Research On A Three-phase Three-level Inverter With Asymmetrical Legs And Its Application In The Active Power Filter

The rapid development of power electronics technology has brought great convenienceto power energy transformation and application, at the same time, also caused the seriouspower quality problems of the power system. Such as harmonic pollution, reactive powerissue. Active Power Filter is recognized as an effective means to control harmonics andreactive power. Inverter is an important part of active power filter, has had a significantimpact on the performance of the filter. A novel asymmetrical multilevel inverter topologyhas been proposed in this paper, and the inverter used in active power filter.Comparative analyzed three traditional three-level inverter topology and the respectiveadvantages and disadvantages of them. The structural parts of the inverter are brieflydescribed, then switching strategy and operational principles of the proposed inverter areexplained and operational topologies are given. The most important feature of this inverter isthe simple structure. Under the premise of no increase in the number of active switches, there isno need of additional clamping diodes or flying-capacitors in the topology. The design of thedrive circuit is easy and simple. Moreover, from the configuration of the proposed inverter, wecan find out that the traditional three-level SVPWM algorithm is completely suitable for thenew topology.The traditional three-level SVPWM algorithm has been improved and linear transformedto the two-level algorithm to avoid the large number of triangular operations. Based on the newalgorithm and the new inverter topology, the root cause of the neutral-point-potential imbalanceis analyzed and the solution of this problem is proposed. The article analyzed a novel strategyfor the control of neutral-point potential based on the particular disposition of all theredundant voltage vectors.The inverter with asymmetrical legs used in active power filter is deeply studied in thisarticle. Three mathematical models is created for the new type of APF. In order to improve thecurrent tracking performance of APF, in this thesis, a SVPWM current method for APF isproposed. In addition, The main circuit parameters of the new type of APF are designed inthis article. Finally, the simulation and experimental results are provided to validate theeffectiveness and advantages of the proposed topology and the configuration.