On-board Power System Research Articles

Design Methodology and Parametric Design Study of the On-Board Electrical Power System for Hybrid Electric Aircraft Propulsion

This paper presents parametric design studies of the on-board Electrical Power System (EPS) for a distributed hybrid aircraft propulsion. The work presents the methodology that has been adopted to develop the physics-based models of the EPS components that comprise the electrical machines, power electronic converters, batteries, solid state circuit breakers and power cables. The EPS model is a sizing tool that can be used to evaluate the mass and dimensions of its main components. In addition, it determines the thermal performance of the EPS over six key flight stages of the aircraft mission. The EPS model has been created within a wider multidisciplinary design platform with the aim of sizing the overall aircraft configuration including the aircraft thermal system, the gas turbines and the electrically propelled fans together with the aircraft structure. This paper focusses on the EPS and presents the assessments of three key parameters which are the battery specific energy density, the electric propulsion power and the power split ratio between the generator and the battery. The assessment results demonstrate the significant impact the aforementioned parameters can have on the weight of the battery, the electrical power system and hence the aircraft fuel burn. The work developed within the Clean Sky 2 TRADE project is vital as it develops and applies important physics-based multidisciplinary tools that are required to identify optimum solutions amidst the large number of available conceptual hybrid aircraft architectures.

Design of Cost-Effective Compensators to Enhance Voltage Stability and Harmonics Contamination of High-Power More Electric Marine Vessels

In recent years, due to the large spread of power electronics converters onboard shipboard power systems (SPSs), harmonic contamination became an inherent problem. Moreover, as the SPSs are mostly operating in an islanded mode with a limited rating of the generators that feed heavy variable loads, voltage stability issues became a challenge as well. To address these issues, implementing PWM-based FACTS devices using IGBTs such as the active power filters may not be very practical for high-power SPSs due to their limited rated powers, high implementation cost, and high losses. The passive power filters (PPFs) and fixed capacitor-thyristor controlled reactors (FC-TCR) can be effective alternatives due to their capability to operate in high-power applications, smaller losses and, lower cost. The aim of this article is to provide more in-depth analytical investigations to evaluate and compare the behavior of the PPFs and the FC-TCR compensator in reducing the harmonics and enhancing the voltage stability concurrently of high-power SPSs. In addition, details of the voltage stability concept are addressed to visualize the potential risk of the voltage collapse. Besides, the modeling of the FC-TCR and design of the closed-loop control algorithm to ensure voltage stability is conducted. Via intensive simulation studies of a practical ship, which are carried out in MATLAB/Simulink environment, it has been demonstrated that the FC-TCR based on the proposed design can enhance the power quality and voltage stability of SPSs better than traditional PPFs filters.

Perspectives and Development of Electrical Systems in More Electric Aircraft

On-board electrical systems are the key components of each modern aircraft. They enable its safer, more comfortable, and environmentally friendlier operation. The strict regulations to reduce pollution and noise are produced by aircraft eventuated in projects like Clean Sky or ICAO Global Coalition for Sustainable Aviation. One solution to environmentally friendlier operation is the full electric propulsion of the aircraft, which enables the reduction of both noise and pollution. Such a concept requires a total change of all on-board power systems and enables the profound change in aircraft design. This paper presents the evolution of aircraft power systems into the so-called more electric aircraft (MEA) and discusses the state-of-the-art electrical systems. Furthermore, the concept of all-electric aircraft (AEA) is presented here.

A Novel Parallel Configured 48-Pulse Auto-Transformer Rectifier for Aviation Application

To satisfy the ever-growing stringent requirement on the power quality of on-board electric power system, a novel parallel configured 48-pulse rectifier, which is formed by two 24-pulse rectifiers connected in parallel through a tapped and coupled interphase reactors respectively, is proposed. Through the comprehensive harmonic analysis on the proposed rectifier, it is revealed that the 23rd and 25th harmonics generated by the two 24-pulse rectifiers are equal in magnitude while opposite in direction, which evidently enables the 48-pulse operation. To better understand the performances of the proposed rectifier, its input current, output voltage, kVA rating, and power losses of magnetic devices are analyzed in detail. Afterward, the validity of the theoretical analysis is verified by simulation and experiment. The results confirm that the proposed 48-pulse rectifier has superior harmonic reduction ability, high reliability, and high power density. More importantly, due to the parallel structure, it also features high fault-tolerant ability, which makes it very suitable for aviation or aerospace applications.

