Auxiliary Loads Research Articles

Investigation of High Frequency AC Power Distribution Benefits for the Automobile Auxiliary Electrical System

This paper aims to indicate the advantages and any drawbacks of high frequency alternating current (HFAC) power for vehicle auxiliary electrical systems. Generally, benefits of HFAC include efficient power distribution and transformation, space and weight saving and load galvanic isolation. In addition, HFAC bus topologies are distributed to the point of use, lending the system to easy fault detection. The paper is structured as follows: first, the main findings of the most relevant automotive HFAC studies are outlined. Next, an HFAC architecture is proposed which is compared to the existing 14V and proposed 42V centralised DC networks in terms of power distribution efficiency and wiring harness weight saving. For this analysis, the case study of a medium-sized passenger vehicle is considered, and a group of intermittent and continuous auxiliary loads with a cumulative power of 2.8kW. The calculations over a 1200s drive cycle show that the power distribution efficiency for a 50kHz, 100V AC power bus increases by 90 per cent and 80 per cent compared to 14V and 42V DC topologies, respectively, and the wiring copper weight drops significantly by 70 per cent and 30 per cent, respectively.

Mathematical analysis of hybrid topologies efficiency for PEM fuel cell power systems design

An efficiency mathematical analysis of the commonly used series and parallel hybrid topologies in distributed generation systems (DGS) is presented. The electrical architecture of the DGS consisting of PEM fuel cells, auxiliary storage devices and electrical loads allows regenerative power flow from the load bus. Criteria for a proper choice of the topology for a given load power profile are derived from the analysis and the inclusion of some practical considerations. A novel series-parallel hybrid topology for uncertain load power profiles is also disclosed. The proposed topology is compared with both series and parallel structures in terms of efficiency and number of converters under non-regenerative power conditions. The theoretical predictions of the mathematical analysis are verified by simulation using a Matlab/Simulink model that integrates a physical model of the PEM fuel cell with its control system, an electrical model of a battery with its state-of-charge regulator, and static models of DC/DC converters described in terms of efficiency.

Voltage source converter with a transformer as an electronic load controller for a stand-alone power generation

This paper presents a new configuration of a voltage and frequency controller for a stand alone pico hydro power generating system employing an Isolated Asynchronous Generator (IAG). The proposed controller is an Electronic Load Controller (ELC), which consists of a three leg IGBT (Insulated Gate Bipolar Junction Transistor) based Voltage Source Converter (VSC), a DC chopper and an auxiliary load at its DC bus. The neutral terminal for the consumer loads is created using a star delta transformer and the proposed system is modelled and simulated in MATLAB using Simulink and PSB toolboxes.

Influence of Operating Parameters on Start/Stop Induced Degradation in Polymer Electrolyte Fuel Cells

In order to investigate the influence of temperature, reactant gas humidification and the application of an auxiliary load on start/stop induced fuel cell degradation under application relevant conditions, alternating purging of the anode electrode with hydrogen and air was used to shut-down and start-up the fuel cell. It was found that loss of active catalyst surface area only significantly influences fuel cell performance at low temperatures and reactant gas humidifications. Under harsh conditions, performance decrease is dominated by mass transport losses which are caused by carbon corrosion induced changes in the structure of the catalyst layer. Measurements of the CO2 content in the cathode exhaust gas showed that corrosion rate depends linearly on water vapor partial pressure for temperatures up to 80{degree sign}C. Due to a strongly increased driving voltage and the longer duration of the detrimental potential, performance loss was dramatically increased for the cell cycled without auxiliary load.

A New Ring Shear Device to Measure the Large Displacement Shearing Behavior of Sands

AbstractAmong devices commonly used to measure the shearing behavior of sands, only the ring shear device can shear a soil to virtually unlimited displacements without creating substantial nonuniformities in stress and strain distributions. However, some limitations have precluded its widespread use. A new ring shear device was constructed at the University of Illinois that has large specimen dimensions to reduce stress and strain nonuniformities, has auxiliary load and torque cells to measure any wall friction that develops along the confining rings, and utilizes quad-rings along the confining rings to prevent soil extrusion. Sample ring shear tests on a dry fine-grained, silty sand specimen demonstrate that the new ring shear device operates properly in both constant volume and drained conditions, providing identical effective stress friction angles at large displacements when shear and effective normal stresses on the shear plane are considered. Parallel drained and undrained triaxial compression tests on saturated specimens illustrate that the new ring shear device provides reasonable values of effective stress friction angle and show that the triaxial test does not shear specimens to sufficient displacement to reach critical state shear strengths for this sand, which was reached at displacements ranging from about 1 to 10 m.

