CN114362574A - Multilevel soft switching inverter circuit and balancing method of intermediate level terminal voltage thereof - Google Patents

Multilevel soft switching inverter circuit and balancing method of intermediate level terminal voltage thereof Download PDF

Info

Publication number
CN114362574A
CN114362574A CN202111491064.2A CN202111491064A CN114362574A CN 114362574 A CN114362574 A CN 114362574A CN 202111491064 A CN202111491064 A CN 202111491064A CN 114362574 A CN114362574 A CN 114362574A
Authority
CN
China
Prior art keywords
switching
module
direct current
voltage
switching device
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202111491064.2A
Other languages
Chinese (zh)
Inventor
周衍
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to CN202111491064.2A priority Critical patent/CN114362574A/en
Publication of CN114362574A publication Critical patent/CN114362574A/en
Priority to CN202211180928.3A priority patent/CN115395810A/en
Priority to PCT/CN2022/134312 priority patent/WO2023103811A1/en
Pending legal-status Critical Current

Links

Images

Classifications

    • 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
    • H02M7/487—Neutral point clamped 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
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Landscapes

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

Abstract

The invention discloses a multilevel soft switch inverter circuit and a method for balancing the voltage of a middle level terminal thereof, wherein the multilevel soft switch inverter circuit comprises inverter driving circuits which are mutually independent in multiple phases and have the same structure; each phase of inversion driving circuit comprises a balance switching module, a voltage window switching module, a soft switch inversion module and a control module. The control module is used for acquiring relevant working information of the multilevel soft switching inverter circuit and controlling the work of each module according to an acquisition result; the voltage window switching module is used for outputting a proper direct-current voltage window to the soft switch inversion module under the control of the control module; the soft switch inversion module is used for converting the direct current provided by the voltage window switching module into alternating current to be output. Under the control of the control module, the balance switching module automatically switches between a normal mode and a compensation mode to compensate charges flowing through each middle-level end in the multi-level direct-current bus, so that the voltage of each middle-level end in the direct-current bus is actively balanced.

