Wireless-control Strategy For Parallel Operation Of Three Phase Inverters In Distributed Generation Systems

With the rapid development of new energy generation technologies, the researchof inverter parallel technologies used in distributed generation systems or microgridare getting more and more attention. The wireless-control strategy for paralleloperation of distributed-generation inverters included, whose control algorithms useonly locally measured variables, and doesn’t depend on the communication linksbetween each inverter, is preferably suitable for distributed generation systems inwhicn the inverters can be located far apart. However the characteristics of theconventional droop method is affected by the system impedance of the parallelinverters system, and it can’t achieve efficient power sharing for the case of a systemwith complex impedance condition.In this paper, the parallel opertaion strategy of three-phase inverters used indistributed generation systems without communication links between each other wasthe recearch content. The mathematical model of the three-phase inverter wasanalysed, the parameters of the three-phase inverter’s voltage and current doubleclosed-loop feedback controller was designed. A novel droop controller that considersthe impact of the complex impedance was proposed, and it can allow efficient powersharing with low sensitivity to unbalances in the line impedance, includinginductive ,resistive, or complex situation. The complex impedance controller of theparallel inverter system was designed, and a small signal model of the system ispresented to investigate the stability and the transient response of the system. TheMATLAB/Simulink software was ued to confirm that the proposed controllerachieves better sharing performance than the classical method. The load switchingsimulation and the inverters’Hot-swappable simulation confirmed that the parallelinverter system had a good stability and transient reponse.Finally, the experimental platform with three 2KW three-phase inverterprototypes was designed, the digital signal processor TMS320F2812 of the TIcompany was used as the control chip, the C language program of the DSP wasfinished, the experiment of the parallel operation of the three-phase inverter wascompleted, the experiment results verified the validity of the proposed control method.