Calculating the maximum penetration capacity of distributed generation considering current protection

With significant increasing penetration of the inverter interfaced distributed generations(IIDG), the radial network turns into a multipower-supply network. Working as an additional source, IIDG may increase the total fault level and altering the magnitude and direction of the fault current, which compromise the correct operation of the overcurrent protection system. This paper presents a new method to calculate the optimal allocation of IIDG without any amendment of protection settings, which will make great convenience for operators to review the accessible capacity of IIDG reported by users. Under the consideration of low voltage ride through(LVRT), the method uses iterative correction to figure out the nonlinear relationship between the fault current of IIDG and the fault voltage of the point of common coupling(PCC) in order to get the optimal capacity which meets the constraints of the current protection's selectivity and sensitivity.