H_? Robust Control Method Research On AC/DC Interface Converter In AC/DC Hybrid Micogrid

The performance of the control strategy of bi-directional AC/DC converter affect the stability of hybrid AC/DC microgrid system. Since there are some uncertainties in the bidirectional converter modeling, as well as the reasons like equipment component aging during operation, the risks of stability and security in the control system will appear. When there is a certain amount of disturbance, parameter perturbation, model uncertainty, H_? robust control method can still ensure control performance and improve the robustness of the system. Therefore, study on robust control of AC/DC hybrid microgrid is of significant importance.Firstly, this paper analyzes the structure and operational characteristics of hybrid AC/DC microgrid and AC/DC interface bi-directional AC/DC converter. In DC microgrid, the voltage is an important indicator reflecting active power balance. Therefore, the voltage stability control is taken as control target of bi-directional AC /DC converter. Based on the research on H_? robust control theory and its standard problems, this paper mainly analyzes the track issues and mixed sensitivity optimization problems. Photovoltaic grid connected problem is converted into H_? robust control tracking. Suppose the grid voltage Us is interference term to simplify the controller design difficulty. Making use of advantage of H_? robust control, which has a strong ability to suppress disturbances, grid connected PV control with strong anti-interference is achieved. On this basis, H_? robust voltage control of ac/dc interface based on mixed sensitivity in ac/dc hybrid micogrid is proposed. The S/R/T mixed sensitivity function built in this paper improves the nominal performance of the ac/dc interface for resisting ac disturbance and dc disturbance, and enhances its robust performance of parameter perturbation. Similarly, taking AC system voltage Us as interference term, and using park transformation to convert the periodic signal into the DC signal, phase tracking ability of the control system is improved. Simulation results show that H_? control theory for robust control in interface bidirectional AC/DC converter of AC/DC microgrid is feasible.