CN110149065B - Buck-boost switched capacitor multi-level inverter and modulation method thereof - Google Patents
Buck-boost switched capacitor multi-level inverter and modulation method thereof Download PDFInfo
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- CN110149065B CN110149065B CN201910395147.8A CN201910395147A CN110149065B CN 110149065 B CN110149065 B CN 110149065B CN 201910395147 A CN201910395147 A CN 201910395147A CN 110149065 B CN110149065 B CN 110149065B
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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
- 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
Abstract
The invention provides a buck-boost switch capacitor multilevel inverter and a modulation method thereof, wherein the buck-boost switch capacitor multilevel inverter is arranged between a direct current input power supply and a load or an alternating current power grid and comprises a buck-boost switch capacitor unit and a full-bridge unit; the boost-buck switch capacitor unit is connected in parallel with the direct-current input power supply, and is used for performing boost or buck conversion on the direct-current input power supply and outputting multi-step voltage; the full-bridge unit is connected with the buck-boost switch capacitor unit in parallel and used for transmitting the multi-step voltage output by the buck-boost switch capacitor unit to the load or the alternating current power grid after positive and negative polarity conversion. The invention integrates the step-up and step-down conversion, realizes the step-up conversion and the step-down conversion of the input power supply, can perform the on-line switching of two control modes, improves the flexibility of an inversion system, and has the advantages of simple structure, self-voltage-sharing of a capacitor and independent application to an inductive load.
Description
Technical Field
The invention relates to the field of electric energy conversion and new energy distributed grid-connected power generation, in particular to a buck-boost switched capacitor multilevel inverter and a modulation method thereof.
Background
With the increasing environmental pollution and energy crisis, the development and utilization of clean and renewable energy sources are receiving much attention. The photovoltaic power generation has been widely used because of its advantages of wide distribution, clean production process, safety, reliability, convenient maintenance, etc.
In a photovoltaic power generation system, a power electronic inverter is a core device of the power generation system. Although the traditional two-level inverter has a simple structure and mature technology, the output waveform of the traditional two-level inverter has high harmonic content and large voltage stress of a switching tube, and can not meet the current power demand gradually. The multilevel inverter has the advantages of good output waveform quality, small harmonic content of output voltage, low voltage stress of a switching device, small requirement on an output filter and the like, and therefore, the multilevel inverter has important application prospects in the fields of photovoltaic power generation and the like.
At present, the main structures of multi-level inverters are a flying capacitor type, a diode clamping type and a cascade H-bridge type, but with the increase of the number of output levels, the circuit structures of the inverters become complex and the control difficulty increases.
In order to reduce the number of devices of a system and control complexity, a switched capacitor technology is applied to a multi-level inverter structure, the switched capacitor structure is a typical nonmagnetic structure and consists of a certain number of switching devices and voltage division capacitors, and the working state of the capacitors is controlled through switches to realize the transmission and conversion of electric energy. The switched capacitor multi-level inverter can generate a higher number of output levels through fewer switching devices, has the advantages of small volume, high efficiency, high power density and the like, and has become a trend for research on power electronic inversion devices, but the existing switched capacitor structure can only perform boost or buck conversion, and an inversion system is not flexible.
In order to solve the above problems, people are always seeking an ideal technical solution.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a buck-boost switched capacitor multilevel inverter and a modulation method thereof.
In order to achieve the purpose, the invention adopts the technical scheme that: a buck-boost switch capacitor multi-level inverter is arranged between a direct current input power supply and a load or an alternating current power grid and comprises a buck-boost switch capacitor unit and a full-bridge unit;
the boost-buck switch capacitor unit is connected in parallel with the direct-current input power supply, and is used for performing boost or buck conversion on the direct-current input power supply and outputting multi-step voltage;
the full-bridge unit is connected with the buck-boost switch capacitor unit in parallel and used for transmitting the multi-step voltage output by the buck-boost switch capacitor unit to the load or the alternating current power grid after positive and negative polarity conversion.
The buck-boost switch capacitor unit comprises a switch tube S5Switch tube S6Switch tube S7Switch tube S8Diode D0And an electrolytic capacitor C1And an electrolytic capacitor C2Said switch tube S5The switch tube S6The switch tube S7And the switching tube S8Respectively connecting a freewheeling diode in reverse parallel;
wherein, the switch tube S5The input end of the switch tube S is connected with the positive output end of the direct current input power supply5Is connected with the diode D0The anode of the diode D0Respectively connected with the switch tube S6And the electrolytic capacitor C1The anode of (1); the switch tube S6Output ends of the two are respectively connected with the switch tube S7And the electrolytic capacitor C2The switching tube S7Output ends of the electrolytic capacitors are respectively connected with the electrolytic capacitors C1And the switching tube S8The electrolytic capacitor C2Respectively connected with the switch tube S8And the negative output terminal of the dc input power supply.
