CN108242884A - Photovoltaic inverter system grid-connected single channel MPPT and its short-circuit protection method - Google Patents
Photovoltaic inverter system grid-connected single channel MPPT and its short-circuit protection method Download PDFInfo
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- CN108242884A CN108242884A CN201611216361.5A CN201611216361A CN108242884A CN 108242884 A CN108242884 A CN 108242884A CN 201611216361 A CN201611216361 A CN 201611216361A CN 108242884 A CN108242884 A CN 108242884A
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
- H02M1/325—Means for protecting converters other than automatic disconnection with means for allowing continuous operation despite a fault, i.e. fault tolerant converters
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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
- 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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Abstract
The present invention relates to grid-connected single channel MPPT photovoltaic inverter systems and its short-circuit protection method.The short-circuit protection method of photovoltaic inverter system grid-connected single channel MPPT includes：The number of design capacity based on each photovoltaic DC-to-AC converter, the rated power of each photovoltaic module and the photovoltaic module connected per road calculates total way of photovoltaic module；The calculation of short-circuit current of total way and every road photovoltaic module based on photovoltaic module goes out the maximum rated current that DC side flows through the reaction diode module；And inverse peak voltage between the DC master row positive and negative anodes output terminal based on the inverter system and the maximum rated current carry out the setting of the reaction diode module, so that the on-state average current of the reaction diode module is more than the maximum rated current, and the repetitive peak reverse voltage of the reaction diode module is caused to be more than the inverse peak voltage.
Description
Technical field
The present invention relates to the short-circuit protection methods and photovoltaic inversion of technical field of photovoltaic power generation, more particularly to photovoltaic DC-to-AC converter
Device system.
Background technology
In single channel MPPT (Maximum Power Point Tracking, MPPT maximum power point tracking) photovoltaic DC-to-AC converter,
Each photovoltaic DC-to-AC converter module DC side is linked together by female (copper) row, manages and track maximum power concentratedly convenient for system
Point.But for DC side since insulation performance reduction or power tube drive signal may cause direct-current short circuit extremely, insulation is breakdown
Part or that bridge arm for simultaneously turning on will become short dot, make exchange side (net side), Support Capacitor, DC side (light
Volt plate side) energy forms short circuit current circuit by this point, and exchange side energy accounts for the overwhelming majority, due to each photovoltaic inversion
Device module is run in DC side parallel, and the energy of the exchange side (net side) of other non-faulting modules can also pass through respective photovoltaic inversion
Afterflow diode is discharged by this short dot in device module, so as to cause power semiconductor switch device in non-faulting module
The damage of part.That is, the dc-side short-circuit of an inverter module can cause to damage to the fly-wheel diode in all inverter modules
Wound so as to which the influence for making failure is further magnified, causes whole inverter system to be paralysed, cause serious interruption of service and compared with
Big economic loss.
Mnemocircuit figure when Fig. 1 is the generation dc-side short-circuit of previous single channel MPPT photovoltaic DC-to-AC converters.With three in parallel
It is illustrated for photovoltaic DC-to-AC converter module.Black broken lined arrows represent that dc-side short-circuit occurs, in figure two groups of difference dotted lines and
The alternating current of each group photovoltaic DC-to-AC converter module when dc-side short-circuit occurs for one group of photovoltaic DC-to-AC converter module is shown respectively in chain-dotted line
The short-circuit loop formed is flowed, arrow represents the flow direction of short circuit current.That is, short circuit event occurs in one group of photovoltaic DC-to-AC converter module
During barrier, in the case of no any short-circuit protection, failure is easy to expand to other non-faulting modules.
Invention content
Based on risk present in above-mentioned photovoltaic inverter system and protection demand, the present invention proposes following technical scheme.
