Mukul Rastogi

Hybrid-active filtering of harmonic currents in power systems

Use of nonlinear loads and devices in power systems is expected to grow rapidly. Examples are thyristor-controlled inductors for FACTS, converters for HVDC transmission and large adjustable speed drives. All of these loads inject harmonic currents into the power system. A novel hybrid filter topology and its control, to prevent such harmonic currents from entering the power system, are presented in this paper. Analysis shows that in the proposed filter, the power electronic converter, required to generate harmonic currents for compensation, has a rating of only 9% when compared to the converter rating in an active filter and approximately one-half of that in a series-hybrid filter discussed in the literature. The proposed topology enables practical implementation of active harmonic current filters. The control of this filter under transient conditions such as start-up and during steady state is demonstrated by means of simulations. Results from a scaled-down hardware prototype are presented to verify the simulations. >

A comparative evaluation of harmonic reduction techniques in three-phase utility interface of power electronic loads

Power electronic loads inject harmonic currents into the utility system. This paper presents a comparative evaluation of harmonic reduction techniques which satisfy the current harmonic limits specified by the IEEE Standard 519, and at the same time provide a regulated DC output voltage. The techniques considered include active and hybrid filters, and various current waveshaping approaches for a three-phase utility interface. These techniques are compared in terms of their complexity (number of switches) and their component ratings. Based on the application requirements and the cost of active and passive components, this paper enables the estimation of the minimum cost topology. >

Third-harmonic modulated power electronics interface with three-phase utility to provide a regulated DC output and to minimize line-current harmonics

A novel approach to achieving nearly sinusoidal line current rectification of three-phase utility voltages is presented. The scheme incorporates two step-up DC-DC power converters to modulate the DC link currents at the third harmonic frequency. The modulated currents are then reinjected on the AC side of the diode bridge rectifier. Simulation results for a three-phase, 208 V (line-to-line), 3 kW system are presented. The sensitivity of the interface to unbalances in various system parameters is included. Results from experimental investigations on a small-scale laboratory model are presented.<<ETX>>

Analysis of a new power electronics interface with approximately sinusoidal 3-phase utility currents and a regulated DC output

A three phase rectification scheme that draws line currents with reduced distortion and provides a regulated DC output voltage is analyzed. The scheme employs two boost DC-DC converters to modulate the DC link currents. The modulation current is injected into the AC side through an impedance network consisting of series tuned L-C branches. The theoretical analysis and the basic simulation results, which can be used to carry out the design of a system based on this approach, are presented. >

Filtering of harmonic currents and damping of resonances in power systems with a hybrid-active filter

A novel hybrid-active filter topology to minimize electric utility current harmonics at high power levels is presented in this paper. The proposed topology combines both passive and active filters to obtain the lowest power converter VA rating as compared to the power converter rating in the active filter and the series-active hybrid filter configurations. This is demonstrated with experimental results from a laboratory model. Transient and steady state operation of the hybrid-active filter is also presented. The control of the proposed filter is extended to provide damping of resonances due to neighboring loads. Simulation results showing the effect of active damping are presented.<<ETX>>

A magnetic device current injection in a three-phase sinusoidal-current utility interface

A magnetic device for current injection in a three-phase, sinusoidal-current utility interface is presented. This class of sinusoidal rectification depends on the injection of a third-harmonic current into the AC side of a three-phase rectifier. The injection network should provide a low and equal impedance in each of the three branches to the modulation current at the third harmonic frequency, and a high impedance to the fundamental frequency voltages. Experimental results from an injection device for a 12.5 kW sinusoidal rectification scheme are presented to support the simulation results obtained by a finite element program.<<ETX>>

Optimization of a novel DC-link current modulated interface with 3-phase utility systems to minimize line current harmonics

A novel three-phase utility interface is discussed. The interface draws near-sinusoidal currents from the utility and provides a regulated DC output voltage. The performance of the system is optimized. Simulation results for a three-phase, 208 V (line-to-line), 3 kW system are presented. The sensitivity of the interface to unbalances in various system parameters is examined. Simulation results indicate that a total harmonic distortion in the line currents lower than 5% can be achieved by the interface. It is shown that there is minimal degradation of performance with changes in system parameters.<<ETX>>

Three-phase sinusoidal current rectifier with zero-current switching

This paper presents a three-phase rectification scheme with nearly sinusoidal line currents. The principle of third harmonic current circulation is used to reduce the distortion in the line currents. Zero-current switching is accomplished with the use of only two switches. A circuit design along with the experimental results are presented. Comparisons between a zero-current switching rectifier and a rectifier using hard-switched converters in terms of component ratings and EMI filter considerations are included.<<ETX>>