CN113037116B - Inverter - Google Patents

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Publication number
CN113037116B
CN113037116B CN202110267970.8A CN202110267970A CN113037116B CN 113037116 B CN113037116 B CN 113037116B CN 202110267970 A CN202110267970 A CN 202110267970A CN 113037116 B CN113037116 B CN 113037116B
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switching tube
diode
power supply
switch tube
capacitor
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CN113037116A (en
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王立乔
单明杰
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Yanshan University
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Yanshan University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—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
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output

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

Abstract

The invention discloses an inverter. The single-phase inverter comprises a direct-current power supply and an inverter circuit; the inverter circuit includes: the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the first diode, the second diode, the third diode, the first capacitor, the second capacitor and the first inductor; the negative electrode of the direct current power supply is respectively connected with the second end of the third switching tube, the cut-off end of the second diode and the second end of the fourth switching tube, the other end of the alternating current load or the other end of the alternating current power supply is connected with the negative electrode of the direct current power supply, and the photovoltaic array is short-circuited to the ground parasitic capacitance.

Description

Inverter
Technical Field
The invention relates to the technical field of power electronics, in particular to an inverter.
Background
In recent years, with the over-exploitation of traditional energy resources, such as petroleum, coal and natural gas, the reserves thereof have been gradually exhausted, and at present, human beings face various production and living problems caused by energy crisis. In addition, the large consumption of traditional energy causes many irreversible negative effects on the environment, such as pollution of atmospheric quality, greenhouse effect, ecological balance damage, and other serious problems, and therefore, the development of renewable clean energy by human beings is urgent. Solar energy, as a novel renewable energy source, has the advantages of no pollution, wide distribution, sufficient storage capacity and the like, and is widely developed in the global scope at present. One way of fully utilizing solar energy is photovoltaic power generation, and an inverter, which is a core component for converting a direct current form generated by a photovoltaic array into an alternating current form, is an indispensable part of a photovoltaic power generation system. The traditional inverter mostly adopts an isolated circuit structure with a transformer, but the transformer has the defects of large volume, low efficiency, low power density and the like, so that a non-isolated inverter becomes a research hotspot in recent years. Because the isolation function of the transformer is lost, a common-mode loop can be formed among the direct current side, the alternating current side and the ground of the non-isolated inverter, and the common-mode leakage current problem caused by the common-mode loop is always the key of the inverter technology. Common mode leakage current is an important cause for shutdown of a photovoltaic power generation system, and large leakage current brings EMI (Electromagnetic Interference) Interference and reduces output waveform quality, and the common mode leakage current threatens personal safety and has potential safety hazard.
The traditional photovoltaic inverter mainly solves the problem of leakage current from a modulation strategy or a circuit structure, but the improved modulation strategy is complex in algorithm and has high requirements on the performance of a control system, and the reliability of a photovoltaic power generation system is reduced and the fault probability of the system is increased due to the fact that the modulation strategy is too complex. The circuit structure is used for solving the problem that the leakage current is generally configured into a symmetrical structure, but the circuit structure has the defects of excessive circuit device number, large volume, high loss and the like. In addition, the above two solutions can only keep the common-mode leakage current not to exceed a specified safety range as much as possible, but the photovoltaic power generation system is susceptible to weather factors, for example, the capacitance value of the parasitic capacitance of the photovoltaic array to the ground changes in rainy and snowy weather, and at this time, the leakage current is more likely to exceed a specified threshold value to cause shutdown.
Disclosure of Invention
The invention aims to provide an inverter with a voltage boosting and reducing capacity, which can effectively restrain common mode leakage current.
In order to achieve the purpose, the invention provides the following scheme:
a single-phase inverter comprising:
a DC power supply and an inverter circuit;
the inverter circuit specifically includes:
the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the first diode, the second diode, the third diode, the first capacitor, the second capacitor and the first inductor;
the positive electrode of the direct current power supply is respectively connected with a first end of the first switch tube and a first end of the second switch tube, a second end of the first switch tube is respectively connected with a first end of the first inductor and a cut-off end of the first diode, a second end of the second switch tube is respectively connected with a conducting end of the first diode and a first end of the first capacitor, a second end of the first inductor is respectively connected with a first end of the third switch tube and a conducting end of the third diode, and a second end of the third switch tube is connected with a negative electrode of the direct current power supply;
the conducting end of the first diode is connected with the first end of the second capacitor, the second end of the first capacitor is connected with the conducting end of the second diode, and the stopping end of the second diode is connected with the negative electrode of the direct current power supply;
a second end of the second capacitor is connected with a cut-off end of the third diode, a first end of the fourth switching tube and a first end of the fifth switching tube respectively, and a second end of the fourth switching tube is connected with a negative electrode of the direct-current power supply;
a first end of the sixth switching tube is connected with a second end of the fifth switching tube, and a second end of the sixth switching tube is connected with a conducting end of the second diode; the second end of the fifth switching tube is connected with one end of an alternating current load or one end of an alternating current power supply, and the other end of the alternating current load or the other end of the alternating current power supply is connected with the negative electrode of the direct current power supply;
when the voltage of the alternating current load or the alternating current power supply is in a first half period, the first switching tube, the second switching tube and the third switching tube are in a conducting state and a disconnecting state alternately, the first switching tube, the second switching tube and the third switching tube are conducted or disconnected simultaneously, the fourth switching tube and the sixth switching tube are in a disconnecting state, and the fifth switching tube is in a conducting state;
when the voltage of the alternating current load or the alternating current power supply is in a second half cycle, the states of the first switch tube, the second switch tube, the third switch tube and the fourth switch tube are alternately switched on and off, the first switch tube, the third switch tube and the fourth switch tube are simultaneously switched on or simultaneously switched off, the second switch tube is switched off when the first switch tube is switched on, the second switch tube is switched on when the first switch tube is switched off, the fifth switch tube is switched off, and the sixth switch tube is switched on.
