Electrical Subsystems Research Articles

Development of Aircraft Electric Starter–Generator System Based on Active Rectification Technology

More-electric aircraft (MEA) has become a dominant trend for modern aircraft. On-board MEA, many functions, which are conventionally driven by pneumatic and hydraulic power, are replaced with electrical subsystems. Starting aircraft engines with an electric motor instead of using pneumatic power from the auxiliary power unit is one of the major characteristics of future aircraft. This paper presents the development of a novel electric starter–generator system for aircraft applications. This paper describes the main achievements of the AEGART (EU CleanSky Project) project in the key areas, including electric machines, power electronic converters, thermal management, and overall system control design. The developed prototype has been tested successfully, and the test results are presented in this paper.

Characterization of a pediatric rotary blood pump

Abstract Introduction A ventricular assist device (VAD) is an electromechanical pump used to treat heart failures. For designing the physiological control system for a VAD, one needs a mathematical model and its related parameters. This paper presents a characterization procedure for determining the model parameter values of the electrical, mechanical, and hydraulic subsystems of a pediatric Rotary Blood Pump (pRBP). Methods An in vitro test setup consisting of a pRBP prototype, a motor driver module, an acrylic reservoir, mechanical resistance and tubings, pressure and fluid flow sensors, and data acquisition, processing, and visualization system. The proposed procedure requires a set of experimental tests, and a parameter estimation algorithm for determining the model parameters values. Results The operating limits of the pRBP were identified from the steady-state data. The relationship between the pressure head, flow rate, and the rotational speed of the pRBP was found from the static tests. For the electrical and mechanical subsystems, the dc motor model has a viscous friction coefficient that varies nonlinearly with the flow. For the hydraulic subsystem, the pressure head is assumed to be a sum of terms related to the resistance, the inertance, the friction coefficient, and the pump speed. Conclusion The proposed methodology was successfully applied to the characterization of the pRBP. The combined use of static and dynamic tests provided a precise lumped parameter model for representing the pRBP dynamics. The agreement, regarding mean squared deviation, between experimental and simulated results demonstrates the correctness and feasibility of the characterization procedure.

Assessing the Factors Impacting on the Reliability of Wind Turbines via Survival Analysis—A Case Study

The failure of wind turbines is a multi-faceted problem and its monetary impact is often unpredictable. In this study, we present a novel application of survival analysis on wind turbine reliability, including accounting for previous failures and the history of scheduled maintenance. We investigated the operational, climatic and geographical factors that affect wind turbine failure and modeled the risk rate of wind turbine failure based on data from 109 turbines in Germany operating for a period of 19 years. Our analysis showed that adequately scheduled maintenance can increase the survival of wind turbine systems and electric subsystems up to 2.8 and 3.8 times, respectively, compared to the systems without scheduled maintenance. Geared-drive wind turbines and their electrical systems were observed to have 1.2- and 1.4- times higher survival, respectively, compared to direct-drive turbines and their electrical systems. It was also found that the survival of frequently-failing wind turbine components, such as switches, was worse in geared-drive than in direct-drive wind turbines. We show that survival analysis is a useful tool to guide the reduction of the operating and maintenance costs of wind turbines.

Electrical power management and optimization with nonlinear energy harvesting structures

In recent years, great advances in understanding the opportunities for nonlinear vibration energy harvesting systems have been achieved giving attention to either the structural or electrical subsystems. Yet, a notable disconnect appears in the knowledge on optimal means to integrate nonlinear energy harvesting structures with effective nonlinear rectifying and power management circuits for practical applications. Motivated to fill this knowledge gap, this research employs impedance principles to investigate power optimization strategies for a nonlinear vibration energy harvester interfaced with a bridge rectifier and a buck-boost converter. The frequency and amplitude dependence of the internal impedance of the harvester structure challenges the conventional impedance matching concepts. Instead, a system-level optimization strategy is established and validated through simulations and experiments. Through careful studies, the means to optimize the electrical power with partial information of the electrical load is revealed and verified in comparison to the full analysis. These results suggest that future study and implementation of optimal nonlinear energy harvesting systems may find effective guidance through power flow concepts built on linear theories despite the presence of nonlinearities in structures and circuits.

