CN109327158B - Current type grid-connected inverter integrating power decoupling and buck-boost functions - Google Patents

Current type grid-connected inverter integrating power decoupling and buck-boost functions Download PDF

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CN109327158B
CN109327158B CN201811158861.7A CN201811158861A CN109327158B CN 109327158 B CN109327158 B CN 109327158B CN 201811158861 A CN201811158861 A CN 201811158861A CN 109327158 B CN109327158 B CN 109327158B
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power
current
grid
inductor
output
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CN109327158A (en
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刘永露
夏子晴
粟梅
孙尧
许国
但汉兵
熊文静
王辉
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Central South University
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Central South University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • H02M7/53873—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 with digital control
    • 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
    • H02M1/14—Arrangements for reducing ripples from dc input or output

Abstract

The invention provides a current type grid-connected inverter integrating power decoupling and buck-boost functions. The inverter comprises an input unit, an inversion buck-boost regulation unit and an output unit which are connected in sequence; the inversion buck-boost regulation and control unit comprises a power buffer circuit and a full-bridge inverter. The invention leads the secondary pulse power in the system to be transmitted to the decoupling capacitor C in the power buffer circuitsAbsorption is carried out, so that the average value of the input current at the direct current side is constant, the use of a large-capacity input filter is avoided, and the power density and the reliability of the system are improved; in addition, the input direct-current power supply voltage is not limited by the value of the input direct-current power supply voltage being less than half of the amplitude of the output alternating-current grid-connected voltage any more, and the application range of the converter is widened.

Description

Current type grid-connected inverter integrating power decoupling and buck-boost functions
Technical Field
The invention belongs to the technical field of inverter power supply, relates to the technical field of circuit modulation, and particularly relates to an inverter.
Background
The single-phase grid-connected inverter is widely applied to a photovoltaic system and a fuel cell system to realize energy grid connection. However, when power conversion is performed, low-frequency input current ripples are caused by grid-connected secondary pulsating power, which affects tracking of a maximum power point and reduces the service life of components such as capacitors and batteries. Therefore, the unbalance of the instantaneous power of the input end and the output end is well processed, and the influence of the secondary pulse power on the system is eliminated.
The passive decoupling technology buffers secondary pulsating power by increasing the capacity of a passive device, and the method has the advantages of simplicity and easiness in implementation, but greatly increases the cost of a system, reduces the power density of the system, is not beneficial to the modular design of a device, and in addition, the service life of the system is limited by the use of a large-capacity electrolytic capacitor, and the reliability of the system is reduced. Another feasible method is an active decoupling technology, which utilizes a switching device to transfer secondary pulsating power to an additional small capacitor to avoid the adverse effect of the secondary pulsating power, and the defects of low power density, large capacitance value and the like of a passive decoupling technology do not exist, so that the passive decoupling technology is widely concerned and researched.
On the other hand, in the current-mode inverter reported in the prior document, in order to ensure normal operation, the amplitude of the direct-current input voltage of the current-mode inverter needs to be smaller than half of the amplitude of the grid-connected voltage, but the application range of the inverter is limited.
Disclosure of Invention
Technical problem to be solved
In view of the above-mentioned drawbacks of the prior art, the present invention provides an inverter device that overcomes the above-mentioned problems, and that has a secondary ripple power decoupling capability and a wide input voltage range, and that can avoid the use of a large-capacity input filter, and improve the power density and reliability of the system.
(II) technical scheme
In order to achieve the purpose, the invention adopts the main technical scheme that:
the invention provides a current type grid-connected inverter integrating power decoupling and buck-boost functions, which comprises an input unit, an inversion buck-boost regulation unit and an output unit which are sequentially connected; the method is characterized in that: the inversion buck-boost regulation and control unit comprises a power buffer circuit and a full-bridge inverter; the power buffer circuit comprises a decoupling capacitor CsPower triode switch tube S0Diode D2And electricityFeeling L; in the inversion buck-boost regulation unit, a power triode switch tube S0Collector and the decoupling capacitor CsOne end of the power triode switch tube S is connected with the positive direct current bus of the input unit0Emitter and diode D2The negative electrode of the inductor is connected with one end of the inductor L; the other end of the inductor L is connected with a negative direct current bus of the input unit and one end of the two input ends of the full-bridge inverter, and the decoupling capacitor CsThe other end and a diode D2Is connected with the other end of the two input ends of the full-bridge inverter.
