CN108933542B - Photovoltaic power generation system and topological structure of three-phase five-level inverter thereof - Google Patents
Photovoltaic power generation system and topological structure of three-phase five-level inverter thereof Download PDFInfo
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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
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- 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
Abstract
The invention discloses a topological structure of a three-phase five-level inverter, which comprises: the three-phase five-level bridge arm comprises a preceding-stage network, a first T source network, a second T source network and a three-phase five-level bridge arm, wherein the preceding-stage network is used for outputting direct current; the first T source network comprises a first transformer and a first capacitor; the second T source network comprises a second transformer and a second capacitor. By applying the topological structure of the three-phase five-level inverter provided by the invention, the three-phase five-level inverter has the functions of boosting and reducing voltage. The invention also provides a photovoltaic power generation system which has corresponding technical effects.
Description
Technical Field
The invention relates to the technical field of photovoltaic power generation, in particular to a photovoltaic power generation system and a topological structure of a three-phase five-level inverter of the photovoltaic power generation system.
Background
The photovoltaic inverter plays an important role in a photovoltaic power generation system and is used for converting direct current in a photovoltaic module into alternating current meeting grid-connection requirements. With the rapid development of renewable energy sources such as wind energy and solar energy, the performance requirements on inverters become higher and higher.
The topological structure of the inverter is an important factor influencing the operation of the system, and the inverters in the prior art are various and have different conversion efficiency, switching loss and the like. A common three-phase five-level topology structure can be seen in fig. 1, and is composed of a preceding network and a three-phase five-level bridge arm, five ports of the preceding network can be referred to as a first end to a fifth end of the preceding network from top to bottom, and these 5 ends are sequentially connected with the first end to the fifth end of the three-phase five-level bridge arm, and fig. 1 is also generally referred to as a three-phase five-level NPC inverter.
With the introduction of power inverter topologies, inverters that implement both boost and buck functions have become more necessary. However, the three-phase five-level NPC inverter in the prior art does not have the functions of boosting and reducing voltage.
In summary, designing a three-phase five-level inverter with voltage boosting and voltage reducing functions is a technical problem that needs to be solved urgently by those skilled in the art.
Disclosure of Invention
The invention aims to provide a photovoltaic power generation system and a topological structure of a three-phase five-level inverter thereof so as to provide the three-phase five-level inverter with the functions of boosting and reducing voltage.
In order to solve the technical problems, the invention provides the following technical scheme:
a topology of a three-phase five-level inverter comprising: the three-phase five-level bridge arm comprises a preceding-stage network, a first T source network, a second T source network and a three-phase five-level bridge arm, wherein the preceding-stage network is used for outputting direct current;
the second end to the fourth end of the preceding-stage network are sequentially connected with the second end to the fourth end of the three-phase five-level bridge arm, the first end of the preceding-stage network is the anode of the preceding-stage network, and the fifth end of the preceding-stage network is the cathode of the preceding-stage network;
the first Tsource network includes:
a first transformer, wherein the first end of the primary winding is connected with the first end of the preceding stage network, the second end of the primary winding is connected with the second end of the secondary winding, the common end of the primary winding is connected with the first end of the first capacitor, and the first end of the secondary winding is connected with the first end of the three-phase five-level bridge arm;
the second end of the first capacitor is connected with the second end of the second capacitor;
the second T source network comprises:
a first transformer, a second transformer, a third transformer and a fourth transformer, wherein the first end of the primary winding is connected with the fifth end of the preceding stage network, the second end of the primary winding is connected with the second end of the secondary winding, the common end of the primary winding is connected with the first end of the second capacitor, and the first end of the secondary winding is connected with the fifth end of the three-phase five-level bridge arm;
the second capacitor;
the first end of the primary winding of the first transformer and the first end of the secondary winding of the first transformer are homonymous ends of the first transformer; and the first end of the primary winding of the second transformer and the first end of the secondary winding of the second transformer are homonymous ends of the second transformer.
