| In view of circulating current, high harmonic in output voltage of stand-alone parallelwind/PV hybrid generation system used at present, the series wind/PV hybrid generationsystem is proposed. All inverters used CPS-SPWM modulation of many wind/PVgeneration units is cascaded in AC side. The output of system is multi-level voltage wave.The structure, control principle of output inverters of system are given in the thesis.The differences in harmonic in output voltage and influence of fluctuation of DC side onoutput voltage between parallel wind/PV hybrid generation system and series wind/PVhybrid generation system are analyzed. Results show that harmonic in output voltage ofseries generation system is lower than parallel generation system, and so is influence offluctuation of DC side on output voltage. These are because the output voltage of seriesgeneration system is combined by output voltage of all inverters.With reasonable approximation, series generation system is equivalent to simplesingle power supply transmission system. The differences in output power and outputvoltage between series generation system and simple infinite system are analyzed. On thisbasis, the voltage stability of system is analyzed by using maximum power method and thecalculation method of load power limitation and critical point is given. The load powerlimitation and critical point are changing following wind speed and light intensity. Somestrengthening measures such as adding compensation unit to closed-loop control of outputvoltage, increasing generation power and formulating reasonable rules of energymanagement are proposed to hold load voltage, elevate load power limitation and enhancecontrol ability of system.The circuit of5units series inverter is built, and output of system is eleven levelsvoltage wave. Result shows that wave quality of series system is better than parallel system,and voltage of DC side of series system is lower in the case of equal output voltage. |
PDF Full Text Request