A coordinated frequency control method including network-constructing type and network-following type energy storage

Abstract

The application provides a kind of collaborative frequency control method of network construction type and follow network type energy storage, comprising: constructing simulation model including network construction type energy storage unit, follow network type energy storage unit, synchronous generator and alternating current load, when simulation model occurs frequency disturbance, the absolute value of frequency deviation is obtained, whether the absolute value of frequency deviation exceeds threshold value is judged, if exceeds set threshold value, then network construction type energy storage unit and follow network type energy storage unit are regulated respectively, if it does not exceed set threshold value, then enter next sampling period, wherein, if exceeds set threshold value, then according to the positive and negative of frequency deviation control energy storage unit charging and discharging.The application gives full play to the virtual inertia support and frequency autonomous support of network construction type energy storage unit, follow network type energy storage unit quickly responds upper control signal, plays better frequency support effect, can quickly and effectively control follow network type energy storage and network construction type energy storage collaborative participation system frequency regulation.

Description

Technical Field

[0001] This invention relates to the field of power system transmission technology, and in particular to a coordinated frequency regulation control method that includes grid-connected and grid-linked energy storage. Background Technology

[0002] In recent years, with the large-scale grid connection of new energy sources via power electronic converters and the continuous access of external DC, my country's power grid has gradually shown a trend of power electronicization, resulting in the overall power system exhibiting characteristics of decreased inertia and uneven distribution, which has significantly weakened the frequency regulation capability and frequency stability of the power system.

[0003] However, because new energy generating units do not possess the rotational inertia of synchronous generators, the new power system exhibits a "low inertia" characteristic. In addition, the intermittent and fluctuating output of new energy generating units reduces the frequency stability of the power system.

[0004] Electrochemical energy storage is a high-quality frequency regulation resource, and applying grid-based control technology to energy storage is currently an effective solution to improve frequency stability during the inertia response phase. Grid-based modification of energy storage can improve system inertia levels and frequency support capabilities; however, grid-based energy storage is prone to overcharging or over-discharging of the State of Charge (SOC) when used for frequency support. Since grid-based energy storage is controlled by the upper-level system, current research largely considers only the coordination between grid-based energy storage systems during frequency regulation or the impact of a single parameter on control performance. With the increasing penetration rate of grid-based energy storage, there is a lack of research on how to effectively utilize the advantages of virtual inertia and frequency support from grid-based energy storage, while simultaneously considering the impact of multiple parameters such as SOC and active power margin on control performance, to achieve coordinated frequency regulation between grid-based and traditional grid-based energy storage.

[0005] Therefore, it is essential to design a coordinated frequency regulation control method that includes grid-based and grid-connected energy storage. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a coordinated frequency regulation control method that includes grid-based and grid-connected energy storage.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] This invention provides a coordinated frequency regulation control method including grid-based and grid-connected energy storage, comprising:

[0009] A simulation model was constructed, including grid-connected energy storage units, grid-linked energy storage units, synchronous generators, and AC loads.

[0010] When the simulation model experiences frequency disturbances, the frequency deviation is acquired, and it is determined whether the absolute value of the frequency deviation exceeds the threshold. If it exceeds the set threshold, the grid-type energy storage unit and the grid-connected energy storage unit are adjusted respectively. If it does not exceed the set threshold, the next sampling cycle is entered.

[0011] If the set threshold is exceeded, the energy storage unit is charged and discharged according to the positive or negative value of the frequency deviation.

[0012] Preferably, the grid-type energy storage unit is regulated, specifically as follows:

[0013] The virtual inertia parameter is adjusted based on the battery state of charge of the grid-type energy storage unit. At the same time, in order to improve the frequency regulation effect, the active-frequency equation is introduced into the grid-type energy storage unit to participate in frequency support.

[0014] Preferably, the virtual inertia parameter is adjusted according to the battery state of charge of the grid-type energy storage unit, specifically as follows:

[0015] When the system frequency decreases, we have:

[0016]

[0017] As the system frequency increases, we have:

[0018]

[0019] In the formula, J i Let J0 be the virtual inertia parameter of the i-th grid-type energy storage in the system, and K be the initial virtual inertia. J For virtual inertia adjustment coefficient, SOC i This represents the state of charge of the i-th grid-type energy storage.

[0020] Preferably, an active-frequency equation is introduced into the grid-type energy storage unit to participate in frequency support, specifically:

[0021] An active-frequency equation is introduced to support the frequency of grid-type energy storage units. The specific formula is as follows:

[0022] P ref =P set +k ω (ω N -ω)

[0023] In the formula, P set This is the set value for active power.

