Fluctuation power smoothing method and system based on hydrogen-electric hybrid energy storage system

Abstract

The present invention provides a method and system for smoothing fluctuating power based on a hydrogen-electric hybrid energy storage system. The method establishes a hydrogen-electric hybrid energy storage system, comprising a supercapacitor array, a hydrogen energy storage unit, an auxiliary power supply, and a converter. The hydrogen energy storage unit comprises an electrolyzer, a fuel cell, and a hydrogen storage tank. The method performs frequency analysis on the original rapid fluctuating power through empirical mode decomposition and Hilbert-Huang transform to obtain a sliding range of a demarcation frequency. The fluctuating power with a frequency higher than the demarcation frequency is allocated to the supercapacitor array, and the fluctuating power with a frequency lower than the demarcation frequency is allocated to the hydrogen energy storage unit. The method calculates the discharge power of the auxiliary power supply based on the power requirements of the supercapacitor array and the hydrogen energy storage unit to compensate for the power loss. The method sets a sliding adjustment rule and performs sliding adjustment on the demarcation frequency to adjust the distribution of the fluctuating power and improve the power absorption rate.

Description

Technical Field

[0001] The present invention relates to the technical field of hybrid energy storage in power systems, and in particular to a method and system for smoothing power fluctuations based on a hydrogen-electric hybrid energy storage system. Background Art

[0002] In recent years, with the increasing global shortage of fossil energy and the promotion of environmental protection, the global energy structure has undergone significant changes, with renewable energy, represented by wind power and photovoltaics, experiencing rapid growth. However, while the continued growth of wind and photovoltaic power generation has brought significant economic and environmental benefits, it has also posed significant challenges to the power grid. Renewable energy generation is significantly affected by natural conditions such as wind speed, sunlight, and temperature. Its output power is highly volatile, intermittent, and random, making it difficult to fully integrate and absorb it into the grid, resulting in a certain amount of energy waste.

[0003] Installing energy storage systems near wind farms and photovoltaic power stations has become an important means of smoothing fluctuations in renewable energy generation. However, single energy storage systems are difficult to cope with the various operating conditions that arise when smoothing wind power fluctuations. Currently, hybrid energy storage systems are mostly used. A lot of research has been conducted on hybrid energy storage systems composed of batteries and supercapacitors. This combination has the advantages of good variable operating conditions and easy control. However, when faced with rapidly fluctuating power, batteries have a short cycle life, require frequent daily maintenance, and pose an environmental pollution risk. Using supercapacitors alone is expensive and insufficient to cope with different operating conditions. In addition, current research on hybrid energy storage systems mainly focuses on capacity configuration. However, when parameters such as system capacity are determined, there is little research on how to improve the effect of fluctuating power through operational control methods. This is very important for application in engineering. Summary of the Invention

[0004] The present invention proposes a method and system for smoothing fluctuating power based on a hydrogen-electric hybrid energy storage system to solve the technical problem of improving the effect of smoothing fluctuating power when parameters such as system capacity are determined.

[0005] To solve the above technical problems, the present invention provides a method and system for smoothing power fluctuations based on a hydrogen-electric hybrid energy storage system, comprising the following steps:

[0006] Step S1: establishing a hydrogen-electric hybrid energy storage system, including a supercapacitor array, a hydrogen energy storage unit, an auxiliary power supply and a converter, wherein the hydrogen energy storage unit includes an electrolyzer, a fuel cell and a hydrogen storage tank;

[0007] Step S2: Performing frequency analysis on the original fast fluctuating power through empirical mode decomposition and Hilbert-Huang transform to obtain a sliding range of a cutoff frequency. Fluctuating power with a frequency higher than the cutoff frequency is allocated to the supercapacitor array, and fluctuating power with a frequency lower than the cutoff frequency is allocated to the hydrogen energy storage unit.

[0008] Step S3: Calculating the discharge power of the auxiliary power supply based on the power requirements of the supercapacitor array and the hydrogen energy storage unit to compensate for the power loss;

[0009] Step S4: setting a sliding adjustment rule and slidingly adjusting the boundary frequency to adjust the distribution of the fluctuating power and improve the power absorption rate.

[0010] Preferably, the expression of the empirical mode decomposition in step S2 is:

[0011]

[0012] Where, P rf (t) represents the rapid fluctuation power at time t, n represents the number of set eigenmode components, c i represents the eigenmode component, r n represents the residual component.

