CN114268126A - Self-adaptive fluctuating renewable energy stable output and grid connection method and system - Google Patents
Self-adaptive fluctuating renewable energy stable output and grid connection method and system Download PDFInfo
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Abstract
The invention discloses a self-adaptive fluctuating renewable energy stable output and grid connection method, which comprises the following steps: the method comprises the steps of obtaining original power of a fluctuating renewable energy power generation system, processing an obtained original power signal by using a variational modal decomposition algorithm, and decomposing the original power signal into k intrinsic modal functions and residual components r on the premise of meeting a renewable energy grid-connected power fluctuation standard; on the basis, the grid-connected mode number k is determined1Will be k before1And (3) grid-connecting the intrinsic mode function and the residual component r, so that the grid-connected power meets the renewable energy grid-connected power fluctuation standard and is as large as possible. The method and the system not only effectively stabilize fluctuation of fluctuating renewable energy sources, but also reduce energy storage capacity allocation, can effectively improve stability and economy of large-scale fluctuating renewable energy source grid connection, and improve electric energy quality of a power grid.
Description
Technical Field
The invention relates to the technical field of fluctuation stabilization of power of fluctuating renewable energy sources, in particular to a method and a system for stably outputting and grid-connecting the fluctuating renewable energy sources, and particularly relates to a self-adaptive method and a system for stably outputting and grid-connecting the fluctuating renewable energy sources based on a variational modal decomposition algorithm.
Background
The fluctuating renewable energy power generation has the characteristics of randomness, instability and the like, and the large-scale fluctuating renewable energy power generation is connected into a power grid, so that higher requirements on peak regulation and frequency modulation of the power grid are provided, and great challenges are provided for operation control of the power grid. By the end of 2021, 9 months, the renewable energy power generation installation in China reaches 9.94 hundred million kilowatts. Wherein, wind power installation machine is 2.97 hundred million kilowatts, photovoltaic power installation machine is 2.78 hundred million kilowatts. 1-9 months in 2021, and the national renewable energy power generation amount reaches 1.75 trillion kilowatt-hours. Wherein, wind power is 4694 hundred million kilowatt hours, and the year-on-year increase is 41.5 percent; photovoltaic power generation 2486 hundred million kilowatt-hours, which is increased by 24.0 percent on a par. The costs of the grid system for this purpose will increase rapidly. The key of improving the stability of the renewable energy power generation, reducing the electricity abandonment, reducing the cost of a source/network/charge system and guaranteeing the healthy development of the renewable energy is to configure energy storage on site in a certain scale.
The energy storage system can rapidly absorb energy and timely release redundant energy, so that the defects of randomness, instability and the like of the fluctuating renewable energy sources are favorably overcome, the stability of the power system is improved, but the energy storage system for the power generation side of the fluctuating renewable energy sources is high in cost at present, and the capacity of the energy storage system is reasonably configured, so that the important significance is realized on further reducing the power generation cost of the fluctuating renewable energy sources. And the grid-connected signal obtained by the current algorithm solution may cause that the fluctuation of the fluctuating renewable energy power is insufficient and cannot meet the fluctuation standard of the fluctuating renewable energy grid-connected power, or the fluctuation is excessive so that the capacity of the energy storage device is increased. Therefore, a fluctuating renewable energy stable grid-connected system with stability and economy is urgently needed to be developed, fluctuation of power of fluctuating renewable energy is stabilized on the basis of ensuring operation reliability and stability of a power grid, and capacity configuration of an energy storage system is optimized. Based on the method, the invention provides a fluctuating renewable energy stable output method based on a self-adaptive variational modal decomposition algorithm and a grid-connected system.
Disclosure of Invention
The invention aims to provide a self-adaptive stable output and grid-connected method and system for fluctuating renewable energy.
In order to achieve the purpose, the invention provides the technical scheme that:
a self-adaptive fluctuating renewable energy stable output and grid connection method comprises the following steps: the method comprises the steps of obtaining original power of a fluctuating renewable energy power generation system, processing an obtained original power signal by using a variational modal decomposition algorithm, and decomposing the original power signal into k intrinsic modal functions and residual components r on the premise of meeting a renewable energy grid-connected power fluctuation standard; on the basis, the grid-connected mode number k is determined1Will be k before1And (3) grid-connecting the intrinsic mode function and the residual component r, so that the grid-connected power meets the renewable energy grid-connected power fluctuation standard and is as large as possible.
