An Adjustable DC Link Voltage-Based Control of Multifunctional Grid Interfaced Solar PV System

Abstract

This paper presents a grid supported solar energy conversion system with an adjustable dc link voltage for common point of interconnection (CP) voltage variations. A two-stage circuit topology is proposed, wherein the first stage is a boost converter, which serves for maximum power point tracking, and the second stage is a grid tied voltage source converter (VSC), which not only feeds extracted solar photovoltaic (PV) energy into the three-phase distribution system but also serves for harmonics mitigation, reactive power compensation, and grid current balancing. An interweaved double-frequency second-order generalized integrator-based control algorithm is proposed for control of this multifunctional VSC, which possesses the feature of good steady-state performance along with fast dynamic response even under sudden load changes at CPI. Moreover, a feed-forward term for the solar PV contribution is used to enhance the dynamic response for climatic changes and CPI voltage variation. An adjustable dc link voltage structure is used to accommodate CPI voltage variation, which helps in reduction of losses in the power circuit. To implement adjustable dc link voltage structure, the reference dc link voltage is adjusted with variation in CPI voltage in real time. A proportional–integral controller is used to regulate dc link voltage to set reference value. A wide range of experimental results are shown to demonstrate the features of the proposed system. The total harmonic distortion of grid current has been found well under IEEE-519 standard even under nonlinear loads at CPI.