Synchronous Mode Of Operation Research Articles

An interleaved single-input multiple-output dc-dc converter combination

This paper analyses, simulates and verifies an experimental prototype of a four-phase interleaved dc-dc converter. It is based on SEPIC-Cuk combination. The developed prototype has been used in single-input multiple-output (SIMO) applications. This combined converter allows obtaining dual output voltages of the same value, from a single input dc voltage and with an only power switch. Multiphase interleaved dc-dc converters achieve a better dynamic response and low ripple, maintaining the efficiency. Each converter is connected in parallel, therefore they manage the losses by distributing them between more components, which facilitates the thermal management of the multiphase converter and allowing to handle high power values in small size respect of solutions of a single phase. Two control strategies were applied: synchronous operation mode (SOM) and interleaved operation mode (IOM). The simulation results allow the comparison of both operation mode, verifying that the IOM presents advantage with respect to the ripple at the input and output currents. The experimental prototype was designed for distributed power architecture and bipolar dc microgrid (MG).

TURBOGENERATOR ROTOR HEATING IN PRESENCE OF ROTOR WINDING DEFECTS AND EXCITATION CURRENT FORCING

Purpose. Research of the TGV-200 turbogenerator rotor heating in case of rotor winding damages, which occur as a result of prolonged operation of the turbogenerator, namely - clogging of the ventilation channels of the rotor winding and the occurrence of short circuits of the rotor windings. Particular attention is paid to heating during short-term increasing of the excitation current, which is performed to keep the generator in synchronous mode of operation. Methods. Field mathematical models are used. Results. It is determined that the clogging of the rotor winding ducts has a greater effect on the rotor heating compared to the short circuits of the individual windings of the rotor winding. It was defined that increasing of the excitation current within the limits regulated by the current standards of the turbogenerators operation becomes impossible with clogging of a small number of ventilation channels of the rotor winding, which impairs the efficiency of the turbogenerator and requires its output to repair. Scientific novelty. A mathematical model of rotor heating is developed in case of typical damages of the rotor winding. Practical value. The areas in the rotor where the temperatures and temperature gradients reach the highest values was determined, which allows to recommend the locations of the optimal temperature sensors placements.

Equivalent structure of a double-fed induction motor with a change in frequency of additional voltage for electric drive systems of mine winders

Using a double-fed machine (DFM) circuit is a promising means of upgrading asynchronous electric drives in mine winders. However, the control range of the DFM speed is limited by an excessive drop in the critical torque and decrease in the rigidity of the mechanical characteristics at a speed reduction. Usage of synchronous mode of DFM operation for high-powered winders is fraught with considerable difficulties, in particular, with the instability of machine operation in this mode. The paper proposes a method for determining and evaluating the effect of the corrective action on the frequency of the rotor additional voltage on the critical torque and the rigidity of the DFM mechanical characteristics; the equivalent structure of a double-fed induction motor with a change in the of the additional voltage frequency on the rotor additional voltage and the results of experimental studies suggesting the possibility and necessity of implementing the method for using the DFM in electric drives of winders are given.

Structural Synthesis of Synchronization Systems with High Dynamic Characteristics

In this paper, we present the results on the structural synthesis of synchronization systems optimized for speed in a transient operation mode. The performance problems of entering a synchronous operation mode are analyzed based on phase portraits of phase-locked loop systems. The global linearization of the phase portrait trajectories, which allowed arguing structural solutions for synchronization systems with improved dynamic characteristics, was performed.

Two-Converters-Based Synchronous Operation and Control of a Brushless Doubly Fed Reluctance Machine

This paper discusses the synchronous operation of a brushless doubly fed reluctance machine (BDFRM). Basic operation theory of a ducted rotor BDFRM is reviewed, and mathematical analysis relating to synchronous operation is presented. Corresponding control strategy for synchronous speed operation is discussed. A prototype machine is built and implemented as a motor drive. Subsequently, the BDFRM drive is tested in synchronous mode of operation at varying speed levels and loads.

Performance Analysis of Grid Integrated Doubly Fed Induction Generator for Small Hydropower Plant

The motive of this work is to present the modeling and simulation of the hydraulic turbine which is driven by the doubly-fed induction generator and the generated ac power given to the grid. For feeding the ac power to the grid, we are using two PWM voltage source converters which are connected back to back between the utility grid and rotor terminals with the help of common dc-link. Machine side converter is used for pertinent excitation. The power flow between AC side and DC bus is controlled by grid side converter (GSC) as well as it allows the system to be operated in less than and greater than synchronous speed mode of operation. MATLAB/SIMULINK is used for Time domain simulations. The system is stable under different load conditions and it is investigated with the help of model and simulations result. To preserve the system stability whenever the power demand is precipitously increasing in the utility grid side, an appropriate system and controller parameter is used.

