CN117477520A - Photovoltaic boosting grid-connected system capable of adjusting power factor and photovoltaic direct-current power generation system - Google Patents

Photovoltaic boosting grid-connected system capable of adjusting power factor and photovoltaic direct-current power generation system Download PDF

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Publication number
CN117477520A
CN117477520A CN202311470915.4A CN202311470915A CN117477520A CN 117477520 A CN117477520 A CN 117477520A CN 202311470915 A CN202311470915 A CN 202311470915A CN 117477520 A CN117477520 A CN 117477520A
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CN
China
Prior art keywords
photovoltaic
power
direct current
converter
photovoltaic direct
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Application number
CN202311470915.4A
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Chinese (zh)
Inventor
杨笑
韩帅
杨海滨
荆玉伟
单冲
李金元
陈昌远
于德强
孙慧颖
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China Construction First Group Corp Ltd
Second Construction Co Ltd of China Construction First Group Co Ltd
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China Construction First Group Corp Ltd
Second Construction Co Ltd of China Construction First Group Co Ltd
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Priority to CN202311470915.4A priority Critical patent/CN117477520A/en
Publication of CN117477520A publication Critical patent/CN117477520A/en
Pending legal-status Critical Current

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Classifications

    • 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
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • 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
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H02J1/106—Parallel operation of dc sources for load balancing, symmetrisation, or sharing
    • 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
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H02J1/12—Parallel operation of dc generators with converters, e.g. with mercury-arc rectifier
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/005—Conversion of dc power input into dc power output using Cuk converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1582—Buck-boost converters
    • 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
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • 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
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • H02J2300/26—The renewable source being solar energy of photovoltaic origin involving maximum power point tracking control for photovoltaic sources

Abstract

The embodiment of the disclosure provides a photovoltaic boosting grid-connected system with adjustable power factor and a photovoltaic direct current power generation system, which belong to the technical field of electricity, wherein the photovoltaic boosting grid-connected system with adjustable power factor comprises: n photovoltaic power generation matrixes, N-1 power balancers, N photovoltaic direct current converters and a group of power compensators; the power compensator is connected to the direct current power grid, and the output end of each photovoltaic direct current converter is sequentially connected in series and then connected to the power compensator; the input end of each photovoltaic direct current converter is respectively connected to the output end of the photovoltaic power generation unit; in each photovoltaic direct current converter connected in series in sequence, a power balancer is arranged between power balancers input by two adjacent photovoltaic direct current converters, and N-1 power balancers correspond to the N photovoltaic direct current converters respectively. By the scheme, the problems of discontinuous rectification output current, high harmonic distortion and low power factor of the common bridge rectifier are solved, and the generated energy of the system is improved.

Description

Photovoltaic boosting grid-connected system capable of adjusting power factor and photovoltaic direct-current power generation system
Technical Field
The embodiment of the disclosure relates to the technical field of electricity, in particular to a photovoltaic boosting grid-connected system with an adjustable power factor and a photovoltaic direct-current power generation system.
Background
At present, the development and utilization of new energy sources such as solar photovoltaic, wind power and the like are important ways for solving the energy crisis and the environmental problem. With the large-scale centralized grid-connected access of the photovoltaic power station, the problems of harmonic resonance, incapability of being absorbed and sent out, large-capacity reactive compensation and the like occur in the traditional alternating-current grid-connected mode, and the problems of more electric energy conversion equipment and conversion links, low efficiency and the like are also caused in the alternating-current grid-connected mode.
Along with the rapid development of medium-high voltage flexible direct current transmission, a photovoltaic direct current boosting, collecting and accessing scheme is proposed at present, so that the problem of sending out of the traditional photovoltaic power station by alternating current grid connection can be effectively avoided, the link of electric energy conversion can be reduced by photovoltaic direct current grid connection, electric energy conversion equipment can be saved, the system cost can be reduced, the overall efficiency of the system can be improved, and the system has obvious economic and technical advantages. Particularly, a photovoltaic direct-current series boosting grid-connected system is a research hot spot at present. The photovoltaic direct current series boost grid-connected system has the technical difficulties that: firstly, when the input power of each photovoltaic direct current converter in the series system is not matched, the problem of overvoltage output by the photovoltaic direct current converter is caused, and meanwhile, the problem of light rejection of the photovoltaic direct current converter is caused. And secondly, the current output by the common bridge rectifier after rectification is pulsating direct current, the current is discontinuous, the harmonic distortion is large, and the power factor is low.