Influence of different Ni coatings on the long-term behavior of ultrasonic welded EN AW 1370 cable/EN CW 004A arrestor dissimilar joints

The increasing demand for energy-efficient vehicles requires suitable methods for cost and weight reduction. This can be achieved by the replacement of copper by aluminum, in particular for the on-board power systems. However, the complete substitution is restricted by the mechanical and physical material properties of aluminum as well as challenges in the aluminum copper interface. The challenges concern the corrosion vulnerability and the occurrence of brittle intermetallic compounds (IMC) which can negatively influence the mechanical properties and the electrical conductivity. Therefore, current investigations focus on the one hand on the realization of dissimilar aluminum copper joints by suitable joining technologies, like ultrasonic welding, and on the other hand on the assurance of a sufficient prevention against harmful corrosion effects. In cases where the joint cannot be protected against corrosion by sealing, nickel coatings can be used to protect the joint. In the present study, the influence of electroless, electroplated, and sulfamate nickel coatings was investigated regarding the long-term stability. The joints were performed as industry-related arrester connections, consisting of EN AW 1370 cables and EN CW 004A terminals. The samples were exposed to corrosive as well as electrical, thermal, and mechanical stress tests according to current standards and regulations.

Modeling and Predictive Control of Shipboard Hybrid DC Power Systems

Although onboard dc power systems bring values for the power and propulsion system of the future hybrid ships, the main barrier for the development of such systems for large-scale vessels is the technical operational issues, such as stability and power quality and how to satisfy the related standards and regulations. In the advanced ship power systems, the conventional diode rectifiers are being replaced with active front-end (AFE) rectifiers providing the control flexibility but at a higher cost. However, to make such devices more profitable, the ship control system can be reconfigured to unlock the potentials of AFEs for the general system stability. This article is dealing with the stability issue of hybrid dc power systems proposing a predictive control approach to improve the voltage regulation and better use of converters. The proposed method replaces the conventional direct power control (DPC) of AFE rectifiers with a model predictive control (MPC) and integrates the dc-dc converters in the same control platform. In this method, optimal control commands for the rectifiers and the dc-dc converter are calculated by the predictive control to minimize the dc bus voltage fluctuations, especially under the fast load changes. The controller is then extended to regulate the load sharing between the different energy units. The effectiveness of the proposed method is evaluated in simulation with a typical shipload profile, as well as a real ship profile, which has several operating modes, such as steep load increase & decrease, high speed, and maneuvering operation. The performance of the proposed control strategy is compared with conventional controllers, and the results show that the new method can provide significant advantages in terms of fast and stable control performance, as well as the steady-state voltage regulation and enhancing the power smoothing function of the battery. Laboratory experimental data are also used for validation.

Fast Solar System transportation with electric propulsion powered by directed energy

Exploration of the Solar System is constrained by interplanetary transfer technology. Current propulsion architectures do not allow for trajectories much faster than Hohmann transfers, implying elevated health risks and mission costs associated with multi-year human spaceflight missions and even longer robotic mission times. Proposed advanced nuclear and exotic systems involve immature component technologies and high degrees of complexity, cost, and risk. Breakthrough improvements may be possible with electric propulsion powered by directed energy, where a large-aperture laser phased array directs energy to photovoltaics on electric propulsion vehicles. Narrowband intensity gain over sunlight would lower onboard power system specific mass (kg/kW) to enable fast Solar System missions without advanced nuclear or exotic power and propulsion systems. The proposed architecture is modular and offers scalability from nanosatellites to human missions, with opportunities for operational systems and Solar System exploration along a technology development roadmap.

Power Flow Approach for Modeling Shipboard Power System in Presence of Energy Storage and Energy Management Systems

Recent improvements in shipboard systems focus on the use of new technological systems and the adoption of innovative operating strategies for both increasing energy efficiency and reduce gas emissions. In such a context, this article studies a ship power system, where an energy storage system and a tailored energy management system are applied. It focuses on a detailed model of the on-board power system and points out a scenario of analysis larger than those usually adopted in the literature. The model is carried out with reference to DC, AC and hybrid AC/DC power grid architectures, by means of a power flow approach. The strategy of the energy management system optimally controls the on-board power system integrated with a battery storage device. The strategy aims to minimizes fuel consumption of the prime movers, while satisfying time-varying load demand under different operating scenarios. The procedure, tested on actual operative conditions of a supply vessel, shows feasibility and effectiveness of the power flow approach, giving evidence to the reduction of fuel consumption, while the correct operation of the power system is guaranteed.

