CN112838778A - Non-isolated current type grid-connected inverter without overlapping time and control method and system thereof - Google Patents

Non-isolated current type grid-connected inverter without overlapping time and control method and system thereof Download PDF

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Publication number
CN112838778A
CN112838778A CN202110012692.1A CN202110012692A CN112838778A CN 112838778 A CN112838778 A CN 112838778A CN 202110012692 A CN202110012692 A CN 202110012692A CN 112838778 A CN112838778 A CN 112838778A
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power switch
switch tube
grid
current
inductor
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陈琪
代云中
鲁庆东
代艳霞
陈启强
李泓廷
刘健洋
屈珣
罗钟雨
游元庆
林虹宇
张鑫坤
彭宇峰
程健钊
冷云松
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Yibin Vocational and Technical College
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Yibin Vocational and Technical College
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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
    • 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
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

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

Abstract

The invention discloses a non-isolated current type grid-connected inverter without overlapping time and a control method and a system thereof1Energy storage inductor L2Filter inductor Lf1Filter inductor Lf2Power switch tube S1Power switch tube S2Power switch tube S3Power switch tube S4Power switch tube S5Filter capacitor CfFilter capacitor C1Filter capacitor C2And the electric network ugThe invention aims to provide a non-isolated current type grid-connected inverter without overlapping time and a control method and a system thereof, wherein a power switch tube S is additionally arranged on the existing current type grid-connected inverter5Filtering ofCapacitor C1And a filter capacitor C2The defects that the current type grid-connected inverter in the prior art needs to set overlapping time, the follow current stage does not realize isolation and the common-mode leakage current is large are overcome.

Description

Non-isolated current type grid-connected inverter without overlapping time and control method and system thereof
Technical Field
The invention relates to the technical field of grid-connected inverters, in particular to a non-isolated current type grid-connected inverter without overlapping time and a control method and system thereof.
Background
Grid-connected inverters (GCI) are used as core power conversion devices of photovoltaic power generation equipment, and with the development of distributed photovoltaic power generation systems, GCI is required to have high power quality and reliability. The Current Source Grid-connected Inverter (CSGCI) uses an inductor as its dc-side energy storage element, and compared with a capacitor, the inductor has stable performance, and can use a dc voltage power supply to cooperate with a large inductor to be equivalent to a Current Source, and can allow the Current to pass through the bridge arm, so that compared with a voltage-type Inverter, the Current-type Grid-connected Inverter has higher safety and reliability. Due to the constant current characteristic of the current source, the output current of the CSGCI is irrelevant to impedance and only relevant to output voltage and impedance, the purpose of controlling the voltage is achieved by changing the impedance value, and the CSGCI has good boosting performance. In addition, the CSGCI output current can directly flow into a power grid through the filter, other additional devices are not needed for signal conversion, and the CSGCI output current has the advantages of high response speed and high power factor. Therefore, the CSGCI is widely applied to systems such as photovoltaic grid-connected power generation and uninterruptible inverter power supply.
The typical structure of the existing bridge type CSGCI is shown in figure 1, and the inverter has the characteristics of simple structure, unipolar modulation, three-level output and the like. However, when the switches connected across the current source are turned off at the same time, the charging path of the current will be blocked, and a large voltage peak will be applied between the switch tubes. Therefore, it is necessary to add an overlap time between the switches when the switching tubes are switching on the same bridge arm. And the introduction of the overlapping time can increase the harmonic content of the grid-connected current and reduce the power quality of GCI. Meanwhile, the German VDE-0126-1-1 standard specifies that the photovoltaic GCI must be cut off from the power grid within 0.3s when the leakage current amplitude is higher than 300 mA. Meanwhile, the topology does not realize the isolation of the photovoltaic cell panel from the power grid in the follow current stage, and when unipolar modulation is adopted, the common-mode voltage changes at high frequency, and the leakage current is large. If the inverter is to be incorporated into a power grid, an isolation transformer needs to be added, the size and the cost of the inverter are increased, and the power density of the system is reduced.
Disclosure of Invention
The invention aims to provide a non-overlap time non-isolated current type grid-connected inverter and a control method and a system thereof, and solves the defects that the non-overlap time non-isolated current type grid-connected inverter in the prior art needs to set overlap time and has larger common-mode leakage current.