It can be seen that there is a need for a photovoltaic boost grid-connected system that can increase power generation and adaptively adjust power factor.
Disclosure of Invention
In view of the above, embodiments of the present disclosure provide a photovoltaic boosting grid-connected system and a photovoltaic direct current power generation system with adjustable power factor, which at least partially solve the problems of low power generation amount, discontinuous current, large harmonic distortion and low power factor in the prior art.
In a first aspect, embodiments of the present disclosure provide a photovoltaic boost grid-connected system with adjustable power factor, including:
n photovoltaic power generation square matrixes, N-1 power balancers, N photovoltaic direct current converters and a group of power compensators, wherein N is more than or equal to 2, and each photovoltaic power generation square matrix at least comprises two groups of parallel photovoltaic group strings;
the power compensator is connected to the direct current power grid, and the output end of each photovoltaic direct current converter is sequentially connected in series and then connected to the power compensator; the input end of each photovoltaic direct current converter is respectively connected to the output end of the photovoltaic power generation unit; in each photovoltaic direct current converter connected in series in sequence, a power balancer is arranged between power balancers input by two adjacent photovoltaic direct current converters, N-1 power balancers respectively correspond to the N photovoltaic direct current converters, and power balancing is carried out on the input of the corresponding photovoltaic direct current converter so as to eliminate the difference of output voltages of the photovoltaic direct current converters; the power compensator compensates by using the valley fill principle, and improves the power factor by limiting the current flowing into the capacitor.
According to a specific implementation of the disclosed embodiments, the photovoltaic direct current converter is a bidirectional Cuk type DC-DC converter.
According to a specific implementation of the disclosed embodiment, the bidirectional Cuk type DC-DC converter includes a typical Cuk converter, a switching tube is antiparallel across a diode of the typical Cuk converter, a power diode is antiparallel across a switching tube of the typical Cuk converter, and an electrolytic capacitor for filtering is disposed at an input end of the switching tube.
According to a specific implementation manner of the embodiment of the present disclosure, the specific process of performing power equalization by the power balancer includes:
after the photovoltaic direct-current series boosting grid-connected system is started normally, the output voltage value V of the ith photovoltaic direct-current converter is obtained i Average value V of output voltage values of N photovoltaic direct-current converters a And performs the following equalization control:
V i ＝V a when the power balancer corresponding to the ith photovoltaic direct current converter does not work;
V i >V a when the power balancer corresponding to the ith photovoltaic direct current converter is in accordance with V i And V is equal to a The negative current is generated by the difference value of the voltage source voltage and the voltage source voltage, and the output current of the photovoltaic power generation unit corresponding to the ith photovoltaic direct current converter is split to reduce the input current of the ith photovoltaic direct current converter;
V i <V a when the power balancer corresponding to the ith photovoltaic direct-current converter is based on V i And V is equal to a And generating forward current by the difference value of the voltage and the current of the output current of the photovoltaic power generation unit corresponding to the ith photovoltaic direct current converter, and converging the output current of the photovoltaic power generation unit corresponding to the ith photovoltaic direct current converter so as to increase the input current of the ith photovoltaic direct current converter.
According to one specific implementation of the disclosed embodiments, the power balancer includes a control signal input terminal, a main power circuit, and a current path connection terminal;
the control signal input end is used for obtaining the output voltage value V of the corresponding photovoltaic direct current converter i Average value V of output voltage values of N photovoltaic direct-current converters a ；
The main power circuit is used for being based on V i And V is equal to a The difference between the two photovoltaic direct current converter input ends controls the current between the two photovoltaic direct current converter input ends;
and two ends of the current path connecting end are respectively connected with the input ends of the two corresponding photovoltaic direct current converters and are used for establishing a current path.
According to a specific implementation manner of the embodiment of the disclosure, each photovoltaic power generation array is configured with a photovoltaic direct current converter for stabilizing boosting.
According to a specific implementation of the disclosed embodiment, the specific process of the power compensator includes:
by stabilizing the voltage of the pulse direct current possibly output by the photovoltaic direct current converter, the power factor of the output line is improved.
