CN117977989B - Isolated single-stage buck-boost inverter and application method thereof - Google Patents
Isolated single-stage buck-boost inverter and application method thereof Download PDFInfo
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Abstract
The invention provides an isolated single-stage buck-boost inverter and a use method thereof, wherein the inverter comprises a transformer, wherein the homonymous end of an excitation inductor of the transformer is electrically connected with a source electrode of a first semiconductor switching device and a collector electrode of a third semiconductor switching device, and the homonymous end is electrically connected with the source electrode of a second semiconductor switching device and the collector electrode of a fourth semiconductor switching device; the emitter of the third semiconductor switching device and the emitter of the fourth semiconductor switching device are electrically connected with one end of the new energy power supply input end and one end of the first capacitor. The invention is not influenced by the power fluctuation of new energy, can realize stable output, realizes the electrical isolation between the power generation end and the power grid end, reduces the leakage current of the system, improves the safety and stability of the system, and has high operation efficiency.
Description
Technical Field
The invention is used in the technical field of electricity, and mainly relates to an isolated single-stage buck-boost inverter and a use method thereof.
Background
Currently, the technology of an optical storage and filling integrated system has become an important development direction in the energy field. The technology integrates the functions of solar photovoltaic power generation, energy storage and charging, and realizes the efficient utilization and sustainable development of energy.
The inverter is used as a core component of the new energy power generation system and is used for converting the energy output by the new energy power generation end and then accessing the energy into a power grid. Because the new energy power generation end is influenced by factors such as environment and the like to cause voltage fluctuation, the traditional inverter which can only work in a step-down mode cannot be directly connected with the new energy power generation end, and in order to solve the problem of voltage fluctuation of new energy power generation output in engineering, a primary DC/DC converter is usually added in front of the inverter, so that the voltage of the new energy power generation end is stabilized to a voltage range in which the inverter can normally grid-connected and output. The two-stage cascade structure increases the loss and volume of the system.
Taking photovoltaic as an example, because a larger parasitic capacitance exists between the photovoltaic panel and the earth, a new energy power generation end-earth-power grid loop is formed between the parasitic capacitance and the earth, the loop causes larger leakage current of the photovoltaic power generation system, the leakage current can lead to grid-connected current distortion, equipment shells are electrified, equipment and even personal safety can be possibly endangered when the equipment shells are serious, the leakage current of the system is reduced by isolating the power generation end from the power grid through a power frequency isolation transformer in engineering, but the power density of the system is further reduced through the power frequency transformer with heavy volume, and the system efficiency is reduced.
The structure of the conventional new energy grid-connected system is shown in fig. 3, wherein the system comprises a DC/DC converter, a DC/AC converter and a power frequency isolation transformer, and the DC/AC converter can only work in a step-down mode. In order to ensure that the grid-connected inverter can normally inject energy into a power grid, the input voltage of the DC/AC converter is required to be within a certain range, a first-stage DC/DC converter is required to be added before the DC/AC converter which can only work in a step-down mode, and meanwhile, in order to realize the isolation between a new energy end and the power grid end, a power frequency isolation transformer is required to be added between the DC/AC converter and the power grid, so that the reliability and the safety of a new energy grid-connected power generation system can be ensured, but the efficiency of the whole system is greatly reduced due to the existence of a front-stage DC/DC converter and the power frequency isolation transformer, and the system becomes bulky.
Disclosure of Invention
In order to solve the problems, the invention discloses an isolated single-stage buck-boost inverter and a use method thereof.