Description

Multilevel soft switching inverter circuit and balancing method of intermediate level terminal voltage thereof
Technical Field
The invention relates to the field of inverter driving circuits, in particular to a multilevel soft switching inverter circuit and a method for balancing voltage of a middle level terminal of the multilevel soft switching inverter circuit.
Background
In the existing multi-level soft switching inverter circuit, an intermediate voltage direct current power supply port in a direct current bus in the application of using single direct current power supply or double direct current power supply input is generally obtained by serially dividing a plurality of groups of capacitors, and the charge-discharge state of the capacitors of the existing four-level input inverter driving circuit structure is changed along with the working state and cannot be balanced in an active mode, so that the intermediate voltage end of the direct current bus cannot obtain stable voltage.
Disclosure of Invention
In view of the problems in the background art, an object of the present invention is to provide a multilevel soft switching inverter circuit and a method for balancing intermediate level voltage thereof.
In order to solve the technical problems, the invention adopts the technical scheme that:
a multi-level soft switching inverter circuit comprises inverter driving circuits which are mutually independent and have the same structure;
each phase of the inversion driving circuit comprises four direct current input ends, an alternating current output end, a balance switching module, a voltage window switching module, a soft switch inversion module and a control module;
the four direct current input ends are direct current buses with four different levels formed by a plurality of direct current power supplies through a capacitance voltage division structure, and the four direct current input ends are a first direct current end, a second direct current end, a third direct current end and a fourth direct current end in sequence according to the sequence of the potentials from high to low;
the balance switching module is provided with two input ends and two output ends, and the two input ends of the balance switching module are respectively connected with the second direct current end and the third direct current end;
the voltage window switching module is provided with four input ends and two output ends, the two input ends of the voltage window switching module are respectively connected with the first direct current end and the fourth direct current end, and the other two input ends are respectively connected with the two output ends of the balance switching module;
the soft switch inversion module is provided with two input ends and one output end, the two input ends of the soft switch inversion module are respectively connected with the two output ends of the voltage window switching module, and the output end of the soft switch inversion module is used as the alternating current output end;
the control module is used for acquiring relevant working information of the multilevel soft switching inverter circuit and controlling the work of each module according to an acquisition result;
the balance switching module is used for compensating charges flowing through the second direct current end and the third direct current end under the control of the control module;
the voltage window switching module is used for outputting a proper direct-current voltage window to the soft switch inversion module under the control of the control module;
the soft switch inversion module is used for converting the direct current provided by the voltage window switching module into alternating current to be output.
In some embodiments, the balancing switching module and the voltage window switching module each include a plurality of switching devices, and a control terminal of each switching device is connected to the control module, so that a switching state of each switching device can be switched under the control of the control module;
the balanced switching module comprises a first switching device TB1A second switching device TB2A third switching device TB3And a fourth switching device TB4(ii) a The voltage window switching module comprises a fifth switching device TL1And a sixth switching device TL2Seventh switching device TL3And an eighth switching device TL4；
The first switching device TB1And a third switching device TB3Are all connected with a second direct current terminal, the second switching device TB2And a fourth switching device TB4Is connected to a third dc terminal, and the first switching device TB1And the other end of the first switching device TB2Is connected to the other end of the first switching element and serves as a first output end of the balanced switching module, and the third switching element TB3And the other end of the fourth switching device TB4The other end of the first switching module is connected with the other end of the second switching module and is used as a second output end of the balanced switching module;
the fifth switching device TL1And a sixth switching device TL2The seventh switching device T is connected in series between the first direct current terminal and the first output terminal of the balanced switching moduleL3And an eighth switching device TL4The second output end of the balanced switching module is connected in series with the fourth direct current end;
the soft switch inverter module comprises a half-bridge circuit or a flying capacitor inverter circuit with a positive input end and a negative input end, an inductor L and a plurality of alternating-current end capacitors, wherein the positive input end of the half-bridge circuit or the flying capacitor inverter circuit is connected with a fifth switching device TL1And a sixth switching device TL2The negative input end of the common end is connected with the seventh switching device TL3And an eighth switching device TL4The output end of the half-bridge circuit or the flying capacitor inverter circuit is connected with the alternating current output end through the inductor L, one end of the alternating current end capacitor is connected with one direct current input end or the neutral potential, and the other end of the alternating current end capacitor is connected with the alternating current output end.
In some embodiments, the control module controls the switching state of each switching device to enable the second dc terminal and the third dc terminal to provide a required output current for the bidirectional dc power supply, so as to supply power to other external circuits.
The invention also provides a method for balancing the voltage of the middle level terminal of the multilevel soft switching inverter circuit, which comprises the following steps:
under the control of the control module, the balance switching module automatically switches between a normal mode and a compensation mode to realize the voltage balance of each middle level end in the direct current bus;
in the normal mode, the first switching device TB1And a fourth switching device TB4Conducting, second switching device TB2And a third switching device TB3Turning off;
the compensation mode is divided into a compensation mode for the second direct current terminal and a compensation mode for the third direct current terminal;
in a compensation mode for the second direct current terminal, the third switching device TB3Conducting, fourth switching device TB4Off, first switching device TB1And a second switching device TB2Not conducting at the same time;
in a compensation mode for the third direct current terminal, the second switching device TB2Conducting, first switching device TB1Turn-off, third switching device TB3And a fourth switching device TB4Not conducting at the same time.
In some embodiments, the circuit uses the potential of the middle point between the first direct current terminal and the fourth direct current terminal as a neutral potential reference point, and the absolute values of the voltages of the first direct current terminal, the second direct current terminal, the third direct current terminal and the fourth direct current terminal are respectively expressed as U by taking the potential as a reference point1、u2、u3And U4Instantaneous value of voltage at AC output terminal is uAC；
Setting a voltage u in a control module2And u3Set value of U2,setAnd U3,setThe control module is used for measuring u2And u3And a set value U2,setAnd U3,setCalculating the working interval of each compensation mode required for compensation operation in each half period of the alternating current output;
according to the calculation result, the control module switches the on-off states of the switching devices in the balance switching module and the voltage window switching module to enable the bus current i where the second direct current end and the third direct current end are located2And i3Average value I in period of AC output2And I3Compensating to the target value so as to make the corresponding voltage u2And u3In a steady state, and finally outputting the alternating current in a period u2And u3Average value of U2And U3Is stabilized at a set value U2,setAnd U3，setThe above.
In some embodiments, the instantaneous current through the inductor L is represented by iLIndicating that the average value of the inductor current in a switching period of the soft-switching inverter module is iL,avgIndicating and setting an inductance reserve voltage U in the control moduleres；
The balance switching module normally works in a normal mode;
when the control module detects that the output end voltage is in the range uAC≥u2+UresThen the control module automatically controls the current iL,avgThe direction control balance switching module is switched to a compensation mode for compensating the second direct current end, and when the compensation operation required by the compensation mode is finished, the control module automatically switches the balance switching module back to a normal mode;
when the control module detects that the output end voltage is in the range uAC≤-u3-UresThen the control module automatically controls the current iL,avgThe direction control balance switching module is switched to a compensation mode for compensating the third direct current end, and after the compensation operation required by the compensation mode is finished, the control module automatically switches the balance switching module back to the normal mode.
In some embodiments, when uAC<u2And uAC>-u3When the switching module is in the normal mode, the balance switching module is kept in the normal mode;
the control module is used for controlling the AC output according to the working state of the AC output and the measured u2And u3Calculating a balance phase or a working interval required by voltage balance;
