Research On Injection Type Hybrid Active Power Filter

Harmonic interference problem is becoming increasingly serious as the power electronics-related appliances are widely used in the industrial applications and transmission system. The active power filter (APF) wildly used in 380V power system can suppress harmonic effectively. But limited by low voltage rank of power electronic device and high cost, APF is seldom used in high voltage grids. the concept of injection type hybrid active power filter (IHAPF) shows great promise in reducing harmonics and improving power factor in high voltage grids with a relatively low capacity active power filter ,due to its lack of fundamental wave voltage. Focusing on the project application of IHAPF, some factors of IHAPF were emphatically discussed, such as detection of harmonic signals, control of IHAPF, electromagnetic interference (EMI) and electromagnetic compatibility (EMC) design of equipment.The detection of harmonic and reactive currents is very important to the compensation performance of IHAPF. The i_p-i_q method was researched in this paper. The transfer function of i_p-i_q method was derived from its time domain model using mathematical tools, from which we know that i_p-i_q method is essentially a band stop filter with center frequency in fundamental frequency. The low pass filter in the method is significant to the detection precision and speed. This paper proposed a novel detection filter which used synthetically the Butterworth Filter and the Average low-pass filter.Based on the analysis of IHAPF, the control model of the proposed IHAPF was established. And then the origin and harm of fundamental current circumfluence were discussed. To eliminate fundamental component of the inverter output current, the paper proposed a novel control strategy composed of injection circuit outer control loop and output current of inverter inner control loop. The outer control loop based on the detection of injection current is used to carry out high precision, while the inner control loop based on the detection of APF output current is used to ensure the system security. Simulation and experimental results have shown the proposed control methods can meet the requirement of IHAPF controller and have high precision, good security and stability.EMI and EMC design are key point in the design of power electronic equipment. Firstly, the source of noise was discussed, including turn-off surge voltage of IGBT and free-wheel diode recovery surge. Then, this paper analyzed the differential-mode conduction and common-mode conduction of noise. Finally, some solutions were pointed out, such as suppression of interference, hardware anti-interferences design and software anti-interferences design.Based on the theoretical analysis of IHAPF, the realization scheme of an integrated system based on IHAPF for harmonic current analysis and suppression was proposed which includes design methods of configuration and parameters for the main circuit, the design of controller and monitoring system.