Contingency Element Type: Injection Group

 

The following describes the options available when creating a contingency element of type Injection Group. Contingency elements are created from the Contingency Element Dialog, and additional details of how to create contingency elements can be found here.

 

Action Settings

Open

The Open action will set the Status of all generators and loads in the selected injection group to Open if the Status is Closed. If the Status is already Open, this action does nothing. If the injection group contains other injection groups, the Status of the generators and loads in the other injection groups will also be set to Open.

When using the Open action, the Make-up Power Sources button is enabled and power sources can be specified to account for real power changes due to the status changes of generators and loads in the contingency action.

The Number Elements option is available to open a specified number of elements in the injection group. The Amount fields will be available to specify the number. Elements will be opened in the order of highest participation factor to lowest. The Status of generators, loads, and switched shunts in the injection group will be set to Open if the Status is Closed. If the Status is already Open, no changes are made to an element.

Open Breakers

See the special topic on Open Breakers for more detail.

Close

The Close action will set the Status of all generators and loads in the selected injection group to Closed if the Status is Open. If the Status is already Closed, this action does nothing. If the injection group contains other injection groups, the Status of the generators and loads in the other injection groups will also be set to Closed.

When using the Close action, the Make-up Power Sources button is enabled and power sources can be specified to account for real power changes due to the status changes of generators and loads in the contingency action.

Added in version 20

The Number Elements option is available to close a specified number of elements in the injection group. The Amount fields will be available to specify the number. Elements will be closed in the order of highest participation factor to lowest. The Status of generators, loads, and switched shunts in the injection group will be set to Closed if the Status is Open. If the Status is already Closed, no changes are made to an element.

Close Breakers

See the Close Breakers for Contingencies topic on the Contingency Element Dialog topic.

Set To

The Set To action will set the real power injection of the injection group to the specified Amount. If loads are included in the injection group, the Mvar load will be adjusted by keeping the power factor constant. The injection can be set in Percent or MW. When setting the injection in Percent, the real power injection is set to the specified percent of the contingency reference state real power injection. The real power injection of the injection group is determined by taking the difference between the total generator MW and total load MW in the injection group. When setting the injection in MW, the real power injection is set to the specified amount.

Scale Order Modified in version 19, build on May 3, 2016

This option determines how the participation points within the injection group will be adjusted to implement the desired action. The following choices are available:

Proportional

All online generators and loads in the injection group with non-zero participation factors are adjusted according to their relative participation factors to meet the desired injection.

Merit Order

Generators and loads will be adjusted in order of highest relative participation factor to lowest with each generator and load in the list being adjusted until it hits either its maximum or minimum MW limit before moving on to the next element. This process continues until the desired injection is met. Mvar load will be adjusted by keeping a constant power factor.

Generators will not be opened in this process, which means all online generators will continue to provide Mvar support.  Loads that have both their minimum and maximum MW limits set to zero will not be allowed to increase. They can only decrease to 0 MW.

Merit Order Open

If this option is chosen and the MW injection being requested is lower (change is negative) than the existing MW injection of the injection group, the merit order dispatch will be modified by only opening generators. (Note: PowerWorld's expectation is that the Change By option would most frequently be used with this option.) In this case, the generator in the injection group with the highest participation factor will have its status changed to Open, followed by the second generator and so on. If the MW injection being requested is higher (change is positive) than the existing MW injection of the injection group, the merit order dispatch will be modified by opening loads. In this case, the load in the injection group with the highest participation factor will have its status changed to Open, followed by the second load and so on.

If the MW output requested is higher (change is positive) than the present MW injection, and there are no loads in the injection group, generators will be increased toward their maximum MW output as though the Merit Order option was chosen. If the MW injection requested is lower (change is negative) than the present MW injection, and there are no generators in the injection group, loads will be increased toward their maximum MW output as though the Merit Order option was chosen.

When an injection group contains another injection group, the entire contained injection group will be opened when it is encountered based on its participation factor.

 

When opening in merit order there are two options used to specify how this is done:

Do Not Exceed Amount - This will open generators or loads until the amount of MW opened is as close to the desired amount as possible but has not exceeded the desired amount of change. If opening an element will cause the amount of MW opened to exceed the desired amount, that element will be skipped and the next one in merit order will be examined.

Allow to Exceed Amount - This will open generators or loads until the amount of MW opened is equal to or greater than the desired amount.

Best Fit Open Added in version 20

When using this option, typically only generators or loads will be opened, but not both. Which types of objects are opened depends on the direction of change for the MW injection being requested. If this option is chosen and the MW injection being requested is lower (change is negative) than the existing MW injection of the injection group, typically only generators will be opened to achieve the change. If the MW injection being requested is higher (change is positive) than the existing MW injection of the injection group, typically only loads will be opened to achieve the change. Atypical opening of generators or loads would occur if they are operating at negative output.

Participation factors do not impact which objects are opened. All generators or loads defined with the injection group can participate if they are online. Specifically which generators or loads open depends on an algorithm that attempts to get the actual injection change within 5% of the desired injection change by opening the smallest number of generators or loads. If Allow to Exceed Amount is used, the action will attempt to achieve an injection change that is above the desired change, but within 5%. If Do Not Exceed Amount is used, the action will attempt to achieve an injection change that is below the desired change, but within 5%.

