CN116683786A - Single-phase five-level grid-connected inverter and active power decoupling control strategy - Google Patents

Single-phase five-level grid-connected inverter and active power decoupling control strategy Download PDF

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Publication number
CN116683786A
CN116683786A CN202310664281.XA CN202310664281A CN116683786A CN 116683786 A CN116683786 A CN 116683786A CN 202310664281 A CN202310664281 A CN 202310664281A CN 116683786 A CN116683786 A CN 116683786A
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bridge arm
circuit
phase
switch tube
bridge
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CN116683786B (en
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郭斌
张欣
马皓
葛小海
金思聪
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Zhejiang University ZJU
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Zhejiang University ZJU
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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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for AC mains or AC distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy

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

Abstract

The invention discloses a single-phase five-level grid-connected inverter which comprises an input direct current source, a first half-bridge boosting circuit, a bus capacitor, a second half-bridge circuit, an H-bridge inverter circuit and a filter circuit, wherein the second half-bridge circuit and the H-bridge inverter circuit form a five-level inverter circuit, and are connected with a power grid to realize grid connection; the direct current source, the first half-bridge boosting circuit and the bus capacitor form a boosting and decoupling circuit. The invention also provides an active power decoupling control strategy. According to the invention, through designing the controllers of the inverter circuit part and the booster circuit part, the power decoupling of the five-level inverter can be automatically realized, and the topology and the control strategy of the five-level inverter realize the multi-level output and boosting, and meanwhile realize the active power decoupling, so that the DC bus capacitance of the inverter can be reduced, and the reliability of the system is improved.

Description

Single-phase five-level grid-connected inverter and active power decoupling control strategy
Technical Field
The invention relates to the technical field of power electronics, in particular to a single-phase five-level grid-connected inverter and a power decoupling control strategy.
Background
With the development of new energy power generation such as photovoltaic, wind energy, energy storage and the like, the generation becomes a focus of attention in the whole society. The inverter is used as an important component of a photovoltaic, energy storage and wind power generation system, and plays a vital role in high-efficiency utilization and reliable conversion of new energy.
With the development of power electronics technology, inverters are being developed to have higher efficiency and higher power density. Compared with the traditional two-level inverter, the multi-level inverter has the advantages of small voltage stress, low grid-connected current harmonic wave, small filter inductance and the like, and is widely applied to inversion occasions such as photovoltaic power generation, vehicle grid (V2G) and the like. However, conventional multilevel inverters (such as neutral point clamped type, flying capacitor type, cascaded H-bridge type multilevel inverters) require a large number of components and do not have a boosting function.
Patent document CN 109742966A discloses a single-phase grid-connected fifteen-level inverter topology structure based on a switched capacitor, the topology structure utilizes three capacitors, two reverse blocking switching tubes, four bidirectional switching tubes and eight unidirectional switching tubes to form the single-phase grid-connected fifteen-level inverter topology structure, the negative electrode of a direct current power supply is directly connected to a neutral point of a power grid, a stable common mode voltage is obtained, and accordingly leakage current output is reduced.
Patent document CN108141147a discloses a high voltage gain five-level inverter topology circuit including a converter leg, an inverter circuit, and a controller. The positive input port of the inverter circuit is connected with the positive input port of the multi-level inverter, the negative input port of the inverter circuit is connected with the negative input port of the multi-level inverter, and the output end of the inverter circuit is connected with the positive output port of the multi-level inverter. The converter bridge arm comprises an upper half bridge arm and a lower half bridge arm, and the midpoint of the bridge arm is connected with the negative output port of the multi-level inverter.
Furthermore, in a single-phase inverter system, the system-inherent double frequency power ripple will affect the grid-tied current power quality. In order to buffer the double frequency power ripple, a larger electrolytic capacitor is usually required to be incorporated on the direct current bus side or an active decoupling circuit is additionally added, but the system cost is increased and the system efficiency is reduced.
Disclosure of Invention
The invention aims to realize multi-level output and boosting functions of an inverter, reduce the cost of a system and improve the reliability of the system.
