CN108448918A - A kind of single-phase grid-connected photovoltaic DC-to-AC converter of transless - Google Patents
A kind of single-phase grid-connected photovoltaic DC-to-AC converter of transless Download PDFInfo
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- CN108448918A CN108448918A CN201810412505.7A CN201810412505A CN108448918A CN 108448918 A CN108448918 A CN 108448918A CN 201810412505 A CN201810412505 A CN 201810412505A CN 108448918 A CN108448918 A CN 108448918A
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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
-
- 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
- H02M1/0048—Circuits or arrangements for reducing losses
- H02M1/0054—Transistor switching losses
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- 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
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
-
- 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
A kind of single-phase grid-connected photovoltaic DC-to-AC converter of transless comprising：Inverter circuit, the direct current for being provided DC power supply are converted to corresponding alternating current and export；Energy storage inductor exists for being played a filtering role in the power transmission stage, and in freewheeling period as current source；First alternating current bypass for constituting current loop in inverter freewheeling period and energy storage inductor to realize afterflow, and realizes the electric isolution of AC network and DC power supply.Inverter proposed by the invention is both provided with new branch at the both ends of afterflow branch to reduce leakage current and single switch loss, which can transmit reactive power, and can be effectively in suppression circuit leakage current.
Description
Technical field
The present invention relates to technical field of photovoltaic power generation, specifically, being related to a kind of single-phase grid-connected photovoltaic inversion of transless
Device.
Background technology
In recent years, for environmental protection and the utilization of resources the considerations of, photovoltaic generation has had a great development, grid-connected
(PV) generation technology also has become the hot spot of research, and gird-connected inverter is shadow as the interface between photovoltaic array and power grid
The key factor of acoustic system reliability service.Photovoltaic system, especially single-phase photovoltaic system, need high reliability, high efficiency, it is low at
This low profile photovoltaic gird-connected inverter.
Transless inverter is increasingly being applied to light due to the characteristic of its intrinsic high efficiency and low cost
Lie prostrate inverter.However, leakage current has become problem in non-isolated gird-connected inverter, leakage current can cause transless inverse
There are problems by the safety of change device and EMI.
Invention content
To solve the above problems, the present invention provides a kind of single-phase grid-connected photovoltaic DC-to-AC converter of transless, the inverter
Including：
Inverter circuit, input terminal with DC power supply for connecting, the direct current for being provided the DC power supply
It is converted to corresponding alternating current and exports；
Energy storage inductor is connected between the inverter circuit and AC load, for being filtered from the power transmission stage
Effect, and exist as current source in freewheeling period；
First alternating current bypass, external-connected port are correspondingly connected with each output end of the inverter circuit respectively, are used for
Inverter freewheeling period and the energy storage inductor constitute current loop to realize afterflow, and realize AC network with it is described straight
The electric isolution in galvanic electricity source.
According to one embodiment of present invention, the inverter circuit includes：
Dc-link capacitance is used to connect with the positive and negative port of the DC power supply, plays stable DC busbar voltage and makees
With；
H bridges control inverter circuit entirely, and input terminal is connect with the both ends of the dc-link capacitance, output end and the energy storage
Inductance and the connection of the first alternating current bypass.
According to one embodiment of present invention, first alternating current bypass includes alternating current bypass energy storage inductor and alternating current bypass
Switching tube, wherein the alternating current bypass energy storage inductor connects to form first alternating current bypass with the alternating current bypass switching tube.
According to one embodiment of present invention, the alternating current bypass energy storage inductor includes the first by-pass inductor and the second bypass
Inductance, wherein the alternating current bypass switching tube is between first by-pass inductor and the second by-pass inductor.
According to one embodiment of present invention, the alternating current bypass switching tube includes the first IGBT units and the 2nd IGBT mono-
Member, wherein
The first output port that the collector of the first IGBT units passes through first inductance and the inverter circuit
Connection, emitter are connect with the emitter of the 2nd IGBT units of the road；
The second output terminal mouth that the collector of the 2nd IGBT units passes through second inductance and the inverter circuit
Connection.
According to one embodiment of present invention, the inverter further includes：
Second alternating current bypass, first port and second port respectively with the first output port of the inverter circuit and
Two output ports connect, and third port connect with the dc-link capacitance midpoint of the inverter circuit and is grounded simultaneously.
According to one embodiment of present invention, second alternating current bypass includes：
3rd IGBT units, collector are connect with the first output port of the inverter circuit；
4th IGBT units, collector are connect with the second output terminal mouth of the inverter circuit, emitter and the road
The emitter of 3rd IGBT units connects；
5th IGBT units, emitter are connect with the emitter of the 3rd IGBT units, collector and the inversion
Upper dc-link capacitance is connected with the points of common connection of lower dc-link capacitance in circuit.
According to one embodiment of present invention, second alternating current bypass further includes third inductance, and the 5th IGBT is mono-
The points of common connection that member passes through upper dc-link capacitance and lower dc-link capacitance in the third inductance and the inverter circuit
Connection.