Preferably, the pre-stage network includes:
the positive electrode is used as a first direct current power supply of the first end of the preceding stage network;
the anode of the first direct current power supply is connected with the cathode of the first direct current power supply, and the common end of the first direct current power supply is used as a second direct current power supply of the second end of the preceding stage network;
the anode of the first direct current power supply is connected with the cathode of the first direct current power supply, and the common end of the first direct current power supply is used as a first direct current power supply of the first end of the preceding stage network;
the positive electrode of the third direct current power supply is connected with the negative electrode of the third direct current power supply, the common end of the third direct current power supply is used as the fourth end of the preceding-stage network, and the negative electrode of the third direct current power supply is used as the fourth direct current power supply of the fifth end of the preceding-stage network;
and the output voltages of the 4 direct current power supplies in the preceding stage network are all equal.
Preferably, the three-phase five-level bridge arm includes 24 switching tubes, and for each phase of the three-phase circuits constituting the three-phase five-level bridge arm, the phase circuit includes:
the first end of the first switch tube is connected with the first end of the secondary winding of the first transformer, and the second end of the first switch tube is connected with the first end of the second switch tube and the first end of the fifth switch tube;
the second end of the second switch tube is connected with the first end of the third switch tube and the first end of the seventh switch tube;
the second end of the third switching tube is connected with the first end of the fourth switching tube and the second end of the eighth switching tube;
the second end of the fourth switching tube is connected with the first end of the secondary winding of the second transformer;
the fifth switching tube is connected with the second end of the preceding stage network at the second end;
a sixth switching tube, a first end of which is connected with the third end of the preceding stage network, and a second end of which is connected with the second end of the seventh switching tube;
the seventh switching tube;
and the first end of the eighth switching tube is connected with the fourth end of the preceding stage network.
Preferably, the 24 switching tubes in the three-phase five-level bridge arm are all IGBTs, wherein a collector of each IGBT is used as a first end of the corresponding switching tube, and an emitter of each IGBT is used as a second end of the corresponding switching tube.
Preferably, the method further comprises the following steps:
the anode of the first diode is connected with the first end of the preceding stage network, and the cathode of the first diode is connected with the first end of the primary winding of the first transformer;
and the cathode of the second diode is connected with the fifth end of the preceding stage network, and the anode of the second diode is connected with the first end of the primary winding of the second transformer.
Preferably, the first transformer and the second transformer are both low leakage inductance transformers.
Preferably, all 4 dc power supplies in the preceding stage network are dc voltage sources.
Preferably, all 4 dc power supplies in the preceding stage network are dc current sources.
Preferably, the first transformer is a transformer with adjustable number of turns of a primary winding and adjustable number of turns of a secondary winding, and the second transformer is a transformer with adjustable number of turns of the primary winding and adjustable number of turns of the secondary winding.
A photovoltaic power generation system comprises the topology of the three-phase five-level inverter.
The technical scheme provided by the embodiment of the invention comprises the following steps: the three-phase five-level bridge arm comprises a preceding-stage network, a first T source network, a second T source network and a three-phase five-level bridge arm, wherein the preceding-stage network is used for outputting direct current; the second end to the fourth end of the preceding-stage network are sequentially connected with the second end to the fourth end of the three-phase five-level bridge arm, the first end of the preceding-stage network is the anode of the preceding-stage network, and the fifth end of the preceding-stage network is the cathode of the preceding-stage network; the first tsource network comprises: the first end of the primary winding is connected with the first end of the preceding stage network, the second end of the primary winding is connected with the second end of the secondary winding, the common end of the primary winding is connected with the first end of the first capacitor, and the first end of the secondary winding is connected with the first end of the three-phase five-level bridge arm; the second end of the first capacitor is connected with the second end of the second capacitor; the second T-source network includes: the first end of the primary winding is connected with the fifth end of the preceding stage network, the second end of the primary winding is connected with the second end of the secondary winding, the common end of the primary winding is connected with the first end of the second capacitor, and the first end of the secondary winding is connected with the fifth end of the three-phase five-level bridge arm; a second capacitor; the first end of the primary winding of the first transformer and the first end of the secondary winding of the first transformer are homonymous ends of the first transformer; the first end of the primary winding of the second transformer and the first end of the secondary winding of the second transformer are homonymous ends of the second transformer.
