Generator Operation Mode Research Articles

Анализ электромагнитных процессов блока возбуждения трехкаскадного стартер-генератора для авиационной энергосистемы

This article discusses the excitation system of a three-stage synchronous generator for aviation use in two distinctive modes of operation: as an electric power generator for an on-board power supply system and an electric starter for gas turbine engines of the aircraft. The article presents the calculation of the starter and generator operating modes of the excitation system. The basic design relations for the semiconductor converter circuit have been obtained and confirmed by simulation modeling in the PowerSIM environment. The problem of synthesizing an automatic control system for the TSG excitation unit operating as part of an on-board power supply system using a method for calculating the parameters of regulators based on the motion separation method has been solved. A two-circuit control system has been created for the generator mode of operation, including PI and PID regulators with output voltage regulation of the main generating stage. To control the excitation unit in the electric star¬ter mode of operation, a single-circuit control system for the current of the excitation winding with the addition of a resonant component has been designed. The evaluation of the efficiency of the designed control systems was carried out on the basis of simulation modeling using PowerSIM and MATLAB/Simulink application software packages for a generator feeding a three-phase AC network in accordance with the requirements of GOST R 54073-2017.The results of mathematical modeling formed the basis for the design of an experimental sample of the power unit in a hybrid integrated design for the TSG voltage regulation system.

Efficiency improvement with intelligent control of induction motor drives

The energy saving potential of induction motor drives is investigated. Two new aspects are identified, a multilevel frequency inverter and the speed control with variable rotor flux. Multilevel inverters with new wide-bandgap semiconductors for low voltage electrical drives (<1000 V) reduce power semiconductor losses, voltage transients at the motor windings and harmonic losses in the cables. The power semiconductor losses of a two-level and a three-level inverter are compared. At 20 kHz switching frequency the losses of the three level inverter are 38 % lower compared to the two-level inverter. Another efficiency improvement potential is the speed control with variable rotor flux instead of commonly used constant flux. The rotor flux for maximum efficiency depends on the actual load and speed of the motor. The optimal rotor flux for maximum motor efficiency can be pre-calculated for each load and speed and implemented as reference value for rotor flux control in the frequency inverter. The maximum efficiency improvement with an 11 kW induction motor at small load reaches 35 % in motor and 45 % in generator operation mode. An increase in efficiency can be reached below 2/3 of rated torque in the whole speed range from 10 to 100 Hz.

ОЦЕНКА ЭФФЕКТИВНОСТИ ПОДАВЛЕНИЯ АММИАКА В ВОЗДУШНЫХ СРЕДАХ ПРОИЗВОДСТВЕННЫХ ПОМЕЩЕНИЙ С ИСПОЛЬЗОВАНИЕМ БАРЬЕРНОГО РАЗРЯДА

One of the main problems in the industrial production of livestock and poultry products is the neutralization of toxic gases in the air removed from livestock premises. Ozonation is used for this. Ozone is produced in dielectric barrier discharge installations. The disadvantages of the method include the dependence of the electrical characteristics of the dielectric barrier discharge on the parameters of the medium and the generation of nitrogen oxides. (Research purpose) The research purpose is determining the effectiveness of ammonia suppression by ozone generated in dielectric barrier discharge installations at various parameters of the generator operating mode. (Materials and methods) Established the effectiveness of ammonia suppression by ozone at various parameters of the ozone generator operation mode. A 25 percent aqueous solution of ammonia with controlled purging over the surface of the solution was used as an ammonia source. The dependences of the mass concentration of ozone (O3), nitrogen oxides (NOx) and hydrogen sulfide (H2S) at the generator output on the operating mode parameters were studied. It was shown that the range of changes in the concentration of gases varied within the following limits: ozone - from 180 to 4, ammonia - from 80 to 2, hydrogen sulfide - from 4 to 0, nitrogen oxides - from 0 to 130 milligrams per cubic meter. (Results and discussion) It was found that the concentration of ammonia decreased from 50 to 10 milligrams per cubic meter; the time to reach the specified values of the concentration of ammonia in the stream was 20-50 seconds; when ozone is generated in all operating modes, nitrogen oxides are formed in the weight ratio O3/NOx from 1.42/1 to 1/1. The dependences of the generation of ozone and nitrogen oxides on the input voltage of the generator power supply unit were determined. It was noted that the optimal pumping rate of plasma-forming gas (atmospheric air) ranged from 0.8 to 1.5 m/ s; the mass ratio of nitrogen oxides to ozone varies from 0.69 to 0.98, which is unacceptable for premises with permanent residence of animals and maintenance personnel. (Conclusions) It was stated that the results obtained in assessing the rational operating modes of ozonators allow us to formulate technical requirements for the development of a specialized ozone generator adapted for use in agricultural production.

