CN111555360A - Photovoltaic grid-connected power generation system - Google Patents

Photovoltaic grid-connected power generation system Download PDF

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Publication number
CN111555360A
CN111555360A CN202010533797.7A CN202010533797A CN111555360A CN 111555360 A CN111555360 A CN 111555360A CN 202010533797 A CN202010533797 A CN 202010533797A CN 111555360 A CN111555360 A CN 111555360A
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photovoltaic
module
phase
inverter
current
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Inventor
赵香桂
朱淇凉
廖资阳
戴伯望
张蓉
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Zhuzhou National Engineering Research Center of Converters Co Ltd
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Zhuzhou National Engineering Research Center of Converters Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics

Abstract

The invention provides a photovoltaic grid-connected power generation system, aiming at the cascaded frequency spectrum characteristics of a series winding transformer, the primary side line voltage of the transformer only contains 12k +/-1 (k is 1,2,3 … …) subharmonic components, and the current harmonics of the primary side and the secondary side are consistent, Specific Harmonic Elimination Pulse Width Modulation (SHEPWM) is adopted, and 12k +/-1 (k is 1,2,3 … …) subharmonic components are selected for elimination.

Description

Photovoltaic grid-connected power generation system
Technical Field
The invention relates to the technical field of photovoltaic, in particular to a photovoltaic grid-connected power generation system.
Background
The photovoltaic is a solar photovoltaic power generation system for short, is a novel power generation system which directly converts solar radiation energy into electric energy by utilizing the photovoltaic effect of a solar cell semiconductor material and has two modes of independent operation and grid-connected operation.
Therefore, how to improve the structure of the photovoltaic inverter to reduce the production cost and how to improve the structure of the photovoltaic grid-connected power generation system to improve the power generation efficiency and the power quality of the photovoltaic power generation system are technical problems to be solved by those skilled in the art.
Disclosure of Invention
In view of the above, in order to solve the above problems, the present invention provides a photovoltaic grid-connected power generation system, which has the following technical scheme:
a grid-connected photovoltaic power generation system, comprising: the photovoltaic solar panel comprises a photovoltaic cell panel, a first photovoltaic inverter, a second photovoltaic inverter, a transformer and a controller;
the first photovoltaic inverter and the second photovoltaic inverter are connected in parallel;
the input ends of the first photovoltaic inverter and the second photovoltaic inverter are connected with the output end of the photovoltaic cell panel, and the photovoltaic cell panel is used as a common direct current input source of the first photovoltaic inverter and the second photovoltaic inverter;
the output ends of the first photovoltaic inverter and the second photovoltaic inverter are respectively connected with the corresponding windings on the secondary side of the transformer;
the primary side of the transformer is connected with a power grid;
the primary side current and the secondary side current of the transformer are in a linear proportional relation; the controller is used for generating PWM driving signals which are respectively input to the first photovoltaic inverter and the second photovoltaic inverter so as to eliminate specific subharmonic components in the primary side voltage signal of the transformer.
Preferably, in the grid-connected photovoltaic power generation system, the transformer includes: a plurality of line resistances, a plurality of line inductances, and a plurality of windings;
the primary side windings of the transformer are connected in a series Y-type mode, and the secondary side windings of the transformer are connected in a Y-type mode and a D-type mode respectively, so that primary side line voltage of the transformer only contains 12k +/-1 (k is 1,2 and 3 … …) subharmonic components, and current harmonics of the primary side and the secondary side are consistent.
Preferably, in the grid-connected photovoltaic power generation system, the first photovoltaic inverter includes: the first capacitor and the first photovoltaic inverter module;
the input end of the first photovoltaic inverter module is connected with the first capacitor in parallel.
Preferably, in the grid-connected photovoltaic power generation system, the second photovoltaic inverter includes: a second capacitor and a second photovoltaic inverter module;
the input end of the second photovoltaic inverter module is connected with the second capacitor in parallel.
