Research On Current-sharing Decoupling Control Strategy Of Inverter Parallel System Based On Output Impedance

With the development of society and economy and the progress of technology, the inverter has been widely used in various industries. To adapt to the requirements of modern power supply equipment for modular, high capacity and high reliability, inverter parallel technology has been researched and developed. This paper studies the inverter waveform control technology which combines dual-loop control and repetitive control, and also studies current-sharing decoupling control strategy of inverter parallel system based on output impedance.Firstly, a state-space averaging inverter mathematical model was established, the dual-loop controller was designed by using pole placement method, on the basis of dual-loop control joined the repetitive control, and the parameters of the composite controller was designed. Then the output impedance of the inverter in open-loop state and closed-loop state was analyzed. Finally, the control strategy to suppress the flux imbalance of transformer was proposed.The parallel system model based on output impedence was established, the characteristic of circulating current and the influence of output impedence on circulating power was analyzed. The coupling relationship between active power, reactive power and amplitude and phase of output voltage was studied. Then the limitations of traditional current-sharing control strategy of the parallel-inverter system was analyzed, and current-sharing decoupling control strategy based on output impedance was proposed. When DC bus voltage of the inverters is not the same, the influence of DC bus voltage difference on active power and reactive power was analyzed. Proved theoretically that current-sharing decoupling control strategy based on output impedance are also applicable to the case when the DC bus voltage is inconsistent.The experimental verification is realized in two three phase inverters. The experiment result verifies control strategy which combines dual-loop control and repetitive control have good dynamic and static performance. Finally, the experimental comparison proved current-sharing decoupling control strategy based on output impedance has better circulating current inhibitory effect than which uses reactive power to regulate voltage magnitude.