CN114709861A - Common-ground single-phase three-level inverter and modulation method thereof - Google Patents

Common-ground single-phase three-level inverter and modulation method thereof Download PDF

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Publication number
CN114709861A
CN114709861A CN202210187599.9A CN202210187599A CN114709861A CN 114709861 A CN114709861 A CN 114709861A CN 202210187599 A CN202210187599 A CN 202210187599A CN 114709861 A CN114709861 A CN 114709861A
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China
Prior art keywords
power
switch tube
power switch
inverter circuit
capacitor
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CN202210187599.9A
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Chinese (zh)
Inventor
曹庆伟
牛晨晖
陈晓路
杭兆峰
郑枫
姚中原
杨立华
管春雨
刘溟江
肖华锋
陈庆东
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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
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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
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Priority to CN202210187599.9A priority Critical patent/CN114709861A/en
Publication of CN114709861A publication Critical patent/CN114709861A/en
Pending legal-status Critical Current

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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
    • 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
    • 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
    • H02M7/53—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
    • H02M7/5387—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 in a bridge configuration
    • H02M7/53871—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 in a bridge configuration with automatic control of output voltage or current
    • 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
    • H02M7/539—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 with automatic control of output wave form or frequency
    • H02M7/5395—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 with automatic control of output wave form or frequency by pulse-width modulation
    • 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

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

Abstract

The invention discloses a common-ground type three-level inverter circuit, which belongs to the technical field of power electronics and comprises a power switch network, a switch capacitor, an independent diode and an alternating current filter inductor. An alternating current output end of the inverter circuit is directly connected with a negative end of an input direct current voltage to form a common ground structure, and the common mode voltage is constant; the output voltage of the inverter circuit is three levels, and the harmonic content of differential mode voltage is low; the switch capacitor works in a switching frequency charging and discharging mode, a charging loop of the switch capacitor is separated from a follow current loop of a power grid, the rising amplitude of the voltage of the switch capacitor under the work of non-unit factors is effectively inhibited, and the switch capacitor is suitable for being applied to a medium-low power non-isolated photovoltaic grid-connected inverter system under the unit and non-unit power factors.

