3-1 Decision of intermediate inductance
The intermediate inductor between the utility voltage and dc link voltage is required because of instantaneous waveform difference This inductor should be designed suitably for better current regulation The decision of the inductance is made by evaluating voltage THD(Vss in Fig 1)
Fig 3 shows the characteristics of the voltage THD for the variance of inductance under the loading condition of 100[%] to 50[%] The vertical axis is the THD and the horizontal axis the inductance It can be seen that THD is effected by the inductance only, and not the loading conditions From these results the inductance can be recommended as about 4 5[mH] in order to maintain the THD value to be lower than 5[%]