A 20-Pulse Autotransformer Rectifier Unit for More Electric Aircrafts

In more electric aircraft (MEA), the power rating and the number of electric loads have considerably been increased. Most of these new loads are power electronics interfacing loads and motor drive systems. As a result, the onboard power system may encounter with power quality problems. To limit the harmonics generated by these loads, multipulse rectifiers with the capability of power factor correction and low total harmonic distortion (THD) are required. An increase in the number of pulses in the multipulse autotransformer rectifier unit (MPATRU) will lead to an increase in the kVA rating, cost, and complexity of the rectifier. Due to the weightlessness and simplicity of the MPATRU, an autotransformer rectifier unit (ATRU) is quite popular and widely employed in the industry. In this article, a novel 20-pulse ATRU based on T-connected autotransformer is introduced, discussed, simulated, and implemented with an acceptable power rating for MEA applications. The T-connected autotransformer makes use of only two main windings, resulting in saving of space, size, volume, weight, and cost. Its simulation results confirm that the proposed novel rectifier has several advantages: it can operate at near-unity power factor and the THD of the input current is less than 8% within IEEE-519 Standard limits for SCR >20. Compared with the other MPATRUs, the kVA rating of the proposed 20-pulse ATRU is 44.48% of the load power.

A Hybrid Ensemble Model for Interval Prediction of Solar Power Output in Ship Onboard Power Systems

Application of solar energy into ship power systems has been increasingly drawing attention. Accordingly, an accurate prediction of solar power plays a significant role in the shipboard power system operation. However, a photovoltaic (PV) generation system on the shipboard, different from the one on land, has to suffer more dramatic power fluctuations caused by weather variations and motions of the ships, which increase the uncertainty of PV power outputs. This paper proposes a hybrid ensemble method for optimal interval prediction of onboard solar power based on a stochastic ship motion model. A set of machine learning techniques are combined together with the particle swarm optimization (PSO) to constitute a hybrid forecasting model, including a back propagation neural network (BPNN), a radial basis function neural network (RBFNN), an extreme learning machine (ELM) and an Elman neural network. Furthermore, for different learning algorithms, an ensemble strategy is employed to reduce the forecasting error and various environmental variables along with ship moving and rolling impacts are taken into account. The developed model has been practically tested on a power system on a large oil tanker penetrated with PV energy and the data along the typical navigation route from Dalian in China to Aden in Yemen are selected for solar power prediction. The simulation results demonstrate its high accuracy, which provides a reliable reference for ship power system operators to achieve a better energy management.

Application of spinning electrodynamic tether system in changing system orbital parameters

Spinning electrodynamic tether system is known to be promising in many applications, including space debris removal, transportation missions, changing orbital parameters of spacecrafts and so on. Feasibility of spinning electrodynamic tether system for changing system orbital parameters is analysed in this paper. The main advantage of spinning electrodynamic tether system is the stability of its movement under the action of perturbations. However, when the conductive tether spins in a magnetic field, the Lorentz force constantly changes its direction, which leads to the need to develop special control methods that ensure desired change in system orbital parameters. In this paper, control laws are proposed for changing the semi-major axis and the eccentricity of the orbit, which take the change of tether spatial position into account. To change the semi-major axis, the current is regulated by the cosine law. To change the eccentricity of the orbit, the onboard power system provides a given amount of current when the system is near the apogee and perigee of the orbit. The combination of executing both manoeuvres at the same time is also studied. The numerical results show that the proposed laws enable spinning electrodynamic tether system to change the parameters of the orbit to the desired values.

All-Electric Ship-Integrated Power Systems: Dependable Design Based on Fault Tree Analysis and Dynamic Modeling

The all-electric ship concept is becoming a standard for ships with large power requirements. At present, the design of the onboard power system [i.e., the integrated power system (IPS)] is done through a well-proven process. This process relies on historical data and trial-and-error procedures developed in nearly 30 years of design experience to address the ship’s complexity. Nowadays, the evolution in IPSs is pushed forward by the introduction of more demanding requirements, which can be complied with only by using new power system architectures and introducing onboard innovative subsystems. However, introducing innovation by means of a design process defined on the basis of past experience is inefficient. Thus, new design paradigms are needed. In this regard, concepts and tools from other technical areas can be used to achieve a “dependable design process” able to ease the introduction of innovation in ships’ IPSs. In this paper, after a brief presentation of the conventional process and the actual drivers pushing toward its revolution, the dependable design process is proposed. The latter integrates both dependability enforcing techniques and dynamic power system modeling. Insights about the process integration in the overall ship design process are given, while an application example is used to show the effectiveness of the proposed approach.