Description

Common-ground single-phase three-level inverter and modulation method thereof
Technical Field
The invention relates to a common-ground single-phase three-level inverter circuit technology, and belongs to the technical field of power electronics.
Background
The non-isolated photovoltaic grid-connected inverter structure does not contain a transformer, so that the non-isolated photovoltaic grid-connected inverter structure has great advantages in device size and efficiency compared with the isolated photovoltaic grid-connected inverter structure. However, the non-isolated photovoltaic grid-connected inverter without the transformer has no electrical isolation, and a common mode loop is formed between the parasitic capacitance between the photovoltaic cell array and the ground and between the photovoltaic grid-connected inverter and the ground, so that leakage current is generated. Leakage currents can cause additional losses and damage equipment in the leakage current flow loop, and even harm personnel safety.
At present, a full-bridge inverter, a half-bridge inverter, a common-ground inverter and the like which are modulated in a bipolar mode are generally adopted in a single-phase non-isolated photovoltaic grid-connected inverter. However, the bipolar modulation full bridge inverter outputs two levels, and the differential mode characteristic is poor. The half-bridge inverter requires that the magnitude of the input voltage at the direct current side is 2 times of the maximum output voltage of the inverter, which is not beneficial to the application of medium-low power photovoltaic grid-connected boosting occasions. The common-ground type inverter directly connects the neutral point of the power grid with the negative electrode of the photovoltaic panel, and the leakage current is eliminated. On one hand, the common ground type inverter needs to ensure that the charging and discharging of a switch capacitor work under a switch frequency scale in design so as to maintain the voltage balance of the capacitor; on the other hand, if the current of the power grid flows through the switch capacitor in the period of the power grid in which the switch capacitor does not participate in discharging, the voltage value of the switch capacitor is greatly increased, and the power grid is not favorable for supplying power for the high power quality of the power grid.
Disclosure of Invention
The invention aims to provide a common-ground single-phase three-level inverter circuit which is simple in structure and control and can effectively inhibit leakage current in a non-isolated photovoltaic grid-connected system and a modulation method thereof. The charging circuit of the switched capacitor is separated from the follow current circuit of the power grid in the follow current stage of the power grid, the voltage balance of the switched capacitor is realized under a unit power factor, the voltage rising amplitude of the switched capacitor is restrained under a non-unit power factor, and the voltage balance and stability of the switched capacitor is maintained, so that the method is suitable for application in a medium and small power non-isolated photovoltaic grid-connected inverter system.
In order to achieve the purpose, the invention adopts the technical scheme that: common-ground single-phase three-level inverter circuit, photovoltaic direct-current power supply (V)dc) A first capacitor (C)1) A first power switch tube (S)1) A second power switch tube (S)2) A third power switch tube (S3) And the fourth power switch tube (S)4) The fifth power switch tube (S)5) A first power diode (D)1) And an AC filter inductor (L)1)；
Photovoltaic DC power supply (V)dc) Positive pole of (2) and first power switch tube (S)1) The drain electrodes of the two transistors are connected; a first power switch tube (S)1) Source electrode of (1) and second power switch tube (S)2) And a first power diode (D)1) The anodes of the anode groups are connected; second power switch tube (S)2) Source and third power switch tube (S)3) The source electrode of the first capacitor, the cathode of the first capacitor and the output port a of the inverter circuit are connected; third power switch tube (S)3) And the fourth power switch tube (S)4) The drain electrodes are connected to form a back-to-back structure;
fourth power switch tube (S)4) Source electrode of (1) and fifth power switch tube (S)5) Source electrode, photovoltaic dc power supply (V)dc) The negative pole of the power grid is connected with a zero line of a central point of the power grid; fifth power switch tube (S)5) Respectively with the first power diode (D)1) Is connected with the anode of the first capacitor, and the output port a of the inverter circuit of the invention of the inverter circuit is connected with the alternating current filter inductor (L)1) One end of the two ends are connected; AC filter inductance (L)1) Another end of (u) and an AC distribution networkg) One end of the two is connected; AC distribution network (u)g) The other end of the DC-DC converter is connected with the output port of the inverter, namely, the DC-side photovoltaic DC power supply (V)dc) Are connected with each other.
As an optional solution of the present invention, the power switch employs a metal-oxide semiconductor field effect transistor, an insulated gate bipolar transistor, or a silicon carbide field effect transistor.
As an alternative of the invention, the power diode D1Which may be a schottky diode or a silicon power switching diode.
As an alternative of the invention, the alternating current filter circuit is an inductive filter (L)1) Or a capacitive filter or a combined inductor-capacitor filter.
As an alternative to the present invention, saidThe load being an AC network (u)g) Or purely resistive or inductive or capacitive loads.