In order to achieve the above purpose, the embodiment of the invention provides a single-phase five-level grid-connected inverter and an active power decoupling control strategy thereof, and the specific technical scheme is as follows:
in a first aspect, an embodiment of the present invention provides a single-phase five-level grid-connected inverter, where the topology includes an input dc source, a first half-bridge boost circuit, a bus capacitor, a second half-bridge circuit, an H-bridge circuit, and a filter circuit.
The H-bridge circuit comprises a first half-bridge reversing circuit and a second half-bridge reversing circuit, the first half-bridge reversing circuit comprises a first upper bridge arm switching tube and a first lower bridge arm switching tube, the middle point of the first half-bridge reversing circuit is connected with one end of the filter circuit, and the other end of the filter circuit is connected with the positive electrode of the power grid.
The second half-bridge reversing circuit comprises a second upper bridge arm switching tube and a second lower bridge arm switching tube, and the midpoint of the second half-bridge reversing circuit is connected with the negative electrode of the power grid.
The first half-bridge boosting circuit comprises a third upper bridge arm switch tube and a third lower bridge arm switch tube, wherein the collector electrode of the third upper bridge arm switch tube is connected with the positive electrode of the bus capacitor, the emitter electrode of the third upper bridge arm switch tube is connected with the collector electrode of the third lower bridge arm switch tube, the connection point of the collector electrode of the third lower bridge arm switch tube is the midpoint of the first half-bridge boosting circuit, meanwhile, the midpoint is connected with one end of a direct current filter inductor, and the other end of the direct current filter inductor is connected with the positive electrode of an input direct current source; and the emitter of the third lower bridge arm switch tube is connected with the negative electrode of the bus capacitor and the negative electrode of the input direct current source.
The second half-bridge circuit comprises a fourth upper bridge arm switch tube and a fourth lower bridge arm switch tube, the collector electrode of the fourth upper bridge arm switch tube is connected with the collector electrode of the third upper bridge arm switch tube and the positive electrode of the bus capacitor, the emitter electrode of the fourth upper bridge arm switch tube is connected with the collector electrode of the fourth lower bridge arm switch tube, the connection point of the collector electrode of the fourth lower bridge arm switch tube is the midpoint of the second half-bridge circuit, and the midpoint is connected with the upper end of the H bridge; and the emitter of the fourth lower bridge arm switch tube is connected with the anode of the input direct current source.
The single-phase five-level inverter topology can output five levels in a power frequency period, and specifically comprises the following steps:
when the first upper bridge arm switch tube is conducted, the second upper bridge arm switch tube or the first lower bridge arm switch tube is conducted, the second lower bridge arm switch tube is conducted, and meanwhile other switch tubes are all turned off, the output voltage of the single-phase five-level grid-connected inverter is 0.
When the fourth lower bridge arm switching tube is turned on, the first upper bridge arm switching tube and the second lower bridge arm switching tube are turned off, and meanwhile, the output voltage of the single-phase five-level grid-connected inverter is the direct current input voltage.
When the fourth upper bridge arm switching tube is turned on, the first upper bridge arm switching tube and the second lower bridge arm switching tube are turned off, and meanwhile, the output voltage of the single-phase five-level grid-connected inverter is the bus voltage.
When the fourth lower bridge arm switching tube is conducted, the first lower bridge arm switching tube and the second upper bridge arm switching tube are turned off, and meanwhile, the output voltage of the single-phase five-level grid-connected inverter is negative direct current input voltage.
When the fourth upper bridge arm switching tube is conducted, the first lower bridge arm switching tube and the second upper bridge arm switching tube are turned off, and meanwhile, the other switching tubes are turned off, and then the output voltage of the single-phase five-level grid-connected inverter is negative bus voltage.
In a second aspect, an embodiment of the present invention provides an active power decoupling control strategy, which is applied to the single-phase five-level grid-connected inverter in the first aspect, where the control method includes:
the inverting function is completed by the second half-bridge circuit and the H-bridge circuit together, and the boosting and active power decoupling functions are completed by the first half-bridge boosting circuit and the input filter inductor.
The control implementation steps of the inversion function are as follows:
and 11, setting the reference voltage of the bus capacitor to be constant, differencing the reference voltage and the feedback voltage processed by the frequency doubling trap, inputting the differenced value into a voltage outer loop controller, and outputting the voltage outer loop controller as the amplitude value of the current inner loop reference.