the control module switches the switching state of the switching device in the voltage window switching module according to the calculation result so as to switch the voltage window provided for the soft switching inversion module, so that the voltages of the second direct current end and the third direct current end are balanced in the period of alternating current output.
In some embodiments, if the multilevel soft switching inverter circuit includes a bidirectional dc power supply additionally established by using a level node where the second dc terminal and the third dc terminal are located, the control module switches the switching states of the switching devices in the balanced switching module and the voltage window switching module to convert the bus current i where the second dc terminal and the third dc terminal are located into the bus current i2And i3Average value I in period of AC output2And I3Compensating to a target value, wherein the target value corresponds to an output value required by the bidirectional direct current power supply;
if the multi-level soft switching inversionThe control module switches the on-off states of the switching devices in the balance switching module and the voltage window switching module to make the bus current i where the second direct current end and the third direct current end are located2And i3Average value I in period of AC output2And I3Compensating to a target value, wherein the target value is 0.
Compared with the prior art, the multilevel soft switching inverter circuit and the balancing method for the voltage of the intermediate level terminal thereof provided by the invention have the advantages that the balancing switching module is added between the voltage window switching module and the multilevel flat current bus on the basis of the multilevel soft switching inverter circuit, and the characteristic of periodic change of voltage and current in alternating current output is combined, so that the current flowing through each intermediate level terminal is compensated on the premise of realizing soft switching of a switching device, and the voltage of each intermediate level terminal is actively balanced.
Drawings
Other objects and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings, and may assist in a comprehensive understanding of the invention.
Fig. 1 is a schematic diagram of a multilevel soft switching inverter circuit provided by the present invention;
fig. 2a and 2b are schematic diagrams of a multi-level soft-switching inverter circuit based on a single dc power input and a dual dc power input, respectively;
fig. 3a, 3b, 3c and 3d are schematic diagrams of four configurations of a soft-switching inverter module, respectively;
FIGS. 4a, 4b and 4c are schematic diagrams of a multilevel soft switching inverter circuit including a bi-directional DC power source;
FIGS. 5a and 5b are waveform diagrams of voltage and current variations with time during an AC output period according to a first embodiment;
FIGS. 6a and 6b are waveform diagrams of voltage and current variations with time during an AC output period according to a second embodiment;
FIGS. 7a and 7b are waveform diagrams of voltage and current variations with time in an AC output period according to a third embodiment;
FIGS. 8a and 8b are waveform diagrams of voltage and current variations with time in an AC output period according to a fourth embodiment;
FIGS. 9a and 9b are waveform diagrams of voltage and current variations with time in an AC output period according to a fifth embodiment;
FIGS. 10a and 10b are waveform diagrams of voltage and current variations with time in an AC output period according to a sixth embodiment;
FIGS. 11a and 11b are waveform diagrams of voltage and current variations with time in an AC output period according to a seventh embodiment;
description of reference numerals:
1. an inverter driving circuit; 2. a soft switch inversion module; 3. a balance switching module; 4. a voltage window switching module; 5. a bi-directional DC power supply.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.
Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs.
Referring to fig. 1, the present invention provides a multilevel soft switching inverter circuit, which includes an inverter driving circuit 1 with multiple phases independent from each other and the same structure; each phase inverter driving circuit 1 comprises four direct current input ends, an alternating current output end, a balance switching module 3, a voltage window switching module 4, a soft switch inverter module 2 and a control module (not shown in the figure); the four direct current input ends are direct current buses with four different levels formed by a plurality of direct current power supplies through a capacitance voltage division structure, and the four direct current input ends are a first direct current end, a second direct current end, a third direct current end and a fourth direct current end in sequence according to the sequence of the potentials from high to low; the balance switching module 3 is provided with two input ends and two output ends, and the two input ends of the balance switching module 3 are respectively connected with the second direct current end and the third direct current end; the voltage window switching module 4 is provided with four input ends and two output ends, two input ends of the voltage window switching module 4 are respectively connected with the first direct current end and the fourth direct current end, and the other two input ends are respectively connected with two output ends of the balance switching module 3; the soft switch inversion module 2 has two input ends and an output end, the two input ends of the soft switch inversion module 2 are respectively connected with the two output ends of the voltage window switching module 4, and the output end of the soft switch inversion module 2 is used as an alternating current output end.
The control module is used for acquiring relevant working information of the multilevel soft switching inverter circuit and controlling the work of each module according to an acquisition result; the balance switching module 3 is used for compensating the charges flowing through the second direct current terminal and the third direct current terminal under the control of the control module; the voltage window switching module 4 is used for outputting a proper direct-current voltage window to the soft switch inversion module 2 under the control of the control module; the soft switch inversion module 2 is used for converting the direct current provided by the voltage window switching module 4 into alternating current to be output.
Preferably, the balance switching module 3 and the voltage window switching module 4 each include a plurality of switching devices, and a control end of each switching device is connected to the control module, so that a switching state of each switching device can be switched under the control of the control module; the balanced switching module 3 comprises a first switching device TB1A second switching device TB2A third switching device TB3And a fourth switching device TB4(ii) a The voltage window switching module 4 comprises a fifth switching device TL1And a sixth switching device TL2Seventh switching device TL3And an eighth switching device TL4(ii) a First switching device TB1And a third switching device TB3Is connected with a second DC terminal, a second switching device TB2And a fourth switching device TB4Is connected with the third DC terminal, and the first switching device TB1And the other end of the first switching device TB2Is connected to the other end of the first switching element and serves as a first output end of the balanced switching module 3, and a third switching element TB3And the other end of the fourth switching device TB4Is connected with the other end of the switching module to serve as a second output end of the balanced switching module 3; fifth switching device TL1And a sixth switching device TL2A seventh switching device T connected in series between the first DC terminal and the first output terminal of the balanced switching module 3L3And an eighth switching device TL4Is connected in series between the fourth dc terminal and the second output terminal of the balanced switching module 3.
With further reference to fig. 3a, 3b, 3c and 3d, the soft-switched inverter module 2 includes a half-bridge circuit (as shown in fig. 3a and 3 b) or a flying capacitor inverter circuit (as shown in fig. 3c and 3 d) having a positive input terminal and a negative input terminal, and an inductor L and a plurality of ac capacitors, wherein the positive input terminal of the half-bridge circuit or the flying capacitor inverter circuit is connected to the fifth switching device TL1And a sixth switching device TL2The negative input end of the common end is connected with the seventh switching device TL3And an eighth switching device TL4A common terminal of (a); the output end of the half-bridge circuit or the flying capacitor inverter circuit is connected with the alternating current output end through an inductor L, one end of an alternating current end capacitor is connected with one direct current input end or neutral potential, and the other end of the alternating current end capacitor is connected with the alternating current output end; the switching device in the soft switching inversion module 2 passes an inductive current i which is alternated in direction in each switching periodLZero Voltage Switching (ZVS) is implemented.
It is understood that in the embodiment shown in fig. 1, what corresponds to the soft-switching inverter module 2 in fig. 3a is a half-bridge circuit and includes two ac-side capacitors C1And C2，C1Are respectively connected with a first DC end and an AC output end, C2Both ends of the first switch are respectively connected with the fourth direct current end and the alternating current output end. In other embodiments, the soft-switching inverter module 2 may be replaced with other structures. If the structure in FIG. 3b is adopted, a half-bridge circuit is adopted, and only one AC terminal capacitor C is included1，C1One end is connected with the neutral potential, and the other end is connected with the alternating current output end; or as in FIG. 3cThe difference from the configuration in fig. 3a is that the half-bridge circuit is replaced with a flying capacitor inverter circuit; or the configuration of figure 3d, differs from that of figure 3b in that the half bridge circuit is replaced by a flying capacitor inverter circuit.
