Voltage droop in generic DER components

Implementation

The Voltage droop Functionality calculates the Voltage Reference Signal when Droop control mode is activated, based on the reactive power error and specified droop characteristics. It implements a simple control method for droop characteristics defined by a coefficient input value and a nominal DER voltage.

$V_{rms ref droop}= ∆Q*\frac{-V_{droop coeff}}{100}*(V_{rms nom}+V_{droop offset})+V_{rms nom}+ V_{droop offset}$

$\Delta Q= \frac{Q_{meas} - Q_{ref}}{2*Q_{max}}$

The difference between $Q_{meas}$ and $Q_{ref}$ must remain within the range [- $Q_{max}$ , + $Q_{max}$ ]. If the difference exceeds this range, it will be limited to either - $Q_{max}$ or + $Q_{max}$ , as appropriate.

With the coeff value the slope of the droop charachteristics is changed (higher coeff value will lead to the higher slope). Reactive power error is calcluated by subtracting filtered measurement of the reactive power and reference reactive power. Simple first order low pass filter is used for this purpose. Reactive power error is limited with generic DER maximal reactive power.

Parameters and I/O

• Parameters
  • Reactive power measurement low pass filter cut-off frequency (defined with 0.1*generic DER nominal frequency)
  • Output voltage reference limit (defined with DER DC Link voltage)
  • Execution rate (equal to the Slower execution rate of the generic DER component)
• Inputs
  • Reactive power reference
  • Reactive power measurement
  • Voltage droop coefficient
  • Voltage droop enable
  • Droop nominal voltage

• Output
  • RMS Voltage reference value