[0024] Preferably, the grid-connected energy storage units are regulated separately, specifically as follows:

[0025] Since grid-connected energy storage units only participate in the primary frequency regulation of the system, the active power of the grid-connected energy storage units is allocated to participate in the system frequency regulation based on the battery's state of charge (SOC) and the adjustable active power margin of the converter as constraints. Here, the number of grid-connected energy storage units is N, and the capacity of each energy storage battery is P. N The SOC of the i-th energy storage battery is SOC i And SOC1 <SOC2<…<SOC N The initial active power emitted by the i-th energy storage is P. i Then the active power margin ΔP of the i-th energy storage battery i =|P N -P i |;

[0026] When the system active load suddenly increases and the system frequency decreases, the power setpoint of the grid-connected energy storage unit is as follows:

[0027] P set,Δf＜0 =K ΔP (K soc ΔP i +P i )+K lim P max

[0028]

[0029] In the formula, K ΔP K is the power margin constraint coefficient. lim The maximum power constraint factor is used when the power margin ΔP i =|P N -P i | If 0, it means that there is no excess active power regulation margin in energy storage, then K ΔP Take 0, K lim If we take 1, the energy storage will generate its maximum active power for one frequency regulation. When the power margin ΔP i =|P N -P i |If not 0, then K ΔP Take 0.95, K lim If the value is set to 0, the grid-type energy storage unit will adjust its power according to the SOC value to ensure that the energy storage with a large SOC can generate as much active power as possible.

[0030] When the system active load suddenly decreases and the system frequency increases, the power setpoint of the grid-connected energy storage unit is as follows:

[0031] P set,Δf＞0 =K ΔP (K soc ΔP i +P i )+Klim P max

[0032]

[0033] In the formula, K ΔP K is the power margin constraint coefficient. lim The maximum power constraint factor is used when the power margin ΔP i =|P N -P i | If 0, it means that there is no excess active power regulation margin in energy storage, then K ΔP Take 0, K lim Take -1, at this time the energy storage absorbs the maximum active power for one frequency regulation, when the power margin ΔP i =|P N -P i |If not 0, then K ΔP Take -0.95, K lim If the value is set to 0, the grid-type energy storage unit will adjust its power according to the SOC value to ensure that the energy storage with a small SOC can absorb as much active power as possible.

[0034] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0035] This invention provides a coordinated frequency regulation control method incorporating grid-based and grid-connected energy storage. The method includes: constructing a simulation model comprising grid-based energy storage units, grid-connected energy storage units, a synchronous generator, and an AC load; when a frequency disturbance occurs in the simulation model, acquiring the frequency deviation; determining whether the absolute value of the frequency deviation exceeds a threshold; if it exceeds the set threshold, regulating both the grid-based and grid-connected energy storage units separately; if it does not exceed the set threshold, proceeding to the next sampling cycle; wherein, if it exceeds the set threshold, controlling the charging and discharging of the energy storage units according to the sign of the frequency deviation. This invention fully leverages the virtual inertia support and autonomous frequency support of the grid-based energy storage units, and the rapid response of the grid-connected energy storage units to upper-level control signals, resulting in better frequency support and enabling rapid and effective control of grid-connected and grid-based energy storage units to collaboratively participate in system frequency regulation. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1The diagram provided in this embodiment of the invention is a schematic diagram of the dynamic response characteristic curve of a system containing energy storage after being disturbed until the frequency returns to normal.

[0038] Figure 2 This is a method block diagram provided in an embodiment of the present invention;

[0039] Figure 3 A simulation system topology diagram of a coordinated frequency modulation control method for grid-based and grid-following energy storage provided in an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram comparing the simulated frequency modulation effects provided in an embodiment of the present invention;

[0041] Figure 5 A schematic diagram of the active power output of three energy storage units provided in an embodiment of the present invention;

[0042] Figure 6 The diagram shows the effect of virtual inertia coefficient adjustment of the grid-type energy storage unit provided in the embodiment of the present invention. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] The purpose of this invention is to provide a coordinated frequency regulation control method that includes grid-type and grid-following energy storage. This method fully leverages the virtual inertia support and frequency autonomy of grid-type energy storage units, while grid-following energy storage units respond quickly to upper-level control signals, resulting in better frequency support. This method can quickly and effectively control grid-following and grid-type energy storage units to participate in the coordinated operation of system frequency regulation.