The full-bridge unit comprises a switch tube S1Switch tube S2Switch tube S3And a switching tube S4(ii) a The switch tube S1The switch tube S2The switch tube S3And the switching tube S4Respectively connecting a freewheeling diode in reverse parallel;
the switch tube S1And the switching tube S2A bridge arm I of the full-bridge unit is formed by forward series connection, and the switch tube S3And the switching tube S4A bridge arm II of the full-bridge unit is formed by connecting the bridge arms in series in the forward direction; the bridge arm I and the bridge arm II are connected in parallel；
And the middle point of the bridge arm I and the middle point of the bridge arm II are used as the output ends of the buck-boost switched capacitor multi-level inverter.
A modulation method of a buck-boost switch capacitor multilevel inverter is applied to the buck-boost switch capacitor multilevel inverter, and the buck-boost switch capacitor multilevel inverter is provided with two control modes:
boost mode
The buck-boost switch capacitor unit is configured to boost and convert the output voltage of the direct current input power supply and then output a first step voltage, and the full-bridge unit converts the positive polarity and the negative polarity of the first step voltage and then outputs the first step voltage to a load or an alternating current power grid;
reduced pressure mode
The buck-boost switch capacitor unit is configured to output a second step voltage after performing buck conversion on the output voltage of the direct current input power supply, and the full-bridge unit outputs the second step voltage to a load or an alternating current power grid after performing positive and negative polarity conversion on the second step voltage.
Based on the above, the boost mode includes five control modes, namely a boost mode I, a boost mode II, a boost mode III, a boost mode IV and a boost mode V;
the voltage reduction mode comprises five control modes, namely a voltage reduction mode I, a voltage reduction mode II, a voltage reduction mode III, a voltage reduction mode IV and a voltage reduction mode V.
Compared with the prior art, the buck-boost switch capacitor multilevel inverter has outstanding substantive characteristics and obvious progress, and particularly provides the buck-boost switch capacitor multilevel inverter and a modulation method thereof, wherein the buck-boost switch capacitor multilevel inverter is arranged between a direct current input power supply and a load or an alternating current power grid and comprises a buck-boost switch capacitor unit and a full-bridge unit; the boost-buck switch capacitor unit performs boost or buck conversion on the direct-current input power supply and outputs multi-step voltage; the full-bridge unit converts the positive polarity and the negative polarity of the multi-step voltage output by the buck-boost switch capacitor unit and transmits the multi-step voltage to the load or the alternating current power grid;
therefore, the invention integrates the voltage boosting and voltage reducing conversion, and can realize the on-line switching of two conversion modes; the boost-buck switch capacitor multi-level inverter is simple in structure and control, and can realize capacitor self-voltage-sharing without an additional control loop or a complex control algorithm; meanwhile, the buck-boost switched capacitor multi-level inverter has the advantages of single power input and independent application to inductive loads.
Drawings
Fig. 1 is a schematic view of a topology of a buck-boost switched capacitor multi-level inverter according to the present invention.
Fig. 2 to 6 are schematic diagrams of working current paths of five working modes when the buck-boost switched capacitor multilevel inverter of the invention is in the boost mode.
Fig. 7 to 11 are schematic diagrams of operating current paths of five operating modes when the buck-boost switched capacitor multilevel inverter of the invention is in the buck mode.
Fig. 12 is a schematic diagram of a modulation method of the buck-boost switched capacitor multilevel inverter in boost mode according to the present invention.
Fig. 13 is a schematic diagram of a modulation method of the buck-boost switched capacitor multilevel inverter in buck mode according to the present invention.
Fig. 14 and 15 are schematic diagrams of output voltage and load current waveforms of the buck-boost switched capacitor multilevel inverter in the boost mode.
Fig. 16 and 17 are schematic diagrams of output voltage and load current waveforms of the buck-boost switched capacitor multilevel inverter in the buck mode according to the present invention.
Fig. 18 and 19 are schematic diagrams of output voltage and load current waveforms when the buck-boost switched capacitor multilevel inverter is in the buck-boost mode and is switched online.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the following describes the technical solutions of the embodiments of the present invention clearly and completely, but the present invention is not limited to these embodiments:
example 1
As shown in fig. 1, a buck-boost switched capacitor multilevel inverter is arranged between a dc input power source and a load or an ac power grid, and includes a buck-boost switched capacitor unit and a full-bridge unit; the boost-buck switch capacitor unit is connected in parallel with the direct-current input power supply, and is used for performing boost or buck conversion on the direct-current input power supply and outputting multi-step voltage; the full-bridge unit is connected with the buck-boost switch capacitor unit in parallel and used for transmitting the multi-step voltage output by the buck-boost switch capacitor unit to the load or the alternating current power grid after positive and negative polarity conversion.
