ACDC-Control – Correction of inter-system errors in hybrid AC/DC transmission systems


Ref.-No. 4638

In the transmission of electrical transmission lines, in which the overhead lines carry both AC and DC cables, special requirements arise for the protection concept. This applies in particular to contact errors between the alternating current and the direct current system.

Depending on the type of fault, it is difficult to detect the respective fault in the AC system in the case of a short circuit between the two systems since the direct current component can be quickly eliminated by the DC system. ACDC control provides a way to detect and interrupt inter-system errors in both networks:

After the fault detection in the DC system, the DC current is first limited by the inverter. The residual current is then regulated to zero by the fault current control of the inverter, while the AC system continues to run. Subsequently, the DC system provides an AC breaking current to the AC system so that the AC system with the existing protection mechanisms can detect the fault and shut down the system. Depending on the type of error, the DC system can also be switched off.

Keywords: Hochspannung, Energieübertragung, Gleichstrom, Gleichstromübertragung, Trasse, Netz, Stromnetz, Kurzschluss, Zwischensystemfehler, High voltage, power, power grid, ac power transmission, electric line, short

Commercial Opportunities

In the transmission of large amounts of energy, high-voltage dc technology has proven to be an advantageous technology and a useful alternative to conventional high-voltage rotary current transmission. However, the approval and construction of new routes is very expensive and time-consuming. Therefore, existing routes should be used for parallel AC and DC transmission so that high voltage transmission towers can carry lines for both transmission modes.

However, this can lead to short circuits between the two systems, which are currently a major challenge. ACDC-Control offers an effective solution that does not require additional hardware. ACDC-Control increases grid security, prevents damage to the grid and reduces downtime.

Competitive Advantages

  • Safe switch off of AC- and DC-grid in cas of inter-system Errors
  • Avoidance of large damage in the electric grid
  • Reduction of downtime

Current Status

A German patent application has been filed, further international patent applications are still possible. On behalf of the RWTH Aachen we offer interested companies the opportunity to licence and further develop the technology.


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