CN113364322A - Single-phase single-stage current source type inverter - Google Patents

Single-phase single-stage current source type inverter Download PDF

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Publication number
CN113364322A
CN113364322A CN202110502225.7A CN202110502225A CN113364322A CN 113364322 A CN113364322 A CN 113364322A CN 202110502225 A CN202110502225 A CN 202110502225A CN 113364322 A CN113364322 A CN 113364322A
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circuit
bridge arm
energy storage
inverter
switch circuit
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CN113364322B (en
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梁炜
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Hunan Ketuo Electronic Technology Co ltd
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Hunan Ketuo Electronic Technology Co ltd
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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
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac 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
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac 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
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1582—Buck-boost converters
    • 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
    • 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 provides a single-phase single-stage current source type inverter, and relates to the technical field of electronic power. The single-phase single-stage current source type inverter can switch between the Buck mode and the Boost mode according to the magnitude relation between the input voltage and the output voltage, has the voltage boosting and reducing capacity, and can greatly reduce the inductance demand of the input side because the input side current does not need to be kept constant direct current any more. Meanwhile, the inverter can keep the common-mode voltage constant in the whole working process, so that the inverter can effectively inhibit the generation of leakage current, and can be effectively applied to the field of photovoltaic power generation.

Description

Single-phase single-stage current source type inverter
Technical Field
The invention relates to the technical field of electronic power, in particular to a single-phase single-stage current source type inverter with small input side inductance and leakage current suppression capability.
Background
The Inverter is divided into a Voltage Source Inverter (VSI) and a Current Source Inverter (CSI) according to the characteristics of a dc power supply, the VSI can only work on the occasion that the dc Voltage is constant and higher than the Voltage peak value of an ac side, the input Current has large pulsation, and a dead zone needs to be added to prevent the occurrence of bridge arm through. Compared with the VSI, the CSI has the advantages of voltage boosting, adjustable power factor, no direct connection protection and the like. In single-stage boost conversion occasions, especially in a photovoltaic cell grid-connected system, CSI is more suitable than VSI. Despite the advantages of CSI, there are still many challenges to its widespread use in grid-connected photovoltaic systems. The first problem to be solved is how to reduce the required amount of the energy storage inductor on the direct current side of the CSI. Conventional CSI, when operating, is equivalent to a constant dc source on the dc side. However, in actual conditions, an ideal direct current source does not exist, and the ideal direct current source is usually obtained by equivalently connecting a direct current voltage source with an inductor in series. In order to reduce the double frequency ripple of the current on the inductor, a huge energy storage inductor is needed on the input side of the current mode inverter, and the value of the inductor is usually several millihenries to hundreds of millihenries. This undoubtedly makes the overall inverter bulky, costly and costly. Secondly, the conventional CSI only has a boosting capability, and on occasions where the input voltage is higher than the grid voltage, the CSI cannot normally operate and cannot operate in a wide input range. Finally, a parasitic capacitor exists between the photovoltaic cell panel and the ground, and when a loop is formed among the parasitic capacitor, the photovoltaic system and the power grid, common-mode current, also called leakage current, may appear on the parasitic capacitor. The VDE-1026-1-1 related standard specifies that the photovoltaic system must be removed from the grid within 0.3 seconds when the peak leakage current is higher than 300 mA. Therefore, suppression of leakage current is also a challenge for the application of CSI in photovoltaic systems.
To solve the above problems, scholars at home and abroad have proposed many interesting solutions. However, many researches are only carried out on one or two problems, and no solution is available to simultaneously solve the three problems.
Disclosure of Invention
Technical problem to be solved
Aiming at the defects of the prior art, the invention provides a single-phase single-stage current source type inverter, which solves the technical problem that the prior art cannot simultaneously solve the three problems.
