Research On Shunt Active Power Filter Without Harmonic Detection

With a lot of power electronic devices, such as the nonlinear load, widely used in the power system, people’s living improved greatly, while also bring more serious harmonic pollution problem.Active power filter can suppress harmonic and compensate reactive power, is an important means of effective harmonic treatment. LCL-APF, which use LCL filter to achieve both good low frequency and high frequency attenuation, have wide bandwidth of compensation and low content of switching ripples. However, the LCL filter is a three-order system, so it may cause resonance at the resonance frequency point and makes the stability control more difficult. Moreover, the existing research focused on the APF harmonic detection technology, the compensation effect is limited by the detection accuracy.The paper studied the structure of the LCL-APF, and to solve the resonance problem, it gave the damping control method, and achieved the LCL-AFP stable conditions through the analysis on the system stability.Based on the analysis above, the paper proposed parallel type LCL-APF control methods integrating with non-harmonic detection technology. The APF control without harmonic detection, omits the load current detection part and the compensation current detection part, and omits the complex harmonic current calculation, achieves lower cost. Then adopted direct power control strategy to improve the dynamic performance and active power damping loop to overcome the LCL resonance problems, and adopted improved dc-side voltage controller to reduce dc-side voltage fluctuation when the load active power changes.To verify the effectiveness of proposed control strategy, it presented the simulation and result analysis through MATLAB tool. It shows that the proposed method can effectively suppress the harmonic and compensate reactive power, improve power quality.