CN114928075B - Control method of subsynchronous oscillation based on instantaneous active power of power grid line - Google Patents
Control method of subsynchronous oscillation based on instantaneous active power of power grid line 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
- 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
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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
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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
- 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
- H02J2300/28—The renewable source being wind energy
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- 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
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/70—Wind energy
- Y02E10/76—Power conversion electric or electronic aspects
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Abstract
The invention provides a control method of subsynchronous oscillation based on instantaneous active power of a power grid line, which comprises the following steps: recording the instantaneous active power and current of a monitoring point when the power grid runs in a steady state; the instantaneous active power passes through a low-pass filter, active power difference values of adjacent sampling points are obtained from output signals, and an average value of the active power difference values in a set time period is obtained; and extracting all frequency components smaller than the power frequency from the monitoring point, if the current amplitude of each component is larger than or equal to a first threshold value, considering that subsynchronous oscillation occurs in the power grid, taking emergency control measures on the power grid, judging and obtaining the active power of the initial power flow and the power after subsynchronous oscillation according to the average value of the active power difference value, searching a new energy station according to the difference value of the active power of the initial power flow and the power after subsynchronous oscillation, and cutting the new energy station from the power grid. The invention can monitor whether the power grid generates subsynchronous oscillation or not, and take emergency control measures for the power grid after the subsynchronous oscillation.
Description
Technical Field
The invention relates to the technical field of power systems and automation thereof, in particular to a control method of subsynchronous oscillation based on instantaneous active power of a power grid line.
Background
The construction of a novel power system taking a new energy station as a main body is one of important ways for achieving the aims of carbon peak, carbon neutralization, however, the access of high-proportion new energy brings new risks and challenges to the safe and stable operation of the power system.
At present, some subsynchronous oscillation events occur in actual power grids accessed by large-scale wind power at home and abroad, and subsynchronous oscillation phenomenon which cannot be converged occurs in the power grid due to control of the wind power generation set or interaction of the wind power generation set and the power grid, so that power grid equipment is damaged, safe and stable operation of a power system is seriously threatened, and therefore, whether subsynchronous oscillation occurs in the power grid or not and subsynchronous oscillation phenomenon of the power grid needs to be eliminated after the subsynchronous oscillation occurs are required to be judged in time.
Disclosure of Invention
The invention aims to provide a control method of subsynchronous oscillation based on instantaneous active power of a power grid line, which can monitor whether subsynchronous oscillation occurs in the power grid and take emergency control measures on the power grid after the subsynchronous oscillation occurs so as to eliminate the subsynchronous oscillation phenomenon of the power grid.
In order to achieve the above object, the present invention provides a method for controlling subsynchronous oscillation based on instantaneous active power of a power grid line, comprising:
step S1: setting monitoring points on a power grid;
Step S2: when the power grid runs stably, recording instantaneous active power and current of a line at different time points of a monitoring point, and enabling all the instantaneous active power to sequentially pass through a low-pass filter, wherein an output signal of the low-pass filter is a graph of the instantaneous active power which changes along with the time point;
Step S3: acquiring active power difference values of adjacent sampling points from the output signals, and simultaneously acquiring an average value of the active power difference values in a set time period;
step S4: if the average value is greater than or equal to a first threshold value, returning to the step S2, and if the average value is less than the first threshold value, taking the average value as the initial power flow active power;
step S5: extracting frequency components smaller than the power frequency of the power grid from the monitoring points, and judging whether the amplitudes of the currents of all the frequency components are smaller than a second threshold value or not;
Step S6: if yes, the power grid is considered to have no subsynchronous oscillation, the step S2 is returned, if not, the power grid is considered to have subsynchronous oscillation, emergency control measures are taken for the power grid, and if the active power difference value is smaller than the first threshold value, the average value is used as power after subsynchronous oscillation;
Step S7: calculating subsynchronous oscillation power according to the subsynchronous oscillation power and the initial power flow active power, searching a new energy station according to the flow direction of the subsynchronous oscillation power, and calculating the participation degree of subsynchronous oscillation of the new energy station;
Step S8: cutting off the new energy stations with the participation degree larger than or equal to the first participation degree evaluation index from the power grid; and
Step S9: and if the current amplitudes of the remaining new energy stations are smaller than a second threshold value, ending the emergency control measure, otherwise, continuing to take the emergency control measure for the power grid, and cutting off the new energy stations with participation degree larger than a second participation degree evaluation index and smaller than the first participation degree evaluation index.