(II) technical scheme
In order to achieve the purpose, the invention is realized by the following technical scheme:
the invention provides a single-phase single-stage current source type inverter, the input side is connected with a photovoltaic array battery, the output side is connected with a power grid, the power grid is grounded, and the inverter also comprises: the device comprises two parasitic capacitors with the same size, a direct current side gating module, a bridge arm module and a filtering module; wherein the content of the first and second substances,
the two parasitic capacitors with the same size respectively ground the positive electrode and the negative electrode of the photovoltaic array battery;
the direct current side gating module comprises a first connecting end, a second connecting end, a third connecting end and a fourth connecting end, and the first connecting end and the second connecting end of the direct current side gating module are respectively connected with the positive electrode and the negative electrode of the photovoltaic array battery; a third connecting end and a fourth connecting end of the direct current side gating module are respectively connected with the upper diagonal and the lower diagonal of the bridge arm module;
the left diagonal angle and the right diagonal angle of the bridge arm module are connected with the power grid through a filtering module;
the direct current side gating module and the bridge arm module are respectively provided with a plurality of control ends, are suitable for being controlled by control signals accessed by the control ends and are suitable for being controlled by control signals accessed by the control ends, and the single-phase single-stage current source type inverter has working conditions: in the first working condition, when the input voltage generated by the photovoltaic array battery is smaller than the peak value of the grid voltage, the single-phase single-stage current source type inverter simultaneously comprises two working modes: when the input voltage is higher than the instantaneous voltage of the power grid, the inverter works in a Buck mode; when the input voltage is lower than the instantaneous voltage of the power grid, the inverter works in a Boost mode; the working condition is that the input voltage is higher than the peak value of the power grid voltage, and the inverter only has a Buck working mode; under different working modes, the common mode voltage is unchanged.
Preferably, the direct current side gating module comprises a first energy storage circuit, a second energy storage circuit, a first switch circuit, a second switch circuit, a third switch circuit and a unidirectional conduction circuit; wherein:
the first end of the first energy storage circuit is connected to the anode of the photovoltaic array battery through the first switch circuit, and the second end of the first energy storage circuit is connected with the upper diagonal of the bridge arm module;
the first end of the second energy storage circuit is connected to the negative electrode of the photovoltaic array battery through the second switch circuit, and the second end of the second energy storage circuit is connected with the lower diagonal of the bridge arm module;
two ends of the third switch circuit are connected to the connecting ends of the first energy storage circuit and the bridge arm module and the second energy storage circuit and the bridge arm module;
and two ends of the unidirectional conduction circuit are connected with the connecting ends of the first energy storage circuit and the first switch circuit, and the second energy storage circuit and the second switch circuit.
Preferably, the first energy storage circuit comprises a first energy storage inductor;
and/or
The second energy storage circuit comprises a second energy storage inductor;
and/or
The first switching circuit comprises a first switching tube at the direct current side;
and/or
The second switching circuit comprises a second switching tube on the direct current side;
and/or
The third switching circuit comprises a third switching tube on the direct current side;
and/or
The unidirectional conducting circuit comprises a diode.
Preferably, the first energy storage inductor and the second energy storage inductor have the same size.
Preferably, the bridge arm module comprises four switching tubes connected to form a bridge circuit, and the switching tubes are connected with a diode in series.
Preferably, the filter module includes a first filter inductor, a second filter inductor and a filter capacitor which are equal in size;
the first end of the first filter inductor is connected with the non-grounding end of the power grid, and the second end of the first filter inductor is connected with the left diagonal of the bridge arm module;
and the first end of the second filter inductor is connected with the grounding end of the power grid, and the second end of the second filter inductor is connected with the right diagonal of the bridge arm module.
Preferably, the negative end of the unidirectional conduction circuit is connected to the connection end of the first energy storage circuit and the first switch circuit;
and the positive end of the unidirectional conduction circuit is connected with the connecting end of the second energy storage circuit and the second switch circuit.
Preferably, the switch tubes are all MOSFETs.
Preferably, the control terminal is used for controlling the first switch circuit, the second switch circuit and the third switch circuit to be switched off and on, and includes the following three conditions:
in the first condition, the first switch circuit and the second switch circuit are switched on, and the third switch circuit is switched off;
in the second case, the first switch circuit, the second switch circuit and the third switch circuit are all switched off;
and in the third condition, the first switch circuit, the second switch circuit and the third switch circuit are all conducted.