Preferably, in the grid-connected photovoltaic power generation system, the controller includes: the device comprises an acquisition module, a phase-locked angle acquisition module, a conversion module and a calculation module;
the acquisition module is used for acquiring a direct-current bus voltage of a public direct-current input source, a first three-phase current of the first photovoltaic inversion module, a second three-phase current of the second photovoltaic inversion module and a power grid voltage of the power grid;
the phase-locked angle acquisition module is used for acquiring a first phase-locked angle of the first photovoltaic inversion module and a second phase-locked angle of the second photovoltaic inversion module;
the conversion module is used for respectively acquiring an active current component and a reactive current component of the first photovoltaic inversion module and the second photovoltaic inversion module in a dq rotation coordinate system;
the calculation module is used for calculating a first arithmetic mean value of current components of the first photovoltaic inversion module and the second photovoltaic inversion module in a d axis and calculating a second arithmetic mean value of current components of the first photovoltaic inversion module and the second photovoltaic inversion module in a q axis.
Preferably, in the above-mentioned grid-connected photovoltaic power generation system, the phase-locked angle acquisition module is a PLL phase-locked loop.
Preferably, in the above-mentioned grid-connected photovoltaic power generation system, the second phase-locked angle is obtained after the phase of the first phase-locked angle is shifted by pi/6.
Preferably, in the above-mentioned grid-connected photovoltaic power generation system, the controller further includes:
the voltage control module is used for controlling the voltage of the direct current bus;
the current regulation module is used for controlling active current components and reactive current components of the first photovoltaic inversion module and the second photovoltaic inversion module, wherein current feedback respectively adopts a first arithmetic mean value of current components of the first photovoltaic inversion module and the second photovoltaic inversion module in a d axis and a second arithmetic mean value of current components of the first photovoltaic inversion module and the second photovoltaic inversion module in a q axis;
the SHEPWM algorithm module is used for selecting a characteristic subharmonic component of 12k +/-1 (k is 1,2,3 … …) contained in the primary side line voltage of the transformer to eliminate, outputting a first PWM driving signal for controlling the first photovoltaic inverter module according to the current modulation degree and the phase angle of a modulation wave, and outputting a second PWM driving signal for controlling the second photovoltaic inverter module.
Preferably, in the grid-connected photovoltaic power generation system, the second PWM drive signal is obtained after the first PWM drive signal is shifted in phase by pi/6.
Preferably, in the grid-connected photovoltaic power generation system,
the first photovoltaic inverter is a three-phase two-level photovoltaic inverter or a three-phase multi-level inverter or a three-phase H-bridge inverter;
the second photovoltaic inverter is a three-phase two-level photovoltaic inverter or a three-phase multi-level inverter or a three-phase H-bridge inverter.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a photovoltaic grid-connected power generation system, which comprises: the photovoltaic solar panel comprises a photovoltaic cell panel, a first photovoltaic inverter, a second photovoltaic inverter, a transformer and a controller; the first photovoltaic inverter and the second photovoltaic inverter are connected in parallel; the input ends of the first photovoltaic inverter and the second photovoltaic inverter are connected with the output end of the photovoltaic cell panel, and the photovoltaic cell panel is used as a common direct current input source of the first photovoltaic inverter and the second photovoltaic inverter; the output ends of the first photovoltaic inverter and the second photovoltaic inverter are respectively connected with the corresponding windings on the secondary side of the transformer; the primary side of the transformer is connected with a power grid; the primary side current and the secondary side current of the transformer are in a linear proportional relation; the controller is used for generating PWM driving signals which are respectively input to the first photovoltaic inverter and the second photovoltaic inverter so as to eliminate specific subharmonic components in the primary side voltage signal of the transformer.
The transformer in the photovoltaic grid-connected power generation system can realize that the primary side current and the secondary side current of the transformer are in a linear proportional relation, and the primary side voltage signal of the transformer only contains part of specific subharmonic components.
Specific subharmonic components in the primary side voltage signal of the transformer can be perfectly eliminated by combining with the logic of the controller, so that high-efficiency grid connection and high-power quality output under low switching frequency can be realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a photovoltaic grid-connected power generation system according to an embodiment of the present invention;
fig. 2 is an equivalent circuit diagram of a transformer according to an embodiment of the present invention;
fig. 3 is a schematic block diagram of a controller according to an embodiment of the present invention;
fig. 4 is a schematic diagram illustrating a principle of parameter acquisition and signal control of a controller according to an embodiment of the present invention;
FIG. 5 is a diagram illustrating a parameter transformation according to an embodiment of the present invention;
fig. 6 is a schematic control principle diagram of a controller according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a photovoltaic grid-connected power generation system according to an embodiment of the present invention.
