CN111293912A - Multi-level inverter, system and control method - Google Patents
Multi-level inverter, system and control method Download PDFInfo
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- CN111293912A CN111293912A CN202010129516.1A CN202010129516A CN111293912A CN 111293912 A CN111293912 A CN 111293912A CN 202010129516 A CN202010129516 A CN 202010129516A CN 111293912 A CN111293912 A CN 111293912A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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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
- 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
- H02M3/06—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider
- H02M3/07—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider using capacitors charged and discharged alternately by semiconductor devices with control electrode, e.g. charge pumps
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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
- 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
Abstract
The invention provides a multi-level inverter, a system and a control method, comprising the following steps: the system comprises a direct-current power supply, a switched capacitor network, a T-shaped inverter bridge and a filter circuit; the output end of the direct current power supply is electrically connected with the input end of the switch capacitor network, the output end of the switch capacitor network is electrically connected with the input end of the T-shaped inverter bridge, the output end of the T-shaped inverter bridge is electrically connected with the input end of the filter circuit, the output end of the filter circuit is used for connecting a load, and the control end of the switch capacitor network and the control end of the T-shaped inverter bridge are used for connecting a control device. The inverter aims to solve the problems that the inverter in the prior art is low in conversion efficiency, the output voltage is not easy to expand to more levels, and the number of input sources is too large.
Description
Technical Field
The invention relates to the field of inversion, in particular to a multi-level inverter, a multi-level inverter system and a multi-level inverter control method.
Background
The multi-level inverter has the advantages of more output levels, low voltage change rate, low harmonic content, small electromagnetic interference, small output filter volume and the like, and has wide application prospect in the field of new energy power generation. The cascade multilevel inverter has no complex capacitance voltage control strategy, has simple structure and is more suitable for occasions with more output levels. The existing cascade multilevel inverter can be divided into two types according to the number of input sources. One is a multi-input source cascade type inverter as shown in fig. 1, which increases the number of output levels by increasing the number of input sources; another type is a single input source cascade type inverter as shown in fig. 2, which realizes the combination of output levels by forming a switched capacitor network with energy storage capacitors.
The traditional multi-input source cascade inverter is formed by connecting n H-bridge modules in series on an alternating current output side, and each output voltage is the superposition of the outputs of the modules. The number of power switch tubes required by the device is small, and the device is more suitable for new energy power generation places such as photovoltaics.
The cascade inverter based on the switched capacitor is formed by combining a switched capacitor circuit and a traditional H-type full-bridge inverter. The switched capacitor unit is formed by combining a diode Di, a power switch tube Si and an energy storage capacitor Ci.
The switching tubes of the multi-input source cascade inverter are few, the output harmonic content is low, the level number can be freely combined, but the number of the required input sources is too much, so that the application occasions are limited; the existing single-input-source cascade type multi-level inverter can realize different output levels only by one input source, but has the problems of low conversion efficiency and excessive quantity of power switch tubes, and the output voltage is not easy to expand to more levels.
Disclosure of Invention
The invention discloses a multi-level inverter, a multi-level inverter system and a multi-level inverter control method, and aims to solve the problems that the inverter in the prior art is low in conversion efficiency, output voltage is not easy to expand to more levels, and the number of input sources is too large.
The invention is realized by the following steps:
a first embodiment of the present invention provides a multilevel inverter including: the system comprises a direct-current power supply, a switched capacitor network, a T-shaped inverter bridge and a filter circuit;
the output end of the direct current power supply is electrically connected with the input end of the switch capacitor network, the output end of the switch capacitor network is electrically connected with the input end of the T-shaped inverter bridge, the output end of the T-shaped inverter bridge is electrically connected with the input end of the filter circuit, the output end of the filter circuit is used for connecting a load, and the control end of the switch capacitor network and the control end of the T-shaped inverter bridge are used for connecting a control device.