[0013] Preferably, the Hilbert-Huang transform in step S2 includes the following steps:

[0014] Step S21: The eigenmode component c i Convolution with 1 / πt, the expression is:

[0015]

[0016] In the formula, τ represents the concept of time;

[0017] Step S22: Combine c(t) and H[c(t)] to form the analytical signal z(t), which is expressed as:

[0018]

[0019] Where a(t) and Represent the instantaneous amplitude and instantaneous phase of the signal respectively;

[0020] Step S23: Calculate the instantaneous frequency:

[0021]

[0022] Preferably, in step S3, the discharge power P of the auxiliary power supply is calculated m The expression of (t) is:

[0023]

[0024] Where, P m,sc (t) represents the auxiliary power output power requirement generated by the operating status of the supercapacitor array, P m,hu(t) is the auxiliary power output power requirement generated by the operating status of the hydrogen unit, α i is the proportional coefficient of each state quantity, P sc (t), P el (t) and P fc (t) are the actual operating power of supercapacitor, electrolyzer and fuel cell, SOC sc (t) and LOH hst (t) are the state of charge of the supercapacitor array and the hydrogen storage level of the hydrogen storage tank, respectively.

[0025] Preferably, the calculation formula for the state of charge of the supercapacitor array is:

[0026]

[0027] Where, E sc,r Indicates the rated capacity of the supercapacitor array, E sc (t) represents the remaining charge in the supercapacitor at time t.

[0028] Preferably, the calculation formula for the hydrogen storage level of the hydrogen storage tank is:

[0029]

[0030] Where, E hst,r Indicates the rated capacity of the hydrogen storage tank, E hst (t) represents the remaining amount of hydrogen in the hydrogen storage tank at time t.

[0031] Preferably, the sliding adjustment rules include:

[0032] 1) When P sc (t)<P sc,max , SOC sc (t)<SOC sc,max 、P el (t)>P el,r When , lower the demarcation frequency;

[0033] 2) When P sc (t)<P sc,max , SOC sc (t)<SOC sc,max 、P el (t)>0、LOH hst (t)>LOH hst,max When , lower the demarcation frequency;

[0034] 3) When P sc (t)>-P sc,max , SOC sc (t)>SOC sc,min 、P fc(t)>P fc,r When , lower the demarcation frequency;

[0035] 4) When P sc (t)>-P sc,max , SOC sc (t)>SOC sc,min 、P fc (t)>0、LOH hst (t)<LOH hst,min When , lower the demarcation frequency;

[0036] 5) When P sc (t)>P sc,max 、P el (t)<P el,r 、LOH hst (t)<LOH hst,max When , increase the demarcation frequency;

[0037] 6) When P sc (t)>0、SOC sc (t)>SOC sc,max 、P el (t)<P el,r 、LOH hst (t)<LOH hst,max When , increase the demarcation frequency;

[0038] 7) When P sc (t)<-P sc,max 、P fc (t)<P fc,r 、LOH hst (t)>LOH hst,min When , increase the demarcation frequency;

[0039] 8) When P sc (t)<0, SOC sc (t)<SOC sc,max 、P fc (t)<P fc,r 、LOH hst (t)>LOH hst,min When , increase the demarcation frequency;

[0040] P sc (t), P el (t), P fc (t) represents the actual operating power of the supercapacitor array, electrolyzer, and fuel cell, respectively. SOC sc (t) represents the state of charge of the supercapacitor array, LOH hst (t) represents the hydrogen storage level of the hydrogen storage tank, P sc,max Indicates the maximum charging power of the supercapacitor array, -Psc,max Represents the maximum discharge power of the supercapacitor array, P el,r and P fc,r Represent the rated power of electrolyzer and fuel cell, SOC sc,max and SOC sc,min Respectively represent the upper and lower limits of the state of charge of the supercapacitor, LOH hst,max and LOH hst,min They respectively represent the upper and lower limits of the hydrogen storage level of the hydrogen storage tank.

[0041] Preferably, the step frequency of the sliding adjustment is set to 1×10 -6 Hz.

[0042] The present invention also proposes a fluctuating power smoothing system based on a hydrogen-electric hybrid energy storage system, the system comprising a hydrogen-electric hybrid energy storage system, a frequency analysis module, an auxiliary power supply power compensation module and a sliding distribution adjustment module;

[0043] The hydrogen-electric hybrid energy storage system includes a supercapacitor array, a hydrogen energy storage unit, an auxiliary power supply and a converter. The hydrogen energy storage unit includes an electrolyzer, a fuel cell and a hydrogen storage tank.

[0044] The frequency analysis module is used to perform frequency analysis on the original rapid fluctuation power through empirical mode decomposition and Hilbert-Huang transform to obtain the sliding range of the boundary frequency;

[0045] The auxiliary power supply power compensation module is used to adjust the discharge power of the auxiliary power supply to compensate for the loss power;

[0046] The sliding allocation adjustment module is used to perform sliding adjustment on the boundary frequency according to a set sliding adjustment rule.

