The story

I got a new game on Steam and got set to downloading it.
For some reason, Steam and Windows have decided that it's better to save some electricity and put my computer to sleep, rather than finish my game.
Today I discovered that instead of playing my game I have to wait for it to finish downloading.
This will be the last time.

Context

I wrote a post about sleep. Basically, sleep is a middle ground between saving power (by turning off components) and staying ready to work in short notice (by keeping RAM alive).
Some programs can tell Windows "I'm doing something, don't sleep now.". This can be your media player playing a movie, or your BitTorrent client downloading something.
These "requests" can be shown using powercfg -requests (as admin). This is an example of my Steam client behaving and asking Windows to keep awake:

C:\Windows\system32>powercfg -requests
DISPLAY:
None.

SYSTEM:
[PROCESS] \Device\HarddiskVolume2\Program Files (x86)\Steam\Steam.exe

AWAYMODE:
None.

EXECUTION:
None.

PERFBOOST:
None.

The Solution

What I want to do is write a PowerShell script that does this request from Windows, waits for the user and then terminates. I wanted this as a PS script because it means there is no compilation involved, so people that can't code can see what's going on and run it without installing weird stuff on their system.
The API I found for this is SetThreadExecutionState, which can be used like this.
I had my work practically done by Stefan Stranger in SuspendPowerPlan.ps1, to which I added a "main" behaviour like here that defaults to running the method doing nothing.

# ---------------------------------------------------
# Script: C:\Users\stefstr\Documents\GitHub\PowerShell\Examples\SuspendPowerPlan.ps1
# Version: 0.1
# Author: Stefan Stranger
# Date: 07/05/2014 15:01:57
# Description: Helper Function to Suspend Power Plan when running PowerShell scripts
# Comments:
# Disclamer: This Sample Code is provided for the purpose of illustration only and is not intended to be used in a production environment.
# ---------------------------------------------------


<#
.Synopsis
   Function to suspend your current Power Plan settings when running a PowerShell script.
.DESCRIPTION
   Function to suspend your current Power Plan settings when running a PowerShell script.
   Scenario: When downloading files using Robocopy from PowerShell you don't want your
   laptop to go into sleep mode.
.EXAMPLE
   Suspend-PowerPlan -script c:\scripts\mylongrunningscript.ps1
   Run mylongrunningscript with sleep idle timeout prevented
.EXAMPLE
   Suspend-Powerplan -script c:\scripts\mylongrunningscript.ps1 -option Display -Verbose
   Run mylongrunningscript with Display idle timeout prevented and verbose messages
.LINK
  http://www.microsofttranslator.com/bv.aspx?from=ru&to=en&a=http%3A%2F%2Fsocial.technet.microsoft.com%2FForums%2Fen-US%2F1f4754cb-37bf-4e1d-a59f-ec0f1aaf9d1c%2Fsetthreadexecutionstate-powershell%3FThread%3A1f4754cb-37bf-4e1d-a59f-ec0f1aaf9d1c%3DMicrosoft.Forums.Data.Models.Discussion%26ThreadViewModel%3A1f4754cb-37bf-4e1d-a59f-ec0f1aaf9d1c%3DMicrosoft.Forums.CachedViewModels.ThreadPageViewModel%26forum%3Dscrlangru
#>
function Suspend-Powerplan
{
    [CmdletBinding()]
    [Alias()]
    [OutputType([int])]
    Param
    (
        # Param1 help description
        [Parameter(Mandatory=$true,
                   Position=0)]
        $script,
        [ValidateSet("Away","Display","System")]
        [string]$option

    )

    $code=@' 
[DllImport("kernel32.dll", CharSet = CharSet.Auto,SetLastError = true)]
  public static extern void SetThreadExecutionState(uint esFlags);
'@

    $ste = Add-Type -memberDefinition $code -name System -namespace Win32 -passThru 
    $ES_CONTINUOUS = [uint32]"0x80000000" #Requests that the other EXECUTION_STATE flags set remain in effect until SetThreadExecutionState is called again with the ES_CONTINUOUS flag set and one of the other EXECUTION_STATE flags cleared.
    $ES_AWAYMODE_REQUIRED = [uint32]"0x00000040" #Requests Away Mode to be enabled.
    $ES_DISPLAY_REQUIRED = [uint32]"0x00000002" #Requests display availability (display idle timeout is prevented).
    $ES_SYSTEM_REQUIRED = [uint32]"0x00000001" #Requests system availability (sleep idle timeout is prevented).

    Switch ($option)
    {
      "Away" {$setting = $ES_AWAYMODE_REQUIRED}
      "Display" {$setting = $ES_DISPLAY_REQUIRED}
      "System" {$setting = $ES_SYSTEM_REQUIRED}
      Default {$setting = $ES_SYSTEM_REQUIRED}

    }

    Write-Verbose "Power Plan suspended with option: $option"

    $ste::SetThreadExecutionState($ES_CONTINUOUS -bor $setting)


    #do something
    Write-Verbose "Executing $script"

    &$script

    Write-Verbose "Power Plan suspension ended"
    $ste::SetThreadExecutionState($ES_CONTINUOUS)


}

# __main__
if (MyInvocation.InvocationName -ne '.') {
    Suspend-Powerplan {Read-Host 'press enter to terminate'}
}

When taking another look in powercfg -requests after running the script, we can see it in action:

C:\Windows\system32>powercfg -requests
DISPLAY:
None.

SYSTEM:
[PROCESS] \Device\HarddiskVolume2\Program Files (x86)\Steam\Steam.exe
[PROCESS] \Device\HarddiskVolume2\Windows\System32\WindowsPowerShell\v1.0\powershell.exe

AWAYMODE:
None.

EXECUTION:
None.

PERFBOOST:
None.

Let me know if it works / breaks!