CN112865131A - Photovoltaic inverter operation control method and system participating in power grid frequency regulation - Google Patents

Photovoltaic inverter operation control method and system participating in power grid frequency regulation Download PDF

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CN112865131A
CN112865131A CN202011622282.0A CN202011622282A CN112865131A CN 112865131 A CN112865131 A CN 112865131A CN 202011622282 A CN202011622282 A CN 202011622282A CN 112865131 A CN112865131 A CN 112865131A
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photovoltaic
photovoltaic inverter
generator set
voltage
power
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焦龙
华光辉
汪春
夏俊荣
杨慧彪
孙大伟
张爽
梁剑
任勇
丁茂生
刘海璇
孔爱良
张军
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
State Grid Ningxia Electric Power Co Ltd
Electric Power Research Institute of State Grid Ningxia Electric Power Co Ltd
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
State Grid Ningxia Electric Power Co Ltd
Electric Power Research Institute of State Grid Ningxia Electric Power Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—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
    • H02J3/50—Controlling the sharing of the out-of-phase component
    • 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
    • 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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  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)
  • Control Of Electrical Variables (AREA)

Abstract

The invention relates to a photovoltaic inverter operation control method and a system participating in power grid frequency regulation, which comprises the following steps: determining the slope variation in the power-voltage characteristic curve of the photovoltaic generator set according to the load shedding rate of the photovoltaic generator set; determining a direct-current side voltage reference value of the photovoltaic inverter by utilizing an improved MPPT algorithm based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set; and controlling the on-off of the IGBT in the photovoltaic inverter based on the direct-current side voltage reference value of the photovoltaic inverter. According to the invention, the influence of the load shedding rate of the photovoltaic generator set on the control of the photovoltaic inverter is considered, and the control accuracy of the photovoltaic inverter is improved.

Description

Photovoltaic inverter operation control method and system participating in power grid frequency regulation
Technical Field
The invention relates to the field of power grid frequency regulation and control, in particular to a photovoltaic inverter operation control method and system participating in power grid frequency regulation.
Background
In order to prevent global warming and energy depletion, development of renewable energy sources such as solar energy and wind power is urgently required. Among various renewable energy sources, solar energy is one of the rapidly developing renewable energy sources due to its advantages of cleanliness, safety, inexhaustibility, and the like. The new installation capacity of the large solar power stations in the world is increased year by year.
The photovoltaic inverter is an indispensable device in a power system, and the accurate control of the photovoltaic inverter can effectively improve the phenomenon of power imbalance at a supply end and a demand end, so that the effect of adjusting the frequency of a power grid is achieved.
A centralized photovoltaic inverter is a photovoltaic inverter widely used, and the centralized photovoltaic inverter adopts a single-stage DC-AC power electronic full-bridge inversion structure, as shown in fig. 1. The centralized photovoltaic inverter is used for boosting voltage and then merging the voltage into a power grid after direct current generated by the photovoltaic module is converted into alternating current. Therefore, the power of the inverter is relatively large.
Compared with the group string type inverter, the capacity of a single group string type inverter is only dozens of kW, the minimum capacity of a single centralized inverter can reach 500kW, and the single group string type inverter is more suitable for large ground power stations above MW level or large commercial roofs, namely more suitable for application scenes of large-scale photovoltaic access power systems.
Since large-scale photovoltaic access to power systems necessarily results in a reduction in system inertia and frequency regulation capability, and affects the power quality of the system. With the increasing photovoltaic permeability, modern power grids gradually require photovoltaic power stations to operate in a load shedding mode, and certain standby power is reserved for power systems, so that the power systems have primary frequency modulation capability.
However, the control technology of the conventional photovoltaic inverter is designed according to the output power tracking maximum output power, and the technology still exists when the photovoltaic power station operates in the load shedding mode, which inevitably leads to the unsatisfactory control effect of the photovoltaic inverter.
In view of the above, it is necessary to develop a control technique for a photovoltaic inverter when a photovoltaic power plant is operated in a load shedding mode.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a photovoltaic inverter operation control method and a system participating in power grid frequency regulation.
The purpose of the invention is realized by adopting the following technical scheme:
the invention provides a photovoltaic inverter operation control method participating in power grid frequency regulation, and the improvement is that the method comprises the following steps:
determining the slope variation in the power-voltage characteristic curve of the photovoltaic generator set according to the load shedding rate of the photovoltaic generator set;
determining a direct-current side voltage reference value of the photovoltaic inverter by utilizing an improved MPPT algorithm based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set;
controlling the on-off of an IGBT in the photovoltaic inverter based on a direct-current side voltage reference value of the photovoltaic inverter;
the improved MPPT algorithm is improved in that a power disturbance term on the direct current side of the photovoltaic inverter is introduced into an active variation quantity calculation formula on the direct current side of the photovoltaic inverter of the MPPT algorithm.
Preferably, the determining the slope variation in the power-voltage characteristic curve of the photovoltaic generator set according to the load shedding rate of the photovoltaic generator set includes:
determining the slope variation of the power-voltage characteristic curve of the photovoltaic generator set at the current moment t according to the following formula
Figure BDA0002876430480000021
Figure BDA0002876430480000022
In the formula, a0(t) is the value of the first fitting coefficient at the current moment t, a1And (t) is the value of the second fitting coefficient at the current moment t, and the sigma percent (t) is the load shedding rate of the photovoltaic generator set at the current moment t.
Further, said a is determined as follows0(t)：
a0(t)＝]0.2795T(t)-62.27]×[-0.054S(t)-0.4705]
Determining said a by1(t)：
a1(t)＝[0.04873T(t)-13.02]×[-3.078e-8×S3(t)+9.517e-5×S(t)2-0.07112S(t)-5.272]
In the above formula, t (t) is the temperature of the photovoltaic cell panel of the photovoltaic generator set at the current time t, and s (t) is the illumination intensity of the photovoltaic cell panel of the photovoltaic generator set at the current time t.
