By this method, desired current can be injected. Waveform of desired current is given as input as voltage waveform(In this case, sine wave is used). Current band can be changed by double clicking on relay and setting switch on and off point. Difference of desired current(input) and actual current(output) is calculated and IGBT is turned on or off according to value of difference. If difference is greater than 0.1, IGBT1 is turned on(IGBT2 is off). If difference is less than -0.1, IGBT2 is turned on (IGBT1 is off). If difference is between -0.1 and 0.1, then state of IGBT is unchanged i.e it remains in the same state as before (like hold state of flip-flop).
It has application in different current compensating devices such as shunt active power filter, STATCOM etc where desired waveform of current is to be injected.