Single-phase Operation Research Articles

Efficiency Evaluation of Three Phase and Single Phase C2C Self-Excited Induction Generator for Micro Hydro Power Application

Squirrel-cage induction motor (SCIM) is used as generator to a great extent for micro hydropower applications due to their robustness, brushless construction, low cost, reliability, rare maintenance, and availability in a wide power range. Squirrel-cage induction generator (SCIG) normally requires excitation capacitors to build up the terminal voltage from residual magnetism. However, for rated and stable voltage and frequency operation, selection of an appropriate size of excitation capacitor is crucial. This paper presents the efficiency evaluation of an SCIG with different excitation capacitors to supply three-phase and single-phase resistive loads. A 1.5-kW three-phase SCIM was selected as the SCIG driven by a 3-kW three-phase SCIM as a prime mover. The shaft speed was controlled by a variable speed drive (Yaskawa A1000) with an incremental encoder for the speed feedback. Shaft torque was obtained from a torque sensor (TRB-2K) installed in between the two machines. Parameters of the SCIG were determined by DC, no-load, and locked rotor tests, then the required excitation capacitance was calculated. For three-phase operation star connected SCIG was excited by the capacitors in star connection to supply a three-phase resistive load. For the single-phase operation, the delta connected SCIG was excited with so-called C2C configuration.

Coupled modeling of a directly heated tubular solar receiver for supercritical carbon dioxide Brayton cycle: Structural and creep-fatigue evaluation

A supercritical carbon dioxide (sCO2) Brayton cycle is an emerging high energy-density cycle undergoing extensive research due to the appealing thermo-physical properties of sCO2 and single phase operation. Development of a solar receiver capable of delivering sCO2 at 20MPa and 700°C is required for implementation of the high efficiency (∼50%) solar powered sCO2 Brayton cycle. In this work, extensive candidate materials are review along with tube size optimization using the ASME Boiler and Pressure Vessel Code. Temperature and pressure distribution obtained from the thermal-fluid modeling (presented in a complementary publication) are used to evaluate the thermal and mechanical stresses along with detailed creep-fatigue analysis of the tubes. The resulting body stresses were used to approximate the lifetime performance of the receiver tubes. A cyclic loading analysis is performed by coupling the Strain-Life approach and the Larson-Miller creep model. The structural integrity of the receiver was examined and it was found that the stresses can be withstood by specific tubes, determined by a parametric geometric analysis. The creep-fatigue analysis displayed the damage accumulation due to cycling and the permanent deformation on the tubes showed that the tubes can operate for the full lifetime of the receiver.

Fault limitation characteristics of a lab-scale resistive type superconducting fault current limiter

With the recent development of advanced YBCO based 2nd generation (2G) coated conductors (CCs), many researchers started developing superconducting fault current limiters (SFCLs) based on these conductors. We have used an electrically insulated CC developed by Super Power to make a simplified laboratory scale resistive (i.e. non-inductive) type superconducting coil for SFCL technology in Indian power sector. This CC has unique thermal and electrical properties when compared to other commercially available HTS conductors. This YBCO based HTS tape has a silver over-layer and is made on Hastelloy®276 substrate which is highly resistive by nature. The conductor has polymide (kapton, 30% overlap) insulation for high voltage safety. Using this conductor, we made a small superconducting coil where adjacent turns carry equal and opposite currents to make it non-inductive. This SFCL coil is rated for 220 Vrms and 400 Arms (single phase) operation. The former of the coil is fabricated in-house using G-10 Glass fiber and fine holes are made on the former for both-side cooling of the CC. In this paper, a simplified design of a resistive SFCL without bypass path is carried out using 2G CCs. After that, the continuous current performance of the coil and voltage drop are measured when 425 Arms is applied. Over-current test on the coil is carried out to measure the effective fault limitation to verify the performance of the resistive SFCL without a bypass path.

