Large Capacity Series Hybrid Three-phase Active Power Filter Based On The Fundamental Magnetic Flux Compensation

In this paper, we propose a novel series hybrid three-phase active power filter based on the fundamental magnetic flux compensation after we summarize all kinds of traditional solutions at home and abroad, The characters of the active power filter and its merits compared with other kinds of traditional solutions are presented by the theoretical analysis and experiment results.Firstly, this paper describes the principle of the series hybrid three-phase active power filter based on the fundamental magnetic flux compensation. A series transformer is chosen and its primary winding is connected in series between the power utility and harmonic-producing loads. The fundamental current component of the transformer's primary winding is detected, and a voltage source PWM converter is applied to follow the detected compensating fundamental current so as to produce a compensating fundamental current, which is injected to the secondary winding of the series transformer. When the injected compensating fundamental current and power utility fundamental current component satisfy a specific condition, the main magnetic flux of the series transformer to fundamental can be compensated to zero. And then the proposed active power filter exhibits low impedance at the fundamental frequency and magnetizing impedance to harmonics so that the harmonic currents are forced to flow into the passive filter branches. And in this paper a method to achieve a large volume active power filter is proposed. We use some compensation windings structure in the secondary winding of the series transformer, then the compensating fundamental current is shared averagely in every compensating branch, so the filter achieve a large capacity.After analyzing the operation principle, this paper describes the design method of the control system from the detection of the fundamental current, the current control circuit and the IGBT driver. The principle and circuit of the uni-polar PWM method is given detailedly. Then, a new design method that the IGBT driver module 2SD315A is applied to substitute EXB841 is proposed.A prototype that the active filter has 2 secondary windings is built in Lab, whose rating power is 80kVA .The different experiments are carried out when the load is rectifier, TCR, or dissymmetry load and the experimental results show the active filter is great effect in eliminating harmonic. Experiments show that this active filter has such merits such as low noise, low cost, excellent dynamic response and high control precision. It can be widely applied in the power system.