According to one specific implementation of the disclosed embodiments, the optical Fu Zhiliu converter uses an input voltage and input current dual closed loop control strategy for maximum power tracking control.
According to one specific implementation of the disclosed embodiments, the power balancer employs photovoltaic dc converter output voltage closed loop control.
In a second aspect, embodiments of the present disclosure provide a photovoltaic direct current power generation system, comprising:
n groups of photovoltaic power generation units and a photovoltaic boosting grid-connected system with adjustable power factors.
The photovoltaic boosting grid-connected system with adjustable power factor in the embodiment of the disclosure comprises: n photovoltaic power generation matrixes, N-1 power balancers, N photovoltaic direct current converters and a group of power compensators, wherein N is more than or equal to 2, and each photovoltaic power generation matrix is not less than two groups of parallel photovoltaic group strings; the power compensator is connected to the direct current power grid, and the output end of each photovoltaic direct current converter is sequentially connected in series and then connected to the power compensator; the input end of each photovoltaic direct current converter is respectively connected to the output end of the photovoltaic power generation unit; in each photovoltaic direct current converter connected in series in sequence, a power balancer is arranged between power balancers input by two adjacent photovoltaic direct current converters, N-1 power balancers respectively correspond to the N photovoltaic direct current converters, and power balancing is carried out on the input of the corresponding photovoltaic direct current converter so as to eliminate the difference of output voltages of the photovoltaic direct current converters; the power compensator compensates by using the valley fill principle, and improves the power factor by limiting the current flowing into the capacitor.
The beneficial effects of the embodiment of the disclosure are that: through the scheme of the disclosure, the bidirectional Cuk DC-DC converter not only continues the self-inductance of the input end and the output end in the circuit structure of the typical Cuk DC converter, has the advantages of small input and output current pulsation, low ripple waves and the like, but also realizes the functions of increasing and reducing the output voltage by controlling the duty ratio of the switching tube, and the whole DC converter circuit is of a symmetrical topological structure, thereby laying a structural foundation for double-quadrant operation. The bidirectional DC converter can not only meet the working process of two independent typical Cuk DC converters, but also meet the double-quadrant operation of energy bidirectional flow at the input side and the output side; the balance half-bridge compensation circuit compensates by using the valley filling principle and D 3 The series resistor R helps to smooth the input current spike, and can also improve the power factor by limiting the current flowing into the capacitor, R having surge buffering and current limiting functions. The problems of discontinuous current output after rectification of a common bridge rectifier, high harmonic distortion and low power factor are solved; the photovoltaic direct-current series boosting grid-connected system solves the problems of light rejection and overvoltage caused by mismatching of input power of each photovoltaic direct-current converter in the photovoltaic direct-current series boosting grid-connected system; the problem of system generated energy reduction caused by mismatching of input power of each photovoltaic direct-current converter is solved, and the system generated energy is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings that are required to be used in the embodiments will be briefly described below.
Fig. 1 is a schematic diagram of a photovoltaic boost grid-connected system with adjustable power factor according to an embodiment of the present disclosure;
fig. 2 is a control block diagram of a photovoltaic dc converter according to an embodiment of the present disclosure;
FIG. 3 is a control block diagram of a power balancer provided by an embodiment of the present disclosure;
FIG. 4 is a schematic diagram of a bi-directional Cuk DC-DC converter provided by an embodiment of the disclosure;
fig. 5 is a schematic diagram of a power compensator provided in an embodiment of the present disclosure.
Summarizing the reference numerals:
the photovoltaic power generation system comprises N groups of photovoltaic power generation square matrixes 101, a power balancer 102, N photovoltaic direct current converters 103, a high-voltage direct current line 104, a direct current power grid 105, a power compensator 106, a photovoltaic direct current converter MPPT voltage control ring 201, a photovoltaic direct current converter input current control ring 202, an MPPT control algorithm module 203, an MPPT voltage controller 204, a photovoltaic direct current converter input current controller 205, a photovoltaic direct current converter output voltage control ring 301 and a photovoltaic direct current converter output voltage controller 302.
Detailed Description
Embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.