And step 12, multiplying the current reference amplitude value by the cosine value of the locking angle of the phase-locked loop to obtain a current loop reference, and sending the current loop reference and the grid-connected feedback current into a current loop controller after the current loop reference is differenced.
And 13, outputting the modulated wave as a modulated wave by the current loop controller, comparing the modulated wave with a laminated carrier or a phase-shifted carrier, and generating a pulse width modulated wave to drive each bridge arm switching tube in the second half-bridge circuit and the H-bridge circuit to execute switching action.
The control implementation steps of the boosting and active power decoupling function are as follows:
step 21, setting a reference voltage at the input side of the first half-bridge booster circuit, feeding the reference voltage and the feedback voltage into a voltage ring controller after the difference, and taking the output of the voltage ring controller as a current ring reference.
Step 22, the current reference and the feedback current are fed into a current loop controller after being differenced, and the current loop controller outputs the current as a modulation wave.
And step 23, comparing the modulated wave with the carrier wave to generate a pulse width modulated wave to drive the third upper bridge arm switching tube and the third lower bridge arm switching tube to execute switching action.
Further, the voltage loop and the current loop controllers in step 21 and step 22 are controllers with harmonic suppression capability, so as to realize power decoupling of the direct current source input side and the inversion output side.
The controller comprises a multi-resonance controller, a repetition controller and a sliding mode controller.
The scheme of the invention has the following beneficial effects:
1. the inverter topology provided by the invention can realize the boosting and five-level output functions only by eight bidirectional switches, and reduces the use of switching devices while realizing the multifunction of the inverter, thereby reducing the system cost;
2. the problem of neutral point voltage balance on the side of the direct current bus is solved, and the control difficulty is reduced.
3. The active power decoupling control strategy provided by the invention can realize the natural decoupling of the power of the system without an additional hardware circuit, so that the capacitance value of the required direct current bus is smaller, and a thin film capacitor can be used for replacing a heavy electrolytic capacitor, thereby improving the reliability and the power density of the system.
Drawings
Fig. 1 is a topology structure diagram of a single-phase five-level grid-connected inverter provided in this embodiment;
fig. 2 is a modulation chart of the single-phase five-level grid-connected inverter provided in the present embodiment;
fig. 3 is a working schematic diagram of the single-phase five-level grid-connected inverter provided in the present embodiment;
fig. 4 is a schematic flow chart of an active power decoupling control strategy according to the present embodiment;
FIG. 5 is a diagram of a dynamic and steady simulation waveform provided in this embodiment;
in the figure, 1, a first half-bridge boosting circuit; 2. a second half-bridge circuit; 3. an H-bridge circuit; 4. a filter circuit.
Detailed Description
In order to make the technical problems, technical solutions and advantages to be solved more apparent, the following detailed description will be given with reference to the accompanying drawings and specific embodiments.
As shown in FIG. 1, the single-phase five-level photovoltaic grid-connected inverter comprises an input power supply and a bus capacitor C dc A first half-bridge boosting circuit 1, a second half-bridge circuit 2, an H-bridge circuit 3 and a filter circuit 4.
Wherein the H-bridge circuit 3 comprises a first halfA bridge commutation circuit and a second half-bridge commutation circuit, the first half-bridge commutation circuit comprising a first upper bridge arm switching tube S 1 And a first lower bridge arm switch tube S 2 The midpoint a of the first half-bridge reversing circuit is connected with one end of the filter circuit 4, and the other end of the filter circuit 4 is connected with the positive electrode of the power grid.
The second half-bridge reversing circuit comprises a second upper bridge arm switch tube S 3 And a second lower bridge arm switch tube S 4 The midpoint b of the second half-bridge commutation circuit is connected to the negative pole of the power grid.
