Pulse Width Modulation Switching Technique Research Articles

Propagation of Supraharmonics in a Data Center With Different Operating Modes of UPS

A data center is a major hub of different converters ensuring continuous power to the server loads. The pulse width modulation switching techniques with frequency emission from 2 to 150 kHz (i.e., supraharmonics) in these converters call for a study of the magnitude and propagation of this emission within data centers where UPS is one of the main contributors of supraharmonics. The paper shows, with measurements and model, the change in magnitude and propagation of supraharmonics with the change in the operating mode of the UPS. The magnitude of supraharmonics shows a non-linear dependency on the power consumed in the online mode. In bypass mode, the magnitude of supraharmonics shows a dependency on the type of load connected. The filter connected between PE-N at the input side of the UPS can cause resonance in the phase conductors. The results show that to study the emission, immunity, and electromagnetic compatibility of supraharmonics for UPS, the factors such as operating mode, the type of load connected, and the input and output impedance need to be considered.

Fault Analysis and Reduction of Harmonics of Three-Level Three Wire and Four-Wire Neutral Point Clamped Inverter using PWM Switching Technique

Energy generation through wind and solar is increasing with the rising interest in the renewable and clean form of energy. Due to energy crises, the world is shifting from nonrenewable energy resources to renewable energy resources. Renewable energy resources are the green and eco-friendly sources and do not affect the climate like the other fossil fuels. Renewable fuels gain popularity due to their sustainability and low carbon emission. To get energy from renewable energy sources, well-defined mechanisms and control devices must be needed. Therefore, the reliability and stability of the system are required. The inverter is one of the tools which have a significant contribution to controlling the operation of the energy conversion system. The inverter is an accessory that changes a Direct Current (DC) source into an Alternative (AC) source. By using that AC source, we can easily derive AC appliances and drive the loads. To gain more power or to derive large power motors whose power ratings are up to several kilo/Megawatts, we need multi-level inverters. One of the types of multi-level inverters is the Neutral Point Clamped inverter (NPC). NPC inverters are used where considerable power is required, such as of several megawatts. The main contribution of this research paper is to design the three levels of neutral point clamped inverters by using the Pulse width Modulation (PWM) and Space Vector Modulation (SVM) Techniques.

Design and development of PWM switching for 5-level multiphase interleaved DC/DC boost converter using FPGA

<p>The continuously increasing demand for control on electric power equipment has led to the rapid technological development in various applications such as renewable energy, electric drives, and communication. Pulse Width Modulation (PWM) switching is an important technique to control the output voltage. PWM signals can either be generated using digital controller or analog controller. Digital controllers are widely used to generate PWM signals due to their reliability in solving complex algorithms within short amount of time. Multiphase boost converter is capable to overcome high input current ripple, current stress and semiconductor losses in conventional boost converter. This paper proposes a PWM switching scheme for multiphase interleaved converter using Field Programmable Gate Array (FPGA). The proposed switching scheme uses PWM switching technique that is implemented by programming Altera DE2-70 board. The duty cycle can be easily adjusted using assigned switches on the Altera board. For validation, switching frequency was set to 100 kHz, and then switching signal was observed using oscilloscope.</p>

Comparative Study of Modified Sinusoidal Carrier Disposition PWM Techniques in a Cascaded H-Bridge Multilevel Inverter

This paper presents the comparative study of different types of carrier disposition modified sinusoidal pulse width modulation (SPWM) of cascaded H-Bridge multilevel inverter (MLI). In this paper modified sinusoidal pulse width modulation switching technique is used. In the modified SPWM, the width of the signal in the peak of the sine wave do not change significantly with the variation of modulation index. By comparing with normal sinusoidal pulse width modulation, the proposed method can improve fundamental component and it can reduce total harmonic distortion. Further, due to the reduction in the number of switching a decrease in the switching losses is noticed. The proposed topology is modeled using Matlab/Simulink.

PWM Switching Technique for Three-Phase Bidirectional Grid-Tie DC–AC–AC Converter With High-Frequency Isolation

Galvanic isolation based high-frequency transformers have become very attractive in bidirectional dc/ac converters. This paper presents a new pulse width modulation (PWM) switching technique for controlling a bidirectional isolated dc–ac–ac converter employing a high-frequency link transformer. The proposed PWM technique has the ability to control the input dc current and to inject a sinusoidal three-phase current to the grid at unity power factor. The primary-side is an H-bridge converter used to convert the dc voltage to a high-frequency square-wave single-phase voltage. The secondary side is a matrix converter used to convert the grid three-phase voltage to a high-frequency single-phase waveform. The dc–ac–ac converter utilizes a high-frequency link transformer for the galvanic isolation between the H-bridge and matrix converters as alternative for the bulky line-frequency transformers (50/60 Hz). The bidirectional power flow is controlled by the phase shift angle between the primary and secondary voltages of the high-frequency transformer. The mathematical model and the circuit operational modes are presented along with the voltage controllable limit. The feasibility of the proposed PWM switching technique and the accuracy of the mathematical model are demonstrated experimentally by using a 200 V/1 kW laboratory prototype system.

PWM Control Techniques for Single-Phase Multilevel Inverter Based Controlled DC Cells

This paper presents a single-phase five-level inverter controlled by two novel pulse width modulation (PWM) switching techniques. The proposed PWM techniques are designed based on minimum switching power loss and minimum total harmonic distortion (THD). In a single-phase five-level inverter employing six switches, the first proposed PWM technique requires four switches to operate at switching frequency and two other switches to operate at line frequency. The second proposed PWM technique requires only two switches to operate at switching frequency and the rest of the switches to operate at line frequency. Compared with conventional PWM techniques for single-phase five-level inverters, the proposed PWM techniques offer high efficiency and low harmonic components in the output voltage. The validity of the proposed PWM switching techniques in controlling single-phase five-level inverters to regulate load voltage is verified experimentally using a 100 V, 500 W laboratory prototype controlled by dspace 1103.

