CN117096944A - Network construction type photovoltaic fault ride-through control method and device - Google Patents

Network construction type photovoltaic fault ride-through control method and device Download PDF

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Publication number
CN117096944A
CN117096944A CN202310978253.5A CN202310978253A CN117096944A CN 117096944 A CN117096944 A CN 117096944A CN 202310978253 A CN202310978253 A CN 202310978253A CN 117096944 A CN117096944 A CN 117096944A
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China
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grid
photovoltaic
voltage
side inverter
control
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CN202310978253.5A
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Chinese (zh)
Inventor
吕思卓
郑超
李文锋
陈怡君
宋瑞华
杨大业
刘文焯
郁舒雁
邓嘉卿
姜静雅
陈艺
王庆军
赵龙
秦琪
汪玉
李宾宾
陈庆涛
丁国成
黄杰
刘鑫
范明豪
马亚彬
翟玥
苏文
包佳佳
杨瑞雪
丁洁
吕鹏飞
刘耕云
宁杨
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China Electric Power Research Institute Co Ltd CEPRI
Electric Power Research Institute of State Grid Anhui Electric Power Co Ltd
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China Electric Power Research Institute Co Ltd CEPRI
Electric Power Research Institute of State Grid Anhui Electric Power Co Ltd
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Priority to CN202310978253.5A priority Critical patent/CN117096944A/en
Publication of CN117096944A publication Critical patent/CN117096944A/en
Pending legal-status Critical Current

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal 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
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal 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, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

A method and a device for controlling network construction type photovoltaic fault ride-through, wherein the method comprises the following steps: obtaining the outlet voltage of a photovoltaic power station; when the outlet voltage of the photovoltaic power station is smaller than or equal to a first threshold value, starting network side inverter control and boost converter control; wherein the grid-side inverter control includes adjusting grid-side inverter active and reactive, introducing a time-varying virtual impedance between a voltage virtual internal potential of the grid-side inverter and an outlet voltage, and adjusting a voltage reference in the grid-side inverter outer loop control, and the boost converter control includes adjusting a power reference of the boost converter. The method and the device provided by the embodiment of the invention can not only keep virtually synchronous control of the rotor equation of motion loop during the fault period and provide inertia support for the power grid, but also reduce the investment and loss of photovoltaic equipment without additionally adding an unloading circuit to inhibit the rise of direct-current voltage.

Description

Network construction type photovoltaic fault ride-through control method and device
Technical Field
The invention relates to the technical field of network construction type photovoltaic, in particular to a network construction type photovoltaic fault ride-through control method and device.
Background
In order to promote the realization of the goals of 'peak reaching of 2030 carbon and carbon neutralization of 2060 carbon' in China, the construction of a novel power system of high-proportion renewable energy sources is quickened, and renewable energy sources such as photovoltaic power generation and the like play an important role. By the end of 2022 years, the accumulated grid-connected capacity of the photovoltaic power generation in China reaches 392.04GW, and the photovoltaic power generation in 2023 years is expected to replace the water power generation to be the renewable energy power generation technology with the largest installed capacity in China. As the proportion of the photovoltaic grid-connected power generation connected to the power grid is larger, the interaction between the photovoltaic grid-connected power generation system and the power system cannot be ignored. Grid-formed control (Grid-formed) converters based on virtual synchronous generator (Virtual Synchronous Generator, VSG) technology can simulate damping and inertia characteristics of synchronous generators, provide voltage and frequency support for systems, become research hot spots in recent years, and are widely focused and applied in fields of wind power, photovoltaics and the like.
But is limited by the overcurrent capability of power electronic devices, and the current fault ride-through control strategy for the grid-structured photovoltaic needs to be further improved. At present, two current limiting strategies aiming at a grid-structured control converter during a fault are mainly adopted, one current limiting strategy is to switch into a control mode, namely, a current source mode is switched during the fault, but a control loop such as a rotor motion equation and the like is invalid during the fault, so that the active supporting effect on a power grid is lost, and the problem of phase locking stability still exists; another is a current limiting strategy based on virtual impedance, but under the condition of a deeper voltage drop, the current limiting requirement is still not satisfied. At present, the research on the fault ride-through strategy of the grid-formed control converter generally takes the direct current side of the inverter as a constant voltage source, and the coordination control of the boost converter and the grid-side inverter is not considered, so that the influence of the dynamic process of the photovoltaic direct current side under large disturbance is ignored.
Disclosure of Invention
In view of the above, the invention provides a grid-structured photovoltaic fault ride-through control method and a device thereof, which aim to solve the problems that the existing grid-structured photovoltaic fault ride-through control method does not consider the coordination control of a boost converter and a grid-side inverter, so that the grid-structured photovoltaic fault ride-through control method is unstable and cannot meet the current limiting requirement.
