CN117526267A - Sequential collaborative constant voltage control method and system for multiple distributed photovoltaic power generation units - Google Patents

Sequential collaborative constant voltage control method and system for multiple distributed photovoltaic power generation units Download PDF

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Publication number
CN117526267A
CN117526267A CN202311519632.4A CN202311519632A CN117526267A CN 117526267 A CN117526267 A CN 117526267A CN 202311519632 A CN202311519632 A CN 202311519632A CN 117526267 A CN117526267 A CN 117526267A
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power generation
photovoltaic power
generation unit
load
voltage
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Inventor
于丹文
曹文君
张岩
孙运涛
李付存
李山
张高峰
张青青
王庆玉
王华佳
刘恩仁
丁浩天
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Electric Power Research Institute of State Grid Shandong Electric Power Co Ltd
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Electric Power Research Institute of State Grid Shandong Electric Power Co Ltd
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Priority to CN202311519632.4A priority Critical patent/CN117526267A/en
Publication of CN117526267A publication Critical patent/CN117526267A/en
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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
    • 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
    • H02J1/109—Scheduling or re-scheduling the operation of the DC sources in a particular order, e.g. connecting or disconnecting the sources in sequential, alternating or in subsets, to meet a given demand
    • 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
    • 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

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Electrical Variables (AREA)

Abstract

The invention discloses a sequential collaborative constant voltage control method and a system of a multi-distributed photovoltaic power generation unit, comprising the following steps: sequentially switching respective control strategies of all photovoltaic power generation units into an improved constant voltage control strategy according to the illumination intensity until the output voltage of the direct current bus meets the reference value of the voltage of the direct current bus; the switching is controlled according to the comparison result of the maximum output power and the load power of the operation of the multi-distributed photovoltaic power generation unit; the improved constant voltage control strategy is to adjust the port voltage of the photovoltaic power generation unit according to load fluctuation, so that the total output power of the photovoltaic meets the load power, and the voltage stability of the direct current bus is realized. The problem of the insufficient voltage regulation ability of single photovoltaic power generation unit when high-power load is switched is solved, according to different illumination intensities, sequential collaborative regulation and control are carried out through a logic control principle, and the running stability of a medium-voltage direct current system is ensured.

Description

Sequential collaborative constant voltage control method and system for multiple distributed photovoltaic power generation units
Technical Field
The invention relates to the technical field of power systems, in particular to a sequential collaborative constant voltage control method and system for multiple distributed photovoltaic power generation units.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
To maximize the utilization of photovoltaic resources, photovoltaic power generation systems are typically targeted to provide maximum electrical energy, and therefore they mainly employ a "maximum power point tracking (Maximum Power Point Tracking, MPPT)" control strategy. However, the characteristics of randomness and volatility of the photovoltaic power generation power affect the stable operation of the medium voltage direct current system.
The medium voltage direct current system with high proportion of distributed photovoltaic can be operated in a grid-connected mode or an off-grid mode. In grid-tie mode, a constant voltage may be provided by the AC/DC converter to the DC system, in which case the photovoltaic operates under MPPT control strategy to output electrical energy at maximum power, which may be analogous to a constant current source without regulation capability.
In off-grid mode, scholars propose an integrated operation mode of photovoltaic and energy storage systems. The research shows that in order to cooperate with the photovoltaic power generation system based on the MPPT control strategy to operate, the energy storage system needs to respond to the power change of the load through charge and discharge according to the fluctuation of photovoltaic power generation power, so that the stable operation of the direct current system is realized.
It can be seen that when the photovoltaic power generation system is independent of other devices to constant the dc bus voltage, the photovoltaic power generation system is difficult to independently operate under the MPPT control strategy because the photovoltaic power generation system does not have the capability of supporting the dc bus voltage, and particularly in the off-grid mode, the dc bus voltage must be controlled to be constant by the other devices.