Optionally, in the control method, the number of the monitoring points is a plurality of, and each monitoring point sequentially executes steps S2 to S9.
Optionally, in the control method, a value of a cutoff frequency of the low-pass filter is smaller than a value of a subsynchronous oscillation frequency.
Optionally, in the control method, the method for obtaining the active power difference value of the adjacent sampling points from the output signal includes:
Δp(tk)＝pdc(tk)-pdc(tk-1)；
Wherein Δp (t k) is the active power difference, p dc(tk) is the active power of the t k th sampling point, and p dc(tk-1) is the active power of the t k-1 th sampling point.
Optionally, in the control method, the method for obtaining the average value of the active power difference values in the set period of time includes:
Wherein, For the average value of the active power difference in the set period, n=Δt×f sample,fsample is the sampling frequency, Δt is the set period, p dc(tk-1) is the active power of the T k-1 th point sampling point, and p dc(tk+N) is the active power of the T k+N th point sampling point.
Optionally, in the control method, the set period of time is 1s.
Optionally, in the control method, the first threshold, the second threshold, the first engagement evaluation index and the second engagement evaluation index are all set values.
Optionally, in the control method, the method for calculating the subsynchronous oscillation power according to the power after the subsynchronous oscillation and the initial power flow active power includes:
PSSO＝P′0-P0；
wherein, P SSO is the subsynchronous oscillation power, P' 0 is the power after subsynchronous oscillation, and P 0 is the active power of the initial tide.
Optionally, in the control method, if P SSO is greater than 0, the flow direction of the subsynchronous oscillation power is consistent with the flow direction of the active power of the initial power flow, and the subsynchronous oscillation source is located at one side of the active power flow of the initial power flow; if P SSO is smaller than 0, the flow direction of the subsynchronous oscillation power is opposite to the flow direction of the active power of the initial power flow, and the subsynchronous oscillation source is positioned at one side of the active power flow of the initial power flow.
Optionally, in the control method, the method for calculating the participation degree of the subsynchronous oscillation of the new energy station includes:
The subsynchronous oscillation power of the new energy station is arranged in the order from big to small, and the subsynchronous oscillation power is numbered in the order;
The participation of the subsynchronous oscillation of the new energy station is calculated by using the following formula:
Wherein subscript i (i, 2,3,) in P SSO,i indicates the subsynchronous oscillation power of the ith new energy station in order from large to small, σ i is the participation degree of the subsynchronous oscillation of the ith new energy station, and P SSO,1 is the subsynchronous oscillation power of the 1 st new energy station.
Optionally, in the control method, the larger the value of the participation degree is, the greater the possibility that the new energy station is an oscillation source is.
Optionally, in the control method, at least one oscillation source is provided.
In the control method of the subsynchronous oscillation based on the instantaneous active power of the power grid line, whether the subsynchronous oscillation occurs in the power grid can be monitored, and emergency control measures are adopted for the power grid after the subsynchronous oscillation occurs so as to eliminate the subsynchronous oscillation phenomenon of the power grid. Thereby protecting the power grid equipment from being damaged and simultaneously ensuring the safe and stable operation of the power system.
Drawings
Fig. 1 is a flowchart of a control method of subsynchronous oscillation based on instantaneous active power of a power grid line according to an embodiment of the present invention.
Detailed Description
Specific embodiments of the present invention will be described in more detail below with reference to the drawings. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are in a very simplified form and are all to a non-precise scale, merely for convenience and clarity in aiding in the description of embodiments of the invention.