Preferably, the multilevel soft switching inverter circuit comprises three inverter driving circuits which are independent from each other and have the same structure.
With further reference to fig. 2a, a multi-level soft switching inverter circuit based on a single DC power input is shown, and it can be seen that the first DC terminal and the fourth DC terminal are positive and negative terminals of the DC power DC and are connected to each other through three capacitors CDC1、CDC2And CDC3The input direct current voltage is divided into two intermediate voltages, namely a second direct current terminal and a third direct current terminal, so that a direct current bus with four different levels is formed. It will be appreciated that other configurations may be used to obtain a dc bus having four different levels, for example, as shown in fig. 2b, two dc power supplies may be connected in series based on two dc power inputs, and two intermediate voltages may be obtained through a plurality of capacitors. The specific manner of obtaining the multi-level dc bus through the capacitive voltage dividing structure is known in the art, and the present invention is not limited in detail herein.
The invention also provides a method for balancing the voltage of the middle level terminal of the multilevel soft switching inverter circuit, which comprises the following steps: under the control of the control module, the balance switching module 3 automatically switches between a normal mode and a compensation mode to realize the voltage balance of each middle level end in the direct current bus.
In the normal mode, the first switching device TB1And a fourth switching device TB4Conducting, second switching device TB2And a third switching device TB3Turning off; the compensation mode is divided into a compensation mode for the second direct current terminal and a compensation mode for the third direct current terminal; in a compensation mode for the second direct current terminal, the third switching device TB3Conducting, fourth switching device TB4Off, first switching device TB1And a second switching device TB2Not conducting at the same time; in a compensation mode for the third DC terminal, aTwo switching devices TB2Conducting, first switching device TB1Turn-off, third switching device TB3And a fourth switching device TB4Not conducting at the same time.
Furthermore, the circuit takes the potential of the middle point between the first direct current terminal and the fourth direct current terminal as a neutral potential reference point, and the absolute values of the voltages of the first direct current terminal, the second direct current terminal, the third direct current terminal and the fourth direct current terminal are respectively expressed as U by taking the potential as reference1、u2、u3And U4It can be understood that the potentials of the first dc terminal and the second dc terminal are positive values, and the potentials of the third dc terminal and the fourth dc terminal are negative values; u for instantaneous value of AC output terminal voltageACRepresents; setting a voltage u in a control module2And u3Set value of U2，setAnd U3,setThe control module is used for measuring u2And u3And a set value U2,setAnd U3,setCalculating the working interval of each compensation mode required for compensation operation in each half period of the alternating current output; according to the calculation result, the control module switches the on-off states of the switching devices in the balance switching module 3 and the voltage window switching module 4 to enable the bus current i where the second direct current end and the third direct current end are located2And i3Average value I in period of AC output2And I3Compensating to a target value (in the embodiment corresponding to fig. 2a and 2b, the target value is 0), so that the corresponding voltage u2And u3In a steady state, and finally outputting the alternating current in a period u2And u3Average value of U2And U3Is stabilized at a set value U2,setAnd U3,setThe above.
Further, the instantaneous current flowing through the inductor L is represented by iLIndicating that the average value of the inductor current in a switching cycle of the soft-switching inverter module 2 is iL,avgIndicating and setting an inductance reserve voltage U in the control moduleres(ii) a The balanced switching module 3 normally operates in the normal mode; when the control module detects that the output end voltage is in the range uAC≥u2+UresThen the control module automatically controls the current iL,avgThe direction control balance switching module 3 is switched to a compensation mode for compensating the second direct current end, and when the compensation operation required by the compensation mode is finished, the control module automatically switches the balance switching module 3 back to a normal mode; when the control module detects that the output end voltage is in the range uAC≤-u3-UresThen the control module automatically controls the current iL,avgThe direction control balance switching module 3 is switched to a compensation mode for compensating the third direct current end, and after the compensation operation required by the compensation mode is finished, the control module automatically switches the balance switching module 3 back to the normal mode. It can be understood that the soft switch inversion module has a high working switching frequency, and the difference between the soft switch inversion module and the AC output is several orders of magnitude compared with the output frequency of the AC outputL,avgThe average value of the inductive current in the switching period of the soft switching inversion module 2 is shown, and the current i is approximately ignored because the reactive power generated by the alternating-current end capacitor on the alternating-current output frequency in practical applicationL,avgCan be equal to the current i of the alternating current output end in engineeringACIn the subsequent analysis, the average value of each current in the direct current bus in the whole alternating current output period is represented by I.
In addition, when uAC<u2And uAC>-u3When the switching module 3 is in the normal mode, the switching module is maintained in the normal mode; the control module is used for controlling the AC output according to the working state of the AC output and the measured u2And u3Calculating a balance phase or a working interval required by voltage balance; the control module switches the switching state of the switching device in the voltage window switching module 4 according to the calculation result to switch the voltage window provided for the soft switching inversion module 2, so that the voltages of the second direct current end and the third direct current end are balanced in the period of alternating current output.
The invention provides a multilevel soft switching inverter circuit and a method for balancing the voltage of an intermediate level terminal thereof, wherein the balancing working principle is as follows:
referring to fig. 1, in order to achieve continuous zero voltage switching in a soft-switching inverter module 2Off (ZVS), the potential of the DC supply terminal of the soft-switching inverter module 2
Figure BDA0003399371210000108
And
Figure BDA0003399371210000109
must satisfy the condition
Figure BDA00033993712100001010
. In the invention, the control module obtains the instantaneous voltage u of the output end through real-time measurementACAverage value i of inductive current in switching period of each soft switch inversion module 2L,avgAn intermediate voltage u2And u3(ii) a The control module controls the switch combination of the balance switching module 3 and the voltage window switching module 4 by judging the voltage condition required by the soft switch inversion module 2 to work and the current condition required by the balance intermediate voltage, and the voltage condition of a Zero Voltage Switch (ZVS) is met
Figure BDA00033993712100001011
On the premise of switching the path of the soft switch inversion module 2 connected with the direct current bus, the current is respectively led into different intermediate level nodes in the direct current bus from the soft switch inversion module 2, and the characteristics of periodic variation of the voltage and the current of alternating current output are utilized to balance the intermediate level end.
Balanced switching module 3 in normal mode, TB1And TB4Conduction, TB2And TB3The switching-off is carried out, and the voltage window switching module 4 can obtain two voltage windows [ -u ] which are mutually overlapped from the direct current bus according to the circuit structure3,U1]And [ -U ]4,u2]Overlap portion [ -u ] with3,u2](ii) a The control module is used for controlling the output end to be in an instantaneous voltage uACThe range control voltage window switching module 4 connects a proper voltage window or an overlapped part thereof with the soft switch inversion module 2; specifically, when T isL2And TL4Off and TL1And TL3When conducting
Figure BDA0003399371210000101
And
Figure BDA0003399371210000102
Figure BDA0003399371210000103
when T isL1And TL3Is turned off and TL2And TL4When conducting
Figure BDA0003399371210000104
And
Figure BDA0003399371210000105
when T isL1And TL4Off and TL2And TL3When conducting
Figure BDA0003399371210000106
And
Figure BDA0003399371210000107
in the compensation mode for the second DC terminal, TB3Conduction, TB4Off, TB1And TB2Not conducting at the same time; in the compensation mode for the third DC terminal, TB2Conduction, TB1Off, TB3And TB4Not conducting at the same time. It will be appreciated that in the compensation mode for the second dc terminal, only T needs to be specifiedB3And TB4Of the switch state ofB1And TB2Since the rear-end line is blocked by the voltage window switching module 4, and there is no current therein, as long as the two are not conducted at the same time, the second dc terminal and the third dc terminal are short-circuited, and other switching states have no influence on the circuit function; the same principle applies to the compensation mode of the third DC terminal, as long as TB3And TB4And conducting the circuit at different times. In the compensation mode, the voltage window obtained by the voltage window switching module 4 is changed, so that the potential of the direct current power supply end of the soft switch inverter module 2 is further changed
Figure BDA0003399371210000111
And
Figure BDA0003399371210000112
