Performance Improvement of Current Controller in Grid-Tie Solar Inverter Using Parameter Estimation

Abstract

Current tracking performance of grid-connected solar inverter suffers from inaccurate estimation of system parameters that are used in the grid-side current control. Inaccuracy in estimated wire/cable resistance and inductance that are used in the current controller results in phase and magnitude error in the grid current developing non-unity power factor of operation. This situation is highly undesirable and increases the grid current magnitude unnecessarily at a given power level. In order to keep the grid current minimum in magnitude and enhance control stability, the current controller needs to get system parameters updated in real time. This paper proposes a simple and excellent parameter autotuning technique capable of correcting inaccurately estimated parameters. An extensive SIMULINK based simulation has been carried out to verify the performance of the proposed technique and demonstrate the efficacy of restoration of unity power factor operation when it is implemented.