MEA Power System
Development Facility
More Electric Aircraft Power System
Development Facility
Introduction
Over the past decade, the aircraft industry has converged on a shared vision for the future of aircraft
power systems. This vision represents a dramatic shift away from various types of power found in
traditional aircraft and offers a wide range of benefits for tomorrow’s commercial and military aircraft.
The non-propulsive power systems in traditional aircraft are typically driven by a combination of
different secondary power types including: hydraulic, pneumatic, electrical and mechanical power [1-6].
All power is extracted from the aircraft engines. Hydraulic power is provided using hydraulic pumps
driven by mechanical rotation sourced from the engine gearbox and is distributed to power various
aircraft systems including flight control actuators, aircraft braking, landing gear extension/retraction,
and door closure. Pneumatic power is extracted from the engine, using software controlled bleed
valves, and is used to power the aircraft Environmental Control System (ECS) and wing anti-icing.
Mechanical power from the engine gearbox also drives lubrication and fuel pumps. While electrical
power contributes to the capability of nearly every aircraft system in modern aircraft that make
increasing use of airborne software controlled electronic systems.
The market demand for more energy efficient aircraft is driven by many stakeholders including airline
operators, legislators, and public opinion. In the meantime, power electronics technology has made
tremendous breakthroughs over the past decade in areas including electromechanical actuators (EMA),
electro-hydrostatic actuators (EHA), fault-tolerant electric motor/generators, and power converters.
This forward-leap of technology creates a viable path, fueled by economic gain, for replacing many and
potentially all of the hydraulic, pneumatic, a mechanically powered non-propulsive systems with
electrically powered systems [1-25] to design a More Electric Aircraft (MEA).
The Challenge
Industry has recently achieved general agreement on key elements of the MEA. For example, industry is
now focusing on technology based on a high-voltage DC power distribution architectures with 270VDC
distribution emerging as the most popular approach. However, optimizing aircraft power systems
technology to support a 270VDC distribution system, including generation, distribution topology, power
conversion, and the design of specific MEA systems, is a complex effort. There is a high-level of
dependency and interaction between the various systems in a given MEA design with complex and fast
dynamics. There is a wide range of technology that must be refined and optimized within the context of
a single aircraft design in order to achieve the cost reduction goals for the MEA. These challenges give
rise to a capability requirement; a requirement for a flexible MEA development platform that can
accelerate the pace of development of MEA technology.
The Solution
The proposed solution relies on Model Based Systems Engineering (MBSE) methodologies and
technology that have evolved rapidly over the past two decades and draws on MBSE technology in the
area of power systems and power electronics. This whitepaper proposes a Power-Hardware-in-the-Loop
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development and test facility that enables MEA technology to be combined with simulated flight and
simulated power system behavior: The MEA Power System Development Facility. The MEA Power
System Development Facility enables technology concepts and prototypes to be tested as pure
simulation in closed-loop with real aircraft power systems, operating with representative electrical
behavior, and evaluated through normal and failure mode flight conditions. The MEA Power System
Development facility is based on Applied Dynamics technology development and contribution to the
current state-of-the-art in the aircraft industry’s drive towards the MEA vision.
More Electric Aircraft Power Systems Development Facility
The More Electric Aircraft Power Systems (MEAPS) Development Facility is a high-performance, realtime, power-hardware-in-the-loop developing and testing capability that: allows high-fidelity aircraft
simulation to be combined with real and/or simulated aircraft power system devices; enables the
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configuration of the MEA power network to be changed and evaluated; allows real and emulated
generators to be connected to the MEA power network; provides high-fidelity active load emulation to
evaluate the effects and performance of electromechanical and electrohydrostatic actuators; and
includes high-speed data acquisition throughout the facility for the characterization of each element of
the system. Components of the MEAPS Development Facility include:
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Active load emulation system
Active load Hyperfast real-time simulator
Generator emulation system
Distributed real-time simulator platform
MEA power network
Flight and aircraft system simulation models
Simulation framework software platform
Active Load Emulation System
The active load emulation system is a power hardware system that provides bidirectional energy
transfer for DC sources or loads. The active load system generates a dynamic DC load and feed the
resulting power back into the facilities 3-phase AC. The DC voltage is controlled by a setpoint input for
each output channel. The figure below shows a schematic of a 3-channel active load emulation system.
The active load emulation system is used in the MEAPS Development Facility to draw DC current off the
HVDC MEA power network with behavior controlled by simulation of dynamics loads. For example, the
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active load Hyperfast real-time simulator is used to run high-fidelity electromechanical or
electrohydrostatic simulation models, the value of this current draw is sent from the Hyperfast real-time
simulator to the active load system which behaves accordingly. The figure below shows the dynamics
DC current behavior generated by the active load emulation system when a flight control position step
change command is sent to an electromechanical flight control actuator simulation and drive the active
load system.