Preferably, the full-bridge inverter comprises a power triode switch S1、S2、S3And S4D power three pole switch tube S1And S3Emitter of and said decoupling capacitor CsIs connected with the other end of the power three-pole switch tube S2And S4The collector of the inductor L is connected with the other end of the inductor L, and the power triode switch tube S1Collector and power triode switch S2The emitting electrodes are all connected with one end of the output unit, and the power three-pole switch tube S4Emitter, power triode switch tube S3The collectors are all connected with the other end of the output unit.
Preferably, the power triode switch tube S0-S4Is an IGBT, a bipolar transistor or a MOS transistor.
Preferably, the decoupling capacitor CsIs a thin film capacitor.
Preferably, the direct current power supply in the input unit is a photovoltaic panel or a fuel cell.
Preferably, the dc power supply voltage V in the input unitinNo longer subject to grid-connected voltage amplitude VmCan be greater or less than the grid-connection voltage amplitude VmHalf of that.
Preferably, the full-bridge inverter operates in a unity power factor mode; at grid-connected voltage ugPositive half period of (1), S1And S4Always off, S2And S3Modulated by PWM wave and switched on or off at the same time; in the networkVoltage ugNegative half period of (S)2And S3Always off, S1And S4Modulated by the PWM wave and switched on or off simultaneously.
Preferably, the output unit includes an inductor LgCapacitor CgAnd AC output power ug(ii) a The inductance LgAnd one end of the power triode switch tube S1Collector electrode of (1) and (S)2Is connected to the emitter of the inductor LgAnd the other end of (b) and the AC output power supply ugIs connected to the ac output power ugAnd the other end of the power triode switch tube S4And S3The collector electrodes are connected; the capacitor CgAre respectively connected with the inductor LgAnd said ac output power ugAnd the other end of the two are connected. Preferably, the current-mode grid-connected inverter device further comprises a sampling conditioning circuit, a controller and a MOSFET driving circuit; the sampling conditioning circuit is used for collecting an input voltage value and a decoupling capacitor C in the power buffer circuitsVoltage value of the inductor L, voltage value of the DC power supply, voltage value of the AC output power supply, and L flowing in the output unitgAnd performing analog-to-digital conversion processing.
Preferably, the controller is configured to obtain an operation signal of each power triode switch tube based on the processed voltage value and current value, and transmit the signal to the MOSFET driving circuit; the MOSFET driving circuit is used for controlling the on and off of each switching device.
(III) advantageous effects
According to the technical scheme, the invention has the following beneficial effects: the invention leads the secondary pulse power in the system to be transmitted to the decoupling capacitor C in the power buffer circuitsAbsorption, so that the output filtering capacity is greatly reduced; the inverter device of the invention improves the power density and reliability of the system; the decoupling capacitor has less voltage operation constraint, so that the voltage stress is low, and the system cost is reduced. The inverter disclosed by the invention has the capability of decoupling secondary pulse power and the capability of providing a wide output voltage range.
Drawings
The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:
fig. 1 is a schematic circuit diagram of a current-mode grid-connected inverter;
FIG. 2 is a schematic diagram of four operating states of the current-mode grid-connected inverter (u)g>0)；
FIG. 3 is a block diagram of a control system of the current grid-connected inverter;
FIGS. 4(a) -4 (e) show the output voltages of the current grid-connected inverter according to the present invention
Figure GDA0002443441140000031
U of timeg、idc、iac、uc、u1Experimental waveform diagram (c).
Description of reference numerals: 1. a direct current input power supply; 2. an input unit; 3. a power buffer unit; 4. a full-bridge inverter; 5. an output unit; 6. a sampling conditioning circuit; 7. a controller; 8. a MOSFET drive circuit.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
the inverter provided by the invention comprises an input unit 2 with a direct current input power supply 1, a power buffer unit 3, a full-bridge inverter 4 and an output unit 5 which are connected in sequence; the power buffer circuit comprises a decoupling capacitor CsAnd the decoupling capacitor CsParallel diode D2Switch S0And an inductance L.
