CN114914933A - Inverter - Google Patents

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Publication number
CN114914933A
CN114914933A CN202210472289.1A CN202210472289A CN114914933A CN 114914933 A CN114914933 A CN 114914933A CN 202210472289 A CN202210472289 A CN 202210472289A CN 114914933 A CN114914933 A CN 114914933A
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CN
China
Prior art keywords
switch
energy storage
storage device
control circuit
inverter
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Application number
CN202210472289.1A
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Chinese (zh)
Inventor
邢云
周炼
孙佳
邓艳平
杨丽
徐兴
赵逸帆
王昱凯
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Shanghai Power Equipment Research Institute Co Ltd
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Shanghai Power Equipment Research Institute Co Ltd
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Application filed by Shanghai Power Equipment Research Institute Co Ltd filed Critical Shanghai Power Equipment Research Institute Co Ltd
Priority to CN202210472289.1A priority Critical patent/CN114914933A/en
Publication of CN114914933A publication Critical patent/CN114914933A/en
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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
    • 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
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
    • H02J7/345—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering using capacitors as storage or buffering 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • 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
    • H02M7/53—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 using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • 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
    • H02J2207/00—Indexing scheme relating to details of circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J2207/50—Charging of capacitors, supercapacitors, ultra-capacitors or double layer capacitors
    • 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 embodiment of the invention discloses an inverter. This inverter sets up between power generation facility and electric wire netting, and the inverter includes: the first energy storage device, the second energy storage device, the first switch control circuit and the second switch control circuit. This dc-to-ac converter is through setting up first energy memory, first switch control circuit and second energy memory form boost circuit, second energy memory and second switch control circuit form inverter circuit, the realization is converted the direct current of power generation facility output into the alternating current after boosting and is exported the electric wire netting end, through with boost circuit and inverter circuit integration inside the dc-to-ac converter, can simplify circuit structure, improve the reliability of dc-to-ac converter, and this topological knot directly links power generation facility negative pole and electric wire netting neutral point equivalence, can eliminate the leakage current completely when realizing boosting on the one hand, on the other hand is through setting up boost circuit and inverter circuit sharing second energy memory, can reduce the use quantity of components and parts, simplify circuit structure, reduce loss and device cost.

Description

Inverter
Technical Field
The embodiment of the invention relates to the technical field of photovoltaic grid-connected power generation, in particular to an inverter.
Background
Due to the existence of the transformer, the isolated photovoltaic grid-connected inverter has large device volume and correspondingly increased cost. And the non-isolated photovoltaic grid-connected inverter omits a transformer, so that the efficiency can be improved, and the volume and the cost can be reduced. However, on one hand, because the system has no electrical isolation, the photovoltaic panel generates leakage current to the ground parasitic capacitance, and potential threats exist to the safety of operators and equipment. However, in practical applications, the parasitic capacitance exists in the switching tube, and the discharge of the parasitic capacitance causes the common mode voltage to change, so that the converter still generates spike-shaped leakage current. On the other hand, the dc power needs to be boosted before inversion, and the conventional boosting methods mainly adopt complicated parallel-interleaved boosting circuits or additionally provide boosting equipment, and these methods need a large number of used devices, have complicated circuit structures and are high in cost. Therefore, it is necessary to research how to simplify the boost structure and eliminate the leakage current of the non-isolated photovoltaic grid-connected inverter.
Disclosure of Invention
The invention provides an inverter, which can eliminate leakage current while boosting, and has simple circuit structure and high reliability.
An embodiment of the present invention provides an inverter, which is disposed between a power generation device and a grid, and includes: the energy storage device comprises a first energy storage device, a second energy storage device, a first switch control circuit and a second switch control circuit; the first energy storage device is respectively and electrically connected with the power generation device and the first switch control circuit, and the first switch control circuit is electrically connected with the power generation device, the second energy storage device and the second switch control circuit; the second energy storage device is electrically connected with the second switch control circuit, and the second switch control circuit is electrically connected with the power grid;
wherein the first energy storage device, the first switch control circuit, and the second energy storage device form a boost circuit; the second energy storage device and the second switch control circuit form an inverter circuit;
the first switch control circuit is used for controlling the charging or discharging state of the first energy storage device so as to enable the voltage boosting circuit to boost the voltage of the second energy storage device; the second switch control circuit is used for controlling the charging or discharging state of the second energy storage device so that the boosted second energy storage device outputs alternating current to the power grid through the inverter circuit.
Optionally, the first energy storage device includes a first inductor, and the first inductor is electrically connected to the power generation device and the first switch control circuit, respectively.
Optionally, the second energy storage device includes a first capacitor, and the first capacitor is electrically connected to the first switch control circuit and the second switch control circuit, respectively.
