CN111555307A - Method for photovoltaic power station to participate in regional power grid frequency adjustment - Google Patents
Method for photovoltaic power station to participate in regional power grid frequency adjustment Download PDFInfo
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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
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- H—ELECTRICITY
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- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/48—Controlling the sharing of the in-phase component
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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- 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
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Abstract
According to the method for the photovoltaic power station to participate in the frequency adjustment of the regional power grid, inverter control participating in the rapid frequency modulation photovoltaic square matrix is modified, so that the method has a single-machine primary frequency modulation function based on change rate frequency modulation and change amount frequency modulation under different active power, and continuous frequency modulation of the rapid frequency modulation and the change amount frequency modulation based on the change rate frequency modulation can be realized; modifying the photovoltaic power station to be not involved in the control of the photovoltaic square matrix inverter of the rapid frequency modulation, so that the photovoltaic square matrix inverter has a primary frequency modulation function based on variable frequency modulation, and can realize continuous frequency modulation; the photovoltaic array and the frequency modulation parameters of the rapid frequency modulation are reasonably set according to the needs of the power grid, so that the frequency support of the photovoltaic to the asynchronous transmitting end power grid can be realized. The method only needs to modify and upgrade control software, does not need to increase and modify hardware and communication, has low modification cost, has shorter response time and higher speed of single-machine frequency modulation response than station-level frequency modulation control, and can provide quick frequency support for an asynchronous transmitting end power grid.
Description
Technical Field
The application relates to the technical field of power system frequency adjustment, in particular to a method for a photovoltaic power station to participate in regional power grid frequency adjustment.
Background
After asynchronous networking of an asynchronous transmitting-end power grid, namely a regional power grid and a main grid is realized, the regional power grid can form a large-machine small-grid multi-direct-current transmitting-end power grid, so that the capacity of the regional power grid is reduced, the disturbance resistance is weakened, and the frequency stability problem replaces the transient stability problem and becomes the main problem threatening the safe and stable operation of the regional power grid. Therefore, new energy of a regional power grid is rapidly developed, by 2018 years in part of province and city regions, the installed proportion of the new energy of the regional power grid reaches 14.45%, the wind power generation capacity exceeds that of thermal power and becomes a second big power supply, and due to the policy of national total consumption of new energy, the power generation proportion of the new energy is continuously increased, during a dry season, particularly during the period of the year, the power generation proportion of the new energy of part of regions reaches 50%, the new energy of large-scale high-proportion power generation is connected to the grid for power generation and does not participate in power grid frequency modulation, and the problem of regional power grid frequency stability is aggravated.
One method adopted for the problem of local power grid stability at present is a primary frequency modulation control method of a photovoltaic power station to control the frequency stability of a regional power grid, wherein the photovoltaic power station comprises a photovoltaic power station and a field station control system; the photovoltaic power station comprises a photovoltaic array and a photovoltaic inverter, wherein the photovoltaic inverter converts direct current electric energy generated by the photovoltaic array into alternating current electric energy; and the station control cabinet is configured to determine the single-machine active power variation according to the running state of the photovoltaic inverter and adjust the active power output by the photovoltaic inverter when the frequency value of the grid-connected point of the photovoltaic power station meets a preset primary frequency modulation triggering condition. The method for realizing the frequency stability of the control area power grid by depending on the field station control cabinet requires adding the field station control cabinet in the secondary equipment room of the booster station of the power station, and simultaneously requires modifying the software of the inverter and transforming the communication from the station-level frequency modulation controller to the photovoltaic inverter. When the frequency of the power grid changes, the station control cabinet is configured to calculate a total active power increment value of the grid-connected point according to the frequency value of the grid-connected point when the frequency value of the grid-connected point meets the primary frequency modulation triggering condition, and generate a single-machine primary frequency modulation command according to the running state of the photovoltaic inverter; and the single machine frequency modulation module is connected with the corresponding photovoltaic inverter and is configured to adjust the active power output by the corresponding photovoltaic inverter according to the single machine primary frequency modulation instruction.
