CN114844384A - Five-level grid-connected inverter structure, inverter and photovoltaic power system - Google Patents

Five-level grid-connected inverter structure, inverter and photovoltaic power system Download PDF

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Publication number
CN114844384A
CN114844384A CN202210649038.6A CN202210649038A CN114844384A CN 114844384 A CN114844384 A CN 114844384A CN 202210649038 A CN202210649038 A CN 202210649038A CN 114844384 A CN114844384 A CN 114844384A
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China
Prior art keywords
power switch
switch tube
inverter
network
power
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Chinese (zh)
Inventor
齐革军
牛晨晖
陈晓路
姚中原
张宇
陈新宇
蒋俊荣
李冬
肖华锋
刘贇
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Huaneng Guanyun Clean Energy Power Generation Co ltd
Southeast University
Clean Energy Branch of Huaneng International Power Jiangsu Energy Development Co Ltd Clean Energy Branch
Huaneng International Power Jiangsu Energy Development Co Ltd
Original Assignee
Huaneng Guanyun Clean Energy Power Generation Co ltd
Southeast University
Clean Energy Branch of Huaneng International Power Jiangsu Energy Development Co Ltd Clean Energy Branch
Huaneng International Power Jiangsu Energy Development Co Ltd
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Application filed by Huaneng Guanyun Clean Energy Power Generation Co ltd, Southeast University, Clean Energy Branch of Huaneng International Power Jiangsu Energy Development Co Ltd Clean Energy Branch, Huaneng International Power Jiangsu Energy Development Co Ltd filed Critical Huaneng Guanyun Clean Energy Power Generation Co ltd
Priority to CN202210649038.6A priority Critical patent/CN114844384A/en
Publication of CN114844384A publication Critical patent/CN114844384A/en
Pending legal-status Critical Current

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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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/50—Controlling the sharing of the out-of-phase component
    • 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
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H02M1/126—Arrangements for reducing harmonics from ac input or output using passive filters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

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

Abstract

The invention discloses a five-level grid-connected inverter structure, an inverter and a photovoltaic power system, and belongs to the field of inverter circuit topology. The inverter circuit comprises a direct current source, an inverter network, an alternating current filter and an external alternating current source, wherein the positive electrode of the direct current source is connected with the input end of the inverter network, the output end of the inverter network is connected with the input end of the alternating current filter, the output end of the alternating current filter is connected with one end of the external alternating current source, the other end of the external alternating current source is grounded, the negative electrode of the direct current source, the grounding end of the inverter network and the grounding end of the alternating current filter network are all grounded, and a driving signal of a power switch tube of the single-phase common-ground five-level inverter circuit is generated by comparing a modulation wave with a carrier wave. The inverter circuit has the characteristics of low harmonic content of differential mode voltage, capability of completely eliminating leakage current and the like, and is suitable for application of medium-small power non-isolated photovoltaic grid-connected inverter systems.

Description

Five-level grid-connected inverter structure, inverter and photovoltaic power system
Technical Field
The invention relates to the field of inverter circuit topology, in particular to a five-level grid-connected inverter structure, an inverter and a photovoltaic power system.
Background
Solar energy is a very important component of clean renewable energy, and distributed photovoltaic power generation plays an increasingly important role as an important component of the power grid. However, a large parasitic capacitance exists between the photovoltaic panel and the ground, and the generated common mode leakage current is large, so that not only can the system efficiency be reduced, but also the safety of personnel and equipment can be influenced. The neutral point of the power grid is directly connected to the common ground structure of the anode or the cathode of the input voltage, so that the parasitic capacitance can be short-circuited, and the leakage current can be completely eliminated. The output voltage of the photovoltaic panel needs to be matched with the peak voltage of the power grid through an inverter circuit; in addition, improving the quality of electric power by increasing the number of output voltage levels has become another main measure of the non-isolated inverter circuit, which facilitates the integration of a smaller-sized ac filter. Therefore, the voltage reduction characteristic of the output voltage of the inverter circuit and the generated leakage current are two main defects of the current non-isolated inverter circuit. In addition, when the output voltage of the inverter circuit is at three levels, a large ac filter needs to be configured to improve the power quality of the injected grid current.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a five-level grid-connected inverter structure, an inverter and a photovoltaic power system.
