PWM Modulation Research Articles

Inverter-Less Integration of Roof-Top Solar PV with Grid Connected Industrial Drives

Green energy from Solar PV is getting increased attention in the industries due to the falling price of solar panels in the world market. A grid-tied inverter is one of the major components in such a system, where the DC energy from PV is converted to AC and synchronized with the grid to obtain power sharing between the PV and the grid for the industrial drives. In this paper, a DC link has been proposed instead of an AC link for interconnection between the solar PV system and the grid to run those industrial drives. In most modern industrial applications, induction motors are driven by VVVF (Variable Voltage and Variable Frequency) inverters to achieve efficient speed control. The inverters commonly have a rectifier section at the front end that rectifies the input AC to DC and the DC is then used in PWM mode to generate the required voltage and frequency for the induction motor operating under variable speed and load conditions. Such an inverter can use both AC or DC as the input so long the supply voltage has the right value for the inverter to operate. In our proposition, we eliminate the grid-tied inverter and use a DC link, created from the rectified AC and the regular Solar PV, to obtain the power-sharing between the PV output and the grid. Using the DC link output directly to energize the VVVF inverter has an impact on the performance of the inverter. In the proposed system, the solar PV array is designed in such a way that the grid remains as the supplementary power source only to supplement any shortfall in the PV output due to variable sunshine conditions. The control circuit used in this novel technique is inexpensive, efficient, and simple in design when compared to the grid-tied inverters. The proposed system has been implemented at Niagara Textiles in Gazipur, Bangladesh. The experimental/practical results are presented to validate the basic concept. Around a 20% reduction in the cost of energy has been reported in this paper, with a more than 90% efficient system. This will definitely make solar PV energy more competitive with regular energy and attractive to industries for its simplicity.

Analysis and Design of H5 Topology in Grid-Connected Single-Phase Transformerless Photovoltaic Inverter System

Objectives: The transformerless inverters are more efficient, less bulky and cost-effective. But the system faces the problem of leakage current on account of the elimination of isolation transformers. Thus, the problem needs to be mitigated through the inverter topology itself. The objective of this paper is to study and analyze a topology designed for reducing the leakage current. The H5 inverter significantly reduces the leakage current by checking the variation of common mode voltages. The topology uses only one extra switch apart from the conventional full bridge and is simple to design. Method: To reduce the leakage current H5 inverter topology has been designed which works on the basis of decoupling. This work is to be implemented in MATLAB/SIMULINK. The main parameters for analysis are efficiency, leakage current, common mode voltage and their variation with load. H4 and H5 topology will be simulated and results will be compared. Findings: The H5 topology has been found to be effective in suppressing the leakage current to a fairly acceptable magnitude. It has been observed that the H5 topology has a lower leakage current than the conventional H4 topology, i.e. 23mA as opposed to 402mA in H4 topology. But the leakage current increases to up to 5 times if the system is used at load less than the full load. Novelty: The study presents the H5 inverter topology and its SPWM modulation strategy. In order to verify the topology, simulation results are provided. The performance has been tested for different loads connected to grid. The leakage current has been found to be reduced to 23.37 mA but it rises to about 100mA if used at 10% of the full load. Keywords: PV Inverters; H5 Inverters; Leakage Current (Common Mode Current); Common-Mode Voltages; Transformerless Power Converters

Current Sharing Strategy of Three-Phase Series Capacitor Buck Converter for Wide Output Voltage Range Application

Series capacitor buck (SC Buck) converters are widely used in voltage regulator modules (VRMs), electric vehicle, photovoltaic (PV) systems, and so on, for the reason that these converters have the characteristics of high step-down ratio and large output current. However, these characteristics can be realized only when the converter operates in a limited duty-cycle range. In this article, a modified pulsewidth modulation (PWM) scheme based on the principle of ampere-second balance is proposed for the three-phase SC Buck converter to solve the problem. The ampere-second balance of series capacitors is used to balance the phase currents over the entire duty-cycle range. The operating modes, voltage gain and current sharing performance of the converter, control diagram of the proposed converter, and parameter variation analysis are given. Theoretical analysis shows that with the proposed PWM scheme, the converter will have a larger output voltage, unified linear voltage gain expression, and sensorless automatic current sharing over the full duty-cycle range. Moreover, the results show that the parameter variation has nearly influence on the current sharing effect and the excellent balanced current can be achieved under steady state and transient state using the proposed PWM scheme. Finally, a 100-W experimental prototype has been fabricated to verify the performance of the proposed PWM scheme.