The existing method needs to determine a single-machine active power variation instruction according to the operation state of photovoltaic when a site station control system detects that the frequency variation exceeds a dead zone, and issues a single-machine active power adjustment instruction, a photovoltaic inverter outputs corresponding active power after receiving the instruction, and the communication time between the site station control system and the photovoltaic inverter is long, so that the single-machine frequency response is slow, and the asynchronous sending-end power grid is difficult to meet the requirement of rapid frequency modulation. The frequency modulation method of the existing station control system adopts a variable-quantity-based frequency modulation mode, the stability of the power grid frequency is considered, and when the frequency modulation is matched with different energy situations, a dead zone of a new energy station based on variable-quantity frequency modulation is generally required to be +/-0.05 Hz, so that the existing method cannot respond to the frequency change of the variable quantity lower than 0.05Hz, and the frequency fluctuation of the power grid at a transmitting end under small interference is frequent. Meanwhile, the existing primary frequency modulation method of the photovoltaic power station is mainly realized by depending on a station control cabinet, but the existing photovoltaic station basically has no configuration, a large amount of equipment transformation is needed, and the software and hardware investment is large.
Disclosure of Invention
The application provides a method for a photovoltaic power station to participate in regional power grid frequency adjustment, and aims to solve the problems that in the existing method for realizing station-level frequency modulation by depending on a station control cabinet, the station control cabinet is required to generate a single-machine primary frequency modulation command according to power grid frequency change and the running state of a photovoltaic inverter, and the frequency modulation command calculation, command issuing and command response time are slower than that of single-machine frequency modulation, so that the requirement of fast frequency modulation of an asynchronous transmitting-end power grid cannot be met.
The technical scheme adopted by the application for solving the technical problems is as follows:
a method of a photovoltaic power plant participating in regional grid frequency regulation, the method comprising the steps of:
the method comprises the steps of building an asynchronous transmitting end power grid electromechanical transient model containing new energy primary frequency modulation, simulating and calculating new energy rapid frequency modulation capacity required by rapid frequency modulation of each photovoltaic power station of a transmitting end power grid under small interference, calculating rapid frequency modulation capacity required by each photovoltaic power station in the power grid according to installation conditions of the new energy field of the transmitting end power grid, and determining the minimum photovoltaic square matrix quantity participating in rapid frequency modulation under different active power according to the calculated new energy rapid frequency modulation capacity required by rapid frequency modulation of each photovoltaic power station and the power generation characteristics of the photovoltaic power stations;
according to the change characteristic of active power along with time in the photovoltaic power station and the rapid frequency modulation capacity required to be provided by the photovoltaic power station, calculating the number of photovoltaic matrixes participating in rapid frequency modulation under different active powers, and modifying the control of inverters participating in the rapid frequency modulation photovoltaic matrixes to enable the inverters to have a single-machine primary frequency modulation function based on change rate frequency modulation and change amount frequency modulation under different active powers;
and modifying the control of other photovoltaic inverters in the whole station except for participating in the rapid frequency modulation so as to enable the photovoltaic inverters to have a single-machine primary frequency modulation function based on the variable frequency modulation.
Optionally, the new energy fast frequency modulation capacity required by the fast frequency modulation of each photovoltaic power station is calculated by using the following formula:
the capacity of the new energy rapid frequency modulation is { (the capacity of the new energy rapid frequency modulation under small interference/the total installed capacity of the new energy of the transmission end power grid) the capacity of the photovoltaic power station }.
Optionally, the minimum number of photovoltaic matrixes participating in the fast frequency modulation under different active powers is calculated by the following formula:
the minimum photovoltaic square matrix quantity participating in the rapid frequency modulation under different active power is the capacity of the rapid frequency modulation of the new energy under small interference/the total installed capacity of the new energy of the transmission-end power grid/the capacity of a photovoltaic power station/the capacity of a single photovoltaic square matrix in different periods.
Optionally, according to the variation characteristic of the active power in the photovoltaic power station along with time and the fast frequency modulation capacity required to be provided by the photovoltaic power station, calculating the number of photovoltaic matrixes participating in fast frequency modulation under different active powers, and modifying inverter control participating in the fast frequency modulation photovoltaic matrixes to enable the photovoltaic matrixes to have a single-machine primary frequency modulation function based on the variation rate frequency modulation and the variation amount frequency modulation under different active powers, the method includes the following steps:
grouping the photovoltaic square matrix, collecting the active power historical curves of the two photovoltaic square matrices according to
Two photovoltaic square matrixes of a photovoltaic power station are divided into different groups with consistency of active power, wherein t is0Representing the starting moment of the detected active power curve; t represents each time point in the dynamic process; v (t) represents a dynamic response value at time t; i. j represents two photovoltaic square arrays; r isigCorrelation coefficients of active power responses of the two photovoltaic square arrays;
setting the quantity and theoretical grade of the photovoltaic square matrixes participating in the rapid frequency modulation according to the grouping result of the photovoltaic square matrixes and the principle that the total frequency modulation power of the photovoltaic square matrixes participating in the rapid frequency modulation at different time periods is equal;
and modifying the control of the photovoltaic array inverter participating in the rapid frequency modulation to enable the photovoltaic array inverter to have the function of automatically switching on and off the primary frequency modulation of the single frequency modulation based on the change rate and the change quantity under different active power.
