Unipolar Pulse Width Modulation Research Articles

High-frequency harmonics suppression in high-speed railway through magnetic integrated LLCL filter.

The traction converter modulation generates switching-frequencies current harmonics. The trapped filters can eliminate these switching harmonics, reducing total inductance and filter size. Nonetheless, in comparison with the typical inductor-capacitor-inductor (LCL) filter, the trap inductor needs a larger magnetic core. Moreover, the trapped filter has not been analyzed in the traction systems. This paper proposes a magnetic integrated inductor-trap-inductor (LLCL) filter to decrease the filter's size and investigate its application in traction converters. In fact, the application range of this filter is quite broad, and it can be used in various electrical power systems, including industrial power systems, renewable energy systems, transportation systems, and building power systems. The LC-trap may be formed by connecting the equivalent trap inductor, introduced through the magnetic coupling between inverter-side and grid-side inductors, in series with the filter capacitor. Furthermore, for H-bridge unipolar pulse width modulation (PWM) traction converters, the prominent switching harmonics are concentrated at the double switching frequencies. Therefore, the stability zone is expanded by moving the resonance above the Nyquist frequency. The presented filter's features and design are thoroughly analyzed. The proposed method is finally validated by the MATLAB/Simulink simulation and hardware-in-the-loop (HIL) experimental results. Compared to the discrete windings, the integrated ones can save two magnetic cores. Furthermore, the proposed filter can meet IEEE criteria with 0.3% for all the harmonics and total harmonic distortion (THD) of 2.15% of the grid-side current.

Multistable dynamics of a control system with unipolar pulse-width modulation

Multistable dynamics of a control system with unipolar pulse-width modulation

A transformerless Z‐source photovoltaic grid‐connected inverter with coupled inductor coil

AbstractThe quasi‐Z‐source H‐bridge grid‐connected inverter (QHGCI) is well known for its advantages of the void of the shoot‐through problem and the high DC‐voltage utilization. But the existence of the common‐mode leakage current in the power frequency cycle, lower power density, and higher thermal stress make it hard applicable to the grid‐penetrating application. Thus with the purpose to conquer the problem relating to the QHGCI, an innovative transformerless Z‐source photovoltaic grid‐connected inverter with a coupled inductor coil (TZPGCI‐CIC) is proposed. The circuitry topology and an unipolar sine pulse width modulation strategy are first introduced in short. Thereafter, the common‐mode voltage in the whole working process is derived and evaluated through the detailed operating mode analysis, in which a constant value of it has been theoretically revealed. Lastly, a prototype platform of TZPGCI‐CIC is set up and its good performance on leakage current suppression, and lower thermal stress are validated with the experimental results.

A Reduced Switch Count Seven-Level Boost ANPC Based Grid Following Inverter Topology With Photovoltaic Integration

A boost active-neutral-point-clamped (BANPC) multilevel inverter based on a switched-capacitor network generally shows a bargain between the number of switches and its voltage rating. Moreover, control complexities are increased with the increase in switch count. In this paper, a new single-phase seven-level boosted ANPC (7L-BANPC) topology using 8(eight) switches, one floating capacitor, and one dc source is presented. The proposed inverter is capable of producing 1.5 times voltage boosting and needs a lower switch voltage rating. The efficiency of the proposed inverter is increased significantly due to lower rating switching devices and a reduced number of total conducting switches. The unipolar level-shifted sine pulse width modulation is considered for controlling the proposed inverter. A three-phase single-stage grid-connected SPV system with the proposed 7L-BANPC inverter is implemented. For the proposed system, theoretical analysis and design calculations are illustrated. The steady-state and dynamic performances of the proposed inverter as well as the grid-connected SPV system under different load power factors, modulation indices, and environmental conditions are simulated using the MATLAB/Simulink software and tested using OPAL-RT real-time emulator. A comparison with existing topologies clearly shows the benefits of the proposed inverter.

태양광 시스템에서 불연속 전압 변조 방법 적용에 따른 단상 5-레벨 T-type NPC 인버터의 전력 반도체 소자의 전력손실 및 열 부하 분석

The pulse width modulation method has a significant effect on the power losses and thermal loadings of power devices of a single-phase five-level T-type NPC photovoltaic (PV) inverter. In this paper, the comparative analysis of the power losses and thermal loadings of a single-phase five-level T-type NPC inverter is performed under the different pulse width modulation methods. When the unipolar pulse width modulation method is applied, the power losses and thermal loadings of the power devices are evaluated, and the reliable critical power devices with the highest thermal loadings are identified. Subsequently, the power losses and thermal loadings of the power devices are analyzed by applying the discontinuous pulse width modulation methods such as one-pole clamping pulse width modulation method and equally distributed discontinuous pulse width modulation method. Their effects on the reliability of the inverter are evaluated. Additionally, the operation of a T-type NPC inverter with three PWM methods is verified through the experiment.

