Ground Power Unit Research Articles

Simulation of Ground Power Unit – 3 (GPU3) Stirling Engine with Air as Working Fluid

Abstract The immediate need to mitigate climate change presents a chance to move civilization in the direction of a more sustainable future. A Stirling Engine has multi-fuel capability such as Biomass, Solar Thermal and Waste Heat and hence can contribute significantly to the energy mix of fuel sources. The most common working fluids for Stirling engines are hydrogen, helium, and air, with air being the least expensive and safest. Studies analysing Stirling Engine performance with 3D CFD are limited, and even fewer use air as the working fluid. This research presents a novel 3D CFD analysis of the Ground Power Unit – 3 (GPU3) Stirling Engine with air as the working fluid using ANSYS Fluent. The fluid domain was modelled in SolidWorks and 1/8th of the geometry was used for simulation with realizable EWT k-ε as eddy viscosity model. It was found that on average there was a reduction in power output by 50% when air was used as working fluid against helium as working fluid. The engine's power output decreases as the engine's speed increases. The impinging effect contributes to vortex formation and temperature variation within the engine components was non-sinusoidal, this is inline with similar studies performed on GPU-3 Stirling engine.

A novel nine‐level inverter, applicable in air plane ground power unit

AbstractIn this study, a novel nine‐level inverter using one voltage source, 10 unidirectional and one bidirectional power switches, and two capacitors has been proposed to utilize in ground power units (GPUs). Selective harmonic elimination method has been applied to reduce the output voltage's THD to less than 3% with 115/200 V and 400 Hz. The proposed converter utilized a lower number of devices to output a nine‐level staircase in comparison to existing converters. Also, the proposed converter uses inherent self‐voltage balancing for capacitors' voltage. So, the control algorithm gets simpler. In this study, the topology analysis, modulation algorithm, capacitor calculation, loss, efficiency, and performance analysis of the proposed topology have been presented. The proposed circuit has been compared to recently published papers in terms of efficiency, switch, capacitor, diode, and source numbers. The theoretical and experimental performance of the topology has been verified by simulation on PSCAD and PSIM software and 350 W experimental setup.

Dead-time compensation and single-loop control strategy for ground power unit

Instead of the auxiliary power system, the ground power unit supplies to airplanes during stopovers in airports, which is an important means of reducing carbon emissions of airport. However, under the restraint of switching frequency and high dynamic response speed, a single control loop is usually implemented in 400 Hz voltage-source inverter, the sampling and control of the inductor current in the LC filter are avoided, result in the design of the control system being more difficult, and the direction of the dead-time compensation can not be obtained due to the lack of the current polarity. In view of the above problem, this paper firstly analyzes the influence on the output voltage of inverter due to the dead-time, including the errors of fundamental amplitude and phase, and the low-order harmonic distortion. Then, according to the state equation of the inductor current, a current observation model without zero drift is proposed to obtain the polarity of the inductor current. On this basis, feedforward compensation is carried out for the voltage error generated by the dead-time. Combined with the amplitude-frequency characteristic curve, the parameter optimization design method of the single closed-loop proportional-resonant controller is presented. Finally, a simulation model and an experimental platform are established to verify the feasibility and effectiveness of the current observation model, dead-time compensation method and controller parameter optimization design method proposed in this paper.

