Multi-level inverter model prediction control method and system

Abstract

The invention discloses a multi-level inverter model prediction control method and system. The method comprises the steps of: presetting a control threshold value for controlling a floating capacitor voltage fluctuation range, and determining the balance priority of a midpoint voltage and a floating capacitor voltage; constructing a neutral-point voltage and floating capacitor voltage balance condition, and screening a switch sequence through the balance condition; constructing a value function, constructing a space vector diagram, performing sector division on the space vector diagram according to a vector value function value, and determining a first target sector where the reference voltage is located; carrying out secondary division in the first target sector by taking a virtual vector as a benchmark, carrying out tertiary division on a second target sector according to a rhombic diagonal line, and determining a final position of the space vector diagram where the reference voltage is located; determining a zero common mode vector according to the final position; reordering the vectors according to an inner and outer ring division principle of the space vector diagram to obtain a sequence with reduced switching loss and fixed switching frequency; and obtaining a duty ratio according to the value function so as to control the action of an inverter switching tube.

Description

technical field [0001] The invention relates to the technical field of multilevel inverters, in particular to a model predictive control method and system for multilevel inverters. Background technique [0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art. [0003] Compared with traditional three-level inverters, multi-level inverters have been widely used in industrial in the field. Among them, the three-phase five-level active medium-voltage point clamp (3P-5L-ANPC) inverter, which is one of the multi-levels, has been applied to fields such as mining industry and photovoltaic power generation. [0004] Each phase of 3P-5L-ANPC is composed of four high frequency switches, four power frequency switches and one floating capacitor. Due to the large number of switches, in addition to the need to control the midpoint balance, the floating capacitance also needs to be controlle...

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Problems solved by technology

In addition, when the weight factor is included in the value function, it will increase the computational burden of the controller, which is not conducive to the rapid response of the system

[0007] When the switching frequency of the inverter is not fixed in each sampling period, it will increase the difficulty of filter design; and when the switching loss is too large, it will reduce the working life of the inverter and increase the maintenance and maintenance costs of the system. It is not conducive to improving the reliability and safety of photovoltaic power generation systems

[0008] To sum up, in the above-mentioned prior art, there is suppression of grid-connected leakage current, the switching frequency is not fixed, the switching loss is large, and the control objectives are many and complex. The traditional MPC with weight factors has a large computational burden when realizing multi-objective control. And other issues

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