CN108667334B - Four-level topological unit - Google Patents
Four-level topological unit Download PDFInfo
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- CN108667334B CN108667334B CN201810451322.6A CN201810451322A CN108667334B CN 108667334 B CN108667334 B CN 108667334B CN 201810451322 A CN201810451322 A CN 201810451322A CN 108667334 B CN108667334 B CN 108667334B
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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
- H02M7/66—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output with possibility of reversal
- H02M7/68—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output with possibility of reversal by static converters
- H02M7/72—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/79—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output with 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
- H02M7/797—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output with 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 using semiconductor devices only
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Abstract
The invention relates to a four-level topological unit, which is connected between the positive pole and the negative pole of a direct current power supply and comprises: the switching device comprises a first switching unit, a second switching unit, a third switching unit, a fourth switching unit, a fifth switching unit, a sixth switching unit, a seventh switching unit, an eighth switching unit, a ninth switching unit, a tenth switching unit, a diode, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor and a current-limiting inductor which are reversely connected in parallel at two ends of each switching unit. The four-level topological unit can provide higher alternating voltage under the condition of keeping low loss, can prevent overvoltage at two ends of a flying capacitor and a part of switching tube or diode, can effectively reduce the cost and loss of the alternating current side of the alternating current-direct current converter, and has higher reliability.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a four-level topological unit.
Background
A bi-directional ac-dc converter is a converter that converts dc electrical energy to ac electrical energy or ac electrical energy to dc electrical energy. With the continuous development and progress of society, the demand of human beings for energy is increasing, and new energy such as photovoltaic, energy storage and the like has an increasing proportion of energy. As a core, photovoltaic inverters and energy storage converters are also increasingly competing in recent market. To meet the market demand, more and more multilevel ac-dc converters, such as four-level ac-dc converters, are being pushed into the market.
In the traditional four-level AC/DC converter, voltage equalizing measures and a larger absorption circuit are needed to prevent overvoltage at two ends of a flying capacitor, a part of switching tube and a diode, so that the problems of increased cost, poor reliability and the like can be caused.
Disclosure of Invention
Based on the above, it is necessary to provide a four-level topology unit aiming at the problems of increased cost and poor reliability caused by the adoption of voltage equalizing measures and a larger absorption circuit in the traditional four-level ac/dc converter to prevent the overvoltage at both ends of the flying capacitor, part of the switching tube and the diode.
A four-level topology unit connected between a positive pole and a negative pole of a direct current power supply, the four-level topology unit comprising: the switching device comprises a first switching unit, a second switching unit, a third switching unit, a fourth switching unit, a fifth switching unit, a sixth switching unit, a seventh switching unit, an eighth switching unit, a ninth switching unit, a tenth switching unit, diodes reversely connected in parallel at two ends of each switching unit, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor and a current-limiting inductor, wherein:
the second end of the first switch unit is connected with the positive electrode of the direct current power supply, and the first end of the first switch unit is connected with the first end of the ninth switch unit;
the second end of the ninth switch unit is connected with the first end of the seventh switch unit;
the second end of the seventh switch unit is connected with the first end of the eighth switch unit, and the connection point is an alternating current end of the four-level topological unit;
the second end of the eighth switch unit is connected with the first end of the tenth switch unit;
the second end of the tenth switch unit is connected with the second end of the sixth switch unit;
the first end of the sixth switching unit is connected with the negative electrode of the direct-current power supply;
the second switch unit, the third switch unit, the fourth switch unit and the fifth switch unit are sequentially connected in series, one end of the second switch unit is connected with the second end of the first switch unit and the positive electrode of the direct current power supply, and the other end of the second switch unit is connected with the first end of the sixth switch unit and the negative electrode of the direct current power supply;
the first capacitor and the second capacitor are sequentially connected in series, one end of the first capacitor is connected to the positive electrode of the direct current power supply, and the other end of the first capacitor is connected to the negative electrode of the direct current power supply;
one end of the third capacitor is connected to the common end of the second switch unit and the third switch unit, and the other end of the third capacitor is connected to the common end of the first switch unit and the ninth switch unit;
one end of the fourth capacitor is connected to the common end of the fourth switching unit and the fifth switching unit, and the other end of the fourth capacitor is connected to the common end of the sixth switching unit and the tenth switching unit;
one end of the current-limiting inductor is connected to the common terminal of the third switch unit and the fourth switch unit, and the other end of the current-limiting inductor is connected to the common terminal of the first capacitor and the second capacitor.
