CN108988649A - The control method and photovoltaic inverting system of one photovoltaic DC-to-AC converter - Google Patents
The control method and photovoltaic inverting system of one photovoltaic DC-to-AC converter Download PDFInfo
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- CN108988649A CN108988649A CN201810863536.4A CN201810863536A CN108988649A CN 108988649 A CN108988649 A CN 108988649A CN 201810863536 A CN201810863536 A CN 201810863536A CN 108988649 A CN108988649 A CN 108988649A
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- 238000000034 method Methods 0.000 title claims abstract description 24
- 238000002955 isolation Methods 0.000 claims abstract description 166
- 238000012544 monitoring process Methods 0.000 claims abstract description 10
- 230000000630 rising effect Effects 0.000 claims description 3
- 230000005611 electricity Effects 0.000 description 7
- 230000008859 change Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 239000003990 capacitor Substances 0.000 description 4
- 230000006870 function Effects 0.000 description 4
- 238000005286 illumination Methods 0.000 description 4
- 239000010409 thin film Substances 0.000 description 4
- 230000003139 buffering effect Effects 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000035772 mutation Effects 0.000 description 2
- 230000001932 seasonal effect Effects 0.000 description 2
- 230000004913 activation Effects 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
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Classifications
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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
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
-
- H02J3/385—
-
- 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
- H02M7/4826—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 operating from a resonant DC source, i.e. the DC input voltage varies periodically, e.g. resonant DC-link inverters
-
- 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
Abstract
This application discloses a kind of control method of photovoltaic DC-to-AC converter and photovoltaic inverting systems, for adjusting the switching frequency and duty ratio of the switching tube of the LLC isolation circuit in photovoltaic DC-to-AC converter, so that the work of LLC isolation circuit reduces the probability that photovoltaic DC-to-AC converter breaks down in resonance point.Wherein, photovoltaic DC-to-AC converter includes sequentially connected booster circuit, LLC isolation circuit and inverter circuit, the control method of photovoltaic DC-to-AC converter includes: the input voltage and output voltage for monitoring the LLC isolation circuit, determines the difference between the output voltage and the input voltage；If the difference between the output voltage and the input voltage is greater than preset threshold, the switching frequency and duty ratio of the switching tube in the LLC isolation circuit are adjusted, to control the starting or operation of the photovoltaic DC-to-AC converter.
Description
Technical field
This application involves technical field of solar, in particular to the control method of a kind of photovoltaic DC-to-AC converter and photovoltaic inversion system
System.
Background technique
Photovoltaic generating system includes the equipment such as solar panel, such as thin-film solar cell panel, photovoltaic DC-to-AC converter,
Middle photovoltaic DC-to-AC converter is that the direct current energy in solar panel is converted to AC energy to export to power grid or AC load
Power supply.Due to the characteristic of thin-film solar cell panel itself, if photovoltaic DC-to-AC converter is directly incorporated into power grid, may generate larger
Leakage current, can not work so as to cause photovoltaic generating system.
In order to avoid photovoltaic DC-to-AC converter to cause photovoltaic generating system that can not work there may be biggish leakage current as far as possible,
Thin film solar electricity generation system is isolated before photovoltaic DC-to-AC converter is connected to the grid using power frequency isolation transformer cabinet, but work
The mode that frequency isolating transformer cabinet is isolated is lost larger, and efficiency is lower.
It is realized in consideration of it, can be added in photovoltaic DC-to-AC converter in thin film solar electricity generation system by LLC isolation circuit
High-frequency isolation module.Due to the variation of solar panel local environment, for example, intensity of illumination and temperature etc. influence solar energy
The output power of solar panel, this results in solar battery in different periods, the maximum power point voltage of Various Seasonal and maximum
Power points electric current is different, that is, the output power of photovoltaic DC-to-AC converter can change at any time, then when power mutates, LLC every
It is possible to be fully operational near resonance point from circuit, that is, LLC isolation circuit not can enter mode of resonance, it may
Cause switching device in LLC isolation circuit etc. due to excessive pressure damages, breaks down so as to cause inverter.
Summary of the invention
The embodiment of the present application provides the control method and photovoltaic inverting system of a kind of photovoltaic DC-to-AC converter, inverse for adjusting photovoltaic
Become the switching frequency and duty ratio of the switching tube of the LLC isolation circuit in device, so that the work of LLC isolation circuit subtracts in resonance point
The probability that small photovoltaic DC-to-AC converter breaks down.