Optionally, the inverter circuit further includes:
a filter circuit;
one end of the filter circuit is connected with the second end of the fifth switching tube, the other end of the filter circuit is connected with the negative electrode of the direct current power supply, and the alternating current load or the alternating current power supply is connected with the filter circuit.
Optionally, the filter circuit specifically includes:
a filter capacitor and a filter inductor;
the first end of the filter inductor is connected with the second end of the fifth switching tube, the second end of the filter inductor is connected with the first end of the filter capacitor, and the second end of the filter capacitor is connected with the negative electrode of the direct-current power supply; the alternating current load or the alternating current power supply is connected with the filter capacitor in parallel.
Optionally, the first capacitor, the second capacitor and the filter capacitor are all non-electrolytic capacitors.
Optionally, a negative electrode of the dc power supply is grounded.
The invention also provides a three-phase inverter based on a discrete power supply, which comprises:
three single-phase inverters as described above;
and the power cathodes of the three single-phase inverters are connected together.
The present invention also provides a single power supply based three-phase inverter, comprising:
a DC power supply and three inverter circuits;
the inverter circuit specifically includes:
the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the first diode, the second diode, the third diode, the first capacitor, the second capacitor and the first inductor;
a first end of the first switch tube is connected with a first end of the second switch tube, a second end of the first switch tube is respectively connected with a first end of the first inductor and a cut-off end of the first diode, a second end of the second switch tube is respectively connected with a conducting end of the first diode and a first end of the first capacitor, and a second end of the first inductor is respectively connected with a first end of the third switch tube and a conducting end of the third diode;
the conducting end of the first diode is connected with the first end of the second capacitor, and the second end of the first capacitor is connected with the conducting end of the second diode;
a second end of the second capacitor is connected with a cut-off end of the third diode, a first end of the fourth switching tube and a first end of the fifth switching tube respectively;
the second end of the third switching tube, the cut-off end of the second diode and the second end of the fourth switching tube are connected together;
a first end of the sixth switching tube is connected with a second end of the fifth switching tube, and a second end of the sixth switching tube is connected with a conducting end of the second diode; the second end of the fifth switching tube is connected with one end of an alternating current load or one end of an alternating current power supply, and the other end of the alternating current load or the other end of the alternating current power supply is connected with the negative electrode of the direct current power supply;
when the voltage of the alternating current load or the alternating current power supply is in a first half period, the first switching tube, the second switching tube and the third switching tube are in a conducting state and a disconnecting state alternately, the first switching tube, the second switching tube and the third switching tube are conducted or disconnected simultaneously, the fourth switching tube and the sixth switching tube are in a disconnecting state, and the fifth switching tube is in a conducting state;
when the voltage of the alternating current load or the alternating current power supply is in a second half cycle, the first switching tube, the second switching tube, the third switching tube and the fourth switching tube are in an on state and an off state alternately, the first switching tube, the third switching tube and the fourth switching tube are in an on state or an off state simultaneously, the second switching tube is off when the first switching tube is on, the second switching tube is on when the first switching tube is off, the fifth switching tube is in an off state, and the sixth switching tube is in an on state;
the positive pole of the direct current power supply is connected with the first end of the first switching tube of each inverter circuit, and the negative pole of the direct current power supply is connected with the cut-off end of the second diode of each inverter circuit.
Optionally, the inverter circuit further includes:
a filter circuit;
one end of the filter circuit is connected with the second end of the fifth switching tube, the other end of the filter circuit is connected with the cut-off end of the second diode, and the alternating current load or the alternating current power supply is connected with the filter circuit.