Airport Microgrid and Its Incorporated Operations

This paper presents the development of an airport bipolar DC microgrid and its interconnected operations with the utility grid, electric vehicle (EV), and more electric aircraft (MEA). The microgrid DC-bus voltage is established by the main sources, photovoltaic (PV) and fuel cell (FC), via unidirectional three-level (3L) boost converters. The proposed one-cycle control (OCC)-based current control scheme and quantitative and robust voltage control scheme are proposed to yield satisfactory responses. Moreover, the PV maximum power point tracking (MPPT) with FC energy-supporting approach is developed to have improved renewable energy extraction characteristics. The equipped hybrid energy storage system (HESS) consists of an energy-type battery and a power-type flywheel; each device is interfaced to the common DC bus via its own 3L bidirectional interface converter. The energy-coordinated operation is achieved by the proposed droop control. A dump load leg is added to avoid overvoltage due to an energy surplus. The grid-connected energy complementary operation is conducted using a neutral point clamped (NPC) 3L three-phase inverter. In addition to the energy support from grid-to-microgrid (G2M), the reverse mcrogrid-to-grid (M2G) operation is also conductible. Moreover, microgrid-to-vehicle (M2V) and vehicle-to-microgrid (V2M) bidirectional operations can also be applicable. The droop control is also applied to perform these interconnected operations. For the grounded aircraft, bidirectional microgrid-to-aircraft (M2A)/aircraft-to-microgrid (A2M) operations can be performed. The aircraft ground power unit (GPU) function can be preserved by the developed microgrid. The MEA on-board facilities can be powered by the microgrid, including the 115 V/400 Hz AC bus, the 270 V DC bus, the switched-reluctance motor (SRM) drive, etc.

A Novel Reduced Switches Nine-Level Inverter Applicable in Aircraft Ground Power Unit

A Novel Reduced Switches Nine-Level Inverter Applicable in Aircraft Ground Power Unit

Improvement of technical performance of heat regenerator of GPU-3 Stirling engine

In this paper, in order of simulate the performance of Stirling engine a novel adiabatic model (irreversible adiabatic) is proposed for the Ground Power Unit Stirling engine, which has higher accuracy than previous models of this Stirling engine. Then the effects of important parameters of Stirling engine such as regenerator length, regenerator porosity, engine rotational speed, and pressure on the performance of the Ground Power Unit engine are investigated and optimal conditions of these parameters are provided for three different operating pressures. The engine modeling is conducted by the Runge–Kutta method and the genetic algorithm technique is used to optimize the engine. The results show that the power output and thermal efficiency of model are in good agreement with the experimental data. Also, at high rotational speeds, by increasing the regenerator length, the pressure drop increases and the power output decreases sharply; therefore, it is better to use short regenerators to achieve proper thermal efficiency. Also, at high rotational speeds and low regenerator porosity, the pressure drop of regenerator increases so much that at 3500 rpm and 0.65 porosity, the pressure drop reaches more than 2.5 bar. For maximize the power and thermal efficiency, a high porosity coefficient is recommended at high rotational speeds.

Ground power unit LUZES as an experimental platform for studying defects for the FAM-C method

Abstract This article addresses studies of basic mechanical defects conducted with the proprietary FAM-C method on a test bench created on the basis of ground power unit LUZES. The following mechanical defects were modelled in laboratory conditions: skewed connections, eccentricity of connections, increased circumferential clearance, increased intertooth clearance, etc. The thesis was put forward that tests on LUZES equipment enable to transfer experience onto the more complex helicopter power unit. The aim is the early defect detection of these units.

Design and Implementation of a Ground Power Unit Based on the Fault-Tolerant Inverter

Due to the widespread use of static power converters in various industries and sensitive applications such as ground power units (GPUs), it is essential that the inverters have high reliability. A failure in the inverters can cause undesirable consequences such as; low performance, shutting down the system, and losing the stability of the entire system. On the other hand, in some critical industrial processes with high standstill cost and safety-aspect concerns, such as aircrafts, high reliability, and survivability of the system are very important. Therefore, the use of fault-tolerant (FT) inverters is inevitable in such applications. In this paper, using an FT inverter, the reliability of the GPUs is increased and it results in higher availability and continuous system performance. Furthermore, a simple automatic fault-detection (FD) algorithm is presented by taking the inverter pole voltage as a fault detection parameter. The inverter is analyzed for open-circuit (OC) fault in the switches and the reliability of the FT inverter is compared with the classic inverter. The simulation and experimental results of the 1 kVA converter prototype are presented to confirm the FT inverter performance and the proposed method.