The invention has the beneficial effects that: the neutral point zero line of the power grid is directly connected with the negative electrode of the photovoltaic panel to form a common ground structure, so that the leakage current caused by the parasitic capacitance of the photovoltaic panel is naturally eliminated; simple control, wherein S1And S5，S2And S4The two pairs of switches are complementary, S3On-off state of and S1The switch states are consistent; the charging circuit of the switch capacitor is separated from the power grid follow current circuit in the power grid follow current stage, the voltage balance of the switch capacitor is realized under a unit power factor, the voltage rise amplitude of the switch capacitor is restrained under a non-unit power factor, and the voltage balance and stability of the switch capacitor are maintained, so that the inverter has excellent reactive power compensation capability as a medium and small power grid-connected inverter, and the quality of electric energy input into the power grid is optimized.
Drawings
Fig. 1 is a schematic structural diagram of a common-ground type single-phase three-level inverter circuit in this embodiment.
Fig. 2 is a schematic diagram of driving signals of a power switch tube of the common-ground single-phase three-level inverter circuit in the present embodiment;
fig. 3(a) shows a positive half cycle energy mode 1 of the grid voltage in this embodiment;
fig. 3(b) shows a freewheeling mode 2 of the positive half cycle and the negative half cycle of the grid voltage in this embodiment;
fig. 3(c) is a working mode 3 of negative half-cycle energy transfer of the grid voltage in this embodiment;
fig. 4(a) shows a positive half cycle energy mode 4 of the grid voltage in this embodiment;
fig. 4(b) shows a freewheeling mode 5 of the positive half cycle and the negative half cycle of the grid voltage in this embodiment;
fig. 4(c) shows a negative half-cycle energy transmission mode 6 of the grid voltage in this embodiment;
FIG. 5 is a graph of the output three levels and the grid voltage waveform in this embodiment;
FIG. 6(a) is an operation waveform at a unit power factor in the present embodiment;
FIG. 6(b) is the operation waveform when the grid current leads the voltage by 30 ° in this embodiment;
FIG. 6(c) is the operating waveform at the grid current lag voltage of 30 in this embodiment;
FIG. 7(a) is a waveform of the first capacitor voltage per unit power factor in the present embodiment;
FIG. 7(b) is the operation waveform when the grid current leads the voltage by 30 ° in this embodiment;
fig. 7(c) shows the operating waveform of the grid current lagging by 30 ° in this embodiment.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and embodiments thereof.
Referring to fig. 1, a common ground type single-phase three-level inverter circuit of the present invention includes: DC power supply VdcA first capacitor C1A first power switch tube S1A second power switch tube S2The third power switch tube S3The fourth power switch tube S4The fifth power switch tube S5A first power diode D1AC filter inductor L1And single-phase AC distribution network ug。
The photovoltaic DC power supply VdcPositive pole and first power switch tube S1The drain electrodes of the two electrodes are connected; first power switch tube S1Source electrode of and the second power switch tube S2And a first power diode D1The anodes of the anode groups are connected; second power switch tube S2Source and third power switch tube S3Source electrode of (1), first capacitor C1The negative pole of the inverter is connected with the output port a of the inverter circuit; third power switch tube S3And the fourth power switch tube S4The drain electrodes of the first and second transistors are connected to form a back-to-back structure; fourth power switch tube S4Source and fifth power switch tube S5Source electrode, photovoltaic DC power supply VdcThe negative pole of the power grid is connected with a zero line of a central point of the power grid; fifth power switch tube S5And the first power diode D1And a first capacitor C1The positive electrodes of (a) and (b) are connected. Output port a of inverter circuit of the invention is connected withCurrent filter inductor L1The left ends of the two are connected; AC filter inductance L1The right end of the AC power distribution network is connected with one end of the AC power distribution network; the other end of the AC distribution network is connected with the output port of the inverter, namely the DC side photovoltaic DC power supply VdcAre connected with each other.
FIG. 2 is a schematic diagram of a driving signal of a power switch tube of a common-ground single-phase three-level inverter circuit, in which a modulating wave vMAt power frequency (50 Hz), vtriA high frequency triangular carrier signal of 50 kHz. v. ofMAnd vtriModulation produces S1～S5The drive signal of (1). Wherein the power switch S1And S3The driving signals are the same and are high-frequency signals in the negative half cycle of the power grid, and a power switch S5And a power switch S1And (4) complementation. Power switch S2And S4Complementary and is a high frequency signal of the positive half cycle of the grid.
The common-ground single-phase three-level inverter has three working modes.
The mode 1 is shown in fig. 3(a), and is a power grid positive half-cycle energy transfer mode, and a first power switch tube S is switched on1A second power switch tube S2And a third power switch tube S3Fourth power switch tube S4The fifth power switch tube S5When the power supply is disconnected, the current does not pass through the third switch tube, and the direct current power supply VdcThe common-ground single-phase three-level inverter circuit is directly connected in series with a power grid, and the output voltage of the common-ground single-phase three-level inverter circuit is equal to the direct-current input voltage.
Mode 2 is shown in fig. 3(b), and is a network follow current and is applied to the first capacitor C1Charging mode of switching on the first power switch tube S1The third power switch tube S3The fourth power switch tube S4Second power switch tube S2The fifth power switch tube S5Off, in this mode, the switching tube S3And a switching tube S4After the inverter circuit is conducted, the output port a and the port N of the inverter circuit are equal in potential, the output voltage is 0V, and the follow current of a power grid flows through the switch tube S3Switch tube S4And an AC filter inductor L1Back to single-phase ac distribution network ug. At the same time, the user can select the desired position,at the switch tube S1After the switch is switched on, the current flowing out from the direct current power supply passes through the switch tube S1Diode D1And a switch tube S3And a switching tube S4The conducting loop is formed by a capacitor C1And charging is carried out. It is worth noting that the charging circuit is separated from the follow current circuit, and the follow current of the power grid does not pass through the switch capacitor C1When the capacitance C is1When the voltage of (D) exceeds the DC power supply voltage, the diode D1The cathode potential of the capacitor C is higher than the anode potential and is cut off, and the charging is stopped1Is maintained below the dc supply voltage.
