CN113972685B - Single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter and control method thereof - Google Patents

Single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter and control method thereof Download PDF

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CN113972685B
CN113972685B CN202111139290.4A CN202111139290A CN113972685B CN 113972685 B CN113972685 B CN 113972685B CN 202111139290 A CN202111139290 A CN 202111139290A CN 113972685 B CN113972685 B CN 113972685B
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switch tube
electrolytic capacitor
tube
switching tube
capacitor
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CN113972685A (en
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华子捷
廖志凌
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Jiangsu University
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Jiangsu University
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    • 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
    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • 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
    • 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
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
    • 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)
  • Control Of Electrical Variables (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a control method of a single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter. The circuit topology comprises a DC power supply U DC Input filter capacitor C 1 Five-level output inverter circuit and output filter inductance L 1 And Grid. From a first switching tube S 1 Second switch tube S 2 Third switch tube S 3 Fourth switching tube S 4 Fifth switch tube S 5 Sixth switching tube S 6 Grid, first electrolytic capacitor C FC1 And a second electrolytic capacitor C FC2 An inverter circuit with five-level output is formed. The invention has the following advantages: 1) Compared with the traditional inversion topology, the common mode current is completely eliminated; 2) The number of the used switching tubes is small, and the cost is relatively low; 3) The voltage of the flying capacitor can be kept stable all the time; 4) Five-level output has smaller output total harmonic distortion.

Description

Single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter and control method thereof
Technical Field
The invention relates to the technical field of power electronic application, in particular to a control method of a single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter, which is applicable to the photovoltaic grid-connected inverter and belongs to the field of direct current/alternating current (DC/AC) converters.
Background
The energy crisis is aggravated in the world at present, the ecological environment is continuously worsened, solar energy is used as renewable energy, the solar energy has the important characteristics of inexhaustible use, and the solar energy is more and more paid attention to, wherein photovoltaic power generation is a main application mode of the solar energy, and a photovoltaic grid-connected inverter is a core device of the photovoltaic power generation.
The photovoltaic grid-connected inverter is divided into two major types of isolation type and non-isolation type, wherein the isolation type photovoltaic grid-connected inverter comprises a transformer, and has the advantages of large volume, high cost, low efficiency and high installation difficulty. The non-isolated photovoltaic grid-connected inverter does not contain a transformer, is small in size, light in weight, low in cost, high in efficiency and low in installation difficulty, but needs to restrain common-mode current, and is low in safety. To optimize the performance of the photovoltaic grid-connected inverter, the topology and control method must be improved, common mode current eliminated and cost saved.
Disclosure of Invention
Aiming at the problems of large volume, low safety, large output current ripple and the like in the traditional photovoltaic grid-connected inverter, the invention provides a control method of a single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter, which has the advantages of high safety, small volume, small output current ripple and the like.
The invention adopts the technical scheme that: a single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter comprises a direct current power supply U connected in parallel DC And input filter capacitor C 1 Input filter capacitor C 1 The two ends of the power supply are connected with the input of a five-level output inverter circuit, and the output of the five-level output inverter circuit is sequentially connected with a filter inductance L 1 And Grid.
Further, the five-level output inversion circuit is formed by a first switching tube S 1 Second switch tube S 2 Third switch tube S 3 Fourth switching tube S 4 Fifth switch tube S 5 Sixth switching tube S 6 First electrolytic capacitor C FC1 And a second electrolytic capacitor C FC2 Composition of the first switch tube S 1 Emitter of (c) and said second switching tube S 2 Collector of said third switching tube S 3 Collector of said fourth switching tube S 4 Emitter of (c), said sixth switching tube S 6 Is connected with the collector of the sixth switching tube S 6 Emitter of (c) and said fifth switching tube S 5 The emitter of the third switch tube S is connected with 3 Is connected with the first electrolytic capacitor C FC1 The negative electrode of the second electrolytic capacitor C is connected with FC2 Is connected with the first electrolytic capacitor C FC1 The negative electrode of the first electrolytic capacitor C is connected with FC1 And the fourth switching tube S 4 The emitter of the second electrolytic capacitor C is connected with FC2 And the fifth switch tube S 5 Is connected to the collector of the capacitor.