In the scheme of the application, two T source networks are arranged, the first T source network comprises a first transformer and a first capacitor, and the second T source network comprises a second transformer and a second capacitor, so that the three-phase five-level inverter has the functions of boosting and reducing voltage. It should be noted that, when only the first T source network or only the second T source network is provided, the three-phase five-level inverter also has the functions of boosting and reducing voltage, but the applicant finds that, when two T source networks in the present application are provided at the same time, the output harmonic is greatly reduced, and the output power of the three-phase five-level inverter is also improved, compared with the case where only one T source network is provided. In summary, the scheme of the application provides a three-phase five-level inverter with voltage boosting and reducing functions.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a three-phase five-level NPC inverter in the prior art;
FIG. 2 is a schematic diagram of a topology of a three-phase five-level inverter according to the present invention;
fig. 3 is another schematic diagram of the topology of the three-phase five-level inverter of the present invention.
Detailed Description
The core of the invention is to provide a topological structure of a three-phase five-level inverter, and provide the three-phase five-level inverter with the functions of boosting and reducing voltage.
In order that those skilled in the art will better understand the disclosure, the invention will be described in further detail with reference to the accompanying drawings and specific embodiments. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 2, fig. 2 is a schematic diagram of a topology of a three-phase five-level inverter according to the present invention, including: the three-phase five-level bridge-arm three-phase five-level alternating current power supply comprises a preceding-stage network 10 for outputting direct current, a first T source network 20, a second T source network 30 and a three-phase five-level bridge arm 40 for outputting three-phase five-level alternating current power through an output end.
The preceding network 10 includes a dc power supply, and in the topology of the three-phase five-level inverter, the preceding network 10 portion generally has 5 output ports for connecting with corresponding three-phase five-level bridge arms 40, so as to convert the dc power output by the preceding network 10 into ac power. Referring to fig. 1, in fig. 1, an anode of a dc power source Vdc is connected to a capacitor C1, a common end of the dc power source Vdc is a first end of the preceding network, correspondingly, a common end of a capacitor C1 and a capacitor C2 is a second end of the preceding network, a common end of a capacitor C2 and a capacitor C3 is a third end of the preceding network, a common end of a capacitor C3 and a capacitor C4 is a fourth end of the preceding network, a cathode of the dc power source Vdc is connected to a capacitor C4, and a common end of the dc power source Vdc is a fifth end of the preceding network.
In the scheme of this application, the second end to the fourth end of the preceding network 10 are connected with the second end to the fourth end of the three-phase five-level bridge arm 40 in sequence, the first end of the preceding network 10 is the anode of the preceding network 10, and the fifth end of the preceding network 10 is the cathode of the preceding network 10. In fig. 2, the first end to the fifth end of the preceding-stage network 10 are sequentially denoted by 1 to 5. Accordingly, in fig. 2, 1 to 5 of the three-phase five-level arm 40 as a subsequent stage portion sequentially represent first to fifth ends of the three-phase five-level arm 40.
The first T-source network 20 includes a first transformer 21 and a first capacitor 22, and the second T-source network 30 includes a second transformer 31 and a second capacitor 32.
A first end of a primary winding of the first transformer 21 is connected to a first end of the pre-stage network 10, a second end of the primary winding of the first transformer 21 is connected to a second end of a secondary winding of the first transformer 21, a common end of the primary winding of the first transformer 21 is connected to a first end of the first capacitor 22, and a first end of the secondary winding of the first transformer 21 is connected to a first end of the three-phase five-level bridge arm 40.
A second terminal of the first capacitor 22 is connected to a second terminal of the second capacitor 32.