Active Load Hyperfast Real-Time Simulator
The active load Hyperfast real-time simulator is a real-time simulation computer system dedicated to
providing control of the active load emulation system. This real-time system is a multi-core,
deterministic simulator capable of running simulation with sub-10us step time. Simulation models (ex:
Simulink, C code, etc.) are locked to a processor core with direct access to analog and/or digital interface
channels. This real-time simulator uses the ADvantage Framework software for system configuration,
operation, and data acquisition. The active load real-time simulator interfaces with the other real-time
simulation computers in the MEAPS Development Facility using the ADvNET distributed real-time
simulation toolbox.
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The figure above illustrates an electromechanical actuator simulation that is executed on the active load
Hyperfast real-time simulator. The position controller, speed controller, current controller, motor, and
gearbox/ballscrew are modelled. The figure below shows this nested closed-loop control simulation
implemented in Simulink. The value of DC current, Iload, becomes the setpoint to the active load
emulation system.
The MEAPS Development Facility allows multiple EMA and EHA actuators to be simulated and allows
their electrical behavior and interaction with the MEA power network to be replicated in real-time. This
allow all the actuators for a single aircraft to be simulated and electrically emulated.
The position and load command sent to the active load Hyperfast real-time simulator is generated by
the real-time flight simulation (ex: 6DOF, aerodynamics, flight control system, etc.) executed in the
distributed real-time simulation platform. This enables the MEA power network, and all real power
systems included in a test to interact with power system dynamics that are highly representative of any
desired flight conditions.
Generator Emulation System
The generator emulation system is a power module that provides bidirectional transfer of energy
between AC source and DC loads. In the case of the MEAPS Development Facility, the MEA power
network acts as the DC load and the generator emulation system acts as a DC voltage generator with
programmable, dynamics voltage setpoint and programmable current limit. The generator emulation
system provides behavior that matches a real engine driven generator with AC-DC converter behavior by
executing real-time simulation models of the gas turbine engine, the generator, the converter, and the
generator/converter control unit. These simulation models are executed on the distributed real-time
simulator platform send voltage setpoints to the generator emulation system, and receive voltage and
current measurement feedback from the generator link to the aircraft power network. This real-time
simulation results in converter output voltage and current characteristics that are sent to the generator
emulation system and performed. The figure below shows a schematic of the generator emulation
power module.
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Distributed real-time simulator platform
The real-time simulator platform provides the ability to execute high fidelity flight simulation, simulation
of aircraft systems, and simulation of power system dynamics with real aircraft systems in-the-loop.
This enables the MEAPS Development Facility to incorporate real electrical loads, connected to the MEA
power network, stimulated to behave as they do during flight. The MEAPS Development Facility uses a
distributed real-time simulation system with multiple simulator nodes, each with multicore processors.
The figure above illustrates the distributed real-time simulator platform. The multiple simulator nodes
communicate with one another across a high-speed distributed communication interface. The
ADvantage Framework software platform allows these systems to be configured and operated as though
they were a single simulation system. A distributed, IRIG-B common clock triggers the time scheduling
of each system and maintain synchronized execution of simulation and I/O scheduling.
Signal interfaces included in the distributed real-time simulator platform put each aircraft system undertest into closed-loop operation with simulation models and/or other aircraft systems providing realistic
and accurate behavior. The real-time simulator platform interface signals can be divided into four main
types. The table below lists these interface signal types.
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Signal Type
Example
Sensor Emulation
Thermocouple, Resistive Temperature Device, Linear Variable Displacement
Transducer (LVDT), Digital Encoder, etc.
Torque Motor, Solenoid, Igniter, etc.
ARINC-664, ARINC-429, CAN, RS232/422/485, MIL-STD-1553, IEEE1394, etc.
Analog, Digital
Actuator Measurement
Serial and Databus
Data Acquisition Channels
MEA power network
The MEA power network is a ‘ring main’ type distribution system offering flexibility for isolating loads,
for re-routing power during faults at various locations throughout the network, and providing the ability
to share power between generating sources. Protective functionality is provided with switchgear that
also provides the ability to insert electrical faults. Fault management, ring configuration and re-routing,
and load management are controlled using a real-time controller.
Load Emulation
Three types of load emulation may be included in the MEAPS Development Facility to represent
different aircraft system load characteristics. These include:
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Resistive loads – This provides a constant load on the DC network in order to replicate
“background” loads found in the aircraft such as avionics systems. A variable resistive load
allows the load level to be increased in steps up to 50kW.
Continuous switching power electronic load – This represents a power electronics interface to
drive a number of continuously running loads, such as the aircraft environmental control
system, electric fuel pump, and radar communications system. This type of load emulation is
provided by the active load emulation system described earlier in this paper.
Dynamics switching power electronic load – This represents the “pulse” loads associated with
electromechanically actuated flight controls. This type of load emulation is provided by the
active load emulation system described earlier in this paper.