In one embodiment, the four-level topological unit has four working modes when in operation, so that alternating current-direct current conversion under different working powers is realized.
In one embodiment, when the four-level topology unit works in the first mode, the first switch unit, the third switch unit, the fourth switch unit, the sixth switch unit, the seventh switch unit and the ninth switch unit are turned on, and the other switch units are turned off.
In one embodiment, when the four-level topology unit works in the second mode, the second switch unit, the fourth switch unit, the sixth switch unit, the seventh switch unit and the ninth switch unit are turned on, and the other switch units are turned off.
In one embodiment, when the four-level topology unit works in the third mode, the first switch unit, the third switch unit, the fourth switch unit, the sixth switch unit, the eighth switch unit and the tenth switch unit are turned on, and the other switch units are turned off.
In one embodiment, when the four-level topology unit works in the fourth mode, the first switch unit, the third switch unit, the fifth switch unit, the eighth switch unit and the tenth switch unit are turned on, and the other switch units are turned off.
In one embodiment, the four-level topology unit further includes a fifteenth diode and a sixteenth diode, the fifteenth diode and the sixteenth diode are connected in series, an anode of the fifteenth diode is connected to a common terminal of the first capacitor and the second capacitor, a cathode of the fifteenth diode is connected to a common terminal of the second switch unit and the third switch unit, an anode of the sixteenth diode is connected to a common terminal of the fourth switch unit and the fifth switch unit, and a cathode of the sixteenth diode is connected to a common terminal of the first capacitor and the second capacitor.
In one embodiment, the second switch unit, the third switch unit, the fourth switch unit, the fifth switch unit, the anti-parallel diode thereof, the fifteenth diode and the sixteenth diode form an I-type three-level structure, and the I-type three-level structure package module may be used.
In one embodiment, the seventh and eighth switching units and their antiparallel diodes use a half-bridge structure package module.
In one embodiment, the first and ninth switching units and their antiparallel diodes use a common collector double tube structure package module, and the sixth and tenth switching units and their antiparallel diodes use a common collector double tube structure package module.
The four-level topological unit can provide higher alternating voltage under the condition of keeping low loss, can prevent overvoltage at two ends of a flying capacitor and a part of switching tube or diode, can effectively reduce the cost and loss of the alternating current side of the alternating current-direct current converter, and has higher reliability. In addition, by adding the ninth switching unit and the tenth switching unit, the alternating current end can meet higher voltage requirements, and the cost and loss of the alternating current side cable, the filter and the grid-connected transformer can be further reduced.
Drawings
FIG. 1 is a schematic diagram of a four-level topology unit according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a four-level topology unit according to another embodiment of the present invention;
FIG. 3 is an equivalent circuit diagram of a four-level topology unit according to an embodiment of the present invention when operating in a first mode;
FIG. 4 is an equivalent circuit diagram of a four-level topology unit according to an embodiment of the present invention when operating in a second mode;
FIG. 5 is an equivalent circuit diagram of a four-level topology unit according to an embodiment of the present invention when operating in a third mode;
FIG. 6 is an equivalent circuit diagram of a four-level topology unit according to an embodiment of the present invention when operating in a fourth mode;
fig. 7 is a timing chart of modulated wave sine signal C, first carrier signal a, second carrier signal B, first switching unit Q1, second switching unit Q2, third switching unit Q3, fourth switching unit Q4, fifth switching unit Q5, sixth switching unit Q6, seventh switching unit Q7, eighth switching unit Q8, ninth switching unit Q9, tenth switching unit Q10, and AC waveforms in the four-level topology unit according to the embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Referring to fig. 1, fig. 1 is a schematic diagram of a four-level topology unit according to an embodiment of the invention.
