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String type photovoltaic inverter SVPWM (Space Vector Pulse Width Modulation) method and system

A technology of photovoltaic inverter and modulation method, which is applied in the direction of photovoltaic power generation, conversion of AC power input to DC power output, output power conversion device, etc., which can solve problems such as increased loss, and achieve high flexibility and balanced loss distribution. Effect

Pending Publication Date: 2022-05-24
SHANGHAI JIAO TONG UNIV +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Patent document CN103138619A injects zero-sequence components by adjusting the distribution of vectors, and adjusts the magnitude of the zero-sequence components of the midpoint potential by adjusting the type of redundant small vectors, thereby achieving the purpose of suppressing midpoint potential fluctuations. However, this method will resulting in a further increase in losses
[0005] It should be noted that for different types of three-level voltage source inverters, harmonic content THD, mid-point potential balance, common-mode voltage and loss are all factors that need to be considered. Using different modulation methods, these performance indicators There must be a trade-off

Method used

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  • String type photovoltaic inverter SVPWM (Space Vector Pulse Width Modulation) method and system
  • String type photovoltaic inverter SVPWM (Space Vector Pulse Width Modulation) method and system
  • String type photovoltaic inverter SVPWM (Space Vector Pulse Width Modulation) method and system

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0078] This example can be used as a specific SVPWM modulation method under the first type of modulation.

[0079] like figure 2 As shown in the vector position relationship, for the first type of null-point voltage vector, there is a relationship of modulation degree m<0.5, the inverter is in a lower modulation degree operation mode, and the position of the voltage reference vector is always in the first large sector. In sector A, similarly, the positions of the voltage reference vectors for the other five large sectors will only be located in the same small sector within the sector. That is, the voltage reference vector is only composed of the small vector and the zero vector at this time.

[0080] Preferably, according to the principle of vector decomposition, a decomposition method of the A sector in the first sector can be selected: (PPO), (POO) and (PPP), or (OON), (ONN, which ensure that the A-phase bridge arm does not operate. ) and (OOO); (OON), (POO) and (OOO) to ...

Embodiment 2

[0084] This example can be used as an SVPWM modulation method under another type of modulation degree that is different from Embodiment 1.

[0085] like figure 2 As shown in the vector position relationship, if there is a relationship modulation degree of 0.5<m<0.5774, it can be seen that the position of the voltage reference vector has experienced the alternation of A sector-C sector-A sector in the first large sector. There is also an alternation of two sectors for the positions of the other five large sector voltage reference vectors.

[0086]Preferably, according to the principle of vector decomposition, a decomposition method of sector A and sector C in the first sector can be selected as: (OON), (POO) and (OOO) in sector A and ( OON), (POO) and (PON), or in A sector (PPO), (POO) and (PPP) and in C sector (PPO), (POO) and (PON), or in A sector ( OON), (ONN) and (NNN) and (OON), (ONN) and (PON) in the C sector. Similarly, for the other five large sectors, a similar vec...

Embodiment 3

[0092] This example can be used as a SVPWM modulation method under the third type of modulation degree that is different from Embodiment 1 and Example 2. It should be noted that the modulation degree must be within the scope of these three examples when the inverter is running stably.

[0093] like figure 2 As shown in the vector position relationship, if there is a relationship modulation degree 0.5774<m<1, that is, the inverter is in a higher modulation degree operation mode, it can be known that the position of the voltage reference vector has experienced B sector in the first large sector The alternation of area-C sector-D sector is also a corresponding alternation process for the other five large sector voltage reference vectors. At this time, the decomposition of the voltage vector is distinguished according to the different sectors.

[0094] Preferably, according to the principle of vector decomposition, a vector decomposition mode of the first sector can be selected:...

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Abstract

The invention provides a string type photovoltaic inverter SVPWM (Space Vector Pulse Width Modulation) modulation method and system, and the method comprises the steps: a space voltage vector sector division step: dividing a space voltage vector into six large sectors, dividing each large sector into four small sectors A, B, C and D, and enabling the vector in each small sector to have a corresponding decomposition method; in the vector decomposition step, the space voltage vectors are divided into three types according to the modulation degree, vector decomposition is conducted on corresponding sectors according to the types of the space voltage vectors and the corresponding decomposition principle, and the action time of the vectors is calculated; and a vector sequence selection step: sorting according to the state of the vector to obtain a control signal in each switching period. According to the invention, by reasonably configuring vectors, reducing the switching action times and adopting small vectors with closer switching states to participate in modulation, the bridge arm breaking times are greatly reduced, so that the switching loss of the photovoltaic inverter is reduced.

Description

technical field [0001] The invention relates to the field of photovoltaic grid-connected inverters, in particular, to a SVPWM modulation method and system of a string-type photovoltaic inverter, and in particular to a three-level SVPWM modulation of a low-voltage and high-power string-type photovoltaic inverter method. Background technique [0002] The development of green new energy technologies represented by photovoltaics is an important measure to solve environmental problems and maintain sustainable economic and social development. The power of string inverters is between centralized inverters and micro-inverters. It has the characteristics of flexible structure, high efficiency and low cost. For string inverters with higher power, only low voltage 380V can be connected to the grid due to the power level. The application of low voltage and high power puts forward higher requirements for the efficiency of string photovoltaic inverters. [0003] The diode-clamped three-...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/5387H02M7/527H02M1/36
CPCH02M7/5387H02M7/487H02M1/088H02M7/5395Y02E10/56
Inventor 陈果王志新包俊
Owner SHANGHAI JIAO TONG UNIV
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