Disclosure of Invention
In order to solve the problems, the invention provides a sequential collaborative constant voltage control method and a sequential collaborative constant voltage control system for a plurality of distributed photovoltaic power generation units, which solve the problem of insufficient voltage regulation capability of a single photovoltaic power generation unit during high-power load switching, and perform sequential collaborative regulation and control according to different illumination intensities through a logic control principle so as to ensure the running stability of a medium-voltage direct current system.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
in a first aspect, the present invention provides a sequential collaborative constant voltage control method for a multi-distributed photovoltaic power generation unit, including:
acquiring the illumination intensity of each photovoltaic power generation unit;
sequentially switching respective control strategies of all photovoltaic power generation units into an improved constant voltage control strategy according to the illumination intensity until the output voltage of the direct current bus meets the reference value of the voltage of the direct current bus;
the switching is controlled according to the comparison result of the maximum output power and the load power of the operation of the multi-distributed photovoltaic power generation unit; the improved constant voltage control strategy is to adjust the port voltage of the photovoltaic power generation unit according to load fluctuation, so that the total output power of the photovoltaic meets the load power.
As an alternative embodiment, the control strategies are sequentially switched from high to low for all photovoltaic power generation units according to the intensity of illumination.
As an alternative embodiment, only one photovoltaic power generation unit performs the improved constant voltage control strategy at a time, and the other photovoltaic power generation units employ the conventional constant voltage control strategy.
As an alternative embodiment, the process of controlling switching according to a comparison result of the maximum output power and the load power of the operation of the multi-distributed photovoltaic power generation unit includes: determining the maximum output power of the common operation of all the photovoltaic power generation units, and subtracting the maximum output power of the common operation of the rest photovoltaic power generation units after one photovoltaic power generation unit is subtracted in sequence; and comparing all maximum output power with load power in turn from large to small, thereby determining the photovoltaic power generation unit switched into the improved constant voltage control strategy.
As an alternative embodiment, N photovoltaic power generation units are provided, and the load power is P load Determining the maximum output power P of a photovoltaic power generation unit 1 Maximum output power P of two photovoltaic power generation units operated together 2 Up to the maximum output power P of all photovoltaic power generation units N ；
When load fluctuates, P N ＞P load ＞P n-1 When the illumination intensity is maximum, the control strategy of the photovoltaic power generation unit is switched to an improved constant-voltage control strategy;
when the load continues to decrease, P n-1 ＞P load ＞P n-2 When the illumination intensity is maximum, the photovoltaic power generation unit executes a constant voltage control strategy, electric energy is output by constant power, and the photovoltaic power generation unit with the illumination intensity being the next highest is switched into an improved constant voltage control strategy;
when the load is continuously reduced, P n-2 ＞P load ＞P n-3 And when the illumination intensity is maximum and the photovoltaic power generation unit with the next largest illumination intensity executes a constant voltage control strategy, electric energy is output at constant power, and the like, the photovoltaic power generation unit is sequentially switched into an improved constant voltage control strategy according to the illumination intensity.
As an alternative embodiment, the load fluctuation means: and obtaining the power variation caused by load fluctuation according to the DC bus output voltage and the DC bus voltage reference value.
Alternatively, the port voltage of the photovoltaic power generation unit is adjusted by adjusting the Boost circuit off angle.
As an alternative embodiment, the improved constant pressure control strategy includes: and obtaining the direct current bus voltage variation according to the difference value of the direct current bus output voltage and the direct current bus voltage reference value, and obtaining the power variation caused by load fluctuation according to the direct current bus voltage variation and the direct current bus output current.
As an alternative embodiment, the port voltage variation to be regulated is obtained according to the quotient of the power variation and the slope of the monotonically increasing interval when the PU curve of the photovoltaic power generation unit is different in environmental conditions, so that the port voltage of the photovoltaic power generation unit is regulated to enable the port voltage to meet the photovoltaic cell voltage reference value.
In a second aspect, the present invention provides a sequential collaborative constant voltage control system of a multi-distributed photovoltaic power generation unit, comprising:
the data acquisition module is configured to acquire the illumination intensity of each photovoltaic power generation unit;
the sequence control module is configured to sequentially switch respective control strategies into improved constant-voltage control strategies for all the photovoltaic power generation units according to the illumination intensity until the output voltage of the direct-current bus meets the reference value of the voltage of the direct-current bus;
the switching is controlled according to the comparison result of the maximum output power and the load power of the operation of the multi-distributed photovoltaic power generation unit; the improved constant voltage control strategy is to adjust the port voltage of the photovoltaic power generation unit according to load fluctuation, so that the total output power of the photovoltaic meets the load power.
In a third aspect, the invention provides an electronic device comprising a memory and a processor and computer instructions stored on the memory and running on the processor, which when executed by the processor, perform the method of the first aspect.
