Multilevel DC-Link Inverter and Control Algorithm to Overcome the PV Partial Shading

Abstract

This letter presents for the first time the application of multilevel dc-link inverter to overcome the problem of partial shading of individual photovoltaic (PV) sources which are connected in series. The "PV permutation algorithm," as a new method, is developed for the control of the inverter so as to extract the maximum power form each PV source under partial shading and to deliver all that power to the load. The algorithm is based on combination of the direct pulsewidth modulation, the sequential permutation PV sources, and the output generation to control the multilevel dc-link inverter. The algorithm is applied successfully to a seven-level inverter with separate maximum power point tracking algorithm for each PV source and under nonuniform irradiance (partial shading). Digital processing unit F28335 eZdsp is used to control the PV system in the real-time mode, and MATLAB-Simulink real-time data exchange is employed to display the extracted power and to control the system parameters via a designed graphical user interface window. The implementation and experimental results are presented.Index Terms-Maximum power point tracking (MPPT), multilevel inverter, photovoltaic partial shading, real-time data exchange (RTDX).

An application of multi-level DC-link converter for optimised permutation control of PV sources under partial shading

“…Unlike the basic algorithm [5], the improved algorithm does not represent the PV source at the output if its offset voltage is zero, except in the case when all offset voltages are zero. The reason for introducing this exception is to initiate the control and it is also required in the case of low PWM reference signals.…”

“…To compare the improved algorithm with its precursor [5], the Fast Fourier Transformation (FFT) is applied to the output waveform to find the voltage spectrum and the total harmonics distortion (THD) which is calculated for the first thousand harmonics. The waveforms were simulated for the five and seven-level DC-link converters operating in the PV system with parameters given in Table 3.…”

“…The experimental results showed that the total achieved power was delivered completely to the load, but it has not been shown if all PV sources operated at individual maximum power point (MPP). In [5], the principles of controlling a multi-level DC-link converter through a novel algorithm based on the permutation of PV sources, is presented. The algorithm ensures that all PV sources of the string operate at their individual MPP under non-uniform irradiance.…”

Optimal control of a multilevel DC-link converter photovoltaic system for maximum power generation

“…An initial investigation [11] has demonstrated the basic converter topology and control concept. It has been shown that the scheme allows flexible control of each PV source to make it operating at its respective MPP corresponding to its light level.…”

Hardware Implementation of Solar based Boost to SEPIC Converter Fed Nine Level Inverter System

“…For this, a new modulation method is proposed to achieve dynamic capacitor voltage balance. In [21], a multilevel DC-link inverter is presented to overcome the problem of partial shading of individual photovoltaic sources that are connected in series. The DC bus of a full-bridge inverter is configured by several individual DC blocks, where each DC block is composed of a solar cell, a power electronic switch, and a diode.…”