Preferably, the switched capacitor network is formed by connecting a plurality of switched capacitor units in series, and the switched capacitor units include: the power switch tube, the energy storage capacitor, the bus diode and the first non-bus diode;
the anode of the bus diode is electrically connected with the collector of the power switch tube, the cathode of the bus diode is electrically connected with the first end of the energy storage capacitor, the emitter of the power switch tube and the second end of the energy storage capacitor are electrically connected with the anode of the first non-bus diode, the anode of the bus diode of the first switch capacitor unit is electrically connected with the anode of the direct-current power supply, the last switch capacitor unit further comprises a second non-bus diode, the first non-bus diode and the second non-bus diode of the last switch capacitor unit are electrically connected with the T-shaped inverter bridge, and the bus diode is electrically connected with the input end of the T-shaped inverter bridge. Preferably, the T-shaped inverter bridge comprises a first bridge arm and a second bridge arm;
the positive input ends of the first bridge arm and the second bridge arm are electrically connected with the output end of the switched capacitor network, the negative input ends of the first bridge arm and the second bridge arm are electrically connected with the negative electrode of the direct current power supply, and the output ends of the first bridge arm and the second bridge arm are electrically connected with the input end of the filter loop.
Preferably, the first leg comprises: first IGBT pipe, third IGBT pipe, fifth IGBT pipe, the second bridge arm includes: the second IGBT tube, the fourth IGBT tube and the sixth IGBT tube;
the collector of the first IGBT tube and the collector of the second IGBT tube are electrically connected with the cathode of the bus diode of the last switched capacitor unit, the emitter of the first IGBT tube is electrically connected with the emitter of the fifth IGBT tube and the collector of the third IGBT tube, the emitter of the second effect tube is electrically connected with the emitter of the sixth IGBT tube and the collector of the fourth IGBT tube, the collector of the fifth IGBT tube is electrically connected with the cathode of the first bus diode of the last switched capacitor unit, the collector of the sixth IGBT tube is electrically connected with the cathode of the second non-bus diode, and the emitter of the third IGBT tube and the emitter of the fourth IGBT tube are electrically connected with the cathode of the DC power supply.
Preferably, the filter loop comprises a filter inductor and a filter capacitor;
the first end of the filter inductor is electrically connected with the first end of the filter capacitor, the second end of the filter capacitor is electrically connected with the emitter electrode of the sixth IGBT tube, and the second end of the filter inductor is electrically connected with the emitter electrode of the fifth IGBT tube.
A second embodiment of the present invention provides a system, which includes a control device and the multilevel inverter as described in any one of the above embodiments, wherein an output terminal of the control device is electrically connected to a control terminal of the switched capacitor network and a control terminal of the T-type inverter bridge.
A third embodiment of the present invention provides a control method as described above, including:
acquiring an input voltage, judging whether the bus voltage meets the inversion requirement or not by comparing the input voltage with a reference sinusoidal signal, and generating a voltage feedforward signal;
when the inversion requirement is not met, outputting an action signal to a control end of the switched capacitor network, and increasing the bus voltage of the switched capacitor network;
acquiring a voltage feedback signal and generating a modulation signal by combining the voltage feedforward signal;
and comparing the modulation signal with the triangular carrier signal to generate a driving signal of the T-shaped inverter bridge.
Preferably, the acquiring the voltage feedback signal and combining the voltage feedforward signal to generate the modulation signal specifically include:
acquiring an output voltage sampling signal, acquiring a comparison result of the output voltage sampling signal and the reference sinusoidal signal, outputting a value PI regulator by the comparison result, generating a voltage feedback signal, and summing the voltage feedback signal and the voltage feedforward signal to generate a modulation signal.
Based on the multi-level inverter, the multi-level inverter system and the control method provided by the invention, the input voltage of the inverter is read through the control device, the input voltage is compared with a reference sinusoidal signal, whether the bus voltage on the switched capacitor network meets the inversion requirement is judged, when the inversion requirement is not met, the control device outputs an action signal to the control end of the switched capacitor network, so that the switched capacitor network acts to lift the bus voltage, the bus voltage meets the inversion requirement, a voltage feedback signal is obtained, the voltage feedback signal is processed to generate a driving signal of a T-shaped bridge inverter bridge, the driving signal is driven to the T-shaped bridge inverter bridge to perform inversion work, and the driving signal is output to a load after passing through a filter loop. The problems that the inverter in the prior art is low in conversion efficiency, the output voltage is not easy to expand to more levels and the number of input sources is too large are effectively solved.
