Fault Ride Through Control Of Magnetic Gear Integrated Wave Power Generation System

With the development of society and economy,the energy shortage and environmental problems are getting worse.Wave energy has the advantages of large reserves,high density,clean and predictable.Making full use of wave energy is of positive significance to relieve energy crisis and realize the long-term development goal of renewable energy.According to the distributed generation grid codes,the wave power system is required to have fault ride through control to guarantee the safe and stable operation of the power system.Therefore,the fault ride through control of magnetic gear integrated wave power generation system is mainly researched and explored.Specifically,a coordinative low voltage ride through control strategy for the grid low voltage fault and a fault current limitation control in the case of multiple inverters in parallel are proposed.The main research work and achievements are shown as follows:(1)The basic structure of the magnetic gear integrated wave power generation system is studied.And the structure and mathematical model of the float-type wave energy converter,the magnetic gear integrated permanent magnet synchronous generator,and the full power converter are analyzed in depth.(2)Combining the characteristic of the wave and the float-type wave energy converter,the zero d-axis current control is adopted to achieve generator-side rectifier energy tracking control and generator rotor energy storage control during grid lowvoltage faults.The supercapacitor energy storage system is studied,and the bidirectional DC-DC converter is used to store or release unbalanced power.At the same time,the reactive power injection control of grid-side converter is studied to support the reactive power during the faults.(3)According to the power deviation characteristic of each link of the magnetic gear integrated wave power generation system during the grid low-voltage fault,a coordinative low voltage ride through control is proposed to help the system to coordinate the machine-side converter,grid-side converter and supercapacitor energy storage system,so as to improve the low voltage ride through performance of the wave power generation system.(4)Aiming at the short circuit faults in a wave power generation array field or multi-inverter system,a fault ride through control strategy based on fault current limitation is proposed.The inverter amplitude and phase angle of each distributed generation unit are changed through common coupling point voltage regulation control and fault current limitation conditions to limit the current amplitude at the fault point.Finally,simulation and d SPACE hardware in the loop experiments test and verify the feasibility of the control.