Pulse Width Modulation Voltage Research Articles

Stabilizing Sets of Current PI Controllers for IM Drives With and Without LC Filter

Connection of an LC filter to the output of voltage source inverter (VSI) in squirrel cage induction motor (SQIM) drive converts the pulse-width modulated (PWM) voltages into smooth sinusoidal voltages. However, this connection may lead to closed-loop instability in the rotor flux-oriented (RFO) vector-controlled (VC) SQIM system. The closed-loop stability of the combined SQIM + LC filter (SQLC) system is complex and has not been analyzed properly in the literature. In this paper, a detailed closed-loop stability analysis of the SQLC system has been presented based on stability region (SR) and accordingly the PI gains of VC has been designed. The SR method is adopted to derive the common stability regions for the SQIM system and SQLC system. Thereby, the paper proves that connecting an LC filter in-between the VSI and the SQIM system does not always destabilize the closed-loop system. Further, for an SQLC system, the complete range of current controller gains is obtained at various operating points. The frequency-domain specifications have been used to select a proper stabilizing set and the effect of parametric variation of LC filter on the stabilizing set has also been discussed. The experimental results are provided to validate the analysis.

Considering the Parameters of Pulse Width Modulation Voltage to Improve the Signal-to-Noise Ratio of Partial Discharge Tests for Inverter-Fed Motors

The improvements in signal-to-noise ratio (SNR) are indispensable to obtain the desired output signal of partial discharge (PD) under square wave pulsewidth modulation (PWM) voltage. In this article, the effect of complex PWM voltage parameters (rise time, fall time, frequency, duty cycle) on the SNR of PD tests is investigated. The results revealed that the sensor's high-frequency gain should be increased to improve the SNR under faster switching. PD impulses are more likely to be submerged in the residual interference under high-frequency voltage. The SNR can be improved by only detecting the PD at the rising front because the PD signal overlaps with commutation noise at the falling front of short duty cycle voltage, such as 0.03% duty cycle. The above results can reference the PWM parameters and improve the SNR in PD tests for rotating machines controlled by power electronics.

Arduino-based PID Control of Humidity in Closed Space by Pulse Width Modulation of AC Voltage

My previous work explored a method for constant temperature proportional-integral-derivative (PID) control in a closed space using an Arduino. Similarly, this paper proposes a method of PID control to keep the humidity constant in a closed space using Arduino. PID control by a pulse width modulation (PWM) signal with Arduino is used to keep the humidity constant due to the heat generated by an incandescent light bulb to which an AC voltage of 100 (V) is applied. Here, the humidity is measured using the temperature/humidity sensor DHT11. Specifically, the target value of humidity is set to 30 (%), and the experimental results of P, PD, PI, and PID controls are compared from the points of quick response and stationary performance. As an evaluation of stationary performance, the mean-square value of 1,000 data of the deviation (target value – measured humidity) is calculated, and the PID control is found to be the preferred control.

An Inrush Current Limiting Method for Grid-Connected Converters Considering Grid Voltage Disturbances

To support the electric power grid, some grid-connected converters are required to ride through abnormal grid conditions, including voltage disturbances. However, at the moment, when a grid voltage disturbance happens, a large inrush current could be induced due to the large difference between the grid and converter output pulsewidth modulation (PWM) voltages. This inrush current could be more severe in the faster switching SiC-based multilevel converter, which only needs a small filter inductance to meet its normal operation requirements, such as harmonics and peak ripple currents. In this article, a PWM mask method is used to limit the inrush current. With this method, the inrush current can be effectively limited to a preset value and can help the converter ride through grid voltage disturbances. The method is validated through experiments conducted on a single-phase SiC-based five-level converter considering low voltage, high voltage, and phase angle disturbances.

A Novel High Power Hybrid Rectifier With Low Cost and High Grid Current Quality for Improved Efficiency of Electrolytic Hydrogen Production

This letter proposes a novel three-phase hybrid rectifier topology and control method for high power electrolytic hydrogen production application. It is composed of a primary rectifier, i.e., a six-pulse silicon controlled rectifier (SCR) and an auxiliary converter, including a pulsewidth modulation (PWM) voltage source converter and a phase-shift-full-bridge converter. SCR undertakes most of the power consumed by electrolysis cell, and the auxiliary converter can compensate dc current ripples and absorb ac current harmonics of primary rectifier simultaneously. Compared with high power PWM rectifier, the proposed hybrid rectifier can keep the main benefits of PWM rectifier, such as the low dc current ripple to realize improved efficiency of electrolytic hydrogen production and high grid current quality at ac side while significantly reducing the cost. The effectiveness of the proposed hybrid rectifier is verified by the simulation as well as experimental results.

