A new control strategy and compensation method on hybrid system of combining APF with shunt capacitors

Abstract

Aiming at reactive power and harmonic current in the low-voltage distribution grid, a hybrid comprehensive dynamic reactive power and harmonic current compensator is designed. The shunt capacitors compensate the fundamental reactive power, the shunt APF eliminates the harmonics and the small amounts of load reactive power. But when they work in the same electric utility there exists resonance problem, in order to avoid resonance, the compensation character of hybrid compensation device under traditional strategies for current type nonlinear load were well studied theoretically and quantitatively by establishing mathematic model. A new current control strategy, which not only suppress line-side harmonic current and reactive power but also avoid resonance between shunt capacitors and line-side impedance, was put forwards. And a new compensator method which the APF only compensates 1/2 reactive power of each shunt capacitor was provided, due to the APF could compensate both inductive and capacitive reactive power. It lower the capacity of APF, and reduce the cost. Simulation show that the new control strategy and the new compensation method work stable, fleetly and effectively eliminates most harmonics and compensates majority reactive power.