Bond graph modelling of marine power systems

The main motivation for writing this article is to develop a model library for an All-Electric Ship that gives an opportunity to simulate both existing and new machinery systems without having to remodel the entire system each time. The model library should support the process of modelling and reuse, while also emphasizing openness to brace the modeller during the development and refinement phase. The bond graph approach is good when it comes to the physical modelling of systems and is a good tool for combining different energy domains to better help in understanding the system. In addition, a bond graph is a powerful method to find dependencies between various components. Using a causal analysis, any problems in the model, for example, algebraic constrains or dependent system variables, will be detected, and the necessary remodelling may be performed to handle such problems. The bond graph approach is therefore used when developing the component library. The component library consists of selected power producers such as diesel and gas engines, fuel cell and synchronous generator and power consumers such as asynchronous motor with a voltage source converter in addition to a generic load used for hotel and auxiliary loads. The library also consists of a ship model and propeller models.

VSC with zigzag transformer based electronic load controller for a stand-alone power generation

This paper presents a novel configuration of a voltage and frequency (VF) controller for a stand-alone pico hydro power generating system employing an asynchronous generator (IAG). The proposed VF controller is an electronic load controller (ELC), which consists of a three leg insulated gate bipolar junction transistor (IGBT) based voltage source converter (VSC), a DC chopper and an auxiliary load at its DC bus. The neutral terminal for the consumer loads is created using a zigzag transformer. Three leg VSC is connected to the tertiary winding of the zigzag transformer to select the optimum voltage rating of the DC bus. The control algorithm of the VF controller is developed to control the system VF under varying consumer loads. The proposed system is modelled and simulated in MATLAB using Simulink and power system blockset (PSB) toolboxes. Extensive simulation results are presented to demonstrate the capability of the controller as a harmonic eliminator, a load balancer, a neutral current compensator along with VF controller.

Power Quality Improvement in Conventional Electronic Load Controller for an Isolated Power Generation

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper deals with the power quality improvement in a conventional electronic load controller (ELC) used for isolated pico-hydropower generation based on an asynchronous generator (AG). The conventional ELC is based on a six-pulse uncontrolled diode bridge rectifier with a chopper and an auxiliary load. It causes harmonic currents injection resulting distortion in the current and terminal voltage of the generator. The proposed ELC employs a 24-pulse rectifier with 14 diodes and a chopper. A polygon wound autotransformer with reduced kilovolts ampere rating for 24-pulse ac–dc converter is designed and developed for harmonic current reduction to meet the power quality requirements as prescribed by IEEE standard-519. The comparative study of two topologies, conventional ELC (six-pulse bridge-rectifier-based ELC) and proposed ELC (24-pulse bridge-rectifier-based ELC) is carried out in MATLAB using SIMULINK and Power System Blockset toolboxes. Experimental validation is carried out for both ELCs for regulating the voltage and frequency of an isolated AG driven by uncontrolled pico-hydroturbine. </para>

An Improved Electronic Load Controller for an Isolated Asynchronous Generator Feeding 3-Phase 4-Wire Loads

This paper deals with a voltage and frequency control of an isolated asynchronous generator feeding 3-phase 4-wire loads in constant power applications where terminal voltage, excitation capacitor, speed and generated power of the generator remain constant under all operating conditions. The proposed controller is functioning as an improved electronic load controller (IELC) to regulate the frequency and as a source of reactive power to regulate the terminal voltage. Three single-phase voltage source converters (VSCs) are connected to each phase of the generator through three single-phase transformers and there is an auxiliary load with a chopper at the self-regulated DC bus of the IELC. These VSCs along with transformers provide their function as a voltage regulator, a harmonic eliminator, a load balancer and a neutral current compensator whereas the chopper and the auxiliary load at the DC bus are used to regulate the frequency. The complete system is modelled and simulated in MATLAB along with Simulink and Power system Block set toolboxes. The simulated results are presented to demonstrate the capability of an isolated generating system driven by uncontrolled pico hydro turbine and feeding 3-phase 4-wire linear/non-linear balanced/unbalanced loads.

Decoupled Voltage and Frequency Controller for Isolated Asynchronous Generators Feeding Three-Phase Four-Wire Loads

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper deals with a decoupled voltage and frequency controller (DVFC) for an isolated asynchronous generator (IAG), also known as the self-excited induction generator (SEIG), used in constant power applications such as pico hydro uncontrolled turbine driven IAG for feeding three-phase four-wire loads. The proposed controller is used to control the voltage and frequency at the generator terminal independently. The proposed decoupled controller is a combination of a STATic synchronous COMpensator (STATCOM) for regulating the voltage and an electronic load controller (ELC) for controlling the power which in turn maintains the system frequency constant. The STATCOM is realized using a 4-leg insulated gate bipolar transistor (IGBT)-based current controlled voltage-sourced converter (CC-VSC) and a self-supporting dc bus, while the ELC consists of a three-phase diode bridge rectifier, a chopper switch and an auxiliary load. The proposed generating system is modeled and simulated in MATLAB along with Simulink and power system blockset (PSB) toolboxes. The simulated results are presented to demonstrate the capability of an isolated generating system for feeding three-phase four-wire loads with the neutral current compensation. </para>

