How can the multi-stage filtering topology of a PCS (Power Control System) in an energy storage system avoid resonance?

PCS employs multi-stage filtering topologies, such as LC-LC structures, which can improve high-frequency attenuation. However, improper impedance matching between stages can easily lead to resonance at specific frequencies, amplifying noise. The core strategies to avoid resonance are impedance mismatch and the introduction of damping. Specific methods include:

1. Parameter mismatch design: Creating a gap between the cutoff frequencies of the preceding and following filter stages. One stage primarily handles low to mid-frequency frequencies, while the other targets high frequencies, preventing both stages from having simultaneously low impedances.

2. Adding damping resistors: Connecting a resistor in parallel with the filter inductor or a small resistor in series with the filter capacitor branch dissipates resonance energy and flattens the filter's impedance curve.

3. Optimizing interconnections: Shortening the connection lines between two filter stages reduces the impact of parasitic inductance.

4. Simulation assistance: Performing AC impedance sweep analysis during the design phase to pre-identify and adjust parameter combinations that may cause resonance.