One aspect of the present invention is related to a kind of short-circuit protection method of the grid-connected photovoltaic inverter systems of single channel MPPT,
The inverter system of photovoltaic module is connected to by respective DC master row for the photovoltaic DC-to-AC converter of multiple parallel connections, each described
In photovoltaic DC-to-AC converter, reaction diode module be connected in series to respectively the anode connection terminal of the switch module of each photovoltaic DC-to-AC converter with
Between the cathode output end of the DC master row and cathode connecting pin of the switch module of each photovoltaic DC-to-AC converter with it is described
Between the cathode output end of DC master row, the short-circuit protection method includes：Design based on each photovoltaic DC-to-AC converter is held
The number of amount, the rated power of each photovoltaic module and the photovoltaic module connected per road calculates total way of photovoltaic module；It is based on
Total way of photovoltaic module and the calculation of short-circuit current of every road photovoltaic module go out DC side and flow through the reaction diode module
Maximum rated current；And the maximum reverse between the DC master row positive and negative anodes output terminal based on the inverter system
Voltage and the maximum rated current carry out the setting of the reaction diode module so that the reaction diode module
On-state average current is more than the maximum rated current, and so that the repetitive peak reverse voltage of the reaction diode module is big
In the inverse peak voltage.
According to above-mentioned short-circuit protection method, the photovoltaic DC-to-AC converter further include for the reaction diode module into
The radiator of row heat dissipation calculates the total power consumption of the reaction diode module in each photovoltaic DC-to-AC converter；Based on it is total
Power consumption, the thermal resistance parameters of the reaction diode inside modules to shell, thermal resistance parameters of shell to the radiator and pre-
Fixed environment temperature calculates the thermal resistance and heat radiation power of the radiator.
According to above-mentioned short-circuit protection method, slope electricity is obtained in the VA characteristic curve based on the reaction diode module
Resistance and threshold voltage；Calculate flow through the on state current of reaction diode module average value in one cycle and
Root-mean-square valve；Institute is calculated based on the slope resistance, the average value of threshold voltage and the on state current and root-mean-square valve
State the total power consumption of reaction diode module.
According to above-mentioned short-circuit protection method, the photovoltaic DC-to-AC converter is further included for the cooling fan of the radiator,
The air quantity of cooling fan is calculated based on the total power consumption and environmental parameter.
Another aspect of the present invention provides a kind of grid-connected photovoltaic inverter systems of single channel MPPT, the inverter system
Configuration is between photovoltaic module and power grid, and including multiple photovoltaic DC-to-AC converters, each photovoltaic DC-to-AC converter includes：Switch module,
Including anode connection terminal and cathode connecting pin；DC master row, the photovoltaic DC-to-AC converter of multiple parallel connections pass through respective direct current
Busbar is connected to photovoltaic module；And reaction diode module, the reaction diode module are connected in series to the switching molding respectively
Between the anode connection terminal of block and the cathode output end of the DC master row and the cathode of the switch module connects
It connects between end end and the cathode output end of the DC master row, the short circuit current when dc-side short-circuit occurs to be prevented to be flowed into not
The single channel MPPT photovoltaic DC-to-AC converters to break down.
According to above-mentioned photovoltaic inverter system, the short circuit current of the reaction diode module flows through institute more than DC side
The maximum rated current of reaction diode module is stated, and the reverse rated voltage of the reaction diode module is more than the inversion
Inverse peak voltage between the DC master row positive and negative anodes output terminal of device system.
According to above-mentioned photovoltaic inverter system, it is connected in series to the anode connection terminal of the switch module and the direct current
The positive terminal of the reaction diode module between the cathode output end of busbar and the cathode output end of the DC master row
Connection, the negative terminal of the reaction diode module are connect with the anode connection terminal of the switch module, are connected in series to described open
The reaction diode module between the cathode connecting pin of pass module and the cathode output end of the DC master row is just
Extreme son is connect with the cathode connecting pin of the switch module, and the negative terminal and the direct current of the reaction diode module are female
The cathode output end connection of row.
According to above-mentioned photovoltaic inverter system, it is provided in the single photovoltaic DC-to-AC converter more than two described anti-reverse
Diode.
According to above-mentioned photovoltaic inverter system, radiator is further included, the radiator is used for the reaction diode
Module radiates.