Optionally, the first switch control circuit at least comprises a first switch and a reverse prevention module, the first switch is electrically connected with the first energy storage device, the reverse prevention module, the power generation device and the second switch control circuit, and the reverse prevention module is electrically connected with the second energy storage device and the second switch control circuit respectively; the first switch is used for controlling the charging of the first energy storage device when the first switch is switched on and controlling the discharging of the first energy storage device when the first switch is switched off so that the voltage of the second energy storage device is raised by the voltage boosting circuit; the anti-reverse module is used for preventing the voltage of the booster circuit from reversely flowing when the first energy storage device is charged.
Optionally, the anti-reverse module is a diode.
Optionally, the second switch control circuit comprises at least a second switch, a third switch, a fourth switch and a fifth switch; wherein the second switch is electrically connected to the first switch control circuit, the second energy storage device, the fifth switch, the power generation device and the power grid, the third switch is electrically connected to the first switch control circuit, the second energy storage device, the fourth switch and the power grid, the fourth switch is electrically connected to the fifth switch, the second energy storage device and the power grid, and the fifth switch is electrically connected to the second energy storage device, the power generation device and the power grid;
the second switch, the third switch, the fourth switch and the fifth switch are turned on or off to control the charging or discharging state of the second energy storage device, so that the boosted second energy storage device outputs alternating current to the power grid through the inverter circuit.
Optionally, the second switch, the third switch and the fourth switch are controlled by unipolar sinusoidal pulse width modulation.
Optionally, the second switch control circuit further comprises a second inductor electrically connected to the third switch, the fourth switch and the power grid.
Optionally, the power generation device is a photovoltaic panel.
Optionally, the inverter further includes a second capacitor and a third capacitor, where the second capacitor is electrically connected to the power generation device, the first energy storage device, the first switch control circuit, and the power grid; and the third capacitor is respectively and electrically connected with the second switch control circuit and the power grid.
The present invention provides an inverter provided between a power generation device and a grid, the inverter including: the first energy storage device, the second energy storage device, the first switch control circuit and the second switch control circuit; the first energy storage device is respectively electrically connected with the power generation device and the first switch control circuit, and the first switch control circuit is electrically connected with the power generation device, the second energy storage device and the second switch control circuit; the second energy storage device is electrically connected with a second switch control circuit, and the second switch control circuit is electrically connected with a power grid; the first energy storage device, the first switch control circuit and the second energy storage device form a booster circuit; the second energy storage device and the second switch control circuit form an inverter circuit; the first switch control circuit is used for controlling the charging or discharging state of the first energy storage device so as to enable the voltage boosting circuit to boost the voltage of the second energy storage device; the second switch control circuit is used for controlling the charging or discharging state of the second energy storage device so that the boosted second energy storage device outputs alternating current to the power grid through the inverter circuit. Therefore, the inverter is provided with the first energy storage device, the first switch control circuit and the second energy storage device form the booster circuit, the second energy storage device and the second switch control circuit form the inverter circuit, the direct current output by the power generation device can be converted into the alternating current after being boosted, the alternating current is output to the power grid end, the booster circuit and the inverter circuit are integrated inside the inverter, the circuit structure can be simplified, the reliability of the inverter is improved, the topological structure enables the negative pole of the power generation device to be directly connected with the neutral point equivalent of the power grid, on one hand, leakage current can be completely eliminated when boosting, on the other hand, the booster circuit and the inverter circuit share the second energy storage device, the using number of components can be reduced, the circuit structure is simplified, and loss and device cost are reduced.
