Brij N. Singh

A review of single-phase improved power quality AC-DC converters

Three-phase AC-DC converters have been developed to a matured level with improved power quality in terms of power-factor correction, reduced total harmonic distortion at input AC mains, and regulated DC output in buck, boost, buck-boost, multilevel, and multipulse modes with unidirectional and bidirectional power flow. This paper presents an exhaustive review of three-phase improved power quality AC-DC converters (IPQCs) configurations, control strategies, selection of components, comparative factors, recent trends, their suitability, and selection for specific applications. It is aimed at presenting a state of the art on the IPQC technology to researchers, designers, and application engineers dealing with three-phase AC-DC converters. A classified list of around 450 research articles on IPQCs is also appended for a quick reference.

An improved control algorithm of shunt active filter for voltage regulation, harmonic elimination, power-factor correction, and balancing of nonlinear loads

This paper deals with an implementation of a new control algorithm for a three-phase shunt active filter to regulate load terminal voltage, eliminate harmonics, correct supply power-factor, and balance the nonlinear unbalanced loads. A three-phase insulated gate bipolar transistor (IGBT) based current controlled voltage source inverter (CC-VSI) with a DC bus capacitor is used as an active filter (AF). The control algorithm of the AF uses two closed loop PI controllers. The DC bus voltage of the AF and three-phase supply voltages are used as feedback signals in the PI controllers. The control algorithm of the AF provides three-phase reference supply currents. A carrier wave pulse width modulation (PWM) current controller is employed over the reference and sensed supply currents to generate gating pulses of IGBTs of the AF. Test results are presented and discussed to demonstrate the voltage regulation, harmonic elimination, power-factor correction and load balancing capabilities of the AF system.

Optimal selection of wavelet basis function applied to ECG signal denoising

Over the years ElectroCardioGram (ECG) signal has been used to assess the cardiovascular condition of humans. In practice, real time acquisition and transmission of the ECG may contain noise signals superimposed on it. In general, the signal processing algorithms employed for denoising provide optimal performance and eliminate the high frequency noise between any two beats contained in a continuous ECG signal. Despite their optimal performance, the signal processing algorithms significantly attenuate the peaks of characteristics wave of the ECG signal. This paper presents a selection procedure of mother wavelet basis functions applied for denoising of the ECG signal in wavelet domain while retaining the signal peaks close to their full amplitude. The obtained wavelet based denoised ECG signals retain the necessary diagnostics information contained in the original ECG signal.

Multipulse AC–DC Converters for Improving Power Quality: A Review

Three-phase multipulse AC-DC converters (MPC) are developed for improving power quality to reduce harmonics in AC mains and ripples in DC output. This paper deals with the multipulse AC-DC converter configurations, state of art, their performance, power quality aspects, components selection considerations, latest trends, future developments, and potential applications. It is targeted to provide broad perspective on multipulse converter technology to the researchers, engineers, and designers dealing with them. A classified list of more than 250 research publications on the subject is also given for quick reference.

Performance comparison of two current control techniques applied to an active filter

This paper compares two types of current control techniques with a view to the problem of switching ripples in the supply current caused by switching of an active power filter (APF). A closed loop control scheme of a three-phase APF is implemented using a TMS320C31 DSP for direct and indirect current control techniques. A current controlled voltage source inverter (CC-VSI) is used as an APF. A three-phase diode bridge rectifier with R-L load is taken as a nonlinear load. Experimental results for both the techniques of current control are compared and the capability of the indirect current control technique towards the elimination of switching ripples is established.

