Pyro Fail Safe SSPC for Fault-Tolerant Converters and Safe HVDC-Power Network

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Pyro Fail Safe SSPC for Fault-Tolerant Converters and Safe HVDC-Power Network


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        <identifier identifierType="DOI">10.23723/10638/20137</identifier><creators><creator><creatorName>Jose Domingo Salvany</creatorName></creator><creator><creatorName>Frederic Richardeau</creatorName></creator></creators><titles>
            <title>Pyro Fail Safe SSPC for Fault-Tolerant Converters and Safe HVDC-Power Network</title></titles>
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	    <date dateType="Created">Sun 1 Oct 2017</date>
	    <date dateType="Updated">Sun 1 Oct 2017</date>
            <date dateType="Submitted">Sat 17 Feb 2018</date>
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NE/DT/RT/105/14-A Page 1/4 Pyro Fail Safe SSPC for Fault-Tolerant Converters and Safe HVDC-Power Network Jose DOMINGO SALVANY (1), Frederic RICHARDEAU (2) 1 : NEXTER Electronics, 2 : LAPLACE Laboratory, University of Toulouse, Abstract: In MEA the implementation of HVDC (High Voltage DC) power networks (PN) is a major topic for airliners and tier 1 manufacturers. On the last years, considerable efforts are done on integrated power converters, inverters and power management, for HVDC-PN. The emergence in the market the SiC MOSFET Power Switches normally off permits to improve the HV requirements associated at the new HVDC-PN standards. The use of Intelligent Power Switches (IPS) inside the inverters, converters or SSPC (Solid State Power Controllers), delivers light and safe power management configurations. This paper discus on the appropriateness to introduce IPS on two major functions: Active Rectifiers (AC/DC Power converters and DC/AC inverters) and SSPC for HVDC-PN. Fault-tolerant architecture and fail safe requirements for critical functions, require introducing new concepts based on pyro fuses, this concept and the associated technologies are highlighted. 1 - Introduction NEXTER Electronics (NE), a subsidiary of Nexter Group is involved on IPS technology development for dual use. Major efforts are done in aero terrestrial platforms implementing PN in the voltage range of 1 kV. Implementation of SiC (Silicon Carbide) IPS solutions for power management and distribution is the major effort done by NE on the last years. The I3 (Intelligent Integrated Interrupter) SSPC products family, created by NE, works in Unipolar or Bipolar HVDC configurations on the range +/-270VDC. The implementation of pyro fuses associated to the IPS introduces new safe and redundant solutions which were studied by Lab. LAPLACE for five years with high level of availability for critical functions (Ex: HVDC-PN generation or Distribution). 2 – HVDC-PN architectures in MEA 2.1 - Global or Local PN One of the factors considered for the optimization of the mass on the More Electric Aircraft (MEA) is the use of HVDC-PN. The transition from conventional architectures using three-phase 115VAC 400Hz or variable frequency power networks for primary distribution, to architectures using +/-270VDC, should be done in different stages. Each aircraft manufacturer has its own analysis on the conditions for the deployment of these HVDC networks; they are conditioned by the level of maturity of the technology associated with these networks functions. Several topologies are being considered for the deployment : HVDC global network or local networks in HVDC. In the transition phase is considered a global AC network for primary power distribution and local power networks in HVDC for high power loads, which is becoming more common given the growing electrification of aircraft. 2.2 – Criticism of functions linked to HVDC-PN Most loads connected on HVDC networks, concern the aircraft operation and they have high requirements in terms of safety, availability and reliability (landing gear, flight controls, thrust reverser...). For the monitoring and control of these loads and to meet the above requirements, it is necessary to introduce appropriate technologies and architectures. 