CN108448918B - 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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- CN108448918B CN108448918B CN201810412505.7A CN201810412505A CN108448918B CN 108448918 B CN108448918 B CN 108448918B CN 201810412505 A CN201810412505 A CN 201810412505A CN 108448918 B CN108448918 B CN 108448918B
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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, for direct current provided by DC power supply to be converted to corresponding alternating current and is exported；Energy storage inductor exists for playing 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 in order to reduce leakage current and single switch loss, which can transmit reactive power, and being capable of leakage current effectively in suppression circuit.
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 technique
In recent years, for environmental protection and the utilization of resources the considerations of, photovoltaic power 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, it is inverse that leakage current will lead to transless
There are problems by the safety for becoming device and EMI.
Summary of the invention
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
Include:
Inverter circuit, input terminal are used for for connecting with DC power supply by direct current provided by 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 filtering from the power transmission stage
Effect, and exist in freewheeling period as current source；
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 and 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 bridge controls 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 unit and the 2nd IGBT mono-
Member, wherein
The first output that the collector of the first IGBT unit passes through first by-pass inductor and the inverter circuit
Port connection, emitter are connect with the emitter of the 2nd IGBT unit；
The second output that the collector of the 2nd IGBT unit passes through second by-pass inductor and the inverter circuit
Port connection.
According to one embodiment of present invention, the inverter further include:
Second alternating current bypass, first port and second port respectively with the first output port of the inverter circuit and
The connection of two output ports, third port connect with the dc-link capacitance midpoint of the inverter circuit and are grounded simultaneously.
According to one embodiment of present invention, second alternating current bypass includes:
3rd IGBT unit, collector are connect with the first output port of the inverter circuit；
4th IGBT unit, collector are connect with the second output terminal mouth of the inverter circuit, emitter and described the
The emitter of three IGBT units connects；
5th IGBT unit, emitter are connect with the emitter of the 3rd IGBT unit, 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 dc-link capacitance and lower dc-link capacitance upper in the third inductance and the inverter circuit
Connection.
According to one embodiment of present invention, the inverter further include:
Control circuit is connect with each switching tube in the inverter, for controlling the operating status of each switching tube,
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 controller is connect with each switching tube in the inverter；
The transmission function of the PR controller are as follows:
Wherein, G (s) indicates transmission function, kpIndicate proportionality coefficient, krIndicate resonance coefficient, ωcAnd ω0Respectively indicate frequency
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 being capable of leakage current effectively in suppression circuit.
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 with other phases can be effectively isolated, help 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 loss, this is because flowing through switch
Electric current is lower.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 provided inverter 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 objectives and other advantages of the invention can be by specification, right
Specifically noted structure is achieved and obtained in claim and attached drawing.
Detailed description of the invention
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 technical 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 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 where transless photovoltaic DC-to-AC converter and common single-phase grid-connected photovoltaic DC-to-AC converter topology output electric current and leakage current wave
Shape schematic diagram.
Specific embodiment
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings and examples, how to apply to the present invention whereby
Technological means solves technical problem, and the realization process for reaching technical effect can fully understand and implement.It needs to illustrate
As long as not constituting conflict, each feature in each embodiment and each embodiment in the present invention can be combined with each other,
It is within the scope of the present invention to be formed by technical solution.
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 power 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 problem is solved 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 bridge 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 indicate are as follows:
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:
ug=Em sin(ωt) (2)
Wherein, EmIndicate that grid voltage amplitude, ω indicate electrical network angular frequency.
For entering the electric current i of power gridgFor, exist:
Wherein,Indicate power network current amplitude, α indicates power-factor angle.
Expression formula (2) and expression formula (3) are substituted into expression formula (1), available:
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 side 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 of the single-phase grid-connected photovoltaic DC-to-AC converter of transless provided by the present embodiment.
As shown in Fig. 2, transless inverter 102 provided by the present embodiment be connected to DC power supply 101 with exchange it is negative
It carries between 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),
Direct current provided by DC power supply 101 can be converted to corresponding alternating current and transmit best friend after filtering 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
Stream stage and energy storage inductor constitute current loop to realize afterflow, and realize the electricity of AC load 103 Yu DC power supply 101
Isolation.