A first end of a primary winding of the second transformer 31 is connected to a fifth end of the pre-stage network 10, a second end of the primary winding of the second transformer 31 is connected to a second end of a secondary winding of the second transformer 31, a common end of the secondary winding of the second transformer 31 is connected to a first end of the second capacitor 32, and a first end of the secondary winding of the second transformer 31 is connected to a fifth end of the three-phase five-level bridge arm 40.
Wherein, the first end of the primary winding of the first transformer 21 and the first end of the secondary winding of the first transformer 21 are the same-name ends of the first transformer 21; the first end of the primary winding of the second transformer 31 and the first end of the secondary winding of the second transformer 31 are the same-name ends of the second transformer 31.
Due to the fact that the two T source networks are arranged, the first T source network 20 comprises the first transformer 21 and the first capacitor 22, and the second T source network 30 comprises the second transformer 31 and the second capacitor 32, the three-phase five-level inverter provided by the application has the capacity of boosting and reducing voltage, and when the three-phase five-level inverter is specifically implemented, the adjustment of the boosting and reducing amplitude of the three-phase five-level inverter can be achieved through setting and adjusting the winding of the first transformer 21 and setting and adjusting the winding of the second transformer 31.
It should be noted that when the scheme of the present application includes only one T-source network, that is, only the first T-source network 20 or only the second T-source network 30, the corresponding three-phase five-level inverter still has the step-up and step-down functions. For example, when only the first T-source network 20 is included, the second end of the first capacitor 22 in the first T-source network 20 is connected to the fifth end of the preceding-stage network 10, so that the winding of the first transformer 21 in the first T-source network 20 can be set and adjusted, and the change of the step-up and step-down amplitude of the inverter can be realized. The applicant finds that, through experimental data and theoretical analysis, two T-source networks are arranged in the topological structure of the three-phase five-level inverter, compared with the arrangement of only one T-source network, the harmonic content of the output voltage of the three-phase five-level inverter is less, and the output power is improved. In addition, in the arrangement of the hardware circuit in the specific implementation, the first T source network 20 and the second T source network 30 may be symmetrically arranged to further reduce harmonics.
The technical scheme provided by the embodiment of the invention comprises the following steps: the three-phase five-level bridge arm comprises a preceding-stage network, a first T source network, a second T source network and a three-phase five-level bridge arm, wherein the preceding-stage network is used for outputting direct current; the second end to the fourth end of the preceding-stage network are sequentially connected with the second end to the fourth end of the three-phase five-level bridge arm, the first end of the preceding-stage network is the anode of the preceding-stage network, and the fifth end of the preceding-stage network is the cathode of the preceding-stage network; the first tsource network comprises: the first end of the primary winding is connected with the first end of the preceding stage network, the second end of the primary winding is connected with the second end of the secondary winding, the common end of the primary winding is connected with the first end of the first capacitor, and the first end of the secondary winding is connected with the first end of the three-phase five-level bridge arm; the second end of the first capacitor is connected with the second end of the second capacitor; the second T-source network includes: the first end of the primary winding is connected with the fifth end of the preceding stage network, the second end of the primary winding is connected with the second end of the secondary winding, the common end of the primary winding is connected with the first end of the second capacitor, and the first end of the secondary winding is connected with the fifth end of the three-phase five-level bridge arm; a second capacitor; the first end of the primary winding of the first transformer and the first end of the secondary winding of the first transformer are homonymous ends of the first transformer; the first end of the primary winding of the second transformer and the first end of the secondary winding of the second transformer are homonymous ends of the second transformer.
In the scheme of the application, two T source networks are arranged, the first T source network comprises a first transformer and a first capacitor, and the second T source network comprises a second transformer and a second capacitor, so that the three-phase five-level inverter has the functions of boosting and reducing voltage. It should be noted that, when only the first T source network or only the second T source network is provided, the three-phase five-level inverter also has the functions of boosting and reducing voltage, but the applicant finds that, when two T source networks in the present application are provided at the same time, the output harmonic is greatly reduced, and the output power of the three-phase five-level inverter is also improved, compared with the case where only one T source network is provided. In summary, the scheme of the application provides a three-phase five-level inverter with voltage boosting and reducing functions.