In the above technical solution, further, the method for determining k is as follows:
carrying out variation mode decomposition with the decomposition mode number k being 1 on the original power of the fluctuating renewable energy source, and judging whether the sub-mode IMF and the residual component r are connected to the grid to meet the fluctuation standard requirement of the fluctuating renewable energy source grid power;
if the grid-connected power fluctuation standard of the fluctuating renewable energy is met, directly taking the original power as grid-connected power Pg；
And if the grid-connected power fluctuation standard of the fluctuating renewable energy sources is not met, circularly deepening the decomposition until the decomposition mode number k is equal to k +1 and outputting k.
Further, determining said k1The method comprises the following steps:
initializing grid-connected mode number k12, performing grid-connected prediction on the first two eigen-submodes and the residual component r, and judging whether the grid-connected power fluctuation standard of the fluctuating renewable energy is met under the condition;
if the current predicted grid-connected power meets the fluctuation standard of the fluctuating renewable energy grid-connected power, enabling k to be1＝k1+1, until the current predicted grid-connected power does not meet the fluctuation standard, outputting k1；
If the current predicted grid-connected power does not meet the fluctuation standard of the fluctuating renewable energy grid-connected power, k is output1＝k1-1。
In addition, the adaptive fluctuating renewable energy stable output and grid-connected system is realized based on the method and comprises a fluctuating renewable energy power generation system, an energy storage system and a central control system, wherein the central control system is used for stabilizing the output power of the fluctuating renewable energy power generation system in an adaptive mode based on a VMD algorithm and a fluctuating standard of fluctuating renewable energy grid-connected power, and simultaneously determining the minimum capacity of the energy storage system; in determining grid-connected power PgThen, the initial power P of the fluctuating renewable energy source is usedEAnd grid-connected power PgThe difference is used as the minimum capacity P of the energy storage systemS。
The invention has the beneficial effects that:
the invention takes the stabilization of fluctuation of the power of the fluctuating renewable energy source as a control target, adopts a variational modal decomposition algorithm, stabilizes the output power of the fluctuating renewable energy source power generation system, and absorbs the stabilized power by the energy storage system. In the variation modal decomposition algorithm, the influence on the decomposition result is caused by selecting too large or too small a modal decomposition number k, when the decomposition modal number k is selected to be too small, the characteristic information in the signal is difficult to decompose, and when the decomposition modal number k is selected to be too large, the false information is caused by aliasing of over-decomposition frequency information. The invention adopts a self-adaptive variation modal decomposition algorithmThe method is characterized in that a proper k value and a grid-connected mode number k are automatically selected according to the standard of the power fluctuation rate of the renewable energy1. The fluctuation of the fluctuating renewable energy sources is effectively stabilized, the energy storage capacity configuration is reduced, the stability and the economy of grid connection of the large-scale fluctuating renewable energy sources can be effectively improved, and the electric energy quality of a power grid is improved.
Drawings
Fig. 1 is a schematic structural diagram of a fluctuating renewable energy stable grid-connected system according to the present invention;
FIG. 2 is a flow diagram of an embodiment of an adaptive variational modal decomposition control of the present invention;
Detailed Description
In order to make the technical solutions of the present invention better understood by those skilled in the art, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.
The invention discloses a self-adaptive fluctuating renewable energy stable output and grid connection method, which comprises the following steps: obtaining original power P of fluctuating renewable energy power generation systemEProcessing the obtained original power signal by using a variational modal decomposition algorithm, and decomposing the original power signal into k intrinsic modal functions and residual components r on the premise of meeting the renewable energy grid-connected power fluctuation standard; on the basis, the grid-connected mode number k is determined1Will be k before1And (3) grid-connecting the intrinsic mode function and the residual component r, so that the grid-connected power meets the renewable energy grid-connected power fluctuation standard and is as large as possible.