The invention is realized by the following technical scheme:
the non-isolated current type grid-connected inverter without overlapping time consists of a photovoltaic cell array PV and an energy storage inductor L1Energy storage inductor L2Filter inductor Lf1Filter inductor Lf2Power switch tube S1Power switch tube S2Power switch tube S3Power switch tube S4Power switch tube S5Filter capacitor CfFilter capacitor C1Filter capacitor C2And the electric network ugComposition is carried out;
the photovoltaic cell array PV direct-current voltage positive end and the energy storage inductor L1Is connected to one end of the energy storage inductor L1And the other end of the power switch tube S5Is connected with the collector of the power switch tube S5And the energy storage inductor L2Is connected to one end of the energy storage inductor L2The other end of the photovoltaic cell array PV is connected with the direct-current voltage negative end of the photovoltaic cell array PV;
the power switch tube S1Collector and the power switch tube S5Is connected with the collector of the power switch tube S1And the power switch tube S3Is connected with the collector of the power switch tube S3And the power switch tube S5The emitter of (3) is connected;
the power switch tube S2Collector and the power switch tube S1Is connected with the collector of the power switch tube S2And the power switch tube S4Is connected with the collector of the power switch tube S4And the power switch tube S3The emitter of (3) is connected;
the filter inductor Lf1And one end of the power switch tube S1Said filter inductance Lf1Is connected to the grid ugIs connected to the grid ugAnd the other end of the filter inductor Lf2Is connected to the filter inductor Lf2And the other end of the power switch tube S2The emitter of (3) is connected;
the filter capacitor C1And one end of the power switch tube S1Is connected to the collector of the filter capacitor C1And the other end of the power switch tube S2The emitter of (3) is connected;
the filter capacitor C2And one end of the power switch tube S3Said filter capacitor C2And the other end of the power switch tube S4Is connected with the collector of the collector;
the filter capacitor CfIs connected to the filter inductor Lf1Said filter capacitor CfIs connected to the filter inductor L at the other endf2。
Preferably, the positive end-to-ground distributed capacitance of the PV direct-current voltage of the photovoltaic cell array is Cpv1The photovoltaic cell array PV direct-current voltage negative end-to-ground distributed capacitance is Cpv2Wherein, Cpv1＝Cpv2。
Preferably, the energy storage inductor L1And an energy storage inductor L2The sensitivity values are the same.
On the other hand, the invention also provides a control method of the non-overlap time non-isolated current type grid-connected inverter, which comprises the following steps:
acquiring a phase angle theta of grid-connected voltage through a phase-locked loop circuit;
inquiring data of a sine table corresponding to the phase angle theta to obtain a reference signal of grid-connected current;
obtaining a modulation signal u according to the deviation value of the grid-connected current and the reference signal thereofc；
Modulating signal u by adopting half-cycle modulation methodcAnd converting the driving signal into a driving signal of a power switching tube in the inverter, thereby realizing the working mode control of the inverter.
Preferably, the operation mode 1 of the inverter, the controlling includes: when the grid-connected current i is detectedg>When 0, controlling the power switch tube S1And the power switch tube S4On, the power switch tube S2The power switch tube S3And the power switch tube S5When the photovoltaic cell array PV and the energy storage inductor L are turned off1The power switch tube S1The filter capacitor CfThe power switch tube S4And the energy storage inductor L2Forming a forward charging closed loop; while the filter inductance Lf1The power grid ugThe filter inductor Lf2And said filter capacitor CfForm a forward charge to the grid ugAnd (5) supplying power.
Preferably, the operation mode 2 of the inverter comprises: when the grid-connected current i is detectedg>When 0, controlling the power switch tube S5On, the power switch tube S1The power switch tube S2The power switch tube S3And the power switch tube S4When the photovoltaic cell array PV and the energy storage inductor L are turned off2The energy storage inductor L1The power switch tube S5Form a forward DC side follow current loop, and the filter inductor Lf1The power grid ugThe filter inductor Lf2And said filter capacitor CfForm a positive discharge to the grid ugAnd (5) supplying power.
Preferably, the operation mode 3 of the inverter comprises: when the grid-connected current i is detectedg<When 0, controlling the power switch tube S2And the power switch tube S3On, the power switch tube S1The power switch tube S4And the power switch tube S5When the photovoltaic cell array PV and the energy storage inductor L are turned off1The power switch tube S2The filter capacitor CfThe power switch tube S3And the energy storage inductor L2Forming a forward charging closed loop; while the filter inductance Lf1The power grid ugThe filter inductor Lf2And said filter capacitor CfForm a reverse charge to the grid ugAnd (5) supplying power.
