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T-type NNPC five-level converter and flying capacitor voltage control method thereof

A voltage control method and technology of flying capacitors, applied in the direction of converting AC power input to DC power output, electrical components, output power conversion devices, etc., can solve the problems of increasing algorithm complexity and uncertainty, and achieve improvement The effect of system stability, improving equipment safety and reducing overall cost

Active Publication Date: 2019-10-22
SHANDONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] The inventor discovered during the research and development process that because each phase in the three-phase NNPC topology uses a flying capacitor as a quarter-level output, and three of the five levels will have an impact on the flying capacitor voltage, Therefore, the selection of the cost function in the MPC algorithm should consider the interaction between the flying capacitor and the output level, and the value of the weight factor λ needs to be obtained through repeated debugging, which significantly increases the complexity and uncertainty of the algorithm.

Method used

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  • T-type NNPC five-level converter and flying capacitor voltage control method thereof
  • T-type NNPC five-level converter and flying capacitor voltage control method thereof
  • T-type NNPC five-level converter and flying capacitor voltage control method thereof

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Embodiment 1

[0053] This embodiment provides a T-type five-level NNPC converter, please refer to the attached figure 1 , the T-type five-level NNPC converter includes three-phase bridge arms connected in parallel, and each phase bridge arm includes four series-connected IGBT tubes Sa1, Sa2, Sa3, Sa4, and one side of the midpoint of each phase bridge arm is connected to the series-connected One end of the two IGBT tubes Sa5 and Sa6 in different directions is connected, and the other ends of the two IGBT tubes Sa5 and Sa6 in different directions in series are respectively connected to two flying capacitors Ca1 and Ca2, and the other end of the flying capacitor Ca1 is connected to The upper connection of the four series connected IGBT tubes, the other end of the flying capacitor Ca2 is connected to the lower connection point of the four series connected IGBT tubes, the voltage of the flying capacitor should be maintained at Vdc / 4, and the other end of the midpoint of each phase bridge One sid...

Embodiment 2

[0058] This embodiment provides a method for controlling the flying capacitor voltage of a T-type NNPC five-level converter. figure 2 It is a traditional five-level space vector diagram, including 61 vector positions and 125 level combinations. This embodiment is based on the simplified vector MPC method to realize the control of the flying capacitor voltage of the T-type five-level NNPC converter.

[0059] Please refer to the attached Figure 7 , the method includes the following steps:

[0060] S101. Establish a mathematical model of the T-type NNPC five-level converter, and sample the three-phase output current value and the three-phase output voltage value of the converter at the current moment.

[0061] The mathematical model topology of the T-type NNPC five-level converter established in this embodiment figure 1 shown.

[0062] Specifically, the three-phase output current value of the converter at the current time k obtained by sampling is:

[0063] i a =sinωt

[...

Embodiment 3

[0090] This embodiment provides a T-type five-level NNPC converter flying capacitor voltage control system, the system includes:

[0091] Model computing module, for setting up the mathematical model of the T-type NNPC five-level converter described in claim 1, sampling the three-phase output current value and the three-phase output voltage value of current moment converter; The three-phase output current value and the three-phase output voltage value are transformed into αβ coordinates, and the required vector at the next moment is calculated by Lagrangian extrapolation method;

[0092] The optimal vector selection module is used to compare the obtained required vector with the zero common mode vector position, and select the optimal vector;

[0093] The vector recombination module is used to convert the obtained optimal vector into an optimal switch state, and select a switch state with a similar level to control the voltage of the flying capacitor.

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Abstract

The invention discloses a T-type NNPC five-level converter and a flying capacitor voltage control method thereof. The converter comprises three phases of parallel bridge arms; each phase bridge arm comprises four series IGBT tubes; and one side of the midpoint of each phase bridge arm is serially connected with two IGBT tubes in different directions and is connected to upper and lower connection places of the four series IGBT tubes through two flying capacitors. The flying capacitor voltage control method comprises steps: a mathematical model for the T-type NNPC five-level converter is built,and three-phase output current values and three-phase output voltage values of the converter at the current time are sampled; alpha beta coordinate transformation is carried out on the three-phase output current values and the three-phase output voltage values of the converter at the current time, and a required vector at the next moment is calculated by adopting Lagrange extrapolation; the obtained required vector is compared with multiple zero common mode vector positions, and the optimal vector is selected; and the obtained optimal vector is converted to the optimal switching state, and thenear-level switching state is selected to control the flying capacitor voltage.

Description

technical field [0001] The present disclosure relates to the technical field of multilevel converter control, in particular to a T-type NNPC five-level converter and a method for controlling the voltage of a flying capacitor. Background technique [0002] Compared with two-level and three-level converters, the comprehensive performance of multi-level converters has been improved, and it has been used more and more in industrial applications such as renewable energy conversion, motor drive, reactive power compensation, and transportation. s concern. The multilevel converter can significantly reduce the total harmonic distortion (Total Harmonic Distortion, THD) of the AC output, reduce the switching loss, reduce the voltage stress (dv / dt) of the switch tube, increase the input voltage range of the converter, reduce the overall volume and output filter volume, thereby reducing cost. [0003] Compared with the traditional five-level topological converter - flying capacitor (F...

Claims

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Application Information

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IPC IPC(8): H02M7/487H02M1/12
CPCH02M1/12H02M7/487H02M1/123
Inventor 邢相洋戴向阳裴文卉张承慧李晓艳胡顺全
Owner SHANDONG UNIV
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