只是在对另一个问题的评论中找到了它

Just found it in one of the comments to another question

为了将参数传递给$ args，请将null用作参数名称，例如 command.Parameters.Add（null， some value）;

In order to pass arguments to the $args pass null as the parameter name, e.g. command.Parameters.Add(null, "some value");

该脚本称为：

.\MergeDocuments.ps1 1.docx 2.docx merge.docx

这里是完整代码：

class OpenXmlPowerTools
{
    static string SCRIPT_PATH = @"..\MergeDocuments.ps1";

    public static void UsingPowerShell(string[] filesToMerge, string outputFilename)
    {
        // create Powershell runspace
        Runspace runspace = RunspaceFactory.CreateRunspace();
        runspace.Open();

        RunspaceInvoke runSpaceInvoker = new RunspaceInvoke(runspace);
        runSpaceInvoker.Invoke("Set-ExecutionPolicy Unrestricted");

        // create a pipeline and feed it the script text
        Pipeline pipeline = runspace.CreatePipeline();
        Command command = new Command(SCRIPT_PATH);
        foreach (var file in filesToMerge)
        {
            command.Parameters.Add(null, file);
        }
        command.Parameters.Add(null, outputFilename);
        pipeline.Commands.Add(command);

        pipeline.Invoke();
        runspace.Close();
    }
}