In order to achieve the above object, the present invention is realized by the following technical scheme:
The isolation type single-stage buck-boost inverter comprises a transformer T, wherein the homonymous end of an excitation inductance L m of the transformer T is electrically connected with a source electrode of a first semiconductor switching device S 1 and a collector electrode of a third semiconductor switching device S 3, and the heteronymous end is electrically connected with a source electrode of a second semiconductor switching device S 2 and a collector electrode of a fourth semiconductor switching device S 4; the emitter of the third semiconductor switching device S 3 and the emitter of the fourth semiconductor switching device S 4 are both electrically connected to one end of the new energy power supply input end and one end of the first capacitor C 1, and the drain of the first semiconductor switching device S 1 and the drain of the second semiconductor switching device S 2 are both electrically connected to the other end of the new energy power supply input end and the other end of the first capacitor C 1;
The same-name end of the secondary coil of the transformer T is electrically connected with the drain electrode of the fifth semiconductor switching device S 5, and the different-name end is electrically connected with the drain electrode of the sixth semiconductor switching device S 6; the source electrode of the fifth semiconductor switching device S 5 is electrically connected to one end of the energy storage capacitor C E and is electrically connected to one end of the load R L through a filter; the source of the sixth semiconductor switching device S 6 is electrically connected to the other end of the storage capacitor C E, the other end of the filter and the load R L.
Further improvements are made in that the first semiconductor switching device S 1, the second semiconductor switching device S 2, the fifth semiconductor switching device S 5 and the sixth semiconductor switching device S 6 are metal oxide semiconductor field effect transistors or insulated gate bipolar transistors.
Further improved, the third semiconductor switching device S 3 and the fourth semiconductor switching device S 4 are triodes.
Further improvements, the filter comprises an output filter inductance L o and an output filter capacitance C o; the source electrode of the fifth semiconductor switching device S 5 is electrically connected to one end of the output filter inductor L o, the other end of the output filter inductor L o is electrically connected to one end of the output filter capacitor C o and one end of the load R L, and the source electrode of the sixth semiconductor switching device S 6 is electrically connected to the other end of the output filter capacitor C o.
Further improvement, the inductance of the exciting inductanceThe value range is as follows:
; wherein/> For the maximum input voltage at the dc side of the inverter,Is maximum value of inductance current ripple,/>The switching frequency of the high-frequency tube of the inverter is d is the duty ratio of the high-frequency switching tube of the inverter, G is the gain of the inverter,/>Is load resistance value,/>Is the converter efficiency;
Capacitance value of energy storage capacitor The value range is as follows:
；
Wherein, For maximum output voltage of inverter,/>For the voltage ripple allowed across the storage capacitor,The switching frequency of the high-frequency tube of the inverter is set;
Filter cut-off frequency The range is as follows:
Wherein, Output frequency for the inverter;
The value range of the capacitance C of the output filter capacitor:
For minimum value of output filter inductance, Q is the quality factor of the inverter filter network,/> The maximum value of the filter inductance is output.
The application method of the isolated single-stage buck-boost inverter comprises the following steps of:
The isolated single-stage buck-boost inverter works in a DCM mode, the working modes are divided into six in one single-phase alternating current output period, and the working modes are a mode 4, a mode 5 and a mode 6 in sequence when the output voltage is in a positive half-wave; when the negative half wave of the output voltage is output, the working modes are a mode 1, a mode 2 and a mode 3 in sequence; the positive half-wave and the negative half-wave of the output voltage symmetrically run, the switching frequency of the first semiconductor switching device S 1 and the second semiconductor switching device S 2 is f sw, the switching period is T sw, the switching signals of the fifth semiconductor switching device S 5 and the third semiconductor switching device S 3 are the same, the switching signals of the fourth semiconductor switching device S 4 and the sixth semiconductor switching device S 6 are the same, the first semiconductor switching device S 1, the second semiconductor switching device S 2, The third semiconductor switching device S 3, the fourth semiconductor switching device S 4, the fifth semiconductor switching device S 5, and the sixth semiconductor switching device S 6 have a duty ratio d, d being greater than 0 and less than 1, and the mode 1 and mode 4 operation sections are dT sw, and then the sum of the mode 2, mode 3, mode 5, and mode 6 operation sections is 1-dT sw .