According to one embodiment of present invention, the inverter further includes：
Control circuit is connect, the operating status for controlling each switching tube with each switching tube in the inverter,
The control circuit is configured to by the way of closed-loop control carry out zero deflection control to networking electric current.
According to one embodiment of present invention, the control circuit includes：
PR controllers are connect with each switching tube in the inverter；
The transmission function of the PR controllers is：
Wherein, G (s) indicates transmission function, kpIndicate proportionality coefficient, krIndicate resonance coefficient, ωcAnd ω0Frequency is indicated respectively
Rate bandwidth and system bandwidth.
Compared with common single-phase grid-connected photovoltaic DC-to-AC converter, inverter proposed by the invention is in order to reduce leakage current and list
A switching loss, being both provided with a new branch at the both ends of afterflow branch, (i.e. the first alternating current bypass and the second exchange are other
Road).The transless inverter can transmit reactive power, and can be effectively in suppression circuit leakage current.
For high-power system, two unidirectional freewheeling circuits are embedded in full-bridge inverter by inverter provided by the present invention
Midpoint between, to obtain photovoltaic battery panel is isolated with power grid during afterflow afterflow channel.Topological freewheeling circuit is main
Bypass circuit is flowed through, the interaction of afterflow phase and other phases can be effectively isolated, is conducive to obtain higher efficiency.Together
When, which may be implemented voltage balance control, it is possible to reduce harmonic current and leakage current.
Compared with dc bypass topology, alternating current bypass topology has lower power attenuation, this is because flowing through switch
Electric current is relatively low.Alternating current bypass topology realizes a new afterflow road by adding a two-way switch at the midpoint of two legs
Diameter.Compared with common full-bridge inverter, the pressure resistance of switching device and switching loss halve, and can effectively reduce the passive member such as filter
The volume and weight of part.During commutation, each power semiconductor is subjected to Udc/ 2 voltage.This helps to improve inverter
Voltage level and power level, for element selection reserve more spaces；Simultaneous Switching loss is smaller, and switching frequency is higher, humorous
Wave is lower.
In addition, under non-unity power factor, the output voltage waveforms of ordinary inverter are and of the invention there are distortion phenomenon
The output waveform of the inverter provided is with good performance.Above-mentioned simulation result also demonstrates control proposed by the present invention simultaneously
The correctness and validity of scheme processed.The inverter eliminates leakage current, realizes excellent network quality waveform.
Other features and advantages of the present invention will be illustrated in the following description, also, partly becomes from specification
It obtains it is clear that understand through the implementation of the invention.The purpose of the present invention and other advantages can be by specification, rights
Specifically noted structure is realized and is obtained in claim and attached drawing.
Description of the drawings
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is required attached drawing in technology description to do simple introduction：
Fig. 1 is the topological structure schematic diagram of the single-phase grid-connected photovoltaic DC-to-AC converter of existing transless；
Fig. 2 is the structural schematic diagram of transless photovoltaic DC-to-AC converter according to an embodiment of the invention；
Fig. 3-Figure 10 is the course of work schematic diagram of transless photovoltaic DC-to-AC converter according to an embodiment of the invention；
Figure 11 is the reactive-load compensation modulation strategy signal of transless photovoltaic DC-to-AC converter according to an embodiment of the invention
Figure；
Figure 12 is artificial circuit schematic diagram according to an embodiment of the invention；
It in unity power factor and power factor is 0.833 lag that Figure 13-Figure 20, which is according to an embodiment of the invention,
In the case of transless photovoltaic DC-to-AC converter and common single-phase grid-connected photovoltaic DC-to-AC converter topology output current and leakage current wave
Shape schematic diagram.
Specific implementation mode
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings and examples, how to be applied to the present invention whereby
Technological means solves technical problem, and the realization process for reaching technique effect can fully understand and implement.It needs to illustrate
As long as not constituting conflict, each embodiment in the present invention and each feature in each embodiment can be combined with each other,
It is formed by technical solution within protection scope of the present invention.
Meanwhile in the following description, for illustrative purposes and numerous specific details are set forth, to provide to of the invention real
Apply the thorough understanding of example.It will be apparent, however, to one skilled in the art, that the present invention can not have to tool here
Body details or described ad hoc fashion are implemented.
In recent years, for environmental protection and the utilization of resources the considerations of, photovoltaic generation has had significant progress.Photovoltaic system,
Especially monophase system, it usually needs high reliability, high efficiency, low cost and the photovoltaic combining inverter of miniaturization.It is positive because
In this way, transless inverter is used more and more due to its intrinsic higher efficiency and lower cost.
However, the problem of leakage current has become urgent need to resolve in non-isolated gird-connected inverter.Many researchers
This is solved the problems, such as by improving the structure of full-bridge inverter.