Nonlinear dynamic modeling of ultrathin conducting polymer actuators including inertial effects

Trilayer conducting polymer (CP) actuators are potential alternatives to piezoelectric and electrostatic actuators due to their large strain, and recently demonstrated operation at hundreds of Hertz. However, these actuators exhibit nonlinear electrical and mechanical properties as a function of their oxidation state, when operated over their full strain range, making it more challenging to accurately predict their mechanical behavior. In this paper, an analytical multi-physics model of the CP actuators is proposed to predict their nonlinear dynamic mechanical behavior. To demonstrate the accuracy of the model, a trilayer actuator composed of a solid polymer electrolyte sandwiched between two poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes was fabricated and characterized. This system consists of an electrical subsystem represented by an RC equivalent circuit, an electro-mechanical coupling matrix, and a mechanical subsystem described by using a rigid finite element method. The electrical conductivity and the volumetric capacitance, an empirical strain-to-charge ratio, and Young’s modulus of the actuator as a function of the PEDOT electrode charge state were also implemented into the model, using measured values. The proposed model was represented using a bond graph formalism. The concordance between the simulations and the measurements confirmed the accuracy of the model in predicting the nonlinear dynamic electrical and mechanical response of the actuators. In addition, the information extracted from the model also provided an insight into the critical parameters of the actuators and how they affect the actuator efficiency, as well as the energy distribution including dissipated, stored, and transferred energy. These are the key parameters for designing, optimizing, and controlling the actuation behavior of a trilayer actuator.

Robustness modelling and assessment of interdependent smart grids

Future smart grids heavily rely on collaboration of two interdependent subsystems: the information and communication (ICT) system and the electrical system itself. The past has shown that malfunctions in one of the systems can propagate into the other system leading to widespread and heavy outages of power supply. Within this PhD project, a methodology for modeling, assessing and quantifying the Smart Grids’ robustness against occurrence of important unpredictable events is developed. Special attention is paid to the interdependencies between ICT and electrical subsystem and a particular novelty to existing approaches is the robustness quantification based on the current state of both subsystems allowing constant evaluation.

Особенности оптимизации подсистемы электроснабжения электрической тяги на железнодорожном транспорте

Objective: To assess the basic factors, innovative technologies, on the basis of which an integrated network of electrified lines of high-speed rail is to be created in Russia. Methods: Optimization of the traction power supply system according to characteristic criteria of resources and energy efficiency minimization. Results: Quality indices of power supply of hauling operations, voltage level of collectors for different electric propulsion systems with direct and single-phase alternating current were analyzed. The key factors, significantly influencing the performance indices, are the voltage level and type of current of an electric powered network. It was shown that the system of electric propulsion is a promissory system and possesses the best competitiveness indices, as its electric power supply subsystem is functioning on high-voltage direct current with the use of a 24 kW direct current electric stock on the basis of a new multipurpose generation converting complex. Practical importance: The suggested justification method of electrification variant by means of a dependence diagram depicting spacing between substations and catenary wire section makes it possible to justify a competitive high-voltage direct current electric propulsion system during the design of electric power infrastructure for busy railway lines.

Control strategy optimization of electrolyte flow rate for all vanadium redox flow battery with consideration of pump

Abstract Under the capacity increase of ocean, solar and wind power, the energy storage technology has been developed to regulate the power of renewable energy and enhance the stability of power network in the past decades. A system model of all vanadium redox flow battery (VRFB) is established including the electric subsystem and hydraulic subsystem, and the accuracy and reliability of this system model are validated. The variation of pump efficiency with flow rate is considered in the proposed system model, which makes the predicted system efficiency and coulomb efficiency more accurate. A new control strategy of variable flow rate is proposed by giving a limitation region of the flow rate. In this new strategy, the coefficients of system model can be determined and adjusted according to the VRFB operating parameters, which can guarantee high system efficiency and coulomb efficiency simultaneously. In application of this new control strategy, the system efficiency and coulomb efficiency under variable flow rate strategy are always higher than that under constant flow rate, with 3.34% increasing for system efficiency and 3.84% increasing for coulomb efficiency by average.