In a first aspect, an embodiment of the present invention provides a method for controlling network-structured photovoltaic fault ride through, which is applied to a primary topology circuit, where the primary topology circuit includes: the photovoltaic cell array, the boost converter, the grid-side inverter and the LC filter circuit, wherein the direct current output by the photovoltaic cell array is boosted by the boost converter and then output to the grid-side inverter, and the alternating current output by the grid-side inverter is integrated into a power grid through the LC filter circuit, and the grid-structured photovoltaic fault ride-through control method comprises the following steps: obtaining an outlet voltage of a photovoltaic power station, wherein the photovoltaic power station comprises a plurality of photovoltaic cell arrays; when the outlet voltage of the photovoltaic power station is smaller than or equal to a first threshold value, starting network side inverter control and boost converter control; wherein the grid-side inverter control includes adjusting grid-side inverter active and reactive, introducing a time-varying virtual impedance between a voltage virtual internal potential of the grid-side inverter and an outlet voltage, and adjusting a voltage reference in the grid-side inverter outer loop control, and the boost converter control includes adjusting a power reference of the boost converter.
Further, the adjusting the network side inverter active and reactive includes: switching the active power reference value and the reactive power reference value of the network side inverter to P respectively ref2 And Q ref2 The method comprises the steps of carrying out a first treatment on the surface of the When the outlet voltage of the photovoltaic power station is smaller than or equal to a second threshold value, P is obtained by adopting the following formula ref2 And Q ref2 ：
Wherein S is fault As the apparent power in the event of a failure,
when the outlet voltage of the photovoltaic power station is greater than a second threshold value, P is obtained by adopting the following formula ref2 And Q ref2 ：
Wherein U is pcc For the outlet voltage of the photovoltaic power station, I L Allowing a current effective value X to flow for a grid-side inverter c For the reactance value of the filter capacitor, U n Is the effective value of rated voltage, K q Is the voltage support coefficient, S N For rated capacity of photovoltaic system, P ref1 And the second threshold value is smaller than the first threshold value for the active power reference value of the grid-side inverter under the steady-state operation.
Further, the time-varying virtual impedance is obtained by:
wherein R is v Is virtual resistance, L v Is virtual reactance, t 0 For the moment of occurrence of failure, t 1 For the fault clearing time, T is the virtual impedance decay time constant omega n Is the rated angular frequency.
Further, the adjusting the voltage reference value in the outer loop control of the grid-side inverter includes: and adjusting the voltage reference value in the outer loop control of the grid-side inverter to be the same as the outlet voltage of the photovoltaic power station.
Further, the power reference value of the boost converter is adjusted as follows: and synchronously switching an initial power reference value of the boost converter to an active power reference value of the grid-side inverter, introducing direct-current voltage feedforward control, and adding an additional quantity generated by a deviation signal of the direct-current side voltage and the reference value through the PI controller to the active power reference value of the grid-side inverter to obtain a final power reference value of the boost converter.
Further, the first threshold is not greater than 0.9pu.
Further, the second threshold is obtained by the following way:
wherein I is L Allowing a current effective value X to flow for a grid-side inverter c For the reactance value of the filter capacitor, U n Is the effective value of rated voltage, K q Is the voltage support coefficient, S N For rated capacity of photovoltaic system, P ref1 Is the active power reference value of the grid-side inverter in steady state operation.
Further, the method further comprises the following steps: and when the outlet voltage of the photovoltaic power station is recovered to be above a first threshold value, the grid-side inverter control and the boost converter control are exited.
In a second aspect, an embodiment of the present invention further provides a network-structured photovoltaic fault ride through control device, which is characterized in that the network-structured photovoltaic fault ride through control device is applied to a primary topology circuit, where the primary topology circuit includes: photovoltaic cell array, boost converter, net side dc-to-ac converter and LC filter circuit, wherein, the direct current that photovoltaic cell array output is exported to net side dc-to-ac converter after stepping up through boost converter, and the alternating current that net side dc-to-ac converter output is incorporated into the electric wire netting through the LC filter circuit, net formula photovoltaic fault passes through controlling means includes: the photovoltaic power station comprises an acquisition unit, a control unit and a control unit, wherein the acquisition unit is used for acquiring the outlet voltage of a photovoltaic power station, and the photovoltaic power station comprises a plurality of photovoltaic cell arrays; the control unit is used for starting network side inverter control and boost converter control when the outlet voltage of the photovoltaic power station is smaller than or equal to a first threshold value; wherein the grid-side inverter control includes adjusting grid-side inverter active and reactive, introducing a time-varying virtual impedance between a voltage virtual internal potential of the grid-side inverter and an outlet voltage, and adjusting a voltage reference in the grid-side inverter outer loop control, and the boost converter control includes adjusting a power reference of the boost converter.