The purpose of the invention can be realized by the following technical scheme:
a five-level grid-connected inverter structure is characterized by comprising: an inverter network and an AC filter;
the input end of the inverter network is connected with the anode of the direct current source; the output end of the inverter network is connected with the input end of the alternating current filter; the output end of the alternating current filter is connected with one end of an external alternating current source, and the other end of the external alternating current source is grounded; the negative electrode of the direct current source, the grounding end of the inversion network and the grounding end of the alternating current filter are all grounded;
the inverter network comprises a first power switch tube, a second power switch tube, a third power switch tube, a fourth power switch tube, a fifth power switch tube, a sixth power switch tube, a seventh power switch tube, an eighth power switch tube, a ninth power switch tube, a first capacitor and a second capacitor;
the drain electrode of the first power switch tube is connected with the drain electrode of the second power switch tube; the source electrode of the first power switch tube and the drain electrode of the fifth power switch tube are connected with the anode of the first capacitor; the source electrode of the second power switch tube, the drain electrode of the third power switch tube and the source electrode of the fourth power switch tube are connected with the cathode of the first capacitor;
the source electrode of the fifth power switching tube and the drain electrode of the sixth power switching tube are connected with the drain electrode of the seventh power switching tube; the drain electrode of the fourth power switch tube is connected with the anode of the second capacitor; the source electrode of the eighth power switch tube and the ninth power switch tube are connected with the negative electrode of the second capacitor; the source electrode of the sixth power switch tube is connected with the drain electrode of the eighth power switch tube;
the drain electrode of the first power switch tube is connected with the positive electrode of the direct current source as the input end of the inverter network; the source electrode of the sixth power switch tube and the drain electrode of the eighth power switch tube are both output ends of the inverter network; and the source electrode of the third power switch tube, the source electrode of the seventh power switch tube and the drain electrode of the ninth power switch tube are all grounded ends of an inverter network and are connected with the negative electrode of a direct current source.
Further, the second power switch tube, the fourth power switch tube, the fifth power switch tube, the sixth power switch tube, the seventh power switch tube, the eighth power switch tube and the ninth power switch tube are all composed of a power transistor and a parallel-reverse diode, a drain electrode or a collector electrode of the power transistor is connected with a cathode of the parallel-reverse diode to form a drain electrode of the power switch tube, and a source electrode or an emitter electrode of the power transistor is connected with an anode of the parallel-reverse diode to form a source electrode of the power switch tube.
Furthermore, the first power switch tube and the third power switch tube are in a series structure that the source electrode of the power switch tube without a reverse diode or the source electrode of the power switch tube with the reverse diode is connected with the anode electrode of the power switch tube.
Furthermore, the ac filter includes a filter inductor and a filter capacitor, one end of the filter inductor is an input end of the ac filter network, the other end of the filter inductor is connected to an anode of the filter capacitor, a connection point between the filter inductor and the filter capacitor is an output end of the ac filter, and a cathode of the filter capacitor is a ground end of the ac filter.
Furthermore, the driving signal of the power switch tube of the inverter network is generated by modulating a modulation wave and a high-frequency carrier wave, wherein the modulation wave is at 50Hz power frequency, and the frequency of the carrier wave is 100 kHz.