On the basis of the buck-boost switched capacitor multilevel inverter of this embodiment, this embodiment provides a corresponding modulation method, and the buck-boost switched capacitor multilevel inverter sets two control modes:
the voltage boosting mode is that the voltage boosting and reducing switch capacitor unit is configured to perform voltage boosting conversion on the output voltage of the direct current input power supply and then output a first step voltage, the two electrolytic capacitors are charged in parallel and discharged in series, and the full-bridge unit performs positive and negative polarity conversion on the first step voltage and then outputs the first step voltage to a load or an alternating current power grid;
and in the voltage reduction mode, the buck-boost switch capacitor unit is configured to perform buck conversion on the output voltage of the direct current input power supply and then output a second step voltage, the two electrolytic capacitors are charged in series and discharged in parallel, and the full-bridge unit performs positive and negative polarity conversion on the second step voltage and then outputs the second step voltage to a load or an alternating current power grid.
Specifically, the boost mode includes five control modes: a boosting mode I, a boosting mode II, a boosting mode III, a boosting mode IV and a boosting mode V; the step-down mode comprises five control modes: a voltage reduction mode I, a voltage reduction mode II, a voltage reduction mode III, a voltage reduction mode IV and a voltage reduction mode V.
In summary, the dc input power supplies provide stable dc power; the buck-boost switch capacitor unit of the buck-boost switch capacitor multi-level inverter realizes boost conversion of the direct-current input power supply and generates multi-step voltage, namely first step voltage; the step-down conversion of the direct current input power supply is realized, and multi-step voltage, namely second step voltage, is generated; the full-bridge unit realizes positive and negative polarity conversion of the preceding-stage multi-step voltage and realizes a DC-AC inversion process.
Therefore, the boost conversion and the buck conversion are integrated, and the boost conversion or the buck conversion is performed on the output voltage of the direct current input power supply through the boost-buck switch capacitor unit, so that the boost-buck switch capacitor multi-level inverter can work in a boost mode and a buck mode, can perform online switching of two conversion states, and improves the flexibility of an inverter system.
Example 2
In this embodiment, a specific implementation manner of a buck-boost switch capacitor unit is provided, and as shown in fig. 1, the buck-boost switch capacitor unit includes a switch tube S5Switch tube S6Switch tube S7Switch tube S8Diode D0And an electrolytic capacitor C1And an electrolytic capacitor C2Said switch tube S5The switch tube S6The switch tube S7And the switching tube S8Respectively connecting a freewheeling diode in reverse parallel; wherein, the switch tube S5The input end of the switch tube S is connected with the positive output end of the direct current input power supply5Is connected with the diode D0The anode of the diode D0Respectively connected with the switch tube S6And the electrolytic capacitor C1The anode of (1); the switch tube S6Output ends of the two are respectively connected with the switch tube S7And the electrolytic capacitor C2The switching tube S7Output ends of the electrolytic capacitors are respectively connected with the electrolytic capacitors C1And the switching tube S8The electrolytic capacitor C2Respectively connected with the switch tube S8And the negative output terminal of the dc input power supply.
This embodiment also provides a specific implementation of a full-bridge unit, which is a full-bridge unitThe unit comprising a switching tube S1Switch tube S2Switch tube S3And a switching tube S4(ii) a The switch tube S1The switch tube S2The switch tube S3And the switching tube S4Respectively connecting a freewheeling diode in reverse parallel; the switch tube S1And the switching tube S2A bridge arm I of the full-bridge unit is formed by forward series connection, and the switch tube S3And the switching tube S4A bridge arm II of the full-bridge unit is formed by connecting the bridge arms in series in the forward direction; the bridge arm I and the bridge arm II are connected in parallel; and the middle point of the bridge arm I and the middle point of the bridge arm II are used as the output ends of the buck-boost switched capacitor multi-level inverter. The output end of the buck-boost switched capacitor multi-level inverter is connected to a load or an alternating current power grid through a filter inductor.
Further, the switch tube S of the full-bridge unit1Switch tube S2Switch tube S3Switch tube S4And a switching tube S of the buck-boost switch capacitor unit5Switch tube S6Switch tube S7Switch tube S8A MOSFET or IGBT full-control type power device is adopted; the diode D0Is a fast recovery diode or an ultrafast recovery diode; the electrolytic capacitor C1And the electrolytic capacitor C2The working state is synchronous all the time, and the specification parameters of the devices are consistent.