In a third aspect, an embodiment of the present invention further provides a computer readable storage medium, where a computer program is stored, where the computer program is executed by a processor to implement the grid-formation type photovoltaic fault ride through control method provided in the foregoing embodiments.
In a fourth aspect, an embodiment of the present invention further provides an electronic device, including: a processor; a memory for storing the processor-executable instructions; the processor is configured to read the executable instruction from the memory, and execute the executable instruction to implement the grid-formation type photovoltaic fault ride-through control method provided in the foregoing embodiments.
According to the grid-structured photovoltaic fault ride through control method and device, when the outlet voltage of the photovoltaic power station is smaller than or equal to the first threshold value, grid-side inverter control and boost converter control are started at the same time, dynamic response of the photovoltaic direct current side is considered, steady state and transient state overcurrent inhibition of the inverter are comprehensively considered, a virtual synchronous control rotor equation of motion loop can be kept in a fault period, inertia support is provided for a power grid, meanwhile, direct voltage rising is restrained without additionally adding an unloading circuit, and investment and loss of photovoltaic equipment can be reduced. The grid-structured photovoltaic fault ride-through control method and device provided by the embodiment of the invention are beneficial to improving the low-voltage ride-through capability of the photovoltaic power station and reducing the running risk of the system.
Drawings
FIG. 1 shows a schematic diagram of a primary topology according to an embodiment of the invention;
FIG. 2 illustrates an exemplary flow chart of a method of grid-built photovoltaic fault ride-through control in accordance with an embodiment of the present invention;
FIG. 3 illustrates an exemplary flow chart of a method of grid-built photovoltaic fault ride-through control in accordance with another embodiment of the present invention;
FIG. 4 illustrates an exemplary block diagram of a grid-side inverter control link in accordance with an embodiment of the present invention;
FIG. 5 illustrates an exemplary block diagram of a boost converter control link in accordance with an embodiment of the present invention;
FIG. 6 shows a failure period U according to an embodiment of the invention pcc A schematic diagram of the grid-connected point voltage at a moderate voltage drop when dropping to 0.6 pu;
FIG. 7 shows a failure period U according to an embodiment of the invention pcc Schematic diagram of grid-connected power under moderate voltage drop when dropping to 0.6 pu;
FIG. 8 shows a failure period U according to an embodiment of the invention pcc Schematic diagram of inverter output current at moderate voltage drop when dropping to 0.6 pu;
FIG. 9 shows a failure period U according to an embodiment of the invention pcc Schematic diagram of dc voltage at moderate voltage dip when dip to 0.6 pu;
FIG. 10 shows a failure period U according to an embodiment of the invention pcc A schematic diagram of the grid-connected point voltage at a moderate voltage drop when dropping to 0.2 pu;
FIG. 11 shows a failure period U according to an embodiment of the invention pcc Schematic diagram of grid-connected power under severe voltage drop when dropping to 0.2 pu;
FIG. 12 shows a failure period U according to an embodiment of the invention pcc Schematic diagram of heavy voltage drop inverter output current when dropping to 0.2 pu;
FIG. 13 shows a failure period U according to an embodiment of the invention pcc Schematic of the heavy voltage drop dc voltage when dropped to 0.2 pu;
fig. 14 shows a schematic structural diagram of a grid-structured photovoltaic failure ride-through control device according to an embodiment of the present invention.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the examples described herein, which are provided to fully and completely disclose the present invention and fully convey the scope of the invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like elements/components are referred to by like reference numerals.
Unless otherwise indicated, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, it will be understood that terms defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
Fig. 1 shows a schematic diagram of a primary topology according to an embodiment of the invention. As shown in fig. 1, the primary topology circuit includes: the photovoltaic cell array, the boost converter, the grid-side inverter and the LC filter circuit, wherein direct current output by the photovoltaic cell array is boosted by the boost converter and then output to the grid-side inverter, and alternating current output by the grid-side inverter is integrated into a power grid through the LC filter circuit.
Fig. 2 shows an exemplary flowchart of a grid-built photovoltaic fault ride-through control method according to an embodiment of the present invention.
