Adaptive Damped Circular Current Limit Control for PV-Grid Tied System

Abstract

This paper proposes a double stage PV (Photo-Voltaic)-grid tied three-phase system with higher order passive filter. It gives a solution of some real issues such as power factor improvement, load balancing, compensation harmonics, reduced filter size and power loss in distribution network. The ripple filter is used in the front end of the voltage source converter (VSC) for eliminating the switching harmonics at the point of common coupling (PCC), with very small value of inductor as compared to regular interfacing inductor. The adaptive damped circular current limit control (ADCCL) filter based technique is used for harmonics elimination in a double-stage grid-connected PV system. The maximum power is tracked from a PV array by an incremental conductance (INC) maximum power point tracking (MPPT) algorithm. However, the boost converter is used for extracting the maximum power from the PV array and feeds it to the grid and the input DC voltage of the voltage source converter (VSC) is maintained at desired level by using a proportional integral (PI) controller. The ADCCL control maintains the balanced grid currents, and injects the active power to the grid, eliminates the harmonics current caused by nonlinear unbalanced loads connected at PCC. This system maintains the grid current total harmonic distortion (THD) in accordance to the IEEE 519 standard. For improving the dynamic response, a PV feed-forward term is used. This control improves the power quality as load balancing, power factor correction and good dynamic response. Test results demonstrate reactive power compensation of balanced and unbalanced nonlinear loads. Moreover, a comparison is made with different controls.