[0105] Examples:
[0106] Analysis of output characteristics of wind and solar combined power generation system
[0107] Table 1 and Table 2 respectively show the parameters of photovoltaic cells and wind turbines in a certain area.
[0108] Table 1 Photovoltaic cell parameters in a certain area
[0109]
[0110] Table 2 Fan parameters in a certain area
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[0112]
[0113] Select the sampling data of 24h a day wind speed, light intensity and temperature in a certain area as the research object, the sampling period is 15min, and the obtained system output power curve is as follows figure 2 Shown:
[0114] Since the wind speed, light intensity and temperature will be very different in different seasons, it will have a great impact on the volatility of the output power of the wind and solar combined power generation system. image 3 It is a graph of system output power in other seasons.
[0115] Compared figure 1 with figure 2 It can be seen that the output power of the wind and solar combined power generation system is greatly affected by seasonal climate changes. In different seasons, there are great differences between wind speed, light intensity and temperature, resulting in great fluctuations in the system output power. Sex, and it is difficult to grasp its laws. From image 3 It can also be seen that the output power of the wind-solar combined power generation system has not fallen as much as the output power of the wind turbine within a period of time. It can be concluded that the output power of the photovoltaic array has played a role in smoothing fluctuations to a certain extent. However, its smoothing effect is not very satisfactory. In most cases, it still cannot meet the requirements of smoothing fluctuations. From the above analysis, although renewable energy power generation has great volatility and irregularities, it can be seen from a large amount of research data that its output power has a certain annual periodicity. Therefore, a certain region is selected for a year. The representative sampling data of one day's scenery resources is used as the research object, and the system output power curve is obtained as Figure 4 Shown:
[0116] Choice of Control Algorithm for Volatility Stabilization
[0117] The present invention first selects two commonly used smoothing control algorithms: moving average method and linear least square method, and compares and analyzes the filtering effects of these two algorithms. Figure 4 As shown, the output power comparison diagram of the system using the 5th and 20th order filtering of the moving average method and the 5th and 20th order filtering of the linear least square method.
[0118] In order to more intuitively see the effect diagram of the two algorithm filtering, change Figure 5 Zoom in to get the contrast effect such as Image 6 Shown.
[0119] From Image 6 It can be seen intuitively that the curve after the 20th-order filtering of the linear least squares method is smoother than the other filtered curves, that is, the filtering effect is the best.
[0120] In order to better quantitatively analyze the smoothing system output power effects of the two control algorithms, the data calculated according to the indicators in the present invention are shown in Table 3.
[0121] Table 3 Index values of fluctuation control method
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[0123]
[0124] Through comparative analysis, The larger the value, the smoother the reference output power curve obtained. Although the M20 Greater than L20 But the Ф=6.0 of M20 is 0.81 larger than the Ф=5.19 of L20, and the required energy storage capacity is much larger, that is, the investment cost of energy storage is relatively high. Considering the values of these two indicators, the 20th-order linear least squares method is finally selected as the optimal algorithm for stabilizing the output power of the system, and the reference output power curve of the wind and solar combined power generation system is obtained as follows: Figure 7 Shown.
[0125] Battery capacity configuration
[0126] After obtaining the reference output power of the system, according to the battery charging and discharging strategy proposed above, considering two restriction conditions: maximum charging and discharging power limitation and capacity limitation, comparative analysis of the battery capacity configured under different conditions on the output of the wind and solar combined power generation system The smoothing effect of power fluctuations.
[0127] First, define the compensation percentage Ψ of the energy storage system, as shown in the definition formula:
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[0129] In the formula: m represents the system output power after energy storage in one day meets the reference output power number, and n represents the reference output power number.
[0130] The actual physics of the compensation percentage Ψ refers to the ratio of the reference output power number to the reference output power number that the output power of the wind and solar combined power generation system after the battery energy storage is applied. If Ψ=100%, it means that the system output power after energy storage is the reference output power; if Ψ=0, it means that the system output power after energy storage does not match the reference output power.