In a fourth aspect, the present invention provides a computer readable storage medium storing computer instructions which, when executed by a processor, perform the method of the first aspect.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a sequential collaborative constant voltage control method and system for multiple distributed photovoltaic power generation units, which reduce the dependence of a photovoltaic power generation system on an energy storage system, reduce the investment and maintenance cost of the energy storage system, solve the problem that the photovoltaic power generation units cannot provide voltage support for a direct current system when operating based on an MPPT control strategy, and realize the control that the photovoltaic power generation system can control the constant voltage of a direct current bus.
For the scene of a medium-voltage direct current system running in an off-grid mode under the condition of no energy storage system, if photovoltaic is controlled to supply energy for a load according to the traditional MPPT control strategy, the defect that the photovoltaic power generation system has no voltage regulation capability can be greatly exposed. The invention provides an improved constant voltage control strategy based on a single photovoltaic power generation unit, and provides a sequential collaborative constant voltage control strategy of a plurality of distributed photovoltaic power generation units regulated and controlled by a logic control principle according to different illumination intensities, so as to realize self-balancing stable operation in a medium-voltage direct current system.
The invention provides a sequential collaborative constant voltage control strategy of multiple distributed photovoltaic power generation units, which is based on an improved constant voltage control strategy and an MPPT control method aiming at a single photovoltaic power generation unit, solves the problem of unstable bus voltage of a medium-voltage direct-current distribution system which comprises multiple distributed photovoltaic power generation units and operates off-grid, solves the problem of insufficient voltage regulation capability of the single photovoltaic power generation unit during high-power load switching, integrally improves the operation performance of the system, and ensures the operation stability of the medium-voltage direct-current system.
Additional aspects of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
Fig. 1 is a sequential collaborative constant voltage control method of a multi-distributed photovoltaic power generation unit provided in embodiment 1 of the present invention;
FIG. 2 is a schematic control diagram of the improved constant voltage control strategy provided in embodiment 1 of the present invention;
fig. 3 is a general control structure diagram of a photovoltaic power generation unit provided in embodiment 1 of the present invention;
fig. 4 is a dc bus equivalent circuit diagram of the medium voltage dc system provided in embodiment 1 of the present invention;
FIG. 5 is a response mechanism of the photovoltaic power generation unit provided in embodiment 1 of the present invention to load power fluctuation;
fig. 6 is a general diagram of a sequential cooperative control strategy based on a multi-distributed photovoltaic power generation unit provided in embodiment 1 of the present invention;
fig. 7 is a graph showing dynamic operation characteristics of multiple distributed photovoltaic units and loads with different illumination intensities according to embodiment 1 of the present invention.
Detailed Description
The invention is further described below with reference to the drawings and examples.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms also are intended to include the plural forms, and furthermore, it is to be understood that the terms "comprises" and "comprising" and any variations thereof are intended to cover non-exclusive inclusions, e.g., processes, methods, systems, products or devices that comprise a series of steps or units, are not necessarily limited to those steps or units that are expressly listed, but may include other steps or units that are not expressly listed or inherent to such processes, methods, products or devices.
Embodiments of the invention and features of the embodiments may be combined with each other without conflict.
Example 1
At present, a control strategy of the photovoltaic power generation unit needs to be changed, so that the control strategy can independently control the constant voltage of the direct current bus to ensure the stable operation of the direct current system. In order to reduce the dependency of the photovoltaic power generation system on the energy storage system, reduce the investment and maintenance cost of the energy storage system, solve the problem that the photovoltaic power generation unit cannot provide voltage support for the direct current system when operating based on the MPPT control strategy, and the photovoltaic power generation system is necessary to provide a control strategy capable of controlling the direct current bus voltage to be constant.
At present, a photovoltaic constant-voltage control strategy is researched and applied to a wind-light ocean current power supply system of a arctic field monitoring device, so that frequent charge and discharge of a storage battery are effectively avoided. The constant voltage control strategy capable of regulating and controlling all working points on the photovoltaic P-U characteristic curve to stably operate is provided on the basis of constant voltage control of a conventional power-limited working mode in a low-voltage direct current system, and the stability of the photovoltaic system in independent operation and grid-connected operation is ensured. In summary, photovoltaic power generation systems are often used to provide voltage support for low voltage dc systems due to their weak regulation capability.
