Auxiliary Power Research Articles

PERFORMANCE EVALUATION OF RESIDENTIAL HEAT-PUMP WATER HEATERS (PART 2): ENERGY CONSUMPTION ESTIMATION METHOD BASED ON HEAT-PUMP COP, STORAGE HEAT LOSS AND AUXILIARY POWER LOSS

The purpose of this study was to develop a method for estimating the energy consumption of residential CO2 refrigerant heat-pump water heaters. This paper considered a calculation model involving the use of actual machine data analyzed in Part 1. It was evaluated by considering the effect of efficiency losses on the ideal system COP. The calculation model estimated "heat-pump COP", "storage heat loss" and "auxiliary power loss". The developed method was applicable to wide-ranging hot water supply conditions. The estimation and test values of the system COP agreed to within a tolerance of around ±0.2.

Assisted Power Transfer for Voltage Balance of Bipolar DC MicroGrids Using Inactive Motor Drives

A voltage balancer remains a good solution of power transfer for bipolar dc grids, which, however, would increase the costs due to its requirement for additional hardware support. In this article, an auxiliary power transfer strategy is proposed by using the inactive motor drives affiliated with the bipolar dc grid. During idle periods of the motor drive, one inverter bridge arm is connected with the bipolar dc grid at their neutral points, allowing bidirectional power transfer between the upper and lower dc-bus sources. The proposed strategy share part of the voltage balancer's power transfer burden without requiring additional hardware and affecting the normal operations of the motor drive. In addition, its effectiveness is verified by experimental results on an interior permanent magnet synchronous motor drive, showing that the power flows among the upper and lower dc-bus power supplies are controlled effectively. Also, the active control of the dc-bus voltages could be achieved by modulation of the phase currents.

Design and Validation of a 20-kVA, Fully Cryogenic, Two-Level GaN-Based Current Source Inverter for Full Electric Aircrafts

This article presents the design of a cryogenic power electronics converter using wide bandgap (WBG) devices. A 20-kVA two-level current source inverter (2L-CSI) is designed and validated under both room temperature (RT) and cryogenic temperature (CT) of 77 K. CSI has been neglected because of the physically large and heavy dc-link inductor compared to the dc-link capacitor of voltage source inverters (VSIs). However, higher power, together with operation at CT in fully electric aircrafts (FEAs), makes them superior in size, volume, and power quality. The advantage in volume is primarily attributed to the utilization of air-core inductors with superconducting tapes as dc-link storage elements. Therefore, a 2L-CSI with both power stage and associated components at CT is designed and evaluated. As part of converter development, commercially off-the-shelf (COTS) products, including integrated circuits (ICs), isolated auxiliary power supplies, and passive components, were utilized. Numerous laboratory prototypes of cryogenic subsystems were built to screen out the cryocompatible components. Based on components screening, converter subsystems, namely, the gate driver (GD) board and the double-pulse test (DPT) platform, were also developed. Characterization of these subsystems was performed both at RT and CT, where both individual testing and integrated testing were carried out.

Fusion power supply advances by the J-TEXT engineering team

To meet the stringent requirements of the fusion power supply for large-scale fusion devices, the J-TEXT engineering team has carried out key technology research and applications in several important directions of fusion power supply. This article presents the advances made by the J-TEXT engineering team in recent years in the following areas: (1) a high-voltage power supply for an auxiliary heating system; (2) a breakdown protection device for an auxiliary heating power supply; (3) magnetic field compatibility; (4) a high-voltage pulsed power supply for a field-reversed configuration; (5) a large physics experimental facility control system. The research backgrounds, technical progress, test results, applications, summaries and prospects are described in detail in each part. These innovative research results and valuable engineering experience can promote the progress of fusion power supply technology, and also lay a foundation for the development of power supplies with higher parameters in the future.