Preferably, of said inverterThe working mode 4, the control comprises: when the grid-connected current i is detectedg<When 0, controlling the power switch tube S5On, the power switch tube S1The power switch tube S2The power switch tube S3And the power switch tube S4When the photovoltaic cell array PV and the energy storage inductor L are turned off1The energy storage inductor L2The power switch tube S5Form a negative DC side follow current loop, and the filter inductor Lf1The power grid ugThe filter inductor Lf2And said filter capacitor CfForm a positive discharge to the grid ugAnd negative power supply is carried out.
Preferably, the control of the operating mode of the inverter includes: in controlling the power switch tube S5Has been turned off and the power switch tube S2And the power switch tube S3When not conducted, the photovoltaic cell array PV and the energy storage inductor L1The filter capacitor C1The filter capacitor C2And the energy storage inductor L2And forming an inductive current follow current loop in the overlapped time period.
In addition, the invention also provides a control system of the non-overlap time non-isolated current type grid-connected inverter, which comprises a sensor, a PLL circuit, a PI controller and a half-cycle modulation module;
the PLL circuit is used for acquiring a phase angle theta of grid-connected voltage;
the sensor is used for acquiring grid-connected current of grid-connected voltage;
the PI controller obtains a modulation signal u according to the deviation value of the grid-connected current and a grid-connected current reference signalc(ii) a The grid-connected current reference signal is obtained by looking up a table according to the phase angle theta;
the half-cycle modulation module is used for modulating a signal ucAnd converting the driving signal into a driving signal of a power switching tube in the inverter and outputting the driving signal to control the opening and closing of the power switching tube of the inverter.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. by introducing a filter capacitor C for preventing current type GCI from being opened between two switching tubes of two bridge arms1And a filter capacitor C2The method has the advantages that the overlapping time is not required to be set, so that the total harmonic distortion of the grid-connected current is small;
2. in the positive half period of the grid-connected inverter, the power switch tube S2And a power switch tube S3Remains off, power switch tube S in negative half-cycle1And a power switch tube S4The switching-off is kept, so that the switching loss of the grid-connected inverter can be effectively reduced;
3. half-cycle modulation method enables common-mode voltage u of mode 1, mode 2, mode 3 and mode 4 of non-isolated current type grid-connected inverter without overlapping timecmvIs maintained as ug/2, no high frequency components; under the condition of no need of an isolation transformer, the common-mode leakage current of the non-isolation current type grid-connected inverter without the overlapping time is effectively inhibited, and the amplitude is only about 13mA, so that the non-isolation current type grid-connected inverter has the characteristic of low leakage current and meets the standard of VDE-0126-1-1.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
fig. 1 is a schematic circuit structure diagram of a non-isolated current grid-connected inverter without overlap time in the prior art;
FIG. 2 is a schematic circuit diagram of a non-isolated current grid-connected inverter without overlap time according to the present invention;
FIG. 3 is a schematic diagram of the half-cycle modulation method of the present invention;
FIG. 4 is a control signal flow diagram of the non-overlap time non-isolated current grid-connected inverter according to the present invention;
FIG. 5 is a schematic diagram of a simplified common-mode equivalent circuit structure of a non-isolated current grid-connected inverter without overlap time according to the present invention;
fig. 6 is a schematic diagram of an equivalent circuit structure of a non-isolated current type grid-connected inverter in mode 1 without overlapping time according to the present invention;
fig. 7 is a schematic diagram of an equivalent circuit structure of a non-isolated current type grid-connected inverter in mode 2 without overlapping time according to the present invention;
fig. 8 is a schematic diagram of an equivalent circuit structure of a non-isolated current type grid-connected inverter in mode 3 according to the present invention;
fig. 9 is a schematic diagram of an equivalent circuit structure of a non-isolated current type grid-connected inverter in mode 4 according to the present invention;
FIG. 10 is a schematic diagram of the actual driving signals of the non-isolated current grid-connected inverter without overlap time according to the present invention;
fig. 11 is a schematic diagram of an equivalent circuit structure of a transition process of a non-isolated current type grid-connected inverter with no overlapping time from mode 1 to mode 2;
FIG. 12 shows a non-isolated current type grid-connected inverter with no overlap time and a direct-current side energy storage inductive current idcThe waveform of (a);
FIG. 13 shows a grid u of a non-isolated current grid-connected inverter according to the present inventiongAnd a grid-connected current igA waveform diagram of (a);
FIG. 14 shows the grid-connected current i of the non-isolated current type grid-connected inverter without the overlap time according to the present inventiongAnd FFT analysis oscillogram thereof;
FIG. 15 shows u of the non-isolated current grid-connected inverter without overlap time according to the present inventionPO、uNOAnd a common mode voltage ucmvA waveform diagram of (a);
FIG. 16 shows the leakage current i of the non-isolated current type grid-connected inverter without the overlap time according to the present inventiontcmA waveform diagram of (a).
