A charge-discharge control method for hybrid energy storage participating in grid frequency modulation

Abstract

The application provides a charge-discharge control method for grid frequency modulation by mixed energy storage, which fully utilizes the respective advantages of power-type energy storage and capacity-type energy storage. When a small-amplitude short-time load step disturbance or a small-amplitude short-time interval load impact disturbance occurs in a power grid, the power-type energy storage (such as flywheel energy storage) alone participates in primary frequency modulation; when the load disturbance amplitude is large or the load disturbance is long-lasting, the power-type energy storage first acts, and the capacity-type energy storage (such as battery energy storage) then acts, thereby making up for the possible power deficiency or SOC deficiency of the power-type energy storage in the operation process. The method of the application also relatively reduces the frequent action of the capacity-type energy storage system, thereby prolonging the service life of the capacity-type energy storage system.

Description

Technical Field

[0001] This invention belongs to the field of power grid frequency regulation technology, and in particular relates to a charging and discharging control method for hybrid energy storage participating in power grid frequency regulation. Background Technology

[0002] With the large-scale integration of new energy sources such as wind power and photovoltaics into the power grid, the volatility and indirectness of the active power output from these sources will severely impact the stability of the power system and power quality. Against this backdrop, maintaining grid frequency stability under conditions of large-scale interconnected power systems and high wind power penetration has become a major challenge for my country's power system. Energy storage participating in grid frequency regulation is an important way to address this issue.

[0003] Meanwhile, the national standard "Technical Specifications and Test Guidelines for Primary Frequency Regulation of Grid-Connected Power Sources" (GB / T40595-2021) was officially released, explicitly requiring energy storage power stations, photovoltaic power stations, and wind power stations to have primary frequency regulation capabilities, and it came into effect on May 1, 2022. In addition, at least 16 provincial power grid companies have also issued relevant documents requiring new energy power stations to have primary frequency regulation capabilities, while provinces that have not issued separate documents have also put forward corresponding requirements in their "two detailed rules." As primary frequency regulation gradually becomes an essential "skill" for new energy power stations, the call for adding energy storage devices to them is growing louder.

[0004] Energy storage systems can convert electrical energy into other forms of energy and flexibly, quickly, and accurately regulate the power supply and demand balance of the system, improving the stability of the power system. Modern power grids have complex and diverse energy and power demands, and a single type of energy storage technology often cannot meet these requirements. However, combining two or more energy storage technologies can leverage their respective strengths and economic advantages, greatly expanding the application scenarios of energy storage systems. Various energy storage technologies have developed rapidly in recent years and are beginning to be widely used in auxiliary grid frequency regulation, achieving good results in this field. Among them, power-type energy storage (such as flywheel energy storage technology) and capacity-type energy storage (such as battery energy storage) have different characteristics and advantages.

[0005] Power-type energy storage, such as flywheel energy storage, is a relatively new mechanical energy storage technology that boasts advantages such as long lifespan, high instantaneous power, and fast response speed. However, it suffers from low energy density, high cost, and poor economic efficiency in large-capacity configurations. Capacity-type energy storage, such as battery energy storage, offers advantages such as high energy density, long charge-discharge duration, and relatively lower cost. However, frequent charge-discharge cycles significantly reduce its usable lifespan. Therefore, this invention, considering the characteristics of both energy storage technologies, proposes a charge-discharge control strategy that fully leverages the advantages of both technologies to achieve better frequency regulation performance than a single type of energy storage. Summary of the Invention

[0006] To address the above problems, this invention proposes a charging and discharging control method for hybrid energy storage participating in grid frequency regulation, comprising the following steps:

[0007] Step 1: Acquire real-time data from the hybrid energy storage system, including the power-type energy storage system within the hybrid energy storage system.

[0008] State of charge State of charge of capacity-type energy storage systems ;

[0009] Step 2: Monitor the state of charge of the hybrid energy storage system in real time and determine the power type obtained in Step 1.

[0010] State of charge of energy storage system State of charge of capacity-type energy storage systems Does it meet the following basic conditions:

[0011] ,

[0012] If the requirements are not met, the hybrid energy storage system will be locked out. , For real-time charging and discharging power of power-type energy storage systems, Real-time charging and discharging power for capacity-type energy storage systems;

[0013] If satisfied, proceed to step 3;

[0014] Step 3: Obtain the AGC allocation to the hybrid energy storage system when a load impact disturbance occurs in the power grid at time t1.