Drawings
Fig. 1 is a schematic block circuit diagram of an inverter according to a first embodiment of the present invention;
fig. 2 is a schematic structural diagram of an inverter according to a second embodiment of the present invention;
FIG. 3 is a simplified equivalent circuit diagram according to a second embodiment of the present invention;
FIG. 4 is a waveform diagram of control signals of switches according to a second embodiment of the present invention;
fig. 5 is a schematic current flow diagram of an inverter according to a second mode of the embodiment of the present invention;
fig. 6 is a schematic current flow diagram of an inverter corresponding to the second mode in the second embodiment of the present invention;
fig. 7 is a schematic current flow diagram of an inverter corresponding to the third mode in the second embodiment of the present invention;
fig. 8 is a schematic current flow diagram of an inverter corresponding to mode four in the second embodiment of the present invention;
fig. 9 is a schematic current flow diagram of an inverter corresponding to mode five in the second embodiment of the present invention;
fig. 10 is a schematic current flow diagram of an inverter corresponding to mode six in the second embodiment of the present invention;
FIG. 11 is a diagram illustrating simulation results of common mode voltage and leakage current according to a second embodiment of the present invention;
fig. 12 is a diagram illustrating simulation results of a power grid according to a second embodiment of the present invention;
fig. 13 is a diagram illustrating simulation results of the first capacitor according to the second embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
Example one
Fig. 1 is a schematic circuit block diagram of an inverter according to a first embodiment of the present invention. Referring to fig. 1, the inverter is provided between a power generation apparatus 10 and a grid 20, and includes: first energy storage device 30, second energy storage device 40, first switch control circuit 50, and second switch control circuit 60; the first energy storage device 30 is electrically connected with the power generation device 10 and the first switch control circuit 40 respectively, and the first switch control circuit 40 is electrically connected with the power generation device 10, the second energy storage device 50 and the second switch control circuit 60; second energy storage device 50 is electrically connected to second switch control circuit 60, and second switch control circuit 60 is electrically connected to power grid 20;
wherein first energy storage device 30, first switch control circuit 40, and second energy storage device 50 form a boost circuit; second energy storage device 50 and second switch control circuit 60 form an inverter circuit;
the first switch control circuit 40 is used for controlling the charging or discharging state of the first energy storage device 30 to enable the voltage boosting circuit to boost the voltage of the second energy storage device 50; the second switch control circuit 60 is configured to control the boosted second energy storage device 50 to output an ac power to the power grid 20 through the inverter circuit.
The first energy storage device 30, the first switch control circuit 40 and the second energy storage device 50 form a boost circuit, and are used for boosting the direct current output by the power generation device 10; the second energy storage device 50 and the second switch control circuit 60 form an inverter circuit for converting the boosted dc power into ac power and outputting the ac power to the power grid 20.
As shown in fig. 1, the inverter is disposed between the power generation device 10 and the power grid 20, and is configured to convert a direct current output by the power generation device 10 into an alternating current through inversion, and send the alternating current to the power grid 20 to supply power to a load end of the power grid. The power generation device 10 may be a photovoltaic cell, a photovoltaic panel, or other power generation equipment. The inverter can be used as a photovoltaic inverter and applied to the photovoltaic field.
The first switch control circuit 40 and the second switch control circuit 60 may be controlled by a controller, for example, a single chip microcomputer outputs corresponding pulse control signals.
Referring to fig. 1, the topology structure of the inverter connects the negative electrode of the power generation device 10 to the neutral point N of the power grid 20, so that the leakage current can be completely eliminated while the boost is realized.
When the first switch control circuit 40 controls the first energy storage device 30 to charge, the direct current output by the power generation device 10 charges the first energy storage device 30; when the first switch control circuit 40 controls the first energy storage device 30 to discharge, the first energy storage device 30 discharges, and the discharge voltage boosts the voltage of the second energy storage device 50 through the boost circuit, so that when the second switch control circuit 60 controls the second energy storage device 50 to discharge, the boosted voltage of the second energy storage device 50 outputs alternating current to the power grid 20 through the inverter circuit, thereby converting direct current into alternating current. The first switch control circuit may include one or more switches, and the first switch control circuit may control the charging or discharging of the first energy storage device by controlling the on or off of the switches. Similarly, the second switch control circuit may also include one or more switches, and the second switch control circuit may control the second energy storage device to be charged or discharged by controlling the on or off of the switch.
In the technical solution of this embodiment, the implementation process of the inverter is as follows: referring to fig. 1, a first energy storage device 30 is electrically connected to a power generation device 10 and a first switch control circuit 40, respectively, the first switch control circuit 40 is electrically connected to the power generation device 10, a second energy storage device 50, and a second switch control circuit 60, and the first energy storage device 30, the first switch control circuit 40, and the second energy storage device 50 form a boost circuit; the second energy storage device 50 is electrically connected to the second switch control circuit 60, the second switch control circuit 60 is electrically connected to the grid 20, and the second energy storage device 50 and the second switch control circuit 60 form an inverter circuit. When the first switch control circuit 40 controls the first energy storage device 30 to charge, the dc power output by the power generation device 10 charges the first energy storage device 30, and when the first switch control circuit 40 controls the first energy storage device 30 to discharge, the discharge voltage of the first energy storage device 30 passes through the voltage boost circuit to boost the voltage of the second energy storage device 50, thereby boosting the voltage of the second energy storage device 50. When the second switch control circuit 60 controls the second energy storage device 50 to discharge, the inverter circuit may output the alternating current to the grid 20 because the voltage of the second energy storage device 50 is boosted by the boost circuit. From this, can realize converting the direct current of power generation facility output into the alternating current after stepping up and export to the electric wire netting end, realize with boost circuit and inverter circuit integration inside the dc-to-ac converter, adopt parallelly connected crisscross complicated boost circuit or additionally provide modes such as step-up equipment with prior art and compare, can simplify circuit structure, improve the reliability of dc-to-ac converter, and this topology knot connects power generation facility negative pole and electric wire netting neutral point equivalent directly, on the one hand can eliminate the leakage current completely when realizing stepping up, on the other hand is through setting up boost circuit and inverter circuit sharing second energy memory, can reduce the use quantity of components and parts, simplify circuit structure, reduce loss and device cost.