In a first aspect, providing a kind of control method of photovoltaic DC-to-AC converter, wherein the photovoltaic DC-to-AC converter includes successively connecting
Booster circuit, LLC isolation circuit and the inverter circuit connect, the control method of stating include:
The input voltage and output voltage for monitoring the LLC isolation circuit determine the output voltage and input electricity
Difference between pressure；
If the difference between the output voltage and the input voltage is greater than preset threshold, the LLC isolation is adjusted
The switching frequency and duty ratio of switching tube in circuit, to control the starting or operation of the photovoltaic DC-to-AC converter.
In the embodiment of the present application, controller is not identical in the output voltage and input voltage for monitoring LLC isolation circuit,
It may be considered that the output power of solar panel may mutate, opening for the switching tube of LLC isolation circuit is adjusted at this time
Close frequency and duty ratio, guarantee LLC isolation circuit work as far as possible in resonance point, thus reduce photovoltaic DC-to-AC converter break down it is general
Rate.
Optionally, if difference between the output voltage and the input voltage is greater than preset threshold, described in adjustment
The switching frequency and duty ratio of switching tube in LLC isolation circuit, comprising:
The current switching frequency of the switching tube is gradually decrease to the humorous of the switching tube according to default first increment
Vibration frequency；
The current duty ratio of the switching tube is gradually risen to the resonance of the switching tube according to default second increment
Duty ratio, so that the LLC isolation circuit enters steady operational status.
In the embodiment of the present application, controller adjusts switching frequency as step-length using default first increment, and using pre-
If the second increment adjusts duty ratio as step-length, so that LLC isolation circuit has a buffering before entering mode of resonance, with anti-as far as possible
Only controller because reduce switching tube switching frequency it is very fast, alternatively, increase switching tube duty ratio amplitude it is larger so that LLC
The switching frequency variation of the switching tube of isolation circuit is very fast, and causes shutdown overvoltage to the switching device in LLC isolation circuit
And switching device is caused to damage.
Optionally, before determining the difference between the output voltage and the input voltage, further includes:
Obtain the current switch frequency and current duty cycle of the switching tube；
The current switch frequency is increased to starting switch frequency, and reduces the current duty cycle to starting duty ratio,
Until the LLC isolation circuit is able to enter starting state.
In present application example, controller will determine that photovoltaic DC-to-AC converter is place before being adjusted to LLC isolation circuit
In starting state, else if LLC isolation circuit is in halted state, then LLC isolation circuit does not also just work, therefore, no
It is related to adjusting the switching frequency and duty ratio of the switching tube in LLC isolation circuit.Controller is only determining at LLC isolation circuit
In starting state, the switching frequency and duty ratio of LLC isolation circuit are adjusted, just to minimize the memory usage of controller.
Optionally, the current switch frequency is increased to starting switch frequency, and reduces the current duty cycle to starting
Duty ratio, comprising:
The current switching frequency is gradually risen into opening to the LLC isolation circuit according to default first increment
Dynamic switching frequency；
The duty ratio is gradually decrease to the starting duty ratio according to default second increment.
In the embodiment of the present application, controller adjusts switching frequency as step-length using default first increment, and using pre-
If the second increment adjusts duty ratio as step-length, so that LLC isolation circuit has a buffering before entering mode of resonance, with anti-as far as possible
Only frequency is very fast because raising starts switch for controller, alternatively, the amplitude for reducing starting duty ratio is larger, so that LLC isolation circuit
Switching tube switching frequency variation it is very fast, and shutdown overvoltage is caused to the switching device in LLC isolation circuit and is caused out
Close device failure.
Optionally, the current duty ratio of the switching tube is being gradually risen to the switch according to default second increment
After the resonance duty ratio of pipe, further includes:
If the difference between the output voltage and the input voltage is still greater than the preset threshold, periodically open
The LLC isolation circuit is moved, until the difference between the output voltage and the input voltage is less than or equal to described pre-
If threshold value.
In the embodiment of the present application, when LLC isolation circuit is in operating status, controller determines the defeated of LLC isolation circuit
The difference between voltage and input voltage is also greater than preset threshold out, such as the AC load of possible photovoltaic DC-to-AC converter has occurred
Mutation or the illumination of solar panel mutate, and controller can continue to the switching tube of LLC isolation circuit at this time
Current switching frequency and current duty ratio are adjusted.Accordingly even when the power of solar panel mutates, control
Device adjusts the switching frequency and duty ratio of the switching tube of LLC isolation circuit with gap, can also make LLC isolation circuit as soon as possible
Into steady operational status, so that the difference between the output voltage and input voltage of LLC isolation circuit is less than preset threshold.