Preferably, the control end is used for controlling the bridge arm of the bridge arm module to be switched on and off, and includes the following three conditions:
in the first case, four bridge arms are all disconnected;
in the second case, the bridge arm between the upper diagonal and the left diagonal, the bridge arm between the right diagonal and the lower diagonal are switched on, and the other bridge arms are switched off;
and in the third case, the bridge arm between the upper diagonal and the left diagonal, the bridge arm between the right diagonal and the lower diagonal are disconnected, and other bridge arms are connected.
(III) advantageous effects
The invention provides a single-phase single-stage current source type inverter. Compared with the prior art, the method has the following beneficial effects:
the single-phase single-stage current source type inverter can switch between the Buck mode and the Boost mode according to the magnitude relation between the input voltage and the output voltage, has the voltage boosting and reducing capacity, and can greatly reduce the inductance demand of the input side because the input side current does not need to be kept constant direct current any more. Meanwhile, the inverter can keep the common-mode voltage constant in the whole working process, so that the inverter can effectively inhibit the generation of leakage current, and can be effectively applied to the field of photovoltaic power generation.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a block diagram of a single-phase single-stage current source inverter according to an embodiment of the present invention;
FIG. 2 is a block diagram of a DC side gating module;
FIG. 3 is a circuit diagram of a single-phase single-stage current source inverter;
FIG. 4 is a circuit diagram of the working mode 1 corresponding to the circuit shown in FIG. 3;
FIG. 5 is a circuit diagram of the circuit of FIG. 3 corresponding to the working mode 2;
FIG. 6 is a circuit diagram of the working mode 3 corresponding to the circuit shown in FIG. 3;
FIG. 7 is a circuit diagram of the working mode 4 corresponding to the circuit shown in FIG. 3;
FIG. 8 is a circuit diagram of the working mode 5 corresponding to the circuit shown in FIG. 3;
FIG. 9 is a circuit diagram of the working mode 6 corresponding to the circuit shown in FIG. 3;
FIG. 10 is a circuit diagram of the corresponding operation mode 7 of the circuit shown in FIG. 3;
FIG. 11 is a circuit diagram of the working mode 8 corresponding to the circuit shown in FIG. 3;
FIG. 12 is a schematic diagram illustrating the operation of the circuit of FIG. 3;
fig. 13 is a schematic diagram of a modulation strategy of the circuit shown in fig. 3.
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 are clearly and completely described, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. 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.
For convenience of description, the term "switching tube" in the embodiment of the present invention refers to a switch, and a MOSFET with a parallel diode embedded therein is taken as an example in the embodiment of the present invention. Since the switching device of the current source inverter cannot withstand a reverse voltage, the switching device requires a specific requirement. The switching devices in the legs need to be connected in series with a diode device that blocks the flow in the direction and takes on the reverse voltage. The switch on the bridge arm can be an IGBT + diode device, an MOSFET + diode device or an RB-IGBT device which selects an inverse isolation gate bipolar transistor.
Note that a diode is used to represent the one-way conduction element, but the one-way conduction element in the present invention is not limited to a diode. The unidirectional conducting element in the embodiment of the invention can also adopt other unidirectional conducting devices besides the diode. The terms "first", "second", and the like are used only for distinguishing the respective components from each other, and do not limit the order of the respective components.
The embodiment of the invention provides a single-phase single-stage current source type inverter, which has a structure shown in figure 1, wherein an input side is connected with a photovoltaic array battery, an output side is connected with a power grid, the power grid is grounded, the positive electrode and the negative electrode of the photovoltaic array battery are respectively grounded through two parasitic capacitors with the same size, and the inverter further comprises a direct current side gating module, a bridge arm module and a filtering module; wherein the content of the first and second substances,
the direct current side gating module comprises a first connecting end, a second connecting end, a third connecting end and a fourth connecting end, wherein the first connecting end and the second connecting end of the direct current side gating module are respectively connected with the positive electrode and the negative electrode of the photovoltaic array battery; a third connecting end and a fourth connecting end of the direct current side gating module are respectively connected with the upper diagonal and the lower diagonal of the bridge arm module;
the left and right opposite angles of the bridge arm module are connected with the power grid through the filtering module.