[0045] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] Figure 1 The dynamic response characteristic curve of a system containing energy storage after being disturbed until the frequency returns to normal, provided for embodiments of the present invention, is described in detail below:

[0047] The process from the occurrence of a disturbance to the lowest frequency point in a power system typically includes disturbance power distribution, inertial response, and primary frequency regulation. Here, t0 is the disturbance time, t1 is the governor action time, and t2 is the lowest frequency point.

[0048] The process of the system preventing frequency drops and restoring normal frequency changes can be roughly divided into the following stages:

[0049] At the beginning of t0, the synchronous generator can automatically share the disturbance power and maintain the system power balance;

[0050] The t0-t1 stage is the inertial response stage. The remaining online generators convert their rotational kinetic energy (inertia) into actual power generation to maintain the power balance of the system. At this time, the energy storage unit with grid-type control has virtual inertia, which can provide virtual inertia to the system to slow down the rate of system frequency reduction.

[0051] The t1-t2 stage is the stage where inertial response and primary frequency regulation work together. At time t1, the speed governor activates to increase mechanical power until the unbalanced power of the system is reduced to zero. At time t2, the lowest frequency point is reached. During this stage, grid-type energy storage can perform autonomous frequency regulation according to its control characteristics, while grid-connected energy storage, due to upper-level regulation, completes its power allocation based on its SOC and active power margin as constraints, thus achieving coordinated frequency regulation between grid-connected and grid-type energy storage.

[0052] t2-t3 represents other frequency response stages, after which secondary frequency modulation and other frequency adjustment measures are implemented.

[0053] Figure 2 The method flowchart provided in the embodiments of the present invention is as follows: Figure 2 As shown, the present invention provides a coordinated frequency regulation control method for grid-based and grid-connected energy storage, comprising:

[0054] A simulation model was constructed, comprising grid-connected energy storage units, grid-linked energy storage units, synchronous generators, and AC loads. The topology diagram of the simulation model is shown below. Figure 3 As shown;

[0055] When the simulation model experiences frequency disturbances, the frequency deviation is acquired, and it is determined whether the absolute value of the frequency deviation exceeds the threshold. If it exceeds the set threshold, the grid-type energy storage unit and the grid-connected energy storage unit are adjusted respectively. If it does not exceed the set threshold, the next sampling cycle is entered.

[0056] If the set threshold is exceeded, the energy storage unit is charged and discharged according to the positive or negative value of the frequency deviation (positive represents charging, negative represents discharging).

[0057] The specific control measures for grid-type energy storage units are as follows:

[0058] If the absolute value of the frequency deviation exceeds the set threshold, during the inertial response phase, the grid-type energy storage relies on its control characteristics to provide virtual inertia support for the grid. In order to optimize the SOC (ensuring that batteries with a large SOC have a large virtual inertia when the system frequency drops, so as to generate the most active power, and energy storage with a small SOC has a large virtual inertia when the frequency rises, so as to output as little power as possible), the virtual inertia parameters are adjusted according to the battery state of charge of the grid-type energy storage unit. At the same time, in order to increase the frequency regulation effect, the active power-frequency equation is introduced into the grid-type energy storage unit to participate in frequency support.

[0059] The virtual inertia parameter is adjusted based on the battery state of charge of the grid-type energy storage unit, specifically as follows:

[0060] When the system frequency decreases, we have:

[0061]

[0062] As the system frequency increases, we have:

[0063]

[0064] In the formula, J i Let J0 be the virtual inertia parameter of the i-th grid-type energy storage in the system, and K be the initial virtual inertia. J For virtual inertia adjustment coefficient, SOC i This represents the state of charge of the i-th grid-type energy storage.

[0065] The active-frequency equation is introduced into the frequency support of the grid-type energy storage unit, specifically as follows:

[0066] An active-frequency equation is introduced to support the frequency of grid-type energy storage units. The specific formula is as follows:

[0067] P ref =P set +k ω (ω N -ω)

[0068] In the formula, P set This is the set value for active power.