Overview of initial negative triangularity plasma studies on the ASDEX Upgrade tokamak

An overview of results of negative triangularity (NT) studies from the ASDEX Upgrade tokamak (AUG) is given. Moderate values of the triangularity in the range of δ average ≈ −0.2 have been obtained. Results from both unfavorable and favorable magnetic configuration in terms of high-confinement mode (H-mode) access are presented. In unfavorable configuration, the ion grad B drift points away from the active x-point, which usually results in a factor of 2 higher power thresholds to enter H-mode. In unfavorable configuration, low-confinement mode (L-mode) operation is confirmed at high auxiliary heating input powers MW at low collisionality. Under these conditions, plasmas with positive triangularity (PT) are usually in H-mode. Highest plasma energies have been obtained using a combination of neutral beam injection, electron- and ion cyclotron resonance heating, where values of the plasma beta of β N ≈ 1.7 have been reached in L-mode. While discharges with mixed auxiliary heating power input show moderate confinement on L-mode levels, plasmas heated with electron cyclotron resonance heating show H-mode like confinement. Operation in favorable configuration, however, leads to H-mode with type-I edge localized modes (ELMs). The power required for the L–H transition is comparable to the typical L–H power threshold in PT cases ( MW), and good confinement of typical PT H-modes is obtained. The ELM frequency is demonstrated to reach 700 Hz. These results show a clear effect of the NT configuration on the ELM behavior in H-modes, and that on AUG, unfavorable configuration is an essential ingredient if H-mode operation is to be avoided in NT plasmas. So far, in all AUG NT plasmas, power degradation is observed. Initial gyrokinetic simulations of the edge plasma in unfavorable configuration reveal the ion-temperature gradient mode as the fastest growing mode with a subdominant trapped-electron-mode.

A Microencapsulated Phase-Change Material Suspension-Based Integrated Thermal Management System for Extended Range Electric Vehicle

Abstract In order to improve the temperature maintenance capacity for the battery of the extended-range electric vehicle (EREV) in a low-temperature environment, a microencapsulated phase-change material suspension (MPCMS)-based integrated thermal management system (ITMS) is proposed. The working modes of the proposed ITMS are divided based on series-parallel connections of the battery thermal management system (BTMS), motor thermal management system, motor thermal management system, and auxiliary power unit (APU) thermal management system; the structural parameters of the proposed ITMS are determined by robust design, and the system performance difference between the proposed ITMS and the traditional BTMS is verified through the comparative simulation in −20 °C environment. The results show that the proposed ITMS can significantly delay the decline of battery temperature in the charge-depleting (CD) stage and can reduce the time of the positive temperature coefficient (PTC) heater being on by 27.26%, and the total time being on by 54.82%. During the charge-sustaining (CS) stage, when the PTC heater is off, the average battery temperature will increase by 15.33 °C compared with the traditional BTMS. Based on the proposed ITMS, the temperature maintenance capability for the battery can be significantly improved, and the energy consumption of the PTC heater and vehicle can be reduced by 48.12–100% and 13.44–33.58%, respectively.

Reducing the L-H transition power threshold in ITER-similar-shape DIII-D hydrogen plasmas