Digital Time-Division Multiplexing Readout Circuit for Sensor Arrays

We have devised a digital time-division multiplexing (TDM) scheme for minimizing the circuit complexity required for an array of sensors. As a proof-of-concept, we have designed, fabricated, and tested a four-channel digital TDM readout circuit. The proposed scheme can be generalized for a larger number of channels. The readout circuit comprises an array of ADCs to digitize sensor outputs, a multiplexing unit, a clock controller, and a counter with parallel-to-serial output interface. For demonstration purposes, we employed low-pass phase modulation–demodulation ADCs running in a synchronous mode of operation. To facilitate an independent verification of circuit operation, we also placed an on-chip pattern generator to apply a unique pattern to each channel. The multiplexing unit is based on an array of sequentially triggered switches, each controlling the flow of data from a single ADC to a common output bus. In our scheme, the switches are realized using RS-flip-flops with nondestructive (RSN) readout cells with only one RSN cell turned on at a time. Multiplexed output data were stored in ripple counter based on T-flip-flops and read out to room temperature electronics using a serial interface. The chip was immersed in liquid helium at 4.2-K temperature and extensively evaluated at sampling frequencies up to 12.8 GHz. By means of embedded pattern generators, we proved the correct operation of each channel and of all four channels combined. We also were able to perform reconstruction of a signal applied to individual ADC. The chip was fabricated using HYPRES’ 4.5-kA/cm2 process with four Nb metal layers. We briefly discuss the proposed scheme's scalability for higher current density and smaller feature size fab processes.

A Stage-Wise Soft-Error Detection Scheme for Flip-Flop Based Pipelines in Secure Cloud Servers

The shrinking feature sizes make transistors increasingly susceptible to soft errors, which can severely degrade the systems’ RAS (Reliability, Availability, and Serviceability). The tough challenge results from not only increasing SER (soft error rate) of storage cells, but also the increasing susceptibility of combinational logics to soft errors. How to efficiently detect soft errors becomes the primary problem in the Backward Error Recovery (BER) schemes that are cost-effective in soft error tolerance. This paper presents a soft error detection scheme, AUDITOR, for flip-flop based pipelines. The AUDITOR copes with both types of soft errors—single event upset (SEU) and single event transient (SET). We propose a “local-audit” fault detection mechanism, by which each pipeline stage is verified independently and the verifying result registers with a dedicated “audit” bit (V-bit). All the V-bits are distributed across the whole pipeline and synergically monitor the pipeline execution. To relax the constraint of SET detection capability imposed by the inherent fully synchronous operation mode in flip-flop based pipelines, we firstly propose using path-compensation technique to address this constraint. Furthermore, a reuse-based design paradigm is employed to reduce the implementation complexity and area overhead. The AUDITOR possesses robust detection capability and short detection latency, at the expense of about 29 % and 50 % increase in area and power consumption, respectively.

Synchronous mode operation of DFIG based wind turbines for improvement of power system inertia

Inertia emulation methods exist to compensate for the reduced inertial support provided by doubly fed induction generator (DFIG) based wind turbines. Instead of emulating inertia, this paper proposes to temporarily convert DFIGs to synchronous generators, enabling supply of real inertia to the system. In order to achieve this, the voltage supplied to the DFIG rotor needs to be made independent of the grid frequency. Feeding the rotor with a fixed dc voltage while it is rotating at synchronous speed enables the DFIG to operate in synchronism with the grid and couple the inertia of its rotating mass to the power system. The rotor side converter of a DFIG can be controlled to function as the dc voltage source, allowing convenient switching between the two operation modes according to system requirements.

Analysis and simplified modelling of brushless doubly‐fed induction machine in synchronous mode of operation

Similar to conventional doubly-fed induction machines (DFIMs), brushless DFIM (BDFIM) obtains variable speed operation by means of a fractionally rated converter. Due to its brushless structure, BDFIM confers higher reliability and requires lower maintenance than the conventional DFIMs. Hence, it has potential future use in offshore wind turbines. This study elaborates the most attractive mode of BDFIM operation, i.e. the synchronous mode. The BDFIM air-gap flux is complex due to the presence of spatial harmonic components with different pole numbers. To facilitate analysis of the BDFIM performance, this study aims to simplify its steady state and dynamic models. To achieve this goal, the BDFIM electromagnetic torque is analysed to induction and synchronous components. Then, considering the share of each torque components, simplifications are proposed in the steady state and dynamic models of BDFIM. Thus, the BDFIM model becomes similar to conventional DFIMs. The equivalent parameters of the proposed simplified model of BDFIM and the model of conventional DFIMs are introduced. Supplementary experiments and simulations are carried out for a prototype D180 4/8 pole BDFIM.

