r2 etc., and stored by a sample-and hold
circuit to produce an amplitude modulated wave b.
Comparison of b with the triangular carrier wave c
produces the points of intersection TI, T2 defining the
switching edges of the PWM pulses d. The
implementation of Fig. 2 is representative of a typical
analogue or discrete digital hardware implementation, as
shown in the diagram in Fig. 3. An important feature of
Fig. 3 is that the modulating frequency , carrier
frequency , and sampling frequency , are in general,
as shown, independent, and therefore any desired
relationship between them can be defined. The simplest
relationship is to set , and therefore to sample the
modulating wave at the carrier frequency, as shown in
Fig. 3. This result in only one sample being taken every
carrier cycle and therefore the sampled modulating wave
is kept constant throughout the carrier period resulting in
each edge of the PWM pulse being modulated equally;
commonly referred to as symmetric modulation, as
illustrated in Figs. 2 and 4. Alternatively, fs = 2fc can be
used such that two samples of the modulating wave are
taken each carrier cycle. The first sample taken at the
start of the carrier cycle is used to modulate the leading
edge of the pulse and the second sample, taken at the
middle of the carrier cycle, used to modulate the trailing
edge, resulting in asymmetric modulation, as shown in
Fig. 4. Since more samples of the modulating wave are
used to produce asymmetric PWM, the harmonic
spectrum is superior to that of symmetric PWM.
3. 2. Delta Modulation (DM) Technique
The delta modulation (DM) technique requires a very
simple circuit implementation, provides a smooth
transition between the PWM and single pulse modes of
operation and offers constant volts per Hertz operation
without the need of additional circuit complexity. Some
of the key voltage waveforms associated with the delta
modulation technique is illustrated in Fig. 5(a), (b). Fig.
5(c) shows their respective circuit implementation. In
particular, Fig. 5(a) illustrates the method by which the
DM switching function (Fig. 5(b)), applicable to the
PWM inverter, is obtained. This method utilizes a sine
reference waveform and a delta-shaped carrier
waveform is allowed to "oscillate" within a
defined "window" extending equally above and below
the reference wave . The minimum "window" width
and the maximum carrier slope determine the maximum
switching frequency of the inverter switchers ,
Therefore, when setting values for these two parameters,
care should be taken so that sufficient time is provided
for the proper turn-on and turn-off of and . Fig.
5(b) shows the DM switching function which
describes the operation of switching elements and
. The subscript of the element that is gated at any
instance is indicated by the sequence of ones and twos
shown in Fig. 5(b). The temporal relation between the
gating sequence of elements and the waveform of
the DM switching function VI yields that the inverter
phase voltage , and have the same waveforms.
Fig. 5(c) depicts a circuit that is capable of producing the
waveforms shown in Figs. 5(a) and 5(b). This circuit
operates in the following manner. Sine reference wave
is supplied to the input of the comparator while
carrier wave VF is generated by the integrator as
follows: whenever the output of exceed the upper or
lower “window” boundaries (which are preset by the
ratio), comparator A 1 reverses the polarity of at
the input of . This action reverses the slope of VF at
the output of , thus forcing to "oscillate" around
the reference waveform at ripple frequency r. This
forced oscillation ensures that the fundamental
component of (i.e. ) and reference wave have
the same amplitudes and that the dominant harmonics of
and waveforms oscillate at frequencies close to
the ripple frequency r.
3. Delta Sigma modulation techniques
The delta-sigma modulator is effectively applied to a
voltage source inverter system with PWM pattern
generating scheme. The major feature of delta-sigma
modulator is the inherent nature of spread spectrum
characteristic in addition to simple configuration
scheme. Besides, delta-sigma modulator can be
considered as a sort of error amplifier. If the inverter
circuit is taken into feedback loop as a quantizer,
external DC voltage disturbances can be reduced in the
output side of inverter.
