Hybrid energy storage system output power distribution method based on edge charge control coefficient

Abstract

The invention discloses a hybrid energy storage system output power distribution method based on an edge charge control coefficient, and the method comprises the steps: adjusting the output distribution of a hybrid energy storage system based on the edge charge control coefficient of an energy type energy storage system according to whether the edge charge control coefficient exceeds a threshold value or not, and adjusting a filter coefficient according to the new charge state of the hybrid energy storage system. According to the method, the characteristic that the operation life of energy-type energy storage is closely related to the charge state of the energy-type energy storage is utilized, power output adjustment is achieved by limiting the charge state of the energy-type energy storage during energy distribution of the hybrid energy storage, additional control quantity does not need to be increased, and it can be ensured that the system safely and stably operates under the charge state balance condition.

Description

Technical Field

[0001] The present invention relates to energy storage technology in the field of renewable energy, and in particular to a method for real-time distribution of output power of a hybrid energy storage system based on an edge charge control coefficient for an offshore wind farm. Background Art

[0002] As a key source of renewable energy, the stability and efficiency of offshore wind farms are crucial to the reliable operation of the power grid. However, the intermittent and unpredictable nature of wind energy poses many challenges to the energy management of offshore wind farms. The volatility of wind power output makes it difficult for the power grid to maintain stable power supply when the wind speed varies greatly. Therefore, how to effectively manage wind power output and smooth out fluctuations has become the key to improving the operating efficiency of offshore wind farms.

[0003] To meet this challenge, energy storage systems are widely used as an important auxiliary technology for wind power systems. Energy storage systems can store excess wind energy when the wind is too strong to avoid energy waste, and release the stored energy when the wind is insufficient, thereby balancing the supply and demand of the power grid.

[0004] Existing energy storage technologies can be roughly divided into two categories, namely energy storage and power storage. Energy storage systems are mainly used for long-term energy storage to provide continuous energy output, while power storage systems are used for short-term high-power output to cope with instantaneous changes in grid load. Although these two types of energy storage systems each have certain advantages, they lack flexibility in dealing with wind power fluctuations, cannot meet the needs of different time scales at the same time, and are difficult to optimize the overall efficiency of the energy storage system when smoothing wind power fluctuations. In hybrid energy storage systems, existing energy storage system energy distribution schemes are often based on predetermined rules or experience, and lack sufficient consideration of the real-time dynamic characteristics of the system. In hybrid energy storage systems, the coordinated work and power distribution of different types of energy storage units usually rely on simple rules or schedules, which makes it difficult to provide efficient and real-time energy scheduling when wind speeds vary greatly and load demand fluctuates.

[0005] Therefore, how to achieve dynamic and automatic adjustment and scheduling between different types of energy storage units and ensure system stability and improve efficiency is a key issue in the optimization of hybrid energy storage systems. Summary of the invention

[0006] The purpose of the present invention is to provide a hybrid energy storage system output power distribution method based on edge charge control coefficient, aiming to solve the defects in the prior art, and can distribute the output power of the hybrid energy storage system in real time, cope with complex, nonlinear and dynamically changing wind power output, reasonably distribute the output power of energy-type and power-type energy storage, smooth out wind power fluctuations, effectively extend the service life of energy storage equipment, and ensure that the charge states of different energy storage devices work together under safe and balanced conditions to achieve efficient operation of offshore wind power systems.

[0007] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical scheme: The output power distribution method of the hybrid energy storage system based on the edge charge control coefficient, the hybrid energy storage system includes an energy type energy storage system and a power type energy storage system, characterized in that: the output power distribution method is based on the power of the hybrid energy storage system at the sampling time , filter coefficient c(t) and edge charge control coefficient k(t) of energy storage system, and determine the output power distribution of energy storage system and power storage system in real time, t is the sampling time; where: , and They represent the upper and lower limits of the state of charge of the energy storage system respectively; Represents the state of charge of the energy storage system at the sampling time; And according to the determined output power distribution, the charge state of the energy storage system and the power storage system is recalculated. If the charge state is within the set upper and lower limits, the current output power distribution is kept unchanged and the distribution result is output. Otherwise, the recalculated charge state of the energy storage system is used, and the edge charge control coefficient is recalculated. The edge charge control coefficient k(t) of the energy storage system is iterated using the recalculated edge charge control coefficient, and the filter coefficient is recalculated. The filter coefficient c(t) is iterated using the recalculated filter coefficient to redetermine the output power distribution of the energy storage system and the power storage system until the charge state of the energy storage system and the power storage system are within the set upper and lower limits.

