Hot Topic: Average Models for Distributed & Renewable Energy Simulation

Hot Topic: Average Models for Distributed & Renewable Energy Simulation

Average Models for Distributed & Renewable Energy Simulation

Power electronic based distributed energy resources such as wind, PV, fuel cells and energy storage are increasingly being integrated in distribution grid systems. Small simulation time-steps (< 4µsecs) are required to accurately model the high switching frequency transients in modern power converter circuits. Detailed modelling of the switching topology in power electronic converters for renewable generation require increased computation demand and place a limitation on the size of the power system that can be simulated.

For certain applications, such as the design of smart grid /microgrid control systems at the distribution level, the switched topology model of the power converters are not required in the simulation model and can be replaced with dynamic average models.  In the RTDS Distribution Mode, the time-step is increased to allow for modeling large power systems. The increased distribution mode time-step is too large to simulate the high switching frequency transients of converter models. Dynamic models that represent the control dynamics and terminal AC and DC voltage-current relationships with sufficient accuracy and reduced computational resources are required for distribution applications.

Dynamic average value models use circuit elements and dependent sources to represent the voltage and current relationship on the AC and DC sides with the same control circuit as the switched converter model but neglect the firing pulse generation and switching transients. Large simulation time steps and an increased network size can be simulated with reduced computation burden.

Available models for distributed resource simulation with reduced computation burden in the RTDS library are:

  • Figure 1: Dynamic PQ sources provide current injections based on given setpoints
  • Figure 2: Single and Three phase average models to interface DC sources (PV, Battery)
  • Figure 3: Three phase average models to interface AC sources (DFIG, PMSM).
Average Models - Figure 1

Figure 1: Single and Three Phase Injection Model

Average Models - Figure 2

Figure 2: Single and Three Phase Average Models for DC sources.

AverageModels-Figure 3

Figure 3: Three Phase Average Models for AC sources.

The latest average models are available in RSCADv5.003.3 and higher.  A Draft library search using keyword average will display the available components.

For simulation cases using these models, please email support@rtds.com

Author: Onyi Nzimako, April 2018