CN115483707B - Power system frequency situation prediction method considering photovoltaic frequency modulation - Google Patents

Power system frequency situation prediction method considering photovoltaic frequency modulation Download PDF

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CN115483707B
CN115483707B CN202211250651.7A CN202211250651A CN115483707B CN 115483707 B CN115483707 B CN 115483707B CN 202211250651 A CN202211250651 A CN 202211250651A CN 115483707 B CN115483707 B CN 115483707B
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frequency
photovoltaic
power system
power
frequency modulation
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CN115483707A (en
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周吉
茆超
张冲标
毕江林
陈金威
钱俊良
翟相秋
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Nanjing Dongbo Intelligent Energy Research Institute Co ltd
Liyang Research Institute of Southeast University
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Nanjing Dongbo Intelligent Energy Research Institute Co ltd
Liyang Research Institute of Southeast University
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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
    • 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
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/48—Controlling the sharing of the in-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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • 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

Abstract

The invention belongs to the field of power systems, and discloses a power system frequency situation prediction method considering photovoltaic frequency modulation, which comprises the following steps: step 1, a traditional power system frequency response model and a photovoltaic unit frequency response model are established, and a power system frequency response model considering photovoltaic participation in frequency modulation is established by integrating control modes of all frequency modulation units; step 2, quantitatively analyzing the frequency characteristics of the power system under the condition that multiple resources participate in frequency modulation by using a model analysis method, and calculating a system frequency characteristic transfer function, an initial frequency change rate and a steady-state frequency error; and 3, verifying the frequency characteristic analysis of the photovoltaic participation power system through a MATLAB/Simulink simulation platform. When the unit control parameters are determined, the absolute value of the initial frequency variation of the power system can be reduced by improving the load damping coefficient, and meanwhile, the steady-state frequency of the power grid can be improved, and the frequency stability of the power grid can be improved.

Description

Power system frequency situation prediction method considering photovoltaic frequency modulation
Technical Field
The invention relates to the technical field of power systems, in particular to a power system frequency situation prediction method considering photovoltaic frequency modulation.
Background
Along with the proposal of the double-carbon target, the power generation physical architecture of the Chinese power grid is changing rapidly. Among them, low carbon and high cleanliness of power generation resources at the power grid source side gradually become a trend. The renewable energy source represented by the photovoltaic is applied on a large scale, so that the problems of traditional coal pollution, high energy consumption and high cost are effectively solved. However, the conventional inertia of the power system is rapidly reduced by the replaced measure of the high-proportion synchronous power generation unit, and a plurality of frequency stability problems of the power system are caused. Therefore, how to predict and analyze the frequency safety and stability problem of the operation after the high-proportion photovoltaic grid connection is needed to be researched.
Currently, research on actively participating in frequency modulation aiming at a power grid source side power generation unit is relatively abundant, and the research mainly starts from the following directions:
1) The load change control is flexibly utilized, the load shedding rate reference value is converted into a photovoltaic direct-current voltage reference value based on discrete electrical data, and the active modulation of the power grid is realized through the adjustment of a photovoltaic array; 2) The frequency modulation power is used as a research object, and the step tracking mode is used for improving the dynamic and steady-state performance of the power, so that the frequency stability of the power system is improved. The research plays an active role in actively participating in frequency modulation of the power grid source side power generation unit, and is deficient in research on the frequency situation of the power system with photovoltaic participating in frequency modulation.
Disclosure of Invention
In order to solve the problems, the invention discloses a method for predicting the frequency situation of a power system by considering photovoltaic frequency modulation, and based on a traditional thermal power frequency response model, a photovoltaic additional frequency control unit is considered to analyze the frequency characteristics of a novel power system by taking photovoltaic participation in frequency modulation.
In order to achieve the above object, the present invention is realized by the following technical scheme:
the invention relates to a power system frequency situation prediction method considering photovoltaic frequency modulation, which comprises the following steps:
step 1, a traditional power system frequency response model and a photovoltaic unit frequency response model are established, and a power system frequency response model considering photovoltaic participation in frequency modulation is established by integrating control modes of all frequency modulation units;
step 2, quantitatively analyzing the frequency characteristics of the power system under the condition that multiple resources participate in frequency modulation by using a model analysis method, and calculating a system frequency characteristic transfer function, an initial frequency change rate and a steady-state frequency error;
and 3, verifying the frequency characteristic analysis of the photovoltaic participation power system through a MATLAB/Simulink simulation platform.