Modelling and control of VIENNA rectifier a single phase approach

Input harmonic and power factor (PF) regulations necessitate the use of front end active PF correction (APFC) circuit for power electronic converters. In recent times, the VIENNA rectifier has become a popular choice for three-phase APFC applications. The converter is a fifth-order system and results in a highly complex model. This calls for a complex control design procedure and involves enormous computation requiring the use of a high end digital signal processor (DSP). This can be simplified if the order of system is reduced. In this study, it is proposed to decouple and analyse the converter as three independent single phase units operating in parallel with current mode control, thereby reducing the order to two, simplifying the analysis and control design. The transfer function of the proposed small-signal model is derived and its Bode plot is drawn. A high bandwidth inner average current controller and a low bandwidth outer voltage controller are designed to obtain a 60° phase margin. With the proposed design, a 10 kW prototype VIENNA rectifier is developed with a low cost analogue integrated circuit (IC) and validated. The results obtained prove the accuracy of the proposed model and effectiveness of the control. Single phase operation is also made feasible with the proposed technique.

Single-phasing detection and classification in distribution systems with a high penetration of distributed generation

This paper presents a robust wavelet-ANN based algorithm for single-phasing detection and single-phasing classification in distribution systems with a high penetration of distributed generation (DG). In traditional vertically integrated distribution systems, single-phasing events are detected easily, as the current of one of the phases is lost completely, resulting in a significant current unbalance ratio. However, this is not the case for distribution systems with a high penetration level of DG units, as the backfeed current from the DG units will support the current in the lost phase, hence masking the single-phasing operation. In the proposed algorithm, the transient current signals generated at the onset of the single-phasing condition are combined into a modal signal. This signal is analyzed using discrete wavelet transform (DWT) to extract the feature vector denoting the distinctive features for each frequency band. Finally, artificial neural networks (ANNs) are used to detect single-phasing conditions and to classify the lost phase. Simulation results have confirmed the dependability and security of the proposed algorithm.

Islanding detection based on asymmetric tripping of feeder circuit breaker in ungrounded power distribution system

An islanding detection method in ungrounded power distribution system based on single-phase operating mechanisms of the circuit breaker (CB) is proposed in this paper. When CB opens three phase circuits to form an island, one phase circuit is opened firstly and the other two phase circuits are opened secondly after certain duration. During the period when only one phase circuit is opened, negative sequence voltage with certain duration is obtained at DG side because of the asymmetric operation of the system. After all three phase circuits are opened, the voltage variation direction of the two phases that are secondly disconnected from the grid follows the voltage variation direction of the firstly disconnected phase. Based on the above voltage characteristics, an islanding detection scheme is proposed to identify genuine islanding from system disturbances. The performance of the proposed scheme is tested in PSCAD/EMTDC using a 10 kV distribution network with synchronous DG interconnection. Simulation results demonstrate the proposed method is effective and reliable to detect islanding formation.

Study of the Two-Phase Operation Mechanism of Three-Phase Motors Based on LC Phase Shifting Method

In the absence of three-phase power supply, it has certain practical significance to connect the three-phase induction motor to the single-phase power supply for single phase operation. This paper analyzes the asymmetric circuit system of the motor by the method of symmetrical components-Lc phase shifting, disassembles the voltage and current of the three-phase motor stator winding into three groups of symmetrical components: positive sequence, negative sequence and zero sequence. We derivate and analysis the LC phase shifting method to simulate and validate the Lc phase shifting method theory, deduce the formula for calculating of optimum external capacitance and inductance, simulate and calculate all kinds of single phase operation method, finally we use the simulation software to simulate and validate three-phase induction motors single phase operation.

D-Q Current Signature-Based Faulted Phase Localization for SM-PMAC Machine Drives

Fault diagnostic algorithms in motor drives prevent damage to the motor, drive, and overall system by providing an additional level of safety. A single phase open (SPO) fault in a field-oriented controlled drive is one of the perilous faults that require immediate detection due to resulting oscillatory electromagnetic torque. SPO fault results in a significantly high electromagnetic torque ripple. The rapid mechanical vibration caused by the torque ripple exposes the system to failure modes. The single open phase fault detection algorithm proposed in this paper enables the rapid detection of the fault, with minimal system resources, compared to existing methods. Proof of accurate fault detection capability for a wide speed range is presented through simulation and experimental results. The proposed method is also capable of localizing the faulted phase via a novel time domain rotor reference frame current signature analysis.