Mode 3 as shown in fig. 3(c), the fourth power switch tube S is turned on for the energy transfer and mode of the negative half cycle of the power grid4The fifth power switch tube S5First power switch tube S1A second power switch tube S2The third power switch tube S3Is disconnected by the first capacitor C1Providing reverse voltage for power grid, current not passing through switch tube S3. Thus, the output voltage of the common-ground single-phase three-level inverter circuit is equal to the negative value of the first capacitor voltage. Meanwhile, in the follow current mode 2, the first capacitor is charged by the direct current power supply, so that the first capacitor performs charge and discharge work under the switching frequency scale of the negative half period, and the voltage of the first capacitor is kept to be equal to the direct current voltage value stably.
Mode 4 is as shown in fig. 4(a), the grid voltage is positive, the grid current is negative, the switching state of the power switching tube is the same as mode 1, and the reverse current does not pass through the switching tube S3The current generated by the network passes through the switch tube S2And S1And the output voltage of the common-ground single-phase three-level inverter circuit is equal to the voltage of the direct-current power supply.
Mode 5 is shown in fig. 4(b), which is the same as the mode 2 switching state at unity power factor, in which freewheeling mode the grid current passes through the switching tube S3And a switching tube S4The formed branch returns to the power grid, so that the power grid cannot be the first capacitor C1Charging while the first capacitor C is supplied by DC power supply1Charging is carried out if the capacitor C1Voltage of (2) is over-directWhen the power supply voltage is flowing, the diode D1The cathode potential of (b) will be higher than the anode potential and turn off, and charging stops.
Mode 6 as shown in fig. 4(C), the grid voltage is negative, the grid current is positive, and the switching state of the power switching tube is the same as mode 3, in which the grid current flows through the first capacitor C1And charging it will result in a capacitor C1Rise in voltage, the magnitude of the rise being related to the non-power factor angle:
in a mode 6 of a non-unity power factor, a capacitor C can be calculated according to an output current and a voltage lead-lag angle psi when the grid voltage is negative and the grid current is positive1The rising amplitude of (c). At this time, the current flows through the capacitor C1Is identical to the current of the power grid according to the capacitance C1Characteristic formula (II)
Figure BDA0003524262180000061
Obtaining the formula (1) and obtaining the capacitor C after being combined with the formula (2)1The rising value of (c). Wherein, IoAnd T is the current peak value of the power grid, and is the power frequency period. M is modulation index M ═ Vo/Vdc,VoIs the output sinusoidal voltage peak. I isoAnd T is the current peak value of the power grid, and is the power frequency period.
Figure BDA0003524262180000062
Figure BDA0003524262180000071
Figure BDA0003524262180000072
FIG. 5 shows a common ground type single-phase three-level inverter circuit outputting three levels uabAnd the network voltage ugWaveform of u, whereinabPeak voltage of and photovoltaic dc power supply voltage VdcThe voltage is 400V, ugHas a peak voltage of311V and the frequency is 50 Hz.
Fig. 6 is an operation waveform of a unit power factor and a non-unit power factor when the common-ground single-phase three-level inverter circuit provided by the invention is in three-level output, wherein fig. 6(a) is an operation waveform of the unit power factor and a grid voltage ugAnd the network inlet current igIn phase, net current igThe peak value is 6.43A; fig. 6(b) is an operation waveform when the grid current leads the voltage by 30 °, and fig. 6(c) is an operation waveform when the grid current lags the voltage by 30 °. It can be seen that the network inlet current i of the present invention operates at unity power factor or at non-unity power factorgThe waveform of the voltage-controlled power supply is smooth, high power quality input can be provided for a power grid, and meanwhile, when reactive power exists in the power grid, the circuit can still normally and stably operate.
FIG. 7 shows a first capacitor C of a common ground type single-phase three-level inverter circuit according to the present invention1The voltage waveforms are shown in fig. 7(a), fig. 7(b), and fig. 7(c), respectively, for the first capacitor voltage at unity power factor, the grid current leading voltage by 30 °, and the grid current lagging voltage by 30 °. It can be seen that when the second capacitor C is used2The capacitance value is 0.1mF, and the first capacitor C is arranged under the unit power factor at the switching frequency of 50kHz1Is stabilized at 400V. When the grid current leads the voltage by 30 degrees and lags the voltage by 30 degrees, the voltage of the first capacitor slightly increases in the negative half period of the grid but still relatively keeps stable, so that the common-ground type single-phase three-level inverter circuit has the capability of transmitting reactive power to the grid to a better degree.
The power switch S of this embodiment1-S5A metal-oxide semiconductor field effect transistor (MOSFET for short) or an insulated gate bipolar transistor or a silicon carbide field effect transistor is adopted. The power diode D of this embodiment1Which may be a schottky diode or a silicon power switching diode, etc.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.