In step 1, the traditional frequency response model of the electric power system keeps the relevant control parameters of the synchronous generator, establishes the number relation of P-f under the operation of the speed regulator of the synchronous generator based on the frequency transfer characteristic of the electric power system,
h is the equivalent inertial time constant of the system; d is damping constant, P L For the active power consumption of the load, R is the primary frequency modulation sagging coefficient, F H Work coefficient T for high-pressure cylinder of prime mover R K is the reheat time constant m For mechanical power factor, P sp To the specific weight of the impact load of the power system to the total load of the system, P m For mechanical power, Δω g And s is a Lawster operator, which is the frequency disturbance quantity of the synchronous machine.
Disturbance of Δp from load L To a frequency disturbance Δω g Is a transfer function of (2):
wherein omega is n For undamped natural frequency, ζ is damping ratio, G 0 Is a proportionality coefficient, z 0 Is the inverse of the prime mover reheat time constant.
And satisfies the following:
if the power system has load active step disturbance, the power grid frequency s domain expression is
Wherein omega is d To damp natural frequency f pu For the reference value (per unit value) of the grid frequency, f ref_pu =1/s, G (s)/s is a frequency disturbance value (per unit value).
Carrying out Laplace inverse transformation on the power grid frequency s domain expression to obtain the frequency expression of the power grid frequency in the time domain as follows:
wherein A is amplitude, beta is phase, and
in step 1, in the photovoltaic fm frequency response model, the conventional inertia control strategy of the photovoltaic is implemented by the dynamic characteristics of the pll, and the following formula is the frequency under pll control:
in U tq Is the q-axis component, k of the inverter terminal voltage p 、k i Is a phase-locked loop control parameter.
According toThe above formula can obtain the active power delta P PV1 The increment is:
i.e.
ΔP PV1 ＝2H PV ·Δf·s
Wherein H is PV Is a photovoltaic virtual inertia time constant.
Therefore, if the photovoltaic only adopts the conventional virtual inertia control mode, the transfer function of the frequency model is as follows
When the photovoltaic array is connected with the low-voltage direct-current capacitor, the change of the output power of the photovoltaic array can be realized by changing the voltage of the capacitor. For this purpose, the photovoltaic array is designed to run to the left of the maximum power point. By means of linear fitting, the output power P 2 The method comprises the following steps:
P 2 ＝aU pv +b
where a, b are fitting coefficients and k is a control coefficient.
Linearizing the above formula to obtain the following formula:
ΔP PV2 ＝a·ΔU pv ＝a·k·Δf
therefore, if the photovoltaic only adopts the frequency modulation strategy, the transfer function of the frequency response model is as follows:
the photovoltaic uses a bipolar power generation structure in which a high voltage DC capacitor C is present b At the same time introducing f-U in the outer ring of inverter voltage dc And (5) frequency compensation links. Bipolar power generation, high voltage dc capacitor voltage equation:
wherein C is b 、U dc 、U dczero 、P dc 、P g The power supply is respectively a high-voltage direct-current capacitor, a high-voltage direct-current voltage initial value, direct-current output power and photovoltaic power generation output power.
Linearizing the above formula:
wherein DeltaP pv 、ΔU dc The power variation and the high-voltage direct-current voltage variation of the photovoltaic unit are respectively.
The transfer function of the frequency response model of the available photovoltaic power generation unit is as follows
Wherein k is pv Is the photovoltaic cell time constant.
In step 1, the penetration of the new energy power generation unit gradually increases the consideration of the grid frequency modulation resource to the unsynchronized power generation unit. The traditional thermal power and the photovoltaic are considered to participate in active modulation of the power system at the same time, so that the system frequency modulation is realized.
