Application Research On Active Power Filter With Control Strategy Of Gradual Change Of DC-link Voltage In Outside Control Loop

With the development and popularization of Power Electric Technology and Automation Technology, there is incessant new breakthrough in the research field of APF (Active Power Filter). How to develop a kind of reliable and practicality APF with high-performance and low-cost is the common target of most researchers. Aiming at the present status of Guangdong Power market, an APF solution based on DSP (Digital Signal Processing) control system and IPM (Intelligent Power Module) is presented in this thesis. It has character of small size, high dynamic and low cost. The experimental prototype based on above solution has passed the production appraisal hosted by Guangdong department of science and technology. And now it is being tested in the industrial field.This thesis simply introduces the operation principle and system configuration of SAPF, and describes the design method of main circuit in detail. Based on some documents, the current HCDM (harmonic currents detection methods) and CS (control strategies) are compared, their advantages and disadvantages are analyzed. This thesis emphasizes on the description of improved HCDM based on rotating d-q reference frame and gradual change of DC-link voltage in outside control loop CS based on digital PI (Proportional and Integral). The effectiveness of the control method with DC-link voltage gradual change is also verified. The proposed HCDM can accurately extract harmonic and reactive currents of nonlinear loads under the conditions of asymmetric and distorted supply voltage, and shorten the software calculation time. The proposed CS can ensure APF to start smoothly and response to the change of load quickly. The validity of proposed method and strategy is verified by the simulation and experiment results.In order to verify the feasibility of above solution, a 100KVA SAPF experimental prototype is built. 7MBP150RA120-type IPM is used asconverter in the main circuit. The control circuit comprises a dual-CPU (ADMC401 & 80C196KC) system. The digital signal processor-ADMC401 performs the function of analogue signal sampling, reference currents calculating, digital PI control and PWM signal generating. The MCU (Micro Computer Unit) 80C196KC performs the function of keyboard control, LCD (Liquid Crystal Display) output, data access and signal transfering. The sampling circuit and gate driving circuit are also introduced in this thesis. Software design is realized by assembly language of each CPU.The experimental results verify the validity of above hardware circuit and control algorithm. And this is a good foundation for the field test.