Optionally, the grouping of the photovoltaic square matrix includes grouping the photovoltaic square matrix of the photovoltaic power station according to the active power curve consistency principle.
Optionally, the photovoltaic matrix inverter control that participates in the fast frequency modulation is modified, so that the photovoltaic matrix inverter control has the function of automatically switching on and off the primary frequency modulation function based on the change rate and the change amount of the frequency modulation single machine according to different active powers, and the method includes the following steps:
calculating the power grid frequency change rate df/dt and the power grid frequency change delta f in real time according to the collected power grid voltage data; setting a frequency modulation of the frequency change rate of the power grid, a variable frequency modulation dead zone and a frequency modulation parameter;
when a power grid is just disturbed and the change rate and the change quantity of the power grid frequency do not exceed the dead zone, the primary frequency modulation function of the photovoltaic matrix inverter participating in the rapid frequency modulation does not respond;
when the frequency change rate df/dt exceeds the dead zone and is greater than 0 and the change amount does not exceed the dead zone, the photovoltaic square matrix inverter participating in the rapid frequency modulation is controlled according to the control principle
Calculating the power variation corresponding to the frequency variation rate to change the active power, wherein Δ P is the active power variation, TjIs the rotational inertia of the generator; f. ofNThe system rated frequency, Hz; pNRated power, MW;
when the frequency change rate df/dt exceeds the dead zone and is greater than 0, and the frequency change amount exceeds the dead zone, participating in the control of the rapid frequency modulation photovoltaic square matrix inverter to perform frequency modulation according to the frequency modulation of the change rate and the frequency modulation of the change amount;
and when the frequency change rate df/dt exceeds the dead zone and is less than 0, and the frequency change amount exceeds the dead zone, participating in the control of the fast frequency modulation photovoltaic square matrix inverter to modulate frequency according to the frequency change amount.
Optionally, modifying the control of other photovoltaic inverters in the total station except for participating in the fast frequency modulation to make the inverter have a single-machine primary frequency modulation function based on the variation frequency modulation, includes:
when the power grid is just disturbed and the power grid frequency variation does not exceed the dead zone, the primary frequency modulation functions of other photovoltaic inverters in the whole station except for participating in the rapid frequency modulation do not respond;
when the frequency variation exceeds the dead zone, the frequency modulation is carried out by controlling other photovoltaic inverters of the whole station except the photovoltaic inverters participating in the rapid frequency modulation according to the frequency variation.
The technical scheme provided by the application comprises the following beneficial technical effects:
according to the method for the photovoltaic power station to participate in the frequency adjustment of the regional power grid, inverter control participating in the rapid frequency modulation photovoltaic square matrix is modified, so that the method has a single-machine primary frequency modulation function based on change rate frequency modulation and change amount frequency modulation under different active power, and continuous frequency modulation of the rapid frequency modulation and the change amount frequency modulation based on the change rate frequency modulation can be realized; modifying the photovoltaic power station to be not involved in the control of the photovoltaic square matrix inverter of the rapid frequency modulation, so that the photovoltaic square matrix inverter has a primary frequency modulation function based on variable frequency modulation, and can realize continuous frequency modulation; the photovoltaic array and the frequency modulation parameters of the rapid frequency modulation are reasonably set according to the needs of the power grid, so that the frequency support of the photovoltaic to the asynchronous transmitting end power grid can be realized. The method only needs modification and upgrading of control software, does not need addition and modification of hardware and communication, is low in modification cost, has shorter response time and higher speed of single-machine frequency modulation response than station-level frequency modulation control, can provide quick frequency support for an asynchronous transmitting-end power grid, has no mechanical rotating part in a photovoltaic square matrix, and can complete the function of primary frequency modulation only by modifying the control of an inverter. The method provided by the application solves the problems that the existing method for realizing station-level frequency modulation by depending on a station control cabinet needs the station control cabinet to generate a single-machine primary frequency modulation command according to the frequency change of a power grid and the running state of a photovoltaic inverter, the frequency modulation command calculation, command issuing and command response time are slower than that of single-machine frequency modulation, and the requirement of the asynchronous sending-end power grid on quick frequency modulation cannot be met.