The single-phase single-stage current source inverter according to the embodiment of the present invention is described in detail below with reference to a specific circuit diagram, a mode analysis, a modulation strategy thereof, and the like.
Fig. 2 is a structural diagram of a dc side gating module, which includes a first energy storage circuit, a second energy storage circuit, a first switch circuit, a second switch circuit, a third switch circuit, and a unidirectional conducting circuit; wherein: the first end of the first energy storage circuit is connected to the anode of the photovoltaic array battery through the first switch circuit, and the second end of the first energy storage circuit is connected with the upper diagonal of the bridge arm module; the first end of the second energy storage circuit is connected to the negative electrode of the photovoltaic array battery through the second switch circuit, and the second end of the second energy storage circuit is connected with the lower diagonal of the bridge arm module; two ends of the third switch circuit are connected to the connecting ends of the first energy storage circuit and the bridge arm module and the second energy storage circuit and the bridge arm module; and two ends of the unidirectional conduction circuit are connected with the connecting ends of the first energy storage circuit and the first switch circuit, and the second energy storage circuit and the second switch circuit.
Fig. 3 shows a circuit diagram of a single-phase single-stage current source type inverter. In the circuit diagram, a voltage stabilizing capacitor C is connected in parallel at two ends of a photovoltaic array battery PVin(ii) a The first energy storage circuit comprises a first energy storage inductor L1(ii) a The second energy storage circuit comprises a second energy storage inductor L2(ii) a The first switch circuit comprises a first switch tube S at the DC side5(ii) a The second switch circuit comprises a DC side second switch tube S6(ii) a The third switch circuit comprises a DC side third switch tube S7(ii) a The unidirectional conducting circuit comprises a diode D5. The first energy storage inductor L1And a second energy storage inductor L2Are equal in size.
S1～S4Four bridge arms of the bridge arm module are provided, each switch tube on the bridge arm is connected with a diode D which blocks the flow in the direction and bears the reverse voltage in series1～D4。
VgAnd the output voltage of the SS-CSI is represented, and the grid voltage is represented when the SS-CSI is connected to the grid. CfIs the filter capacitance of the output. First filter inductor Lf1And a second filter inductance Lf2Are two output filter inductors of equal size. Cpv1And Cpv2Respectively, the parasitic capacitance of the positive and negative electrodes of the photovoltaic array battery to the ground.
The inverter shown in fig. 3 has 8 operating modes, which are modes 1 to 8. The modes 1-4 are modes of the inverter working in a positive half period, and the modes 5-8 are modes of the inverter working in a negative half period.
Fig. 4 to 11 show 8 different modes of operation. The method comprises the following specific steps:
the point P is the positive end of the photovoltaic array cell PV, the point N is the negative end of the photovoltaic array cell PV, the point A is the left diagonal of the bridge arm module, and the point B is the left diagonal of the bridge arm module.
Working mode 1: as shown in FIG. 4, the current flows in the forward direction, and the switch tube S is turned on or off5，S1，S4，S6Conducting, other switch tubes are turned off, and the current flow path is P → S5→S1→S4→S6→ N, this mode occurs in the positive half-cycle of the grid voltage and the input voltage VinAbove the instantaneous value of the grid voltage Vg. Namely, the inverter operates in the Buck mode at this time, and the operation mode 1 is similar to the charging stage of the conventional Buck circuit. Definition VcmCommon mode voltage, its magnitude is: vcm＝(VAN+VBN)/2. Then V in that modecmThe size of (A) is as follows: vin/2。
And (3) working mode 2: as shown in FIG. 5, the current flows in the forward direction, and the switch tube S is turned on or off1，S4，D5The other switch tubes are switched off, and the current flow path is L1→S1→S4→L2→D5→L1The mode occurs in the positive half-cycle of the grid voltage and the input voltage VinAbove the instantaneous value of the grid voltage Vg. That is, the inverter operates in the Buck mode at this time, and the operation mode 2 is similar to the discharging stage of the conventional Buck circuit. Definition VcmCommon mode voltage, its magnitude is: vcm＝(VAN+VBN)/2. Then V in that modecmThe size of (A) is as follows: vin/2. The working mode 1 and the working mode 2 are matched together to form a complete Buck working mode. When the input voltage VinHigher than the output voltage VgAnd during the operation, the inverter is switched back and forth between the working mode 1 and the working mode 2, so that the inverter works in a voltage reduction mode.
