Wind energy is one of the most important drivers of the energy transition, and the demand for powerful wind turbines is growing continuously. With every new model, the demands on technology and reliability increase. To ensure that wind turbines can be connected to the grid safely and efficiently, they must meet strict requirements – particularly grid code compliance.
Compliance with the grid codes is crucial for the stability of the power grid and the certification of new systems. Traditional testing methods are extremely expensive and require extensive hardware. In the following application, we demonstrate how an innovative power HIL test bench makes the validation of full converters (also known as back‑to‑back converters) more efficient and flexible.
This use case is based on the VirTuOS (Virtualization of Wind Turbine Test Procedures through Online Services) project. VirTuOS involves several research institutes of the Center for Wind Power Drives (CWD) at RWTH Aachen University, including ACS, AIA, IEM, IRT, and PGS.
Sponsored project partners include dSPACE and FGH Zertifizierungsgesellschaft mbH. The project is funded by the Federal Ministry for Economic Affairs and Energy (BMWE).
What tasks do full converters perform for grid code compliance?
In full converter wind turbine architectures, the converter plays a central role in ensuring grid code compliance and a secure grid connection. They connect the wind turbine to the power grid and ensure that the energy generated is fed into the grid in a stable and grid-compliant manner, regardless of changing wind conditions.
To achieve this certification, full converters must prove that they meet the requirements of the grid codes, for example:
- Behavior in the event of network faults (fault ride-through, etc.)
- Provision of reactive power
- Frequency maintenance
- Voltage quality
This validation is the only way to ensure that wind turbines can feed into the grid in a stable and flexible manner and make a reliable contribution to the energy supply, even in the event of disruptions.
What challenges arise when certifying full converters?
Until now, the certification of full converter for wind turbines involved a great deal of effort. Traditional test methods such as field tests are cost-intensive, time-consuming, and heavily dependent on external conditions. Nacelle test benches and laboratory tests with large chokes require additional complex mechanical and electrical setups and offer only limited flexibility.
To make validation more efficient and reproducible, laboratory tests in which the grid and generator are emulated under controlled conditions are increasingly being used. This method makes it possible to specifically simulate a wide range of operating states and comprehensively test the performance of the full converter.
However, emulating the grid and generator at full power brings additional technical challenges: In addition to safely handling high currents and voltages and complex scenarios such as fault ride-through (FRT), the power HIL power electronics device must meet the highest requirements in terms of emulation accuracy and dielectric strength.
What solution does dSPACE offer for full converter testing in wind turbines?
To overcome these challenges in validating full converters, dSPACE, together with RWTH Aachen University, developed a power HIL test bench. It enables the realistic emulation of the grid and generator under full-load conditions in real time and thus addresses the central challenges of classic test procedures: flexibility, efficiency, and robustness.
Realistic Emulation of the Electrical Environment
Real-time models for the grid and generator run on FPGAs and continuously simulate the behavior of both components. The calculated reference values are transmitted via a high-speed interface to electronic load modules that act as power amplifiers. This means that all relevant grid situations and faults can be tested precisely and reproducibly.
Modular Design and High Performance
The first test bench to be put into operation is based on 96 electronic load modules of the type DS5386 High-Voltage Electronic Load Module, distributed across six cabinets. The load modules function as bidirectional current sinks and sources and precisely simulate the electrical behavior of the grid and generator.
By connecting several modules in parallel, each side – mains and generator – can be realized:
- Power: up to 1.84 MW
- Voltage: up to 1,250 V
- Effective current: up to 1,200 A per phase
This scalability enables tests under realistic conditions without relying on physical generators or mains.
Overview of the power HIL test bench: All mains and generator connections of the full converter are connected to electronic load modules. The modular architecture enables RMS currents of up to 1,200 A per phase, a maximum voltage of 1,250 V, and an output of up to 1.84 MW per side.
Advantages of the Power HIL Test Bench
Flexibility through decentralized power control
- Each load module has its own highly dynamic control system.
- Enables precise and independent adjustment of the currents.
- Fast response to load changes and flexible adaptation to test requirements.
Efficient energy distribution through a shared DC link
- Connection of all modules via a central DC link busbar.
- Circulating power flow reduces the load on the grid.
- Mains supply only covers the power loss.
Robustness in critical operating conditions
- Supercapacitor bank providing voltage support in the fault ride-through (FRT) application.
- Prevents critical voltage dips.
- Ensures reliable operation even under extreme conditions.