The inverter device is a device for converting direct current into alternating current, and the load of the inverter device can be an alternating current load, a rectifier and the like.
Wherein the output terminal of the DC input power supply is connected to the diode D of the input unit1The output end of the input unit is connected to the input end of the power buffer unit, the output end of the power buffer unit is connected to the input end of the full-bridge inverter, the output end of the inverter is connected to the input end of the output unit, and the tail end of the input end is an alternating current output power supply.
The inversion buck-boost regulation and control unit has the regulation and control functions of buck-boost and unit power factor correction. When electric energy flows through the inverter, the decoupling capacitor in the power buffer circuit absorbs secondary pulsating power in a system, so that the average value of input current at the direct current side is constant, and the use of a large-capacity input filter is avoided.
In a preferred embodiment, the power buffer circuit further comprises: switching device S0An inductor L and a buck-boost converter; preferably, the buck-boost converter comprises a switching device S0Inductor L, diode D2(ii) a Said S0Collector and the decoupling capacitor CsOne end is connected with the other end, S0And said diode D2The negative electrode of the inductor L is connected with one end of the inductor L, and the other end of the inductor L is connected with the inverter unit. The decoupling capacitor CsThe other end of the diode D2The positive pole of the inverter is connected with the inverter unit.
That is, the power buffer circuit includes 1 switching device (switching device S)0) 1 decoupling capacitor C s1 inductor L and 1 diode D2. Switching device S0Emitter and diode D2The cathodes of the two inductors are connected with one end of an inductor L; the other end of the inductor L is connected with the inverter unit; decoupling capacitor CsThe other end and a diode D2The positive pole of the inverter is connected with the inverter unit.
When switching device S0Decoupling capacitor C when onsDischarging, the inductor L is charged, when it is onOff device S0Decoupling capacitor C when turned offsCharging and discharging the inductor L.
In the embodiment of the invention, the secondary pulse power in the system is formed by a decoupling capacitor CsBuffer and decoupling capacitor CsMay be a thin film capacitor.
The power buffer circuit and the full-bridge inverter jointly realize the functions of unit power factor correction and inversion.
In a preferred embodiment, the inverting buck-boost regulation unit comprises a power buffer circuit 3 comprising a buck-boost converter and a full-bridge inverter 4.
The input unit 2 is connected with the power buffer circuit 3, the power buffer circuit 3 is connected with the full-bridge inverter 4, and the full-bridge inverter 4 is connected with the output unit 5.
That is, the output terminal of the input unit 2 is connected to the power buffer circuit 3, the output terminal of the power buffer circuit 3 is connected to the full-bridge inverter 4, and the output terminal of the full-bridge inverter 4 is connected to the output unit 5.
In a preferred embodiment, the full-bridge inverter comprises a full-bridge power triode switch tube S1、S2、S3、S4(ii) a Switching device S1Emitter and switching device S3Emitter equalizing and decoupling capacitor CsIs connected to the other end of the switching device S2Collector and switching device S4Are connected to the other end of the inductor L, and a switching device S1Collector electrode of (1) and S2Are all connected with one end of the output unit, S4Emitter electrode of, S3The collectors of the first and second transistors are connected with the other end of the output unit.
Inductor LgA third inductor L connected to the full bridge invertergAnd said switching device S1Collector electrode of (1) and (S)2Is connected to the emitter of the inductor LgAnd the other end of (1) and an AC output power supply ugIs connected to an AC output power source ugAnother end of (1) and S4And S3Is connected to the collector of the collector.
In a preferred embodiment, the output unit includes a first output unitThree-inductor LgA third capacitor CgAnd AC output power ug；
Inductor LgAnd one end of (A) and S1Collector electrode of (1) and S2Is connected to the emitter of the inductor LgAnd the other end of (1) and an AC output power supply ugIs connected to an AC output power source ugAnother end of (1) and S4And S3Is connected to the collector of a capacitor CgAre respectively connected with the inductors LgAnd said AC output power ugTwo ends of the formed series circuit.
Example 2:
as shown in fig. 1, the inverter device with secondary pulse power decoupling capability and wide output voltage range disclosed in this embodiment includes an input unit 2, inverting buck- boost regulation units 3 and 4, and an output unit 5 of a dc input power supply 1.