A Three-Phase Frequency-Adaptive Phase-Locked Loop for Independent Single-Phase Operation

This letter proposes a phase-locked loop (PLL) able to operate as an independent single-phase PLL in the context of three-phase systems. Its key advantage is that the extracted information allows the independent control of both the active and reactive powers for each phase. The proposed PLL utilizes moving average filters and, hence, remains robust under unbalanced and highly distorted voltages. A frequency estimator is also presented and incorporated in the PLL angle detector path to make it frequency adaptive. The performance of the proposed PLL is verified experimentally and results for frequency change, phase-angle jump, and unbalanced voltage sag are reported as a confirmation of its potential.

Local single- and two-phase heat transfer from an impinging cross-shaped jet

Abstract Local single- and two-phase heat transfer distributions are measured under a confined impinging jet issuing from a cross-shaped orifice. Spatially resolved temperature maps and convection coefficients resulting from the impinging flow are obtained via infrared imaging of a thin-foil heat source. The cooling patterns in single- and two-phase operation are explained by an accompanying numerical investigation of the fluid flow issuing from the orifice; computed velocity magnitudes and turbulence intensities are presented. In single-phase operation, the coolest surface temperatures correspond to areas with high liquid velocities. High velocities and developing turbulence are also shown to increase convective heat transfer along the diagonal outflow directions from the impinging jet. During two-phase transport, boiling preferentially begins in regions of low velocity, providing enhanced heat transfer in the areas least affected by the impingement. The cross-shaped orifice achieves local heat transfer coefficients that exceed the stagnation-point value of a circular jet of equivalent open orifice area by up to 1.5 times, while resulting in an increased pressure drop only 1.1 times higher than that of the circular jet.

A Gravitational Search Algorithm (GSA) based Photo-Voltaic (PV) excitation control strategy for single phase operation of three phase wind-turbine coupled induction generator

Three phase induction generators are widely used for single phase operation in wind based micro-generation schemes to cater single phase loads due to various advantages. This paper presents an improved control methodology for self excited three phase induction generator operating in single phase mode. The excitation is controlled through an inverter with Photo-Voltaic (PV) panels providing power to the dc bus. The proposed technique enables the generator for building up voltage from low wind speeds compared to conventional three phase machines. A capacitor connected across load terminals reduces the reactive power supplied by the inverter connected across the other two phases. Gravitational search algorithm (GSA) is used to calculate the switching angles of the inverter under various load and wind speeds for minimum Total Harmonic Distortion (THD) of the generated voltage. The proposed induction generator is aimed to be conveniently used in remote and grid isolated areas as a portable source of electrical power driving single phase loads. Simulations and experiments performed on a 3-phase 1 kW, 415 V, 50 Hz, 1440 r/min induction machine validates the proposed concept.

Confined Jet Impingement With Boiling on a Variety of Enhanced Surfaces

Confined jet impingement with boiling offers unique and attractive performance characteristics for thermal management of high heat flux components. Two-phase operation of jet impingement has been shown to provide high heat transfer coefficients while maintaining a uniform temperature over a target surface. This can be achieved with minimal increases in pumping power compared to single-phase operation. To investigate further enhancements in heat transfer coefficients and increases in the maximum heat flux supported by two-phase jet impingement, an experimental study of surface enhancements is performed using the dielectric working fluid HFE-7100. The performance of a single, 3.75 mm-diameter jet orifice is compared across four distinct copper target surfaces of varying enhancement scales: a baseline smooth flat surface, a flat surface coated with a microporous layer, a surface with macroscale area enhancement (extended square pin fins), and a hybrid surface on which the pin fins are coated with the microporous layer. The heat transfer performance of each surface is compared in single- and two-phase operation at three volumetric flow rates (450 ml/min, 900 ml/min, and 1800 ml/min); area-averaged heat transfer parameters and pressure drop are reported. The mechanisms resulting in enhanced performance for the different surfaces are identified, with a special focus on the coated pin fins. This hybrid surface showed the best enhancement of all those tested, and resulted in an extension of critical heat flux (CHF) by a maximum of 2.42 times compared to the smooth flat surface at the lowest flow rate investigated; no increase in the overall pressure drop was measured.