Example two
Fig. 2 is a schematic structural diagram of an inverter according to a second embodiment of the present invention. On the basis of the first embodiment, optionally, referring to fig. 2, the first energy storage device includes a first inductor L1, and the first inductor L1 is electrically connected to the power generation device and the first switch control circuit 40, respectively.
The first inductor L1 is an energy storage element, and the first switch control circuit 40 can control the charging or discharging of the first inductor L1.
Optionally, with continued reference to fig. 2, the second energy storage device includes a first capacitor C1, the first capacitor C1 being electrically connected to the first switch control circuit 40 and the second switch control circuit 60, respectively.
The first inductor L1, the first switch control circuit 40 and the first capacitor C1 form a boost circuit, which is used for boosting the direct current output by the power generation device; the first capacitor C1 and the second switch control circuit 60 form an inverter circuit for converting the boosted dc power into ac power and outputting the ac power to the grid.
The first capacitor C1 is an energy storage element, and the second switch control circuit 60 can control the charging or discharging of the first capacitor C1.
Optionally, with continued reference to fig. 2, the first switch control circuit 40 at least includes a first switch S1 and an anti-reverse module 41, the first switch S1 is electrically connected with the first energy storage device, the anti-reverse module 41, the power generation device and the second switch control circuit 60, and the anti-reverse module 41 is electrically connected with the second energy storage device and the second switch control circuit 60, respectively; the first switch S1 is used for controlling the charging of the first energy storage device when the first energy storage device is switched on and controlling the discharging of the first energy storage device when the first energy storage device is switched off so that the voltage boosting circuit boosts the voltage of the second energy storage device; the reverse blocking module 41 is used for preventing the voltage of the voltage boosting circuit from reversely flowing when the first energy storage device is charged.
For example, referring to fig. 2, the first energy storage device is a first inductor L1, the second energy storage device is a first capacitor C1, the first switch S1 is electrically connected to the first inductor L1, the anti-reverse module 41, the power generation device 10 and the second switch control circuit 60, and the anti-reverse module 41 is electrically connected to the first capacitor C1 and the second switch control circuit 60, respectively; the first switch S1 is used to control the power generation device 10 to charge the first inductor L1 when turned on, and to control the first inductor L1 to discharge when turned off to boost the voltage of the first capacitor C1 through the boost circuit, so as to achieve boost. The first inductor L1, the first switch S1, the anti-reverse module 41 and the first capacitor C1 form a DC-DC boost circuit for boosting the direct current output by the power generation device.
When the first switch S1 is turned off, the first inductor L1 discharges, and the first inductor L1 discharges to raise the voltage of the first capacitor C1. Therefore, when the first inductor L1 is charged (the first switch S1 is closed), the voltage of the first capacitor C1 is increased, which causes the discharge voltage of the second capacitor C1 to reversely flow into the first inductor L1 or the power generation device, thereby burning the device. Therefore, as shown in fig. 2, the anti-reverse module 41 is disposed on the connection circuit between the first inductor L1 and the first capacitor C1, and can be used to prevent the device from being damaged due to the reverse voltage of the voltage boost circuit when the first inductor L1 is charged.
The first switch S1 may be a switching transistor, such as an NMOS type transistor.
Optionally, the anti-reflection module 41 is a diode D1.
The diode D1 is used to prevent the voltage reflux of the boost circuit from damaging the device when the first inductor L1 is charged.
Optionally, with continued reference to fig. 2, the second switch control circuit 60 includes at least a second switch S2, a third switch S3, a fourth switch S4, and a fifth switch S5; the second switch S2 is electrically connected with the first switch control circuit 40, the second energy storage device, the fifth switch S5, the power generation device 10 and the power grid 20, the third switch S3 is electrically connected with the first switch control circuit 40, the second energy storage device, the fourth switch S4 and the power grid 20, the fourth switch S4 is electrically connected with the fifth switch S5, the second energy storage device and the power grid 20, and the fifth switch S5 is electrically connected with the second energy storage device, the power generation device 10 and the power grid 20;
the on or off of the second switch S2, the third switch S3, the fourth switch S4, and the fifth switch S5 controls the charging or discharging state of the second energy storage device, so that the boosted second energy storage device outputs alternating current to the grid 20 through the inverter circuit.