Design of Uninterruptible Power Supply Inverters for Different Modulation Techniques Using Pareto Front for Cost and Efficiency Optimization

This work presents a design for uninterruptible power supply inverters using Pareto front optimization for improved cost and efficiency. Three PWM modulation techniques applied to the full-bridge inverter are analyzed. As a result, the best MOSFET design solution in terms of the cost and efficiency of the inverter is evaluated based on a database with 47 power MOSFETs. Using the Pareto front, the optimal and sub-optimal solutions are compared, considering the three modulation techniques and the characteristics of MOSFETs manufactured for different voltage levels. Thermal and electrical measurements are used to validate the models.

Fully Decoupled Current Control and Current Balancing of the Modular Structure for LED Color-Mixing System

For LED color-mixing, the different color LEDs need to be controlled independently, so a fully decoupled current control and current balancing of the modular structure is proposed for LED color-mixing system. The capacitive current-balancing structure is combined with the quasi-boost converter to realize the decoupled current control and current balancing in each module. The capacitive current-balancing structure is based on the relative reactance of the capacitor with respect to the equivalent resistance of the associated LED string. The inductor in quasi-boost converter is used to further stable the output current flowing through each LED string, and the switch in quasi-boost converter for controlling the current of each LED string adopts the parallel connection to protect LEDs from the current-spike caused by the switch. The structure is modularity and scalability so that the different color LEDs can be added and removed easily. Compared with SIMO (Single-Inductor-Multiple-Output) structure, the proposed structure has no cross-coupling issues. The LED string currents working with PWM mode have a good current-balancing performance since the equivalent resistance of LED string is much smaller than the reactance of capacitors. In addition, the resonant capacitors separate the grounds of the power source and LED strings, so all the switches in parallel with LED strings do not need the isolated gate drivers. A prototype with RGB modules has been built and evaluated, and the experimental results have a good agreement with the theoretical analysis.

An Active Rectifier With Pulse Width Modulation (PWM) Mode On- and Off-Delay Compensation for Wireless Power Transfer (WPT) System

An Active Rectifier With Pulse Width Modulation (PWM) Mode On- and Off-Delay Compensation for Wireless Power Transfer (WPT) System

METHODOLOGICAL AND INSTRUMENTAL SUPPORT TO DEVELOPMENT OF ELECTRIC TRACTION SYSTEMS WITH ASYNCHRONOUS MOTOR

The present work aims to analyze from a methodological and instrumental point of view the development of asynchronous motor propulsion systems. For this purpose, PWM and SVM modulation methods, FOC and DTC vector control techniques, as well as their advantages and disadvantages are described. The theoretical bases and functional schemes of FOC and DTC control are given, including the asynchronous motor mathematical model, similar to the direct current motor model. Special attention is paid to creating of a common meaning for describing the components operation equations of the traction system, equations that can be used for system modeling and simulation. The paper also refers to a series of modern voltage converters with vector control, which are produced by several companies in different countries and are intended for the control of three-phase asynchronous motors. The results of the study create a basis for research and development of traction systems with multiphase asynchronous motors for urban electric passenger vehicles.

ИСПОЛЬЗОВАНИЕ ШИРОТНО-ИМПУЛЬСНОЙ МОДУЛЯЦИИ ДЛЯ УПРАВЛЕНИЯ РЕЗОНАНСНЫМ ИНВЕРТОРОМ

Relevance In connection with the need to regulate the output parameters in resonant inverters, various control methods are widely used, one of which is pulse-width modulation. This method is widespread because of the possibility of precise control by changing the pulse width for effective control of energy conversion. In order to study the process of controlling the output parameters and improving the parameters of electrical energy alternating current simulation is done in a system Matlab/Simulink, using the library Power System, which allows you to clarify the modes of operation and study parameters. Aim of research In this paper the research of the control method of the resonant inverter with a multifunctional integrated electromagnetic component (MIEC), which allows to improve the output parameters and the efficiency of the transformation of electrical energy is carried out. The main task is to obtain the results of computer simulation and study them. Research methods The basis of research in this work is the analysis of scientific publications and the creation of a computer model using the software package Matlab. Results The authors have developed a computer model in Matlab and implemented PWM modulation to control the output parameters of the resonant inverter on the basis of MIEC and evaluated the effectiveness of this method of inverter control.