Recent dedicated DIII-D experiments in low-torque, ITER-similar-shape (ISS) hydrogen plasmas (at a plasma current I p ∼ 1.5 MA and ITER-similar edge safety factor q 95 ∼ 3.6) show that the L-H transition power threshold P LH can be reduced substantially (∼30%) with L-mode helium admixtures n He/n e ⩽ 25%. In the ensuing H-mode, helium ion fractions n He/n H remain below 25%. H-mode normalized pressure and confinement quality are only slightly affected by helium seeding, and Z eff ⩽ 2.15 (including helium and carbon content). The plasmas investigated here are electron-heat dominated, with temperatures T e(0)/T i(0) ⩾ 1 and edge heat flux ratio Q e/Q i(ρ = 0.95) ∼ 1.2–1.5. Without mitigation, P LH is higher by a factor of 2–3 in comparison to similar ISS deuterium plasmas. ISS hydrogen plasmas with lower plasma current I p ∼ 1 MA (increased edge safety factor q 95 ∼ 5.1) exhibit a substantially lower power threshold. This plasma current dependence, also observed previously on ASDEX-U and in JET, is not accounted for by the commonly used 2008 ITPA multi-machine threshold scaling, but could potentially allow H-mode access at marginal heating power during the initial plasma current ramp-up. Attempts to reduce P LH with low-field- and high-field-side hydrogen pellet injection, using 1.7 mm diameter pellets, have not demonstrated a robust threshold reduction, in contrast to successful earlier experiments with larger 2.7 mm pellets. Techniques for reducing P LH are very important for ITER, in particular for accessing H-mode in hydrogen plasmas during the Pre-Fusion Power Operation-1 (PFPO-1) campaign with marginal auxiliary heating power (20–30 MW of ECH).

Towards renewable public transport: Mining the performance of electric buses using solar-radiation as an auxiliary power source

• Developing a framework to estimate solar PV potential of urban fleet-wide electric buses. • Publicly street-view panoramas, GPS trajectory data and DEM data are used as input. • A case study of Qingdao, China with 547 bus routes, 28,661 street-view panoramas is studied. • Benefits under different driving conditions and operation schedules are evaluated. Transforming the road public transport to run on renewable energy is vital solution to achieve carbon neutral and net zero goals. This paper evaluates the potential of using solar radiation-generated electricity as an auxiliary power supplementary for the battery of electric buses, based on a developed framework that using publicly street-view panoramas, GPS trajectory data and DEM data as input parameters of solar radiation model. A case study of Qingdao, China with 547 bus routes, 28,661 street-view panoramas shows that the solar-radiation electricity generated at noon during the operation accounts for about one-fifth, one-eighth of the total electricity consumption of a bus traveling one kilometer in a sunny day and a cloudy day, respectively. Spatial variability shows significant solar-radiation power generation advantages in newly-launched areas and expressway. The solar power generated in a sunny day can make a bus half of passengers and with air conditioner off at least one extra trip in 2:1 replacement schedule, and nearly close to one extra trip in 4:3 replacement schedule. A correlated relation between the solar-radiation power generation benefit and the operation schedule of electric buses is observed, implying that the high cost of 2:1 replacement schedule for long-distance routes during summer or winter can be reduced. The proposed framework can help us evaluate and understand the feasibility of solar radiation-generated electricity energy of electric bus fleets covering the large-scale urban areas at different times, locations, and weather conditions, so as to support effective decisions at better planning of PV-integrated electric buses.

Fully Self-Powered Inductor-Less Electromagnetic Vibration Energy Harvesting System Using Auxiliary Coils for Hysteresis Current MPPT Control

Utilizing coil inductor of electromagnetic vibration energy harvester (EVEH) to form single stage ac–dc boost converter can make the self-powered milli-power system more compact. However, large output current harmonics of EVEH significantly degraded the output power in such system. This article proposes a new approach of adopting hysteresis current control to realize maximum power point tracking (MPPT) and reduce current harmonics in inductor-less converter by using auxiliary coils. The output characteristics and correlations between multiple coils are firstly studied to verify the feasibility of using auxiliary coil to represent the output of main coil. The optimal winding strategy for main coil and auxiliary coils is revealed for no degradation on maximum output power of main coil. Based upon these, a completely self-powered multicoil EVEH system is designed with auxiliary coils as reference for MPPT controller and as auxiliary power supply in cold-start. Experiments show that the designed prototype can obtain 9.54 mW output power at acceleration of 3 m/s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , with the overall efficiency of 77.6%. To charge a 10 mF supercapacitor from zero to 5 V, an average output power of 7.27 mW can be obtained with an average charging efficiency of 62.4%. In addition, the start-up method adopting auxiliary coil allows the system to cold-start when the output voltage is lower as 0.5 V. The proposed approach has been demonstrated to achieve high overall efficiency in milli-power self-powered EVEH system and also has significant advantages in cost and volume compared with using external devices to obtain reference.