As shown in fig. 2, the network-structured photovoltaic fault ride through control method is applied to a primary topology circuit, and includes:
step S201: obtaining an outlet voltage of a photovoltaic power station, wherein the photovoltaic power station comprises a plurality of photovoltaic cell arrays;
step S202: when the outlet voltage of the photovoltaic power station is smaller than or equal to a first threshold value, starting network side inverter control and boost converter control; wherein the grid-side inverter control includes adjusting grid-side inverter active and reactive, introducing a time-varying virtual impedance between a voltage virtual internal potential of the grid-side inverter and an outlet voltage, and adjusting a voltage reference in the grid-side inverter outer loop control, and the boost converter control includes adjusting a power reference of the boost converter.
Further, the network construction type photovoltaic fault ride-through control method further comprises the following steps:
when the outlet voltage of the photovoltaic power station is recovered to be above a first threshold value, the grid-side inverter control and the boost converter control are exited.
Further, the first threshold is not greater than 0.9pu. Further preferably, the first threshold is 0.9pu.
Fig. 3 illustrates an exemplary flow chart of a method of grid-built photovoltaic fault ride-through control in accordance with another embodiment of the present invention. As shown in fig. 3, in the network side inverter control link, during steady state operation, the network side inverter has active and reactive power of P respectively ref1 、Q ref1 . When the outlet voltage U of the photovoltaic power station is detected pcc When falling below 0.9pu, the fault is startedThe crossing control comprises two parts: and (5) network side inverter control and boost converter control. When U is pcc When the voltage is recovered to be more than 0.9pu, the fault ride-through control mode is exited, namely the grid-side inverter control and the boost converter control are exited: the virtual impedance control is exited, and the active and reactive of the network side inverter are respectively controlled by P ref2 、Q ref2 Switching to P ref1 、Q ref1 The voltage reference value in the outer loop control is changed from the measured value to the rated value, and the power reference value of the boost converter is switched to P ref1 。
Fig. 4 shows an exemplary block diagram of a grid-side inverter control link in accordance with an embodiment of the present invention. As shown in fig. 4:
further, adjusting the network side inverter active and reactive includes:
switching the active power reference value and the reactive power reference value of the network side inverter to P respectively ref2 And Q ref2 ；
When the outlet voltage of the photovoltaic power station is smaller than or equal to a second threshold value, P is obtained by adopting the following formula ref2 And Q ref2 ：
Wherein S is fault As the apparent power in the event of a failure,
when the voltage at the outlet of the photovoltaic power station is greater than a second threshold value, P is obtained by adopting the following formula ref2 And Q ref2 ：
Wherein U is pcc For the outlet voltage of the photovoltaic power station, I L Allowing a current effective value X to flow for a grid-side inverter c For the reactance value of the filter capacitor, U n Is the effective value of rated voltage, K q Is the voltage support coefficient, S N For rated capacity of photovoltaic system, P ref1 Is the active power reference value of the grid-side inverter in steady state operation.
Further, the second threshold is obtained as follows:
wherein I is L Allowing a current effective value X to flow for a grid-side inverter c For the reactance value of the filter capacitor, U n Is the effective value of rated voltage, K q Is the voltage support coefficient, S N For rated capacity of photovoltaic system, P ref1 The second threshold is less than the first threshold for the active power reference of the grid-side inverter in steady state operation.
When the outlet voltage U of the photovoltaic power station pcc When falling below 0.9pu, the active and reactive of the grid-side inverter are respectively controlled by P ref1 、Q ref1 Switching to P ref2 、Q ref2 . When U is pcc Falls to U th In the above-mentioned case, the reactive power requirement of the system is small, so that the photovoltaic power station should output as much active power as possible to the power grid to increase the photoelectric conversion efficiency, and the fault ride-through control mode 1 is adopted, i.e. P is calculated according to formulas (3) and (4) ref2 、Q ref2 The method comprises the steps of carrying out a first treatment on the surface of the When U is pcc When falling below Uth, the reactive power demand of the system is larger, and a fault ride-through control mode 2 is adopted, namely P is calculated according to formulas (1) and (2) ref2 、Q ref2 。
Further, a time-varying virtual impedance is obtained as follows:
wherein R is v Is virtual resistance, L v Is virtual reactance, t 0 For the moment of occurrence of failure, t 1 For the fault clearing time, T is the virtual impedance decay time constant omega n Is the rated angular frequency.
The dq-axis voltage components generated by the virtual impedance are respectively superimposed on the internal potential generated by the power outer loop to generate a new internal potential dq-axis reference voltage, and the dq-axis voltage components generated by the virtual impedance are as follows:
in the method, in the process of the invention,and->Respectively, dq-axis voltage superposition components, i, generated for virtual impedance d 、i q Respectively the inverter output current dq axis component.