A CMOS Dual-mode DC-DC Converter with a Digital Dual-mode Controller

This paper describes a CMOS dual-mode DC-DC converter with a digital mode controller, which includes PFM controller and PWM controller. The proposed dual mode controller employs 3-bit control circuit to select a number of counts from a 5-bit digital counter, so that the 3-bit control circuit is capable of adjusting the transient boundary load current between PFM mode and PWM mode. The proposed dual-mode DC-DC converter with a digital dual-mode controller was implemented with a 180 nm 1P/6M BCDMOS process. The measurement results demonstrated the wide range of the input voltage from 2.2 V to 5.0 V with a fixed output voltage of 1.2 V with 3-bit digital capability to control boundary current between PFM mode and PWM mode. The proposed DC-DC converter achieved the peak PFM and PWM power efficiencies of 85% and 91 %, respectively, with an output ripple voltage of 12-32 mV at a switching frequency range of 60 kHz to 2.3 MHz and a load current range of 10 mA to 500 mA.

An Extended Control of the Input Angle for Matrix Converters Connected With the Nonunity Power Factor Loads

This article proposes a novel pulsewidth modulation (PWM) modulation algorithm for multiphase conventional matrix converters, with three inputs and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$k$</tex-math></inline-formula> outputs, using the transfer function of the load angle. The proposed approach extends the range of power angle control at the input during the operation with a maximum voltage transfer ratio. The proposed concept is based on the direct analytic voltage PWM modulation with an elliptical trajectory of reference load voltages. The proposal has been verified using the circuit simulation in PSIM software, symbolic analysis using MATLAB, and finally through an experiment.

Investigation of ZVS Criteria and Optimization of Switching Loss in a Triple Active Bridge Converter Using Penta-Phase-Shift Modulation

Triple active bridge (TAB) as an isolated multiport dc–dc converter is a promising solution for integrated energy management systems to maintain an efficient power flow between the ports. This article presents the design, modeling, and switching loss optimized phase-duty-controlled PWM modulation scheme of a TAB converter composed of three full-bridge modules and a high-frequency planar transformer. The work aims at the derivation and analysis of the zero-voltage switching (ZVS) conditions for a TAB, where the turn-on switching loss is mitigated along with attaining an improved EMI performance, comprising of reduced noise peaks. Moreover, an optimized five-variable control-based TAB PWM modulation technique is proposed in this article in order to achieve minimized switching loss and the overall system loss for a wide voltage gain and load range. The instantaneous switching currents, responsible for the switching losses at the devices, are derived from the transformer winding current expressions, formulated employing the generalized harmonic approximation (GHA) technique. The various loss minimization techniques and the theoretically obtained criteria for ZVS are experimentally verified using a laboratory-developed prototype of an 800-W TAB converter. With the implementation of the proposed optimal phase-duty control, the experimental results show a nonunity gain light-load efficiency increment up to 10% compared to the conventional phase-shift modulation alone.

Three-Phase Current Reconstruction for PMSM Drive With Modified Twelve Sector Space Vector Pulse Width Modulation

To reduce the cost and size of the power converters, techniques of reconstructing three-phase current through a single current sensor have been employed in permanent-magnet synchronous motors. In existing studies, the reconstruction precision is largely affected by current reconstruction dead zones in the space vector pulsewidth modulation (PWM) plane, which requires additional algorithms to compensateeither by modifying PWM modulation strategy or by phase-shifting of PWM signal. In this article, a phase current reconstruction method for three-phase inverter with the modification of a twelve sector space vector pulsewidth modulation (TS-SVPWM) is proposed. By arranging a single current sensor on a circuit branch between two power switches, the proposed method can reconstruct the three-phase current of the voltage source inverter and avoid the dead zones located at the sector boundary region. This method can be realized not only with a single Hall-effect current sensor but also with a single shunt resistor, which can expand its application. The proposed method can be a fault-tolerance solution when there are phase current sensor faults. Beside, the three-phase current can be reconstructed when there are open-circuit faults in the power switches. Compared with previous methods, the proposed TS-SVPWM can reduce the phase current harmonics. The effectiveness of the proposed method is validated by experiments.

