In my experience, the designer must be careful to fully model the physical characteristics of real LC components (and interconnects!) in the analysis/simulations. One must also follow good grounding and shielding practices (there are many texts). Finally, keep in mind that it is the currents that are going to create noise, particularly uncontrolled return currents. All components must operate efficiently at the power and frequency of the requirements.

Dear Prof, 

   Attached documents will be useful to you to understand the level of harmonic reduction by only using LC filters.

The impedance of a circuit is defined as the frequency domain ratio of the voltage to the current. It represents the opposition that the circuit presents to the flow of sinusoidal current. Admittance is the reciprocal of impedance, that is, it is the ratio of the phasor current to the phasor voltage. The concept of immittance combines the impedance and admittance of a system or circuit. An immittance converter is a four-terminal network in which the input impedance is directly dependent on the admittance of the load at the output terminals. The main characteristic of this converter is that the output current is proportional to the input voltage and the output voltage is proportional to the input current. Therefore, the output current does not depend on the load. This makes the converter ideal/suitable for constant current applications and dynamic load applications. Thereto I support to use π-CLC type and T-LCL configurations in multilevel inverter.

It depends on the number of steps in the multilevel inverter and THD generated in the inverter output. Besides, you need to design your filter based on the required Q (quality)