A Direct Modulation for Matrix Converters Based on the One-Cycle Atomic Operation Developed in Verilog HDL

This article presents a fast direct pulsewidth modulation (PWM) algorithm for the conventional matrix converters developed in Verilog hardware description language. All PWM duty cycle calculations are performed in one cycle by an atomic operation designed as a digital module using field-programmable gate array basic blocks. The algorithm can be extended to any number of output phases. The improved version of the discontinuous direct analytic voltage PWM (DAV-PWM) method is proposed, in which the use of trigonometry, angles, and program loops has been eliminated. The proposed DAV-PWM is equivalent to the space vector modulation; it can be applied during input asymmetry and also allows for the control of the displacement input angle. The proposal has been verified using the circuit simulation in PSIM, digital structure modeling in ModelSim, and finally through an experiment.

An Improved Control Strategy of PMSM Drive System with Integrated Bidirectional DC/DC

With the development of power electronic technology, adding bidirectional DC/DC to the DC side of the motor controller has become an effective way to broaden the speed of motors. However, the motor drive system integrated with bidirectional DC/DC increases the switching loss and current harmonics of the inverter. Therefore, in this paper, a method based on fixed space vector pulse width modulation (SVPWM) modulation index and voltage instruction compensation are proposed, In this method, by considering the back electromotive force of the motor and the security margin of the weak magnetic region, the output voltage command amplitude of the current loop and the limit value of the inverter output is judged, and the optimal inverter input voltage is obtained, which effectively reduces the switching loss of the inverter, broadens the high efficient area of motor operation, and improves the efficiency of the controller. At the same time, the standardized benchmark composed of motor parameters is used to per-nit the permanent magnet synchronous motor (PMSM) mathematical model, which is helpful for the derivation of the formula and dramatically simplifies the calculation amount of the microcontroller. Moreover, the simulation and experimental results prove the effectiveness and feasibility of the algorithm.

Robust Optimal Control Design for Performance Enhancement of PWM Voltage Source Inverter.

PWM (pulse-width modulation) voltage source inverters are used in a wide range of AC power systems where the output voltage must be controlled to follow a sinusoidal reference waveform. In order to achieve precision and fast-tracking control, restrictive sliding mode control (RSMC) provides a fast system state convergence time. However, the RSMC still suffers from the chattering problem, which leads to high harmonic distortion and slow response of the inverter output state. Furthermore, the load of the inverter may be severe load changing and the control parameters become difficult to adjust, worsening the adaptability to achieve the desired control of the inverter output. In this paper, a robust optimal control design comprised of an enhanced restrictive sliding mode control (ERSMC) and density particle swarm optimization (DPSO) algorithm is proposed, and then applied to PWM voltage source inverters. The ERSMC not only has finite time convergence but also provides chatter elimination. The DPSO is highly adaptable for acquiring the control parameters of the ERSMC and finding the best solution in the global domain. The proposed controller is realized for the actual PWM voltage source inverter controlled by a TI DSP-based development platform, so that the inverter output voltage has fast dynamic response and satisfactory steady-state behavior despite high load changing and non-linear disturbances.

Photovoltaic‐based grid‐connected transformer‐less three‐phase cascaded diode‐clamped multilevel inverter with reduced leakage current

AbstractA photovoltaic (PV) transformer‐less grid‐connected cascaded diode‐clamped half‐bridge multilevel inverter (MLI) is presented in this paper. Compared with the conventional cascaded H‐bridge (CHB) multilevel inverter, the projected inverter permits connection of double the DC‐link voltage and hence enhances its rating. The most common problem the PV‐based transformer‐less grid‐connected CHB MLI system faces is the flow of leakage currents created by parasitic capacitances due to the disparity in common‐mode voltage. As per the German standards VDE‐V‐0126‐1‐1, the leakage current must be less than 30 mA. In the proposed inverter, due to the high‐frequency pulse width modulation of voltage, a peak leakage current flow of nearly 300 mA at switching frequency (2500 Hz) and about 150 mA at its subsequent harmonics is observed. Therefore, LC‐filters are employed in the proposed inverter to suppress the peak leakage currents to less than 3 mA. Also, the LC‐filters improve the total harmonic distortion (THD) profile of the injected grid current. Further, the proposed inverter is also designed to address the temporary faults. The proposed transformer‐less inverter is simulated using the MatLab/Simulink platform, and the results are experimentally validated by performing on a real‐time hardware‐in‐the‐loop using OPAL‐RT OP5700 digital simulator as plant and dSPACE 1202 as controller.