The photovoltaic grid-connected power generation system comprises: photovoltaic cell panel 11, first photovoltaic inverter 12, second photovoltaic inverter 13, transformer 14 and controller 15.
The first photovoltaic inverter 12 and the second photovoltaic inverter 13 are connected in parallel.
The input ends of the first photovoltaic inverter 12 and the second photovoltaic inverter 13 are both connected with the output end of the photovoltaic cell panel 11, and the photovoltaic cell panel 11 serves as a common direct current input source of the first photovoltaic inverter 12 and the second photovoltaic inverter 13.
The output ends of the first photovoltaic inverter 12 and the second photovoltaic inverter 13 are respectively connected with the corresponding windings on the secondary side of the transformer 14.
The primary side of the transformer 14 is connected to the grid.
Wherein, the primary side current and the secondary side current of the transformer 14 are in a linear proportional relationship; the controller 15 is configured to generate PWM driving signals respectively input to the first photovoltaic inverter 12 and the second photovoltaic inverter 13 to eliminate specific subharmonic components in the primary side voltage signal of the transformer 14.
In the embodiment, the transformer in the grid-connected photovoltaic power generation system can realize that the primary side current and the secondary side current of the transformer are in a linear proportional relationship, and the primary side voltage signal of the transformer only contains part of specific subharmonic components. Specific subharmonic components in the primary side voltage signal of the transformer can be perfectly eliminated by combining with the logic of the controller, so that high-efficiency grid connection and high-power quality output under low switching frequency can be realized.
The primary side of the transformer 14 is a high-voltage side, and the secondary side thereof is a low-voltage side.
Further, based on the above-mentioned embodiment of the present invention, referring to fig. 2, fig. 2 is an equivalent circuit diagram of a transformer according to an embodiment of the present invention.
The transformer 14 includes: a plurality of line resistances, a plurality of line inductances, and a plurality of windings.
The primary winding of the transformer 14 is connected in series in a wye-type manner, and the secondary winding of the transformer 14 is connected in a wye-type manner and a D-type manner, respectively, so that the primary line voltage of the transformer contains only 12k ± 1(k is 1,2,3 … …) subharmonic components, and the current harmonics of the primary side and the secondary side are consistent.
In this embodiment, the primary winding of the transformer 14 adopts a Y-connection of series windings, and the connection groups of the secondary windings adopt a Y-connection and a D-connection, respectively, wherein the phase shift angles of the Y-connection and D-connection of the secondary windings of the transformer 14 are 0 ° and 30 °, respectively, the phase shift between the voltages of the homonymous terminal lines of the secondary windings of the first photovoltaic inverter 12 and the second photovoltaic inverter 13 is also 30 °, and the voltage of the secondary winding of the transformer 14 is represented as:
Figure BDA0002536328610000061
Figure BDA0002536328610000062
when the line voltage V on the secondary side of the transformer 142ab，V3abWhen converted to the primary side of the transformer 14, the corresponding primary side line voltage can be expressed as:
Figure BDA0002536328610000063
Figure BDA0002536328610000064
further, the line voltage on the primary side of the transformer 14 can be obtained as follows:
Figure BDA0002536328610000071
as can be seen, the primary side of the transformer 14 adopts a Y-connection method with series windings, and the secondary side of the transformer 14 adopts a Y-connection method and a D-connection method, respectively, so that the line voltage on the primary side of the transformer 14 contains only 12k ± 1(k is 1,2,3 … …) subharmonic components.
The current on the primary side and the current on the secondary side of the transformer 14 are in a linear proportional relationship, and the current THD is the same, and satisfies the following conditions:
i2＝k1·i1，i3＝k2·i1
wherein k is1，k2The transformer transformation ratios of the Y/Y connection and the Y/D connection are respectively, the first photovoltaic inverter and the second photovoltaic inverter which are connected in parallel have the same technical parameters, the output line voltages are the same, and therefore the transformation ratio relation meets the following requirements:
Figure BDA0002536328610000072
further, based on the above-described embodiment of the present invention, as shown in fig. 1,
the first photovoltaic inverter 12 includes: a first capacitor C1 and a first photovoltaic inverter module inv 1.
Wherein the input end of the first photovoltaic inverter module inv1 is connected in parallel with the first capacitor C1.
The second photovoltaic inverter 13 includes: a second capacitor C2 and a second photovoltaic inverter module inv 2.