In this embodiment, as shown in fig. 1, a sequential collaborative constant voltage control method of a multi-distributed photovoltaic power generation unit is provided, including:
acquiring the illumination intensity of each photovoltaic power generation unit;
sequentially switching respective control strategies of all photovoltaic power generation units into an improved constant voltage control strategy according to the illumination intensity until the output voltage of the direct current bus meets the reference value of the voltage of the direct current bus;
the switching is controlled according to the comparison result of the maximum output power and the load power of the operation of the multi-distributed photovoltaic power generation unit; the improved constant voltage control strategy is to adjust the port voltage of the photovoltaic power generation unit according to load fluctuation, so that the total output power of the photovoltaic meets the load power.
In the embodiment, the supporting capability of the photovoltaic power generation unit to the medium-voltage direct-current bus voltage is focused, so that the medium-voltage direct-current system can be ensured to stably operate. Based on the traditional constant voltage control strategy, an improved constant voltage control strategy is provided, wherein a monotonically rising stage and a steady stage of a P-U curve of a photovoltaic cell are used as power adjusting ranges, and after a load is suddenly changed, the output power of the photovoltaic cell is changed, so that the system power is balanced.
In a medium-voltage direct current system, a photovoltaic cell and a two-stage Boost-LLC high-frequency converter form a photovoltaic power generation unit, and a plurality of photovoltaic power generation units supply power for a load in a direct current collection mode. When the load fluctuates, the photovoltaic cell can adjust the output port voltage according to the dynamic output characteristic of the photovoltaic cell, so that the light output power is adjusted to maintain the voltage stability of the direct current bus; the LLC high-frequency converter only plays roles in boosting and energy transfer in the photovoltaic power generation unit, so that the purpose of adjusting the voltage of the output port of the photovoltaic cell can be achieved only by adjusting the Boost circuit Guan Duanjiao beta.
As shown in figure 2 which is a schematic block diagram based on the improved constant voltage control strategy,and->Respectively a direct current bus voltage reference value and a photovoltaic cell voltage reference value, delta U DC Is->The voltage variation of the direct current bus after the difference value of the voltage I is passed through the PI controller DC For outputting current, delta P, of DC bus DC For the amount of power variation, k, caused by load fluctuations PV Is the slope of monotonically increasing interval, deltaU of the photovoltaic cell P-U curve under different environmental conditions PV The voltage variation of the photovoltaic cell port corresponding to the monotonically increasing interval of the photovoltaic cell P-U curve caused by the load variation is obtained.
The improved constant voltage control strategy specifically comprises the following steps: obtaining the output voltage U of a direct current bus DC According toObtaining the voltage variation of the direct current bus by the difference value between the output voltage of the direct current bus and the reference value of the voltage of the direct current bus; obtaining the power variation caused by load fluctuation according to the product of the voltage variation of the direct current bus and the output current of the direct current bus; according to the power variation and the slope k PV The quotient of (1) obtains the port voltage variation to be regulated, and then the port voltage of the photovoltaic power generation unit is regulated by regulating the Boost circuit Guan Duanjiao beta, so that the port voltage meets the photovoltaic cell voltage reference value, and the total output power of the photovoltaic meets the load power.
Because the voltage regulating capability of a single photovoltaic power generation unit is limited, the stable operation of a medium-voltage direct current system cannot be met by only one photovoltaic power generation unit, and a plurality of photovoltaic power generation units are required to cooperatively operate. When the multiple photovoltaic power generation units are in coordinated operation, an improved constant voltage control strategy for operation of the photovoltaic power generation units is needed to ensure the stability of the voltage of the direct current bus, and other photovoltaic power generation units can select a reasonable control strategy according to the operation requirement of the system.
Fig. 3 is a general control structure diagram of the photovoltaic power generation unit; executing MPPT strategy when the switch is 0, and adjusting the port voltage U of the photovoltaic cell according to the environmental data PV Ensure U PV ＝U MPP The maximum power point tracking control is realized;
when the switch is 1, an improved constant voltage control strategy is implemented, and the port voltage U of the photovoltaic cell is regulated according to load fluctuation PV The power emitted by the photovoltaic cell is equal to the power required by the load until the output voltage of the direct current bus meets the reference value of the voltage of the direct current bus, and the voltage of the direct current bus is stabilized.
In order to analyze the dynamic characteristics between the multi-distributed photovoltaic power generation units and the load in the medium-voltage direct-current system, the dynamic operation characteristics of the multi-distributed photovoltaic power generation units and the load need to be obtained according to the dynamic response of the power and the voltage in the system after disturbance occurs. Taking two photovoltaic power generation units as an example, wherein PV 1 To improve constant voltage control strategy, PV 2 An equivalent circuit diagram of the MPPT control strategy is shown in fig. 4.
