PPV extraction through PSS simulation

Recently, I’m studying perturbation projection vector(PPV) based phase noise computation. There are three simulation methods to extract PPV, of which PSS is the fastest and most convenient method. As claimed in the paper titled"A Comparison of Simulation Strategies for Estimating Phase Noise in Oscillators", the PPV vector is automatically calculated during the PSS simulation without any other processing.  I found that there is a “save osc ppv” option in spectre PSS simulation, and I can get the node voltage based PPV through result browser(the results seem odd), whose unit is V-1. My problem is how to get current based PPV  through PSS simulation just like in the aforementioned paper, whose unit is A-1？