Design And Implementation Of Under Frequency Load Shedding In The Isolated Grid

With the growing scale of production, many enterprises choose to invest in the construction of their own power plant in order to keep a secure and reliable power supply. The way of isolated grid disconnected from power grid will be adapted, specially when it is in failure or under maintenance. Meanwhile, this vulnerable mode render the system of Under Frequency Load Shedding which can restrain the decline of isolated grid frequency very essential.The frequency characteristic and the load type have been analyzed in this paper. With the combination of the principle of Under Frequency Load Shedding and actual operation of isolated grid, this paper eventually presents the design method of Under Frequency Load Shedding system, which postulate many kind of shortage states in isolated grid by basic rounds as priority and accessional rounds as supplement, set operating value of the installation of Under Frequency Load Shedding in advance and remove default load in reasonable order, which can gradually balance the effective power and recover the frequency. This method is justified by related standards and easy to calculate and adjust.The UNISLAN DCAP-3066D network-disconnecting divice is used as hardware implementation in this method. Connect the loads to the network-disconnecting divice, and set the parameters in it. When the frequency is abnormal, the device is removed according to the preset value, to maintain the stability of the isolated grid.The test of simulating model by using Matlab/Simulink shows that the design presented in this paper can effectively recover the frequency that descending in isolated grid to the operable range, in case of occurrence of over-disconnecting and system concussion, which also shows the great value of practical application of this method.