CN108206502B - Single channel MPPT grid-connected inverter system and its configuration method - Google Patents
Single channel MPPT grid-connected inverter system and its configuration method Download PDFInfo
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- CN108206502B CN108206502B CN201611177676.3A CN201611177676A CN108206502B CN 108206502 B CN108206502 B CN 108206502B CN 201611177676 A CN201611177676 A CN 201611177676A CN 108206502 B CN108206502 B CN 108206502B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
- H02H3/093—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current with timing means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
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- H02H3/06—Details with automatic reconnection
- H02H3/066—Reconnection being a consequence of eliminating the fault which caused disconnection
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Abstract
The present invention relates to single channel MPPT grid-connected inverter system and its configuration methods.In the configuration method of photovoltaic DC-to-AC converter, the short-circuit impedance on the uniline of inverter described in one group when dc-side short-circuit occurs in the inverter system is calculated；Output rated voltage based on the short-circuit impedance and the inverter calculates the short circuit current on the uniline；Surge thermal energy based on one freewheeling diode of the calculation of short-circuit current；It can be carried out the matching of the freewheeling diode based on the maximum heat surge that the surge thermal energy and the freewheeling diode are able to bear, so that the surge thermal energy is less than the maximum surge thermal energy in the given time；The breaker is selected based on the short circuit current after matching, so that the breaker disconnects within the predetermined time.
Description
Technical field
The present invention relates to technical field of photovoltaic power generation, in particular to single channel MPPT grid-connected inverter system is matched
Set method and the grid-connected inverter system of single channel MPPT.
Background technique
In single channel MPPT (Maximum Power Point Tracking, MPPT maximum power point tracking) photovoltaic combining inverter
In system, each MPPT photovoltaic DC-to-AC converter module DC side passes through female (copper) row and links together, in order to system centralized management and
Maximum power point is tracked, but there is also following problems.Power semiconductor switch module in inverter is that the rate of breaking down is higher
Part, if moment over-voltage, gate pole trigger signal are abnormal etc. to be caused entirely because certain reason occurs on a pipe
Then breakdown bridge arm just immediately becomes short dot dc-side short-circuit occurs for bridge arm breakdown failure, makes to exchange side (net side), branch
It supports capacitor, DC side (photovoltaic module side) energy and short circuit current circuit is formed by the short dot.Short circuit current is greatly
Short-circuit loop is formed via freewheeling diode in power semiconductor switch module by grid side.Due to each MPPT photovoltaic DC-to-AC converter mould
The operation of block DC side parallel, exchange side (net side) energy of other non-faulting MPPT photovoltaic DC-to-AC converter module can also pass through respective mould
Afterflow diode is discharged in block, to cause the damage of power semiconductor switch in non-faulting module.That is, a light
Volt inverter module dc-side short-circuit the freewheeling diode in all modules can be caused to damage, thus make the influence of failure into
The extension of one step, causes whole inverter system to be paralysed, causes serious interruption of service and biggish economic loss.
It in the past, is usually to install fuse additional in inverter ac side for the protection of power semiconductor switch module.But
In case of short trouble, fuse carry out fuse protection and after shutting down, need operation maintenance personnel to the fuse after damage into
Machine could be restarted after row replacement.There are problems that bringing the loss of device after execution is protected in the technology.In addition, due to
It needs to shut down after executing protection, personnel carry out replacement operation, spend the time longer, this period will cause photovoltaic power generation quantity
Loss.
