Rapid energy storage in machine drives results in lower total cost of ownership

Many drivetrains of machines make back-and-forth motions, generating oscillating power on the drive shaft. To avoid unwanted high speed variations in the drive shaft and/or unwanted energy flows between machine and network, a rapid energy storage system must be added to the machine.

This can be done using

  • mechanical energy storage (flywheels, springs)
  • electrical storage (capacities and coils combined with a passive rectifier)
  • magnetic spring storage

The important thing here is to come to a selection or a combination of different types of energy storage that results in the lowest possible total cost of ownership, both in terms of energy storage and in terms of the cost of the required machine parts.

This selection depends on the operational requirements that the machine must meet:

  • mechanical requirements: e.g. requirements set to the motion profile of the drive shaft and to the life span of the storage technology
  • economic requirements: e.g. the allowable pollution caused by the machine on the electricity grid

Considering the mutual differences between machines and their corresponding requirements, it is not always obvious to establish the best possible technology and the way in which to design it. Besides, a given choice also has an impact on the other components of the drivetrain such as the motor and motor electronics. As a result, machine designers often select the energy storage method based on experience, which does not always result in optimal solutions.

Model-based design tool

Together with its partners, Flanders Make developed a model-based design tool for selecting and designing the energy technology and for selecting the suitable other components of the drivetrain (motor, motor electronics). By drawing up a mechanical and electrical machine model and defining the corresponding machine requirements, different architectures can be rapidly assessed. The design tool makes use of a comprehensive library of the component and cost models of the various drivetrain components to be optimised. Based on these models, the design tool will minimise the total cost of ownership of the drivetrain and automatically optimise its various components. Click here for more information on this project.

Experimental validation

A weaving machine makes several back-and-forth motions. Flanders Make validated the developed model-based design tool for the specific batten motions of a Picanol weaving machine. The oscillating power of the batten motions should cause only limited variations in the speed of the drive shaft so as to avoid negative effects on the quality of the fabric. Apart from this, requirements are set to the power quality of the weaving machine and the machine must be able to start and stop sufficiently fast. As a result, the mere use of flywheels as storage technology will not suffice.

To be able to rapidly assess potential energy storage architectures, Flanders Make and its partners developed modular test systems for the different storage technology types.

  • Using switches, a (sub)set of 3 coils of a coil box for the passive rectifier of the machine can be switched.
  • Similarly, we have a capacity box to which a (sub)set of 6 capacities can be added as energy buffer to the DC bus of the passive rectifier (PFE or Passive Front End).
  • In addition, the passive rectifier can also be replaced by an active rectifier (AFE or Active Front End), which allows to further improve the power quality.
  • Finally, 3 different flywheels can be attached to the machine.

With an NI rapid prototyping measuring system using current and voltage sensors, the impact of each architecture on the power quality is analysed. This rapid prototyping system is also used to check the drive motor of the machine. Below, you’ll find an overview of this set-up.

For validation purposes, the model-based design tool was applied onto a given set of operating conditions for the weaving machine. To this end, we designed a web-based tool, which calculates the power quality for a given mechanical load profile and electrical configuration. This resulted in an optimised solution, which is then compared with the actual machine measurements.

The web-based design tool is freely available. The active rectifier, modular capacity box and modular coil box can be easily connected to most machines so as to rapidly assess their impact on the power quality using the NI measuring system and, subsequently, make improvements.

Watch the video on the use of an active rectifier for energy management with an oscillating load.

Testimonies from our partners

"Our weaving machines make different back-and-forth motions, generating an oscillating power in the machine", says Dimitri Coemelck of Picanol Group. “Thanks to the model-based design tool that was developed in the research project, we can now rapidly select and dimension the best possible storage technology. As a result, the energy that is released by the oscillating motions can be used in our newest generation of weaving machines in the most cost-effective way."

Steven Thielemans of NV Michel Van de Wiele also stresses the added value of the newly developed tools:

"The models and model-based design tool result in a better design of the storage technology that is used in our weaving machines, taking into account the requirements and conditions of the electricity grid. The models that have been developed help us to better assess the life span and performances of the electrical configuration of our machines."

Finally, Piet Vanassche of Triphase NV adds the following:

"The improved control of an active rectifier for energy management in the event of an oscillating load, as developed in this project, allows to improve the performance of the active rectifier and, at the same time, downsize the rectifier itself. This offers extra opportunities for the application of our system in machines with oscillating loads."

Conclusion

The research cooperation between academic and industrial partners has led to a model-based approach for the optimal selection and design of the rapid energy storage system in a machine’s drivetrain. All building blocks are available to apply this approach to other machines with oscillating motions. Furthermore, these improved architectures can also be rapidly assessed using modular test systems.
 

Apply rapid energy storage to lower your TCO?

Davy Maes - Senior Project Manager
Author

Davy Maes - Senior Project Manager

Davy Maes is a senior project manager at Flanders Make. Davy holds an MSc in electronics and software. After his graduation, Davy worked for 10 years in various R&D departments within the semiconductor and consumer electronics business. He joined Flanders Make in 2011, where he is leading research projects on model-based systems engineering and energy efficient system design.

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