A fog based load forecasting strategy for smart grids using big electrical data

Internet of things (IoT) enables the smart electrical grids (SEGs) to support a lot of tasks throughout the generation, transmission, distribution and consumption of energy. Large amounts of data are generated through these smart devices, which can be sent to the cloud for further processing. Hence, appropriate actions can be taken based on the cloud processing. However, sending the complete captured data directly to the cloud would lead to resource wastage. To overcome the cloud challenges, fog computing tier acts as a bridge in the middle between the IoT devices embedded in SEG and the cloud. Thus, a 3-tiers architecture is proposed to replace 2-tiers one. The added fog tier offers a place for collecting, computing, storing smart meter data before transmitting them to the cloud. In this paper, a new electrical load forecasting (ELF) strategy has been proposed based on the pre-mentioned three tiers architecture. The proposed strategy consists of two phases; which are; (i) data pre-processing phase (DP2) and (ii) load prediction phase (LP2). Both phases take place at a cloud data center (CDC) on the collected data, which is received from all fogs connected to the entire cloud. The aim of the data preprocessing phase is to; (i) reject outliers from the collected data, and (ii) feature selection. The main contribution of this paper lied on the feature selection, which elects only the effective features for the next load prediction phase. Features selection is an essential pre-processing operation to reduce the dataset dimensions from all irrelevant features leading to enable the ELF from taking fast and correct decision for other electrical subsystems. A new feature selection methodology called fuzzy based feature selection (FBFS) is presented, which involves two stages; feature ranking stage (FRS) and feature selection stage (FS2). FBFS is a hybrid method based on both features selection methods filter and wrapper providing fast and more accurate significant features. Then, during LP2, the filtered data is used to give a fast and accurate load prediction. Experimental results have shown that the proposed FBFS promotes the load forecasting efficiency in terms of precision, recall, accuracy and F-measure compared with recent features selection methodologies. FBFS provides the highest precision, recall, and accuracy results. On the other hand, it provides the lowest error value.

Belt-Driven Open Source Circuit Mill Using Low-Cost 3-D Printer Components

Barriers to inventing electronic devices involve challenges of iterating electronic designs due to long lead times for professional circuit board milling or high costs of commercial milling machines. To overcome these barriers, this study provides open source (OS) designs for a low-cost circuit milling machine. First, design modifications for mechanical and electrical subsystems of the OS Distributed 3-D (D3D) Robotics prototyping system are provided. Next, Copper Carve, an OS custom graphical user interface, is developed to enable circuit board milling by implementing backlash and substrate distortion compensation. The performance of the OS D3D circuit mill is then quantified and validated for: positional accuracy, cut quality, feature accuracy, and distortion compensation. Finally, the return on investment is calculated for inventors using it. The results show by properly compensating for motion inaccuracies with Copper Carve, the machine achieves a motion resolution of 10 microns, which is more than adequate for most circuit designs. The mill is at least five times less expensive than all commercial alternatives and the material costs of the D3D mill are repaid from fabricating 20–43 boards. The results show that the OS circuit mill is of high-enough quality to enable rapid invention and distributed manufacturing of complex products containing custom electronics.

Using a new wind turbine emulator to analyze tower shadow and yaw error effects

The majority of the available wind turbine emulators (WTEs) utilize the detailed electrical sub-systems, whereas the simplified models are considered for the other aspects. However, wind turbines (WTs) are complicated systems with different aspects that should be appropriately modeled for a realistic assessment. This paper presents a new wind turbine emulator which considers aerodynamic, mechanical, and electrical aspects of the WTs. Some tests are performed to evaluate the capabilities and limitations of the emulator; then, the proposed emulator is used to analyze the tower shadow and yaw error effects which can produce power fluctuations and fatigue loads. In addition to tower shadow effect, the yaw error which has a more severe effect is studied in this paper considering the mechanical dynamics of the WT which were not considered in literature. The proposed emulator utilizes the AeroDyn and FAST software tools to model the aerodynamic and mechanical aspects of a WT considering the real electrical sub-systems. Moreover, the tower shadow and yaw error effects are modeled in simulation and the results are compared with the emulation results. The electrical sub-systems are modeled in the MATLAB/Simulink for simulation, whereas the real mechanically coupled induction motor-induction generator set is used for the emulator.

