Generator inverter test bench
The Generator Converter Test Bench (GeCoLab) can be used to research both conventional and innovative converter and generator concepts, including converter-related control and methods for filter design in the MW range. The implemented universal test bench enables the investigation of steady-state and dynamic properties of electrical machines and converters, including converter-machine interactions. This includes studies of dynamics and system stability, steady-state and transient thermal loading, various methods of grid injection and control, and behavior in the event of grid faults such as voltage dips, phase shorts, or ground faults. The test bench will also enable research into interactions between the converter and generator and their influence on other plant components such as bearings and gearboxes.
Experimental investigation of MW-class electrical machines and converters is costly, and industry often lacks available experimental capacity for long-term, in-depth work. The universal test stand realized through a grant from the BMWi – primarily, but not exclusively, geared to wind energy – enables the investigation of steady-state and dynamic properties of electrical machines and converters, including converter-machine interactions.
Within the field of energy research, GeCoLab is part of a larger network with the North German universities of Hannover, Oldenburg and Bremen (ForWind) and the Fraunhofer Institute for Wind Energy Systems (IWES). The network also coordinates the mutual use and further development of experimental facilities and results. While the nacelle test stand operated at IWES in Bremerhaven is mainly aimed at testing and verification accompanying product development and optimization and thus requires test facilities in a ratio of 1:1, the generator-inverter test stand at Leibniz Universität Hannover covers the preliminary development of the electric drive train as well as the (university) research and development of new concepts and calculation tools. In these phases of the innovation process, plants are mapped on a smaller scale for cost reasons. The power class of approx. 1.5 MW selected here allows meaningful investigations to be carried out for target systems of even greater power, e.g. at a scale of approx. 1:10. This also makes the facility interesting for industrial partners who want to test new concepts as part of apron developments.
It will also be possible to investigate new converter concepts, such as modular multilevel converters, on a reduced scale in the GeCoLab test field environment. This requires the flexibility to exchange test bench converters for converters under investigation.
The development of electrical machines and converters in the MW range is far from complete, despite decades of experience in the field. One of the reasons for this is that requirements change and the materials and electronic components used are constantly being developed. In addition, there is the constant demand for improved economic efficiency with increased efficiency or increased reliability. With the Generator Converter Test Bench (GeCoLab), both conventional and innovative converter and generator concepts, including converter-related control and filter design methods, can now be researched in detail. This includes studies of dynamics and system stability, steady-state and transient thermal loading, various methods of grid injection and control, and behavior in the event of grid faults such as voltage dips, phase shorts, or ground faults. The test bench will also enable research into interactions between the converter and generator and their influence on other plant components such as bearings and gearboxes. Examples include the effects of harmonics in the current waveform, additional heating, local saturation effects, and bearing voltages and currents. In turn, the results obtained allow improved validation of calculation programs, diagnostic procedures and extended simulation models for electrical and affected mechanical components in order to take the requirements mentioned at the beginning into account already in the design phase.
Equipment of the test bench
The generator inverter test bench was realized in a complete configuration, so that the test bench is already functional without any further components. In order to carry out further tests, individual components can be exchanged for test specimens in the plant. The following components are intended to be exchanged for a DUT:
- Double-fed asynchronous generator (DFIG)
- Rotor side converter for DFIG
- Synchronous generator (SG)
- Full converter for synchronous generator
When exchanging a generator together with the associated converter, a variety of other combinations can also be realized, for example, the DFIG can be exchanged for an asynchronous generator with full converter. A clamping field and a 20t crane provided by the customer enable the components to be changed quickly. The machine foundation is decoupled from the building by means of pneumatic spring elements. An easily accessible terminal panel was also installed for changing the inverters for a DUT.