According to above-mentioned photovoltaic inverter system, cooling fan is further included, the radiator is produced by the cooling fan
Air quantity is given birth to radiate.
In accordance with the invention it is possible to effectively photovoltaic DC-to-AC converter module is protected by reaction diode module.In addition,
The extension of the failure after generation direct-current short circuit in photovoltaic inverter system can be effectively prevented.
Description of the drawings
Mnemocircuit when Fig. 1 is the generation dc-side short-circuit of the grid-connected photovoltaic inverter systems of existing single channel MPPT
Figure；
It is brief when Fig. 2 is the generation dc-side short-circuit of the grid-connected inverter systems of single channel MPPT of the present invention
Circuit diagram；
Fig. 3 is the flow chart of the reaction diode module setting of photovoltaic DC-to-AC converter of the present invention；
Fig. 4 is the Matlab/ of the photovoltaic inverter system grid-connected to single channel MPPT of the present invention
The model schematic of Simulink emulation；
Fig. 5 is the schematic diagram of the direct-current short circuit electric current of failure photovoltaic DC-to-AC converter module #1；
Fig. 6 is the schematic diagram of the direct-current short circuit electric current of non-faulting photovoltaic DC-to-AC converter module #2；
Fig. 7 is the schematic diagram of the direct-current short circuit electric current of non-faulting photovoltaic DC-to-AC converter module #3.
Specific embodiment
The present invention may be better understood to the description of specific embodiment of the present invention with reference to attached drawing, wherein, it is identical or
Similar reference numeral represents the same or similar feature.
The feature and exemplary embodiment of various aspects of the invention is described more fully below.In following detailed description
In, it is proposed that many details, in order to provide complete understanding of the present invention.But to those skilled in the art
It will be apparent that the present invention can be implemented in the case of some details in not needing to these details.Below to implementing
The description of example is used for the purpose of by showing that the example of the present invention is better understood from the present invention to provide.The present invention never limits
In any concrete configuration set forth below and algorithm, but cover under the premise of without departing from the spirit of the present invention element,
Any modification, replacement and the improvement of component and algorithm.In the the accompanying drawings and the following description, well known structure and skill is not shown
Art is unnecessary fuzzy to avoid causing the present invention.
Letter when Fig. 2 is the generation dc-side short-circuit of the grid-connected inverter systems of single channel MPPT of the present invention
Want circuit diagram.Inverter system is arranged between photovoltaic module and power grid.The inverter system includes multigroup photovoltaic DC-to-AC converter
Module.Each photovoltaic DC-to-AC converter module includes：Switch module 10, the switch module 10 includes anode connection terminal and cathode connects
End；DC master row (not shown), the photovoltaic DC-to-AC converter of multiple parallel connections are connected to photovoltaic module by DC master row；With
And reaction diode module 20, the reaction diode module 20 are connected in series to the anode connection of the switch module 10 respectively
Between end and the cathode output end of the DC master row and cathode connecting pin of the switch module 10 and the direct current
It is inverse short circuit current to be prevented when dc-side short-circuit occurs to be flowed into the photovoltaic not broken down between the cathode output end of busbar
Become device module.
In the following description, it is in parallel using three groups of inverter modules and pass through respective DC master row be connected to photovoltaic module as
Example is illustrated.The switch module of each photovoltaic DC-to-AC converter module includes the first bridge arm, the second bridge arm and third bridge arm, described
First bridge arm, the second bridge arm and third bridge arm respectively include the upper bridge arm and lower bridge arm being connected in series with, and the upper bridge arm is under
Bridge arm respectively includes the power semiconductor switch module of power semiconductor switch composition in parallel with fly-wheel diode, each described
The upper end of upper bridge arm is connected to each other, and forms anode connection terminal, and the lower end of each lower bridge arm is connected to each other, and is formed cathode and is connected
Connect end.The inverter module further includes the bearing capacitance for connecting above-mentioned anode connection terminal and above-mentioned cathode connecting pin and incites somebody to action
Upper bridge arm and the tie point of lower bridge arm are connected to the reactor (not shown) of the filtering of power grid.Power semiconductor switch can
Be SCR (silicon-controlled), GTO (gate pole automatic shutoff thyristor), GTR (huge transistor), (vertical MOS field-effect is brilliant by VMOSFET
Body pipe) and IGBT (insulated gate bipolar transistor) etc., insulated gate gate pole crystal is selected with power semiconductor switch below
It is illustrated for pipe (Insulated Gate Bipolar Translator, hereinafter referred to as IGBT), by IGBT and afterflow
The parallel-connection structure of diode is known as IGBT module.