Further, the five-level grid-connected inverter structure comprises the following working modes:
the first mode is as follows: the output voltage of the inverter network is equal to the direct current source, and the first power switch tube, the third power switch tube, the fifth power switch tube and the sixth power switch tube are switched on; the second power switch tube, the fourth power switch tube, the seventh power switch tube, the eighth power switch tube and the ninth power switch tube are disconnected;
mode two: the output voltage of the inverter network is equal to twice of the direct current source, and the second power switch tube, the fourth power switch tube, the fifth power switch tube, the sixth power switch tube and the ninth power switch tube are switched on; the first power switch tube, the third power switch tube, the seventh power switch tube and the eighth power switch tube are disconnected;
mode three: the output voltage of the inverter network is equal to 0, and the first power switch tube, the third power switch tube, the eighth power switch tube and the ninth power switch tube are switched on; the second power switch tube, the fourth power switch tube, the fifth power switch tube, the sixth power switch tube and the seventh power switch tube are disconnected;
and a fourth mode: the output voltage of the inverter network is equal to 0; the second power switch tube, the fourth power switch tube, the eighth power switch tube and the ninth power switch tube are switched on; the first power switch tube, the third power switch tube, the fifth power switch tube, the sixth power switch tube and the seventh power switch tube are disconnected;
a fifth mode: the output voltage of the inverter network is equal to minus one time of the direct current source; the first power switch tube, the third power switch tube, the fourth power switch tube and the eighth power switch tube are switched on; the second power switch tube, the fifth power switch tube, the sixth power switch tube, the seventh power switch tube and the ninth power switch tube are disconnected;
a sixth mode: the output voltage of the inversion network is equal to twice of the direct current source; the fourth power switch tube, the fifth power switch tube, the seventh power switch tube and the eighth power switch tube are switched on; the first power switch tube, the second power switch tube, the third power switch tube, the sixth power switch tube and the ninth power switch tube are disconnected.
The invention also provides an inverter which comprises the five-level grid-connected inverter structure.
The present invention also provides a photovoltaic power system, comprising:
an optoelectronic device as a dc power supply for outputting a dc voltage;
an alternating current distribution network;
the inverter as described above, an input end of the inverter is connected to the photovoltaic apparatus, an output end of the inverter is connected to the ac distribution network, and the inverter is configured to convert the dc voltage into an ac voltage and output the ac voltage to the ac distribution network.
The invention has the beneficial effects that:
the inverter circuit clamps the voltage on the parasitic capacitor between the photovoltaic panel and the ground to 0 through the common-ground structure, so that the leakage current in a non-isolated grid-connected inverter system can be completely eliminated; the inverter circuit can output five-level voltage, reduce the volume of an alternating current filter and grid-connected current harmonic waves, and realize a boosting function; the inverter circuit has the capability of transmitting reactive power to a power grid, and is suitable for application of medium-small power non-isolated photovoltaic grid-connected inverter systems.
Drawings
The invention will be further described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of an inverter circuit according to the present invention;
FIG. 2 is a schematic diagram of a power switch driving signal of the inverter circuit according to the present invention;
FIG. 3 is a schematic diagram of an inverter circuit according to the present invention;
FIG. 4 is a diagram of a mode two of an inverter circuit according to the present invention;
FIG. 5 is a schematic diagram of an inverter circuit according to the present invention;
FIG. 6 is a diagram illustrating a mode four of an inverter circuit according to the present invention;
FIG. 7 is a schematic diagram of an inverter circuit according to the present invention;
FIG. 8 is a diagram illustrating a sixth mode of an inverter circuit according to the present invention;
FIG. 9 shows a V of an inverter circuit according to the present invention in And v ab A waveform diagram of (a);
FIG. 10 is a waveform of a capacitor voltage of the inverter circuit according to the present invention;
FIG. 11 is a waveform showing the operation of the inverter circuit of the present invention at a unit power factor;
FIG. 12 is a waveform showing the operation of the inverter circuit with the advance of the grid current at a non-unity power factor;
fig. 13 is an operation waveform of the inverter circuit according to the present invention when the grid-incoming current lags due to a non-unity power factor.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.
