Research On Multi-module-inverter Parallel Based On Common DC-Bus

With the development of high-power UPS,motor-driven and distributed generation of renewable energy,the parallel operation of inverters has became more and more widespread.Inverter parallel,to achieve high power,has an advantage of expansion,achieving redundant design,and being convenient to produce and install.In this paper,multi-inverter module parallel system circulation and balance control problems are studied.First of all,the developing status and trends of inverter parallel technology at home and abroad are introduced summarized,analyzing and comparing the advantages and disadvantages of various control strategies.Secondly,the mathematical model of three-phase inverter in three-phase stationary coordinate system,two-phase stationary coordinate system and two-phase synchronous rotating coordinate system is analyzed.Based on the model of inverter in two-phase synchronous rotating coordinate system,a double-closed-loop control strategy,current inner loop and voltage outer loop,is established.And the filter parameters and controller parameters of the inverter are designed.And the simulation results have been presented to prove the effectiveness of the double-closed-loop control strategy.Then,the equivalent model,circulating current,instantaneous active and reactive power calculation of inverter parallel system are analyzed.Furthermore,the droop characteristics under different impedances are analyzed.The simulation results show that the parallel operation of two inverters is validated.Finally,the experimental platform of two 30kVA/380V inverters parallel system were built,developing the monitoring software.The parallel operation of two inverters was verified.