Optionally, the filter circuit specifically includes:
a filter capacitor and a filter inductor;
the first end of the filter inductor is connected with the second end of the fifth switching tube, the second end of the filter inductor is connected with the first end of the filter capacitor, and the second end of the filter capacitor is connected with the cut-off end of the second diode; the alternating current load or the alternating current power supply is connected with the filter capacitor in parallel.
Optionally, the first capacitor, the second capacitor and the filter capacitor are all non-electrolytic capacitors.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a single-phase inverter, wherein the cathode of a direct-current power supply is respectively connected with the second end of a third switching tube, the cut-off end of a second diode and the second end of a fourth switching tube, the other end of an alternating-current load or the other end of an alternating-current power supply is connected with the cathode of the direct-current power supply, and a photovoltaic array is short-circuited to the stray capacitance of the ground, so that leakage current can be effectively inhibited.
In addition, the inverter circuit does not contain an electrolytic capacitor, and adopts a non-electrolytic capacitor with a smaller capacitance value, thereby being beneficial to improving the whole service life and the circuit performance of the circuit.
The invention also provides a three-phase inverter based on the discrete power supply and a three-phase inverter based on the single power supply, which improve the application range of the inverter circuit on the basis of having the voltage boosting and reducing capability and effectively inhibiting the common mode leakage current, and are more suitable for high-power photovoltaic application occasions.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a block diagram of a single-phase inverter according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of control signals of the switching tube according to the embodiment of the present invention;
FIG. 3 is a schematic view of an embodiment of the present invention in an operating mode I;
FIG. 4 is a diagram illustrating an exemplary working mode II according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of an embodiment of an operating mode III;
FIG. 6 is a schematic diagram of an operating mode IV according to an embodiment of the present invention;
FIG. 7 is a diagram illustrating an exemplary operating mode V according to the present invention;
FIG. 8 is a schematic view of an operating mode VI in an embodiment of the present invention;
FIG. 9 is a diagram illustrating voltages of a first capacitor according to an embodiment of the present invention;
FIG. 10 is a diagram illustrating a second capacitor voltage according to an embodiment of the present invention;
FIG. 11 is a diagram illustrating waveforms of the DC side inductor current, the first capacitor voltage, and the second capacitor voltage according to an embodiment of the present invention;
FIG. 12 is a waveform diagram of the DC input voltage and the output AC voltage under the boost inversion according to the embodiment of the present invention;
FIG. 13 is a waveform diagram of the DC input voltage and the output AC voltage under isobaric inversion according to an embodiment of the present invention;
FIG. 14 is a waveform diagram of the DC input voltage and the output AC voltage under buck inversion according to an embodiment of the present invention;
FIG. 15 is a diagram showing a structure of a control circuit according to an embodiment of the present invention;
FIG. 16 is a schematic diagram of a three-phase inverter based on a discrete power source in an embodiment of the present invention;
fig. 17 is a structure diagram of a single power supply-based three-phase inverter in the embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide an inverter with a voltage boosting and reducing capacity, which can effectively restrain common mode leakage current.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Example one
Fig. 1 is a structural diagram of a single-phase inverter according to an embodiment of the present invention, and as shown in fig. 1, a single-phase inverter includes: a direct current power source E and an inverter circuit.
The inverter circuit specifically includes: first switch tube S1A second switch tube S2A third switch tube S3The fourth switch tube S4The fifth switch tube S5The sixth switching tube S6A first diode D1A second diode D2A third diode D3A first capacitor C1A second capacitor C2A first inductor L1And a filter circuit.
The positive pole of the DC power supply E is respectively connected with the first switch tube S through the P end of the DC bus1First terminal and second switching tube S2Is connected with a first end of a first switch tube S1Respectively with the first inductor L1First terminal and first diode D1Is connected with a cut-off end of a second switching tube S2Second terminals of the first and second diodes are connected to the first and second diodes D, respectively1And the first capacitor C1Is connected to a first terminal of a first inductor L1Respectively with a third switch tube S3First terminal and third diode D3Is connected with the conducting end of the third switching tube S3The second end of the second switch is connected with the negative electrode of the direct current power supply E;
first diode D1The conducting terminal and the second capacitor C2Is connected to a first terminal of a first capacitor C1Second terminal and second diode D2Is connected to the conducting terminal of a second diode D2The cut-off end of the direct current power supply E is connected with the negative electrode of the direct current power supply E;
second capacitor C2Respectively with a third diode D3The cut-off end of the fourth switching tube S4First terminal and fifth switching tube S5Is connected with the first end of the fourth switching tube S4The second end of the second switch is connected with the negative electrode of the direct current power supply E;
sixth switching tube S6First end of and a fifth switch tube S5Is connected with the second end of the sixth switch tube S6Second terminal and second diode D2The conducting end of the first switch is connected; fifth switch tube S5The second end of the second switch is connected with one end of an alternating current load or one end of an alternating current power supply, and the other end of the alternating current load or the other end of the alternating current power supply is connected with the negative electrode of a direct current power supply E; namely, the other end of the load or the power grid is connected with the N end of the direct current bus, and the output end of the load or the power grid is the B end. The input end N is directly connected with the output end B, and the photovoltaic array is short-circuited to the ground parasitic capacitance, so that leakage current can be effectively inhibited.