Drawings
In order to more clearly explain the technical solution of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious to those skilled in the art that other drawings can be obtained according to the drawings without any creative effort.
Fig. 1 is a flowchart of a method for a photovoltaic power station to participate in frequency adjustment of a regional power grid according to an embodiment of the present application;
fig. 2 is a primary frequency modulation active-frequency curve of a wind turbine generator provided in an embodiment of the present application;
fig. 3 is a primary frequency modulation active-frequency curve of a photovoltaic power station according to an embodiment of the present application.
Detailed Description
In order to make the technical solutions in the present application better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application; it is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. 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 application.
Referring to fig. 1, fig. 1 is a flowchart of a method for a photovoltaic power plant to participate in regional power grid frequency adjustment according to an embodiment of the present application, where the method includes the following steps:
s1: the method comprises the steps of building an asynchronous transmitting end power grid electromechanical transient model containing new energy primary frequency modulation, simulating and calculating new energy rapid frequency modulation capacity required by rapid frequency modulation of each photovoltaic power station of a transmitting end power grid under small interference, calculating rapid frequency modulation capacity required by each photovoltaic power station in the power grid according to installation conditions of the new energy field of the transmitting end power grid, and determining the minimum photovoltaic square matrix quantity participating in rapid frequency modulation under different active power according to the calculated new energy rapid frequency modulation capacity required by rapid frequency modulation of each photovoltaic power station and the power generation characteristics of the photovoltaic power stations;
the capacity of the new energy rapid frequency modulation required by rapid frequency modulation of each photovoltaic power station is calculated by adopting the following formula:
the capacity of the new energy rapid frequency modulation is { (the capacity of the new energy rapid frequency modulation under small interference/the total installed capacity of the new energy of the transmission end power grid) the capacity of the photovoltaic power station }.
The minimum photovoltaic array quantity participating in the rapid frequency modulation under different active powers is calculated by the following formula:
the minimum photovoltaic square matrix quantity participating in the rapid frequency modulation under different active power is the capacity of the rapid frequency modulation of the new energy under small interference/the total installed capacity of the new energy of the transmission-end power grid/the capacity of a photovoltaic power station/the capacity of a single photovoltaic square matrix in different periods.
S2: according to the change characteristic of active power along with time in the photovoltaic power station and the rapid frequency modulation capacity required to be provided by the photovoltaic power station, calculating the number of photovoltaic matrixes participating in rapid frequency modulation under different active powers, and modifying the control of inverters participating in the rapid frequency modulation photovoltaic matrixes to enable the inverters to have a single-machine primary frequency modulation function based on change rate frequency modulation and change amount frequency modulation under different active powers;
based on the fact that different photovoltaic matrixes of the same photovoltaic power station are located in different external environments and the same power station has units of different manufacturers, dynamic performances of different inverters are different, and therefore the photovoltaic matrixes of different manufacturers can participate in rapid frequency reliable response of a power grid, and the photovoltaic matrixes with the same external characteristic curve must be selected to participate in rapid frequency modulation.
Grouping photovoltaic power station photovoltaic square matrixes, wherein the dynamic characteristics of the photovoltaic square matrixes mainly comprise illumination intensity, temperature and real-time active power, and the photovoltaic square matrixes of the photovoltaic power stations are grouped according to the principle that active power curves are consistent as primary frequency modulation actually changes active changes according to set frequency change responses;
grouping indexes: and (3) making the grouped samples as active power curves, judging the similarity of active power dynamic curves of different photovoltaic matrixes by adopting a related system method, and defining the similarity:
in the formula: t is t0Representing the starting moment of the detected active power curve; t represents each time point in the dynamic process; v (t) represents a dynamic response value at time t; i. j represents two photovoltaic square arrays; r isigAnd the active power dynamic curves of different units at the same moment are consistent, wherein the active power response correlation coefficients of the two photovoltaic square arrays are the active power response correlation coefficients of the different units at the same moment. When r isigThe positive correlation of the active power responses of the two photovoltaic square arrays is shown when the power is greater than 0, and r isig< 0 indicates that the active power responses of the two photovoltaic square arrays are negatively correlated, rigThe closer to 1 the absolute value of (A) is, the more similar the active power dynamic curves of the two photovoltaic square arrays are, the easier the two photovoltaic square arrays are divided into a group.