In the description of the present invention, it is to be understood that the terms "opening," "upper," "lower," "thickness," "top," "middle," "length," "inner," "peripheral," and the like are used in an orientation or positional relationship that is merely for convenience in describing and simplifying the description, and do not indicate or imply that the referenced component or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be considered as limiting the present invention.
In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
A single-phase common-ground five-level inverter circuit comprises a DC source, an inverter network, an AC filter and an external AC source, as shown in FIG. 1, wherein the positive pole of the DC source is connected with the input end of the inverter network, the output end of the inverter network is connected with the input end of the AC filter, the output end of the AC filter is connected with one end of the external AC source, the other end of the external AC source is grounded, the negative pole of the DC source, the grounding end of the inverter network and the grounding end of the AC filter are grounded, and the DC source is voltage V in The voltage across the external AC source is the grid voltage u g The current on the external AC source being the incoming current i g 。
The inverter network comprises a first power switch tube S 1 A second power switch tube S 2 The third power switch tube S 3 The fourth power switch tube S 4 The fifth power switch tube S 5 Sixth power switch tube S 6 Seventh power switch tube S 7 The eighth power switch tube S 8 The ninth power switch tube S 9 A first capacitor C 1 A second capacitor C 2 。
Second power switch tube S 2 The fourth workRate switching tube S 4 The fifth power switch tube S 5 Sixth power switch tube S 6 Seventh power switch tube S 7 The eighth power switch tube S 8 Ninth power switch tube S 9 The power transistor is composed of a power transistor and a reverse parallel diode, a drain electrode or a collector electrode of the power transistor is connected with a cathode of the reverse parallel diode to form a drain electrode of the power switch tube, and a source electrode or an emitter electrode of the power transistor is connected with an anode of the reverse parallel diode to form a source electrode of the power switch tube.
First power switch tube S 1 And a third power switch tube S 3 The power switch tube without the anti-parallel diode or the series structure of the source electrode of the power switch tube with the anti-parallel diode and the anode of the power switch tube is adopted.
First power switch tube S 1 And the second power switch tube S 2 Is connected with the drain electrode of the first power switch tube S 1 Source electrode of the fifth power switch tube S 5 Drain electrode of and the first capacitor C 1 Is connected with the anode of the second power switch tube S 2 Source electrode of the first power switch tube S 3 Drain electrode of the fourth power switch tube S 4 Source electrode of and the first capacitor C 1 The negative electrodes are connected;
fifth power switch tube S 5 Source electrode of, sixth power switch tube S 6 Drain electrode of and seventh power switch tube S 7 Is connected with the drain of the fourth power switch tube S 4 Drain electrode of and the second capacitor C 2 Is connected with the positive pole of the eighth power switch tube S 8 Source electrode of, ninth power switch tube S 9 And a second capacitor C 2 Is connected with the negative pole of the sixth power switch tube S 6 Source and eighth power switch tube S 8 The drain electrodes of the two electrodes are connected;
first power switch tube S 1 The drain electrode of the inverter network is an input end of the inverter network and a direct current source V in Positive pole connected sixth power switch tube S 6 Source electrode of, eighth power switch tube S 8 The drain electrodes of the first and second power switch tubes S are output ends of an inverter network 3 Source electrode of, seventh power switch tube S 7 Source electrode of and ninth power switch tube S 9 The drain electrode of the inverter is the grounding end of the inverter network and the direct current source V in The negative electrodes are connected.
The AC filter comprises a filter inductor L f And a filter capacitor C f Filter inductance L f One end of the filter is an input end of an alternating current filter network, and the other end of the filter is connected with a filter capacitor C f Is connected with the positive pole of the filter inductor L f And a filter capacitor C f Is connected with the output end of the AC filter and the filter capacitor C f The negative pole of (2) is the grounding end of the alternating current filter.
