T-type three-level inverter finite set model prediction control method and system

Abstract

The invention belongs to the technical field of photovoltaic grid-connected inverters, and particularly relates to a T-type three-level inverter finite set model prediction control method and system, which have the advantages that the delay time is shortened when rapid dynamic response is ensured and a nonlinear system is introduced. The prediction control method comprises the following steps: the three-phase output of an inverter is grid-connected with a power grid through inductance and resistance loads under the condition that an equation is met, wherein the equation, R and L are respectively an resistance load and an inductance load; u refers to the voltage vector generated by the inverter, e refers to the voltage vector of the power grid, and I refers to current vectors of the loads; a voltage uaN, a voltage ubN and a voltage ucN of output phases of the inverter are converted through Clark, and an abc three-phase static coordinate system is converted into an alpha-phase and a beta-phase static coordinate system.

Description

technical field [0001] The invention belongs to the field of photovoltaic grid-connected inverter technology, and in particular relates to a finite set model predictive control method and system for a T-type three-level inverter. Background technique [0002] Three-level inverter technology is mainly used in high-voltage and high-power occasions. Photovoltaic grid-connected power generation is one of the important applications of three-level technology. Photovoltaic grid-connected power generation combines unstable photovoltaic panels and passes through multi-level power electronics. The converters are combined, and finally output a constant frequency AC voltage and run on the grid. In photovoltaic grid-connected power generation, the inverter plays a key role. With the continuous development of switching devices, the topology, modulation mode and control strategy of the inverter are also continuously developed, and the control theory is applied in the control of the invert...

AI Technical Summary

Problems solved by technology

In a three-level grid-connected inverter, the unbalanced midpoint potential on the DC side will lead to an increase in the maximum reverse voltage of the switch tube, and even damage the device in severe cases, greatly reducing system reliability. In addition, when the midpoint potential is unbalanced , the inverter output voltage contains low-order harmonics, which directly affect the output performance of the grid-connected inverter, so the midpoint potential of the DC side must be controlled

In order to keep the midpoint voltage balanced, scholars have proposed modulation strategies, such as sinusoidal PWM control, space vector PWM control, switching frequency optimized PWM control, etc. Generally speaking, these methods can well ensure the balance of the midpoint potential, but The modulation method is computationally complex, requiring triangular transformation and table lookup, which takes up a lot of storage space

Commonly used grid-connected current control technologies include PI control, hysteresis control, repetitive control, etc., but PI control needs to eliminate coupling, the switching frequency of hysteresis control is not fixed, and the dynamic response of repetitive control is relatively slow, so it is generally not used alone

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