Grid interfacing of distributed energy sources by three-level BtB NPC converter under distorted grid voltage

This paper presents complete control algorithm for grid-connected Pulse Width Modulated (PWM) 3-level BtB (back to back) converter intended for industrial drives and renewable energy applications. The objective of control is to limit current harmonics distortion and provide ride through capability during voltage dips. Moreover, Maximum Power Point Tracking (MPPT) and Active Power Feedforward (PF) has been implemented end tested for optimizing energy flow control. Grid Side Converter (GSC) is controlled by Voltage Oriented Control (VOC) supported by synchronization loop with positive sequence extraction, resonant current controllers for higher harmonics compensation, grid voltage feedforward loop for dips compensation and DC voltage filter. At Machine Side Converter (MSC) Direct Torque Control Space Vector Modulated (DTC-SVM) has been used. Algorithm is tested in simulations and experiment from 3kVA up to 15kVA platform using three-level BtB NPC converter with LCL filter. Both controls of GSC and MSC are interacting by Power Feedforward for energy flow optimization between grid and active load.