The power switch tube driving signal of the single-phase common-ground five-level inverter circuit is composed of a modulation wave u m And a carrier v tri Comparing the generated, modulated wave u m The power frequency is 50 Hz; carrier v tri Is 100 kHz; the two are modulated to generate a driving signal to control the switching mode of the power switching tube so as to complete the state switching of the inverter network and realize the energy exchange between the direct current source and an external alternating current source;
the working modes of the inverter circuit on the switching frequency scale include mode one, mode two, mode three, mode four, mode five and mode six, as shown in fig. 2, the mode one is t 3 -t 4 Working mode of time interval, the mode two is t 4 -t 5 Working mode of time interval, the mode three is t 1 -t 2 The unit power factor working mode of the time interval, the mode four is t 6 -t 7 Working mode of time interval, the mode five is t 8 -t 9 Unit power factor working mode of time interval, the six modes are t 9 -t 10 Unit power factor mode of operation of a time period.
The output voltage of the inversion network of mode one is equal to the DC source as V in As shown in fig. 3, the first power switch tube S 1 The third power switch tube S 3 The fifth power switch tube S 5 And a sixth power switch tube S 6 On, second power switch tube S 2 The fourth power switch tube S 4 Seventh power switch tube S 7 The eighth power switch tube S 8 And a ninth power switch tube S 9 Breaking, network-in current i g Can be bidirectionalAnd (4) flowing.
The output voltage of the inversion network of the second mode is twice that of the DC source of 2V in As shown in fig. 4, the second power switch tube S 2 The fourth power switch tube S 4 The fifth power switch tube S 5 Sixth power switch tube S 6 And a ninth power switch tube S 9 Switching on, the first power switch tube S 1 The third power switch tube S 3 Seventh power switch tube S 7 And an eighth power switch tube S 8 Breaking, network-in current i g Can flow in both directions.
The output voltage of the inversion network of mode three is equal to 0, as shown in fig. 5, which is a follow current mode of the positive half cycle of the power grid, and the first power switch tube S 1 The third power switch tube S 3 The eighth power switch tube S 8 And a ninth power switch tube S 9 A second power switch tube S 2 Fourth power switch tube S 4 The fifth power switch tube S 5 Sixth power switch tube S 6 And a seventh power switch tube S 7 Breaking, network-in current i g Can flow in both directions.
The output voltage of the inversion network in the fourth mode is equal to 0, as shown in fig. 6, which is a follow current mode of the negative half cycle of the power grid, and the second power switch tube S 2 Fourth power switch tube S 4 The eighth power switch tube S 8 And a ninth power switch tube S 9 Switching on, the first power switch tube S 1 The third power switch tube S 3 The fifth power switch tube S 5 Sixth power switch tube S 6 And a seventh power switch tube S 7 Breaking, network-in current i g Can flow in both directions.
The direct current source with the output voltage of the inversion network of the mode five being equal to minus one time is-V in As shown in fig. 7, the first power switch tube S 1 The third power switch tube S 3 The fourth power switch tube S 4 And an eighth power switch tube S 8 On, second power switch tube S 2 The fifth power switch tube S 5 Sixth power switch tube S 6 Seventh power switch tube S 7 And a ninth power switchClosing pipe S 9 Breaking, network-in current i g Can flow in two directions;
the output voltage of the inversion network with the sixth mode is equal to two times of that of a DC source with the voltage of-2V in As shown in fig. 8, the fourth power switch tube S 4 The fifth power switch tube S 5 Seventh power switch tube S 7 And an eighth power switch tube S 8 Switching on, the first power switch tube S 1 A second power switch tube S 2 The third power switch tube S 3 Sixth power switch tube S 6 And a ninth power switch tube S 9 Breaking, network-in current i g Can flow in two directions;
when all the power switch tubes work according to the driving signals, the inverter network continuously switches among the five output levels, and energy exchange between input direct-current voltage and external alternating current is achieved.
The operation waveform of the inverter circuit of the present invention at five-level output is shown as V in FIG. 9 dc And v ab In the waveform diagram of (1), the input voltage (200V in the figure) is lower than the peak value of the output five-level voltage (400V in the figure), so that the inverter circuit can realize the boosting function.