In the following, the terms "first," "second," and the like are used to distinguish between similar elements and are not necessarily used to describe a particular order or chronological order. It is to be understood that such terms so used are interchangeable under appropriate circumstances. Similarly, if a method described herein comprises a series of steps, and the order of the steps presented herein is not necessarily the only order in which the steps may be performed, and some of the described steps may be omitted and/or some other steps not described herein may be added to the method.
The method takes the line active power after the subsynchronous oscillation of the power grid as a monitoring object, obtains the subsynchronous oscillation power distribution condition by calculating the variation quantity of the line active power, and backtracks to the new energy stations, thereby judging the participation degree of each station in the oscillation, and taking the participation degree as the basis to guide the emergency control measures after the oscillation, and ensuring the oscillation elimination after the measures are taken. Real-time monitoring the instantaneous active power of the line; the active power after the generation of the line initial power flow active and subsynchronous oscillation is obtained and recorded through signal processing; calculating the change quantity of active power, and reversely tracing to a new energy station; and calculating the participation degree of each station, and determining the wheel-dividing control target. The basic principle can be understood as: after the subsynchronous oscillation occurs, the active power of each line is changed relative to the active power of the initial power flow, and the active power can be decomposed into a direct current component and an oscillation alternating current component, wherein the direct current component is equal to the algebraic sum of the active power of the initial power flow and the subsynchronous oscillation power. The source of subsynchronous oscillation power can be judged by monitoring the initial tidal current active power of the line in real time and calculating the variation of the line before and after oscillation, so as to guide the emergency control after oscillation. Referring to fig. 1, the present invention provides a method for controlling subsynchronous oscillation based on instantaneous power of a power grid line, comprising:
step S1: setting monitoring points on a power grid;
Step S2: when the power grid runs stably, recording instantaneous active power and current of a line at different time points of a monitoring point, and enabling all instantaneous active power to sequentially pass through a low-pass filter, wherein an output signal of the low-pass filter is a graph of the instantaneous active power which changes along with the time point;
Step S3: acquiring active power difference values of adjacent sampling points from an output signal, and simultaneously acquiring an average value of the active power difference values in a set time period;
step S4: if the average value is greater than or equal to the first threshold value, returning to the step S2, and if the average value is less than the first threshold value, taking the average value as the initial power flow active power;
Step S5: extracting frequency components smaller than power frequency of a power grid from monitoring points, and judging whether the amplitudes of currents of all the frequency components are smaller than a second threshold value or not;
Step S6: if yes, the power grid is considered to have no subsynchronous oscillation, the step S2 is returned, if not, the power grid is considered to have subsynchronous oscillation, emergency control measures are taken for the power grid, and if the active power difference value is smaller than a first threshold value, the average value is used as power after subsynchronous oscillation;
Step S7: calculating subsynchronous oscillation power according to the power after subsynchronous oscillation and the initial power flow active power, searching a new energy station according to the flow direction of the subsynchronous oscillation power, and calculating the participation degree of the subsynchronous oscillation of the new energy station;
step S8: cutting off a new energy station with participation degree larger than or equal to the first participation degree evaluation index from the power grid; and
Step S9: and if the current amplitudes of the residual new energy stations are smaller than a second threshold value, ending the emergency control measure, otherwise, continuing to take the emergency control measure for the power grid, cutting off the new energy stations with participation degree larger than the second participation degree evaluation index and smaller than the first participation degree evaluation, and ending the emergency control measure no matter the states of the residual new energy stations after cutting off.
