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 users has not suffered modification; so it is used the constant power compensation strategy. In this way, the supply instantaneous power after compensation is constant. This kind of compensation strategy has obtained good results in the case of balanced and sinusoidal voltages, however it has not been appropriate in the case of unbalanced or non

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... al voltages. In this paper it has been researched about the modifications necessary, into the p-q theory frame, to get control strategies which allow to attack the unit power factor compensation or the balanced and sinusoidal currents compensation.