Preferably, the determining the dc-side voltage reference value of the photovoltaic inverter by using the improved MPPT algorithm based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set includes:
based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set, determining the direct-current side reference voltage of the photovoltaic inverter during load shedding control of the photovoltaic generator set by adopting an improved MPPT algorithm;
and taking the sum of the direct current side reference voltage of the photovoltaic inverter during the load shedding control of the photovoltaic generator set and the direct current side reference voltage of the photovoltaic inverter during the droop control of the photovoltaic generator set as a direct current side voltage reference value of the photovoltaic inverter.
Further, the determining, based on a slope variation in a power-voltage characteristic curve of the photovoltaic generator set, a dc-side reference voltage of the photovoltaic inverter during the load shedding control of the photovoltaic generator set by using an improved MPPT algorithm includes:
based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set at the current moment t, obtaining the active variation delta P (t) at the direct current side of the photovoltaic inverter by introducing the power disturbance item at the direct current side of the photovoltaic inverter into the current moment t through the following formula,
Figure BDA0002876430480000031
if Δ P (t) is not equal to 0 and Δ U (t) is not greater than 0, then
Figure BDA0002876430480000032
If Δ P (t) is not equal to 0 and Δ U (t) is greater than 0, then
Figure BDA0002876430480000033
If not, then,
Figure BDA0002876430480000034
wherein Δ u (t) u (t-1), P (t) I (t) u (t), P (t-1) I (t-1) u (t-1),
Figure BDA0002876430480000035
the term of the disturbance of the DC side power of the photovoltaic inverter at the current moment t, and delta U (t) is the voltage variation of the DC side of the photovoltaic inverter at the current moment t,
Figure BDA0002876430480000036
the method comprises the steps that a direct current side reference voltage of a photovoltaic inverter is obtained when a photovoltaic generating set is subjected to load shedding control at the current moment t, u (t) is a direct current side voltage measured value of the photovoltaic inverter at the current moment t, delta d is a disturbance step length, P (t) is direct current side active power of the photovoltaic inverter at the current moment t, I (t) is a direct current side current measured value of the photovoltaic inverter at the current moment t, P (t-1) is direct current side active power of the photovoltaic inverter at the moment t-1, I (t-1) is a direct current side current measured value of the photovoltaic inverter at the moment t-1, and u (t-1) is a direct current side voltage measured value of the photovoltaic inverter at the moment t-1.
Further, the process of obtaining the reference voltage on the dc side of the photovoltaic inverter during the droop control of the photovoltaic generator set includes:
calculating the primary frequency modulation active power deviation of the photovoltaic generator set according to the power grid frequency deviation and the droop coefficient of the photovoltaic generator set;
substituting the primary frequency modulation active power deviation of the photovoltaic generator set into the first PI controller to obtain the direct-current side reference voltage of the photovoltaic inverter corresponding to the droop control;
and the grid frequency deviation value is the difference between the grid frequency measured value and the grid frequency reference value.
Further, the calculating the primary frequency modulation active power deviation amount of the photovoltaic generator set according to the grid frequency deviation amount and the droop coefficient of the photovoltaic generator set includes:
determining primary frequency modulation active power deviation delta P of photovoltaic generator set at current time t according to the following formulax(t)：
ΔPx(t)＝kd(t)·Δf(t)
In the formula, kd(t) is the value of the droop coefficient at the current moment t, and delta f (t) is the power grid frequency deviation amount at the current moment t;
wherein said k is determined as followsd(t)：
Figure BDA0002876430480000041
In the formula, Pc(t) is the actual output power of the photovoltaic generator set at the current moment t, sigma% is the load shedding rate of the photovoltaic generator set, PnRated output power, k, of a photovoltaic generator setdmaxIs the maximum value of the sag factor, kdminIs the minimum value of the droop coefficient.
Preferably, the controlling the on-off of the IGBT in the photovoltaic inverter based on the dc side voltage reference value of the photovoltaic inverter includes:
determining a d-axis modulation voltage of the grid side of the photovoltaic inverter based on a direct-current side voltage reference value of the photovoltaic inverter;
determining q-axis modulation voltage of the grid side of the photovoltaic inverter based on the reactive power reference value of the photovoltaic inverter;
performing PWM (pulse-width modulation) on d-axis modulation voltage at the power grid side of the photovoltaic inverter and q-axis modulation voltage at the power grid side of the photovoltaic inverter to obtain switching control pulse of an IGBT (insulated gate bipolar translator) in the photovoltaic inverter;
and controlling the on-off of the IGBT in the photovoltaic inverter by using the switch control pulse of the IGBT in the photovoltaic inverter.
Further, the determining the d-axis modulation voltage on the grid side of the photovoltaic inverter based on the dc-side voltage reference value of the photovoltaic inverter includes:
and determining the d-axis modulation voltage of the grid side of the photovoltaic inverter by adopting a photovoltaic inverter direct current side fixed direct current voltage control technology according to the direct current side voltage measured value of the photovoltaic inverter, the direct current side voltage reference value of the photovoltaic inverter, the grid side d-axis current component of the photovoltaic inverter, the grid side q-axis current component of the photovoltaic inverter and the grid side d-axis voltage component of the photovoltaic inverter.
Further, the determining the q-axis modulation voltage of the grid side of the photovoltaic inverter based on the reference value of the reactive power output by the photovoltaic inverter comprises:
and determining q-axis modulation voltage at the grid side of the photovoltaic inverter by adopting a photovoltaic inverter direct current side constant reactive power control technology according to the reactive power measured value of the photovoltaic inverter, the reactive power reference value output by the photovoltaic inverter, the grid side q-axis current component of the photovoltaic inverter, the grid side d-axis current component of the photovoltaic inverter and the grid side q-axis voltage component of the photovoltaic inverter.