Claims (5)

1. The utility model provides a single-phase three-level inverter circuit of type altogether which characterized in that: photovoltaic DC power supply (V)dc) A first capacitor (C)1) A first power switch tube (S)1) A second power switch tube (S)2) And the third power switch tube (S)3) And the fourth power switch tube (S)4) The fifth power switch tube (S)5) A first power diode (D)1) And an AC filter inductor (L)1)；
Photovoltaic DC power supply (V)dc) And the first power switch tube (S)1) The drain electrodes of the two electrodes are connected; a first power switch tube (S)1) Source and second power switch tube (S)2) And a first power diode (D)1) Are connected with each other; second power switch tube (S)2) Source and third power switch tube (S)3) The source electrode of the first capacitor, the cathode of the first capacitor and the output port a of the inverter circuit are connected; third power switch tube (S)3) And the fourth power switch tube (S)4) The drain electrodes of the first and second transistors are connected to form a back-to-back structure;
fourth power switch tube (S)4) Source electrode of (1) and fifth power switch tube (S)5) Source electrode, photovoltaic dc power supply (V)dc) The negative pole of the power grid is connected with a zero line of a central point of the power grid; fifth power switch tube (S)5) Respectively with the first power diode (D)1) Is connected with the positive electrode of the first capacitor, and the output port a of the inverter circuit of the invention of the inverter circuit is connected with the alternating current filter inductor (L)1) One end of the two ends are connected; AC filter inductance (L)1) Another end of (u) and an AC distribution networkg) One end of the two ends are connected; AC distribution network (u)g) The other end of the DC-DC converter is connected with the output port of the inverter, namely, the DC-side photovoltaic DC power supply (V)dc) Are connected with each other.
2. The common-ground type single-phase three-level inverter circuit according to claim 1, wherein: the power switch adopts a metal-oxide semiconductor field effect transistor or an insulated gate bipolar transistor or a silicon carbide field effect transistor.
3. The common ground type single-phase three-level inverter circuit according to claim 1, wherein: the power diode D1Which may be schottky diodes or silicon power switching diodes.
4. The common-ground type single-phase three-level inverter circuit according to claim 1, wherein: the AC filter circuit is an inductance type filter (L)1) Or a capacitive filter or a combined inductor-capacitor filter.
5. The common ground type single-phase three-level inverter circuit according to claim 1, wherein: the load is an alternating current network (u)g) Or purely resistive or inductive or capacitive loading.
CN202210187599.9A 2022-02-28 2022-02-28 Common-ground single-phase three-level inverter and modulation method thereof Pending CN114709861A (en)

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