In photovoltaic inverter system grid-connected the single channel MPPT of Fig. 1, it is short that broken lined arrows represent that DC side occurs
Road, each dotted line represent the circulation path of short circuit current, and the arrow in dotted line frame represents the circulating direction of short circuit current, due to each light
Volt inverter module shares same DC voltage, if so short circuit, each photovoltaic DC-to-AC converter module DC side occur for DC side
It is all short-circuited, due to existing from this short-circuit loop of exchange side-fly-wheel diode-direct-current short circuit point, if so be not added with any
If protecting device, photovoltaic DC-to-AC converter module have short circuit current from grid side by IGBT module to dc-side short-circuit point sink
Stream, short-circuit-type is similar to AC three-phase short circuit, and according to the size of instantaneous line voltage, short circuit current passes through upper bridge from one phase of exchange
Arm using direct-current short circuit point, then flows into lower bridge arm, and back to another phase of line voltage, three line voltages are all from upper bridge arm
Go out, lower bridge arm returns, and flows through set of the total current of direct-current short circuit point for the short circuit current under three line voltages " driving ", therefore
Dc-side short-circuit electric current is all from DC side anode to cathode, and short circuit current has consistent directionality, this direction is just and simultaneously
The direction of DC current during net inverter system normal operation is opposite.Power diode is the semiconductor for having unilateral conduction
Device, short circuit current have one-way, and with the DC current direction of normal operation on the contrary, therefore installing anti-reverse two additional in DC side
Pole pipe can prevent the diffusion of short circuit current well, while meet current flowing requirement when working normally again.
Based on above-mentioned analysis, single channel MPPT photovoltaic DC-to-AC converters shown in Fig. 2 further include anti-reverse two pole for short-circuit protection
Tube module 20.In fig. 2, dc-side short-circuit has occurred in broken lined arrows expression, and dotted line represents the circulation path of short circuit current, arrow
Represent the circulating direction of short circuit current.The anode that the reaction diode module 20 is not connected in series to above-mentioned switch module 10 connects
Connect between end and the cathode output end of the DC master row and the cathode connecting pin of the switch module 10 with it is described straight
Between the cathode output end for flowing busbar.The anode connection terminal of the switch module 10 is connected in series to the DC master row just
The positive terminal of the reaction diode module 20 between the output terminal of pole is connect with the cathode output end of the DC master row, institute
The negative terminal for stating reaction diode module is connect with the anode connection terminal of the switch module 10；It is connected in series to the switch module
The anode of the reaction diode module 20 between the 10 cathode connecting pin and the cathode output end of the DC master row
Terminal is connect with the cathode connecting pin of the switch module, and the negative terminal and the direct current of the reaction diode module 20 are female
The cathode output end connection of row.In the circuit, as needed can also multiple reaction diode modules 20 be connected in series with into
Row protection.
The on-state average current of above-mentioned reaction diode module 20 is more than flows through described anti-reverse two by above-mentioned DC master row
The maximum rated current of pole pipe module, and the repetitive peak reverse voltage of the reaction diode module is more than the inverter system
Inverse peak voltage between the DC master row positive and negative anodes output terminal of system.
Above-mentioned inverter module further includes radiator, and the radiator is used to dissipate the reaction diode module
Heat, to realize the effective protection of reaction diode.
Above-mentioned inverter module further includes cooling fan, and the cooling fan makes radiator in time, reliably radiate.
