New-Password.ps1

 <#
    .SYNOPSIS
        Generate set of passwords
    .DESCRIPTION
        Generate set of passwords based on character usage rules
    .OUTPUTS
        Array of string
    .PARAMETER Length
        The password length
    .PARAMETER Count
        Count of returned passwords
    .PARAMETER Charsets
        Set of characters used for password generation
    .EXAMPLE
        #Generate 8-symbols password
        New-Password
    .EXAMPLE
        #Generate 12-symbols password
        New-Password 12
    .EXAMPLE
        #Generate two 10-symbols passwords
        New-Password 10 2
    .EXAMPLE
        #Generate two 10-symbols passwords with only small and big letters
        New-Password -Length 10 -Count 2 -Charsets 'b','s'
    .LINK
        https://gist.github.com/MVKozlov/5d8accbc7f010e70c0a61cbeef06e4dd
#>
param (
    [Parameter(Mandatory=$False,Position=0)]
    [int]$Length = 8,
    [Parameter(Mandatory=$False,Position=1)]
    [int]$Count = 1,
    [Parameter(Mandatory=$False,Position=2)]
    [ValidateSet('smallLetters','s', 'bigLetters','b', 'Digits','d', 'SpecialChars','p', 'VerySpecialChars','v' )]
    [string[]]$Charsets = @('smallLetters', 'bigLetters', 'Digits', 'SpecialChars')
)
BEGIN {
    $AllChars = @{
        smallLetters = @{
            Probability = 8
            Characters = 'abcdefghijklmnopwrstuvwxyz'
        }
        bigLetters = @{
            Probability = 8
            Characters = 'ABCDEFGHIJKLMNOPWRSTUVWXYZ'
        }
        Digits = @{
            Probability = 8
            Characters = '0123456789'
        }
        SpecialChars = @{
            Probability = 4
            Characters = '!@#$()_+-={[}];''<,>.'
        }
        VerySpecialChars = @{
            Probability = 3
            Characters = '`~%^&*:"\/?|'
        }
    }
    if ($Charsets -contains 's') { $Charsets += 'smallLetters' }
    if ($Charsets -contains 'b') { $Charsets += 'bigLetters' }
    if ($Charsets -contains 'd') { $Charsets += 'Digits' }
    if ($Charsets -contains 'p') { $Charsets += 'SpecialChars' }
    if ($Charsets -contains 'v') { $Charsets += 'VerySpecialChars' }

    $AvailableSets = $AllChars[$Charsets]
    [System.Text.StringBuilder]$CharList = ''
    foreach ($set in $AvailableSets) {
        foreach ($i in (1..$set.Probability)) {
            [void]$CharList.Append($set.Characters)
        }
    }
    $FullCharset = $CharList.ToString();
}

PROCESS {
    foreach ($c in 1..$Count) {
       $s = ''
       foreach ($l in 1..$Length) {
          # Strong random algorithm
          # $RandomBytes = [Byte[]]@(0,0,0,0) # will need 4 random bytes...
          # $RNG = [Security.Cryptography.RNGCryptoServiceProvider]::Create()
          # $RNG.GetBytes($RandomBytes)
          $s += $FullCharset[(Get-Random -Maximum $FullCharset.Length)]
       }
       $s
    }
}