Modeling oscillation modal interaction in a hydroelectric generating system

Global hydropower growth continues to accelerate with 25% of total capacity installed in just the last 10 years. This accelerating expansion and the important storage facility hydropower means it is increasingly important to understand the reasons for operational failures. This is a challenge because the major reason for failures involves the complex interaction of hydraulic, mechanical and electric subsystems. Historically, reliability modelling has been split in two directions, focusing on different sub-systems, and has not yet been unified. Here these approaches are unified with a novel expression of unbalanced forces. This model with operational data are validated and the important modes of oscillation in the shaft are identified. Finally, the mechanism of the first-order oscillation mode exciting a second-order mode is presented. This integrated and accurate mathematical model is a major advance in the diagnosis and prediction of failures in hydropower operation.

Tutorial: Product properties in multiferroic nanocomposites

The coupling between magnetic and electric subsystems in composites of ferromagnetic and ferroelectric phases is a product property that is facilitated by mechanical strain that arises due to magnetostriction and the piezoelectric effect in the constituent phases. Such multiferroic composites are of immense interests for studies on the physics of electromagnetic coupling and for use in a variety of applications. Here, we focus on magneto-electric (ME) coupling in nanocomposites. Particular emphasis is on core-shell particles and coaxial fibers, thin film heterostructures, and planar structures with a variety of mechanical connectivity. A brief review of models that predict strong ME effects in nanostructures is followed by synthesis and characterization. Core-shell particulate composites can be prepared by hydrothermal processes and chemical or deoxyribonucleic acid-assisted assembly. Electrospinning techniques have been utilized to prepare defect free core-shell nanofibers. Core-shell particles and fibers can be assembled into superstructures with the aid of magnetic and electric fields and characterized for possible use in advanced technologies. Chemical-vapor deposition techniques have been shown to be effective for the preparation of heterostructures of ferrites and ferroelectrics. Exotic planar multiferroic structures with potential for enhancing ME coupling strengths are also considered. Scanning probe microscopy techniques are ideal for probing the nature of direct- and converse-ME coupling in individual nanostructures. Magnetoelectric characterization of assemblies of nanocomposites can be done by ME voltage coefficient, magnetic field induced polarization, and magneto-dielectric effects. We conclude with a brief discussion on possible avenues for strengthening the product properties in the nanocomposites.

Burden on hydropower units for short-term balancing of renewable power systems

There is a general need to change hydropower operational regimes to balance the growing contribution of variable renewable energy sources in power systems. Quantifying the burden on generation equipment is increasingly uncertain and difficult. Here, we propose a framework combining technical and economic indicators to analyze primary frequency control (PFC) on a timescale of seconds. We develop a model integrating hydraulic, mechanical, and electrical subsystems to characterize efficiency loss, wear and fatigue, regulation mileage, and frequency quality. We evaluate burden relief strategies under three idealized remuneration schemes for PFC, inspired by those used in Sweden, the USA, and China, respectively. We show how burden and compensation vary under future scenarios of renewable power systems. Our framework can be used by producers to develop favorable operation strategies that reduce burden and increase economic value, and by transmission system operators to provide insights on the relation between incentive structures and regulating performance.

METHODS OF STRUCTURAL AND PARAMETRIC SYNTHESIS OF COMBINED GENERATOR OF RECIPROCATING POWER PLANTS FOR ROBOTIC SYSTEMS ON THE BASIS OF A FREE PISTON ENGINE

Power supply system of advanced robotic systems requires the development of electromechanical energy converters with high energy and minimum weight and overall dimensions. In this regard, a free piston engine with an electric generator is considered as a promising plant.Interest in the study of power plants based on free piston engines is caused by several advantages compared to conventional internal combustion engines with a crank mechanism: relative simplicity of the design, 40 % fewer elements, which reduces the overall capacity, specific gravity and metal content of the free piston engine in 2.5–3 times. In addition, the fuel consumption is 30 % lower. Also an important design advantage of power plants based on free piston engines is a relatively simple modular construction. Reciprocating electric generators with transverse increment of the magnetic flux are the most commonly used ones in currently developed power plants based on free piston engines of foreign countries (USA, Russia, Germany, China, UK, Japan, Sweden, Israel, etc.) as the electrical AC machines. The main disadvantage of this type of generators are the absence of coordination of electrical and mechanical subsystems of the power plant at the extreme points of the operating cycle, which limits the efficiency of the free piston engine and reduces the reliability of the power plant.To solve this problem it is proposed to use Electromechanical energy Converter with transverse and longitudinal increment of the magnetic flux (combo generator). However, currently there is no scientifically valid method of synthesis of this type of generator. To address this problem we have developed the methodology of structural and parametric synthesis of combined generator of the reciprocating type for a plant on the basis of free piston engine, which is based on the use of the specific gravity of the combined generator as the objective function. It allows synthesizing electric machine of the reciprocating type with the specified efficiency and minimum specific mass.

