Transient Stability: Load Distributed Generation Model

Added in Version 19

For more detail on specific models, see the Transient Stability Block Diagram PDF document. This help topic describes the general behavior of these models.

Each load has information related to the amount of distributed generation associated with this load. The NetMW is then the subtraction of TotalLoadMW - DistMW and same for Mvar as described in the help topic on Load Modeling. The Load Distributed Generation Model is then the transient stability model that defines the behavior of this distributed generation. The Load Characteristic models apply to the TotalLoad, while the Load Distributed Generation Model applies to the DistMW and DistMvar.

Determining which Distributed Generation Model to Use

Load Distributed Generation Models may be applied to either a load, Load Model Group, bus, owner, zone, area, or the entire system. During the simulation, a particular load record will use a the following priority when determining what to use as the distributed generation model in the stability simulation. In addition the DistGenMVABase is specified as described here.

TSDistGenMVABase numbers for a Load, LoadModelGroup, Bus, Owner, Zone, and Area were added in Version 20, Build on March 23, 2018

If a load-specific model exist, this will be used
Else if the Load is assigned to a Load Model Group which has a model, this will be used (along with the Load object's TSDistGenMVABase *see exception below)
Else if a bus-specific model exists at the terminal bus, this will be used (along with the Bus object's TSDistGenMVABase *see exception below)
Else if an owner-specific model exists for the load's owner, this will be used (along with the Owner object's TSDistGenMVABase *see exception below)
Else if an zone-specific model exists for the load's zone, this will be used (along with the Zone object's TSDistGenMVABase *see exception below)
Else if an area-specific model exists for the area's zone, this will be used (along with the Area object's TSDistGenMVABase *see exception below)
Else if an system-specific model exists for the power system, this will be used (the entire case does not have a default TSDistGenMVABase as this wouldn't make sense anyway)
Else the distributed generation will be lumped in with the load and obey the load characteristic model assigned.

Exception: if the Load object's TSDistGenMVABase <> 0, that value will always be used directly even if the distribution generation model is obtained from one of the aggregation objects of a Load Model Group, bus, owner, zone, area.

Coordination of Initialization with Distribution Equivalent

When used in combination with a distribution equivalent model, then the MW and Mvar portion of the distributed generation will be translated directly to the load bus (after the transformer and the feeder). The impact of the losses in the distribution equivalent will all be applied to the portion of the load assigned the load characteristic model.

Consider the example below. Presently it takes the “NetMW +jNewMvar” as the P and Q taken from the initial condition of the power flow case seen at the transmission bus. It then goes through a process of translating this P+jQ across a transformer and feeder and ultimately there is a “Pnew + jQnew” seen at the Load Bus. This Pnew+jQnew is then applied to the load model parameters. (We’re leaving out some details here related to the Fb term and initializing motors, but this is the general idea).

When including the distributed generation model portion, then this same process will occur, but the portion of the load representing distributed generation would translate directly to the load bus, so you’d translate the “Pdg + jQdg” directly to the distributed generation model down at the end of the distribution equivalent. The load amounts then are processed by the load characteristic models in the same manner as with any load characteristic with the amount of MW and Mvar would be modified to “(Pnew+ Pdg) + j (Qnew+ Qdg)”. This is described visually as follows.