[0069] The grid-connected energy storage units are regulated separately, specifically as follows:

[0070] Since grid-connected energy storage units only participate in the primary frequency regulation of the system, the active power of the grid-connected energy storage units is allocated to participate in the system frequency regulation based on the battery's state of charge (SOC) and the adjustable active power margin of the converter as constraints. Here, the number of grid-connected energy storage units is N, and the capacity of each energy storage battery is P. N The SOC of the i-th energy storage battery is SOC i And SOC1 <SOC2<…<SOCN The initial active power emitted by the i-th energy storage is P. i Then the active power margin ΔP of the i-th energy storage battery i =|P N -P i |;

[0071] When the system active load suddenly increases and the system frequency decreases, the power setpoint of the grid-connected energy storage unit is as follows:

[0072] P set,Δf＜0 =K ΔP (K soc ΔP i +P i )+K lim P max

[0073]

[0074] In the formula, K ΔP K is the power margin constraint coefficient. lim The maximum power constraint factor is used when the power margin ΔP i =|P N -P i | If 0, it means that there is no excess active power regulation margin in energy storage, then K ΔP Take 0, K lim If we take 1, the energy storage will generate its maximum active power for one frequency regulation. When the power margin ΔP i =|P N -P i |If not 0, then K ΔP Take 0.95, K lim If the value is set to 0, the grid-type energy storage unit will adjust its power according to the SOC value to ensure that the energy storage with a large SOC can generate as much active power as possible.

[0075] When the system active load suddenly decreases and the system frequency increases, the power setpoint of the grid-connected energy storage unit is as follows:

[0076] P set,Δf＞0 =K ΔP (K soc ΔP i +P i )+K lim P max

[0077]

[0078] In the formula, K ΔP K is the power margin constraint coefficient. lim The maximum power constraint factor is used when the power margin ΔP i=|P N -P i | If 0, it means that there is no excess active power regulation margin in energy storage, then K ΔP Take 0, K lim Take -1 (positive and negative represent discharging / charging respectively). At this time, the energy storage absorbs the maximum active power for one frequency regulation. When the power margin ΔP i =|P N -P i |If not 0, then K ΔP Take -0.95, K lim If the value is set to 0, the grid-type energy storage unit will adjust its power according to the SOC value to ensure that the energy storage with a small SOC can absorb as much active power as possible.

[0079] Based on the above method, the present invention also provides a coordinated frequency regulation control system including grid-type and grid-following type energy storage, the system including a Simulink simulation system and a computing module;

[0080] Among them, simulation models including grid-type energy storage units, grid-connected energy storage units, synchronous generators and AC loads are built in the Simulink simulation system;

[0081] In the Simulink simulation system, an active load disturbance is set, and the frequency from the start to the end of the simulation is collected based on the acquisition module in the Simulink simulation system. The difference between the rated frequency and the actual frequency collected is the frequency deviation, and the absolute value of the frequency deviation is |Δf|. It is determined whether the absolute value of the frequency deviation exceeds the set threshold.

[0082] The calculation module is used when the absolute value of the frequency deviation exceeds the threshold. Based on the virtual synchronous generator control, the grid-type energy storage provides virtual inertia to the system. At the same time, it controls the dynamic adjustment of the virtual inertia parameters to adapt to the changes in SOC. The active frequency droop control ensures that the grid-type energy storage can provide autonomous frequency support. The grid-connected energy storage optimizes the power allocation based on the battery SOC and the adjustable active power margin of the converter as constraints, so as to achieve coordinated frequency support between the grid-type energy storage and the grid-connected energy storage.

[0083] The present invention also provides a simulation embodiment, which uses a grid-type energy storage unit, two grid-connected energy storage units, a synchronous generator and an AC load. The simulation condition is based on a sudden load increase of 20%, and the simulation parameters are shown in Table 1.

[0084] Table 1 Main System Parameters

[0085]

[0086]

[0087] Figure 4The diagram shows the frequency modulation effect of a coordinated frequency modulation control method for grid-based and grid-connected energy storage provided by the present invention. It can be seen that when the system frequency decreases, the lowest point of frequency decrease using the frequency modulation control method provided by the present invention is significantly raised.

[0088] Figure 5 The active power output of one grid-type energy storage and two grid-connected energy storage systems provided in this embodiment of the invention is shown in detail below when the active load suddenly increases by 20%.

[0089] like Figure 5 As shown, the grid-connected energy storage unit responds rapidly to an 8-second load surge, autonomously emitting active power to support the system frequency drop. The grid-connected energy storage unit 1 has an initial active power of 2MW and a relatively high initial SOC of 85%. When the frequency drops, it emits approximately 4.5MW of active power, controlling its output to generate more active power to support the system frequency drop. Once the absolute value of the frequency deviation is less than a set threshold, it resumes its initial output. The grid-connected energy storage unit 2 has an initial active power of 5MW and an initial SOC of 40%. It controls its output to generate less active power to avoid over-discharge of the SOC. When the frequency drops, it emits approximately 5.5MW of active power, and once the absolute value of the frequency deviation is less than a set threshold, it resumes its initial output.