An Improved Control Algorithm for Active Filters

This paper proposes a new control algorithm resulting in significant advantages toward smooth control of an active filter (AF). The majority of existing feedforward control methods of the AF system result in switching notches (sharp-rising ripples) in the supply current during transitions of stepped waveshaped nonlinear load current. This is due to switching signals for the AF devices, which are obtained by comparison of the sensed and reference currents of the AF. The proposed control algorithm is based on feedback control, wherein, switching signals for the AF devices are obtained by comparing sensed and reference supply currents. This not only eliminates switching notches in the supply currents but also reduces the supply current total demand distortion below the 5% mark recommended by the IEEE-519 standard. A TMS320C31 digital signal processor is used for real-time implementation of the proposed algorithm. To establish its viability and flexibility, the proposed algorithm is also experimented with a laboratory prototype of the AF system made of a reduced number of switches

Fuzzy control algorithm for universal active filter

In this paper, a fuzzy algorithm is employed to control a three-phase unified power quality conditioner (UPQC). The UPQC is an active filter (AF) and it compensates the reactive power and harmonics in both the voltage and current caused by nonlinear loads. The UPQC makes use of two back-to-back connected IGBT-based voltage source inverters (VSIs) with a common DC bus. One inverter is connected in series while other is placed in shunt with the nonlinear load. The shunt inverter works as a current source and compensates current harmonics caused by nonlinear loads. The series inverter works as a voltage source and helps in compensating the voltage harmonics caused by nonlinear loads. A diode bridge rectifier feeding an R-L load is considered as a nonlinear current load while a source of voltage harmonics is considered in shunt with the load. With a view to examining the steady state and transient performance of the UPQC, a suitable mathematical model of the system is developed. The capability of the UPQC is demonstrated in the filtering of voltage and current harmonics along with the reactive power compensation of nonlinear loads. Simulated results are given and discussed in detail. Experimental results are also given.

Digital implementation of a new type of hybrid filter with simplified control strategy

A new type of hybrid active filter to compensate harmonics of a nonlinear load is presented in this paper. The proposed topology of hybrid filter combines a shunt passive filter (PF) and a shunt active filter (AF). A series inductor between both the filters is introduced to create a harmonic voltage source at the input of nonlinear load. A diode bridge rectifier with R-C load is considered as a nonlinear load. An indirect current controlled voltage source inverter (ICC-VSI) is considered as an AF. A simple control algorithm based on proportional plus integral control of a self-supporting DC bus voltage of the shunt AF is implemented on a TMS320C31 DSP. The passive filter is tuned to compensate 5/sup th/ and 7/sup th/ harmonics, while the AF compensates the rest of harmonics of the load current. A laboratory prototype model of the proposed hybrid filter is developed and its performance is examined. Experimental results are given and discussed.

Experience in the development of microhydel grid independent power generation scheme using induction generators for Indian conditions

This paper deals with stand alone micro hydel units typically of unit sizes up to 100 kW, based on the experience of the authors in developing appropriate technologies for a project supported by the Department of Science and Technology (Govt. of India). A laboratory model is built for the complete power generation scheme relating to field installation of a 6 kW unit at a chosen site in Kerala jointly with Integrated Rural Technology Centre (IRTC), Kerala.

A new topology of active filter to correct power-factor, compensate harmonics, reactive power and unbalance of three-phase four-wire loads

This paper proposes a new topology of an active filter (AF) with improved control algorithm. The reactive power theory of three-phase circuits is used to obtain reference currents as control quantities for the AF. The developed improved control algorithm is first tested with a standard topology of the AF, thereafter, extended to control a new topology of four-pole AF system. The new topology of the AF system is capable to compensate harmonics and reactive power, correct power-factor and unbalance in three-phase four-wire balanced/unbalanced linear/nonlinear loads. The proposed new topology of the AF system fully compensates neutral current for nonlinear unbalanced load connected in a three-phase four-wire supply system, thereby preventing heating and bursting of neutral conductor. The new topology of the AF system is free from shoot through fault and exhibits a desired performance. The developed control algorithm is implemented using a TMS320C31 DSP system and performance of new topology of the four-pole AF system with improved control algorithm is simulated. Simulation as well as experimental results are given and discussed in detail.