The first half-bridge boost circuit 1 comprises a third upper bridge arm switch tube S 5 And a third lower bridge arm switch tube S 6 The third upper bridge arm switch tube S 5 Collector and bus capacitance C of (C) dc The positive electrodes are connected, and a third upper bridge arm switch tube S 5 Emitter and third lower bridge arm switch tube S 6 Is connected with the collector of the third lower bridge arm switch tube S 6 The connection point of the collector is the midpoint of the first half-bridge boosting circuit 1, and the midpoint and the direct current filter inductance L 1 One end is connected with the direct current filter inductance L 1 The other end of (2) is connected with an input direct current source C in The positive electrode is connected; third lower bridge arm switch tube S 6 Emitter and bus capacitor C of (C) dc Is input to the negative electrode C of the DC source in Are connected.
The second half-bridge circuit 2 comprises a fourth upper bridge arm switch tube S 7 And a fourth lower bridge arm switch tube S 8 The fourth upper bridge arm switch tube S 7 Collector and third upper bridge arm switching tube S 5 Collector and bus capacitor C dc The positive pole is connected with a fourth upper bridge arm switch tube S 7 Emitter and fourth lower bridge arm switch tube S 8 Is connected with the collector of the fourth lower bridge arm switch tube S 7 The connection point of the collector electrode is the midpoint of the second half-bridge circuit 2, the midpoint is connected with the upper end of the H bridge, and the fourth lower bridge arm switch tube S 8 Emitter of (2) and input DC source C in The positive electrode is connected.
The filtering circuit 4 may be an L-type filter, an LC or LCL-type filter.
It should be noted that all the switching tubes are composed of switching tubes with antiparallel diodes.
As shown in fig. 2, a modulation waveform diagram of the single-phase five-level inverter provided in this embodiment is shown.
As shown in fig. 3, the working schematic diagram of the single-phase five-level inverter provided in this embodiment is as follows:
as shown in fig. 3 (a) and (b), when the first upper arm switching tube S 1 Second upper bridge arm switch tube S 3 Switch on or first lower bridge arm switch tube S 2 Second lower bridge arm switch tube S 4 When the other switching tubes are turned on and the other switching tubes are turned off, the output voltage of the converter is 0 level. As shown in fig. 3 (c), when the fourth lower arm switching tube S 8 First upper bridge arm switch tube S 1 And a second lower bridge arm switch tube S 4 When the other switching tubes are turned off, the output voltage of the converter is V in . As shown in fig. 3 (d), when the fourth lower arm switching tube S 8 First lower bridge arm switch tube S 2 And a second upper bridge arm switch tube S 3 When the other switching tubes are turned off, the output voltage of the converter is-V in . As shown in fig. 3 (e), when the fourth upper arm switching tube S 7 First upper bridge arm switch tube S 1 And a second lower bridge arm switch tube S 4 When the other switching tubes are turned off, the output voltage of the converter is V dc . As shown in fig. 3 (f), when the fourth upper arm switching tube S 7 First lower bridge arm switch tube S 2 And a second upper bridge arm switch tube S 3 When the other switching tubes are turned off, the output voltage of the converter is-V dc 。
Based on the single-phase five-level inverter provided by the embodiment of the invention, the embodiment of the invention provides an active power decoupling control strategy for the circuit, and a control structure schematic diagram of the active power decoupling control strategy is shown in fig. 4. Wherein, the control of the system comprises an inversion part and a boost decoupling circuit part.
The control implementation steps of the inversion part are as follows:
step 11: setting the voltage reference of the bus capacitor to be V dcref The reference voltage of the bus capacitor is connected with the voltage of the second harmonic trap G noth (s) differencing the processed feedback voltages, and outputting the differenced valueVoltage input outer loop controller G iv (s) the voltage loop controller outputs the amplitude I as a current inner loop reference m The method comprises the steps of carrying out a first treatment on the surface of the Wherein the transfer function of the frequency doubling trap is:
where ζ is the bandwidth coefficient, ω n ＝4πf 0 For fundamental angular frequency, f 0 And s is a frequency domain operator and is the fundamental frequency.
Step 12: current reference amplitude I m Multiplying the sine value of the locking angle of the phase-locked loop to obtain a current loop reference I gref The current loop reference and the grid-connected feedback current are fed into a current loop controller G after being differenced ii (s)。
Step 13: the current loop controller outputs as a modulated wave v ref As shown in fig. 2, the modulated wave is combined with a phase-shifted carrier or a laminated carrier v cr After comparison, PWM wave is generated to drive the switching tube S 1 ，S 2 ，S 3 ，S 4 ，S 7 And S is 8 。
It should be emphasized that the voltage loop controller in step 11 may be a proportional integral and sliding mode controller, and the current loop controller in step 12 may be a proportional resonance, repetitive control, sliding mode control, hysteresis control, etc. controller, so as to achieve high power quality current grid connection.