It is noted that various aspects of the embodiments are described below within the scope of the following claims. It should be apparent that the aspects described herein may be embodied in a wide variety of forms and that any specific structure and/or function described herein is merely illustrative. Based on this disclosure, one skilled in the art will appreciate that one aspect described herein may be implemented independently of any other aspects and that two or more of these aspects may be combined in various ways.
In addition, in the following description, specific details are provided in order to provide a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects may be practiced without these specific details.
The embodiment of the disclosure provides a photovoltaic boosting grid-connected system with an adjustable power factor, and the method can be applied to a photovoltaic power generation transmission process of a power generation scene.
Referring to fig. 1, a schematic diagram of a result of a photovoltaic boost grid-connected system with adjustable power factor is provided in an embodiment of the present disclosure. As shown in fig. 1, the system mainly includes:
n photovoltaic power generation square matrixes, N-1 power balancers, N photovoltaic direct current converters and a group of power compensators, wherein N is more than or equal to 2, and each photovoltaic power generation square matrix at least comprises two groups of parallel photovoltaic group strings;
the power compensator is connected to the direct current power grid, and the output end of each photovoltaic direct current converter is sequentially connected in series and then connected to the power compensator; the input end of each photovoltaic direct current converter is respectively connected to the output end of the photovoltaic power generation unit; in each photovoltaic direct current converter connected in series in sequence, a power balancer is arranged between power balancers input by two adjacent photovoltaic direct current converters, N-1 power balancers respectively correspond to the N photovoltaic direct current converters, and power balancing is carried out on the input of the corresponding photovoltaic direct current converter so as to eliminate the difference of output voltages of the photovoltaic direct current converters; the power compensator compensates by using the valley fill principle, and improves the power factor by limiting the current flowing into the capacitor.
On the basis of the embodiment, the photovoltaic direct-current converter is a bidirectional Cuk type DC-DC converter.
Further, the bidirectional Cuk type DC-DC converter comprises a typical Cuk converter, switching tubes are connected in anti-parallel to two ends of a diode of the typical Cuk converter, meanwhile, power diodes are connected in anti-parallel to two ends of the switching tubes of the typical Cuk converter, and an electrolytic capacitor for filtering is arranged at an input end of the typical Cuk converter.
Further, the specific process of the power balancer for power balancing includes:
after the photovoltaic direct-current series boosting grid-connected system is started normally, the output voltage value V of the ith photovoltaic direct-current converter is obtained i Average value V of output voltage values of N photovoltaic direct-current converters a And performs the following equalization control:
V i ＝V a when the power balancer corresponding to the ith photovoltaic direct current converter does not work;
V i >V a when the power balancer corresponding to the ith photovoltaic direct-current converter is based on V i And V is equal to a Generates negative current by the difference value of (i) th photovoltaicThe output current of the photovoltaic power generation unit corresponding to the direct current converter is split, so that the input current of the ith photovoltaic direct current converter is reduced;
V i <V a when the power balancer corresponding to the ith photovoltaic direct-current converter is based on V i And V is equal to a And generating forward current by the difference value of the voltage and the current of the output current of the photovoltaic power generation unit corresponding to the ith photovoltaic direct current converter, and converging the output current of the photovoltaic power generation unit corresponding to the ith photovoltaic direct current converter so as to increase the input current of the ith photovoltaic direct current converter.
Further, the power balancer comprises a control signal input end, a main power circuit and a current path connecting end;
the control signal input end is used for obtaining the output voltage value V of the corresponding photovoltaic direct current converter i Average value V of output voltage values of N photovoltaic direct-current converters a ；
The main power circuit is used for being based on V i And V is equal to a The difference between the two photovoltaic direct current converter input ends controls the current between the two photovoltaic direct current converter input ends;
and two ends of the current path connecting end are respectively connected with the input ends of the two corresponding photovoltaic direct current converters and are used for establishing a current path.
Furthermore, each photovoltaic power generation matrix is provided with a photovoltaic direct current converter for stable boosting.
Further, the specific process of the power compensator includes:
by stabilizing the voltage of the pulse direct current possibly output by the photovoltaic direct current converter, the power factor of the output line is improved.
Further, the optical Fu Zhiliu converter adopts a dual closed-loop control strategy of input voltage and input current to carry out maximum power tracking control.
Further, the power balancer adopts the closed-loop control of the output voltage of the photovoltaic direct-current converter.