The invention provides a photovoltaic inverter operation control system participating in power grid frequency regulation, and the improvement is that the system comprises:
the first determining module is used for determining the slope variation in the power-voltage characteristic curve of the photovoltaic generator set according to the load shedding rate of the photovoltaic generator set;
the second determination module is used for determining a direct-current side voltage reference value of the photovoltaic inverter by utilizing an improved MPPT algorithm based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set;
the control module is used for controlling the on-off of the IGBT in the photovoltaic inverter based on the direct-current side voltage reference value of the photovoltaic inverter;
the improved MPPT algorithm is improved in that a power disturbance term on the direct current side of the photovoltaic inverter is introduced into an active variation quantity calculation formula on the direct current side of the photovoltaic inverter of the MPPT algorithm.
Compared with the closest prior art, the invention has the following beneficial effects:
according to the technical scheme provided by the invention, the slope variation in the power-voltage characteristic curve of the photovoltaic generator set is determined according to the load shedding rate of the photovoltaic generator set; determining a direct-current side voltage reference value of the photovoltaic inverter by utilizing an improved MPPT algorithm based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set; and controlling the on-off of the IGBT in the photovoltaic inverter based on the direct-current side voltage reference value of the photovoltaic inverter. According to the scheme, the influence of the load shedding rate of the photovoltaic generator set on the control of the photovoltaic inverter is considered, and the control accuracy of the photovoltaic inverter is improved.
Drawings
Fig. 1 is a diagram of a grid-connected system of a centralized photovoltaic inverter;
FIG. 2 is a flow chart of a method for controlling operation of a photovoltaic inverter participating in grid frequency regulation;
FIG. 3 is a control block diagram of the constant DC voltage control and the constant reactive power control on the DC side of the photovoltaic inverter in the embodiment of the invention;
fig. 4 is a diagram of a photovoltaic inverter operation control system participating in grid frequency regulation.
Detailed Description
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
the invention provides a photovoltaic inverter operation control method participating in power grid frequency regulation, as shown in fig. 2, the method comprises the following steps:
step 101, determining slope variation in a power-voltage characteristic curve of a photovoltaic generator set according to the load shedding rate of the photovoltaic generator set;
step 102, determining a direct-current side voltage reference value of a photovoltaic inverter by using an improved MPPT algorithm based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set;
103, controlling the on-off of an IGBT in the photovoltaic inverter based on a direct-current side voltage reference value of the photovoltaic inverter;
the improved MPPT algorithm is improved in that a power disturbance term on the direct current side of the photovoltaic inverter is introduced into an active variation quantity calculation formula on the direct current side of the photovoltaic inverter of the MPPT algorithm.
In the best embodiment of the invention, since the photovoltaic generator set has no rotating equipment, the photovoltaic generator set simulates the inertia response of a conventional generator set by changing the voltage of the direct current side, so that the photovoltaic generator set has similar frequency modulation performance as a synchronous generator. The photovoltaic inverter is a device directly connected with the photovoltaic generator set, and the accurate control of the photovoltaic inverter can realize the balance of supply and demand ends and maintain the stability of the frequency of a power grid;
the DC side reference voltage of the photovoltaic inverter is controlled by the load shedding of the photovoltaic generator set when the DC side voltage reference value of the photovoltaic inverter is controlled by the load shedding of the photovoltaic generator set
Figure BDA0002876430480000061
And the DC side reference voltage delta U of the photovoltaic inverter during the droop control of the photovoltaic generator setfAdding to obtain:
obtaining the slope variation in the power-voltage characteristic curve of the photovoltaic generator set by fitting the load shedding rate, the temperature and the illumination intensity, obtaining the direct-current side reference voltage of the photovoltaic inverter during load shedding control of the photovoltaic generator set under the time-varying illumination intensity and temperature conditions based on the slope variation and the improved MPPT algorithm, and obtaining the direct-current side reference voltage delta U of the photovoltaic inverter during droop control of the photovoltaic generator setfIn order to match the regulation capability of droop control under different illumination and temperature conditions, the value of the droop coefficient is directly proportional to the actual power of the photovoltaic system. The common regulation of the load shedding control and the droop control enables the photovoltaic system to actively participate in the frequency regulation of the power grid, and the stability of the power grid is improved.
Specifically, the step 101 includes:
determining the power-voltage characteristic curve of the photovoltaic generator set at the current moment t according to the following formulaSlope variation
Figure BDA0002876430480000062
Figure BDA0002876430480000063
In the formula, a0(t) is the value of the first fitting coefficient at the current moment t, a1And (t) is the value of the second fitting coefficient at the current moment t, and the sigma percent (t) is the load shedding rate of the photovoltaic generator set at the current moment t.
Further, said a is determined as follows0(t)：
a0(t)＝[0.2795T(t)-62.27]×[-0.054S(t)-0.4705]
Determining said a by1(t)：
a1(t)＝[0.04873T(t)-13.02]×[-3.078e-8×S3(t)+9.517e-5×S(t)2-0.07112S(t)-5.272]
In the above formula, t (t) is the temperature of the photovoltaic cell panel of the photovoltaic generator set at the current time t, and s (t) is the illumination intensity of the photovoltaic cell panel of the photovoltaic generator set at the current time t.
Specifically, the step 102 includes:
102-1, determining a direct-current side reference voltage of a photovoltaic inverter during load shedding control of the photovoltaic generator set by adopting an improved MPPT algorithm based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set;
and 102-2, taking the sum of the direct current side reference voltage of the photovoltaic inverter during the load shedding control of the photovoltaic generator set and the direct current side reference voltage of the photovoltaic inverter during the droop control of the photovoltaic generator set as the direct current side voltage reference value of the photovoltaic inverter.