The control implementation steps of the boost and power decoupling part are as follows:
step 21: setting the reference voltage of the input direct current source as V inref The reference voltage and the feedback voltage are fed into a voltage loop controller G after being differenced bv (s) the voltage loop controller output is the current loop reference I Lref 。
Step 22: the current reference and the feedback current are fed into a current loop controller G after being differenced bi (s) the output of the current loop controller is a modulated wave v b 。
Step 23: as shown in fig. 2, the modulated wave is combined with a carrier wave v cr3 After comparison, PWM wave is generated to drive the switching tube S 5 And S is 6 。
It should be emphasized that the voltage loop controller G in steps 21 and 22 bv (s) and current loop controller G bi And(s) the power decoupling of the direct current source input side and the inversion output side is realized by adopting a controller with harmonic suppression capability of fundamental frequency, 2 times, 3 times, 5 times, 7 times and the like, such as multi-resonance control or repeated control or sliding mode control and the like.
In order to verify the superiority and effectiveness of the proposed topology structure and decoupling control strategy, a single-phase five-level grid-connected inverter simulation platform shown in fig. 1 is built, wherein an input direct current source is a photovoltaic cell, and system parameters are shown in the following table 1.
Table 1 system parameters
Fig. 5 (a) is a simulation waveform diagram in steady state, in which it can be seen that the input voltage contains little low frequency ripple and the grid-connected current harmonic distortion rate is low.
Fig. 5 (b) is a dynamic simulation waveform diagram of the system when the illumination is suddenly changed, and it can be seen from the diagram that the system has good dynamic performance. As can be seen from fig. 5, the inverter provided by the invention has the advantages of boosting and five-level output and simultaneously realizes good power decoupling, so that the topology and decoupling control strategy of the inverter are very suitable for photovoltaic power generation, V2G, ac/dc micro-grid and other application occasions. While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present invention, and such modifications and adaptations are intended to be comprehended within the scope of the present invention.

Claims (9)

1. The single-phase five-level grid-connected inverter is characterized by comprising an input direct current source, a first half-bridge boosting circuit, a bus capacitor, a second half-bridge circuit, an H-bridge circuit and a filter circuit;
the H-bridge circuit comprises a first half-bridge reversing circuit and a second half-bridge reversing circuit, the first half-bridge reversing circuit comprises a first upper bridge arm switching tube and a first lower bridge arm switching tube, the middle point of the first half-bridge reversing circuit is connected with one end of the filter circuit, and the other end of the filter circuit is connected with the positive electrode of the power grid;
the second half-bridge reversing circuit comprises a second upper bridge arm switching tube and a second lower bridge arm switching tube, and the midpoint of the second half-bridge reversing circuit is connected with the negative electrode of the power grid;
the first half-bridge boosting circuit comprises a third upper bridge arm switch tube and a third lower bridge arm switch tube, wherein the collector electrode of the third upper bridge arm switch tube is connected with the positive electrode of the bus capacitor, the emitter electrode of the third upper bridge arm switch tube is connected with the collector electrode of the third lower bridge arm switch tube, the connection point of the collector electrode of the third lower bridge arm switch tube is the midpoint of the first half-bridge boosting circuit, meanwhile, the midpoint is connected with one end of a direct current filter inductor, and the other end of the direct current filter inductor is connected with the positive electrode of an input direct current source; the emitter of the third lower bridge arm switch tube is connected with the negative electrode of the bus capacitor and the negative electrode of the input direct current source;
the second half-bridge circuit comprises a fourth upper bridge arm switch tube and a fourth lower bridge arm switch tube, the collector electrode of the fourth upper bridge arm switch tube is connected with the collector electrode of the third upper bridge arm switch tube and the positive electrode of the bus capacitor, the emitter electrode of the fourth upper bridge arm switch tube is connected with the collector electrode of the fourth lower bridge arm switch tube, the connection point of the collector electrode of the fourth lower bridge arm switch tube is the midpoint of the second half-bridge circuit, and the midpoint is connected with the upper end of the H bridge; and the emitter of the fourth lower bridge arm switch tube is connected with the anode of the input direct current source.
