WO2017150989A1 - Ensemble onduleur électrique - Google Patents

Ensemble onduleur électrique Download PDF

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Publication number
WO2017150989A1
WO2017150989A1 PCT/NZ2017/050020 NZ2017050020W WO2017150989A1 WO 2017150989 A1 WO2017150989 A1 WO 2017150989A1 NZ 2017050020 W NZ2017050020 W NZ 2017050020W WO 2017150989 A1 WO2017150989 A1 WO 2017150989A1
Authority
WO
WIPO (PCT)
Prior art keywords
inverter
electrical
capacitors
bank
inverters
Prior art date
Application number
PCT/NZ2017/050020
Other languages
English (en)
Inventor
Nihal Kularatna
Original Assignee
University Of Waikato
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by University Of Waikato filed Critical University Of Waikato
Publication of WO2017150989A1 publication Critical patent/WO2017150989A1/fr

Links

Classifications

    • 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
    • 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
    • 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
    • H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
    • 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
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/0074—Plural converter units whose inputs are connected in series

Definitions

  • This invention relates to an electrical inverter assembly used to provide alternating electrical current when connected to a direct current source.
  • Electrical DC-AC converters or inverters are circuits used in applications where a direct current source is employed to power electrical loads designed to work with alternating currents. Electrical inverter technology is
  • inverter circuits consumes electrical energy in the inverter components as direct current is converted to alternating current. It is preferable to have an inverter circuit or assembly which is as efficient as possible, lowering energy wastage within the system and mitigating heat dissipation issues.
  • a common design approach used within prior art inverters is to provide a single inverter circuit capable of receiving the entire input power of a direct current source and suppling an alternating current output with desired output characteristics.
  • the higher the input DC current received by such circuits the more significant the ripple current issues within the operation of the inverter.
  • an electrical inverter assembly arranged to connect to a direct current electrical supply and configured to supply alternating current to at least one electrical load, the inverter assembly including
  • each inverter having a set of input terminals and output terminals
  • capacitor switching structure associated with each pair of inverters, said capacitor switching structure being arranged to cyclically connect a discharged energy storage capacitor bank in series with the input terminals of the primary inverter and the direct current electrical supply to charge said capacitor bank, and to concurrently connect a charged energy storage capacitor bank with the input terminals of the secondary inverter to discharge said capacitor bank.
  • step (i) repeating the above steps starting from step (i) after the second bank of capacitors has become at least partially charged while the first bank of capacitors has become at least partially discharged.
  • the present invention provides an electrical inverter assembly.
  • This assembly is arranged to connect to a direct current electrical energy supply and to output an alternating current to at least one electrical load.
  • the invention may be connected to a variety of direct current sources - such as, for example, photovoltaic solar cells, battery systems, fuel cells or any equivalent or effective source of direct current electrical energy.
  • direct current sources such as, for example, photovoltaic solar cells, battery systems, fuel cells or any equivalent or effective source of direct current electrical energy.
  • an electrical inverter assembly provided by the invention may be connected to any one or combination of photovoltaic solar cells, battery systems and/or fuel cells.
  • the inverter assembly provided by the invention incorporates a combination or collection of existing prior art standalone inverter circuits. These inverter circuits can be assembled together in conjunction with the invention to provide a novel and innovative arrangement.
  • Each individual inverter incorporated within the invention defines a set of input terminals used to connect to a DC source and a set of output terminals provided to deliver output alternating current.
  • the individual inverters selected for the invention's assembly can be drawn from any known inverter circuit arrangement depending on the particular application in which the invention is used, or the electrical loads to be supplied by the invention. Those skilled in the art will appreciate that the invention may incorporate various forms of square wave, modified sine wave or true sine wave type inverters in a range of embodiments.
  • the assembly provided by the invention is designed or specified with the input voltage and current of the direct current source in mind in combination with the output power characteristics required for the various alternating current loads to be supplied.
  • the invention provides an alternative to the prior art which employs a single inverter circuit design to receive the entire output power of a direct current source.
  • each inverter of the assembly receives a portion or a fraction of the output power received from the direct current source or to be delivered to an AC load.
  • the invention operates to supply a fraction of the initial input direct current to each inverter to reduce ripple current magnitudes.
  • the output of each of the inventions "fractional" inverters can then be recombined to deliver alternating current with the desired power
  • the invention therefore provides a significant degree of flexibility in terms of how these fractional inverter outputs can be combined.
  • these inverter outputs can be connected in series in some embodiments, in parallel in others, or in any combination of serial and parallel connections if required.
  • the invention may provide one distinct output, whereas in other cases two or more separate output AC power supplies may be implemented as required.
  • An inverter assembly provided by the invention includes at least one pair of inverters, each member of the pair defined as either the primary inverter or alternatively the secondary inverter.
  • the assembly provided by the invention may include a single pair of primary and secondary inverters, or alternatively may include multiple pairs of inverters.
  • this assembly may be formed from two inverters only defining a single pair, four inverters defining two pairs or potentially six or eight inverters defining three and four pairs respectively.
  • the physical size of the assembly, the cost of individual components, and the performance required of the assembly may dictate the number of primary and secondary inverter pairs provided.
  • references made throughout this specification to various components being connected ⁇ series' encompasses both the direct physical connection of these components to each other, in addition to a connection made through an intervening component
  • the invention's use of at least two banks of energy storage capacitors provides connections for these components so that they act as ripple current smoothing capacitors.
  • the serial connection of a capacitor being charged with the input terminals of a primary inverter also provides the resistance of the primary inverter as a useful resistance in the capacitor charging path.
  • the invention employs at least two energy storage capacitor banks for each pair of primary and secondary inverters incorporated into the invention.
  • a bank of such energy storage capacitors may be formed in some
  • the invention may employ large energy storage capacitors provided by electrical double layer capacitors.
  • EDL or electrical double layer capacitors are also known as super capacitors or ultra-capacitors.