Further, the input filter capacitor C 1 Is an electrolytic capacitor, the positive electrode of which is connected with the positive electrode of the DC power supply and the first switch tube S 1 A negative electrode of the collector is connected with the negative electrode of the DC power supply and the second switch tube S 2 Is provided.
Further, the output filter inductance L 1 One end of the capacitor is connected with the first electrolytic capacitor C FC1 Is connected with the negative electrode of the output filter inductance L 1 Is arranged at the other end of (2)And connecting the power Grid.
Further, the direct current power supply U DC One end of the power Grid is grounded.
The invention discloses a control method of a single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter, which comprises the following steps:
working mode 1: a power transmission mode, the first switch tube S 1 Third switch tube S 3 Conduction, second switch tube S 2 Fourth switching tube S 4 Fifth switch tube S 5 Sixth switching tube S 6 Turn-off, the first electrolytic capacitor C FC1 And a second electrolytic capacitor C FC2 Are all in a suspension state;
working mode 2: a power transmission mode, the first switch tube S 1 Fifth switch tube S 5 Sixth switching tube S 6 Conduction, second switch tube S 2 Third switch tube S 3 Fourth switching tube S 4 Turn-off, the first electrolytic capacitor C FC1 Suspension, second electrolytic capacitor C FC2 Charging;
working mode 3: follow current mode, the second switch tube S 2 Third switch tube S 3 Conduction, first switch tube S 1 Fourth switching tube S 4 Fifth switch tube S 5 Sixth switching tube S 6 Turn-off, the first electrolytic capacitor C FC1 And a second electrolytic capacitor C FC2 Are all in a suspension state;
working mode 4: follow current mode, the first switch tube S 1 Fourth switching tube S 4 Conduction, second switch tube S 2 Third switch tube S 3 Fifth switch tube S 5 Sixth switching tube S 6 Turn-off, the first electrolytic capacitor C FC1 Charging, a second electrolytic capacitor C FC2 Suspending;
working mode 5: a power transmission mode, the second switch tube S 2 Fifth switch tube S 5 Sixth switching tube S 6 Conduction, first switch tube S 1 Third switch tube S 3 Fourth switching tube S 4 Shut off, first electrolytic capacitorC FC1 Suspension, second electrolytic capacitor C FC2 Discharging;
working mode 6: a power transmission mode, the second switch tube S 2 Fourth switching tube S 4 Conduction, first switch tube S 1 Third switch tube S 3 Fifth switch tube S 5 Sixth switching tube S 6 Turn-off, the first electrolytic capacitor C FC1 Discharging, a second electrolytic capacitor C FC2 And (5) suspending.
Further, a first electrolytic capacitor C FC1 And a second electrolytic capacitor C FC2 All require pre-charging, wherein the first electrolytic capacitor C FC1 Is charged to the voltage and DC power supply U DC The same, second electrolytic capacitor C FC2 Is charged to a voltage which is 0.5 times of the voltage of the direct current power supply U DC The same applies.
Further, by the model predictive control based on the DSP, the control section is made free from the modulation circuit while the dynamic response speed is quickened. And the model prediction control calculates a current prediction value corresponding to each mode at the next moment, and then selects the working mode closest to the reference value as the optimal mode.
Further, the method comprises the steps that the controller samples and uses model prediction control to calculate an optimal mode, and when the obtained optimal mode is a power transmission mode, a corresponding transmission mode is selected; when the obtained optimal mode is the follow current mode, judging the first electrolytic capacitor C FC1 And a second electrolytic capacitor C FC2 If the voltage of the capacitor is lower than the precharge value, selecting a freewheel mode for charging the capacitor, and if the voltage of the capacitor is greater than or equal to the precharge value, selecting an operating mode for suspending the capacitor.
Furthermore, the neutral point of the power grid is directly connected with the negative electrode of the solar panel through the common ground structure, which is equivalent to short-circuiting the common mode capacitor, and the common mode current is completely eliminated.
Further, in different working modes, different flying capacitors are connected in series and whether direct-current voltage is connected in or not is selected, so that five-level output is realized, and output current ripple is reduced; all modes can realize bidirectional current circulation, and reactive power compensation can be realized by only adjusting the reference current phase in the controller.
