NTPOAPI.H

The public symbol file NTKRPAMP.PDB for the original release of Windows 10 tells that the kernel is built with the NTPOAPI.H header at

d:\th.public.fre\ddk\inc

and draws from it the following type definitions:

Line Number Type
1409 enum _SYSTEM_POWER_STATE
1422 enum POWER_ACTION
1434 enum _DEVICE_POWER_STATE
1449 enum _USER_ACTIVITY_PRESENCE
1461 union _POWER_STATE
1466 enum _POWER_STATE_TYPE
1472 struct _SYSTEM_POWER_STATE_CONTEXT
1564 enum _POWER_REQUEST_TYPE
1805 enum SYSTEM_POWER_CONDITION
1920 struct BATTERY_REPORTING_SCALE
2399 struct POWER_ACTION_POLICY
2436 struct SYSTEM_POWER_LEVEL
2451 struct _SYSTEM_POWER_POLICY
2511 struct PROCESSOR_IDLESTATE_INFO
2518 struct PROCESSOR_IDLESTATE_POLICY
2520 unnamed union Flags in PROCESSOR_IDLESTATE_POLICY
2589 struct PROCESSOR_PERFSTATE_POLICY
2596 unnamed union Flags in PROCESSOR_PERFSTATE_POLICY
2705 struct SYSTEM_POWER_CAPABILITIES
2916 enum _REQUESTER_TYPE
2936 struct _DIAGNOSTIC_BUFFER

The header NTPOAPI.H has long been supplied with the publicly available Device Driver Kit (DDK) and Windows Driver Kit (WDK).