Research On Key Techniques Of Multi-Module-Type Active Power Filtering

The pollution of Low-Voltage and High-Current harmonic source broadly exists in the power grid. These hannonic sources, such as steel rolling, aluminum electrolyzing and market lighting, have a strong impact on reliability of the grid and electric equipment. Compared to the many disadvantages of passive filters, active filters are highly controllable, quickly responding and can timely and precisely compensate the grid harmonics, which makes it the most effective technical means of solving power quality problems. With the growing number of electric equipment, high current hannonic sources of pollution gradually become a critical factor of threatening grid security and stability. In recent years, the technology of suppressing this harmonic has become the development direction and research hotspot. While stand-alone device is limited by device capacity, switching frequency, heat dissipation, reliability and cost, modularized multiple devices parallel connection technology is highly expandable, reliable and capable to combine with redundancy control technology. In this paper, the technology of parallel-connected modularized multiple devices is researched thoroughly, to provide a strong technical support for the highly reliable and precisely low voltage high current active filters.Firstly, in the aspect of harmonic current control strategy of single device, the existing APF harmonic control strategies are innovatively compared in this paper from system configuration, structure and hannonic individually controlling. An improved hannonic detection is proposed, which is based on two kinds of operation modes:single PI controller. Finally, the feasibility and superiority of the proposed method are verified by simulation and experiment.Secondly, about the key technology of the system, which is the key technology of the low voltage and high current active power filter technology, this paper makes a comparative study of the three traditional modular parallel operation mode of APF. In view of the shortcomings of the three traditional coordination strategies and the load characteristics of typical low voltage and high current harmonic pollution sources, two improved coordination control strategies are presented, one is the multi machine full compensation and sub compensation combination,another is double compensation point the multi machine sub and closed loop closing.Thirdly, in the system stability analysis and control of the system, the APF voltage of the power system, and the system of PCC, the system’s stability analysis and control of the two aspects. the paper presents the stability analysis of the system is proposed for the first time, and then the paper proposes the stability analysis method based on the global admittance. After all the simulation results, verify the results of this chapter.Finally, in industrial prototype design and commissioning experiment, a 3P4W four-leg APF prototype design is proposed from aspects of power circuit, control circuit and control program. Especially for the main circuit connection interface, a four-branch four-phase individual filtering circuit topology is innovatively proposed. The optimal main circuit parameters are obtained by filtering performance, which is quite beneficial to APF main circuit unit modularization. Moreover, the prototype is commissioned to several industrial applications, such as stand-alone device fully filtering building’s energy saving lamp load, four-units-parallel-connected filtering conventional uncontrolled rectifying load and six-units-parallel-connected filtering high power phase-controlled rectifying load. Comprehensive experimental results have fully verified that the designed prototype can effectively treat low voltage high current harmonics with high precision and reliability, which have further verified the proposed.