Fig. 1 illustrates the topological structure schematic diagram of the single-phase grid-connected photovoltaic DC-to-AC converter of existing transless.It can by Fig. 1
Know, existing single-phase grid-connected photovoltaic DC-to-AC converter uses H bridges and controls inverter circuit entirely to realize the inversion conversion to direct current.The list
The voltage equation of phase grid-connected photovoltaic inverter can be expressed as：
Wherein, uABIndicate contravarianter voltage, ugIndicate that network voltage, L indicate inductance value, igIndicate entry into the electricity of power grid
Stream, t indicate the time.
For network voltage ugFor, exist：
Wherein, EmIndicate that grid voltage amplitude, ω indicate electrical network angular frequency.
For entering the electric current i of power gridgFor, exist：
Wherein,Indicate that power network current amplitude, α indicate power-factor angle.
Expression formula (2) and expression formula (3) are substituted into expression formula (1), can be obtained：
Wherein,
In order to reduce the leakage current in existing single-phase inverter, the present invention provides a kind of new transless inversions
Device, the inverter obtain the afterflow channel that DC power supply is isolated with AC load by increasing bypass circuit in the sides AC.It should
Inverter is preferably used in photovoltaic generating system, wherein DC power supply is correspondingly photovoltaic battery panel, and AC load is then corresponding
Ground is power grid.
Fig. 2 shows the structural schematic diagrams for the single-phase grid-connected photovoltaic DC-to-AC converter of transless that the present embodiment is provided.
As shown in Fig. 2, the transless inverter 102 that the present embodiment is provided be connected to DC power supply 101 with exchange it is negative
Between carrying 103, which includes：Inverter circuit, energy storage inductor and alternating current bypass.Wherein, the input terminal of inverter circuit
(i.e. DC terminal) is connect with DC power supply 101, and output end is connect by energy storage inductor with AC load 103 (such as power grid),
The direct current that DC power supply 101 is provided can be converted to corresponding alternating current and transmit best friend after being filtered by energy storage inductor
Current load 103.
The external-connected port of alternating current bypass is correspondingly connected with each output end of inverter circuit respectively, for continuous in inverter
The stream stage constitutes current loop to realize afterflow with energy storage inductor, and realizes the electricity of AC load 103 and DC power supply 101
Isolation.
Specifically, in the present embodiment, inverter circuit controls inverter circuit entirely preferably by dc-link capacitance and H bridges.Its
In, dc-link capacitance is connected between the positive and negative port of DC power supply 101, and H bridges control full the input terminal of inverter circuit then with
The both ends of dc-link capacitance connect, and output end is then connect with energy storage inductor and alternating current bypass.
As shown in Fig. 2, in the present embodiment, inverter circuit preferably includes the first dc-link capacitance C1 and the second direct current is female
Line capacitance C2.Wherein, the first end of the first dc-link capacitance C1 is connect with the anode of DC power supply 101, second end and second
The first end of dc-link capacitance C2 connects, and the second end of the second dc-link capacitance C2 then connects with the cathode of DC power supply 101
It connects.In the present embodiment, the first dc-link capacitance C1 is preferably identical as the parameter of the second dc-link capacitance C2, and first
Dc-link capacitance C1 is preferably connect with ground GND with the public connecting end of the second dc-link capacitance C2.
Certainly, in other embodiments of the invention, according to actual needs, the first dc-link capacitance C1 and the second direct current
The public connecting end of bus capacitor C2 may also connect to other reasonable current potentials, and the invention is not limited thereto.
As shown in Fig. 2, in the present embodiment, it includes four switching tubes that H bridges control inverter circuit entirely, these switching tubes are preferably adopted
(i.e. the first inversion IGBT cell Ss 1, the second inversion IGBT cell Ss 2,3 and of third inversion IGBT cell Ss are realized with IGBT units
4th inversion IGBT cell Ss 4).Wherein, the first reverse phase diode D1, the second inversion are provided in the first inversion IGBT cell Ss 1
It is provided with the second reverse phase diode D2 in IGBT cell Ss 2, third reverse phase diode is provided in third inversion IGBT cell Ss 3
D3 is provided with the 4th reverse phase diode D4 in the 4th inversion IGBT cell Ss 4.
In the present embodiment, inverter preferably includes two energy storage inductors (i.e. the first inductance L1 and the second inductance L2),
In, the first inductance L1 be connected to the first output port (i.e. port A) of inverter circuit and AC load 103 first port it
Between, and the second inductance L2 is then connected to the second port of second output terminal mouth (i.e. the port B) and AC load 103 of inverter circuit
Between.
Certainly, in other embodiments of the invention, the quantity for the energy storage inductor that inverter is included is according to actual needs
Other reasonable values (such as one or three with first-class) are also configured as, the invention is not limited thereto.For example, the one of the present invention
Can only include above-mentioned first inductance L1 or the second inductance L2 in inverter in a embodiment.
