Regularized NLMS Control for Power Quality Improvement in Grid-connected PV Systems

Solar photovoltaic (SPV) power generating systems requires a robust and reliable control to perform the multitasking operation under different operating conditions. This paper presents an application of new square-error regularized NLMS (normalized least mean square) algorithm for integrating SPV system to the utility grid. Here, variable step-size regularization is adopted in order to fix the problem associated with fixed regularization including high steady state error and low convergence speed. This adaptive time varying parameter is designed by taking the inverse of weighted square error and implemented to the fundamental weight extraction mechanism for generating the inverter reference current. Subsequently, the proposed control algorithm enables this inverter to perform the multiple objectives including grid current harmonic alleviation, reactive current support, power factor correction and load balancing without affecting their major task of real power injection. Moreover, this control ably regulates the DC-bus voltage within the acceptable limits to maintain good dynamic response under transient conditions. The adopted two-stage grid connected SPV system with proposed control has been modelled using MATLAB/Simulink software for performing simulation study. Further these simulation results are verified through laboratory developed prototype using waijung environment of ARM cortex M4 microcontroller.