When the system is concretely implemented, the photovoltaic boosting grid-connected system with the power balancer and the adjustable power factor comprises N photovoltaic power generation matrixes, N-1 power balancers, N photovoltaic direct current converters and a group of power compensators, wherein N is more than or equal to 2; each photovoltaic power generation matrix comprises at least two groups of photovoltaic group strings connected in parallel. The power compensator is connected to the direct current power grid; the output ends of the photovoltaic direct current converters are sequentially connected in series and then connected into a power compensator; the input end of each photovoltaic direct current converter is respectively connected with the output end of the photovoltaic power generation unit; in each photovoltaic direct current converter which is sequentially connected in series, a power balancer is arranged between the input ends of two adjacent photovoltaic direct current converters; the N-1 power balancers are respectively arranged corresponding to the set N photovoltaic direct current converters and are used for carrying out power balance on the input of the corresponding photovoltaic direct current converters so as to eliminate the difference of the output voltages of the photovoltaic direct current converters.
The photovoltaic power generation unit can be a photovoltaic module, a photovoltaic group string or a photovoltaic power generation matrix. In this embodiment, the photovoltaic power generation units are photovoltaic power generation matrixes, as shown in fig. 1, N groups of photovoltaic power generation matrixes 101 are respectively and correspondingly arranged with N photovoltaic dc converters 103 one by one, after the N photovoltaic dc converters 103 are serially connected in sequence, the N photovoltaic dc converters pass through a power compensator 106, and then are connected into a dc power grid 105 through a high-voltage dc line 104, a power balancer 102 is arranged between two adjacent photovoltaic dc converters 103, and the power balancer 102 is respectively connected with the input ends of two adjacent photovoltaic dc converters 103.
As shown in fig. 2, in a photovoltaic boost grid-connected system with a power balancer and an adjustable power factor, each photovoltaic direct current converter detects output voltage V of a corresponding photovoltaic power generation matrix in real time pv And output current I pv The maximum power tracking algorithm is then implemented by a maximum power tracking controller (MPPT). Given MPPT reference voltage V pv-ref Then the actual output voltage V of the photovoltaic power generation matrix pv With a given MPPT reference voltage V pv-ref Comparing to obtain voltage difference V pv-e The method comprises the steps of carrying out a first treatment on the surface of the After passing through the voltage controller, the input current reference value I 'of the photovoltaic direct-current converter is given' in Then the actual input current I of the photovoltaic direct-current converter in With input current reference I' in Comparing to obtain a current difference I pv-e The method comprises the steps of carrying out a first treatment on the surface of the The photovoltaic direct current conversion is given after passing through the current controllerAnd the control duty ratio d of the converter finally realizes the maximum power tracking double closed-loop control of the photovoltaic direct-current converter. In fig. 2, a photovoltaic dc converter MPPT voltage control loop 201, a photovoltaic dc converter input current control loop 202, an MPPT control algorithm module 203, an MPPT voltage controller 204, and a photovoltaic dc converter input current controller 205 are shown.
The power balancer comprises a control signal input end, a main power circuit and a current path connecting end; the control signal input end is used for obtaining the output voltage value V of the corresponding photovoltaic direct current converter i Average value V of output voltage values of N photovoltaic direct-current converters a The method comprises the steps of carrying out a first treatment on the surface of the The main power circuit is used for being based on V i And V is equal to a Controlling the current between the two photovoltaic dc converter inputs; and two ends of the current path connecting end are respectively connected with the input ends of the two corresponding photovoltaic direct current converters and are used for establishing a current path. As shown in fig. 3, the corresponding ith photovoltaic dc converter in the ith power balancer detects its output voltage V in real time i Average value V of output voltage values of all photovoltaic direct current converters a (V a ＝V s N, where V s Sum of output voltage values of all photovoltaic DC converters) to obtain voltage difference V i_e The control duty ratio d of the power balancer is given after passing through the voltage controller, so that the conduction direction and the current magnitude of the current in the power balancer are controlled. In fig. 3 a photovoltaic dc converter output voltage control loop 301 is shown, a photovoltaic dc converter output voltage controller 302.