Design and implementation of ground power unit using a three‐level fault‐tolerant neutral point clamped inverter

AbstractDue to the widespread use of static power converters in various industries and sensitive applications such as ground power units (GPUs), it is essential that the inverters have high reliability. A failure in the inverters can cause undesirable consequences such as low performance, shutting down the system, and losing the stability of the entire system. On the other hand, in some critical industrial processes with high standstill costs and safety‐aspect concerns, such as aircraft, high reliability, and survivability of the system, are very important. Therefore, the use of fault‐tolerant (FT) inverters is inevitable in such applications. In this paper, using a three‐level fault‐tolerant neutral point clamped (FT‐NPC) inverter, the reliability of the GPUs is increased and it results in higher availability and continuous system performance. Furthermore, a simple automatic fault detection (FD) algorithm is presented by taking the inverter pole voltage as a FD parameter. The inverter is analyzed for open‐circuit fault in the switches, and the reliability of the FT‐NPC inverter is compared with the classic inverter. The simulation and experimental results of the 2‐kVA converter prototype are presented to confirm the FT inverter performance and the proposed method.

Development of an Aircraft Electric Power Architecture With Integrated Ground Power Unit

This article presents a switch-mode rectifier-based electric power architecture with an integrated ground power unit for more electric aircraft. The well-regulated high-voltage dc-bus is established from the aircraft generator. And the conventional major 270-Vdc, 28-Vdc, and 115-Vac/400-Hz buses are also preserved. In landed conditions, the ground power unit function powered by the mains is inherently possessed thanks to the proposed integrated schematic. First, the developed switch-mode rectifier using a silicon-carbide device with a wide frequency range covering utility line frequency and aircraft generated varied high frequency is presented. The allowable energy storage inductances using the embedded generator armature winding are derived. Good generator armature power quality and well-regulated dc output voltage are preserved by the designed current and voltage control schemes. Next, the utility grid-powered ground power unit established by the embedded schematic is introduced. Finally, the inverter for generating the 115-Vac/400-Hz three-phase source and the dc–dc converter for establishing the 270-Vdc bus are constructed. Normal operations, good dynamic, and steady-state performances of all the constructed power stages are verified experimentally, which can confirm the feasibility of the proposed aircraft power architecture.

Power Performance Comparison of SiC-IGBT and Si-IGBT Switches in a Three-Phase Inverter for Aircraft Applications.

The converters used to integrate the ground power station of planes with the utility grid are generally created with silicon-insulated gate bipolar transistor (Si-IGBT)-based semiconductor technologies. The Si-IGBT switch-based converters are inefficient, oversized, and have trouble achieving pure sine wave voltages requirements. The efficiency of the aircraft ground power units (AGPU) can be increased by replacing existing Si-IGBT transistors with silicon carbide (SiC) IGBTs because of the physical constraints of Si-IGBT switches. The primary purpose of this research was to prove that the efficiency increase could be obtained in the case of using SiC-IGBTs in conventional AGPU systems with the realized experimental studies. In this study, three different experimental systems were discussed for this purpose. The first system was the traditional APGU system. The other two systems were single-phase test (SPT) and three-phase inverter systems, respectively. The SPT system and three-phase inverter systems were designed and implemented to compare and make analyses of Si-IGBTs and SiC-IGBTs performance. The efficiency and detailed hard switching behavior comparison were performed between the 1200-V SiC-IGBT- and 1200-V Si-IGBT-based experimental systems. The APGU system and Si-IGBT modules were examined, the switching characteristic and efficiency of the system were obtained in the first experimental study. The second experimental study was carried out on the SPT system. The single-pulse test system was created using Si-IGBTs and SiC-IGBTs switches in the second experimental system. The third experiment included a three-phase-inverter-based test system. The system was created with Si-IGBTs and SiC-IGBTs to compare the two different switch-based inverters under RL loads. The turning off and turning on processes of the IGBT switches were examined and the results were presented. The Si-IGBT efficiency was 77% experimentally in the SPT experimental system. The efficiency of the third experimental system was increased up to 95% by replacing the old Si transistor with a SiC. The efficiency of the three-phase Si-IGBT-based system was 86% for the six-switch case. The efficiencies of the SiC-IGBT-based system were increased to around 92% in the three-phase inverter system experimentally. The findings of the experimental results demonstrated that the SiC-IGBT had a faster switching speed and a smaller loss than the classical Si-IGBT. As a result of the experimental studies, the efficiency increase that could be obtained in the case of using SiC-IGBTs in conventional AGPU systems was revealed.

