High Dynamic Fuel Cell Test Station

Why dynamic testing?

As fuel cells moved into focus as an environmentally friendly power source for automotive applications, the standards for fuel cell test stations have changed. Formerly used for long-term, steady-state testing, now fast transient analysis and drive cycle simulations are mandatory. Hence, a new system was designed from scratch with prospects of high dynamics, Hardware-in-the-Loop simulation, platform independent communication, and expandability. Uncompromising safe operation is crucial for the unit under test and the operator alike. Unattended 24/7 testing, high temperatures and currents, H₂ and O₂ use require an unreserved reliable system.

What is unique?

Based on National Instruments CompactRIO, an inherently safe, self-sustained control system was developed. FPGA and Real-Time employment facilitate multiple layers of safety and extremely fast alarm counteracting while harboring the entire control strategy. Although no dedicated PC is required to run the test station, data can be exchanged with multiple nodes via UDP. Computers of different platforms may transmit and receive data in parallel, forming a unique network of simulation, scripted testing, data storing and visualization while achieving performance that is unrivaled among fuel cell test stations. The modular software architecture and new signal conditioning hardware allow quick adaptation and are also suitable for economic retro-fitting of existing test stands.

What is the gain?

Fuel cell test stands for dynamic applications have so far been upgraded standard test stands. Hence, they are not optimized, run by a Windows-based host PC, and simulations need a CAN interface to hook-up. All this results in response times of 800ms and more for load following. With the new breed of test stations, the response time could cut down to less than 50ms. No additional hardware is required to hook-up simulation targets. Since safety systems are encapsulated and centralized on the RT controller, customer get open-source code of the functional RT kernel and the main GUI to implement their specific capabilities without compromising the overall safety and reliability.

How it works

Block Chart of Data I/O and Controller

At a glance: the controller

- Pure Real-Time (RT) controller, no PC required to run the test station
- First data validation and alarm counteracting on FPGA backbone, no CPU involved
- 3 static and 2 dynamic alarm levels with optional delay times
- UDP transfer to GUIs, simulation targets or any other computer of any platform
- Parallel communication allows multiple simulations and scripts
- Ring buffer for post-mortem snapshot
- Generic architecture with open-source Plug-In VI for specific functionality
- Flexible set-up, also great for retro-fitting existing test stands

At a glance: connectivity and signal conditioning

- 2 x 32 differential, analog input channels with modular signal conditioning (left)
- dual channel modules available for RTD, TC, 4-20mA, Voltage amplifiers
- Bread-board module with 24V, 5V and +/-15V supply for custom solutions
- 16 analog output channels, voltage or current output
- 2 x 32 high current digital outputs, 24V, 1.5A/channel, 12A/module (right)
- Recovery diodes for directly switching solenoids and conductors
- 32 digital input channels, optically isolated
- Bus communication to adjunct instruments via RS232, RS485 or SPI.

 At a glance: the GUI

- Optional, open-source GUI with intuitive P&ID and DIN-standard like controls
- Pipe color changes with medium for immediate overview
- Configurable synchronizing and ramping of any set points
- Change all controller parameters "on-the-fly"
- Data storage in Citadel™ data base
- Modular architecture for custom adaptation
- Add-ons for specialty measurements, calibration, custom units, and much more
- View test runs and export to data mining applications

Graphic User Interface (GUI) with interactive Piping and Instrumentation Diagram (P&ID)

High- End cell voltage monitor and diagnosis system for fuel cell stacks
and
High frequency impedance analyzer for individual cells of a fuel cell stack

- 16 channel per module, stackable up to 240 channels total
- Fast read out (24us/Channel+200us)
- 12 bit resolution
- Real-Time support
- True differential input
- Galvanic isolation: channel to channel > 300V
- Galvanic isolation: input (test item) to output (SPI interface) > 1000V
- Simultaneous sampling of all channels with hardware trigger line for exact timing
- Custom specific PCB interface for connecting test item, no cable adapters needed
- Industrial standard DIN rail mount close to UUT (unit-under-test)
- SPI interface to controller, other interfaces planned (Ethernet, CAN, USB, …)