Cavitation Detection in a Tonpilz-Type Transducer for Active SONAR Transmission System

The active sound navigation and ranging (SONAR) transmission system emits acoustic pulses underwater using a wave generator, a SONAR power amplifier (SPA), and a projector. The acoustic pulse travel in the direction of the target and return as an echo to a hydrophone to learn the range or speed of the object. Often the same device is used as a hydrophone and a projector; in this context, it is known as a transducer. In order to obtain a maximum range of detection in the SONAR, it is desirable to generate the maximum amount of acoustic power until the point in which the echo can be detectable in an atmosphere with non-wished noise. Therefore, a high value of source level (SL) is required that depends largely on the value of electrical power applied to the transducer (Pe). However, when trying to obtain the maximum range of detection in the SONAR system there are the following three peculiar limitations that affect performance: The cavitation, the reverberation, and the effect of interaction in the near field. In this paper, an experimental measurement methodology is presented to detect the cavitation effects in a tonpilz-type transducer for an active SONAR transmission system using a transducer as a projector and a calibrated hydrophone in a hydroacoustic tank by measuring the parameters of total harmonic distortion of the fundamental waveform (THD-F) of the generated acoustic pulse, transmitting voltage response (TVR) to characterize the system and sound pressure level (SPL) that indicates the intensity of sound at a given distance. Whereas the reverberation and the interaction effect in the near field are objects of other study cases. A 570.21 W and THD-F < 5% switched-mode power amplifier (SMPA) prototype was developed to excite the electroacoustic transducer employing a full-bridge inverter (FBI) topology and a digital controller using a field-programmable gate array (FPGA) for unipolar sine pulse width modulation (SPWM) to generate a continuous wave (CW) acoustic pulse at a frequency 11.6 kHz. The results obtained show that from the level of Pe=196.05 W with the transducer at 1 m of depth, the value of THD-F increases significantly while the behavior of the TVR and SPL parameters is affected since it is not as expected and is attributed when cavitation occurs.

Modeling of Switching Power Losses in Cascaded H-Bridges With Unipolar PWM

This paper studies the extraction of an equivalent resistance for calculation of the switching power losses in cascaded H-bridge multilevel inverters with unipolar pulse width modulation. The concept of local and global rms currents and switching power losses are introduced in each H-bridge considering different frequencies of the inverter output and the switching network, i.e., transistor and diode. Energy conservation law has been utilized to show that the equivalent averaged local and global resistances for switching power losses are functions of load power factor angle, load rms current, and modulation index. This dependency is then reduced to only load rms current when the equivalent resistances are transformed to the inverter output branch based on the reflection rule. Consequently, a resistive model of switching power losses of the inverter is deduced, which depends neither on the knowledge of the physics of the switch, nor on complicated nonlinear equations of the semiconductor devices, and loop inductances. Double-pulse tests are conducted to acquire reliable data on the switching characteristics of the devices for different operating points.

BLDC Motor Drives with A Programmable Simplified C-Block to Generate Accurate Six-Step PWM Based on STM32 Microcontroller

This paper presents a digital implementation of a brushless direct current motor (BLDCM) drive with a six-step pulse width modulation (PWM) using a programmable simplified C-block based on the STM32 microcontroller. The implementation is conducted through the PSIM simulation platform, which is commonly used for power electronics and motor control. This approach combines the benefits of using a programmable simplified C-block for precise and flexible programming with the PWM concepts of the STM32 microcontroller. The PWM method used on the BLDCM drive is the unipolar upper PWM technique (H~PWM_L~ON). The performance of the PWM implementation is analyzed in detail, including the accuracy of the PWM generation using a Fast Fourier Transform (FFT), the gating of the IGBTs in the three-phase inverter, and the effect of the duty cycle on the BLDCM's speed, phase voltage, and phase current.