Exemplarily, referring to fig. 2, the first energy storage device is a first inductor L1, the second energy storage device is a first capacitor C1, the second switch S2 is electrically connected to the first switch control circuit 40, the first capacitor C1, the fifth switch S5, the power generation device 10 and the grid 20, the third switch S3 is electrically connected to the first switch control circuit 40, the first capacitor C1, the fourth switch S4 and the grid 20, the fourth switch S4 is electrically connected to the fifth switch S5, the first capacitor C1 and the grid 20, and the fifth switch S5 is electrically connected to the first capacitor C1, the power generation device 10 and the grid 20;
the on or off of the second switch S2, the third switch S3, the fourth switch S4, and the fifth switch S5 controls the charging or discharging state of the first capacitor C1 so that the boosted first capacitor C1 outputs alternating current to the grid 20 through the inverter circuit.
The first inductor L1, the first switch S1, the anti-reverse module 41 and the first capacitor C1 form a DC-DC boost circuit, and the DC-DC boost circuit is used for boosting the direct current output by the power generation device; the first capacitor C1, the second switch S2, the third switch S3, the fourth switch S4 and the fifth switch S5 form a DC-AC inverter circuit for converting the DC voltage boosted by the front-end DC-DC boost circuit into an AC power to be output to the grid, and the DC-AC topology structure formed by the first capacitor C1, the second switch S2, the third switch S3, the fourth switch S4 and the fifth switch S5 can completely eliminate leakage current. The DC-DC booster circuit and the DC-AC inverter circuit share the first capacitor C1, so that on one hand, the use number of components can be reduced, the circuit structure is simplified, the loss and cost of the components are reduced, and the efficiency is improved, and on the other hand, the converter can completely eliminate leakage current while boosting under the topological structure. And a DC-DC boost circuit formed by the first inductor L1, the first switch S1, the anti-reverse module 41 and the first capacitor C1 and a DC-AC inverter circuit formed by the first capacitor C1, the second switch S2, the third switch S3, the fourth switch S4 and the fifth switch S5 can be integrated in the inverter.
Among them, the second switch S2, the third switch S3, the fourth switch S4, and the fifth switch S5 may be switching transistors, such as NMOS type transistors.
The control terminals of the first switch S1, the second switch S2, the third switch S3, the fourth switch S4 and the fifth switch S5 may be controlled by a controller, for example, a single chip microcomputer outputs a pulse control signal to control the on or off of the switches.
Optionally, with continued reference to fig. 2, the second switch control circuit 60 further includes a second inductor L2, the second inductor L2 being electrically connected with the third switch S3, the fourth switch S4, and the power grid 20.
The second inductor L2 is used to implement filtering, for example, filtering the AC power output by the DC-AC inverter circuit to obtain a sine-wave AC power.
Optionally, the power generation device 10 is a photovoltaic panel PV.
Optionally, with continued reference to fig. 2, the inverter further includes a second capacitor C2 and a third capacitor C3, the second capacitor C2 being electrically connected to the power generation device 10, the first energy storage device, the first switch control circuit 10 and the grid 20; the third capacitor C3 is electrically connected to the second switch control circuit 60 and the power grid 20, respectively.
The second capacitor C2 and the third capacitor C3 are used for filtering, so that the reliability of the circuit is improved.
Fig. 3 is a simplified equivalent circuit diagram provided in the second embodiment of the present invention. With reference to fig. 2 and 3, the principle that the inverter can completely eliminate the leakage current is as follows: from fig. 2 and 3, it is possible to obtain:
U TCM ＝U CM +U DMC
Figure BDA0003623262180000111
from the complementary diagram of FIG. 2, it can be seen that，L 2 When the above formula is substituted, 0 can give:
Figure BDA0003623262180000112
therefore, the inverter output point B provided by the embodiment of the invention is directly connected with the negative electrode of the power generation device, namely, the common-mode voltage U TCM ＝U BN Therefore, the leakage current is always zero, i.e., complete elimination of the leakage current can be achieved.
Fig. 4 is a waveform diagram of control signals of switches provided in the second embodiment of the present invention. Optionally, the second switch S2, the third switch S3 and the fourth switch S4 are controlled by unipolar sinusoidal pulse width modulation.
In FIG. 4, u g For mains supply U Grid The voltage of (c) in a cycle, i g For mains supply U Grid The current of (2) during a cycle, S 1 Is a graph of the control signal of the first switch S1 during one cycle, S 2 Is a graph of the control signal of the second switch S2 during one cycle, S 3 For the control signal profile of the third switch S3 in one cycle, S 4 Is a control signal profile of the fourth switch S4 in one cycle, S 5 Is a graph of the control signal of the fifth switch S5 over one cycle. The second switch S2, the third switch S3 and the fourth switch S4 are controlled by unipolar sinusoidal pulse width modulation, as shown in fig. 4.