Summary of the invention
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 provides a kind of configuration method of inverter system that single channel MPPT is grid-connected, institute
It states inverter system to be arranged between photovoltaic module and power grid, and includes: one or more groups of inverters, the inverter includes the
One to third bridge arm, described first to third bridge arm respectively include be connected in series upper bridge arm and lower bridge arm, the upper bridge arm and
Lower bridge arm respectively includes the power semiconductor switch and freewheeling diode being connected in parallel；And breaker, the breaker
It is connected between the tie point and the power grid between the upper bridge arm and the lower bridge arm, the configuration method includes: to calculate
The short-circuit impedance on the uniline of inverter described in one group when dc-side short-circuit in the inverter system occurs；Based on institute
The output rated voltage for stating short-circuit impedance and the inverter calculates short circuit current on the uniline；Based on the short circuit
Electric current calculates the surge thermal energy of a freewheeling diode；It can be held based on the surge thermal energy and the freewheeling diode
The maximum heat surge received can be carried out the matching of the freewheeling diode, so that described in the surge thermal energy is less than in the given time
Maximum surge thermal energy；And the breaker is selected based on the short circuit current after matching, so that the breaker is described pre-
It fixes time interior disconnection.
According to above-mentioned configuration method, the surge thermal energy is the integrated value square relative to the time of the short circuit current.
According to above-mentioned configuration method, when the output rated voltage of the inverter is set as UN, by inverter described in one group
The all-in resistance of uniline be set as RΣ1, total reactance of the uniline of inverter described in one group is set as XΣ1When, the short circuit
Electric current is set as I, calculation formula are as follows:
According to above-mentioned configuration method, in the matching for carrying out the freewheeling diode, hindered by increasing the short circuit
Resist to reduce the short circuit current, to reduce the surge thermal energy.
According to above-mentioned configuration method, the inverter is also configured with the radiator to radiate to the freewheeling diode,
In the matching, the work temperature of the freewheeling diode is reduced by improving the heat sinking function of the radiator
Degree, to improve the maximum surge thermal energy.
According to above-mentioned configuration method, the inverter further includes transformer, by the short-circuit impedance for improving the transformer
To improve the short-circuit impedance on the uniline.
According to above-mentioned configuration method, the inverter further includes reactor, is mentioned by improving the inductance of the reactor
The high short-circuit impedance.
Another aspect of the present invention provides a kind of inverter system that single channel MPPT is grid-connected, the inverter system
It is arranged between photovoltaic module and power grid, and includes: one or more groups of inverters, the inverter includes first to third bridge
Arm, described first to third bridge arm respectively includes the upper bridge arm being connected in series and lower bridge arm, the upper bridge arm and lower bridge arm difference
Including the power semiconductor switch and freewheeling diode being connected in parallel；And breaker, the breaker are connected on described
It is in the given time, described when dc-side short-circuit occurs between tie point and power grid between upper bridge arm and the lower bridge arm
The surge thermal energy of freewheeling diode is less than the maximum surge thermal energy that the freewheeling diode is able to bear, and the breaker is described
It is disconnected in predetermined time.
According to above-mentioned inverter system, the surge thermal energy is the square opposite of short circuit current when dc-side short-circuit occurs
In the integrated value of time.
Configuration method and single channel MPPT photovoltaic inversion based on above-mentioned single channel MPPT grid-connected inverter system
Device system reduces freewheeling diode in malfunctioning module when dc-side short-circuit occurs for single channel MPPT photovoltaic synchronization inverter system
Damage number.In addition, according to the present invention, avoiding causing to damage to freewheeling diode in non-faulting inverter module, event is prevented
Barrier extension.It is intelligence in addition, according to the present invention, after dc-side short-circuit occurs, the restarting in the most fast time may be implemented
It can control and seamless continuous operation provides basis.
