Analysis and Simulation of Passive and
Active Damping Control of Resonances in
Parallel Gird Connected Inverters
Shah zaman
Power Electronics and Renewable Energy Research Center
Xi’an Jiaotong University
Content
Introduction
LCL filter resonance
Damping(Passive, Active)
Current/Power sharing control
Simulation results
Conclusion
Introduction
L Filter(high switching frequency)
Adv: Smooth the current injected in gird.
Disadv: Bulky and costly passive filters,require high switching
frequencies to acceptably attenuate switching harmonics
LCL filters(low switching frequency)
Adv: Better ripple and harmonic attenuation over higher frequency
Disadv: Zero or very low impedance , inferring resonance(close loop
instability).
Complicate current control design.
LCL filter resonances
LCL filter inherent resonance
LCL filter will filter off high frequency. However, with the
mechanical topology, it could not filter off the resonant frequency, or
even amplify it.
Parallel resonance
The internal current distortion will lead to parallel resonance.
Impedance at resonance is high.
Series resonance
External interference and injected distortion will lead to series resonance.
The impedance at the resonance islow.
Passive and active damping
Passive damping (resistor in series with capacitor)
Adv: Effectively smooth the gird current.
Disadv: Higher losses, down grade second order system
Active damping(feedback other control variables to current loop)
Adv: No power losses
Disadv: Requires additional current and voltage sensors.
Both are found to be incapable of achieving high efficiency and simplicity
simultaneously, despite improvement in stability