Concept of Modal Repulsion for Examining the Sub-Synchronous Oscillations in Power Systems

This paper investigates the modal repulsion happened in the sub-synchronous resonance between a synchronous generator and series-compensated transmission line. The investigation is based on the closed-loop model of the series-compensated power system consisted of the torsional and electrical open-loop subsystems. Analytical explanation is presented to show how the SSO modal repulsion is formed as the result of moving close and apart between two open-loop SSO modes. Analysis is carried out to indicate that the peak of the SSO modal repulsion occurs when the two open-loop SSO modes from the torsional and electrical subsystem are closest to each other on the complex plane, which is referred to as the open-loop modal coupling. Estimation on the peak, i.e., the maximum damping degradation of the SSO modes, is derived in the paper. Subsequently, a method of open-loop modal analysis is proposed. Applications of the proposed method of open-loop modal analysis to study the SSOs caused by the DFIGs under the condition of the modal repulsion in the power system are demonstrated and evaluated by example power systems. The concept of modal repulsion explains why the grid connection of the DFIGs may bring about the SSO instability risk in the power system.

Failure Analysis to Derive the Causes of Abnormal Condition of Electric Locomotive Subsystem

Failure Analysis to Derive the Causes of Abnormal Condition of Electric Locomotive Subsystem

Security modelling of integrated gas and electrical power systems by analyzing critical situations and potentials for performance optimization

Having in view the current balance of natural resources, uncertain economic conditions and the expansion of gas infrastructure, it seems reasonable to have a significant number of gas power plants incorporated into the existing power system. The purpose of this paper is to show, through quantification of impacts of the integrated gas and electric power network, that the failures of the radial gas subsystem, in terms of security, as a rule, are more critical for the integrated electric power system than failures in the electric power subsystem. In the second part of the paper the predictive control actions are analyzed in order to minimize the negative impact of failures in the gas subsystem. In such a way the optimal operation of the gas power subsystem can be achieved. This approach is feasible under the condition that gas power plants are included in smart grid with continuous data acquisition from the gas plants and the pipeline system.

Design and experimental results of the 1-T Bitter Electromagnet Testing Apparatus (BETA).

The Bitter Electromagnet Testing Apparatus (BETA) is a 1-Tesla (T) technical prototype of the 10 T Adjustable Long Pulsed High-Field Apparatus. BETA's final design specifications are highlighted in this paper which include electromagnetic, thermal, and stress analyses. We discuss here the design and fabrication of BETA's core, vessel, cooling, and electrical subsystems. The electrical system of BETA is composed of a scalable solid-state DC breaker circuit. Experimental results display the stable operation of BETA at 1 T. These results are compared to both analytical design and finite element calculations. Experimental results validate analytical magnet designing methods developed at the Dusty Plasma Laboratory. The theoretical steady state maxima and the limits of BETA's design are explored in this paper.

Strong sub-synchronous control interactions caused by open-loop modal resonance between the DFIG and series-compensated power system

This paper examines sub-synchronous control interactions (SSCIs) caused by open-loop modal resonance in a series-compensated power system with a doubly-fed induction generator (DFIG). The examination employs a closed-loop interconnected model consisting of an open-loop DFIG subsystem and an open-loop electrical subsystem with series compensation. The open-loop modal resonance is created when two open-loop sub-synchronous oscillation (SSO) modes outside of the DFIG and electrical subsystems are close to each other on the complex plane. The analysis results indicate that the open-loop modal resonance may cause strong SSCIs between the DFIG and electrical subsystem, and thereby degrade the ability to dampen SSOs in the power system. The degree of damping degradation can be estimated by computing the open-loop resonance residue. The principle of open-loop modal resonance introduced in this paper is based on improvements to a previous modal resonance analysis involving the concept of near strong modal resonance. Here, the relationship between the open-loop modal resonance and the near strong modal resonance is evaluated to determine the mechanism by which DFIGs result in strong SSCIs from the perspective of open-loop modal resonance.