When the input power of each photovoltaic direct current converter in the series system is balanced, each photovoltaic direct current converter can normally realize maximum power tracking, and the system runs in a maximum power tracking mode, and almost no current flows in a power balancer; when the input power of each photovoltaic direct current converter in the series system is unbalanced, each photovoltaic direct current converter can still normally realize maximum power tracking, and operates in a maximum power tracking mode, at the moment, the power balancer is controlled to work by detecting the relation between the actual output voltage and the average output voltage of each photovoltaic direct current converter, current flows in the power balancer, and the direction of the current is determined by the relation between the actual output voltage and the average output voltage of the photovoltaic direct current converter, so that the input power balance of each photovoltaic direct current converter in the series system can be realized, and the output voltage of the photovoltaic direct current converter is maintained at the average output voltage.
V-based in a power balancer i And V is equal to a The difference between the two photovoltaic DC converter input terminals is controlled by the method that:
V i ＝V a when the power balancer corresponding to the ith photovoltaic direct current converter does not work;
V i >V a when the power balancer corresponding to the ith photovoltaic direct-current converter is based on V i And V is equal to a The negative current is generated by the difference value of the voltage source voltage and the voltage source voltage, and the output current of the photovoltaic power generation unit corresponding to the ith photovoltaic direct current converter is split to reduce the input current of the ith photovoltaic direct current converter;
V i <V a when the power balancer corresponding to the ith photovoltaic direct-current converter is based on V i And V is equal to a And generating forward current by the difference value of the voltage and the current of the output current of the photovoltaic power generation unit corresponding to the ith photovoltaic direct current converter, and converging the output current of the photovoltaic power generation unit corresponding to the ith photovoltaic direct current converter so as to increase the input current of the ith photovoltaic direct current converter.
As shown in fig. 4, the two ends of the diode D are connected in anti-parallel to the switching tube, and the two ends of the switching tube Q are connected in anti-parallel to the power diode, so as to finally optimize the integrated bidirectional Cuk type DC-DC converter. MOS switch tube Q used after two ends of switch tube Q are connected with power diode in anti-parallel 1 And diode D 1 Representing that the MOS switch tube Q is used after the two ends of the diode D are connected with the switch tube in anti-parallel 2 And diode D 2 Indicating that an electrolytic capacitor C with filtering function is added at the input end 3 So as to output filtering in the reverse boost operating mode while taking into account the input filtering function.
As shown in fig. 5, the balance half-bridge compensation circuit, C 1 And D 1 One arm, C, forming a half-bridge 2 And D 2 Another arm, D, constituting a half-bridge 3 And R form a charging connection path, and the charging connection path is formed by using the valley filling principleAnd (5) row compensation. Filter capacitor C 1 And C 2 Series connection, the voltage across the capacitor being up to half the input voltage, diode D once the line voltage drops below half the input voltage 1 And D 2 Will be positively biased to cause C 1 And C 2 The parallel discharge is started. And D 3 The series resistor R helps to smooth the input current spike, and can also be used to limit the inflow to the capacitor C 1 And C 2 To improve the power factor. R has surge buffering and current limiting functions.
In this embodiment, the optical Fu Zhiliu converter performs maximum power tracking control by adopting a dual closed-loop control strategy of input voltage and input current. The power balancer adopts the closed-loop control of the output voltage of the photovoltaic direct-current converter.
In this embodiment, all the photovoltaic dc converters need to limit the output voltage, and all the power balancers need to limit the current, so as to ensure the safety of the photovoltaic dc converters and the power balancers.
The control of the photovoltaic boosting grid-connected system with the power balancer and the adjustable power factor can be divided into two parts, one part is the control of each photovoltaic direct current converter in a series system, the controllers of all photovoltaic direct current converters in the series system can be regarded as mutually independent, the maximum power tracking control of a corresponding photovoltaic power generation matrix is mainly realized, and an input voltage and input current double closed-loop control strategy is adopted; the other part is the control of N-1 power balancers in a series system, each power balancer is mainly controlled by the relation between the real-time output voltage of the corresponding photovoltaic direct-current converter and the average output voltage of the corresponding photovoltaic direct-current converter, and the output voltage of the photovoltaic direct-current converter is controlled in a closed loop mode. Therefore, the self-adaptive coordination control of N photovoltaic direct current converters and N-1 power balancers in a series system can be realized.