[0015] Frequency load command increment ;

[0016] Step 4: The charging and discharging control of the hybrid energy storage system is carried out according to the principle that the power-type energy storage system takes priority in operation, and the capacity-type energy storage system enters the charging and discharging state at an appropriate time to make up for the shortcomings of the power-type energy storage system.

[0017] Furthermore, in step 4, the power-type energy storage system starts outputting power at time t1, and the capacity-type energy storage system starts outputting power at time t2. The time interval between t2 and t1 is... , t4 is the step descent time of the frequency regulation load command allocated by AGC to the energy storage system. When the hybrid energy storage system is in operation, The reference value can be calculated using the following formula:

[0018] ,

[0019] in, For the rated capacity of power-type energy storage systems, This refers to the rated power of a power-type energy storage system.

[0020] when hour:

[0021] ,

[0022] when At that time, the output of the hybrid energy storage system is controlled according to three situations: insufficient power of the power-type energy storage system and sufficient current stored power; sufficient power and insufficient current stored power; and insufficient power and insufficient current stored power.

[0023] Furthermore, when At time t2, the power-type energy storage system has insufficient power but sufficient stored energy. , Then we have:

[0024] ,

[0025] in, This refers to the rated power of a capacity-type energy storage system.

[0026] Furthermore, when At time t2, the power-type energy storage system has sufficient power but insufficient stored energy. , ,

[0027] when hour:

[0028] ,

[0029] Until time t3, the power-type energy storage system begins to operate at a stable power output. After charging, the output of the hybrid energy storage system is set as follows:

[0030] when hour:

[0031] ,

[0032] The charging power for the power-type energy storage system is negative; t3 is the moment the power-type energy storage system stops outputting power; and K is the constant-rate decrease coefficient of the power storage system's output.

[0033] .

[0034] Furthermore, when At time t2, both the power and the current stored energy of the power-type energy storage system are insufficient. , ,

[0035] when hour:

[0036] ,

[0037] Until time t3, the power-type energy storage system begins to maintain a stable power output. After charging, the output of the hybrid energy storage system is set as follows:

[0038] when hour:

[0039] ,

[0040] when hour:

[0041] ,

[0042] △t is the constant-speed power reduction time of the power-type energy storage system.

[0043] Furthermore, power-type energy storage systems include flywheel energy storage systems and supercapacitor energy storage systems.

[0044] Furthermore, capacity-type energy storage systems include battery energy storage systems.

[0045] The beneficial effects of this invention are as follows: This invention proposes a charging and discharging method for a hybrid energy storage system during load disturbances, which fully utilizes the advantages of both power-type and capacity-type energy storage. When the power grid experiences a small-amplitude, short-term load step disturbance or a small-amplitude, short-interval load impact disturbance, power-type energy storage (such as flywheel energy storage) participates in primary frequency regulation alone; while when the load disturbance is large in amplitude or prolonged in duration, power-type energy storage operates first, followed by capacity-type energy storage (such as battery energy storage), compensating for potential power insufficiency or SOC insufficiency issues that may occur during the operation of power-type energy storage. This strategy also relatively reduces the frequent operation of capacity-type energy storage systems, thus extending their lifespan. Attached Figure Description

[0046] Figure 1 This is a flowchart of the hybrid energy storage system of the present invention participating in grid frequency regulation;

[0047] Figure 2 This is the frequency regulation command allocated to the hybrid energy storage system under load impact disturbance in this invention;

[0048] Figure 3 This is a schematic diagram of the output of the hybrid energy storage system when the flywheel energy storage system is underpowered;

[0049] Figure 4 This is a schematic diagram of the output of a hybrid energy storage system when the flywheel energy storage system's SOC is insufficient;

[0050] Figure 5 This is a schematic diagram of the output of a hybrid energy storage system when both the power and SOC of the flywheel energy storage system are insufficient. Detailed Implementation

[0051] The embodiments will now be described in detail with reference to the accompanying drawings.

[0052] Figure 1 The flowchart below shows the charging and discharging control method for a hybrid energy storage system participating in grid frequency regulation according to an embodiment of the present invention, which includes the following steps. In this embodiment, the hybrid energy storage system includes a flywheel energy storage system (power-type energy storage system) and a battery energy storage system (capacity-type energy storage system).