An Overview of Four-Leg Converters: Topologies, Modulations, Control and Applications

In three-phase unbalanced systems, where the circulation of zero sequence current is necessary, four-leg converters provide a neutral connection for single-phase or other unbalanced loads typically utilized in three-phase distribution systems. In addition, control of the magnitude and phase of the zero-sequence voltage and/or current are also achieved using four-leg power converters. However, even when four-leg converters have become very important in several fields as for instance, four-leg microgrids and aerospace applications, a comprehensive review of the converter topologies, control methods, modulation methods and output filters have not been hitherto published. In this paper, a comprehensive overview of the state-of-the-art of four-leg converters is presented, based on the selection of over 400 papers published in journals and conferences, identifying mature and incipient topologies, modulation strategies, control schemes and applications. Each topic presented in this work is thoroughly discussed and reviewed, analyzing characteristics, implementation issues, and reported advantages and disadvantages to provide a comprehensive overview of the current research and future challenges in four-leg converters. The most important applications of four-leg converters are also discussed in this work, including stand-alone power supply, uninterruptible power supplies, grid-connected 4-leg inverters, ground power units for aerospace applications, active filtering for power quality enhancement, cooperative control of 4-leg converters for micro-grid applications, among others. Finally, future work and conclusions are highlighted in this paper.

Model Predictive Control of the Input Current and Output Voltage of a Matrix Converter as a Ground Power Unit for Airplane Servicing

This paper deals with the design, control, and implementation of a three-phase ac–ac mobile utility power supply using a matrix converter for airplane servicing applications. Using a matrix converter as a compact direct ac-to-ac converter can provide savings in terms of the size and cost of a mobile power supply compared to common back-to-back converters. Furthermore, using the proposed direct matrix converter eliminates the need for bulky electrolytic capacitors and increases the system’s reliability and lifetime. A finite control set model predictive control is used to generate a high-quality 115 V/400 Hz output voltage and a low-harmonic-distortion source current with a unity input power factor for various load conditions, including balanced, unbalanced, linear, and nonlinear loads. The predictive strategy is used to control the output voltage and source current for each possible switching state in order to simultaneously track the references. To achieve a further reduction in the system’s size and cost, an active damping strategy is used to compensate for the instability caused by the input filter in contrast to the passive method. Experimental tests were conducted on a prototype matrix converter to validate the performance of the proposed control strategy.

Voltage balance evaluation strategy for DC-port faults in centralized aircraft ground power unit based on three-level neutral point clamped cascaded converter

Voltage balance evaluation strategy for DC-port faults in centralized aircraft ground power unit based on three-level neutral point clamped cascaded converter

Performance analysis of a novel outer rotor flux‐switching permanent magnet machine as motor/generator for vehicular and aircraft applications

Herein, a novel study on outer rotor flux-switching permanent magnet (OR-FSPM) machines for motor/generator applications is presented. An improved magnetic equivalent circuit (MEC) is used for saturable machine model, and the performance analysis is presented in both dynamic and steady-state cases. A flexible MEC-based method is used, where the machines with arbitrary properties can be analysed. Moreover, the model accuracy can be tuned by selective parameters in the proposed method. It is shown that the machine can be used as a high efficiency 400 Hz Ground Power Unit (GPU) for aircraft application. Furthermore, the machine usage for in-wheel application in the hybrid and electric vehicles (HVs and EVs) is analysed. Comparison with 2D and 3D finite-element-method (FEM) shows the effectiveness and accuracy of the proposed MEC method, where shorter processing time is obtained compared with FEM.

Comparative analysis of voltage controllers for a single stage AC-AC converter for Aircraft Ground power unit application

In this paper, analysis and comparison of various voltage controllers for a direct AC-AC converter suitable for Aircraft Ground power Unit (AGPU) system is discussed. Simulation of the proposed converter is executed and behaviour of the system is studied for various load conditions. A source disturbance is created to check the capability of the system to cope with change in input. By using the open loop simulation parameters, a voltage control loop using P, PI and PID controller is designed and simulated. The expediency of the controller is tested by observing the converter’s response to changes in input parameters.

