Research On Power Transformation System Of Tidal Power Station Based On BOOST Converter

As one of the most promising renewable energy, Ocean Tidal Current Energy attracts theworld’s attention. Especially in21st Century, with energy shortage increasingly remarkable,the power generation technology of Tidal Current Energy, which was non-popular ever,became the hot topic researched by scholars worldwide. Compared to wind power system,Tidal had advantages in many aspects which make it superior to other renewable energy.Despite that China has abundant tidal resources with rich deposits according to someinvestigation，the generation technology of it has got far behind developed country. Althoughinstitutions of this renewable energy internal had made much useful exploration on itsgeneration technology in recent years, there was still no report on project schedule put intopractical operation.In this paper, we designed a kind of Ocean Tidal Current Energy Generation Systemconnected to DC Grid with a capacity of50kW, in which the Permanent MagnetSynchronous Generator (PMSG) was directly driven by Hydraulic Turbine in a variablespeed controlling mode, and research on Power Transformation System based on BOOSTCircuit was mainly carried out. Because of tidal current velocity varying with time, therotating speed of generator should be controlled at an optimal value to maximize theefficiency of generation system via regulating the input-current of power convertor connectedto Generator. For the purpose of boosting the output voltage steplessly, Multiple-BOOSTChopper was proposed in this paper for its pretty performance of reducing input currentripple enormously, which make it suitable to regulate the speed of Generator by adjustinginput-current of BOOST Convertor, and thereby it was widely used in renewable energygeneration system.In this paper the basic theory of Tidal Generation System was summarized, includingthe model of Tidal Current, Hydraulic Turbine, PMSG and Triple-BOOST Converter withDiode Rectifier connected to the Generator, therefore principles about variable-speedcontrolling method of the generation system and the process of power transformation wereshow clearly. Next section was firstly about parameter calculation of BOOST Convertor,including capacitors and inductors values of main circuit, model selection of powercomponent and lossless snubber circuit, and grid resistor value of IGBTs, then aiming at theproblem of switching smoothly from variable speed controlling mode by regulating theinput-current of BOOST Convertor when hill-climbing searchinging the Maximum Power Point of the power system to limit the output-voltage when paralleled in the power grid, astrategy called limited-voltage and variable-current controllimg mode was applied in thissystem, and some practical improvements like Current Sharing Technology of inductors andDigutal Moving Average Filter are also given in details. Finally a simulation of the systemwas performed using Matlab/Simulink software, which consists of the emulation of the wholetidal generation system and generation systems paralleled together, and hardware was testedas well, including open loop experiments, current closed-loop experiments with MaximumPower Point Tracking (MPPT) control, parallel connection experiments of BOOSTConverters and combined debugging experiments of the generation system. Both thehardware and software testing results demonstrated better performances. Meanwhile plentifulpractical experiences had also been gained from this experiment, and it made for a goodfoundation for engineering commissioning on site.