Number relationship of power system frequency, power:
when the power disturbance delta P occurs in the power grid L When the power system power variation is:
ΔP＝-ΔP L -ΔP PV -ΔP R
＝-ΔP L -{G pv (s)+G R (s)}·Δf
wherein G is R (s) is the traditional thermal power frequencyResponse transfer function, and satisfies:
in step 2, a model analysis method is utilized, and based on a classical low-order power system frequency corresponding model, a power system frequency response model under the condition that new energy participates in frequency modulation is established by considering the traditional synchronous generator and photovoltaic participation in frequency modulation. The frequency characteristic transfer function of the available power system is as follows:
the frequency domain expression of the power system frequency variation can be obtained by the above formula:
wherein a is a polynomial on the frequency domain differential operator s and satisfies:
A＝k pv C b U dczero +H pv +2H。
in the step 2, when disturbance occurs in the power system, calculating the initial change rate of the frequency of the power system under the condition of photovoltaic participation frequency modulation according to an initial value theorem
From the above formula, the photovoltaic power generation adopts bipolar power generation and introduces f-U in the outer ring dc In the frequency compensation link, when certain power disturbance occurs, the initial frequency change rate of the power system, the photovoltaic response coefficient, the high-voltage direct-current capacitor, the direct-current voltage initial value and the photovoltaic unitThe constant is related to the inertia time constant of the power system, namely the initial frequency change rate of the power system is only related to the control parameters of the photovoltaic frequency modulation unit and the equivalent inertia of the system.
In the step 2, the steady-state frequency error directly reflects the steady-state frequency characteristic of the power system, and the steady-state frequency error of the power system after being subjected to power disturbance is quantitatively calculated based on a final value theorem:
as can be seen from the above equation, the steady-state frequency error is related to the thermal primary sag factor, but is independent of the control factor of the photovoltaic fm unit.
And (5) examining the influence of the load damping on the frequency of the power system. Deriving a damping coefficient according to a steady-state frequency error formula of the power system:
the derivation of the face formula shows that when ΔP L When the steady-state frequency error is larger than zero, the deviation of the steady-state frequency error to the damping coefficient D is larger than zero, namely, the magnitude of the steady-state frequency error value of the power system is increased along with the increase of the damping coefficient.
According to the steady-state frequency error formula of the power system, when the primary frequency modulation droop coefficient, the damping coefficient and the power disturbance value of the synchronous generator are all larger than zero, the steady-state frequency error value of the power system is smaller than zero. Therefore, according to the steady-state frequency error formula and the damping coefficient derivative formula of the power system, the steady-state characteristic of the power system is correspondingly improved along with the increase of the damping coefficient.
In step 3, a new energy power system frequency response model considering photovoltaic frequency modulation is established based on MATLAB/Simulink. The photovoltaic module adopts a bipolar photovoltaic power generation structure, the inverter collects dynamic characteristics of a high-voltage side direct current capacitor to simulate inertia response of the synchronous generator, low-voltage direct current voltage is maintained at a fixed value, and steady-state value of output power of the photovoltaic array is unchanged.
The invention has the beneficial effects that:
the load change control is used for converting the load shedding rate reference value into a photovoltaic direct-current voltage reference value based on discrete electrical data, and the active modulation of the power grid is realized through the adjustment of a photovoltaic array; frequency modulation power is taken as a research object, and step tracking mode is used for improving dynamic and steady-state performance of power, so that frequency stability of a power system is improved
Drawings
FIG. 1 is a specific step of a novel power system frequency situation prediction method considering photovoltaic frequency modulation;
FIG. 2 is a frequency response model of a conventional power system;
FIG. 3 is a model of the frequency response of a photovoltaic unit
FIG. 4 is an aggregate power system frequency response model;
FIG. 5 is a three-dimensional factor graph of the initial frequency change rate of the power system;
FIG. 6 is a graph of system frequency for different modulation schemes;
FIG. 7 is a plot of the rate of change of system frequency for different photovoltaic inertial time constants;
FIG. 8 is a plot of system frequency for different damping coefficients.
Detailed Description
The present invention is further illustrated in the following drawings and detailed description, which are to be understood as being merely illustrative of the invention and not limiting the scope of the invention. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to directions in the drawings, and the words "inner" and "outer" refer to directions toward or away from, respectively, the geometric center of a particular component.