In one embodiment of the present invention, the preceding-stage network 10 includes:
the positive electrode is used as a first direct current power supply of the first end of the preceding stage network 10;
the anode is connected with the cathode of the first direct current power supply, and the common end of the first direct current power supply is used as a second direct current power supply of the second end of the preceding stage network 10;
the anode is connected with the cathode of the second direct current power supply, and the common end of the second direct current power supply is used as a third direct current power supply of the third end of the preceding stage network 10;
the positive electrode of the fourth direct current power supply is connected with the negative electrode of the third direct current power supply, the common end of the fourth direct current power supply is used as the fourth end of the preceding network 10, and the negative electrode of the fourth direct current power supply is used as the fifth end of the preceding network 10;
wherein, the output voltages of the 4 dc power supplies in the preceding stage network 10 are all equal.
In a typical multi-level inverter, a dc power source and several capacitors are used to divide the dc power source, and ideally, the capacitors have the same voltage across them. In consideration of the fact that the capacitor voltage fluctuates in practical application, so that the output voltage deviates, in this embodiment, a scheme that 4 direct current power supplies are used to replace a conventional power supply and a plurality of capacitors is adopted, the output voltages of the direct current power supplies are equal, and the fluctuation situation of the capacitor voltage is avoided. Referring to fig. 3, in this embodiment, 4 dc voltage sources are used, that is, the first to fourth dc power sources are all dc voltage sources, and are sequentially denoted as udc1, udc2, udc3 and udc4 in fig. 3. Of course, in other embodiments, each dc power supply may be a dc current source according to actual needs, and the implementation of the present invention is not affected.
In an embodiment of the present invention, the three-phase five-level bridge arm 40 includes 24 switching tubes, and for each phase circuit in the three-phase circuits forming the three-phase five-level bridge arm 40, the phase circuit includes:
a first switching tube having a first end connected to the first end of the secondary winding of the first transformer 21 and a second end connected to the first end of the second switching tube and the first end of the fifth switching tube;
the second end of the second switch tube is connected with the first end of the third switch tube and the first end of the seventh switch tube;
the second end of the third switching tube is connected with the first end of the fourth switching tube and the second end of the eighth switching tube;
a fourth switching tube having a second end connected to the first end of the secondary winding of the second transformer 31;
a fifth switching tube having a second end connected to the second end of the preceding stage network 10;
a sixth switching tube, a first end of which is connected with the third end of the preceding stage network 10, and a second end of which is connected with the second end of the seventh switching tube;
a seventh switching tube;
and an eighth switching tube with a first end connected with the fourth end of the preceding stage network 10.
In this embodiment of the present application, the three-phase five-level bridge arm 40 includes 24 switching tubes, and compared with a bridge arm of a three-phase five-level NPC inverter in the prior art, the use of 18 clamping diodes is reduced, so that the structure is simpler, and therefore, the cost of the three-phase five-level inverter can be lower, and the reliability is higher. In specific implementation, the 24 switching tubes may be all IGBT tubes, and as shown in fig. 3, Sa1 to Sa8 sequentially represent the first to eighth switching tubes of an a-phase circuit, correspondingly, Sb1 to Sb8 sequentially represent the first to eighth switching tubes of a B-phase circuit, and Sc1 to Sc8 sequentially represent the first to eighth switching tubes of a C-phase circuit. When an IGBT is used as a switching tube, the collector of the IGBT may be used as the first terminal of the corresponding switching tube, the emitter may be used as the second terminal of the corresponding switching tube, and the gate may be used as the control terminal to receive a control signal from the control unit of the inverter to control the on state of the IGBT. In fig. 3, all the 24 switching tubes are IGBT tubes. The switching states of the individual IGBTs can be seen in the table below.