After entering a fault ride-through control mode, virtual impedance control is put into, and time-varying virtual impedance is introduced between the virtual internal potential of the voltage of the grid-side inverter and the outlet voltage so as to limit transient current surge and accelerate short-circuit current decay. When the device exits, the virtual impedance is slowly reduced to zero by adopting a virtual impedance exponential decay form, so as to achieve a better current limiting effect.
Further, adjusting the voltage reference value in the outer loop control of the grid-side inverter includes:
and adjusting the voltage reference value in the outer loop control of the grid-side inverter to be the same as the outlet voltage of the photovoltaic power station.
After entering a fault ride-through control mode, the voltage reference value U in the outer loop control of the grid-side inverter is obtained n From nominal value to outlet voltage measurement of inverter, i.e. outlet of photovoltaic power stationVoltage measurement U pcc 。
Fig. 5 shows an exemplary block diagram of a boost converter control link according to an embodiment of the invention.
As shown in fig. 5:
further, the power reference value of the boost converter is adjusted as follows:
and synchronously switching the initial power reference value of the boost converter to the active power reference value of the grid-side inverter, introducing direct-current voltage feedforward control, and adding an additional quantity generated by a deviation signal of the direct-current side voltage and the reference value through the PI controller to the active power reference value of the grid-side inverter to obtain the final power reference value of the boost converter.
In a control link of the boost converter, when detecting that the outlet voltage of the photovoltaic power station drops below 0.9pu, starting fault ride-through control, and synchronously switching the power reference value of the boost converter to P during the fault ride-through control ref2 Meanwhile, in order to accelerate the direct-current voltage dynamic recovery process, direct-current voltage feedforward control is introduced, and the deviation signal of the direct-current side voltage and the reference value is subjected to the additional quantity and P generated by a PI controller ref2 The addition is used as the final power reference value.
According to the embodiment, when the outlet voltage of the photovoltaic power station is smaller than or equal to the first threshold value, the grid-side inverter control and the boost converter control are started at the same time, the dynamic response of the photovoltaic direct current side is considered, the steady state and transient state overcurrent inhibition of the inverter are comprehensively considered, the virtual synchronous control rotor motion equation loop can be kept in a fault period, inertia support is provided for the power grid, meanwhile, the direct current voltage rising is inhibited without additionally adding an unloading circuit, and investment and loss of photovoltaic equipment can be reduced. The network construction type photovoltaic fault ride-through control method provided by the embodiment of the invention is beneficial to improving the low voltage ride-through capability of the photovoltaic power station and reducing the running risk of the system.
Example 1
And building a primary topological circuit of the photovoltaic power generation system shown in the figure 1 on a PSCAD simulation platform, wherein the primary topological circuit comprises a photovoltaic cell array, a boost converter, a grid-side inverter and an LC filter circuit. The control links of the boost converter and the control links of the grid-side inverter are sequentially established in the control links of the grid-formed photovoltaic fault ride-through control method, and the control system structures of the boost converter control links and the grid-side inverter control links are shown in fig. 5 and 4. The system simulation parameters are shown in table 1.
Table 1 simulation parameters
Parameters (parameters) Numerical value Parameters (parameters) Numerical value
Single machine rated power/MW 0.5 Filter capacitor L/mH 0.3
Photovoltaic grid-connected voltage/kV 0.4 Filter inductance C/uf 100
System frequency/Hz 50 D p 0.0002
DC voltage/kV 2 J 5000000
Capacitor C 1 /μF 1000 D q 0.5
Capacitor C 2 /μF 2500 Virtual resistor R v /Ω 0.1
Current limiting/pu 1.2 Virtual reactance L v /mH 0.48
In the control link of the grid-side inverter, when the outlet voltage of the photovoltaic power station is detected to drop below 0.9pu, fault ride-through control is started, and active and reactive instructions of the grid-side inverter are respectively controlled by P ref1 、Q ref1 Switching to P ref2 、Q ref2 . Calculating the allowable falling depth U of grid-connected points th
Examples K q 1.5, S N Is 0.5MW, I L Is 1.2 times rated current, U n 0.4kV, P ref1 Is 0.5MW. Obtaining the maximum depth U of the grid-connected point allowed to fall according to the calculation th 0.496pu.