2.3 – Functions description In this article we discuss the relevance to use new technologies and topologies to meet the constraints of availability and criticality of the functions attached to a local network HVDC: 1. The first example is a 6 switch fault tolerant active rectifier based on (3+1) legs topology, the use of the 4 th leg in replacement of the leg in default, is obtained by the use of "Pyrotechnical Circuit Breakers” (Pyro CB) Fig 1 : Standard 3 phase, 2 levels, PWM rectifier 2. The second example is a fault tolerant Vienna 3 levels rectifier, using the Pyro CB to insulate the switch in default. NE/DT/RT/105/14-A Page 2/4 Fig 2 : Vienna 3 Level Active Rectifier 3. The third example is a bipolar SSPC "Fail Safe" using Pyro CB for the protection of HVDC Power Distribution. Fig 3 : Fail Safe SSPC Architecture 3 – Technology implemented This § presents the technology used to improve the power density, increase the efficiency and respond to the function criticism. 3.1 – Power Switch’s Technology High Voltage, High Temperature and fast switching operating conditions, are the major characteristics of SiC MOSFET switches used for the new generation of power management (converters, inverters) and power distribution. These characteristics will permit to reduce the heat sinks, the mass on inductive components and more. Fig 4 : Figure of merit for different WBG 1 technologies vs. Silicon The major effort in progress on GaN & SiC IPS 2 is to include the “short-circuit” reflex protections on the same package to reduce losses, and improve the efficiency. 1 WBG : Wide Band Gap 2 An IPS includes: Power Switch, Current and temperature measurement, Gate driver, short-circuit detection. 3.2 – Pyro Fuses & CB: State of the art Some technologies are available to open the HVDC power lines in “Fail Safe” conditions: • Pyro electrical fuses and circuit breakers, • Remote Control Circuit Breakers, based on electromechanical solutions, • Controlled Thermal fuses, based on temperature alloys, Fig 5 : Examples of “Fail Safe” protections 4 - Topologies 4.2 – Active Rectifier On the first and second examples we assume a Tri phase AC 115V FV 3 main power input. The energy stored in the converter mesh is poor and the implementation of PyCB or fuse breakers on printed board is possible. Fig 6 : PWM rectifier using PyCB or fuse breakers to isolate the leg in default and automatically connect the auxiliary leg through rectifier diodes. It is supposed that power devices have a fail-to-short failure mode. 4.2.1 – Requirements & Hypothesis Non insulated AC/DC Converter topologies are used to create HVDC (+/-270VDC) PN. The main advantage of the architectures discussed on [1] are the high power density (6kw/l) obtained by the use of high switching frequency and new generation of SiC (Silicon Carbide) power switch’s. The second advantage of this topology is the capability to correct the THD on the input and regulate the voltage on the output. The use of PyCB or Fuse breakers on the previous architectures depends on the capability of the Power Bus (PB) to deliver the fuse trip energy. In some implementations the energy delivered by the PB is insufficient and it’s not possible to use de fuse 3 FV : Variable frequency 400..800 Hz NE/DT/RT/105/14-A Page 3/4 breakers and the energy will be delivered by Pyro actuators integrated on PCB [2,3]. Fig 7 : Example of Pyro Actuators embedded on PCB (300V/25ARMS/100ms) (Collab. LAPLACE – SNPE Matériaux Energétiques) 4.2.2 – Coherency with the use of IPS & Pyro The use of IPS including short-circuit protections will facilitate the construction of fault tolerant converters or inverters, the fast response of “reflex” function implemented on IPS protect against short circuit on the distributed power line (default 1 on fig 8), nevertheless for defects associated at power switch itself (default 2 on fig 8) it’s necessary to protect the inverter leg with a fuse to prevent a short-circuit on HVDC bus. Fig 8 : Defects treated in a inverter implementing IPS and fuses When the default is on power switch itself, the energy available in the HVDC bus must be sufficient to melt the fuse implemented on the leg, otherwise it’s necessary to use pyrotechnical circuit breakers and electronic circuits to detect the short-circuit and initiate pyrotechnical protections. PyCb with fast time response (2ms) are available and are currently used in safe functions. 