Drawings
Fig. 1 is a conventional multi-input source cascade type multi-level inverter;
fig. 2 is a cascade-type inverter of switched capacitors;
fig. 3 is a schematic circuit diagram of a multilevel inverter according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a control strategy of a multilevel inverter according to an embodiment of the present invention;
fig. 5 is a control waveform diagram of a multilevel inverter according to an embodiment of the invention;
fig. 6 is an equivalent circuit of the multilevel inverter provided by the embodiment of the invention in the interval of the first stage [ t0-t1, t4-t5] in fig. 5;
fig. 7 is an equivalent circuit of the multilevel inverter in the interval of stage two [ t1-t2, t3-t4] in fig. 5 according to the embodiment of the invention;
fig. 8 is an equivalent circuit of a multilevel inverter provided by the embodiment of the invention in a section of three stages [ t2-t3] in fig. 5.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
The following detailed description of specific embodiments of the invention refers to the accompanying drawings.
The invention discloses a multi-level inverter, a multi-level inverter system and a multi-level inverter control method, and aims to solve the problems that the inverter in the prior art is low in conversion efficiency, output voltage is not easy to expand to more levels, and the number of input sources is too large.
The invention is realized by the following steps:
referring to fig. 3, a multi-level inverter according to a first embodiment of the present invention includes: the system comprises a direct-current power supply 1, a switched capacitor network 2, a T-shaped inverter bridge 3 and a filter circuit 4;
the output end of the direct current power supply 1 is electrically connected with the input end of the switched capacitor network 2, the output end of the switched capacitor network 2 is electrically connected with the input end of the T-shaped inverter bridge 3, the output end of the T-shaped inverter bridge 3 is electrically connected with the input end of the filter circuit 4, the output end of the filter circuit 4 is used for connecting a load, and the control end of the switched capacitor network 2 and the control end of the T-shaped inverter bridge 3 are used for connecting a control device.
It should be noted that, for convenience of understanding, in this embodiment, the switched capacitor network 2 is formed by connecting two switched capacitor units in series, that is, a first switched capacitor unit and a last switched capacitor unit are stored;
in this embodiment, the switched capacitor network is formed by serially connecting a plurality of switched capacitor units, and the switched capacitor units include: the power switch tube STI, the energy storage capacitor CI, a bus diode D1I and a first non-bus diode D2I; it is noted that i is a component of the first switched-capacitor unit.
The anode of the bus diode D1I is electrically connected to the collector of the power switching tube STI, the cathode of the bus diode D1I is electrically connected to the first end of the energy storage capacitor CI, the emitter of the power switching tube STI and the second end of the energy storage capacitor CI are electrically connected to the anode of the first non-bus diode D2I, the anode of the bus diode D1I of the first switched capacitor unit is electrically connected to the anode of the dc power supply 1, the last switched capacitor unit further includes a second non-bus diode D2N ', the first non-bus diode D2I and the second non-bus diode D2N' of the last switched capacitor unit are electrically connected to the T-type bridge, and the bus diode D1I is electrically connected to the input end of the T-type inverter bridge 2T-type inverter bridge 23.
Preferably, the T-type inverter bridge 2T-type inverter bridge 23 includes a first bridge arm and a second bridge arm;
the positive input ends of the first bridge arm and the second bridge arm are electrically connected with the output end of the switched capacitor network, the negative input ends of the first bridge arm and the second bridge arm are electrically connected with the negative electrode of the direct current power supply 1, and the output ends of the first bridge arm and the second bridge arm are electrically connected with the input end of the filter circuit 4.
In this embodiment, the first leg includes: first IGBT pipe S1, third IGBT pipe S3, and fifth IGBT pipe S5, and the second arm includes: a second IGBT tube S2, a fourth IGBT tube S4 and a sixth IGBT tube S6;
wherein a collector of the first IGBT tube S1, a collector of the second IGBT tube S2, and a cathode of a bus diode D1I of the last switched capacitor unit are electrically connected, an emitter of the first IGBT tube S1 is electrically connected to an emitter of the fifth IGBT tube S5 and a collector of the third IGBT tube S3, an emitter of the second IGBT tube S2 is electrically connected to an emitter of the sixth IGBT tube S6 and a collector of the fourth IGBT tube S4, a collector of the fifth IGBT tube S5 is electrically connected to a cathode of the first bus diode of the last switched capacitor unit, a collector of the sixth IGBT tube S6 is electrically connected to a cathode of the second non-bus diode D2N', and an emitter of the third IGBT tube S3 and an emitter of the fourth IGBT tube S4 are electrically connected to a cathode of the dc power supply 1.
