A Predictive Current Control Strategy For Three-Level NPC Inverter

Due to the current shortage of fossil energy,the industry has updated requirements for the quality and feedback of electrical energy.Among them,power converters have seen as the focus in the power industry.The development of traditional power conversion devices such as diodes,gate turn-off thyristors(GTO)and integrated gate-commutated thyristors(IGCT)has greatly promoted the application of voltage source converters in medium-voltage.These types of power converters are more suitable for use in a two-level topology.But for the situation above the medium voltage,the two-level topology gives rise to an extreme high voltage stress on a single device,which can cause damage to the converter easily.In addition,it should be noted that the switching frequency of the power device of the traditional two-level converter is higher,and the output current harmonics are larger,in order to solve these problems,multilevel power converter(multilevel power converter)came into being.The improvement of insulated gate bipolar transistor(IGBT)has greatly promoted the development of multi-level power converters,and also facilitated the widespread use of power converters in high voltage and high power occasions greatly.There are many devices with multi-level topology at present.In this article,we take the three-level Neutral Point Clamped(NPC)topology as an example,establishing a hardware system including a surface permanent magnet synchronous motor driven by the three-level NPC inverter to study its application in the field of inverters.The system consists of an independent DC power supply,a three-level inverter and a permanent magnet synchronous motor.In the traditional predictive current control method,the current harmonics output by the inverter and the torque ripple are larger.On the basis of the traditional single control vector predictive current control of the limitedcontrol set,a dual-vector predictive current control strategy for three-level inverter is proposed in this paper.The strategy applies two switching sequences in a sampling period,which can not only reduce the current ripple,but also balance the midpoint potential voltage of the three-level NPC inverter more effectively.The method also designs multiple system constraints and controlled objectives to reduce the computational load.The results of experiments show the effectiveness and feasibility of the method.