The Study on Svpwm Modulation and Grid Connection Control of Four-wire Three-level Inverter
|Course||Motor and electrical|
|Keywords||three phase four wire three-level converter 3DSVPWM DSP FPGA LCLfiter|
Nowadays,improving the energy structure and developing new energy sources hasbecome the development trend of energy industry in China. The grid-connected inverter isthe core of the new energy system. In order to solve the The problems which high powerand high voltage level bring, the multi-level grid-connected inverter came into being.Three-leg three-phase four-wire multi-leve inverters become a hotspot of the three phasefour wire system restarch for it’s simple structure and excellent control with zero-sequencevoltage. This thesis focuses on the space vector PWM modulation(SVPWM) of Three-legthree-phase four-wire three-leve inverter and the grid-connected conrtol strategy base onthe inverter with an LCL fiter.After comparing the advantages and disadvantages of three main multi-level inverters,the diode clamped four-wire three-level inverter has been choosed as the main circuittopology in this thesis. An improved three-dimensional space vector PWMmodulation(3DSVPWM) algorithm bases on abc coordinate has been proposed. Theproposed algorithm is simpler and easilier for digital application. DSP and FPGA has beenchoosed as the master chip, the grid connected control algorithm is realized by DSP andthe modulation strategy is implemented by FPGA. The two complement each other toenhance the system operational speed, so the real-time, accuracy and reliability of thesystem are ensured.In addition, the mathmetical modle and several main current control strategies of thegrid-connected converter with a LCL fiter has been analysed in this thesis. Finally, theclosed-loop control strategy of the grid side current has been choosed.In order to verify the correctness of the control strategy, a three-phase four-wirethree-level grid connected inverter experimental platform has been bulit, and some relatedexperiments was implemented on the platform.