Working mode 3: as shown in fig. 6, current flowA forward flow, switch tube S5，S7，S6Conducting, other switch tubes are turned off, and the current flow path is P → S5→L1→S7→L2→S6→ N, this mode occurs in the positive half-cycle of the grid voltage and the input voltage VinBelow the network voltage VgInstantaneous value of (a). That is, the inverter operates in the Boost mode at this time, and the operation mode 3 is similar to the charging stage of the conventional Boost circuit. In this mode VcmThe size of (A) is as follows: vin/2。
The working mode 4 is as follows: as shown in FIG. 7, the current flows in the forward direction, and the switch tube S is turned on or off5，S1，S4，S6Conducting, other switch tubes are turned off, and the current flow path is P → S5→L1→S1→S4→L2→S6→ N, this mode occurs in the positive half-cycle of the grid voltage and the input voltage VinBelow the network voltage VgInstantaneous value of (a). That is, the inverter operates in the Boost mode at this time, and the operation mode 4 is similar to the discharging stage of the conventional Boost circuit. In this mode VcmThe size of (A) is as follows: vin/2. The working mode 3 and the working mode 4 are matched together to form a complete Boost working mode. When the input voltage VinBelow the output voltage VgAnd when the inverter is switched back and forth between the working mode 3 and the working mode 4, the inverter works in a boosting mode.
Working mode 5: as shown in FIG. 8, the current flows in the forward direction, and the switch tube S is turned on and off5，S3，S2，S6Conducting, other switch tubes are turned off, and the current flow path is P → S5→S3→S2→S6→ N, this mode occurs in the negative half-cycle of the grid voltage and the input voltage VinAbove the instantaneous value of the grid voltage Vg. That is, the inverter operates in Buck mode at this time, and the operation mode 5 is similar to the charging stage of the conventional Buck circuit, and is symmetrical to the operation mode 1, one occurs in the positive half period and one occurs in the negative half period. In this mode VcmThe size of (A) is as follows: vin/2。
Work byModality 6: as shown in FIG. 9, the current flows in the forward direction, and the switch tube S is turned on and off3，S2，D5The other switch tubes are switched off, and the current flow path is L1→S3→S2→L2→D5→L1The mode occurs in the negative half-cycle of the grid voltage and the input voltage VinHigher than the network voltage VgInstantaneous value of (a). That is, the inverter operates in Buck mode at this time, and the operation mode 6 is similar to the discharging stage of the conventional Buck circuit. In this mode VcmThe size of (A) is as follows: vin/2. The working modes 5 and 6 cooperate together to form a complete Buck working mode. When a negative half period, the input voltage VinHigher than the output voltage VgAnd when the inverter is switched back and forth between the working modes 5 and 6, the inverter works in a voltage reduction mode.
The working mode 7 is as follows: as shown in FIG. 10, the current flows in the forward direction, and the switch tube S is turned on and off5，S7，S6Conducting, other switch tubes are turned off, and the current flow path is P → S5→L1→S7→L2→S6→ N, this mode occurs in the negative half-cycle of the grid voltage and the input voltage VinBelow the network voltage VgInstantaneous value of (a). That is, the inverter operates in the Boost mode at this time, and the operation mode 7 is similar to the charging stage of the conventional Boost circuit. In this mode VcmThe size of (A) is as follows: vin/2。
The working mode 8 is as follows: as shown in FIG. 11, the current flows in the forward direction, and the switch tube S is turned on and off5，S3，S2，S6Conducting, other switch tubes are turned off, and the current flow path is P → S5→L1→S1→S4→L2→S6→ N, this mode occurs in the negative half-cycle of the grid voltage and the input voltage VinBelow the network voltage VgInstantaneous value of (a). That is, the inverter operates in the Boost mode at this time, and the operation mode 8 is similar to the discharging stage of the conventional Boost circuit. In this mode VcmThe size of (A) is as follows: vin/2. The working mode 7 and the working mode 8 are matched together to form a complete Boost mode of operation. When a negative half period, the input voltage VinBelow the output voltage VgIn the meantime, the inverter is switched back and forth between the working mode 7 and the working mode 8, so that the inverter works in a boosting mode.