In this embodiment, the four-level topology unit is connected between the positive electrode and the negative electrode of the dc power supply, and includes: the first switching unit Q1, the second switching unit Q2, the third switching unit Q3, the fourth switching unit Q4, the fifth switching unit Q5, the sixth switching unit Q6, the seventh switching unit Q7, the eighth switching unit Q8, the ninth switching unit Q9, the tenth switching unit Q10, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a seventh diode D7, an eighth diode D8, a ninth diode D9, a tenth diode D10, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4 and a current limiting inductance L1, which are connected in reverse parallel to both ends of each switching unit, wherein:
the second end of the first switch unit Q1 is connected with the positive electrode DC+ of the direct current power supply, and the first end of the first switch unit Q1 is connected with the first end of the ninth switch unit Q9;
the second end of the ninth switching unit Q9 is connected with the first end of the seventh switching unit Q7;
the second end of the seventh switch unit Q7 is connected with the first end of the eighth switch unit Q8, and the connection point is an alternating current end AC of the four-level topological unit;
the second end of the eighth switching unit Q8 is connected with the first end of the tenth switching unit Q10;
the second end of the tenth switching unit Q10 is connected with the second end of the sixth switching unit Q6;
the first end of the sixth switch unit Q6 is connected with the negative electrode DC-of the direct current power supply;
the second switching unit Q2, the third switching unit Q3, the fourth switching unit Q4 and the fifth switching unit Q5 are sequentially connected in series, one end of the second switching unit Q2 is connected with the second end of the first switching unit Q1 and the positive DC+ of the direct current power supply, and the other end of the second switching unit Q2 is connected with the first end of the sixth switching unit Q6 and the negative DC-of the direct current power supply;
the first capacitor C1 and the second capacitor C2 are sequentially connected in series, one end of the first capacitor C1 is connected to the positive electrode DC+ of the direct current power supply, and the other end of the first capacitor C2 is connected to the negative electrode DC-of the direct current power supply;
one end of the third capacitor C3 is connected to the common ends of the second switching unit Q2 and the third switching unit Q3, and the other end is connected to the common ends of the first switching unit Q1 and the ninth switching unit Q9;
one end of the fourth capacitor C4 is connected to the common ends of the fourth switching unit Q4 and the fifth switching unit Q5, and the other end is connected to the common ends of the sixth switching unit Q6 and the tenth switching unit Q10;
one end of the current-limiting inductor L1 is connected to the common terminal of the third switching unit Q3 and the fourth switching unit Q4, and the other end is connected to the common terminal of the first capacitor C1 and the second capacitor C2.
In this embodiment, the switching unit is a switching tube. In other embodiments, the switch unit may be other elements, and only needs to function as a switch.
In this embodiment, the current limiting inductor L1 is used to limit the charge and discharge currents of the third capacitor C3 and the fourth capacitor C4. In this embodiment, one end of the current limiting inductor L1 is connected to the common terminal of the third switching unit Q3 and the fourth switching unit Q4, and the other end is connected to the common terminal of the first capacitor C1 and the second capacitor C2. In other embodiments, the current limiting inductor may be multiple and may be connected at other positions, so long as the current limiting function is achieved.
In this embodiment, the second switching unit Q2, the third switching unit Q3, the fourth switching unit Q4, the fifth switching unit Q5 and the anti-parallel diode thereof may use a type I three-level structure package module.
In this embodiment, the seventh switching unit Q7 and the eighth switching unit Q8 and the anti-parallel diode thereof may use a half-bridge structure package module. In this embodiment, the voltage levels of the half-bridge structure package modules used by the seventh switch unit Q7 and the eighth switch unit Q8 that are applicable in practical applications are several fixed voltage values, and the effect of increasing the AC voltage at the AC end cannot be achieved by increasing the static withstand voltage of the half-bridge structure package modules of the seventh switch unit Q7 and the eighth switch unit Q8 at will.
