CN110677120B - Photovoltaic inverter system and control method thereof - Google Patents
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
- H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
- H02S40/30—Electrical components
- H02S40/32—Electrical components comprising DC/AC inverter means associated with the PV module itself, e.g. AC modules
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
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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
Abstract
The invention discloses a photovoltaic inversion system and a control method thereof, wherein the photovoltaic inversion system comprises: optimizing the component string and the inverter; the optimization component string comprises a plurality of optimization components, the input end of each optimization component is coupled with at least one photovoltaic component, and the output ends of the optimization components are connected in series; each optimization component comprises a control unit; the input end of the inverter is coupled to the output end of the optimized component string, the inverter comprises an auxiliary detection module, the auxiliary detection module is used for detecting the output current of the optimized component string in an auxiliary mode, and the control unit controls the output voltage of the optimized component string according to the output current of the optimized component string to enable the output voltage to meet the starting condition of the inverter.
Description
Technical Field
The invention relates to a photovoltaic inverter system and a control method thereof, in particular to a photovoltaic inverter system without traditional communication between an inverter and an optimization component and a control method thereof.
Background
At present, the photovoltaic power generation technology has developed and matured, and is widely applied at home and abroad. The photovoltaic power generation system comprises a photovoltaic panel, a junction box, an inverter and the like, wherein the photovoltaic panel converts received solar light energy into direct current electric energy, and the inverter converts the direct current electric energy into required alternating current electric energy which is merged into a power grid or directly supplied to customers for use.
The photovoltaic inversion system using the optimizer can ensure the maximum power tracking output of the photovoltaic panel and improve the conversion efficiency of the photovoltaic panel. The photovoltaic panels connected in series and in parallel have very high voltage and energy, and when sudden events (earthquakes, fires and the like) occur, the photovoltaic panels with high voltage and high energy need to be disconnected, so that the panels with high voltage and high energy are prevented from causing larger disasters, and the protection effect is also realized on personnel in charge of rescue. Conventional photovoltaic systems require rapid turn-off devices to be incorporated into the photovoltaic panels, while photovoltaic systems employing optimizers can achieve panel-level rapid turn-off via the optimizer. Meanwhile, the use of the optimizer needs to communicate with the inverter at the later stage, but because a modulation and demodulation circuit is added, the cost is high, and the transmission data is easily interfered by energy signals.
In addition, during the starting process of the photovoltaic system, the situation that a plurality of optimizers temporarily do not output voltage due to the shielding of black clouds or building shadows sometimes occurs. In the prior photovoltaic optimizer starting scheme, the part of the optimizer cannot be started, so that waste of power devices and loss of economic benefits are caused.
Therefore, it is urgently needed to develop a photovoltaic inverter system and a control method thereof, which overcome the above defects.
Disclosure of Invention
In order to overcome the problems in the prior art, an object of the present invention is to provide a photovoltaic inverter system and a control method thereof, which can reduce communication cost and improve system reliability, so that the photovoltaic inverter system can be safely started, operated and quickly turned off without communication.
The invention provides a photovoltaic inverter system, which comprises: optimizing the component string and the inverter; the optimization component string comprises a plurality of optimization components, the input end of each optimization component is coupled with at least one photovoltaic component, and the output ends of the optimization components are connected in series; each of the optimization components comprises a control unit; the input end of the inverter is coupled to the output end of the optimized component string, the inverter comprises an auxiliary detection module, the auxiliary detection module is used for detecting the output current of the optimized component string in an auxiliary mode, and the control unit controls the output voltage of the optimized component string according to the output current of the optimized component string, so that the output voltage meets the starting condition of the inverter.
In the above photovoltaic inverter system, the control unit further controls the optimized component string to be turned off rapidly according to the output current of the optimized component string.
In the above photovoltaic inverter system, the auxiliary detection module is integrated inside the inverter.
The photovoltaic inverter system, wherein the auxiliary detection module comprises a power resistor.
The photovoltaic inverter system, wherein the auxiliary detection module comprises a controllable current source.