When an injection group contains another injection group, the injection impact of the entire injection group is taken into account in the best fit algorithm. The entire injection group will be opened if needed.

Modified in version 22, build on May 26, 2021

The algorithm attempts to find the smallest number of devices that can meet the desired amount. The more devices there are to consider the more time it takes to determine all of the possible combinations. If there are more than 20 devices (2^20 = 1,048,572 combinations), the devices will be sorted from high to low impact and examined in blocks of 20. If the entire 20 devices are needed to meet the desired amount all will be opened and then the next block of 20 devices will be used to meet the remaining amount. This process continues until it is not necessary that a set of 20 devices are all required to meet the remaining amount. This block will use the combination algorithm to fine tune which devices are opened.

 

When using the Set To action, the Make-up Power Sources button is enabled and power sources can be specified to account for real power changes due to the status changes of generators and loads in the contingency action.

Change By

The Change By action will change the real power injection of the injection group to the specified Amount. If loads are included in the injection group, the Mvar load will be adjusted by keeping the power factor constant. The injection can be set in Percent, MW, or MW Effect. When setting the injection in Percent, the real power injection is set to the specified percent of the contingency reference state real power injection. The real power injection of the injection group is determined by taking the difference between the total generator MW and total load MW in the injection group. When setting the injection in MW, the real power injection is set to the specified amount.

MW Effect option was added in Version 19

When choosing the MW Effect option, the Scale Order option Best Fit Open is automatically checked. The value that is specified with the action will be the desired MW Effect that the action should have. The participation factors defined with the Injection Group will be interpreted as effectiveness factors akin to transfer distribution factors. These factors are supplied as input by the user when defining the injection group. The effectiveness factors are multiplied by the present output of generators (or loads) in the injection group to determine how much effect they will have if dropped. If the effect is in the opposite direction of the desired effect, that object will be skipped. The action will find the smallest number of generator (or loads) to drop that results in a total MW Effect that is within 5% of the desired MW Effect. If the option is picked to Allow to Exceed Amount then the action will attempt to achieve a MW effect that is above the value specified, but within 5%. If the option is picked to Do Not Exceed Amount, then the action will attempt to achieve a MW effect that is below the value specified, but within 5%.

 

Scale Order Modified in version 19, build on May 3, 2016

This option determines how the participation points within the injection group will be adjusted to implement the desired action. The following choices are available:

Proportional

Same as Set To section.

Merit Order

Same as Set To section.

Merit Order Open

Same as Set To section.

Best Fit Open

Same as Set To section for changing in MW or Percent. This option could only be used with MW Effect in Version 19, but it is available with Percent, MW, and MW Effect in in Version 20.

 

When using the Change By action, the Make-up Power Sources button is enabled and power sources can be specified to account for real power changes due to the status changes of generators and loads in the contingency action.

Evaluate Part Points in Reference State

When using an action that requires participation factors, this option can be used to indicate that participation factors should be determined in the contingency reference state. This will only be done for participation points using having an Initial Value that indicates the factor should be dynamically determined and the AutoCalc field is set to YES for the participation point. See the participation point records topic for more information on these settings.

 

Accounting for Generation Drop Overlapping

Injection group actions can be used to implement remedial action schemes (RAS). These schemes can be made up of generation drop scenarios in which the same generators can be part of one or more RAS. Too much generation might be dropped if the amount of overlapping generation is not accounted for. If using either the Set To or Change By action type and using the options for Merit Order Open, overlapping of generators is accounted for unless the option Disable Gen Drop Overlap is checked. When accounting for overlapping generators, generators that have already been dropped will be included in the total of generation that is dropped for a particular injection group, which will prevent that injection group from exceeding the desired amount of generation drop.

As an example assume that Injection Group A and Injection Group B are both using Generator 1 that is online at 100 MW. Injection Group A action occurs first and needs to drop 500 MW. As part of this action, Generator 1 drops 100 MW and the remaining 400 MW is made up from other generators in Injection Group A. Injection Group B action occurs next and needs to drop 300 MW. When using the gen overlap accounting, the 100 MW that has already been dropped by Generator 1 is included in the total drop for Injection Group B. This means that Injection Group B only needs to drop an additional 200 MW from other generators. By accounting for the overlap, Injection Group B does not exceed its total desired gen drop. If we were not accounting for the overlap, Injection Group B would drop 300 MW from generators in addition to Generator 1. This would mean that the total gen drop for Injection Group B is 400 MW.

When accounting for overlapping generators, the What Occurred results will indicate how much gen overlap was encountered during the contingency for each injection group action. There are also two fields that are available with contingency records that give information about how much gen dropped occurred during a contingency. The Dropped Gen field indicates the total amount of MW generation that was dropped by injection groups using the specific option settings required for the accounting of gen drop overlap. The Overlap Gen field indicates how much MW overlap was found when dropping generation from injection groups using the specific option settings required for the accounting of gen drop overlap.

Modified in version 24

When using the Best Fit Open Scale Order option, generators that have already been dropped due to other injection group actions will be included if the impact of dropping the generator is in the same direction as specified by the Amount of the action. The Amount will be adjusted to include the impact of generation that has already been dropped, and the Best Fit algorithm will be applied on this adjusted amount. When determining if a change is close enough to the desired amount, 5% of the original Amount will be used as the tolerance.