Detailed description of the invention
Fig. 1 is the simplified diagram of single channel MPPT photovoltaic synchronization inverter system of the present invention；
Fig. 2 is the flow chart of the matching process of photovoltaic synchronization inverter system of the present invention；
Fig. 3 is the short-circuit impedance schematic diagram of photovoltaic synchronization inverter system；
Fig. 4 A and Fig. 4 B are in the A phase that photovoltaic synchronization inverter system occurs when dc-side short-circuit in single group inverter module
Bridge arm diode current circuit diagram；
Fig. 4 C and Fig. 4 D are in the B phase that photovoltaic synchronization inverter system occurs when dc-side short-circuit in single group inverter module
Bridge arm diode current circuit diagram；
Fig. 4 E and Fig. 4 F are in the C phase that photovoltaic synchronization inverter system occurs when dc-side short-circuit in single group inverter module
Bridge arm diode current circuit diagram；
Fig. 5 is to establish the schematic diagram of inverter short circuit test model in matlab/simulink；
Fig. 6 is AC single phase short circuit current and freewheeling diode short circuit current simulation waveform；
The surge thermal energy time history plot of freewheeling diode when Fig. 7 is short circuit；
Fig. 8 A is two pole of afterflow under each vendor module freewheeling diode maximum surge thermal energy curve and actual short electric current
The comparison figure of the surge thermal energy curve of pipe；
Fig. 8 B be adjustment after each vendor module freewheeling diode maximum surge thermal energy curve and actual short electric current under
The comparison figure of the surge thermal energy curve of freewheeling diode.
Specific embodiment
The present invention may be better understood to the description of a specific embodiment of the invention in conjunction with attached drawing, wherein it is identical or
Similar appended drawing reference indicates 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, many details are proposed, 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 where not needing some details in these details.Below to implementation
The description of example is used for the purpose of providing by showing example of the invention and better understanding of the invention.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 to the present invention.
Fig. 1 is the simplified diagram of single channel MPPT photovoltaic synchronization inverter system of the present invention.The inverter system
System is arranged between photovoltaic module and power grid.The inverter system includes one or more groups of inverter modules and breaker.
The inverter module includes first to third bridge arm, and the first bridge arm, the second bridge arm and third bridge arm respectively include series connection and connect
The upper bridge arm and lower bridge arm connect, upper bridge arm and lower bridge arm respectively include the power semiconductor switch being connected in parallel and afterflow two
The upper end of pole pipe, each upper bridge arm is connected to each other, and constitutes the DC master row anode for connecting inverter module itself
The lower end of anode connection terminal, each lower bridge arm is connected to each other, and constitutes the DC master row for connecting inverter module itself
The cathode connecting pin of cathode.The inverter module further includes the bearing for connecting above-mentioned anode connection terminal and above-mentioned cathode connecting pin
Capacitor and the reactor (not shown) that the tie point of upper bridge arm and lower bridge arm is connected to the filtering of power grid.Breaker point
It is not connected in series between bridge arm and tie point A, B, C and power grid of lower bridge arm.In addition, though being not shown in figure, but inverse
Becoming device also includes the transformer etc. for boosting.In Fig. 1, one group of inverter module is only shown, but not limited to this, it is being multiple groups
Inverter module is in parallel.Power semiconductor switch can be SCR (silicon-controlled), GTO (gate pole automatic shutoff thyristor), GTR
(huge transistor), VMOSFET (vertical MOS field effect transistor) and IGBT (insulated gate bipolar transistor) etc., below with
Power semiconductor switch selection insulated gate gate transistors (Insulated Gate Bipolar Translator, below
Referred to as IGBT) for be illustrated, the parallel-connection structure of IGBT and freewheeling diode is known as IGBT module.
As shown in Figure 1, breaker for example can be breaker of plastic casing (MouldedCase Circuit Breaker, also letter
Referred to as MCCB).Being installed in series respectively between each upper bridge arm and lower bridge arm tie point A, B, C and grid side has breaker, when straight
When flowing side generation short circuit, each breaker independently carries out separating brake protection act, to cut off before freewheeling diode damage
Short-circuit loop, reduces the damage number of freewheeling diode in malfunctioning module, and failure is avoided to expand to non-faulting inverter mould
Block, to protect photovoltaic synchronization inverter system.That is, when dc-side short-circuit occurs, in the given time, freewheeling diode
Surge thermal energy be less than the maximum surge thermal energy being able to bear of freewheeling diode, breaker disconnects within the predetermined time,
The integrated value square relative to the time of short circuit current when the surge thermal energy is short circuit.
Optionally, remote operating mechanisms can be installed additional for breaker, it, can be most in short-term after fault recognition and excision
It is interior that non-faulting inverter module is carried out to restart operation, reduce the generated energy loss that replacement device time-bands are come, realizes
" seamless " continuous operation.