Therefore, the preceding stage buck-boost switch capacitor unit in the buck-boost switch capacitor multi-level inverter charges two electrolytic capacitors in series and in parallel through a power supply, so that boost conversion or buck conversion of an input power supply is realized, a multi-step level is formed, and the subsequent stage full-bridge unit realizes an inversion process of the preceding stage multi-step level to generate multi-level output.
Based on the buck-boost switched capacitor multilevel inverter of the present embodiment, the present embodiment describes a modulation method of the buck-boost switched capacitor multilevel inverter in detail.
In the modulation method of the buck-boost switched capacitor multi-level inverter, a boost mode and a buck mode both comprise five control modes.
(1) The five control modes of the boosting mode are as follows:
a boost mode I for controlling the switch tube S1The switch tube S4And the switching tube S7Are all conducted, the switch tube S2The switch tube S3The switch tube S5The switch tube S6And the switching tube S8All are turned off; two electrolytic capacitors C1And C2Series discharge with a voltage of 2VdcThe output level of the buck-boost switched capacitor multi-level inverter is 2VdcThe working current path is shown in figure 2;
a boost mode II for controlling the switching tube S1The switch tube S4The switch tube S5The switch tube S6And the switching tube S8Are all conducted, the switch tube S2The switch tube S3And the switching tube S7All are turned off; power supply VdcFor two electrolytic capacitors C connected in parallel1、C2Charging with a charging voltage of V between two capacitorsdc(ii) a At the same time, the power supply VdcSwitching tube S through full bridge unit1、S4The output level of the buck-boost switch capacitor multi-level inverter is VdcThe working current path is shown in figure 3;
a boost mode III for controlling the switch tube S2The switch tube S4The switch tube S5The switch tube S6And the switching tube S8Are all conducted, the switch tube S1The switch tube S3And the switching tube S7All are turned off; power supply VdcFor two electrolytic capacitors C connected in parallel1、C2Charging with a charging voltage of V between two capacitorsdcThe output level of the buck-boost switched capacitor multi-level inverter is 0, and the working current path of the buck-boost switched capacitor multi-level inverter is shown in figure 4;
a boost mode IV for controlling the switching tube S2The switch tube S3The switch tube S5The switch tube S6And the switching tube S8Are all turned on, soThe switch tube S1The switch tube S4And the switching tube S7All are turned off; power supply VdcFor two electrolytic capacitors C connected in parallel1、C2Charging with a charging voltage of V between two capacitorsdc(ii) a At the same time, the power supply VdcSwitching tube S through full bridge unit2、S3The output level of the buck-boost switch capacitor multi-level inverter is-VdcThe working current path is shown in figure 5;
a voltage boosting mode V for controlling the switching tube S2The switch tube S3And the switching tube S7Are all conducted, the switch tube S1The switch tube S4The switch tube S5The switch tube S6And the switching tube S8All are turned off; two electrolytic capacitors C1And C2Series discharge with a voltage of 2VdcThe output level of the buck-boost switched capacitor multi-level inverter is-2VdcThe working current path is shown in figure 6.
When the buck-boost switched capacitor multi-level inverter works in a boost mode, the two electrolytic capacitors C1And C2Parallel charging and series discharging, the parallel charging voltage of two electrolytic capacitors is VdcThe series discharge voltage is 2VdcThe preceding stage buck-boost switch capacitor unit generates Vdc、2VdcThe rear-end full-bridge unit realizes the positive and negative polarity conversion of step voltage, and the output level of the buck-boost switched capacitor multi-level inverter is 2V in the modedc、Vdc、0、-Vdc、-2Vdc。
As shown in fig. 12, when the buck-boost switched capacitor multilevel inverter operates in the boost mode, the switch tube S1To the switching tube S8The logical combination of the drive signals of (a) is:
S1＝u2
S4＝u3
a sine modulation wave ArefWith four triangular carrier waves A with the same frequency and the same amplitudec1～Ac4Comparing, and outputting a high level when the sine modulation wave is larger than the triangular carrier wave, otherwise, outputting a low level; through the comparison between sine wave and triangular carrier wave, the logic generation circuit generates four paths of logic switching signals u1～u4For four-way logic switch signal u1～u4And carrying out logic combination to obtain driving signals of eight switching tubes of the buck-boost switching capacitor multi-level inverter.