for controlling the intermediate voltage u at the intermediate level terminal2And u3Setting an intermediate voltage u in the control module according to the balanced voltage2And u3Set value of U2,setAnd U3,set. The control module is used for measuring the intermediate voltage u2And u3And a set value U2,setAnd U3,setDeviation of (3) and voltage U of the AC outputACCurrent IACCalculating the working interval of each compensation mode required for compensation operation in each half period of the alternating current output; and the balance switching module 3 is controlled to switch between a normal mode and a compensation mode according to specific required voltage conditions and current conditions, and the voltage window switching module 4 is controlled to be matched to form a corresponding switch combination. In order to realize Zero Voltage Switching (ZVS) in the soft switch inverter module 2, an inductance reserved voltage U is arranged in the control module according to the design requirement of the inverter circuitresIn the compensation mode, the voltage is used to provide a voltage with alternating direction to the inductor L to establish the alternating inductor current i required for a Zero Voltage Switching (ZVS) in each switching cycle of the soft-switching inverter module 2L。
The control module measures the instantaneous voltage u of the output end in real timeACAn intermediate voltage u2And u3The control balance switching module 3 and the voltage window switching module 4; when the instantaneous voltage u at the voltage output terminalACOr current iL,avgWhen the condition required by the compensation mode is not met, the balance switching module 3 is kept in the normal mode; at the moment, the control module is used for controlling the output end to be in an instantaneous voltage u according to the instantaneous voltage uACThe range controls the switch state of the voltage window switching module 4, so that the input end potential of the soft switch inversion module 2 always accords with the voltage condition
Figure BDA0003399371210000113
To ensure the switch thereinThe device may operate in a Zero Voltage Switching (ZVS) state.
For the case of a higher output voltage, if uAC≥u2+UresOr uAC≤-u3-Ures。
During the balancing process for the second DC terminal, the intermediate voltage u2When the rising trend is presented in the normal mode, the control module judges the required voltage condition u according to the result of real-time measurementAC≥u2+UresAnd current condition iL,avg>If 0A is satisfied, the control module switches the balance switching module 3 from the normal mode to the intermediate voltage u according to the working interval of the required compensation operation when the two are satisfied simultaneously2The compensation mode of (1); when the intermediate voltage u is2When the voltage shows a descending trend in a normal mode, the control module judges the required voltage condition u according to the real-time measurement resultAC≥u2+UresAnd current condition iL,avg<If 0A is satisfied, the control module switches the balance switching module 3 from the normal mode to the intermediate voltage u according to the working interval of the required compensation operation when the two are satisfied simultaneously2The compensation mode of (1); the potential of the DC power supply terminal of the soft-switching inverter module 2 in this compensation operation
Figure BDA0003399371210000121
And
Figure BDA0003399371210000122
are respectively equal to U1And u2The control module switches the balance switching module 3 back to the normal mode after the required compensation operation is finished.
Similarly, during balancing for the third dc terminal, the intermediate voltage u3When the rising trend is presented in the normal mode, the control module judges the required voltage condition u according to the result of real-time measurementAC≤-u3-UresAnd current condition iL,avg<Whether 0A is satisfied at the same time, and when both are satisfied at the same time, the control module switches the balance of the module according to the working interval of the required compensation operation3 switching from normal mode to intermediate voltage u3The compensation mode of (1); when the intermediate voltage u is3When the voltage shows a descending trend in a normal mode, the control module judges the required voltage condition u according to the real-time measurement resultAC≤-u3-UresAnd current condition iL,avg>If 0A is satisfied, the control module switches the balance switching module 3 from the normal mode to the intermediate voltage u according to the working interval of the required compensation operation when the two are satisfied simultaneously3The compensation mode of (1); the potential of the DC power supply terminal of the soft-switching inverter module 2 in this compensation operation
Figure BDA0003399371210000123
And
Figure BDA0003399371210000124
are each equal to-u3and-U4The control module switches the balance switching module 3 back to the normal mode after the required compensation operation is finished.
In addition, for the case of a lower output voltage, if uAC<u2And uAC>-u3In this case, the treatment can be carried out according to the following two schemes.
In the first scheme, the balanced switching module 3 is kept in the normal mode; the control module outputs working state and intermediate voltage u according to alternating current2And u3Calculating a balance phase required by voltage balance; when current iL,avgWhen a half cycle begins to enter, the control module keeps the current switching state of the voltage window switching module 4 unchanged to a required balance phase, and at the moment, the voltage window connected to the soft switch inversion module 2 keeps unchanged; when the required balance phase is reached, the control module switches the switching state of the voltage window switching module 4, and the other corresponding voltage window in the direct current bus is connected to the soft switch inversion module 2. The current i generated in the DC bus when each voltage window is connected to the soft switch inverter module 2 by using the periodicity of the AC current2And i3Equilibrium is achieved in its corresponding half-cycle i2And i3Respectively represent and intermediate voltage u2And u3And the direct current bus current corresponds to the level node.
In the second scheme, the balanced switching module 3 is kept in the normal mode; the control module outputs working state and intermediate voltage u according to alternating current2And u3Calculates the intermediate voltage u2And an intermediate voltage u3Balancing the required working interval of the operation; in this balancing method, the control module controls the switching device T in the voltage window switching module 4L1And TL4Off, TL2And TL3On, overlap of voltage windows [ -u [ ]3,u2]Is connected to the soft switch inversion module 2; when the intermediate voltage u is reached2Control module controls switching device T in voltage window switching module 4 during balanced operating intervalL1And TL3Off, TL2And TL4Conducting to connect the voltage window [ -U [)4,u2]A soft switch inversion module 2 is connected; when the intermediate voltage u is reached3Control module controls switching device T in voltage window switching module 4 during balanced operating intervalL2And TL4Off, TL1And TL3Conducting to connect the voltage window [ -u [)3,U1]A soft switch inversion module 2 is connected; after the working interval of the balance operation is finished, the control module switches the voltage connected into the soft switch inversion module 2 back to the overlapped part [ -u ] of the voltage window3,u2]The method utilizes the characteristic that the current distribution in the soft switch inversion module 2 changes along with the accessed direct current input voltage to ensure that the current i in the direct current bus2And i3Balancing is achieved in different switch combinations.
Further, the intermediate bus current i2And i3The average values in the switching period during which one soft-switching inverter module 2 operates are respectively represented as i2,avgAnd i3,avg. Referring to FIG. 1, the current i is known from the circuit structure2,avgAnd i3,avgDirection of and current iL,avgIn the same direction, when the voltage u needs to be reduced2When a current i is requiredL,avgIn the positive direction, when the voltage u needs to be increased2When a current i is requiredL,avgIs in the negative direction; when the voltage u needs to be reduced3When a current i is requiredL,avgIn the negative direction when the voltage u needs to be raised3When a current i is requiredL,avgIn the positive direction. Average value U of intermediate voltage when positive active power is output from AC output terminal2And U3The voltage rises when the balanced switching module 3 is in the normal mode; when the AC output terminal outputs negative active power, the average value U of the intermediate voltage2And U3The voltage drops when the balanced switching module 3 is in the normal mode; when the AC output end outputs pure reactive power, the average value U of the intermediate voltage2And U3The voltage of the balanced switching module 3 remains unchanged in the balanced state when it is in the normal mode.
The switching state and the voltage variation trend of each switching device can be referred to the following table:
Figure BDA0003399371210000141
in the table, the switch states: 1 is ON, 0 is OFF, X and
Figure BDA0003399371210000142
indicating a state of not conducting simultaneously; voltage change: ↓ is rising, ↓ is descending, and N is unchanged.
Wherein in the connected state A, C, E the balanced switching module 3 is in the normal mode and in the connected state B the balanced switching module 3 is at the intermediate voltage u2In the connected state D, the balanced switching module 3 is at the intermediate voltage u3The compensation mode of (1). In the normal mode, the control module is dependent on the voltage uACThe inverter circuit is switched between connection states A, C, E within the range, so that the potential connected to the DC input end of the soft switch inverter module 2 satisfies the condition of Zero Voltage Switching (ZVS)
Figure BDA0003399371210000143
When the intermediate voltage needs to be balanced, the control module controls the balance switching module 3 to be switched to a connection state B or D for respectively balancing the intermediate voltage u2Or u3And (6) balancing.
Specific balancing procedures in various embodiments are described below in conjunction with the figures.
Referring to fig. 5a and 5b, in a first embodiment, the output terminal voltage uACAnd current iL,avgThe phase difference of (1) is 0, and the output is positive active power; intermediate voltage u in this operating state2And u3Rises when the balanced switching module 3 is in the normal mode. At t1The instantaneous voltage of the time output end meets the condition uAC≥u2+UresAnd current iL,avgHas been in the positive half cycle, and satisfies the intermediate voltage u2The control module controls the balance switching module (3) to switch from the normal mode to the intermediate voltage u2The connection state is switched from a to B; by means of the current distribution characteristic of the soft-switching inverter module 2 and the periodic characteristic of the alternating current, the interval t1,t2]And [ TAC/2,t3]、[t4,TAC]Current I formed2Compensated to 0, the equilibrium state is mathematically expressed as follows:
Figure BDA0003399371210000151
at t3The instantaneous voltage of the time output end meets the condition uAC≤-u3-UresAnd current iL,avgHas been in a negative half cycle, at which time the intermediate voltage u is satisfied3In the condition of performing the balancing operation, the control module controls the balancing switching module 3 to switch from the normal mode to the intermediate voltage u3The connection state is switched from C to D; by means of the current distribution characteristic of the soft-switching inverter module 2 and the periodic characteristic of the alternating current, the interval t3，t4]And [0, t1]、[t2,TAC/2]Current I formed3Compensated to 0, the equilibrium state is mathematically expressed as follows:
Figure BDA0003399371210000152
referring to fig. 6a and 6b, in a second embodiment, the output terminal voltage uACAnd current iL,avgThe phase difference is more than 0 and less than 90 degrees, and the output is positive active power; intermediate voltage u in this operating state2And u3Rises when the balanced switching module 3 is in the normal mode. At t1The instantaneous voltage of the output end at the moment meets the condition uAC≥u2+UresAnd current iL,avgIn the positive half cycle, the intermediate voltage u is satisfied2In the condition of performing the balancing operation, the control module controls the balancing switching module 3 to switch from the normal mode to the intermediate voltage u2The connection state is switched from a to B; by means of the current distribution characteristic of the soft-switching inverter module 2 and the periodic characteristic of the alternating current, the interval t1,t2]And [ TAC/2,t3]、[t4,TAC]Current I formed2Is compensated to 0. At t3The instantaneous voltage of the output end at the moment meets the condition uAC≤-u3-UresAnd current iL,avgIn the negative half cycle, when the intermediate voltage u is satisfied3In the condition of performing the balancing operation, the control module controls the balancing switching module 3 to switch from the normal mode to the intermediate voltage u3In the compensation mode (C), i.e. the connection state is switched from C to D, by means of the current distribution characteristic of the soft-switching inverter module 2 and the periodic characteristic of the alternating current in such a way that in the interval t3,t4]And [0, t1]、[t2,TAC/2]Current I formed3Is compensated to 0.
Referring to fig. 7a and 7b, in a third embodiment, the output terminal voltage uACAnd current iL,avgThe phase difference is more than 90 and less than 180 degrees, and the output is negative active power; intermediate voltage u in this operating state2And u3And falls when the balanced switching module 3 is in the normal mode. At t1The instantaneous voltage of the time output end meets the condition uAC≥u2+UresAnd current iL,avgHas been in a negative half cycle, at which time the intermediate voltage u is satisfied2Strip for carrying out balancing operationsThe control module controls the balance switching module 3 to switch from the normal mode to the intermediate voltage u2The connection state is switched from a to B; by means of the current distribution characteristic of the soft-switching inverter module 2 and the periodic characteristic of the alternating current, the interval t1,t2]And [ TAC/2,t3]、[t4,TAC]Current I formed2Is compensated to 0. At t3The instantaneous voltage of the time output end meets the condition uAC≤-u3-UresAnd current iL,avgHas been in the positive half cycle, and satisfies the intermediate voltage u3In the condition of performing the balancing operation, the control module controls the balancing switching module 3 to switch from the normal mode to the intermediate voltage u3In the compensation mode of (2), i.e. switching from the connection state C to the connection state D, by means of the current distribution characteristic of the soft-switching inverter module 2 and the periodic characteristic of the alternating current in the interval t3,t4]And [0, t1]、[t2,TAC/2]Current I formed3Is compensated to 0.
Referring to fig. 8a and 8b, in the fourth embodiment, the difference from the scheme in the previous embodiment is that the instantaneous voltage u is outputACVoltage window [ -u ] above a set voltage threshold3,U1]Is switched to the soft switch inversion module 2; when the instantaneous voltage u at the output terminalACVoltage window-U below a set voltage threshold4,u2]Is switched to the soft switch inversion module 2; wherein for an intermediate voltage u2And u3The balancing method of (3) is the same as that in the first to third embodiments described above.
Referring to fig. 9a and 9b, in the fifth embodiment, the difference from the scheme in the previous embodiment is that the instantaneous voltage u is outputACIn the overlapping part of the voltage window [ -u [ ]3,u2]The time-voltage window switching module 4 connects the overlapped part into the soft switch inversion module 2 to wait for the instantaneous voltage u at the output endACAfter the corresponding threshold value is exceeded, the control module controls the voltage window switching module 4 to access the corresponding voltage window into the soft switch inversion module 2; wherein for an intermediate voltage u2And u3The balancing method of (3) is the same as that in the first to third embodiments described above.
Referring to fig. 10a and 10b, in the sixth embodiment, the difference from the previous embodiments is that the instantaneous voltage u is outputACIn this embodiment, the first scheme is adopted, and the control module switches the voltage window switching module 4 between the connection states a and C, and switches the time point of the voltage window switching and the current iL,avgGenerates phase difference by simulating the working state of pure reactive power to ensure that the intermediate voltage u2And u3The balance is achieved during the period of the ac output. The mathematical expression of the equilibrium state is:
Figure BDA0003399371210000171
Figure BDA0003399371210000172
referring to FIGS. 11a and 11b, in the seventh embodiment, the instantaneous voltage u is generated due to the output terminalACThe difference between the sixth embodiment, in which the operating condition of the compensation mode in the balanced switching module 3 is not satisfied in the whole period, and the output end voltage is low, is that the second scheme is adopted in this embodiment, and the control module switches the voltage window switching module 4 between the connection states A, C and E, and uses the characteristics of the current distribution ratio of the soft-switching inverter module 2 and the ratio of the dc input voltage to the output end voltage to respectively control the intermediate voltage u2And u3The currents at the level nodes are balanced. The mathematical expression of the equilibrium state is:
Figure BDA0003399371210000173
Figure BDA0003399371210000181
in addition, for the multilevel soft switching inverter circuit provided by the invention, the working range of the compensation operation can be changed to break the situation of the intermediate voltage u2And u3A charge balance state is established on the level node, so that the difference of the injected charges can be controlled at the intermediate voltage u2And u3The level nodes at which (i.e. the second dc terminal and the third dc terminal) a bi-directional dc power supply 5 is established to provide power to external devices, as described with reference to fig. 4 a-4 c.
Fig. 4a shows a multi-level soft switching inverter circuit with single dc power input and multi-phase ac output including a bi-directional dc power supply 5; fig. 4b shows a multilevel soft switching inverter circuit with dual dc power inputs and multi-phase ac outputs comprising a bi-directional dc power supply 5; fig. 4c shows a multilevel soft switching inverter circuit with dual dc power inputs and multi-phase ac outputs comprising two bi-directional dc power supplies 5.
For the multilevel soft switching inverter circuit of the bidirectional direct current power supply 5, the control method is similar to the method, and the balance switching module 3 and the voltage window switching module 4 are switched to be in the connection state according to the requirement under the control of the control module, so as to obtain the stably required intermediate voltage u2And u3It is possible to realize the establishment of the stable bidirectional direct-current power supply 5 thereon while stably balancing the intermediate voltage. It will be appreciated that, unlike the seven embodiments described above, it is necessary to have the average current I during a full ac output period2And I3Is compensated to 0; in applications involving a bi-directional DC power supply 5, when it is desired to provide an output current, I2And I3Is not 0, but is controlled by a control module2And I3Compensating to a target value corresponding to the output value of the bidirectional DC power supply 5, and balancing the intermediate voltage u2And u3Meanwhile, the second direct current terminal and the third direct current terminal output current with required direction and magnitude.
In the invention, based on the control signal of the Switching device in the soft Switching inversion module 2, Zero Current Switching (ZCS) can be realized in the Switching devices of the balanced Switching module 3 and the voltage window Switching module 4 in a synchronous Switching manner, so as to further reduce the Switching loss of the system and improve the electric energy conversion efficiency.
In summary, the multi-level soft switch inverter circuit and the method for balancing the voltage at the intermediate level thereof provided by the present invention compensate the charge flowing through each intermediate level end on the premise of realizing soft switching by adding the balancing switching module between the voltage window switching module and the multi-level flat current bus and combining the characteristic of the periodic variation of the voltage and the current in the alternating current output on the basis of the existing multi-level soft switch inverter circuit, thereby actively balancing each intermediate level end in the direct current bus to obtain stable voltage.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (8)