[0047] Preferably, the sliding adjustment rules set by the sliding allocation adjustment module include:

[0048] 1) When P sc (t)<P sc,max , SOC sc (t)<SOC sc,max 、P el (t)>P el,r When , lower the demarcation frequency;

[0049] 2) When P sc (t)<P sc,max , SOC sc (t)<SOC sc,max 、P el (t)>0、LOH hst (t)>LOH hst,max When , lower the demarcation frequency;

[0050] 3) When P sc (t)>-P sc,max , SOC sc (t)>SOC sc,min 、P fc (t)>P fc,r When , lower the demarcation frequency;

[0051] 4) When P sc (t)>-P sc,max , SOC sc (t)>SOC sc,min 、P fc (t)>0、LOH hst (t)<LOH hst,min When , lower the demarcation frequency;

[0052] 5) When P sc (t)>P sc,max 、P el (t)<P el,r 、LOH hst (t)<LOH hst,max When , increase the demarcation frequency;

[0053] 6) When P sc (t)>0、SOC sc (t)>SOC sc,max 、P el (t)<P el,r 、LOH hst (t)<LOH hst,max When , increase the demarcation frequency;

[0054] 7) When P sc (t)<-P sc,max 、P fc (t)<P fc,r 、LOH hst (t)>LOH hst,min When , increase the demarcation frequency;

[0055] 8) When P sc (t)<0, SOC sc (t)<SOC sc,max 、P fc (t)<P fc,r 、LOH hst (t)>LOH hst,min When , increase the demarcation frequency;

[0056] P sc (t), P el (t), P fc(t) represents the actual operating power of the supercapacitor array, electrolyzer, and fuel cell, respectively. SOC sc (t) represents the state of charge of the supercapacitor array, LOH hst (t) represents the hydrogen storage level of the hydrogen storage tank, P sc,max Indicates the maximum charging power of the supercapacitor array, -P sc,max Represents the maximum discharge power of the supercapacitor array, P el,r and P fc,r Represent the rated power of electrolyzer and fuel cell, SOC sc,max and SOC sc,min Respectively represent the upper and lower limits of the state of charge of the supercapacitor, LOH hst,max and LOH hst,min They respectively represent the upper and lower limits of the hydrogen storage level of the hydrogen storage tank.

[0057] The beneficial effects of the present invention include at least: establishing a hydrogen-electric hybrid energy storage system, using an auxiliary power supply for power compensation, distributing rapidly fluctuating power by setting a set boundary frequency, and adaptively sliding the boundary frequency to improve the rapidly fluctuating power absorption rate of the hydrogen-electric hybrid energy storage system under the premise of unchanged capacity, while ensuring the normal operation of each energy storage component, effectively smoothing the fluctuating power. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 is a flow chart of a method according to an embodiment of the present invention;

[0059] Figure 2 Schematic diagram of a hydrogen-electric hybrid energy storage system according to an embodiment of the present invention;

[0060] Figure 3 This is a schematic diagram of rapid power fluctuation according to an embodiment of the present invention;

[0061] Figure 4 A schematic diagram of the Hilbert spectrum according to an embodiment of the present invention;

[0062] Figure 5 Schematic diagram of the supercapacitor array operating domain and the hydrogen energy storage unit operating domain when the boundary frequency is not slipping and the auxiliary power supply is not started;

[0063] Figure 6 for Figure 5 Schematic diagram of unprocessed power;

[0064] Figure 7 Schematic diagram of the supercapacitor array operating domain and hydrogen energy storage unit operating domain when the boundary frequency slides and the auxiliary power supply is started;

[0065] Figure 8 Schematic diagram of the supercapacitor array charge state and hydrogen storage tank capacity when the boundary frequency slides and the auxiliary power supply is started;

[0066] Figure 9 Schematic diagram of auxiliary power supply motion power and boundary frequency sliding. DETAILED DESCRIPTION

[0067] The following is a clear and complete description of the technical solutions in the embodiments of the present invention, in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0068] like Figure 1 As shown, an embodiment of the present invention provides a method and system for smoothing power fluctuations based on a hydrogen-electric hybrid energy storage system, including the following steps:

[0069] Step S1: Establish a hydrogen-electric hybrid energy storage system such as Figure 2 As shown, it includes a supercapacitor array, a hydrogen energy storage unit, an auxiliary power supply and a converter. The hydrogen energy storage unit includes an electrolyzer, a fuel cell and a hydrogen storage tank.

[0070] The supercapacitor array is responsible for processing the high-frequency part of the rapidly fluctuating power, absorbing positive power to store electrical energy, and releasing electrical energy when it is negative.

[0071] The hydrogen energy storage unit is responsible for processing the low-frequency portion of rapidly fluctuating power. The electrolyzer absorbs positive power to produce hydrogen, which is stored in a hydrogen storage tank and then supplied to the fuel cell for discharge when needed to compensate for negative power.

