AU2021101990A4 - Inventive optimization tactics to diminish harmonic distortion in component count waned normally bypassed cascaded sources multilevel inverter - Google Patents
Inventive optimization tactics to diminish harmonic distortion in component count waned normally bypassed cascaded sources multilevel inverter Download PDFInfo
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- 238000000034 method Methods 0.000 abstract description 8
- 230000001965 increasing effect Effects 0.000 abstract description 6
- 230000002068 genetic effect Effects 0.000 abstract description 4
- 230000010354 integration Effects 0.000 abstract description 4
- 230000002708 enhancing effect Effects 0.000 abstract description 2
- 238000001228 spectrum Methods 0.000 abstract description 2
- 210000000349 chromosome Anatomy 0.000 description 11
- 210000004027 cell Anatomy 0.000 description 10
- 230000002194 synthesizing effect Effects 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000035772 mutation Effects 0.000 description 2
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
- H02M7/49—Combination of the output voltage waveforms of a plurality of converters
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/12—Arrangements for reducing harmonics from ac input or output
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Inverter Devices (AREA)
Abstract
INVENTIVE OPTIMIZATION TACTICS TO DIMINISH HARMONIC
DISTORTION IN COMPONENT COUNT WANED NORMALLY BYPASSED
CASCADED SOURCES MULTILEVEL INVERTER
Abstract:
The photovoltaic (PV) sources dominated distributed generation (DG) in the Indian
power system requires high performance grid integration power converters to ensure the
minimal line voltage distortion. The multilevel inverters (MLIs) bestowed a solution not only
for the objectionable harmonic profile, which is being offered by the classical two level
inverter (TLI) but also to the individual device stress to a great extend. Though the increase
in the output levels enhances the output voltage (Voac) quality of the MLI, it demands a
complex structure involving higher component counts. In research purposes, the seven-level
inverter is subsumed as an acceptable balance between the circuit complexity and the
distortion level in the output voltage. Further reduction in the total harmonic distortion
(THD) and swaying of harmonic profile can be actualized using the operational tactics. In
this proposal, a component count reduced MLI structure is operated intelligently to improve
the output voltage's harmonic spectrum further, without increasing the number of levels.
Three operational ways or optimization options are indentified for the performance
enhancement of the single phase seven level normally bypassed cascaded sources MLI
(NBCSMLI) to improve the harmonic profile. Here the improvement in the harmonic profile
means enhancing the fundamental component of the output voltage, suppressing the lower
order harmonics, and reducing the THD. The three operational ways are (i) optimizing the
three associated switching angles (01, 02 and 03) of the seven level output (refer the figure),
(ii) optimizing the voltage values (Vdcl, Vdc2 and Vdc3) of the separate dc sources (SDCs)
(hence operating the MLI in asymmetrical mode), and (iii) optimizing both switching angles
and the voltage values, all together. The simple refined genetic algorithm (RGA) based
optimization does the optimization. Though all the three options perform well when
compared to the NBCSMLI's working without the optimization, the options (i) and (ii)
outperform. About 35% reduction in the THD is evidenced in the mathematical equation
based analysis and also in the software simulation tool based study. A proof-of-concept
(POC) hardware prototype corroborates the harmonic profile of the suggested switching
technique. The suggested optimization technique can be adopted to any MLI topology, and
the duo (MLI structure plus optimization) can be used for the PV system-grid integration.
1
INVENTIVE OPTIMIZATION TACTICS TO DIMINISH HARMONIC DISTORTION IN
COMPONENT COUNT WANED NORMALLY BYPASSED CASCADED SOURCES
MULTILEVEL INVERTER
Vdcl
JSei j SH SH2
Vdc2
LOAD |--
Voac
Se2 SH3 jSH4
Vdc3
_____T
Figure 1: Structure of single phase 7-level NBCSMLI
1
Description
Vdcl
JSei j SH SH2
Vdc2 LOAD |--
Voac
Se2 SH3 jSH4
Vdc3 _____T
Figure 1: Structure of single phase 7-level NBCSMLI
Description Field of Invention: The prominence of voltage source inverters (VSIs) is rising day by day in domains like power supplies, drives, flexible AC transmission systems (FACTS), custom power devices (CPDs), etc. Multilevel power conversion has becoming universal in the past few decades. Plenteous multilevel inverter (MLI) topologies have been presented and considered generally for drive, utility and other applications. The present invention is about developing a component reduced MLI topology and application of Refined Genetic Algorithm (RGA) based optimization technique for reducing the distortion level in the output voltage of the developed topology.
