A Control Method of Reduced Reactive Power Ripple in Grid-connected Converters under Unbalanced Grid Conditions

Many studies on instantaneous reactive power have been in progress for several decades. The definition of instantaneous reactive power that was first published [1] was widely used for nonlinear load compensation using active power filters. However, conventional theory has limitations in the unbalanced condition of the grid voltage. In the conventional instantaneous reactive power theory, there is a ripple of instantaneous reactive power in a grid unbalanced condition. Currently, since the regulation of FRT (Fault Ride Through) is becoming more important, good quality reactive power compensation is required. So, we defined a new instantaneous reactive power to remove the ripple component of the instantaneous reactive power, and proved that the ripple is removed even in an unbalanced grid conditions by controlling it with the defined instantaneous reactive power. In this paper, a control method for removing the ripple of instantaneous power and instantaneous reactive power is proposed.