The Research Of Tri-level Shunt APF Based On SVPWM Control

The widespread use of power electronics brings convenience to humans’ manufacture and life, but serious harmonic pollution may also be brought into the power grid simultaneously. However, the rapid increasing of various kinds of automation and electronic equipment requires higher and higher power quality. Hence, the power grid with increasing harmonic pollution will not be able to meet the requirement of electrical equipments for power quality if the governance of harmonic pollution is not strengthened. At present lots of measures are taken to control harmonic pollution. In low voltage and capacity situation, tri-level shunt APF is favored because of its merits such as better compensation ability, less harmonic component, higher utilization rate of DC side voltage. But there are still technical problems blocking practical applications of APF, such as high switch losses, degradation of compensation performance and reliability duo to DC capacitive neutral voltage fluctuation.The 1-shaped tri-level shunt APF had been taken as the research object in this dissertation and the research focused on optimized control method of SVPWM technology. In view of the dead-zone effect of tri-level APF, the direct impulse correction method based on the current interval judgment has been put forward. Main circuit parameters were estimated according to circuit theory and engineering implementation requirements. The influence law of the main circuit parameters on the compensation characteristics was explored through the Matlab simulation. Specific contents were as follows.1) Starting from the introduction to the research status and classification of APF, tri-level shunt APF applicable occasions, advantages and disadvantages as well as problems remaining to be solved were defined.2) Main circuit topology of tri-level shunt APF, operating principles and mathematical model were introduced. The relationships between the APF output voltage and the parameters of DC side voltage, capacitances as well as the AC side inductances were analyzed in order to prepare for experimental parameters determination and further optimization control study.3) Tri-level shunt APF harmonic current detection, current tracking control and DC side voltage control methods were studied respectively so that specific impact of each link to the performance of APF could be found.4) Based on the basic principles of SVPWM, the output voltage vector distribution, space voltage vector of interval judgment and steps, the duration and sequence of basic voltage vector were analyzed and derived in turn, then neutral voltage balance control method was put forward. The dead zone effect on tri-level APF was analyzed and a method of reducing the dead zone effect was derived.5) Based on the principles of main circuit parameters design, the main circuit parameters were estimated and the range of main circuit parameters was determined as well. The control variate method was used to study the influence law of main circuit parameters on the compensation characteristics. The experimental parameters were determined.6) The issue that 12 PWM output waveforms through the DWO module of dSPACE were not synchronous has been settled through programming the module. Tri-level type shunt APF experiment platform was set up based on dSPACE. The precise control of APF was realized through the experimental platform. The correctness of the selection method of hardware parameters and the feasibility of the optimized SVPWM technology were validated.