Compared with the prior art, the invention has the characteristics and advantages that: 1) Five-level output is realized, and output current ripple is small; 2) The common mode current is thoroughly eliminated by using a common ground connection method; 3) Only 6 switching tubes are used, so that the cost is low; 4) Model predictive control is used to avoid the control part from a modulation circuit and speed up dynamic response; 5) Reactive power compensation can be achieved.
Drawings
FIG. 1 is a topological structure diagram of a single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter;
FIG. 2 is a schematic diagram of a mode selection process for a single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter according to the present invention;
fig. 3 is an equivalent circuit of each switching mode of the single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter in one switching period. (a) is a modal 1 equivalent circuit; 1 (b) is a modal 2 equivalent circuit; (c) is a modal 3 equivalent circuit; (d) is a modal 4 equivalent circuit; (e) is a modal 5 equivalent circuit; (f) is a modal 6 equivalent circuit.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
As shown in FIG. 1, a single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter comprises a DC power supply U DC Input filter capacitor C 1 Five-level output inverter circuit and output filter inductance L 1 And a power Grid, the output filter inductance L 1 One end of the capacitor is connected with the first electrolytic capacitor C FC1 Is connected with the negative electrode of the output filter inductance L 1 The other end of the power Grid is connected with the power Grid.
The five-level output inversion circuit is formed by a first switch tube S 1 Second switch tube S 2 Third switch tube S 3 Fourth switching tube S 4 Fifth switch tube S 5 Sixth switching tube S 6 First electrolytic capacitor C FC1 And a second electrolytic capacitor C FC2 Composition, the first switchTube S 1 Emitter of (c) and said second switching tube S 2 Collector of said third switching tube S 3 Collector of said fourth switching tube S 4 Emitter of (c), said sixth switching tube S 6 Is connected with the collector of the sixth switching tube S 6 Emitter of (c) and said fifth switching tube S 5 The emitter of the third switch tube S is connected with 3 Is connected with the first electrolytic capacitor C FC1 The negative electrode of the second electrolytic capacitor C is connected with FC2 Is connected with the first electrolytic capacitor C FC1 The negative electrode of the first electrolytic capacitor C is connected with FC1 And the fourth switching tube S 4 The emitter of the second electrolytic capacitor C is connected with FC2 And the fifth switch tube S 5 Is connected to the collector of the capacitor. Further, the Boost circuit is formed by a first switch tube Q 1 First inductance L 1 Energy storage capacitor C 1 First diode D 1 And a second diode D 2 Composition is prepared. First inductance L 1 One end of the first inductor L is connected with the cathode of the first diode Dr1 1 The other end is connected with a first diode D 1 And a second diode D 2 Anode of the first switch tube Q 1 Is connected with the second diode D 2 Cathode of the first switch tube Q 1 Is connected with the energy storage capacitor C 1 Is a negative electrode of the energy storage capacitor C 1 Is connected with the first diode D 1 Is provided.
The input filter capacitor C 1 Is an electrolytic capacitor, the positive electrode of which is connected with the positive electrode of the DC power supply and the first switch tube S 1 A negative electrode of the collector is connected with the negative electrode of the DC power supply and the second switch tube S 2 Is provided.
As shown in fig. 2, the topology structure provided by the invention determines the operation mode selected by the topology through model predictive control and judgment on the voltage value of the capacitor, and the operation mode is as follows:
working mode 1: the first switch tube S 1 Third switch tube S 3 Conduction, second switch tube S 2 Fourth switching tube S 4 Fifth switch tube S 5 Sixth switching tube S 6 Turn-off, the first electrolytic capacitor C FC1 And a second electrolytic capacitor C FC2 Are all in a suspended state. In this mode, the grid voltage U g >0, topology output voltage U out ＝U DC The transmission of power is achieved.
Working mode 2: the first switch tube S 1 Fifth switch tube S 5 Sixth switching tube S 6 Conduction, second switch tube S 2 Third switch tube S 3 Fourth switching tube S 4 Turn-off, the first electrolytic capacitor C FC1 Suspension, second electrolytic capacitor C FC2 And (5) charging. In this mode, the grid voltage U g >0, topology output voltage U out ＝0.5U DC The transmission of power is achieved.