The waveform of the capacitor voltage when the inverter circuit of the present invention is in five-level output is shown in fig. 10, and it can be seen that the capacitor voltage (200V in the figure) is equal to the input voltage.
The unit power factor, the advance of the network access current and the operation waveform of the inverter circuit in the five-level output state are shown in fig. 11, fig. 12 and fig. 13, and it can be known that the single-phase five-level inverter circuit has the capability of transmitting reactive power to the power grid.
In summary, according to the single-phase common-ground five-level inverter circuit and the switch control strategy thereof, the voltage on the parasitic capacitor between the photovoltaic panel and the ground is clamped at 0V through the common-ground structure, so that the leakage current in the non-isolated grid-connected inverter system can be completely eliminated, the volume of the alternating current filter and the current harmonic of the power grid can be reduced through the output five-level voltage, and the boosting function is realized. The inverter circuit has the capability of transmitting reactive power to a power grid, and is suitable for application of medium-small power non-isolated photovoltaic grid-connected inverter systems.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed.

Claims (8)

1. A five-level grid-connected inverter structure is characterized by comprising: an inverter network and an AC filter;
the input end of the inverter network is connected with the anode of the direct current source; the output end of the inverter network is connected with the input end of the alternating current filter; the output end of the alternating current filter is connected with one end of an external alternating current source, and the other end of the external alternating current source is grounded; the negative electrode of the direct current source, the grounding end of the inversion network and the grounding end of the alternating current filter are all grounded;
the inverter network comprises a first power switch tube, a second power switch tube, a third power switch tube, a fourth power switch tube, a fifth power switch tube, a sixth power switch tube, a seventh power switch tube, an eighth power switch tube, a ninth power switch tube, a first capacitor and a second capacitor;
the drain electrode of the first power switch tube is connected with the drain electrode of the second power switch tube; the source electrode of the first power switch tube and the drain electrode of the fifth power switch tube are connected with the anode of the first capacitor; the source electrode of the second power switch tube, the drain electrode of the third power switch tube and the source electrode of the fourth power switch tube are connected with the cathode of the first capacitor;
the source electrode of the fifth power switching tube and the drain electrode of the sixth power switching tube are connected with the drain electrode of the seventh power switching tube; the drain electrode of the fourth power switch tube is connected with the anode of the second capacitor; the source electrode of the eighth power switch tube and the ninth power switch tube are connected with the negative electrode of the second capacitor; the source electrode of the sixth power switch tube is connected with the drain electrode of the eighth power switch tube;
the drain electrode of the first power switch tube is connected with the positive electrode of the direct current source as the input end of the inverter network; the source electrode of the sixth power switch tube and the drain electrode of the eighth power switch tube are both output ends of the inverter network; and the source electrode of the third power switch tube, the source electrode of the seventh power switch tube and the drain electrode of the ninth power switch tube are all grounded ends of an inverter network and are connected with the negative electrode of a direct current source.
2. The five-level grid-connected inverter structure according to claim 1, wherein the second power switch tube, the fourth power switch tube, the fifth power switch tube, the sixth power switch tube, the seventh power switch tube, the eighth power switch tube, and the ninth power switch tube are all composed of a power transistor and a nand diode, a drain or a collector of the power transistor is connected to a cathode of the nand diode to form a drain of the power switch tube, and a source or an emitter of the power transistor is connected to an anode of the nand diode to form a source of the power switch tube.
3. The five-level grid-connected inverter structure according to claim 1, wherein the first power switch tube and the third power switch tube are in a series structure in which a source of the power switch tube without a merged diode or a source of the power switch tube with a merged diode is connected to an anode of the power switch tube.
4. The five-level grid-connected inverter structure according to claim 1, wherein the ac filter includes a filter inductor and a filter capacitor, one end of the filter inductor is an input end of an ac filter network, the other end of the filter inductor is connected to an anode of the filter capacitor, a connection point of the filter inductor and the filter capacitor is an output end of the ac filter, and a cathode of the filter capacitor is a ground end of the ac filter.