[0053] Step 1: Obtain real-time data

[0054] The energy storage management system obtains the current state of charge of the hybrid energy storage system. and , and This indicates the current amount of electricity stored in the hybrid energy storage system. State of charge of the flywheel energy storage system This represents the state of charge (SOC) of the battery energy storage system. Its value ranges from 0 to 1. The closer it is to 1, the stronger the discharge capability; the closer it is to 0, the stronger the charging capability.

[0055] Step 2: Real-time state of charge monitoring of the energy storage system

[0056] Determine whether the state of charge obtained in step 1 meets the following basic conditions:

[0057] ,

[0058] If the requirements are not met, the energy storage system will be locked out. ; Real-time charging and discharging power for flywheel energy storage systems Provides real-time charging and discharging power for the battery energy storage system.

[0059] If the conditions are met, proceed to step 3.

[0060] Step 3: Obtain the frequency regulation load command increment of the hybrid energy storage system

[0061] When a load surge disturbance occurs in the power grid at time t1, the frequency regulation load command increment allocated by AGC (Automatic Generation Control) to the hybrid energy storage system is... ,like Figure 2 As shown, t1 is the step-up time of the frequency regulation load command allocated by AGC to the hybrid energy storage system.

[0062] Step 4: Charge and discharge control of the hybrid energy storage system

[0063] Power-type energy storage, such as supercapacitors and flywheel energy storage, can discharge high power instantaneously, but its overall capacity is generally small, making it unsuitable for prolonged energy release. Taking flywheel energy storage as an example, its system response is fast, and frequent charging and discharging have little impact on its lifespan; therefore, flywheel energy storage systems are prioritized for operation. Because flywheel energy storage systems generally have small capacities, when frequency regulation commands are allocated to hybrid energy storage systems, they may encounter three scenarios: insufficient power but sufficient stored energy; sufficient power but insufficient stored energy; and insufficient power and insufficient stored energy. This fails to adequately improve the primary frequency regulation effect of the power grid. Therefore, capacity-type energy storage systems (such as battery energy storage systems) need to enter charging and discharging states at appropriate times to compensate for the shortcomings of flywheel energy storage.

[0064] The flywheel energy storage system starts generating power at time t1, and the battery energy storage system starts generating power at time t2. The time interval between t2 and t1 is... This refers to the interval between when the flywheel energy storage system and the battery energy storage system begin to output power. .

[0065] The reference value can be calculated using the following formula:

[0066] ,

[0067] in The rated capacity of the flywheel energy storage system, This refers to the rated power of the flywheel energy storage system.

[0068] when hour:

[0069] ,

[0070] in, The moment when the hybrid energy storage system is providing power.

[0071] when At that time, the output of the hybrid energy storage system is different for the three cases of the flywheel energy storage system. t4 is the step drop moment when the frequency regulation load command allocated by AGC to the energy storage system decreases.

[0072] The first scenario: The flywheel energy storage system has insufficient power, but the currently stored energy is sufficient, i.e., at time t2. , In this case, the output of the hybrid energy storage system is as follows: Figure 3 As shown, we have:

[0073] ,

[0074] This refers to the rated power of the battery energy storage system.

[0075] The second scenario: The flywheel energy storage system has sufficient power, but the currently stored energy is insufficient, i.e., at time t2. , In this case, the output of the hybrid energy storage system is as follows: Figure 4 As shown.

[0076] At this point, the flywheel energy storage system's capacity is insufficient, requiring a reduction in output. A constant-rate decrease coefficient K for the flywheel energy storage system's output is set. K is set based on the current capacity of the flywheel energy storage system; K is positively correlated with the reciprocal of the capacity and can be manually adjusted according to the configured capacity of the flywheel energy storage system.

[0077] ,

[0078] That is when hour:

[0079] ,

[0080] The charging power of the flywheel energy storage system is negative, and t3 is the moment when the flywheel energy storage system stops outputting power.

[0081] Until time t3, when the flywheel energy storage system begins to operate at a stable power... After charging, the output of the hybrid energy storage system is set as follows.

[0082] That is when hour:

[0083] ,

[0084] The third scenario: The flywheel energy storage system's power and the current stored energy are both insufficient, i.e., at time t2. , In this case, the output of the hybrid energy storage system is as follows: Figure 5 As shown.

