A decoupled adaptive noise detection based control approach for grid supportive SPV system

Abstract

This paper deals with a three phase multifunctional grid connected SECS (Solar Energy Conversion system). A two stage topology is used in this work, in which the first stage is a boost converter, which serves the purpose of MPPT (Maximum Power Point Tracking) and the second stage is a 4-leg VSC (Voltage Source Converter) which serves the purpose of feeding extracted energy along with power quality improvement in the distribution system. The SECS not only feeds solar PV (Photo-Voltaic) energy into the grid but also serves purpose of grid currents balancing, reactive power compensation, harmonics elimination and neutral current mitigation. A feed-forward term for the solar contribution is used to improve the dynamic response for climatic changes. The PV array voltage is continuously adjusted with the help of boost converter to achieve MPPT whereas the DC link voltage of VSC is kept constant with the help of a PI (Proportional-Integral) controller. Decoupled adaptive noise detection (DAND) based control approach is proposed for control of four-leg VSC. The DAND is a simple approach using two multipliers, one integrator and one summer per phase for detection of useful component of load current. The proposed control algorithm gives features such as simple structure, fast convergence, frequency adaptive detection and good steady state performance. A wide variety of experimental results are shown to prove the feasibility of the concept. The THDs (Total Harmonic Distortion) of the grid currents are found well under IEEE-519 standard (below 5 %) even under nonlinear and unbalanced loads at CPI (Common Point of Interconnection).