Wherein the input end of the second photovoltaic inverter module inv2 is connected in parallel with the second capacitor C2.
In this embodiment, neither the first photovoltaic inverter 12 nor the second photovoltaic inverter 13 needs to be provided with a large inductor and a large filter, so that the structure of the photovoltaic inverter is effectively simplified, and the production cost is further reduced.
Optionally, the first pv inverter 12 and the second pv inverter 13 include, but are not limited to, a three-phase two-level pv inverter, a three-phase multi-level inverter, or a three-phase H-bridge inverter.
Further, based on the above-mentioned embodiment of the present invention, referring to fig. 3, fig. 3 is a schematic diagram of a module structure of a controller according to an embodiment of the present invention. Referring to fig. 4, fig. 4 is a schematic diagram illustrating a principle of parameter acquisition and signal control of a controller according to an embodiment of the present invention, where PT denotes a voltage transformer. Referring to fig. 5, fig. 5 is a schematic diagram of parameter conversion according to an embodiment of the present invention.
The controller includes: an acquisition module 31, a phase-locked angle acquisition module 32, a conversion module 33 and a calculation module 34.
The acquisition module 31 is used for acquiring the dc bus voltage U of the common dc input sourcedcA first three-phase current i of the first photovoltaic inverter module inv1abc1A second three-phase current i of the second photovoltaic inverter module inv2abc2And the network voltage U of the networkabc。
The phase-locking angle acquisition module 32 is configured to acquire a first phase-locking angle of the first photovoltaic inverter module inv1 and a second phase-locking angle of the second photovoltaic inverter module inv 2. And obtaining the second phase locking angle after the phase of the first phase locking angle is shifted by pi/6.
The conversion module 33 is configured to obtain rotation coordinates of the first photovoltaic inversion module inv1 and the second photovoltaic inversion module inv2 in dq respectivelyActive current component i under systemd1、id2And a reactive current component iq1、iq2。
The calculation module 34 is configured to calculate a first arithmetic mean i of current components of the first photovoltaic inverter module inv1 and the second photovoltaic inverter module inv2 on the d-axismdAnd calculating a second arithmetic mean i of the q-axis current components of the first and second photovoltaic inverter modules inv1, inv2mq。
Optionally, the phase-locked angle obtaining module 32 is a PLL phase-locked loop.
Further, based on the above-mentioned embodiment of the present invention, referring to fig. 6, fig. 6 is a schematic diagram of a control principle of a controller according to an embodiment of the present invention.
The controller further includes:
a voltage control module AVR for controlling the DC bus voltage Udc。
A current regulation module ACR for controlling the active current component i of the first and second photovoltaic inverter modules inv1 and inv2d1、id2And a reactive current component iq1、iq2Wherein the current feedback respectively adopts a first arithmetic mean i of current components of the first photovoltaic inverter module inv1 and the second photovoltaic inverter module inv2 on the d-axismdAnd a second arithmetic mean i of the q-axis current components of the first and second photovoltaic inverter modules inv1, inv2mq。
The SHEPWM algorithm module is used for selecting characteristic subharmonic components of 12k +/-1 (k is 1,2 and 3 … …) contained in the primary side line voltage of the transformer to eliminate, outputting a first PWM driving signal for controlling the first photovoltaic inverter module inv1 according to the current modulation degree and the phase angle of a modulation wave, and outputting a second PWM driving signal for controlling the second photovoltaic inverter module inv2, wherein the second PWM driving signal is obtained after the phase of the first PWM driving signal is shifted by pi/6.
As can be seen from the above description, the modulation algorithms of the first photovoltaic inverter 12 and the second photovoltaic inverter 13 in the present invention are modulated using a specific harmonic cancellation pulse modulation algorithm (SHEPWM).
The level is switched at a specific moment in the power frequency period of 1/4 by using symmetry, so that certain specific times of harmonic waves can be eliminated according to the selection of the number of the switching angles.
In the embodiment of the invention, on the basis of the transformer cascade structure shown in fig. 2, a SHEPWM algorithm is adopted to modulate and eliminate specific 12k +/-1 (k is 1,2,3 … …) subharmonic components, so that the low subharmonic content and the switching frequency of the output voltage of the system are effectively reduced, and the utilization rate of the direct-current voltage is improved.