The photovoltaic boosting grid-connected system with the power balancer capable of adjusting the power factor is based on the photovoltaic boosting grid-connected system with the power balancer capable of adjusting the power factor, after the system is started under the condition that the starting condition is met, each photovoltaic direct current converter gradually enters a maximum power tracking mode, and each power balancer balances the input power of the corresponding photovoltaic direct current converter;
taking the ith photovoltaic direct current converter and the corresponding ith power balancer as an example, obtaining the output voltage value V of the ith photovoltaic direct current converter i Average value V of output voltage values of N photovoltaic direct-current converters a And performs the following equalization control:
(1) When V is i ＝V a When the photovoltaic direct current converter works in the maximum power tracking mode, and the power balancer corresponding to the ith photovoltaic direct current converter does not work, namely no current flows in the ith power balancer;
(2) When V is i >V a When the photovoltaic direct current converter works in the maximum power tracking mode, and at least one photovoltaic direct current converter output voltage in the series system is smaller than the average output voltage of the converter, namely the input power of each photovoltaic direct current converter in the series system is unbalanced, at the moment, the ith power balancer starts to work and is based on V i And V is equal to a And (3) generating negative current, and splitting the output current of the photovoltaic power generation unit corresponding to the ith photovoltaic direct current converter to reduce the input current of the ith photovoltaic direct current converter, thereby reducing the input power and the output voltage of the photovoltaic direct current converter, compensating the photovoltaic direct current converters with the input power and the output voltage lower than the average input power and the average output voltage of the converter, and finally realizing the balance of the input power and the output voltage of all the photovoltaic direct current converters in the series system.
(3) When V is i <V a When the photovoltaic direct current converter works in the maximum power tracking mode, and at least one photovoltaic direct current converter output voltage in the series system is larger than the average output voltage of the converter, namely the input power of each photovoltaic direct current converter in the series system is unbalanced, at the moment, the ith power balancer starts to work and is based on V i And V is equal to a Generates forward current, and the output current of the photovoltaic power generation unit corresponding to the ith photovoltaic direct current converter is combined to increase the input of the ith photovoltaic direct current converterAnd the current is increased, so that the input power and the output voltage of the photovoltaic direct-current converter are increased, the photovoltaic direct-current converter with the input power and the output voltage larger than the average input power and the average output voltage of the converter is eliminated, and finally, the balance of the input power and the output voltage of all the photovoltaic direct-current converters in the series system is realized.
The embodiment of the disclosure also provides a photovoltaic direct current power generation system, which comprises N groups of photovoltaic power generation units and the photovoltaic boosting grid-connected system with the adjustable power factor and the power balancer and the power compensator.
It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working process and the related description of the photovoltaic direct current power generation system described above may refer to the corresponding process in the embodiment of the photovoltaic direct current series boost grid-connected system with the power balancer and the power compensator, which is not described herein again.
The photovoltaic boosting grid-connected system with the adjustable power factor, provided by the embodiment, not only continues the self inductance of the input end and the output end in the circuit structure of the typical Cuk direct current converter through the bidirectional Cuk direct current-direct current converter, has the advantages of small input and output current pulsation, low ripple and the like, but also realizes the function of increasing and decreasing the output voltage through controlling the duty ratio of the switching tube, and the whole direct current converter circuit is of a symmetrical topological structure, thereby laying a structural foundation for double-quadrant operation. The bidirectional DC converter can not only meet the working process of two independent typical Cuk DC converters, but also meet the double-quadrant operation of energy bidirectional flow at the input side and the output side; the balance half-bridge compensation circuit compensates by using the valley filling principle and D 3 The series resistor R helps to smooth the input current spike, and can also improve the power factor by limiting the current flowing into the capacitor, R having surge buffering and current limiting functions. The problems of discontinuous current output after rectification of a common bridge rectifier, high harmonic distortion and low power factor are solved; the photovoltaic direct-current series boosting grid-connected system solves the problems of light rejection and overvoltage caused by mismatching of input power of each photovoltaic direct-current converter in the photovoltaic direct-current series boosting grid-connected system; solves the problem of direct photovoltaic generation due to each stationThe problem of system generated energy reduction caused by unmatched input power of the flow converter is solved, the system generated energy is improved, the circuit loss is reduced, and the power factor is improved.
It should be understood that portions of the present disclosure may be implemented in hardware, software, firmware, or a combination thereof.