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
Example 1
A non-isolated current type grid-connected inverter without overlap time is disclosed, as shown in figure 2, the inverter mainly comprises a photovoltaic cell array PV and an energy storage inductorL1Energy storage inductor L2Filter inductor Lf1Filter inductor Lf1Power switch tube S1Power switch tube S2Power switch tube S3Power switch tube S4Power switch tube S5Filter capacitor CfFilter capacitor C1Filter capacitor C2And the electric network ugAnd (4) forming.
The photovoltaic cell array PV direct-current voltage positive end and the energy storage inductor L are connected with the photovoltaic cell array PV direct-current voltage positive end1Is connected with one end of an energy storage inductor L1The other end of the power switch tube S5Is connected with the collector of the power switch tube S5Emitter and energy storage inductor L2Is connected with one end of an energy storage inductor L2The other end of the photovoltaic cell array PV is connected with the DC voltage negative end of the photovoltaic cell array PV;
power switch tube S1Collector and power switch tube S5Is connected with the collector of the power switch tube S1Emitter and power switch tube S3Is connected with the collector of the power switch tube S3Emitter and power switch tube S5The emitter of (3) is connected;
power switch tube S2Collector and power switch tube S1Is connected with the collector of the power switch tube S2Emitter and power switch tube S4Is connected with the collector of the power switch tube S4Emitter and power switch tube S3The emitter of (3) is connected;
filter inductance Lf1One end of and a power switch tube S1Is connected with the filter inductor Lf1Another end of (d) and the grid ugIs connected to the grid ugAnother end of (1) and a filter inductor Lf2Is connected to a filter inductor Lf2The other end of the power switch tube S2The emitter of (3) is connected;
filter capacitor C1One end of and a power switch tube S1Is connected with the collector of the filter capacitor C1The other end of the power switch tube S2The emitter of (3) is connected;
filter capacitor C2One terminal of and power switchClosing pipe S3Is connected to the filter capacitor C2The other end of the power switch tube S4Is connected with the collector of the collector;
filter capacitor CfOne end of is connected to the filter inductor Lf1Filter capacitor CfIs connected to the filter inductor L at the other endf2。
Wherein C ispv1And Cpv2Respectively distributing capacitors to the ground for the positive terminal P and the negative terminal N of the DC voltage of the photovoltaic cell array, wherein Cpv1＝Cpv2＝Cpv；S1～S5Is a power switch tube of the main circuit of the inverter. L isf1And Lf2Is a filter inductance of the AC side, L1And L2An energy-storage inductor on the DC side, the function of which can be used for energy storage, CfIs a filter capacitor; i.e. ioOutputting current for a bridge arm of the inverter; u. ofgAnd igRespectively grid-connected voltage and grid-connected current; i.e. ioOutputting current for the bridge arm; i isdcThe average value of the energy storage inductance current at the direct current side is obtained.
The inverter of the embodiment can effectively inhibit high-frequency common-mode leakage current, and meanwhile, a filter capacitor for preventing the current type grid-connected inverter from being opened is introduced between the two switching tubes of the two bridge arms, so that current conversion can be smoothly completed without setting overlapping time.
Example 2
The working mode of the non-overlap time non-isolated current grid-connected inverter proposed in embodiment 1 is controlled by adopting a half-cycle modulation method, and the principle of the half-cycle modulation method of the embodiment is shown in fig. 3, so that the power switch tube S is enabled1Power switch tube S4And a power switch tube S5Conducting in positive half period, the power switch tube S2Power switch tube S3And a power switch tube S5Conducting in the negative half cycle. Wherein u isrBeing a unipolar triangular carrier wave, ucFor modulating the wave, f is the grid voltage frequency. In the modulated wave ucOf a positive half-cycle, unipolar triangular carrier urAnd a modulated wave ucComparison generating power switch tube S1And a power switch tube S4Drive signal ofPower switch tube S2And a power switch tube S3Keep off and make the power switch tube S1And a power switch tube S4Are the same, power switch tube S5And a power switch tube S4Are complementary to each other. In the modulated wave ucNegative half period of (d), unipolar triangular carrier urAnd a modulated wave ucComparison generating power switch tube S2And a power switch tube S3Of a power switch tube S1And a power switch tube S4Keep off and make the power switch tube S2And a power switch tube S3Are the same, power switch tube S5And a power switch tube S3Are complementary to each other. As can be seen from fig. 3, the non-overlap time non-isolated current grid-connected inverter using half-cycle modulation has only three switching tubes for high-frequency switching in a half power cycle. During the positive half period S2And S3Remains off for a negative half period S1And S4And the switching-off is kept, so that the switching loss of the inverter can be effectively reduced.