Background of Invention: Traditional two level pulse width modulation (PWM) inverters provide an AC voltage with both adjustable magnitude and frequency. With a higher switching (carrier) frequency, the harmonics can be located to the higher frequency band, which is not feasible in the fundamental switching (square wave operation). That is, the required dead band is created in the harmonic spectrum of the output voltage at the cost of increased switching losses. Another main drawback with the two level inverters (TLIs) is objectionable device stress, device voltage rating and high dv/dt rating.
The MLIs are the breed of VSIs, which can synthesize a high voltage AC in minimal distortion using low voltage/power switches at either the fundamental switching or the low frequency switching. Hence the MLI structures offer a significant reduction in the device voltage stress, a greater power density and a lower distortion in the output. Thus the MLIs offer a closer sinusoidal output even without the output filter at relatively a lower switching frequency. The increase in the number of levels (in) decreases the distortion, and theoretically the infinite value of 'in' results in pure sinusoidal voltage, i.e. zero total harmonic distortion (THD). The MLI circuits for the higher levels demand more number of components, which increase both the circuit and the control complexity.
The value of THD is 17% for a seven level inverter output. The common way to reduce the THD value is increasing the value of 'm'. However, this proposal identifies three operational ways or optimization options for the performance enhancement of the single phase seven level normally bypassed cascaded sources MLI (NBCSMLI) to improve the harmonic profile.
S. Thamizharasan et al have developed a cross-switched MLI using auxiliary reverse voltage sources. PWM pulses are given only to the H-bridge switches while the other complementary module works at the fundamental switching. A clever switching method has been adopted. (IET Power Electronics, 2014)
US9787213B2 shows a MLI involving H-bridge, power cells and bypass tactics in which a power cell switching circuit is selectively disconnected from the power cell output. The bypass switch is closed to connect first and second cell output terminals to selectively bypass a power stage of the ML.
W02011042050A1 shows an invention concerns with a voltage source converter consists of a group of phase legs. It involves at least three connection terminals for connecting the phase legs to power transmission elements, a first group of cells in each phase leg and a second group of cells. The cells in the first group are only capable of providing unipolar voltage contributions to the converter and connected for only being capable of such unipolar voltage contributions, while the cells in the second group are connected to the corresponding cells of the first group and arranged to have bipolar voltage contribution capability.
The present invention however differs from the prior contributions and deals with the shortcomings of the prior contributions.
Objectives of the Invention: • To design a novel hybrid MLI configuration with less number of components while retaining the other pristine merits of MLIs. The invented NBCSMLI has a multilevel dc link synthesizing module (the source cascading section plus the bypassing section), and a conventional H-bridge module.
• To identify three operational ways or optimization options for the performance enhancement of the single phase seven level NBCSMLI to improve the harmonic profile.
• To apply Refined Genetic Algorithm (RGA) based optimization process to minimize the harmonic contents of the output voltage.
Summary of the Invention:
• The NBCSMLI wane the component count and is suitable for solar energy conversion systems. • The single-phase seven level NBCSMLI prototype is designed and constructed as proof of concept (PoC) and can be extended for any number of levels. • Experimental results show that the RGA optimization is effective for the harmonic reduction even at the fundamental switching strategy. Particularly, at low modulation indices, it is possible to reduce the THD without increasing the number of switching per cycle, considerably. • In practice, this method is particularly suitable for the control of MLIs, where each DC voltage can be self-maintained of individually controlled. • Moreover it is easy to implement the optimization principle evolved in this study to other multilevel converter structures. To further improvise the harmonic profile (better harmonic power distribution, subtle widening of dead band, etc.), the optimization may be coded appropriately with the low switching frequency instead of the fundamental switching. • The component count reduced NBCSMLI finds its application in PV systems and the optimal filter design encouraged minimal DC link capacitor usage, which spurs to drives and FACTS applications.
Detailed Description of the Invention:
The improvement in the harmonic profile means enhancing the fundamental component of the output voltage, suppressing the lower order harmonics, and reducing the THD. The three operational ways are (i) optimizing the three associated switching angles (01, 02 and 03) of the 7-level output, (ii) optimizing the voltage values (Vdcl, Vc2 and Vdc3) of the separate DC sources
(SDCs) (hence operating the MLI in asymmetrical mode), and (iii) optimizing both switching angles and the voltage values, all together.
The simple Refined Genetic Algorithm (RGA) based optimization does the required task of optimization. Though all the three options perform well when compared to the NBCSMLIs working without the optimization, the options (i) and (ii) outperform. About 35% reduction in the THD is evidenced in the mathematical equation based analysis and also in the software simulation tool based study. A proof-of-concept (POC) hardware prototype corroborates the harmonic profile of the suggested switching technique. The suggested optimization technique can be adopted to any MLI topology, and the duo can be used for the PV system-grid integration.