When the inverter is operating in mode 1: the first semiconductor switching device S 1, the fourth semiconductor switching device S 4 and the sixth semiconductor switching device S 6 are conducted, the second semiconductor switching device S 2, the third semiconductor switching device S 3 and the fifth semiconductor switching device S 5 are turned off, an input power supply charges exciting inductance L m through the first semiconductor switching device S 1 and the fourth semiconductor switching device S 4, at this time, the exciting inductance L m stores energy, and energy stored by an energy storage capacitor C E supplies power to load R L through a low-pass filter consisting of an output filter inductance L o and an output filter capacitor C o;
When the inverter is operating in mode 2: the fourth semiconductor switching device S 4, the fifth semiconductor switching device S 5, and the sixth semiconductor switching device S 6 are turned on, and the first semiconductor switching device S 1, the second semiconductor switching device S 2, and the third semiconductor switching device S 3 are turned off; the energy stored by the excitation inductor L m passes through the transformer T, the fifth semiconductor switching device S 5 and the sixth semiconductor switching device S 6, the energy storage capacitor C E, the filter formed by the output filter inductor L o and the output filter capacitor C o supplies power to the load R L, and the voltage of the secondary side port of the transformer is opposite to that of the primary side transformer port;
When the inverter is operating in mode 3: in the case of mode 2, when the energy stored in the exciting inductance L m is completely released, the fourth semiconductor switching device S 4 and the fifth semiconductor switching device S 5 are turned on, the switching device first semiconductor switching device S 1, the second semiconductor switching device S 2 and the third semiconductor switching device S 3 and the sixth semiconductor switching device S 6 are turned off, the converter is switched from mode 2 to mode 3, and the energy stored in the energy storage capacitor C E is supplied to the load R L through the low-pass filter consisting of the output filter inductance L o and the output filter capacitor C o.
Further improvement, the inverter is operated in mode 4: the second semiconductor switching device S 2, the third semiconductor switching device S 3 and the fifth semiconductor switching device S 5 are turned on, the first semiconductor switching device S 1, the fourth semiconductor switching device S 4 and the sixth semiconductor switching device S 6 are turned off, an input power supply charges the exciting inductance L m through the second semiconductor switching device S 2 and the third semiconductor switching device S 3, at this time, the exciting inductance L m stores energy, and the energy stored by the energy storage capacitor C E supplies power to the load R L through a low-pass filter consisting of an output filter inductance L o and an output filter capacitor C o;
When the inverter is operating in mode 5: the third semiconductor switching device S 3, the fifth semiconductor switching device S 5 and the sixth semiconductor switching device S 6 are conducted, the first semiconductor switching device S 1, the second semiconductor switching device S 2 and the fourth semiconductor switching device S 4 are turned off, energy stored in the exciting inductor L m passes through the transformer T, the low-pass filter consisting of the fifth semiconductor switching device S 5, the sixth semiconductor switching device S 6, the energy storage capacitor C E, the output filter inductor L o and the output filter capacitor C o supplies power to the load R L, and the voltage of a secondary side port of the transformer is opposite to that of a primary side port of the transformer;
When the inverter is operating in mode 6: in the case of mode 5, when the energy stored in the excitation inductance L m is completely released, the third semiconductor switching device S 3 and the sixth semiconductor switching device S 6 are turned on, the first semiconductor switching device S 1, the second semiconductor switching device S 2, the fourth semiconductor switching device S 4 and the fifth semiconductor switching device S 5 are turned off, the converter is switched from mode 5 to mode 6, the energy stored in the excitation inductance L m is completely released, and the energy stored in the energy storage capacitor C E supplies power to the load R L through a low-pass filter composed of the output filter inductance L o and the output filter capacitor C o.
Compared with the prior art, the method has the following advantages:
The inverter has the functions of isolation and buck-boost, photovoltaic output can be directly connected into the inverter, a primary DC/DC converter is not required to be additionally added, energy emitted by new energy is directly connected into an alternating current power grid after high-frequency isolation of the buck-boost converter, an intermediate DC/DC converter and a power frequency isolation transformer with heavy volume are omitted, the structure of a new energy power generation grid-connected system is simplified, the output of the inverter is not influenced by power fluctuation of the new energy, stable output can be realized, the electrical isolation between a power generation end and a power grid end is realized, leakage current of the system is reduced, the safety and stability of the system are improved, and the operation efficiency of the system is high.