In this embodiment, the fluctuating renewable energy power signal is processed by using a variational modal decomposition method, and is decomposed into one or more eigenmode functions and residual components. The variational modal decomposition algorithm is to decompose the signal into a plurality of modal components, solve the optimal value of the constraint variational model, continuously and alternately update the central frequency and the bandwidth of each component, and finally obtain the component, namely the intrinsic mode function IMF. If the original power P of the fluctuating renewable energy source is usedEPerforming variation modal decomposition to obtain k different subsequences uk(t), the sum of the subsequences is equal to the output power P of the fluctuating renewable energy power generation systemEBy two timesThe penalty factor alpha ensures the signal recombination precision, the Lagrange multiplier lambda (t) ensures the constraint condition strictness, the optimal solution of the unconstrained variational problem under the condition of Gaussian noise existence of the variational modal decomposition is finally realized to replace the constrained variational problem to be solved, the augmented Lagrange function is introduced, the constrained variational problem is solved, the time domain is updated to the frequency domain through Fourier equidistant transformation, and if the precision meets the iteration stop condition, the iteration is stopped.
The determination of the number k of the sub-modes of the variational modal decomposition is based on the standard that the central frequencies do not appear similar modes, and the judgment method is as follows: when the decomposed subsequence is k +1, similar modal components appear in the decomposition, that is, an over-solution appears, so that the number k of the decomposed subsequences is selected to be k. The Intrinsic Mode Function (IMF) is characterized in that the number of waveform extreme values is equal to the number of zero points or the difference between the number of the extreme values and the number of the zero points is one, and the signal is similar to a sinusoidal signal and is favorable for being used as an input signal of the energy storage element and stabilizing the energy storage element by charging and discharging.
As shown in fig. 1, the grid-connected system in this example includes a fluctuating renewable energy power generation system, an energy storage system, and a central control system, where the central control system determines the output of the fluctuating renewable energy power generation system and the capacity of the energy storage system by using an adaptive variational modal decomposition algorithm, and specifically, as shown in fig. 2, the method mainly includes determining a decomposition modal number k and determining a grid-connected modal number k1Two stages, specifically as follows:
step 1: and (3) carrying out variation mode decomposition with the decomposition mode number k being 1 on the original power of the fluctuating renewable energy source, and judging whether the submode IMF1+ residual component r meets the fluctuation standard requirement of the fluctuating renewable energy source grid-connected power.
Step 2: if the IMF1+ r meets the fluctuation standard of the grid-connected power of the fluctuating renewable energy source, directly taking the original power as the grid-connected power Pg。
And step 3: and if the IMF1+ r does not meet the fluctuation standard of the grid-connected power of the fluctuating renewable energy sources, circularly deepening the decomposition until the decomposition mode number k is k +1 and outputting k.
And 4, step 4: initializing grid-tie modalitiesNumber k1And 2, grid connection is carried out on the sub-model IMF1+ IMF2+ r, and whether the grid connection power fluctuation standard of the fluctuating renewable energy is met is judged.
And 5: if power P is connected to the gridgIf the grid-connected power fluctuation standard of the fluctuating renewable energy sources is met, k is ordered1＝k1+1, until the ripple criterion is not met, output k1。
Step 6: if PgIf the grid-connected power fluctuation standard of the fluctuating renewable energy sources is not met, k is output1＝k1-1, and the fluctuating renewable energy initial power PEAnd PgThe difference is used as the stored energy power PS。
In the invention, the fluctuation rate of the fluctuating renewable energy grid-connected power can be determined by adopting the following method:
in the formula: maxPgIs a fluctuating renewable energy power maximum over a period of time; minPgIs a fluctuating renewable energy power minimum over a period of time; pratedThe capacity of the wave renewable energy source is installed. As shown in FIG. 2, the fluctuation criterion is set to R.ltoreq.10%/5 min. The invention takes the stabilization of fluctuation of the power of the fluctuating renewable energy source as a control target, adopts a variational modal decomposition algorithm, stabilizes the output power of the fluctuating renewable energy source power generation system, and absorbs the stabilized power by the energy storage system. The method solves the problem of poor stabilizing effect of the traditional algorithm, and achieves the purposes that the energy storage system stabilizes the power fluctuation of the renewable energy source and the fluctuating renewable energy source is stably connected to the grid. Simulation analysis is carried out on measured data of a new energy power station with certain installed capacity of 30MW, the original fluctuation rate of the renewable energy is 16.50%/5 min, the fluctuation rate is reduced to 9.68%/5 min after stabilization, and the fluctuation standard of the grid-connected power of the renewable energy is met. Compared with the existing method, the power borne by the energy storage system can be reduced by about 20%.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (6)
1. A self-adaptive fluctuating renewable energy stable output and grid connection method is characterized by comprising the following steps: the method comprises the steps of obtaining original power of a fluctuating renewable energy power generation system, processing an obtained original power signal by using a variational modal decomposition algorithm, and decomposing the original power signal into k intrinsic modal functions and residual components r on the premise of meeting a renewable energy grid-connected power fluctuation standard; on the basis, the grid-connected mode number k is determined1Will be k before1And (3) grid-connecting the intrinsic mode function and the residual component r, so that the grid-connected power meets the renewable energy grid-connected power fluctuation standard and is as large as possible.