Specifically, as shown in fig. 4, the control process of this embodiment (implemented based on the control system shown in fig. 4, where the control system includes a phase-locked loop circuit, a PI controller, a sensor, and a half-cycle modulation module) specifically includes:
obtaining u by Phase locked loop circuit (PLL)gThe phase angle θ of;
the executive program inquires the corresponding sine table data sin theta to obtain igThe reference signal of is then iref＝Im×sin(wt+θ)；
Comparison igAnd irefObtaining the modulation signal u through the PI controllerc(ii) a Grid-connected current igThe detection is obtained by an alternating current sensor, and a hall sensor can be adopted in the embodiment.
ucThe driving signal of the non-overlap time non-isolated current type grid-connected inverter of the embodiment 1 is obtained by a half-cycle modulation method, so that u can be realizedgAnd igIn phase (c).
Controlling each power switch tube S of the inverter by the driving signal1～S5Therefore, the method realizes the control of each working mode of the inverter, and comprises the following steps:
setting the grid current igThe current from the bridge arm midpoint a to B is positive. Because two parasitic capacitances are in parallel connection, the equivalent capacitance is 2Cpv。CpvHas the function of isolating the DC power supply, so that the leakage current itcmOnly with respect to the ac voltage source. For eliminating differential mode leakage current1＝L2＝L。uPOAnd uNOThe voltages of the P terminal and the N terminal to the ground O point are respectively. When the leakage current i of the DC current source is not consideredtcmIn the influence of (3), the common-mode loop equivalent model of the non-overlap time non-isolated current grid-connected inverter of the present embodiment is as shown in fig. 5, and therefore, there are:
Figure BDA0002885583950000061
as can be seen from FIG. 5 and equation (1), the leakage current i in the looptcmIs a common-mode voltage u varying at high frequencycmvAnd (4) causing.
Setting the grid current igPositive from a to B. According to S in FIGS. 2 and 31～S5The non-overlap time non-isolated current grid-connected inverter of the present embodiment can be divided into the following four modes, which are shown in fig. 6 to 9:
mode 1:
when current i is connected to the gridg>0, power switch tube S1And a power switch tube S4Conducting power switch tube S2Power switch tube S3And a power switch tube S5When the grid-connected inverter is turned off, the non-overlap time non-isolated current type grid-connected inverter of the present embodiment operates in mode 1, and an equivalent circuit of the non-overlap time non-isolated current type grid-connected inverter is shown in fig. 6. As can be seen from fig. 6, the photovoltaic cell array PV and the energy storage inductor L1Power switch tube S1Filter capacitor CfPower switch tube S4And an energy storage inductor L2Forming a forward charging closed loop; simultaneous filtering inductor Lf1Electric networkugFilter inductor Lf2And a filter capacitor CfForm positive charging to the grid ugAnd (5) supplying power. Further, as can be seen from FIG. 6, i0＝Idc，uPO＝uAO＝ug，uNO＝u BO0. Therefore, according to the formula (1), the common mode voltage u of the mode 1 can be obtainedcmvIs composed of
Figure BDA0002885583950000071
Wherein i0Outputting current for a bridge arm of the inverter; i isdcThe average value of the energy storage inductance current at the direct current side is obtained.
Mode 2:
when current i is connected to the gridg>0, power switch tube S5Conducting power switch tube S1Power switch tube S2Power switch tube S3And a power switch tube S4When the grid-connected inverter is turned off, the non-overlap time non-isolated current type grid-connected inverter of the present embodiment operates in mode 2, and an equivalent circuit of the non-overlap time non-isolated current type grid-connected inverter is shown in fig. 7. As can be seen from fig. 7, the photovoltaic cell array PV and the energy storage inductor L2Energy storage inductor L1And a power switch tube S5Form a forward DC side follow current loop and simultaneously filter the inductor Lf1Power grid ugFilter inductor Lf2And a filter capacitor CfForm a positive discharge to the grid ugAnd (5) supplying power. i.e. i00, from KVL law and FIG. 7
Figure BDA0002885583950000072
Figure BDA0002885583950000073
uAO＝ug uBO＝0 (5)
Wherein u iss1，us2，us3And us4Is divided intoOther than the power switch tube S1Power switch tube S2Power switch tube S3And a power switch tube S4Voltage stress of (d).