Mechanism and Cancellation of DC Current Fluctuation in MMC Excited by Circulating Current Mitigation Under Nearest Level Control

For modular multilevel converter (MMC) under Nearest Level Control (NLC) with dozens of or less sub-modules (SMs), circulating current suppression control (CCSC) can lead to severe fluctuation in dc current of MMC due to insufficient voltage levels to modulate the control voltages generated from circulating current suppression. This article presents a detailed analysis of the mechanisms of the above-mentioned problems, and a solution by using a dual-mode modulation method combining pulsewidth modulation (PWM) and NLC modulation is presented. In this method, two SMs in each arm are selected to operate under PWM modes to precisely modulate the control voltages from circulating current suppression, and the rest of SMs are operated under NLC modes to roughly modulate the output ac voltage of MMC. A voltage balancing control method for both of the two different modulated SMs is also investigated. The proposed method not only eliminates the dc current fluctuation in MMC, but also achieves voltage balancing among SMs. Finally, validation by RTDS is given to verify the effectiveness of the proposed method.

A Novel Representation Method of Space Vector PWM Schemes with Zero Voltage Vector Ratio as a Parameter

Various PWM modulation schemes have been proposed for three-phase voltage source inverters with different representation methods. This paper proposes a novel representation method for various modulation schemes in a unified manner by introducing a variable called the zero-voltage vector ratio. This paper also shows that the proposed method can represent three conventional modulation schemes.

Two-vector Dimensionless Model Predictive Control of PMSM Drives Based on Fuzzy Decision Making

Model predictive controls (MPCs) with the merits of non-linear multi-variable control can achieve better performance than other commonly used control methods for permanent magnet synchronous motor (PMSM) drives. However, the conventional MPCs have various issues, including unsatisfactory steady-state performance, variable switching frequency, and difficult selection of appropriate weighting factors. This paper proposes two different improved MPC methods to deal with these issues. One method is the two-vector dimensionless model predictive torque control (MPTC). Two cost functions (torque and flux) and fuzzy decision-making are used to eliminate the weighting factor and select the first optimum vector. The torque cost function selects a second vector whose duty cycle is determined based on the torque error. The other method is the two-vector dimensionless model predictive current control (MPCC). The first vector is selected the same as in the conventional MPC method. Two separate current cost functions and fuzzy decision-making are used to select the second vector whose duty cycle is determined based on the current error. Both proposed methods utilize the space vector PWM modulator to regulate the switching frequency. Numerical simulation results show that the proposed methods have better steady-state and transient performances than the conventional MPCs and other existing improved MPCs.

A novel multilevel inverter with reduced components and minimized voltage unbalance

Multilevel inverters are an emerging area of research in the field of power electronic circuits and applications. It has many advantages like near-sinusoidal output voltage, lower total harmonic distortion (THD), reduced dv/dt stress, lower peak inverse voltage (PIV) and so on. But there are some associated problems as well such as cost, size complexity, and capacitor unbalance voltage. Here a novel nine level inverter topology has been proposed which addresses the issue of high no of switching and capacitor voltage unbalance. The proposed system has numerous advantages. The cost, size and complexity are reduced and the voltage unbalance problem is solved. The voltage stress across the switches is also reduced. The power loss distribution among the switches is optimum. So, the efficiency of the system is improved. Hence the overall system performance is improved. The system performs well for varying load like resistive, inductive as well as motor load. The stator voltage speed control of a single-phase induction motor has also successfully been achieved. The pulse width modulation PWM technique has been used for producing the switching pulses. The complete simulation analysis of these systems has been realized using MATLAB software. A comparative analysis of this system with the recently proposed systems has been done which shows significant advantages in all the above mention areas.

Triple Phase Shift Control of Wireless Charging DAB LCC Resonant Converter for Unity Power Factor Operation with Optimized Rectifier AC Load Resistance