The first switch tube S is arranged when the voltage of the AC load or the AC power supply is in the first half period1A second switch tube S2And a third switching tube S3Is alternately turned on and off, and the first switching tube S1A second switch tube S2And a third switching tube S3A fourth switching tube S which is switched on or off simultaneously4And a sixth switching tube S6In an off state, the fifth switch tube S5Is in a conducting state;
when the voltage of the AC load or the AC power supply is in the second half period, the first switch tube S1A second switch tube S2A third switch tube S3And a fourth switching tube S4Is alternately turned on and off, and the first switching tube S1A third switch tube S3And a fourth switching tube S4Are switched on or off simultaneously, in the first switching tube S1The second switch tube is turned off S when being conducted2In the first switch tube S1Second switching tube S when turned off2Conducting the fifth switch tube S5In an off state, the sixth switching tube S6Is in an on state.
One end of the filter circuit and the fifth switch tube S5The other end of the filter circuit is connected with the negative electrode of the direct current power supply E, and the alternating current load or the alternating current power supply is connected with the filter circuit.
Wherein, the filter circuit specifically includes: filter capacitor CfAnd a filter inductance Lf. Filter inductance LfFirst end of and a fifth switch tube S5Is connected to the second terminal of the filter inductor LfSecond terminal and filter capacitor CfIs connected to the filter capacitor CfThe second end of the second switch is connected with the negative electrode of the direct current power supply; AC load or AC power supply and filter capacitor CfAre connected in parallel.
A first capacitor C1A second capacitor C2And a filter capacitor CfAll are non-electrolytic capacitors; the negative electrode of the dc power supply E is grounded.
According to the switching logic shown in fig. 2, the inverter of the present invention can be divided into six operating modes, wherein the operating modes belong to positive modes i, ii, and iii of output voltage, and belong to negative modes iv, v, and vi of output voltage, which are as follows:
working mode I
The specific inverter operation in this mode is shown in fig. 3. First switch tube S1A second switch tube S2A third switch tube S3In a conducting state, the fourth switching tube S4The sixth switching tube S6In the off state, the fifth switching tube S5Is in a conducting state. The power supply E passes through the first switch tube S1A third switch tube S3To the first inductor L1Charging; power supply E passes through the second switchClosing pipe S2A second diode D2To the first capacitor C1Charging; the power supply E passes through the second switch tube S2A second capacitor C2The fifth switch tube S5Filter inductor LfPower is supplied to the load side.
Working mode II
The specific inverter operation in this mode is shown in fig. 4. First switch tube S1A second switch tube S2A third switch tube S3In the off state, the fourth switching tube S4The sixth switching tube S6In the off state, the fifth switching tube S5Is in a conducting state. First inductance L1Discharging to a second capacitor through the first diode and the third diode; filter inductance LfThrough a load and a fourth switching tube S4Anti-parallel diode and fifth switch tube S5And then follow current.
Mode of operation III
The specific inverter operation in this mode is shown in fig. 5. First switch tube S1A second switch tube S2A third switch tube S3In the off state, the fourth switching tube S4The sixth switching tube S6In the off state, the fifth switching tube S5Is in a conducting state. First inductance L1Finishing the discharge; filter inductance LfThrough a load and a fourth switching tube S4Anti-parallel diode and fifth switch tube S5And then follow current.
Operating mode IV
The specific inverter operation in this mode is shown in fig. 6. First switch tube S1A third switch tube S3And a fourth switching tube S4The sixth switching tube S6In a conducting state, the second switch tube S2The fifth switch tube S5In an off state. The power supply E passes through the first switch tube S1A third switch tube S3To the first inductor L1Charging; a first capacitor C1Through a second capacitor C2And a fourth switching tube S4Filter inductor LfThe sixth switching tube S6Power is supplied to the load.
Mode of operation V
The specific inverter operation in this mode is shown in fig. 7. First switch tube S1A third switch tube S3And a fourth switching tube S4The fifth switch tube S5In the off state, the second switch tube S2The sixth switching tube S6Is in a conducting state. The power supply E passes through the second switch tube S2A second diode D2To the first capacitance C1Charging; first inductance L1Discharging to a second capacitor through the first diode and the third diode; filter inductor LfThrough a loaded sixth switching tube S6A second diode D2And then follow current.
Working mode VI
The specific inverter operation in this mode is shown in fig. 8. First switch tube S1A third switch tube S3And a fourth switching tube S4The fifth switch tube S5In the off state, the second switch tube S2The sixth switching tube S6Is in a conducting state. The power supply E passes through the second switch tube S2A second diode D2To the first capacitor C1Charging; first inductance L1Finishing the discharge; filter inductance LfThrough a loaded sixth switching tube S6A second diode D2And then follow current.
