http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

Electric power distribution systems of many commercial and industrial sites often employ variable frequency drives and other loads that internally utilize dc. Such loads are often based on front-end line-commutated rectifiers. The detailed switch-level models of such rectifier systems can be readily implemented using a number of widely available digital programs and transient simulation tools, including the Electromagnetic Transient (EMT)-based programs and Matlab/Simulink. To improve the simulation efficiency for the system-level transient studies with a large number of such subsystems, the so-called dynamic average models have been utilized. This paper presents the average-value modeling methodologies for the conventional three-phase (six-pulse) front-end rectifier loads. We demonstrate the system operation and the dynamic performance of the developed average models in discontinuous and continuous modes, as well as under balanced and unbalanced operation.

Dynamic Average Modeling of Front-End Diode Rectifier Loads Considering Discontinuous Conduction Mode and Unbalanced Operation

https://ro.uow.edu.au/cgi/viewcontent.cgi?article=2162&context=eispapers1

Vibration control of an energy regenerative seat suspension with variable external resistance

A three-phase nonlinear load emulator using a power electronic converter is presented in this study. The proposed nonlinear load emulator is intended to be used in an ultrawide-area grid transmission network emulator, also called hardware testbed (HTB). The emulator converter is controlled in rectifier mode to act as the real nonlinear three-phase diode rectifier load. This paper presents an accurate controller for the nonlinear load emulator based on a three-phase diode rectifier system to be used in the HTB. This study also demonstrates simulation and experimental results for verification of the proposed controller.

Power Converter-Based Three-Phase Nonlinear Load Emulator for a Hardware Testbed System

When applying an active harmonic filter (AHF) to mitigate the harmonic currents of voltage source inverter-fed drives (VSI), the required capacity of the AHF is generally determined by the measured harmonic current of the drives. However, when the AHF is connected to an electrical power distribution system, the total harmonic current distortion of the load actually increases owing to the change in the rectifier commutation behavior. Therefore, a higher AHF output capacity is needed to meet the expected filtering requirement. This paper investigates the impact of the AHF on the changes of the harmonic current distortion of the VSI. For this purpose, correlation analysis models are constructed, and case studies are presented to illustrate the effect with different system short-circuit levels, load conditions, and ac chokes of the VSI. Furthermore, several actual field measurement results are presented for verification. On the basis of the measured and calculated results, a margin factor is recommended for use when determining the capacity of the AHF.

Impact of Shunt Active Harmonic Filter on Harmonic Current Distortion of Voltage Source Inverter-Fed Drives

This paper presents a time domain method to analyze the three phase rectifier with capacitor output filter. As demonstrated in the paper, the proposed method analytically evaluates harmonics, and obtains exact switching functions by iteratively solving for the switching instants. An analytical Jacobian of the mismatch equations is obtained to ensure a quadratic convergence rate for the iteration process. It is also demonstrated that a unified approach exists to analyze converters operating in the continuous conduction mode and discontinuous conduction mode. One potential application of the proposed model is to incorporate it into a harmonic power flow program to yield improved accuracy.

B.K. Perkins

Papers

Harmonic Analysis of a Three-Phase Diode Bridge Rectifier Based on Sampled-Data Model