The instantaneous active power can be obtained by directly adopting a synchronous vector measurement unit (PMU) device configured in the current power grid to calculate monitoring signals of three-phase voltage and current, and the expression is as follows:
Pi-j,0(t)＝ua(t)*ia(t)+ub(t)*ib(t)+uc(t)*ic(t)；
Wherein P i-j,0 (t) is the instantaneous active power at the time t, u a(t)、ub (t) and u c (t) respectively represent the three-phase voltage instantaneous values of the monitoring point at the time t, and i a(t)、ib (t) and i c (t) represent the three-phase current instantaneous values flowing out of the monitoring point at the time t. In theory, the instantaneous active power is always monitored, and similarly, whether the power grid generates subsynchronous oscillation is always judged, so that the time t is always changed, and the monitored instantaneous active power is also real-time data and is changed along with the time. Once a certain data is judged that subsynchronous oscillation occurs, emergency control measures are needed to solve the subsynchronous oscillation, and if the subsynchronous oscillation does not occur at the moment, whether subsynchronous oscillation occurs to a power grid at the next moment is continued.
Preferably, the number of the monitoring points is a plurality of, and each monitoring point sequentially executes the steps S2 to S9. The new energy station generates electric power and is transmitted to various places through a power grid, a plurality of transmission lines can be provided, whether subsynchronous oscillation occurs can be judged through the current on the lines or the value of instantaneous active power, meanwhile, the new energy station is traced back according to the lines with the subsynchronous oscillation, and emergency control measures are adopted for the new energy station. Therefore, a plurality of monitoring points can be set according to the arrangement of the circuit, the data of each monitoring point is separately monitored and judged, whether subsynchronous oscillation occurs is judged by monitoring the current and the instantaneous active power values of the monitoring points, and once the current and the instantaneous active power values of a certain monitoring point can be judged to occur, a corresponding new energy station is needed to be found according to the monitoring point, and emergency control measures are adopted for the new energy station.
Preferably, the cut-off frequency of the Low Pass Filter (LPF) has a value that is less than the value of the subsynchronous oscillation frequency. The cut-off frequency of the low-pass filter is set, and the reference for setting is set according to the frequency at which the subsynchronous oscillation occurs historically, for example, the value of the cut-off frequency of the low-pass filter according to the embodiment of the present invention may be f c =1 Hz. The low-frequency instantaneous active power is output after passing through the low-pass filter, and in the step S2, the instantaneous active power of the monitoring point is continuously monitored, and the instantaneous active power is continuously input into the low-pass filter, so that the value of the output of the low-pass filter is continuously changed, the value of the sampling point is also changed, and the active power difference value and the average value of the active power difference value are also changed. Therefore, both the active power difference and the average value of the active power difference may change after returning to step S2.
Preferably, the method for obtaining the active power difference value of the adjacent sampling points from the output signal comprises the following steps:
Δp(tk)＝pdc(tk)-pdc(tk-1)；
Wherein Δp (t k) is the active power difference, p dc(tk) is the active power of the t k th sampling point, p dc(tk-1) is the active power of the t k-1 th sampling point, and t k and t k-1 are adjacent sampling points, which may change with time t.
Preferably, the method for obtaining the average value of the active power difference value in the set time period includes:
Wherein, For the average value of the active power difference in the set period, n=Δt×f sample,fsample is the sampling frequency, Δt is the set period, p dc(tk-1) is the active power of the T k-1 th point sampling point, and p dc(tk+N) is the active power of the T k+N th point sampling point. The set time period DeltaT of the embodiment of the invention is selected to be 1s,/>To calculate the average of Δp (T k) over a time window (T, t+ΔT), the time of T is varied,/>The value of (2) may also vary.
