NPC three-level inverter optimal sequence model prediction control device and method

Abstract

The invention discloses an NPC three-level inverter optimal sequence model prediction control device and method. The device comprises an NPC three-phase three-level inverter, a digital processing control module and a driving circuit, wherein the digital processing control module comprises a sampling unit, a sector pre-selection unit, a vector action time calculation unit, a prediction calculationunit and a modulation unit. The method comprises the following steps of: calculating a reference voltage vector and carrying out sector selection on a pre-generated three-vector sequence, calculatingincrements of the current and the neutral-point voltage according to the sampling information, calculating vector action time and correcting the vector action time, predicting, calculating and selecting an optimal vector sequence and action time, and generating a switching signal by the modulation unit to drive the NPC three-phase three-level inverter to work. The method is low in hardware cost, accurate in control and wide in application range, fixed switching frequency grid-connected control over the NPC three-phase three-level inverter can be achieved, the total harmonic distortion rate ofthe network access current is reduced, and meanwhile fluctuation of the midpoint voltage of the direct-current side is effectively restrained.

Description

technical field [0001] The invention relates to the technical field of DC-AC converters of electric energy conversion devices, in particular to an optimal sequence model predictive control device and method for an NPC three-level inverter. Background technique [0002] The NPC (Neutral Point Clamped) three-phase three-level grid-connected inverter plays the role of an energy conversion interface in a distributed grid-connected power generation system, and its working status greatly affects the power quality of the grid. At present, there are many control strategies applied to grid-connected inverters, mainly including: PI control, PR control, hysteresis control and model predictive control, among which model predictive control is an emerging nonlinear control method with strong robustness, fast The advantages of uniqueness, easy digital implementation and multi-variable control have attracted extensive attention in the grid-connected control of multi-level inverters. [000...

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Problems solved by technology

[0003] However, the traditional model predictive control also has disadvantages such as poor grid-connected current quality and unstable switching frequency, especially the problem that the output current spectrum is not fixed, which will significantly increase the difficulty of designing the subsequent grid-connected filter. Limits the application of model predictive control in grid-connected inverter control

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