As shown in fig. 1, the specific steps of the power system frequency situation prediction method considering photovoltaic frequency modulation in the invention are as follows:
step 1, a traditional power system frequency response model and a photovoltaic unit frequency response model are established, and a power system frequency response model considering photovoltaic participation in frequency modulation is established by integrating control modes of all frequency modulation units;
step 2, quantitatively analyzing the frequency characteristics of the power system under the condition that multiple resources participate in frequency modulation by using a model analysis method, and calculating a system frequency characteristic transfer function, an initial frequency change rate and a steady-state frequency error;
and 3, verifying the frequency characteristic analysis of the photovoltaic participation power system through a MATLAB/Simulink simulation platform.
In step 1, the conventional frequency response model of the electric power system maintains the relevant control parameters of the synchronous generator, and establishes the number relationship of P-f under the operation of the speed regulator of the synchronous generator based on the frequency transfer characteristic of the electric power system, as shown in fig. 2.
In fig. 2, H is the system equivalent inertial time constant; d is damping constant, P L For the active power consumption of the load, R is the primary frequency modulation sagging coefficient, F H Work coefficient T for high-pressure cylinder of prime mover R K is the reheat time constant m For mechanical power factor, P sp To the specific weight of the impact load of the power system to the total load of the system, P m For mechanical power, Δω g And s is a Lawster operator, which is the frequency disturbance quantity of the synchronous machine.
From FIG. 2, the slave load disturbance ΔP can be calculated L To a frequency disturbance Δω g Is a transfer function of (2):
wherein omega is n For undamped natural frequency, ζ is damping ratio, G 0 Is a proportionality coefficient, z 0 Is the inverse of the prime mover reheat time constant.
And satisfies the following:
if the power system has load active step disturbance, the power grid frequency s domain expression is
Wherein omega is d To damp natural frequency f pu For the reference value (per unit value) of the grid frequency, f ref_pu =1/s, G (s)/s is a frequency disturbance value (per unit value).
Carrying out Laplace inverse transformation on the power grid frequency s domain expression to obtain the frequency expression of the power grid frequency in the time domain as follows:
wherein A is amplitude, beta is phase, and
in step 1, in the photovoltaic fm frequency response model, the conventional inertia control strategy of the photovoltaic is implemented by the dynamic characteristics of the pll, and the following formula is the frequency under pll control:
in U tq Is the q-axis component, k of the inverter terminal voltage p 、k i Is a phase-locked loop control parameter.
The active power DeltaP can be obtained according to the above formula PV1 The increment is:
i.e.
ΔP PV1 ＝2H PV ·Δf·s
Wherein H is PV Is a photovoltaic virtual inertia time constant.
Therefore, if the photovoltaic only adopts the conventional virtual inertia control mode, the transfer function of the frequency model is as follows
When the photovoltaic array is connected with the low-voltage direct-current capacitor, the change of the output power of the photovoltaic array can be realized by changing the voltage of the capacitor. For this purpose, the photovoltaic array is designed to run to the left of the maximum power point. By means of linear fitting, the output power P 2 The method comprises the following steps:
P 2 ＝aU pv +b
where a, b are fitting coefficients and k is a control coefficient.
Linearizing the above formula to obtain the following formula:
ΔP PV2 ＝a·ΔU pv ＝a·k·Δf
therefore, if the photovoltaic only adopts the frequency modulation strategy, the transfer function of the frequency response model is as follows:
the photovoltaic uses a bipolar power generation structure in which there is a high voltageDC capacitor C b At the same time introducing f-U in the outer ring of inverter voltage dc And (5) frequency compensation links. Bipolar power generation, high voltage dc capacitor voltage equation:
wherein C is b 、U dc 、U dczero 、P dc 、P g The power supply is respectively a high-voltage direct-current capacitor, a high-voltage direct-current voltage initial value, direct-current output power and photovoltaic power generation output power.
Linearizing the above formula:
wherein DeltaP pv 、ΔU dc The power variation and the high-voltage direct-current voltage variation of the photovoltaic unit are respectively.
