A Model Predictive Control Method for Three-level PWM Rectifier

Abstract

The invention discloses a three-level PWM rectifier model prediction control method. The method firstly establishes a three-level PWM rectifier discrete prediction model, samples the state of the PWM rectifier system, and then performs the state of the PWM rectifier system according to the discrete prediction model. Predict and get the corresponding predicted value and expected value, solve the value function value corresponding to each switch state, compare the value function value one by one, and filter and compare the switch state with the smallest corresponding value function, and the corresponding switch state is FCS ‑MPC optimal solution. Under this control method, the dynamic and steady-state performance of the system can be effectively improved, the output quality of the PWM rectifier is high, the offline planning shows a high degree of perfection and strong adaptability, and it can effectively reduce the switching frequency of the system and greatly reduce the switching loss.

Description

technical field [0001] The invention relates to the field of power electronics, in particular to a model predictive control method for a three-level PWM rectifier. Background technique [0002] The PWM rectifier is a necessary component for the power variable frequency drive to be connected to the power grid, and it can realize the two-way transmission of the power grid and the motor load energy. At present, the main solutions of the PWM rectifier system are roughly divided into two categories: "vector control" and "direct power control". Power regulation is the only indicator, ignoring the multiplicity of design indicators of PWM rectifiers in actual use; specifically, the "vector control" solution adopts a multi-loop structure, the inner and outer loop stability margins are cross-coupled, and any loop's Oscillation or instability will cause the output quality of the PWM rectifier to decline, and even affect the normal operation of the PWM rectifier. The optimization inde...

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Problems solved by technology

At present, the main solutions of the PWM rectifier system are roughly divided into two categories: "vector control" and "direct power control". Power regulation is the only indicator, ignoring the multiplicity of PWM rectifier design indicators in actual use; specifically, the "vector control" solution adopts a multi-loop structure, the inner and outer loop stability margins are cross-coupled, and any loop Oscillation or instability will cause the output quality of the PWM rectifier to decline, and even affect the normal operation of the PWM rectifier. The optimization index of the frequency conversion system is not fixed; at this time, the off-line planning shows the disadvantages of lack of perfection and poor adaptability; moreover, the various indexes and constraints of the PWM rectifier are not independent and decoupled. There are serious conflicts and contradictions. The two pursue excessively the optimization of the output power of the PWM rectifier, which makes the PWM rectifier easy to fall into the misunderstanding of local optimum.

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