In the above photovoltaic inverter system, the auxiliary detection module is externally connected to the inverter.
In the above photovoltaic inverter system, the starting condition of the inverter is that the input voltage of the inverter is in a first voltage interval.
The invention also provides a control method for the photovoltaic inverter system, wherein the control method comprises the following steps:
step S1: controlling each optimized component to output an initial voltage;
step S2: detecting and judging the output voltage of the optimized component string, and accessing the auxiliary detection module when the output voltage of the optimized component string is in a second voltage interval;
step S3: detecting the output current or the output voltage of the optimized component string, and calculating the number of optimized components actually connected in the optimized component string;
step S4: and the control unit of the optimization component controls the corresponding optimization component according to the number of the optimization components, so that the output voltage of the optimization component string meets the starting condition of the inverter.
The control method described above, wherein the control method further includes:
step S5: and detecting and judging the output current of the optimized component string, and when the output current is smaller than a preset minimum current, controlling the corresponding optimized component to output the initial voltage by the control unit of the optimized component.
In the above control method, the starting condition of the inverter is that the input voltage of the inverter is in a first voltage interval.
In the above control method, step S3 includes:
step S31: the control unit of the optimization component detects the output current of the optimization component string and calculates the output voltage of the optimization component string;
step S32: and the control unit of the optimization component detects the output voltage of the corresponding optimization component and calculates the number of the optimization components actually connected in the optimization component string.
In the above control method, step S3 includes:
step S31: the inverter detects the output voltage of the optimized component string and calculates the number of optimized components actually connected in the optimized component string;
step S32: and controlling the auxiliary detection module to switch on-off states and sending pulses to the optimization component string, wherein the number of the pulses is proportional to the number of the optimization components.
In the above control method, step S4 includes:
step S41: the control unit of the optimization component controls the corresponding optimization component to output maximum voltage according to the number of the optimization components, wherein the maximum voltage enables the output voltage of the optimization component string to meet the starting condition of the inverter;
step S42: and the inverter detects the output voltage of the optimized component string, and when the starting condition is met, the inverter is started to connect the photovoltaic inverter system into a power grid.
In the control method, the auxiliary detection module includes a plurality of parallel power resistors.
In the above control method, step S2 includes:
step S21: detecting and judging the output voltage of the optimized component string, and accessing a first power resistor when the output voltage of the optimized component string is in a second voltage interval;
step S22: detecting and judging the output current of the optimized component string, and controlling the corresponding optimized component to output a set voltage by the control unit when the output current of the optimized component string is in a first current interval;
step S23: detecting and judging the output voltage of the optimized component string, and disconnecting the first power resistor and connecting the second power resistor when the output voltage of the optimized component string is in a third voltage interval; and when the output voltage of the optimized component string is in a fourth voltage interval, disconnecting the first power resistor and connecting the third power resistor.
In the control method, the auxiliary detection module includes a controllable current source.
The control method described above, wherein the step S4 further includes:
step S43: and the control unit of the optimization component controls the corresponding optimization component to operate in the MPPT mode.
The control method described above, wherein the control method further includes:
step S6: and the control unit of the optimization component detects the output current of the corresponding optimization component, and when the output current is greater than a preset threshold current and lasts for a preset threshold time, the corresponding optimization component is controlled to operate in an MPPT mode.
Aiming at the prior art, the invention has the following effects: through the collection to optimizing subassembly output voltage, output current, the optimizing subassembly of this application need not to carry out traditional communication with the inverter and can control photovoltaic inverter system's operating condition, not only can rationally control the output voltage who optimizes the subassembly and ensure the inverter safe start, can realize the MPPT (Maximum Power Point Tracking) mode operation and the RSD (Rapid Shut-Down) function of optimizing the subassembly simultaneously, its topology is simple, the reliability is high, easily control, the debugging is convenient, the function is perfect.