The transfer function of the frequency response model of the available photovoltaic power generation unit is as follows
Wherein k is pv Is the photovoltaic cell time constant. The photovoltaic unit frequency response model is shown in figure 3
In step 1, the penetration of the new energy power generation unit gradually increases the consideration of the grid frequency modulation resource to the unsynchronized power generation unit. The traditional thermal power and the photovoltaic are considered to participate in active modulation of the power system at the same time, so that the system frequency modulation is realized. Fig. 4 is a model of the frequency response of the power system taking into account the participation of photovoltaic in frequency modulation.
From fig. 3, the relationship between the frequency and the power of the power system can be seen:
when the power disturbance delta P occurs in the power grid L When the power system power variation is:
ΔP＝-ΔP L -ΔP PV -ΔP R
＝-ΔP L -{G pv (s)+G R (s)}·Δf
wherein G is R (s) is a traditional thermal power frequency response transfer function, and satisfies:
in step 2, a model analysis method is utilized, and based on a classical low-order power system frequency corresponding model, a power system frequency response model under the condition that new energy participates in frequency modulation is established by considering the traditional synchronous generator and photovoltaic participation in frequency modulation. The frequency characteristic transfer function of the available power system is as follows:
the frequency domain expression of the power system frequency variation can be obtained by the above formula:
wherein a is a polynomial on the frequency domain differential operator s and satisfies:
A＝k pv C b U dczero +H pv +2H
in the step 2, when disturbance occurs in the power system, calculating the initial change rate of the frequency of the power system under the condition of photovoltaic participation frequency modulation according to an initial value theorem
From the above formula, the photovoltaic power generation adopts bipolar power generation and introduces f-U in the outer ring dc And in the frequency compensation link, when certain power disturbance occurs, the initial frequency change rate of the power system is related to the photovoltaic response coefficient, the high-voltage direct-current capacitor, the direct-current voltage initial value, the photovoltaic unit time constant and the power system inertia time constant, namely, the initial frequency change rate of the power system is only related to the control parameters of the photovoltaic frequency modulation unit and the system equivalent inertia.
Fig. 5 is a three-dimensional factor graph of the initial frequency change rate obtained according to the formula (24), and the initial frequency change rate value is per unit value. From fig. 5, it can be seen that the larger the equivalent inertia time constant and the photovoltaic inertia time constant of the system, the smaller the absolute value of the initial change rate of the frequency of the power system.
In the step 2, the steady-state frequency error directly reflects the steady-state frequency characteristic of the power system, and the steady-state frequency error of the power system after being subjected to power disturbance is quantitatively calculated based on a final value theorem:
as can be seen from the above equation, the steady-state frequency error is related to the thermal primary sag factor, but is independent of the control factor of the photovoltaic fm unit.
And (5) examining the influence of the load damping on the frequency of the power system. Deriving a damping coefficient according to a steady-state frequency error formula of the power system:
from the above formula, when ΔP is calculated L When the steady-state frequency error is larger than zero, the deviation of the steady-state frequency error to the damping coefficient D is larger than zero, namely, the magnitude of the steady-state frequency error value of the power system is increased along with the increase of the damping coefficient.
According to the steady-state frequency error formula of the power system, when the primary frequency modulation droop coefficient, the damping coefficient and the power disturbance value of the synchronous generator are all larger than zero, the steady-state frequency error value of the power system is smaller than zero. Therefore, according to the steady-state frequency error formula and the damping coefficient derivative formula of the power system, the steady-state characteristic of the power system is correspondingly improved along with the increase of the damping coefficient.
In step 3, a new energy power system frequency response model considering photovoltaic frequency modulation is established based on MATLAB/Simulink. The photovoltaic module adopts a bipolar photovoltaic power generation structure, the inverter collects dynamic characteristics of a high-voltage side direct current capacitor to simulate inertia response of the synchronous generator, low-voltage direct current voltage is maintained at a fixed value, and steady-state value of output power of the photovoltaic array is unchanged. The frequency characteristic change of the power system under different working conditions is analyzed, the load is 1000MW, the rated power of wind power is 200MW, and the load disturbance is 60MW (0.06 p.u).
In step 3, in order to verify the feasibility of the photovoltaic participation in frequency modulation, quantitative analysis is performed on frequency characteristics under two conditions, and frequency deviation conditions of the power system under different frequency modulation modes are examined. Wherein, set parameters: the wind speed of the wind farm is constant, and parameters of each unit are shown in table 1:
TABLE 1 System parameter set points
The power system frequency changes in different frequency modulation modes are shown in fig. 6.
