Single-Phase Cascaded Grid Connected Multilevel Inverter for Interfacing Renewable Energy Sources With Microgrid

Abstract

In this paper, a novel single-phase cascaded grid connected multilevel inverter (MLI) is proposed for feeding power to microgrid from renewable energy sources (RESs). The proposed inverter is capable of feeding power to microgrid with low total harmonic distortion (THD). The proposed inverter consists of two H bridge inverters connected in cascade, namely, upper and lower inverters. The upper inverter is fed from photovoltaic (PV) array through a DC–DC boost converter, whereas the lower inverter is fed from wind turbine (WT) coupled to permanent magnet synchronous generator (PMSG) through an uncontrolled rectifier and DC–DC boost converter. The upper inverter operates at high frequency, whereas the lower inverter operates at fundamental frequency. To extract maximum power from the WT and PV array, a sliding mode control based maximum power point tracker (MPPT) is used. The proposed inverter is connected to the single phase 230 V, 50 Hz grid, and the control algorithm is implemented in the SPARTAN 3A digital signal processor (DSP) board. The proposed inverter is simulated using matlab/simulink, and detailed experimental results are presented to show the efficacy of the proposed inverter under different environmental conditions.

A Novel Asymmetrical Single-Phase Multilevel Inverter Suitable for Hybrid Renewable Energy Sources

“…Hence Maximum Power Point Tracking (MPPT) is essential in PV arrays in order to draw maximum power from it irrespective of the climatic and load conditions [14]. A similar situation exists in Wind Turbine also [5]. Generally DC-DC boost converter is used next to PV module for two main reasons.…”

“…[1]- [4]. The energy generated from RES depends upon the environmental conditions [5] (i.e. energy generated from solar energy conversion system depends upon the solar irradiation and energy generated from wind energy conversion system depends upon the wind speed), whereas the electrical grid requires constant voltage and frequency.…”

“…energy generated from solar energy conversion system depends upon the solar irradiation and energy generated from wind energy conversion system depends upon the wind speed), whereas the electrical grid requires constant voltage and frequency. Hence proper power electronic interface must be provided between the renewable energy and the grid for stable operation [5].…”

“…To improve the harmonic profile of the output voltage of the inverter Multilevel Inverters (MLIs) are suggested in [1]- [5]. MLIs have nearly sinusoidal output voltage and current waveforms with improved harmonic profile, less stress in power electronic switches due to reduced voltages, lower switching losses when compared to conventional three-level inverters, smaller filter size and reduced electromagnetic interference [6].…”

Solar Photovoltaic Fed Three-Phase Multifunctional Converter Operation Using a Nonlinear Control Strategy

“…One significant focus of that study was on increasing the performance of MFCs by the use of nonlinear control techniques and so-called advanced control strategies. Sliding mode controller (SMC) for grid-integrated PV systems was reported in [15][16][17]. SMC has the benefit of being more resistant to external disturbances and parameter uncertainties.…”