Optionally, referring to fig. 4, the inverter includes six operating modes, and the specific operating process is as follows:
fig. 5 is a schematic current flow diagram of an inverter corresponding to the mode provided in the second embodiment of the present invention; in the mode, the power supply U of the power grid is combined with the power grids shown in fig. 4 and 5 Grid The second switch S2 and the fourth switch S4 are always off, the first switch S1 and the fifth switch S5 are on, and the third switch S3 adopts unipolar sinusoidal pulse width modulation, and is in a conduction state in a mode one. Since the first switch S1 is turned on, the photovoltaic panel PV charges the first inductor L1(the charging circuit thereof is the first circuit L11 shown in fig. 5). Since the third switch S3 and the fifth switch S5 are turned on and the second switch S2 and the fourth switch S4 are turned off, the first capacitor C1 (whose voltage is always raised since each mode is continuously changed with the period) is discharged, and outputs a voltage to the grid, which is equal to the voltage of the first capacitor C1. The discharging circuit of the first capacitor C1 is the second circuit L12 shown in fig. 5.
Fig. 6 is a schematic current flow diagram of an inverter corresponding to the second mode provided in the second embodiment of the present invention; in combination with fig. 4 and 6, in mode two, the power supply U of the power grid Grid The first switch S1, the second switch S2, and the fourth switch S4 are turned off, the fifth switch S5 is turned on, and the third switch S3 adopts unipolar sinusoidal pulse width modulation, and is in a conduction state in mode two. Since the first switch S1 is turned off, the first inductor L1 discharges, and the first inductor L1 discharges to raise the voltage of the first capacitor C1. Since the third switch S3 and the fifth switch S5 are turned on and the second switch S2 and the fourth switch S4 are turned off, the first capacitor C1 (whose voltage is always raised since each mode is continuously changed with the period) is discharged, and outputs a voltage to the grid, which is equal to the voltage of the first capacitor C1. The voltage boosting loop for discharging and boosting the voltage of the first capacitor C1 by the first inductor L1 is a third loop L21 shown in fig. 6; the first capacitor C1 discharges to form an inverter loop with the third switch S1, the fifth switch S5 and the like, and the inverter loop is a fourth loop L22 shown in fig. 6.
It should be noted that, between the first mode and the second mode, the power supply U of the power grid is provided Grid The second switch S2 and the fourth switch S4 are always off, and the fifth switch S5 is always on, and the specific control states include four cases: when both the first switch S1 and the third switch S3 are turned off, the voltage output to the grid is zero; when the first switch S1 and the third switch S3 are both turned on, the voltage output to the power grid is the voltage of the first capacitor; when the first switch S1 is turned off and the third switch S3 is turned on, the voltage output to the grid is the voltage of the first capacitor; when the first switch S1 is turned on and the third switch is turned onWhen the switch S3 is turned off, the voltage output to the grid is zero.
Fig. 7 is a schematic current flow diagram of an inverter corresponding to the third mode provided in the second embodiment of the present invention; in combination with fig. 4 and 7, in mode three, the power supply U of the power grid Grid The first switch S1, the second switch S2, and the fourth switch S4 are turned off, the fifth switch S5 is turned on, and the third switch S3 adopts unipolar sinusoidal pulse width modulation, and is turned off in mode three. Since the first switch S1 is turned off, the first inductor L1 discharges, and the first inductor L1 discharges to raise the voltage of the first capacitor C1. Since the second switch S2, the third switch S3, and the fourth switch S4 are turned off, and the fifth switch S5 is turned on, the first capacitor C1 cannot form an inverter loop, and therefore, the discharge voltage of the first capacitor C1 (since each mode is continuously changed with the period, the voltage of the first capacitor is always raised) cannot be output to the grid, so that the voltage of the grid is zero. The boosting loop for discharging the first inductor L1 to boost the voltage of the first capacitor C1 is the fifth loop L31 shown in fig. 7.
It should be noted that, between the second mode and the third mode, the power supply U of the power grid is provided Grid The second switch S2 and the fourth switch S4 are always off, and the fifth switch S5 is always on, and the specific control states include four cases: when both the first switch S1 and the third switch S3 are turned off, the voltage output to the grid is zero; when the first switch S1 and the third switch S3 are both turned on, the voltage output to the power grid is the voltage of the first capacitor; when the first switch S1 is turned off and the third switch S3 is turned on, the voltage output to the grid is the voltage of the first capacitor; when the first switch S1 is turned on and the third switch S3 is turned off, the magnitude of the voltage output to the grid is zero.