Wherein, the output end of the input power source 1 is connected to the anode of the diode D1 of the input unit 2, two ends of the output end of the input unit 2 are connected to two input ends of the power buffer circuit 3, the output end of the power buffer circuit 3 is connected to the full-bridge inverter 4, and the output end of the full-bridge inverter 4 is connected to the output unit 5.
The input unit comprises a DC power supply and 1 diode D1(ii) a The direct current power supply is connected with the input unit, the input unit is connected with the power buffer circuit, the power buffer circuit is connected with the full-bridge inverter, and the full-bridge inverter is connected with the output unit.
The power buffer circuit 3 includes 1 switching device (switching device S)0) 1 decoupling capacitor C s1 inductor L and 1 diode D2；S0And a diode D2The cathodes of the two inductors are connected with one end of an inductor L; the other end of the inductor L is connected with the inverter unit; decoupling capacitor CsThe other end and a diode D2The positive pole of the inverter is connected with the inverter unit. Decoupling capacitor C in power buffer circuitsA thin film capacitor is used.
The full bridge inverter 4 includes 4 switching devices (S)1、S2、S3、S4The specific type is IGBTBipolar transistors or MOS transistors); s1And S2Emitter equalizing and decoupling capacitor CsAre connected at the other end, S2Collector electrode of (1) and S4Are all connected with the other end of the inductor L, S1Collector electrode of (1) and S2Are all connected with one end of an output unit, S4Emitter electrode of, S3The collectors of the first and second transistors are connected with the other end of the output unit.
The output unit 5 comprises 1 inductor L g1 capacitor CgAnd 1 AC output power source ug(ii) a Inductor LgAnd one end of (A) and S1Collector electrode of (1) and S2Is connected to the emitter of the inductor LgAnd the other end of (1) and an AC output power supply ugIs connected to an AC output power source ugAnother end of (1) and S4And S3Is connected to the collector of a capacitor CgAre respectively connected with the inductors LgAnd said AC output power ugTwo ends of the formed series circuit. As shown in fig. 2, the following four operating states are provided:
s in operating State 10Conduction, S1And S2Off (noted as S)0＝1、S1＝0、S2＝0)；
Operating State 2S2Conduction, S0And S1Off (noted as S)2＝1、S0＝0、S1＝0)；(ug<Is S at 01Conduction, S0And S2Shut off)
Operating State 3S0、S1And S2Off (noted as S)0＝0、S1＝0、S2＝0)；
S in operating State 40And S2Conduction, S1Off (noted as S)0＝1、S1＝0、S2＝1)。(ug<Is S at 00And S1Conduction, S2Off).
When S is0Off (operating states 3 and 4) and current flows through the decoupling capacitance. In the operating state 3, most energy is injected from the power grid to decouple the powerContainer Cs(ii) a And in the operation state 4, the decoupling capacitor releases energy to the inverter and the first inductor L. When S is0Switching on (operating states 1 and 2) decoupling capacitor CsIs bypassed. For the full bridge inverter and the output unit, when S is2On (operating states 2 and 4) and current flows through the inverter device, when S2Off (operating states 1 and 3) and current flows through the first inductor L.
Known from the control strategy, S2And S3Complementary, all with S1Are independent of each other.
According to the working state of the inverter, when the input power in the inverter is greater than the output power, the excess energy is absorbed by the decoupling capacitor; when the input power is smaller than the output power, the decoupling capacitor releases the absorbed energy to keep the output power constant.
Fig. 3 is a block diagram of a control system of the present invention, and the control circuit includes a corresponding sampling conditioning circuit 6, a controller 7 and a MOSFET driving circuit 8; the left part of the sampling circuit of the sampling conditioning circuit 6 is responsible for sampling and conditioning the input voltage, the inductor L current and the voltage of the decoupling capacitor, and the right part of the sampling circuit is responsible for the inductor LgCapacitor CgAnd sampling and conditioning of the output voltage. The controller 7 is responsible for important work such as calculation and modulation, and transmits each switching signal to the driving circuit 8. The control method is used for controlling, and the decoupling of ripple power is automatically realized in the control process. In addition, other controllers such as a fuzzy controller, a PID controller, an adaptive voltage control, etc. may be used to obtain a better control effect.
