The Research On Grid-side Harmonic Current Control For Active Power Filter

Power electronic equipments are widely used in the world, which provide an efficient method for electric energy utilization. However, the power quality problems caused by the nonlinear loads, including the power electronic equipments also become more and more serious, especially the problem of the harmonic pollution. Active power filter (APF) is the popular way to reduce the impact of harmonic pollution, which has gained more and more attention. This thesis carried out studies on grid-side harmonic current control for APF. The major contents and achievements are as follows:In order to solve the dispute relating to the control performance of multiple rotation integrator (MRI) and sine signal integrator (SSI), which are the control methods of harmonic current compensation for APF, the equivalent relationship between the MRI and SSI under the condition of time delay compensation is studied. Moreover, the experiment results support the controllability of the MRI and SSI for the high frequency harmonic current.In practical applications, it is difficult to get the time delay compensation angle for the control of every harmonic current. Therefore, the influence of time delay compensation on the system stability is analyzed in detail. And on this basis, a simple and effective method to get the time delay compensation angle is proposed, which solves the problem to get the time delay compensation angle in real application.A new high-order filter for APF named the inductor-trap-capacitor-inductor (LTCL) filter is proposed, in which multiple LC trap filters are inserted in parallel with the branch of the capacitor in the traditional LCL filter to compose multiple series resonant circuits at the selected frequencies. Particularly, the LTCL filter can attenuate the harmonic currents around the multiples of switching frequencies and guarantee-60dB/decade attenuation in the high-frequency band, leading to a decrease of the total inductance and volume. The basic parameter selection criteria and the parameter design procedure of the LTCL filter are introduced. Moreover, the sensitivity analysis of the LTCL filter is analyzed and discussed in detail. The comparative analysis and discussion considering the LCL filter, the LLCL filter, the multi-tuned traps filter, and the proposed LTCL filter, have been presented and evaluated, which show the superiority of the LTCL filter.On the basis of the above research, the physical experiment platform of the APF is set up. The harmonic current compensation control experiments, the comparative experiments considering different filters and the time delay compensation experiments are performed on the experiment platform. The experimental results validate the theoretical analysis, the effectiveness of the new method to get the time delay compensation angle, and the superiority of the LTCL filter.