Drawings
Fig. 1 is a topological structure diagram of an isolated single-stage buck-boost inverter according to the present invention;
fig. 2 is a schematic diagram of an isolated single-stage buck-boost inverter modulation strategy according to the present invention;
FIG. 3 is a block diagram of a conventional new energy grid-connected inverter;
fig. 4a is a schematic diagram of an operation mode of the inverter in mode 1 according to the present invention;
fig. 4b is a schematic diagram of an operation mode of the inverter in mode 2 according to the present invention;
fig. 4c is a schematic diagram of an operation mode of the inverter in mode 3 according to the present invention;
fig. 4d is a schematic diagram of an operation mode of the inverter in mode 4 according to the present invention;
fig. 4e is a schematic diagram of an operation mode of the inverter in mode 5 according to the present invention;
fig. 4f is a schematic diagram of an operation mode of the inverter in mode 6 according to the present invention;
FIG. 5 is a schematic diagram of an isolated single-stage buck-boost inverter according to the present invention without regard to the gain of the transformer ratio as a function of the duty cycle;
fig. 6 is a waveform diagram showing the stability of the output of the proposed isolated single-stage buck-boost inverter with the change of the input voltage.
Detailed Description
The invention will now be described in further detail with reference to the drawings and to specific embodiments.
As shown in fig. 1, the isolated single-stage buck-boost inverter provided by the invention comprises a direct-current side four-switch circuit, a high-frequency isolation transformer, an alternating-current side two-switch circuit and an alternating-current side filter circuit. The isolated single-stage buck-boost inverter is used for directly integrating the energy output by the new energy source into an alternating current power grid without adding additional conversion and electrical isolation.
As shown in fig. 2, the isolated single-stage buck-boost inverter in the embodiment of the invention is formed by a switching device S 1、S2、S3、S4、S5、S6 ,(S3、S4, a transformer T (primary side excitation inductance of the transformer is L m, primary-secondary side turn ratio is 1: n), an energy storage capacitor C E, an output filter capacitor C o, and an output filter inductance L o, wherein the input end of the proposed isolated single-stage buck-boost inverter is directly connected with a new energy power generation end, the switching devices S 1、S2 and S 3、S4 form two half-bridge circuits, the primary side ends of the transformer T are respectively connected with the midpoints of the two half-bridge circuits, the drain electrode of the switching device S 5、S6 is respectively connected with the secondary side ends of the transformer T, the source electrode of the switching device S 5、S6 is respectively connected with the two ends of the energy storage capacitor C E, the output filter inductance L o and the output filter capacitor C o form a low-pass filter, the input end of the low-pass filter is connected with the energy storage capacitor C E, and the output end of the low-pass filter is connected with a load R L.
The topology control method of the isolated single-stage buck-boost inverter provided in the embodiment mainly comprises the following steps:
The sine wave modulation strategy of the output voltage U o of the isolated single-stage buck-boost inverter is shown in fig. 3, the inverter works in a DCM mode, the working modes are divided into six in one single-phase alternating current output period, and the working modes are a mode 4, a mode 5 and a mode 6 when the output voltage is in a positive half wave. And when the output voltage is in a negative half-wave, the working modes are mode 1, mode 2 and mode 3. The positive half wave and the negative half wave of the output voltage symmetrically operate, the switching frequency of the high-frequency switching device S 1、S2 is defined as f sw, the switching period is T sw,S5 and the switching signal of S 3 are the same, and the switching signals of S 4 and S 6 are the same. The switching device duty cycle is defined as d, d being greater than 0 and less than 1. And the working intervals of the mode 1 and the mode 4 are dT sw, and the working intervals of the mode 2, the mode 3 and the mode 5, the mode 6 are (1-d) T sw .