Optionally, before the current switch frequency and current duty cycle for obtaining the switching tube, further includes:
Determine the output voltage of the booster circuit；
If the output voltage of the booster circuit controls the boosting circuit boosts institute less than the first default starting voltage
State the output voltage of booster circuit, wherein it is pre- that the output voltage of the booster circuit after promotion is greater than or equal to described first
If starting voltage.
In the embodiment of the present application, in order to maximally utilise the electric energy of solar panel, controller be can control
Booster circuit works or does not work, to guarantee that it is default that the input voltage of LLC isolation circuit can be greater than or equal to first as far as possible
Start voltage.
Second aspect provides a kind of photovoltaic inverting system, which includes:
Photovoltaic DC-to-AC converter, including sequentially connected booster circuit, LLC isolation circuit and inverter circuit；
Controller, the controller are connect with the booster circuit and the LLC isolation circuit；
Wherein, the controller is set as monitoring the input voltage and output voltage of the LLC isolation circuit, determine described in
Difference between output voltage and the input voltage, the difference between the output voltage and the input voltage are greater than pre-
If when threshold value, the switching frequency and duty ratio of the switching tube in the LLC isolation circuit are adjusted, to control the photovoltaic DC-to-AC converter
Starting or operation.
Optionally, the controller setting are as follows:
The current switching frequency of the switching tube is gradually decrease to the humorous of the switching tube according to default first increment
Vibration frequency；
The current duty ratio of the switching tube is gradually risen to the resonance of the switching tube according to default second increment
Duty ratio, so that the LLC isolation circuit enters steady operational status.
Optionally, the controller setting are as follows:
Obtain the current switch frequency and current duty cycle of the switching tube；
The current switch frequency is increased, and reduces the current duty cycle, until the LLC isolation circuit is able to enter
Starting state.
Optionally, the controller setting are as follows:
It is humorous to the switching tube gradually rising the current duty ratio of the switching tube according to default second increment
After duty ratio of shaking, if the difference between the output voltage and the input voltage is still greater than the preset threshold, period
Start the LLC isolation circuit to property, until the difference between the output voltage and the input voltage is less than or equal to
The preset threshold.
The technical effect of photovoltaic inverting system provided by the embodiments of the present application may refer to each reality of above-mentioned first aspect
The technical effect of existing mode, details are not described herein again.
In the embodiment of the present application, monitoring control devices photovoltaic inverting system, in the output voltage for monitoring LLC isolation circuit
Difference between input voltage is greater than some preset threshold, then it is assumed that the output power of solar panel may dash forward
Become, the switching frequency and duty ratio of the switching tube in the LLC isolation circuit of controller adjustment at this time, to guarantee LLC isolation electricity as far as possible
Road works in resonance point, to reduce the probability that photovoltaic DC-to-AC converter breaks down.
Detailed description of the invention
Fig. 1 is the structural schematic diagram of photovoltaic DC-to-AC converter provided by the embodiments of the present application；
Fig. 2 is the flow diagram of the control method of photovoltaic DC-to-AC converter provided by the embodiments of the present application；
Fig. 3 is the flow diagram of photovoltaic inverting system provided by the embodiments of the present application starting；
Fig. 4 is the flow diagram of the control method of photovoltaic DC-to-AC converter provided by the embodiments of the present application；
Fig. 5 is the structural schematic diagram of photovoltaic inverting system provided by the embodiments of the present application.
Specific embodiment
For the purposes, technical schemes and advantages of the application are more clearly understood, below in conjunction in the embodiment of the present application
Attached drawing, the technical scheme in the embodiment of the application is clearly and completely described.
Referring to Figure 1, the embodiment of the present application provides a kind of photovoltaic DC-to-AC converter, which includes sequentially connected
Booster circuit, LLC isolation circuit and inverter circuit.Wherein, the booster circuit in solar panel connection photovoltaic DC-to-AC converter
Input side, the voltage output that booster circuit exports gives LLC isolation circuit, then passes through the rectified current on high-frequency isolation transformer pair side
AC conversion is direct current electricity output to inverter circuit by road.The DC conversion that inverter circuit is used to input is that alternating current is defeated
Out, and it will be incorporated to AC network with the AC sine electric current of phase with frequency with network voltage, powered for AC load.