The above six operating modes are shown in table 1.
TABLE 1 inverter switching tube combination status
Figure BDA0002973013570000091
Figure BDA0002973013570000101
For the purpose of simplifying the analysis, the circuit of the invention makes the following assumptions:
(1) all components in the circuit are ideal components; (2) the circuit operates in a steady state.
Due to the fact thatThe inverter has a symmetrical structure, so that a single circuit can be used for analysis. Make the first switch tube S1The ratio of the on-time to the switching period within one switching period is the duty cycle d. In conjunction with fig. 9, the following relationship holds:
when the first capacitor C1When discharging, neglecting the current flowing on the filter capacitor:
ic1≈io (1)
Figure BDA0002973013570000102
Figure BDA0002973013570000103
Figure BDA0002973013570000104
Figure BDA0002973013570000105
the combinations (1), (2), (3), (4) and (5) are as follows:
Figure BDA0002973013570000106
defining a voltage ripple coefficient of
Figure BDA0002973013570000107
Wherein ic1Is a first capacitance current ioTo output current,. DELTA.Vc1Is a first amount of fluctuation of the capacitor voltage, VoTo output an effective value of the voltage, fsTo the switching frequency, TsFor the switching period, R is the load resistance, d is the duty cycle, Vc1Is the first capacitor voltage and P is the power.
The inverter is suitable for a low-power application environment, the power range is 100-3000W, in order to well explain capacitance value, the duty ratio d is taken as a limit value which is 1, the effective value of output voltage is 220V, and the ripple requirement on the capacitance voltage is not very high because the inverter belongs to an alternating current application occasion, so the ripple coefficient is taken as gamma1At 20%, the inverter is controlled by SPWM, so the switching frequency is usually very large, and the invention takes 20 khz. Table 2 gives the values of the first capacitance at different output powers.
TABLE 2 first capacitance values at different powers
Figure BDA0002973013570000111
In connection with fig. 10, the following relationship holds:
neglecting the current flowing on the filter capacitor is:
ic2≈io(8)
Figure BDA0002973013570000112
Figure BDA0002973013570000113
Figure BDA0002973013570000114
in addition have
Figure BDA0002973013570000115
The combinations (8), (9), (10), (11) and (12) are provided with
Figure BDA0002973013570000116
Defining a voltage ripple coefficient of
Figure BDA0002973013570000117
Wherein ic2Is the second capacitance current, ioTo output current, Δ Vc2Is the second amount of fluctuation of the capacitor voltage, VoFor the effective value of the output voltage, R is the load resistance, fsTo the switching frequency, Vc2Is the second capacitor voltage.
Similarly, since the inverter is suitable for a low-power application environment, the power range is 100-3000W, in order to well explain the capacitance value, the duty ratio d is taken as a limit value which is 1, the effective value of the output voltage is 220V, and since the inverter belongs to an alternating current application occasion, the ripple requirement on the capacitance voltage is not very high, the ripple coefficient is taken as gamma1At 20%, the inverter is controlled by SPWM, so the switching frequency is usually very large, and the invention takes 20 khz. Table 3 gives the values of the second capacitance for different output powers.
TABLE 3 second capacitance values at different powers
Figure BDA0002973013570000121
As can be seen from tables 2 and 3, the inverter of the present invention has a first capacitor C in a wide power range1A second capacitor C2The values are all small; in addition, the filter capacitor C is high in switching frequencyfValues are small, typically 1.5 to 5uF, so that the capacitors in the inverter circuit can be replaced by thin-film capacitors instead of electrolytic capacitors.
The inverter circuit does not contain electrolytic capacitors, and adopts non-electrolytic capacitors with smaller capacitance values, so that the overall service life of the circuit and the circuit performance are favorably improved, the voltage waveforms of the capacitors are shown in fig. 11, and as can be seen from fig. 11, the voltage fluctuation of the capacitors is very small after the non-electrolytic capacitors are adopted, so that the selection of the non-electrolytic capacitors is reasonable. And meanwhile, the inductance parameter is small, and the size and the weight of the inductor are favorably reduced. The voltage resistance requirement of the second capacitor C2 is lower than that of other inverter circuits, and the terminal voltage of the second capacitor C2 is always kept as the peak value of the output voltage, namely 311V, so that the cost is reduced, and the reliability of the circuit is improved; first electric capacity C1 is as direct current bus capacitance, can charge in whole power frequency cycle, and only discharges in the negative half cycle, reaches the purpose of precharging the bus capacitance, is favorable to improving the waveform quality, knows that the capacitor voltage is undulant in less within range from figure 11, can satisfy the normal work demand of inverter well.