Flight and Aircraft System Simulation Models
Applied Dynamics offers the iAircraft Simulink aircraft model library providing real-time simulation of
flight and aircraft systems. iAircraft is a comprehensive set of aircraft simulation capability used in the
aircraft industry for a wide range of applications. The iAircraft library is an open architecture set of
models enabling users to parameterize, reconfigure, and replace Simulink subsystems as needed. The
iAircraft library includes the following:
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High fidelity 6-degree-of-freedom flight dynamics model with rotating spherical earth &
configurable aerodynamics
Configurable landing gear with nose wheel steering as a function of rudder pedal and tiller
travel, high-fidelity tire model, and dynamics gear suspension
Comprehensive autopilot modules including intercept & track, heading hold, bank angle hold,
and more
Aircraft ‘trim’ module for initializing flight at a selected stable flight condition
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Scriptable ILS landing capability
High fidelity gas turbine engine model for testing application that include an EEC or low fidelity
model engine pressure ration based model for simpler development and testing applications
High fidelity Environmental Control System (ECS) blockset
Out-The-Window (OTW) visuals interface
The figure below shows the iAircraft library within the Simulink browser.
The iAircraft flight controls library components can be used to simulation hydraulic, electromechanical,
or electrohydrostatic flight control actuators and can be put in closed-loop with the dynamics load
system.
The iAircraft landing gear library components include high-fidelity runway interaction with high-fidelity
lateral and longitudinal tire model for steering and antiskid braking. The landing gear model provides
the fidelity and detail required to drive the dynamic load system with antiskid braking power behavior.
The figure below shows an example iAircraft braking and steering configuration.
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Power System Simulation
Aircraft power system simulation models are required to provide accurate dynamics behavior of all
emulated power system components. These power system models include:
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Generator and generator control unit models – switch level model including exciter, rotating
rectifier, and diode bridge/inverter output stage
Electrical distribution unit model – feeder electrical dynamics between the generator inverter
converter controller (ICC), the actuator loads, and generic loads
DC-DC converter models – RMS current models and average current models for boost and buck
mode converter operation
EMA and EHA actuator models – segment level actuator models including input EMI filters,
active switching, and rotating machine
All aircraft power system simulation models are developed in Simulink using the SimPowerSystems
toolbox. The accuracy and detail of component blocks within SimPowerSystems are ideally suited for
modeling complex electrical behavior. However, the real-time performance of these models can be
problematic in terms of the computational efficiency of the generated code and the ability to execute
these models at a frequency sufficient to represent fast dynamics. Applied Dynamics has been
successful in solving this problem by systematically replacing some of the inefficient generated code
with highly optimized code[40]. The figure below shows a Simulink SimPowerSystems model of the MAE
electrical distribution unit.
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Simulation framework software platform
Software to rapidly configure and operate the MEAPS Development Facility is provided using the
ADvantage Framework MBSE software platform. ADvantage provides real-time simulation and analysis
capability for advanced aircraft development projects throughout the world and at leading aerospace
and defense companies including: Boeing, Gulfstream, Rolls-Royce, Crane Aerospace, Parker Aerospace,
COMAC, BAE Systems, Mitsubishi Heavy Industries, and General Dynamics.
ADvantage includes desktop tools and run-time services software. Tools include:
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ADvantageDE – Development environment used to configure the MEAPS facility, add Simulink
models, connect real and simulated equipment, compile and package projects
ADvantageVI – Operator environment used to control the facility through interactive or
automated tests
SIMplotter – Data acquisition, plotting and analysis of distributed real-time streaming data
ADvantageDB – Configuration of analysis of serial and databus networks
ADvantageFC – Electrical fault insertion macro definition and control
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The ADvantage run-time services software provides the high-performance software capabilities within
each real-time simulator in the MEAPS facility including: logical device engine, serial communications
handler, assembly containers probe engine, data acquisition engine, real-time scripting engine,
supervisory schedule, and Ethernet connected control adapter.
Generator-in-the-Loop
In addition to generator emulation, the MEAPS Development Facility also allows real generators to be
put in-the-loop for the development of generator control units, to evaluate performance, fault
tolerance, etc. The figure below shows a real generator incorporated into the MEAPS Development
Facility.
In order to add a real generator to the facility, a dynamometer is used to provide mechanical drive that
is controlled in closed-loop with the gas turbine engine simulation. A control loop is incorporated within
the real-time simulator to set speed commands to the dynamometer AC drive, measure shaft load, and
turn the real generator with behavior matching the generator operating during simulated flight.
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Testing Aircraft Electrical Network Protection
HVDC aircraft power networks represent significant challenges for electrical network protection. The
high levels of stored energy and low impedance interconnections between systems can lead to the
creation of high peak fault current magnitudes and rapidly propagating fault effects. Therefore, very
fast acting protection schemes must be developed to
achieve the desired levels of protection to minimize
disruption to the remainder of the electrical network.
Furthermore, the electronic converters required by this
type of HVDC network worsen the protection challenge.
The MEAPS facility is the ideal development and test
platform for developing protection strategies and testing
prototype fault protection equipment. Significant work is
on-going across the industry to develop fast acting solidstate circuit breakers such as the Emitter Turn Off (ETO)
based DC circuit breaker shown below.
Test and Evaluation of Advanced Power Electronics
A critical component of the MEA HVDC architecture is high-efficiency DC-DC converter used to convert
from 270VDC distributed power to low voltage
power used by aircraft systems. Significant
innovation is happening across the industry for
a range of MAE power electronics technologies.
The figure below shows an advanced Dual
Active Bridge (DAB) DC-DC converter designed
for MEA applications and tested at the IEPNEF
facility in the UK.
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