Further, the step 102-1 includes:
102-1-1, obtaining a power disturbance item introduced to the direct current side of the photovoltaic inverter at the current moment t through the following formula based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set at the current moment tThe active change quantity delta P (t) of the direct current side of the photovoltaic inverter,
Figure BDA0002876430480000071
step 102-1-2, if Δ P (t) is not equal to 0 and Δ U (t) is not greater than 0, then
Figure BDA0002876430480000072
If Δ P (t) is not equal to 0 and Δ U (t) is greater than 0, then
Figure BDA0002876430480000073
If not, then,
Figure BDA0002876430480000074
wherein Δ u (t) u (t-1), P (t) I (t) u (t), P (t-1) I (t-1) u (t-1),
Figure BDA0002876430480000075
the term of the disturbance of the DC side power of the photovoltaic inverter at the current moment t, and delta U (t) is the voltage variation of the DC side of the photovoltaic inverter at the current moment t,
Figure BDA0002876430480000076
the method comprises the steps that a direct current side reference voltage of a photovoltaic inverter is obtained when a photovoltaic generating set is subjected to load shedding control at the current moment t, u (t) is a direct current side voltage measured value of the photovoltaic inverter at the current moment t, delta d is a disturbance step length, P (t) is direct current side active power of the photovoltaic inverter at the current moment t, I (t) is a direct current side current measured value of the photovoltaic inverter at the current moment t, P (t-1) is direct current side active power of the photovoltaic inverter at the moment t-1, I (t-1) is a direct current side current measured value of the photovoltaic inverter at the moment t-1, and u (t-1) is a direct current side voltage measured value of the photovoltaic inverter at the moment t-1.
Wherein, Δ u (t) is a difference value between a measured value of the dc side voltage of the pv inverter at the time t-1 and a measured value of the dc side voltage of the pv inverter at the current time t;
further, the process of obtaining the reference voltage on the dc side of the photovoltaic inverter during the droop control of the photovoltaic generator set includes:
calculating the primary frequency modulation active power deviation of the photovoltaic generator set according to the power grid frequency deviation and the droop coefficient of the photovoltaic generator set;
substituting the primary frequency modulation active power deviation of the photovoltaic generator set into the first PI controller to obtain the direct-current side reference voltage of the photovoltaic inverter corresponding to the droop control;
and the grid frequency deviation value is the difference between the grid frequency measured value and the grid frequency reference value.
Further, the calculating the primary frequency modulation active power deviation amount of the photovoltaic generator set according to the grid frequency deviation amount and the droop coefficient of the photovoltaic generator set includes:
determining primary frequency modulation active power deviation delta P of photovoltaic generator set at current time t according to the following formulax(t)：
ΔPx(t)＝kd(t)·Δf(t)
In the formula, kd(t) is the value of the droop coefficient at the current time t, Δ f (t) is the power grid frequency deviation amount at the current time t, and Δ f (t) is the difference between the power grid frequency measured value and the power grid frequency reference value at the current time t.
Wherein said k is determined as followsd(t)：
Figure BDA0002876430480000081
In the formula, Pc(t) is the actual output power of the photovoltaic generator set at the current moment t, sigma% is the load shedding rate of the photovoltaic generator set, PnRated output power, k, of a photovoltaic generator setdmaxIs the maximum value of the sag factor, kdminIs the minimum value of the droop coefficient.
Specifically, the step 103 includes:
103-1, determining a d-axis modulation voltage at the power grid side of the photovoltaic inverter based on a direct-current side voltage reference value of the photovoltaic inverter;
103-2, determining q-axis modulation voltage of the grid side of the photovoltaic inverter based on the reference value of the reactive power of the photovoltaic inverter;
103-3, performing PWM (pulse-width modulation) on the d-axis modulation voltage at the power grid side of the photovoltaic inverter and the q-axis modulation voltage at the power grid side of the photovoltaic inverter to obtain a switching control pulse of an IGBT (insulated gate bipolar translator) in the photovoltaic inverter;
and 103-4, controlling the on-off of the IGBT in the photovoltaic inverter by using the switch control pulse of the IGBT in the photovoltaic inverter.
The reference value of the reactive power of the photovoltaic inverter is preset.
Further, the step 103-1 is configured to:
and determining the d-axis modulation voltage of the grid side of the photovoltaic inverter by adopting a photovoltaic inverter direct current side fixed direct current voltage control technology according to the direct current side voltage measured value of the photovoltaic inverter, the direct current side voltage reference value of the photovoltaic inverter, the grid side d-axis current component of the photovoltaic inverter, the grid side q-axis current component of the photovoltaic inverter and the grid side d-axis voltage component of the photovoltaic inverter.
Further, the step 103-2 is configured to:
and determining q-axis modulation voltage at the grid side of the photovoltaic inverter by adopting a photovoltaic inverter direct current side constant reactive power control technology according to the reactive power measured value of the photovoltaic inverter, the reactive power reference value output by the photovoltaic inverter, the grid side q-axis current component of the photovoltaic inverter, the grid side d-axis current component of the photovoltaic inverter and the grid side q-axis voltage component of the photovoltaic inverter.
The invention is characterized in that: time-varying illumination and temperature based load shedding control and variable droop coefficient active power-frequency droop control. The photovoltaic inverter is controlled by constant direct current side voltage and constant reactive power; the load shedding control comprises introducing an intermediate variable, fitting a curve of illumination intensity S and temperature T with a load shedding rate, and obtaining direct-current side voltage by improving an MPPT algorithm; the droop control comprises a proportional controller and a PI controller, and the variable quantity of the active power when the frequency of the power grid changes is obtained through calculation.
