Modulation Variants in DC Circuits of Power Rectifier Systems with Improved Quality of Energy Conversion—Part I

Tomasz Pajchrowski,Dominik Matecki,Michał Krystkowiak

doi:10.3390/en14071876

Abstract

The article presents various concepts of three-phase power rectifiers with improved quality of converted electric power. This effect is obtained by modulating the currents in the DC output circuits of the rectifiers by means of power electronics controlled voltage or current sources, working as a so-called voltage or current modulators. For further quality improvement of the grid currents of the analyzed systems, it was proposed to use an additional controlled current source connected in parallel to the DC load, hereinafter referred to as a supporting system. The original elaborated method of controlling this source (supporting system) was presented. The main goal of the work was to propose a solution for an effective method of improving the quality of energy conversion in rectifier systems, especially high power ones, by using controlled current sources in DC circuits, operating as the power electronics current modulator and the supporting system.

Highlights

Rectifiers are power electronics devices that convert AC energy into DC energy
The classic 12-pulse rectifier system, consisting of two parallel-connected three-phase rectifier bridges, supplied with voltages of appropriate phase shifts, is characterized by consumption of the higher harmonics from the power grid. Helpful in their significant reduction is the use of the controlled voltage or current sources in the DC circuit, which act as the voltage and current modulator, respectively [12,13]
On the basis of the obtained results, it can be stated that the quality of the grid current signals has slightly deteriorated in comparison to the results achieved for the current modulator based on the ideal current source

Summary

Introduction

Rectifiers are power electronics devices that convert AC energy into DC energy. They are widely used in many branches of industry, e.g., in rail transport, metallurgy and mining. The described methods are relatively expensive and require complex high-current, measurement and control structures For this reason, a very attractive way to improve the quality of energy conversion is to use modulation in the rectifier output circuits. A very attractive way to improve the quality of energy conversion is to use modulation in the rectifier output circuits For this purpose, a controlled voltage or current source with given parameters should be used in parallel or in series with the load. The original method of controlling this source, developed as part of the work, was presented It allows to achieve grid currents very close to sinusoidal signals, while minimizing reactive power and maintaining the required energy balance of the system. The authors confirm the legitimacy of using the proposed solutions and present the planned further research

General Concept of Modulation in the Rectifier Output Circuit

Voltage Modulator in a Rectifier System

Parameters of the Built Experimental Model

Findings

Conclusions