In the boost mode, the working states of the switching tubes of the boost-buck switching capacitor multilevel inverter are as follows:
as can be seen from the above table and the analysis of the five control modes of the boost mode in this embodiment, the boost-buck switched capacitor multi-level inversion is performedWhen the device is in a boosting mode, the electrolytic capacitor C in the boost-buck switch capacitor unit1And C2The charging and discharging states of the step-up and step-down switch capacitor multi-level inverter are always the same, so that the self-equalization of the capacitor voltage can be realized.
(2) The five control modes of the voltage reduction mode are as follows:
a voltage reduction mode I for controlling the switch tube S1The switch tube S4And the switching tube S5Are all conducted, the switch tube S2The switch tube S3The switch tube S6The switch tube S7And the switching tube S8All are turned off; power supply VdcTo two electrolytic capacitors C connected in series1、C2Charging with a charging voltage of V between two capacitorsdc/2, power supply VdcSwitching tube S through full bridge unit1、S4The output level of the buck-boost switch capacitor multi-level inverter is VdcThe working current path is shown in figure 7;
a voltage reduction mode II for controlling the switch tube S1The switch tube S4The switch tube S6And the switching tube S8Are all conducted, the switch tube S2The switch tube S3The switch tube S5And the switching tube S7All are turned off; two electrolytic capacitors C1、C2Parallel discharge with a voltage VdcThe output level of the buck-boost switched capacitor multi-level inverter is VdcThe working current path is shown in figure 8;
a voltage reduction mode III for controlling the switch tube S2The switch tube S4And the switching tube S5Are all conducted, the switch tube S1The switch tube S3The switch tube S6The switch tube S7And the switching tube S8All are turned off; power supply VdcTo two electrolytic capacitors C connected in series1、C2Charging with a charging voltage of V between two capacitorsdcThe output level of the buck-boost switched capacitor multi-level inverter is 0, and the working current path of the buck-boost switched capacitor multi-level inverter isAs shown in fig. 9;
a voltage reduction mode IV for controlling the switching tube S2The switch tube S3The switch tube S6And the switching tube S8Are all conducted, the switch tube S1The switch tube S4The switch tube S5And the switching tube S7 are both turned off; two electrolytic capacitors C1、C2Parallel discharge with a voltage VdcThe output level of the buck-boost switching capacitor multi-level inverter is-VdcThe working current path is shown in the figure 10;
a voltage reduction mode V for controlling the switching tube S2The switch tube S3And the switching tube S5Are all conducted, the switch tube S1The switch tube S4The switch tube S6The switch tube S7And the switching tube S8All are turned off; power supply VdcTo two capacitors C connected in series1、C2Charging with a charging voltage of V between two capacitors dc2; power supply VdcSwitching tube S through full bridge unit2、S3The output level of the buck-boost switch capacitor multi-level inverter is-VdcThe working current path is shown in figure 11.
As shown in fig. 13, when the buck-boost switched capacitor multilevel inverter operates in the buck mode, the logic combination of the driving signals of the switching tubes is as follows;
S1＝u2
S4＝u3
S7＝0
a sine modulation wave ArefWith four triangular carrier waves A with the same frequency and the same amplitudec1～Ac4Comparing, and outputting a high level when the sine modulation wave is larger than the triangular carrier wave, otherwise, outputting a low level; through the comparison between sine wave and triangular carrier wave, the logic generation circuit generates four paths of logic switching signals u1～u4For four-way logic switch signal u1～u4And carrying out logic combination to obtain driving signals of eight switching tubes of the buck-boost switching capacitor multi-level inverter.
In the step-down mode, the working states of the switching devices of the buck-boost switched capacitor multilevel inverter are shown in the following table:
as can be seen from the above table and the analysis of the five control modes of the buck mode in this embodiment, when the buck-boost switched capacitor multilevel inverter is in the buck mode, the electrolytic capacitor C in the buck-boost switched capacitor unit1And C2The charging and discharging states of the step-up and step-down switch capacitor multi-level inverter are always the same, so that the self-equalization of the capacitor voltage can be realized.
When the buck-boost switched capacitor multi-level inverter works in a buck mode, the two electrolytic capacitors C1And C2Series charging, parallel discharging, two capacitors series charging voltage VdcV2, parallel discharge voltagedc/2, preceding stage buck-boost switch capacitorUnit generation Vdc/2、VdcThe rear-end full-bridge unit realizes the positive and negative polarity conversion of step voltage, and the output level of the buck-boost switched capacitor multi-level inverter is V in the modedc、Vdc/2、0、-Vdc/2、-Vdc. Wherein, VdcIs the output voltage of the direct current input power supply.
In this embodiment, the amplitude of the triangular carrier is arefThe amplitude of the triangular carrier wave is AcThe inverter modulation ratio M is
The value range of the modulation ratio M is 0.5-1; the output of the buck-boost switched capacitor multi-level inverter is five levels.