The system is simulated, and the simulation working conditions are as follows: setting three-phase short circuit fault at active power of 0.5MW and reactive power of 0Mvar in initial state and 5 seconds, setting grounding resistance to 3 omega, duration of 1 second, and setting fault period U pcc Falls offTo 0.6pu, the photovoltaic grid-tied system transient response is shown in fig. 6-9. Due to the period of failure of 0.496pu<U pcc And the voltage is less than or equal to 0.9pu, the photovoltaic system is switched into a fault ride-through control mode 1, active power reference values and reactive power reference values are calculated according to formulas (3) and (4) respectively, the grid-formed photovoltaic outputs 0.3MW of active power and 0.2Mvar of reactive power to the system, a certain voltage support can be provided for the system, grid-connected voltage can be quickly recovered after fault clearing, and the active output is recovered to a rated value after 0.2s, so that fault ride-through is realized. At the moment of failure, the highest transient impact amplitude of the inverter output current is 1.3pu, and the output current is limited to 1.2pu during the failure period and has little harmonic content. The voltage impact of the DC side of the inverter reaches 2.61kV at the moment of failure, the active power switching instruction is introduced into the boost converter to reduce the active output of the photovoltaic array, so that the DC voltage can be maintained at 2kV during the failure period, and the continuous charging overvoltage damage of the connecting capacitor can not be caused.
Give U pcc Further drop to 0.2pu and the photovoltaic system transient response is shown in figures 10-13. Along with U pcc Reduced to U th The following inverter will switch to the fault ride through control mode 2 and the photovoltaic outputs active power 0.1MW and reactive power 0.12Mvar to the system according to formulas (1), (2). After the fault is over, the reactive power output is rapidly reduced to a reference value before the fault, and compared with the reactive power response lag caused by the delay characteristic of a control system of the grid-type photovoltaic, the grid-type photovoltaic can reduce the transient overvoltage risk of equipment. During the fault period, the transient impact of the output current of the inverter reaches 1.54pu and rapidly decays, the steady state value of the output current of the inverter is limited to 1.2 times of rated current during the fault period, and the overcurrent amplitude in the recovery stage is 1.28pu; the voltage surge of the DC side of the inverter reaches 2.74kV, and the connecting capacitor generally has 1.5 times of overvoltage capacity, so that the whole fault process can not cause overvoltage and overcurrent damage of the device. As the active output is reduced during the fault period, the relative power angle difference between the photovoltaic power generation and the system is reduced, and compared with the transient power angle instability of the photovoltaic power generation under the fault-free ride-through control, the provided control strategy can improve the transient stability of the photovoltaic grid-connected system under the large disturbance, and reduce the risk of the power angle instability.
Fig. 14 shows a schematic structural diagram of a grid-structured photovoltaic failure ride-through control device according to an embodiment of the present invention.
As shown in fig. 14, the network-structured photovoltaic fault ride through control device is applied to a primary topology circuit, and the primary topology circuit comprises: the photovoltaic cell array, boost converter, net side dc-to-ac converter and LC filter circuit, wherein, the direct current that photovoltaic cell array output exports to net side dc-to-ac converter after stepping up through boost converter, merges the alternating current that net side dc-to-ac converter output into the electric wire netting through LC filter circuit, includes:
an obtaining unit 1401, configured to obtain an outlet voltage of a photovoltaic power station, where the photovoltaic power station includes a plurality of photovoltaic cell arrays;
a control unit 1402 for starting grid-side inverter control and boost converter control when the outlet voltage of the photovoltaic power plant is less than or equal to a first threshold; wherein the grid-side inverter control includes adjusting grid-side inverter active and reactive, introducing a time-varying virtual impedance between a voltage virtual internal potential of the grid-side inverter and an outlet voltage, and adjusting a voltage reference in the grid-side inverter outer loop control, and the boost converter control includes adjusting a power reference of the boost converter.
Further, the network-structured photovoltaic fault ride through control device further comprises:
and the exit unit is used for exiting the grid-side inverter control and the boost converter control when the outlet voltage of the photovoltaic power station is recovered to be above a first threshold value.
Further, the first threshold is not greater than 0.9pu.
Further, adjusting the network side inverter active and reactive includes:
switching the active power reference value and the reactive power reference value of the network side inverter to P respectively ref2 And Q ref2 ；
When the outlet voltage of the photovoltaic power station is smaller than or equal to a second threshold value, P is obtained by adopting the following formula ref2 And Q ref2 ：
Wherein S is fault As the apparent power in the event of a failure,
when the outlet voltage of the photovoltaic power station is greater than a second threshold value, P is obtained by adopting the following formula ref2 And Q ref2 ：
Wherein U is pcc For the outlet voltage of the photovoltaic power station, I L Allowing a current effective value X to flow for a grid-side inverter c For the reactance value of the filter capacitor, U n Is the effective value of rated voltage, K q Is the voltage support coefficient, S N For rated capacity of photovoltaic system, P ref1 The second threshold is less than the first threshold for the active power reference of the grid-side inverter in steady state operation.