In order to maximally utilise electric energy in solar panel, photovoltaic DC-to-AC converter can be carried out in the process of running most
High-power tracking.In the embodiment of the present application, photovoltaic DC-to-AC converter can carry out maximum power tracing by booster circuit.In the sun
When the voltage of energy solar panel output is less than the first default starting voltage, booster circuit can carry out boosting to the voltage of input makes it
Rise to the first default starting voltage.If being greater than or equal to the first default starting voltage in the voltage of solar panel output
When, booster circuit can stop working.Ensure that the output voltage of booster circuit is consistently greater than or is equal to first in advance in this way
If starting voltage.Wherein, the first default starting voltage can be according to the voltage value or AC load that the power grid to be incorporated to provides
Required supply voltage is configured, for example, first is pre- if supply voltage required for AC load is usually 380V
If starting voltage can be 700V, to guarantee photovoltaic DC-to-AC converter full-load run, solar panel is maximally utilised as far as possible
Middle electric energy.
Although carrying out maximum power tracing using booster circuit, due to the variation of solar panel local environment,
For example, intensity of illumination etc. influences the electric energy of solar panel, this results in solar battery in different periods, Various Seasonal
Maximum power point voltage is different with maximum power point electric current, that is, the output power of photovoltaic DC-to-AC converter can change at any time.Therefore,
Photovoltaic DC-to-AC converter is other than carrying out maximum power tracing in the process of running, can also be according to solar panel the case where,
Starting in time stops.For example, starting photovoltaic DC-to-AC converter in the case where having illumination in the morning；And at night or cloudy
Under the conditions of, when solar panel can not provide sufficient energy, then close photovoltaic DC-to-AC converter.
In the embodiment of the present application, controller can monitor the output voltage of solar panel, work as solar panel
Output voltage be higher than the second default starting voltage, then start photovoltaic DC-to-AC converter.Wherein, the second default starting voltage can basis
Voltage needed for booster circuit real work in photovoltaic system is preset.If the second default starting voltage setting is excessively high,
Do not start when then photovoltaic DC-to-AC converter has certain electric energy in solar panel, leads to the electric energy wave in solar panel
Take, the efficiency of solar energy utilization is lower.And if the second default starting voltage setting is lower, the electric energy of solar panel can not prop up
Photovoltaic DC-to-AC converter operation is supportted, photovoltaic DC-to-AC converter may be started or stoped continually repeatedly, this results in making for photovoltaic DC-to-AC converter
Use the lost of life.In possible embodiment, starting voltage can be the free voltage positioned at 200V-300V, to guarantee as far as possible
The utilization rate of solar energy is higher, and photovoltaic DC-to-AC converter lasts a long time.
In the embodiment of the present application, due to the variation of solar panel local environment, it may cause solar panel
Power mutate.And photovoltaic DC-to-AC converter includes more perceptual device and capacitive device, for example, photovoltaic DC-to-AC converter includes rising
The perceptual devices such as voltage inductance, resonant inductance, magnetizing inductance and filter inductance.In another example photovoltaic DC-to-AC converter include Support Capacitor, it is humorous
Shake the capacitive devices such as capacitor and filter capacitor.When photovoltaic DC-to-AC converter starting, if LLC isolation circuit cannot be quickly into humorous
Vibration mode, it is easy to which impact over-voltage or overcurrent are caused to perceptual device or capacitive device.
In consideration of it, referring to Fig. 2, the embodiment of the present application provides a kind of control method of photovoltaic DC-to-AC converter, the controlling party
Method can control photovoltaic DC-to-AC converter as shown in Figure 1, for adjust the LLC isolation circuit in photovoltaic DC-to-AC converter switching frequency and
Duty ratio, so that the work of LLC isolation circuit reduces the probability that photovoltaic DC-to-AC converter breaks down in resonance point.The control method
Process is described as follows:
S201, the input voltage and output voltage for monitoring LLC isolation circuit, determine between output voltage and input voltage
Difference；
If the difference between S202, output voltage and input voltage is greater than preset threshold, adjusts and opened in LLC isolation circuit
The switching frequency and duty ratio of pipe are closed, to control the starting or operation of photovoltaic DC-to-AC converter.
Due to the variation of solar panel local environment, the output power of solar panel may change always,
Even, the input power of solar panel may increase suddenly or reduce, such as the black clouds that the sun is walked blocks.This
When, since the input power of solar panel is mutated, resonant state changes LLC isolation circuit, when input power reduces
When, the output voltage of the transformer in LLC isolation circuit correspondinglys increase.Change when input power improves, in LLC isolation circuit
The output voltage of depressor accordingly reduces.So when the resonant state of LLC isolation circuit changes, the input of LLC isolation circuit
Voltage just can not be equal with output voltage.