A 100 W 5.1-Channel Digital Class-D Audio Amplifier With Single-Chip Design

A 100 W, 5.1-channel, single-chip, digital-input class-D audio amplifier with a low-voltage (LV) digital circuit and high-voltage (HV) switching power stage is designed for moderate-performance and cost-effective speaker systems. The LV portion, including multi-channel audio processors, delta-sigma modulators (DSMs), and pulse-width modulation (PWM) generators, is implemented with a standard CMOS digital cell-library. A dual-loop resonator is proposed to increase the stable input range of the DSM so that the low-distortion output power of the class-D amplifier can be increased. For the HV portion, distortion caused by parasitic resistances of the power stage is analyzed to obtain a better design. A multi-phase PWM switching technique is proposed to prevent the multi-channel output stages from simultaneously switching, and thus the supply bouncing can be reduced. An over-current protection circuit with high supply noise immunity is also presented. Fabricated with 0.35/3-μm 3.3/18-V 1P3M CMOS technology, the 5.1-channel amplifier achieves a total root-mean-square (RMS) output power of 100 W, a distortion of less than 0.7%, and a power efficiency of 88% with a total chip area of 48.9 mm2.

Inherent Chaotic Behavior in Vector Control Drives of Induction Machines

In the present article, the existence of chaotic behavior in vector control drives of induction machines is investigated, and a method for avoiding this phenomenon is proposed. It is shown that, contrary to previous research, not only do errors in the estimation of rotor and stator resistances and pulse-width modulation switching techniques cause chaotic behavior in the drives, but these drives may show this phenomenon inherently even with exact parameters. Also, a modified second-order map is introduced to analyze and achieve necessary conditions for the occurrence of bifurcation and chaotic responses. Using this map, the bounds of different parameters to avoid chaotic response can be determined. In addition, a method to compute the largest Lyapunov exponent is explained and implemented to the system for proving the existence of chaotic response. Finally, an experimental setup is prepared to verify analytical and numerical results.

New PWM switching technique for an optimum inverter operation

The main purpose of Pulse-Width -Modulation (PWM) technique in power inverters is to control the output voltage. The most familiar techniques: uniform-pulse-width-modulation and sinusoidal-pulse-width-modulation. A Small Boundary-Pulse-Width (SBPW) technique for improving the inverter performance is proposed. The new method is based on pulse-width technique. Varied pulse-widths for the middle and boundary pulses are produced, to obtain an improved inverter operation with less generation of harmonics. Simulation results show that the SBPW technique outperforms some of the traditional methods.

PSCAD/EMTDC Simulation of Unified Series-Shunt Compensator for Power Quality Improvement

This paper deals with the simulation of a unified series-shunt compensator (USSC) aimed at examining its capability in improving power quality in a power distribution systems. The USSC simulation model comprises of two 12-pulse inverters which are connected in series and in shunt to the system. A generalized sinusoidal pulse width modulation switching technique is developed in the proposed controller design for fast control action of the USSC. Simulations were carried out using the PSCAD/EMTDC electromagnetic transient program to validate the performance of the USSC model. Simulation results verify the capabilities of the USSC in performing voltage sag compensation, flicker reduction, voltage unbalance mitigation, UPS mode, power-flow control and harmonics elimination. A comparison of the USSC with other custom power devices shows that the USSC gives a better performance in power-quality mitigation.

Simulation and digital implementation of a simple technique of active filter for elimination of switching ripples/distortion in the supply current

AbstractThis paper deals with a digital signal processor (DSP) based implementation of a three‐phase shunt active filter (AF) to compensate harmonics and reactive power of nonlinear loads. A three‐phase diode bridge rectifier with R‐L and R‐C loads is taken as the nonlinear load. It is observed that the AF systems suffer from the problems of switching ripples (in case of R‐L nonlinear load) and distortion (in case of R‐C nonlinear load). The switching ripples and distortion in the supply currents contribute considerably to its Total Harmonics Distortion (THD). This investigation proposes a new, cost free and simple approach for the elimination of switching ripples and distortion in the supply current. A pulse width modulation (PWM) current controlled voltage source inverter (CCVSI) is used as the AF. The AF system is tested with two types of PWM switching techniques, namely, carrier‐less (hysteresis) and carrier based techniques. Two types of current control techniques, namely, direct current control and indirect current control are designed to obtain PWM switching signals for the devices of the AF. The capability of the indirect current control technique towards the elimination of switching ripples and distortion is established. Simulated and experimental results for steady state and transient operating conditions of the AF for R‐L as well as R‐C nonlinear loads are given and discussed in detail.

A centroid-based PWM switching technique for full-bridge inverter applications

A novel centroid-based pulse-width-modulation (PWM) switching strategy is proposed which is suitable for full-bridge inverter applications. This method is evaluated, and its performance is compared with existing PWM switching strategies. The performance evaluation and comparison are based on the total harmonic distortion (THD) and number of pulses per cycle of the inverter output waveform. The objective of the new switching strategy is to minimize both the THD and low-order harmonics. Simulation results show that this technique yields a significant improvement in performance. In addition, a hybrid switching sequence is developed for the proposed scheme, which can lead to further reduction in switching losses.