Preferably, the first threshold, the second threshold, the first engagement evaluation index and the second engagement evaluation index are all set values. The first threshold epsilon 1 is used for avoiding error recording of the line active power change caused by the tide mode as a steady state tide value, the first threshold epsilon 1 should be determined according to the change range of the line power measurement value in the actual operation of the current power grid, and the value is generally epsilon 1 =1MW. The second threshold I thre may be set according to the actual condition of the power grid, and is used to determine whether there is a subsynchronous component in the current, which may be I thre＝5％Idc, in this embodiment, I thre =0.1 kA. In step S5, the frequency component may be extracted, first, fast fourier analysis may be performed on the current at the monitoring point, and then, the current magnitudes I ω,i at all frequency points below the power frequency may be extracted, if all I ω,i are smaller than the threshold value I thre, it is considered that subsynchronous oscillation does not occur in the power grid, where the current magnitude I ω,i represents the current magnitude of the ith frequency component. The first engagement evaluation index η 1 and the second engagement evaluation index η 2 are indexes actually set according to the current power grid, and are used for judging the relative relationship of a plurality of oscillation sources in the round of emergency control, and are set to η 1＝95％、η2 =90% in the present embodiment.
Preferably, the method of calculating the subsynchronous oscillation power includes:
PSSO＝P′0-P0；
Wherein, P SSO is the subsynchronous oscillation power, P' 0 is the power after subsynchronous oscillation, and P 0 is the active power of the initial tide. According to the calculation from step S4 to step S6, the real-time average value under different conditions can be met As the initial tidal current active power or the power after subsynchronous oscillation, the subsynchronous oscillation power is calculated. With the change of time, the average value is always changed, so that the situation that the average value is larger than the first threshold value and smaller than the first threshold value, subsynchronous oscillation occurs and subsynchronous oscillation does not occur may occur, and when any one of the situations occurs, the current corresponding to the current time point is searched.
In step S2, since the direction of the instantaneous active power may be defined, for example, the direction P i-j,0 (t) > 0 is defined as the positive direction, the determination of the positive and negative directions of the power after the subsynchronous oscillation and the initial power flow active power and the determination of the direction of the instantaneous active power are identical, that is, the positive direction of the power after the synchronous oscillation and the positive direction of the initial power flow active power are the positive direction of the instantaneous active power. If P SSO is more than 0, the flow direction of the subsynchronous oscillation power is consistent with the flow direction of the active power of the initial power flow, and the subsynchronous oscillation source is positioned at one side of the active power flow of the initial power flow; if P SSO is less than 0, the flow direction of the subsynchronous oscillation power is opposite to the flow direction of the active power of the initial power flow, and the subsynchronous oscillation source is positioned at one side of the active power flow of the initial power flow.
Preferably, the method for calculating the participation degree of the subsynchronous oscillation of the new energy station comprises the following steps:
The subsynchronous oscillation power of the new energy station is arranged in the order from big to small, and the subsynchronous oscillation power is numbered in the order;
The participation of the subsynchronous oscillation of the new energy station is calculated by using the following formula:
Wherein subscript i (i, 2,3,) in P SSO,i indicates the subsynchronous oscillation power of the ith new energy station in order from large to small, σ i is the participation degree of the subsynchronous oscillation of the ith new energy station, and P SSO,1 is the subsynchronous oscillation power of the 1 st new energy station. Specifically, the power flow direction of the subsynchronous vibration power P SSO obtained in step S7 may be traced back to the new energy station node to obtain the magnitude and direction of the vibration power P SSO,i of each new energy station in the subsynchronous vibration (table i below represents different new energy stations), and the sequence of P SSO,i from large to small, and meanwhile, the subsynchronous vibration participation σ i of each new energy station is calculated, and the obtained sequence of P SSO is obtained.
Preferably, the larger the value of the engagement σ i, the greater the likelihood that the new energy station is an oscillation source. At least one oscillation source is adopted, and obviously the participation degree is calculated after the occurrence of subsynchronous oscillation is judged, so that a new energy station traced back must have one oscillation source, and the new energy station is arranged from large to small according to P SSO,i, and P SSO,1 is the oscillation source. Further, the larger the value of the participation σ i, the greater the possibility that the ith new energy station and P SSO,1 are both oscillation sources. In the subsynchronous oscillation process, a plurality of oscillation sources can exist, and the sources can be judged at one time through sigma i, so that emergency control is conveniently guided.