Mode 1: as shown in fig. 4a, the switching device S 1、S4、S6 is turned on, the switching device S 2、S3、S5 is turned off, the input power supply charges the exciting inductor L m through S 1、S4, at this time, the exciting inductor L m stores energy, and the energy stored in the energy storage capacitor C E supplies power to the load RL through the low-pass filter composed of the output filter inductor L o and the output filter capacitor C o.
Mode 2: as shown in fig. 4b, switching device S 4、S5、S6 is on and switching device S 1、S2、S3 is off. The energy stored in the excitation inductance L m is supplied to the load RL through a filter consisting of the transformer T, the switching device S 5、S6, the energy storage capacitor C E,Lo and the energy storage capacitor C o, and the voltage of the secondary side port of the transformer is opposite to that of the primary side transformer.
Mode 3: as shown in fig. 4c, switching device S 4、S5 is on and switching device S 1、S2、S3、S6 is off. The energy stored in the exciting inductance L m is completely released, the converter works in the DCM mode, and the energy stored in the energy storage capacitor C E is used for supplying power to the load RL through a low-pass filter consisting of the output filter inductance L o and the output filter capacitor C o.
Mode 4: as shown in fig. 4d, the switching device S 2、S3、S5 is turned on, the switching device S 1、S4、S6 is turned off, the input power supply charges the exciting inductor L m through S 2、S3, at this time, the exciting inductor L m stores energy, and the energy stored in the energy storage capacitor C E supplies power to the load RL through the low-pass filter composed of the output filter inductor L o and the output filter capacitor C o.
Mode 5: as shown in fig. 4e, switching device S 3、S5、S6 is on and switching device S 1、S2、S4 is off. The energy stored in the excitation inductance L m is supplied to the load RL through a filter consisting of the transformer T, the switching device S 5、S6, the energy storage capacitor C E,Lo and the energy storage capacitor C o, and the voltage of the secondary side port of the transformer is opposite to that of the primary side transformer.
Mode 6: as shown in fig. 4f, switching device S 3、S6 is on and switching device S 1、S2、S4、S5 is off. The energy stored in the exciting inductance L m is completely released, the converter works in the DCM mode, and the energy stored in the energy storage capacitor C E is used for supplying power to the load RL through a low-pass filter consisting of the output filter inductance L o and the output filter capacitor C o.
According to the sine wave modulation strategy of the output voltage U o of the isolated type liftable single-stage switching power amplifier, in the dT sw interval of the mode 1 and the mode 4, the transformer excitation inductance L m stores energy, and the energy stored by the inductance is stored in the conduction timeThe method comprises the following steps:
(1)
In dT sw section of mode 1 and mode 4, the energy storage inductor ripple current The method comprises the following steps:
(2)
In the (1-d) T sw interval of mode 2 plus mode 3 and mode 5 plus mode 6, the load resistance is Power output by inverter/>The method comprises the following steps:
(3)
During steady state operation of the inverter, the energy output by the converter is equal to the input energy multiplied by the converter operating efficiency:
(4)
the Gain of the proposed inverter can be obtained according to equations (1) (2) (3) (4) as:
(5)
Wherein, The switching frequency of the high-frequency tube of the inverter is d is the duty ratio of the high-frequency switching tube of the inverter,/>For the converter efficiency,/>Is the excitation inductance value.
Under the condition that only the gain of the converter is considered and the transformation ratio of the transformer is not considered, the derived converter gain formula can know that the gain of the converter is mainly influenced by the ratio of the load to the energy storage inductance, and the formula 5 can know that the condition that the inverter can realize the buck-boost conversion is as follows:
(6)
According to the condition of formula 6, the gain curves of the converter under different load conditions are plotted, wherein R1> R2> R3. According to the gain curve, the voltage-boosting and voltage-boosting output of the inverter can be realized by reasonably designing the size of the excitation inductance of the transformer.
