PLL Parameter Tuning Tool

Problem context

Tuning an SRF-PLL PI controller is often reduced to adjusting Kp and Ki, but closed-loop bandwidth, damping ratio, and phase error also depend on phase voltage magnitude, fundamental frequency, and per-unit base. Experience-only tuning can produce insufficient bandwidth, excessive overshoot, or poor phase tracking, especially when moving between voltage levels such as 690V and 380V.

How it works

The skill uses a second-order linearized model as the calculation basis: it derives wn, zeta, and the bandwidth extension factor C from the open-loop transfer function, then converts the result into practical per-unit PI parameters.

• Forward design: given f_BW_target, together with Unom, f0, and zeta, it computes KPLLp_pu and KPLLi_pu
• Reverse analysis: given existing per-unit PI values, it back-calculates wn, zeta, and actual bandwidth
• Interaction guard: if Unom or direction-specific parameters are missing, it prompts for them instead of silently using defaults

Boundaries

It is intended for engineering estimates and parameter cross-checks, not full nonlinear stability simulation. Results rely on linearized assumptions; strong harmonics, saturation, weak-grid impedance, or frequent switching conditions should still be verified with simulation or measurements.