Stabilization at the DC link: Droop Line control for inverter VP600

A regulation of the voltage level under varying load conditions is essential for an efficient energy management. There is now a clever solution to this technological challenge!

For electrical systems with distributed consumers and energy sources, it is a challenge to main-tain a voltage level under load in the given parameters. This is because the voltage drops – to a varying extent – with every electrical energy source, whether it is a battery, fuel cell, superca-pacitor, or generator. In an efficiency-optimized system, the voltage level must fluctuate within a defined range. However, if the permissible fluctuation range is not adhered to, this means that the consumers in the system either have to be designed for a greater voltage range or they cannot generate their full output. In both cases, the efficiency of the consumers and of the system suffers. In the worst case, the system can break down.


  • Overdimensioning of the energy source(s) → cost factor
  • A higher-level control connected to all energy sources and consumers → complexity
  • Power electronics function for controlling the energy in the system

Technological background

The system becomes more inefficient when a voltage drop occurs, especially due to the increasing loss of electrical resistance, which is the squared value of the current. In other words, when the current doubles, the resistance quadruples. It is therefore ideal for a system to keep the voltage level stable.

To stabilize the voltage in a system with distributed consumers and energy sources – in a so-called DC link – the energy source(s) must always “increase” the voltage and/or the output of the consumers must be reduced when a voltage drop occurs. Since a drive output usually cannot be simply reduced, the stabilization frequently has to occur via the energy sources. In the case of batteries, supercapacitors, and fuel cells, a DC/DC converter is necessary to increase the voltage if needed (e.g., the VECTOPOWER VP5000 product family from ARADEX). For generators, there are inverters/rectifiers from the VP600 product family that can immediately adapt the voltage increase.

Solution with Droop Line technology

For coordination of the individual system components without a central control and additional communication bus, the Droopline concept controls the voltage depending on the required power for energy sources and can limit the power depending on the voltage for consumers. This is exactly what can be configured for the VECTOPOWER DC/DC converters according to the application with the “Droopline-Controlled” function module. It is thus possible to specify a curve on the DC/DC converter that determines what voltage is output at what power, so that the voltage in the DC link does not fall below or exceed your configuration, regardless of the battery, supercapacitor, or fuel cell.

Your advantage

This allows easy energy management via the energy source as well as a stabilized DC link with fixed upper and lower limits, which is the basis for an optimally efficient energy management.

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