  • EDL capacitors have a high capacitance giving these components high relative time constants and relatively long charging periods.
  • other types of capacitors - such as for example hybrid capacitors - may also be used as energy storage capacitors in conjunction with the present invention.
  • storage capacitors with large capacitance values may be employed within the invention. For example, in a number of preferred embodiments storage capacitors with capacitance values greater than or equal to at least 0.2 Farad may be used.
  • the present invention also incorporates at least one capacitor switching structure arranged to cyclically connect and disconnect the capacitor banks of the assembly in various configurations.
  • a microprocessor may be provided as a capacitor switching structure.
  • a capacitor switching structure may be formed by a low frequency oscillator circuit.
  • Those skilled in the art will appreciate that various types of switching technologies may be used to implement such a capacitor switching structure in different embodiments.
  • a single capacitor switching structure may be provided for each pair of primary and secondary inverters integrated into the assembly, or alternatively a single switching structure may be provided to service all pairs of inverters incorporated into the assembly.
  • the capacitor switching structure is configured to periodically or cyclically swap the connections of two banks of capacitors provided in association with an inverter pair.
  • a first bank of capacitors - which is normally discharged - is connected in series with the direct current source and the input terminals of one of the primary inverters. These connections result in the recharging of the first discharged capacitor bank while the primary inverter is supplied with direct current from the direct current source.
  • the switching structure also connects a second bank of capacitors - normally being charged energy storage capacitors - across the input terminals of the secondary inverter of the pa ir. This connection results in the dischargi ng of the second capacitor ba nk to supply di rect current energy to the secondary i nverter.
  • the capacitor switching structure can therefore drive the operation of the inverter assembly provided by the invention, continuously swapping the connections of two banks of energy storage capacitors to supply direct current to a secondary inverter from one bank whi le the other ban k is being recharged in series with the pri mary i nverter.
  • the present i nvention may therefore provide many potential advantages over the prior art, or i n the least provide the public with an alternative choice .
  • the i nvention's use of charging and discharging capacitor paths ca n mitigate the problem of high i nput currents.
  • the multiple fractiona l inverters employed by the i nvention initially drop the input DC current suppl ied to each separate i nverter circuit, leading to a reduction in ripple cu rrent magnitudes.
  • the large capacitance of these components acts to smooth a nd attenuation the effects of such currents.
  • the serial connection of a ca pacitor bei ng cha rged with the input stage of a primary inverter can also i mprove the overall efficiency in the resulting inverter assembly design .
  • the pri mary i nverter provides a useful resistance RL in the ca pacitor charging path havi ng an initial resistance R, where it is assumed RL> > R - reducing energy losses by a factor of RL / R + RL by circumventing the losses in the capacitor charging loop.
  • the invention improves energy efficiencies by recovering resistive losses in the capacitor charging loop which are supplied to the paired secondary inverter when the capacitor is discharged.
  • Figure 1 shows a basic schematic view of an improved electrical
  • Figure 2a shows a plot of voltage against time for the primary and secondary capacitor bank pair CI, C3 of Figure 1,
  • Figure 2b shows a plot of voltage against time for the primary and secondary capacitor bank pair C2, C4 of Figure 1,
  • FIG. 2c shows a plot of high frequency filtered voltage against time at the output terminals of Inverter 1 of Figure 1,
  • Figure 2d shows a plot of high frequency filtered voltage against time at the output of the inverter assembly of Figure 1.
  • Figure 1 shows an electrical inverter assembly as provided in accordance with one embodiment of the invention with the example of 480V DC input supply and a 240V AC output inverter capable of 10 A root mean square current.
  • This assembly is connected to a direct current electrical supply which delivers 5 Amps at 480 Volts, as shown by the connection terminals illustrated to the left side of Figure 1.
  • the assembly incorporates four prior art inverters - being inverters 1 through 4.
  • the four inverters are arranged in two pairs, with inverter 1 being a primary inverter and inverter 3 being a secondary inverter of the first of these pairs.
  • the second pair is composed of inverter 2 as the primary inverter and inverter 4 as the secondary inverter.
  • Each inverter has a set of input terminals as shown to the left of figure 1, and a set of output terminals as shown to the right of figure 1.
  • the output terminals of all four inverters are connected in series to deliver 10 Amps of alternating current at 240 Volts to the connection terminals illustrated to the right side of Figure 1.
  • connection terminals illustrated to the right side of Figure 1. As will be appreciated by those skilled in the art other connection combinations of these inverter outputs may also be implemented in other embodiments.
  • Each pair of primary and secondary inverters are associated with two energy storage capacitor banks.
  • the paired combination of primary inverter 1 and secondary inverter 3 is associated with capacitor banks CI and C3.
  • the paired combination of primary inverter 2 and secondary inverter 4 is associated with capacitor banks C2 and C4.
  • each capacitor bank is made up of a collection of EDL capacitors or
  • This assembly also includes two capacitor switching structures, each associated with one of the pairs of inverters. These structures are
  • the capacitor switching structures work to cyclically connect a discharged energy storage capacitor bank in series with the input terminals of the primary inverter and the direct current electrical supply to charge said capacitor bank. At the same time they connect a charged energy storage capacitor bank with the input terminals of the secondary inverter to discharge this capacitor.
  • CI represents a discharged capacitor bank which is being recharged in series with the DC supply and inverter 1
  • C3 represents a charged capacitor bank which is being
  • C2 represents a discharged capacitor bank which is being recharged in series with the DC supply and inverter 2
  • C4 represents a charged capacitor bank which is being discharged into the input terminals of inverter 4.
  • C3 provides a discharged capacitor bank which is being recharged in series with the DC supply and inverter 1, while CI provides a charged capacitor bank which is being discharged into the input terminals of inverter 3.
  • C4 provides a discharged capacitor bank which is being recharged in series with the DC supply and inverter 2, while C2 provides a charged capacitor bank which is being discharged into the input terminals of inverter 4.
  • Figure 2c shows a plot of high frequency filtered voltage against time at the output terminals of Inverter 1 of Figure 1.
  • the output terminals of Inverter 1 provide a 60 V RMS 50/60 Hz alternating current output.
  • An equivalent 60 V RMS 50/60 Hz alternating current is also provided at the output terminals of Inverters 2, 3 and 4.
  • Figure 2d shows a plot of high frequency filtered voltage against time at the output of the inverter assembly of Figure 1. This figure shows how the outputs of each of Inverters 1 , 2, 3 and 4 are summed together to provide a 240 V RMS 50/60 Hz alternating current.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