In the following, being needed to realize that IGBT module and non-faulting inverter module is effectively protected in breaker
Appropriate matching is realized in single channel MPPT photovoltaic synchronization inverter system.Below to single channel MPPT photovoltaic synchronization inverter system
Matching process be illustrated.
As shown in Fig. 2, the matching process for the single channel MPPT photovoltaic synchronization inverter system that the present embodiment is related to, including it is following
Step: S1 is calculated short on the uniline of inverter described in one group when dc-side short-circuit occurs in the inverter system
Roadlock is anti-；S2, the output rated voltage based on the short-circuit impedance and the inverter calculate the short circuit on the uniline
Electric current；S3, the surge thermal energy based on one freewheeling diode of the calculation of short-circuit current；S4 is based on the surge thermal energy
And the maximum heat surge that is able to bear of the freewheeling diode can be carried out the matching of the freewheeling diode, so that in pre- timing
The interior surge thermal energy is less than the maximum surge thermal energy；And S5, it is selected based on the short circuit current after matching described disconnected
Road device, so that the breaker disconnects within the predetermined time.Here, surge thermal energy can be square of the short circuit current
Integrated value relative to the time.
Firstly, the phase line of the single group photovoltaic DC-to-AC converter in the photovoltaic inverter system described when dc-side short-circuit occurs
The calculating of the impedance of road is illustrated.Fig. 3 is the short-circuit impedance schematic diagram of photovoltaic synchronization inverter system.Photovoltaic grid-connected inversion
Short-circuit impedance in device system includes the impedance of net side system short-circuit, Transformer Short Circuit Impedance, common bus line impedance, inverter
Internal cable impedance (not shown) and reactor impedance.
The calculating of each impedance when being below three to inverter module number in single channel MPPT photovoltaic synchronization inverter system
For be illustrated.
In the capacity of short circuit S of known high voltage side of transformerdx, in the case where transformer voltage rating U, single channel MPPT photovoltaic is simultaneously
The net side system short-circuit reactance X of net inverter systemSAs shown in following formula 1.
If actual circuit is three inverter module parallel connections, the single-phase net side system impedance X of each inverter moduleS1
As shown in Equation 2.
Xs1=3 × XsFormula 2
In known transformer rated capacity SN, no-load voltage ratio k, short-circuit impedance percentage Uz△ P, transformation is lost in %, transformer active
The average voltage U of the outlet side of deviceeIn the case where, the short-circuit resistance of transformer is as shown in Equation 3.
And short-circuit resistance percentage U is calculated by formula 4, formula 5r% and short-circuit reactance percentage Ux%, and as formula 6 that
Sample calculates the short-circuit reactance X of transformerb。
If actual circuit is three inverter module parallel connections, the single-phase transformer resistance R of each inverter moduleb1With
Reactance Xb1Respectively as shown in following formula 7 and formula 8.
Rb1=3 × RbFormula 7
Xb1=3 × XbFormula 8
It can be obtained by engineering experience, reactor inductance value generally drops to original 10% or so when short-circuit, it is known that system electricity
Anti- device inductance ratings value L.In addition, the impedance of reactor is only considered by reactance in short-circuit loop.Therefore the reactance of reactor
Value Xd1As shown in following formula 9.
Xd1=ω L=2 π f × L formula 9
In addition, common bus line resistance is set as Rl1, reactance be set as Xl1, inverter module Internal cable resistance is set
For RN1, reactance be set as XN1, it is calculated by known method here, description is omitted.
According to above-mentioned, on the uniline of an inverter module all-in resistance R∑1With total reactance X∑1Respectively such as 10 He of formula
Shown in formula 11.
