Evaluating and handling parameter variation influence on status estimation of LCL filter for grid connected inverters

Distributed renewable energy generations bring to attention the grid-connected inverter with LCL filter, whose control performance can be largely influenced by filter parameter variations. This paper has proposed a “comprehensive-loop-search, pattern-recognition, key-parameter-scan” method to evaluate the parameter variation influence, especially grid-side inductance and filter capacitance variation, on model-based full status estimation of the inverter using LCL filter. By certain patterns in the result of searching comprehensive parameters mismatch influences, it is found out that each state variable is mainly affected by a single corresponding filter parameter. Such single parameter influence is then studied in detail, it is demonstrated that choosing smaller value of the parameter in observer can result in lower observation error in larger parameter variation range. Based on the findings, grid-connected filter with LCL filter can be controlled using a single sensor while providing adaption for parameter variation, which could reduce the overall cost of the inverter. The proposed parameter selection strategy is validated by experimental results in both transients and steady states.