Working mode 3: the second switching tube S 2 Third switch tube S 3 Conduction, first switch tube S 1 Fourth switching tube S 4 Fifth switch tube S 5 Sixth switching tube S 6 Turn-off, the first electrolytic capacitor C FC1 And a second electrolytic capacitor C FC2 Are all in a suspended state. When the voltage of the flying capacitor is larger than or equal to the set value, the mode is selected, and the topology output voltage U is generated under the mode out =0, a freewheel pass mode is achieved.
Working mode 4: the first switch tube S 1 Fourth switching tube S 4 Conduction, second switch tube S 2 Third switch tube S 3 Fifth switch tube S 5 Sixth switching tube S 6 Turn-off, the first electrolytic capacitor C FC1 Charging, a second electrolytic capacitor C FC2 And (5) suspending. When the flying capacitor voltage is smaller than the set value, the mode is selected, and the topology output voltage U is in the mode out =0, a freewheel pass mode is achieved.
Working mode 5: the second switching tube S 2 Fifth switch tube S 5 Sixth switching tube S 6 Conduction, first switch tube S 1 Third switch tube S 3 Fourth switching tube S 4 Turn-off, the first electrolytic capacitor C FC1 Suspending, second electrolysisCapacitor C FC2 And (5) discharging. In this mode, the grid voltage U g <0, topology output voltage U out ＝-0.5U DC The transmission of power is achieved.
Working mode 6: the second switching tube S 2 Fourth switching tube S 4 Conduction, first switch tube S 1 Third switch tube S 3 Fifth switch tube S 5 Sixth switching tube S 6 Turn-off, the first electrolytic capacitor C FC1 Discharging, a second electrolytic capacitor C FC2 And (5) suspending. In this mode, the grid voltage U g <0, topology output voltage U out ＝-U DC The transmission of power is achieved.
According to the invention, on the basis of a traditional three-level photovoltaic grid-connected inverter, the topology is improved to realize five-level output, and the output ripple wave is reduced; through the common-ground structure, the common-mode current of the non-isolated grid-connected inverter is thoroughly eliminated, and the safety is greatly improved; the control part is protected from the modulation circuit by using model predictive control, and the dynamic response speed is accelerated.
In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., means 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, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.

Claims (6)

1. Single-phase non-isolated type common-ground five-level photovoltaicGrid-connected inverter is characterized by comprising a parallel direct current power supply U DC And input filter capacitor C 1 Input filter capacitor C 1 The two ends of the power supply are connected with the input of a five-level output inverter circuit, and the output of the five-level output inverter circuit is sequentially connected with a filter inductance L 1 And a Grid;
the five-level output inversion circuit is formed by a first switch tube S 1 Second switch tube S 2 Third switch tube S 3 Fourth switching tube S 4 Fifth switch tube S 5 Sixth switching tube S 6 First electrolytic capacitor C FC1 And a second electrolytic capacitor C FC2 Composition of the first switch tube S 1 Emitter of (c) and said second switching tube S 2 Collector of said third switching tube S 3 Collector of said fourth switching tube S 4 Emitter of (c), said sixth switching tube S 6 Is connected with the collector of the sixth switching tube S 6 Emitter of (c) and said fifth switching tube S 5 The emitter of the third switch tube S is connected with 3 Is connected with the first electrolytic capacitor C FC1 The negative electrode of the second electrolytic capacitor C is connected with FC2 Is connected with the first electrolytic capacitor C FC1 The negative electrode of the first electrolytic capacitor C is connected with FC1 And the fourth switching tube S 4 The emitter of the second electrolytic capacitor C is connected with FC2 And the fifth switch tube S 5 Is connected with the collector electrode of the power supply;
the input filter capacitor C 1 Is an electrolytic capacitor, the positive electrode of which is connected with the positive electrode of the DC power supply and the first switch tube S 1 A negative electrode of the collector is connected with the negative electrode of the DC power supply and the second switch tube S 2 An emitter of (a);
the output filter inductance L 1 One end of the capacitor is connected with the first electrolytic capacitor C FC1 Is connected with the negative electrode of the output filter inductance L 1 The other end of the power Grid is connected with the power Grid;
the direct current power supply U DC One end of the power Grid is grounded.