1. A multi-level soft switching inverter circuit is characterized by comprising inverter driving circuits (1) which are mutually independent and have the same structure;
each phase of the inversion driving circuit (1) comprises four direct current input ends, an alternating current output end, a balance switching module (3), a voltage window switching module (4), a soft switch inversion module (2) and a control module;
the four direct current input ends are direct current buses with four different levels formed by a plurality of direct current power supplies through a capacitance voltage division structure, and the four direct current input ends are a first direct current end, a second direct current end, a third direct current end and a fourth direct current end in sequence according to the sequence of the potentials from high to low;
the balance switching module (3) is provided with two input ends and two output ends, and the two input ends of the balance switching module (3) are respectively connected with the second direct current end and the third direct current end;
the voltage window switching module (4) is provided with four input ends and two output ends, the two input ends of the voltage window switching module (4) are respectively connected with the first direct current end and the fourth direct current end, and the other two input ends are respectively connected with the two output ends of the balance switching module (3);
the soft switch inversion module (2) is provided with two input ends and an output end, the two input ends of the soft switch inversion module (2) are respectively connected with the two output ends of the voltage window switching module (4), and the output end of the soft switch inversion module (2) is used as the alternating current output end;
the control module is used for acquiring relevant working information of the multilevel soft switching inverter circuit and controlling the work of each module according to an acquisition result;
the balance switching module (3) is used for compensating charges flowing through the second direct current end and the third direct current end under the control of the control module;
the voltage window switching module (4) is used for outputting a proper direct-current voltage window to the soft switch inversion module (2) under the control of the control module;
the soft switch inversion module (2) is used for converting the direct current provided by the voltage window switching module (4) into alternating current to be output.
2. The multilevel soft switching inverter circuit according to claim 1, wherein the balanced switching module (3) and the voltage window switching module (4) each comprise a plurality of switching devices, and a control terminal of each switching device is connected to the control module, so that a switching state of each switching device can be switched under the control of the control module;
the balanced switching module (3) comprises a first switching device TB1A second switching device TB2A third switching device TB3And a fourth switching device TB4(ii) a The voltage window switching module (4) comprises a fifth switching device TL1And a sixth switching device TL2Seventh switching device TL3And an eighth switching device TL4；
The first switching device TB1And a third switching device TB3Are all connected with a second direct current terminal, the second switching device TB2And a fourth switching device TB4Is connected to a third dc terminal, and the first switching device TB1And the other end of the first switching device TB2Is connected to the other end of the first switching element and is used as a first output end of the balanced switching module (3), and the third switching element TB3And the other end of the fourth switching device TB4Is connected with the other end of the switching module and is used as a second output end of the balanced switching module (3);
the fifth switching device TL1And a sixth switching device TL2The seventh switching device T is connected between the first direct current end and the first output end of the balanced switching module (3) in seriesL3And an eighth switching device TL4Is connected in series between the fourth direct current end and the second output end of the balanced switching module (3);
the soft switch inverter module (2) comprises a half-bridge circuit or a flying capacitor inverter circuit with a positive input end and a negative input end, an inductor L and a plurality of alternating-current end capacitors, wherein the positive input end of the half-bridge circuit or the flying capacitor inverter circuit is connected with a fifth switching device TL1And a sixth switching device TL2The negative input end of the common end is connected with the seventh switching device TL3And an eighth switching device TL4The output end of the half-bridge circuit or the flying capacitor inverter circuit is connected with the alternating current output end through the inductor L, one end of the alternating current end capacitor is connected with one direct current input end or the neutral potential, and the other end of the alternating current end capacitor is connected with the alternating current output end.
3. The multilevel soft switching inverter circuit according to claim 2, further comprising a bi-directional dc power supply (5) additionally established by a level node where the second dc terminal and the third dc terminal are located.
4. A method of balancing intermediate-level terminal voltages of a multilevel soft-switching inverter circuit according to claim 2, characterized in that:
under the control of the control module, the balance switching module (3) automatically switches between a normal mode and a compensation mode to realize the voltage balance of each middle level end in the direct current bus;
in the normal mode, the first switching device TB1And a fourth switching device TB4Conducting, second switching device TB2And a third switching device TB3Turning off;
the compensation mode is divided into a compensation mode for the second direct current terminal and a compensation mode for the third direct current terminal;
in a compensation mode for the second direct current terminal, the third switching device TB3Conducting, fourth switching device TB4Off, first switching device TB1And a second switching device TB2Not conducting at the same time;
in a compensation mode for the third direct current terminal, the second switching device TB2Conducting, first switching device TB1Turn-off, third switching device TB3And a fourth switching device TB4Not conducting at the same time.
5. The method according to claim 4, wherein the neutral potential reference point is a potential at a midpoint between the first DC terminal and the fourth DC terminal, and the absolute values of the voltages at the first DC terminal, the second DC terminal, the third DC terminal and the fourth DC terminal are expressed as Uc, respectively, with reference to the neutral potential reference point1、u2、u3And U4Instantaneous value of voltage at AC output terminal is uAC；
Setting a voltage u in a control module2And u3Set value of U2，setAnd U3，setThe control module is used for measuring u2And u3And a set value U2，setAnd U3，setAnd the working state of the alternating current output, calculating the compensation operation required by each compensation mode in the half period of each alternating current outputA working interval is made;
according to the calculation result, the control module switches the on-off states of the switching devices in the balance switching module (3) and the voltage window switching module (4) to enable the bus current i where the second direct current end and the third direct current end are located2And i3Average value I in period of AC output2And I3Compensating to the target value so as to make the corresponding voltage u2And u3In a steady state, and finally outputting the alternating current in a period u2And u3Average value of U2And U3Is stabilized at a set value U2，setAnd U3，setThe above.
6. The method of claim 5, wherein the instantaneous current through the inductor L is represented by iLIndicating that the average value of the inductive current in a switching period of the soft-switching inverter module (2) is iL，avgIndicating and setting an inductance reserve voltage U in the control moduleres；
The balanced switching module (3) normally operates in a normal mode;
when the control module detects that the output end voltage is in the range uACU of2+UresThen the control module automatically controls the current iL，avgThe direction control balance switching module (3) is switched to a compensation mode for compensating the second direct current end, and after the compensation operation required by the compensation mode is finished, the control module automatically switches the balance switching module (3) back to a normal mode;
when the control module detects that the output end voltage is in the range uAC≤-u3-UresThen the control module automatically controls the current iL，avgThe direction control balance switching module (3) is switched to a compensation mode for compensating the third direct current end, and after the compensation operation required by the compensation mode is finished, the control module automatically switches the balance switching module (3) back to a normal mode.
7. The method of claim 5,
when u isAC＜u2And uAC＞-u3When the switching module (3) is in the normal mode, the balance switching module (3) is kept in the normal mode;
the control module is used for controlling the AC output according to the working state of the AC output and the measured u2And u3Calculating a balance phase or a working interval required by voltage balance;
and the control module switches the switching state of a switching device in the voltage window switching module (4) according to the calculation result so as to switch the voltage window provided for the soft switching inversion module (2), so that the voltages of the second direct current end and the third direct current end are balanced in the period of alternating current output.
8. The method according to claim 5, wherein if the multilevel soft switching inverter circuit comprises a bidirectional DC power supply (5) established by using a level node where the second DC terminal and the third DC terminal are located, the control module switches the switching states of the switching devices in the balanced switching module (3) and the voltage window switching module (4) to change the bus current i where the second DC terminal and the third DC terminal are located2And i3Average value I in period of AC output2And I3Compensating to a target value, wherein the target value corresponds to an output value required by the bidirectional direct current power supply (5);
if the multi-level soft switching inverter circuit does not comprise the bidirectional direct current power supply (5), the control module switches the switching states of the switching devices in the balance switching module (3) and the voltage window switching module (4) to enable the bus current i where the second direct current end and the third direct current end are located2And i3Average value I in period of AC output2And I3Compensating to a target value, wherein the target value is 0.
CN202111491064.2A 2021-12-08 2021-12-08 Multilevel soft switching inverter circuit and balancing method of intermediate level terminal voltage thereof Pending CN114362574A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
CN202111491064.2A CN114362574A (en) 2021-12-08 2021-12-08 Multilevel soft switching inverter circuit and balancing method of intermediate level terminal voltage thereof
CN202211180928.3A CN115395810A (en) 2021-12-08 2022-09-27 Multilevel soft switch inverter circuit and balancing method of intermediate level terminal voltage thereof
PCT/CN2022/134312 WO2023103811A1 (en) 2021-12-08 2022-11-25 Multi-level soft switching inverter circuit, and balancing method for voltage at intermediate level therefor

