PWM Signal Generation Research Articles

New adaptive hysteresis band width control for direct torque control of induction machine drives

This paper presents a new adaptive hysteresis band control approach used in direct torque control (DTC) of the induction motor (IM) drives with the switching tables for the generation of PWM signals. Constant Hysteresis Direct torque control (CHB-DTC) method used the torque and stator flux errors to generate the stator voltage reference and frequency vectors for controlling the three-phase induction motor. The CHB-DTC gives better torque transient performance but it has large steady state ripples. To reduce torque and stator current ripples in CHB-DTC controlled induction motor drives a new adaptive hysteresis band control (AHB) approach is proposed, where the hysteresis band is adapted in real time with the stator flux and torque errors variation, instead of fixed bandwidth. Both classical CHB-DTC method and the proposed adaptive hysteresis band DTC (AHB-DTC) fed three induction motor have been simulated using Matlab/Simulink. The simulation results at different operating conditions over a wide speed range demonstrate the validity, effectiveness, and feasibility of the proposed scheme. The measurements showed that torque ripples were significantly decrease with the new AHB-DTC technique and better speed response in step up or down compared to the CHB-DTC.

PWM signal generation for a quad-rotor with variable geometry arms

This paper presents a methodology to transform two PWM signals into four is presented to generate the motion of the arms of a quadcopter having a variable frame geometry. Each arm can rotate around each axis by arms’ actuators. The four angles describing the angular position of the arms have been introduced. Based on the different geometric configurations of arms, the pitch and roll rotation of the quadcopter is developed. The algorithm that characterizes the control’s logic is based on few assumptions derived from the structure of the joystick’s motion and the maximum PWM width that each servo can develop corresponding to the maximum rotation of the arm. A specific geometric constraint is introduced so that all possible values of two combined PWM signals can be transformed that do not violate the maximum amount of PWM signal directed to the servo. The experimental validation is built up by using a commercial hardware characterized by four servos, a rotary encoder, one control board and an oscilloscope to validate the generated signal developed by the mathematical algorithm installed on the control board.

Practical Online Modulation Method for Current Ripple and Switching Losses Reduction in the Three-Phase Voltage Source Inverters

Convectional optimal pulsewidth modulation (PWM) current ripple reduction methods divide the vector space sectors into subsectors, where the reference vector is synthesized with a theoretically optimal sequence. However, extra CPLD/FPGA is needed for the lookup table and the PWM signal generation for alternative sequences. Moreover, when swapping in between sequences, extra switching and losses are introduced, which is particularly significant for low sample ratio operations. This article starts with an intuitive perspective on the sequence for current ripple reduction. Then, an online method is proposed to dynamically compute and select the sequence with the lower current ripples throughout the vector space. The proposed stationary frame current ripple vector locus peak computation and comparison methods can be efficiently implemented in DSPs. The proposed online method is equally effective in ripple reduction as the CPLD/FPGA based offline-optimized methods. Moreover, with low sample ratio commonly used in practice, the proposed method has even less switching losses, as it avoids extra switching during the sequences swapping. Elaborate lab setup makes it possible to obtain the switching losses of the previous methods over wide ranges of motor drive operation. Thereby, the switching losses advantages of the proposed method are validated.

Developing Wide Flexible Robust PWM Driver by Flip Flop For Supporting The SMPS Technology

The limitation of the operational area of the PWM signal generator provided by the microprocessor or chip, give the opportunity to develop flip flop technology that has been widely used in digital technology as a latch, counter, register, memory and so on, will be able to be developed into a PWM driver. Flip flop technology has developed and is able to reach a very wide operational area regarding voltage and frequency variations. So in this research flip flop technology was developed as a PWM signal driver and the results were better, involving the ability to vary voltage from 6 to 60 Volts, frequencies from 2 to 81 kHz and duty cycles of 10 -75%. Furthermore, if a component with higher capability is selected, it will be able to operate in very low to very high operating areas, exceeding the capabilities of the microprocessor or chip.