According to the invention, the boost-buck inversion can be realized, and under the boost output working condition, the peak value of the output alternating current voltage is higher than the direct current input voltage, so that the inverter has the boost inversion capability, and the simulation waveform of the inverter is shown in fig. 12. Under the isobaric output working condition, the peak value of the output alternating current voltage is equal to the direct current input voltage, so that the inverter has isobaric inversion capability, and the simulation waveform of the inverter is shown in fig. 13. Under the working condition of voltage reduction output, the peak value of output alternating current voltage is lower than direct current input voltage, so that the inverter has the voltage reduction and inversion capacity, and the simulation waveform of the inverter is shown in a figure 14 in the attached drawing of the specification.
FIG. 15 is a structural diagram of a control circuit of the present invention, wherein the control strategy adopts a single closed loop control of voltage or current, an error signal is regulated by a regulator and input to a comparator to generate a PWM signal, and finally the PWM signal drives a switch tube through a driving circuit. V in FIG. 15refIs a reference voltage, IrefIs a reference current.
The invention can adopt single closed-loop control of voltage or current, has simple control structure, fast dynamic response and good tracking performance, can adopt single-cycle control, can better resist direct-current input disturbance, improves the robustness of the circuit and is more suitable for photovoltaic power generation application occasions.
The inverter circuit of the invention is easy to expand into a three-phase inverter, the expanded three-phase inverter can adopt a discrete power supply and can also adopt a single power supply, so that the use is more flexible, the expanded two topologies are respectively shown in figures 16 and 17 in the attached drawing of the specification, the application range of the circuit is improved, and the inverter circuit is more suitable for high-power application occasions.
Example two
Fig. 16 is a structural diagram of a three-phase inverter based on a discrete power supply according to an embodiment of the present invention, and as shown in fig. 16, a three-phase inverter based on a discrete power supply includes: three single-phase inverters. The power cathodes of the three single-phase inverters are connected together. The structure of each single-phase inverter is the same as that of the single-phase inverter of the first embodiment. Three separate dc voltage sources supply each phase.
In particular, the method comprises the following steps of,
a first single-phase inverter comprising: DC power supply E1A first switch tube S11A second switch tube S21A third switch tube S31And a fourth switching tube S41The fifth switch tube S51The sixth switching tube S61A first diode D11A second diode D21A third diode D31A first capacitor C11A second capacitor C21A first inductor L11Filter capacitor Cf1And a filter inductance Lf1。
A second single-phase inverter, comprising: DC power supply E2A first switch tube S12A second switch tube S22A third switch tube S32And a fourth switching tube S42The fifth switch tube S52The sixth switching tube S62A first diode D12A second diode D22A third diode D32A first capacitor C12A second capacitor C22A first inductor L12Filter capacitor Cf2And a filter inductance Lf2。
A third single-phase inverter comprising: DC power supply E3A first switch tube S13A second switch tube S23A third switch tube S33And a fourth switching tube S43The fifth switch tube S53The sixth switching tube S63A first diode D13A second diode D23A third diode D33A first capacitor C13A second capacitor C23A first inductor L13Filter capacitor Cf3And a filter inductance Lf3。
Direct currentSource E1DC power supply E2And a DC power supply E3Connected together, a filter capacitor Cf1Filter capacitor Cf2And a filter capacitor Cf3Respectively connected in parallel with a group of alternating current loads or alternating current power supplies.
The expanded three-phase inverter adopts a discrete power supply, improves the application range of the circuit, and is more suitable for high-power application occasions.
EXAMPLE III
Fig. 17 is a structural diagram of a single-power-supply-based three-phase inverter according to an embodiment of the present invention, and as shown in fig. 17, a single-power-supply-based three-phase inverter includes: a direct current power source E and three inverter circuits. One dc voltage source supplies each phase.
Inverter circuit specifically includes: the circuit comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a first diode, a second diode, a third diode, a first capacitor, a second capacitor, a first inductor and a filter circuit.
