INDIS: Indra HVDC Distribution System for a new more electrical aircraft of Piaggio Aerospace

Project Description

The goal of this project is the development of a new primary electrical power distribution system (PPDS) to be integrated in an aircraft/plane platform from the aircraft manufacturer Piaggio Aerospace.

Regarding to the environmental green objectives targeted by the European Commission through the CleanSky2 program (CS2), being part of the H2020 European Frame program, the goal of the INDIS project is to achieve an electrical power distribution system more efficient and that allow finally to produce some more electrical aircrafts and in a feasible way, as long as this new electrical system will be the core and the backbone of the new electrical air platforms. The CS2 program has as one of its main pillars the development of more electrical aircrafts (MEA) or even, total electrical aircraft (TEA), in order to achieve an general aircraft more efficient, competitive and capable to achieve a reduction in contaminant emissions and noise.

So, the INDIS system is going to optimize the power distribution in low voltage (LV), by increasing power density (more power in less space and weight) and allowing a better control of the power installed, load and protections management. And also, INDIS develop the elements and items for distribution, load management and protection in a new high voltage DC network (HVDC network). HV network allows a global reduction of weight and volume in the onboard electrical system.

Then, the INDIS electrical power distribution system developed by Indra has been based in the following points or principles:

• Smart management of the electrical power.
• Weight and volumen optimization.
• Same or higher compliance levels in safety, redundancy and segregation requirements at aircraft level where electrical system will be a critical one.
• Integration of DC networks in air platforms, as in low voltage networks (LV or 28Vdc) as in high voltage networks (HV or 270Vdc).

In order to achieve these objectives, Indra has get advantage of its previous experience in SSPCs (Solid State Power Controllers) and it has also developed new specific SSPCs for high power and some new local controllers (or CMCs), that jointly with traditional contactors, has allowed to build a new subassembly named as “S-Contactors” (or smart contactor).

Example of some previous INDRA’s units based in electrical power distribution and SSPCs.

The general control of the system has been based in the mix of local controllers (SSPCs y CMCs) that at the same time, are associated to a main controller, that then, in the global architecture, it is associated to one of the different segregated distribution zones (HV left zone, HV right zone, LV left zone, LV right zone and LV central zone), and with a different main controller associated to each distribution zone.

It is also important to highlight that in the INDIS development it have been applied principles of segregation and redundancy in the global architecture, so as dissimilarity criteria over critical elements/items, in order to have a redundant and dissimilar control (by using simple and complex control in parallel) in order to comply with the future aircraft requirements of safety and certification.

Moreover, regarding to the internal elements considered as complex (as microcontrollers + SW), a dedicated design has been also applied in order to increase the redundancy and dissimilarity. This has been done by the use of the following:

• Applying a mix of discrete and digital signals entering and leaving to/from DSP (microcontroller) and that communicate with the rest of the system.
• Applying a design reserve for future development, including in a control and communication stage based the “triple-redundancy” concept inside of the DSP and with an independent logic for voting process between the tree controls and tree communications working in parallel, and at the same time,.

To note that this architecture and logic based in “triple redundancy” has been applied as over the main controllers and over the local controllers (CMCs and SSPCs).

Example of the new architecture/topology using main and local control with “triple-redundant” logic.

To comment also, that despite the distribution elements in low voltage LV (LV - 28Vdc) and high voltage (HV – 270Vdc), the global INDIS Project has also included the development of a new and dedicate regulated power converter, in charged to pass energy from the traditional LV network to the new HV network. This converter has been designed using a new topology more efficient and using a modular approach (in order to adjust power converter to the power needs in different future (or potential) platforms by power escalation or number of power modules installed, and with use of and interleaving technic also, that has allow to improve to power quality of the HV energy generated.

Initially, the Project duration was estimated in 36 months, in accordance with the customer request and agreement of Indra due to its previous experience. But finally, due to the open points in the SAT architecture and customer specification, complexity of the design and high impacts due to the COVIC pandemic, the Project duration was extended officially up to 48 months. And despite this calendar for Project finalization, Indra has been working longer that these 48 months in order to continue giving support to the customer in the final integration phase in the SAT rig tests bench and in the future aircraft test benches.

The Project has been developed under several phases:

• Phase-1, for requirement analysis and agreement of baseline with the customer..
• Phase-2, for concept and preliminary design and pre-prototypes preparation, for risks reduction and technological feasibility analysis.
• Phase-3, for detail design and application of changes coming from pre-prototypes validation.
• Phase-4, for critical development with the generation of all the documentation for manufacturing and mounting.
• Phase-5, for PCBs and subassemblies mounting, and validation actions.
• Phase-6, for units mounting and validation at equipment level..
• Phase-7, for final pre-integration at Indra facilities and verification tests, by using own a/c emulators designed by Indra itself.
• Phase-8, for customer delivery and Indra support to SAT Rig integration activities.