[0090] Figure 6 The virtual inertia adjustment process of the grid-type energy storage unit provided in the embodiment of the present invention when the frequency decreases is illustrated below:

[0091] like Figure 6 As shown, the initial virtual inertia of the grid-type energy storage is approximately 3.185 kg·m. 2 To ensure that batteries with a large SOC have a large virtual inertia when the system frequency drops, so as to generate the maximum active power.

[0092] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0093] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A coordinated frequency regulation control method comprising grid-based and grid-connected energy storage, characterized in that, include: A simulation model was constructed, including grid-connected energy storage units, grid-linked energy storage units, synchronous generators, and AC loads. When the simulation model experiences frequency disturbances, the frequency deviation is acquired, and it is determined whether the absolute value of the frequency deviation exceeds the set threshold. If it exceeds the set threshold, the grid-type energy storage unit and the grid-connected energy storage unit are adjusted respectively. If it does not exceed the set threshold, the next sampling cycle is entered. If the set threshold is exceeded, the energy storage unit is charged and discharged according to the positive or negative value of the frequency deviation. Specifically, the regulation of grid-type energy storage units includes: The virtual inertia parameter is adjusted based on the battery state of charge of the grid-type energy storage unit, specifically as follows: When the system frequency decreases, we have: As the system frequency increases, we have: In the formula, J i Let J0 be the virtual inertia parameter of the i-th grid-type energy storage in the system, and K be the initial virtual inertia. J For virtual inertia adjustment coefficient, SOC i This represents the state of charge of the i-th grid-type energy storage.

2. The method according to claim 1, characterized in that, The specific control measures for grid-type energy storage units are as follows: The virtual inertia parameter is adjusted based on the battery state of charge of the grid-type energy storage unit. At the same time, in order to improve the frequency regulation effect, the active-frequency equation is introduced into the grid-type energy storage unit to participate in frequency support.

3. The method according to claim 2, characterized in that, The active-frequency equation is introduced into the frequency support of the grid-type energy storage unit, specifically as follows: An active-frequency equation is introduced to support the frequency of grid-type energy storage units. The specific formula is as follows: P ref =P set +k ω (oh N -oh) In the formula, P set This is the set value for active power.

4. The method according to claim 3, characterized in that, The grid-connected energy storage units are regulated separately, specifically as follows: Since grid-connected energy storage units only participate in the primary frequency regulation of the system, the active power of the grid-connected energy storage units is allocated to participate in the system frequency regulation based on the battery state of charge (SOC) and the adjustable active power margin of the converter as constraints. Here, the number of grid-connected energy storage units is N, and the capacity of each energy storage battery is P. N The SOC of the i-th energy storage battery is SOC i And SOC1 <SOC2<…<SOC N The initial active power emitted by the i-th energy storage is P. i Then the active power margin ΔP of the i-th energy storage battery i =|P N -P i |; When the system active load suddenly increases and the system frequency decreases, the power setpoint of the grid-connected energy storage unit is as follows: P set,Δf＜0 =K ΔP (K soc ΔP i +P i )+K lim P max In the formula, K ΔP K is the power margin constraint coefficient. lim The maximum power constraint factor is used when the power margin ΔP i =|P N -P i | If 0, it means that there is no excess active power regulation margin in energy storage, then K ΔP Take 0, K lim If we take 1, the energy storage will generate its maximum active power for one frequency regulation. When the power margin ΔP i =|P N -P i |If not 0, then K ΔP Take 0.95, K lim If the value is set to 0, the grid-type energy storage unit will adjust its power according to the SOC value to ensure that the energy storage with a large SOC can generate as much active power as possible. When the system active load suddenly decreases and the system frequency increases, the power setpoint of the grid-connected energy storage unit is as follows: P set,Δf＞0 =K ΔP (K soc ΔP i +P i )+K lim P max In the formula, K ΔP K is the power margin constraint coefficient. lim The maximum power constraint factor is used when the power margin ΔP i =|P N -P i | If 0, it means that there is no excess active power regulation margin in energy storage, then K ΔP Take 0, K lim Take -1, at this time the energy storage absorbs the maximum active power for one frequency regulation, when the power margin ΔP i =|P N -P i |If not 0, then K ΔP Take -0.95, K lim If the value is set to 0, the grid-type energy storage unit will adjust its power according to the SOC value to ensure that the energy storage with a small SOC can absorb as much active power as possible.

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