Further, the second threshold is obtained as follows:
wherein I is L Allowing a current effective value X to flow for a grid-side inverter c For the reactance value of the filter capacitor, U n Is the effective value of rated voltage, K q Is the voltage support coefficient, S N For rated capacity of photovoltaic system, P ref1 Is the active power reference value of the grid-side inverter in steady state operation.
Further, a time-varying virtual impedance is obtained as follows:
wherein R is v Is virtual resistance, L v Is virtual reactance, t 0 For the moment of occurrence of failure, t 1 For the fault clearing time, T is the virtual impedance decay time constant omega n Is the rated angular frequency.
Further, adjusting the voltage reference value in the outer loop control of the grid-side inverter includes:
and adjusting the voltage reference value in the outer loop control of the grid-side inverter to be the same as the outlet voltage of the photovoltaic power station.
Further, the power reference value of the boost converter is adjusted as follows:
and synchronously switching the initial power reference value of the boost converter to the active power reference value of the grid-side inverter, introducing direct-current voltage feedforward control, and adding an additional quantity generated by a deviation signal of the direct-current side voltage and the reference value through the PI controller to the active power reference value of the grid-side inverter to obtain the final power reference value of the boost converter.
According to the embodiment, when the outlet voltage of the photovoltaic power station is smaller than or equal to the first threshold value, the grid-side inverter control and the boost converter control are started at the same time, the dynamic response of the photovoltaic direct current side is considered, the steady state and transient state overcurrent inhibition of the inverter are comprehensively considered, the virtual synchronous control rotor motion equation loop can be kept in a fault period, inertia support is provided for the power grid, meanwhile, the direct current voltage rising is inhibited without additionally adding an unloading circuit, and investment and loss of photovoltaic equipment can be reduced. The network-structured photovoltaic fault ride-through control device provided by the embodiment of the invention is beneficial to improving the low-voltage ride-through capability of a photovoltaic power station and reducing the running risk of a system.
It should be noted that, when the apparatus provided in the foregoing embodiment performs the functions thereof, only the division of the foregoing functional modules is used as an example, in practical application, the foregoing functional allocation may be performed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules, so as to perform all or part of the functions described above. In addition, the apparatus and the method embodiments provided in the foregoing embodiments belong to the same concept, and specific implementation processes of the apparatus and the method embodiments are detailed in the method embodiments and are not repeated herein.
The embodiment of the invention also provides a computer readable storage medium, on which a computer program is stored, which when being executed by a processor, realizes the grid-built photovoltaic fault ride-through control method provided by the above embodiments.
The embodiment of the invention also provides electronic equipment, which comprises: a processor; a memory for storing processor-executable instructions; the processor is configured to read the executable instruction from the memory, and execute the instruction to implement the network-structured photovoltaic fault ride-through control method provided in the foregoing embodiments.
The invention has been described with reference to a few embodiments. However, as is well known to those skilled in the art, other embodiments than the above disclosed invention are equally possible within the scope of the invention, as defined by the appended patent claims.
Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise therein. All references to "a/an/the [ means, component, etc. ]" are to be interpreted openly as referring to at least one instance of said means, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.
It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical aspects of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made to the specific embodiments of the invention without departing from the spirit and scope of the invention, which is intended to be covered by the claims.

Claims (11)

1. The network-structured photovoltaic fault ride through control method is characterized by being applied to a primary topological circuit, wherein the primary topological circuit comprises the following components: the photovoltaic cell array, the boost converter, the grid-side inverter and the LC filter circuit, wherein the direct current output by the photovoltaic cell array is boosted by the boost converter and then output to the grid-side inverter, and the alternating current output by the grid-side inverter is integrated into a power grid through the LC filter circuit, and the grid-structured photovoltaic fault ride-through control method comprises the following steps:
obtaining an outlet voltage of a photovoltaic power station, wherein the photovoltaic power station comprises a plurality of photovoltaic cell arrays;
when the outlet voltage of the photovoltaic power station is smaller than or equal to a first threshold value, starting network side inverter control and boost converter control; wherein the grid-side inverter control includes adjusting grid-side inverter active and reactive, introducing a time-varying virtual impedance between a voltage virtual internal potential of the grid-side inverter and an outlet voltage, and adjusting a voltage reference in the grid-side inverter outer loop control, and the boost converter control includes adjusting a power reference of the boost converter.