Continuous dynamic sliding mode control strategy of PWM based voltage source inverter under load variations

For closed-loop controlled DC-AC inverter system, the performance is highly influenced by load variations and online current measurement. Any variation in the load will introduce unwanted periodic error at the inverter output voltage. In addition, when the current sensor is in faulty condition, the current measurement will be imprecise and the designed feedback control law will be ineffective. In this paper, a sensorless continuous sliding mode control (SMC) scheme has been proposed to address these issues. The chattering effect due to the discontinuous switching nature of SMC has been attenuated by designing a novel boundary-based saturation function where the selection of the thickness of boundary is dependent to the PWM signal generation of the inverter. In order to remove the dependency on the current sensor, a particle swarm optimization(PSO) based modified observer is proposed to estimate the inductor current in which the observer gains are optimized using PSO by reducing the estimation errors cost function. The proposed dynamic smooth SMC algorithm has been simulated in MATLAB Simulink environment for 0.2-kVA DC-AC inverter and the results exhibit rapid dynamic response with a steady-state error of 0.4V peak-to-peak voltage under linear and nonlinear load perturbations. The total harmonic distortion (THD) is also reduced to 0.20% and 1.14% for linear and non-linear loads, respectively.

A finite-time distributed cooperative control approach for microgrids

The reactive power sharing cannot be achieved using many existing microgrid (MG) control methods, and the convergence speed of these methods is slow. To solve these problems, a finite-time distributed control approach is proposed in this paper, which is based on the hierarchical control structure. The hierarchical control structure consists of dual loop control, droop control used as primary control and secondary control. Firstly, the secondary controller is modeled, and the MG system composed of distributed generators (DGs) is considered as a multi-agent system. The secondary controller consists of frequency regulator, voltage regulator and power regulator. Secondly, the adaptive virtual impedance module is established, taking the output of the reactive power regulator as its input. Thirdly, the dual loop controller is combined with primary controller and secondary controller to generate PWM signal to control the power and voltage of MG. In order to reduce the fluctuation of MG, damping module is introduced when the structure of the system changes. Finally, the stability of the proposed control strategy is proved by the related theorems. A simulation system is established in Matlab environment, and the simulation results show that the proposed method is effective.

Control Strategy to Generate PWM Signals with Stability Analysis for Dual Input Power Converter System

The prime role of a renewable resource based DC hybrid power system is, to maintain the output voltage constant with higher efficiency. In order to achieve this the duty cycles of the converter switches are dynamically controlled. Multiple input single output (MISO) converter uses separate controller for adjusting the duty cycle, this complicates the design and implementation of the system. Hence, to overcome this limitation a centralized controller is used. The control strategy depends on the pattern of gating signals given to the converter switches. When independent controller is employed, then gating signals of any pattern can be used to drive the switches. However, if a single controller is used, and then a definite pattern is very much essential otherwise, the output voltage and efficiency gets affected. In this paper, an attempt is made to validate and evaluate the performance parameters of MISO converter with two pattern of gating signals; they are synchronized and unsynchronized pulses at their rising edge. The control strategy focusses on the generation of these gating pulses. PID controller is tuned appropriately to determine the gains to achieve the stability of the proposed converter. The dual input power converter validated to show how the PWM pattern affects the efficiency, ripple and regulation of the converter. Using MATLAB SIMULINK platform the simulation of the proposed concept with dual input converter in closed loop is validated. Simulation results proves that synchronized pulses gives DC efficiency of 87% at designed output of 12V output. Converter with unsynchronized PWM pulses operates at lesser efficiency of 75% and the output voltage is of 10V.

Control Strategy to Generate PWM Signals with Stability Analysis for Dual Input Power Converter System

