Efficient coupling of AC power supply networks

The invention describes a novel high-voltage direct-current (HVDC) transmission clutch unit and a method for coupling at least two AC voltage power supply networks with each other.


HVDC transmission refers (inter alia) to coupling of two or more AC voltage power supply networks. AC power grids can be for instance single-phase or three-phase (rotary current) power grids. For coupling of AC power grids HVDC clutch devices are known, which include controllable inverters coupled via a DC intermediate circuit. However, the coordination of the active and reactive power at the connection points to the AC power supply networks requires a huge regulatory effort. This is especially the case for the independent adjustment of the respective performance in relation to the achievable overall functionality of the system. HVDC systems are usually limited to two-point connections, since (according to conventional methods) the control engineering effort increases significantly with a larger/increased number of coupled AC power grids.

Our Solution

Scientists from the Clausthal University of Technology have developed a HVDC unit and method for coupling at least two AC power grids with each other. The HVDC clutch unit (Fig. 1) has a computing unit (incl. a tailored computer program) as the central component and a DC voltage intermediate circuit. Each of the AC power grids is connected to the DC voltage intermediate circuit via three-phase controllable inverter. The coupling of the AC power supply network to the assigned inverter takes place via throttles. The computing unit is equipped for each of the AC voltage-energy supply networks for calculative simulation of a rotary flywheel mass, such that the speed of the flywheel mass is proportional to the actual frequency of the alternating current voltage-energy supply networks. According to an advantageous embodiment of the invention, the arithmetic unit for one, several or each of the computationally simulated flywheel masses for the computational simulation of a synchronous machine is set up, which contains the computationally simulated flywheel mass. Hence, the behavior of a real synchronous machine is virtually replicated by the mathematically simulated synchronous machine.

CPA 2266 T171 Figure 1Fig. 1: HVDC transmission clutch unit, which couples three AC power grids in the form of three-phase (rotary current) power grids (adapted from patent applications).


  • Computational replication of mechanical coupling between at least two rotating flywheels
  • Improved system damping properties
  • Distribution of the virtual mechanical energy of an overfrequency AC power supply network to a plurality of low-frequency AC power supply networks
  • Coupling of AC power supply networks with different network target frequencies possible
  • Mathematical simulation of a flexible mechanical coupling possible
  • Improvement of transient properties of AC power grids (e.g. dynamic short-circuit power)


  • Coupling and power coordination of mutliple AC power supply networks
  • Control engineering
  • Computational replication of a differential gear and an energy balancing gear

Development Status

The coupling facility/setup and method have been successfully developed and experimentally approved.

Patent Status

German patent applications granted:
Patent holder: Clausthal University of Technology


Dr. Mirza Mackovic
Patent Manager Technology
E-Mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Tel.: +49 551 30724 153
Reference: CPA-2266-T171

Tags: Measurement and analysis technology, Physics and Technology & Software


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