Modelling and control of auxiliary loads in heavy vehicles

Improved control of the auxiliary units is a possible method to save fuel in heavy vehicles. Today, the auxiliaries are often mechanically driven by the engine, and are constrained to rotate with a fixed ratio to the engine speed. This mechanical constraint results in energy losses. In the paper, the benefits of driving the auxiliaries with electricity are evaluated. The output of an electrically driven auxiliary can at every time instant be controlled to match the actual need. Considered auxiliaries are electrical generator, water pump, cooling fan, air compressor, air conditioning compressor, oil pump and power steering pump. Upper limits on what fuel saving that can be achieved if the auxiliaries are redesigned are first discussed. Simulations indicate that the fuel consumption caused by the auxiliary units is in the range of 5–7% of the total consumption. A Modelica library used for simulation of the energy consumption of the auxiliary units is presented. The cooling system of the library is described in some detail. A case study on optimal control of the cooling system is then performed. Control actuators are the electrical generator, the cooling fan and the water pump. The fan and the pump are supposed to be electrically driven. The control design is based on a simplified model derived from physical principles. It is evaluated through simulations with external variables collected from experiments. The results show that significant energy savings can be obtained.

Preventing substation tripping

This article describes an actual case history of substation nuisance tripping caused by a transformer differential relay due to rolled-out current-transformer (CT) connections. One set of differential relay CTs was installed averse order, and it's wiring was installed as if the CTs were stalled in the correct order. It was after several weeks of substation initial energization, when all plant auxiliary loads, such as lighting and small 480-V equipment, were in operation, the substation main transformer tripped on a line-to-ground arcing fault on the 480 V-system. Transformer differential relay settings, which caused tripping of the transformer for this through fault, were suspected to be in error. It was thought that perhaps arcing ground fault on the 480-V system contained a relatively higher magnitude of harmonic currents. Relay-setting calculations, especially the harmonic restraint, percent slope, tap ratio adjustment, and percent mismatch were reviewed and found to be within acceptable ranges. After thorough checking of relay settings and visual inspection of the substation transformer and switchgear, the field crew reenergized the substation while the technical investigation by the author was still in progress.

The Exergy of Lift and Aircraft Exergy Flow Diagrams

Aside from incidental, auxiliary loads, in level flight the principal load on the aircraft propulsion engine is the power required to provide the continuous lift. To construct an exergy flow diagram for an aircraft – for example, for the purpose of pinpointing inefficiencies and for costing – an expression is needed for the exergy delivered to and by the wings. That is, an expression is needed for the exergy of lift. The purpose of this paper is to present an expression developed for the exergy of lift, applicable not only in level flight but in other modes of flight as well. In order to illustrate the relevance of exergy of lift, two exergy flow diagrams are presented for a light aircraft, one for level flight, and one for climb.

Performance evaluation and energy conservation potential of earth–air–tunnel system coupled with non-air-conditioned building

A numerical model to predict energy conservation potential of earth–air heat exchanger system and passive thermal performance of building has been developed. This model improves upon previous studies by incorporating effects of ground temperature gradient, surface conditions, moisture content and various design aspects of earth–air–tunnel (EAT). The model is based on simultaneously coupled heat and mass transfer in the EAT and is developed within the scope of numerical techniques of Finite Difference and FFT (Matlab). The model is validated against experimental data of a similar tunnel in Mathura (India), and is then used to predict the tube-extracted temperature for various parameters such as humidity variations of circulating air, airflow rate and ambient air temperature. The model is found to be more accurate in predicting tube extracted temperature variations along the length (error range ±1.6%). These results are further used to study the thermal performance of a non-air-conditioned building. Cooling potential of 80-m earth tunnel is found adequate (19 kW) to maintain an average room temperature 27.65°C. However, auxiliary energy load of 1.5 kW for winter season is required in achieving comfort conditions with EAT system affecting an average room temperature of 24.48°C. The present model can be easily coupled to different greenhouse and building simulation codes.

Asymmetric problem of a row of revolutional ellipsoidal cavities using singular integral equations

This paper deals with numerical solution of singular integral equations of the body force method in an interaction problem of revolutional ellipsoidal cavities under asymmetric uniaxial tension. The problem is solved on the superposition of two auxiliary loads; (i) biaxial tension and (ii) plane state of pure shear. These problems are formulated as a system of singular integral equations with Cauchy-type singularities, where the unknowns are densities of body forces distributed in the r, θ, z directions. In order to satisfy the boundary conditions along the ellipsoidal boundaries, eight kinds of fundamental density functions proposed in our previous papers are applied. In the analysis, the number, shape, and spacing of cavities are varied systematically; then the magnitude and position of the maximum stress are examined. For any fixed shape and size of cavities, the maximum stress is shown to be linear with the reciprocal of squared number of cavities. The present method is found to yield rapidly converging numerical results for various geometrical conditions of cavities.

