Just use the module name as power port name. (As it will be PS1/PS2)

module-types/HPE/720478-B21.yaml

@@ -6,6 +6,6 @@ description: 500W Flex Slot Power Supply Kit for ProLiant G9
 weight: 1
 weight_unit: kg
 power-ports:
-  - name: PS{module}
+  - name: '{module}'
     type: iec-60320-c14
     maximum_draw: 500