Distorted and unbalanced systems compensation within instantaneous reactive power framework

p-q theory has been widely used to control active power filters since its formulation in 1983. The compensation strategy used by the p-q theory has not suffered modification; so it used the constant power compensation strategy. In this way, the supply instantaneous power after compensation is constant. This kind of compensation strategy presents good results in the case of balanced and sinusoidal voltages; however, it is not appropriate in the case of unbalanced or nonsinusoidal voltages. This paper extends the p-q theory to get control strategies which allow to attack the unity power factor compensation or the balanced and sinusoidal currents compensation.