Periodic Reporting for period 3 - HVDCGEN (High Speed HVDC Generator / Motor)
Reporting period: 2020-03-01 to 2021-08-31
Existing aircraft architectures make use of a 115/230 Volt electrical network for their onboard power demands. This Voltage level is analogous to that used in domestic appliances and is typically provided by generators mounted on the aircraft’s engines. The power is distributed around aircraft systems by cables which, with increasing electrical energy demands, are large and of significant weight.
New aircraft architectures include increased numbers of electrical systems with increased power demands. As an example, an Airbus A320 has a typical power demand of 50kW whereas a Boeing 787 has a demand of 500kW.
The increased electrical energy demand on the 787 comes from the electrical air conditioning system, electrical cabin pressurisation and electrical wing de-icing.
The next generation civil tilt rotor is taking a similar approach to the 787 with increased electrical energy demands.
To minimise cable and generator weight there is a requirement for a High Voltage network, to be provided and controlled by a high efficiency, High Voltage DC generator and control unit.
In the next generation tilt rotor this will minimise cable weight, eliminate the use of bleed air and eliminate centralised hydraulics.
As part of the project, research has been undertaken on performance of existing generators on board aircraft. As an example, the Airbus A320 has 2 x 90kW integrated drive generators. Typical kW/kg data available for these items is 1.5kW/kg giving a mass per 90kW generator of 60kg. Against this background, the call objective of 23kg for 90kW is a significant challenge.
2. Why is this important for society?
By developing a high speed HVDC generator/motor Denis Ferranti will:
• Address safety
• Reduce aircraft mass
• Facilitate more electric systems, eliminating the use of bleed air from the engines which will reduce fuel consumption by 2% at cruise conditions.
• Improve efficiency
These impacts are key enablers ensuring the NextGENCTR can meet the goals of ACARE, horizon 2020 and flightpath 2050 by reducing fuel consumption, CO2 and NOx.
Simultaneously strengthening and anchoring industrial competitiveness in the European aeronautical industry in line with horizon 2020 objectives for smart green and integrated transport.
Growing industrial leadership in the sector: Growing revenue, Improving productivity, Increasing rate of high level employment (good jobs, not just jobs), Exploit R and D, Grow the knowledge/innovation economy
In line with flightpath 2050 ensuring 90% of door to door trips in Europe are < 4hrs
3. What are the overall objectives?
3.1 Project/action/call objectives
In the framework of Clean Sky 2 FRC IADP the call objective is to provide innovative engineering solutions for the TiltrotorNextGen CTR demonstrator HVDC generator/motor by designing, developing and manufacturing a new generator/motor.
Its high level objectives, along with all specified requirements, will be:
• To attain high electrical power from the HVDC generators through the bus bars in accordance with stringent power supply quality standards.
• High levels of safety
• High levels of efficiency
• To attain the power in line with high availability due to flight critical loads
• Reduced mass
• Increased reliability
• Easier maintainability
• To provide motor power for aircraft accessories
3.2 Project/action/call measurables
• Provision of power: 90kW. 270VDC Voltage: ± 1%, Current ripple: ± 5A. EN 2282 and/or Mil standard 704F.
• Safety objectives met for CAT events < 1 x 10^-10/FH
• Efficiency > 90%
• Availability criteria better: < 1x10^-5 (assuming duplex HVDCG at a/c level)
• Reduced mass: < 23 kg
• Increased reliability MTBO >7,500 hrs
• Easier maintainability: LRU < 16kg. Change out times < 1 hour.
• Provide mechanical power 5 kW.
4.1 Project deliverables
The deliverables complete in the scope of the project are:
D1.1 Implementation agreement
D2.1 SRR minutes
D3.1 PDR minutes
D5.2 TRL4 review
4.2 TRL 4 phase
In line with our proposal responding to the call, the initial step in the program was to create a TRL 4 demonstrator.
The aim of this phase is to design, manufacture and test a development prototype model identical in form, fit and function with the specified equipment. It is to be used on a dynamic test bench connected to a simulated electrical network verifying the full range of operation.
From a technical perspective the TRL 4 purpose is to elicit requirements and mitigate architecture risks by test:
Delivery of power quality, duration and thermal (continuous)
High speed nature
High speed fan
De clutch mechanism
Multi level GCU
Control system and associate processor
Software protection functions
Packaging and interfaces
Short circuit protection hardware
4.3 TRL 4 deliverables
The deliverables are provided for the following items:
• GCU (power controller and inverter)
• Monitoring controller
• Cooling system
For each item the following deliverables have been completed:
• Requirements specification
• Compliance matrix
• Design description document
• Design Justification Document
• Interface Control Document
• Design Definition File
• Acceptance Test Procedure
System review complete
2 prototypes delivered and run at 70kW (90 kW specification). Full power anticipated in next project phase.
Given the demanding safety requirements and the use of permanent magnet technology, an innovative architecture has been proposed including a clutch, DAL B power controller and DAL A monitoring and protection controller.
An innovative clutch has been developed which is the subject of a patent application. This facilitates the use of permanent magnet technology.
In order to optimise system mass we have a combination of high speed (24,000rpm nominal) and 6 magnetic poles which provides a nominal fundamental frequency of 1,200 Hz. Given this fundamental frequency, in order to meet the performance, current and voltage ripple requirements it is necessary to accurately control the phase current by sampling the input control parameters and switching the Silicon Carbide transistors at 30kHz. This provides 25 samples per sinusoidal period and the time to perform the control algorithm calculations therefor needs to be less than 33 micro seconds. This is a significant challenge given the low calculation frequency of aerospace and military micro controllers and the extensive control algorithm required for a 3-level inverter/rectifier.