[0072] Rapidly fluctuating power refers to the difference between the original output power of renewable energy generation and the allowed grid-connected power, or other fluctuating power generated in the power system that varies between positive and negative values. This positive and negative switching is usually in the hours and minutes.

[0073] Smoothing means that the positive power of the above-mentioned rapidly fluctuating power is absorbed and stored through the hybrid energy storage system, and the negative power is compensated by the energy released by the hybrid energy storage system.

[0074] Step S2: Perform frequency analysis on the original fast fluctuating power through empirical mode decomposition and Hilbert-Huang transform to obtain the sliding range of the demarcation frequency. The fluctuating power with a frequency higher than the demarcation frequency is allocated to the supercapacitor array, and the fluctuating power with a frequency lower than the demarcation frequency is allocated to the hydrogen energy storage unit.

[0075] Specifically, empirical mode decomposition and Hilbert-Huang transform are a signal processing method. Hilbert-Huang transform needs to first perform empirical mode decomposition on the original signal to obtain the intrinsic mode components (IMF) c in different frequency ranges. i and the residual component r n , i is the number of pre-set intrinsic mode components IMF, c i One-to-one correspondence with the IMF.

[0076] The expression of empirical mode decomposition is:

[0077]

[0078] Where, P rf (t) represents the rapid fluctuation power at time t, n represents the number of set eigenmode components, c i represents the eigenmode component, r n represents the residual component.

[0079] The Hilbert-Huang transform consists of the following steps:

[0080] Step S21: The eigenmode component c i Convolution with 1 / πt, the expression is:

[0081]

[0082] In the formula, τ represents the concept of time;

[0083] Step S22: Combine c(t) and H[c(t)] to form the analytical signal z(t), which is expressed as:

[0084]

[0085] Where a(t) and Represent the instantaneous amplitude and instantaneous phase of the signal respectively;

[0086] Step S23: Calculate the instantaneous frequency:

[0087]

[0088] Step S3: Calculating the discharge power of the auxiliary power supply based on the power requirements of the supercapacitor array and the hydrogen energy storage unit to compensate for the power loss.

[0089] The role of an auxiliary power supply is to compensate for the internal operating losses of the hybrid energy storage system. Generally, over a period of time, the total charge and discharge required by the hybrid energy storage system to handle fluctuating power are roughly equal. However, internal losses, primarily heat generation, waste a portion of the power during operation, with fuel cells being the most severely affected. This can result in the actual charge capacity not meeting the required discharge capacity. Therefore, an auxiliary power supply is designed into the system to maintain the hybrid energy storage system's charge and discharge balance.

[0090] The discharge power of the auxiliary power supply is determined by the operating state of the hybrid energy storage system. Its discharge power P m The expression of (t) is:

[0091]

[0092] Where, P m,sc (t) represents the auxiliary power output power requirement generated by the operating status of the supercapacitor array, P m,hu (t) is the auxiliary power output power requirement generated by the operating status of the hydrogen unit, α sc,i Represents the proportional coefficient of the supercapacitor array state quantity, α hu,i The proportional coefficient of the hydrogen unit state quantity, P sc (t), P el (t) and P fc (t) are the actual operating power of supercapacitor, electrolyzer and fuel cell, SOC sc (t) and LOH hst (t) are the state of charge of the supercapacitor array and the hydrogen storage level of the hydrogen storage tank, respectively.

[0093] State of charge SOC of the supercapacitor array in the embodiment of the present invention sc The calculation formula for (t) is:

[0094]

[0095] Where, E sc,r Indicates the rated capacity of the supercapacitor array, E sc (t) represents the remaining capacity in the supercapacitor at time t;

[0096] Hydrogen storage level LOH of hydrogen storage tank hst The calculation formula for (t) is:

[0097]

[0098] Where, E hst,r Indicates the rated capacity of the hydrogen storage tank, E hst (t) represents the remaining amount of hydrogen in the hydrogen storage tank at time t.

[0099] Step S4: setting a sliding adjustment rule and slidingly adjusting the boundary frequency to adjust the distribution of the fluctuating power and improve the power absorption rate.

[0100] Specifically, the demarcation frequency f c (t) needs to be changed according to the operating state to meet the needs of different working conditions; therefore, the sliding range of the demarcation frequency obtained in step S2 [0,f c,max ], the dividing frequency f c (t) will be based on the working conditions of the internal equipment of the hybrid energy storage system in [0,f c,max ] Slide within the interval, f c,max Indicates that the frequency of the power allocated to the hydrogen energy storage unit is not allowed to be higher than this value.