Specifically, the embodiment of the invention takes 6 monitoring points as an example, takes a new energy centralized access area position in a certain power grid as an implementation object, 6 new energy stations in the area respectively transmit power to a main network through 6 lines, the monitoring points are respectively arranged on the 6 lines, and the instantaneous active power of the line where the 6 monitoring points are located is shown in table 1.
TABLE 1
If the power grid generates subsynchronous oscillation, andThe current average value is recorded as post-subsynchronous oscillation power P' 0, and the power variation is calculated as subsynchronous oscillation power P SSO.
Wherein, the expression of the subsynchronous oscillation power P SSO is:
PSSO＝P′0-P0。
If P SSO is greater than 0, the flow direction of the subsynchronous oscillation power is consistent with the initial power flow, and if P SSO is less than 0, the flow direction of the subsynchronous oscillation power is opposite to the initial power flow, the greater P SSO is, the greater the subsynchronous oscillation power provided by the power flow side is, and the closer the subsynchronous oscillation power is to the oscillation source. And then, judging the power flow direction of the line according to P SSO, reversely tracing to the new energy station node to obtain the size and direction of the oscillating power P SSO,i of each new energy station in the subsynchronous oscillation, sequencing according to the sequence from the large to the small of P SSO,i, and simultaneously calculating the subsynchronous oscillation participation degree sigma i of each new energy station. The expression of the subsynchronous oscillation participation σ i is:
the sub-synchronous vibration power distribution and participation degree conditions obtained by completing the above steps are shown in table 2:
TABLE 2
| Monitoring point | ① | ② | ③ | ④ | ⑤ | ⑥ |
| PSSO/MW | 7.35 | 1.27 | -7.1 | 0.06 | -0.07 | 0.49 |
| σi | 100％ | 17.3％ | —— | 0.8％ | —— | 6.7％ |
Therefore, all the new energy stations are ordered to be ①、②、④、⑥ according to the sequence from big to small, and the other two monitoring points are not positioned on one side of the oscillation source.
Then, emergency control measures are taken, all stations of sigma i≥η1 are cut off in the first round, and whether subsynchronous oscillation disappears or not is judged. If the oscillation is disappeared, the emergency control measure is ended, if the oscillation is not ended, the second round of control is continued, all stations of eta 1＜σi＜η2 in the rest stations are cut off, and after the two rounds of control, the emergency control measure is ended no matter whether the oscillation is disappeared or not. Thus, in this embodiment, station ① is determined to be the only source of oscillation in combination with the engagement index. The wind turbine generator system of the station ① is cut off, and subsynchronous oscillation is eliminated, so that the emergency control can be finished by cutting off only one wheel, and oscillation suppression is finished.
In summary, in the control method for subsynchronous oscillation based on instantaneous power of a power grid line provided by the embodiment of the invention, whether subsynchronous oscillation occurs in the power grid can be monitored, and emergency control measures are taken on the power grid after the subsynchronous oscillation occurs so as to eliminate the subsynchronous oscillation phenomenon of the power grid. Thereby protecting the power grid equipment from being damaged and simultaneously ensuring the safe and stable operation of the power system.
The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art will make any equivalent substitution or modification to the technical solution and technical content disclosed in the invention without departing from the scope of the technical solution of the invention, and the technical solution of the invention is not departing from the scope of the invention.