Frequency Domain Electromagnetic System Based on Unmanned Aerial Vehicles Platform for Detecting Shallow Subsurface Targets

Due to the advantages of being nondestructive, rapid, and convenient, the electromagnetic detection method has attracted growing interest in the field of shallow subsurface detection. With the rapid development of unmanned aerial vehicle (UAV) technology, the use of the UAV platform for measurement can not only improve work efficiency but also avoid the significant losses that may be caused by humans working in dangerous areas. Therefore, we propose a broadband frequency domain electromagnetic system AFEM-3 based on a UAV platform for shallow subsurface targets detection (within less than 2 m). The sensor head adopts a concentric planar coil structure with a high spatial resolution, and a bucking coil connected in reverse series with the transmitting coil is used to suppress the primary field at the receiving coil. We designed a transmitting module based on unipolar frequency multiplication sinusoidal pulse width modulation technology that can generate multi-frequency arbitrary combination transmitting waveforms with low total harmonic distortion. It can also be matched to a variety of different transmitter coils by using the same hardware circuit. In addition, the global navigation satellite system and inertial measurement unit are integrated on the sensor head. The measurement response value, position, and attitude information can be displayed in real-time through the host computer. Through the static experiment of a standard coil, we verified the consistency between the AFEM-3 system with the theory. The performance of the system was evaluated through field experiments. The experimental results show that the system can effectively detect multiple metal targets in shallow subsurface areas. For different metal targets, the AFEM-3 system can provide obvious frequency domain characteristics.

THE ANALYSIS OF REDUCTION IN SWITCHING LOSS WITH FEEDFORWARD CONTROL IN GRID-TIED MICRO GRID SYSTEM

This paper proposes the simplified pulse widthmodulation (PWM ) strategy in the bidirectionalac/dc single-phase converter with the feed-forwardcontrol scheme. In this, the number of switching ofthe proposed simplified PWM strategy is reduced toone-fourth to that of the unipolar & bipolar PWM.The feed-forward control scheme is used to achievebetter performance of the ac/dc converter in both therectifier & inverter mode as compared with theconventional dual-loop control scheme. Thesimplified PWM strategy with feed-forward controlscheme has higher efficiency than that of the unipolarPWM & bipolar PWM strategies. Also, the totalharmonic distortion is less in this PWM strategy. Thesimulation & experiments are carried out to verify thevalidity of the proposed PWM strategy & controlscheme. The proposed simplified PWM strategy withthe proposed feedforward control scheme has lowertotal harmonic distortion than the bipolar PWM andhigher efficiency than both unipolar and bipolarPWMs. Furthermore, the proposed simplified PWMoperated in the inverter mode also has largeravailable fundamental output voltage VAB than boththe unipolar and bipolar PWMs. A prototype systemis constructed and the control scheme is implementedusing FPGA Spartan-3E XC3S250E. Both simulationand experimental results verify.

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.

Modified unipolar SPWM inverter for solar PV applications using MATLAB/Simulink model interfaced with dSPACE DS1104

PurposeThe purpose of this paper is to check the Solar Photovoltaic (PV) inverter working condition with modified unipolar switching pulse. The gate pulse for the inverter switches is generated in MATLAB simulation and interfaced with hardware protype. Simulation results can be compared with hardware results.Design/methodology/approachA considerable amount of research has been done on different Pulse Width Modulation (PWM) techniques. Based on the findings, a modified Unipolar Sinusoidal PWM technique was created with one reference signal and two carrier signals+ (one for the positive half cycle and the other for the negative half cycle) and simulated in the MATLAB/Simulink platform. The prototype inverter module receives the simulated switching pulses via dSPACE DS1104 hardware software interfacing board. The hardware implementation has been done, and the hardware results compared with simulation results for various input voltage levels using resistive load.FindingsThis modified switching pulse has dead band and additional hardware setup is not required. 3-phase multi-level inverter output waveform has been achieved with six switches in this method and with low filter values, pure sine wave output can be obtained in simulation. By this method of switching pulse generation and testing, for every modification in switching pulse hardware gate driver is not required. Resulting time consumption and money investment are lower.Originality/valueModified Unipolar SPWM pulse generation technique is novel method for solar PV inverter. The switching pulse has been designed and tested in both MATLAB/Simulation and hardware prototype inverter. Hardware and software results are identical. This method of pulse generation and hardware implementation has not been done anywhere before.

