How to suppress grid-interactive resonance in a PCS (Power Storage System)?

Cross-resonance may occur between the PCS and the grid impedance, especially in weak grids or environments with large capacitive loads (such as long cables or reactive power compensation devices), manifesting as harmonic amplification or instability at specific frequencies. Suppression measures include:

1. PCS-side output impedance reshaping: Introducing active damping strategies into the control algorithm, using methods such as virtual impedance to change the phase and amplitude of the PCS's output impedance in the resonant frequency band, thus disrupting the resonance condition.

2. Adding passive damping: Connecting a damping resistor (usually in series with a capacitor to form an RC branch) in series or parallel on the PCS's AC output side directly consumes resonant energy, but introduces additional losses.

3. Optimizing filter parameters: Adjusting the parameters of the output LCL filter to keep its resonant frequency away from the frequency band where cross-resonance may occur (usually the subsynchronous or supersynchronous frequency band).

4. Harmonic injection suppression: After detecting resonance, injecting opposite harmonic currents to cancel it out.

5. Grid-side measures: Optimizing the grid structure, such as adding line reactors. This requires the PCS to have grid impedance identification or wideband control capabilities.