Shyama P. Das

Experimental Investigation of a Single-Phase UPQC With Minimum VA Loading

The paper deals with an optimized unified power-quality conditioner (UPQC), which aims at the integration of series active and shunt active power filters with minimum volt-ampere (VA) loading of the UPQC. The series active filter is a dynamic voltage restorer (DVR), which regulates the voltage at the load end with minimum VA loading of the overall UPQC by injecting the voltage at an optimum angle. The proposed scheme is validated by an experimental prototype in the laboratory. Selected experimental results are reported along with analytical findings, which show the effectiveness of the proposed UPQC

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.

Observer-based stator-flux-oriented vector control of cycloconverter-fed synchronous motor drive

A six-pulse noncirculating-current cycloconverter-fed synchronous motor with stator-flux-oriented vector control for high-power and low-speed applications is discussed here. Vector control is achieved by stator flux estimation through a novel closed-loop reduced-order observer exhibiting stable speed regulation. Variable displacement factor operation is incorporated to keep both the system current continuous and the system utilization optimum. A simple method is used in designing the controller for armature current regulation with good performance. A generalized digital simulation of the drive system is made, and the simulation results are validated by a low-cost laboratory implementation of the drive with a 386DX PC-based system with 80387 floating point support.

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.

Fault diagnosis and condition monitoring of electrical machines - A Review

Electrical equipments are the workhorses of industry; their failure may result in complete shut down of a plant or even cause an unexpected disaster. Researchers had pursued rigorously various diagnostic approaches for electrical machines. Apart from analyzing the conventional vibration, current, voltage signals people are trying to explore fault signatures from torque, power, speed, flux etc. Methods such as offline/online, with/without additional sensor, model-based, signal-based etc. are being explored vastly. A number of signal processing techniques and fault detection decision-making tools are being reported frequently. Undoubtedly this field is vast in scope. Hence keeping this in mind to avoid repetition as well to facilitate future research a brief review is presented in this paper. Nearly 80% electrical motors used in industries are induction motors and hence industries depend on the performance of them to a great extend. This paper will mainly concentrate on induction machines with a very brief review of other machines.

A sliding mode controller based optimum UPQC with minimum VA loading

The paper deals with an optimized unified power quality conditioner (UPQC), which aims at the integration of series active and shunt active power filters with minimum VA loading of the UPQC. The series active filter is a dynamic voltage restorer (DVR), which is operated in twofold functioning mode. During the unbalanced voltage sag, the DVR compensates the unbalance in the voltage sag. It also regulates the voltage at the load end with minimum VA loading of the overall UPQC by voltage injection at optimum angle. Sliding mode controller with constant frequency is employed to ensure the exact tracking of the reference voltage by DVR. Validity of the proposed scheme is proved through extensive simulation results.

Experimental investigation of DVR with sliding mode control

Voltage sags and swells are vital power quality problems and the dynamic voltage restorer (DVR) is known as an effective device to mitigate voltage sags and swells. The paper deals with the sliding mode control of single phase DVR for voltage sag/swell correction. A sliding mode controller is designed and developed for a single phase DVR. Using sliding mode control to the DVR, additional sag/swell detection method is eliminated. This improves the dynamic response of the DVR and also DVR is able to compensate for any variation in source voltage. Usage of sliding mode control to DVR, makes it multifunctional, such as compensation for voltage sag, swell, voltage flicker and voltage harmonics as well. Validity of the proposed control is verified through extensive simulation and experimental results

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.

Control and protection strategy for a three-phase single-stage boost type grid-connected current source inverter for PV applications

Renewable or Sustainable Energy (SE) sources such as photovoltaic (PV) cells usually generate variable power. Hence power electronic circuits are used to extract maximum power from these sources at all times. Further, Grid-integration demands tight technical standards to be met. Hence novel power electronic converter topologies are used to bring down the level of harmonics while interfacing the SE sources with the utility of fixed grid voltage. These two functions can be performed using two separate power conversion stages. But this would reduce the overall efficiency and reliability of the system. Hence, it is desirable to use a single power electronic conversion stage to perform both the functions. This paper evaluates a single stage power electronic converter topology capable of boosting the variable dc voltage towards the ac mains. The chosen topology, a Current Source Inverter (CSI), is used as an interface between the PV source and the utility. The paper discusses the principle of operation, control and protection strategy used for this topology. Experimental results of the Grid-Connected (GC) Current Source Inverter (CSI) based PV system using real time Digital Signal Processor dSPACE are also presented. Finally three phase sinusoidal currents are injected into the grid at unity power factor (UPF).

A new public-domain simulator for power electronic circuits

A new public-domain simulator (SEQUEL) for power electronic circuits is described. The organization of the simulator is briefly discussed. The most important feature of the simulator is that the user can define new elements in a flexible manner. The differences between the new simulator and other simulators are enumerated. Some simulation examples are discussed to demonstrate the applications of the simulator. It is pointed out that the new simulator is particularly attractive for engineering institutes in developing countries where access to expensive commercial packages with similar capabilities may be difficult.