The method specifically comprises the following steps:
s201: grouping photovoltaic square matrixes of the photovoltaic power station according to the principle that active power curves are consistent, collecting active power historical curves of the two photovoltaic square matrixes, and performing photovoltaic power station grouping according to the active power historical curves
Two photovoltaic square matrixes of a photovoltaic power station are divided into different groups with consistency of active power, wherein t is0Representing the starting moment of the detected active power curve; t represents each time point in the dynamic process; v (t) represents a dynamic response value at time t; i. j represents two photovoltaic square arrays; r isigCorrelation coefficients of active power responses of the two photovoltaic square arrays;
s202: setting the quantity and theoretical grade of the photovoltaic square matrixes participating in the rapid frequency modulation according to the grouping result of the photovoltaic square matrixes and the principle that the total frequency modulation power of the photovoltaic square matrixes participating in the rapid frequency modulation at different time periods is equal;
the following examples are given:
and selecting from the photovoltaic grouping results, wherein N photovoltaic square matrixes with consistent active power are provided, and the N photovoltaic square matrixes comprise L or M square matrixes (L < M < N).
Assuming that a photovoltaic square matrix cluster which can participate in fast frequency modulation in early, middle and late three periods (i.e. simple representation methods under different powers) is L, M or N photovoltaic square matrices, wherein it can be set in detail that when the active power of the photovoltaic square matrix is P1(Pmax is not less than P1> P2, Pmax is the maximum active power of each photovoltaic square matrix), L photovoltaic square matrices participate in fast frequency modulation, when the active power of the photovoltaic square matrix is P2(P1 is not less than P2> P3), M square matrices participate in fast frequency modulation, when the active power of the photovoltaic square matrix is P3(P2 is not less than P3>0), N square matrices participate in fast frequency modulation, wherein the power of the photovoltaic square matrix cluster which participates in fast frequency modulation is equal to that P1L is P2M is P3 (L is N; the quantity (such as L, M, N) and the theoretical grade (such as L, M, N, theoretical grade 3) of the photovoltaic square matrix participating in the fast frequency modulation can be set according to the principle that the total frequency modulation power of the photovoltaic square matrix participating in the fast frequency modulation is equal in different time periods.
S203: modifying the control of the photovoltaic array inverter participating in the rapid frequency modulation to enable the photovoltaic array inverter to have the function of automatically switching on and off the primary frequency modulation of the single frequency modulation machine based on the change rate and the change quantity under different active power;
under different active powers, the inverter PLL (phase-locked loop) of the photovoltaic square matrix with L or M or N photovoltaic square matrices respectively participating in the rapid frequency modulation calculates the grid frequency change rate df/dt and the grid frequency change delta f in real time according to the collected grid voltage data; setting a grid frequency change rate frequency modulation and variation frequency modulation dead zone and frequency modulation parameters, wherein if the change rate frequency modulation dead zone is (for example, +/-0.05 Hz/S, the grid frequency change rate df/dt of the area under actual small disturbance is basically greater than +0.05Hz/S), the variation frequency modulation dead zone is +/-0.05 Hz;
when a power grid is just disturbed and the change rate and the change quantity of the power grid frequency do not exceed the dead zone, the primary frequency modulation function of the photovoltaic matrix inverter participating in the rapid frequency modulation does not respond;
when the frequency change rate df/dt exceeds the dead zone and is greater than 0 and the change amount does not exceed the dead zone, the photovoltaic square matrix inverter participating in the rapid frequency modulation is controlled according to the control principle
And calculating the power variation corresponding to the frequency variation rate to change the active power. Specifically, the method comprises the following steps: when the direct current of the asynchronous transmitting-end power grid is locked, the frequency is increased, the frequency df/dt of the power grid is increased, and the photovoltaic inverter participating in the rapid frequency modulation is controlled according to the
And (4) calculating the result and adjusting the power. When the frequency variation under small disturbance generally does not exceed the variation dead zone and the frequency variation under large disturbance does not exceed the variation frequency modulation dead zone, the method based on variation frequency modulation by the station-level frequency modulation controller cannot provide frequency support at presentThe output is reduced, the generated energy is influenced, and the income of the power station is further influenced, the method evenly distributes the rapid frequency modulation capacity according to the capacity of the power station, only a plurality of units of the new energy field station are needed to participate in rapid frequency modulation, and the power generation loss is less;
when the frequency change rate df/dt exceeds the dead zone and is greater than 0, and the frequency change amount exceeds the dead zone, participating in the control of the fast frequency modulation photovoltaic square matrix inverter to perform frequency modulation jointly according to the frequency modulation of the change rate and the frequency modulation of the change amount, specifically: when the direct current of the asynchronous transmitting-end power grid is locked, the frequency is increased, the frequency df/dt and delta f of the power grid are increased, and the photovoltaic inverter participates in the rapid frequency modulation according to the principle that
Calculating the frequency change rate down-regulation power and the sum down-regulation power of the frequency change amount down-regulation power;
when the frequency change rate df/dt exceeds the dead zone and is less than 0, and the frequency change amount exceeds the dead zone, participating in the control of the fast frequency modulation photovoltaic square matrix inverter to modulate frequency according to the frequency change amount, specifically: when the direct current of the asynchronous sending end power grid is locked, the frequency is increased, the frequency delta f of the power grid is increased, and the photovoltaic inverter is controlled according to the result
And (4) calculating the result and adjusting the power.
