Stability analysis of electric power systems for ‘more electric’ aircraft

This paper presents a comprehensive assessment of small-signal stability for a “more-electric” aircraft power system consisting of a synchronous variable-frequency generator which supplies several power electronic controlled loads via an 18-pulse autotransformer rectifier unit (ATRU) for AC-DC conversion. Functional models for key power system components and loads are derived. Numerical tools employed for the automatic calculation of linearized equations and operating points are described, and the influence of leading design and operational parameter on system stability is evaluated

Matrix Converter for More Electric Aircraft

This proposed chapter discusses three methods that do not allow regenerative power from the matrix converter (MC) motor drive onto the aircraft power supply. According to aerospace power quality specifications, the regenerative power must be dissipated in the drive itself to avoid instability problem in aircraft power supply. These are bidirectional switch (BDS) method, input power clamp (IPC) method, and standard clamp circuit (SCC) method for aerospace applications. To identify regeneration in a matrix converter drive, two novel techniques are proposed. These are power comparison technique (PC) and input voltage reference technique (IVR). In both techniques, output power of MC and direction of speed, these factors are used to detect regeneration in MC drive. The electrical braking is important in many aerospace applications such as surface actuation and air-to-air (in-flight) refueling system. Therefore, the inherent regeneration capability of the matrix converter drive is not desirable for aerospace applications so it has to be avoided. The proposed methods are demonstrated through detailed simulation results and experimental verification. In order to prove the proposed methods with novel techniques, a 7.5-kW matrix converter fed 4-kW induction motor (IM) with inertial load has experimentally implemented. The obtained results using BDS method with PC technique proved avoiding regeneration with a matrix converter is feasible. This chapter is valuable for 150-kVA matrix converter for high-power application

Challenges and Opportunities for Wound Field Synchronous Generators in Future More Electric Aircraft

Electrical machines and drives keep moving away from traditional technologies such as brushed machines and wound field machines towards lighter, ‘easier to maintain’ machines. A very interesting aspect is that certain transport applications, especially the aerospace industry, still favour the classical wound field machine for its main generating system such as the Boeing 787. This paper focuses on investigating this particular trend by presenting a detailed overview of historical power generation systems on aircraft. This paper compares the current state of the art of wound field machines with other generator families. The results of this analysis are then projected into the needs of the electrical power generation and distribution system on aircraft. While power density is a major objective for any aerospace application, however the extra benefits associated with wound field systems are still essential in modern aircraft. The paper then focuses on the main challenges for improving power density of wound field machines. Recommendations, opportunities and improvements related to wound field machines are discussed. In conclusion, if robust designs for higher speed wound field generators were consolidated, it would be very probable that these classical machines might still be implemented on future MEA platforms

Prognostic Reasoner based adaptive power management system for a more electric aircraft

This research work presents a novel approach that addresses the concept of an adaptive power management system design and development framed in the Prognostics and Health Monitoring(PHM) perspective of an Electrical power Generation and distribution system(EPGS).PHM algorithms were developed to detect the health status of EPGS components which can accurately predict the failures and also able to calculate the Remaining Useful Life(RUL), and in many cases reconfigure for the identified system and subsystem faults. By introducing these approach on Electrical power Management system controller, we are gaining a few minutes lead time to failures with an accurate prediction horizon on critical systems and subsystems components that may introduce catastrophic secondary damages including loss of aircraft. The warning time on critical components and related system reconfiguration must permits safe return to landing as the minimum criteria and would enhance safety. A distributed architecture has been developed for the dynamic power management for electrical distribution system by which all the electrically supplied loads can be effectively controlled.A hybrid mathematical model based on the Direct-Quadrature (d-q) axis transformation of the generator have been formulated for studying various structural and parametric faults. The different failure modes were generated by injecting faults into the electrical power system using a fault injection mechanism. The data captured during these studies have been recorded to form a “Failure Database” for electrical system. A hardware in loop experimental study were carried out to validate the power management algorithm with FPGA-DSP controller. In order to meet the reliability requirements a Tri-redundant electrical power management system based on DSP and FPGA has been develope

Analysis of motors for more electric aircraft

In questo lavoro di tesi si cercherà di analizzare il funzionamento di due possibili motori elettrici per svincolare il più possibile l'aereo dai combustibili fossili, in modo da renderlo meno impattante sull'ambiente. In particolare, l'analisi di questi motori parte dagli articoli citati nella bibliografia di A. Cavagnino e S. Shoujun e collaboratori

Maturing DC protection methods for the more-electric aircraft

With the increasing electrification of modern aircraft designs, there is a growing dependence on the aircraft’s electrical power system for safe flight. Novel enabling technologies such as new converter topologies, DC power distribution and composite airframes however present challenging fault modes, which in turn require the application of new protection schemes and circuit breaking technologies. Hardware testing of such schemes is a critical stage of their maturation. This requires the use of dedicated protection rigs which capture key network elements influencing the system fault response and which can safely withstand full fault effects without risk of equipment damage. This paper presents such a protection rig being developed at the University of Strathclyde, designed to enable the evaluation and maturation of protection concepts and development of algorithms for compact DC aerospace power systems

Generator Power Optimisation for a More-Electric Aircraft by Use of a Virtual Iron Bird

A prodedure is developed to minimise the generator design power within the electric power system of a future more-/ all-electric aircraft. This allows to save weight on the generators and on other equipment of the electic power system. Execution of the optimisation procedure by hand demonstrates the complexity of the problem. An automation of the process shows the capabilities of integrated modelling, simulation and optimisation tools

12-Pulse Active Rectifier for More Electric Aircraft Applications

The Aircraft industry is moving very quickly towards what it known as More Electric Aircraft (MEA). In a modern aircraft power technology system instead of using a fixed 400 Hz supply, a variable frequency supply (360 to 800 Hz) is used, which is dependent on the aircraft speed. In MEA electrical energy feeds the aircraft subsystems such as the flight control actuation, environmental control system, and utility function instead of mechanical, hydraulic and pneumatic energy. Although the new technology of MEA goes towards variable frequency supply, one of the essential parts of the power distribution systems require DC power sources to feed different DC loads, and a portion of load may require a fixed 400 Hz supply. This chapter simulation model of 12-pulse active rectifier for More Electric Aircraft applications

A smart transformer-rectifier unit for the more electric aircraft

In the framework of the More Electric Aircraft (MEA), an efficient and flexible power distribution system is of paramount importance. Considering the presence of both AC and DC loads at multiple voltage levels, the distribution system of the most modern aircrafts is intrinsically hybrid. In this scenario, the different buses are connected by AC/DC converters. The simplest approach is to use a Transformer-Rectifier Unit (TRU) based on a low-frequency transformer followed by passive rectifiers to perform the AC/DC conversion. This solution, however, is intrinsically uni-directional, introduces current harmonics in the AC side and can have a considerable size. This paper proposes the use of a Smart-TRU, based on a Cascaded H-Bridge topology and a multi-port DC/DC converter, to solve the issues of the traditional TRU, increasing the controllability of the system. Experiments show how the proposed STRU is resilient to faults in the AC side