Example 2:
the invention provides a photovoltaic inverter operation control system participating in power grid frequency regulation, as shown in fig. 4, the system comprises:
the first determining module is used for determining the slope variation in the power-voltage characteristic curve of the photovoltaic generator set according to the load shedding rate of the photovoltaic generator set;
the second determination module is used for determining a direct-current side voltage reference value of the photovoltaic inverter by utilizing an improved MPPT algorithm based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set;
the control module is used for controlling the on-off of the IGBT in the photovoltaic inverter based on the direct-current side voltage reference value of the photovoltaic inverter;
the improved MPPT algorithm is improved in that a power disturbance term on the direct current side of the photovoltaic inverter is introduced into an active variation quantity calculation formula on the direct current side of the photovoltaic inverter of the MPPT algorithm.
Specifically, the first determining module is configured to:
determining the slope variation of the power-voltage characteristic curve of the photovoltaic generator set at the current moment t according to the following formula
Figure BDA0002876430480000091
Figure BDA0002876430480000092
In the formula, a0(t) is the value of the first fitting coefficient at the current moment t, a1And (t) is the value of the second fitting coefficient at the current moment t, and the sigma percent (t) is the load shedding rate of the photovoltaic generator set at the current moment t.
Further, said a is determined as follows0(t)：
a0(t)＝]0.2795T(t)-62.27]×[-0.054S(t)-0.4705]
Determining said a by1(t)：
a1(t)＝[0.04873T(t)-13.02]×[-3.078e-8×S3(t)+9.517e-5×S(t)2-0.07112S(t)-5.272]
In the above formula, t (t) is the temperature of the photovoltaic cell panel of the photovoltaic generator set at the current time t, and s (t) is the illumination intensity of the photovoltaic cell panel of the photovoltaic generator set at the current time t.
Specifically, the second determining module includes:
the first determining unit is used for determining the direct-current side reference voltage of the photovoltaic inverter during load shedding control of the photovoltaic generator set by adopting an improved MPPT algorithm based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set;
and the setting unit is used for taking the sum of the direct-current side reference voltage of the photovoltaic inverter during the load shedding control of the photovoltaic generator set and the direct-current side reference voltage of the photovoltaic inverter during the droop control of the photovoltaic generator set as the direct-current side voltage reference value of the photovoltaic inverter.
Further, the first determining unit includes:
a first calculating subunit, configured to obtain, based on a slope variation in a power-voltage characteristic curve of the photovoltaic generator set at a current time t, an active variation Δ p (t) on the dc side of the photovoltaic inverter, where the current time t introduces a power disturbance term on the dc side of the photovoltaic inverter, according to the following formula,
Figure BDA0002876430480000101
a judging subunit, configured to, if Δ p (t) is not equal to 0 and Δ u (t) is not greater than 0
Figure BDA0002876430480000102
If Δ P (t) is not equal to 0 and Δ U (t) is greater than 0, then
Figure BDA0002876430480000103
If not, then,
Figure BDA0002876430480000104
wherein Δ u (t) u (t-1), P (t) I (t) u (t), P (t-1) I (t-1) u (t-1),
Figure BDA0002876430480000105
the term of the disturbance of the DC side power of the photovoltaic inverter at the current moment t, and delta U (t) is the voltage variation of the DC side of the photovoltaic inverter at the current moment t,
Figure BDA0002876430480000106
the method comprises the steps that a direct current side reference voltage of a photovoltaic inverter is obtained when a photovoltaic generating set is subjected to load shedding control at the current moment t, u (t) is a direct current side voltage measured value of the photovoltaic inverter at the current moment t, delta d is a disturbance step length, P (t) is direct current side active power of the photovoltaic inverter at the current moment t, I (t) is a direct current side current measured value of the photovoltaic inverter at the current moment t, P (t-1) is direct current side active power of the photovoltaic inverter at the moment t-1, I (t-1) is a direct current side current measured value of the photovoltaic inverter at the moment t-1, and u (t-1) is a direct current side voltage measured value of the photovoltaic inverter at the moment t-1.
Specifically, the second determining module includes an obtaining unit for obtaining a reference voltage at a dc side of the photovoltaic inverter during droop control of the photovoltaic generator set, where the obtaining unit includes:
the second calculating subunit is used for calculating the primary frequency modulation active power deviation of the photovoltaic generator set according to the power grid frequency deviation and the droop coefficient of the photovoltaic generator set;
the substituting subunit is used for substituting the primary frequency modulation active power deviation amount of the photovoltaic generator set into the first PI controller to obtain the direct-current side reference voltage of the photovoltaic inverter corresponding to the droop control;
and the grid frequency deviation value is the difference between the grid frequency measured value and the grid frequency reference value.
Specifically, the second calculating subunit is configured to:
determining primary frequency modulation active power deviation delta P of photovoltaic generator set at current time t according to the following formulax(t)：
ΔPx(t)＝kd(t)·Δf(t)
In the formula, kd(t) is the value of the droop coefficient at the current moment t, and delta f (t) is the power grid frequency deviation amount at the current moment t;
wherein said k is determined as followsd(t)：
Figure BDA0002876430480000111
In the formula, Pc(t) is the actual output power of the photovoltaic generator set at the current moment t, sigma% is the load shedding rate of the photovoltaic generator set, PnRated output power, k, of a photovoltaic generator setdmaxIs the maximum value of the sag factor, kdminIs the minimum value of the droop coefficient.
Specifically, the control module includes:
a second determination unit for determining a d-axis modulation voltage on the grid side of the photovoltaic inverter based on a direct-current side voltage reference value of the photovoltaic inverter;
a third determination unit, configured to determine a q-axis modulation voltage on the grid side of the photovoltaic inverter based on the photovoltaic inverter reactive power reference value;
the modulation unit is used for carrying out PWM (pulse-width modulation) on d-axis modulation voltage at the power grid side of the photovoltaic inverter and q-axis modulation voltage at the power grid side of the photovoltaic inverter to obtain switching control pulses of the IGBT (insulated gate bipolar translator) in the photovoltaic inverter;
and the control unit is used for controlling the on-off of the IGBT in the photovoltaic inverter by utilizing the on-off control pulse of the IGBT in the photovoltaic inverter.
