Reference arrow system

TwinCAT Power Control uses the generator reference arrow system as shown in the figure below. The generator reference arrow system is also used by the EN standards. In contrast, the VDE standards use the load reference arrow system. This means that all the characteristic curves and parameters listed there can be transferred to the generator reference arrow system for comparison with TwinCAT Power Plant Control.

Sign convention for Q and cos φ in the generator reference arrow system

The following sign convention applies to the reactive power (Q):

• Q > 0: Plant feeds reactive power into the grid
• Q < 0: Plant absorbs reactive power from the grid

As the power factor (cos φ) is by definition unsigned, its sign is derived from the reactive power:

• cos φ > 0: Plant feeds reactive power into the grid (Q > 0)
• cos φ < 0: Plant absorbs reactive power from the grid (Q < 0)