[0008] On the basis of adopting the above technical solutions, the present invention may also adopt the following further technical solutions, or use these further technical solutions in combination: The hybrid energy storage system output power distribution method comprises the following steps: (1) Calculate the edge charge control coefficient k(t) and compare it with the edge charge control coefficient threshold k*. When the k(t) value is less than or equal to k*, the energy storage system triggers the attenuation mechanism and the attenuation coefficient ; When the value of k(t) is greater than k*, the attenuation coefficient b(t) =1, full power output of energy storage system; The output power allocated to the energy storage system at the sampling time Calculate based on the sampling time value of the filter coefficient used in the first-order filter algorithm, and calculate based on the power of the hybrid energy storage system With the output power Obtain the output power allocated to the power type energy storage system at the sampling time ,in, ; (2) After determining the output power distribution of the energy storage system and the power storage system, the charge state of the energy storage system and the power storage system are calculated in real time. If the charge state is within the set upper and lower limits, the current output power distribution ratio is kept unchanged and the distribution result is output; if the charge state of the energy storage system and / or the charge state of the power storage system exceeds their upper and lower limits, the marginal charge control coefficient is recalculated using the recalculated charge state of the energy storage system, and the filter coefficient is recalculated based on the recalculated marginal charge control coefficient. The filter coefficient value c(t) is iterated using the recalculated filter coefficient to recalculate the output power allocated to the energy storage system, and the output power allocated to the energy storage system at the sampling time in step (1) is replaced by the recalculated output power. , return to step (1).

[0009] Recalculate the filter coefficient using the following formula: , c'(t) is the filtering coefficient at the iterated sampling moment.

[0010] The following formula is used to calculate the output power allocated to the energy storage system: , t-1 is the previous sampling time of sampling time t.

[0011] The k*=0.5.

[0012] Before output power distribution is performed, the filter coefficients in the first-order filter algorithm in the output power distribution of the hybrid energy storage system are initialized.

[0013] Before distributing the output power of the hybrid energy storage system, obtain the value.

[0014] Due to the adoption of the technical solution of the present invention, the beneficial effects of the present invention are: Traditional dispatch strategies do not specifically monitor the state of charge (SOC) of energy storage, and cannot ensure that the output of the hybrid energy storage system can operate under safe and stable conditions. The present invention utilizes the characteristics that the operation of energy storage units is closely related to their state of charge, and realizes power output adjustment by limiting their state of charge when distributing energy in the hybrid energy storage system. At the same time, there is no need to add additional control quantities, which can ensure that the system operates safely and stably under SOC equilibrium conditions.

[0015] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1is a flow chart of the present invention; Figure 2 It is the power that the offshore wind farm in the example of the present invention needs to bear after low-pass filtering within 30 minutes by the hybrid energy storage; Figure 3 The real-time power distribution of the energy storage system in the hybrid energy storage system within 30 minutes after the method of the present invention is adopted; Figure 4 The real-time power distribution of the power-type energy storage system in the hybrid energy storage system within 30 minutes after the method of the present invention is adopted.

[0017] Figure 5 After adopting the method of the present invention, the SOC change of the energy type energy storage system in the hybrid energy storage system within 30 minutes.

[0018] Figure 6 After adopting the method of the present invention, the SOC change of the power type energy storage system in the hybrid energy storage system within 30 minutes. DETAILED DESCRIPTION

[0019] In one embodiment of the present invention, the offshore wind power-hybrid energy storage system composed of a power-type energy storage system and an energy-type energy storage system is optimized by the following steps, wherein in this example, the power-type energy storage adopts supercapacitors and the energy-type energy storage adopts battery energy storage; Reference Figure 1 The output power distribution method of the hybrid energy storage system based on the edge charge control coefficient provided by the present invention comprises the following steps: (1) Calculate the edge charge control coefficient k(t) and compare it with the edge charge control coefficient threshold k*. The preferred value of k* is 0.5. When the k(t) value is less than or equal to k*, the energy storage system triggers the attenuation mechanism, and the attenuation coefficient ; When the value of k(t) is greater than k*, the attenuation coefficient b(t) =1, the energy storage system has full power output; k(t) is calculated using the following method: , t is the sampling time; and They represent the upper and lower limits of the state of charge of the energy storage system respectively; The state of charge of the energy storage system representing the sampling time is calculated using the following formula: , is the initial charge number in the energy storage system, , Respectively represent the charging and discharging efficiency of the energy storage system, , are the charging and discharging power of the energy storage system, is the rated charge number of the energy storage system. This formula is also applicable to the calculation of the state of charge of the power storage system.

