Power Converters and Control of Grid-Connected Photovoltaic Systems

Abstract

Photovoltaic (PV) installations have had an exponential growth mainly due to the governments and utility companies that support programs that focus on grid-connected PV systems (Haeberlin H (2001) Evolution of inverters for grid-connected PV systems from 1989 to 2000, in Proceedings of the 17th European Photovoltaic Solar Energy Conference, pp. 426–430. Munich). In an effort to use solar energy effectively, a great deal of research has been done on the grid-connected PV generation systems. Out of the total PV power installed in the Europe, 98.7 % are grid-connected PV systems and 1.3 % are off-grid PV systems. Therefore, in grid-connected PV systems, the inverter which converts the output direct current (DC) of the solar modules to alternating current (AC) is receiving increased interest in order to generate power to utility. A key consideration in the design and operation of inverters is how to achieve high efficiency with power output for different power configurations. The requirements for inverter connection include maximum power point, high efficiency, control power injected into the grid, and low total harmonic distortion of the currents injected into the grid. Consequently, the performance of the inverters connected to the grid depends largely on the control strategy applied. Many topologies are used for this purpose.

An overview of power inverter topologies and control structures for grid-connected PV systems are presented. The first section describes the various configurations for grid-connected PV systems and power inverter topologies. The following sections report and present control structures for single-phase and three-phase inverters. Some solutions to control the power injected into the grid and functional structures of each configuration are also proposed.