Review and design of modular multilevel inverter with modified multicarrier PWM techniques for solar PV applications

PurposeThese implementations not only generate excessive voltage levels to enhance the quality of power but also include a detailed investigating of the various modulation methods and control schemes for multilevel inverter (MLI) topologies. Reduced harmonic modulation technology is used to produce 11-level output voltage with the production of renewable energy applications. The simulation is done in the MATLAB/Simulink for 11-level symmetric MLI and is correlated with the conventional inverter design.Design/methodology/approachThis paper is focused on investigating the different types of asymmetric, symmetric and hybrid topologies and control methods used for the modular multilevel inverter (MMI) operation. Classical MLI configurations are affected by performance issues such as poor power quality, uneconomic structure and low efficiency.FindingsThe variations in both carrier and reference signals and their performance are analyzed for the proposed inverter topologies. The simulation result compares unipolar and bipolar pulse-width modulation (PWM) techniques with total harmonic distortion (THD) results. The solar-fed 11-level MMI is controlled using various modulation strategies, which are connected to marine emergency lighting loads. Various modulation techniques are used to control the solar-fed 11-level MMI, which is connected to marine emergency lighting loads. The entire hardware system is controlled by using SPARTAN 3A field programmable gate array (FPGA) board and the least harmonics are obtained by improving the power quality.Originality/valueThe simulation result compares unipolar and bipolar PWM techniques with THD results. Various modulation techniques are used to control the solar-fed 11-level MMI, which is connected to marine emergency lighting loads. The entire hardware system is controlled by a SPARTAN 3A field programmable gate array (FPGA) board, and the power quality is improved to achieve the lowest harmonics possible.

Versatile AC Current Control Technique for a Battery Using Power Converters

Although a battery is a DC device, AC current is often necessary for testing, preheating, impedance spectroscopy, and advanced charging. This paper presents a versatile control technique to inject AC current to a battery. Synchronous buck and H-bridge topologies are operated in bidirectional mode and controlled by uni-polar and bi-polar pulse width modulation techniques for the AC current injection. The input and output passive circuits are specially designed considering AC current and the properties of the battery. A controller is proposed considering a small internal impedance, small AC ripple voltage, and variable DC offset voltage of a battery. The controller is capable of maintaining stable operation of AC current injection in two power quadrant within a small DC voltage boundary of a battery. The controller is comprised of a feedback compensator, a feedforward term, and an estimator. The feedback gain is designed considering the internal impedance. The feedforward gain is designed based on estimated open circuit battery voltage and input voltage. The open circuit voltage estimator is designed based on filters and battery model. For validation, AC current is injected to a Valence U-12XP battery. The battery is rated for 40 Ah nominal capacity and 13.8 V nominal voltage The controller successfully injected AC current to a battery with +10 A, 0 A and −10 A DC currents. The magnitude and frequency of the AC current was up to 5 A and 2 kHz respectively.

Novel ripple reduction method using three-level inverters with unipolar PWM

This paper proposes a novel method to reduce voltage and current ripple for the inverters by using three-level inverters with unipolar pulse width modulation (PWM) (3LFB-2U). A simple technique of switching signal generation by using carrier-based dipolar modulation of three-phase three-level inverters is extended to single-phase inverters that can be done by generating all possible switching patterns of the single-phase three-level inverters. Moreover, the concept of carrier-based dipolar modulation and the construction of reference voltages from desired output voltage and added zero voltage to control unipolar switching is also shown. The research results reveal that the proposed method can reduce the voltage and current ripple. Furthermore, the voltage and current harmonics can reduce by 27.80% and 1.79%, respectively less than two-level inverters without a loss of a simple modulation to generate the switching signals.

Design of type-1 servo controller for grid voltage modulated direct-power control of single-phase grid-connected PV inverter

This paper presents direct control of active and reactive power using grid voltage modulation for single-phase grid-connected photovoltaic inverter. A design of type-1 servo system based on pole-placement method is proposed to control the power flow using a simplified multiple-input multiple-output (MIMO) model of the system. Phase-locked loop (PLL) with a quarter cycle time delay is used to estimate the grid phase angle for the purpose of performing the stationary and synchronous reference frame transformation. Unipolar pulse width modulation (PWM) technique is used to control a single-phase inverter with 2.7 KVA capacity connected to the photovoltaic system. The proposed controller can simply be tuned using minimum number of controller gains to achieve the transient and steady-state performance requirements. The proposed system, was capable of operating for a wide range of solar irradiance levels with a power factor in the range of 0.95 (leading/lagging), for the reactive power compensation purposes.

