Research On Cooperative Control Of Cascaded H-bridge Multilevel Converter

The objective of the thesis is to research an hierarchical cooperative controlstrategy for high-frequency isolated multilevel converter which can work as an interfaceequipment to connect traditional distribution network with micro grid. The workingprinciples of rectifying stage, transmitting stage and inverting stage have been discussed,separately. The mathematical models of them have been established in discretez-domain, as well as the disturbed small-signal model. Hence, the cooperative controlstrategy has been proposed base on the derived models. The cooperative control strategyconsists of three parts, current and voltage regulation based on state feedback in singlephase synchronous frame, voltage balancing modulation based on balanced SOA, andpower balance control without current sensor. Moreover, the parameter design has alsobeen involved, especially for ac-side inductor, dc-link capacitor and high-frequencytransformer leakage inductor. The simulation and experiment have been designed inorder to check the validity of the proposed control strategy.