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A Quantitatively Optimized Space Vector Modulation Method for Cascaded Inverters

A technology of space vector modulation and quantitative optimization, applied in the direction of output power conversion device, AC power input conversion to DC power output, AC network circuit, etc., can solve the problem of limited control effect of unit DC voltage, increase, output voltage waveform distortion In order to ensure the quality of the output voltage waveform, simplify the controller structure and expand the selection range

Active Publication Date: 2022-03-04
HUBEI UNIV OF TECH
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Problems solved by technology

[0007] (1) It is only qualitatively judging the effect of the switch vector on the rise or fall of the supercapacitor voltage. There is no quantitative comparison of the magnitude of the capacitor voltage change caused by each vector, and it is impossible to truly select the vector combination that best meets the DC voltage control objectives of all units. Therefore, the unit DC The voltage control effect is limited
[0008] (2) Only according to the rising and falling trend of the capacitor voltage, delete the vectors that do not meet the requirements on the one-dimensional coordinate axis, and there may be no optional vectors on the left or right of the output voltage reference value
[0009] (3) The quality of the output waveform is not considered
After deleting the unqualified vectors on the one-dimensional coordinate axis, there may be a large difference in the output levels of the left and right vectors of the remaining adjacent output voltage reference value, increasing dv / dt, resulting in the distortion rate of the output voltage waveform raised

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  • A Quantitatively Optimized Space Vector Modulation Method for Cascaded Inverters
  • A Quantitatively Optimized Space Vector Modulation Method for Cascaded Inverters
  • A Quantitatively Optimized Space Vector Modulation Method for Cascaded Inverters

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Embodiment Construction

[0039] Embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be understood that the implementation examples described here are only used to illustrate and explain the present invention, not to limit the present invention.

[0040] Figure 1(a) shows a schematic diagram of the structure of an N-unit cascaded inverter. In the single-phase N-unit cascaded inverter, when the DC voltage of each unit is not equal, the switching vector has 3 N , will 3 N switch vector g j (j=1,2...) According to its corresponding level value P j (j=1,2...) size to sort and partition the collection. DC voltage U of each unit dci (i=1,2...N) sum is U dcsum . Then the output level values ​​of all switch vectors are in [-U dcsum ,U dcsum ] range. Pair-U dcsum , -U dcsum *(N-1) / N,...-U dcsum / N, 0, U dcsum / N...,U dcsum *(N-1) / N, U dcsum Any one of a total of 2N+1 values, if the difference between its left and right i...

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Abstract

The invention discloses a quantitatively optimized cascaded inverter space vector modulation method. The DC power supply of each unit of the cascaded inverter can be a photovoltaic cell or an energy storage element. Firstly, in the one-dimensional space of inverter output vectors, all vectors are divided into several vector sets according to their level values, and the vectors corresponding to the two level values ​​closest to the output voltage command value and their respective vectors are found. vector set; then apply the least squares method to construct a vector selection function, calculate the vector selection function value of each switch vector in the two vector sets, and use the vector with the smallest calculated value in each set as the switch vector of the next switch cycle; finally calculate the Empty ratio. This modulation method applies the quantitatively optimized space vector modulation method to cascaded inverters of photovoltaic power generation systems, energy storage systems or hybrid energy storage systems, replacing the part of the unit DC voltage equalization control in the controller algorithm, simplifying the controller structure while ensuring the quality of the output waveform.

Description

technical field [0001] The invention belongs to the technical field of new energy power generation and energy storage control, and in particular relates to a quantitatively optimized cascaded inverter space vector modulation method. Background technique [0002] In photovoltaic power generation, energy storage devices or other hybrid energy storage systems, inverters are required to convert DC power into AC power. The cascaded inverter can meet the capacity and output voltage expansion requirements of this type of system. In a cascaded inverter, each photovoltaic cell (or energy storage element) and the single-phase inverter connected to it are called a unit. The energy storage element may be an element capable of storing electric energy such as a storage battery or a supercapacitor. [0003] The power generation of photovoltaic cells is closely related to factors such as light intensity, temperature, surface shading, and the dispersion of photovoltaic cell parameters. If...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M7/5387H02M7/493H02J3/38
CPCH02M7/53871H02M7/493H02J3/381
Inventor 熊兰朱雨洁
Owner HUBEI UNIV OF TECH
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