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Multi-level single-carrier modulation method and system

A single-carrier modulation, multi-level technology, used in electrical components, output power conversion devices, and AC power input to DC power output, etc. It can solve the problem of large amount of calculation, complex control algorithm, and inability to achieve bus capacitor voltage balance. and other problems, to achieve the effect of simple control, easy implementation, avoiding mathematical operations and complex programming

Active Publication Date: 2019-05-24
TSINGHUA UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The schematic diagram of multi-level carrier stacked PWM is as follows: Figure 4 As shown, using n triangular carriers to compare with a modulation wave to generate n switching signals has the advantages of simple control, easy implementation, and good harmonic performance, but it cannot achieve the bus capacitor voltage within the full modulation ratio and full power factor range. balance
As the number of levels increases in space vector PWM, redundant vectors increase sharply, and in order to realize bus capacitor voltage balance control, it is usually necessary to use multiple redundant vectors to synthesize a virtual vector. also extremely complex

Method used

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Examples

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Effect test

Embodiment 1

[0080] Embodiment 1: Three-level (n=2)

[0081] For a midpoint clamped three-level converter, substituting n=2 into Equations 2 and 4 gives:

[0082]

[0083] suppose u refx It is a symmetrical sinusoidal waveform. According to formula 9, the reference voltage, the control signal of each switch and the output phase voltage at this time can be drawn as Image 6 shown. from Figure 7 It can be seen that the modulation strategy at this time is completely equivalent to the traditional three-level carrier stacked modulation strategy, which further verifies the correctness of the modulation strategy in the embodiment of the present invention.

Embodiment 2

[0084] Embodiment 2: four levels (n=3)

[0085] For a mid-point clamped four-level converter, substituting n=3 into formulas 2 and 4 gives:

[0086]

[0087] suppose u refx It is a symmetrical sinusoidal waveform. According to formula 10, the reference voltage, the control signal of each switch and the output phase voltage at this time can be drawn as Figure 8 shown. It can be seen that the output phase voltage waveform is 4 levels.

Embodiment 3

[0088] Embodiment 3: five levels (n=4)

[0089] For a midpoint clamped five-level converter, substituting n=4 into Equations 2 and 4 gives:

[0090]

[0091] suppose u refx It is a symmetrical sinusoidal waveform. According to formula 11, the reference voltage, the control signal of each switch and the output phase voltage at this time can be drawn as Figure 9 As shown, therefore, it can be seen that the output phase voltage waveform is 5 levels.

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Abstract

The invention discloses a multi-level single-carrier modulation method and system. The method comprises the following steps: the values of modulation waves corresponding to n pairs of switch transistors are acquired according to reference voltage in each control cycle, and n modulation wave values are obtained, wherein n is a positive integer; triangular carrier signals with an amplitude of n aregenerated, the triangular carrier signals are compared with the n modulation wave values respectively, and control signals of n pairs of switch transistors are obtained; and in view of each phase, thecontrol signals and complementary signals are inputted to the switch transistor corresponding to each phase bridge arm. The method can realize self-balancing of DC bus capacitance and voltage of a neutral-point clamped multilevel converter, and has the outstanding advantages of simple control, small calculation and easy realization.

Description

technical field [0001] The invention relates to the technical field of multilevel converter control, in particular to a multilevel single carrier modulation method and system. Background technique [0002] NPC (Neutral-Point Clamped) multilevel converters are widely used in offshore wind power, photovoltaic power generation and other fields due to the advantages of fewer switching devices and high power density. However, as the number of levels increases, there is a problem that the bus capacitor voltage is difficult to balance, which limits its application in higher voltage applications. [0003] The mid-point clamped converter includes different topological structures such as diode clamping and T-type structure. The mid-point clamping multilevel converter using diode clamping is as follows: figure 1 As shown, the mid-point clamped multilevel converter with T-shaped structure is shown as figure 2 As shown, this type of topology can be equivalent to a image 3 The single...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/487
Inventor 王奎郑泽东李永东
Owner TSINGHUA UNIV
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