An improved Droop Control Strategy for Parallel Three Phase Inverters in weak grid

In weak grids, due to differences in line impedance and non-negligible grid impedance, the control of parallel three-phase inverters employing conventional droop control is incapable of justifiably distributing power in accordance with the droop. When considering efficiency, the system’s dynamic response will be sluggish, and the grid’s synchronization capability will be subpar, among other issues. To address this, a droop control strategy with an adaptive adjustment mechanism is proposed to dynamically adjust the size and nature of the virtual impedance of the inverter according to its capacity, reducing the influence of line impedance. Concurrently, a varied connection is introduced to improve the control system’s dynamic response speed and to quickly address grid disruptions. Simulation results show that the proposed method has fast dynamic response speed and strong stability, which can not only realize the precise control and reasonable distribution of active and reactive power but also cope with sudden load changes and grid faults.