In this embodiment, the first switching unit Q1 and the ninth switching unit Q9 and their anti-parallel diodes may use a common-collector dual-tube structure package module, and the sixth switching unit Q6 and the tenth switching unit Q10 and their anti-parallel diodes may use a common-collector dual-tube structure package module.
In this embodiment, the common connection terminal M1 of the current-limiting inductor L1, the first capacitor C1 and the second capacitor C2 is a dc power midpoint, the common connection terminal M2 of the first switching unit Q1, the ninth switching unit Q9 and the third capacitor C3, and the common connection terminal M3 of the sixth switching unit Q6, the tenth switching unit Q10 and the fourth capacitor C4.
In this embodiment, when the topology unit works in the second mode, since the voltage of the AC end AC relative to the midpoint M1 of the DC power supply is the sum of the voltages of the first capacitor C1 and the third capacitor C3, the voltage of the AC end AC to the negative DC-power supply is the sum of the first capacitor C1, the second capacitor C2 and the third capacitor C3, the voltage is commonly born by the eighth switching unit Q8 and the tenth switching unit Q10, when the tenth switching unit Q10 is not present, the voltage born by the eighth switching unit Q8 alone is lower, the voltage of the AC end AC needs to be reduced, and the highest voltage of the corresponding DC power supply needs to be reduced, so that the ninth switching unit Q9 and the anti-parallel diode thereof can meet the higher AC voltage of the AC end, and it needs to be explained that the voltage of the mode belongs to the static voltage, and the eighth switching unit Q8 and the anti-parallel diode thereof and the tenth switching unit Q10 thereof keep the state of the switching unit H2 and the first mode H1 in the switching process, so that the current does not flow through the switching unit Q10 and the anti-parallel diode thereof has no loss; the seventh switching unit Q7 and its anti-parallel diode and the ninth switching unit Q9 and its anti-parallel diode remain in a conductive state, so that they have no switching loss. The tenth switching unit Q10 functions similarly. The ninth and tenth switching units Q9 and Q10 can thus enable the AC terminal AC to meet higher voltage requirements, which can further reduce the costs and losses of the AC side line, the filter and the grid-connected transformer.
Referring to fig. 2, fig. 2 is a schematic diagram of a four-level topology unit according to another embodiment of the invention.
In this embodiment, the four-level topology unit further includes a fifteenth diode D15 and a sixteenth diode D16, and the fifteenth diode D15 and the sixteenth diode D16 are sequentially connected in series. Specifically, the anode of the fifteenth diode D15 is connected to the common terminal of the first capacitor C1 and the second capacitor C2, the cathode is connected to the common terminal of the second switch unit Q2 and the third switch unit Q3, the anode of the sixteenth diode D16 is connected to the common terminal of the fourth switch unit Q4 and the fifth switch unit Q5, and the cathode is connected to the common terminal of the first capacitor C1 and the second capacitor C2. The rest of the four-level topology unit in this embodiment is the same as the embodiment shown in fig. 1, and will not be described again.
In this embodiment, the second switching unit Q2, the third switching unit Q3, the fourth switching unit Q4, the fifth switching unit Q5, the antiparallel diode thereof, the fifteenth diode D15 and the sixteenth diode D16 form an I-type three-level structure, and the I-type three-level structure package module may be used. If the type I three-level structure package module is not used, the fifteenth diode D15 and the sixteenth diode D16 may be omitted, which does not affect the system performance.