Micrometeorological Observations for the Evaluation of the Selective Inverted Sink against Radiation Frost and the Potential of a New Hybrid System

For the radiation frost in agricultural fields, it is difficult to determine a satisfactory solution. To solve this problem, Selective Inverted Sink (SIS) is proposed as a new active frost protection method. However, the interactions of the SIS (also known as tower less wind machine) with some topo climatic effects such as cold air drainage and inversion strength are not well known. Consequently, this study was dedicated to two main objectives: First, different micro- topographic conditions are compared to validate the capability of SIS against the radiation frost. Second, a new hybrid system was proposed to improve the SIS effects. For these two purposes, three meteorological field campaigns were conducted on the fields of a vineyard and an orchard in Quebec, Canada. The air temperature was recorded with a fine spatiotemporal resolution min and spatial resolution in a synchronous mode of operation. In addition, the air temperature and humidity were recorded with mobile measurements and launching balloons to infer the general variations of temperature and specific humidity. Based on the topographic maps and field measurement, the several locations for SIS installation were determined. The high-resolution isotherms maps were used to evaluate the influence of SIS on nocturnal air-cooling. These results did not provide conclusive observational evidence that the SIS has impartial efficiency on nocturnal cooling. Indeed, a minor part of the SIS's exhausted flux was from horizontal direction, essentially due to land surface roughness. In contrast, a major part of the flux was from the upper layer around the SIS, which behaves like a funnel. The wind speed in the funnel's direction was 3 times greater than the wind speed in the horizontal direction. Therefore, the SIS was not able to remove a sufficient amount of cold air pool or stagnant air. To elucidate the second objective, a simple and affordable innovation with reliable testing was performed. A hot water SIS hybrid system (HWSH) was proposed to use the “forced convection” produced by the SIS to disperse a maximum of water vapors into the air in order to decrease the air dryness. In this system, hot water with a temperature of 60° C was deployed under the SIS. The observation during a radiation frost night demonstrated that, although the reference area (35 m away from the HWSH) was affected by frost, hybrid system's location area was not affected. However, there was no significant temperature gradient between two points, but the moist enthalpy calculated at 18 m altitude was higher above the HWSH in comparison to reference point. In conclusion, the main physical notion throughout this study is moist enthalpy, which depicts heat content. Nocturnal cooling rate decreased by increasing the moist enthalpy using HWSH system. This environmentally clean hybrid system has potential to be considered as an alternative to some frost protection methods such as heaters and fires burning. In addition, the importance of fine-scale measurement in agricultural field is highlighted in this study.

Battery Charging Using Doubly Fed Induction Generator Connected to Variable Speed Wind Turbine

Abstract Wind energy, one of the renewable energy sources can be used as an alternate fuel. The main objective of this paper is to make the system with a variable speed wind turbine using DFIG to supply the local loads. The proposed system using DFIG is modelled and simulated in MATLAB. The slip power from the DFIG in its super synchronous mode of operation can be used for battery charging through back to back connected converters. Here machine side converter acts as the rectifier and the battery side converter as inverter. The simulations analysis for battery charging is done here using MATLAB Simulink model.

Adaptive second order sliding mode control of doubly fed induction generator in wind energy conversion system

A dynamic synchronous d-q reference frame based modeling and a novel adaptive higher order sliding mode control theory for doubly fed induction generator (DFIG) based wind energy conversion system (WECS) have been proposed in this paper. As depicted from the literature, the sliding mode control strategy involving computation of converter currents introduces some inaccuracies for optimal extraction of the power references of the DFIG. On the contrary, the proposed method contributes with some important features such as chatter-free performance and heftiness in terms of transient response of the non-linear systems subjected to dynamic conditions such as lower and higher wind speeds. Consequently, a higher order sliding mode controller using the active and reactive power of the DFIG as controller inputs has been proposed in this paper. As compared with the other two methods, the proposed higher order sliding mode power control souvenirs a significantly improved as well as stable performance of the DFIG based WECS in terms of reduced settling time as well as quickly damping out the oscillations exhibited by the system. The robustness and stability of the proposed control strategy has been validated in MATLAB environment, in terms of the comparison of its performance with traditional proportional-integral and existing first-order sliding mode controller (employing converter current as input) subjected to a wide range of disturbances for sub and super synchronous mode of operation of the DFIG subjected to lower and higher wind speeds along with the available practical wind speed data, as depicted in the simulation and result section.

An Assessment of the Effect of the Accuracy of the Telemetry of the Frequency of the Electric Current on the Automatic Recognition of Asynchronous Operating Zones

An approach based on nonparametric methods of data analysis is proposed, which enables groups of objects of a power system, characterizing a synchronous mode of operation, to be determined when there is incomplete information and inaccurate telemetering.