And when solar panel has a voltage output, but the voltage exported is less than the second predeterminated voltage, then photovoltaic is sent out
Electric system cannot start.Therefore, Fig. 3 is referred to, in the embodiment of the present application, when solar panel has voltage output,
Be exactly booster circuit input voltage be greater than some value, then can star photovoltaic generating system.In order to maximally utilise too
The electric energy of positive energy solar panel, controller can be in the input voltages for determining booster circuit less than the first default starting voltage, also
It is predeterminated voltage above-mentioned, such as when 700V, then can control booster circuit and input voltage is promoted, input voltage is mentioned
700V is risen to, to meet the voltage requirement of LLC isolation circuit starting.
In the embodiment of the present application, after photovoltaic generating system starting, controller can control the work of LLC isolation circuit
Mode enables photovoltaic DC-to-AC converter to work normally.Specifically, controller can monitor LLC isolation circuit input voltage and
Output voltage, if the difference between the output voltage and input voltage of LLC isolation circuit is larger, it may be considered that LLC every
Resonant state from circuit is changed, at this time the switching frequency and duty of the switching tube in adjustable LLC isolation circuit
Than the work of guarantee LLC isolation circuit is in resonance point as far as possible.
If LLC isolation circuit is in halted state, LLC isolation circuit does not also just work, and therefore, is not related to adjusting
The switching frequency and duty ratio of switching tube in LLC isolation circuit.Only starting state or operation shape are in LLC isolation circuit
State is just related to adjusting the switching frequency and duty ratio of switching tube in LLC isolation circuit.Therefore, in the embodiment of the present application, control
Device processed is before being adjusted LLC isolation circuit, it is thus necessary to determine that the working condition of photovoltaic DC-to-AC converter, for example, if controller
Determine that photovoltaic DC-to-AC converter is in halted state, then controller can not control LLC isolation circuit.And if control
Device determines that photovoltaic DC-to-AC converter is in starting state or operating status, then controller can control LLC isolation circuit.
Specifically, refer to Fig. 4, if the input voltage of LLC isolation circuit be greater than or equal to 700V, then it is assumed that LLC every
It is likely to be at working condition from circuit, the controller switching frequency of switching tube and duty ratio in LLC isolation circuit are adjusted
Before whole, the state of LLC isolation circuit is determined.Controller reads the status signal of LLC isolation circuit output, wherein state letter
Number it is used to indicate LLC isolation circuit state in which, it may be possible to starting state, it is also possible to operating status, it is also possible to be off
State.
If the controller determine that LLC isolation circuit is in starting state, then controller is to the switching tube in LLC isolation circuit
Switching frequency and duty ratio be adjusted.At this time if being directly LLC with the switching frequency of the switching tube in LLC isolation circuit
The resonance frequency of isolation circuit, duty ratio are 50% starting LLC isolation circuit, resonant inductance due to LLC isolation circuit with encourage
Magnetoelectricity sense is not establish magnetic field before activation, and LLC isolation circuit cannot immediately enter mode of resonance, this will lead to LLC
Switching device in isolation circuit turns off over-voltage, to damage switching device.
Controller is if it is determined that LLC isolation circuit is in operating status, then LLC isolation circuit has been in stable, at this time
The switching frequency of LLC isolation circuit is exactly resonance frequency, and duty ratio is exactly 50%, does not have to adjustment.Controller if it is determined that LLC every
It is in starting state from circuit, then it is determined that LLC isolation circuit is also unstable, in order to avoid allowing LLC isolation circuit to immediately enter
Mode of resonance, so that the switching device in LLC isolation circuit is damaged because of over-voltage, controller can be to opening in LLC isolation circuit
The switching frequency and duty ratio for closing pipe are adjusted, so that LLC isolation circuit enters mode of resonance and has a buffering course.
Specifically, controller can start switch frequency and starting duty ratio with the switching tube in LLC isolation circuit,
In, starting switch frequency can be the maximum switching frequency fmax of pre-set LLC isolation circuit, and starting duty ratio can be
The minimum duty cycle of pre-set LLC isolation circuit.Controller can reduce the frequency that starts switch of acquisition, and increase starting
Duty ratio, until LLC isolation circuit can start, so that LLC isolation circuit tends towards stability.
