Hi,I think you'd better present your model here.
As I know,kundert provided model of two domains:1,time domain,to model the transient process of the PLL.
2,phase domain,to simulate the phase noise and its transfer function in the PLL.
The sigma-delta modulation's phase noise is described by a noisetable function.
So we simulate the sigma-delta output phase noise by cadenceRF or matlab,extracted the parameter like bw,n,fc for the noisetable.then we obtain the phase noise by the phase domain model.
Good luck!