R∑1=Rb1+R11+RN1Formula 10
X∑1=Xs1+Xb1+Xl1+XN1+Xd1Formula 11
Then, it is calculated based on above-mentioned calculated all-in resistance and total reactance and inverter module output rated voltage
Short circuit current when short-circuit.Namely based on the all-in resistance R on the uniline of the above-mentioned single group inverter module calculated∑1With
Total reactance X∑1And the output rated voltage U of inverter moduleNCalculate short circuit current, single group inverter module it is single-phase short
Road current alternating component stable state virtual value I (hereinafter referred to as short circuit current I) is shown in formula 12.
Fig. 4 A~Fig. 4 F is photovoltaic synchronization inverter system to be shown respectively single group inverter module when dc-side short-circuit occurs
In current loop schematic diagram.In Fig. 4 A~Fig. 4 F, broken lined arrows indicate that DC side has occurred in photovoltaic synchronization inverter system
Short circuit, dotted line frame indicate the short circuit current when dc-side short-circuit occurs for photovoltaic synchronization inverter system in single group inverter module
Circulation path, and the arrow in dotted line frame indicates the flow direction of short circuit current.Bridge arm in A phase when Fig. 4 A and Fig. 4 B are short circuit
Diode circuit schematic diagram；Bridge arm diode circuit schematic diagram in B phase when Fig. 4 C and Fig. 4 D are short circuit；Fig. 4 E and Fig. 4 F are short circuit
When C phase on bridge arm diode circuit schematic diagram.
As shown in Fig. 4 A~Fig. 4 F, when dc-side short-circuit occurs for photovoltaic combining inverter, the ac line voltage of net side is logical
It crosses freewheeling diode in IGBT module and forms short-circuit loop, form biggish short circuit current, and on the circuit and device flowed through
A large amount of heat is generated, will lead to the failure of freewheeling diode.It include transient state component and steady-state component in short circuit current, if only
The changing rule for seeing steady-state component, since DC side is shorted, then DC voltage is close to 0, different from diode rectifier bridge
The size of line voltage is leaned in conducting, and the conducting of diode is determined by phase voltage size at that time completely at this time, positive and negative according to phase voltage
Alternately change and upper bridge arm diode and lower bridge arm diode alternate conduction, and the conducting between each bridge arm is mutually indepedent
's.Pass through the short circuit current circulation path (as illustrated with the dotted box) of each pipe shown in Fig. 4 A~Fig. 4 F, it can be seen that single
Diode 120 ° of progress commutations of every conducting, a cycle (such as 20ms) are connected 180 ° altogether.
On the basis of above-mentioned analysis, after calculating above-mentioned short circuit current I, in order to carry out of photovoltaic inverter system
Match, calculate the surge thermal energy of freewheeling diode, the surge thermal energy is above-mentioned short circuit current I square relative to time t's
Integrated value (I2T), wherein t is the time of short circuit current effect.By reaching for above-mentioned surge thermal energy and the afterflow diode to be selected
Permitted maximum heat surge, which can be carried out, before to cause thermal damage compares, and wherein the maximum surge thermal energy value of freewheeling diode is according to every
A diode is different under different operating temperatures, provides or estimates as known parameters.
Fig. 5 is to establish the schematic diagram of inverter direct-flow side short-circuit test model in matlab/simulink, to DC side electricity
Capacitance and initial voltage are configured, and net side is replaced with three-phase alternating current constant pressure source (for the electricity of equivalent capacity infinity
Net), the impedance of short-circuit equivalent circuit resistance and inductance are indicated to concentrate, short trouble is simulated with time switch, it is interior
Resistance be 10m Ω, switch in 0.2s be closed simulate short circuit there is a situation where when.
In one cycle, short circuit may occur at various moments.Under each initial switching phase angle, short circuit occurs
When steady-state current be it is identical, since period 1 current waveform is formed by stacking by steady-state component and transient state component, so phase
The influence of parallactic angle is mainly reflected on the waveform of period 1, and when short-circuit entrance angle α=0 °, short circuit current is the largest, and is generated
Above-mentioned surge thermal energy I2T is also the largest, thus we in simulations by the short-circuit entrance angle α=0 ° moment generation short circuit
Short circuit current is as selective analysis.