S3: modifying the control of other photovoltaic inverters in the whole station except for participating in the rapid frequency modulation so as to enable the photovoltaic inverters to have a single-machine primary frequency modulation function based on variable frequency modulation, and the method comprises the following steps:
when the power grid is just disturbed and the power grid frequency variation does not exceed the dead zone, the primary frequency modulation functions of other photovoltaic inverters in the whole station except for participating in the rapid frequency modulation do not respond;
when the frequency variation exceeds the dead zone, the other photovoltaic inverters in the whole station except for participating in the fast frequency modulation control frequency modulation according to the frequency variation, specifically: when the direct current of the asynchronous sending end power grid is locked, the frequency is increased, the frequency delta f of the power grid is increased, and the photovoltaic inverter is controlled according to the result
And (4) calculating the result and adjusting the power.
In addition, the primary frequency modulation, the variation rate frequency modulation, the variation frequency modulation, and the Phase Locked Loop (PLL) given in the embodiments of the present application respectively represent the following meanings:
the primary frequency modulation, such as the primary frequency modulation active-frequency curve of the wind turbine generator shown in fig. 2, refers to an automatic control process in which a control system of a unit in a power grid automatically controls the increase and decrease of the active power of the unit once the frequency of the power grid deviates from a rated value, so as to limit the change of the power grid frequency and maintain the power grid frequency stable. When the frequency of the power grid exceeds the dead zone, the frequency f of the power grid is increased, and the primary frequency modulation function requires that the unit adjusts the power P down according to a Kf2 curve; when the frequency f of the power grid is reduced, the primary frequency modulation function requires the unit to adjust the power P upwards according to a Kf1 curve. The regional power grid mainly faces high frequency problems caused by direct current blocking, namely, the requirement of a primary frequency modulation curve of the regional power grid is a KF2 curve, the frequency is increased, and the active power is reduced.
Frequency modulation of variation rate, such as the primary frequency modulation active-frequency curve of a photovoltaic power station shown in fig. 3; when the frequency of the power grid changes, the frequency change rate df/dt is calculated, the frequency change rate dead zone is assumed to be 0.05Hz/S, and when the frequency change rate df/dt exceeds the dead zone (for example, 0.05Hz/S, the frequency change rate of the actual regional power grid is df/dt ═ 0.16HZ/S), the photovoltaic power station is based on the fact that
And calculating the power variation corresponding to the frequency variation rate to realize the frequency modulation response of the variation rate. When the grid frequency exceeds the dead zone, the grid frequency df/dt is increased, and the primary frequency modulation function requires the unit to operate according to the requirements
Calculating the result to lower the power; when the grid frequency df/dt is reduced, the primary frequency modulation function requires the unit to be according to
The calculation result adjusts the power P up.
Variable quantity frequency modulation: the new energy station realizes a quick frequency response function according to an active-frequency characteristic curve function, and the formula is as follows:
wherein:
fd-a fast frequency response action threshold;
PN-nominal power;
percent-rate of difference;
P0-initial value of power.
When the output power of the new energy station is greater than 20% of the rated value of the full-field active power, the primary frequency modulation function can be started. Fast frequency response action threshold fdAdjustable, the suggested value is 50 +/-0.06 Hz; the adjustment rate% is adjustable, and the suggested value is 2% -3%; the primary frequency modulation response amplitude limiting is not less than 10% of the rated output of the new energy station. When the power grid is in a high-frequency disturbance condition, the active power can not be regulated downwards when the active power reaches 10% of rated output.
