Multilevel power conditioner for grid-connected photovoltaic applications

Abstract

A novel scheme for three-phase grid-connected photovoltaic (PV) generation systems is presented in this paper. The proposed scheme is based on two insulated strings of PV panels, each one feeding a standard two-level three-phase voltage source inverter (VSI). Inverters are connected to grid by a threephase transformer with the open winding configuration on inverters side. The resulting conversion structure performs as a multilevel power active filter, doubling the power capability of a single VSI with given current rating. An original control method has been introduced to regulate the dc-link voltages of each VSI. The proposed algorithm has been verified by numerical simulations with reference to different operating conditions. The results confirm the effectiveness of the whole conversion structure.

Experimental tests on a multilevel converter for grid-connected photovoltaic systems

“…The control algorithm utilized in this paper is based on simple PI controllers [3], [4]. The problem is somewhat similar to power sharing problem investigated in automotive applications, where proper multilevel voltage modulation strategy has been addressed [9].…”

“…Although it results in steady-state current error it is not a critical drawback since the controlled variable is dc voltage [3], [4]. In particular, the reference voltage * v is here calculated as…”

“…For the dual inverter configuration, total voltage reference must be satisfied, so in case of voltage saturation of one inverter the second has to make up the missing part. This problem is addressed in [4].…”

“…The novel topology for PV grid-connected systems proposed by the Authors in [3], [4] (Fig. 1) has been recently implemented and the experimental results are given in this paper.…”

Grid-connected PV-wind-fuel cell hybrid system employing a supercapacitor bank as storage device to supply a critical DC load

“…From 2000 to now, many works referring grid-connected systems were published [8][9][10][11], relating aspects as power converters design, control strategies, PV and WT maximum power point tracker (MPPT), reactive compensation, active filtering and so on. In addition, important institutions as IEEE and lAS have developed standards and recommendations to guide the designers.…”