As can be seen from fig. 6: 1) Compared with the traditional synchronous generator which is used for independently modulating frequency, the frequency stability of the power system under the condition that the photovoltaic participates in frequency modulation is stronger, the absolute value of the maximum frequency deviation is reduced, and the time point of the maximum frequency deviation is delayed; 2) The steady-state frequency error of the photovoltaic participated in frequency modulation is not changed, so that when the power system tends to be stable, the steady-state frequency error is irrelevant to the photovoltaic frequency modulation control parameter, namely the photovoltaic frequency modulation unit does not participate in the frequency modulation of the power system, and the conclusion of the steady-state frequency error formula of the power system is the same.
In step 3, when the traditional synchronous generator set and the new energy photovoltaic set participate in the frequency modulation control parameter determination, the photovoltaic inertia time constant has a certain influence on the frequency change rate of the power system. The frequency modulation control parameters of the traditional thermal power generating unit and the new energy unit refer to the table 1, photovoltaic inertia time constants are set to be 2s, 4s and 6s respectively, and frequency characteristic indexes of a power system such as initial frequency change rate, maximum frequency deviation time and the like of the power system under different photovoltaic inertia time constants are inspected.
As can be seen from fig. 7: 1) As the photovoltaic inertia time constant increases, the absolute value of the initial frequency change rate of the power system is reduced, which is consistent with the conclusion of the equation (24) of section 2.2 and the conclusion of fig. 4; 2) Photovoltaic inertia time constant increases, t 1 <t 2 <t 3 I.e. the time delay for the grid to reach the maximum frequency deviation.
In step 3, along with the improvement of the frequency response capability of the load side, the source-load coordination capability of the novel power system is enhanced, the damping coefficients of different power systems are set in this section, and the frequency stability of the power system is analyzed through simulation. Wherein, the control parameters of the traditional thermal power generating unit and the new energy unit refer to the table 1, different equivalent inertia time constants D are respectively set to be 2, 4 and 8, and a system simulation waveform chart is shown in fig. 8. As can be seen from fig. 8: 1) Along with the increase of the load damping coefficient, the absolute value of the initial frequency change rate of the power system is unchanged, namely the magnitude of the initial frequency change rate is irrelevant to the load damping coefficient and is consistent with the result of the initial frequency change rate formula of the power system under the condition that photovoltaics participate in frequency modulation; 2) The absolute value of the steady-state frequency error is reduced along with the increase of the damping coefficient of the power system, namely the steady-state frequency characteristic of the power system in the photovoltaic participation frequency modulation mode is improved, and the conclusion is the same as that of a damping coefficient formula; 3) When the photovoltaic participates in the frequency modulation control of the traditional power system, the maximum frequency deviation is reduced by increasing the damping coefficient, and the time of the maximum frequency deviation is advanced.
Aiming at the problem of frequency stability of a novel power system, the invention considers the frequency regulation of the power system of the photovoltaic participation, analyzes the influence factors of the frequency stability of the power system under the control strategy of the photovoltaic participation frequency modulation through theoretical quantitative analysis and simulation verification, and the research result shows that:
1) Under the traditional synchronous generator and photovoltaic unit joint participation frequency modulation control strategy, the frequency of the power system is more stable than that of a single thermal power frequency modulation control strategy, and the control strategy of the new energy photovoltaic participation frequency modulation is feasible.
2) The initial frequency change rate of the power system under the condition of photovoltaic participation frequency modulation is related to the control parameters of the photovoltaic frequency modulation unit and the equivalent inertia of the system; when the unit control parameters are determined, the load damping coefficient is improved, the absolute value of the initial frequency change rate of the power system can be reduced, the steady-state frequency of the power grid can be improved, and the frequency stability of the power grid can be improved.
The technical means disclosed by the scheme of the invention is not limited to the technical means disclosed by the embodiment, and also comprises the technical scheme formed by any combination of the technical features.