[0020] For power-type energy storage systems and energy-type energy storage systems, the state of charge calculation and constraints are:

[0021] The subscript B indicates an energy storage system, the subscript SC indicates a power storage system, the subscripts ch and dis indicate the charging process and the discharging process respectively; the superscripts min and max indicate the lower and upper limits respectively; SOC indicates the state of charge, t indicates the sampling time, P indicates the power, , Represent the rated charge number of energy storage system and power storage system respectively. The calculation process fully considers the power output fluctuation of wind farm and the dynamic characteristics of energy storage system, such as battery charging and discharging efficiency and rated energy and power; The output power allocated to the energy storage system at the sampling time Calculate based on the sampling time value of the filter coefficient used in the first-order filter algorithm, and calculate based on the power of the hybrid energy storage system With the output power Obtain the output power allocated to the power type energy storage system at the sampling time ,in, .

[0022] in, Obtained based on the hybrid energy storage system's ability to smooth fluctuations. For any sampling time t, the total output power is scheduled to a certain value through the scheduling plan , which is composed of: The real-time total system output power can be obtained by filtering the offshore wind power system using the first-order filtering method. Real-time output power of offshore wind power The relationship is , where c1 is the filter coefficient for smoothing wind farm fluctuations at the sampling time, and t-1 is the previous sampling time. Therefore, for any sampling time t, the real-time power of the hybrid energy storage can be obtained by At the same time, the low-pass filtering algorithm is used, that is, , calculate the output power allocated to the energy storage system at sampling time t, t-1 is the previous sampling time of sampling time t. When calculating the output power allocated to the energy storage system for the first time at each sampling time, b(t) can be set to an initial value based on experience, such as 0.5.

[0023] The filter coefficient of the hybrid energy storage system needs to be initialized. The initial value is any value between 0 and 1. The power required by the energy storage system after initialization is obtained. , subsequently, the initial value of the filter coefficient at each sampling moment first adopts the filter coefficient value at the previous sampling moment or the filter coefficient value after iteration.

[0024] (2) After determining the output power distribution of the energy storage system and the power storage system, the charge state of the energy storage system and the power storage system are calculated in real time. If the charge state is within the set upper and lower limits, the current output power distribution ratio is kept unchanged and the distribution result is output; if the charge state of the energy storage system and / or the charge state of the power storage system exceeds its upper and lower limits, the recalculated charge state of the energy storage system is used to recalculate the marginal charge control coefficient, and the filter coefficient is recalculated based on the recalculated marginal charge control coefficient. The filter coefficient value c(t) is iterated using the recalculated filter coefficient, and the filter coefficient value c(t) is recalculated based on the formula Calculate the output power allocated to the energy storage system, and replace the output power allocated to the energy storage system at the sampling time in step (1) with the recalculated output power , return to step (1).

[0025] Recalculate the filter coefficient using the following formula: , c'(t) is the filtering coefficient at the iterated sampling moment.

[0026] Combine the following Figure 2-Figure 6 The present invention is further illustrated with reference to the accompanying drawings and embodiments.

[0027] Figure 2 The figure shows the power distribution that the hybrid energy storage system needs to bear in a 12MW offshore wind farm within 30 minutes after low-pass filtering. The low-pass filter is used to remove high-frequency fluctuations in wind power output and smooth the wind power curve. The figure shows that during periods of large wind power fluctuations, the energy storage system needs to respond quickly to maintain the stability of the power grid. Through this smoothing process, the impact of wind power fluctuations on the power grid can be reduced, providing reasonable power scheduling requirements for the energy storage system.

[0028] Figure 3 The power distribution of the energy storage system (battery) in the hybrid energy storage system within 30 minutes after the method of the present invention is adopted is demonstrated. It can be seen that the battery is relatively stable during this process and does not start and stop frequently. Each power on and off lasts for a long time, indicating that the battery is mainly responsible for medium and long-term power regulation tasks to ensure that the system provides sufficient energy supply during peak demand. The battery balances the output fluctuations of the wind farm by gradually discharging and charging, while avoiding frequent charging and discharging operations to extend the service life of the battery.

[0029] Figure 4 It shows the real-time power distribution of the power type energy storage system (supercapacitor) in the hybrid energy storage system within 30 minutes after adopting the method of the present invention. Unlike batteries, supercapacitors are mainly used to quickly respond to high-frequency fluctuations in wind farm power, and therefore exhibit obvious frequent start and stop phenomena. Through this high-frequency opening and closing operation, supercapacitors can quickly suppress the high-frequency components in wind power output, thereby achieving grid stability. However, too frequent starts and stops will increase the wear and tear of the equipment, so it is necessary to reasonably control the charging and discharging strategy of the supercapacitor during design to ensure the stability of the system and the service life of the equipment.