Table 1:
in one embodiment of the present invention, the method further comprises:
a first diode having an anode connected to a first end of the pre-stage network 10 and a cathode connected to a first end of a primary winding of the first transformer 21;
and a second diode having a cathode connected to the fifth terminal of the preceding network 10 and an anode connected to the first terminal of the primary winding of the second transformer 31.
The arrangement of the first diode and the second diode can ensure single-phase flow of current, avoid damage to each direct current power supply caused by reverse current, and improve the quality of output alternating voltage. Referring to fig. 3, the first diode is denoted as D1, the second diode is denoted as D2,
in one embodiment of the present invention, the first transformer 21 and the second transformer 31 are low leakage inductance transformers. Considering that the leakage inductance of the transformer is large, the transmission efficiency of the transformer is low, and the output power of the inverter is affected, and in addition, the leakage inductance of the transformer and a capacitor device in a circuit may form an oscillation circuit, which causes adverse conditions such as electromagnetic interference. Therefore, in implementation, the first transformer 21 with low leakage inductance and the second transformer 31 with low leakage inductance may be selected. Of course, in practical application, the selection of other types of transformers can be performed according to actual needs, and the implementation of the invention is not affected.
In an embodiment of the present invention, the first transformer 21 is a transformer in which the number of turns of the primary winding and the number of turns of the secondary winding are both adjustable, and the second transformer 31 is a transformer in which the number of turns of the primary winding and the number of turns of the secondary winding are both adjustable. Considering that the windings of the first transformer 21 and the second transformer 31 may resonate with the capacitance in the circuit during the starting process of the inverter, the first transformer 21 and the second transformer 31 may be selected, where the number of turns of the primary winding and the number of turns of the secondary winding are both adjustable, and the resonant condition with the capacitance in the circuit during the starting process is avoided by adjusting the number of turns of the primary winding and the secondary winding of the first transformer 21 and adjusting the number of turns of the primary winding and the secondary winding of the second transformer 31 during the starting process.
Correspondingly to the above-mentioned embodiment of the topology of the three-phase five-level inverter, the embodiment of the present invention further provides a photovoltaic power generation system, which may include the topology of the three-phase five-level inverter in any of the above-mentioned embodiments, and a description thereof will not be repeated here.
It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same or similar parts among the embodiments are referred to each other. For the photovoltaic power generation system disclosed in the embodiment, since the photovoltaic power generation system corresponds to the topology of the three-phase five-level inverter disclosed in the embodiment, the description is relatively simple, and for the relevant points, reference may be made to the description of the part of the topology of the three-phase five-level inverter.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. The principle and the implementation of the present invention are explained in the present application by using specific examples, and the above description of the embodiments is only used to help understanding the technical solution and the core idea of the present invention. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (10)
1. A topology of a three-phase five-level inverter, comprising: the three-phase five-level bridge arm comprises a preceding-stage network, a first T source network, a second T source network and a three-phase five-level bridge arm, wherein the preceding-stage network is used for outputting direct current;
the second end to the fourth end of the preceding-stage network are sequentially connected with the second end to the fourth end of the three-phase five-level bridge arm, the first end of the preceding-stage network is the anode of the preceding-stage network, and the fifth end of the preceding-stage network is the cathode of the preceding-stage network;
the first Tsource network includes:
a first transformer, wherein the first end of the primary winding is connected with the first end of the preceding stage network, the second end of the primary winding is connected with the second end of the secondary winding, the common end of the primary winding is connected with the first end of the first capacitor, and the first end of the secondary winding is connected with the first end of the three-phase five-level bridge arm;
the second end of the first capacitor is connected with the second end of the second capacitor;
the second T source network comprises:
a first transformer, a second transformer, a third transformer and a fourth transformer, wherein the first end of the primary winding is connected with the fifth end of the preceding stage network, the second end of the primary winding is connected with the second end of the secondary winding, the common end of the primary winding is connected with the first end of the second capacitor, and the first end of the secondary winding is connected with the fifth end of the three-phase five-level bridge arm;
the second capacitor;
the first end of the primary winding of the first transformer and the first end of the secondary winding of the first transformer are homonymous ends of the first transformer; and the first end of the primary winding of the second transformer and the first end of the secondary winding of the second transformer are homonymous ends of the second transformer.
