Abstract
Active power filter is an important means to improve power quality, and power topology is an important part of active power filter. Therefore, the research on power topology has important practical value. This paper proposes a simple-structure topology that employs eight switching power devices, two capacitors, and eight diodes to realize nine-level voltage output. The proposed topology can effectively reduce the volume and weight of the device and achieve multilevel output. Simultaneously, a compound control strategy, consisting of integrated phase voltage control and cell capacitance voltage control, is proposed for unit voltage equalization control. Finally, taking the three-phase active power filter as the research object, simulation and experimental verification are carried out with the proposed topology. The results show that the proposed topology and control scheme are feasible, and in the case of sudden load change, the fluctuation of capacitor voltage V1 is less than 3 V, the fluctuation of capacitor voltage V2 is less than 1 V, and the THD (Total Harmonic Distortion) of the phase current is well suppressed to 3.84%.
Highlights
The rapid development of power conversion technology has led to a large number of applications of power electronic devices
This paper proposes a novel nine-level power topology with only eight switching devices, two capacitors, and eight diodes
The results reveal that the capacitor voltages, V1 and V2, can be maintained stably at the reference value, respectively, under a balanced and unbalanced power grid
Summary
The rapid development of power conversion technology has led to a large number of applications of power electronic devices. Three main structures have been proposed: diodeclamped, flying capacitor, and cascade H-bridge multilevel converter [10,11] When these topologies are extended to higher output levels, more switching devices and clamp devices are needed, resulting in a sharp increase in cost. Compared with the traditional NPC topology, it only needs four capacitors and eight switches to achieve nine-level output; capacitor voltage control is complex, the number of capacitors can be cut in half. Reference [14] proposed a topology that employs eight switching power devices, four diodes and four numbers of sources to realize nine-level voltage output. This paper proposes a simple topology, which consists of eight switching power devices, two capacitors and eight diodes to realize nine levels voltage output.
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