Analysis of the design of ultrasonic electronic generators

The design and operation of electronic generators for ultrasonic intensification of processes in gaseous and liquid media will be considered. General requirements and new approaches to electronic generators have been developed based on the analysis of the characteristics of modern piezoelectric vibration systems that perform large amplitude oscillations (quality factor, multi-frequency, multilayer piezoelectric elements). Continuous monitoring of system parameters and setting of optimal operating modes of the electronic generator were studied.

Interconnected operation of the ozone generator with the power supply unit

This article is addressed to the inductivity of the feeder transformer influence on of the plate-type ozone generator operating modes. The equation characterises the ozone generator interconnected operation with the transformer, in discharge and non-discharge modes is represented. Use of the near-resonant mode of operation is proposed with a view to reach maximum output capacity. With that end in view, it is proposed to use the transformer with higher inductance. Oscillograph charts of two modes of operation of the ozone generator are analysed. Current waveform factors are determined by the harmonic analysis method. Experiments proved that current waveform factor increase in value for the account of continuous discharge is conductive to increase of ozone output by 25-30 % and power loss reduction by 10-15 %.

전기추진 선박의 연료비용 분석에 따른 최적 발전시스템 구성방안 및 에너지 저장장치 적용의 효용성 분석

This paper presents how to design the configuration of generation system for shipboard power system based on fuel cost analysis. We propose a sophisticated economic analysis method with detailed fuel cost evaluation, which can be obtained from actual specific fuel consumption (SFC) characteristics of the gas-turbine and diesel generators installed in existing ships. Using the proposed method, we analyze economic benefits for optimal configurations of shipboard generation system for both hybrid propulsion ships such as CODLOG (COmbined Diesel-eLectric Or Gas-turbine) and COGLOG (COmbined Gas-turbine eLectric Or Gas-turbine) and full electric propulsion ships. In addition, we analyze the effects of energy storage system (ESS) in shipboard power systems in terms of spinning reserve management and single generator operation mode to meet the reliability and survivability requirement. The effectiveness of the proposed method is verified through multiple case studies with actual measurement data in ships that are currently in operation.

Wind generator protection with ESSs considering grid connected and island mode operations

This paper proposes a novel scheme to protect a Wind Generator (WG) with Energy Storage Systems (ESSs). In the scheme, data are dealt with in an iterative way to obtain the relay coordination considering both generator operating modes: grid connected and island. The proposition relies on conventional protection functions adapted to the operational system requirements. A set of well-known protection functions (under-voltage, over-current, differential and unbalance) operating together in an innovative arrangement, was the main objective of this research. In order to validate the proposed scheme, a Wind Energy Conversion System (WECS) with a Vanadium Redox Flow Battery (VRFB) as an EES was implemented in a real time digital simulator (RTDS®) to perform hardware-in-the-loop simulations. The simulation system consisted of a Wind Generator with grounded stator connected to the system through a DC link in order to investigate its behavior subjected to internal and external faults. Very promising results considering the proposed scheme are presented.

Torsional Vibrations of the Steam Turbine Shaft Line and Estimation of the Residual Life of Its Elements