Further, the second determining unit is configured to:
and determining the d-axis modulation voltage of the grid side of the photovoltaic inverter by adopting a photovoltaic inverter direct current side fixed direct current voltage control technology according to the direct current side voltage measured value of the photovoltaic inverter, the direct current side voltage reference value of the photovoltaic inverter, the grid side d-axis current component of the photovoltaic inverter, the grid side q-axis current component of the photovoltaic inverter and the grid side d-axis voltage component of the photovoltaic inverter.
Further, the third determining unit is configured to:
and determining q-axis modulation voltage at the grid side of the photovoltaic inverter by adopting a photovoltaic inverter direct current side constant reactive power control technology according to the reactive power measured value of the photovoltaic inverter, the reactive power reference value output by the photovoltaic inverter, the grid side q-axis current component of the photovoltaic inverter, the grid side d-axis current component of the photovoltaic inverter and the grid side q-axis voltage component of the photovoltaic inverter.
Example 3:
step A: measuring voltage V on the mains sidea,b,cAnd the grid side current Ia,b,c，Va,b,cThe frequency f of the power grid side is obtained by phase-locked loop (PLL) measurementreqAnd phase ωt；
Va,b,cAnd Ia,b,cObtaining d-axis q-axis component U of the voltage after respectively carrying out park conversiontd、UtqAnd d-axis q-axis component i of the currentd、iq；
And B: P-V single-peak characteristic curve based on photovoltaic cell
Figure BDA0002876430480000121
When the system is operated at the right side of the maximum power point,
Figure BDA0002876430480000122
the power is monotonous, when the load reduction rate sigma% is reduced, the voltage of the direct current side is reduced, and the output power is properly improved; when in use
Figure BDA0002876430480000123
The time is the maximum power point as long as
Figure BDA0002876430480000124
Not greater than 0 ensures that the curve provides the correct frequency response.
Comparing the standard deviations of the second, third and fourth order fit functions to 1.138, 0.8614, 0.5868, respectively, the standard deviation using the fit function shown below is small, only 0.5012, and the curve fit was chosen, where a0、a1Are the corresponding fitting coefficients.
Figure BDA0002876430480000125
Through the experiments, the method has the advantages that,
Figure BDA0002876430480000126
coefficient a0、a1By introducing the fitting function, the method can obtain
Figure BDA0002876430480000127
And σ%.
And C: to convert the load shedding rate sigma% into the DC side reference voltage of the photovoltaic inverter during the load shedding control of the photovoltaic generator set
Figure BDA0002876430480000128
The original MPPT algorithm needs to be improved.
First, the voltage and current U of the photovoltaic cell are measuredk、Uk-1、Ik、Ik-1Calculate PkAnd Pk-1，Pk＝Uk×Ik，Pk-1＝Uk-1×Ik-1K is the sampling moment of the current time, and k-1 is the last sampling moment;
in the original criterion of delta P ═ Pk-Pk-1Subtracting a new perturbation term on the basis
Figure BDA0002876430480000129
Get the criterion
Figure BDA00028764304800001210
Wherein Δ U ═ Uk-Uk-1The direct-current side reference voltage of the photovoltaic inverter during the load shedding control of the photovoltaic generator set can be obtained by improving the MPPT algorithm
Figure BDA00028764304800001211
Wherein, the direct current side reference voltage of the photovoltaic inverter can be obtained by improving the MPPT algorithm when the photovoltaic generator set carries out load shedding control
Figure BDA00028764304800001212
The specific process comprises the following steps:
if Δ P (t) is not equal to 0 and Δ U (t) is not greater than 0, then
Figure BDA00028764304800001213
If Δ P (t) is not equal to 0 and Δ U (t) is greater than 0, then
Figure BDA00028764304800001214
If not, then,
Figure BDA00028764304800001215
step D: introducing droop control delta P ═ k at the direct current sidedΔf，kdThe droop coefficient is an important index for evaluating the frequency modulation capability of the power grid. In order to match the regulation capability of droop control under different illumination and temperature conditions, the value of the droop coefficient is directly proportional to the actual power of the photovoltaic system. Calculating the measured power grid frequency deviation delta f through droop control to obtain a frequency deviation delta P, and taking a droop coefficient as
Figure BDA0002876430480000131
Wherein P iskFor actual output power of the photovoltaic array, PnRated power, k, for the photovoltaic arraydmaxAnd kdminThe maximum value and the minimum value of the droop coefficient are respectively, the droop coefficient is similar to a conventional unit, the reciprocal of the droop coefficient is a difference adjustment coefficient, and the difference adjustment coefficient is generally 2% -5%, so that the maximum value and the minimum value of the droop coefficient are respectively kdmax＝50，kdmin＝20。
Step E: direct-current side reference voltage of photovoltaic inverter during load shedding control of photovoltaic generator set
Figure BDA0002876430480000132
And the DC side reference voltage delta U of the photovoltaic inverter during the droop control of the photovoltaic generator setfAdding the voltage reference value U of the direct current side of the photovoltaic inverterdcref：
Figure BDA0002876430480000133
Step F: referring to a control block diagram adopting constant direct current side voltage and constant reactive power to obtain Ud、Uq；
The fixed direct current side voltage control specifically comprises the following steps: the measured value U of the voltage on the direct current side of the photovoltaic inverterdcDirect-current side voltage reference value U of photovoltaic inverterdcrefSubstituting into a PI controller to obtain a d-axis current reference value i of the photovoltaic inverterdrefThe grid side d-axis current reference value i of the photovoltaic inverterdrefAnd grid side d-axis current component i of photovoltaic inverterdSubstituting the voltage into a PI controller to obtain a grid side d-axis voltage reference value U of the photovoltaic inverterdrefBased on UdrefGrid side q-axis current component i of photovoltaic inverterqGrid side d-axis voltage component U of photovoltaic invertertdDetermining the d-axis modulation voltage U of the grid side of the photovoltaic inverter by the inductance value and the frequency of the photovoltaic inverterd；
The fixed reactive power control specifically comprises the following steps: the real reactive power value Q of the photovoltaic inverter and the reference reactive power value Q output by the photovoltaic inverterrefSubstituting into a PI controller to obtain a q-axis current reference value i of the photovoltaic inverterqrefReference value i of q-axis current of photovoltaic inverterqrefAnd a grid-side q-axis current component i of the photovoltaic inverterqSubstituting into a PI controller to obtain a grid side q-axis voltage reference value U of the photovoltaic inverterqrefBased on UqrefGrid side d-axis current component i of photovoltaic inverterdGrid side q-axis voltage component U of photovoltaic invertertqDetermining the q-axis modulation voltage U of the grid side of the photovoltaic inverter by the inductance value and the frequency of the photovoltaic inverterq；
U obtained under the controld、UqThe pulse is input to a PWM controller to obtain a pulse, and the inverter IGBT is controlled to operate.