Drawings
Fig. 1 is a schematic structural diagram of a photovoltaic inverter system according to a first embodiment of the present invention;
fig. 2 is a schematic structural diagram of a photovoltaic inverter system according to a second embodiment of the present invention;
FIG. 3 is a flowchart of a first embodiment of a control method of the present invention;
FIGS. 4-6 are flow charts of the substeps of FIG. 3;
fig. 7 is a flowchart illustrating a substep of step S3 in the second embodiment of the control method of the present invention;
FIG. 8 is a schematic diagram of an optimization component circuit;
FIGS. 9 and 10 are equivalent circuit diagrams of the optimized device circuit of FIG. 8 operating in buck mode;
FIG. 11 is a waveform diagram illustrating the switching driving signals and the output voltages thereof when the optimized device circuit of FIG. 8 operates in the buck mode;
FIGS. 12 and 13 are equivalent circuit diagrams of the optimized component circuit of FIG. 8 operating in boost mode; and
fig. 14 is a waveform diagram of the switch driving signals and the output voltage when the optimized device circuit of fig. 8 operates in the boost mode.
Detailed Description
The invention is described in further detail below with reference to specific embodiments and with reference to the following figures: the embodiment is implemented on the premise of the technical scheme of the invention, and the implementation mode and the operation process are given, but the protection scope of the invention is not limited by the following embodiments.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a photovoltaic inverter system according to a first embodiment of the invention. As shown in fig. 1, the photovoltaic inverter system of the present invention includes: the method comprises the following steps: optimizing the component string 1 and the inverter 2; the optimized component string comprises a plurality of optimized components 11 …1n, each optimization module 11 … 1n having an input coupled to at least one photovoltaic module, which may be a PV panel, where n is a positive integer, and the outputs of the plurality of optimization modules 11 … 1n are connected in series; each optimizing assembly 11 … 1n includes a control unit; the input end of the inverter 2 is coupled to the output end of the optimized component string, the inverter 2 comprises an auxiliary detection module 21, the auxiliary detection module 21 is connected with the input end of the inverter 2 in parallel, the auxiliary detection module 21 is used for detecting the output current of the optimized component string 1 in an auxiliary manner, the control unit controls the output voltage of the optimized component string 1 according to the output current of the optimized component string 1, the output voltage meets the starting condition of the inverter 2, wherein the starting condition of the inverter 2 is the input voltage V of the inverter 2busIn a first voltage interval, i.e. Vmin≤Vbus≤VmaxIn which V isminMinimum voltage, V, to satisfy inverter starting conditionsmaxThe maximum voltage is a maximum voltage for satisfying the inverter starting condition, but the invention is not limited thereto.
Further, the control unit also controls the fast turn-off of the optimized component string 1 according to the output current of the optimized component string 1.
Still further, in the present embodiment, the auxiliary detection module 21 may be integrated inside the inverter 2, but the invention is not limited thereto, and in other embodiments, the auxiliary detection module 21 is externally connected to the inverter 2.
Furthermore, the auxiliary detection module 21 includes a first power resistor R1, a second power resistor R2, and a third power resistor R3.
Referring to fig. 2, fig. 2 is a schematic structural diagram of a photovoltaic inverter system according to a second embodiment of the present invention. The structure of the photovoltaic inverter system shown in fig. 2 is substantially the same as that of the photovoltaic inverter system shown in fig. 1, and therefore, the same parts are not described herein again, and different parts will now be described below. In this embodiment, the auxiliary detection module 21 comprises a controllable current source 211.