The foregoing is merely specific embodiments of the disclosure, but the protection scope of the disclosure is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the disclosure are intended to be covered by the protection scope of the disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims (10)

1. A photovoltaic boost grid-tie system with adjustable power factor, the system comprising:
n photovoltaic power generation matrixes, N-1 power balancers, N photovoltaic direct current converters and a group of power compensators, wherein N is more than or equal to 2, and each photovoltaic power generation matrix is not less than two groups of parallel photovoltaic group strings;
the power compensator is connected to the direct current power grid, and the output end of each photovoltaic direct current converter is sequentially connected in series and then connected to the power compensator; the input end of each photovoltaic direct current converter is respectively connected to the output end of the photovoltaic power generation unit; in each photovoltaic direct current converter connected in series in sequence, a power balancer is arranged between power balancers input by two adjacent photovoltaic direct current converters, N-1 power balancers respectively correspond to the N photovoltaic direct current converters, and power balancing is carried out on the input of the corresponding photovoltaic direct current converter so as to eliminate the difference of output voltages of the photovoltaic direct current converters; the power compensator compensates by using the valley fill principle, and improves the power factor by limiting the current flowing into the capacitor.
2. The system of claim 1, wherein the photovoltaic direct current converter is a bi-directional Cuk DC-DC converter.
3. The system of claim 2, wherein the bi-directional Cuk-type DC-DC converter comprises a typical Cuk converter having a switching tube connected in anti-parallel across a diode of the typical Cuk converter, and having a power diode connected in anti-parallel across a switching tube of the typical Cuk converter, and having an electrolytic capacitor for filtering at an input terminal.
4. The system of claim 1, wherein the specific process of power balancing by the power balancer comprises:
after the photovoltaic direct-current series boosting grid-connected system is started normally, the output voltage value V of the ith photovoltaic direct-current converter is obtained i Average value V of output voltage values of N photovoltaic direct-current converters a And performs the following equalization control:
V i ＝V a when the power balancer corresponding to the ith photovoltaic direct current converter does not work;
V i >V a when the power balancer corresponding to the ith photovoltaic direct current converter is in accordance with V i And V is equal to a The negative current is generated by the difference value of the voltage source voltage and the voltage source voltage, and the output current of the photovoltaic power generation unit corresponding to the ith photovoltaic direct current converter is split to reduce the input current of the ith photovoltaic direct current converter;
V i <V a when the power balancer corresponding to the ith photovoltaic direct-current converter is based on V i And V is equal to a And generating forward current by the difference value of the voltage and the current of the output current of the photovoltaic power generation unit corresponding to the ith photovoltaic direct current converter, and converging the output current of the photovoltaic power generation unit corresponding to the ith photovoltaic direct current converter so as to increase the input current of the ith photovoltaic direct current converter.
5. The system of claim 1, wherein the power balancer comprises a control signal input, a main power circuit, a current path connection;
the control signal input end is used for obtaining the output voltage value V of the corresponding photovoltaic direct current converter i Average value V of output voltage values of N photovoltaic direct-current converters a ；
The main power electricRoad is based on V i And V is equal to a The difference between the two photovoltaic direct current converter input ends controls the current between the two photovoltaic direct current converter input ends;
and two ends of the current path connecting end are respectively connected with the input ends of the two corresponding photovoltaic direct current converters and are used for establishing a current path.
6. The system of claim 1, wherein each of said photovoltaic power generation arrays is configured with a photovoltaic dc converter for stable boosting.
7. The system of claim 1, wherein the specific process of the power compensator comprises:
by stabilizing the voltage of the pulse direct current possibly output by the photovoltaic direct current converter, the power factor of the output line is improved.
8. The system of claims 1-7, wherein the optical Fu Zhiliu converter employs an input voltage and input current dual closed loop control strategy for maximum power tracking control.
9. The system of claims 1-7, wherein the power balancer employs closed loop control of the photovoltaic dc converter output voltage.
10. A photovoltaic direct current power generation system, comprising:
n groups of photovoltaic power generation units and a photovoltaic boosting grid-connected system with adjustable power factors.
CN202311470915.4A 2023-11-07 2023-11-07 Photovoltaic boosting grid-connected system capable of adjusting power factor and photovoltaic direct-current power generation system Pending CN117477520A (en)

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