According to the invention, the influence of the load shedding control and the droop control of the photovoltaic generator set on the voltage reference value of the direct current side of the photovoltaic inverter is considered, and the direct current side voltage is controlled to adapt to the inertia response working state of the photovoltaic generator set simulating the conventional generator set, so that the photovoltaic grid-connected structure has the frequency modulation capability similar to that of a synchronous generator and can actively participate in the frequency adjustment of a power grid.
The invention fits the functions of the illumination intensity and the temperature with the intermediate quantity, and the invention fits the functions of the illumination intensity, the temperature and the intermediate quantity
Figure BDA0002876430480000141
Such that the load shedding control is achieved at time-varying temperatures and light intensities; and converting the load shedding rate into a direct current side voltage output reference value of the photovoltaic inverter by improving an MPPT algorithm, adding the direct current side voltage to a direct current side voltage reference value obtained through droop control to obtain a new direct current side voltage reference value, and controlling the inverter to act through double-loop voltage control of the inverter.
The control strategy of the invention can maintain the stability of the system frequency when the load of the power grid changes. Has the advantages of reasonable scientificity, strong practicability, good effect and the like.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application 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 application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams 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 solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims (11)

1. A method of controlling operation of a photovoltaic inverter participating in grid frequency regulation, the method comprising:
determining the slope variation in the power-voltage characteristic curve of the photovoltaic generator set according to the load shedding rate of the photovoltaic generator set;
determining a direct-current side voltage reference value of the photovoltaic inverter by utilizing an improved MPPT algorithm based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set;
controlling the on-off of an IGBT in the photovoltaic inverter based on a direct-current side voltage reference value of the photovoltaic inverter;
the improved MPPT algorithm is improved in that a power disturbance term on the direct current side of the photovoltaic inverter is introduced into an active variation quantity calculation formula on the direct current side of the photovoltaic inverter of the MPPT algorithm.
2. The method of claim 1, wherein determining an amount of slope change in a power-voltage characteristic of the photovoltaic generator set based on a rate of load shedding of the photovoltaic generator set comprises:
determining the slope variation of the power-voltage characteristic curve of the photovoltaic generator set at the current moment t according to the following formula
Figure FDA0002876430470000011
Figure FDA0002876430470000012
In the formula, a0(t) is the value of the first fitting coefficient at the current moment t, a1And (t) is the value of the second fitting coefficient at the current moment t, and the sigma percent (t) is the load shedding rate of the photovoltaic generator set at the current moment t.
3. The method of claim 2, wherein said a is determined as follows0(t)：
a0(t)＝[0.2795T(t)-62.27]×[-0.054S(t)-0.4705]
Determining said a by1(t)：
a1(t)＝[0.04873T(t)-13.02]×[-3.078e-8×S3(t)+9.517e-5×S(t)2-0.07112S(t)-5.272[
In the above formula, t (t) is the temperature of the photovoltaic cell panel of the photovoltaic generator set at the current time t, and s (t) is the illumination intensity of the photovoltaic cell panel of the photovoltaic generator set at the current time t.
4. The method of claim 1, wherein determining the dc side voltage reference of the photovoltaic inverter using the modified MPPT algorithm based on a slope change in a power-voltage characteristic of the photovoltaic generator set comprises:
based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set, determining the direct-current side reference voltage of the photovoltaic inverter during load shedding control of the photovoltaic generator set by adopting an improved MPPT algorithm;
and taking the sum of the direct current side reference voltage of the photovoltaic inverter during the load shedding control of the photovoltaic generator set and the direct current side reference voltage of the photovoltaic inverter during the droop control of the photovoltaic generator set as a direct current side voltage reference value of the photovoltaic inverter.
5. The method of claim 4, wherein determining the DC-side reference voltage of the photovoltaic inverter during the de-rating control of the photovoltaic generator set using the modified MPPT algorithm based on a slope change in a power-voltage characteristic curve of the photovoltaic generator set comprises:
based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set at the current moment t, obtaining the active variation delta P (t) at the direct current side of the photovoltaic inverter by introducing the power disturbance item at the direct current side of the photovoltaic inverter into the current moment t through the following formula,
Figure FDA0002876430470000021
if Δ P (t) is not equal to 0 and Δ U (t) is not greater than 0, then
Figure FDA0002876430470000022
If Δ P (t) is not equal to 0 and Δ U (t) is greater than 0, then
Figure FDA0002876430470000023
If not, then,
Figure FDA0002876430470000024
wherein Δ u (t) u (t-1), P (t) I (t) u (t), P (t-1) I (t-1) u (t-1),
Figure FDA0002876430470000025
the term of the disturbance of the DC side power of the photovoltaic inverter at the current moment t, and delta U (t) is the voltage variation of the DC side of the photovoltaic inverter at the current moment t,
Figure FDA0002876430470000026
the method comprises the steps of obtaining a direct-current side reference voltage of a photovoltaic inverter during load shedding control of a photovoltaic generator set at a current moment t, u (t) is a direct-current side voltage measured value of the photovoltaic inverter at the current moment t, delta d is a disturbance step length, P (t) is direct-current side active power of the photovoltaic inverter at the current moment t, I (t) is a direct-current side current measured value of the photovoltaic inverter at the current moment t, P (t-1) is direct-current side active power of the photovoltaic inverter at the moment t-1, I (t-1) is a direct-current side current measured value of the photovoltaic inverter at the moment t-1, u (t-1) is a direct-current side voltage measured value of the photovoltaic inverter at the moment t-1, and t-1 is a previous moment of the current moment t.