In other embodiments, the first bridge arm and the second bridge arm may also be formed by field effect transistors or GTR transistors, and sources, gates, and drains of the field effect transistors are correspondingly connected, which is not specifically limited herein, but these schemes are within the protection scope of the present invention.
In this embodiment, the filter circuit 4 includes a filter inductor Lf and a filter circuit Cf; two ends of the filtering loop Cf are used for being connected with a load loop 5;
a first end of the filter inductor Lf is electrically connected to a first end of the filter circuit Cf, a second end of the filter circuit Cf is electrically connected to the emitter of the sixth IGBT tube S6, and a second end of the filter inductor Lf is electrically connected to the emitter of the fifth IGBT tube S5.
Referring to fig. 4 to 8, the control device is configured to read the input voltage ui, compare the input voltage ui with the reference sinusoidal signal uoref, determine whether the bus voltage upn can meet the inversion requirement, and when the requirement is not met, the control device outputs an action signal to turn on the power switching tube STi (i is 1, 2, the same below) to raise the bus voltage upn, compare the output voltage sampling signal uo with the reference sinusoidal signal uoref, and obtain the output voltage feedback signal uej (j is 1, 2, 3, the same below) through a PI regulator, where the sum of the output voltage sampling signal uo and the input voltage feedforward amount ufj generates a modulation signal usj, and then compares the modulation signal usj with a triangular carrier signal uc to obtain driving signals ugeS1, ugeS2 of the first IGBT tube S1 and the second IGBT tube S2; the fourth IGBT tube S4 and the third IGBT tube S3 respectively work in the positive and negative half working cycles of the inverter, and the fourth IGBT tube S4 and the third IGBT tube S3 and the action signals of the switch capacitor network switch are combined to form the driving signals uges5 and uges6 of the fifth IGBT tube S5 and the sixth IGBT tube S6 of the T-shaped inverter bridge.
With reference to fig. 5, when the output voltage uo is a positive value, the fourth IGBT transistor S4 in the T-type inverter bridge is turned on constantly, and the first IGBT transistor S1 operates in the SPWM state; when the output voltage uo is a negative value, the third IGBT tube S3 in the T-shaped inverter bridge is constantly switched on, and the second IGBT tube S2 works in an SPWM state;
when Ui > uo, the power switch tube ST1 and the power switch tube ST2 are turned off, and the energy storage capacitor C1 and the energy storage capacitor C2 are charged in parallel;
when 2Ui > uo > Ui, the power switch tube ST1 in the switch capacitor network is conducted, the power switch tube ST2 is turned off, and the energy storage capacitor C1 and the energy storage capacitor C2 are connected in parallel and discharged in series together with an input voltage source Ui;
when uo >3Ui, the power switch tube ST1 in the switch capacitor network is conducted, the power switch tube ST2 is conducted, and the energy storage capacitor C1 and the energy storage capacitor C2 are discharged in series together with an input voltage source Ui.
For convenience of explanation, the positive half axis of the output voltage is taken as an example, i.e., the interval t0-t5 in fig. 5. Fig. 6 to 8 show equivalent circuit diagrams for different levels. The specific operation of the present invention will be described with reference to fig. 6 to 8, with reference to the circuit structures and control strategies shown in fig. 3 to 5.
The equivalent circuit of the inverter in the interval of stage one [ t0-t1, t4-t5] in fig. 5 is shown in fig. 6. At this time, uo < Ui. The fourth IGBT tube S4 and the sixth IGBT tube S6 are turned on, and the input voltage Ui charges the energy storage capacitor C1 and the energy storage capacitor C2 through a circuit formed by the bus diode D11, the energy storage capacitor C1, the bus diodes D21 and D22 ', the sixth IGBT tube S6, and the fourth IGBT tube S4, and a circuit formed by the bus diode D11, the bus diode D12, the energy storage capacitor C2, the bus diode D22', the sixth IGBT tube S6, and the fourth IGBT tube S4, respectively. The first IGBT tube S1 works in an SPWM chopping state. The inverter output voltage uab switches between zero voltage and Ui.
