Unlock instant, AI-driven research and patent intelligence for your innovation.
Optimal pulse method for three-level inverter with minimum midpoint charge
What is Al technical title?
Al technical title is built by PatSnap Al team. It summarizes the technical point description of the patent document.
A three-level inverter, midpoint technology, applied to high voltage, to achieve the effect of reducing midpoint potential fluctuations
Active Publication Date: 2021-08-10
SHANGHAI UNIV
View PDF7 Cites 0 Cited by
Summary
Abstract
Description
Claims
Application Information
AI Technical Summary
This helps you quickly interpret patents by identifying the three key elements:
Problems solved by technology
Method used
Benefits of technology
Problems solved by technology
[0006] Aiming at the midpoint potential fluctuation problem of the diode midpoint clamp type three-level inverter at low switching frequency, the present invention provides an optimized pulse method for the three-level inverter with the smallest midpoint charge to make the inverter work at lower switching frequencies while reducing midpoint potential fluctuations
Method used
the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
View more
Image
Smart Image Click on the blue labels to locate them in the text.
Viewing Examples
Smart Image
Click on the blue label to locate the original text in one second.
Reading with bidirectional positioning of images and text.
Smart Image
Examples
Experimental program
Comparison scheme
Effect test
Embodiment 1
[0040] see figure 1 , the optimized pulse method of the three-level inverter with the smallest neutral point charge, the operation steps are as follows: 1) A new optimized pulse sequence with opposite polarity is used to replace the traditional optimized pulse sequence. 2) A mathematical model of the midpoint charge is established by the novel optimized pulse sequence combined with the relationship between the midpoint current and the three-phase current. 3) Introduce the weight factor λ of the total harmonic distortion (THD) and the midpoint charge, and define a new switching angle solution objective function. In the process of finding the minimum value, the current harmonic distortion and the midpoint charge are simultaneously as small as possible. 4) Select a set of suitable pulse sequences to drive the inverter through the midpoint charge optimization algorithm.
Embodiment 2
[0042] This embodiment is basically the same as Embodiment 1, and the special feature is that in the step 1), the new pulse sequence with opposite polarity outputs an opposite polarity near the voltage zero crossing on the basis of synchronous and symmetrical optimized pulses. pulses to form a bipolar modulation ( figure 2 ). While reducing the influence of the medium vector on the midpoint potential, the compensation effect of the small vector on the medium vector is increased. In order to compensate for the harmonics brought by the opposite polarity pulses, a switching angle is added to the original pulse sequence to ensure that the current distortion rate is within an acceptable range.
[0043] In the step 2), the mathematical model of the midpoint charge is established by the midpoint current and the three-phase current. For the midpoint current i of a three-phase three-level NPC inverter np Have
[0044] i np (t)=[1-abs(S a )]·i a +[1-abs(S b )]·i b +[1-abs(S c )...
Embodiment 3
[0060] This embodiment is basically the same as the second embodiment, and the special features are as follows: the segmented synchronous modulation strategy is adopted, the constant voltage frequency ratio control is adopted, and the modulation degree m has
[0061]
[0062] Where f is the actual frequency of the voltage, f max is the maximum voltage frequency, f in this example max 50Hz.
[0063] For the new optimized pulse sequence with pulses of opposite polarity, the degree of modulation m is related to the switching angle as follows
[0064]
[0065] According to the different modulation degrees m and the number of switching angles N in a quarter cycle, the switching frequency range of each segment can be obtained, as shown in Table 1.
[0066] Table I
[0067]
[0068] According to Table 1, when the segmented synchronous modulation strategy is adopted, the switching frequency range corresponding to each modulation degree is below 500 Hz, which belongs to the...
the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to View More
PUM
Login to View More
Abstract
The invention provides an optimized pulse method for a three-level inverter with the smallest midpoint charge. The operation steps of the method are as follows: 1) The traditional optimized pulse sequence is replaced by a new optimized pulse sequence with opposite polarity. 2), using the new optimized pulse sequence, combined with the relationship between the mid-point current and the three-phase current to establish a mathematical model of the mid-point charge. 3), introducing the weighting factor of total harmonic distortion (THD) and midpoint charge lambda , define a new switching angle to solve the objective function, in the process of finding the minimum value, make the current harmonic distortion and the midpoint charge as small as possible at the same time. 4) Select a set of optimized pulse sequences through the midpoint charge optimization algorithm. The traditional optimized pulse sequence corresponds to large fluctuations in the midpoint potential. The invention can make the inverter work at a low switching frequency, ensure the THD within an acceptable range, and reduce the midpoint potential fluctuation as much as possible, and has good application prospects in the medium, high voltage and high power fields.
Description
technical field [0001] The invention relates to medium, high voltage and high power fields, in particular to a three-level inverter optimized pulse method with minimum midpoint charge. [0002] technical background [0003] Compared with the traditional two-level inverter, the three-level inverter has one more level of output voltage, which is closer to a sine wave, and has better harmonic performance; more power semiconductor devices are used, which can reduce the The withstand voltage level of the device increases the capacity of the DC bus voltage. Due to its simple structure, the diode neutral point clamped (NPC) three-level inverter is widely used in medium, high voltage and high power applications. [0004] Limited by the switching capability of power semiconductor devices, the switching frequency of the inverter should not be too high; in order to reduce the switching loss, it is also hoped that the inverter works at a lower switching frequency. Generally, the switch...
Claims
the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to View More
Application Information
Patent Timeline
Application Date:The date an application was filed.
Publication Date:The date a patent or application was officially published.
First Publication Date:The earliest publication date of a patent with the same application number.
Issue Date:Publication date of the patent grant document.
PCT Entry Date:The Entry date of PCT National Phase.
Estimated Expiry Date:The statutory expiry date of a patent right according to the Patent Law, and it is the longest term of protection that the patent right can achieve without the termination of the patent right due to other reasons(Term extension factor has been taken into account ).
Invalid Date:Actual expiry date is based on effective date or publication date of legal transaction data of invalid patent.
Login to View More 
Login to View More