# ANDES xlsx#

The ANDES xlsx format allows one to use Excel for convenient viewing and editing. If you don't have Excel, there are alternatives such as the free and open-source LibreOffice or the non-paid WPS Office.

## Format definition#

The ANDES xlsx format contains multiple workbooks (also known as "sheets") shown as tabs at the bottom. The name of a workbook is a model name, and each workbook contains the parameters of all devices that are instances of the model.

In each sheet, the first row contains the names of parameters of the model. Starting from the second row, each row corresponds to a device instance with the parameters in the corresponding columns. An example of the Bus sheet is shown in the following screenshot.

## Common parameters#

A few columns are used across all models. That includes uid, idx, name and u:

• uid is an unique index that is generated and used internally. This column can be left empty when the sheet is being created manually. Exporting systems to xlsx with --convert (see Format converter) will have the uid overwritten.

• idx is the unique index to identify a device of the model. An unique idx should be provided explicitly for each instance for best consistency. Accepted types for idx include numbers and strings without spaces.

Warning

ANDES will check the uniqueness of idx and assign new ones when duplication is detected. Duplicate idx indicates data inconsistency and will likely cause simulations to fail.

• u is the connectivity status of the instance. Accepted values are 0 for disconnected (turned off) and 1 for connected (turned on). Disconnected devices will still have the variables assigned in ANDES but will not interact with the simulation. Unexpected behaviors may occur if numerical values other than 0 and 1 are assigned, as u is often used as a multiplier in equations.

• name is the name for the device instance. It is used for display purposes and can be left empty.

## Connecting devices#

Most importantly, idx is the unique index for referencing a device, so that it can be properly connected by supported devices. In a system, a PQ (constant PQ load) device needs to connect to a Bus device to inject power. That is, the PQ device needs to indicate the Bus device to which it is connected. Such connection is done in the PQ sheet by setting the bus parameter to the idx of the connected bus.

The screenshot above is from the case file andes/cases/kundur/kundur_fault.xlsx. In this PQ workbook, there are two PQ instances (also known as "devices") called PQ_0 and PQ_1 (referred to by idx). They are connected to buses 7 and 8, respectively. The bus parameter of PQ is konwn as an indexing parameter (andes.core.param.IdxParam) through which the connections are specified. To get the connection actually work, on the Bus sheet, two rows must exist for two bus devices, respectively, with idx being 7 and 8.

To find out the IdxParams of a device for connecting to other devices, refer to Model reference. For example, to find out how a device of the exciter model EXDC2 should be connected to a synchronous generator, in the Parameters section, check the Properties column for mandatory parameters. Almost all IdxParams are mandatory, meaning that they must be specified to build a consistent test case. It can be seen that for EXDC2, syn is mandatory. From the description, one can tell that this is the "Synchronous generator idx", which should be the idx of an existing synchronous generator, i.e., GENROU or GENCLS.

Typically, models of the same group use the same IdxParams to connect to other models. Each link on the left sidebar of Model reference is a group, such as the Exciter group. With this convention, all exciters have a syn parameter for connecting to synchronous generators.

## Creating cases#

It is often easier to modify from existing cases than creating from scratch. We recommend that you get familiar with the cases available with ANDES, see Test Cases.

Adding devices to an existing workbook is straightforward. Navigate to the sheet corresponding to the model and add a new line below the existing lines.

Almost all models have so-called mandatory parameters. They are essential to describe a complete and consistent test case. For example, the PQ model has the bus parameter as mandatory to indicate the connected bus. To look up mandatory parameters, see Model reference or use andes doc MODEL_NAME. Check for "mandatory" in the last column called "Properties". This column also contains other data consistency requirements discussed in the following.

Non-mandatory parameters are optional, meaning that if not provided, ANDES will use the default parameters. The default values can also be found in Model reference. This does not mean that such parameters should always be left blank. For example, the p0 (active power load) of PQ is optional, but likely one wants to set it to a non-zero value.

There are consistency requirements for parameters, such as non_zero, non_negative or non_positive. If unmet, the default values will be used. See the class reference in andes.core.param.NumParam.

## Autofill data#

When you finished adding devices but left some optional parameters empty, you can use ANDES to autofill them. This is useful when you want to populate a large number of devices with the same parameters that can be modified later.

The autofill is done through the data converter, namely, --convert or -c. ANDES will read in the Excel file, fill the optional parameters with default values, fix the inconsistent values, and then export the data back to Excel.

Warning

Please backup the spreadsheet if it contains customized edits. Inconsistent data will be replaced during the conversion. Formatting in the spreadsheet will be lost. Unrecognized sheets will also be discarded.

To autofill kundur_full.xlsx, do

andes run kundur_full.xlsx -c


You will be prompted to confirm the overwrite.

Since this autofill feature utilizes the converter, the autofilled data can be exported to other formats, such as .json. To do so, use -c json.

If one wants to add workbooks for models that does not exist in an xlsx file, one can use --add-book ADD_BOOK (or -b ADD_BOOK), where ADD_BOOK can be a single model name or comma-separated model names (without space). For example,

andes run kundur_full.xlsx -b Fault


will add an empty Fault sheet to kundur_full.xlsx.

Warning

With --add-book, the xlsx file will be overwritten with the same parameter corrections as in the autofill. Please make backups as needed.

Format conversion and workbook addition can be performed together. To convert a PSS/E raw file and a dyr file into an xlsx file and add a workbook for Fault, do

andes run kundur.raw -addfile kundur_full.dyr -c -b Fault


The output will have the same name as the raw file.

## Data Consistency#

Input data needs to have consistent types for idx. Both string and numerical types are allowed for idx, but the original type and the referencing type must be the same. Suppose we have a bus and a connected PQ. The Bus device may use 1 or '1' as its idx, as long as the PQ device uses the same value for its bus parameter.

The ANDES xlsx reader will try to convert data into numerical types when possible. This is especially relevant when the input idx is string literal of numbers, the exported file will have them converted to numbers. The conversion does not affect the consistency of data.

## Parameter Check#

The following parameter checks are applied after converting input values to array:

• Any NaN values will raise a ValueError

• Any inf will be replaced with $$10^{8}$$, and -inf will be replaced with $$-10^{8}$$.