[0085] In this situation, the flywheel energy storage system has insufficient capacity and needs to reduce its output. At the same time, the real-time power is also insufficient to meet the demand. The battery energy storage system needs to discharge quickly to compensate for the power difference. The output settings of the energy storage system are as follows:

[0086] That is when hour:

[0087] ,

[0088] △t is the time for the flywheel energy storage system to decrease output at a constant speed (the time for the battery energy storage system to increase output at a constant speed).

[0089] Until time t3, when the flywheel energy storage system begins to operate at a stable power output. After charging, the output of the hybrid energy storage system is set as follows:

[0090] That is when hour:

[0091] ,

[0092] when hour:

[0093] ,

[0094] This embodiment is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A charge-discharge control method for hybrid energy storage participating in grid frequency modulation, characterized in that, The method comprises the following steps: Step 1: acquiring real-time data of the hybrid energy storage system, including the power type energy storage system in the hybrid energy storage system State of charge State of charge ; Step 2: monitoring the state of charge of the hybrid energy storage system in real time, judging the power type energy storage system obtained in the step 1 State of charge of an energy storage system State of charge of an energy storage system whether the following basic conditions are met: ， If not satisfied, the hybrid energy storage system is locked out, , is the real-time charge-discharge power of the power-type energy storage system, is the real-time charge-discharge power of the capacity-type energy storage system; If the condition is met, then go to step 3; Step 3: acquiring AGC (Automatic Generation Control) data of the power grid when the load impact disturbance occurs at the t1 moment Control) is assigned to the hybrid energy storage system frequency regulation load command increment ; Step 4: performing the charging and discharging control of the hybrid energy storage system according to the principle that the power type energy storage system acts preferentially and the capacity type energy storage system enters the charging and discharging state at a reasonable time to make up for the deficiency of the power type energy storage system; In step 4, the power-type energy storage system starts to output at time t1, the capacity-type energy storage system starts to output at time t2, and the time interval between t2 and t1 is , , t4 is the time at which the frequency regulation load instruction step-down assigned to the energy storage system by the AGC, is the output time of the hybrid energy storage system, The reference value can be calculated by the following formula: ， wherein, Cp is the rated capacity of the power-type energy storage system, Cp is the rated capacity of the power-type energy storage system, When Time: ， When the power of the power-type energy storage system is insufficient, the current storage power is sufficient, the power is sufficient, the current storage power is insufficient, and both the power and the current storage power are insufficient, the output of the hybrid energy storage system is controlled. When the power type energy storage system is insufficient in power and sufficient in current stored energy, i.e. at time t2 , then: ， wherein, Pnom is the rated power of the energy storage system. 2.The charge and discharge control method of hybrid energy storage participating in grid frequency modulation according to claim 1, characterized in that, When the power type energy storage system is power sufficient and current storage power insufficient, i.e. at time t2 , , When time: ， Until the time t3, at which time the power-type energy storage system starts to output a stable power charging, after which the output of the hybrid energy storage system is set as follows: When Time: ， is the charging power of the power-type energy storage system and is negative, t3 is the time when the power-type energy storage system stops outputting power, is the rated power of the capacity-type energy storage system, K is the constant-speed reduction coefficient of the power-type energy storage system output, 。 3.The charge and discharge control method of hybrid energy storage participating in grid frequency modulation according to claim 1, characterized in that, When the power type energy storage system is insufficient in both power and current storage capacity, i.e. at time t2 , , When Time: ， Until time t3, at which time the power-type energy storage system starts to output a stable power charging, after which the output of the hybrid energy storage system is set as follows: When Time: ， When time: ， wherein, is the charging power of the power-type energy storage system and is negative, t3 is the time when the power-type energy storage system stops outputting power, is the rated power of the capacity-type energy storage system, Δt is the constant-speed power reduction time of the power-type energy storage system, and K is the constant-speed power reduction coefficient of the power-type energy storage system. 。 4. The charge and discharge control method for participating in grid frequency modulation of a hybrid energy storage according to any one of claims 1-3, characterized in that, The power type energy storage system comprises a flywheel energy storage system and a super capacitor energy storage system.

5. The charge and discharge control method for participating in grid frequency modulation of a hybrid energy storage according to any one of claims 1-3, characterized in that, The capacity type energy storage system comprises a battery energy storage system.

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