Referring to fig. 3 to 6, fig. 3 to 6 are equivalent circuit diagrams of the four-level topology unit according to the embodiment of the present invention when the four-level topology unit is operated in 4 different modes during dc-ac conversion, fig. 3 is an equivalent circuit diagram of the four-level topology unit according to the embodiment of the present invention when the four-level topology unit is operated in the first mode H1, fig. 4 is an equivalent circuit diagram of the four-level topology unit according to the embodiment of the present invention when the four-level topology unit is operated in the second mode H2, fig. 5 is an equivalent circuit diagram of the four-level topology unit according to the embodiment of the present invention when the four-level topology unit is operated in the third mode H3, and fig. 6 is an equivalent circuit diagram of the four-level topology unit according to the embodiment of the present invention when the four-level topology unit is operated in the fourth mode H4.
Specifically, when the four-level topology unit works in the first mode H1, the first switch unit Q1, the third switch unit Q3, the fourth switch unit Q4, the sixth switch unit Q6, the seventh switch unit Q7, and the ninth switch unit Q9 are turned on, and the other switch units are turned off. The positive pole DC+ of the direct current power supply supplies current to the alternating current end AC through the first diode D1, the seventh switching unit Q7 and the ninth switching unit Q9; or the alternating current end AC supplies current to the positive electrode DC+ of the direct current power supply through the seventh diode D7, the ninth diode D9 and the first switching unit Q1; meanwhile, the positive electrode DC+ of the direct-current power supply charges the third capacitor C3 through the first diode D1, the third switching unit Q3 and the current-limiting inductor L1; or the third capacitor C3 supplies current to the dc side through the current limiting inductor L1, the third diode D3 and the first switching unit Q1.
Specifically, when the four-level topology unit works in the second mode H2, the second switching unit Q2, the fourth switching unit Q4, the sixth switching unit Q6, the seventh switching unit Q7, the ninth switching unit Q9 are turned on, and the other switching units are turned off. The potential of the common connection segment M2 is raised to the sum of the voltages across the first capacitor C1 and the third capacitor C3. The positive electrode DC+ of the direct-current power supply supplies current to the alternating-current terminal AC through the second switching unit Q2, the third capacitor C3, the seventh switching unit Q7 and the ninth switching unit Q9; or the alternating current terminal AC supplies current to the positive electrode dc+ of the direct current power supply through the seventh diode D7, the ninth diode D9, the third capacitor C3 and the second diode D2.
Specifically, when the four-level topology unit works in the third mode H3, the first switching unit Q1, the third switching unit Q3, the fourth switching unit Q4, the sixth switching unit Q6, the eighth switching unit Q8, and the tenth switching unit Q10 are turned on, and the other switching units are turned off. The alternating current end AC supplies current to the negative electrode DC-of the direct current power supply through the sixth diode D6, the eighth switching unit Q8 and the tenth switching unit Q10; or the negative electrode DC-of the direct current power supply supplies current to the alternating current terminal AC through the eighth diode D8, the tenth diode D10 and the sixth switching unit Q6; meanwhile, the negative electrode DC of the direct current power supply charges the fourth capacitor C4 through the sixth diode D6, the fourth switching unit Q4 and the current-limiting inductor L1; or the fourth capacitor C4 supplies current to the dc side through the current limiting inductor L1, the fourth diode D4 and the sixth switching unit Q6.
Specifically, when the four-level topology unit works in the fourth mode H4, the first switching unit Q1, the third switching unit Q3, the fifth switching unit Q5, the eighth switching unit Q8, and the tenth switching unit Q10 are turned on, and the other switching units are turned off. The potential of the common connection terminal M3 is pulled down to the sum of the voltages across the second capacitor C2 and the fourth capacitor C4. The alternating current end AC supplies current to the negative electrode DC-of the direct current power supply through the eighth switching unit Q8, the tenth switching unit Q10, the fourth capacitor C4 and the fifth switching unit Q5; or the direct current power supply negative electrode DC-supplies current to the alternating current terminal AC through the fifth diode D5, the fourth capacitor C4, the eighth diode D8 and the tenth diode D10.
Through the switching of the four modes, the four-level topological unit can realize AC/DC conversion under different working powers, and simultaneously, each working mode does not need all the switch units to work simultaneously, so that the loss is reduced, and the efficiency is improved.