Fig. 8 is a schematic current flow diagram of an inverter corresponding to mode four provided in the second embodiment of the present invention; in combination with fig. 4 and 8, in mode four, the power supply U of the power grid Grid The first switch S1, the second switch S2, and the fourth switch S4 are turned off, the fifth switch S5 is turned on, and the third switch S3 adopts unipolar sinusoidal pulse width modulation, and is turned off in mode three.Since the first switch S1 is turned off, the first inductor L1 discharges, and the first inductor L1 discharges to raise the voltage of the first capacitor C1. Since the second switch S2, the third switch S3, and the fourth switch S4 are turned off, and the fifth switch S5 is turned on, the first capacitor C1 cannot form an inverter loop, and therefore, the discharge voltage of the first capacitor C1 (since each mode is continuously changed with the period, the voltage of the first capacitor is always raised) cannot be output to the grid, so that the voltage of the grid is zero. The boosting loop for discharging the first inductor L1 to boost the voltage of the first capacitor C1 is the sixth loop L41 shown in fig. 8.
It should be noted that, between the third mode and the fourth mode, when the power supply U of the power grid is used Grid When both the voltage and current of (a) are positive: the second switch S2 and the fourth switch S4 are always turned off, and the fifth switch S5 is always turned on, if the first switch S1 and the third switch S3 are both turned on, the voltage output to the grid is the voltage of the first capacitor, and if the first switch S1 is turned on and the third switch S3 is turned off, the voltage output to the grid is zero; as the power supply U of the power grid Grid When the voltage and current are both in reverse: the third switch S3 is always off, if the second switch S2 and the fourth switch S4 are off, and the fifth switch S5 is on, the voltage output to the grid is zero; if the second switch S2 and the fourth switch S4 are turned on and the fifth switch S5 is turned off, the voltage level output to the grid is the voltage of the first capacitor.
Fig. 9 is a schematic current flow diagram of an inverter corresponding to mode five provided in the second embodiment of the present invention; in combination with fig. 4 and 9, in mode five, the power supply U of the power grid Grid The third switch S3 and the fifth switch S5 are turned off, the first switch S1 is turned on, the second switch S2 and the fourth switch S4 both use unipolar sinusoidal pulse width modulation, and are both on states in mode five. Since the first switch S1 is turned on, the photovoltaic panel PV charges the first inductor L1. Since the second switch S2 and the fourth switch S2 are turned on and the third switch S3 and the fifth switch S5 are turned off, the first capacitor C1 (whose voltage is always raised since each mode is continuously varied with the period) is discharged to the electric powerThe net outputs a voltage whose magnitude is the voltage of the first capacitor C1. The boosting loop for discharging and boosting the voltage of the first capacitor C1 by the first inductor L1 is a seventh loop L51 shown in fig. 9; the first capacitor C1 discharges to form an inverter loop with the second switch S2, the fourth switch S4 and the like, and the eighth loop L52 is shown in fig. 9.
It should be noted that, between mode four and mode five, the power supply U of the power grid is Grid Is in the reverse direction, the third switch S3 is always off, and if the second switch S2 and the fourth switch S4 are on and the fifth switch S5 is off, the voltage output to the grid is the voltage of the first capacitor; if the second switch S2, the fourth switch S4, and the fifth switch S5 are turned off, the magnitude of the voltage output to the grid is zero.
Fig. 10 is a schematic current flow diagram of an inverter corresponding to mode six provided in the second embodiment of the present invention; in combination with fig. 4 and 10, in mode six, the power supply U of the power grid Grid The voltage and the current of the first switch S5 are all reversed, the third switch S3 and the fifth switch S5 are always turned off, the first switch S1 is turned on, the second switch S2 and the fourth switch S4 both adopt unipolar sinusoidal pulse width modulation, and both are turned off in a mode six. Since the first switch S1 is turned on, the photovoltaic panel PV charges the first inductor L1 (the charging loop thereof is shown as a ninth loop L61 in fig. 10). In mode six, since the second switch S2, the third switch S3, the fourth switch S4 and the fifth switch S5 are turned off, the first capacitor C1 does not discharge and cannot form an inverter circuit, and thus the charging stage of the first inductor L1 is performed at this stage, but the first capacitor C1 does not supply power to the grid output.
In addition, since the boosting transformation ratio of the boosting circuit depends on the conduction time of the first switch S1, a dead zone exists between the first switch S1 and the second switch S2, and the second switch S2 is unipolar sinusoidal pulse width modulation, and the duty ratio thereof is 1/2, so that there is a case of mode five.
It should be noted that, between mode five and mode six, the power supply U of the power grid is Grid Is reversed, the third switch S3 is always off, if the second switch S2 and the fourth switch S4 are on, and the fifth switch S5 is off, the output isThe voltage to the power grid is the voltage of the first capacitor; if the second switch S2, the fourth switch S4 and the fifth switch S5 are turned off, the magnitude of the voltage output to the grid is zero.