A Novel Analysis on a New DC-Excited Flux-Switching Machine Using Modified MEC Method for Ground Power Unit Application

This article presents a novel analysis on a new DC-Excited Flux-Switching Machine (DC-FSM) for Ground Power Unit (GPU) application. The performance of machine under different structures can be studied by a flexible Magnetic Equivalent Circuit (MEC), where the core non-linearity can be fixed on the material B-H curve. The model accuracy can also be adjusted arbitrary by determining the number of proposed MEC elements (flux tubes) for a given structure. The performance analysis of two sample DC-FSMs as two high-frequency 120 V generators is performed by the proposed MEC and validated by 2D and 3D FEM based simulations. The obtained results show a very good improvement in processing time with valuable accuracy. In general, introducing a new DC-FSM for the GPU application and analyzing its performance by proposing a modified MEC approach are the paper novelties which are studied in this work. Since the suggested MEC is more flexible than FEM, it is recommended for designing, modeling, and optimization purposes.

Data-Driven Method to Study the Impact of Utilizing Electric Ground Power Systems on Airport Electricity Demand Profile

Gate electrification provides electricity and preconditioned air to stationary aircraft at airport gates as an alternative to the use of auxiliary power units. This includes a preconditioned air unit (PCA) and a ground power unit (GPU). This study aims to explore the impact of utilizing these units on the electricity demand of airports and analyzes the associated costs for both the cases of purchasing the electricity from a utility following a typical large commercial rate structure, and participating in the wholesale electricity market. The possibility of benefiting from solar energy to supply this electricity demand is also examined. The demand for gate electrification was measured at a gate at Des Moines International Airport in Iowa, U.S.A., and combined with other data including weather conditions and aircraft types to identify significant explanatory variables for electricity demand. This analysis revealed that ambient temperature is the main PCA demand predictor while aircraft type is the main factor driving the GPU demand. A linear regression model was developed to estimate the PCA electricity demand based on the ambient temperature. For the GPU, the typical demand was used based on aircraft type. This analysis shows that gate electrification used across all gates can contribute to up to 87% of the measured peak demand of the airport; the cost of participating in the wholesale market would be 57% less than following the current large commercial rate structure, and the airport can benefit from installing a photovoltaic system if the surplus electricity is utilized.

Concept of Modular, Self-Supporting Cable for Powering the Hovering Unmanned Aerial Vehicle

Hovering unmanned aerial vehicles, or drones, can function as distant platforms for mounted sensors, as signal transceivers or for other purposes. However, they must be tethered, the tether functioning as a power cable which connects a tethered drone with a ground power unit. In this article we developed a concept in which a power cable is of modular structure, consisting of mutually identical modules. Each module has motorised propellers and is capable of preserving itself in a given, hovering position. We formulate an equation for current that, for a given set of parameters, make possible hovering of a drone with such a modular cable. The developed concept does not show significant improvement in maximal height of a drone thereby obtained. Causes of that are extracted from a set of assumptions defining the concept.

A Design Methodology of Multiresonant Controllers for High Performance 400 Hz Ground Power Units

In aerospace applications, a ground power unit has to provide balanced and sinusoidal $\text{400}\,\text{Hz}$ phase-to-neutral voltages to unbalanced and nonlinear single-phase loads. Compensation of high-order harmonics is complex, as the ratio between the sampling frequency and compensated harmonics can be very small. Thus, multiple superimposed resonant controllers or proportional-integral (PI) nested controllers in multiple $dq$ frames are not good alternatives. The first approach cannot ensure stability, while the second cannot track the sinusoidal zero-sequence components typically present in unbalanced systems, and unattainably high bandwidth at the inner current control loop is typically required. In this paper, a simple methodology for designing a single-loop, multiple resonant controller for simultaneous mitigation of several high-order harmonics, ensuring stability, is presented. Experimental results, based on a 6 kW four-leg neutral point clamped converter, validate the proposed controller design, showing excellent steady-state and transient performance.