sorry to all.
the shunt active power filter is to minimize harmonics in the source current when feeding a non linear load. so we can provide another load in parallel that would require a current which will make the source current sinusoidal. the so called shunt load comprises of IGBT bridge ckt with a capacitor in the o/p.the actual capacitor voltage is fed to a PI controller along with a reference voltage to generate proportional current. it is then multiplied with the normalized value of phase voltages to get three reference phase currents which are fed to a hysterisis controller to get six pulses for firing the IGBTs. the values of voltage and current are updated rvery time using a closed loop.the PI control will be using a microcontroller and i have no idea about the hysterisis controller. this is a paper whose practical implementation is being done by me on low voltage levels.
lets hope if you can make something out of this info.
i will send u the paper-link in the next reply if u are intrested.
thank you