HV-PPDUs units under verification and pre-integration tests in Indra facilities.

LV-PPDUs unit under verification and pre-integration tests preparation in Indra facilities.

LVDC/HVDC Power Converter unit under verification and pre-integration tests in Indra facilities.

Next elements are the main ones developed inside of the INDIS Project and explained just after:

• Pre-prototypes for new SSPCs of 100-400A, CMCs and Smart contactors for HV.

Examples of some of the pre-prototypes and preliminary tests of the INDIS project.

• HV-PPDU units: Development of 2 units for HV smart distribution based in HV-SSPCs (270Vdc) and up to 50A, using natural conduction/convection cooling. One unit is performed under minimum sized and 4 channels, while the second unit is designed to manage 8 channels in modular internal configuration for future scalability.

Images of both HV-PPDUs (4-channel unit and 8-channel units) ready to expedition and delivery to the customer (Piaggio Aerospace) for SAT-Rig integration tests.

• LV-PPDU unit: Development of one big unit for complete Smart distribution in LV network (28Vdc) and composed of 7 smart-contactors (contactor + CMCs) of 400A/600A, 24 HP-SSPC channels (of 15-100A) and 32 LP/MP-SSPC (of 1-35A), shared in 3 different zones, mechanically isolated, and with dissimilar and redundant control.

Images of LV-PPDU s/n 00P1 ready to expedition and delivery to customer (Piaggio Aerospace) for SAT-Rig integration tests.

• LVDC/HVDC Power Converter Unit: Development of a power converter of 5kW-6kWp based in modular approach (2 x 2.5kW/3kWp), using interleaving technics and analog control. It also includes monitoring and communication using discrete signals and digital bus (CAN-Bus) managed by a DSP+SW.

Images of LVDC/HVDC Power Converter s/n 00P1 ready to expedition and delivery to (Piaggio Aerospace) for SAT-Rig integration tests.

• Testing items and units: additionally to the previous units, inside of the INDIS Project, it have been developed other additional units, test boards and other elements used during debug and validation/verification activities and also units for digital communication distribution and SW(HW a/c emulator boxes.

Examples of other elements developed for use in the INDIS project (Cut-boxes for PCBs debug, dedicated test board for debug propose, CANBuses termination boxes, Power Converter remote control box, Power-Diode for protection under reverse current in HV-GENs, CanBUS-emulator access-point box, A/C-panels emulator boxes, HV power loads bench, HV and LV emulators SWs and Load-Management SW).

At the end of the INDIS project, the different units developed have reached a technological readiness level equivalent to TRL6..

Despite all difficulties found along the INDIS Project and delays, as Piaggio as the CSJU, have recognized the good job and effort performed by Indra in this Project and its dedication and compromise, so as the interest of this project for future upgrade and application to real aircraft platforms or new applications..

Collaborating Companies or Organisations

Indra's Role

Indra has performed this project by itself as it has all capabilities and knowledge to do it without the need of additional partners or third parties.

This project was based on Indra´s previous experiences and products in this area, and it has allowed an evolution of the technology and components for the new performances of this project and the optimization/improvement of Indra´s own technology.

Due to this, Indra has been in charged of all activities associated to this Project, from management activities, moving through all the development, manufacturing and tests activities to the reporting activities, technological dissemination and planning for future industrialization/commercialization.

Technologies used

As already commented before, the technologies used along this Project have been the following:

• High power SSPCs technologies using SiC devices for HV channels and Si devices for LV channels.
• Smart contactors to be used in power input channels and in reconfiguration channels (800-1000A), but using technologies for control, monitoring and protections used in similar way tan in Indra’s SSPCs.
• Intelligent control based in a “triple-redundancy” concept and mix of centralized control (at system/unit level) and distributed/local (at commutation/protection device level).
• Optimized regulated power conversion based in new components and technologies (SiC devices, local control, planar magnetics devices, modular approach with interleaving technic, …).
• New designs for power connection based in new Indra power terminals with captive solutions.
• New mechanical and cooling solutions for weight and volume optimization and cooling optimization by natural conduction/convection.

More information

This project, con reference number H2020-755654, has been partially funded by the European Commission through the CleanSky2 program, which is part of the Technological European H2020 frame program.

https://cordis.europa.eu/project/id/755654/es

The Project has been supervised by Piaggio Aerospace (as “Topic Manager” or customer) and by the CSJU (on behalf of the European Commission).