An Improved Hysteresis Current Controller for Grid-Connected Inverter System to Address Power Quality Issues at Reduced Switching Frequency

The hysteresis current controllers (HCC) for grid-connected inverter (GCI) system is a well-known controller for its robustness, fast reference tracking, better dynamics, and easier implementation compared to other controllers. This article proposes a modified double-band HCC (MDBHCC) for single-phase GCI system with LCL -filter. The proposed algorithm implements an unipolar symmetrical pulse width modulation (PWM) strategy for reducing inverter switching losses through a sequential logic, with an adaptive clock. It improves the variation in switching frequency and limits the maximum switching frequency of HCC while enhancing the total harmonic distortion (THD) of the injected current into the grid. In order to alleviate power quality problems, two such MDBHCC schemes, i.e., MDBHCC1 and MDBHCC2, are implemented. Where MDBHCC2 operates at the higher switching frequency with lesser % THD and MDBHCC1 operates at lower switching frequency. Simulation and experimental results are presented with a significant decrease in switching frequency and an improvement in grid current harmonics at both steady-state and dynamic conditions.

RETRACTED: A hybrid technique used in grid integration of photovoltaic system for maximum power point tracking with multilevel inverter

A new hybrid technique for grid integration of solar photovoltaic system using modified incremental conductance maximum power point tracking algorithm with multi-output converter and multilevel inverter is proposed in the paper. The proposed hybrid technique is the joint execution of improved dolphin echolocation algorithm and gradient boosting decision trees and this way the proposed technique is named as IDE-GBDT technique. The novelty of the proposed work is the dolphin echolocation algorithm, which is integrated by the crossover and the mutation function so it is named as IDE. In the proposed technique, the multi-output converter is the combination of boost converter and switched capacitor function to generate different self-balanced output voltages. The utilization of multilevel inverter in the proposed system provides better quality of output voltage and current waveform thereby reducing the size of passive filters. Also, eliminates the requirement of bulky transformers for grid integration. Multicarrier unipolar phase disposition pulse width modulation technique is employed for triggering the switches of the multilevel inverter. The maximum power point tracking algorithm uses the estimated active power output of the generator as its input and generates command speed so that maximum power is transferred to the dc link. This control system also incorporates a loss minimization approach to minimize the losses in the generator and hence to improve the efficiency of the photovoltaic system. Finally, the performance of the proposed maximum power point tracking control of wind and photovoltaic power generation schemes is executed in Matrix Laboratory/Simulink working platform and the execution is assessed with the existing techniques. The proposed technique is compared with the existing techniques and the observed total harmonic distortion of the proposed technique in all the cases is 0.67%, 0.51%, 0.58%, 0.63%, 0.92%, and 1.03% and the total harmonic distortion is found to be very less compared with existing techniques.

A Modified Quasi-Z-Source Inverter with Enhanced Boost Capability

This paper proposes a modified single phase quasi-Z-source inverter (qZSI) with enhanced boost cabalitiy. The total harmonic distortion (THD) values of output voltage and current are reduced using the unipolar pulse width modulation (PWM) technique. At the same time, the voltage gain ability of the circuit is improved with the help of an additional boost switch connected in parallel with the impedance network and power MOSFETs. The operation of the unipolar PWM technique adapted for the qZSI is explained and the working principle of the proposed circuit with the boost switch is described using mathematical expressions. Simulations are carried out to show the effectiveness of the circuit for different modulation indexes using Matlab/Simulink environment. Compared with the classic qZSI topologies, the presented circuit has lower THD and increased voltage gain clearly.

Integrated Common and Differential Mode Filter With Capacitor-Voltage Feedforward Active Damping for Single-Phase Transformerless PV Inverters

Recently, several publications have discussed the design of LCL filters and current controllers for grid-connected converters. However, the focus was the LCL filter used as a differential mode (DM) filter. Besides its conventional application as DM filter, a modified LCL filter configuration can be used as an integrated common mode (CM) and DM filter, which is particularly interesting for transformerless photovoltaic (PV) inverters, whereby the CM leakage current must be limited to comply with standards. This article proposes the joint design procedure for an integrated CM and DM filter plus the current controller used in single-phase grid-connected transformerless PV inverters. The increased number of components and resonance frequencies, compared to the conventional LCL filter, requires a careful analysis of the location of resonance and anti-resonance frequencies, taking into account parameters variation. The design procedure considers the extended region of stability for the DM resonance frequency allocation provided by the filter capacitor-voltage feedforward active damping with converter-side current feedback. It also considers continuous and discontinuous unipolar pulsewidth modulation. Design examples and simulation results for 1.5 and 10 kVA are presented. The effectiveness of the proposed design procedure is verified by experimental results obtained from a 1.5 kVA inverter.