The prime role of a renewable resource based DC hybrid power system is, to maintain the output voltage constant with higher efficiency. In order to achieve this the duty cycles of the converter switches are dynamically controlled. Multiple input single output (MISO) converter uses separate controller for adjusting the duty cycle, this complicates the design and implementation of the system. Hence, to overcome this limitation a centralized controller is used. The control strategy depends on the pattern of gating signals given to the converter switches. When independent controller is employed, then gating signals of any pattern can be used to drive the switches. However, if a single controller is used, and then a definite pattern is very much essential otherwise, the output voltage and efficiency gets affected. In this paper, an attempt is made to validate and evaluate the performance parameters of MISO converter with two pattern of gating signals; they are synchronized and unsynchronized pulses at their rising edge. The control strategy focusses on the generation of these gating pulses. PID controller is tuned appropriately to determine the gains to achieve the stability of the proposed converter. The dual input power converter validated to show how the PWM pattern affects the efficiency, ripple and regulation of the converter. Using MATLAB SIMULINK platform the simulation of the proposed concept with dual input converter in closed loop is validated. Simulation results proves that synchronized pulses gives DC efficiency of 87% at designed output of 12V output. Converter with unsynchronized PWM pulses operates at lesser efficiency of 75% and the output voltage is of 10V.

Modeling & design of a ANN controller for a BLDC motor on Propulsion Application for Hybrid Electric Vehicle

This paper proposes the brushless direct current (BLDC) motor with high power density and high efficiency characteristics may be used to propulsion framework for electric vehicle. The progressive model for BLDC motor under rotor flux linkage route reference frame might have been providing. Here we analyzed the chart of ann vector and principal of ann control strategies and proposing the ann based reactive power with BLDC motor. To make ann based framework on active power, torque ripple, dc voltage, power factors can be used BLDC motor was designed. After designed simulation results was test the validity of field weakening based on reactive power with BLDC for electric vehicle application. In this research work will introduced artificial neural network (ANN) for non electrical input used. To control the BLDC motor speed it can using pulse width modulated control of the voltage source inverter (VLSI) using DC link voltage (Vdc) controller. To perform electronic commutation by hall signal sensing they are using PWM signal, to generate PWM signal inbuilt encoder can be used in this circuit. Analyze the BLDC motor performance driving propulsion framework is carried out under the MATLAB/Simulink software’s and efficiency of whole frame work is calculated under various source conditions

Design and Analysis of Boost DC-DC Converter with PI Controller

This paper covenants owing to the working of PI Controller fed Boost converter. As PI controller removes the delay and offers quick control, it is preferred in this paper. Out of many controllers which provide effective output, PI is chosen which eliminates the necessity for constant operator attention and instinctive control to the system. In the PI Controller, the gains Kp and Ki are calculated by Ziegler and Nichols method. This PI Controller is used as the effective controller for the Boost Converter. In this converter the output voltage is stepped up (increased) for the given input voltage. The PWM Signal generator is used for commutation purpose in the proposed circuit. The Boost converter maintains a constant voltage at the output.

PV integrated series active filter for sag voltage and harmonic compensation

<span lang="EN-US">The use of loads in the past few days is becoming vast, giving an alarm signal to the power system and electronics engineers in terms of power quality. Due to the large amount of non-linear power electronics, utilities frequently experience voltage and harmonic distortions every day. In this paper, the combination of the Series active power filter SAPF with a PV source is deliberated. The PV based on the SAPF aims to compensate voltage deviations or disturbances that occur in the system caused by power quality issues. The proposed system consists of a PV source connected to the DC link through two dc-dc converters, the first extracts the maximum power of the PV source through pulse with modulation PWM signals generated from the maximum power point tracker MPPT controller. Thus, the second converter is used to regulate the high voltage side of the converter through closed control loops using Fuzzy Logic Controller FLC, in addition to a voltage source inverter VSI and a series injection transformer. Despite of fluctuations of the DC link during the compensation of the needed energy, MPPT and closed control loops generate PWM signals to the switching devices of dc-dc boost converters in order to extract maximum PV power and to maintain the bus voltage within its limits and around its reference values respectively. The proposed topology is simulated in Matlab Simulink software, where simulation results show that the proposed PV based SAPF can efficiently reduce problems of voltage sag and harmonic.</span>

Gate Driver Circuit Design, PWM signal generation using FEZ Panda III and Arduino for Inverter

This paper presents the gate driver circuit design and PWM signal generation using FEZ panda III and Arduino boards for Inverter. FEZ panda III works on .net micro framework and all its programming, debugging features are available through Microsoft’s Visual studio whereas Arduino features are available through Arduino software. Inverters are used in various applications like in motor drives and solar and wind power applications. This paper is commenced by basic understanding of need of gate driver circuit for inverter and different types of PWM techniques for generating gate signals for inverter. Simulation of SPWM inverter in both open loop and closed loop operation is done and its respective gate voltage waveforms are studied and later hardware implementation of gate driver circuit using TLP250H IC is carried out and gate voltages at different duty cycles is studied with the help of FEZ Panda III and Arduino boards.