2. The single-phase five-level grid-connected inverter according to claim 1, wherein each bridge arm switching tube in the single-phase five-level grid-connected inverter is a switching tube with an anti-parallel diode.
3. The single-phase five-level grid-connected inverter according to claim 1, wherein the output voltage of the single-phase five-level grid-connected inverter is 0 when the first upper bridge arm switch tube is turned on, the second upper bridge arm switch tube is turned on, or the first lower bridge arm switch tube is turned on, and the second lower bridge arm switch tube is turned off, and the other switch tubes are turned off.
4. The single-phase five-level grid-connected inverter according to claim 1, wherein the fourth lower bridge arm switching tube, the first upper bridge arm switching tube and the second lower bridge arm switching tube are turned on, and the other switching tubes are turned off at the same time, so that the output voltage of the single-phase five-level grid-connected inverter is the direct current input voltage.
5. The single-phase five-level grid-connected inverter according to claim 1, wherein the fourth upper bridge arm switching tube, the first upper bridge arm switching tube and the second lower bridge arm switching tube are turned on, and the other switching tubes are turned off at the same time, so that the output voltage of the single-phase five-level grid-connected inverter is a bus voltage.
6. The single-phase five-level grid-connected inverter according to claim 1, wherein the fourth lower bridge arm switching tube, the first lower bridge arm switching tube and the second upper bridge arm switching tube are turned on, and the other switching tubes are turned off at the same time, so that the output voltage of the single-phase five-level grid-connected inverter is a negative direct current input voltage.
7. The single-phase five-level grid-connected inverter according to claim 1, wherein the fourth upper bridge arm switching tube, the first lower bridge arm switching tube and the second upper bridge arm switching tube are turned on, and the other switching tubes are turned off at the same time, so that the output voltage of the single-phase five-level grid-connected inverter is a negative bus voltage.
8. An active power decoupling control strategy for a single-phase five-level grid-connected inverter is characterized in that the single-phase five-level grid-connected inverter as claimed in claims 1 to 7 is adopted, and the active power decoupling control strategy comprises an inversion function jointly completed by a second half-bridge circuit and an H-bridge circuit, and a boosting and active power decoupling function completed by a first half-bridge boosting circuit and an input filter inductor;
the control implementation steps of the inversion function are as follows:
step 11, setting the reference voltage of the bus capacitor to be constant, making a difference between the reference voltage and the feedback voltage processed by the frequency doubling trap, and inputting the value obtained after the difference into a voltage outer ring controller, wherein the voltage outer ring controller outputs the value as the amplitude value of the current inner ring reference;
step 12, multiplying the current reference amplitude value by the cosine value of the locking angle of the phase-locked loop to obtain a current loop reference, and sending the current loop reference and the grid-connected feedback current into a current loop controller after the current loop reference is differenced;
step 13, outputting the modulated wave as a modulated wave by the current loop controller, and comparing the modulated wave with a laminated carrier or a phase-shifted carrier to generate a pulse width modulated wave so as to drive each bridge arm switching tube in the second half-bridge circuit and the H-bridge circuit to execute switching action;
the control implementation steps of the boosting and active power decoupling function are as follows:
step 21, setting a reference voltage at the input side of a first half-bridge booster circuit, feeding the reference voltage and a feedback voltage into a voltage ring controller after the difference, and taking the output of the voltage ring controller as a current ring reference;
step 22, the current reference and the feedback current are fed into a current loop controller after being differenced, and the current loop controller outputs modulated waves;
and step 23, comparing the modulated wave with the carrier wave to generate a pulse width modulated wave to drive the third upper bridge arm switching tube and the third lower bridge arm switching tube to execute switching action.
9. The active power decoupling control strategy of claim 8, wherein the voltage loop and the current loop controllers in step 21 and step 22 are controllers with harmonic suppression capability to achieve power decoupling of the dc source input side and the inverter output side;
the controller comprises a multi-resonance controller, a repetition controller and a sliding mode controller.
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