Research On The Three-Phase Inverters In Parallel Without Interconnection Based On Virtual Impedance Control

In order to obtain huge capability and redundancy power supply, improves the power supply agility and stability, paralleling operation of multi-inverters was an effective way. Compared to other methods of parallel inverters, the scheme without control interconnection has a lot of merits, such as fewer interconnections, the stronger anti-interference and easy expansion, it is studied more and more nowadays.In this paper, the paralleling operation of three-phase inverters was the research content, the mathematical model of a three-phase inverter was analyzed, controller parameters of double closed loop of voltage and current were designed to make the inverter for resistive output impedance, to reduce the coupling of active power and reactive power affected by the output impedance; Small signal model of paralleling system based on droop control were established, and a design method of the drop coefficient based on a small signal model was given; Emphasized on the problem of output current can't sharing caused by the difference of device parameters and attachment impedance in the system of parallel inverters, an improved control strategy on the basis of conventional droop method: introducing a virtual impedance ring of inductor current instantaneous feedback regulation at the reference voltage was proposed, the theoretical analysis and the simulation of MATLAB has been proofed that the loop effectively improved the characteristic of current sharing and stability of the parallel system.Three prototypes were designed, and the result of experiment verified that the method of control and parameter design involved in this paper is effective and can be implicated.