Droop Control Method to Achieve Maximum Power Output of Photovoltaic for Parallel Inverter System

In general, the power distribution of a parallel inverter is achieved by the use of droop control in a microgrid system, which consists of PV inverters and non-regeneration energy source inverters without energy storage devices in an islanded mode. If the shared load power is no more than the available maximum PV inverter output power, then there is a power waste for the PV inverter. In addition, due to the intermittency of PV sources, the system may become unstable if the shared load power is more than the available maximum power output of the PV (MPO-PV) inverter. Therefore, in order to avoid power waste and potential instability caused by insufficient PV power by traditional droop control, this paper recommends an improved droop control scheme to maximize the power output of PV units. As required by the load, the remaining power is composed of the other inverters, which can effectively improve the utilization rating of renewable energy sources and system stability. At the same time, according to the system stability analysis based on small signal modeling, it has been designed around the droop coefficients of the improved droop control loop. In the end, the simulation and experimental results show that the suggested scheme has a varied validity and robustness.