Grid-connected power electronic devices, such asvoltage-source inverters (VSIs), are increasingly installed in thegrid for the utilization of renewable energy sources. Under highpenetration, the weak grid contains ple...Grid-connected power electronic devices, such asvoltage-source inverters (VSIs), are increasingly installed in thegrid for the utilization of renewable energy sources. Under highpenetration, the weak grid contains plentiful harmonics and complexgrid impedance values, which have deep impacts on systemstability as well as its control performance. Online impedancemeasurement is needed for impedance based adaptive controland analysis. This paper proposes a variable carrier frequencyPWM (VCFPWM) based online grid impedance measurementtechnology. This method broadens the available working rangein the high frequency band without increasing the low bandperturbations. Through good analysis and design of the carrierfrequency, the VCFPWM method injects sufficient harmonicenergy at specified high frequency points and guarantees lowTHDs at the same time. The detailed design considerations ofthe carrier frequency are clarified and the characteristics of theVCFPWM based excitations are analyzed in this paper. Finally,the simulation and experimental results based on a three-phasegrid-connected VSI are presented to verify the effectiveness ofthe proposed method.展开更多
文摘Grid-connected power electronic devices, such asvoltage-source inverters (VSIs), are increasingly installed in thegrid for the utilization of renewable energy sources. Under highpenetration, the weak grid contains plentiful harmonics and complexgrid impedance values, which have deep impacts on systemstability as well as its control performance. Online impedancemeasurement is needed for impedance based adaptive controland analysis. This paper proposes a variable carrier frequencyPWM (VCFPWM) based online grid impedance measurementtechnology. This method broadens the available working rangein the high frequency band without increasing the low bandperturbations. Through good analysis and design of the carrierfrequency, the VCFPWM method injects sufficient harmonicenergy at specified high frequency points and guarantees lowTHDs at the same time. The detailed design considerations ofthe carrier frequency are clarified and the characteristics of theVCFPWM based excitations are analyzed in this paper. Finally,the simulation and experimental results based on a three-phasegrid-connected VSI are presented to verify the effectiveness ofthe proposed method.
