Zero common-mode voltage space vector modulation method for parallel three-level converters in photovoltaic grid-connected applications

A space vector modulation, common mode voltage technology, applied in photovoltaic power generation, single grid parallel feeding arrangement, etc., can solve the problems of low waveform quality and large output current harmonics of the converter, so as to ensure the differential mode and common mode circulating current. , the effect of improving the quality of output current

Active Publication Date: 2022-06-07
HARBIN INST OF TECH
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Problems solved by technology

[0005] The present invention aims to solve the problem that the traditional zero-common-mode voltage space vector modulation method of the three-level converter uses only vectors with a common-mode voltage of zero to synthesize the target vector, resulting in large harmonics and low waveform quality in the output current of the converter. Provide a zero-common-mode voltage space vector modulation method suitable for parallel three-level converters in photovoltaic grid-connected applications

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  • Zero common-mode voltage space vector modulation method for parallel three-level converters in photovoltaic grid-connected applications
  • Zero common-mode voltage space vector modulation method for parallel three-level converters in photovoltaic grid-connected applications
  • Zero common-mode voltage space vector modulation method for parallel three-level converters in photovoltaic grid-connected applications

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specific Embodiment approach 1

[0078] According to the above analysis, in this embodiment, the zero-common-mode voltage space vector modulation method suitable for parallel three-level converters in photovoltaic grid-connected applications, the parallel three-level converters are regarded as a five-level system. Among all five-level fundamental vectors of the level system, 19 fundamental vectors corresponding to zero common-mode voltage are selected. Then, based on these 19 zero common-mode voltage vectors, the adjacent three zero common-mode voltage vectors are formed into an equilateral triangle in the vector space of the five-level system. The vector space is partitioned to obtain 24 cells, which can be obtained as figure 2 The zero common-mode voltage vector space is shown.

[0079] Area division steps:

[0080] With a zero common-mode voltage vector V located at the center of the vector space 0 The point is the center of the circle, the center of the circle is the origin, the αβ plane rectangular c...

specific Embodiment approach 2

[0117] Embodiment 2: This embodiment is a further description of the zero common-mode voltage space vector modulation method for parallel three-level converters in photovoltaic grid-connected applications described in Embodiment 1. In this embodiment, it is assumed that the reference The vector is in figure 2 Medium I sector 1 cell, then the three vertex vectors corresponding to the cell are V 0 , V 54 , V 49 , the corresponding vector action times are respectively T 0 , T 54 , T 49 , then the corresponding five-level switch sequence is: 222-312-321-|-321-312-222. Corresponding the sequence with the vector action time, a schematic diagram of the switching sequence within a switching cycle is obtained, as shown in image 3 shown.

[0118] Since the circulating current can only ensure the normal operation of the system, there are two basic principles: one is to make the circulating current return to the value at the beginning of the cycle at the end of a switching cycle,...

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Abstract

The invention relates to a zero-common-mode voltage space vector modulation method suitable for parallel three-level converters in photovoltaic grid-connected applications, and relates to the technical field of three-level converter control. The present invention aims to solve the problem that the traditional zero-common-mode voltage space vector modulation method of the three-level converter uses only vectors with a common-mode voltage of zero to synthesize the target vector, resulting in large output current harmonics and low waveform quality of the converter. The zero-common-mode voltage space vector modulation method suitable for parallel three-level converters described in the present invention uses basic vectors with zero common-mode voltage to form a new five-level vector space, and deduces partition judgment and vector action Timing and switching sequence generation process. Furthermore, proper distribution of the five-level switching sequence to the paralleled three-level converters greatly improves the output current quality of the paralleled system while ensuring that the common-mode voltage is zero and ensures that the average differential-mode and common-mode circulating currents are always to zero.

Description

technical field [0001] The invention belongs to the technical field of three-level converter control, in particular to the modulation of a zero common mode voltage space vector. Background technique [0002] Three-level voltage source converters have been widely used in power electronic applications such as solar energy, wind energy and power transmission due to their advantages such as low voltage stress of switching devices, high output current waveform quality, and many control redundant vectors. Three-level converters operating in parallel can provide greater power levels, higher levels of system redundancy / reliability and modularity, and are increasingly used in offshore wind and distributed wind / photovoltaic industries . However, as a common phenomenon of all PWM converters, common mode voltage can cause many problems such as leakage current, electromagnetic interference and current waveform distortion in three-level converter applications. Therefore, measures must b...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/38
CPCY02E10/56
Inventor 张学广李伟伟庄嫣媛徐殿国
Owner HARBIN INST OF TECH
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