How to run a PowerShell script from C# as non-elevated user

I'm trying to run a PowerShell script from a C# application and I need the script to run when my C# app is running as a non-admin user (e.g. Network Service or some other domain account).

Previously, I was using the following code:

using (RunspaceInvoke invoker = new RunspaceInvoke())
{
    // load the powershell module
    invoker.Invoke("Import-Module MyModule");

    // run the cmdlet defined in the module 
    invoker.Invoke("MyCmdlet");
}

I don't know whether this is the best approach for running cmdlets defined in a module (please teach me if there's a better way!). In any case, this works perfectly if I'm running as an administrative user. I tried running this as Network Service, however, and I got an unfriendly error in the constructor of RunspaceInvoke:

Requested registry access is not allowed.

Is there a way I can run my PowerShell cmdlets as a non-elevated user such as Network Service? I do not need or desire to access the registry. The cmdlet itself also does not require elevated privileges.