Add voltage transformer component category

Voltage transformers are used to step up or step down the voltage,
keeping the power somewhat constant by increasing or decreasing the
current. If voltage is stepped up, current is stepped down, and vice
versa. Note that voltage transformers have efficiency losses, so the
output power is always less than the input power.

This change allows our API to support voltage transformers. E.g., the
Microgrid API could be extended to support voltage transformers in
component graphs.

Signed-off-by: Tiyash Basu <[email protected]>

Author: tiyash-basu-frequenz

RELEASE_NOTES.md

@@ -14,6 +14,9 @@
 
 - Added a new component category variant: `COMPONENT_CATEGORY_FUSE`.
 
+- Added a new component category variant:
+  `COMPONENT_CATEGORY_VOLTAGE_TRANSFORMER`.
+
 ## Bug Fixes
 
 <!-- Here goes notable bug fixes that are worth a special mention or explanation -->

proto/frequenz/api/common/v1/components.proto

@@ -64,6 +64,14 @@ enum ComponentCategory {
   // A fuse.
   // Fuses are used to protect electrical components from overcurrents.
   COMPONENT_CATEGORY_FUSE = 13;
+
+  // A voltage transformer.
+  // Voltage transformers are used to step up or step down the voltage, keeping
+  // the power somewhat constant by increasing or decreasing the current.
+  // If voltage is stepped up, current is stepped down, and vice versa.
+  // Note that voltage transformers have efficiency losses, so the output power
+  // is always less than the input power.
+  COMPONENT_CATEGORY_VOLTAGE_TRANSFORMER = 14;
 }
 
 // Enumerated battery types.