2. The topology of a three-phase five-level inverter of claim 1, wherein the pre-stage network comprises:
the positive electrode is used as a first direct current power supply of the first end of the preceding stage network;
the anode of the first direct current power supply is connected with the cathode of the first direct current power supply, and the common end of the first direct current power supply is used as a second direct current power supply of the second end of the preceding stage network;
the anode of the first direct current power supply is connected with the cathode of the first direct current power supply, and the common end of the first direct current power supply is used as a first direct current power supply of the first end of the preceding stage network;
the positive electrode of the third direct current power supply is connected with the negative electrode of the third direct current power supply, the common end of the third direct current power supply is used as the fourth end of the preceding-stage network, and the negative electrode of the third direct current power supply is used as the fourth direct current power supply of the fifth end of the preceding-stage network;
and the output voltages of the 4 direct current power supplies in the preceding stage network are all equal.
3. The topology of a three-phase five-level inverter according to claim 1, wherein the three-phase five-level bridge arm comprises 24 switching tubes, and for each of the three-phase circuits constituting the three-phase five-level bridge arm, the phase circuit comprises:
the first end of the first switch tube is connected with the first end of the secondary winding of the first transformer, and the second end of the first switch tube is connected with the first end of the second switch tube and the first end of the fifth switch tube;
the second end of the second switch tube is connected with the first end of the third switch tube and the first end of the seventh switch tube;
the second end of the third switching tube is connected with the first end of the fourth switching tube and the second end of the eighth switching tube;
the second end of the fourth switching tube is connected with the first end of the secondary winding of the second transformer;
the fifth switching tube is connected with the second end of the preceding stage network at the second end;
a sixth switching tube, a first end of which is connected with the third end of the preceding stage network, and a second end of which is connected with the second end of the seventh switching tube;
the seventh switching tube;
and the first end of the eighth switching tube is connected with the fourth end of the preceding stage network.
4. The topology of a three-phase five-level inverter according to claim 3, wherein the 24 switching tubes in the three-phase five-level bridge arm are all IGBTs, wherein a collector of each IGBT serves as a first end of the corresponding switching tube, and an emitter of each IGBT serves as a second end of the corresponding switching tube.
5. The topology of a three-phase five-level inverter of claim 1, further comprising:
the anode of the first diode is connected with the first end of the preceding stage network, and the cathode of the first diode is connected with the first end of the primary winding of the first transformer;
and the cathode of the second diode is connected with the fifth end of the preceding stage network, and the anode of the second diode is connected with the first end of the primary winding of the second transformer.
6. The topology of a three-phase five-level inverter of claim 1, wherein the first transformer and the second transformer are low leakage inductance transformers.
7. The topology of a three-phase five-level inverter according to claim 2, wherein 4 dc power sources in the pre-stage network are all dc voltage sources.
8. The topology of a three-phase five-level inverter according to claim 2, wherein the 4 dc power sources in the pre-stage network are all dc current sources.
9. The topology of any one of claims 1 to 8, wherein the first transformer is a transformer with adjustable number of turns of a primary winding and adjustable number of turns of a secondary winding, and the second transformer is a transformer with adjustable number of turns of a primary winding and adjustable number of turns of a secondary winding.
10. A photovoltaic power generation system, characterized by comprising a topology of a three-phase five-level inverter according to any of claims 1 to 9.
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| "New Type T-Source Inverter";Ryszard Strzelecki,et.al.;《2009 Compatibility and Power Electronics》;20090706;第191-195页 * |
| "新型Z源T型五电平逆变器及其调制策略";蔡智林，侯涛;《高电压技术》;20170430;第43卷(第4期);第1203-1213页 * |
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