Referring to fig. 3-6, fig. 3 is a flowchart illustrating a control method according to a first embodiment of the present invention; fig. 4 to 6 are flow charts of the substeps of fig. 3. The following describes the control method of the photovoltaic inverter system according to the present invention with reference to fig. 1 and fig. 3 to 6. The control method comprises the following steps:
step S1: controlling each optimized group to output an initial voltage VOstartWherein, in the embodiment, 0V is less than or equal to VOstartLess than or equal to 2V and initial voltage VOstartFor example, a smaller voltage value of 1V is set, but the invention is not limited thereto;
step S2: detecting and determining an output voltage V of an optimized component stringbusWhen optimizing the output voltage V of the component stringbusIn a second voltage interval, the auxiliary detection module, i.e. V, is switched inmin1≤Vbus≤Vmax1；
Step S3: detecting output current I of optimized component stringoOr the output voltage VbusAnd calculating the number of optimized components actually connected in the optimized component string, it should be noted that, in this embodiment, step S3 is to detect the output current I of the optimized component stringoHowever, the invention is not limited thereto, and in other embodiments, the output voltage V of the device string can be detectedbusAs will be described in detail later;
step S4: the control unit of the optimization component controls the corresponding optimization components according to the number of the optimization components, so that the output voltage V of the optimization component stringbusSatisfying the starting condition of the inverter, i.e. Vmin1≤Vbus≤Vmax1。
Further, step S2 includes:
step S21: detecting and judging the output voltage of the optimized component string, when the output voltage of the optimized component string is in a second voltage interval, namely Vmin2≤Vbus≤Vmax2A first power resistor R1 is connected, wherein V is more than or equal to 5V in the embodimentbusThe preferred embodiment is no more than 30V and the resistance of the first power resistor R1 is 5 Ω, but the invention is not limited thereto;
step S22: detecting and determining output current I of optimized component stringoWhen optimizing the output current I of the component stringoIn a first current interval, i.e. Imin1≤Io≤Imax1The control unit controls the corresponding optimized component to output a set voltage VsetWherein in the present implementationIn the examples, 1A. ltoreq.IoLess than or equal to 3A and VsetA preferred embodiment is 5V;
step S23: detecting and judging the output voltage of the optimized component string, when the output voltage of the optimized component string is in a third voltage interval, namely Vmin3≤Vbus≤Vmax3The first power resistor R1 is disconnected and the second power resistor R2 is connected; when the output voltage of the optimized component string is in the fourth voltage interval, i.e. Vmin4≤Vbus≤Vmax4The first power resistor R1 is disconnected and the third power resistor R3 is connected. In the embodiment, the third voltage interval is 20V ≦ VbusNot more than 50V, and the fourth voltage interval is not less than 60VbusThe resistance value of the second power resistor R2 is less than or equal to 100V, and the resistance value of the third power resistor R3 is 110 omega.
Still further, step S3 includes:
step S31: the control unit of the optimization assembly detects the output current I of the optimization assembly stringoAnd calculating the output voltage V of the optimized component stringbus，Vbus＝IoX R2, or Vbus＝Io×R3；
Step S32: the control unit of the optimization component detects the output voltage of the corresponding optimization component, and calculates the number N of the optimization components actually connected in the optimization component string, wherein the output voltage of each optimization component is VsetWhereby the control unit of each optimizing component is based on a formula
And obtaining the number of the optimized components which are actually accessed.
Still further, step S4 includes:
step S41: the control unit of the optimization component controls the corresponding optimization component to output the maximum voltage V according to the number of the optimization componentsomaxWherein the maximum voltage VomaxEnabling the output voltage of the optimized component string to meet the starting condition of the inverter;
step S42: output voltage V of inverter detection optimizing component stringbusWhen the start-up strip is satisfiedDuring the operation, the inverter is started, and the photovoltaic inverter system is connected to a power grid.
In another embodiment of the present invention, step S4 may further include:
step S43: the control unit of the optimization component controls the corresponding optimization component to operate in the MPPT mode.
Referring to fig. 7, fig. 7 is a flowchart illustrating a sub-step of step S3 according to a second embodiment of the control method of the present invention. The steps of the control method shown in fig. 7 are substantially the same as those of the control method shown in fig. 3-6, and therefore, the same parts are not described herein again, and different parts will now be described below.
As shown in fig. 7, step S3 includes:
step S31': output voltage V of inverter detection optimizing component stringbusAnd calculating the number N of the optimization components actually connected in the optimization component string, wherein the inverter stores the set voltage V of each optimization component in advancesetTherefore, the inverter obtains the number N of actually connected optimized components according to the following formula:
step S32': and controlling the auxiliary detection module to switch on-off states and sending pulses to the optimization component string, wherein the number of the pulses is proportional to the number of the optimization components. For example, when N optimized components are detected, the inverter is controlled to send N-5N pulses. The number N of pulses sent by the inverter is detected by the optimizing component, and then the number N of the optimizing component is calculated to be N/5, wherein N is the minimum integer which is more than or equal to N/5. In this embodiment, only when the number of lost pulses in the pulse transmission process is greater than or equal to 5, an error of counting one less optimized component occurs, and the fault tolerance rate is improved, but the invention is not limited thereto.