Analysis of Two-Phase Operation Mechanism of Three-Phase Motor Based on Capacitor Phase Shift Method

In the absence of a three-phase power source, single-phase operation of three-phase induction motor used single-phase power source had a certain practical significance. In this paper, utilized symmetrical component method analysed the asymmetric circuit system of motor, will be voltage and current of the three-phase stator windings decomposed into positive, negative and zero sequence three groups symmetrical components. The theory is analyzed and the formula is deduced of capacitor phase shift method, solved the problem of starting torque, proposed to add starting capacitors and deduced the optimal value of starting capacitor. Finally, the single-phase operation of three-phase induction motor is simulated and verified by simulation software.

Decreasing the influence of arc feed currents and transient recovery voltages in single-phase conditions in EHV lines

One of the most efficient ways to solve the problem of reactive power compensation connected with restriction of unacceptable levels of voltage on extrahigh voltage (EHV) power-transmission lines is installation of additional shunting reactors (SR) in the EHV networks. Moreover, installation of shunting reactors leads to the occurrence of resonance overvoltages under single-phase operation conditions of power transmission (for example within the one-phase automatic reclosing time), as well as to the occurrence of deenergized current phase of the arc feed in the arc channel, which prevents fast deionization of another channel and increasing transient recovery voltage. In this paper, measures for decreasing the influence of arc feed currents and transient recovery voltages in single-phase conditions of EHV lines are considered.

PSS Sustainability Assessment and Monitoring Framework (PSS-SAM) – Case Study of a Multi-module PSS Solution

Business-to-business Product Service System (PSS) solutions are characterized by intensive interaction among PSS providers, suppliers, and customers, as well as an integration of physical and immaterial solution modules. These factors increase the complexity and interdisciplinary of such offerings. Furthermore, the characteristics complicate sustainability assessment and monitoring of PSS, as environmental, social, and economic concerns have to be integrated into a PSS by minimizing negative impacts of the PSS on these three axes throughout the PSS lifecycle. The indicator-based framework “PSS Sustainability Assessment and Monitoring (PSS-SAM)” has been specifically developed to support managers and decision makers in dealing with the complex situation described above. This framework considers the most important sustainability aspects throughout the entire PSS lifecycle and adheres to European standard requirements. The results of a previous work have already confirmed the usability of the framework to assess the sustainability of one PSS module (availability of spindle) within a single PSS lifecycle phase (operating phase). The aim of this paper is to present the improvements of the PSS-SAM framework that facilitate sustainability assessment of PSS solutions with multiple modules throughout their entire lifecycle. The improved framework has been validated by a case study of an industrial micro-production PSS solution including multiple modules (spindle, maintenance, training, etc.). The long-term goal is to develop IT solutions that support the sustainability assessment of PSS.

Numerical Investigation of Two-Phase Flow in Natural Gas Ejector

Increasing production and recovery from the mature oil and gas fields often requires a boosting system when the gas pressure is lower than that demanded by the transportation or process system. The supersonic ejector, considered to be a cost-effective way to boost the production of a low-pressure gas well, was introduced into the industrial field. However, the exploitation of natural gas often accompanies with water. The computational fluid dynamics (CFD) technique was employed to investigate the two-phase effect (water droplets) on the performance of natural gas ejector for the motive pressure ranging from 11.0 MPa to 13.0 MPa, induced pressure from 3.0 MPa to 5.0 MPa, and backpressure from 5.1 MPa to 5.6 MPa, while the injected water flow rate was less than 0.03 kg s−1. The numerical results show that the entrainment ratio of the two-phase operation was higher than that of the single-phase operation with the variation of backpressure. Meanwhile, the entrainment ratio increased with the increase of injected water flow rate into the primary flow. When the water was injected into the secondary flow, the entrainment ratio decreased as the injected water flow rate increased, but the critical backpressure remained unchanged.