Fig. 6 is AC single phase short circuit current and shorted diode current simulations waveform diagram.All-wave is AC single phase short circuit electricity
Waveform is flowed, half-wave is shorted diode current waveform.Due to the unilateral conduction of freewheeling diode, only at half period (10ms)
There is electric current to flow through freewheeling diode, therefore the above-mentioned surge thermal energy I of freewheeling diode2T can increase in preceding half period, and latter half
Period maintains a stationary value, and then gradually stepped increase, surge thermal energy when Fig. 7 shows freewheeling diode short circuit is at any time
Between (S) change curve graph.The surge thermal energy I at crucial 10ms moment will be obtained from Fig. 72t。
The maximum surge thermal energy curve and single afterflow under actual short electric current that Fig. 8 A is each vendor module freewheeling diode
The comparison figure of the surge thermal energy curve of diode.
When a short circuit occurs, the part of appliance influenced by failure is thermally stressed, thermal stress size and short circuit current it is flat
Side is directly proportional to the integrated value of time, i.e. surge thermal energy.In order to which freewheeling diode is effectively protected, occur in breaker
It disconnects come before realizing protection, the surge energy of freewheeling diode can be held no more than freewheeling diode in actual short circuit
The maximum surge thermal energy received.It is illustrated by taking breaker of plastic casing (MCCB) as an example below, the short-circuit instantaneous protection of breaker of plastic casing
Function is limited by disjunction principle, and most of break all concentrates between 20ms~80ms (having difference because producer's technique is different
Not), and most of practical break is between 20~40ms, therefore we select this period of 0.2s~0.24s to weigh
Point concern.
As shown in Figure 8 A, when selecting company, Infineon to provide Y600A module as freewheeling diode, from Tj=125
DEG C when each moment maximum surge thermal energy I2It is substantially in a linear relationship to be incremented by from the point of view of t, since the heat resistance of device is with heat
It accumulates and reduces, as the time has the tendency that slowing down.Followed by semix603 module is finally certain domestic brand.
With reference to the measured value of the freewheeling diode surge current of certain domestic 600A module, the value at 10ms is observed,
Freewheeling diode maximum surge thermal energy I at Tj=25 DEG C of junction temperature2T is 82037, the maximum heat surge at Tj=125 DEG C of junction temperature
It can I2T is 67548, difference 14489.Assuming that maximum surge thermal energy under two extreme temperatures of the freewheeling diode of same producer's model
I2T difference is also so big, then the maximum surge thermal energy I according to the freewheeling diode of Y600A module at Tj=125 DEG C2T is
35000, maximum surge thermal energy I of the freewheeling diode of Semi603 module at Tj=25 DEG C2T is 66450, it is estimated that
Maximum surge thermal energy I of the freewheeling diode of Y600A module at Tj=25 DEG C2T is the afterflow two of 49489, Semi603 module
Maximum surge thermal energy I of the pole pipe at Tj=125 DEG C2T is 51961.As can be seen from the figure freewheeling diode is actually flowed through
Surge thermal energy I2T (10ms) has been more than the maximum surge thermal energy of the freewheeling diode of Y600A and Semi603 module, subsequent
The surge thermal energy I for actually flowing through freewheeling diode at the moment such as 20ms, 30ms2T has also exceeded maximum surge thermal energy, therefore is selecting
When with Y600A and Semi603 module freewheeling diode, breaker instantaneous short-circuit disjunction is not enough to protect freewheeling diode.
In real work, initial junction temperature when IGBT module works normally is at 100 DEG C and hereinafter, therefore to 100 DEG C or so
The maximum surge thermal energy I of the freewheeling diode of junction temperature2T is studied.Check that the freewheeling diode of certain domestic 600A module exists
Maximum surge thermal energy I at 10ms2T is 73366, greater than the surge generated when actual short electric current flows through freewheeling diode at this time
Thermal energy 70000, and in terms of the trend of curve at this temperature, the surge thermal energy I of diode when in actual short2T curve
Top, so if selecting producer's diode (led) module as freewheeling diode, from the theory of breaker protection freewheeling diode
It is feasible that angle, which is seen,.
