cascade of boost converter and an inverter
in the simulation it works fine but not in practice

A simulation uses a (simplified) model of reality. All models are just that, models and models are a simplification of reality. So what you have encountered is some effect which is not modeled but is present in the real world.

Let me name a few of these effects which might not be modelled:


series resistance of wires, PCB, connectors.
Saturation of the transformer.
Higher than simulated on resistance of a transistor .


The engineer's approach now is to measure and simulate to see where the differences are