Predictive current control method for cascaded h-bridge inverter permanent magnet motor system

Abstract

The invention discloses a predictive current control method for a cascaded H-bridge inverter permanent magnet motor system. The method comprises the steps: connecting a surface-mounted permanent magnet synchronous motor to the three-phase output side of a cascaded H-bridge multilevel inverter, and establishing a discretization mathematic model in a complex vector form under a d-q coordinate system; acquiring a predicted current vector of a voltage vector actually acting in a kth control period under the action of a (k+1)th control period based on the model; constructing a value function according to the relationship between the current vector and the voltage vector increment; and determining the hysteresis width and the increment of an optimal voltage vector according to the amplitude andphase angle of a current error vector, and determining an optimal voltage vector of the (k+1)th control period according to an optimal voltage vector under the action of the kth control period. The prediction frequency and the value function optimization frequency can be reduced, the complexity of a multi-level model predictive control algorithm can be greatly reduced, and the method has better dynamic and stable performances.

Description

technical field [0001] The present invention relates to the field of multilevel inverter and motor drive control, in particular to a predictive current control method for cascaded H-bridge inverter permanent magnet motor system, which can be applied to rail transit traction and ship propulsion systems Medium and high-voltage high-power AC motor frequency conversion and speed regulation field. Background technique [0002] In the field of medium and high-voltage high-power drives, due to the limitation of the withstand voltage and loss of a single power electronic device, two-level inverters have problems such as high dv / dt, high harmonic content, large switching losses of power devices, and serious electromagnetic interference. A series of problems limit its application. For this reason, multilevel inverters have attracted the attention of domestic and foreign researchers because of their unique advantages in high-voltage and high-power applications. As a representative mu...

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Problems solved by technology

However, for the cascaded H-bridge multilevel inverter-permanent magnet synchronous motor system (CHB-PMSM), with the increase of cascaded units and the increase of the number of levels, the number of space voltage vectors and the number of switch states are proportional to each other. The exponential form increases. For example, the number of switching states of the three-phase five-level cascaded H-bridge inverter is (4^6=4096), and it is obviously difficult to realize the system output under all switching states using the traditional model predictive control method. of

[0004] Some researchers have proposed a variety of improved methods to reduce the amount of calculation, one of which is the model prediction method that only considers the adjacent vector (MPC-adj), that is, only the regular hexagonal area adjacent to the optimal vector selected in the previous control cycle The optimal voltage vector at the current moment is selected within the current moment, but it is still necessary to perform 7 calculations of the prediction model and 7 comparisons of the value function, and sacrifice the dynamic performance of the system; another method to obtain the reference voltage vector combined with deadbeat control The method of selecting the nearest voltage vector for the position, this method requires only one prediction, but requires an additional algorithm for locating the position of the nearest triangle, and when the system is disturbed, the reference voltage vector obtained by only one prediction is no longer accurate

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