As shown in Fig. 2, in the present embodiment, alternating current bypass includes the first alternating current bypass 201.Specifically, the first alternating current bypass
201 preferably include alternating current bypass energy storage inductor and alternating current bypass switching tube, and alternating current bypass energy storage inductor is switched with alternating current bypass
Pipe connects to form the first alternating current bypass 201.Specifically, alternating current bypass energy storage inductor preferably includes the first by-pass inductor L3 and
Two by-pass inductor L4.Wherein, alternating current bypass switching tube is between the first by-pass inductor L3 and the second by-pass inductor L4.
Specifically, in the present embodiment, the alternating current bypass switching tube in the first alternating current bypass 201 preferably includes the first IGBT
Cell S 5 and the 2nd IGBT cell Ss 6.Wherein, the collector of the first IGBT cell Ss 5 passes through the first by-pass inductor L3 and inversion electricity
First output port (i.e. port A) on road connects, and emitter is connect with the emitter of the 2nd IGBT cell Ss 6 of road.2nd IGBT is mono-
The collector of first S6 is then connected by the second output terminal mouth (i.e. port B) of the second by-pass inductor L4 and inverter circuit.
In the present embodiment, it is provided with the diode D5 of parallel connected in reverse phase in the first IGBT cell Ss 5, in the 2nd IGBT cell Ss 6
It is again provided with the diode D6 of parallel connected in reverse phase.
As shown in Fig. 2, in the present embodiment, inverter 102 further includes the second alternating current bypass 202.Second alternating current bypass, 202 shape
At there are three ports.Wherein, the first port and second port of the second alternating current bypass 202 are exported with the first of inverter circuit respectively
Port (i.e. port A) and second output terminal mouth (i.e. port B) connection, third port then connect with inverter circuit dc-link capacitance
It connects.Specifically, the third port of the second alternating current bypass 202 is preferably electric with the first dc-link capacitance C1 and the second DC bus
Hold the common ground point connection of C2.
Specifically, in the present embodiment, the second alternating current bypass 202 preferably includes three IGBT units, and (i.e. the 3rd IGBT is mono-
First S7, the 4th IGBT cell Ss 8 and the 5th IGBT cell Ss 9).Wherein, the collector and inverter circuit of the 3rd IGBT cell Ss 7
First output port (i.e. port A) connects, and the emitter of the 3rd IGBT cell Ss 7 is connect with the emitter of the 4th GIBT cell Ss 8,
The collector of 4th IGBT cell Ss 8 is then connect with the second output terminal mouth of inverter circuit (i.e. port B).5th IGBT cell Ss 9
Emitter connect (due to the hair of the emitter and the 4th IGBT units of the 3rd IGBT units with the emitter of the 3rd IGBT units
Emitter-base bandgap grading is electrically connected, therefore the emitter of the 5th IGBT units also can be just electrically connected with the emitter of the 4th IGBT units simultaneously),
Collector then passes through the first dc-link capacitance C1 (i.e. upper dc-link capacitance) in third inductance L5 and inverter circuit and the
The points of common connection of two dc-link capacitance C2 (descending dc-link capacitance) connects.
It should be pointed out that in other embodiments of the invention, according to actual needs, the second alternating current bypass 202 may be used also
Not configure third inductance L5, the invention is not limited thereto.
The course of work for the transless inverter that the present embodiment is provided is divided into positive and negative period two parts, wherein positive week
Phase and negative cycle include power transmission stage, reverse charging stage and freewheeling period three phases.Specifically, as Fig. 3~
Figure 10 shows the course of work schematic diagram of the inverter in the present embodiment.
As shown in figure 3, when transless inverter is in forward power and transmits the stage, H bridges control inverter circuit entirely at this time
In the first inversion IGBT cell Ss 1 and the 4th inversion IGBT cell Ss 4 will it is in the conduction state to DC power supply 101 with hand over
Galvanic circle is formed between current load 103, the electric energy that such DC power supply 101 is provided can also be transmitted to AC load
103。
And if when transless inverter is in the reverse charging stage of positive period, as shown in figure 4, H bridges are controlled entirely at this time
The first inversion IGBT cell Ss 1 and the 4th inversion IGBT cell Ss 4 in inverter circuit will be become an OFF state by conducting state,
Due to the presence of the first inductance L1 and the second inductance L2, the diode D2 in the second inversion IGBT cell Ss 2 and third are inverse at this time
The diode D3 become in IGBT cell Ss 3 will be in the conduction state.Diode D2 and diode D3 will also form at this time
Galvanic circle between one inductance L1, the second inductance L2 and DC power supply 101, in such first inductance L1, the second inductance L2
The electric energy stored will also flow to dc-link capacitance and DC power supply 101 by above-mentioned diode, to realize positive week
The reverse charging of phase.
