It is useful that you break the circuit in several parts. For example, you can only simulate transformer and get the results. If the results are expected ones, (such as output voltage ratio is equal to turn ratio) then complete the whole circuit step by step.
Although I do not know what you do specifically, I take the content of my undergraduate graduation design as an example you can use as a reference. My undergraduate work is to use prediction theory to design a permanent magnet synchronous motor control system, the basic core control is to design the expected IGBT control signal so as to achieve the control effect. The basic core control is to design the expected IGBT control signal to achieve the control effect. It is mainly to control the frequency of sinusoidal current at a certain power, combined with the predictive control link and PWM link to produce a specific motor drive current. The summary is the frequency as the core in my example.