It should be noted that, in the first and second embodiments, the auxiliary detection module includes a plurality of power resistors connected in parallel for illustration, but the invention is not limited thereto.
In another embodiment of the present invention, the control method further includes step S5: detecting and determining output current I of optimized component stringoWhen outputting a current IoLess than a predetermined minimum current IminWhen the voltage is lower than the initial voltage V, the control unit of the optimization component controls the corresponding optimization component to output the initial voltage VOstart. Specifically, the optimization component detects a rapid decrease in the sampled current once the sampled current I is detected after the inverter is disconnected from the grido<IminWhile optimizing the output initial voltage V of the assemblyOstartAnd a quick turn-off function is realized. Wherein VOstartSet to a small voltage value (0V is less than or equal to V)Ostart2V or less) for ensuring that the output voltage of the series optimized component can be controlled at a lower voltage level when being rapidly turned off, thereby preventing the photovoltaic panel with high voltage and high energy from causing greater disasters when sudden events (earthquakes, fires, etc.) occur, and also protecting the personnel in charge of rescue.
In another embodiment of the present invention, the control method may further include step S6: the control unit of the optimization component detects the output current I of the corresponding optimization componentoWhen outputting a current IoGreater than a predetermined threshold current IsetAnd the operation lasts for a preset threshold time T, and the corresponding optimization component is controlled to operate in the MPPT mode. Specifically, in the starting process, when the sampling current at the output side of the optimization component is within a certain range, it indicates that the optimization component can start to enter a starting process at the moment until the inverter is successfully started and stably operates. When the sampling current of the output side of the optimization component does not accord with the starting condition, the optimization component does not perform the starting action, but waits for the sampling current to be larger than the threshold current and stably continues for a certain time, at the moment, the inverter is known to be successfully started, the bus voltage is controlled by the inverter side, and the optimization component can directly enter the MPPT mode and stably run. Therefore, even if there are several optimized components in the photovoltaic system that cannot be started temporarily due to occlusion of cloud or building shadows, the optimized components enter the system in the MPPT mode and operate stably after the inverter is successfully started.
The optimized component circuit for switching between the boost mode and the buck mode is described with reference to fig. 8-14. Fig. 8 is a schematic diagram of an optimized component circuit.
The optimized component circuit has the advantages of simple topological structure, small harmonic wave and good electromagnetic compatibility. The circuit can work in a voltage boosting and reducing mode, is equivalent to a voltage boosting circuit and a voltage reducing circuit which are independent of each other, and realizes complete decoupling of voltage boosting and reducing. The optimized component circuit comprises a first capacitor C1First inductance L1First to fourth switching tubes S1-S4E.g. IGBT or MOSFET, second inductance L2A second capacitor C2And a third capacitor C3. First inductance L1One end of which is connected with a first capacitor C1One end of (1), a first inductance L1The other end of the first switch tube S is connected with the first switch tube S1And a second switching tube S2A first terminal (e.g., source of MOSFET), a second switching tube S2Is connected to a second capacitor C (e.g. the drain of a MOSFET)2And a third switching tube S3E.g. the drain of a MOSFET), a third switching transistor S3Is connected to the fourth switching tube S (e.g. the source of the MOSFET)4And a second inductance L (e.g., the drain of a MOSFET)2One terminal of (1), a second inductance L2Is connected with a third capacitor C3One end of (a); a first capacitor C1The other end of the first switch tube S is connected with the first switch tube S1A second terminal (e.g., source of MOSFET), a second capacitor C2The other end of the first switch tube S and a fourth switch tube S4A second terminal (e.g., source of MOSFET) and a third capacitor C3And the other end of the same.