If controller reduction starts switch, frequency is very fast, alternatively, the amplitude for increasing starting duty ratio is larger, so that LLC
The switching frequency of isolation circuit is very fast, may or can cause over-voltage to the switching device in LLC isolation circuit and damage.Cause
This, in the embodiment of the present application, controller can will start switch frequency according to default first increment △ f and be gradually decrease to LLC
The resonance frequency of isolation circuit, and duty ratio will be started according to default second increment △ D and be gradually increased to 50% so that LLC every
It is gradually increased from circuit energy, the resonant inductance of LLC isolation circuit and the magnetic field of magnetizing inductance are slowly established, thus will not be right
Switching device in LLC isolation circuit causes biggish impact, to reduce the probability that photovoltaic DC-to-AC converter breaks down.Work as LLC
Isolation circuit starting, during magnetic field is established, the bus Support Capacitor of the transformer secondary in LLC isolation circuit is filled
Electricity, when the starting of LLC isolation circuit terminates, into after stable state, the input voltage of LLC isolation circuit is equal to output voltage, at this point, line
The impact on road is minimized, while inverter circuit starts to carry out two close cycles work.
Wherein, it starts switch the value fmax of frequency and starts the value Dmin of duty ratio, it can be according to switch conduction times
Length determines.In possible embodiment, the value fmax for starting switch frequency can be 2.5 times of resonance frequency, start duty
The value Dmin of ratio can be 5%.Default first increment △ f can be positioned at 2KHz-5KHz] arbitrary value in range, optionally,
Default first increment △ f can be 4KHz.Default second increment △ D can be the arbitrary value positioned at 1%-2%, optionally, in advance
If the second increment △ D can be 1%.
After the starting of LLC isolation circuit, due to the mutation of the output power of solar panel, LLC isolation circuit is opened
The resonance frequency that frequency may not be LLC isolation circuit is closed, causes the input voltage of LLC isolation circuit and output voltage may not
Equally.In order to enable the input voltage and output voltage of LLC isolation circuit are consistent, controller once monitors that LLC is isolated
The input voltage and output voltage of circuit are inconsistent, alternatively, controller determines the output voltage and input voltage of LLC isolation circuit
Between difference be greater than preset threshold, such as 20V, controller is just to the current switching frequency of switching tube in LLC isolation circuit
And current duty ratio is adjusted, to guarantee the work of LLC isolation circuit as far as possible in resonance point, to reduce photovoltaic DC-to-AC converter hair
The probability of raw failure.
Specifically, the current switch frequency and current duty cycle of the switching tube in the available LLC isolation circuit of controller,
The current switching frequency of LLC isolation circuit is gradually risen into starting switch to LLC isolation circuit according to default first increment △ f
Frequency, and the current duty ratio of LLC isolation circuit is gradually decrease to opening for LLC isolation circuit according to default second increment △ D
Dynamic duty ratio enters operating status after the starting of LLC isolation circuit so that LLC isolation circuit reenters starting state.
When LLC isolation circuit is in operating status, controller can obtain the input voltage of LLC isolation circuit and defeated again
Voltage out, if the difference between the output voltage and input voltage that obtain also is greater than preset threshold, such as may photovoltaic it is inverse
The AC load for becoming device is changed, it may be considered that LLC isolation circuit does not maximally utilise solar panel also
Electric energy, controller can continue to be adjusted the current switching frequency of LLC isolation circuit and current duty ratio at this time.
In possible embodiment, controller is if it is determined that the difference between output voltage and input voltage is greater than default threshold
Value, then can be periodically turned on LLC isolation circuit, until the output voltage of LLC isolation circuit and the input of LLC isolation circuit
Less than one threshold value of difference between voltage.Controller can be spaced △ T time, restart LLC isolation circuit, start every time
When, the value for starting switch frequency of setting LLC isolation circuit is fmax, and the value for starting duty ratio is Dmin, and controller is to starting
Switching frequency and starting duty ratio are adjusted, until LLC isolation circuit enters operating status.Accordingly even when solar panel
Power change always, controller adjusts the switching frequency and duty ratio of LLC isolation circuit periodically, i.e., periodically adjustment
The starting or operation of LLC isolation circuit can also maximally utilise the electric energy of solar panel as far as possible.
Illustrate how controller realizes the switching frequency and duty of the switching tube to LLC isolation circuit below with reference to Fig. 5
The adjustment of ratio.