2. The control method of the single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter according to claim 1, comprising the following steps:
working mode 1: a power transmission mode, the first switch tube S 1 Third switch tube S 3 Conduction, second switch tube S 2 Fourth switching tube S 4 Fifth switch tube S 5 Sixth switching tube S 6 Turn-off, the first electrolytic capacitor C FC1 And a second electrolytic capacitor C FC2 Are all in a suspension state;
working mode 2: a power transmission mode, the first switch tube S 1 Fifth switch tube S 5 Sixth switching tube S 6 Conduction, second switch tube S 2 Third switch tube S 3 Fourth switching tube S 4 Turn-off, the first electrolytic capacitor C FC1 Suspension, second electrolytic capacitor C FC2 Charging;
working mode 3: follow current mode, the second switch tube S 2 Third switch tube S 3 Conduction, first switch tube S 1 Fourth switching tube S 4 Fifth switch tube S 5 Sixth switching tube S 6 Turn-off, the first electrolytic capacitor C FC1 And a second electrolytic capacitor C FC2 Are all in a suspension state;
working mode 4: follow current mode, the first switch tube S 1 Fourth switching tube S 4 Conduction, second switch tube S 2 Third switch tube S 3 Fifth switch tube S 5 Sixth switching tube S 6 Turn-off, the first electrolytic capacitor C FC1 Charging, a second electrolytic capacitor C FC2 Suspending;
working mode 5: a power transmission mode, the second switch tube S 2 Fifth switch tube S 5 Sixth switching tube S 6 Conduction, first switch tube S 1 Third switch tube S 3 Fourth switching tube S 4 Turn-off, the first electrolytic capacitor C FC1 Suspension, second electrolytic capacitor C FC2 Discharging;
working mode 6: power transmissionMode, the second switch tube S 2 Fourth switching tube S 4 Conduction, first switch tube S 1 Third switch tube S 3 Fifth switch tube S 5 Sixth switching tube S 6 Turn-off, the first electrolytic capacitor C FC1 Discharging, a second electrolytic capacitor C FC2 And (5) suspending.
3. The control method of the single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter as claimed in claim 2, wherein the first electrolytic capacitor C FC1 And a second electrolytic capacitor C FC2 All require pre-charging, wherein the first electrolytic capacitor C FC1 Is charged to the voltage and DC power supply U DC The same, second electrolytic capacitor C FC2 Is charged to a voltage which is 0.5 times of the voltage of the direct current power supply U DC The same applies.
4. The control method of a single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter according to claim 2, further comprising the steps of sampling and calculating by using a model prediction control to obtain an optimal mode, and selecting a corresponding transmission mode when the obtained optimal mode is a power transmission mode; when the obtained optimal mode is the follow current mode, judging the first electrolytic capacitor C FC1 And a second electrolytic capacitor C FC2 If the voltage of the capacitor is lower than the precharge value, selecting a freewheel mode for charging the capacitor, and if the voltage of the capacitor is greater than or equal to the precharge value, selecting an operating mode for suspending the capacitor.
5. The method for controlling a single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter according to claim 2, further comprising directly connecting a grid neutral point and a solar panel negative electrode through a common-ground structure.
6. The single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter according to claim 2, wherein in different working modes, different flying capacitors are connected in series and whether direct-current voltage is connected in or not is selected, so that five-level output is realized, and output current ripple is reduced; all modes can realize bidirectional current circulation, and reactive power compensation can be realized only by adjusting the reference current phase in the controller.
CN202111139290.4A 2021-09-27 2021-09-27 Single-phase non-isolated common-ground five-level photovoltaic grid-connected inverter and control method thereof Active CN113972685B (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109194175A (en) * 2018-08-27 2019-01-11 江苏大学 A kind of non-isolated grid-connected inverter circuit of type leakage current and control method altogether
CN111049182A (en) * 2019-12-24 2020-04-21 江苏大学 Five-level common-ground type single-phase non-isolated photovoltaic grid-connected inverter circuit and modulation method thereof

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109194175A (en) * 2018-08-27 2019-01-11 江苏大学 A kind of non-isolated grid-connected inverter circuit of type leakage current and control method altogether
CN111049182A (en) * 2019-12-24 2020-04-21 江苏大学 Five-level common-ground type single-phase non-isolated photovoltaic grid-connected inverter circuit and modulation method thereof

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