The related parameters of the primary frequency modulation can be set on line, and the control strategy can be upgraded according to the specific requirements of the power grid.
Phase Locked Loop (PLL): the PLL is a phase control link for tracking the frequency and the phase of the voltage of the power grid in the control of the fan frequency converter, and the setting of the PLL can enable a sinusoidal signal output by the fan frequency converter to be consistent with the frequency and the phase of the voltage of the power grid, so that grid connection conditions are achieved, and smooth grid connection action of a wind power plant is guaranteed.
According to the method for the photovoltaic power station to participate in the frequency adjustment of the regional power grid, inverter control participating in the fast frequency modulation photovoltaic square matrix is modified, so that the method has a single-machine primary frequency modulation function based on frequency modulation of change rate and frequency modulation of change amount under different active power, and continuous frequency modulation of the fast frequency modulation and the frequency modulation of the change amount can be realized based on the frequency modulation of the change rate; modifying the photovoltaic power station to be not involved in the control of the photovoltaic square matrix inverter of the rapid frequency modulation, so that the photovoltaic square matrix inverter has a primary frequency modulation function based on variable frequency modulation, and can realize continuous frequency modulation; the photovoltaic array and the frequency modulation parameters of the rapid frequency modulation are reasonably set according to the needs of the power grid, so that the frequency support of the photovoltaic to the asynchronous transmitting end power grid can be realized. The method only needs modification and upgrading of control software, does not need addition and modification of hardware and communication, is low in modification cost, has shorter response time and higher speed of single-machine frequency modulation response than station-level frequency modulation control, can provide quick frequency support for an asynchronous transmitting-end power grid, has no mechanical rotating part in a photovoltaic square matrix, and can complete the function of primary frequency modulation only by modifying the control of an inverter. The method provided by the application solves the problems that the existing method for realizing station-level frequency modulation by depending on a station control cabinet needs the station control cabinet to generate a single-machine primary frequency modulation command according to the frequency change of a power grid and the running state of a photovoltaic inverter, the frequency modulation command calculation, command issuing and command response time are slower than that of single-machine frequency modulation, and the requirement of the asynchronous sending-end power grid on quick frequency modulation cannot be met.
The method for frequency modulation of partial photovoltaic square array single machines based on frequency change rate and frequency modulation of all photovoltaic square array single machines based on frequency change amount is provided for solving the problem that a Yunnan power grid is in shortage of rapid frequency modulation resources, frequent system frequency fluctuation under small interference, frequency resource shortage under large disturbance and increased frequency instability risk, and can be popularized and applied in a large area due to the fact that an asynchronous networking mode is used as a future power grid development situation.
It is to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
It will be understood that the present application is not limited to what has been described above and shown in the accompanying drawings, and that various modifications and changes can be made without departing from the scope thereof. The scope of the application is limited only by the appended claims.
Claims (7)
1. A method of a photovoltaic power plant participating in regional grid frequency regulation, the method comprising the steps of:
the method comprises the steps of building an asynchronous transmitting end power grid electromechanical transient model containing new energy primary frequency modulation, simulating and calculating new energy rapid frequency modulation capacity required by rapid frequency modulation of each photovoltaic power station of a transmitting end power grid under small interference, calculating rapid frequency modulation capacity required by each photovoltaic power station in the power grid according to installation conditions of the new energy field of the transmitting end power grid, and determining the minimum photovoltaic square matrix quantity participating in rapid frequency modulation under different active power according to the calculated new energy rapid frequency modulation capacity required by rapid frequency modulation of each photovoltaic power station and the power generation characteristics of the photovoltaic power stations;
according to the change characteristic of active power along with time in the photovoltaic power station and the rapid frequency modulation capacity required to be provided by the photovoltaic power station, calculating the number of photovoltaic matrixes participating in rapid frequency modulation under different active powers, and modifying the control of inverters participating in the rapid frequency modulation photovoltaic matrixes to enable the inverters to have a single-machine primary frequency modulation function based on change rate frequency modulation and change amount frequency modulation under different active powers;
and modifying the control of other photovoltaic inverters in the whole station except for participating in the rapid frequency modulation so as to enable the photovoltaic inverters to have a single-machine primary frequency modulation function based on the variable frequency modulation.
2. The method of claim 1, wherein the new energy fast frequency modulation capacity required for fast frequency modulation of each photovoltaic power plant is calculated using the following equation:
the capacity of the new energy rapid frequency modulation is { (the capacity of the new energy rapid frequency modulation under small interference/the total installed capacity of the new energy of the transmission end power grid) the capacity of the photovoltaic power station }.