Systematic Reliability Modeling and Evaluation for On-Board Power Systems of More Electric Aircrafts

Modern aircrafts are evolving toward more electric aircraft (MEA), resulting in greater reliance on the electrical system for safe flight. On-board power system of MEA integrates a large number of power electronic converters, and it is reported that semiconductor devices and electrolytic capacitors in power converters are the most vulnerable links impacted by loading conditions; thus, reliability becomes a critical concern in an MEA power system. This paper proposes a hierarchical approach for systematic reliability modeling and evaluation for the on-board power system of MEAs. It consists of three hierarchical levels (HLs): component level (HL1), subsystem level (HL2), and system level (HL3). In HL1, failure rates of power electronic components are modeled considering relevant inner structure and loading conditions; in HL2, the reliability of individual subsystems such as converters are constructed; in HL3, the system reliability is quantified based on the network architecture and reliability of the subsystems. The impacts of different parts (components/subsystems) on the overall system are assessed effectively with the identification of the vulnerable parts. This also provides a guideline for reliability enhancement by using thermal control techniques, adding redundancies or performing maintenance on the vulnerable parts to ensure the satisfactory of system reliability requirements. The proposed method is demonstrated on the future MEA power system architectures (hybrid ac-dc architecture and HVdc architecture).

Changes of On-board Power Systems of Modern Aircraft in the Context of Wider Electrification

This article analyzes the changes of on-board electrical power systems of modern transport aircraft with a higher degree of electrification, so-called MEA (More Electric Aircraft) compared to the traditional architectures, in the field of standardized electrical power parameters. Developments in this field are characterized by increased requirements for power of installed power sources and switching to higher voltage values and source units with a non-stabilized frequency value of the generated voltage, so-called frequency wild systems.

Design and Analysis of New Harbour Grid Models to Facilitate Multiple Scenarios of Battery Charging and Onshore Supply for Modern Vessels

The main objective of this study is to develop and analyse different harbour grid configurations that can facilitate the charging of batteries for modern vessels and supply onshore power. The use of battery energy storage systems in modern hybrid or entirely electric vessels is rapidly increasing globally in order to reduce emissions, save fuel and increase energy efficiency of ships. To fully utilise their benefits, certain technical issues need to be addressed. One of the most important aspects is to explore alternative ways of charging batteries with high power capacities for modern vessels. The paper presents a comprehensive overview of battery-charging configurations and discusses the technical challenges of each design from the perspective of their practical implementation, both onshore and onboard a vessel. It is found that the proposed models are suitable for vessels operating either entirely on battery storage or having it integrated into the onboard power system. Moreover, the proposed charging models in a harbour area can solve the problem of charging batteries for future hybrid and electric vessels and can open new business opportunities for ship owners and port administrators. The performance of the proposed models is validated by simulating two case studies in PSCAD: slow charging (based onshore) and fast charging (based onboard).

Liquid interlayer formation during torsional ultrasonic welding of EN CW004A and EN AW1050

Due to the constantly increasing industrial requirements, such as cost reduction and energy efficiency, new challenges for manufacturing and joining technology are demanded. In the automotive industry, the onboard power system offers a good potential to save weight and costs of a vehicle. In this case, copper is increasingly substituted by aluminum to reach an improved energy efficiency by weight reduction and simultaneous cost reduction. In many industrial applications, a complete substitution of copper by aluminum is not possible; hence, mixed compounds have to be created. In this investigation, the joining of EN CW 004A and EN AW 1050 via a torsional ultrasonic welding process was observed. The influence of the amplitude on the bond formation and on the mechanical properties of the joint was analyzed. It was shown that a higher energy input was reached due to higher amplitudes. The metallographic evaluation revealed intermetallic phases and eutectic phases in the interface. The resulting eutectic phases consisted mainly of globular, disordered structures. As part of the mechanical investigation, the failure behavior and the failure load were analyzed via tensile shear test. Different failure characteristics depending on the plunging depth of the sonotrode and the welding temperature could be worked out.