The single channel MPPT photovoltaic inverter systems for being equipped with reaction diode module are illustrated above.Below to above-mentioned
Illustrate that the short-circuit protection method of reaction diode module illustrates.
Fig. 3 is the setting process figure of the reaction diode module of photovoltaic DC-to-AC converter of the present invention.The implementation of the present invention
Example provides the short-circuit protection method of reaction diode module, specifically comprises the steps of：S1, based on each photovoltaic DC-to-AC converter
Design capacity, each photovoltaic module rated power and per road series connection photovoltaic module number calculate photovoltaic module total road
Number；S2, total way based on photovoltaic module and the calculation of short-circuit current per road photovoltaic module go out DC side flow through it is described anti-reverse
The maximum rated current of diode (led) module；And S3, the DC master row positive and negative anodes output terminal based on the inverter system
Between inverse peak voltage and the maximum rated current carry out the setting of the reaction diode module so that it is described anti-
On-state average current under the direct current of inverse diode (led) module is more than the maximum rated current, and causes the reaction diode mould
The repetitive peak reverse voltage of block is more than the inverse peak voltage.
In single channel MPPT photovoltaic inverter systems, when carrying out photovoltaic generation, what photovoltaic DC-to-AC converter DC side flowed through is
One-way flexible DC current from such as photovoltaic module of crystal silicon battery plate, it is known that the design of each photovoltaic DC-to-AC converter unit is held
Measure W, the overload factor k that can be born, photovoltaic module rated power be w1, per road input connected number of photovoltaic modules as S,
Then header box exports total way N as shown in formula 1.
The known short circuit current per road photovoltaic module is I1, which is calibrating parameters, represent can by maximum pacify
Total current.Then the rated current In by reaction diode module of DC side outflow is shown in formula 2.
In=I1× N formulas 2
Fluctuation and other abnormal conditions in view of usually electric current, the safety factor of 1.1 times of setting, therefore finally flow through anti-
The maximum rated current I of inverse diodeNAs shown in following formula 3.
IN=1.1 × InFormula 3
In addition, in the case where considering switching overvoltage, it is known that between the positive and negative anodes of the DC master row of inverter module
Inverse peak voltage UDM, the UDMIt is set according to engineering experience.
Based on maximum rated current INWith inverse peak voltage UDMTo select the reaction diode for short-circuit protection so that
On-state average current under the direct current of reaction diode is more than above-mentioned maximum rated current, and causes the anti-of the reaction diode
It is more than above-mentioned inverse peak voltage to repetitive peak voltage.
It is illustrated below with specific example.
For example, the design capacity W of each photovoltaic DC-to-AC converter unit is 210kW, the overload factor that can be born is 1.1.Photovoltaic
Component is by taking English profit 260W (that is, rated power 260W) component at present on the market as an example, and per road, the number of photovoltaic modules S of series connection is
22.Based on above-mentioned, header box exports total way N and is：
40 tunnels of N=210000*1.1/260/22 ≈
The total way of input of photovoltaic DC-to-AC converter is 40 tunnels.The photovoltaic group connected according to photovoltaic module design parameter per road
The short circuit current of part is 8.98A.
Then DC side flows through rated current In=8.98 × 40=502.88A of reaction diode
Fluctuation and other abnormal conditions in view of usually electric current, take 1.1 safety factor, therefore finally flow through DC side
The maximum rated current I of diodeN=1.1 × 502.88A=553.168A.
According to engineering experience, in the case where considering switching overvoltage, the above-mentioned DC master row of inverter system is just
Inverse peak voltage U between negative output terminalDM=1500V.
Select the MDK800 diode (led) modules (common cathode, two parallel connections) of xX models, repetitive peak reverse voltage URRMFor
2600V, on-state average current are IF=800A, repetitive peak reverse voltage are that the diode (led) module can repeat to apply most
Peak voltage, on-state average current are the parameters of its nominal rated current, be set as DC side be connected in series with two it is anti-reverse
Diode (led) module.IF＞ IN, electric current meets the requirements.In addition, the reverse peak voltage U of diode (led) moduleRRMMore than maximum reverse electricity
Press UDM, therefore voltage is also met the requirements.