Using the inverter of this embodiment, the DC input power is 200W, the voltage is 50V, and the output voltage is
Figure GDA0002443441140000076
Inductor L, Lg3mH and 2mH respectively, and a decoupling capacitor CsHas a capacity of 50 μ F, a capacitance C g10 μ F. The sampling frequency and the switching frequency are both 50 kHz.
FIGS. 4(a) -4 (e) are diagrams illustrating the configuration of the output voltage of
Figure GDA0002443441140000077
When idc、uc、iac、ugAnd u1Respective experimental waveform diagrams; by setting a decoupling capacitor CsThe invention improves the reliability and power density of the system for the thin film capacitor.
Example 3:
as shown in FIGS. 2-3, the sampling and conditioning circuit includes a sampling input voltage VinVoltage value u of decoupling capacitor in power buffer circuitcCurrent value i of inductor LdcVoltage value u of AC output power sourcegAnd flow through L in output unitgCurrent value i ofac(ii) a The controller is used for obtaining action signals of each switching device based on the processed voltage values and current values and transmitting the signals to the MOSFET driving circuit; the MOSFET driving circuit is used for controlling the on and off of each switching device. In the sampling conditioning circuit, the acquired voltage value and current value are usually subjected to analog-to-digital conversion and transmitted to the controller.
In a preferred embodiment, the calculation of the operating signal of each MOSFET power triode switch tube based on the voltage value and the current value is specifically: at grid-connected voltage ugPositive half period of (1), S1And S4Always off, S2And S3Modulated by PWM wave and switched on or off at the same time; at grid-connected voltage ugNegative half period of (S)2And S3Always off, S1And S4Modulated by the PWM wave and switched on or off simultaneously.
In a preferred embodiment, d1、d2、d3、d4Represent the duty cycles of the four states in fig. 2, respectively:
when the inductor is charged and the capacitor is discharged, d is1～d4The values of (A) are:
Figure GDA0002443441140000073
d2＝0；
Figure GDA0002443441140000074
Figure GDA0002443441140000075
when the inductor is discharged and the capacitor is charged, d is the time1～d4The values of (A) are:
Figure GDA0002443441140000081
Figure GDA0002443441140000082
d3＝0；
Figure GDA0002443441140000083
wherein idcIs the current value of the first inductor L, iacIs a third inductance L3Current value of idTo decouple the capacitance CsCharging current of (I)inIs the input terminal current.
By the above-mentioned duty ratio d1、d2、d3And d4Obtaining S in one switching period0、S1And S2The on-off time of the switching power supply is that a sawtooth wave which has the same frequency as the switching frequency and has the amplitude of 0-1 is compared with the duty ratio, when the value of the sawtooth wave is larger than the duty ratio, the output is low level, and when the value of the sawtooth wave is smaller than the duty ratio, the output is high level.
Wherein, when the inductor is charged and the capacitor is discharged, d1The control target of (2) is an input current, d3+d4The control target of (1) is an output current;
wherein, when the inductor discharges and the capacitor charges, d1+d2The control target of (2) is an input current, d4Is outputAnd (6) discharging current.
In a preferred embodiment of the invention, the current value reference I is desired to be controlledac_rIs based on the value of the output voltage, the value of the output power and the voltage value of the decoupling capacitance.
The method specifically comprises the following steps:
single-phase output voltage detection value usPhase information ω t is obtained through phase-locked loop calculation, and a corresponding cosine value cos (ω t) is obtained based on ω t, wherein ω is the angular frequency of the single-phase power supply voltage, and ω t is the phase of the single-phase input power supply voltage;
a notch filter is utilized to filter second-order and high-order frequency signals of the decoupling capacitor voltage to obtain a signal U of the decoupling capacitor voltage with interference being filteredc_dcDecoupling the average reference voltage of the capacitor from Uc_dcPerforming difference to obtain an error value of the decoupling capacitor voltage;
the voltage error value of the decoupling capacitor is output as a current amplitude reference I through a proportional-integral controller_ref1. And is combined with the output current steady state feedforward component I_ref2Differencing to obtain a reference value I of the output current expected to be controlled_ref(ii) a Will output a reference value I of the current_refThe product of the sum and cos (ω t) is used as the reference value I of the current value to be controlledac_r＝I_refcos (ω t) and utilizes a proportional-resonant controller to achieve steady-state tracking of the output reference current.