As can be seen from fig. 4, the dynamic balance relationship of the internal power of the medium voltage dc system is:
in U DC Is the voltage of a direct current bus; c (C) DC The equivalent capacitance is a medium-voltage direct current bus; p (P) PV The total output power of the multi-distributed photovoltaic power generation unit; p (P) load Is the load power.
The dynamic characteristic of the medium-voltage direct-current system is basically the interactive influence of active power and direct-current bus voltage, and the P-U relation is as follows:
FIG. 5 is a schematic diagram showing the response mechanism of the photovoltaic power generation unit to load power fluctuation, wherein as can be seen from the formulas (2) and 4, when the load power is increased, for example, new electrical equipment is put in or the original load power is increased, if the photovoltaic power generation system does not increase the power generation amount, then P load (t+Δt)＞P PV (t) the dc bus voltage decreases; the photovoltaic power generation unit working in the improved control strategy can improve the voltage of an output port and increase the power generation capacity by adjusting the Boost circuit Guan Duanjiao beta; the photovoltaic power generation unit working in MPPT control causes the fluctuation of the port voltage due to the fluctuation of the direct current bus voltage, so that the power is reduced slightly, then is increased to the maximum value, and finally U is formed DC And recovering the rated voltage, and realizing stable operation of the medium-voltage direct-current system.
In summary, in order to ensure the stable operation of the medium voltage direct current system, the coordination and unified operation of the source network load are required, so that the constant voltage of the medium voltage direct current bus is maintained.
When a plurality of photovoltaic power generation units run in different illumination intensities, in order to reasonably use the dynamic characteristics of photovoltaic cells and prevent the disordered actions of the photovoltaic power generation units, the embodiment provides a sequential collaborative control strategy, under the collaborative strategy, only one photovoltaic power generation unit runs in an improved constant voltage control strategy at a time, other photovoltaic power generation units can select a reasonable control strategy according to the running requirement of a system, for example, the constant voltage control strategy is executed, and the MPPT control strategy is sequentially executed to the improved constant voltage control strategy according to the sequence from the photovoltaic power generation units with high illumination intensity to the photovoltaic power generation units with low illumination intensity so as to stabilize the voltage of a direct current bus.
Specifically, the switching is controlled according to the comparison result of the maximum output power and the load power of the operation of the multi-distributed photovoltaic power generation unit, and the switching method comprises the following steps: determining the maximum output power of the common operation of all the photovoltaic power generation units, and subtracting the maximum output power of the common operation of the rest photovoltaic power generation units after one photovoltaic power generation unit is subtracted in sequence; and comparing all maximum output power with load power in turn from large to small, thereby determining the photovoltaic power generation unit switched into the improved constant voltage control strategy.
Furthermore, N photovoltaic power generation units are provided, and the load power is P load Determining the maximum output power P of a photovoltaic power generation unit 1 Maximum output power P of two photovoltaic power generation units operated together 2 Up to the maximum output power P of all photovoltaic power generation units N ；
When load fluctuates, P N ＞P load ＞P n-1 When the illumination intensity is maximum, the control strategy of the photovoltaic power generation unit is switched to an improved constant-voltage control strategy;
when the load continues to decrease, P n-1 ＞P load ＞P n-2 When the illumination intensity is maximum, the photovoltaic power generation unit executes a constant voltage control strategy, electric energy is output by constant power, and the photovoltaic power generation unit with the illumination intensity being the next highest is switched into an improved constant voltage control strategy;
when the load is continuously reduced, P n-2 ＞P load ＞P n-3 And when the illumination intensity is maximum and the photovoltaic power generation unit with the next largest illumination intensity executes a constant voltage control strategy, electric energy is output at constant power, and the like, the photovoltaic power generation unit is sequentially switched into an improved constant voltage control strategy according to the illumination intensity.