6. The method of claim 4, wherein the obtaining of the reference voltage on the DC side of the photovoltaic inverter during the droop control of the photovoltaic generator set comprises:
calculating the primary frequency modulation active power deviation of the photovoltaic generator set according to the power grid frequency deviation and the droop coefficient of the photovoltaic generator set;
substituting the primary frequency modulation active power deviation of the photovoltaic generator set into the first PI controller to obtain the direct-current side reference voltage of the photovoltaic inverter corresponding to the droop control;
and the grid frequency deviation value is the difference between the grid frequency measured value and the grid frequency reference value.
7. The method of claim 6, wherein calculating the primary frequency modulation active power deviation of the photovoltaic generator set according to the grid frequency deviation and the droop coefficient of the photovoltaic generator set comprises:
determining primary frequency modulation active power deviation delta P of photovoltaic generator set at current time t according to the following formulax(t)：
ΔPx(t)＝kd(t)·Δf(t)
In the formula, kd(t) is the value of the droop coefficient at the current moment t, and delta f (t) is the power grid frequency deviation amount at the current moment t;
wherein said k is determined as followsd(t)：
Figure FDA0002876430470000031
In the formula, Pc(t) is the actual output power of the photovoltaic generator set at the current moment t, sigma% is the load shedding rate of the photovoltaic generator set, PnRated output power, k, of a photovoltaic generator setdmaxIs the maximum value of the sag factor, kdminIs the minimum value of the droop coefficient.
8. The method of claim 1, wherein controlling the switching of the IGBTs in the photovoltaic inverter based on the DC side voltage reference of the photovoltaic inverter comprises:
determining a d-axis modulation voltage of the grid side of the photovoltaic inverter based on a direct-current side voltage reference value of the photovoltaic inverter;
determining q-axis modulation voltage of the grid side of the photovoltaic inverter based on the reactive power reference value of the photovoltaic inverter;
performing PWM (pulse-width modulation) on d-axis modulation voltage at the power grid side of the photovoltaic inverter and q-axis modulation voltage at the power grid side of the photovoltaic inverter to obtain switching control pulse of an IGBT (insulated gate bipolar translator) in the photovoltaic inverter;
and controlling the on-off of the IGBT in the photovoltaic inverter by using the switch control pulse of the IGBT in the photovoltaic inverter.
9. The method of claim 8, wherein determining the grid-side d-axis modulation voltage of the photovoltaic inverter based on the dc-side voltage reference of the photovoltaic inverter comprises:
and determining the d-axis modulation voltage of the grid side of the photovoltaic inverter by adopting a photovoltaic inverter direct current side fixed direct current voltage control technology according to the direct current side voltage measured value of the photovoltaic inverter, the direct current side voltage reference value of the photovoltaic inverter, the grid side d-axis current component of the photovoltaic inverter, the grid side q-axis current component of the photovoltaic inverter and the grid side d-axis voltage component of the photovoltaic inverter.
10. The method of claim 8, wherein determining the grid-side q-axis modulation voltage of the photovoltaic inverter based on the photovoltaic inverter output reactive power reference value comprises:
and determining q-axis modulation voltage at the grid side of the photovoltaic inverter by adopting a photovoltaic inverter direct current side constant reactive power control technology according to the reactive power measured value of the photovoltaic inverter, the reactive power reference value output by the photovoltaic inverter, the grid side q-axis current component of the photovoltaic inverter, the grid side d-axis current component of the photovoltaic inverter and the grid side q-axis voltage component of the photovoltaic inverter.
11. A photovoltaic inverter operation control system participating in grid frequency regulation, the system comprising:
the first determining module is used for determining the slope variation in the power-voltage characteristic curve of the photovoltaic generator set according to the load shedding rate of the photovoltaic generator set;
the second determination module is used for determining a direct-current side voltage reference value of the photovoltaic inverter by utilizing an improved MPPT algorithm based on the slope variation in the power-voltage characteristic curve of the photovoltaic generator set;
the control module is used for controlling the on-off of the IGBT in the photovoltaic inverter based on the direct-current side voltage reference value of the photovoltaic inverter;
the improved MPPT algorithm is improved in that a power disturbance term on the direct current side of the photovoltaic inverter is introduced into an active variation quantity calculation formula on the direct current side of the photovoltaic inverter of the MPPT algorithm.
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CN114884139A (en) * 2022-05-12 2022-08-09 湖南工业大学 Photovoltaic inverter droop control method with maximum power point tracking function
WO2024022543A1 (en) * 2022-07-27 2024-02-01 国网青海省电力公司电力科学研究院 Consistency algorithm-based distributed frequency control method for photovoltaic power station partition

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CN114884139A (en) * 2022-05-12 2022-08-09 湖南工业大学 Photovoltaic inverter droop control method with maximum power point tracking function
CN114884139B (en) * 2022-05-12 2024-05-31 湖南工业大学 Photovoltaic inverter droop control method with maximum power point tracking function
WO2024022543A1 (en) * 2022-07-27 2024-02-01 国网青海省电力公司电力科学研究院 Consistency algorithm-based distributed frequency control method for photovoltaic power station partition

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