[0101] In the embodiment of the present invention, the step frequency of the sliding adjustment is set to 1×10 -6 Hz to achieve precise adjustment, the sliding adjustment rules include:

[0102] 1) When P sc (t)<P sc,max , SOC sc (t)<SOC sc,max 、P el (t)>P el,r When , lower the demarcation frequency;

[0103] 2) When P sc (t)<P sc,max , SOC sc (t)<SOC sc,max 、P el (t)>0、LOH hst (t)>LOH hst,max When , lower the demarcation frequency;

[0104] 3) When P sc (t)>-P sc,max , SOC sc (t)>SOC sc,min 、P fc (t)>P fc,r When , lower the demarcation frequency;

[0105] 4) When P sc (t)>-P sc,max , SOC sc (t)>SOC sc,min 、P fc (t)>0、LOH hst (t)<LOH hst,min When , lower the demarcation frequency;

[0106] 5) When P sc(t)>P sc,max 、P el (t)<P el,r 、LOH hst (t)<LOH hst,max When , increase the demarcation frequency;

[0107] 6) When P sc (t)>0、SOC sc (t)>SOC sc,max 、P el (t)<P el,r 、LOH hst (t)<LOH hst,max When , increase the demarcation frequency;

[0108] 7) When P sc (t)<-P sc,max 、P fc (t)<P fc,r 、LOH hst (t)>LOH hst,min When , increase the demarcation frequency;

[0109] 8) When P sc (t)<0, SOC sc (t)<SOC sc,max 、P fc (t)<P fc,r 、LOH hst (t)>LOH hst,min When , increase the demarcation frequency;

[0110] P sc (t), P el (t), P fc (t) represents the actual operating power of the supercapacitor array, electrolyzer, and fuel cell, respectively. SOC sc (t) represents the state of charge of the supercapacitor array, LOH hst (t) represents the hydrogen storage level of the hydrogen storage tank, P sc,max Indicates the maximum charging power of the supercapacitor array, -P sc,max Represents the maximum discharge power of the supercapacitor array, P el,r and P fc,r Represent the rated power of electrolyzer and fuel cell, SOC sc,max and SOC sc,min Respectively represent the upper and lower limits of the state of charge of the supercapacitor, LOH hst,max and LOH hst,min They respectively represent the upper and lower limits of the hydrogen storage level of the hydrogen storage tank.

[0111] The reason for sliding the demarcation frequency is that supercapacitors can handle both high-frequency and low-frequency fluctuations. During periods when the supercapacitor array is idle or operating at low power, some of the low-frequency power originally handled by the hydrogen energy storage unit is allocated to the supercapacitor array, helping the hydrogen energy storage unit absorb the unavailable allocated power. This unavailable allocated power may be caused by the allocated power exceeding the rated power of the equipment or by the hydrogen storage tank reaching its upper or lower limit.

[0112] The present invention also provides a fluctuating power smoothing system based on a hydrogen-electric hybrid energy storage system, comprising a hydrogen-electric hybrid energy storage system, a frequency analysis module, an auxiliary power supply power compensation module, and a sliding distribution adjustment module;

[0113] The hydrogen-electric hybrid energy storage system includes a supercapacitor array, a hydrogen energy storage unit, an auxiliary power supply and a converter. The hydrogen energy storage unit includes an electrolyzer, a fuel cell and a hydrogen storage tank.

[0114] The frequency analysis module is used to perform frequency analysis on the original rapid fluctuation power through empirical mode decomposition and Hilbert-Huang transform to obtain the sliding range of the boundary frequency;

[0115] The auxiliary power supply power compensation module is used to adjust the discharge power of the auxiliary power supply to compensate for the loss power;

[0116] The sliding allocation adjustment module is used to perform sliding adjustment on the boundary frequency according to a set sliding adjustment rule.

[0117] The sliding adjustment rules set by the sliding allocation adjustment module are shown in Table 1:

[0118] Table 1

[0119]

[0120]

[0121] Specifically:

[0122] 1) When P sc (t)<P sc,max , SOC sc (t)<SOC sc,max 、P el (t)>P el,r When , lower the demarcation frequency;

[0123] 2) When P sc (t)<P sc,max , SOC sc (t)<SOC sc,max 、P el (t)>0、LOHhst (t)>LOH hst,max When , lower the demarcation frequency;

[0124] 3) When P sc (t)>-P sc,max , SOC sc (t)>SOC sc,min 、P fc (t)>P fc,r When , lower the demarcation frequency;

[0125] 4) When P sc (t)>-P sc,max , SOC sc (t)>SOC sc,min 、P fc (t)>0、LOH hst (t)<LOH hst,min When , lower the demarcation frequency;

[0126] 5) When P sc (t)>P sc,max 、P el (t)<P el,r 、LOH hst (t)<LOH hst,max When , increase the demarcation frequency;

[0127] 6) When P sc (t)>0、SOC sc (t)>SOC sc,max 、P el (t)<P el,r 、LOH hst (t)<LOH hst,max When , increase the demarcation frequency;

[0128] 7) When P sc (t)<-P sc,max 、P fc (t)<P fc,r 、LOH hst (t)>LOH hst,min When , increase the demarcation frequency;