A comparative quantitative assessment of the damage and residual life of the shaft line elements for differ-ent types of high-power steam turbines at the end of their design life is made by mathematical modeling. The analysis covers all elements of the shaft line: from the steam turbine Central pump to the turbine generator ex-citer. The simulated circuit includes turbo generators, transformers, gate converters, AC and DC power lines. When modeling, an approach is used from the position of proper coordinates, which provides maximum meth-odological consistency of the models of the listed devices and allows you to directly reproduce electromagnetic and mechanical transients with the determination of instantaneous values of currents, voltages, electromagnet-ic and torsional moments. To estimate damage, we used the deformation criterion for soft and hard loads in the zone of low-cycle and force criterion in the zone of multi-cycle fatigue. The influence of the number of starts and running time of a steam turbine on the damage and residual life of its shaft elements is studied. When de-termining the remaining life, in addition to starts, other abnormal operating modes of the turbo generator were taken into account during the turbine operating time: short circuits and their disconnections, unsuccessful high-speed automatic re-activation, subsynchronous resonance due to both the operation of the control system of the PPT and the automatic generator excitation regulator. The influence of attenuation of electromagnetic transients in the generator and damping of torsional vibrations on the degree of reduction of the residual life of the shaft elements is analyzed. The results obtained can be used for a comprehensive solution of the issue of further operation of steam turbines that have spent their design life.

Principles of the Functioning of Nonreactive Double Memristor Oscillators

Abstract—A new class of nonreactive memristor generators is considered. It is shown that the double memristor generator has wide functionality for controlling and modulating output signals. The various operation modes of such generators are studied, including those characteristic of artificial neurons nodes, such as excitation and inhibition, control of pulse trains, and change in the repetition rate in a packet.

Dc arc emission analysis of rare earth metals and their oxides with sorption preconcentration of impurities

The analytical capabilities of arc atomic emission determination of As, Bi, Sb, Cu, Te in rare earth metals (REM) and their oxides after preparatory group concentration using S,N-containing heterochain polymer sorbent are studied on a high-resolution spectrometer “Grand- Extra” (“WMC-Optoelectron-ics” company, Russia). Sorption kinetics and dependence of the degree of the impurity extraction on the solution acidity are analyzed to specify conditions of sorption concentration. To optimize the procedure of arc atomic emission determination of As, Bi, Sb, Cu, and Te various schemes of their sorption preconcentration and subsequent processing of the resulted concentrate with the addition of a collector at different stages of the sorption process have been considered. Graphite powder is used as a collector in analysis of rare earth oxides due to universality and relative simplicity of the emission spectrum. Conditions of analysis and parameters of the spectrometer that affect the analytical signal (mass and composition of the sample, shape and size of the electrodes, current intensity and generator operation mode, interelectrode spacing, wavelengths of the analytical lines) are chosen. The evaporation curves of the determinable impurities were studied and the exposure time of As, Bi, Sb, Cu, and Te in the resulted sorption concentrate was determined. Correctness of the obtained results was evaluated using standard samples of the composition and in comparisons between methods. The results of the study are used to develop a method of arc chemical-atomic emission analysis of yttrium, gadolinium, neodymium, europium, scandium and their oxides in a concentration range of n x (10-2 - 10-5) wt.%.

Totally Enclosed Self-Circulation Axial Ventilation System Design and Thermal Analysis of a 1.65-MW Direct-Drive PMSM

This paper presents a totally enclosed self-circulation (TESC) axial ventilation system (AVS) for large direct-drive permanent magnet synchronous machines (PMSMs). The configuration and the cooling air circulation process of the cooling system are described in detail. Then, the lumped parameter (LP) based airflow analysis and thermal analysis applicable to large PMSMs with the presented TESC AVS are proposed. The airflow network model and thermal network model are set up, respectively, and both of them are programmed. In order to verify the feasibility of the ventilation system and the accuracy of the LP models, a 1.65-MW PMSM prototype with the proposed ventilation system is developed and manufactured, and the temperature rise of the prototype is tested under generator operation mode. The accuracies of the developed airflow network model and thermal network model are verified by comparing the calculation results of the temperature rise with the test results. The LP models can be used to investigate the effects of different geometrical and operational conditions on the distributions of the airflow rate and the temperature of PMSMs with the TESC AVS.