This paper presents a new triple phase shift (TPS) closed-loop control scheme of a dual active bridge (DAB) LCC resonant DC/DC converter to improve wireless charging power transfer efficiency. The primary side inverter phase shift angle regulates the battery charging current/voltage. The secondary side rectifier phase shift angle regulates the rectifier AC load resistance to match its optimized setting. The inverter-to-rectifier phase shift angle is set to achieve unity power factor operation of the DAB rectifier and inverter. The mathematical formulation of the TPS shift control is given for each phase shift angle. The analytical calculation, circuit simulation, and experimental test are carried out in a power scaled-down DAB LCC resonant wireless charging converter laboratory hardware setup to validate the proposed TPS close-loop control scheme. The PLECS circuit simulation shows that DAB LCC resonant SiC MOSFET operates at zero-voltage-switching (ZVS) with a unity power factor in emulated constant current (CC) mode battery charging. In constant voltage (CV) mode operation, one inverter/rectifier Leg does not operate at ZVS switching when Sic MOSFET is switched on near zero current. The experimental results show that the efficiency is greatly improved for CV mode charging with large DC load resistance connected if rectifier AC load resistance matching control is enabled. The measured efficiency matches well with the analytical calculation. The estimated efficiency improvement will be much more significant for EV applications in the kW power range with greater winding loss. The challenges and possible solutions to implement TPS PWM modulation in two separate inverter and rectifier control hardware are explained for future TPS control algorithm development in practical wireless charging products.

Efficiency of the autonomous modular system in the implementation of the spray application process in the vineyard

Autonomous modular system mounted on a conventional (CON) sprayer operating on the principle of pulse-width modulation (PWM) control of electromagnetic valves represents state-of-the-art technology for implementation controlled application of spray mixture without changing the operating parameters of the sprayer (e.g. spray pressure, nozzle size). In accordance with the principles of precision viticulture, the pulse width modulation control is the primary technology, which allows the application of the required amount of spray mixture exclusively to the target areas of the vine without changing the droplet size spectrum and allows for even deposit quality and reducing the drift outside the target areas. In the vineyard, we tested an autonomous axial sprayer prototype throughout the entire spraying season in 2021 on which we have installed an autonomous modular system with enabled pulse-width control. We tested two modes of operation of the sprayer prototype, namely autonomous (continuous duty cycle control (DC: 0 to 100%)) and conventional (nozzle fully open at all time), at a steady spray speed of 6 kmh-1. We compared the amount of PPP expressed as a percentage between autonomous and conventional mode of operation of the sprayer through individual nozzles on the sprayer. The maximum saving of the spray mixture of 69.8%, through an individual nozzle was measured at phenological stage of the vine BBCH 55. A comparative analysis between the CON and PWM mode of the spray mixture application showed that we saved 626.24 l per year in the automated mode of operation.

Improved Modulation Methods of the Dual-inverter Fed Open-end Winding Three-phase Motor Drives with Equal DC-link Voltage

This paper investigates PWM method for the dual-inverter fed open end winding three-phase induction motor drives. This is aimed to improve the quality of the output voltage as well as to enhance the motor performance by solving the drawback of the PWM method. The proposed PWM method operates two inverters in different technique, i.e one inverter operates in square wave mode (slow switching) and one inverter in PWM mode (fast switching). Although the PWM method can improve the quality of the inverter output voltage over the two-level inverter output, the proposed PWM method causes an excessive ripple in both torque and stator current especially at the transient period. The drawback is solved by applying a new switching strategy that manage the inverter switches operate in turn between slow switching and fast switching in one circle of operation. The proposed method is verified via simulation. The result shows that the quality of output voltages improves for all modulation indices in comparison with two-level inverter. Furthermore, torque ripple is reduced, and current ripple are improved as the current waveform is enhanced to be more symmetrical.

Implementation of cascaded H-bridge DC-link inverter for marine electric propulsion drives

Abstract This paper presents a single-phase seven level Cascaded H-Bridge DC-Link (CHBDCL) inverter for marine electric propulsion drives. The speed of propulsion drive can be changed by CHBDCL inverter by converting DC output from the rectifier to variable output voltage with or without change in frequency. The proposed CHBDCL inverter generates more output voltage with minimum harmonic content than classical Multilevel Inverters (MLIs). The CHBDCL inverter necessitates only ‘m + 3’ power devices for ‘m’ number of levels, although the classical MLIs requires ‘(2m − 1)’ power devices. CHBDCL inverter can have the effective performance by utilizing unipolar Sine Pulse Width Modulation (SPWM) and unipolar Space Vector PWM (SVPWM) with sine carrier. The effectiveness of the proposed CHBDCL inverter topology has been verified by using MATLAB/SIMULINK for various modulation indices in terms of voltage levels and harmonic analysis. Furthermore, an experimental setup involving pulse generation from a Field Programmable Gate Array (FPGA) has been used to test the performance of the proposed CHBDCL inverter.