Optionally, when selecting diode, repetitive peak reverse voltage URRMIt can in the circuit that preferably diode is worked
The inverse peak voltage U that can be bornDM2~3 times, such as in UDMIn the case of=1500V, if repetitive peak reverse voltage
3 times of inverse peak voltage, then repetitive peak reverse voltage needs to reach 4500V, and two diodes being connected in series with
The repetitive peak reverse voltage that can be born is 2600V × 2=5200V, and more than 4500V, therefore above-mentioned diode at this time is anti-
To repetitive peak voltage URRMAlso it meets the requirements.
Simulating, verifying is set for above-mentioned parameter.Fig. 4 is to single channel MPPT photovoltaic inverter systems of the present invention
Matlab/Simulink emulation model schematic.According to photovoltaic DC-to-AC converter module in parallel anti-reverse two are installed additional in DC side
The working condition of pole pipe m carries out the foundation of simulation model, malfunctioning module #1, non-faulting mould when model is including generation direct-current short circuit
Block #2 and #3, the reaction diode module m of series connection, the short-circuit equivalent switch that direct-current short circuit point carries internal resistance with one.It controls short
Road equivalent switch can simulate a photovoltaic DC-to-AC converter module, and there is a situation where dc-side short-circuits.Main simulation parameter is such as
Under：Line voltage Up-p=315V, frequency F=50Hz, internal resistance R=8.5m Ω, the L=18.6uH of power supply/transformer；Reactor
R1=1.12m Ω, L1=0.03mH；Short-circuit impedance R2=1m Ω；DC support capacitance：C=3.32mF；Reaction diode internal resistance
R3=1m Ω；Short-circuit equivalent switch will be connected 0.3s, that is, direct-current short circuit is happened at 0.3s after emulation starts.
For simulation result as shown in Fig. 5,6,7, Fig. 5 is the signal of the direct-current short circuit electric current of failure photovoltaic DC-to-AC converter module #1
Figure；Fig. 6 is the schematic diagram of the direct-current short circuit electric current of non-faulting photovoltaic DC-to-AC converter module #2；Fig. 7 is non-faulting photovoltaic DC-to-AC converter mould
The schematic diagram of the direct-current short circuit electric current of block 3#.#1 modules are malfunctioning module (short circuit occurs), and #2, #3 module are non-faulting module.
It can be seen that by adding reaction diode module in DC side, when breaking down, the DC current of #1 modules is left for 14kA
The right side, the DC side of #2, #3 module are flowed through without short circuit current.The short circuit current of 1# modules is cut under AC circuit breaker protection act
Go out major loop, then normal table is run #2, #3 module.
After reaction diode module is selected, the protection to reaction diode module is then considered.Photovoltaic DC-to-AC converter system
System further includes radiator for radiating to the reaction diode module, so as to effectively to reaction diode module into
Row protection.
Optionally, the total power consumption of the reaction diode module in an inverter module is calculated；Based on institute's total work
Consumption, the thermal resistance parameters of inverter chip interior to shell, the thermal resistance parameters of shell to radiator and highest environment temperature calculate
Go out the thermal resistance and heat radiation power of radiator.
Optionally, in the calculating of the total power consumption of the power diode module, the volt-ampere based on reaction diode module
Slope resistance and threshold voltage is obtained in characteristic curve；Calculate on state current average value in one cycle and r.m.s.
Value；It is calculated based on the slope resistance, the average value of threshold voltage and the on state current and root-mean-square valve described anti-reverse
The total power consumption of diode (led) module.
For the electric current flowed through on the DC master row of photovoltaic DC-to-AC converter module, the main reason for on-state loss is its fever.