In fig. 2 to 11 of the present embodiment, a solid line indicates a current path in the forward direction of current, and a broken line indicates a current path in the reverse direction of current.
In conclusion, the buck-boost switched capacitor multi-level inverter can work in a boost mode and a buck mode, and the two modes can be switched with each other, so that the system output is flexible, and the application range is wide; and as can be seen from fig. 2 to 11, the forward current path and the reverse current path in all operating states have the same output level, so that the buck-boost switched capacitor multilevel inverter can be independently applied to an inductive load to provide reactive power.
In other embodiments, a user may control the buck-boost switched capacitor multi-level inverter to output three levels by adjusting a value range of the modulation ratio M of the buck-boost switched capacitor multi-level inverter. Wherein the value range of the modulation ratio M is 0-0.5; in the boost mode, the output level of the boost-buck switch capacitor multi-level inverter is V dc0 and-Vdc(ii) a In the step-down mode, the output level of the buck-boost switched capacitor multi-level inverter is 1/2Vdc、0、-1/2Vdc。
Example 3
The buck-boost switched capacitor multi-level inverter and the modulation method thereof are verified through simulation.
In the boost mode, the boost-buck switched capacitor multi-level inverter is modulated by using the modulation method in embodiment 2, fig. 14 is a waveform diagram of an example of the output voltage of the boost-buck switched capacitor multi-level inverter, and fig. 15 is a waveform diagram of an example of the load current of the boost-buck switched capacitor multi-level inverter; when the input voltage is 200V, it can be known from fig. 14 that the buck-boost switched capacitor multi-level inverter can generate a five-level voltage waveform with a maximum voltage of 400V, which proves the correctness of the boost mode of the inverter structure of the buck-boost switched capacitor multi-level inverter, and fig. 15 shows that the load current is a relatively smooth sine wave, and the current phase lags behind the voltage phase, which proves that the buck-boost switched capacitor multi-level inverter can be applied to an inductive load;
in the buck mode, fig. 16 is a waveform diagram of an example of an output voltage of the buck-boost switched capacitor multi-level inverter, and fig. 17 is a waveform diagram of an example of a load current of the buck-boost switched capacitor multi-level inverter; when the input voltage is 200V, it can be seen from fig. 16 that the boost-buck switching capacitor multi-level inverter outputs a five-level voltage waveform with a minimum voltage of 100V, which proves the correctness of the buck mode of the boost-buck switching capacitor multi-level inverter structure, and the load current in fig. 17 is also a relatively smooth sine wave, which proves that the boost-buck switching capacitor multi-level inverter structure can be applied to an inductive load.
As shown in fig. 18 and 19, in this embodiment, waveform diagrams of examples of the inverter output voltage and the load current are given when the boost/buck mode of the buck-boost switched capacitor multilevel inverter is switched online, when the boost/buck mode of the inverter system is switched online, the inverter output voltage and the load current can quickly reach a target working state following the mode switching, the system mode is switched quickly, and the output waveform before and after the switching is stable, which proves the feasibility and the correctness of the switching of the online mode of the inverter.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention and not to limit it; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art will understand that: modifications to the specific embodiments of the invention or equivalent substitutions for parts of the technical features may be made; without departing from the spirit of the present invention, it is intended to cover all aspects of the invention as defined by the appended claims.