The above analysis results show that the common-mode voltage of the inverter can maintain a constant value in each mode, and the system does not generate leakage current, and table 1 shows the magnitude of the common-mode voltage and the voltage on the parasitic capacitor in the whole inverter working mode.
TABLE 1 device State and common mode Voltage magnitudes
Figure BDA0003056854110000121
The above description is mainly the case of both the step-up and step-down. When the input voltage is always higher than the output voltage, the inverter has only a Buck mode and no Boost mode. Namely, the whole inverter only has four modes 1, 2, 5 and 6, and 4 less modes are compared with the original working modes.
As can be seen from the analysis of fig. 12, the single-phase single-stage current source inverter is actually equivalent to an inverter topology formed by combining a conventional Buck circuit and a conventional Boost circuit. The working mode of the inverter is mainly determined according to the relation between the input voltage and the output voltage. Thus, the inverter can have both the step-up capability and the step-down capability. In addition, because the conventional Buck or Boost circuit can work without the direct current with constant input-side current, an inverter formed by the two basic circuits does not need huge input-side inductance to maintain the input current to be constant direct current, and the effect of reducing the input-side inductance is realized.
A single-phase single-stage current source inverter modulation strategy with small input-side inductance and leakage current suppression capability is shown in fig. 13, which shows the duty cycle waveforms of the individual switches in the inverter. Wherein d is1(t)-d7(t) respectively represent switches S1-S7Duty ratio of (1), T1(T) and T2(t) to assist correct generation of switching devicesAn auxiliary signal for PWM. Buck mode appears at input voltage VinAbove the instantaneous value of the grid voltage, the inverter has two Buck modes in the positive half cycle and the negative half cycle respectively. Respectively, occur in the time periods t shown in fig. 130-t1]，[t2-t3]，[t3-t4]，[t5-t6]. Because, in this mode, the switch S1And S4Are the same, switch S2And S3Switch S5And S6The same applies to the actions of (1). The Boost mode occurs at the input voltage VinBelow the instantaneous value of the grid voltage, the inverter has a Boost mode in each of the positive half-cycle and the negative half-cycle. Respectively, occur in the time periods t shown in fig. 131-t2]And [ t4-t5]。
In summary, compared with the prior art, the embodiment of the present application has the following beneficial effects:
1. the small input side inductor enables the size and cost of the inductor to be greatly reduced, and the power density and use cost of a product can be improved in the actual use process.
2. The leakage current suppression capability enables the photovoltaic power generation system to have higher reliability and safety.
3. And meanwhile, the voltage boosting and reducing capacity is realized, the range of the input side voltage is wide, the inverter can be applied to wider occasions, and the application is more flexible.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (10)

1. A single-phase single-stage current source type inverter, the input side connects the photovoltaic array battery, the output side connects the electric wire netting, the electric wire netting ground connection, characterized by still includes: the device comprises two parasitic capacitors with the same size, a direct current side gating module, a bridge arm module and a filtering module; wherein the content of the first and second substances,
the two parasitic capacitors with the same size respectively ground the positive electrode and the negative electrode of the photovoltaic array battery;
the direct current side gating module comprises a first connecting end, a second connecting end, a third connecting end and a fourth connecting end, and the first connecting end and the second connecting end of the direct current side gating module are respectively connected with the positive electrode and the negative electrode of the photovoltaic array battery; a third connecting end and a fourth connecting end of the direct current side gating module are respectively connected with the upper diagonal and the lower diagonal of the bridge arm module;
the left diagonal angle and the right diagonal angle of the bridge arm module are connected with the power grid through a filtering module;
the direct current side gating module and the bridge arm module are respectively provided with a plurality of control ends, are suitable for being controlled by control signals accessed by the control ends and are suitable for being controlled by control signals accessed by the control ends, and the single-phase single-stage current source type inverter has working conditions: in the first working condition, when the input voltage generated by the photovoltaic array battery is smaller than the peak value of the grid voltage, the single-phase single-stage current source type inverter simultaneously comprises two working modes: when the input voltage is higher than the instantaneous voltage of the power grid, the inverter works in a Buck mode; when the input voltage is lower than the instantaneous voltage of the power grid, the inverter works in a Boost mode; the working condition is that the input voltage is higher than the peak value of the power grid voltage, and the inverter only has a Buck working mode; under different working modes, the common mode voltage is unchanged.