The proposed MLI is shown in Figure 1. The MLI involves the conventional H-bridge, and Sei and Se2 switches. The SDCs are connected/disconnected by these two switches in order to achieve the necessary time-sharing output. The SHi, SH2, SH3 and SH4 switches are the H-bridge switches operated at the output/fundamental frequency to unfold the multilevel DC voltage waveform, created by the multilevel dc link synthesizing module (MLDCLSM).
The Optimization algorithms for the present invention are given as follows.
Step 1: The initial population of chromosomes is generated randomly and referred as current population. Step 2: The fitness of each chromosome is calculated from thefitness function. Step 3: Each chromosome is checked for quality requirements. If it satisfies, the solution will become optimal solution. Otherwise go to the next step.
Step 4: The new population of chromosomes is generated from the current population in the following way: (a) For the current population, the fitness function values of all the chromosomes are evaluated. From the value of crossover probability (Pc), the parent chromosomes are selected for the crossover. (b) Using the selected parents, two child chromosomes from every pair of chromosomes are produced for the next generation by applying the uniform crossover operator. (c) Repeat the selection steps (a) and (b) until 's' child chromosomes are formed for the next generation. (d) With the specified mutation probability (Pm), apply the mutation operator to each bit of all chromosomes in the current population. Step 5: The new population formed in step 4 is now taken to be the current population. Repeat the process from step 2 for the maximum number of generations.
In the above procedure, step 3 is responsible for generating's' chromosomes and it can be regarded as iteration in the solution process.
1. Claim-I: The component count waned multilevel voltage source inverter (VSI), the normally bypassed cascaded sources multilevel inverter (NBCSMLI), which is recommended for the distributed generation (DG)-grid integration consists of two modules or stages. a. The first module is a multilevel dc link synthesizing module (MLDCLSM), which establishes a dc link voltage in the staircase (near sinusoidal) shape. The dc voltage has a shape exactly same as one obtained if the MLI output is rectified using the single phase full wave rectifier. b. The second module is the classical H-bridge which accommodates the load, and also unfolds the multilevel dc link voltage to a seven level AC output voltage (Voac).
2. The claim-II is a suggestion on reduction in the total harmonic distortion (THD) in the Voac without increasing the number of levels (m), through the optimization of level switching angles e1, 02 and 03 and the voltage values of separate dc sources (SDCs).
3. The NBCSMLI for integrating DGs with the grid described in claim-I can be useful for integrating photovoltaic (PV) systems, fuel cells, batteries etc. with appropriate control schemes.
4. The claim-III is the reduction in about 35% THD without increasing the value of 'm', that is without adding additional devices.
INVENTIVE OPTIMIZATION TACTICS TO DIMINISH HARMONIC DISTORTION IN 16 Apr 2021
COMPONENT COUNT WANED NORMALLY BYPASSED CASCADED SOURCES MULTILEVEL INVERTER 2021101990
Figure 1: Structure of single phase 7-level NBCSMLI
Se2 ωt Se1 ωt
Gate Signals SH1, SH4
ωt SH2, SH3 ωt Voac
Output waveform V3 V2 V1 ωt
ɵ1 ɵ2 ɵ3 V1=Vdc1 V2=Vdc1+ Vdc2 V3=Vdc1+ Vdc2+ Vdc3
Figure 2: Gate signals and output waveform
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113904335A (en) * | 2021-11-05 | 2022-01-07 | 内蒙古电力(集团)有限责任公司内蒙古电力科学研究院分公司 | Method for micro-grid load harmonic current compensation and feeder resonance damping |
| CN115118139A (en) * | 2022-06-06 | 2022-09-27 | 重庆大学 | Multitasking method and system for modular multilevel converter |
-
2021
- 2021-04-16 AU AU2021101990A patent/AU2021101990A4/en not_active Ceased
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113904335A (en) * | 2021-11-05 | 2022-01-07 | 内蒙古电力(集团)有限责任公司内蒙古电力科学研究院分公司 | Method for micro-grid load harmonic current compensation and feeder resonance damping |
| CN115118139A (en) * | 2022-06-06 | 2022-09-27 | 重庆大学 | Multitasking method and system for modular multilevel converter |
| CN115118139B (en) * | 2022-06-06 | 2024-04-16 | 重庆大学 | Multitasking method and system for modularized multi-level converter |
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