2. The grid-formation type photovoltaic fault ride-through control method according to claim 1, wherein the adjusting the network side inverter active and reactive comprises:
switching the active power reference value and the reactive power reference value of the network side inverter to P respectively ref2 And Q ref2 ；
When the outlet voltage of the photovoltaic power station is smaller than or equal to a second threshold value, P is obtained by adopting the following formula ref2 And Q ref2 ：
Wherein S is fault As the apparent power in the event of a failure,
when the outlet voltage of the photovoltaic power station is greater than a second threshold value, P is obtained by adopting the following formula ref2 And Q ref2 ：
Wherein U is pcc For the outlet voltage of the photovoltaic power station, I L Allowing a current effective value X to flow for a grid-side inverter c For the reactance value of the filter capacitor, U n Is the effective value of rated voltage, K q Is the voltage support coefficient, S N For rated capacity of photovoltaic system, P ref1 And the second threshold value is smaller than the first threshold value for the active power reference value of the grid-side inverter under the steady-state operation.
3. The method for controlling network formation type photovoltaic fault ride through according to claim 1, wherein the time-varying virtual impedance is obtained by adopting the following method:
wherein R is v Is virtual resistance, L v Is virtual reactance, t 0 For the moment of occurrence of failure, t 1 For the fault clearing time, T is the virtual impedance decay time constant omega n Is the rated angular frequency.
4. The grid-structured photovoltaic fault ride through control method according to claim 1, wherein the adjusting the voltage reference value in the grid-side inverter outer loop control comprises:
and adjusting the voltage reference value in the outer loop control of the grid-side inverter to be the same as the outlet voltage of the photovoltaic power station.
5. The method for grid-structured photovoltaic fault ride through control according to claim 1, wherein the power reference value of the boost converter is adjusted by:
and synchronously switching the initial power reference value of the boost converter to the active power reference value of the grid-side inverter, introducing direct-current voltage feedforward control, and adding an additional quantity generated by a deviation signal of the direct-current side voltage and the reference value through the PI controller to the active power reference value of the grid-side inverter to obtain the final power reference value of the boost converter.
6. The method of claim 1, wherein the first threshold is not greater than 0.9pu.
7. The method for controlling network formation type photovoltaic fault ride through according to claim 2, wherein the second threshold value is obtained by the following method:
wherein I is L Allowing a current effective value X to flow for a grid-side inverter c For the reactance value of the filter capacitor, U n Is the effective value of rated voltage, K q Is the voltage support coefficient, S N For rated capacity of photovoltaic system, P ref1 Is the active power reference value of the grid-side inverter in steady state operation.
8. The method of claim 1, further comprising:
and when the outlet voltage of the photovoltaic power station is recovered to be above a first threshold value, the grid-side inverter control and the boost converter control are exited.
9. The utility model provides a net formula photovoltaic fault passes through controlling means which characterized in that is applied to primary topology circuit, primary topology circuit includes: photovoltaic cell array, boost converter, net side dc-to-ac converter and LC filter circuit, wherein, the direct current that photovoltaic cell array output is exported to net side dc-to-ac converter after stepping up through boost converter, and the alternating current that net side dc-to-ac converter output is incorporated into the electric wire netting through the LC filter circuit, net formula photovoltaic fault passes through controlling means includes:
the photovoltaic power station comprises an acquisition unit, a control unit and a control unit, wherein the acquisition unit is used for acquiring the outlet voltage of a photovoltaic power station, and the photovoltaic power station comprises a plurality of photovoltaic cell arrays;
the control unit is used for starting network side inverter control and boost converter control when the outlet voltage of the photovoltaic power station is smaller than or equal to a first threshold value; wherein the grid-side inverter control includes adjusting grid-side inverter active and reactive, introducing a time-varying virtual impedance between a voltage virtual internal potential of the grid-side inverter and an outlet voltage, and adjusting a voltage reference in the grid-side inverter outer loop control, and the boost converter control includes adjusting a power reference of the boost converter.
10. A computer readable storage medium having stored thereon a computer program, characterized in that the computer program, when executed by a processor, implements the network-structured photovoltaic fault ride-through control method of any of claims 1-8.
11. An electronic device, comprising:
a processor;
a memory for storing the processor-executable instructions;
the processor is configured to read the executable instructions from the memory and execute the executable instructions to implement the grid-formation photovoltaic fault ride-through control method of any one of claims 1-8.
CN202310978253.5A 2023-08-04 2023-08-04 Network construction type photovoltaic fault ride-through control method and device Pending CN117096944A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117871929A (en) * 2024-02-05 2024-04-12 中国电力科学研究院有限公司 Method and device for determining maximum current of SVG during transient overvoltage suppression

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117871929A (en) * 2024-02-05 2024-04-12 中国电力科学研究院有限公司 Method and device for determining maximum current of SVG during transient overvoltage suppression

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