Text: Martin Flach, Tobias Hamberger, Christian Stangl Pictures: © ENERCON, MicroNova
Wind energy is one of the most environmentally friendly energy sources. Wind turbines are becoming more popular and their technological development is advancing at a rapid pace. As product cycles in this industry are becoming ever shorter – similar to what is happening in the automotive sector – manufacturers are looking for ways to make development more efficient and faster. Modern and tried-and-tested tools from automotive development are available to help manufacturers cope with the increasing complexity of control unit development.
The wind turbine manufacturer Enercon has already been using a Hardware-in-the-Loop (HiL) system from MicroNova for several years and has carried out initial component tests in the area of blade pitch control. Since these tests were very satisfactory the company, based in Aurich, Germany, decided to integrate a new test concept into its development process and to set up a test landscape with five HiL simulators in cooperation with MicroNova. The electronic control systems should as early as possible be confronted with all the conditions that occur subsequently during operation of the wind turbine and their correct functioning should be validated.
MicroNova’s testing solutions team therefore developed the following HiL systems:/> One HiL simulator tests the safety related functions of the components at the base of the tower, in the nacelle and for the rotor blades. Another HiL system validates the control unit, which ensures controlled starting and stopping of the wind turbine as well as the higher-level power regulation and load control during operation.
Three NovaCarts CBP simulators were manufactured for the rotor blade control units. CBP stands for ‘Control Board Pitch’ and describes the system for blade pitch control, which is mainly used for power regulation in wind turbines. For example, at many wind turbines the rotational speed of the rotor is determined by the orientation of the blades relative to the wind direction. An electric motor rotates one of the rotor blades until it assumes the ideal position for power generation in relation to the incoming wind. This continuous and rapid regulation ensures that the rotor blade immediately finds its optimum position when conditions change.
The three new CBP systems offer two and a half times more I/Os than the existing system. In addition, it is now possible to simulate four electric motors per test bench instead of two, and multiple control units can be distributed over up to three real part plug-in modules. This makes it possible to expand test activities in future to include other control and regulating components of the wind turbine – if required also in synchronized interconnected operation.
Enercon has set up its own test area to jointly operate all five new systems. In this test area, it is now possible to validate individual functions of the wind turbines at an early stage in the development process with the aid of corresponding simulation models, such as blade pitch control in thresholds or generator functionality.
The central requirements for the seamless interaction of the HiL systems are precise, time-synchronous data acquisition and reliable, real-time data exchange between systems. To ensure this, a neutral point controller was used in addition to the five control computers already built into the test benches. This acts as a timing master and ensures common mode and a system time that is accurate to the microsecond on all components in the HiL network. In addition, the neutral point coordinates the exchange of data between test benches and in its own simulation model calculates variables that are relevant for all connected HiL systems, such as wind speed.
The scale of the project and the wind energy sector were the main attractions of this task. David Hirschhäuser, team leader for HiL projects at MicroNova, confirms: “For us, it was the first project of this magnitude outside the automotive sector. It was a question of developing a comprehensive concept for a system that was as flexible, efficient and durable as possible. I think we have worked together very well over the last two years, learned a lot from each other and can be very satisfied with the result.”
Der Entwicklung und Auslieferung der HiL-Systeme vorangegangen war eine ausführliche Analyse der Testanforderungen beim Turbinenhersteller. Hier konnten die Experten der Abteilung Consulting & Services von MicroNova auf ihre umfangreiche Erfahrung aus dem Automotive-Testing-Bereich zurückgreifen. In enger Zusammenarbeit mit den Projektverantwortlichen beim Auftraggeber entstand so ein vollständiges Testkonzept inklusive Simulationsmodellen sowie Testautomatisierung und -design. Projektbegleitend unterstützte MicroNova auch beim Aufbau einer entsprechenden Abteilung für Verifikation & Validierung bei Enercon.
Neben der Konzeptionierung und Einführung der HiL-Systeme übernimmt MicroNova zudem den Support und die Wartung der Testlandschaft. Eine weitere Aufgabe ist es, die Testautomatisierung zu etablieren. Hierfür kommt EXAM zum Einsatz, eine Software zur grafischen Entwicklung von Testfällen im Bereich der Testautomatisierung. Da MicroNova seit über zehn Jahren EXAM gemeinsam mit zwei großen Automobilherstellern entwickelt, kann Enercon auch hier von Know-how aus erster Hand profitieren.
The stakeholders at the Aurich-based wind energy company are very satisfied with the results of the two-year cooperation: “Thanks to our modern and interconnected HiL test landscape, adaptations to the software can now be implemented much more quickly and we get the test results practically overnight. With manual tests and manual analysis of the measurement results, this used to take up to a week,” explains PhDr. Monika Dávideková, Team Leader Software Validation at Enercon. “In addition, test cases are now stored more accurately together with their results and can be easily referenced in secondary tools such as XRay or Jira. We were able to learn a lot from the automotive industry and significantly accelerate our development work.”
The great advantages of the automated and reproducible tests have convinced Enercon so much that an extension of the test facilities has already been put forward. This will focus more on the modularization and reusability of the test landscape for other projects in order to test the numerous control units and their software even more quickly and more flexibly.
ENERCON has been a technology leader in the wind energy sector for over 30 years. The company was the first manufacturer to opt for a gearless drive concept, which is characteristic of all ENERCON wind turbines. ENERCON also continues to set technological standards in areas such as rotor blade design, control technology and grid connection.
ENERCON wind turbines are fitted with a grid feed-in system certified according to the latest connection requirements. This means they can easily be inte-grated into all supply and distribution grid structures.
ENERCON considers it as a major challenge to advance the supply of regenerative solutions worldwide and is playing a key role in future technologies such as energy storage, electromobility and smart grids. Internationally, ENERCON has a presence in the major markets with a decentral-ized service and sales network.
For more than thirty years, wind power has been used to generate electricity on a large scale. Wind turbines and other renewable energies have become firmly es-tablished, not least due to rising oil/gas prices and growing environmental awareness. According to the German Wind Energy Association, wind turbines installed in Germany alone produced almost 112 billion kilowatt hours (kWh) of electricity in 2018 – equivalent to 20.4 percent of German electricity production.