Cooling and heating potential of earth-air tunnel heat exchanger (EATHE) for non-air-conditioned building

A numerical model to predict energy conservation potential of earth-air heat exchanger system and passive thermal performance of building has been developed. This model improves upon previous studies by incorporating effects of ground temperature gradient, surface conditions, moisture content and various design aspects of earth-air-tunnel heat exchanger (EATHE). The model is based on simultaneously coupled heat and mass transfer in the EATHE and is developed within the scope of numerical techniques of finite difference techniques and FFT (Matlab). The model is validated against experimental data of a similar tunnel in Mathura (India), and is then used to predict the tube-extracted temperature for various parameters such as humidity variations of circulating air, airflow rate and ambient air temperature. The model is found to be more accurate in predicting tube extracted temperature variations along the length (error range &#177;1.6%). The earth-air-tunnel is further coupled to a non-air-conditioned building to study reduction in cooling and heating loads. The cooling potential of an 8m earth tunnel is found adequate (19KW) to maintain an average room temperature 27.65&#176;C. However, an auxiliary energy load of 1.5KW for the winter season is required to achieve comfort conditions with an EATHE system affecting an average room temperature of 24.48&#176;C. The present model can be easily coupled to different greenhouse and building simulation codes.

Hybrid propulsion with separate connection of motor and auxiliary loads to fuel cell or energy store

Hybrid propulsion with separate connection of motor and auxiliary loads to fuel cell or energy store

Analysis of Intensity of Singular Stress Fields at the End of a Cylindrical Inclusion under Asymmetric Uniaxial Tension.

This paper deals with generalized stress intensity factors at the end of an elastic cylindrical inclusion in an infinite body under asymmetric uniaxial tension. These stress intensity factors control singular stress fields at the end of inclusion. The problem is solved on the superposition of two auxiliary loads;(i)biaxial tension and (ii)plane state of pure shear. The problem is formulated as a system of integral equations with Caushy-type or logarithmic-type singularities, where un-knowns are densities of body force distributed in infinite bodies having the same elastic constants as those of the matrix and inclusion. In the numerical analysis, the unknown functions of the body force densities are expressed as fundamental density functions and weight functions. Fundamental density functions are chosen to express the symmetric stress singularity of the from 1/γ1-λ11/γ1-λ3 and the skew-symmetric stress singularity of the form 1/γ1-λ21/γ1-λ4. Then, the singular stress fields at the end of a cylindrical inclusion are discussed with varying the fiber length and elastic ratio. The results are compared with the ones of a cylindrical inclusion under longitudinal tension and the ones of a rectangular inclusion under transverse tension.

Generic functions for fuel consumption and engine-out emissions of HC, CO and NOx of spark-ignition engines

The prediction of fuel consumption and engine-out emissions of spark-ignition engines from characteristic relationships has been investigated. For spark-ignition engines operating on homogeneous mixtures, indicated specific fuel consumption based on gross indicated power is related to compression ratio and spark timing relative to optimum values. The influence of burn rate is largely accounted for by differences in spark timings required to phase combustion correctly. For engine-out emissions of HC, CO and NO x, generic functions have been derived that relate the emissions index in each case to air-fuel ratio, spark timing relative to the optimum and burned gas fraction present during compression. The effects of exhaust gas recirculation and residual gas dilution are accounted for. Brake specific performance maps can be generated. This requires knowledge or predictions of calibrations, cylinder volumetric efficiency, rubbing friction, auxiliary loads and exhaust back pressure. A closed set of equations and illustrative results are given.

Interaction of a Row of Ellipsoidal Inclusions in an Infinite Body under Asymmetric Uniaxial Tension.

This paper deals with an interaction problem of a row of ellipsoidal inclusions under asymmetric uniaxial tension using singular integral equations of the body force method. The problem is solved on the superposition of two auxiliary loads ; (i) biaxial tension and (ii) plane state of pure shear. These problems are formulated as a system of singular integral equations with Cauchy-type or logarithmic-type singularities, where unknown functions are densities of body forces distributed in the γ, θ, z directions in infinite bodies having the same elastic constants as those of the matrix and inclusions. In order to satisfy the boundary conditions along the ellipsoidal boundaries, the unknown functions are approximated by a linear combination of fundamental density functions and polynominals. The present method is found to yield rapidly converging numerical results for stress distributions along the boundaries. For any fixed shape and spacing of inclusions, the maximum stress is shown to be linear with the reciprocal of the squared number of inclusions.