In a preferred embodiment of the invention, the voltage reference V is desired to be controlledL_rIs based on the output dc voltage reference value, the sampled value of the output dc voltage and the sampled value of the inductor current.
The method specifically comprises the following steps: will output the instantaneous magnitude i of the currentacAbsolute value of (d) and rated value I of input currentinAfter addition, as the current reference value I of the inductance Ldc_refAnd tracking of the reference value is realized by utilizing a proportional-integral controller.
Finally, the above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the invention, and any modifications, equivalents, improvements and the like that are within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. A current type grid-connected inverter integrating power decoupling and buck-boost functions comprises an input unit, an inverting buck-boost regulation unit and an output unit which are sequentially connected; the method is characterized in that: the inversion buck-boost regulation and control unit comprises a power buffer circuit and a full-bridge inverter; the power buffer circuit comprises a decoupling capacitor CsPower triode switch tube S0Diode D2And an inductance L; in the inversion buck-boost regulation unit, a power triode switch tube S0Collector and the decoupling capacitor CsOne end of the power triode switch tube S is connected with the positive direct current bus of the input unit0Emitter and diode D2The negative electrode of the inductor is connected with one end of the inductor L; the other end of the inductor L is connected with a negative direct current bus of the input unit and one end of the two input ends of the full-bridge inverter, and the decoupling capacitor CsThe other end and a diode D2Is connected with the other end of the two input ends of the full-bridge inverter.
2. A current grid-connected inverter according to claim 1, wherein the full-bridge inverter comprises a power triode switch S1、S2、S3And S4D power three pole switch tube S1And S3Emitter of and said decoupling capacitor CsIs connected with the other end of the power three-pole switch tube S2And S4The collector of the inductor L is connected with the other end of the inductor L, and the power triode switch tube S1Collector and power triode switch S2The emitting electrodes are all connected with one end of the output unit, and the power three-pole switch tube S4Emitter, power triode switch tube S3The collectors are all connected with the other end of the output unit.
3. A current grid-connected inverter according to claim 2, wherein the power triode switch S0-S4Is of the type IGBT, bipolar transistor or MOS transistor.
4. The current grid-connected inverter according to claim 1, wherein the decoupling capacitor C is connected to the gridsIs a thin film capacitor.
5. A current grid-connected inverter according to claim 1, wherein the dc power source in the input unit is a photovoltaic panel or a fuel cell.
6. A current grid-connected inverter according to claim 1, wherein the dc power supply voltage V in the input unitinNo longer subject to grid-connected voltage amplitude VmCan be greater or less than the grid-connection voltage amplitude VmHalf of that.
7. A current grid-connected inverter according to claim 3, wherein the full-bridge inverter operates in unity power factor mode; at grid-connected voltage ugPositive half period of (1), S1And S4Always off, S2And S3Modulated by PWM wave and switched on or off at the same time; at grid-connected voltage ugNegative half period of (S)2And S3Always off, S1And S4Modulated by the PWM wave and switched on or off simultaneously.
8. A current grid-connected inverter according to claim 3, wherein the output unit comprises an inductor LgCapacitor CgAnd AC output power ug(ii) a The inductance LgAnd one end of the power triode switch tube S1Collector electrode of (1) and (S)2Is connected to the emitter of the inductor LgAnd the other end of (b) and the AC output power supply ugIs connected to the ac output power ugAnd the other end of the power triode switch tube S4And S3The collector electrodes are connected; the capacitor CgAre respectively connected with the inductor LgToTerminal and the AC output power ugAnd the other end of the two are connected.
9. A current-mode grid-connected inverter according to claim 8, further comprising a sampling conditioning circuit, a controller and a MOSFET driving circuit; the sampling conditioning circuit is used for collecting an input voltage value and a decoupling capacitor C in the power buffer circuitsVoltage value of the inductor L, voltage value of the DC power supply, voltage value of the AC output power supply, and L flowing in the output unitgAnd performing analog-to-digital conversion processing.
10. A current grid-connected inverter according to claim 9, wherein the controller is configured to obtain an operating signal of each power triode switch based on the processed voltage and current values, and to transmit the operating signal to the MOSFET driving circuit; the MOSFET driving circuit is used for controlling the on and off of each switching device.
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