Research On Strategy Of Parallel Control For Distributed Inverters

The control strategy of parallel inverters is crucial and difficult to the Distributed grid connected technology. Distributed inverters operation in parallel can greatly increase the capacity of power supply system; moreover, it can increase the system reliability and flexibility. The redundancy power supply mode can reduce hardware investment of inverter and improve the power density of smart grid. In this context, a detailed research will be carried out on inverter parallel control strategy in this paper.The objective of parallel control is keep output power balance of parallel inverters, that is, current sharing. First this paper build a parallel model and analysis the circulating current Influence factors such as difference magnitude or phase or output impedance of inverter Equivalent model. These researches are the foundation of parallel control strategy.In allusion to the traditional droop control strategy such as droop control, improved droop control or virtual impedance control, this point out the new trend of parallel control and proposed a Parallel Control Strategy of Single-Phase Inverters Based on controllable Virtual Impedance. The strategy adds a current compensation loop and a current feedforward in traditional voltage tracking control method. Output impedance of the inverter can be controlled accurately by design the virtual impedance and dynamic and steady performance can be improved. Moreover, Redesigned output impedance reasonable can achieve power sharing with power rating ratio.On the basis of theoretical analysis, Simulation results are presented to prove the efficiency and feasibility of proposed control strategy. The simulation results show that the proposed control has a good performance on circulating current eliminating and Harmonic restraining. The system has a good dynamic and steady performance with the proposed control strategy.