Steady‐state analysis and performance of a brushless doubly fed machine accounting for core loss

In this study a steady-state equivalent circuit for a brushless doubly fed machine (BDFM), based upon earlier work, is introduced which takes account of core losses. Based upon some loss approximations, simple relationships have been derived, which show that the synchronous mode operation, in terms of core loss, of the BDFM is similar to the cascaded doubly fed machine. The slip-dependence of core loss resistances in the equivalent circuit has been investigated by applying energy conservation to derive machine steady-state torque–speed relations in the presence of core loss. Experimental speed measurements of the BDFM in the simple induction mode were used to identify the core loss resistance values.

Modeling, Analysis, and Experimental Validation of Frequency Dividers with Direct Injection

An analytical model and a methodology are presented for the analysis of CMOS injection-locked frequency dividers with direct injection, which are used in modern wireless communication systems. The amplitude and phase of the oscillation in the synchronous operation mode, as well as the locking range, are found in explicit form. The width of the locking range is determined by the condition of the existence and stability of synchronous oscillations. The accuracy of the model and of the presented formulas is validated through a comparison with experimental results, which are in good agreement with the analytical ones.

Synchrony Relationships between the Left Ventricle and a left Ventricular Assist Device: An Experimental Study in Pigs

Synchronization between the left ventricle and a left ventricular assist device (LVAD) may be important for ventricular unloading and coronary perfusion. We assessed the synchrony between cardiac and LVAD cycles by increasing delays in steps of 100 msec throughout the cycle, under conditions of total and partial left ventricular support. We studied 7 healthy minipigs weighing 30-40 kg. A 60-cc Berlin Heart Excor LVAD was implanted and connected to a BCM 1200 console, making it possible to synchronize the LVAD systole and the EKG signal with a prefixed delay. We recorded hemodynamic parameters (including aortic, pulmonary, and left ventricular pressure) and LVAD flow for each delay. Intraventricular pressure during LVAD systole was minimized with delays of around 40-80% of one cycle. In addition, total flow was higher under these conditions. This study shows that the synchronous mode of LVAD operation is feasible. Moreover, a delay in device contraction until the second half of the cardiac cycle optimizes ventricular unloading and may eventually improve myocardial recovery.

Computer-controlled dynamic mode multidirectional UV lithography for 3D microfabrication

Computer-controlled dynamic mode multidirectional ultraviolet (UV) lithography has been demonstrated using a collimated UV light source, a substrate-holding stage equipped with two stepper motors (one for tilting and the other for rotation), a controller with programming software and a laptop computer. The tilting and rotational angles of the stage in motion are accurately controlled during UV exposure as programmed by the user to produce complex three-dimensional (3D) microstructures. Process parameters include the initial and final tilting and rotational angles of the stage, and the relative angular velocities of the two motors in addition to the normal fabrication process parameters of UV lithography such as optical dose, baking time, and developing time and condition. Symmetric patterns can be generated by a simple synchronous mode dynamic operation, where both the angular velocities of the tilting motion and the rotating motion are set equal or harmonically related. More complex and non-symmetric patterns can be obtained using a piecewise synchronous mode, where the relationship between the angular velocities of the two motors is described not with a single coefficient but with a set of coefficients. 3D structures fabricated from the synchronous mode operation include the four-leaf clover horn and the cardiac horn while the ones from the piecewise synchronous mode are a vertical triangular slab, a screwed wind vane and arbitrary shape horns. Ray trace simulation has been performed using a mathematical tool in a spherical coordinate system and the simulated 3D patterns show good agreement with the fabricated ones.

A Simplified Sensorless Vector Control Based on Average DC Bus Current for Fan Motor

This paper describes a simplified sensorless vector control based on the average DC bus current for PMSM. This method can be used to design a drive control system at a relatively low cost because the microcontroller does not require a precise timer and the calculation load is slight. In the proposed method, one of the two possible current estimation processes is chosen according to the operation mode. First, the controller estimates d-axis current and identifies the back-EMF parameter in the synchronous operation mode at low speeds. The error in the back-EMF identification affects the efficiency of the proposed system, so it needs to be zero. Second, the controller estimates q-axis current in vector control mode. The identified parameter and q-axis current define voltage reference to realize high efficiency drive. The obtained experimental results confirm the effectiveness of the proposed method.

Real-Time Two-Dimensional Asynchronous Control of a Remote-Controlled Car Using a Single Electroencephalographic Electrode

A brain-machine interface (BMI) can generate control commands using signals from the brain. These devices have great potential to assist individuals with severe mobility impairments. Despite enormous advances in this field, most BMI systems have restricted information transfer rates limiting the potential applications for this technology. An important factor limiting information transfer rate is the synchronous (cue-based) mode of operation, currently used by most BMI systems. We present a novel approach that uses electroencephalographic signals from a single electroencephalographic (EEG) electrode to control asynchronously a remote-controlled vehicle moving in two dimensions.