Power Control of Grid-Connected Inverters Using One-Cycle Control Method for PV Systems

In this paper, one-cycle control (OCC) method as an appropriate control scheme is applied and developed to control grid-connected inverters with the LCL filter for VAR compensation and injecting power to the grid. Also, particle swarm optimization (PSO) algorithm is employed to find the optimal LCL filter parameters by minimizing the total harmonic distortion (THD) of AC-side current as a cost function. LCL filters are generally applied in renewable power generation systems to smooth the injected current into the network because of their better attenuation capability and smaller elements than other filters. Although an LCL filter attenuates harmonics created by switches more effectively, due to its inherent resonance, it may cause stability issues. To create stable performance, either an active damping algorithm or a physical damping resistor should be used. However, a physical resistor causes additional power loss and slower dynamic response, while by adding a digital filter as a conventional virtual resistor and modifying the control scheme, the above-mentioned problems could be solved.