4.3 – SSPC Fail Safe SSPC includes an AC or DC line switching and protection functions. The protection functions includes: line protection against short circuit and line overload protections (I²t). SSPC are used on stationary applications (home, industry) or on-board in air-land and naval platforms. The implementation of SSPC to protect the power distribution on embedded HVDC (+/-270V) power networks has become a priority within the MEA. 4.3.1 – Requirements & Hypothesis To meet the requirements of security, an SSPC operating on HVDC must cut the two poles of the protected line. Figure 9 shows the architecture of a bipolar SSPC, manufactured by NEXTER Electronics (4], working on HVDC-PN and including the protections: • Overload and Short Circuit (Instant Trip) Protection • I 2 t protection • Thermal protection • ON, OFF control • ESD (electrostatic discharge on power contact) • Soft start with auto soft start • +1,5A differential trip • Bidirectional reflex short circuit protection • Parallel arc-fault Fig 9: Architecture of a bipolar (+/-270V) SSPC Previous SSPC integrates SiC Power Switchs to respect the requirements in terms of voltage transients on bipolar (+/-270V) or unipolar (540V) HVDC power networks. The fast time response of SiC technology permits to attempt high performances in terms of power line breaking. The implementation of SSPC on embedded applications requires considering the criticism on the line protections. To guard against double event: short circuit on the line and short-circuit on SSPC power switch, the SSPC will be "Fail Safe" (FS) 4 . The probability of short-circuit default in a MOSFET power switch is around 80%. To meet the criterion FS it’s necessary to implement several power switch’s in serial (2 power switch’s in the fig 9). The most popular configuration to obtain a FS SSPC is to put in serial a fuse with the SSPC power switch and consider that the HVDC network is powerful enough to blow the fuse. 4.3.2 – Coherency with the use of IPS & Pyro Each switch on architecture presented in the fig 9 will 4 has this to say to get safely (open circuit) when it is inoperative NE/DT/RT/105/14-A Page 4/4 be considered as an IPS including short-circuit line protections, the I²t overload protection being implemented at each of the control units associated with each IPS In some cases the main input of HVDC local PN not have the sufficient energy to blow the fuse and is necessary to use Pyro CB instead fuses. The figure 10 presents a bipolar reversible HVDC FS SSPC architecture compatible with high level of criticism (DAL-A), mainly dedicated for aeronautical platforms. In front of active rectifier examples, previously explained, the energy involved on SSPC is higher, because is necessary to consider the energy stored on wires inductance. Figure 11 presents an example of Pyro actuator [5] used to cut the HVDC power line. Fig 10 : Fail Safe bipolar (AC) SSPC architecture using Pyro CB. a) • Tf middle : 2,9 ms • Piston stroke : 4,2 mm • Piston effort > 1000 N b) • 1ms • 300A Fig 11 : Examples of Pyro Actuator a) from NEXTER and b) BDSD (Batterie Disconnect Safety Device) from Delphi™ (HEV/EV automotive application) 5 – Conclusion On the frame of the more electrical aircraft and land platforms, this article presented the possibilities offered by the use of intelligent power switch (IPS) in power converters and power distribution functions embedded on aero terrestrial platforms. Were shown the contributions of the use of devices reconfiguration power converters or SSPC based on pyrotechnic solutions (PyCB), allowing them to increase the availability and / or safety. Most of the concepts discussed were the subject of laboratory research and have a low/medium level of technological maturity (TRL3); they require additional effort before they can be integrated into the operational configurations validation. 6 - References [1] “Ultra-Compact and Ultra-Efficient Three-Phase PWM Rectifier Systems for More Electric Aircraft”, MICHAEL HARTMANN, 2011 [2] «Contribution à l’étude de nouveaux convertisseurs sécurisés à tolérance de panne pour systèmes critiques à haute performance. Application à un PFC Double-Boost 5 Niveaux» Thèse de T.T.L.Pham par L’Université de Toulouse, Nov. 2011. http://ethesis.inp- [3] « Sûreté de fonctionnement des convertisseurs. Nouvelles structures de redondances pour onduleurs sécurisés à tolérance de pannes ». Thèse de Zhifeng DOU, par L’Université de Toulouse Nov. 2011. [4] DataSheet of I3-540D2B15R6 SSPC manufactured by NEXTER Electronics [5] DataSheet “Pousseur Electro-Pyrotechnique 1A- 1W”. NEXTER Munitions.