Supercapacitor Control System Based on Fuzzy PID and Active Equalization Technology

In this paper, a supercapacitor control system is designed to improve the motion performance of small unmanned vehicles. The supercapacitor is used as the auxiliary power supply for the chassis of the unmanned vehicle. When working at low power, the lithium battery supplies power to the chassis and charges the supercapacitor. When climbing or accelerating, the supercapacitor is used to assist the power supply to improve the body’s movement ability. The current and voltage values are collected by high-precision sensors and the system charging control is completed by fuzzy PID. It has a good effect on the test, which significantly improves the motion performance of the unmanned vehicle.

Multi-stage voltage droop compensation based on resonant circuit for unipolar solid-state Marx Generators.

The low-voltage droop of high-voltage pulses is required to provide stable pulsed electric fields in many applications. Increasing the capacitance of energy storage capacitors increases both the size and the cost of the system. In this paper, four compensation stages based on the resonant circuit have been inserted into a 16-stage solid-state Marx generator to compensate for the voltage droop in different conditions. The nearly linear part of the sinusoidal voltage is precisely added to the load during discharging as compensation, and the rectangular pulsed voltage with little droop can be realized. Different numbers of compensation stages and different resonant inductances can compensate the droop to different levels, which means the compensation effect is also adjustable. Moreover, these compensation stages can operate as common stages in Marx generators as long as we open-circuit the resonant circuits. Since the capacitors in resonant compensation stages are also charged in parallel with capacitors in common stages, no auxiliary power supply is required. Simulating and experimental results show that the droop of a 9kV pulse can be ideally compensated over a 500Ω resistive load at various pulse widths. The pulse width should be shorter than the length of the nearly linear part of the sinusoidal voltage.

A fault diagnosis method for VRLA battery in data center

The Valve-Regulated Lead–Acid (VRLA) battery is one of the important components of the auxiliary power supply system in the data center. Battery failure in the data center poses a great threat to the smooth operations in the data center. The biggest challenge for the data centers is how to accurately diagnose the faulty battery in real-time in order to ensure the safe operations of the data center. According to the working characteristics of VRLA battery, a battery fault diagnosis algorithm is proposed based on the historical data of battery voltage and internal resistance. The algorithm combines the growth rate of voltage and internal resistance to obtain the indicator that characterizes the performance change of the battery during the working by statistical method. The real-time diagnosis of the faulty battery is estimated by using the Pauta criterion to discriminate the indicator of the battery performance. The effectiveness of the method was verified through a real-time diagnostic test of VRLA battery in a data center. The fault diagnosis method in this paper is compared with the median absolute deviation (MAD) algorithm in the same data set to avoids the missed diagnosis due to voltage value not reaching the fault limits and the false diagnosis caused by power surge or charge–discharge cycle. Compared with the hierarchical clustering based on K-shape algorithm, our algorithm does not need to diagnose the battery in groups. The diagnosis result of the faulty battery is about 7 days faster, and there is no misdiagnosis when multiple batteries fail at the same time. The algorithm can also set the corresponding fault limits for battery fault diagnosis according to the different performance requirements of VRLA battery in data center.

수소생산을 위한 수증기-메탄-개질 반응기의 성능 분석 및 설계

This study is to design a steam methane reforming (SMR) reactor that can produce hydrogen from methane, the main component of LNG, by extracting a portion of the gas (BOG) generated from the fuel tank to use a fuel cell as an auxiliary power source for an LNG propulsion ships. Prior to the design, performance was analyzed using several parameters. As the pressure in the reforming reactor increased, the methane conversion rate decreased. The yield to hydrogen is maximal at a temperature of 750 to 800℃, with almost 40% being reduced to hydrogen. At a low temperature, the methane conversion rate was low, and the concentrations of other compositions were also low. At a temperature above 700℃, the concentration of carbon monoxide continued to increase, while the concentration of carbon dioxide decreased. It can be seen that the water gas conversion reaction does not occur smoothly at high temperatures. The reactor design was carried out in the temperature range of 700 to 900℃, and it was found that for each 50℃ increase, the total heat transfer area required increased in the range of about 17~25%.