5. The five-level grid-connected inverter structure according to claim 1, wherein the driving signal of the power switch tube of the inverter network is generated by modulating a modulation wave and a high-frequency carrier wave, the modulation wave is at a power frequency of 50Hz, and the frequency of the carrier wave is 100 kHz.
6. The five-level grid-connected inverter structure according to claim 1, wherein the five-level grid-connected inverter structure comprises the following working modes:
a first mode: the output voltage of the inverter network is equal to the direct current source, and the first power switch tube, the third power switch tube, the fifth power switch tube and the sixth power switch tube are switched on; the second power switch tube, the fourth power switch tube, the seventh power switch tube, the eighth power switch tube and the ninth power switch tube are disconnected;
mode two: the output voltage of the inverter network is equal to twice of the direct current source, and the second power switch tube, the fourth power switch tube, the fifth power switch tube, the sixth power switch tube and the ninth power switch tube are switched on; the first power switch tube, the third power switch tube, the seventh power switch tube and the eighth power switch tube are disconnected;
mode three: the output voltage of the inverter network is equal to 0, and the first power switch tube, the third power switch tube, the eighth power switch tube and the ninth power switch tube are switched on; the second power switch tube, the fourth power switch tube, the fifth power switch tube, the sixth power switch tube and the seventh power switch tube are disconnected;
and a fourth mode: the output voltage of the inverter network is equal to 0; the second power switch tube, the fourth power switch tube, the eighth power switch tube and the ninth power switch tube are switched on; the first power switch tube, the third power switch tube, the fifth power switch tube, the sixth power switch tube and the seventh power switch tube are disconnected;
a fifth mode: the output voltage of the inverter network is equal to minus one time of the direct current source; the first power switch tube, the third power switch tube, the fourth power switch tube and the eighth power switch tube are switched on; the second power switch tube, the fifth power switch tube, the sixth power switch tube, the seventh power switch tube and the ninth power switch tube are disconnected;
a sixth mode: the output voltage of the inversion network is equal to twice of the direct current source; the fourth power switch tube, the fifth power switch tube, the seventh power switch tube and the eighth power switch tube are switched on; the first power switch tube, the second power switch tube, the third power switch tube, the sixth power switch tube and the ninth power switch tube are disconnected.
7. An inverter comprising the five-level grid-connected inverter structure according to any one of claims 1 to 6.
8. A photovoltaic power system, comprising:
an optoelectronic device as a dc power supply for outputting a dc voltage;
an alternating current distribution network;
the inverter of claim 7, wherein the input of the inverter is connected to the photovoltaic device, the output of the inverter is connected to the ac distribution network, and the inverter is configured to convert the dc voltage into an ac voltage and output the ac voltage to the ac distribution network.
CN202210649038.6A 2022-06-09 2022-06-09 Five-level grid-connected inverter structure, inverter and photovoltaic power system Pending CN114844384A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116404864A (en) * 2023-06-07 2023-07-07 西南交通大学 Power decoupling step-up and step-down common-ground power factor correction method and topological structure
CN117792136A (en) * 2024-02-28 2024-03-29 南京师范大学 Multi-level inverter topological structure for photovoltaic grid connection

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116404864A (en) * 2023-06-07 2023-07-07 西南交通大学 Power decoupling step-up and step-down common-ground power factor correction method and topological structure
CN116404864B (en) * 2023-06-07 2023-08-08 西南交通大学 Power decoupling step-up and step-down common-ground power factor correction method and topological structure
CN117792136A (en) * 2024-02-28 2024-03-29 南京师范大学 Multi-level inverter topological structure for photovoltaic grid connection
CN117792136B (en) * 2024-02-28 2024-04-26 南京师范大学 Multi-level inverter topological structure for photovoltaic grid connection

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