Claims (4)
1. The utility model provides a many level inverter of buck-boost switched capacitor, sets up between direct current input power and load or alternating current electric wire netting, its characterized in that: the buck-boost switch capacitor unit comprises a buck-boost switch capacitor unit and a full-bridge unit;
the boost-buck switch capacitor unit is connected in parallel with the direct-current input power supply, and is used for performing boost or buck conversion on the direct-current input power supply and outputting multi-step voltage;
the buck-boost switch capacitor unit comprises a switch tube S5Switch tube S6Switch tube S7Switch tube S8Diode D0And an electrolytic capacitor C1And an electrolytic capacitor C2Said switch tube S5The switch tube S6The switch tube S7And the switching tube S8Respectively connecting a freewheeling diode in reverse parallel;
wherein, the switch tube S5The input end of the switch tube S is connected with the positive output end of the direct current input power supply5Is connected with the diode D0The anode of the diode D0Respectively connected with the switch tube S6And the electrolytic capacitor C1The anode of (1); the switch tube S6Output ends of the two are respectively connected with the switch tube S7And the electrolytic capacitor C2The switching tube S7Output ends of the electrolytic capacitors are respectively connected with the electrolytic capacitors C1And the switching tube S8The electrolytic capacitor C2Respectively connected with the switch tube S8And a negative output terminal of the dc input power supply;
the full-bridge unit is connected in parallel with the buck-boost switch capacitor unit and is used for converting the positive polarity and the negative polarity of the multi-step voltage output by the buck-boost switch capacitor unit and transmitting the multi-step voltage to the load or the alternating current power grid;
the full-bridge unit comprises a switch tube S1Switch tube S2Switch tube S3And a switching tube S4(ii) a The switch tube S1The switch tube S2The switch tube S3And the switching tube S4Respectively connecting a freewheeling diode in reverse parallel; the switch tube S1And the switching tube S2A bridge arm I of the full-bridge unit is formed by forward series connection, and the switch tube S3And the switching tube S4A bridge arm II of the full-bridge unit is formed by connecting the bridge arms in series in the forward direction; the bridge arm I and the bridge arm II are connected in parallel; the middle point of the bridge arm I and the middle point of the bridge arm II are used as the output ends of the buck-boost switched capacitor multi-level inverter;
when the buck-boost switched capacitor multi-level inverter works in a boost mode, the two electrolytic capacitors C1And C2Parallel charging and series discharging, the parallel charging voltage of two electrolytic capacitors is VdcThe series discharge voltage is 2VdcThe preceding stage buck-boost switch capacitor unit generates Vdc、2VdcThe rear-end full-bridge unit realizes the positive and negative polarity conversion of step voltage, and the output level of the buck-boost switched capacitor multi-level inverter is 2V in the modedc、Vdc、0、-Vdc、-2Vdc；
When the buck-boost switched capacitor multi-level inverter works in a buck mode, the two electrolytic capacitors C1And C2Series charging, parallel discharging, two capacitors series charging voltage VdcV2, parallel discharge voltagedc/2, the preceding stage buck-boost switched capacitor unit generates Vdc/2、VdcThe rear-end full-bridge unit realizes the positive and negative polarity conversion of step voltage, and the output level of the buck-boost switched capacitor multi-level inverter is V in the modedc、Vdc/2、0、-Vdc/2、-Vdc；
Wherein, VdcIs the output voltage of the direct current input power supply.
2. A modulation method of a buck-boost switched capacitor multi-level inverter is applied to the buck-boost switched capacitor multi-level inverter disclosed by claim 1, and the buck-boost switched capacitor multi-level inverter is characterized in that two control modes are set:
boost mode
The buck-boost switch capacitor unit is configured to boost and convert the output voltage of the direct current input power supply and then output a first step voltage, and the full-bridge unit converts the positive polarity and the negative polarity of the first step voltage and then outputs the first step voltage to a load or an alternating current power grid; the boost mode comprises five control modes of a boost mode I, a boost mode II, a boost mode III, a boost mode IV and a boost mode V, and the five control modes of the boost mode are as follows:
a boost mode I for controlling the switch tube S1The switch tube S4And the switching tube S7Are all conducted, the switch tube S2The switch tube S3The switch tube S5The switch tube S6And the switching tube S8All are turned off; two electrolytic capacitors C1And C2Series discharge with a voltage of 2VdcThe output level of the buck-boost switched capacitor multi-level inverter is 2Vdc；
A boost mode II for controlling the switching tube S1The switch tube S4The switch tube S5The switch tube S6And the switching tube S8Are all conducted, the switch tube S2The switch tube S3And the switching tube S7All are turned off; power supply VdcFor two electrolytic capacitors C connected in parallel1、C2Charging with a charging voltage of V between two capacitorsdc(ii) a At the same time, the power supply VdcSwitching tube S through full bridge unit1、S4The output level of the buck-boost switch capacitor multi-level inverter is Vdc；
A boost mode III for controlling the switch tube S2The switch tube S4The switch tube S5The switch tubeS6And the switching tube S8Are all conducted, the switch tube S1The switch tube S3And the switching tube S7All are turned off; power supply VdcFor two electrolytic capacitors C connected in parallel1、C2Charging with a charging voltage of V between two capacitorsdcThe output level of the buck-boost switch capacitor multi-level inverter is 0;
