A Systematic Approach to Design High-Order Phase-Locked Loops

A basic approach to improve the performance of phase-locked loop (PLL) under adverse grid condition is to incorporate a first-order low-pass filter (LPF) into its control loop. The first-order LPF, however, has a limited ability to suppress grid disturbances. A natural thought to further improve the disturbance rejection capability of PLL is to use high order LPFs, resulting in high order PLLs. Application of high order LPFs, however, results in high order PLLs, which rather complicates the PLL analysis and design procedure. To overcome this challenge, a systematic method to design high order PLLs is presented in this letter. The suggested approach has a general theme, which means it can be applied to design the PLL control parameters regardless of the order of in-loop LPF. The effectiveness of suggested design method is confirmed through different design cases.