ChangeADPWD.ps1

$domain          = "mydomain"
$adminUsername    = "someadmin"
$adminPassword    = "password"
$targetAccount   = "targetAccount"
$newPassword     = "NewPassword123"

$path          = "LDAP://$domain"
$searchAccount = "(sAMAccountName=$targetAccount)"

# Run via admin account
Write-Output "Changing password..."
$Root   = New-Object System.DirectoryServices.DirectoryEntry $path, $adminUsername, $adminPassword
$Search = New-Object System.DirectoryServices.DirectorySearcher $Root, $searchAccount
$Match  = $Search.FindOne()
$Entry  = $Match.GetDirectoryEntry()
$Entry.UsePropertyCache = $true
$passwordObject = @($newPassword)
$Entry.Invoke("SetPassword", $passwordObject)
Write-Output "Done"