가상운영 시뮬레이터를 활용한 철도차량 보조전원장치 신뢰성 입증

Electric railway vehicle is constituted by various components, which have an important role associated with safety. Therefore, for important safety-related electronic components of railway vehicles, timely maintenance is required based on reliability evaluation such as life expectancy calculation. This paper deals with the reliability evaluation of auxiliary power units in railway vehicles, which play an important role in safety and passenger service, but have few reliability demonstration test cases because they are complex and consist of many parts. In particular, it is characterized in that a virtual operation simulator is applied to perform an efficient and stable verification test for complex electronic components of railway vehicles.

Optimization control and economic evaluation of energy storage combined thermal power participating in frequency regulation based on multivariable fuzzy double-layer optimization

Energy storage auxiliary thermal power participating in frequency regulation of the power grid can effectively improve operating efficiency of thermal power units, but how to realize power distribution between energy storage system and thermal power units is the key to the frequency regulation operation of energy storage and thermal power combined system. Aiming at problems that full power compensation strategy is not conducive to the sustainability of energy storage output, a frequency regulation optimization control strategy of thermal powers and energy storage combined system based on multivariable fuzzy double-layer optimization is proposed in this paper. According to the output and compensation weights of the fuzzy controller, the state of charge for energy storage system can be adjusted adaptively to help thermal power units improve the dynamic frequency regulation performance of power grid. The equivalent cycle life of energy storage system is calculated by the rain-flow counting method, and the economy of system is evaluated by the net present value method in the whole life cycle of energy storage system. The effectiveness of the proposed control strategy is verified by the simulation analysis on the actual operation data which can provide a theoretical basis for frequency regulation of automatic generation control.

Analysis of a gas turbine auxiliary power unit system based on a fuel cell combustor

In this study, a gas turbine (GT) system for auxiliary power units (APUs) is proposed based on a fuel cell combustor, which separates combustion into three processes: fuel-rich combustion, electrochemical reaction through solid oxide fuel cells (SOFCs), and fuel-lean combustion. Compared with the traditional GT system, the efficiency of the proposed system is much higher due to the high efficiency of the electrochemical conversion process in SOFCs. Meanwhile, the advantage of the GT's high power density is conserved to improve the system power density by increasing the GT power proportion, which makes it possible to be used as an APU for aircraft. First, the system was simulated and evaluated at the base case with electrical efficiency reaching 45.62% and power density reaching 0.43 kW/kg. Then, extra fuel was added into the fuel-lean combustion chamber to increase the GT power proportion, which led to an increase in power density and a decrease in efficiency. Finally, the concept of a superhigh-temperature SOFC was proposed to further increase the system power density. When the SOFCs operate at a superhigh temperature of 1473 K, the power density of the system reaches 2.67 kW/kg, which is much higher than that of conventional SOFC-GT hybrid systems.

Development of a Resonant Auxiliary Power Supply Control Algorithm and Resonant Destruction Detecting for Railway Vehicles

In this paper, the method and a control algorithm for detecting resonant destruction of a resonant auxiliary power supply for railway vehicle are proposed. It is essential to reduce the weight of the electric equipment attached to the lower part of the railway vehicle because it greatly affects the life of the railway vehicle, such as wheel and bearing. In order to reduce the weight and volume of the auxiliary power supply, in the case of windings, high-speed switching should be performed by lowering the input voltage. Therefore, in this paper, the auxiliary power supply control algorithm using an LLC resonant converter to reduce the weight of auxiliary power supply for railway vehicle is proposed, and the method of detecting resonant destruction due to device failure of a resonant converter is proposed. The proposed algorithm steps down the wire voltage using an input buck converter for high-speed switching, and the inverter input voltage is controlled through the LLC resonant converter. In addition, ZVS (Zero Voltage Switching) is operated to minimize the loss of the resonant converter, and the optimal design of the resonant tank is also proposed. In order to detect resonant destruction, a detection method formulated by analyzing the resonant current peak value for the load capacity is proposed. The algorithm proposed in this paper is verified by simulation and experiment.