Volt-ampere of characteristic diode slope of a curve resistance is being set as rd, by UTOBe set as threshold voltage, by state current in a cycle
Interior average value is set as IAV, the root-mean-square value of on state current in one cycle is set as IRMSWhen, the reaction diode module
On-state loss engineering on calculation formula it is as shown in Equation 4.
Continuation is illustrated by taking the reaction diode module of above-mentioned selection as an example, then the power consumption of single diode (led) module isTherefore two diodes
The total power consumption of module is 304W × 2=608W.According to the product manual of selected diode (led) module, chip interior is obtained to outer
The thermal resistance R of shelljc=0.019 DEG C/W, the thermal resistance R of shell to radiatorcs=0.04 DEG C/W.The highest environment temperature of design is set as
The thermal resistance R of Ta, then radiator to airsaMeet following formula 5.
(Rjc+Rcs+Rsa125 DEG C of formulas 5 of) × 250+Ta ＜
Assuming that Ta=55 DEG C of the environment temperature of design, then Rsa0.221 DEG C/W of ＜.Therefore the radiator to be selected is in 55 DEG C of rings
At a temperature of border, to meet thermal resistance Rsa0.221 DEG C/W of ＜, heat radiation power Ps ＞ 608W.
Further optionally, above-mentioned to thermal resistance RsaUnder restriction with heat radiation power Ps, based on the total power consumption and environment
Parameter calculates the air quantity of the cooling fan of radiator.
Continue to illustrating for above-mentioned example.
Environmental parameter is set, it is assumed that the humidity that temperature is 20 DEG C, atmospheric pressure 760mmHg, humidity are 65% is empty
Gas is normal air, and the density of air is 1200g/m3 at this time.It is also known that the specific heat at constant pressure of air is Cp=0.24 (Kcal/
Kg DEG C), the temperature that allows of 1cal=4.2J, diode (led) module rise -55 DEG C=70 DEG C of maximum temperature rise △ Tc=125 DEG C,
In addition, the volume of air of CMM, CFM all referring to exclusion per minute, the former unit for cube m/min, the latter's unit is
Cubic feet/per minute, 1CMM=35.3CFM.
Based on heat and the heat of radiator heat-dissipation, i.e. equation or so above-mentioned, sent out within reaction diode module 1s
Both sides are equal, and Q is the air quantity of radiator fan, and P is the heating power of diode (led) module.
0.24 × (Q/60*1200) × △ Tc=P × 1/4.2
Q=(P × 60)/(1200 × 4.2 × 0.24 × △ Tc)=1.76 × P/ △ Tc=1.76 × 608/70=
15.3CFM=0.433CMM
Therefore the air quantity of the cooling fan of selection is not lower than 0.433m3/min.Cooling fan is selected based on this.
Above-mentioned combination specific example carries out the short-circuit protection method of the reaction diode of single channel MPPT photovoltaic DC-to-AC converters
Explanation.Appropriate reaction diode is set by above-mentioned setting, realizing has non-faulting module when short circuit occurs
Effect protection.Simultaneously by setting the radiator and cooling fan of setting, can have to the reaction diode module in work
Effect protection.
The present invention can realize in other specific forms, without departing from its spirit and essential characteristics.Therefore, current reality
Apply example be all counted as being exemplary rather than in all respects it is limited, the scope of the present invention by appended claims rather than on
State description definition, also, fall into claim meaning and equivalent in the range of whole change all to be included in this
Among the range of invention.Also, the different technologies feature occurred in different embodiments can be combined, to obtain beneficial to effect
Fruit.Those skilled in the art will be understood that and realize revealed on the basis of research attached drawing, specification and claims
The embodiment of other variations of embodiment.