A Novel Methodology for Macroscale, Thermal Characterization of Carbon Fiber-Reinforced Polymer for Integrated Aircraft Electrical Power Systems

Carbon fiber-reinforced polymer (CFRP) is increasingly used for aero-structure applications due to their high strength-to-weight ratio. The integration of the on-board electrical power system (EPS) with CFRP is challenging due to the requirement to thermally and electrically isolate these systems to meet existing safety standards. By capturing the thermal characteristics of CFRP at a macro (component) scale for CFRP components, it is possible to understand, and design for, the increased integration of the EPS into CFRP aero-components. A significant challenge is to develop a macroscale characterization of CFRP, which is not only of an appropriate fidelity for compatibility with systems-level models of an EPS but also can be used to represent different geometries of CFRP components. This paper presents a novel methodology for capturing a transient, macroscale thermal characterization of CFRP with regard to component layup and geometry (thickness). The methodology uses experimentally derived thermal responses of specific resin and ply orientation CFRP samples to create a generalized relationship for the prediction of thermal transfer in other sample thicknesses of the same material type. This methodology can be used to characterize thermal gradients across CFRP components in aircraft EPS integration applications, ultimately informing the optimized integration of the EPS with CFRP.

Constraint Equations of Physical and Geometrical Parameters of an Arbitrary Branched Hydraulic System of the General Form

The development trends of aviation technology impose stringent requirements for the quality of aircraft design in general and its onboard power systems in particular. The article considers an arbitrary branched hydraulic system of the aircraft. With known output characteristics of the hydraulic system, i.e. the function that it must perform, the internal parameters of the system that provide efficient flow distribution required for the calculated operation of the mechanisms are determined. The problem of obtaining a system of equations of the general form linking the physical parameters of the hydraulic system, such as supply power, pressure in consumers and flow rate in all functional subsystems, with the geometric parameters of the pipelines and consumers of the system is solved by an analytical method. The equations in the resulting system are considered in the space of physical parameters. As the geometric parameters of the elements are not specified in an explicit form, it allows the authors to obtain the only unique solution for an arbitrary number of pipelines and consumers, excluding an iterative process. Besides, the final equations clearly determine the most effective mode of operation of the power supply.

C-Balls: A Modular Soft Robot Connected and Driven via Magnet Forced

This paper describes a cellular robot(C-Balls) consisting of soft spherical modules with on-board actuation, power, computation and wireless control system. The robot modules maintain connection and realize relative movement by utilizing magnetic force and friction force between driving units inside the soft modules. Preliminary tests of locomotion and deformation of the robot are proposed. The rolling experiment displays the mobility of the robot of two spherical modules. The deforming experiments indicate that the robot with five spherical modules deforms from linear to circular configuration successfully. Further more, a climbing experiment is conducted, which shows the robot can climb on various surfaces including soft materials.

Coupled magneto-mechanical modeling of non-linear ferromagnetic diaphragm systems

Magnetic polymer composites (MPC) are shape-changing materials capable of wireless actuation. There is growing interest in MPC for biomedical and robotic applications because it removes the need for on-board power systems and electronics. Finite element (FE) methods provide a powerful platform to design and simulate MPC-driven devices. However, the accuracy of previously reported FE MPC models using magnetic body force methods is unknown given the lack of experimental validation.In this paper, a new finite element model for an MPC diaphragm actuator is proposed and experimentally validated. Here, the geometrical and electrical properties of the electromagnet were explicitly modeled. A comparative study was conducted to validate three well known magneto-mechanical coupling approaches; Maxwell stress tensor and the Kelvin magnetization force, with and without the surface force contribution. In addition, a new method for estimating the nonlinear soft-magnetic properties of MPC was also presented.Experimental validation revealed the Kelvin magnetization force with surface force contribution resulted in greater simulation accuracy. Using this method, diaphragm deflection was simulated with an RMS error of less than 0.2 mm and a mean absolute error (relative to maximum displacement) well below 10%, showing good agreement across all recorded trials.The versatility of the proposed model supports many use cases, ranging from lab-on-a-chip to implantable drug delivery. The generalizable nature of this work also provides the potential for translation to other deformation modes and MPC actuator configurations.