The first controller includes a digital control unit 1222 and a pulse modulation unit 1221. The digital control unit receives the current and the voltage at the input side of the optimization component circuit and the voltage and the current at the output side of the optimization component circuit, outputs a control signal according to the voltage and the current at the input side of the optimization component circuit, the voltage at the output side and the current, converts the control signal into a PWM signal by the pulse modulation unit 1221 and outputs the PWM signal to the switching tube S in the optimization component circuit1-S4For controlling the switching tube S in the optimized component circuit1-S4To change the operating state of the optimized component circuit. The first controller 121 is digitally controlled, so that the control is more convenient, the debugging is convenient, and the functions are complete.
Fig. 9 and 10 are equivalent circuit diagrams of the optimized device circuit of fig. 8 operating in the buck mode.
When Vin is greater than or equal to Vout, the first controller 121 controls the switch tube S1Complete cut-off and switching tube S2Is kept normally open and controls the switch tube S3、S4And working in a switch state. The first controller 121 controls the switch tube S4And a switching tube S3Complementary conduction and control of the switching tube S3Duty ratio of D1The voltage reduction function of the optimized component circuit is realized, so that the output voltage Vo ═ D of the optimized component circuit is realized1Vin。
FIG. 11 is a waveform diagram of the driving signals and the output voltage of the switch tube when the optimized component circuit of FIG. 8 is in the buck mode, illustrating four MOSFET (metal-oxide semiconductor field effect transistor) switch tubes S1-S4Drive signal V ofs1-Vs2And optimizing the output voltage V of the component circuitoA waveform diagram of (a).
Fig. 12 and 13 are equivalent circuit diagrams of the optimized device circuit of fig. 8 operating in the boost mode.
When Vin<Vout, the first controller 121 controls the switch tube S3Keep normally open and switch tube S4Is completely cut off and controls the switch tube S1、S2And working in a switch state. The first controller 121 controls the switch tube S1And a switching tube S2Complementary conduction and controlling the duty ratio of the switching tube to be D2The boosting function of the optimized component circuit is realized, so that the output end voltage Vo of the optimized component circuit is Vin/(1-D)2)。
FIG. 14 is an equivalent circuit of the optimized component circuit of FIG. 8 operating in boost mode, depicting four MOSFET (Metal-oxide-semiconductor field Effect transistor) transistors S1-S4Is driven bySignal Vs1-Vs2And optimizing the output voltage V of the component circuitoSchematic diagram of the waveform of (1).
The above description is merely exemplary in nature and is not intended to limit the present invention.
In summary, through the collection of the output voltage and the output current of the optimization component, the optimization component can control the working state of the optimization component without traditional communication with the inverter, reasonably control the output voltage of the optimization component to ensure the safe starting of the inverter, and simultaneously realize the MPPT function and the RSD function.
It should be noted that: the above embodiments are merely illustrative of the present invention, and do not limit the technical solutions described in the present invention; meanwhile, although the present invention has been described in detail with reference to the above embodiments, it will be understood by those skilled in the art that the present invention may be modified and equivalents may be substituted; therefore, all technical solutions and modifications which do not depart from the spirit and scope of the present invention should be construed as being included in the scope of the appended claims.
Claims (18)
1. A photovoltaic inverter system, comprising: optimizing the component string and the inverter; the optimization component string comprises a plurality of optimization components, the input end of each optimization component is coupled with at least one photovoltaic component, and the output ends of the optimization components are connected in series; each of the optimization components comprises a control unit; the input end of the inverter is coupled to the output end of the optimized component string, the inverter comprises an auxiliary detection module, the auxiliary detection module is used for detecting the output current or the output voltage of the optimized component string in an auxiliary mode and calculating the number of optimized components actually connected in the optimized component string, and the control unit controls the corresponding optimized components according to the number of the optimized components to enable the output voltage to meet the starting condition of the inverter;
wherein the inverter sends pulses to the string of optimized components, the number of pulses being proportional to the number of optimized components.
2. The photovoltaic inversion system of claim 1, wherein the control unit further controls a fast turn off of the optimized component string according to an output current of the optimized component string.