In the present embodiment, due to the presence of the first alternating current bypass and the second alternating current bypass, the positive period of the inverter
Freewheeling period is preferably divided into two sub-stages (i.e. the first freewheeling period and the second freewheeling period).Specifically, at inverter
When the first freewheeling period, as shown in figure 5, H bridges control IGBT units in inverter circuit entirely at this time and respective diode goes out
Off state, and the 2nd IGBT cell Ss 6 in the first alternating current bypass will be in the conduction state, and in the first IGBT cell Ss 5
Diode D5 then can be in the conduction state, and the diode D5 and the 2nd IGBT cell Ss 6 in such first IGBT cell Ss 5 also can
Two output ports (i.e. port A and port B) straight line to control inverter circuit entirely in H bridges forms galvanic circle, the first inductance L1
The first by-pass inductor L3 and the second by-pass inductor L4 can be also flowed to the electric energy stored in the second inductance L2, to by the
One by-pass inductor L3 and the second by-pass inductor L4 realizes the storage of electric energy.
And when inverter is in the second freewheeling period, as shown in fig. 6, in the present embodiment, in the second alternating current bypass 202
3rd IGBT cell Ss 7 will be in the conduction state, at the same the diode D8 in the 4th IGBT cell Ss 8 will forward conduction, the 5th
IGBT cell Ss 9 equally can be in the conduction state, and such first by-pass inductor L3 and electric energy stored by the second by-pass inductor L4 are just
Diode D5, the 2nd IGBT cell Ss 6, the 3rd IGBT cell Ss 7 and the 4th IGBT units in the first IGBT cell Ss 5 can be flowed through
Diode D8 in S8 can also form galvanic circle.And if stored by the first by-pass inductor L3 and the second by-pass inductor L4
Electric energy differ, then the 5th IGBT cell Ss 9 have electric current with the third by-pass inductor L5 branches formed and flow through, and compensate, real
Existing first by-pass inductor L3 and the second by-pass inductor L4 voltage balancing functions.
Similarly, when transless inverter is in the reverse power transmission stage, as shown in fig. 7, at this time H bridges control entirely it is inverse
The second inversion IGBT cell Ss 2 and third inversion IGBT cell Ss 3 in change circuit will be in the conduction state in DC power supply
Galvanic circle is formed between 101 and AC load 103, the electric energy that such DC power supply 101 is provided can also transmit best friend
Current load 103.
And if when transless inverter is in the reverse charging stage of positive period, as shown in figure 8, H bridges are controlled entirely at this time
The second inversion IGBT cell Ss 2 and third inversion IGBT cell Ss 3 in inverter circuit will be become an OFF state by conducting state,
Due to the presence of the first inductance L1 and the second inductance L2, the diode D1 and the 4th in the first inversion IGBT cell Ss 1 is inverse at this time
The diode D4 become in IGBT cell Ss 4 will be in the conduction state.Diode D1 and diode D4 will also form at this time
Galvanic circle between one inductance L1, the second inductance L2 and DC power supply 101, in such first inductance L1, the second inductance L2
The electric energy stored will also flow to dc-link capacitance and DC power supply 101 by above-mentioned diode, to realize negative week
The reverse charging of phase.
In the present embodiment, due to the presence of the first alternating current bypass and the second alternating current bypass, the negative cycle of the inverter
Freewheeling period is preferably divided into two sub-stages (i.e. the first freewheeling period and the second freewheeling period).Specifically, at inverter
When the first freewheeling period, as shown in figure 9, H bridges control IGBT units in inverter circuit entirely at this time and respective diode goes out
Off state, and the first IGBT cell Ss 5 in the first alternating current bypass will be in the conduction state, and in the 2nd IGBT cell Ss 6
Diode D6 then can be in the conduction state, and the diode D6 in such first IGBT cell Ss 5 and the 2nd IGBT cell Ss 6 also can
Two output ports (i.e. port A and port B) straight line to control inverter circuit entirely in H bridges forms galvanic circle, the first inductance L1
The first by-pass inductor L3 and the second by-pass inductor L4 can be also flowed to the electric energy stored in the second inductance L2, to by the
One by-pass inductor L3 and the second by-pass inductor L4 realizes the storage of electric energy.
And when inverter is in the second freewheeling period, as shown in Figure 10, in the present embodiment, in the second alternating current bypass 202
The 4th IGBT cell Ss 8 will be in the conduction state, while the diode D7 in the 3rd IGBT cell Ss 7 will forward conduction,
Five IGBT cell Ss 9 equally can be in the conduction state, such first by-pass inductor L3 and the electric energy stored by the second by-pass inductor L4
The diode D7 in diode D5 in the first IGBT cell Ss 5, the 2nd IGBT cell Ss 6, the 3rd IGBT cell Ss 7 will be flowed through
And the 4th IGBT cell Ss 8 can also form galvanic circle.And if the first by-pass inductor L3 and the second by-pass inductor L4 are stored up
The electric energy deposited differs, then the 5th IGBT cell Ss 9 have electric current with the third by-pass inductor L5 branches formed and flow through, and compensate,
Realize the first by-pass inductor L3 and the second by-pass inductor L4 voltage balancing functions.