When power switch tube S5When conducting, uPNWhen the value is 0, then:
Figure BDA0002885583950000074
the united type (1) and (3) to (6) can be obtained:
Figure BDA0002885583950000075
modality 3:
when current i is connected to the gridg<0, power switch tube S2And a power switch tube S3Conducting power switch tube S1Power switch tube S4And a power switch tube S5When the grid-connected inverter is turned off, the non-overlap time non-isolated current type grid-connected inverter of the present embodiment operates in the mode 3, and the equivalent circuit of the non-overlap time non-isolated current type grid-connected inverter is shown in fig. 8. As can be seen from fig. 8, the photovoltaic cell array PV and the energy storage inductor L1Power switch tube S2Filter capacitor CfPower switch tube S3And an energy storage inductor L2Forming a forward charging closed loop; simultaneous filtering inductor Lf1Power grid ugFilter inductor Lf2And a filter capacitor CfForm reverse charging to the grid ugAnd (5) supplying power. As can be seen from FIG. 8, i0＝-Idc，uPO＝uBO＝0，uNO＝uAO＝ug. Thus, according to the formula (1), u of the mode 3 can be obtainedcmvIs composed of
Figure BDA0002885583950000081
Modality 4:
when current i is connected to the gridg<0, power switch tube S5Conducting, power switchPipe S1Power switch tube S2Power switch tube S3And a power switch tube S4When the grid-connected inverter is turned off, the non-overlap time non-isolated current type grid-connected inverter of the present embodiment operates in the mode 4, and an equivalent circuit of the non-overlap time non-isolated current type grid-connected inverter is shown in fig. 9. As can be seen from fig. 9, the photovoltaic cell array PV and the energy storage inductor L1Energy storage inductor L2Power switch tube S5Form a negative DC side follow current loop and filter the inductor Lf1Power grid ugFilter inductor Lf2And a filter capacitor CfForm a positive discharge to the grid ugAnd negative power supply is carried out. Similar to modality 2, can be given i 00, mode 4 ucmvIs composed of
Figure BDA0002885583950000082
The switching states and common mode voltages of the non-overlap time non-isolated current grid-connected inverter of the present embodiment are shown in table 1.
Table 1 non-overlap time non-isolated current type grid-connected inverter switching state of the present embodiment and u thereofcmv
Figure BDA0002885583950000083
As can be seen from Table 1, the mode 2, the mode 3 and the mode 4 have the same ucmv＝0.5ugThe common mode voltage only contains a power grid component, and no high-frequency component exists. Therefore, the non-isolated current type grid-connected inverter without the overlapping time can effectively suppress the high-frequency common-mode leakage current of a grid-connected inverter system while realizing three levels of output current.
Ideally, the inverter circuit complements the driving signal power switch tube S in the positive half cycle5And power switch tube S1And a power switch tube S3The switching-off is not carried out at the same time, namely the switching-on and the switching-off have no time delay after the control signal is sent out. In practical cases, however, the switching tube cannot be turned on or offCan be done instantaneously as shown in fig. 10.
Because the power switch tube S is converted into the mode 2 in the process of converting the mode 1 into the mode 25And power switch tube S1And a power switch tube S3The work condition of simultaneous turn-off can appear, and the follow current can't be accomplished to current mode grid-connected inverter, can appear huge voltage peak value on the switch tube, causes the contravariant to fail and the device is burnt out. Therefore, the power switch tube S is required to be connected5Is delayed by a time period, i.e. the overlap time TeEnsuring the power switch tube S1And a power switch tube S3After reliable connection, the power switch tube S5Then the power is cut off, so that the commutation process is smoothly completed. The addition of the overlapping time can introduce low-order harmonic components which are difficult to filter into the grid-connected current of the current type grid-connected inverter. In addition, if the overlapping time is improperly set, the output current of the grid-connected inverter is seriously distorted, so that the requirement of photovoltaic power generation on the voltage and power quality is difficult to meet.
Therefore, in this embodiment, two filter capacitors C are introduced between the two arms of the inverter1And C2. When power switch tube S5Has been turned off, the power switch tube S2And a power switch tube S3Fig. 11 shows an equivalent circuit of a current grid-connected inverter without the overlap time in the case where the current grid-connected inverter is not turned on, that is, in the time period in which the overlap time needs to be set. At the moment, the photovoltaic cell array PV and the energy storage inductor L1Filter capacitor C1Filter capacitor C2And an energy storage inductor L2An inductive current follow current loop in the overlapping time period is formed, so that the CSGCI inductive current smoothly finishes follow current, and a large voltage peak value cannot appear on a power switch tube. Therefore, during the mode conversion process, the non-overlap time non-isolated current grid-connected inverter of the embodiment can smoothly complete the commutation without setting the overlap time.