4. Space vector modulation
Multiphase motor drives are a very promising
technology, especially for medium and high power
ranges. As known, a multiphase motor drive cannot be
analyzed using the space vector representation in a
single d-q plane, but it is necessary to introduce multiple
d-q planes. So far a general space vector modulation for
multiphase inverters is not available due to the inherent
4. difficulty of synthesizing more than one independent
space vector simultaneously in different d-q planes The
basic scheme of a three-phase inverter is shown in Fig.
6. The signals are switch commands of the
three inverter branches, and can assume only the values
0 or 1. The inverter output pole voltages are
Where is the dc-link voltage.
The main problem is to control the load phase voltages
and according to the requirements
imposed by the application, e.g. vector control of ac
machines. An elegant solution to this problem is the
space vector representation of the load voltages, which
describes the inverter pole voltages introducing a space
vector and a zero sequence component as
follows:
(2)
(3)
Where the coefficients k=1,2,3) are defined as follows:
(4)
The space vector and the zero sequence components can
be expressed as functions of s1, s2 and s3 by substituting
(1) in (2) and (3).
(5)
(6)
It is well-known that the load voltages depend only on
the space vector of the pole voltages, whereas the
inverter zero sequence component affects only the
potential of the load neutral point. In other words, to
control the load, it is sufficient to control the
vector .
SVM for Three-Phase Inverters
The modulation problem consists in controlling the
switch states such that the mean values of the inverter
output voltages are equal to the desired values in any
switching period Tp. There are eight (namely )
possible configurations for a three-phase inverter,
depending on the states of the three switch commands
s1, s2 and s3. Six configurations correspond to voltage
vectors with non-null magnitudes. These vectors, usually
referred to as active vectors, are represented in Fig. 2,
where the configurations of each vector are also
expressed in the form ( . Two configurations,
i.e. and
lead to voltage vectors with null magnitudes, usually
referred to as zero vectors. The space vector modulation
selects two activevectors and applies each of them to the
load for a certain fraction of the switching period.
Finally, the switching period is completed by applying
the zero vectors. The active vectors and their duty-cycles
are determined so that the mean value of the output
voltage vector in the switching period is equal to the
desired voltage vector. The best choice is given by the
two vectors delimiting the sector in which the reference
voltage vector lies. Since two consecutive vectors differ
only for the state of one switch, this choice allows
ordering the active and the zero vectors so as to
minimize the number of switch commutations in a
switching period. For example, if the desired voltage
vector lies in sector 1, as shown in Fig. 7, the two
adjacent voltage vectors are and , whose
configurations (0,0,1) and (0,1,1) differ for only one bit.
After the active vectors have been chosen, the requested
voltage can be expressed as a combination of them as
follows:
(7)
where and are the duty-cycles of and in the
switching period.
5. The explicit expressions of and can be easily calculated
evaluating the following dot products:
(8)
(9)
(10)
(11)
Once and have been calculated, the designer can
still choose in which proportion the two zero vectors are
used to fill the switching period. Fig. 8 shows the vector
sequence corresponding to the example of Fig. 7. In the
sequence of Fig. 3, the zero vectors are equally
distributed in the switching period.
6. Hysteresis Pulse Width Modulation
Hysteresis PWM refers to the technique where the
output is allowed to oscillate within a predefined error
band, called "hysteresis band". The switching instants in
this case are generated from the vertices of the triangular
wave shown in Fig. 9. Hysteresis PWM techniques does
not require any information about the inverter load
characteristics. As long as the reference signal is known
and the inverter output voltage is not saturated, the
inverter output will always follow the reference.
However, the switching frequency of power devices is
not fixed for this technique and will vary depending on
the magnitude and frequency of the reference,. Therefore,
switching losses for this techniques can be higher
compared to other techniques.
IV CONCLUSION
In this term paper pulse width modulation inverter
techniques has been presented. Through various
modulation techniques a general hierarchical consensus
appears to have emerged from this work which ranks
space vector modulation techniques, regular sampled
modulation and sine-triangle modulation strategies in
decreasing order of merit based on harmonics
performance
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