The equivalent circuit of the inverter in the interval of the second stage [ t1-t2, t3-t4] of fig. 5 is shown in fig. 7. At this time, 2Ui > uo > Ui. The power switch tube ST1 is conducted, and the energy storage capacitor C1 and the energy storage capacitor C2 are connected in parallel through the bus diode D12 and the bus diode D21 and are connected in series with an input source to raise the bus voltage upn to 2 Ui. The bus diode D11 and the bus diode D22 are subjected to a reverse voltage and are in an off state. The fourth IGBT tube S4 and the fifth IGBT tube S5 are conducted, the first IGBT tube S1 is in an SPWM chopping state, and the inverter output voltage uab is switched between 2Ui and 3 Ui.
The equivalent circuit of the inverter in the interval of stage two [ t2-t3] in fig. 5 is shown in fig. 8. At this time, 3Ui > uo >2 Ui. The power switch tube ST1 and the power switch tube ST2 are conducted, and the energy storage capacitor C1, the energy storage capacitor C2 and an input source are connected in series through the power switch tube ST1 and the power switch tube ST2 to raise the bus voltage upn to 3 Ui. The bus diode D12, the bus diode D21, and the bus diode D22 are subjected to a reverse voltage and are in an off state. The fourth IGBT tube S4 and the fifth IGBT tube S5 are conducted, the first IGBT tube S1 is in an SPWM chopping state, and the inverter output voltage uab is switched between 2Ui and 3 Ui.
Since the operation modes of the inverter in the interval t5-t10 are the same as those in the interval t0-t5, the description is omitted.
A second embodiment of the present invention provides a system, which includes a control device and the multilevel inverter as described in any one of the above embodiments, wherein an output terminal of the control device is electrically connected to a control terminal of the switched capacitor network and a control terminal of the T-type inverter bridge.
A third embodiment of the present invention provides a control method as described above, including:
acquiring an input voltage, judging whether the bus voltage meets the inversion requirement or not by comparing the input voltage with a reference sinusoidal signal, and generating a voltage feedforward signal;
when the inversion requirement is not met, outputting an action signal to a control end of the switched capacitor network, and increasing the bus voltage of the switched capacitor network;
acquiring a voltage feedback signal and generating a modulation signal by combining the voltage feedforward signal;
and comparing the modulation signal with the triangular carrier signal to generate a driving signal of the T-shaped inverter bridge.
In this embodiment, the obtaining a voltage feedback signal and combining the voltage feedforward signal to generate a modulation signal specifically includes:
acquiring an output voltage sampling signal, acquiring a comparison result of the output voltage sampling signal and the reference sinusoidal signal, outputting a value PI regulator by the comparison result, generating a voltage feedback signal, and summing the voltage feedback signal and the voltage feedforward signal to generate a modulation signal.
It should be noted that, in other embodiments, the modulation signal may be generated in other manners, and may be set according to actual situations, which is not specifically limited herein, but these schemes are within the protection scope of the present invention.
Based on the multi-level inverter, the multi-level inverter system and the control method provided by the invention, the input voltage of the inverter is read through the control device, the input voltage is compared with a reference sinusoidal signal, whether the bus voltage on the switched capacitor network meets the inversion requirement is judged, when the inversion requirement is not met, the control device outputs an action signal to the control end of the switched capacitor network, so that the switched capacitor network acts to lift the bus voltage, the bus voltage meets the inversion requirement, a voltage feedback signal is obtained, the voltage feedback signal is processed to generate a driving signal of a T-shaped bridge inverter bridge, the driving signal is driven to the T-shaped bridge inverter bridge to perform inversion work, and the driving signal is output to a load after passing through a filter loop. The problems that the inverter in the prior art is low in conversion efficiency, the output voltage is not easy to expand to more levels and the number of input sources is too large are effectively solved.
The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention.