The driving signals of the first switching unit Q1, the second switching unit Q2, the third switching unit Q3, the fourth switching unit Q4, the fifth switching unit Q5, the sixth switching unit Q6, the seventh switching unit Q7, the eighth switching unit Q8, the ninth switching unit Q9 and the tenth switching unit Q10 of the four-level topology unit are determined by comparing the modulated wave sine signal C with the first carrier signal a or the second carrier signal B. Referring to fig. 7, fig. 7 is a timing chart of modulated wave sine signal C, first carrier signal a, second carrier signal B, first switching unit Q1, second switching unit Q2, third switching unit Q3, fourth switching unit Q4, fifth switching unit Q5, sixth switching unit Q6, seventh switching unit Q7, eighth switching unit Q8, ninth switching unit Q9, tenth switching unit Q10, and AC waveforms in the four-level topology unit according to an embodiment of the invention.
Specifically, the driving signal of the first switching unit Q1 is generated by comparing the modulated wave sinusoidal signal C with the first carrier signal a, and when the modulated wave sinusoidal signal C is smaller than the first carrier signal a, the first switching unit Q1 is turned on, and is turned off;
the driving signal of the second switching unit Q2 is generated by comparing the modulated wave sinusoidal signal C with the first carrier signal a, and when the modulated wave sinusoidal signal C is greater than the first carrier signal a, the second switching unit Q2 is turned on, and conversely turned off;
the driving signal of the third switching unit Q3 is generated by comparing the modulated wave sinusoidal signal C with the first carrier signal a, and when the modulated wave sinusoidal signal C is smaller than the first carrier signal a, the third switching unit Q3 is turned on, and vice versa;
the driving signal of the fourth switching unit Q4 is generated by comparing the inverted wave of the modulated wave sinusoidal signal C with the first carrier signal a, and when the inverted wave of the modulated wave sinusoidal signal C is smaller than the first carrier signal a, the fourth switching unit Q4 is turned on, and is turned off;
the driving signal of the fifth switching unit Q5 is generated by comparing the inverted wave of the modulated wave sinusoidal signal C with the first carrier signal a, and when the inverted wave of the modulated wave sinusoidal signal C is greater than the first carrier signal a, the fifth switching unit Q5 is turned on, and is turned off;
the driving signal of the sixth switching unit Q6 is generated by comparing the inverted wave of the modulated wave sinusoidal signal C with the first carrier signal a, and when the inverted wave of the modulated wave sinusoidal signal C is smaller than the first carrier signal a, the sixth switching unit Q6 is turned on, and is turned off;
the driving signal of the seventh switching unit Q7 is generated by comparing the modulated wave sinusoidal signal C with the second carrier signal B, and when the modulated wave sinusoidal signal C is greater than the second carrier signal B, the seventh switching unit Q7 is turned on, and vice versa;
the driving signal of the eighth switching unit Q8 is generated by comparing the modulated wave sinusoidal signal C with the second carrier signal B, and when the modulated wave sinusoidal signal C is smaller than the second carrier signal B, the eighth switching unit Q8 is turned on, and otherwise turned off;
the driving signal of the ninth switching unit Q9 depends on the positive and negative waveforms of the modulated wave, and the ninth switching unit Q9 is turned on and off in the positive half cycle of the modulated wave sinusoidal signal C;
the driving signal of the tenth switching unit Q10 depends on the positive and negative waveforms of the modulated wave, and the tenth switching unit Q10 is turned on and off at the negative half cycle of the modulated wave sine signal C.
In this embodiment, the first carrier signal a and the second carrier signal B have the same amplitude and frequency. In other embodiments, the first carrier signal a and the second carrier signal B may have different magnitudes and frequencies.
The waveform timing diagram of the AC terminal AC in fig. 7 indicates the timing sequence corresponding to the four-level topology unit when the four-level topology unit works in four working modes.