Trip-level energy consumption prediction model for electric bus combining Markov-based speed profile generation and Gaussian processing regression

Electric bus energy consumption prediction is conducive to bus route scheduling and charging optimization management. However, existing prediction models do not comprehensively consider vehicle parameters, auxiliary power, speed profile and external factors. In particular, there is a lack of in-depth research on generating speed profile based on low-resolution data for electric bus. The aim of this study involves predicting bus trip-level energy consumption. Thus, the temperature effect on powertrain efficiency and auxiliary power was first analyzed, and then a Markov-based speed profile generation method considering the speed state transition spatiotemporal characteristics and driving style was developed. Reliable process-related variables extracted from the aforementioned model development in conjunction with external-related variables are used as the input of Markov-based Gaussian processing regression model (M-GPR). Finally, 7919 regular bus driving samples on the same route were extracted from the raw bus operation dataset to verify the model effectiveness in improving the prediction accuracy of trip-level energy consumption. The results indicate that M-GPR exhibits a better prediction performance with an average prediction error of 8.69%, which decreases by 0.62%–5.41% compared with other models. Furthermore, M-GPR presents wide applicability, with average errors between 7.01% and 9.90% in different operating scenarios.

Distribution of energy efficiency design index for tankers in Indonesia

Greenhouse gas emissions resulting from shipping activities increased by 9% in 2018. Tankers are one of the contributors to total ship emissions. To reduce these emissions, the International Maritime Organization adopted the Green House Gas Strategy by issuing a regulation in the form of the Energy Efficiency Design Index (EEDI). This study aims to obtain the distribution of EEDI tankers in Indonesia. The EEDI calculation uses empirical equations that consider the main engine power, auxiliary engine power, and reference speed. The ship data used are 638 units of Indonesian-flagged tankers, including ship particulars from the classification agency. The results of this study indicate that compliance with the EEDI regulation is 26%. Through the application of engine power limitation technology and innovative technology in the form of weather routing, waste heat recovery, solar panels, and electronically controlled engines, EEDI fulfillment increased to 78%.

High-fidelity CFD modeling of pollutant dispersion from aircraft auxiliary power units (APUs) at a realistic airport and the effects on airport air quality

Many studies have investigated air-traffic impact on airport air quality through main-engine emissions, however very few have characterized the APU-related impact. As field-monitoring remains limited, our study used CFD simulations to provide a high-fidelity representation of 19 APU dispersion plumes in a realistic airport configuration. Results of three dominant wind configurations show that the global dispersion plume (from all APUs) was transported by incident winds. Depending on wind direction, pollutant trapping within a large downwash region was observed downstream of the terminal-building. Local differences were observed depending on source locations; emissions within the downwash region were pushed against the terminal-facade which promoted emission spillover on terminal-roof, while plumes within the unperturbed boundary layer were transported by incident winds. Quantitatively, APU pollutant concentrations dropped overall by 3–4 orders of magnitude around the terminal-building, while diluted concentrations by 5–6 orders of magnitude were monitored at the airport exit. Given source concentrations with an appropriate experimental apparatus, this model can serve as an airport air quality decision-making tool to finely characterize individual source impacts. Such information can help assist airport operation management (taxi to gate/runway, gate assignment, safe corridors for ground-handling personnel) so as to reduce/prevent the impact of pollutant hot spots depending on wind configurations.