Claims (8)
1. A multilevel inverter, comprising: the system comprises a direct-current power supply, a switched capacitor network, a T-shaped inverter bridge and a filter circuit;
the output end of the direct current power supply is electrically connected with the input end of the switch capacitor network, the output end of the switch capacitor network is electrically connected with the input end of the T-shaped inverter bridge, the output end of the T-shaped inverter bridge is electrically connected with the input end of the filter circuit, the output end of the filter circuit is used for connecting a load, and the control end of the switch capacitor network and the control end of the T-shaped inverter bridge are used for connecting a control device.
2. The multilevel inverter of claim 1, wherein the switched capacitor network is formed by serially connecting a plurality of switched capacitor cells, the switched capacitor cells comprising: the power switch tube, the energy storage capacitor, the bus diode and the first non-bus diode;
the anode of the bus diode is electrically connected with the collector of the power switch tube, the cathode of the bus diode is electrically connected with the first end of the energy storage capacitor, the emitter of the power switch tube and the second end of the energy storage capacitor are electrically connected with the anode of the first non-bus diode, the anode of the bus diode of the first switch capacitor unit is electrically connected with the anode of the direct-current power supply, the last switch capacitor unit further comprises a second non-bus diode, the first non-bus diode and the second non-bus diode of the last switch capacitor unit are electrically connected with the T-shaped inverter bridge, and the bus diode is electrically connected with the input end of the T-shaped inverter bridge.
3. The multilevel inverter of claim 2, wherein the T-shaped inverter bridge comprises a first leg and a second leg;
the positive input ends of the first bridge arm and the second bridge arm are electrically connected with the output end of the switched capacitor network, the negative input ends of the first bridge arm and the second bridge arm are electrically connected with the negative electrode of the direct current power supply, and the output ends of the first bridge arm and the second bridge arm are electrically connected with the input end of the filter loop.
4. The multilevel inverter of claim 3, wherein the first leg comprises: first IGBT pipe, third IGBT pipe, fifth IGBT pipe, the second bridge arm includes: the second IGBT tube, the fourth IGBT tube and the sixth IGBT tube;
the collector of the first IGBT tube and the collector of the second IGBT tube are electrically connected with the cathode of the bus diode of the last switched capacitor unit, the emitter of the first IGBT tube is electrically connected with the emitter of the fifth IGBT tube and the collector of the third IGBT tube, the emitter of the second effect tube is electrically connected with the emitter of the sixth IGBT tube and the collector of the fourth IGBT tube, the collector of the fifth IGBT tube is electrically connected with the cathode of the first bus diode of the last switched capacitor unit, the collector of the sixth IGBT tube is electrically connected with the cathode of the second non-bus diode, and the emitter of the third IGBT tube and the emitter of the fourth IGBT tube are electrically connected with the cathode of the DC power supply.
5. The multilevel inverter of claim 4, wherein the filter loop comprises a filter inductor, a filter capacitor;
the first end of the filter inductor is electrically connected with the first end of the filter capacitor, the second end of the filter capacitor is electrically connected with the emitter electrode of the sixth IGBT tube, and the second end of the filter inductor is electrically connected with the emitter electrode of the fifth IGBT tube.
6. A system comprising control means and a multilevel inverter according to any of claims 1 to 5, wherein the output of the control means is electrically connected to the control terminal of the switched capacitor network and the control terminal of the T-inverter bridge.
7. A control method according to claim 6, comprising:
acquiring an input voltage, judging whether the bus voltage meets the inversion requirement or not by comparing the input voltage with a reference sinusoidal signal, and generating a voltage feedforward signal;
when the inversion requirement is not met, outputting an action signal to a control end of the switched capacitor network, and increasing the bus voltage of the switched capacitor network;
acquiring a voltage feedback signal and generating a modulation signal by combining the voltage feedforward signal;
and comparing the modulation signal with the triangular carrier signal to generate a driving signal of the T-shaped inverter bridge.
8. The control method according to claim 7, wherein the obtaining of the voltage feedback signal and the combining of the voltage feedforward signal to generate the modulation signal are specifically:
acquiring an output voltage sampling signal, acquiring a comparison result of the output voltage sampling signal and the reference sinusoidal signal, outputting a value PI regulator by the comparison result, generating a voltage feedback signal, and summing the voltage feedback signal and the voltage feedforward signal to generate a modulation signal.
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