For breaker, since freewheeling diode thermal accumlation is mainly generated at first half cycle (0~10ms), so
The sooner the better at first half cycle (10ms) disconnection moment, the later half period only requires disconnection, does not all have much affect sooner or later.
Therefore breaker appropriate is selected with reference to the turn-off time of the short circuit current of short-circuit loop and requirement, in freewheeling diode
Surge thermal energy was less than in the predetermined time of the maximum surge thermal energy of the freewheeling diode, disconnected breaker, it can be achieved that afterflow
The effective protection of diode.
As can be seen from Figure 8A, the parameter based on calculated surge thermal energy and each freewheeling diode, we can select
Select freewheeling diode and breaker appropriate.
On the other hand, when short circuit current is excessively high, may meeting the freewheeling diode of condition to selection, there are excessive limits
System.Such as according to Fig. 8 A it is found that Y600A and Semi603 module diode can not be selected.
Optionally, the radiator to radiate to the freewheeling diode is also configured in inverter module, described
In matching, the operating temperature of the freewheeling diode is reduced by improving the heat sinking function of the radiator, to improve institute
State maximum surge thermal energy.From certain domestic 600A module of Fig. 8 A 25 DEG C, 100 DEG C, 125 DEG C at a temperature of curve can
Out, junction temperature is higher, the permitted maximum surge thermal energy I of freewheeling diode2T is smaller, and junction temperature is lower, and freewheeling diode is permitted
Maximum surge thermal energy I2T is bigger.Therefore we can by reduce as far as possible the temperature of IGBT module come for protect freewheeling diode
Reserve allowance.
Further optionally, in the matching, reduce the short circuit current by increasing the short-circuit impedance.To
Reduce the surge thermal energy I of freewheeling diode in actual short circuit2t.Such as it can be by improving in the photovoltaic DC-to-AC converter
Transformer Short Circuit Impedance improves the short-circuit impedance.After increasing short-circuit impedance and reducing short circuit current, corresponding system is joined
Number brings simulation model into and carries out analytical calculation.Fig. 8 B be after adjustment each vendor module diode allow maximum surge thermal energy curve and
The comparison figure of the surge thermal energy curve of single freewheeling diode when actual short, it can be seen that due to increasing short-circuit impedance, short circuit
Current reduction, at 10ms, the surge thermal energy I of freewheeling diode2T falls to 23000 or so, continuous less than Y600A module at this time
Flow the surge thermal energy I of diode2The data (Tj=125 DEG C) that t is 35000.According to Fig. 8 B, it is known that actually flow through diode
Surge thermal energy I2T curve is between 0.2-0.24s in the maximum surge thermal energy I of Y600A module freewheeling diode2Under t curve
Be surrounded, thus this time interval inner breaker can cut-off loop protect freewheeling diode, freewheeling diode can select
With Y600A module.In addition, breaker opening times are preferably within 40ms, because as the time increases diode maximum surge
Thermal energy tends to definite value (less than 60000), and has crossed after 40ms, the practical surge thermal energy I of freewheeling diode2T has reached 60000
More than, it cannot achieve the effective protection to freewheeling diode.According to emulation, the exchange breaker of plastic casing actual switch-off actually selected
Speed in 20ms or so, then can fully meet protection and require by test.
More than, the configuration method in the design of single channel MPPT photovoltaic inverter system is illustrated, in matched process
In, short circuit current can be reduced by increasing short-circuit impedance, to reduce surge thermal energy；Or by reducing afterflow in inverter
Junction temperature when diode operation improves the maximum surge thermal energy of freewheeling diode, so as to freewheeling diode and breaker
Carry out better choice.
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
Description definition is stated, also, falls into the meaning of claim and whole changes in the range of equivalent to all 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 studying attached drawing, specification and claims
The embodiment of other variations of embodiment.
