Vision converter

The Vision Excel converter converts the Excel exports from Vision to PGM data format. As mentioned in Converters, Vision Excel converter is an implementation of the tabular converter. The default mapping of all attributes is stored in the vision_en.yaml and vision_nl.yaml files in config directory. Custom mapping files are supported via passing the file directory to the constructor of the converter.

Load rate of elements

Certain elements in Vision, i.e., appliances like transformer loads and induction motor have a result parameter of load rate. In Vision, load rates are calculated without considering the simultaneity factors of connected nodes. So we may observe a variation in power inflow/outflow result (i.e., P, Q and S) due to different simultaneity factors. But the load rate always corresponds to simultaneity of loads=1.

When we make conversion to PGM, the input data attributes of PGM for loads like p_specified and q_specified are modified as per simultaneity. The resulting loading then takes simultaneity into account. Hence, the loading of such elements may not correspond to the load rate obtained in Vision

Transformer load modeling

power-grid-model-io converts the transformer load into a individual transformer and a load for usage in power-grid-model. To the best of our knowledge, Vision modeles a transformer load differently than an individual transformer plus load. There is a minor difference in both the reactive power consumed and generated. This might correspond to a minor voltage deviation in the results.

Tip

To avoid this issue, it is recommended to split the transformer load into individual components in Vision beforehand. This can be done by first selecting the transformer loads: [Start | Select | Object -> Element -> Check Transformer load -> Ok], then split it into individual components: [Start | Edit | Topological | Split]

Voltage angle of buses in symmetric power-flow

Note that in symmetrical calculations, Vision does not include clock angles of transformers in the result of voltage angles. power-grid-model, however, does consider them. Therefore when doing a direct comparison of angle results, this needs to be taken into consideration.

Modeling differences or unsupported attributes

Some components are yet to be modeled for conversions because they might not have a straightforward mapping in power-grid-model. Those are listed here.

  • power-grid-model currently does not support PV(Active Power-Voltage) bus and related corresponding features.

  • Currently, the efficiency type of PVs(Photovoltaics) element is also unsupported for all types except the 100% type. For the efficiency type: 0, 1 pu: 93 %; 1 pu: 97 %, the generation power is multiplied by 97% as a closest approximation.

  • The conversions for load behaviors of industry, residential and business are not yet modeled. The load behaviors usually do not create a significant difference in power-flow results for most grids when the voltage at bus is close to 1 pu. Hence, the conversion of the mentioned load behaviors is approximated to be of Constant Power type for the time being.

  • The source bus in power-grid-model is mapped with a source impedance. Sk"nom, R/X and Z0/Z1 are the attributes used in modeling source impedance. In Vision, these attributes are used only for short circuit calculations

  • The load rate for transformer is calculated in Vision by current i.e., load_rate = max(u1 * I1, u2 * I2) * sqrt(3) / Snom * 100. Whereas in power-grid-model, loading is calculated by power, i.e., loading = max(s1,s2)/sn. (Note: The attribute names are as per relevant notation in Vision and PGM respectively). This gives a slight difference in load rate of transformer.

  • A minor difference in results is expected since Vision uses a power mismatch in p.u. as convergence criteria whereas power-grid-model uses voltage mismatch.