2. The single-phase single-stage current source inverter of claim 1, wherein the dc-side gating module comprises a first tank circuit, a second tank circuit, a first switch circuit, a second switch circuit, a third switch circuit, and a unidirectional conducting circuit; wherein:
the first end of the first energy storage circuit is connected to the anode of the photovoltaic array battery through the first switch circuit, and the second end of the first energy storage circuit is connected with the upper diagonal of the bridge arm module;
the first end of the second energy storage circuit is connected to the negative electrode of the photovoltaic array battery through the second switch circuit, and the second end of the second energy storage circuit is connected with the lower diagonal of the bridge arm module;
two ends of the third switch circuit are connected to the connecting ends of the first energy storage circuit and the bridge arm module and the second energy storage circuit and the bridge arm module;
and two ends of the unidirectional conduction circuit are connected with the connecting ends of the first energy storage circuit and the first switch circuit, and the second energy storage circuit and the second switch circuit.
3. The single-phase single-stage current source inverter of claim 2, wherein the first tank circuit comprises a first tank inductor;
and/or
The second energy storage circuit comprises a second energy storage inductor;
and/or
The first switching circuit comprises a first switching tube at the direct current side;
and/or
The second switching circuit comprises a second switching tube on the direct current side;
and/or
The third switching circuit comprises a third switching tube on the direct current side;
and/or
The unidirectional conducting circuit comprises a diode.
4. The single-phase single-stage current source inverter of claim 3, wherein the first energy storage inductor and the second energy storage inductor are equal in size.
5. The single-phase single-stage current source inverter of any one of claims 1 to 4, wherein the bridge arm module comprises four switching tubes connected in a bridge circuit, and the switching tubes are connected in series with a diode.
6. The single-phase single-stage current source inverter according to any one of claims 1 to 4, wherein the filter module comprises a first filter inductor, a second filter inductor and a filter capacitor which are equal in size;
the first end of the first filter inductor is connected with the non-grounding end of the power grid, and the second end of the first filter inductor is connected with the left diagonal of the bridge arm module;
and the first end of the second filter inductor is connected with the grounding end of the power grid, and the second end of the second filter inductor is connected with the right diagonal of the bridge arm module.
7. The single-phase single-stage current source inverter according to any one of claims 2 to 3, wherein a negative end of the unidirectional conducting circuit is connected to a connection end of the first energy storage circuit and the first switching circuit;
and the positive end of the unidirectional conduction circuit is connected with the connecting end of the second energy storage circuit and the second switch circuit.
8. The single-phase single-stage current source inverter according to any one of claims 2 to 3, wherein the switching tubes are MOSFETs.
9. The single-phase single-stage current source inverter according to any one of claims 2 to 3, wherein the control terminal is used for controlling the first switching circuit, the second switching circuit and the third switching circuit to be turned off and on, and comprises the following three conditions:
in the first condition, the first switch circuit and the second switch circuit are switched on, and the third switch circuit is switched off;
in the second case, the first switch circuit, the second switch circuit and the third switch circuit are all switched off;
and in the third condition, the first switch circuit, the second switch circuit and the third switch circuit are all conducted.
10. The single-phase single-stage current source inverter of any one of claims 1 to 4, wherein the control terminal is used for controlling the bridge arm of the bridge arm module to be switched off and on, and the three conditions are as follows:
in the first case, four bridge arms are all disconnected;
in the second case, the bridge arm between the upper diagonal and the left diagonal, the bridge arm between the right diagonal and the lower diagonal are switched on, and the other bridge arms are switched off;
and in the third case, the bridge arm between the upper diagonal and the left diagonal, the bridge arm between the right diagonal and the lower diagonal are disconnected, and other bridge arms are connected.
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