Specifically, in the present embodiment, inverter circuit preferably uses dc-link capacitance and H bridge to control inverter circuit entirely.Its
In, dc-link capacitance is connected between the positive and negative port of DC power supply 101, and H bridge 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, inverter circuit preferably includes the first dc-link capacitance C1 and the second direct current is female in the present embodiment
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, it includes four switching tubes that H bridge controls inverter circuit entirely in the present embodiment, these switching tubes are preferably adopted
(i.e. the first inversion IGBT cell S 1, the second inversion IGBT cell S 2,3 and of third inversion IGBT cell S are realized with IGBT unit
4th inversion IGBT cell S 4).Wherein, the first reverse phase diode D1, the second inversion are provided in the first inversion IGBT cell S 1
It is provided with the second reverse phase diode D2 in IGBT cell S 2, is provided with third reverse phase diode in third inversion IGBT cell S 3
D3 is provided with the 4th reverse phase diode D4 in the 4th inversion IGBT cell S 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 inverter circuit the first output port (i.e. port A) 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
It is also configured as other reasonable values (such as one or three with first-class), the invention is not limited thereto.For example, of the invention one
It can only include above-mentioned first inductance L1 or the second inductance L2 in inverter in a embodiment.
As shown in Fig. 2, alternating current bypass includes the first alternating current bypass 201 in the present embodiment.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 and alternating current bypass switch
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 S 6.Wherein, the collector of the first IGBT cell S 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 S 6 of road.2nd IGBT is mono-
The collector of first S6 then passes through the second by-pass inductor L4 and the second output terminal mouth (i.e. port B) of inverter circuit connects.
In the present embodiment, it is provided with the diode D5 of parallel connected in reverse phase in the first IGBT cell S 5, in the 2nd IGBT cell S 6
It is again provided with the diode D6 of parallel connected in reverse phase.
As shown in Fig. 2, inverter 102 further includes the second alternating current bypass 202 in the present embodiment.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 S 8 and the 5th IGBT cell S 9).Wherein, the collector and inverter circuit of the 3rd IGBT cell S 7
First output port (i.e. port A) connection, the emitter of the 3rd IGBT cell S 7 are connect with the emitter of the 4th GIBT cell S 8,
The collector of 4th IGBT cell S 8 is then connect with the second output terminal mouth (i.e. port B) of inverter circuit.5th IGBT cell S 9
Emitter connect with the emitter of the 3rd IGBT unit (due to the emitter of the 3rd IGBT unit and the hair of the 4th IGBT unit
Emitter-base bandgap grading electrical connection, therefore the emitter of the 5th IGBT unit also can be just electrically connected with the emitter of the 4th IGBT unit 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 of transless inverter provided by the present embodiment 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, H bridge controls inverter circuit entirely at this time when transless inverter is in the forward power transmission stage
In the first inversion IGBT cell S 1 and the 4th inversion IGBT cell S 4 will it is in the conductive state to DC power supply 101 and hand over
Galvanic circle is formed between current load 103, electric energy provided by such DC power supply 101 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 bridge is controlled entirely at this time
The first inversion IGBT cell S 1 and the 4th inversion IGBT cell S 4 in inverter circuit will be become an OFF state by state,
Due to the presence of the first inductance L1 and the second inductance L2, the diode D2 in the second inversion IGBT cell S 2 and third are inverse at this time
The diode D3 become in IGBT cell S 3 will be in the conductive state.Diode D2 and diode D3 also just will 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 bridge controls IGBT unit in inverter circuit entirely at this time and respective diode goes out
Off state, and the 2nd IGBT cell S 6 in the first alternating current bypass will be in the conductive state, and in the first IGBT cell S 5
Diode D5 then can be in the conductive state, and the diode D5 and the 2nd IGBT cell S 6 in such first IGBT cell S 5 also can
Galvanic circle, the first inductance L1 are formed to control two output ports (i.e. port A and port B) straight line of inverter circuit entirely in H bridge
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, thus by
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 S 7 will be in the conductive state, at the same the diode D8 in the 4th IGBT cell S 8 will forward conduction, the 5th
IGBT cell S 9 equally can be in the conductive 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 S 6, the 3rd IGBT cell S 7 and the 4th IGBT unit in the first IGBT cell S 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 S 9 has electric current with the third by-pass inductor L5 branch formed and flows through, and compensates, real
Existing first by-pass inductor L3 and the second by-pass inductor L4 voltage balancing function.