In the stage as shown in figs. 6 and 10, the first by-pass inductor L3 and the second by-pass inductor L4 can be equivalent to one
Current source can be that the 3rd IGBT cell Ss 7 and the 4th IGBT cell Ss 8 provide turn-on current, so that the 3rd IGBT is mono-
First S7 and the 4th IGBT cell Ss 8 can zero current passing, and then reduce the switching loss of afterflow IGBT, and reduce the leakage of electric current
Electric current.
Again as shown in Fig. 2, in the present embodiment, it is preferable that also include control circuit 203 in inverter 102.Control electricity
Road 203 is connect with each switching tube in inverter, can control the operating status of each switching tube, and then control inverter circuit
And the state of alternating current bypass.In the present embodiment, control circuit 203 is preferably come to networking electric current by the way of closed-loop control
Zero deflection control is carried out, the drive signal corresponding to each switching tube can be generated using PWM wave modulation system, to control
Make the operating status of each switching tube..
Specifically, in the present embodiment, operation shape of the control circuit 203 preferably by controlling each switching tube in inverter
State, to make the current tracking network voltage of inverter.And for control circuit, in the present embodiment, control circuit 203 is preferably
Including ratio resonance (PR) controller.
Compared with common PID controller and repeating control (RC) controller, the nothing of exchange input may be implemented in PR controllers
Dead zone function.In addition, PR controllers realize that low order harmonics compensation is more easy, contribute to the structure of simplified control system, because
This selection PR controller controls proposed topological structure.
In a continuous mode, the transmission function of PR controllers is as follows：
Wherein, G (s) indicates transmission function, kpIndicate proportionality coefficient, krIndicate resonance coefficient, ωcAnd ω0Frequency is indicated respectively
Rate bandwidth and system bandwidth.
Design of Simulation uses discrete mode, therefore the discretization that above-mentioned formula is realized in bilinear transformation may be used.Deposit
：
Wherein, T indicates the discrete sampling time.
For PR controllers, the bandwidth required according to controller can determine frequency bandwidth ωc, and according to controller
Supercharging can then determine resonance coefficient kr, proportionality coefficient kpIt then can be used for optimizing the stable state of the system based on harmonic impedance
Performance and interference free performance.
It should be pointed out that in other embodiments of the invention, according to actual needs, the control in control circuit 203
Device can also use other rational controllers, and the invention is not limited thereto.For example, in one embodiment of the invention, control
Controller in circuit 203 can also use PID controller, repetitive controller or clockless controller.
In the present embodiment, the inverter is preferably by unipolarity modulation system.Unipolarity modulated inverter topology has
Good grid-connected waveform quality and at low cost, the small feature of volume and weight.
Due to the presence of unidirectional free wheeling path, under traditional modulation, bridge arm output voltage uABIt can only be with network voltage
Same phase, idle output cannot achieve.And for the inverter that the present embodiment is provided, if the full bridge inverter is in
Freewheeling period and power transistor S1 to S4 are turned off, then power transistor S5 to S9 can then be modulated to allow freewheel current root
Change according to forward position or lag command current, not only maintain the output power of reaction in this way, but also can also realize Sofe Switch work(
Energy.
Based on above-mentioned thought, in the present embodiment, modulation reference wave can be divided into four fans according to the direction of voltage and current
Area, it is specific as shown in table 1.
Table 1
In sector II and sector IV, electric current is identical with voltage direction, can conventionally be modulated.Namely
It says, modulation reference wave is in positive (sector II), IGBT cell Ss 1 and IGBT cell Ss 4 by high frequency modulated, and positive afterflow rank
Section IGBT cell Ss 5 are connected, and S6 is almost always in sector II.When the reference wave of modulation is at negative direction (sector IV), IGBT is mono-
First S2 and IGBT cell Ss 3 are by high frequency modulated, and reversed freewheeling period IGBT cell Ss 6 are open-minded, S5 sector IV almost always
It connects.
When the direction of electric current and voltage opposite (i.e. in the sectors I and the sectors III), it is notable that when inverter is opened up
When flutterring structure output reactive power and being operated in sector I and sector III, transported on other sectors or unity power factor
Its modulation system of row difference is also different.IGBT cell Ss 5 and IGBT cell Ss 6 are high frequency modulateds, and are opened in freewheeling period
Logical, on off state is consistent.
And IGBT cell Ss 7, IGBT cell Ss 8 and IGBT cell Ss 9 are then remained up in freewheeling period and are not entirely to continue
The stream stage connects, but waits for that inductance L3 and inductance L4 are fully charged and then connect, this modulation system can be such that S7, S8 zero current opens
It is logical.
When electric current lags behind voltage phase angle α, reactive-load compensation modulation strategy is as shown in figure 11.When electric current leading voltage
When, similar modulation strategy can be obtained.In fig. 11, ugIndicate network voltage, igIndicate that power network current, α indicate network voltage
ugLag behind power network current igAngle, irefIndicate modulation reference current waveform.