Claims (10)
1. a kind of short-circuit protection method of photovoltaic inverter system grid-connected single channel MPPT, which is characterized in that
The photovoltaic inverter system includes the photovoltaic DC-to-AC converter of multiple parallel connections, and multiple photovoltaic DC-to-AC converters pass through respective straight
Stream busbar is connected to photovoltaic module, and the photovoltaic DC-to-AC converter includes switch module, the anode connection terminal of the switch module and institute
State between the cathode output end of DC master row and the cathode connecting pin of the switch module and the cathode of the DC master row it is defeated
Reaction diode module is serially connected between outlet, the short-circuit protection method includes：
The rated power of design capacity, each photovoltaic module based on each photovoltaic DC-to-AC converter and the photovoltaic group connected per road
The number of part calculates total way of photovoltaic module；
Total way based on photovoltaic module and the calculation of short-circuit current per road photovoltaic module go out DC side and flow through described anti-reverse two
The maximum rated current of pole pipe module；And
Institute is carried out based on the inverse peak voltage between the DC master row positive and negative anodes output terminal and the maximum rated current
State the setting of reaction diode module so that the on-state average current of the reaction diode module is more than the maximum rated electricity
Stream, and the repetitive peak reverse voltage of the reaction diode module is caused to be more than the inverse peak voltage.
2. short-circuit protection method according to claim 1, which is characterized in that
The photovoltaic DC-to-AC converter further includes the radiator for radiating to the reaction diode module,
Calculate the total power consumption of each reaction diode module；
Based on institute's total power consumption, the thermal resistance parameters of the reaction diode inside modules to shell, the heat of shell to the radiator
Parameter and scheduled environment temperature are hindered, calculates the thermal resistance and heat radiation power of the radiator.
3. short-circuit protection method according to claim 2, which is characterized in that
The total power consumption for calculating each reaction diode module, specifically includes：
Slope resistance and threshold voltage is obtained in VA characteristic curve based on the reaction diode module；
It calculates and flows through the on state current of reaction diode module average value in one cycle and root-mean-square valve；
It is calculated based on the slope resistance, the average value of threshold voltage and the on state current and root-mean-square valve described anti-reverse
The total power consumption of diode (led) module.
4. the short-circuit protection method according to Claims 2 or 3, which is characterized in that
The photovoltaic DC-to-AC converter is further included for the cooling fan of the radiator,
The air quantity of cooling fan is calculated based on the total power consumption and environmental parameter.
5. a kind of photovoltaic inverter system grid-connected single channel MPPT, which is characterized in that
Photovoltaic inverter system configuration is between photovoltaic module and power grid, and including multiple photovoltaic DC-to-AC converters,
Each photovoltaic DC-to-AC converter includes：
Switch module, including anode connection terminal and cathode connecting pin；
DC master row, the photovoltaic DC-to-AC converter of multiple parallel connections are connected to photovoltaic module by respective DC master row；And
Reaction diode module, the reaction diode module be connected in series to respectively the anode connection terminal of the switch module with
Between the cathode output end of the DC master row and cathode connecting pin end of the switch module and the DC master row
Cathode output end between, the short circuit current when dc-side short-circuit occurs to be prevented to be flowed into the single channel not broken down
MPPT photovoltaic DC-to-AC converters.
6. photovoltaic inverter system according to claim 5, which is characterized in that
The short circuit current of the reaction diode module is more than the maximum rated electricity that DC side flows through the reaction diode module
Stream, and the reverse rated voltage of the reaction diode module is defeated more than the DC master row positive and negative anodes of the inverter system
Inverse peak voltage between outlet.
7. photovoltaic inverter system according to claim 5, which is characterized in that
The positive terminal of the reaction diode module is connect with the cathode output end of the DC master row, the reaction diode
The negative terminal of module is connect with the anode connection terminal of the switch module,
The positive terminal of the reaction diode module is connect with the cathode connecting pin of the switch module, the reaction diode
The negative terminal of module is connect with the cathode output end of the DC master row.
8. photovoltaic inverter system according to claim 5, which is characterized in that
More than two reaction diodes are provided in the single photovoltaic DC-to-AC converter.
9. photovoltaic inverter system according to claim 5, which is characterized in that
Radiator is further included, the radiator is used to radiate to the reaction diode module.
10. photovoltaic inverter system according to claim 9, which is characterized in that
Cooling fan is further included, the radiator generates air quantity to radiate by the cooling fan.
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