Active Damping in LCL-Filter Based Three Phase Converter Using Lead-Lag Network and Kalman Filter

Interfacing power converters to the power grid requires an L or LC or LCL filter to reduce the switching frequency ripple. Among the options mentioned above, the LCL filter provides good performance at a lower cost due to the reduced size of used inductors. However, stability problems occur in the converter control system if the present resonance is not decently damped. Damping can be either passive or active. Passive damping inserts a physical resistor to one of the components of the LCL-filter in series or parallel. A simple process yet causes increased power losses and encumbrances. In contrast, active damping is an entire control solution, allowing the system to remain resonance-free without dissipative elements but requiring auxiliary sensors to build feedback loops. The lead-lag network method is one of the most used procedures to incorporate active damping for its feasibility. However, an additional sensor is still required, meaning additional cost and noise are introduced to the system. Thus, this paper uses Kalman Filter to estimate the capacitor voltage to build the lead-lag network damping method. On account of the Kalman filter accuracy and reactivity, it is selected and verified in the following paper. Simulations results of the Kalman-based damping method show similar results as with a sensor.