In the photovoltaic system using the isolated photovoltaic combining inverter of transless, the main reason for leakage current is photovoltaic
Parasitic capacitance between component and ground.When photovoltaic array-parasitic capacitance-power grid forming circuit, common-mode voltage, which will act on, to be posted
Raw capacitance simultaneously generates common mode current.
Topological performance is proposed in order to verify, using artificial circuit as shown in figure 12 come to this implementation in the present embodiment
The performance for the transless inverter that example is provided is emulated, and simulation result is as shown in Figure 13 to Figure 20.In fig. 12, it leaks
For current loop as shown in the dotted portion in figure, simulation parameter is as shown in table 2.
Table 2
| Inverter parameters | Numerical value |
| Photovoltaic DC voltage Udc | 360V |
| Network voltage/frequency | 220V/50Hz |
| Switching frequency | 20KHz |
| Capacitance C1, C2 | 3mF |
| Filter inductance L1, L2 | 3mH |
| Inductance L3, L4, L5 | 1mH |
| Parasitic capacitance CPV1,CPV2 | 0.04μF |
| Line impedance Rg | 1Ω |
Figure 13 to Figure 20 is mainly shown in the case where unity power factor and power factor are 0.833 lag, is carried
The output current and leakage current waveform of the topology and common single-phase grid-connected photovoltaic DC-to-AC converter topology that go out.Wherein, Figure 13 is shown
The simulation waveform of voltage and current under unity power factor under common single-phase grid-connected photovoltaic DC-to-AC converter, Figure 14 show specific work
The leakage current i of common single-phase grid-connected photovoltaic DC-to-AC converter under rate factorleakageSimulation waveform, Figure 15 shows unity power factor
The simulation waveform of voltage and current under the transless inverter that lower the present embodiment is provided, Figure 16 show unit power because
Leakage current i under the transless inverter that several lower the present embodiment are providedleakageSimulation waveform.
Figure 17 shows power factor be voltage in the case of 0.833 lag under common single-phase grid-connected photovoltaic DC-to-AC converter and
The simulation waveform of electric current, Figure 18 show that power factor is common single-phase grid-connected photovoltaic DC-to-AC converter in the case of 0.833 lag
Leakage current ileakageSimulation waveform, Figure 19 shows that power factor is provided by the present embodiment in the case of 0.833 lag
The simulation waveform of voltage and current under transless inverter, in the case that Figure 20 shows that power factor is 0.833 lag
Leakage current i under the transless inverter that the present embodiment is providedleakageSimulation waveform.
Pass through contrast simulation waveform, it is found that in high-power photovoltaic system, common single-phase photovoltaic grid-connected inverter is opened up
The leakage current for flutterring structure is about 80mA, but the topological structure leakage current of inverter that the present embodiment is proposed declines to a great extent, about
3mA.From this it can be concluded that the topological structure for the transless inverter that the present embodiment is proposed is to inhibiting leakage current very
It is helpful, enable to leakage current to be almost reduced to zero, and this means that system loss is very low.
From foregoing description as can be seen that compared with common single-phase grid-connected photovoltaic DC-to-AC converter, proposed by the invention is inverse
Become device to reduce leakage current and single switch loss, a new branch (i.e. first is both provided at the both ends of afterflow branch
Alternating current bypass and the second alternating current bypass).The transless inverter can transmit reactive power, and being capable of effective suppression circuit
In leakage current.
For high-power system, two unidirectional freewheeling circuits are embedded in full-bridge inverter by inverter provided by the present invention
Midpoint between, to obtain photovoltaic battery panel is isolated with power grid during afterflow afterflow channel.Topological freewheeling circuit is main
Bypass circuit is flowed through, the interaction of afterflow phase and other phases can be effectively isolated, is conducive to obtain higher efficiency.Together
When, which does not need to input voltage distribution control, it is possible to reduce harmonic current and leakage current.
Compared with dc bypass topology, alternating current bypass topology has lower power attenuation, this is because flowing through switch
Electric current is relatively low.Alternating current bypass topology realizes a new afterflow road by adding a two-way switch at the midpoint of two legs
Diameter.Compared with common full-bridge inverter, the pressure resistance of switching device and switching loss halve, and can effectively reduce the passive member such as filter
The volume and weight of part.During commutation, each power semiconductor is subjected to Udc/ 2 voltage.This helps to improve inverter
Voltage level and power level, for element selection reserve more spaces；Simultaneous Switching loss is smaller, and switching frequency is higher, humorous
Wave is lower.
In addition, under non-unity power factor, the output voltage waveforms of ordinary inverter are and of the invention there are distortion phenomenon
The output waveform of the inverter provided is with good performance.Above-mentioned simulation result also demonstrates control proposed by the present invention simultaneously
The correctness and validity of scheme processed.The inverter eliminates leakage current, realizes excellent network quality waveform.
