basically there are four types of stabilizer 1) servo voltage stabilizer 2) relay type voltage stabilizer 3) tape change voltage stabilizer 4) static voltage stabilizer these all are stabilizer are used as its application. in servo stabilizer due to low correction speed there will be voltage overshoot and voltage dip and it’s also bulkier and heavy. in relay type stabilize have periodic maintenance due to relay failure. also because of complex wiring and stepped regulation output are not tight regulated step change voltage stabilizer is not so useful in many application. static voltage stabilizer is a static switch based pwm type buck-boost voltage stabilizer which has tight regulation and fast correction speed which is impossible to obtain using conventional methods such as servo voltage stabilizers, scr / triac type stabilizer, relay type stabilizer etc. in this static switch based type static voltage stabilizer only the difference voltage is switched through igbt and will be added or subtracted from the mains. this is done electronically without any step changing in voltage which occurs when the system regulates. this is achieved by a feedback control system using microcontroller.