[0129] 8) When P sc (t)<0, SOC sc (t)<SOC sc,max 、P fc (t)<P fc,r 、LOH hst (t)>LOH hst,min When , increase the demarcation frequency;

[0130] P sc (t), Pel (t), P fc (t) represents the actual operating power of the supercapacitor array, electrolyzer, and fuel cell, respectively. SOC sc (t) represents the state of charge of the supercapacitor array, LOH hst (t) represents the hydrogen storage level of the hydrogen storage tank, P sc,max Indicates the maximum charging power of the supercapacitor array, -P sc,max Represents the maximum discharge power of the supercapacitor array, P el,r and P fc,r Represent the rated power of electrolyzer and fuel cell, SOC sc,max and SOC sc,min Respectively represent the upper and lower limits of the state of charge of the supercapacitor, LOH hst,max and LOH hst,min They respectively represent the upper and lower limits of the hydrogen storage level of the hydrogen storage tank.

[0131] The present invention is further described below by means of specific examples:

[0132] like Figure 3 As shown in Table 2, the fluctuation of the original wind power output of a 2MW wind farm for 43,200 minutes a month that needs to be smoothed before grid connection is used as the rapid fluctuation power input of the present invention. The equipment parameters of the hydrogen-electric hybrid energy storage system are shown in Table 2.

[0133] Table 2

[0134]

[0135] The rapidly fluctuating power input P rf (t) Perform empirical mode decomposition, set the number of IMFs to 5, and obtain the intrinsic mode components IMF1-5 and the residual component r n , we find that IMF1 and IMF2 are the main components, accounting for 94.01%, and the frequency range is 1.27×10 -4 Hz to 1.39×10 -3 Hz, the embodiment of the present invention performs HHT analysis on IMF1 and IMF2 of the main components to obtain the Hilbert spectrum as follows Figure 4 shown.

[0136] From the frequencies of IMF1 and IMF2, we can see that the fast fluctuating power input P rf Each positive and negative alternation of (t) is concentrated in the order of hours and minutes. It can be seen from the analysis in the figure that when the frequency is less than 2.77×10 -4 Hz almost disappears, so the maximum cutoff frequency f c,max =2.77×10 -4 Hz, the frequency is lower than fc The supercapacitor array bears the power fluctuations in other frequency ranges.

[0137] The rapidly fluctuating power input P rf (t) Perform empirical mode decomposition, set the number of IMFs to 5, and obtain the intrinsic mode components IMF1-5 and the residual component r n , we find that IMF1 and IMF2 are the main components, accounting for 94.01%, and the frequency range is 1.27×10 -4 Hz to 1.39×10 -3 Hz. Therefore, we only need to perform HHT analysis on IMF1 and IMF2 to obtain the Hilbert spectrum, such as Figure 4 shown.

[0138] Therefore, according to the maximum cutoff frequency f c,max The supercapacitor array operation domain P obtained by power allocation sc,ref (t) and hydrogen energy storage unit operation domain P hu,ref (t) Figure 5 As shown, the auxiliary power supply is not working at this time, f c Fixed to f c,max No sliding, P sc,ref (t) positive value represents charging of supercapacitor array, negative value represents discharging, hydrogen energy storage unit P hu,ref Positive values ​​of (t) represent the electrolyzer consuming electricity to produce hydrogen, while negative values ​​represent the fuel cell consuming hydrogen to discharge. It can be seen that the power allocated to the supercapacitor fluctuates significantly more frequently.

[0139] Combined with Table 2 and Figure 5 , it can be clearly found that there is a peak power in the distribution domain that is much larger than the rated power of the energy storage device. If the auxiliary power supply does not work and f c If no sliding is performed, this part of the power will not be processed. Figure 6 shown.

[0140] At this time, let the auxiliary power supply P m (t) Auxiliary power supply, boundary frequency f c (t) Adaptive sliding is performed according to the established rules. The actual operation domain and the unexecuted operation domain of the supercapacitor array and hydrogen energy storage unit are as follows: Figure 7 As shown, the energy storage devices are all operating within the rated power and no operation domain is executed in P m,sc (t) and f c (t), it is almost 0.

[0141] SOC of supercapacitor array sc (t) and LOH of hydrogen storage tank hst (t) Figure 8As shown, the upper and lower limits were not exceeded, and the charging and discharging balance of the hydrogen-electric hybrid energy storage system was achieved.

[0142] Auxiliary power supply P m (t) and the cut-off frequency f c The changes of (t) are as follows Figure 9 As shown, where P m (t) respectively show P m,sc (t) and P m,hu (t). In order to quickly improve SOC in the early stage of operation sc (t) and LOH hst (t), P m (t) is large, then gradually decreases, and later rises rapidly again in order to improve the energy storage level of the hybrid energy storage system. c (t) changes compared to P m (t) is more gentle, which also indicates that there are fewer large-scale peak power in this month.