Power Management Strategy for an Autonomous DC Microgrid

Owing to the intermittent nature of renewable energy, microgrids in islanding operation mode require backup power sources. The diesel generator is the most popular backup source, but does not offer an instantaneous start-up and cannot immediately provide the necessary power. Therefore, supercapacitors are used to assist the power balance during diesel generator start-up thanks to their responsiveness and high-power density. This paper proposed a power management strategy for an autonomous DC microgrid based on a photovoltaic source, electrochemical storage, a supercapacitor, and a diesel generator. The proposed control system aimed at power balance while accounting for the slow start-up characteristic of the diesel generator, the self-discharge of the supercapacitor, the dynamic load management, and the economic operating mode of the diesel generator. The main contribution of this paper centered on a power management strategy solving the above issues integrally, and economic analysis for the diesel generator and microgrid. Experimental studies were carried out for different scenarios and the results obtained confirmed the effectiveness of the proposed strategy. Furthermore, the study provided a comparison between the economic operating and load-following modes of the diesel generator and demonstrated that the economic operating mode of the diesel generator can reduce the total energy cost of the DC microgrid.

Bifurcation surfaces and multi-stability analysis of state feedback control of PMSM

The paper presents a thorough bifurcation analysis of detailed permanent magnet machine with feedback drive, showing the effect of different control and system parameters on the bifurcation and the associated system stability. This study addresses the nonlinear behavior of the PMSM under parametric variation. The analysis of the phase space and parametric singularities are developed in order to identify some specific properties of the PMSM either uncontrolled or under state feedback control. A bifurcation structure of the uncontrolled PMSM in both motor and generator operating modes is identified in the speed-torque chart. The analysis of the complex dynamics of state feedback control of the PMSM permitted to define analytically the bifurcation surfaces of saddle-node (Limit point) and Hopf bifurcations. Seeking broader areas of parametric singularities led to establish the analytical existence conditions of bifurcation manifolds and particularly the bifurcation surfaces. The appearance of intermittent chaotic areas interspersed with cascading bifurcations by doubling the period of limit cycle has been observed in the controlled PMSM. The analysis of the attraction basins in the phase plane, and the synchronization regions in the parametric plane with constant initialization, pave the way to further characterization of the PMSM dynamics with different types of control methods.

Using LabView environment for the demonstration of generator dynamic behavior

Under consideration is a virtual device (VD) in NI – LabVIEW environment for the demonstration of a generator dynamic behavior close to borders of its stability area. The generator is operating for the unlimited power system. Capabilities of VD are demonstrated on a specific example. It was established that dynamic modes of various complexity – from stationary mode to attractors of different types that correspond to different modes of the generator under study can be observed in the system under consideration. Identification of chaotic modes of generator operation is a topical task as deterministic chaos due to its unpredictability is certainly an inadmissible phenomenon from the point of view of dynamic stability of its operation.

Unipolar Modulation for a BLDC Motor With Simultaneously Switching of Two Transistors With Closed Loop Control for Four-Quadrant Operation

The paper describes a method of unipolar modulation that permits easy transition from motor to generator operation mode of a brush-less direct-current (BLDC) machine. This method is characterized by simultaneous switching of both transistors, which yields an increased frequency of current ripple component, when in a typical unipolar modulation only one transistor is switched. A BLDC motor control system is also presented, which reflects the idea of a logic rectifier for the determination of an equivalent dc value. The described modulation methods and control systems constitute a coherent conception of digital control for the BLDC motor operation.

From 2D to 3D Bifurcation Structures in Field Oriented Control of a PMSM

This paper presents new aspects of bifurcation structures in a Permanent Magnet Synchronous Machine (PMSM) in both motor and generator operating modes. It considers the case where the PMSM speed is regulated with a Field-oriented control (FOC). A period doubling bifurcation cascade under the variation of a proportional control parameter leading to chaotic states, was identified. The investigation of parametric singularities allows us to identify a complex bifurcation structure including three generic bifurcations. Such structure is made of the Limit Point (LP), the Hopf (H) and the Bogdanov-Takens (BT) bifurcation sets. Sufficient conditions of the existence of the main bifurcations are given analytically. An overview of the phase space singularities associated to the parametric singularities is presented. Moreover, embedding 2D bifurcation sets in a 3D parametric space, led to identify certain bifurcation surface structures. The bifurcation surfaces established correspond to limit point bifurcation for the motor and generator operating mode, and for period doubling period bifurcation. The 3D bifurcation sets play an important role to study the combined effect of three different parameters on the PMSM dynamics, and permit to control the complex PMSM dynamics to a stable equilibrium dot by an adequate tuning of either control and system parameters.