Fast Calculation of Electromagnetic Forces in IPMSMs Under PWM VSI Supply Based on Small-Signal Time-Harmonic Finite Element Method

This paper introduces a novel method for fast calculating the electromagnetic forces in interior permanent magnet synchronous machines (IPMSMs) under pulse width modulation (PWM) voltage source inverter (VSI) supply based on the small-signal time-harmonic finite element analysis (THFEA), which has been successfully utilized for fast calculating the PWM-induced losses in silicon steel sheets and permanent magnets. Based on the small-signal THFEA, the functional relationships between high-frequency harmonic voltages (HFHVs) and corresponding airgap flux densities are established, which are used for calculating the flux density spectra caused by each HFHV in the PWM voltage spectra. Then, the superposition principle is applied for calculating the flux density spectra caused by fundamental currents and all HFHVs, which are converted to the electromagnetic force spectra at last. The relative errors between the force density spectra calculated with the proposed method and those obtained from traditional time-stepping finite element analysis (TSFEA) using PWM voltages as input are within 3.1%, while the proposed method is 24 times faster than the traditional TSFEA.

Comparison of backstepping, sliding mode and PID regulators for a voltage inverter

<p><span>In the present paper, an efficient and performant nonlinear regulator is designed for the control of the pulse width modulation (PWM) voltage inverter that can be used in a standalone photovoltaic microgrid. The main objective of our control is to produce a sinusoidal voltage output signal with amplitude and frequency that are fixed by the reference signal for different loads including linear or nonlinear types. A comparative performance study of controllers based on linear and non-linear techniques such as backstepping, sliding mode, and proportional integral derivative (PID) is developed to ensure the best choice among these three types of controllers. The performance of the system is investigated and compared under various operating conditions by simulations in the MATLAB/Simulink environment to demonstrate the effectiveness of the control methods. Our investigation shows that the backstepping controller can give better performance than the sliding mode and PID controllers. The accuracy and efficiency of the proposed backstepping controller are verified experimentally in terms of tracking objectives.</span></p>

Classification of Partial Discharges Originating From Multilevel PWM Using Machine Learning

A partial discharge (PD) is a small, localized breakdown which often appears in high-voltage insulation systems. PDs can be initiated within material defects such as voids or cracks when exposed to sufficiently high electric field levels. In this research work, we study and propose a machine learning (ML) approach to detect and classify PDs originating from multilevel pulsewidth modulation (PWM) waveforms as utilized in power electronic devices, such as inverters and variable frequency drives. Due to the increased use of power conversion units, new types of higher magnitude PDs have been observed to increase insulation degradation. By creating a cavity placed at different locations within the test object and exposing it to PWM voltage waveforms with two different rise times, a total of 345 660 PD events are recorded and organized into ten different classes. The maximum PD amplitude, duration, the time distance between consecutive PDs, and the area under the PD are used as features for PD classification. A unique way of concatenating a sequence of the extracted features to capture the temporal dependence of consecutive PDs is also presented. It is observed that when creating a sequence of information from consecutive observed PDs, a significant increase in classification accuracy can be obtained. Trained classifiers based on ensemble bagged decision trees (DTs) and long short-term memory (LSTM) architecture resulted in 95.3% and 98.5% average classification accuracy on test data respectively.

Assessment of filtering properties of asynchronous electric drive with pulse width modulation

The process of pulse-width modulation in the converter-motor system is considered. It is noted that the main task of pulse width modulation of voltage formed by the electronic key converter in the converter-motor system is to reduce current pulsations during the modulation period. It is established, that the dynamic process of current change in the electric machine during the period of pulse-width modulation can be approximated by R, L filter. It is shown, that the most important task of pulse-width modulation is minimization of modulation error by current in electric motor. The analysis of possible criteria of estimation of modulation process quality in control systems of electric drive is carried out. It is noted that as a criterion of optimality to assess the quality of modulation in the converter-electromotor system, it is advisable to use the integral quadratic criterion of relative error, called the local variance of the current, as well as the average value of the local variance of the current at the period of the modulating function, called the integral variance of current. The process of estimating the filtering ability of electric machines as part of the electric drive is considered. A system of basic values based on nominal values of electric motor stator voltage, its nominal angular speed and nominal stator current has been selected. The index of filtering properties of the load considering introduction of basic values has been proposed. The equations of an asynchronous electric machine with constant coefficients in the complex form of writing are given. The dependency of the real part of roots of the characteristic equation for an asynchronous machine as a function of angular speed of the rotor rotation is constructed. An analytical expression for the estimation of the filtering properties of asynchronous machines is obtained. The comparison of different types of electric machines according to this parameter is made.