The first end of the first switch tube is connected with the first end of the second switch tube, the second end of the first switch tube is respectively connected with the first end of the first inductor and the cut-off end of the first diode, the second end of the second switch tube is respectively connected with the conducting end of the first diode and the first end of the first capacitor, and the second end of the first inductor is respectively connected with the first end of the third switch tube and the conducting end of the third diode;
the conducting end of the first diode is connected with the first end of the second capacitor, and the second end of the first capacitor is connected with the conducting end of the second diode;
the second end of the second capacitor is respectively connected with the cut-off end of the third diode, the first end of the fourth switching tube and the first end of the fifth switching tube;
the second end of the third switching tube, the cut-off end of the second diode and the second end of the fourth switching tube are connected together;
the first end of the sixth switching tube is connected with the second end of the fifth switching tube, and the second end of the sixth switching tube is connected with the conduction end of the second diode; the second end of the fifth switching tube is connected with one end of an alternating current load or one end of an alternating current power supply, and the other end of the alternating current load or the other end of the alternating current power supply is connected with the negative electrode of the direct current power supply;
when the voltage of the alternating current load or the alternating current power supply is in the first half period, the states of the first switching tube, the second switching tube and the third switching tube are alternately conducted, the first switching tube, the second switching tube and the third switching tube are conducted or turned off simultaneously, the fourth switching tube and the sixth switching tube are in a turn-off state, and the fifth switching tube is in a turn-on state;
when the voltage of an alternating current load or an alternating current power supply is in a second half period, the states of a first switching tube, a second switching tube, a third switching tube and a fourth switching tube are alternately switched on and off, the first switching tube, the third switching tube and the fourth switching tube are simultaneously switched on or simultaneously switched off, the second switching tube is switched off when the first switching tube is switched on, the second switching tube is switched on when the first switching tube is switched off, the fifth switching tube is in a switched off state, and the sixth switching tube is in a switched on state;
the positive pole of the direct current power supply is connected with the first end of the first switching tube of each inverter circuit, and the negative pole of the direct current power supply is connected with the cut-off end of the second diode of each inverter circuit.
One end of the filter circuit is connected with the second end of the fifth switching tube, the other end of the filter circuit is connected with the cut-off end of the second diode, and the alternating current load or the alternating current power supply is connected with the filter circuit.
The filter circuit specifically includes: a filter capacitor and a filter inductor; the first end of the filter inductor is connected with the second end of the fifth switching tube, the second end of the filter inductor is connected with the first end of the filter capacitor, and the second end of the filter capacitor is connected with the cut-off end of the second diode; an alternating current load or an alternating current power supply is connected in parallel with the filter capacitor. The first capacitor, the second capacitor and the filter capacitor are all non-electrolytic capacitors.
In particular, the method comprises the following steps of,
a first inverter circuit comprising: first switch tube S11A second switch tube S21A third switch tube S31And a fourth switching tube S41Fifth, theSwitch tube S51The sixth switching tube S61A first diode D11A second diode D21A third diode D31A first capacitor C11A second capacitor C21A first inductor L11Filter capacitor Cf1And a filter inductance Lf1。
A second inverter circuit comprising: first switch tube S12A second switch tube S22A third switch tube S32And a fourth switching tube S42The fifth switch tube S52The sixth switching tube S62A first diode D12A second diode D22A third diode D32A first capacitor C12A second capacitor C22A first inductor L12Filter capacitor Cf2And a filter inductance Lf2。
A third inverter circuit comprising: first switch tube S13A second switch tube S23A third switch tube S33And a fourth switching tube S43The fifth switch tube S53And a sixth switching tube S63A first diode D13A second diode D23A third diode D33A first capacitor C13A second capacitor C23A first inductor L13Filter capacitor Cf3And a filter inductance Lf3。
The DC power supply E is respectively connected with the first switch tube S11A second switch tube S21A first switch tube S12A second switch tube S22A first switch tube S13A second switch tube S23Connecting, filtering capacitor Cf1Filter capacitor Cf2And a filter capacitor Cf3Respectively connected in parallel with a group of alternating current loads or alternating current power supplies.
The expanded three-phase inverter adopts a single power supply, improves the application range of the circuit, and is more suitable for high-power application occasions.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In summary, this summary should not be construed to limit the present invention.

Claims (10)

1. A single-phase inverter, comprising:
a DC power supply and an inverter circuit;
the inverter circuit specifically includes:
the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the first diode, the second diode, the third diode, the first capacitor, the second capacitor and the first inductor;
the positive electrode of the direct current power supply is respectively connected with a first end of the first switch tube and a first end of the second switch tube, a second end of the first switch tube is respectively connected with a first end of the first inductor and a cut-off end of the first diode, a second end of the second switch tube is respectively connected with a conducting end of the first diode and a first end of the first capacitor, a second end of the first inductor is respectively connected with a first end of the third switch tube and a conducting end of the third diode, and a second end of the third switch tube is connected with a negative electrode of the direct current power supply;
the conducting end of the first diode is connected with the first end of the second capacitor, the second end of the first capacitor is connected with the conducting end of the second diode, and the stopping end of the second diode is connected with the negative electrode of the direct current power supply;
a second end of the second capacitor is connected with a cut-off end of the third diode, a first end of the fourth switching tube and a first end of the fifth switching tube respectively, and a second end of the fourth switching tube is connected with a negative electrode of the direct-current power supply;
a first end of the sixth switching tube is connected with a second end of the fifth switching tube, and a second end of the sixth switching tube is connected with a conducting end of the second diode; the second end of the fifth switching tube is connected with one end of an alternating current load or one end of an alternating current power supply, and the other end of the alternating current load or the other end of the alternating current power supply is connected with the negative electrode of the direct current power supply;
when the voltage of the alternating current load or the alternating current power supply is in a first half period, the first switching tube, the second switching tube and the third switching tube are simultaneously turned on or turned off, the fourth switching tube and the sixth switching tube are in a turned-off state, and the fifth switching tube is in a turned-on state;
when alternating current load or alternating current power supply's voltage is in latter half cycle, first switch tube, third switch tube and fourth switch tube switch on simultaneously or turn-off simultaneously, when first switch tube switches on the second switch tube cuts off, when first switch tube cuts off the second switch tube switches on, the fifth switch tube is the off-state, the sixth switch tube is the on-state.