[0143] The above-mentioned specific embodiments have effectively demonstrated that the present invention is effective in smoothing fluctuating power when applied to a scenario where the models and parameters of each device in a hybrid energy storage system are determined, and has good application prospects.

[0144] The technical features of the above embodiments may be combined in any manner. To simplify the description, not all possible combinations of the technical features in the above embodiments are described. Only preferred embodiments of the present invention are presented. While the description is relatively specific and detailed, it should not be construed as limiting the scope of the present invention. As long as there are no contradictions in the combination of these technical features, they should be considered to be within the scope of this specification.

[0145] It should be noted that those skilled in the art may make various modifications and improvements without departing from the scope of the present invention, and these modifications and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be based on the appended claims.

Claims

1. A method for smoothing fluctuating power based on a hydrogen-electric hybrid energy storage system, characterized by: The following steps are involved: Step S1: establishing a hydrogen-electric hybrid energy storage system, including a supercapacitor array, a hydrogen energy storage unit, an auxiliary power supply and a converter, wherein the hydrogen energy storage unit includes an electrolyzer, a fuel cell and a hydrogen storage tank; Step S2: Performing frequency analysis on the original fast fluctuating power through empirical mode decomposition and Hilbert-Huang transform to obtain a sliding range of a cutoff frequency. Fluctuating power with a frequency higher than the cutoff frequency is allocated to the supercapacitor array, and fluctuating power with a frequency lower than the cutoff frequency is allocated to the hydrogen energy storage unit. Step S3: Calculating the discharge power of the auxiliary power supply based on the power requirements of the supercapacitor array and the hydrogen energy storage unit to compensate for the power loss; Step S4: setting a sliding adjustment rule to perform sliding adjustment on the boundary frequency to adjust the distribution of fluctuating power and improve the power absorption rate; The expression of the empirical mode decomposition in step S2 is: Where, P rf (t) represents the rapid fluctuation power at time t, n represents the number of set eigenmode components, c i represents the eigenmode component, r n represents the residual component; In step S4, the sliding adjustment rules include: 1) When P sc (t)<P sc,max , SOC sc (t)<SOC sc,max 、P el (t)>P el,r When , lower the demarcation frequency; 2) When P sc (t)<P sc,max , SOC sc (t)<SOC sc,max 、P el (t)>0、LOH hst (t)>LOH hst,max When , lower the demarcation frequency; 3) When P sc (t)>-P sc,max , SOC sc (t)>SOC sc,min 、P fc (t)>P fc,r When , lower the demarcation frequency; 4) When P sc (t)>-P sc,max , SOC sc (t)>SOC sc,min 、P fc (t)>0、LOH hst (t)<LOH hst,min When , lower the demarcation frequency; 5) When P sc (t)>P sc,max 、P el (t)<P el,r 、LOH hst (t)<LOH hst,max When , increase the demarcation frequency; 6) When P sc (t)>0、SOC sc (t)>SOC sc,max 、P el (t)<P el,r 、LOH hst (t)<LOH hst,max When , increase the demarcation frequency; 7) When P sc (t)<-P sc,max 、P fc (t)<P fc,r 、LOH hst (t)>LOH hst,min When , increase the demarcation frequency; 8) When P sc (t)<0, SOC sc (t)<SOC sc,max 、P fc (t)<P fc,r 、LOH hst (t)>LOH hst,min When , increase the demarcation frequency; P sc (t), P el (t), P fc (t) represents the actual operating power of the supercapacitor array, electrolyzer, and fuel cell, respectively. SOC sc (t) represents the state of charge of the supercapacitor array, LOH hst (t) represents the hydrogen storage level of the hydrogen storage tank, P sc,max Indicates the maximum charging power of the supercapacitor array, -P sc,max Represents the maximum discharge power of the supercapacitor array, P el,r and P fc,r Represent the rated power of electrolyzer and fuel cell, SOC sc,max and SOC sc,min Respectively represent the upper and lower limits of the state of charge of the supercapacitor, LOH hst,max and LOH hst,min They respectively represent the upper and lower limits of the hydrogen storage level of the hydrogen storage tank.