Similarly, in the commutation processes of the non-overlap time non-isolated current grid-connected inverter in the negative half-cycle mode 3 and the mode 4, the commutation equivalent circuit of the non-overlap time non-isolated current grid-connected inverter is shown in fig. 11, and the analysis is the same as that of the positive half-cycle. Therefore, the non-isolated current type grid-connected inverter without the overlap time has the advantages that the overlap time does not need to be set, and the total harmonic distortion of grid-connected current is small.
Further, in this embodiment, a verification is performed on the non-overlap time non-isolated current grid-connected inverter provided in this embodiment, and the verification specifically includes:
a circuit simulation model based on MATLAB/simulink is built, and circuit parameters in the circuit simulation model are shown in table 2, wherein ImFor reference current amplitude, switching frequency fs5kHz, grid-connected voltage amplitude Um＝220V。
TABLE 2 System parameters
Figure BDA0002885583950000091
The simulation results are shown in fig. 12-16, wherein fig. 12 shows the dc side energy storage inductor current idcThe waveform of (1), held at 10.5A; FIG. 13 shows a grid ugAnd a grid-connected current igCan be seen from the figure, the grid ugAnd a grid-connected current igKeeping the same phase, grid ugIs about 220V, grid-connected current igIs about 10A; FIG. 14 shows grid-connected current igAnd FFT analysis waveform thereof, and grid-connected current i can be seen from the figuregThe total harmonic distortion rate THD of 0.45%. Therefore, the non-isolated current type grid-connected inverter without the overlapping time, the control method and the system thereof can realize stable inversion, and the system has higher power factor and electric energy quality. FIG. 15 shows uPO，uNOAnd a common mode voltage ucmvCan be seen from the figure, the common mode voltage ucmvThe peak-to-peak value is about 220V and the frequency is 50Hz, so the inverter contains only low frequency components. FIG. 16 shows leakage current itcmCan be seen from the figure, the leakage current itcmIs about 13 mA. Therefore, the analysis shows that the leakage current of the grid-connected inverter can be effectively inhibited, and the requirements of the VDE-0126-1-1 standard on the leakage current of the photovoltaic grid-connected inverter are met.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. The non-isolated current type grid-connected inverter without the overlapping time is characterized by comprising a photovoltaic cell array PV and an energy storage inductor L1Energy storage inductor L2Filter inductor Lf1Filter inductor Lf2Power switch tube S1Power switch tube S2Power switch tube S3Power switch tube S4Power switch tube S5Filter capacitor CfFilter capacitor C1Filter capacitor C2And the electric network ugComposition is carried out;
the photovoltaic cell array PV direct-current voltage positive end and the energy storage inductor L1Is connected to one end of the energy storage inductor L1And the other end of the power switch tube S5Is connected with the collector of the power switch tube S5And the energy storage inductor L2Is connected to one end of the energy storage inductor L2The other end of the photovoltaic cell array PV is connected with the direct-current voltage negative end of the photovoltaic cell array PV;
the power switch tube S1Collector and the power switch tube S5Is connected with the collector of the power switch tube S1And the power switch tube S3Is connected with the collector of the power switch tube S3And the power switch tube S5The emitter of (3) is connected;
the power switch tube S2Collector and the power switch tube S1Is connected with the collector of the power switch tube S2And the power switch tube S4Is connected with the collector of the power switch tube S4Emitter and the power switch tubeS3The emitter of (3) is connected;
the filter inductor Lf1And one end of the power switch tube S1Said filter inductance Lf1Is connected to the grid ugIs connected to the grid ugAnd the other end of the filter inductor Lf2Is connected to the filter inductor Lf2And the other end of the power switch tube S2The emitter of (3) is connected;
the filter capacitor C1And one end of the power switch tube S1Is connected to the collector of the filter capacitor C1And the other end of the power switch tube S2The emitter of (3) is connected;
the filter capacitor C2And one end of the power switch tube S3Said filter capacitor C2And the other end of the power switch tube S4Is connected with the collector of the collector;
the filter capacitor CfIs connected to the filter inductor Lf1Said filter capacitor CfIs connected to the filter inductor L at the other endf2。
2. The non-overlap time non-isolated current grid-connected inverter according to claim 1, wherein the PV dc voltage positive end-to-ground distributed capacitance of the PV cell array is Cpv1The photovoltaic cell array PV direct-current voltage negative end-to-ground distributed capacitance is Cpv2Wherein, Cpv1＝Cpv2。
3. The non-overlap time non-isolated current grid-connected inverter according to claim 1, wherein the energy storage inductor L1And an energy storage inductor L2The sensitivity values are the same.