It should be understood that disclosed embodiment of this invention is not limited to specific structure disclosed herein or processing step
Suddenly, the equivalent substitute for these features that those of ordinary skill in the related art are understood should be extended to.It should also be understood that
It is that term as used herein is used only for the purpose of describing specific embodiments, and is not intended to limit.
" one embodiment " or " embodiment " mentioned in specification means the special characteristic described in conjunction with the embodiments, structure
Or characteristic includes at least one embodiment of the present invention.Therefore, the phrase " reality that specification various places throughout occurs
Apply example " or " embodiment " the same embodiment might not be referred both to.
Although above-mentioned example is used to illustrate principle of the present invention in one or more application, for the technology of this field
For personnel, without departing substantially from the principle of the present invention and thought, hence it is evident that can in form, the details of usage and implementation
It is upper that various modifications may be made and does not have to make the creative labor.Therefore, the present invention is defined by the appended claims.
Claims (10)
1. a kind of single-phase grid-connected photovoltaic DC-to-AC converter of transless, which is characterized in that the inverter includes：
Inverter circuit, input terminal with DC power supply for connecting, the direct current conversion for being provided the DC power supply
For corresponding alternating current and export；
Energy storage inductor is connected between the inverter circuit and AC load, for being played a filtering role in the power transmission stage,
And exist as current source in freewheeling period；
First alternating current bypass, external-connected port are correspondingly connected with each output end of the inverter circuit respectively, in inversion
Device freewheeling period constitutes current loop to realize afterflow with the energy storage inductor, and realizes AC network and the direct current
The electric isolution in source.
2. inverter as described in claim 1, which is characterized in that the inverter circuit includes：
Dc-link capacitance is used to connect with the positive and negative port of the DC power supply, plays stable DC busbar voltage；
H bridges control inverter circuit entirely, and input terminal is connect with the both ends of the dc-link capacitance, output end and the energy storage inductor
It is connected with the first alternating current bypass.
3. inverter as claimed in claim 2, which is characterized in that first alternating current bypass includes alternating current bypass energy storage inductor
With alternating current bypass switching tube, wherein the alternating current bypass energy storage inductor connects to form described with the alternating current bypass switching tube
One alternating current bypass.
4. inverter as claimed in claim 3, which is characterized in that the alternating current bypass energy storage inductor includes the first by-pass inductor
With the second by-pass inductor, wherein the alternating current bypass switching tube is between first by-pass inductor and the second by-pass inductor.
5. inverter as claimed in claim 4, which is characterized in that the alternating current bypass switching tube include the first IGBT units and
2nd IGBT units, wherein
The collector of the first IGBT units is connect by first inductance with the first output port of the inverter circuit,
Emitter is connect with the emitter of the 2nd IGBT units of the road；
The collector of the 2nd IGBT units is connect by second inductance with the second output terminal mouth of the inverter circuit.
6. such as inverter according to any one of claims 1 to 5, which is characterized in that the inverter further includes：
Second alternating current bypass, first port and second port are defeated with the first output port of the inverter circuit and second respectively
Exit port connects, and third port connect with the dc-link capacitance midpoint of the inverter circuit and is grounded simultaneously.
7. inverter as claimed in claim 6, which is characterized in that second alternating current bypass includes：
3rd IGBT units, collector are connect with the first output port of the inverter circuit；
4th IGBT units, collector are connect with the second output terminal mouth of the inverter circuit, emitter and the road third
The emitter of IGBT units connects；
5th IGBT units, emitter are connect with the emitter of the 3rd IGBT units, collector and the inverter circuit
In upper dc-link capacitance connected with the points of common connection of lower dc-link capacitance.
8. inverter as claimed in claim 7, which is characterized in that second alternating current bypass further includes third inductance, described
5th IGBT units pass through upper dc-link capacitance in the third inductance and the inverter circuit and lower dc-link capacitance
Points of common connection connects.
9. such as inverter according to any one of claims 1 to 8, which is characterized in that the inverter further includes：
Control circuit, connect with each switching tube in the inverter, and the operating status for controlling each switching tube is described
Control circuit is configured to by the way of closed-loop control carry out zero deflection control to networking electric current.
10. inverter as claimed in claim 9, which is characterized in that the control circuit includes：
PR controllers are connect with each switching tube in the inverter；
The transmission function of the PR controllers is：
Wherein, G (s) indicates transmission function, kpIndicate proportionality coefficient, krIndicate resonance coefficient, ωcAnd ω0Frequency band is indicated respectively
Wide and system bandwidth.
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| CN112260561A (en) * | 2020-09-23 | 2021-01-22 | 北方工业大学 | Voltage support type boost conversion circuit and grid connection method |
| US10965220B2 (en) | 2019-06-18 | 2021-03-30 | Delta Electronics (Shanghai) Co., Ltd. | Non-isolated inverting apparatus, control method thereof and photovoltaic system having the same |
| GR1010619B (en) * | 2023-04-10 | 2024-01-25 | Ευτυχιος Γεωργιου Κουτρουλης | Reconfigurable dc-ac converter powered by photovoltaic array |
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