Simplified model forecasting control method of network voltage unbalance three-level rectifier

Abstract

The invention belongs to the field of converter control, and relates to a simplified model forecasting control method of a network voltage unbalance three-level rectifier. The simplified model forecasting control method of the network voltage unbalance three-level rectifier comprises the steps that (1) positive and negative sequence separation is carried out on three-phase network voltage and current to obtain positive and negative sequence components; (2) coordinate transformation is carried out on three-phase positive sequence voltage and current to obtain positive sequence voltage and current under a two-phase static coordinate system; (3) according to the three-phase positive sequence voltage, three levels are changed into two levels in an order reduction mode through reference voltage; (4) an active power reference value and a current reference value are calculated; (5) a current forecasting value of the rectifier, a direct current side capacitance voltage forecasting value and the changing number of switching elements are calculated; (6) current control, neutral-point potential control and switching frequency control are forecast according to a model, and the best switching state is selected. The simplified model forecasting control method of the network voltage unbalance three-level rectifier can effectively suppress double-frequency fluctuation of input power of the rectifier, lower the switching frequency of the elements, shorten circulation calculation time, control neutral-point potential balance, and improve the operation efficiency of the system.

Description

technical field [0001] The invention relates to a control method for a grid voltage unbalanced three-level rectifier, in particular to a grid voltage unbalanced three-level rectifier low switching frequency simplified model predictive control method. Background technique [0002] With the rapid development of new power electronic devices and technologies, three-phase PWM rectifiers have the characteristics of sinusoidal grid-side voltage, unit power factor operation, and bidirectional energy flow, so they have good application prospects in high-voltage and high-power applications. Under the condition of obtaining the same control function, the switching frequency of the three-level PWM rectifier is doubled, and the current harmonics can be effectively reduced, so the research on high-power three-level PWM rectifier and its control has become a hot spot, and the model predictive control The algorithm is widely used in the design of the rectifier control system because of its ...

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Problems solved by technology

Existing solutions use proportional-integral (PI), proportional resonant (PR) controllers and some nonlinear controllers to control the current inner loop, but there are still problems of accurate tracking of current a

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