3. The method of claim 1, wherein the minimum number of photovoltaic matrices participating in the fast frequency modulation at different active powers is calculated by:
the minimum photovoltaic square matrix quantity participating in the rapid frequency modulation under different active power is the capacity of the rapid frequency modulation of the new energy under small interference/the total installed capacity of the new energy of the transmission-end power grid/the capacity of a photovoltaic power station/the capacity of a single photovoltaic square matrix in different periods.
4. The method of claim 1, wherein the method comprises the steps of calculating the number of photovoltaic matrixes participating in the fast frequency modulation under different active powers according to the change characteristics of the active power in the photovoltaic power station along with time and the fast frequency modulation capacity required to be provided by the photovoltaic power station, and modifying the inverter control participating in the fast frequency modulation photovoltaic matrixes to enable the inverter control to have a single-machine primary frequency modulation function based on the frequency modulation of the variable rate and the frequency modulation of the variable amount under different active powers, and comprises the following steps:
grouping the photovoltaic square matrix, collecting the active power historical curves of the two photovoltaic square matrices according to
To photovoltaic electricityTwo photovoltaic arrays of a station are divided into different groups with active power consistency, where t is0Representing the starting moment of the detected active power curve; t represents each time point in the dynamic process; v (t) represents a dynamic response value at time t; i. j represents two photovoltaic square arrays; r isigCorrelation coefficients of active power responses of the two photovoltaic square arrays;
setting the quantity and theoretical grade of the photovoltaic square matrixes participating in the rapid frequency modulation according to the grouping result of the photovoltaic square matrixes and the principle that the total frequency modulation power of the photovoltaic square matrixes participating in the rapid frequency modulation at different time periods is equal;
and modifying the control of the photovoltaic array inverter participating in the rapid frequency modulation to enable the photovoltaic array inverter to have the function of automatically switching on and off the primary frequency modulation of the single frequency modulation based on the change rate and the change quantity under different active power.
5. The method of claim 4 in which the clustering photovoltaic matrices includes clustering photovoltaic matrices of photovoltaic power plants according to active power curve conformance principles.
6. The method of claim 4, wherein the step of modifying the photovoltaic grid inverter control participating in the fast frequency modulation to have the function of automatically switching on and off the frequency modulation single-machine primary frequency modulation based on the change rate and the change amount according to different active powers comprises:
calculating the power grid frequency change rate df/dt and the power grid frequency change delta f in real time according to the collected power grid voltage data; setting a frequency modulation of the frequency change rate of the power grid, a variable frequency modulation dead zone and a frequency modulation parameter;
when a power grid is just disturbed and the change rate and the change quantity of the power grid frequency do not exceed the dead zone, the primary frequency modulation function of the photovoltaic matrix inverter participating in the rapid frequency modulation does not respond;
when the frequency change rate df/dt exceeds the dead zone and is greater than 0 and the change amount does not exceed the dead zone, the photovoltaic square matrix inverter participating in the rapid frequency modulation is controlled according to the control principle
Calculating the power variation corresponding to the frequency variation rate to change the active power, wherein Δ P is the active power variation, TjIs the rotational inertia of the generator; f. ofNThe system rated frequency, Hz; pNRated power, MW;
when the frequency change rate df/dt exceeds the dead zone and is greater than 0, and the frequency change amount exceeds the dead zone, participating in the control of the rapid frequency modulation photovoltaic square matrix inverter to perform frequency modulation according to the frequency modulation of the change rate and the frequency modulation of the change amount;
and when the frequency change rate df/dt exceeds the dead zone and is less than 0, and the frequency change amount exceeds the dead zone, participating in the control of the fast frequency modulation photovoltaic square matrix inverter to modulate frequency according to the frequency change amount.
7. The method of claim 1, wherein the modifying the control of other photovoltaic inverters in the total station except for the fast frequency modulation to have a single primary frequency modulation function based on delta frequency modulation comprises:
when the power grid is just disturbed and the power grid frequency variation does not exceed the dead zone, the primary frequency modulation functions of other photovoltaic inverters in the whole station except for participating in the rapid frequency modulation do not respond;
when the frequency variation exceeds the dead zone, the frequency modulation is carried out by controlling other photovoltaic inverters of the whole station except the photovoltaic inverters participating in the rapid frequency modulation according to the frequency variation.
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