2. The single-phase inverter of claim 1, wherein the inverter circuit further comprises:
a filter circuit;
one end of the filter circuit is connected with the second end of the fifth switching tube, the other end of the filter circuit is connected with the negative electrode of the direct current power supply, and the alternating current load or the alternating current power supply is connected with the filter circuit.
3. The single-phase inverter according to claim 2, wherein the filter circuit specifically comprises:
a filter capacitor and a filter inductor;
the first end of the filter inductor is connected with the second end of the fifth switching tube, the second end of the filter inductor is connected with the first end of the filter capacitor, and the second end of the filter capacitor is connected with the negative electrode of the direct-current power supply; the alternating current load or the alternating current power supply is connected with the filter capacitor in parallel.
4. The single-phase inverter of claim 3, wherein the first capacitor, the second capacitor, and the filter capacitor are all non-electrolytic capacitors.
5. The single-phase inverter of claim 1, wherein a negative pole of the dc power source is grounded.
6. A three-phase inverter based on a discrete power supply, comprising:
three single-phase inverters according to any one of claims 1 to 5;
the power cathodes of the three single-phase inverters are connected together.
7. A single power supply based three-phase inverter comprising:
a DC power supply and three inverter circuits;
the inverter circuit specifically includes:
the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the first diode, the second diode, the third diode, the first capacitor, the second capacitor and the first inductor;
a first end of the first switch tube is connected with a first end of the second switch tube, a second end of the first switch tube is respectively connected with a first end of the first inductor and a cut-off end of the first diode, a second end of the second switch tube is respectively connected with a conducting end of the first diode and a first end of the first capacitor, and a second end of the first inductor is respectively connected with a first end of the third switch tube and a conducting end of the third diode;
the conducting end of the first diode is connected with the first end of the second capacitor, and the second end of the first capacitor is connected with the conducting end of the second diode;
a second end of the second capacitor is connected with a cut-off end of the third diode, a first end of the fourth switching tube and a first end of the fifth switching tube respectively;
the second end of the third switching tube, the cut-off end of the second diode and the second end of the fourth switching tube are connected together;
a first end of the sixth switching tube is connected with a second end of the fifth switching tube, and a second end of the sixth switching tube is connected with a conducting end of the second diode; the second end of the fifth switching tube is connected with one end of an alternating current load or one end of an alternating current power supply, and the other end of the alternating current load or the other end of the alternating current power supply is connected with the negative electrode of the direct current power supply;
when the voltage of the alternating current load or the alternating current power supply is in a first half period, the first switching tube, the second switching tube and the third switching tube are simultaneously turned on or turned off, the fourth switching tube and the sixth switching tube are in a turned-off state, and the fifth switching tube is in a turned-on state;
when the voltage of the alternating current load or the alternating current power supply is in a second half cycle, the first switching tube, the third switching tube and the fourth switching tube are simultaneously connected or disconnected, the second switching tube is disconnected when the first switching tube is connected, the second switching tube is connected when the first switching tube is disconnected, the fifth switching tube is in a disconnection state, and the sixth switching tube is in a connection state;
the positive pole of the direct current power supply is connected with the first end of the first switching tube of each inverter circuit, and the negative pole of the direct current power supply is connected with the cut-off end of the second diode of each inverter circuit.
8. The single-power-supply-based three-phase inverter according to claim 7, wherein the inverter circuit further comprises:
a filter circuit;
one end of the filter circuit is connected with the second end of the fifth switching tube, the other end of the filter circuit is connected with the cut-off end of the second diode, and the alternating current load or the alternating current power supply is connected with the filter circuit.
9. The single-power-supply-based three-phase inverter according to claim 8, wherein the filter circuit specifically comprises:
a filter capacitor and a filter inductor;
the first end of the filter inductor is connected with the second end of the fifth switching tube, the second end of the filter inductor is connected with the first end of the filter capacitor, and the second end of the filter capacitor is connected with the cut-off end of the second diode; the alternating current load or the alternating current power supply is connected with the filter capacitor in parallel.
10. The single power supply based three-phase inverter of claim 9, wherein the first capacitor, the second capacitor and the filter capacitor are all non-electrolytic capacitors.
CN202110267970.8A 2021-03-12 2021-03-12 Inverter Active CN113037116B (en)

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