As shown in figure 5, controller is connect with booster circuit, LLC isolation circuit, wherein controller can be to have and calculate
The processing chip of ability, for example, TMS320F28335.In the embodiment of the present application, LLC isolation circuit can use two groups of switches
Pipe, every group of switching tube include 4 switches, as shown in figure 3, first group of switching tube may include switch S1, switch S2, switch S3 and
Switch S4.Second group of switching tube may include switch S5, switch S6, switch S7 and switch S8.It is with regard to first group of switching tube below
Example introduces controller to the switching frequency of the switching tube of LLC isolation circuit and the adjustment of duty ratio.
In first group of switching tube, switch S1 and switch S2 are the same driving signals, and switch S1 ratio switch S2 slightly shifts to an earlier date
Shutdown.Switch S3 and switch S4 is the same driving signal, and switch S4 ratio switch S3 is slightly turned off in advance.Switch S1 and switch S2
Driving signal it is complementary with the driving signal of switch S3 and switch S4, and it is 50% that duty ratio is all permanent.Controller can export control
Signal processed makes switch S1 and switch S2 while open-minded, and the switching frequency and duty ratio of LLC isolation circuit change, LLC every
Mode of resonance is slowly carried out from circuit, is tended towards stability.At this point, controller can control switch S1 shutdown, switch S2 is still connected.Prolong
When a little while after, switch S2 is also switched off, and switch S3 and switch S4 are connected, and switch S3 and switch S4 are connected and no-voltage may be implemented
It is open-minded.Controller can control the shutdown duration or conducting duration of switch S1, switch S2 and switch S3 and switch S4, thus real
The now adjustment of the switching frequency to LLC isolation circuit and duty ratio.
In the embodiment of the present application, the control of second group of switching tube is with the control of first group of switching tube, and which is not described herein again.
The embodiment of the present application uses two groups of switching tubes, and the power of every group of switching tube can be smaller, lower to circuit requirement, therefore, LLC
Isolation circuit is easier to realize.In addition, connecting after transformer secondary electricity pressuring meridian rectification circuit in photovoltaic DC-to-AC converter, can guarantee defeated
It is consistent to enter output voltage.
In conclusion controller is in the output voltage and input voltage for monitoring LLC isolation circuit in the embodiment of the present application
It is not identical, it may be considered that the output power of solar panel may mutate, adjusts switched in LLC isolation circuit at this time
The switching frequency and duty ratio of pipe, the as far as possible work of guarantee LLC isolation circuit are in resonance point, so that reducing photovoltaic DC-to-AC converter occurs event
The probability of barrier.
It is apparent to those skilled in the art that for convenience and simplicity of description, only with above-mentioned each function
The division progress of module can according to need and for example, in practical application by above-mentioned function distribution by different function moulds
Block is completed, i.e., the internal structure of device is divided into different functional modules, to complete all or part of function described above
Energy.
Obviously, those skilled in the art can carry out various modification and variations without departing from the essence of the application to the application
Mind and range.In this way, if these modifications and variations of the application belong to the range of the claim of this application and its equivalent technologies
Within, then the application is also intended to include these modifications and variations.
Claims (10)
1. a kind of control method of photovoltaic DC-to-AC converter, wherein the photovoltaic DC-to-AC converter includes sequentially connected booster circuit, LLC
Isolation circuit and inverter circuit, which is characterized in that the control method includes:
The input voltage and output voltage for monitoring the LLC isolation circuit, determine the output voltage and the input voltage it
Between difference；
If the difference between the output voltage and the input voltage is greater than preset threshold, the LLC isolation circuit is adjusted
In switching tube switching frequency and duty ratio, to control the starting or operation of the photovoltaic DC-to-AC converter.
2. the method as described in claim 1, which is characterized in that if the difference between the output voltage and the input voltage
Greater than preset threshold, then the switching frequency and duty ratio of the switching tube in the LLC isolation circuit are adjusted, comprising:
The current switching frequency of the switching tube is gradually decrease to the resonance frequency of the switching tube according to default first increment
Rate；
The current duty ratio of the switching tube is gradually risen to the resonance duty of the switching tube according to default second increment
Than so that the LLC isolation circuit enters steady operational status.
3. method according to claim 2, which is characterized in that determining between the output voltage and the input voltage
Before difference, further includes:
Obtain the current switch frequency and current duty cycle of the switching tube；
The current switch frequency is increased to starting switch frequency, and reduces the current duty cycle to starting duty ratio, until
The LLC isolation circuit is able to enter starting state.