서해에서 측정된 수중 주변 소음의 공간 코히런스 분석

코히런스 분석은 두 수신신호의 유사성을 분석하는 방법으로, 수중음향에서는 음파의 시간 및 공간 특성을 나타낼 수 있는 유용한 분석 방법이다. 본 논문에서는 한국해양과학기술원과 한양대학교가 공동으로 수행한 해양음향 실험의 일부로, 3개의 수중청음기로 구성된 수직선배열센서를 이용하여 수중에서 주변 소음을 측정하였다. 조사선 발전기가 작동할 때와 정지했을 때, 총 두 가지 경우에 대하여 주변 소음이 측정되었고 각각에 대한 코히런스 분석을 수행하였다. 조사선 발전기가 작동하는 경우의 코히런스 결과는 조사선 발전기 소음의 전달 손실을 고려하여 계산된 방향 밀도함수를 이용한 코히런스 결과와 비교되며, 조사선 발전기가 정지한 경우인 주변 소음의 코히런스 결과는 해수면 소음원, 해저면 구성성분 및 원거리 선박 소음이 반영된 코히런스 모델 결과와 비교, 분석되어진다. Coherence describing the similarity between physical quantities of two signals is a very useful tool to investigate the temporal and spatial characteristics of signals propagating in underwater acoustic waveguide. Ambient noise measurements were made by the vertical received array consisting of three hydrophones as part of the KIOST-HYU joint acoustics experiment, and the coherence for the underwater ambient noise was analyzed. In this paper, the coherence results in cases that the generator in the research vessel was off and turned on are presented. The coherence estimated in the case of the generator operation mode are compared to the predictions obtained using the theoretical model with the directional density function dominated by vertical components propagating downward from the ship. In the case of the generator switch-off, the results are compared to the model predictions with directional density function including the effects of sea surface noise and long-distance shipping noise.

Mathematical Modeling as an Educational Method of Synchronous Generator Operating Modes in a Diesel Power Plant

Mathematical modeling is widely used to study the performance of technical objects. So, it is very important nowadays for electrical engineering specialists to be a master in modeling of electromechanical converters. The course Mathematical Simulation in Electromechanics is intended to teach students to use mathematical modeling methods. It is necessary to connect the academic process with practical needs of engineers in order to form strong knowledge and practical skills. The modeling process described in this paper shows that software simulation of a real system can be successfully combined with a traditional form of electromechanical converter's studying. The practical task of researching the synchronous generator operating at a variable speed is considered to provide the professional content in students’ education. The modeling process on example of a diesel power plant's synchronous generator is described.

Kalman-Filter-Based Indicator for Online Interturn Short Circuits Detection in Permanent-Magnet Synchronous Generators

Kalman filtering has been largely used in adaptive control for motor drive applications. However, few works relate to applications in the field of monitoring. In this paper, a fault indicator for interturn short circuits detection in permanent-magnet synchronous generators (PMSGs) is introduced. Based on the extended form of the Kalman filter and associated to an appropriate model of PMSG expressed in the $dq$ frame, this indicator has been developed through the identification of parameters specifically introduced to point out stator faults. Special attention has been paid to the indicator sensitivity and its robustness to the generator operation mode, which implies a large range of operating points. The indicator performances have been first evaluated using an appropriate simulation model. A complete experimental campaign has been performed to validate previous simulation results. A faulty PMSG, specifically built for stator fault experiments, has been associated to a digital signal processor for an online implementation of the proposed indicator. Finally, the issue of parameter uncertainties is solved by introducing a variable threshold for detection improvement.

Theoretical investigation of operation modes of MHD generators for energy-bypass engines

A MHD generator with different arrangements of electromagnetic fields will lead the generator working in three modes. A quasi-one-dimensional approximation is used for the model of the MHD generator to analyze the inner mechanism of operation modes. For the MHD generator with a uniform constant magnetic field, a specific critical electric field Ecr is required to decelerate a supersonic entrance flow into a subsonic exit flow. Otherwise, the generator works in a steady mode with a larger electric field than Ecr in which a steady supersonic flow is provided at the exit, or the generator works in a choked mode with a smaller electric field than Ecr in which the supersonic entrance flow is choked in the channel. The detailed flow field characteristics in different operation modes are discussed, demonstrating the relationship of operation modes with electromagnetic fields.