A Simplified PWM Strategy for Three-Level Converters on Three-Phase Four-Wire Active Power Filter

Presently, the neutral-point potential offset is an inherent problem for three-level converters on three-phase four-wire active power filters. The conventional three-dimensional space vector pulse width modulation (3-D-SVPWM) strategy is adopted as a normal solution to the problem, but the selection of space vector sectors for four-wire converter is both abstract and complicated in practice. This paper proposes a new PWM strategy accordingly to simplify the selection process and the calculation of duration. Compared to the conventional 3D-SVPWM, the proposed method locates the sector of optimal vector directly with the polarity of three-phase reference voltage. Then, by applying voltage–second balance rule, it can perform a fast calculation of the duration and generate PWM signals to control the switching devices’ on/off. As an approach to correct the imbalance dc-link capacitor voltage, this strategy reconstructs the switching sequence. A portion of state O duration is disassembled into states P and N to suppress the neutral-point potential offset. The proposed strategy is validated with a range of experiments. The results indicate that this simplified PWM strategy can effectively reduce the computational burden, and also the dc-link capacitor voltage is well controlled.

Speed Estimation Rotor Flux Vector-Controlled Induction Motor Drive with Motor Resistance Parameter Identification

In this study, a full-order flux observer-based speed estimation approach has been used to achieve rotor flux vector control (RFVC) of an induction motor (IM) drive. The RFVC IM drive was established by using stator current and rotor flux. A model reference adaptive system was utilized to identify the stator resistance parameter and the fixed trace algorithm was used to develop a rotor resistance parameter online adjustment scheme. Both proposed adaptive resistance parameter identification approaches can guarantee speed estimation and the coordinate transformation of an RFVC IM is unaffected by the motor resistance–temperature effect. The MATLAB\\Simulink toolbox was used to simulate this system and all the control algorithms were realized using a 32 bit Renesas RX62T micro-control chip to generate PWM signals for the power stage to run the motor and to validate these approaches. Both simulation and experimental results verified the effectiveness of the proposed system.

분산 제어 기법을 사용한 삼상 인버터 제어기 개발

Electric power conversion system market is expanding as renewable energy industry rapidly grows. Most of these electric power conversion systems typically ranging from 10kW to 250kW, are controlled by high speed digital signal processor. This paper proposes a three phase inverter system each arm of which is equipped with DSP together with gate driver. In existing inverters, main DSP generates PWM signals and controls all three arms. In the proposed inverter, each arm is independently self-controlled by dedicated DSP that measures phase voltage/current and generates PWM signals, according to synchronization and control reference data sent by main DSP via serial communication ie. CAN communication. The proposed controller can be used for unballenced 3phase load. The experimental results are proposed for proving the control methode.

Pulse width modulation as energy-saving strategy of shape memory alloy based smart soft composite actuator

This paper presents electrical power consumption decreased in actuating a shape memory alloy (SMA) based smart soft composite (SSC) actuator using pulse width modulation (PWM). A DC current input generator and a PWM signal generator were designed to apply inputs to SSCs. Experiments were carried out on two types of SSC: one conventional, using a single SMA wire, and the other using multiple wires. The blocking force was measured to analyze the performance of the SSC. The experiments demonstrated that the PWM signal was able to reduce the actuation energy while showing the same performance as an analog current input. These results suggest that a PWM signal could be an alternative candidate for the input paradigm for SSCs to reduce energy consumption, expanding the uses of SSC actuators in robotic applications.