The four-level topological unit can provide higher alternating voltage under the condition of keeping low loss, can effectively reduce the alternating side cost and loss of the alternating-current/direct-current converter, and meanwhile, the switching tube is uniformly packaged, so that the reliability is higher. In addition, by adding the ninth switching unit Q9 and its antiparallel diode and the tenth switching unit Q10 and its antiparallel diode, the AC terminal AC can meet higher voltage requirements, which further reduces the cost and loss of the AC side, the filter and the grid-connected transformer. And the cost pressure brought by re-packaging is reduced, the reliability and the universality of the product are improved, and meanwhile, the circuit has a smaller current circulation path and lower switch tube stress. When the invention is applied to a photovoltaic power generation system and the like, the invention can meet higher alternating voltage under the same PV voltage level, so that the cost and loss of the alternating-current side grid-connected transformer and the alternating-current cable can be further reduced. In addition, the invention can solve the problems of huge volume, increased cost, increased loss, reduced efficiency and the like of the whole machine caused by adopting voltage equalizing measures and larger absorption circuits to prevent overvoltage at two ends of partial switching tubes or diodes in the traditional four-level technology. Meanwhile, the invention can use the existing mature three-level structure packaging module, and solves the problems of low reliability, high cost, poor universality and the like caused by the fact that the traditional four-level structure packaging module is not uniformly packaged and needs to be packaged again. Further, the dynamic voltage stress of the first switching unit Q1, the second switching unit Q2, the third switching unit Q3, the fourth switching unit Q4, the fifth switching unit Q5, the sixth switching unit Q6, the seventh switching unit Q7, and the eighth switching unit Q8 is only half of the bus voltage, which brings the benefit that the switching units with lower voltage level can be used to meet higher ac voltage, so that the cost of the power device is reduced, and meanwhile, the stress of the second switching unit Q2, the third switching unit Q3, the fourth switching unit Q4, and the fifth switching unit Q5 is small because the first switching unit Q1 and the sixth switching unit Q6 have no switching loss, so that the switching tube loss is small, the requirements of an absorption and heat dissipation system are small, the system cost is low, the reliability is improved, and the efficiency is improved. The invention can also meet the requirement of higher alternating-current side voltage, particularly for the current photovoltaic market and energy storage market, the alternating-current side of the invention needs to be connected to a medium-voltage power grid of 10KVAc or 35KVAc, under the same direct-current voltage grade and the same power grade, the invention can reduce the cost and loss of an alternating-current side grid-connected transformer and an alternating-current cable, thereby reducing the cost of the whole system and improving the system efficiency, because the higher the voltage of the alternating-current side is, the smaller the alternating current under the same power is, the smaller the wire diameter of the alternating-current side can be used, and the turn ratio of the transformer is also smaller.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (4)
1. A four-level topology unit connected between a positive electrode and a negative electrode of a direct current power supply, the four-level topology unit comprising: the switching device comprises a first switching unit, a second switching unit, a third switching unit, a fourth switching unit, a fifth switching unit, a sixth switching unit, a seventh switching unit, an eighth switching unit, a ninth switching unit, a tenth switching unit, diodes reversely connected in parallel at two ends of each switching unit, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor and a current-limiting inductor, wherein:
the second end of the first switch unit is connected with the positive electrode of the direct current power supply, and the first end of the first switch unit is connected with the first end of the ninth switch unit;
the second end of the ninth switch unit is connected with the first end of the seventh switch unit;
the second end of the seventh switch unit is connected with the first end of the eighth switch unit, and the connection point is an alternating current end of the four-level topological unit;
the second end of the eighth switch unit is connected with the first end of the tenth switch unit;
the second end of the tenth switch unit is connected with the second end of the sixth switch unit;
the first end of the sixth switching unit is connected with the negative electrode of the direct-current power supply;