In PV 1 、PV 2 And PV (photovoltaic) 3 Three photovoltaic power generation units are exemplified, wherein,PV 1 the illumination intensity > PV of (2) 2 The illumination intensity > PV of (2) 3 Fig. 6 is a total graph of a multi-distributed photovoltaic power generation unit based on a sequential cooperative control strategy, wherein an improved constant voltage control strategy is adopted when k=1, and an MPPT control strategy is adopted when k=0; FIG. 7 is a graph showing the dynamic relationship between multiple power generation units with different illumination intensities and load, wherein P s1 For three dynamic operation curves of the photovoltaic power generation unit, P 1 Maximum output power for this operation; p (P) s2 For PV 2 And PV (photovoltaic) 3 Dynamic running curve of P 2 Maximum output power for this operation; p (P) s1 For PV 3 Dynamic running curve of P 3 Maximum output power for this operation; p (P) load Is the load power.
The logic control steps of the multi-photovoltaic power generation unit based on sequential cooperative control according to load fluctuation are as follows:
step1: when the load fluctuates in a small range, the load reaches P 1 ＞P load ＞P 2 Order (K) 1 ,K 2 ,K 3 )＝(1,0,0)，PV 1 Executing an improved constant voltage control strategy, consisting of a PV 1 And controlling the output voltage of the direct current bus.
Step2: when the load suddenly decreases until P 2 ＞P load ＞P 3 At this time, PV 1 Operating at the lowest voltage, executing a constant voltage control strategy to output electric energy at constant power, and switching K 2 Will be from M 20 Switching to M 21 At this time (K) 1 ,K 2 ,K 3 )＝(1,1,0)，PV 2 Executing an improved constant voltage control strategy, consisting of a PV 2 And controlling the output voltage of the direct current bus.
Step3: if the load is continuously reduced until P load ＜P 3 At this time, PV 1 And PV (photovoltaic) 2 At the same time, electric energy is output at constant power, a constant voltage control strategy is executed, and a switch K is switched 3 Will be from M 30 Switching to M 31 At this time (K) 1 ,K 2 ,K 3 )＝(1,1,1)，PV 3 Executing an improved constant voltage control strategy, consisting of a PV 3 And controlling the output voltage of the direct current bus.
Step4: if the load P load ＞20 2 /P PVmax The voltage of the direct current bus is less than 20kV, the output power of the photovoltaic cell is reduced, the photovoltaic cell cannot output at the maximum power, and the voltage of the direct current bus cannot be maintained stable.
Step5: similarly, if P load ＜P 4 When the power required by the load is smaller than the minimum value provided by the photovoltaic cell, the voltage of the direct current bus is increased, so that the system cannot normally operate, and in this case, other methods are needed to consume redundant electric energy so as to stabilize the voltage of the direct current bus.
Aiming at the distributed photovoltaic system, the embodiment provides a sequential collaborative constant voltage control strategy based on a multi-distributed photovoltaic power generation unit, so that the distributed photovoltaic system maintains constant voltage of a medium-voltage direct current bus, and the situation that the medium-voltage direct current system cannot stably run without energy storage during off-grid running is avoided.
Example 2
The embodiment provides a sequential collaborative constant voltage control system of a multi-distributed photovoltaic power generation unit, which is characterized by comprising:
the data acquisition module is configured to acquire the illumination intensity of each photovoltaic power generation unit;
the sequence control module is configured to sequentially switch respective control strategies into improved constant-voltage control strategies for all the photovoltaic power generation units according to the illumination intensity until the output voltage of the direct-current bus meets the reference value of the voltage of the direct-current bus;
the switching is controlled according to the comparison result of the maximum output power and the load power of the operation of the multi-distributed photovoltaic power generation unit; the improved constant voltage control strategy is to adjust the port voltage of the photovoltaic power generation unit according to load fluctuation, so that the total output power of the photovoltaic meets the load power.
In this embodiment, the control strategies are sequentially switched from high to low for all photovoltaic power generation units according to the intensity of illumination.
In this embodiment, only one photovoltaic power generation unit performs the improved constant voltage control strategy at a time, and the other photovoltaic power generation units adopt the conventional constant voltage control strategy.
In this embodiment, the process of controlling switching according to the comparison result of the maximum output power and the load power of the operation of the multi-distributed photovoltaic power generation unit includes: determining the maximum output power of the common operation of all the photovoltaic power generation units, and subtracting the maximum output power of the common operation of the rest photovoltaic power generation units after one photovoltaic power generation unit is subtracted in sequence; and comparing all maximum output power with load power in turn from large to small, thereby determining the photovoltaic power generation unit switched into the improved constant voltage control strategy.