The parameter calculation of the isolated single-stage buck-boost inverter provided by the invention comprises the following steps: the related parameter calculation method of the isolated single-stage step-up and step-down inverter transformer excitation inductance L m, the energy storage capacitor C E, the output filter inductance L o and the output filter capacitor C o.
Setting the maximum ripple current allowed by the inductance of the excitation inductance L m of the isolated single-stage buck-boost inverter transformer asThe duty cycle/>, when the converter is operating in DCM, can be obtained according to equation 5Is the maximum point/>, of the inductance current ripple：
(7)
As can be obtained from equation 7, the inductor current at the energy storage inductor L m allows the ripple to beThe selection value range of the energy storage inductor is as follows:
(8)
setting the expected gain of the isolated single-stage buck-boost inverter as G, and obtaining according to a formula (5):
(9)
the inductance value ranges obtained according to the formulas (8) and (9) are as follows:
Inductance of excitation inductance The value range is as follows:
(10) ; wherein/> For maximum input voltage of DC end of inverter,/>Is maximum value of inductance current ripple,/>The switching frequency of the high-frequency tube of the inverter is d is the duty ratio of the high-frequency switching tube of the inverter, G is the gain of the inverter,/>Is load resistance value,/>Is the converter efficiency;
setting the allowable ripple wave of the voltage at two ends of the output filter capacitor C f of the isolated single-stage buck-boost inverter as Load is/>. The voltage calculation formula according to the capacity is as follows:
(11)
The duty cycle of the converter when operating in DCM mode is obtained according to equation 10 Is the maximum point of the ripple of the capacitor voltage:
(12)
As can be obtained from equation 9, the voltage across the storage capacitor C E allows ripple to be The selection value range of the energy storage capacitor is as follows:
(13)
Wherein, For maximum output voltage of inverter,/>Voltage ripple allowed for both ends of energy storage capacitor,/>The switching frequency of the high-frequency tube of the inverter.
Grid-connected inverter needs to consider grid-connected current harmonic wave, in order to filter switching times in output waveform of the proposed isolated single-stage buck-boost inverterThe filter cut-off frequency should be greater than 10 times the output frequency and less than/>/>I.e. filter cut-off frequency/>The range is as follows:
(14)
Wherein, Output frequency for the inverter;
the transfer function of the low-pass filter consisting of LC is as follows:
(15)
wherein C is the capacitance of the filter output filter capacitor, L is the inductance of the filter output filter inductor, Is the load resistance;
the filter quality factor is:
(16)
The filter turning frequency is:
(17)
According to the filter frequency design range and the selected filter quality factor Q and the filter turning frequency When the gain of the converter to a certain frequency component is g (0 < g < 1), filtering to the frequency component is realized, and the output filter inductance parameter range can be obtained by formulas (14), (15), (16) and (17):
(18)
The range of the output filter inductance can be obtained according to the formula 18, and the maximum value of the output filter inductance can be obtained Minimum/>And the selected Q value can determine the value range of the output filter capacitor:
(19)
as shown in FIG. 6, simulation results show that the isolated single-stage buck-boost inverter and the control method thereof provided by the invention have the buck capacity when the input power supply voltage changes, and can realize stable voltage output when the input power supply voltage fluctuates.
The foregoing is merely a specific guiding embodiment of the present invention, but the design concept of the present invention is not limited thereto, and any insubstantial modification of the present invention by using the concept should be construed as infringement of the protection scope of the present invention.