Claims (1)

1. The power system frequency situation prediction method considering photovoltaic frequency modulation is characterized by comprising the following steps of:
step 1, a traditional power system frequency response model and a photovoltaic unit frequency response model are established, and a power system frequency response model considering photovoltaic participation in frequency modulation is established by integrating control modes of all frequency modulation units;
the slave load disturbance delta P can be calculated according to the traditional power system frequency response model L To a frequency disturbance Δω g Is a transfer function of (2):
wherein omega is n For undamped natural frequency, ζ is damping ratio, G 0 Is a proportionality coefficient, z 0 Reciprocal of the prime mover reheat time constant; h is the equivalent inertial time constant of the system; d is damping constant, R is primary frequency modulation sagging coefficient, F H Work coefficient T for high-pressure cylinder of prime mover R S is a Law operator and is a reheat time constant;
in step 1, if a load active step disturbance occurs in the power system, the power grid frequency s domain expression is:
wherein G is 0 Is a proportionality coefficient; omega d To damp natural frequency f pu Is the reference value of the frequency of the power grid, f ref_pu =1/s, G (s)/s is the frequency disturbance value expressed in per unit value, ζ is the damping ratio, ω n To be undamped in natural frequency, z 0 S is a Law operator, which is the reciprocal of the reheating time constant of the prime motor;
carrying out Laplace inverse transformation on the formula to obtain a frequency expression of the grid frequency in the time domain, wherein the frequency expression is as follows:
wherein A1 is amplitude, beta is phase, G 0 Is a proportionality coefficient, z 0 Is the reciprocal of the reheating time constant of the prime motor, omega d To damp natural frequency omega n Is natural frequency without damping, t is time, and xi is damping ratio; and is also provided with
The conventional inertia control strategy of the photovoltaic is realized through the dynamic characteristics of a phase-locked loop, and the frequency expression under the control of the phase-locked loop is as follows:
in U tq Is the q-axis component, k of the inverter terminal voltage p 、k i Is a phase-locked loop control parameter;
if the photovoltaic only adopts the conventional virtual inertia control mode, the transfer function of the frequency model is as follows
Wherein DeltaP PV1 Only labeling function, representing the active power increment when only adopting a conventional virtual inertia control mode, wherein Deltaf is the frequency change frequency domain of the power system, and H pv The virtual inertia time constant is photovoltaic, s is a pull operator;
if the photovoltaic adopts a frequency modulation strategy considering the p-U external characteristics, the transfer function of the frequency response model is that
Wherein DeltaP PV1 Only labeling, namely the active power increment when only adopting a conventional virtual inertia control mode, wherein Deltaf is the frequency domain of the frequency change of the power system, and a and k are fitting coefficients;
in the step 1, a photovoltaic frequency modulation frequency response model integrating virtual inertia control and P-U external characteristics is obtained, and a transfer function of the photovoltaic power generation unit frequency response model is obtained as follows
Wherein DeltaP PV As the photovoltaic variation, Δf is the frequency domain of the power system frequency variation, k pv Is the time constant of the photovoltaic unit, s is a pull operator, and C b U is a high-voltage direct-current capacitor dczero Is the initial value of high-voltage direct-current voltage, H pv Is a photovoltaic virtual inertia time constant;
step 2, quantitatively analyzing the frequency characteristics of the power system under the condition that multiple resources participate in frequency modulation by using a model analysis method, and calculating a system frequency characteristic transfer function, an initial frequency change rate and a steady-state frequency error;
based on a classical low-order power system frequency corresponding model by using a model analysis method, taking the traditional synchronous generator and the photovoltaic participation in frequency modulation into consideration, establishing a power system frequency response model under the participation of new energy in frequency modulation,
the frequency characteristic transfer function is
Wherein Δf is the frequency domain of the power system frequency variation, ΔP L G is power disturbance pv (s) is the transfer function of the frequency response model of the photovoltaic power generation unit, G R (s) is a traditional thermal power frequency response transfer function, H is a system equivalent inertia time constant, s is a Lawster operator, and D is a damping constant; k (k) pv For photovoltaic control factor, C b U is a high-voltage direct-current capacitor dczero Is the initial value of high-voltage direct-current voltage, H pv Is a photovoltaic virtual inertia time constant, k m For mechanical power factor, F H Work coefficient T for high-pressure cylinder of prime mover R R is a primary frequency modulation sagging coefficient, which is a reheat time constant;
