National Instruments has created a new real-time test system for hardware-in-the-loop (HIL) testing of the embedded control software releases of Siemens wind turbine control systems using NI TestStand, the LabVIEW Real-Time and LabVIEW FPGA modules, and the NI PXI platform. Sami Biko of Siemens Wind Power explains
A wind turbine system consists of several components including the rotor, gear, converter and transformer used to convert kinetic wind energy to electricity. The control system interfaces with these components through hundreds of I/O signals and multiple communication protocols. And the most complex part of the control system is the embedded control software executing the control loops.
Because our software developers regularly release a new software version for the controller, we need to test the software to verify that these releases will execute reliably in the wind park’s conditions. With every software release we perform factory acceptance testing before the software can be used in the field. This new test system gives us the ability to automate this process.
Our previous test system was developed ten years ago and based on another software environment and PCI data acquisition boards. The test system architecture and performance did not meet our new requirements for test time and scalability: it was difficult to maintain and did not have sufficient automation capabilities for efficient testing. It also lacked automatic test result documentation and test case traceability and did not provide the required remote control capabilities. In addition, the old HIL test environment did not support multicore processing, which prevented us from taking advantage of the computing power of the latest multicore processors.
Decision for future systems
After evaluating the available technologies, we selected LabVIEW software and PXI-based real-time and field-programmable gate array (FPGA) hardware to develop our new test solution. We believe this technology gives us the flexibility and expandability to meet our future technical requirements. Also, we have established confidence in the solution with the high level of service and quality of the products from NI.
Because we did not have in-depth development expertise for test systems in-house, we contracted the development to CIM Industrial Systems in Denmark. We chose CIM because they had the test engineering capability available — and the largest number of certified LabVIEW architects in Europe.
This new test system simulates the behavior of the real wind turbine components by running simulation models for these components in the LabVIEW Real-Time system to supply simulated signals to the system under test.
The host computer has an intuitive LabVIEW GUI that users can easily adapt by moving the components in the panel. The Windows OS application also communicates with two external instruments that were not real-time compatible.
Software on the host computer communicates with the LabVIEW Real-Time target in a PXI-1042Q chassis over Ethernet. LabVIEW Real-Time runs simulation software that typically consists of 20 to 25 simulation DLLs executing in parallel. This solution can call user models built with almost any modeling environment such as the NI LabVIEW Control Design and Simulation Module, The MathWorks Simulink software, or ANSI C code. A typical execution rate of our simulation loop is 24ms, leaving plenty of processing capacity to meet future expansion needs.
FPGA boards for custom wind turbine protocols
There are a lot of custom communication protocols used in wind turbines because of the lack of existing standards. Using an NI PXI-7833R FPGA-based multifunction RIO module with the LabVIEW FPGA Module, we can interface with and simulate these protocols. In addition to protocol interfacing, we are using the device to simulate magnetic sensors and for accurate three-phase voltage and current simulations. The other FPGA board is connected to an NI 9151 R Series expansion chassis to further increase the system channel count.
This new Siemens Wind Power test system has several benefits over the previous generation solution. Because of the modularity of the system it is easy to improve, adapt, and further develop. The system under test can be quickly replaced without any changes in the test system architecture. Remote control capability and simple replication of the system gives us the flexibility to copy the system to other sites as our operations expand. The simulator provides an environment to effectively verify the new software releases and test special situations in our laboratory. It also gives us a tool to test new technologies and concepts we are working on.
Its modular architecture allows us to scale-up the system to meet the growing requirements of rapidly evolving wind energy technology. We envision dividing the simulation to multiple LabVIEW Real-Time targets to meet our future testing needs. We are also going to use NI TestStand to further automate test execution.