Feasibility of operating a solid–liquid bioreactor with used automobile tires as the sequestering phase for the biodegradation of inhibitory compounds

Finding new uses for waste or discarded material is an important environmental goal; being able to use a waste material to treat another waste is an even more attractive objective, and this was the purpose of the present work. We previously showed that used automobile tires have an affinity for a toxic contaminant, dichlorophenol (DCP), absorbing and releasing it based on concentration driving forces. Here we have exploited this phenomenon by using used tires as the sequestering phase in a Two-Phase Partitioning Bioreactor (TPPB) to treat otherwise-toxic levels of DCP, far out-performing single phase operation in a sequencing batch bioreactor. A comprehensive examination of substrate loading, reactor exchange ratio, and tire fraction used, demonstrated that the tire-TPPB system could handle a 40% higher influent substrate loading and an increase of the exchange ratio value from 0.5 (prohibitive for single phase operation) to 0.7. Such improvement was obtained with a tire fraction ≤9%, comparable to that for commercial polymers previously employed in TPPBs. This study has opened the door to the identification of other waste plastics suitable for use in TPPBs for the treatment of recalcitrant organic contaminants.

Reactive Power Compensation in Single-Phase Operation of Microgrid

A coordinated control of distributed generators (DG) and distribution static compensator (DSTATCOM) in a microgrid is proposed in this paper. With high penetration of distributed sources and single-phase operation of the system, voltage unbalance can often go beyond the acceptable limit. With the feeders geographically spread out, it is not always possible to achieve reactive compensation at optimum location with the three-phase devices. In this paper, a simple control strategy for DSTATCOM with communication in loop is proposed. The proposed reactive compensation technique is based on the voltage sag and the power flow in the line. The power flow and the voltage at different locations of the feeders are communicated to the DSTATCOM to modulate the reactive compensation. The single-phase DSTATCOM compensates for the reactive power deficiency in the phase while the DGs supply “maximum available active power.” During reactive power limit of the DG, the “maximum available active power” is fixed to a value lower than maximum active power to increase reactive power injection capability of the DGs. A primary control loop based on local measurement in the DSTATCOM always ensures a part of reactive compensation in case of communication failure. It is shown that the proposed method can always ensure to achieve acceptable voltage regulation. The data traffic analysis of the communication scheme and closed-loop simulation of power network and communication network are presented to validate the proposed method.

Simulation Research on the Single-Phase Operation of a Line Start Permanent Magnet Synchronous Motor

In this paper, the single-phase operation of a line start permanent magnet synchronous motor (LSPMSM) has been analyzed in detail. At first, based on symmetrical component method, the condition for balanced operation is derived. Secondly, steady state performances are analyzed by computer programming. Thirdly, the transient performances are studied on the basis of MTLAB/Simulink. The results demonstrated that the LSPMSM running on a single-phase supply has lower efficiency but higher power factor than three-phase balanced operation, besides good starting and operating performances can be achieved.

Polymer characterization and optimization of conditions for the enhanced bioproduction of benzaldehyde by Pichia pastoris in a two‐ ;phase partitioning bioreactor

Benzaldehyde, with its apricot and almond-like aroma, is the second most abundantly used molecule in the flavor industry, and is most commonly produced via chemical routes, such as by the oxidation of toluene. Biologically produced benzaldehyde, whether by extraction of plant material or via microbial biotransformation, commands a substantial price advantage, and greater consumer acceptance. Methylotrophic yeast, such as Pichia pastoris, contain the enzyme alcohol oxidase (AOX), which, in the presence of alcohols other than methanol, are able to yield aldehydes as dead-end products, for example, benzaldehyde from benzyl alcohol. In this work, we have determined that benzaldehyde, and not benzyl alcohol, is inhibitory to the transformation reaction by P. pastoris, prompting the development of a selection strategy for identifying sequestering polymers for use in a partitioning bioreactor that was based on the ratio of partition coefficients (PCs) for the two target molecules. Additionally, we have now confirmed for the first time, that the mechanism of solute uptake by amorphous polymers is via absorption, not adsorption. Finally, we have adopted a common strategy used for the production of heterologous proteins by P. pastoris, namely the use of a mixed methanol/glycerol feed for inducing the required AOX enzyme, while reducing the time required for high density biomass generation. All of these components were combined in a final experiment in which 10% of the polymer Kraton D1102K, whose PC ratio of benzaldehyde to benzyl alcohol was 14.9, was used to detoxify the biotransformation in a 5 L partitioning bioreactor, resulting in a 3.4-fold increase in benzaldehyde produced (14.4 g vs. 4.2 g) relative to single phase operation, at more than double the volumetric productivity (97 mg L(-1) h(-1) vs. 41 mg L(-1) h(-1) ).