the frequency domain expression of the frequency variation of the power system is
Wherein G is sys (s) is the transfer function of the frequency characteristic of the power system, delta P L (s) is a power disturbance function, R is a primary frequency modulation droop coefficient, T R Is reheat time constant, s is Lawster operator, D is damping constant, k m For mechanical power factor, F H For the prime mover high pressure cylinder acting coefficient, A is a polynomial about a frequency domain differential operator s, and satisfies:
A＝k pv C b U dczero +H pv +2H；
wherein k is pv For photovoltaic control factor, C b U is a high-voltage direct-current capacitor dczero Is the initial value of high-voltage direct-current voltage, H pv The system is characterized in that the system is a photovoltaic virtual inertia time constant, and H is a system equivalent inertia time constant;
when the power system is disturbed, calculating the initial change rate of the frequency of the power system under the condition of photovoltaic participation frequency modulation according to the initial value theorem
The initial frequency change rate of the power system is only related to the control parameters of the photovoltaic frequency modulation unit and the equivalent inertia of the system; wherein Deltaf (t) is a frequency domain function of the frequency change of the power system, s is a Law operator, deltaP L (s) is a power disturbance function, G sys (s) is the transfer function of the frequency characteristic of the power system, k pv For photovoltaic control factor, C b U is a high-voltage direct-current capacitor dczero For the initiation of high-voltage DC voltageA value; h pv The system is characterized in that the system is a photovoltaic virtual inertia time constant, and H is a system equivalent inertia time constant;
steady state frequency error of power system after power disturbance
The control coefficient of the photovoltaic frequency modulation unit is related to the primary frequency modulation sagging coefficient of the thermal power, but is not related to the control coefficient of the photovoltaic frequency modulation unit;
wherein DeltaP L (s) is a power disturbance function, G sys (s) is the transfer function of the frequency characteristic of the power system, s is a Lawster operator, D is a damping constant, R is a primary frequency modulation droop coefficient, and k m Is a mechanical power factor.
And 3, verifying the frequency characteristic analysis of the photovoltaic participation power system through a MATLAB/Simulink simulation platform.
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107968441A (en) * 2017-11-16 2018-04-27 国家电网公司华中分部 A kind of mains frequency situation on-line prediction method for considering wind-powered electricity generation and Demand Side Response
CN108964032A (en) * 2018-07-13 2018-12-07 华北电力大学（保定） A method of establishing the system frequency response model containing wind-powered electricity generation
CN109103927A (en) * 2018-08-23 2018-12-28 国网江苏省电力有限公司 Improve the speed-regulating system PID controller parameter setting method of primary frequency modulation dynamic response characteristic
CN113364006A (en) * 2021-05-21 2021-09-07 大连理工大学 Electrochemical energy storage two-type adjusting parameter selection and setting method in multi-resource frequency response
CN113904386A (en) * 2021-10-25 2022-01-07 国网宁夏电力有限公司 Photovoltaic frequency modulation control parameter optimization method considering equivalent inertia and damping requirements

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107968441A (en) * 2017-11-16 2018-04-27 国家电网公司华中分部 A kind of mains frequency situation on-line prediction method for considering wind-powered electricity generation and Demand Side Response
CN108964032A (en) * 2018-07-13 2018-12-07 华北电力大学（保定） A method of establishing the system frequency response model containing wind-powered electricity generation
CN109103927A (en) * 2018-08-23 2018-12-28 国网江苏省电力有限公司 Improve the speed-regulating system PID controller parameter setting method of primary frequency modulation dynamic response characteristic
CN113364006A (en) * 2021-05-21 2021-09-07 大连理工大学 Electrochemical energy storage two-type adjusting parameter selection and setting method in multi-resource frequency response
CN113904386A (en) * 2021-10-25 2022-01-07 国网宁夏电力有限公司 Photovoltaic frequency modulation control parameter optimization method considering equivalent inertia and damping requirements

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
电池储能参与电网一次调频的自适应综合控制策略研究;吴启帆 等;电网技术;第44卷(第10期);3829-3836 *

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