In this embodiment, a total of N photovoltaic power generation units are provided, and the load power is P load Determining the maximum output power P of a photovoltaic power generation unit 1 Maximum output power P of two photovoltaic power generation units operated together 2 Up to the maximum output power P of all photovoltaic power generation units N ；
When load fluctuates, P N ＞P load ＞P n-1 When the illumination intensity is maximum, the control strategy of the photovoltaic power generation unit is switched to an improved constant-voltage control strategy;
when the load continues to decrease, P n-1 ＞P load ＞P n-2 When the illumination intensity is maximum, the photovoltaic power generation unit executes a constant voltage control strategy, electric energy is output by constant power, and the photovoltaic power generation unit with the illumination intensity being the next highest is switched into an improved constant voltage control strategy;
when the load is continuously reduced, P n-2 ＞P load ＞P n-3 And when the illumination intensity is maximum and the photovoltaic power generation unit with the next largest illumination intensity executes a constant voltage control strategy, electric energy is output at constant power, and the like, the photovoltaic power generation unit is sequentially switched into an improved constant voltage control strategy according to the illumination intensity.
In this embodiment, the improved constant pressure control strategy includes: and obtaining the voltage variation of the direct current bus according to the difference value between the output voltage of the direct current bus and the reference value of the voltage of the direct current bus, and obtaining the power variation caused by load fluctuation.
In this embodiment, the improved constant pressure control strategy includes: and obtaining the direct current bus voltage variation according to the difference value of the direct current bus output voltage and the direct current bus voltage reference value, and obtaining the power variation caused by load fluctuation according to the direct current bus voltage variation and the direct current bus output current.
In this embodiment, the port voltage variation to be adjusted is obtained according to the quotient of the power variation and the slope of the monotonically increasing interval when the PU curve of the photovoltaic power generation unit is different in environmental conditions, so that the port voltage of the photovoltaic power generation unit is adjusted to enable the port voltage to meet the photovoltaic cell voltage reference value.
In this embodiment, the port voltage of the photovoltaic power generation unit is adjusted by adjusting the Boost circuit off angle.
It should be noted that the above modules correspond to the steps described in embodiment 1, and the above modules are the same as examples and application scenarios implemented by the corresponding steps, but are not limited to those disclosed in embodiment 1. It should be noted that the modules described above may be implemented as part of a system in a computer system, such as a set of computer-executable instructions.
In further embodiments, there is also provided:
an electronic device comprising a memory and a processor and computer instructions stored on the memory and running on the processor, which when executed by the processor, perform the method described in embodiment 1. For brevity, the description is omitted here.
It should be understood that in this embodiment, the processor may be a central processing unit CPU, and the processor may also be other general purpose processors, digital signal processors DSP, application specific integrated circuits ASIC, off-the-shelf programmable gate array FPGA or other programmable logic device, discrete gate or transistor logic devices, discrete hardware components, or the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The memory may include read only memory and random access memory and provide instructions and data to the processor, and a portion of the memory may also include non-volatile random access memory. For example, the memory may also store information of the device type.
A computer readable storage medium storing computer instructions which, when executed by a processor, perform the method described in embodiment 1.
The method in embodiment 1 may be directly embodied as a hardware processor executing or executed with a combination of hardware and software modules in the processor. The software modules may be located in a random access memory, flash memory, read only memory, programmable read only memory, or electrically erasable programmable memory, registers, etc. as well known in the art. The storage medium is located in a memory, and the processor reads the information in the memory and, in combination with its hardware, performs the steps of the above method. To avoid repetition, a detailed description is not provided herein.
Those of ordinary skill in the art will appreciate that the elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
While the foregoing description of the embodiments of the present invention has been presented in conjunction with the drawings, it should be understood that it is not intended to limit the scope of the invention, but rather, it is intended to cover all modifications or variations within the scope of the invention as defined by the claims of the present invention.

Claims (10)

1. The sequential collaborative constant voltage control method of the multi-distributed photovoltaic power generation unit is characterized by comprising the following steps of:
acquiring the illumination intensity of each photovoltaic power generation unit;
sequentially switching respective control strategies of all photovoltaic power generation units into an improved constant voltage control strategy according to the illumination intensity until the output voltage of the direct current bus meets the reference value of the voltage of the direct current bus;
the switching is controlled according to the comparison result of the maximum output power and the load power of the operation of the multi-distributed photovoltaic power generation unit; the improved constant voltage control strategy is to adjust the port voltage of the photovoltaic power generation unit according to load fluctuation, so that the total output power of the photovoltaic meets the load power.
