Gopal K. Dubey

An instantaneous reactive volt-ampere compensator and harmonic suppressor system

A novel control method for a reactive volt-ampere compensator and harmonic suppressor system is proposed. It operates without sensing the reactive volt-ampere demand and nonlinearities present in the load. The compensation process is instantaneous, which is achieved without employing any complicated and involved control logic. The compensator is operated in cycle-by-cycle reference-current-controlled mode to achieve the instantaneous compensating feature. A mathematical model of the scheme is developed. Detailed analysis and simulation results are presented. A laboratory prototype of the compensator is developed to validate the results.

Three-phase switch mode rectifier with hysteresis current control

A three-phase configuration of a switch mode rectifier (SMR) that makes use of continuous conduction waveform of the input supply current is suggested. Continuous conduction is achieved by the hysteresis current control (HCC) technique. This three-phase SMR operates at close to unity power factor and has reduced current stresses on the switching devices because of the continuous nature of input current. The conduction period considered for the rectifier diodes is 180/spl deg/. Digitally simulated performance results are provided. Selected experimental results demonstrating the SMR operation are also presented.

Mixed-mode operation of boost switch-mode rectifier for wide range of load variations

A mixed-mode input current sensorless predictive current control at constant but two different switching frequencies for a single-phase boost type switch-mode rectifier (SMR) with single switch topology is proposed. The SMR operates in continuous input current mode (CCM) or in discontinuous input current mode (DCM) depending upon the load. This load dependent operating mode selection avoids the operation of the SMR in the dual mode, where the input current harmonic distortion is maximum. The closed loop output voltage regulation is achieved without the need of an input current sensor. The control scheme is optimized to result in an economic size of the boost inductor along with the compliance of IEC 1000-3-2 harmonic limits for input current.

Performance study of UPQC-Q for load compensation and voltage sag mitigation

Unified power quality conditioner (UPQC) is one of the major custom power solutions that is capable of mitigating the effect of supply voltage sag at the load end or the point of common coupling (PCC). It also prevents load current harmonics from entering the utility and corrects the input power factor of the load. The control of series compensator is such that it injects voltage in quadrature advance to the supply current, so that no active power is consumed by the series compensator at steady state. The UPQC employing this type of quadrature voltage injection in series is termed UPQC-Q. The present paper discusses the VA requirement issues of series and shunt compensators of UPQC-Q and its performance is verified in a laboratory prototype. The phasor diagram, control block diagram and typical experimental results are presented to confirm the validity of the theory.

Programmable input power factor correction method for switch-mode rectifiers

A programmable method for single- and three-phase switch-mode rectifiers (SMRs), operating with discontinuous current conduction to control input power factor close to unity, is presented. Single-phase SMR operation is based on variable turn-on time, while three-phase SMR operation is based on constant turn-on time.

Bang-bang current control with predecided switching frequency for switch-mode rectifiers

An active current waveshaping/control technique with continuous conduction of input current and suitable for single-phase switch-mode rectifiers (SMRs) is proposed. The nature of input current is similar to that of bang-bang hysteresis current control. The technique does not require a reference hysteresis window. Current control is achieved with constant switching frequency for a given load current. The switching frequency varies inversely with the load current, but is known and predecided. Simulated performance results and selected experimental results are provided.

Experimental investigation of performance of a single phase UPQC for voltage sensitive and non-linear loads

A unified power quality conditioner (UPQC) is proposed in this paper. It protects the consumer at the load end from supply voltage sag, and provides unity power factor condition at the utility for different values of load power factor. A PC-based closed loop control scheme is proposed and experimental investigation is carried out in the laboratory. Selected experimental results are reported along with control circuit and phasor diagram to validate the proposition.

Series equivalence/operation of current-controlled boost-type single-phase voltage source converters for bidirectional power flow

Single-phase voltage source power converters (VSCs) under consideration are AC-DC current-controlled boost-type power converters with bidirectional power-handling capability. Equivalence between two series-connected two-level power converters and a single three-level power converter is considered here. Further considered is the series operation of three-level power converters. Simulation results and experimental verification for both are provided. Economical configurations of three-level power converters leading to multilevel waveforms are presented thereafter.

Harmonic elimination in voltage source converters using parallel converter with zero active power

An effective combination of a GTO based voltage source converter (VSC) which can handle large power and a parallel operating VSC using high speed switching devices such as power transistors, MOSFETs or IGBTs is used to reduce the supply current harmonics. The parallel operating VSC handles no active power but only harmonic power. It injects current harmonics of opposite polarity into the supply of that of the harmonics generated by the GTO based VSC. Three types of harmonic elimination technique are suggested and digitally simulated elimination results are presented.<<ETX>>

Stability Analysis, Design, and Simulation of a Closed-Loop Converter-Controlled DC Drive

A method for the design of controllers for closed-loop converter-controlled dc drives is given. Popovs stability criterion has been applied for analyzing stability in the large of the drive system. The paper includes experimental and digital simulation results of a dc drive.