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202111491064.2A CN114362574A (en) 2021-12-08 2021-12-08 Multilevel soft switching inverter circuit and balancing method of intermediate level terminal voltage thereof

Publications (1)

Publication Number Publication Date
CN114362574A true CN114362574A (en) 2022-04-15

Family

ID=81096934

Family Applications (2)

Application Number Title Priority Date Filing Date
CN202111491064.2A Pending CN114362574A (en) 2021-12-08 2021-12-08 Multilevel soft switching inverter circuit and balancing method of intermediate level terminal voltage thereof
CN202211180928.3A Pending CN115395810A (en) 2021-12-08 2022-09-27 Multilevel soft switch inverter circuit and balancing method of intermediate level terminal voltage thereof

Family Applications After (1)

Application Number Title Priority Date Filing Date
CN202211180928.3A Pending CN115395810A (en) 2021-12-08 2022-09-27 Multilevel soft switch inverter circuit and balancing method of intermediate level terminal voltage thereof

Country Status (2)

Country Link
CN (2) CN114362574A (en)
WO (1) WO2023103811A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115514218A (en) * 2022-09-15 2022-12-23 芯洲科技(北京)股份有限公司 Power supply system and power supply system for power supply system
WO2023103811A1 (en) * 2021-12-08 2023-06-15 周衍 Multi-level soft switching inverter circuit, and balancing method for voltage at intermediate level therefor

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5397203B2 (en) * 2009-12-15 2014-01-22 富士電機株式会社 Power converter
KR101297320B1 (en) * 2012-07-02 2013-08-16 전남대학교산학협력단 Single phase full-bridge inverter for providing enhanced power quality
CN105827129B (en) * 2015-01-04 2020-06-02 华为技术有限公司 Circuit and power converter with multi-level topology
CN111697861B (en) * 2020-06-22 2022-03-22 周衍 Multilevel soft switch inversion driving system and voltage window switching method thereof
CN114362574A (en) * 2021-12-08 2022-04-15 周衍 Multilevel soft switching inverter circuit and balancing method of intermediate level terminal voltage thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023103811A1 (en) * 2021-12-08 2023-06-15 周衍 Multi-level soft switching inverter circuit, and balancing method for voltage at intermediate level therefor
CN115514218A (en) * 2022-09-15 2022-12-23 芯洲科技(北京)股份有限公司 Power supply system and power supply system for power supply system

Also Published As

Publication number Publication date
CN115395810A (en) 2022-11-25
WO2023103811A1 (en) 2023-06-15

Similar Documents

Publication Publication Date Title
CN107078665B (en) Power-converting device
JP4745234B2 (en) Power supply
CN102624266B (en) Three-level inverter circuit
CN107210684B (en) Five level topology units and five-electrical level inverter
Nishida et al. A predictive instantaneous-current PWM controlled rectifier with AC-side harmonic current reduction
CN107408898B (en) Converter module for a multilevel energy converter
CN115395810A (en) Multilevel soft switch inverter circuit and balancing method of intermediate level terminal voltage thereof
US8923027B2 (en) Five-level DC-AC converter
WO2013150572A1 (en) Power conversion device
CN102347703A (en) Power conversion device
CN105900328B (en) Power conversion device
WO2020248651A1 (en) Off-line phase split device and inverter system
JPWO2015045485A1 (en) Power converter
CN110752763A (en) Modular multilevel converter topology and modulation method thereof
US20190280615A1 (en) Modulation method and apparatus based on three-phase neutral point clamped inverter
CN105141153A (en) Three-phase rectifier and booster circuit and control method thereof and uninterruptible power supply
CN104584407A (en) Power conversion device
Zhang et al. A hybrid modulation method for single-phase quasi-Z source inverter
CN104115389A (en) Power conversion apparatus
CN106787859A (en) Combined three phase single-stage APFC converters and its control device based on full bridge structure
CN103812366A (en) Three phase controllable rectification circuit
WO2021259091A1 (en) Multi-level soft-switching inversion driving system and voltage window switching method therefor
CN103780118A (en) Resonant DC link three-level soft switching inverter circuit
CN108880316A (en) The grid-connection converter Predictive Control System and control method of compensation with voltage
CN104081644B (en) Power conversion device

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
WD01 Invention patent application deemed withdrawn after publication
WD01 Invention patent application deemed withdrawn after publication

Application publication date: 20220415