Claims (6)
1. The isolation type single-stage buck-boost inverter is characterized by comprising a transformer (T), wherein the homonymous end of an excitation inductor (L m) of the transformer (T) is electrically connected with a source electrode of a first semiconductor switching device (S 1) and a collector electrode of a third semiconductor switching device (S 3), and the heteronymous end is electrically connected with a source electrode of a second semiconductor switching device (S 2) and a collector electrode of a fourth semiconductor switching device (S 4); the emitter of the third semiconductor switching device (S 3) and the emitter of the fourth semiconductor switching device (S 4) are electrically connected with one end of the new energy power supply input end and one end of the first capacitor (C 1), and the drain of the first semiconductor switching device (S 1) and the drain of the second semiconductor switching device (S 2) are electrically connected with the other end of the new energy power supply input end and the other end of the first capacitor (C 1);
The same-name end of the secondary coil of the transformer (T) is electrically connected with the drain electrode of the fifth semiconductor switching device (S5), and the different-name end is electrically connected with the drain electrode of the sixth semiconductor switching device (S6); a source electrode of the fifth semiconductor switching device (S5) is electrically connected with one end of the energy storage Capacitor (CE) and is electrically connected with one end of the load (RL) through the filter; a source electrode of the sixth semiconductor switching device (S6) is electrically connected with the other end of the energy storage Capacitor (CE), the other end of the filter and the load (RL);
Inductance of the excitation inductance The value range is as follows:
wherein/> For maximum input voltage of DC end of inverter,/>Is maximum value of inductance current ripple,/>The switching frequency of the high-frequency tube of the inverter is d is the duty ratio of the high-frequency switching tube of the inverter, G is the gain of the inverter,/>Is load resistance value,/>Is the converter efficiency;
Capacitance value of energy storage capacitor The value range is as follows:
；
Wherein, For maximum output voltage of inverter,/>Voltage ripple allowed for both ends of energy storage capacitor,/>The switching frequency of the high-frequency tube of the inverter is set;
Filter cut-off frequency The range is as follows:
；
Wherein, Output frequency for the inverter;
The value range of the capacitance C of the output filter capacitor:
；
For minimum value of output filter inductance, Q is the quality factor of the inverter filter network,/> The maximum value of the filter inductance is output.
2. The isolated single-stage buck-boost inverter of claim 1, wherein the first semiconductor switching device (S 1), the second semiconductor switching device (S 2), the fifth semiconductor switching device (S 5), and the sixth semiconductor switching device (S 6) are metal oxide semiconductor field effect transistors or insulated gate bipolar transistors.
3. The isolated single-stage buck-boost inverter of claim 1, wherein the third semiconductor switching device (S 3) and the fourth semiconductor switching device (S 4) are transistors.
4. The isolated single-stage buck-boost inverter of claim 1, wherein the filter includes an output filter inductance (Lo) and an output filter capacitance (Co); the source electrode of the fifth semiconductor switching device (S5) is electrically connected with one end of an output filter inductance (Lo), the other end of the output filter inductance (Lo) is electrically connected with one end of an output filter capacitance (Co) and one end of a load (RL), and the source electrode of the sixth semiconductor switching device (S6) is electrically connected with the other end of the output filter capacitance (Co).
5. A method of using an isolated single-stage buck-boost inverter, the isolated single-stage buck-boost inverter as claimed in any one of claims 1 to 4, comprising the steps of:
The isolated single-stage buck-boost inverter works in a DCM mode, and in a single-phase alternating-current output period, the working modes are divided into six types, and when the output voltage is in a positive half-wave state, the working modes are a mode 4, a mode 5 and a mode 6 in sequence; when the negative half wave of the output voltage is output, the working modes are a mode 1, a mode 2 and a mode 3 in sequence; the positive half-wave and the negative half-wave of the output voltage are symmetrically operated, the switching frequency of the first semiconductor switching device (S1) and the second semiconductor switching device (S2) is fsw, the switching period is Tsw, the switching signals of the fifth semiconductor switching device (S5) and the third semiconductor switching device (S3) are the same, the switching signals of the fourth semiconductor switching device (S4) and the sixth semiconductor switching device (S6) are the same, the duty ratio of the first semiconductor switching device (S1), the second semiconductor switching device (S2), the third semiconductor switching device (S3), the fourth semiconductor switching device (S4), the fifth semiconductor switching device (S5) and the sixth semiconductor switching device (S6) is d, d is more than 0 and less than 1, the operating interval of the mode 1 and the mode 4 is dTsw, and the sum of the operating intervals of the mode 2, the mode 3, the mode 5 and the mode 6 is (1-d) Tsw;