FPGA-Based Reconfigurable PWM Generator for Power Electronic Converter Applications

Application of digital hardware based on FPGA in power electronic converters control systems has grew up in recent years. One of the most important issues in hardware implementation of power converters controller systems is the PWM signal generation. This issue is more important in case of multi-level converters with several carries. Implementation of these types of PWM strategies with conventional PWM peripherals in existing DSPs and microcontroller is very complicated and sometimes impossible, because existing PWM generation peripherals are based on single carrier and optimized for two-level inverter applications. This paper presents a multi-carrier-based generalized reconfigurable PWM generator hardware that can be used in power electronic converters control systems. The proposed hardware can be implemented on both FPGA and ASIC as a peripheral for a main processor. The proposed architecture can be easily configured to support several PWM strategies including conventional single-carrier and novel multi-carrier PWM techniques. The proposed hardware includes output control and programmable dead-band generator module as well. The system function selection and other configurations can be carried out using dedicated control and configuration registers. Whole architecture and internal modules are designed and implemented in Verilog HDL and simulated then synthesized and tested successfully on Altera Cyclone II FPGA using FPGA development board and laboratory prototypes. Simulation and experimental results for various types of modulation strategies are presented verifying generality and reconfigurability of the proposed hardware.

Design and Implementation of Single Phase Inverter Based on Cuk Converter for PV System

In this paper, analysis and hardware implementation of a single phase inverter based on Cuk converter for PV system is presented. The buck-boost characteristic of such a converter promotes flexibility for both grid tied as well as standalone connections where the ac voltage is either higher than or lesser than the dc input voltage. Further Cuk based topologies have the better efficiency and voltage regulation, which is a lacking feature in a basic boost or a buck configuration. The proposed system not only offers continuous input and output current but also controlled voltage over a wider range. Hence this topology can serve as an expedient alternative converter stage for photovoltaic applications. In the proposed bidirectional two-switch Cuk converter, DSPIC30F2010 controller is used for controlling the duty ratio of switching pulses. Also, this controller generates PWM signals for the switches of single phase H-bridge inverter. The hardware results for the developed prototype of a Cuk converter based single phase inverter are presented. The developed scheme can easily be scalable to a much larger rating of the PV system.

Open-circuit switch fault tolerant wind energy conversion system based on six/five-leg reconfigurable converter

In this paper, an FPGA-controlled fault tolerant back-to-back converter for DFIG-based wind energy conversion application is studied. Before an open-circuit failure in one of the semiconductors, the fault tolerant converter operates as a conventional back-to-back six-leg one. After the fault occurrence in one of the switches, the converter will continue its operation with the remaining five healthy legs. Design, implementation, simulation and experimental verification of a reconfigurable control strategy for the fault tolerant six/five leg converter used in wind energy conversion are discussed. The proposed reconfigurable control strategy allows the uninterrupted operation of the converter with minimum affection from an open-circuit switch failure in one of the semiconductors. Software reconfiguration is also necessary in PWM signal generation unit, to assure that proper gate signals are calculated and generated based on the actual five-leg structure Simulations and experimental tests are carried out and the results are presented and compared. They all confirm the capability of the studied reconfigurable control and proposed fault tolerant architecture in ensuring the system's service continuity.

On design and implementation of three phase three level shunt active power filter for harmonic reduction using synchronous reference frame theory

Shunt active power filter is commonly used to eliminate current harmonics generated in the source side due to presence of non-linear loads. This scheme consists of three phase three level diode clamped multilevel inverter and a DC capacitor that act as a shunt active power filter to mitigate the supply current harmonics and inject the required reactive power to non-linear loads. In this paper, using synchronous reference frame algorithm, a three phase three level SAPF is implemented on an embedded platform. In SRF theory, reference signals are transformed from a–b–c stationary frame to 0–d–q rotating frame. The reference signals in the 0–d–q rotating frame are controlled to get the desired reference signals using PI controller. The PWM signal generation for the three phase three level inverter is computed directly from the sampled amplitudes of the reference phase voltages. The practical implementation of the SAPF is realized using Xilinx XC3SD1800A – FG676-4 Spartan 3A DSP FPGA controller. This system is simulated using MATLAB/SIMULINK and the simulation results are compared with prototype hardware model for validating the effectiveness of the proposed system. Based on the studies, it is concluded that the SAPF is easy for implementation for reducing the Total Harmonic Distortion below 5% as per IEEE-519 standard.