2. The method for smoothing power fluctuations based on a hydrogen-electric hybrid energy storage system according to claim 1, characterized in that: The Hilbert-Huang transform in step S2 includes the following steps: Step S21: The eigenmode component c i Convolution with 1 / πt, the expression is: In the formula, τ represents the concept of time; Step S22: Combine c(t) and H[c(t)] to form the analytical signal z(t), which is expressed as: Where a(t) and Represent the instantaneous amplitude and instantaneous phase of the signal respectively; Step S23: Calculate the instantaneous frequency:

3. The method for smoothing power fluctuations based on a hydrogen-electric hybrid energy storage system according to claim 2, characterized in that: In step S3, the discharge power P of the auxiliary power supply is calculated. m The expression of (t) is: Where, P m,sc (t) represents the auxiliary power output power requirement generated by the operating status of the supercapacitor array, P m,hu (t) is the auxiliary power output power requirement generated by the operating status of the hydrogen unit, α i is the proportional coefficient of each state quantity, P sc (t), P el (t) and P fc (t) are the actual operating power of supercapacitor, electrolyzer and fuel cell, SOC sc (t) and LOH hst (t) are the state of charge of the supercapacitor array and the hydrogen storage level of the hydrogen storage tank, respectively.

4. The method for smoothing power fluctuations based on a hydrogen-electric hybrid energy storage system according to claim 3, characterized in that: The calculation formula of the state of charge of the supercapacitor array is: Where, E sc,r Indicates the rated capacity of the supercapacitor array, E sc (t) represents the remaining charge in the supercapacitor at time t.

5. The method for smoothing power fluctuations based on a hydrogen-electric hybrid energy storage system according to claim 3, characterized in that: The calculation formula for the hydrogen storage level of the hydrogen storage tank is: Where, E hst,r Indicates the rated capacity of the hydrogen storage tank, E hst (t) represents the remaining amount of hydrogen in the hydrogen storage tank at time t.

6. The method for smoothing power fluctuations based on a hydrogen-electric hybrid energy storage system according to claim 1, characterized in that: The sliding adjustment step frequency is set to 1×10 -6 Hz.

7. A fluctuating power smoothing system based on a hydrogen-electric hybrid energy storage system, based on a fluctuating power smoothing method based on a hydrogen-electric hybrid energy storage system according to any one of claims 1 to 6, characterized in that: The system includes a hydrogen-electric hybrid energy storage system, a frequency analysis module, an auxiliary power supply power compensation module and a sliding distribution adjustment module; The hydrogen-electric hybrid energy storage system includes a supercapacitor array, a hydrogen energy storage unit, an auxiliary power supply and a converter. The hydrogen energy storage unit includes an electrolyzer, a fuel cell and a hydrogen storage tank. The frequency analysis module is used to perform frequency analysis on the original rapid fluctuation power through empirical mode decomposition and Hilbert-Huang transform to obtain the sliding range of the boundary frequency; The auxiliary power supply power compensation module is used to adjust the discharge power of the auxiliary power supply to compensate for the loss power; The sliding allocation adjustment module is used to perform sliding adjustment on the boundary frequency according to a set sliding adjustment rule.

8. The power fluctuation smoothing system based on the hydrogen-electric hybrid energy storage system according to claim 7 is characterized by: The sliding adjustment rules set by the sliding allocation adjustment module include: 1) When P sc (t)<P sc,max , SOC sc (t)<SOC sc,max 、P el (t)>P el,r When , lower the demarcation frequency; 2) When P sc (t)<P sc,max , SOC sc (t)<SOC sc,max 、P el (t)>0、LOH hst (t)>LOH hst,max When , lower the demarcation frequency; 3) When P sc (t)>-P sc,max , SOC sc (t)>SOC sc,min 、P fc (t)>P fc,r When , lower the demarcation frequency; 4) When P sc (t)>-P sc,max , SOC sc (t)>SOC sc,min 、P fc (t)>0、LOH hst (t)<LOH hst,min When , lower the demarcation frequency; 5) When P sc (t)>P sc,max 、P el (t)<P el,r 、LOH hst (t)<LOH hst,max When , increase the demarcation frequency; 6) When P sc (t)>0、SOC sc (t)>SOC sc,max 、P el (t)<P el,r 、LOH hst (t)<LOH hst,max When , increase the demarcation frequency; 7) When P sc (t)<-P sc,max 、P fc (t)<P fc,r 、LOH hst (t)>LOH hst,min When , increase the demarcation frequency; 8) When P sc (t)<0, SOC sc (t)<SOC sc,max 、P fc (t)<P fc,r 、LOH hst (t)>LOH hst,min When , increase the demarcation frequency; P sc (t), P el (t), P fc (t) represents the actual operating power of the supercapacitor array, electrolyzer, and fuel cell, respectively. SOC sc (t) represents the state of charge of the supercapacitor array, LOH hst (t) represents the hydrogen storage level of the hydrogen storage tank, P sc,max Indicates the maximum charging power of the supercapacitor array, -P sc,max Represents the maximum discharge power of the supercapacitor array, P el,r and P fc,r Represent the rated power of electrolyzer and fuel cell, SOC sc,max and SOC sc,min Respectively represent the upper and lower limits of the state of charge of the supercapacitor, LOH hst,max and LOH hst,min They respectively represent the upper and lower limits of the hydrogen storage level of the hydrogen storage tank.

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