Researchs On The Power Convertion System Of Tidal Generation

Under different tidal current velocity, the speed of hydraulic turbine is different. Theelectric power of generator output, which range of voltage and frequency is wide, can’t usedirectly. Project requirement is that electric power feed into DC grid, and that the power needisolate between generator and DC grid.In order to solve above problems, this thesis designs a new topological structure ofelectrical conversion system which contains two parts: PWM rectifier circuit andphase-shifted full-bridge circuit. The PWM rectifier circuit makes the generator achieves aunity power factor and output a sinusoidal current; the phase-shifted full-bridge circuit withhigh-frequency transformer can realize the isolation and soft-switching, making the powerloss lower and electrical conversion achieves reliability operation.Overall closed loop control strategy is proposed in this paper, the top level adopts PWMrectifier circuit by the current and voltage double closed-loop. The last level adopts the currentclosed loop. The power will be fed into the DC grid by the current forms. For the top levelchanging wide problems, the thesis design an adaptive software phase-locked loop, whichlocked phase accurate under positive-negative rotating of the generator and imbalance ofvoltage. In view of the previous algorithm of SVPWM, the new algorithm is improved,making it simple, doing not need coordinate transformation, being not dependent on the DCvoltage, and reducing the amount of calculation significantly. For LCL filter circuit, resonantpeak of AC is no inhibition to interference, the thesis puts forward the virtual impedancecontrol links, which improve the filtering effect of issues in the LCL filter circuit.The thesis calculated the PWM rectifier circuit AC side inductor, DC side capacitor andthe phase-shift full-bridge circuit of each parameter, and determined the devices type. Inorder to achieve the independent drive circuit and control circuit designed the drive circuitand control circuit board, and respectively select ST company STM32F407IGT6chip ascontrol chip. The thesis designed the signal conditioning circuit, protection circuit,communication interface circuit, etc. Finally the thesis separately designed PWM rectifiercircuit and phase-shift full-bridge circuit closed-loop controller and the correspondingimproved algorithm of the software.The results of the circuit simulation verify that the components parameters, controlalgorithm and control strategy are correct and effective.The thesis construct electrical energy conversion system device of tidal generation electricity, and do a number of experiment. The results of experiment verify the effectivenessof topological structure in the paper, the correctness of the improved algorithm and thecomponents parameters, and the reliability of the control strategy.