a boost mode IV for controlling the switching tube S2The switch tube S3The switch tube S5The switch tube S6And the switching tube S8Are all conducted, the switch tube S1The switch tube S4And the switching tube S7All are turned off; power supply VdcFor two electrolytic capacitors C connected in parallel1、C2Charging with a charging voltage of V between two capacitorsdc(ii) a At the same time, the power supply VdcSwitching tube S through full bridge unit2、S3The output level of the buck-boost switch capacitor multi-level inverter is-Vdc；
A voltage boosting mode V for controlling the switching tube S2The switch tube S3And the switching tube S7Are all conducted, the switch tube S1The switch tube S4The switch tube S5The switch tube S6And the switching tube S8All are turned off; two electrolytic capacitors C1And C2Series discharge with a voltage of 2VdcThe output level of the buck-boost switched capacitor multi-level inverter is-2Vdc；
Reduced pressure mode
The buck-boost switch capacitor unit is configured to perform buck conversion on the output voltage of the direct current input power supply and output a second step voltage, and the full-bridge unit performs positive and negative polarity conversion on the second step voltage and outputs the second step voltage to a load or an alternating current power grid; the voltage reduction mode comprises five control modes, namely a voltage reduction mode I, a voltage reduction mode II, a voltage reduction mode III, a voltage reduction mode IV and a voltage reduction mode V; the five control modes of the voltage reduction mode are as follows:
a voltage reduction mode I for controlling the switch tubeS1The switch tube S4And the switching tube S5Are all conducted, the switch tube S2The switch tube S3The switch tube S6The switch tube S7And the switching tube S8All are turned off; power supply VdcTo two electrolytic capacitors C connected in series1、C2Charging with a charging voltage of V between two capacitorsdc/2, power supply VdcSwitching tube S through full bridge unit1、S4The output level of the buck-boost switch capacitor multi-level inverter is Vdc；
A voltage reduction mode II for controlling the switch tube S1The switch tube S4The switch tube S6And the switching tube S8Are all conducted, the switch tube S2The switch tube S3The switch tube S5And the switching tube S7All are turned off; two electrolytic capacitors C1、C2Parallel discharge with a voltage VdcThe output level of the buck-boost switched capacitor multi-level inverter is Vdc/2；
A voltage reduction mode III for controlling the switch tube S2The switch tube S4And the switching tube S5Are all conducted, the switch tube S1The switch tube S3The switch tube S6The switch tube S7And the switching tube S8All are turned off; power supply VdcTo two electrolytic capacitors C connected in series1、C2Charging with a charging voltage of V between two capacitorsdcThe output level of the buck-boost switching capacitor multi-level inverter is 0;
a voltage reduction mode IV for controlling the switching tube S2The switch tube S3The switch tube S6And the switching tube S8Are all conducted, the switch tube S1The switch tube S4The switch tube S5And the switching tube S7 are both turned off; two electrolytic capacitors C1、C2Parallel discharge with a voltage VdcThe output level of the buck-boost switching capacitor multi-level inverter is-Vdc/2；
A voltage reduction mode V for controlling the switching tube S2The switch tube S3And the switching tube S5Are all conducted, the switch tube S1The switch tube S4The switch tube S6The switch tube S7And the switching tube S8All are turned off; power supply VdcTo two capacitors C connected in series1、C2Charging with a charging voltage of V between two capacitorsdc2; power supply VdcSwitching tube S through full bridge unit2、S3The output level of the buck-boost switch capacitor multi-level inverter is-Vdc。
3. The modulation method according to claim 2, characterized in that: when the boost-buck switched capacitor multi-level inverter works in a boost mode, a sine modulation wave A is inputrefWith four triangular carrier waves A with the same frequency and the same amplitudec1~Ac4The signals are compared and logically combined to be used as driving signals of each switching tube; the switch tube S1To the switching tube S8The logical combination of the drive signals of (a) is:
wherein, four-way logic switch signal u1~u4By a sine-modulated wave ArefWith four triangular carrier waves A with the same frequency and the same amplitudec1~Ac4And performing comparison logic obtaining.
4. The modulation method according to claim 2, characterized in that: when the buck-boost switched capacitor multi-level inverter works in a buck mode, a sine modulation wave A is inputrefWith four triangular carrier waves A with the same frequency and the same amplitudec1~Ac4The signals are compared and logically combined to be used as driving signals of each switching tube; the switch tube S1To the switching tube S8Of (2)The logic combination of the dynamic signals is;
wherein, four-way logic switch signal u1~u4By a sine-modulated wave ArefWith four triangular carrier waves A with the same frequency and the same amplitudec1~Ac4And performing comparison logic obtaining.
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| CN111049403B (en) * | 2019-12-18 | 2022-11-01 | 南京理工大学 | Nine-level inverter of buck-boost type switched capacitor |
| CN111030490B (en) * | 2019-12-18 | 2022-11-04 | 南京理工大学 | Nine-level inverter of boost type switched capacitor |
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| CN113783449A (en) * | 2021-09-03 | 2021-12-10 | 南京理工大学 | Common-ground type double-output switch capacitance type multi-level inverter |
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