Research On Grid-Connected Inverter For Tidal-Current Generator System

With the aggravation of environmental pollution, as well as the increasing depletion of traditional fossil energy sources, the development of new energy becoming a matter of great urgency .The ocean stores a huge energy ,including tidal current energy ,tidal power ,wave power ,and so on .The development of tidal current energy is already quite mature ,a series of sea trials has been fulfilled .The content of this paper is the electric transformation equipment of the total tidal current energy system include the maximum output power of the turbine tracking and the grid connected inverter control.This paper first analyzes the necessity and urgency of tidal current energy development,and then compared the power converter schemes at home and abroad, and from the comparison a scheme is selected .Then the mathematical model of the power converter device is made in order to designing the controller .The controller includes turbine maximum power tracking and grid connected inverter and the inverter control is the focus of this paper.In the tracking of the maximum power of the turbine, using the Boost inductance current loop and climbing on self - optimizing acquisition strategy .Firstly the mathematical model of hydraulic turbine is established,and then combined with MATLAB simulation circuit of Boost on MPPT algorithm simulation, to verify the MPPT strategy.For the control of grid connected inverter ,the inverter modulation techniques is studied ,from the analysis of the advantages and disadvantages of two kinds of modulation technology ,the SVPWM modulation technology was selected .Then the grid phase lock technique of inverter was studied ,The final choice of grid phase lock technique is based on T/4 delay phase locked technology with the advantage of anting unbalanced power grid .And then the power control strategy of the grid connected inverter was made ,the DC bus voltage loop and the grid current and grid voltage with the same phase strategy was selected .Finally the inverter DC bus voltage protection technique and detection of inverter islanding phenomenon was processed.Based on the above theoretical research, the system circuit design was made, including power circuit design and control circuit design. The design of power circuit comprises a three-phase uncontrolled rectifier unit design, Boost circuit design, and circuit design of grid connected inverter, the inverter design is the focus of this article. The control circuit design,including AD sampling design,PWM signal isolation output design and power supply of control system design.In the end the whole system simulation was made, including the turbine, uncontrolled rectifier, inverter system, Boost system ,the power grid .In order to verify the anti-jamming performance of the whole system ,a system simulation was done with the water flow speed uprush and anticlimax ,the results show that the anting disturbance performance of the system is good .Finally the hardware experiment was made ,validated the feasibility of the Boost inductor current closed-loop control, realize the control of grid connected inverter with 10KVA.