Similarly, when transless inverter is in the reverse power transmission stage, as shown in fig. 7, at this time H bridge control entirely it is inverse
The second inversion IGBT cell S 2 and third inversion IGBT cell S 3 in power transformation road are by the conductive state in DC power supply
Galvanic circle is formed between 101 and AC load 103, electric energy provided by such DC power supply 101 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 bridge is controlled entirely at this time
The second inversion IGBT cell S 2 and third inversion IGBT cell S 3 in inverter circuit will be become an OFF state by 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 S 1 is inverse at this time
The diode D4 become in IGBT cell S 4 will be in the conductive state.Diode D1 and diode D4 also just will 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 bridge controls IGBT unit in inverter circuit entirely at this time and respective diode goes out
Off state, and the first IGBT cell S 5 in the first alternating current bypass will be in the conductive state, and in the 2nd IGBT cell S 6
Diode D6 then can be in the conductive state, and the diode D6 in such first IGBT cell S 5 and the 2nd IGBT cell S 6 also can
Galvanic circle, the first inductance L1 are formed to control two output ports (i.e. port A and port B) straight line of inverter circuit entirely in H bridge
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, thus by
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 S 8 will be in the conductive state, while the diode D7 in the 3rd IGBT cell S 7 will forward conduction,
Five IGBT cell Ss 9 equally can be in the conductive state, such first by-pass inductor L3 and the electric energy stored by the second by-pass inductor L4
Diode D5 in the first IGBT cell S 5, the 2nd IGBT cell S 6, the diode D7 in the 3rd IGBT cell S 7 will be flowed through
And the 4th IGBT cell S 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 S 9 has electric current with the third by-pass inductor L5 branch formed and flows through, and compensates,
Realize the first by-pass inductor L3 and the second by-pass inductor L4 voltage balancing function.
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 provide turn-on current for the 3rd IGBT cell S 7 and the 4th IGBT cell S 8, so that the 3rd IGBT is mono-
First S7 and the 4th IGBT cell S 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 switching tube each 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 driving 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, control circuit 203 preferably passes through the operation shape of each switching tube in control inverter
State carrys out the current tracking network voltage so that 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 is may be implemented in PR controller
Dead zone function.In addition, PR controller realizes that low order harmonics compensation is more easy, facilitate the structure of simplified control system, because
This selection PR controller controls proposed topological structure.
In a continuous mode, the transmission function of PR controller is as follows:
Wherein, G (s) indicates transmission function, kpIndicate proportionality coefficient, krIndicate resonance coefficient, ωcAnd ω0Respectively indicate frequency
Rate bandwidth and system bandwidth.
Design of Simulation uses discrete mode, therefore the discretization of above-mentioned formula can be realized using bilinear transformation.Deposit
:
Wherein, T indicates the discrete sampling time.
For PR controller, frequency bandwidth ω can be determined according to the bandwidth that controller requiresc, and according to controller
Pressurization 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 reasonable 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, which preferably uses 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 provided by the present embodiment, if the full bridge inverter is in
Freewheeling period and power transistor S1 to S4 shutdown, 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 is able to achieve Sofe Switch function
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 S 1 and IGBT cell S 4 by high frequency modulated, and positive afterflow rank
Section IGBT cell S 5 is 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 S 3 is by high frequency modulated, and reversed freewheeling period IGBT cell S 6 is open-minded, S5 sector IV almost always
It connects.
When contrary (i.e. in the sector I and the sector III) of electric current and voltage, 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 S 5 and IGBT cell S 6 are high frequency modulateds, and are opened in freewheeling period
Logical, switch state is consistent.
And IGBT cell S 7, IGBT cell S 8 and IGBT cell S 9 are then remained up in freewheeling period and are not entirely to continue
The stream stage connects, but fully charged to inductance L3 and inductance L4 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 compensation modulation strategy is as shown in figure 11.When electric current leading voltage
When, available similar modulation strategy.In Figure 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 capacitor 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 of transless inverter provided by example is emulated, and simulation result is as shown in Figure 13 to Figure 20.In Figure 12, leakage
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 |
| Capacitor 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 mentioned
The output electric current and leakage current waveform of topology and common single-phase grid-connected photovoltaic DC-to-AC converter topology 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 transless inverter provided by lower the present embodiment, Figure 16 show unit power because
Leakage current i under transless inverter provided by several lower the present embodimentleakageSimulation waveform.