[0131] Regardless of any restrictions, the battery is configured for power and capacity. This state is called the full energy storage state, that is, the compensation percentage Ψ=100%. At this time, the required maximum charging power of the battery is 29.76kw, the maximum discharge power is 20.28kw, the capacity of the battery is 29.44kwh, and the battery charging and discharging power is as Figure 8 Shown:
[0132] From Figure 8 It can be seen that the upper part of the curve y=0 indicates that the battery is working in a state of charge, and the lower part of the curve indicates that it is working in a state of discharging; in the state of full energy storage, the combination of wind and solar energy after the storage of the battery The output power of the power generation system is completely consistent with the reference output power, and its correlation coefficient r=1; most of the charging and discharging power of the battery is within 15kw. If the battery specifications are configured according to the full energy storage state, although the smoothing effect is very good, The output power curve obtained is the reference output power curve, but the cost of the battery is expensive, which leads to poor economy of the entire system. By optimizing the energy storage capacity of the battery, a trade-off between the smoothing effect and the economic investment cost can be achieved.
[0133] For example, when the compensation percentage Ψ=90%, the maximum charging power of the battery required to be configured is 19.33kw, the maximum discharge power is 15.14kw, and the capacity of the battery is 18.93kwh. At this time, the working state of the battery is compared with the working state under full energy storage. Picture 9 Shown.
[0134] From Picture 9 It can be clearly seen that when the compensation percentage Ψ is 90%, the battery has capacity limitations, that is, when the battery is charged to the rated capacity, the battery cannot continue to be charged, and when the discharge reaches the minimum capacity, the battery cannot continue to discharge , So that its charging and discharging power cannot be fully compensated. The output power curve of the system after the battery energy storage is as follows Picture 10 Shown.
[0135] From Picture 10 It can be seen that when the compensation percentage Ψ is 90%, the output power curve is in good agreement with the reference power curve, which has a good effect on the output power fluctuation of the wind and solar combined power generation system.
[0136] When changing the magnitude of the compensation percentage Ψ, the analysis process is similar to the case where Ψ is 90%, so it will not be repeated.
[0137] Smoothing effect evaluation and economic analysis
[0138] Analyze the energy storage capacity configuration, fluctuation stabilization effect and economic cost when the compensation percentage Ψ is 100%, 90%, 80%, 70%, and 60%. The market price of the battery is known to be about 3000 yuan/kwh. The results are shown in Table 4.
[0139] Table 4 Smoothing effect evaluation index value
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[0141] It can be seen from Table 4 that when the compensation percentage Ψ is 100%, the smoothing effect is obviously the best, but due to the higher cost of the battery, it brings a certain degree of uneconomical efficiency. When the compensation percentage Ψ is 60%, the maximum output power fluctuation reduction percentage α is reduced to 35.6%, and its smoothing effect is poor, which basically cannot meet the requirements for smoothing output power fluctuations. When the compensation percentage Ψ is less than 60%, the smoothing effect is worse than that with a compensation percentage Ψ of 60%, so there is no need to discuss it again.
[0142] In summary, the higher the compensation percentage Ψ, the larger the battery energy storage specification required, the higher the corresponding investment cost, and the smoother the output power curve of the corresponding wind-wind combined power generation system. Therefore, if the output power smoothness is required to be high, the battery energy storage capacity can be optimized according to the compensation percentage Ψ between 100% and 90%. In this interval, the maximum fluctuation of the output power of the wind and solar combined power generation system is reduced. The percentage α dropped from 83.7% to 73.6%, and the energy storage investment cost also dropped from 88,32 thousand yuan to 56.79 million yuan; if the battery economic investment cost is required to be lower, and the requirements for smoothing the output power fluctuation effect are second, the compensation percentage can be used Ψ is between 90% and 80% to optimize the configuration of battery energy storage capacity. In this interval, the reduction percentage α of the maximum fluctuation of the output power of the wind and solar combined power generation system is reduced from 73.6% to 56.1%, and the energy storage investment cost is reduced from 56.79 million Yuan dropped to 44,97 thousand yuan. Although the smoothing effect is slightly poor, the economic investment cost is significantly reduced; if there are restrictions on output power fluctuations, it can be configured according to the minimum energy storage capacity that meets the fluctuation restrictions; comprehensive considerations For the effect of smoothing the output power and the investment cost of the battery, the present invention proposes to optimize the capacity of the battery according to the compensation percentage Ψ of 80%, thereby realizing the trade-off between the smooth output of the wind and solar combined power generation system and the investment cost of the battery.
