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Single-phase three-level converter neutral point potential balance control method, controller and system

A potential balance and control method technology, 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 zero vector non-adjustable midpoint potential and limited midpoint potential adjustment ability , to achieve the effects of reducing the content of middle and low harmonics, reducing voltage stress, and small steady-state error

Active Publication Date: 2020-07-03
SHANDONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] However, the inventors found that because the traditional SVPWM midpoint potential balance algorithm uses zero vectors and redundant small vectors as basic voltage vectors to synthesize reference voltage vectors in each switching cycle II and III sectors, and zero vectors have no adjustment midpoint Therefore, the midpoint potential can only be adjusted by redundant small vectors
That is to say, in sectors II and III, the action time of the redundant small vector is much shorter than the switching period, which greatly limits the ability of the system to adjust the midpoint potential, and the problem will be more serious when the load is unbalanced

Method used

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  • Single-phase three-level converter neutral point potential balance control method, controller and system
  • Single-phase three-level converter neutral point potential balance control method, controller and system
  • Single-phase three-level converter neutral point potential balance control method, controller and system

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Embodiment 1

[0040] In order to solve the problem of unbalanced midpoint potential of single-phase NPC converters, the midpoint potential balance control method of single-phase three-level converters in this embodiment is a new space vector modulation method based on half-period reverse vectors, which can realize single-phase Mid-point potential balance control of three-level NPC converter under load balance and unbalance conditions.

[0041] In the midpoint potential balance control method of the single-phase three-level converter in this embodiment, the switch states corresponding to the nine operating modes of the single-phase three-level NPC converter are defined as corresponding switch vectors, respectively denoted as V 1 ···V 9 . The switch vectors corresponding to the aforementioned switch states are divided into five types of vectors, namely zero vector, positive small vector, positive large vector, negative small vector and negative large vector. Specifically, V 1 , V 5 , V 9...

Embodiment 2

[0080] This embodiment provides a midpoint potential balance controller for a single-phase three-level converter.

[0081] The switch states corresponding to the 9 working modes of the single-phase three-level NPC converter define the corresponding switch vectors, which are expressed as V 1 ···V 9 . The switch vectors corresponding to the aforementioned switch states are divided into five types of vectors, namely zero vector, positive small vector, positive large vector, negative small vector and negative large vector. Specifically, V 1 , V 5 , V 9 is the zero vector (Z); V 2 , V 6 is a positive small vector (SP), V 3 is a positive vector (LP); V 4 , V 8 is a negative small vector (SN); V 7 is a negative large vector (LN).

[0082] figure 1 It is a topological structure diagram of a single-phase three-level NPC converter, and the voltage across the capacitor C1 on the DC side is u 1 , the voltage across the lower capacitor C2 is u 2 , the AC side input port volta...

Embodiment 3

[0118] This embodiment provides a single-phase three-level converter midpoint potential balance control system, which includes the single-phase three-level converter midpoint potential balance controller as described in the second embodiment.

[0119] The midpoint potential balance control system of the single-phase three-level converter in this embodiment can greatly improve the midpoint potential balance control capability of the single-phase three-level converter, and is especially suitable for unbalanced load conditions, which can effectively reduce the output voltage of the DC side The low and medium harmonic content reduces the voltage stress of the switching tube and improves the system reliability.

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Abstract

The invention belongs to the field of single-phase three-level converters, and provides a single-phase three-level converter neutral point potential balance control method, controller and system, andthe control method comprises the steps: generating a per-unit reference voltage vector, and judging a sector where the per-unit reference voltage vector is located; selecting two voltage vectors in the sector as basic voltage vectors to participate in the synthesis of a reference voltage vector, obtaining a vector action sequence according to the basic voltage vector selected by each sector, and calculating the time distribution of the vector action sequence in one switching period; generating PWM signals. The method overcomes the defect of neutral-point potential balance control of a traditional SVPWM modulation strategy in a three-level NPC converter, improves the working performance of the converter, and is wide in application prospect.

Description

technical field [0001] The invention belongs to the field of single-phase three-level converter control, and in particular relates to a single-phase three-level converter midpoint potential balance control method, controller and system. 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] Multilevel converters have the advantages of high withstand voltage and low output harmonics, and are widely used in electric vehicle charging and discharging, new energy power generation, motor driving and other fields. Among them, a diode-clamped three-level converter, also known as a neutral point clamped converter (Neutral Point Clamped, NPC), is one of the most widely used solutions. However, the three-level NPC converter has an inherent problem of unbalanced midpoint potential, which is manifested by the deviation of the upper and lower capacitor voltag...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/219H02M1/14
CPCH02M1/14H02M7/219
Inventor 张承慧王涛徐英辉张晨宋金秋陈志远段彬
Owner SHANDONG UNIV
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