Визначення оптимальних параметрів широтно- імпульсно модульваної напруги для живлення електромагнітного віброприводу

Goal. To determine the optimal parameters of various types of pulse-width modulated (PWM) voltage, which is used in the control systems of the electromagnetic vibration drive to create resonant vibrating machines and control the parameters of the working body of the vibrating machine in the resonant mode. Method. The work is based on the analysis of the spectrum of the main three forms of PWM signals in their low-frequency region, to which the oscillating mechanical system of vibrating machines responds. To estimate the PWM-encoded sine wave corresponding to the resonant frequency of the vibrating machine, the mean square deviation was used in the time domain, and the nonlinear distortion coefficient (harmonic) was used in the spectral domain. Results. The results. A mathematical apparatus was built and a connection was established between the oscillating mechanical system of the vibrating machine, the external PWM parameters and the characteristics of the sinusoidal signal encoded by it in the time and spectral domains. Scientific novelty. For the first time, a mathematical model was obtained and the influence of the parameters of the oscillating mechanical system of the vibrating machine and the carrier frequency of the pulse-width modulated voltage on the root-mean-square deviation and the coefficient of nonlinear distortions (harmonics) of the signal feeding the electromagnetic vibration drive was simulated. Practical significance. A technique for calculating the carrier frequency of the PWM sinusoidal voltage is proposed, which can be used to develop an algorithm for controlling power switches (transistors) and choosing the type of power switches at the stage of designing the power part of control systems with an electromagnetic vibration drive of controlled and adaptive vibration machines.

Computationally Efficient Stator AC Winding Loss Analysis Model for Traction Motors Used in High-Speed Railway Electric Multiple Unit

The aim of this proposed work is to develop a computationally efficient and accurate AC winding loss analysis model for the traction motors for use in high-speed railways (HSRs). The goal of the model is to be able to study AC winding loss under both sinusoidal and pulse width modulated (PWM) inverter voltage sources. The traction motor model considered for the proposed study is a form wound winding permanent magnet (PM) assisted synchronous reluctance motor (PMaSynRM). The traction motor uses an open slot with two-layer winding. First, a flux linkage table is built using finite element analysis (FEA) with sinusoidal current as the input. The machine model then includes the effect of the PWM inverter voltage source with the current controller. For the AC winding loss analysis, the fundamental component and the harmonics due to PWM are considered separately. To find the loss due to the fundamental component only, the vector potential of the slot region is mapped to the subconductors of the form wound winding and the eddy current distribution and the AC winding loss are calculated. The effect of the harmonics due to the PWM switching is then added in the post-processing stage by analytically evaluating the individual harmonic effect. The whole AC loss analysis model proposed in this work is computationally more efficient than the conventional FEA because the transient state of the system is removed. Moroover, the PWM voltage source effect is divided into the effects of the fundamental component and switching harmonics by combining the vector potentia mapping and post-processing analytical calculation.

IPWM Based IBMSC DC-AC Converter Using Solar Power for Wide Voltage Conversion System Convertisseur DC-AC IBMSC basé sur l’IPWM et utilisant l’énergie solaire pour un système de conversion à large tension

This article proposes isolated bidirectional micro dc-ac single phase controlled (IBMSC) converter based on in-phase–voltage pulsewidth modulation (IPWM). This resonant IPWM converter, ratio of voltage conversion can be controlled from 0 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\infty $</tex-math> </inline-formula> . So, this converter is highly referred for huge range voltage conversion. However, voltage conversion ratio determines power transfer direction and duty ratio. Power flow direction and duty cycle value can be varying smoothly, so it is suitable for dc-ac bidirectional power conversion application. Inverter mode and also rectifier mode are possible from bidirectional operation, which is controlled by a unified current controller. The proposed solution can achieve smooth switching grid operation with high efficiency. Working principle, design procedure, control strategy, and characteristics of the proposed converter are implemented with a prototype model of power rating 500 W with a voltage range of 20–50 V to test the ability of withstanding. Performance, feasibility, and effectiveness of the proposed converter are tested with this hardware test-bench model.

