Power Balance Control Strategy For Distributed Input-series-output-parallel Connected Inverter System

Input-series output-parallel (ISOP) inverter system, in which multiple inverter modules areconnected in series at the input side and parallel at the output side. It is very suitable for high inputvoltage and high output current power conversion applications. The key issue of researching ISOPinverter system is to guarantee input voltage sharing (IVS) and output current sharing (OCS) amongthe constituent modules in order to achieve power balance, and adopting distributed control to realizefully modularity is another important control objective. This paper researches input voltage sharingand output current sharing control strategies for ISOP inverter system under distributed controlarchitecture, and guarantees power balance among the constituent modules and at the same timeachieves fully modularity of the system.First of all, this paper describes input terminal and output terminal control strategies for ISOPinverter system, then presents the compound control strategy which can realize power balance at bothinput and output terminals——namely controls input voltage sharing at the input side andsimultaneously controls inductor current phase angle the same or inductor current amplitude the sameat the output side. In the meanwhile, to realize the fully modularity, a new solution dedicated todistributed configuration is proposed. Only three buses, namely output voltage reference synchronousbus, input voltage sharing bus and average current bus are adopted to communicate among themodules of the system. Then this paper describes the two control strategies with the concept ofcompound control and the specific implementations. One of two approaches is IVS control combinedwith the same inductor current phase angle and the other is IVS control combined with the sameinductor current amplitude. Phasor diagrams and simulation results are presented to verify theeffectiveness of the proposed two different control methods. Then the decoupling analysis of moduleinput voltage sharing loop and output voltage loop are presented, and the control loop design of thetwo loops are also discussed in detail.On the basis of theoretical analysis, an ISOP inverter system which consists of two invertermodules is fabricated, experimental results are presented to verify the effectiveness and validity of theproposed two different control methods, and also verify the effectiveness of the proposed distributedconfiguration at the same time, namely illustrates that the proposed control scheme achieves the twocontrol objectives (power balance and fully modularity) effectively.