For example, if there are N switching angles in 1/4 cycles of the voltage waveform, the switching frequency of the power device corresponding to the three-phase PWM inverter is 2N +1 times the power frequency (50Hz), so that N-1 specific subharmonics in the output line voltage can be eliminated, when the amplitude of the selected 12k ± 1(k is 1,2,3 … …) lower harmonics is zero, specifically when there are N switching angles in 1/4 cycles, the 11/13/23/25/37/39/47/49 subharmonics can be eliminated, that is, when the switching frequency is 950Hz, the harmonics within 50 can be eliminated.
As shown in FIG. 4, the DC bus voltage U of the common DC input source is collected by a collection module (including but not limited to a sensor)dcThe first three-phase current i of the first photovoltaic inverter moduleabc1The second three-phase current i of the second photovoltaic inverter moduleabc2And the network voltage U of the networkabc。
According to the Y/Y connection and Y/D connection transformer, a phase-locked angle acquisition module (including but not limited to a PLL phase-locked loop) is used for acquiring a first phase-locked angle of the first photovoltaic inversion module and a second phase-locked angle of the second photovoltaic inversion module, wherein the second phase-locked angle is acquired after the phase of the first phase-locked angle is shifted by pi/6.
Coordinate conversion is carried out through a conversion module, and active current components i of the first photovoltaic inversion module and the second photovoltaic inversion module in a dq rotation coordinate system are obtained respectivelyd1、id2And a reactive current component iq1、iq2。
And the first photovoltaic inversion module is calculated by a calculation moduleFirst arithmetic mean i of current components in dq axismdAnd calculating a second arithmetic mean i of the current components of the second photovoltaic inverter module in the dq axismq。
As shown in fig. 6, a control architecture of a voltage loop and a current loop double closed loop is adopted, and the voltage control module AVR is used for controlling the dc bus voltage U of the common dc input sourcedcAnd (5) controlling.
The current regulation module ACR is used for adjusting the active current component i of the first photovoltaic inversion module and the second photovoltaic inversion moduled1、id2And a reactive current component iq1、iq2Wherein the current feedback respectively adopts a first arithmetic mean value i of current components of the first photovoltaic inverter module on dq axismdAnd a second arithmetic mean i of the current components of said second photovoltaic inverter module in the dq axismq。
And the SHEPWM algorithm module is used for outputting a first PWM driving signal PWM1 for controlling the first photovoltaic inverter module and a second PWM driving signal PWM2 for controlling the second photovoltaic inverter module according to the current modulation degree and the phase angle of the modulation wave, wherein the second PWM driving signal is obtained after the phase of the first PWM driving signal is shifted by pi/6.
That is to say, according to the embodiments of the present invention, for the cascaded spectral characteristics of the series winding transformer, the primary-side line voltage of the transformer only contains 12k ± 1(k is 1,2,3 … …) subharmonic components, and the current harmonics of the primary side and the secondary side are consistent, a specific harmonic cancellation pulse width modulation (SHEPWM) is used, and the 12k ± 1(k is 1,2,3 … …) subharmonic components are selected for cancellation.
The photovoltaic grid-connected power generation system provided by the invention is described in detail, a specific example is applied in the description to explain the principle and the implementation mode of the invention, and the description of the embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
It should be noted that, in the present specification, the embodiments are all described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include or include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A grid-connected photovoltaic power generation system, characterized in that, grid-connected photovoltaic power generation system includes: the photovoltaic solar panel comprises a photovoltaic cell panel, a first photovoltaic inverter, a second photovoltaic inverter, a transformer and a controller;
the first photovoltaic inverter and the second photovoltaic inverter are connected in parallel;
the input ends of the first photovoltaic inverter and the second photovoltaic inverter are connected with the output end of the photovoltaic cell panel, and the photovoltaic cell panel is used as a common direct current input source of the first photovoltaic inverter and the second photovoltaic inverter;
the output ends of the first photovoltaic inverter and the second photovoltaic inverter are respectively connected with the corresponding windings on the secondary side of the transformer;
the primary side of the transformer is connected with a power grid;
the primary side current and the secondary side current of the transformer are in a linear proportional relation; the controller is used for generating PWM driving signals which are respectively input to the first photovoltaic inverter and the second photovoltaic inverter so as to eliminate specific subharmonic components in the primary side voltage signal of the transformer.