Dans un aspect, l'invention concerne un ensemble onduleur électrique conçu pour se connecter à une alimentation électrique en courant continu (CC) et configuré pour fournir un courant alternatif (CA) à au moins une charge électrique. Cet ensemble onduleur comporte au moins une paire d'onduleurs, qui sont un onduleur primaire et un onduleur secondaire, chaque onduleur comprenant un jeu de bornes d'entrée et de bornes de sortie. L'invention comprend également au moins deux batteries de condensateurs de stockage d'énergie associées à chaque paire d'onduleurs primaire et secondaire, et une structure de commutation de condensateurs associée à chaque paire d'onduleurs. Cette structure de commutation de condensateurs est conçue pour connecter de façon cyclique une batterie de condensateurs de stockage d'énergie déchargée en série avec les bornes d'entrée de l'onduleur primaire et l'alimentation électrique en courant continu afin de charger la batterie de condensateurs, et pour connecter simultanément une batterie de condensateurs de stockage d'énergie chargée avec les bornes d'entrée de l'onduleur secondaire afin de décharger la batterie de condensateurs.
PCT/NZ2017/050020 2016-02-29 2017-02-28 Ensemble onduleur électrique WO2017150989A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NZ71746716 2016-02-29
NZ717467 2016-02-29

Publications (1)

Publication Number Publication Date
WO2017150989A1 true WO2017150989A1 (fr) 2017-09-08

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PCT/NZ2017/050020 WO2017150989A1 (fr) 2016-02-29 2017-02-28 Ensemble onduleur électrique

Country Status (1)

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WO (1) WO2017150989A1 (fr)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130094260A1 (en) * 2010-04-19 2013-04-18 Power-One Italy S.P.A. Multi-Level DC/AC Converter
JP2013172627A (ja) * 2012-02-23 2013-09-02 Fuji Electric Co Ltd マルチレベル電力変換回路

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130094260A1 (en) * 2010-04-19 2013-04-18 Power-One Italy S.P.A. Multi-Level DC/AC Converter
JP2013172627A (ja) * 2012-02-23 2013-09-02 Fuji Electric Co Ltd マルチレベル電力変換回路

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