3. The photovoltaic inversion system of claim 1, wherein the auxiliary detection module is integrated within the inverter.
4. The photovoltaic inversion system of claim 3, wherein the auxiliary detection module includes a power resistor.
5. The photovoltaic inversion system of claim 3, wherein the auxiliary detection module comprises a controllable current source.
6. The photovoltaic inversion system of claim 1, wherein the auxiliary detection module is external to the inverter.
7. The photovoltaic inversion system of claim 1, wherein the inverter is started under a condition that an input voltage of the inverter is in a first voltage interval.
8. A control method for the photovoltaic inverter system according to claim 1, wherein the control method comprises:
step S1: controlling each optimized component to output an initial voltage;
step S2: detecting and judging the output voltage of the optimized component string, and accessing the auxiliary detection module when the output voltage of the optimized component string is in a second voltage interval;
step S3: detecting the output current or the output voltage of the optimized component string, and calculating the number of optimized components actually connected in the optimized component string, wherein the inverter sends pulses to the optimized component string, and the number of the pulses is proportional to the number of the optimized components;
step S4: and the control unit of the optimization component controls the corresponding optimization component according to the number of the optimization components, so that the output voltage of the optimization component string meets the starting condition of the inverter.
9. The control method according to claim 8, characterized by further comprising:
step S5: and detecting and judging the output current of the optimized component string, and when the output current is smaller than a preset minimum current, controlling the corresponding optimized component to output the initial voltage by the control unit of the optimized component.
10. The control method according to claim 8, wherein the start condition of the inverter is that an input voltage of the inverter is in a first voltage section.
11. The control method according to claim 8, wherein said step S3 includes:
step S31: the control unit of the optimization component detects the output current of the optimization component string and calculates the output voltage of the optimization component string;
step S32: and the control unit of the optimization component detects the output voltage of the corresponding optimization component and calculates the number of the optimization components actually connected in the optimization component string.
12. The control method according to claim 8, wherein said step S3 includes:
step S31: the inverter detects the output voltage of the optimized component string and calculates the number of optimized components actually connected in the optimized component string;
step S32: and controlling the auxiliary detection module to switch on-off states and sending pulses to the optimization component string, wherein the number of the pulses is proportional to the number of the optimization components.
13. The control method according to claim 8, wherein said step S4 includes:
step S41: the control unit of the optimization component controls the corresponding optimization component to output maximum voltage according to the number of the optimization components, wherein the maximum voltage enables the output voltage of the optimization component string to meet the starting condition of the inverter;
step S42: and the inverter detects the output voltage of the optimized component string, and when the starting condition is met, the inverter is started to connect the photovoltaic inverter system into a power grid.
14. The control method according to claim 11 or 12, wherein the auxiliary detection module comprises a plurality of power resistors connected in parallel.
15. The control method according to claim 14, wherein said step S2 includes:
step S21: detecting and judging the output voltage of the optimized component string, and accessing a first power resistor when the output voltage of the optimized component string is in a second voltage interval;
step S22: detecting and judging the output current of the optimized component string, and controlling the corresponding optimized component to output a set voltage by the control unit when the output current of the optimized component string is in a first current interval;
step S23: detecting and judging the output voltage of the optimized component string, and disconnecting the first power resistor and connecting the first power resistor to a second power resistor when the output voltage of the optimized component string is in a third voltage interval; and when the output voltage of the optimized component string is in a fourth voltage interval, disconnecting the first power resistor and connecting a third power resistor.
16. The control method of claim 12, wherein the auxiliary detection module comprises a controllable current source.
17. The control method according to claim 13, wherein the step S4 further includes:
step S43: and the control unit of the optimization component controls the corresponding optimization component to operate in the MPPT mode.
18. The control method according to claim 8, characterized by further comprising:
step S6: and the control unit of the optimization component detects the output current of the corresponding optimization component, and when the output current is greater than a preset threshold current and lasts for a preset threshold time, the corresponding optimization component is controlled to operate in an MPPT mode.
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