Figure 17 shows power factor be voltage in the case where 0.833 lag under common single-phase grid-connected photovoltaic DC-to-AC converter and
The simulation waveform of electric current, it is common single-phase grid-connected photovoltaic DC-to-AC converter in the case where 0.833 lag that Figure 18, which shows power factor,
Leakage current ileakageSimulation waveform, it is in the case where 0.833 lag provided by the present embodiment that Figure 19, which shows power factor,
The simulation waveform of voltage and current under transless inverter, in the case that Figure 20 shows power factor as 0.833 lag
Leakage current i under transless inverter provided by the present embodimentleakageSimulation 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 to inhibit 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, is both provided with a new branch (i.e. first 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 with other phases can be effectively isolated, help to obtain higher efficiency.Together
When, which does not need 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 loss, this is because flowing through switch
Electric current is lower.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 provided inverter 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 is included 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 from the principles and ideas of the present invention, 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 (9)
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, for converting direct current provided by 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 in freewheeling period as current source；
First alternating current bypass, external-connected port are correspondingly connected with each output end of the inverter circuit respectively, in inversion
Device freewheeling period and the energy storage inductor constitute current loop to realize afterflow, and realize AC network and the direct current
The electric isolution in source；
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 connection, third port connect with the dc-link capacitance midpoint of the inverter circuit and are grounded simultaneously.
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 bridge controls 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 unit and
2nd IGBT unit, wherein
The collector of the first IGBT unit passes through the first output port of first by-pass inductor and the inverter circuit
Connection, emitter are connect with the emitter of the 2nd IGBT unit；
The second output terminal mouth that the collector of the 2nd IGBT unit passes through second by-pass inductor and the inverter circuit
Connection.
6. such as inverter according to any one of claims 1 to 5, which is characterized in that second alternating current bypass includes:
3rd IGBT unit, collector are connect with the first output port of the inverter circuit；
4th IGBT unit, collector are connect with the second output terminal mouth of the inverter circuit, emitter and the third
The emitter of IGBT unit connects；
5th IGBT unit, emitter are connect with the emitter of the 3rd IGBT unit, collector and the inverter circuit
In upper dc-link capacitance connected with the points of common connection of lower dc-link capacitance.
7. inverter as claimed in claim 6, which is characterized in that second alternating current bypass further includes third inductance, described
5th IGBT unit passes through upper dc-link capacitance in the third inductance and the inverter circuit and lower dc-link capacitance
Points of common connection connection.
8. such as inverter according to any one of claims 1 to 5, which is characterized in that the inverter further include:
Control circuit is connect with each switching tube in the inverter, described for controlling the operating status of each switching tube
Control circuit is configured to by the way of closed-loop control carry out zero deflection control to networking electric current.
9. inverter as claimed in claim 8, which is characterized in that the control circuit includes:
PR controller is connect with each switching tube in the inverter；
The transmission function of the PR controller are as follows:
Wherein, G (s) indicates transmission function, kpIndicate proportionality coefficient, krIndicate resonance coefficient, ωcAnd ω0Respectively indicate frequency band
Wide and system bandwidth.
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| CN112104249B (en) | 2019-06-18 | 2021-06-18 | 台达电子企业管理（上海）有限公司 | Non-isolated inverter device, control method thereof and photovoltaic system with non-isolated inverter device |
| CN112260561B (en) * | 2020-09-23 | 2022-06-10 | 北方工业大学 | Voltage support type boost conversion circuit and grid connection method |
| GR1010619B (en) * | 2023-04-10 | 2024-01-25 | Ευτυχιος Γεωργιου Κουτρουλης | Reconfigurable dc-ac converter powered by photovoltaic array |
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| CN101741275A (en) * | 2010-01-15 | 2010-06-16 | 南京航空航天大学 | Control method of modular full-bridge grid-connected inverters capable of parallel operation |
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| CN105978020A (en) * | 2016-04-25 | 2016-09-28 | 中南大学 | Optimal modulation method and optimal modulation system for non-isolated alternating-current bypass single-phase grid-connected inverter |
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| CN102983765A (en) * | 2011-09-07 | 2013-03-20 | 艾伏新能源科技(上海)股份有限公司 | Efficient no-transformer single phase photovoltaic grid-connected inverter |
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| CN101741275A (en) * | 2010-01-15 | 2010-06-16 | 南京航空航天大学 | Control method of modular full-bridge grid-connected inverters capable of parallel operation |
| CN102163935A (en) * | 2011-03-04 | 2011-08-24 | 东南大学 | Photovoltaic grid-connected converter with alternating bypass unit |
| CN104092245A (en) * | 2014-07-24 | 2014-10-08 | 阳光电源股份有限公司 | Alternating-current bypass single-phase photovoltaic inverter and control method and control device thereof |
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