4. The control method of the non-overlap time non-isolated current grid-connected inverter according to any one of claims 1 to 3, wherein the method comprises:
acquiring a phase angle theta of grid-connected voltage through a phase-locked loop circuit;
inquiring data of a sine table corresponding to the phase angle theta to obtain a reference signal of grid-connected current;
obtaining a modulation signal u according to the deviation value of the grid-connected current and the reference signal thereofc；
Modulating signal u by adopting half-cycle modulation methodcAnd converting the driving signal into a driving signal of a power switching tube in the inverter, thereby realizing the working mode control of the inverter.
5. The control method according to claim 4, wherein the inverter has an operation mode 1, and the control includes: when the grid-connected current i is detectedg>When 0, controlling the power switch tube S1And the power switch tube S4On, the power switch tube S2The power switch tube S3And the power switch tube S5When the photovoltaic cell array PV and the energy storage inductor L are turned off1The power switch tube S1The filter capacitor CfThe power switch tube S4And the energy storage inductor L2Forming a forward charging closed loop; while the filter inductance Lf1The power grid ugThe filter inductor Lf2And said filter capacitor CfForm a forward charge to the grid ugAnd (5) supplying power.
6. The control method according to claim 4, wherein the inverter has an operation mode of 2, and the control includes: when the grid-connected current i is detectedg>When 0, controlling the power switch tube S5On, the power switch tube S1The power switch tube S2The power switch tube S3And the power switch tube S4When the photovoltaic cell array PV and the energy storage inductor L are turned off2The energy storage inductor L1The power switch tube S5Form a forward DC side follow current loop, and the filter inductor Lf1The power grid ugThe filter inductor Lf2And said filter capacitor CfForm a positive discharge to the grid ugAnd (5) supplying power.
7. The control method according to claim 4, wherein the operation mode 3 of the inverter comprises: when the grid-connected current i is detectedg<When 0, controlling the power switch tube S2And the power switch tube S3On, the power switch tube S1The power switch tube S4And the power switch tube S5When the photovoltaic cell array PV and the energy storage inductor L are turned off1The power switch tube S2The filter capacitor CfThe power switch tube S3And the energy storage inductor L2Forming a forward charging closed loop; while the filter inductance Lf1The power grid ugThe filter inductor Lf2And said filter capacitor CfForm a reverse charge to the grid ugAnd (5) supplying power.
8. The control method according to claim 4, wherein the inverter has an operation mode of 4, and the control includes: when the grid-connected current i is detectedg<When 0, controlling the power switch tube S5On, the power switch tube S1The power switch tube S2The power switch tube S3And the power switch tube S4When the photovoltaic cell array PV and the energy storage inductor L are turned off1The energy storage inductor L2The power switch tube S5Form a negative DC side follow current loop, and the filter inductor Lf1The power grid ugThe filter inductor Lf2And said filter capacitor CfForm a reverse discharge to the grid ugAnd negative power supply is carried out.
9. The control method according to claim 4, wherein the operation mode control of the inverter comprises: in controlling the workRate switching tube S5Has been turned off and the power switch tube S2And the power switch tube S3When not conducted, the photovoltaic cell array PV and the energy storage inductor L1The filter capacitor C1The filter capacitor C2And the energy storage inductor L2And forming an inductive current follow current loop in the overlapped time period.
10. The control system of the non-overlap time non-isolated current grid-connected inverter according to any of claims 1 to 3, wherein the system comprises a sensor, a PLL circuit, a PI controller and a half-cycle modulation module;
the PLL circuit is used for acquiring a phase angle theta of grid-connected voltage;
the sensor is used for acquiring grid-connected current of grid-connected voltage;
the PI controller obtains a modulation signal u according to the deviation value of the grid-connected current and a grid-connected current reference signalc(ii) a The grid-connected current reference signal is obtained by looking up a table according to the phase angle theta;
the half-cycle modulation module is used for modulating a signal ucAnd converting the driving signal into a driving signal of a power switching tube in the inverter and outputting the driving signal to control the opening and closing of the power switching tube of the inverter.
CN202110012692.1A 2021-01-06 2021-01-06 Non-isolated current type grid-connected inverter without overlapping time and control method and system thereof Pending CN112838778A (en)

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