When the inverter is operating in mode 1: the first semiconductor switching device (S1), the fourth semiconductor switching device (S4) and the sixth semiconductor switching device (S6) are turned on, the second semiconductor switching device (S2), the third semiconductor switching device (S3) and the fifth semiconductor switching device (S5) are turned off, an input power supply charges an excitation inductor (Lm) through the first semiconductor switching device (S1) and the fourth semiconductor switching device (S4), at this time, the excitation inductor (Lm) stores energy, and the energy stored by the energy storage Capacitor (CE) supplies power to a load (RL) through a low-pass filter consisting of an output filter inductor (Lo) and an output filter capacitor (Co);
When the inverter is operating in mode 2: the fourth semiconductor switching device (S4), the fifth semiconductor switching device (S5) and the sixth semiconductor switching device (S6) are turned on, and the first semiconductor switching device (S1), the second semiconductor switching device (S2) and the third semiconductor switching device (S3) are turned off; the energy stored by the excitation inductor (Lm) is supplied to a load (RL) through a filter consisting of a transformer (T), a fifth semiconductor switching device (S5) and a sixth semiconductor switching device (S6), an energy storage Capacitor (CE), an output filter inductor (Lo) and an output filter capacitor (Co), and the voltage of the secondary side port of the transformer is opposite to the voltage of the primary side transformer port;
When the inverter is operating in mode 3: in the case of mode 2, when the energy stored in the excitation inductance (Lm) is completely released, the fourth semiconductor switching device (S4) and the fifth semiconductor switching device (S5) are turned on, the switching devices first semiconductor switching device (S1), the second semiconductor switching device (S2), the third semiconductor switching device (S3) and the sixth semiconductor switching device (S6) are turned off, the converter is switched from mode 2 to mode 3, and the energy stored in the energy storage Capacitor (CE) is supplied to the load (RL) through the low-pass filter consisting of the output filter inductance (Lo) and the output filter capacitance (Co).
6. The method of claim 5, wherein,
When the inverter is operated in mode 4: the second semiconductor switching device (S2), the third semiconductor switching device (S3) and the fifth semiconductor switching device (S5) are turned on, the first semiconductor switching device (S1), the fourth semiconductor switching device (S4) and the sixth semiconductor switching device (S6) are turned off, an input power supply charges an excitation inductor (Lm) through the second semiconductor switching device (S2) and the third semiconductor switching device (S3), at the moment, the excitation inductor (Lm) stores energy, and the energy stored by the energy storage Capacitor (CE) supplies power to a load (RL) through a low-pass filter consisting of an output filter inductor (Lo) and an output filter capacitor (Co);
When the inverter is operating in mode 5: the third semiconductor switching device (S3), the fifth semiconductor switching device (S5) and the sixth semiconductor switching device (S6) are turned on, the first semiconductor switching device (S1), the second semiconductor switching device (S2) and the fourth semiconductor switching device (S4) are turned off, energy stored by the excitation inductor (Lm) passes through the transformer (T), and a low-pass filter consisting of the fifth semiconductor switching device (S5), the sixth semiconductor switching device (S6), the energy storage Capacitor (CE), the output filter inductor (Lo) and the output filter capacitor (Co) supplies power to the load (RL), and the secondary port voltage of the transformer is opposite to the primary port voltage of the transformer;
When the inverter is operating in mode 6: in the case of mode 5, when the energy stored in the excitation inductance (Lm) is completely released, the third semiconductor switching device (S3) and the sixth semiconductor switching device (S6) are turned on, the first semiconductor switching device (S1), the second semiconductor switching device (S2), the fourth semiconductor switching device (S4), and the fifth semiconductor switching device (S5) are turned off, the converter is switched from mode 5 to mode 6, the energy stored in the excitation inductance (Lm) is completely released, and the energy stored in the energy storage Capacitance (CE) supplies power to the load (RL) through the low-pass filter composed of the output filter inductance (Lo) and the output filter capacitance (Co).
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