2. The adaptive fluctuating renewable energy steady output and grid connection method according to claim 1, wherein the k is determined by the following method:
carrying out variation mode decomposition with the decomposition mode number k being 1 on the original power of the fluctuating renewable energy source, and judging whether the sub-mode IMF and the residual component r are connected to the grid to meet the fluctuation standard requirement of the fluctuating renewable energy source grid power;
if the grid-connected power fluctuation standard of the fluctuating renewable energy is met, directly taking the original power as grid-connected power Pg；
And if the grid-connected power fluctuation standard of the fluctuating renewable energy sources is not met, circularly deepening the decomposition until the decomposition mode number k is equal to k +1 and outputting k.
3. The adaptive fluctuating renewable energy steady output and grid connection method according to claim 1, wherein the k is determined1The method comprises the following steps:
initializing grid-connected mode number k1Is the number of 2, and the number of the second,performing grid-connected prediction on the first two eigen-submodes and the residual component r, and judging whether the grid-connected power fluctuation standard of the fluctuating renewable energy is met under the condition;
if the current predicted grid-connected power meets the fluctuation standard of the fluctuating renewable energy grid-connected power, enabling k to be1＝k1+1, until the current predicted grid-connected power does not meet the fluctuation standard, outputting k1；
If the current predicted grid-connected power does not meet the fluctuation standard of the fluctuating renewable energy grid-connected power, k is output1＝k1-1。
4. An adaptive fluctuating renewable energy stable output and grid-connection system, characterized in that the system is realized based on the method of any one of claims 1-3, and comprises a fluctuating renewable energy power generation system, an energy storage system and a central control system, wherein the central control system is used for stabilizing the output power of the fluctuating renewable energy power generation system in an adaptive manner based on a VMD algorithm and a fluctuating standard of fluctuating renewable energy grid-connection power, and simultaneously determining the minimum capacity of the energy storage system.
5. The adaptive fluctuating renewable energy steady output and grid connection system according to claim 4, wherein the grid connection power P is determinedgThen, the initial power P of the fluctuating renewable energy source is usedEAnd grid-connected power PgThe difference is used as the minimum capacity P of the energy storage systemS。
6. The adaptive fluctuating renewable energy stable output and grid-connection system according to claim 4, wherein the fluctuating standard of the fluctuating renewable energy grid-connection power is a standard set for a fluctuating rate, the fluctuating rate being:
in the formula: maxPgIs a fluctuating renewable energy power maximum; minPgIs a fluctuating renewable energy power minimum; pratedThe fluctuation standard is set according to specific requirements for fluctuating renewable energy installed capacity.
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| CN110726875A (en) * | 2019-12-02 | 2020-01-24 | 山东大学 | New energy flexible direct-current grid-connected transient harmonic detection method and system |
| CN112531744A (en) * | 2020-12-11 | 2021-03-19 | 福州大学 | Wind power fluctuation stabilizing method based on variational modal decomposition |
| CN113178880A (en) * | 2021-03-25 | 2021-07-27 | 浙江大学 | Hybrid energy storage optimization constant volume and regulation method based on wind power probability prediction |
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