2. The grid-connected photovoltaic power generation system according to claim 1, wherein the transformer comprises: a plurality of line resistances, a plurality of line inductances, and a plurality of windings;
the primary side windings of the transformer are connected in a series Y-type mode, and the secondary side windings of the transformer are connected in a Y-type mode and a D-type mode respectively, so that primary side line voltage of the transformer only contains 12k +/-1 (k is 1,2 and 3 … …) subharmonic components, and current harmonics of the primary side and the secondary side are consistent.
3. The grid-connected PV power generation system of claim 2, wherein the first PV inverter comprises: the first capacitor and the first photovoltaic inverter module;
the input end of the first photovoltaic inverter module is connected with the first capacitor in parallel.
4. The grid-connected PV power generation system of claim 3, wherein the second PV inverter comprises: a second capacitor and a second photovoltaic inverter module;
the input end of the second photovoltaic inverter module is connected with the second capacitor in parallel.
5. The grid-connected PV power generation system of claim 4, wherein the controller comprises: the device comprises an acquisition module, a phase-locked angle acquisition module, a conversion module and a calculation module;
the acquisition module is used for acquiring a direct-current bus voltage of a public direct-current input source, a first three-phase current of the first photovoltaic inversion module, a second three-phase current of the second photovoltaic inversion module and a power grid voltage of the power grid;
the phase-locked angle acquisition module is used for acquiring a first phase-locked angle of the first photovoltaic inversion module and a second phase-locked angle of the second photovoltaic inversion module;
the conversion module is used for respectively acquiring an active current component and a reactive current component of the first photovoltaic inversion module and the second photovoltaic inversion module in a dq rotation coordinate system;
the calculation module is used for calculating a first arithmetic mean value of current components of the first photovoltaic inversion module and the second photovoltaic inversion module in a d axis and calculating a second arithmetic mean value of current components of the first photovoltaic inversion module and the second photovoltaic inversion module in a q axis.
6. The grid-connected PV power generation system of claim 5, wherein the phase-locked loop acquisition module is a PLL phase-locked loop.
7. The grid-connected PV power generation system of claim 5, wherein the second phase-locked angle is obtained after the phase shift of the first phase-locked angle by pi/6.
8. The grid-connected photovoltaic power generation system according to claim 5, wherein the controller further comprises:
the voltage control module is used for controlling the voltage of the direct current bus;
the current regulation module is used for controlling active current components and reactive current components of the first photovoltaic inversion module and the second photovoltaic inversion module, wherein current feedback respectively adopts a first arithmetic mean value of current components of the first photovoltaic inversion module and the second photovoltaic inversion module in a d axis and a second arithmetic mean value of current components of the first photovoltaic inversion module and the second photovoltaic inversion module in a q axis;
the SHEPWM algorithm module is used for selecting a characteristic subharmonic component of 12k +/-1 (k is 1,2,3 … …) contained in the primary side line voltage of the transformer to eliminate, outputting a first PWM driving signal for controlling the first photovoltaic inverter module according to the current modulation degree and the phase angle of a modulation wave, and outputting a second PWM driving signal for controlling the second photovoltaic inverter module.
9. The grid-connected PV power generation system of claim 8, wherein the second PWM driving signal is obtained after the first PWM driving signal is phase shifted by pi/6.
10. The grid-connected PV power generation system of claim 1,
the first photovoltaic inverter is a three-phase two-level photovoltaic inverter or a three-phase multi-level inverter or a three-phase H-bridge inverter;
the second photovoltaic inverter is a three-phase two-level photovoltaic inverter or a three-phase multi-level inverter or a three-phase H-bridge inverter.
CN202010533797.7A 2020-06-12 2020-06-12 Photovoltaic grid-connected power generation system Pending CN111555360A (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104852376A (en) * 2015-05-22 2015-08-19 南车株洲电力机车研究所有限公司 Grid-side main circuit of industrial transmission system, transformer and control method
CN106786770A (en) * 2017-01-19 2017-05-31 株洲中车时代电气股份有限公司 A kind of photovoltaic inversion unit and three-phase photovoltaic grid-connected TRT

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104852376A (en) * 2015-05-22 2015-08-19 南车株洲电力机车研究所有限公司 Grid-side main circuit of industrial transmission system, transformer and control method
CN106786770A (en) * 2017-01-19 2017-05-31 株洲中车时代电气股份有限公司 A kind of photovoltaic inversion unit and three-phase photovoltaic grid-connected TRT

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