Claims (7)
1. a kind of configuration method for the inverter system that single channel MPPT is grid-connected, which is characterized in that
The inverter system is arranged between photovoltaic module and power grid, and includes:
One or more groups of inverters, the inverter are respectively included including first to third bridge arm, described first to third bridge arm
The upper bridge arm and lower bridge arm, the upper bridge arm and lower bridge arm being connected in series respectively include the power semiconductor switch device being connected in parallel
Part and freewheeling diode；And
Breaker, the breaker are connected between the tie point and the power grid between the upper bridge arm and the lower bridge arm,
The configuration method includes:
Calculate the short circuit resistance on the uniline of inverter described in one group when dc-side short-circuit occurs in the inverter system
It is anti-；
Output rated voltage based on the short-circuit impedance and the inverter calculates the short circuit current on the uniline；
Surge thermal energy based on one freewheeling diode of the calculation of short-circuit current；
It can be carried out two pole of afterflow based on the maximum heat surge that the surge thermal energy and the freewheeling diode are able to bear
The matching of pipe, so that the surge thermal energy is less than the maximum surge thermal energy in the given time；And
The breaker is selected based on the short circuit current after matching, so that the breaker disconnects within the predetermined time,
The surge thermal energy is the integrated value square relative to the time of the short circuit current.
2. configuration method according to claim 1, which is characterized in that
When the output rated voltage of the inverter is set as UN, the all-in resistance of the uniline of inverter described in one group is set as
RΣ1, total reactance of the uniline of inverter described in one group is set as XΣ1When, the short circuit current is set as I, calculation formula are as follows:
3. configuration method according to claim 1, which is characterized in that
In the matching for carrying out the freewheeling diode, reduce the short circuit current by increasing the short-circuit impedance,
To reduce the surge thermal energy.
4. configuration method according to claim 1, which is characterized in that
The inverter is also configured with the radiator to radiate to the freewheeling diode,
In the matching for carrying out the freewheeling diode, reduced by improving the heat sinking function of the radiator described continuous
The operating temperature of diode is flowed, to improve the maximum surge thermal energy.
5. configuration method according to claim 3, which is characterized in that
The inverter further includes transformer,
The short-circuit impedance on the uniline is improved by improving the short-circuit impedance of the transformer.
6. configuration method according to claim 3, which is characterized in that
The inverter further includes reactor,
The short-circuit impedance is improved by improving the inductance of the reactor.
7. a kind of inverter system that single channel MPPT is grid-connected, which is characterized in that
The inverter system is arranged between photovoltaic module and power grid, and includes:
One or more groups of inverters, the inverter are respectively included including first to third bridge arm, described first to third bridge arm
The upper bridge arm and lower bridge arm, the upper bridge arm and lower bridge arm being connected in series respectively include the power semiconductor switch device being connected in parallel
Part and freewheeling diode；And
Breaker, the breaker are connected between the tie point and power grid between the upper bridge arm and the lower bridge arm,
When dc-side short-circuit occurs, in the given time, the surge thermal energy of the freewheeling diode is less than two pole of afterflow
The maximum surge thermal energy that pipe is able to bear, the breaker disconnect within the predetermined time,
The surge thermal energy is the integrated value square relative to the time of short circuit current when dc-side short-circuit occurs.
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| CN102709890A (en) * | 2012-06-04 | 2012-10-03 | 山东电力集团公司济南供电公司 | Distribution network protection method taking randomness of photovoltaic power station into consideration |
| JP2016140192A (en) * | 2015-01-28 | 2016-08-04 | オムロン株式会社 | Bidirectional dc-dc converter, power conditioner and distributed power supply system |
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| CN102709890A (en) * | 2012-06-04 | 2012-10-03 | 山东电力集团公司济南供电公司 | Distribution network protection method taking randomness of photovoltaic power station into consideration |
| JP2016140192A (en) * | 2015-01-28 | 2016-08-04 | オムロン株式会社 | Bidirectional dc-dc converter, power conditioner and distributed power supply system |
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| Title |
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| 一种新型高效单相非隔离光伏并网逆变器;童鑫等;《电源学报》;20140930;第51-55页 |
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