the second switch unit, the third switch unit, the fourth switch unit and the fifth switch unit are sequentially connected in series, one end of the second switch unit is connected with the second end of the first switch unit and the positive electrode of the direct current power supply, and the other end of the second switch unit is connected with the first end of the sixth switch unit and the negative electrode of the direct current power supply;
the first capacitor and the second capacitor are sequentially connected in series, one end of the first capacitor is connected to the positive electrode of the direct current power supply, and the other end of the first capacitor is connected to the negative electrode of the direct current power supply;
one end of the third capacitor is connected to the common end of the second switch unit and the third switch unit, and the other end of the third capacitor is connected to the common end of the first switch unit and the ninth switch unit;
one end of the fourth capacitor is connected to the common end of the fourth switching unit and the fifth switching unit, and the other end of the fourth capacitor is connected to the common end of the sixth switching unit and the tenth switching unit;
one end of the current-limiting inductor is connected to the common end of the third switch unit and the fourth switch unit, and the other end of the current-limiting inductor is connected to the common end of the first capacitor and the second capacitor;
when the four-level topological unit works, four working modes exist, and alternating current-direct current conversion under different working powers is realized;
when the four-level topological unit works in a first mode, the first switch unit, the third switch unit, the fourth switch unit, the sixth switch unit, the seventh switch unit and the ninth switch unit are turned on, and the other switch units are turned off;
when the four-level topological unit works in a second mode, the second switch unit, the fourth switch unit, the sixth switch unit, the seventh switch unit and the ninth switch unit are turned on, and the other switch units are turned off;
when the four-level topological unit works in a third mode, the first switch unit, the third switch unit, the fourth switch unit, the sixth switch unit, the eighth switch unit and the tenth switch unit are turned on, and the other switch units are turned off;
when the four-level topological unit works in a fourth mode, the first switch unit, the third switch unit, the fifth switch unit, the eighth switch unit and the tenth switch unit are turned on, and the other switch units are turned off;
the first switch unit, the ninth switch unit and the anti-parallel diode of the ninth switch unit use a common-collector double-tube structure packaging module, and the sixth switch unit, the tenth switch unit and the anti-parallel diode of the tenth switch unit use a common-collector double-tube structure packaging module.
2. The four-level topology unit of claim 1, further comprising a fifteenth diode and a sixteenth diode connected in series, an anode of the fifteenth diode connected to a common terminal of the first capacitor and the second capacitor, a cathode connected to a common terminal of the second switch unit and the third switch unit, an anode of the sixteenth diode connected to a common terminal of the fourth switch unit and the fifth switch unit, and a cathode connected to a common terminal of the first capacitor and the second capacitor.
3. The four-level topology unit of claim 2, wherein the second switching unit, the third switching unit, the fourth switching unit, the fifth switching unit, and anti-parallel diodes thereof, and the fifteenth diode and the sixteenth diode form an I-type three-level structure, and an I-type three-level structure package module may be used.
4. The four-level topology cell of claim 1, wherein said seventh and eighth switching cells and their antiparallel diodes use half-bridge structured packaging modules.
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| CN102594188A (en) * | 2012-02-20 | 2012-07-18 | 阳光电源股份有限公司 | Four-level topological unit and application circuit of four-level topological unit |
| CN102594185A (en) * | 2012-02-20 | 2012-07-18 | 阳光电源股份有限公司 | Four-level topology unit and application circuit thereof |
| CN102594186A (en) * | 2012-02-20 | 2012-07-18 | 阳光电源股份有限公司 | Four-level topological unit and application circuits thereof |
| CA2963665A1 (en) * | 2016-04-11 | 2017-10-11 | Tianshu Liu | Two-phase three-level converter and controller therefor |
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| CN104038085B (en) * | 2013-03-08 | 2016-07-06 | 台达电子工业股份有限公司 | Three Level Converter |
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| CN102594188A (en) * | 2012-02-20 | 2012-07-18 | 阳光电源股份有限公司 | Four-level topological unit and application circuit of four-level topological unit |
| CN102594185A (en) * | 2012-02-20 | 2012-07-18 | 阳光电源股份有限公司 | Four-level topology unit and application circuit thereof |
| CN102594186A (en) * | 2012-02-20 | 2012-07-18 | 阳光电源股份有限公司 | Four-level topological unit and application circuits thereof |
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