Fig. 11 is a schematic diagram of simulation results of common mode voltage and leakage current provided in the second embodiment of the present invention, fig. 12 is a schematic diagram of simulation results of a power grid provided in the second embodiment of the present invention, and fig. 13 is a schematic diagram of simulation results of a first capacitor provided in the second embodiment of the present invention. A simulation experiment is performed on the inverter, and as shown in fig. 11, the common-mode voltage and the leakage current of the inverter are both zero, which indicates that the inverter can completely eliminate the leakage current. The voltage and current output by the inverter to the grid can be referred to the voltage and current transformation curve shown in fig. 12, and the voltage and current are known to be periodically changed in a sine wave manner. In addition, referring to fig. 13, the voltage ripple of the first capacitor, i.e., the flying capacitor, is very small, and a better inversion waveform can be obtained through the control of the second switch control circuit.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims (10)

1. An inverter, provided between a power generation device and a grid, comprising: the energy storage device comprises a first energy storage device, a second energy storage device, a first switch control circuit and a second switch control circuit; the first energy storage device is respectively and electrically connected with the power generation device and the first switch control circuit, and the first switch control circuit is electrically connected with the power generation device, the second energy storage device and the second switch control circuit; the second energy storage device is electrically connected with the second switch control circuit, and the second switch control circuit is electrically connected with the power grid;
wherein the first energy storage device, the first switch control circuit, and the second energy storage device form a boost circuit; the second energy storage device and the second switch control circuit form an inverter circuit;
the first switch control circuit is used for controlling the charging or discharging state of the first energy storage device so as to enable the voltage boosting circuit to boost the voltage of the second energy storage device; the second switch control circuit is used for controlling the charging or discharging state of the second energy storage device so that the boosted second energy storage device outputs alternating current to the power grid through the inverter circuit.
2. The inverter of claim 1, wherein the first energy storage device comprises a first inductor electrically connected to the power generation device and the first switch control circuit, respectively.
3. The inverter of claim 1, wherein the second energy storage device comprises a first capacitor electrically connected to the first and second switch control circuits, respectively.
4. The inverter of claim 1, wherein the first switch control circuit comprises at least a first switch and a kickback prevention module, the first switch being electrically connected to the first energy storage device, the kickback prevention module, the power generation device and the second switch control circuit, the kickback prevention module being electrically connected to the second energy storage device and the second switch control circuit, respectively; the first switch is used for controlling the charging of the first energy storage device when the first switch is switched on and controlling the discharging of the first energy storage device when the first switch is switched off so that the voltage of the second energy storage device is raised by the voltage boosting circuit; the reverse prevention module is used for preventing the voltage of the booster circuit from reversely flowing when the first energy storage device is charged.
5. The inverter of claim 4, wherein the anti-kickback module is a diode.
6. The inverter of claim 1, wherein the second switch control circuit comprises at least a second switch, a third switch, a fourth switch, and a fifth switch; wherein the second switch is electrically connected to the first switch control circuit, the second energy storage device, the fifth switch, the power generation device and the power grid, the third switch is electrically connected to the first switch control circuit, the second energy storage device, the fourth switch and the power grid, the fourth switch is electrically connected to the fifth switch, the second energy storage device and the power grid, and the fifth switch is electrically connected to the second energy storage device, the power generation device and the power grid;
the second switch, the third switch, the fourth switch and the fifth switch are turned on or off to control the charging or discharging state of the second energy storage device, so that the boosted second energy storage device outputs alternating current to the power grid through the inverter circuit.
7. The inverter according to claim 6, wherein the second switch, the third switch, and the fourth switch are controlled by unipolar sinusoidal pulse width modulation.
8. The inverter of claim 6, wherein the second switch control circuit further comprises a second inductor electrically connected to the third switch, the fourth switch, and the grid.
9. The inverter of claim 1, wherein the power generation device is a photovoltaic panel.
10. The inverter of claim 1, further comprising a second capacitor and a third capacitor, the second capacitor being electrically connected to the power generation device, the first energy storage device, the first switch control circuit, and the grid; and the third capacitor is respectively and electrically connected with the second switch control circuit and the power grid.
CN202210472289.1A 2022-04-29 2022-04-29 Inverter Pending CN114914933A (en)

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CN202210472289.1A CN114914933A (en) 2022-04-29 2022-04-29 Inverter

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CN202210472289.1A CN114914933A (en) 2022-04-29 2022-04-29 Inverter

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CN114914933A true CN114914933A (en) 2022-08-16

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