[0030] Figure 5 and Figure 6 The above diagrams show the changes in the state of charge of the energy storage system (battery) and the power storage system (supercapacitor) after the method of the present invention is adopted. The upper and lower straight lines in the figure are the minimum and maximum values ​​of the specified state of charge, respectively. It can be seen that each energy storage system has not exceeded the state of charge limit. It can also be seen from the waveform that the fluctuation of battery energy storage (energy storage system) is much lower than that of supercapacitor (power storage system), which meets the requirements of high and low frequency power distribution.

[0031] In summary, the technical solution of the present invention utilizes the different state of charge characteristics of energy-type energy storage and power-type energy storage to achieve real-time allocation of a hybrid energy storage system based on edge control of the state of charge of energy-type energy storage. At the same time, no additional control quantity is required, and the system can be ensured to operate safely and stably under SOC equilibrium conditions.

[0032] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A hybrid energy storage system output power distribution method based on edge charge control coefficient, wherein the hybrid energy storage system includes an energy type energy storage system and a power type energy storage system, and is characterized in that: The output power distribution method is based on the hybrid energy storage system power at the sampling time. , filter coefficient c(t) and edge charge control coefficient k(t) of energy storage system, and determine the output power distribution of energy storage system and power storage system in real time, t is the sampling time; where: , and They represent the upper and lower limits of the state of charge of the energy storage system respectively; Represents the state of charge of the energy storage system at the sampling time; And according to the determined output power distribution, the charge state of the energy storage system and the power storage system is recalculated. If the charge state is within the set upper and lower limits, the current output power distribution is kept unchanged and the distribution result is output. Otherwise, the recalculated charge state of the energy storage system is used, and the edge charge control coefficient is recalculated. The edge charge control coefficient k(t) of the energy storage system is iterated using the recalculated edge charge control coefficient, and the filter coefficient is recalculated. The filter coefficient c(t) is iterated using the recalculated filter coefficient to redetermine the output power distribution of the energy storage system and the power storage system until the charge state of the energy storage system and the power storage system are within the set upper and lower limits.

2. The method for distributing output power of a hybrid energy storage system according to claim 1, characterized in that: The hybrid energy storage system output power distribution method comprises the following steps: (1) Calculate the edge charge control coefficient k(t) and compare it with the edge charge control coefficient threshold k*. When the k(t) value is less than or equal to k*, the energy storage system triggers the attenuation mechanism and the attenuation coefficient ; When the value of k(t) is greater than k*, the attenuation coefficient b(t) =1, full power output of energy storage system; The output power allocated to the energy storage system at the sampling time Calculate based on the sampling time value of the filter coefficient used in the first-order filter algorithm, and calculate based on the power of the hybrid energy storage system With the output power Obtain the output power allocated to the power type energy storage system at the sampling time ,in, ; (2) After determining the output power distribution of the energy storage system and the power storage system, the charge state of the energy storage system and the power storage system are calculated in real time. If the charge state is within the set upper and lower limits, the current output power distribution ratio is kept unchanged and the distribution result is output; if the charge state of the energy storage system and / or the charge state of the power storage system exceeds their upper and lower limits, the marginal charge control coefficient is recalculated using the recalculated charge state of the energy storage system, and the filter coefficient is recalculated based on the recalculated marginal charge control coefficient. The filter coefficient value c(t) is iterated using the recalculated filter coefficient to recalculate the output power allocated to the energy storage system, and the output power allocated to the energy storage system at the sampling time in step (1) is replaced by the recalculated output power. , return to step (1).

3. The hybrid energy storage system output power distribution method according to claim 1, characterized in that: Recalculate the filter coefficient using the following formula: , c'(t) is the filtering coefficient at the iterated sampling moment.

4. The hybrid energy storage system output power distribution method according to claim 2, characterized in that: The following formula is used to calculate the output power allocated to the energy storage system: , t-1 is the previous sampling time of sampling time t.

5. The hybrid energy storage system output power distribution method according to claim 2, characterized in that: The k*=0.

5.

6. The hybrid energy storage system output power distribution method according to claim 1, characterized in that: Before output power distribution is performed, the filter coefficients in the first-order filter algorithm in the output power distribution of the hybrid energy storage system are initialized.

7. The hybrid energy storage system output power distribution method according to claim 1, characterized in that: Before distributing the output power of the hybrid energy storage system, obtain the value.

Images