An Analysis of Minor Hysteresis Loops Behavior under PWM Voltage - Electromagnetic Device at No-Load and Loaded Conditions

This paper addresses the influence of the primary and secondary resistances on the behavior of minor hysteresis loops when the electromagnetic device is fed by three-level PWM (pulse width modulation) voltage. To study the device transferring energy to a load, the experimental approaches are different of traditional procedures to material characterization, where problems inherent to the process are added. Analytical, FEM and experimental analysis are performed on a toroidal transformer equipped with a flux sensing coil. The leakage fluxes related to the primary and secondary currents are shown to cause errors in the measurement of the core magnetization current. A solution to mitigate this problem is employed, consisting in twisting and winding together primary and secondary conductors. Experimental methodologies for obtaining the value of the iron losses when the device is transferring energy to a load are also performed. The study shown showed that supply voltage with three-level PWM waveform causes minor hysteresis loops and the greater the resistance value of the excitation winding, the larger the areas of the minor hysteresis loops. On the other hand, by increasing the energy transferring to a load the minor loops areas tend to decrease.

Increasing Energy Efficiency With Fuzzy Logic Control in FPGA-Based Electromagnetic Stirrer

In this study, a new field-programmable gate array (FPGA)-based electromagnetic stirrer system was developed allowing mixing on a single axis, and the energy efficiency of the system was increased with fuzzy logic control. The electromagnetic stirrer system was designed with three phases and each phase is fed with pulsewidth modulation (PWM) voltage with 120° phase difference. Ranked control of phases in the system used the FPGA structure in the myRIO® embedded system to determine the PWM signal production, increase intervals for phase frequencies, and rotation rate of the magnetic stir bar. In the system, to increase the energy efficiency with fuzzy logic control, the ARM® microcontroller structure in the myRIO® embedded system was used. Programming of the myRIO® embedded system was provided through the graphic-based LabVIEW <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> software. In situations where the system is operated with 100% duty cycle, the force affecting the magnetic stir bar should be continuous and have fixed value until the next phase change. As a result, the magnetic stir bar performs more than 120° rotation and a braking effect of the force is observed. To resolve this situation, fuzzy logic control ensured operation of a different duty cycle without loss of speed of the stir bar. Thus, the energy efficiency of the system was increased with lower current and lower stimulation duration. Within the scope of this article, the experimental results obtained about the structure, control, and energy efficiency of the electromagnetic stirrer system are discussed in detail.

Harmonics Mitigation of a Solar PV-Fuel Cell Based Microgrid System using a Shunt Active Power Filter

The increased penetration of distributed energy resources is inspiring the entire design of conventional electrical power systems. A Microgrid (MG) includes distributed generation, loads, energy storage, and a control system capable of operating in grid-connected mode and/or island mode. The power quality (PQ) issue is one of the main technical challenges in an MG power system. To improve PQ, it is necessary to analyze the harmonic distortion of the system. Moreover, harmonic distortion in MG networks has significantly reduced PQ, affecting the stability of the system. The shunt active power filter (SAPF) has been extensively used to diminish the current harmonics and verified as being the best solution. Hence, in this paper, the impact of PQ issues in an adopted standalone MG system (comprising solar and fuel cell based renewable energy sources) is investigated in the presence of SAPF. The SAPF is realized using a conventional synchronous reference frame (SRF) technique for current generation with a pulse-width modulation voltage source inverter technique to generate pulses for the inverter along with a PI controller to regulate the DC-link capacitor voltage. The proposed model is developed in MATLAB/SIMULINK and the results validate the superiority of the proposed technique over others in terms of harmonic elimination.

Comparison of Methods Using Different Sources for Computing PWM Effects on Permanent Magnet Machines Considering Eddy Current Reaction

This article compares two methods for computing high-frequency harmonic currents (HFHCs) and losses in permanent magnet synchronous machines (PMSMs) driven by pulsewidth modulation (PWM) voltage-source inverters (VSIs). The first method uses the currents containing HFHCs, which are obtained from the SIMULINK-based inverter-motor simulation system, as input for time-stepping finite-element analysis (TSFEA) to compute the PWM effects, while the second method directly uses PWM voltage sources as input for conducting the coupled field-circuit TSFEA. It is pointed out that the HFHCs are underestimated with the first method due to neglecting the eddy current reaction effect. Hence, both the iron and permanent magnet losses will be underestimated with the first method. On the contrary, the second method is better for computing the PWM effects because high-frequency harmonic voltages are independent on the eddy current reaction effect under PWM VSI supply and are directly related to high-frequency flux density variations, which determine high-frequency losses. Experiment on an interior PMSM was conducted to validate the simulation in this article.