R. Kalpana

Autoconnected-Transformer-Based 20-Pulse AC–DC Converter for Telecommunication Power Supply

In this paper, an autoconnected-transformer-based 20-pulse ac-dc converter is proposed for harmonic current reduction in switched-mode power supplies (SMPSs) of moderate rating (10-15 kW). The proposed ac-dc converter is realized with a fractional magnetic rating of the load. The supply current is nearly sinusoidal with low total harmonic distortion, and the power factor is close to unity. A set of power quality indices at three-phase utility for an SMPS is presented for both 20- and 6-pulse converters to compare their performances. It is determined that the power quality indices at ac mains with a 20-pulse converter meet IEEE Standard 519 even at varying loads. A laboratory prototype of an autoconnected-transformer-based 20-pulse ac-dc converter has been designed and developed to validate the findings from simulation. Various tests have been conducted on it, and the test results conform to the simulation results.

Direct Single-stage Power Converter with Power Factor Improvement for Switched Mode Power Supply

This paper presents a direct single-stage power converter using single-phase isolated full- bridge converter modules, with inherent power factor correction (PFC) for a 12 kW switched mode power supply (SMPS). The advantages of the proposed converter are its simple control strategy, reduc- tion in number of conversion stage, low input line current harmonics, and improvement in power fac- tor. Analysis of the single-stage converter is carried out in continuous conduction mode of operation. Steady-state analysis of the proposed converter is conducted to obtain converter parameters. A system- atic design procedure is also presented for a 12k W converter with a design example. The effect of load variation on SMPS is also studied in order to demonstrate the effectiveness of the proposed converter for the complete range of load conditions. A set of power quality indices on input ac mains for an SMPS fed from a single-stage converter is also presented for easy comparison of their performance.

A 12kW three-phase modular converter with unity power factor for telecom power supplies

In this paper, a new 12kW single stage modular ac-dc converter is presented with unity power factor for telecom power applications. The combination of three single phase modules and a virtual neutral terminal device is a powerful method to design a three-phase modular converter system with power factor correction. It is based on the principle of connecting three single-phase modules in a three-phase group by creating a virtual neutral using a zig-zag transformer. The steady state analysis and design of the modular converter in continuous conduction mode (CCM) is illustrated with a simplified design example. The performance of such a modular converter system is studied and evaluated with extensive MATLAB simulation.

Design and implementation of high frequency isolated AC-DC converter for switched mode power supplies

In this paper the design and implementation of DC-DC converter based SMPS for a telecommunication system is presented. A high frequency transformer is used to provide the galvanic isolation between the input and output. A complete design methodology of high frequency transformer used for full-bridge buck derived topology is presented. The operating modes, analysis, and design considerations are explained for the proposed converter. Simulation and experimental results are also presented to demonstrate the performance of the proposed converter.

Single stage modular converter with power factor improvement for telecom power supply

In this paper a single stage modular converter with power factor correction is proposed for telecommunications power supply system. The proposed converter system is formed by three single-phase modules with series connected dc outputs. The series connection of the converters at the output stage yields balanced three phase currents. The use of a high frequency transformer offers galvanic isolation. Both these factors put together provides 6-pulse rectification, resulting in small output filter components. An average current mode control technique is used in the proposed modular converter to provide excellent line and load regulation. The simulation and analysis of the proposed converter is carried out in MATLAB environment to obtain the converter performance which validate its design and working.

Modular three-phase single-stage full-bridge converter for medium power SMPS

In this paper, a three-phase single stage modular converter for medium power supply for telecom power applications is presented based on the novel principle of connecting three single-phase modules in a three-phase group by creating a virtual neutral using a zig-zag transformer. The combination of three single phase modules and a virtual neutral point device is a powerful method to design a three-phase modular converter system with power factor correction. The performance of such a modular full-bridge dc- dc converter system is studied and evaluated with simulation based on a MATLAB model.

Power Quality Improvement in Switched Mode Power Supplies Using Autoconnected Transformer Based 9-Phase ac-dc Converters

Abstract Switched Mode Power Supplies (SMPS) of medium power ratings are extensively used in heating, welding and telecommunication power supply applications. Invariably, they use a 3-phase ac-dc converter at the front end. In this paper, different autoconnected transformer-based 9-phase ac-dc converter configurations are designed, modeled and simulated to feed such medium capacity SMPS for improving the power quality indices at the point of common coupling (PCC). The autoconnected transformer is designed suitable for producing 9-phase voltages of same magnitude and having equal phase shift. The proposed 9-phase ac-dc converters are found capable of suppressing up to 17th harmonic in the supply current along with the power factor improvement close to unity at varying loads. A set of power quality indices on input ac mains and magnetic ratings for various autoconnected transformer configurations for this SMPS are also presented so that the best converter configuration can be chosen according to the requirements for a particular application.

Three-phase modular single stage full-bridge converter for switched mode power supplies

In this paper, the modular development of a three-phase single stage ac-dc power converter based on single-phase ac-dc isolated full-bridge converter for telecom power supply applications is presented. Three single-phase converter modules are series connected to form a three-phase converter system to achieve balanced three-phase currents. This paper analyses the operation of a modular converter in continuous conduction mode (CCM) of power factor correction. The performance of such a modular full-bridge converter system has been evaluated with simulation based on a MATLAB model and the results are also presented. The main objective of the proposed system is to reduce the number of stages and improve the power factor of the input ac mains current. The proposed scheme offers simple control strategy, electrically isolated output, single-stage power conversion, elimination of power transformer at the front end and inherent power factor correction (PFC) for medium rating power supplies.

Unity power factor operation of three-phase AC-DC converter based on modular approach for telecom applications

High power telecommunication power supply systems consist of a three-phase switch mode converter followed by a dc-dc converter to supply 12kW SMPS. These rectifiers draw significant harmonic currents from the utility, resulting in poor input power factor with high total harmonic distortion (THD). In this paper, a three-phase ac-dc converter based on modular approach is proposed for telecommunication applications. The proposed system is formed by three single-phase modules with series connected dc outputs to increase the power level. The series connection of converter yields balanced three phase currents and galvanic isolation with the use of a high frequency transformer, and provides 6-pulse rectification, both together resulting in a smaller output filter components. A design example and simulation results are presented to validate the model of the proposed three-phase 12-kW SMPS converter.

High performance improved three-phase power converter for telecom power systems

In this paper a high performance improved three-phase power converter in modular approach for telecom power systems is proposed. The proposed system is formed by three single-phase modules with series connected dc outputs. The series connection of converter yields balanced dc link currents and galvanic isolation with the use of a high frequency transformer. Further it also and provides 6-pulse rectification, both together resulting in a small output filter components. The design methodology of the proposed converter is illustrated with an example. The design concepts are verified by the digital simulation of the proposed converter.