2. The sequential collaborative constant voltage control method of a multi-distributed photovoltaic power generation unit according to claim 1, wherein control strategies are sequentially switched from high to low for all photovoltaic power generation units according to the intensity of illumination;
or, only one photovoltaic power generation unit executes the improved constant voltage control strategy at a time, and other photovoltaic power generation units adopt the traditional constant voltage control strategy.
3. The sequential collaborative constant voltage control method of a multi-distributed photovoltaic power generation unit of claim 1, wherein controlling switching based on a comparison of maximum output power and load power of the multi-distributed photovoltaic power generation unit operation comprises: determining the maximum output power of the common operation of all the photovoltaic power generation units, and subtracting the maximum output power of the common operation of the rest photovoltaic power generation units after one photovoltaic power generation unit is subtracted in sequence; and comparing all maximum output power with load power in turn from large to small, thereby determining the photovoltaic power generation unit switched into the improved constant voltage control strategy.
4. The method for sequential collaborative constant voltage control of a plurality of distributed photovoltaic power generation units according to claim 3, wherein a total of N photovoltaic power generation units are provided, and the load power is P load Determining the maximum output power P of a photovoltaic power generation unit 1 Maximum output power P of two photovoltaic power generation units operated together 2 Up to the maximum output power P of all photovoltaic power generation units N ；
When load fluctuates, P N ＞P load ＞P n-1 When the illumination intensity is maximumThe control strategy of the photovoltaic power generation unit is switched to an improved constant voltage control strategy;
when the load continues to decrease, P n-1 ＞P load ＞P n-2 When the illumination intensity is maximum, the photovoltaic power generation unit executes a constant voltage control strategy, electric energy is output by constant power, and the photovoltaic power generation unit with the illumination intensity being the next highest is switched into an improved constant voltage control strategy;
when the load is continuously reduced, P n-2 ＞P load ＞P n-3 And when the illumination intensity is maximum and the photovoltaic power generation unit with the next largest illumination intensity executes a constant voltage control strategy, electric energy is output at constant power, and the like, the photovoltaic power generation unit is sequentially switched into an improved constant voltage control strategy according to the illumination intensity.
5. The sequential collaborative constant pressure control method of a multi-distributed photovoltaic power generation unit of claim 1, wherein the load fluctuations refer to: obtaining a power variation caused by load fluctuation according to the DC bus output voltage and the DC bus voltage reference value;
or, the port voltage of the photovoltaic power generation unit is regulated by regulating the off angle of the Boost circuit.
6. The sequential collaborative constant pressure control method of a multi-distributed photovoltaic power generation unit of claim 1, wherein the improved constant pressure control strategy comprises: and obtaining the direct current bus voltage variation according to the difference value of the direct current bus output voltage and the direct current bus voltage reference value, and obtaining the power variation caused by load fluctuation according to the direct current bus voltage variation and the direct current bus output current.
7. The sequential collaborative constant voltage control method of a multi-distributed photovoltaic power generation unit according to claim 6, wherein the port voltage variation to be adjusted is obtained according to the quotient of the power variation and the slope of a monotonically increasing interval of the photovoltaic power generation unit PU curve under different environmental conditions, thereby adjusting the port voltage of the photovoltaic power generation unit to satisfy the photovoltaic cell voltage reference value.
8. Sequential collaborative constant voltage control system of many distributed photovoltaic power generation units, its characterized in that includes:
the data acquisition module is configured to acquire the illumination intensity of each photovoltaic power generation unit;
the sequence control module is configured to sequentially switch respective control strategies into improved constant-voltage control strategies for all the photovoltaic power generation units according to the illumination intensity until the output voltage of the direct-current bus meets the reference value of the voltage of the direct-current bus;
the switching is controlled according to the comparison result of the maximum output power and the load power of the operation of the multi-distributed photovoltaic power generation unit; the improved constant voltage control strategy is to adjust the port voltage of the photovoltaic power generation unit according to load fluctuation, so that the total output power of the photovoltaic meets the load power.
9. An electronic device comprising a memory and a processor and computer instructions stored on the memory and running on the processor, which when executed by the processor, perform the method of any one of claims 1-7.
10. A computer readable storage medium storing computer instructions which, when executed by a processor, perform the method of any of claims 1-7.
CN202311519632.4A 2023-11-14 2023-11-14 Sequential collaborative constant voltage control method and system for multiple distributed photovoltaic power generation units Pending CN117526267A (en)

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