Claims (11)
1. A method for controlling subsynchronous oscillations based on instantaneous active power of a power grid line, comprising:
step S1: setting monitoring points on a power grid;
Step S2: when the power grid runs stably, recording instantaneous active power and current of a line at different time points of a monitoring point, and enabling all the instantaneous active power to sequentially pass through a low-pass filter, wherein an output signal of the low-pass filter is a graph of the instantaneous active power which changes along with the time point;
Step S3: acquiring active power difference values of adjacent sampling points from the output signals, and simultaneously acquiring an average value of the active power difference values in a set time period;
step S4: if the average value is greater than or equal to a first threshold value, returning to the step S2, and if the average value is less than the first threshold value, taking the average value as the initial power flow active power;
step S5: extracting frequency components smaller than the power frequency of the power grid from the monitoring points, and judging whether the amplitudes of the currents of all the frequency components are smaller than a second threshold value or not;
Step S6: if yes, the power grid is considered to have no subsynchronous oscillation, the step S2 is returned, if not, the power grid is considered to have subsynchronous oscillation, emergency control measures are taken for the power grid, and if the active power difference value is smaller than the first threshold value, the average value is used as power after subsynchronous oscillation;
Step S7: calculating subsynchronous oscillation power according to the subsynchronous oscillation power and the initial power flow active power, searching a new energy station according to the flow direction of the subsynchronous oscillation power, and calculating the participation degree of subsynchronous oscillation of the new energy station;
Step S8: cutting off the new energy stations with the participation degree larger than or equal to the first participation degree evaluation index from the power grid; and
Step S9: ending the emergency control measure if the current amplitudes of the remaining new energy stations are smaller than the second threshold value, otherwise, continuing to take the emergency control measure for the power grid, and cutting off the new energy stations with participation degree larger than a second participation degree evaluation index and smaller than the first participation degree evaluation;
the method for calculating the participation degree of the subsynchronous oscillation of the new energy station comprises the following steps:
The subsynchronous oscillation power of the new energy station is arranged in the order from big to small, and the subsynchronous oscillation power is numbered in the order;
The participation of the subsynchronous oscillation of the new energy station is calculated by using the following formula:
Wherein subscript i (i, 2,3,) in P SSO,i indicates the subsynchronous oscillation power of the ith new energy station in order from large to small, σ i is the participation degree of the subsynchronous oscillation of the ith new energy station, and P SSO,1 is the subsynchronous oscillation power of the 1 st new energy station.
2. The control method according to claim 1, wherein the number of the monitoring points is a plurality, and each monitoring point sequentially performs steps S2 to S9.
3. The control method according to claim 1, wherein a value of a cutoff frequency of the low-pass filter is smaller than a value of a subsynchronous oscillation frequency.
4. The control method of claim 1, wherein the step of obtaining active power differences for adjacent sample points from the output signal comprises:
Δp(tk)＝pdc(tk)-pdc(tk-1)；
Wherein Δp (t k) is the active power difference, p dc(tk) is the active power of the t k th sampling point, and p dc(tk-1) is the active power of the t k-1 th sampling point.
5. The control method according to claim 1, wherein the method of obtaining the average value of the active power difference value over the set period of time includes:
Wherein, For the average value of the active power difference in the set period, n=Δt×f sample,fsample is the sampling frequency, Δt is the set period, p dc(tk-1) is the active power of the T k-1 th point sampling point, and p dc(tk+N) is the active power of the T k+N th point sampling point.
6. The control method according to claim 1 or claim 4, wherein the set period of time is 1s.
7. The control method according to claim 1, wherein the first threshold value, the second threshold value, the first engagement evaluation index, and the second engagement evaluation index are all set values.
8. The control method according to claim 1, wherein the method of calculating subsynchronous oscillation power from the subsynchronous oscillation power and the initial tidal current active power comprises:
PSSO＝P′0-P0；
wherein, P SSO is the subsynchronous oscillation power, P' 0 is the power after subsynchronous oscillation, and P 0 is the active power of the initial tide.
9. The control method according to claim 8, wherein if P SSO > 0, the flow direction of the subsynchronous oscillation power is identical to the flow direction of the active power of the initial power flow, and the subsynchronous oscillation source is located at one side of the active power flow of the initial power flow; if P SSO is smaller than 0, the flow direction of the subsynchronous oscillation power is opposite to the flow direction of the active power of the initial power flow, and the subsynchronous oscillation source is positioned at one side of the active power flow of the initial power flow.
10. The control method according to claim 1, wherein the larger the value of the engagement degree is, the greater the possibility that the new energy station is an oscillation source is.
11. The control method of claim 10, wherein the oscillation source is at least one.
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