4. method as claimed in claim 3, which is characterized in that the current switch frequency is increased to starting switch frequency, and
The current duty cycle is reduced to starting duty ratio, comprising:
It is opened according to the starting that default first increment gradually rises the current switching frequency to the LLC isolation circuit
Close frequency；
The duty ratio is gradually decrease to the starting duty ratio according to default second increment.
5. method according to claim 2, which is characterized in that according to default second increment by the current of the switching tube
Duty ratio gradually rises to the resonance duty ratio of the switching tube, further includes:
If the difference between the output voltage and the input voltage is still greater than the preset threshold, it is periodically turned on institute
LLC isolation circuit is stated, until the difference between the output voltage and the input voltage is less than or equal to the default threshold
Value.
6. method as claimed in claim 3, which is characterized in that in the current switch frequency for obtaining the switching tube and currently account for
Before sky ratio, further includes:
Determine the output voltage of the booster circuit；
If the output voltage of the booster circuit controls liter described in the boosting circuit boosts less than the first default starting voltage
The output voltage of volt circuit, wherein the output voltage of the booster circuit after promotion is default more than or equal to described first to be opened
Dynamic voltage.
7. a kind of photovoltaic inverting system characterized by comprising
Photovoltaic DC-to-AC converter, including sequentially connected booster circuit, LLC isolation circuit and inverter circuit；
Controller, the controller are connect with the booster circuit and the LLC isolation circuit；
Wherein, the controller is set as monitoring the input voltage and output voltage of the LLC isolation circuit, determines the output
Difference between voltage and the input voltage, the difference between the output voltage and the input voltage are greater than default threshold
When value, the switching frequency and duty ratio of the switching tube in the LLC isolation circuit are adjusted, to control opening for the photovoltaic DC-to-AC converter
Dynamic or operation.
8. photovoltaic inverting system as claimed in claim 7, which is characterized in that the controller setting are as follows:
The current switching frequency of the switching tube is gradually decrease to the resonance frequency of the switching tube according to default first increment
Rate；
The current duty ratio of the switching tube is gradually risen to the resonance duty of the switching tube according to default second increment
Than so that the LLC isolation circuit enters steady operational status.
9. photovoltaic inverting system as claimed in claim 7, which is characterized in that the controller setting are as follows:
Obtain the current switch frequency and current duty cycle of the switching tube；
The current switch frequency is increased, and reduces the current duty cycle, until the LLC isolation circuit is able to enter starting
State.
10. photovoltaic inverting system as claimed in claim 8, which is characterized in that the controller setting are as follows:
It is accounted for gradually rising the current duty ratio of the switching tube to the resonance of the switching tube according to default second increment
After sky ratio, if the difference between the output voltage and the input voltage is still greater than the preset threshold, periodically
Start the LLC isolation circuit, until the difference between the output voltage and the input voltage is less than or equal to described
Preset threshold.
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| CN201810863536.4A CN108988649A (en) | 2018-08-01 | 2018-08-01 | The control method and photovoltaic inverting system of one photovoltaic DC-to-AC converter |
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| CN201810863536.4A CN108988649A (en) | 2018-08-01 | 2018-08-01 | The control method and photovoltaic inverting system of one photovoltaic DC-to-AC converter |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114785131A (en) * | 2022-06-20 | 2022-07-22 | 深圳市泰德半导体有限公司 | Frequency control circuit and power management chip |
| CN115833166A (en) * | 2022-11-04 | 2023-03-21 | 上海正泰电源系统有限公司 | Resonance protection design method of grid-connected inverter |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107834599A (en) * | 2017-11-14 | 2018-03-23 | 江苏佳讯纳通能源技术有限公司 | A kind of soft-start method of parallel network power generation equipment |
-
2018
- 2018-08-01 CN CN201810863536.4A patent/CN108988649A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107834599A (en) * | 2017-11-14 | 2018-03-23 | 江苏佳讯纳通能源技术有限公司 | A kind of soft-start method of parallel network power generation equipment |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114785131A (en) * | 2022-06-20 | 2022-07-22 | 深圳市泰德半导体有限公司 | Frequency control circuit and power management chip |
| CN115833166A (en) * | 2022-11-04 | 2023-03-21 | 上海正泰电源系统有限公司 | Resonance protection design method of grid-connected inverter |
| CN115833166B (en) * | 2022-11-04 | 2024-03-22 | 上海正泰电源系统有限公司 | Resonance protection design method for grid-connected inverter |
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