A coordinated control method between energy storage and traditional third-line defense when participating in frequency correction control.

Abstract

This invention relates to a coordinated control method between energy storage and traditional third-line defense when energy storage participates in frequency correction control. The invention proposes an energy storage frequency regulation control strategy, including frequency response threshold setting, model predictive control rolling optimization, and error correction; it formulates frequency response strategies for different scenarios based on frequency deviation and energy storage operating status; the energy storage further optimizes its charging and discharging power using model predictive control according to different response strategies to control the energy storage system to charge or discharge, thereby changing the grid frequency and ensuring that the grid frequency always fluctuates smoothly within a safe range to guarantee the safe and stable operation of the grid.

Description

Technical Field

[0001] This invention relates to the field of power system control technology, specifically to a coordinated control method for energy storage participating in frequency correction control and the traditional third line of defense. Background Technology

[0002] With the large-scale grid connection of new energy power generation and the rapid growth of inter-regional DC transmission capacity, the proportion of traditional synchronous power sources is gradually decreasing. The grid frequency's ability to resist disturbances and regulate is declining. Transient frequency security has become a bottleneck problem restricting the development of new power systems. In recent years, there have been many large frequency difference disturbance events at home and abroad. Frequency security has become a bottleneck problem restricting the development of new power systems.

[0003] Energy storage is a crucial regulatory resource for power systems dominated by new energy sources. Electrochemical energy storage, in particular, with its flexible, rapid response and bidirectional regulation capabilities, is a key resource for ensuring the frequency security and stability of power grids with a high proportion of new energy. Currently, my country's power grid security defense system relies primarily on three lines of defense: preventative control under normal grid conditions, emergency control in response to anticipated faults, and corrective control after severe exceedances in grid frequency and voltage limits. Frequency security defense aims to ensure that frequency deviations remain within permissible operating ranges after faults or disturbances. If system operation control fails to guarantee frequency deviations within the appropriate range, power sources may exit operation during system frequency decline, further deteriorating the system frequency and ultimately leading to system frequency collapse. Energy storage is a vital regulatory resource for power systems dominated by new energy sources and a key resource for ensuring the frequency security and stability of power grids with a high proportion of new energy. However, research on energy storage's participation in emergency and corrective frequency control, and its coordination and optimization with other resources, is still insufficient. Furthermore, for the same energy storage power station, how to coordinate its role in the three lines of frequency security defense while considering system safety and economy is also a key issue that needs to be considered when considering energy storage's participation in frequency stability control. Overall, in terms of transient frequency security defense, there is still a lack of comprehensive consideration to integrate energy storage resources into my country's existing frequency security defense system. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a coordinated control method between energy storage and traditional third-line defense when energy storage participates in frequency correction control, thereby improving the frequency stability of energy storage when participating in frequency adjustment of the traditional third-line defense of the power system and ensuring the safe and stable operation of the power system.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for coordinated control of energy storage with traditional third-line defense when participating in frequency correction control, characterized by comprising the following steps:

[0007] Step 1: Establish a frequency response model for energy storage to participate in the frequency adjustment of the traditional third line of defense, and control the active power charging and discharging state of energy storage, as shown in equations (1) and (2):

[0008] At that time, ;

[0009] At that time, ;

[0010] In the above formula, Δ f For frequency deviation, Δ f dead The action threshold for the third line of defense. P B The active power used to charge and discharge the energy storage system. P 3rd The active power provided for the third line of defense, Δ P load This refers to changes in the system's active power load.

[0011] Step 2: Based on the frequency deviation and the state of charge (SOC) of the energy storage power station described in Step 1, formulate an energy storage charging and discharging control strategy.

[0012] Step 3: Utilize model predictive control to further optimize the output of energy storage, and use feedback correction to correct the output error of energy storage, thereby improving the frequency stability of the power grid.

[0013] Based on the above scheme, the Δ mentioned in step 2 f Frequency deviation Δ f This includes multiple segmented thresholds, specifically: small frequency deviation threshold Δ f low Mid-frequency deviation threshold Δ f mid Large frequency deviation threshold Δ f high , and Δ f dead <Δ f low <Δ f mid <Δ f high ;

[0014] The charging and discharging power of the energy storage is set according to the different frequency deviations mentioned above, as shown in the following formula (3):

[0015] ;

[0016] In the above formula, K low , Kmid , K high They are respectively energy storage Δ f low Δ f mid Δ f high The droop coefficient at that time;

[0017] The relationship between the above droop coefficient and the active power of the energy storage system is as follows: (4)-(6):

[0018] ;

[0019] ;

[0020] ;

[0021] In equations (4)-(6) above, the droop coefficient K yes K low , K mid , K high The set, SOC t and SOC t-1 They are t Time and t- SOC of energy storage at 1 moment P B,t for t The active power of energy storage during charging and discharging. E B It refers to the energy storage capacity. SOC min and SOC max These are the minimum and maximum SOC (State of Charge) thresholds allowed for energy storage.

[0022] Based on the above scheme, step 3 specifically involves:

[0023] Set an overall frequency adjustment optimization target, recalculate the energy storage output in each optimization period, and carry the optimization error between the two optimizations into the next optimization process to provide feedback correction for the energy storage output;

[0024] Based on the adjustable charging and discharging power characteristics of energy storage, model predictive control is used to optimize the charging and discharging power of energy storage. In order to ensure the frequency security of the power system, the rolling optimization model aims to minimize the system frequency deviation and the energy storage output error. The objective function is shown in the following equation (7):

[0025] ;

[0026] In the above formula, The objective function is... To optimize the time domain; and for Weighting coefficients at each time point; For the first Optimize energy storage output at specific times; for Actual output of stored energy at any given moment;

[0027] To ensure the output accuracy of energy storage, the actual active power of energy storage in the current system is used as the initial value for the new round of rolling optimization, as shown in the following formula (8):

[0028] ;

[0029] In the above formula, for Time-corrected energy storage rolling optimized charge and discharge power For the first Energy storage and output at all times.

[0030] The beneficial effects of the coordinated control method between energy storage and traditional third-line defense when participating in frequency correction control as described in this invention are as follows:

[0031] This method obtains the frequency deviation of the power grid and the state of charge of the energy storage as a reference for the active power charging and discharging of the energy storage. It can more accurately reflect the frequency stability of the power grid. By using model predictive control to optimize the charging and discharging power of the energy storage in real time, it can more accurately respond to the power demand of the power grid frequency regulation, avoid disorderly charging and discharging of the energy storage, and ensure the safety and stability of the power grid frequency. Attached Figure Description

[0032] The present invention includes the following figures:

[0033] Figure 1 This is a flowchart illustrating a coordinated control method between energy storage and traditional third-line defense when energy storage participates in frequency correction control according to the present invention.

[0034] Figure 2 A schematic diagram showing the different frequency deviation thresholds for the third line of defense and energy storage response;

[0035] Figure 3 This is a schematic diagram illustrating the constraints of different SOC states for energy storage. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings.

[0037] This application aims to provide a coordinated control method between energy storage and traditional third-line defense when energy storage participates in frequency correction control. This method, while ensuring the energy storage's state of charge and charge / discharge constraints, allows it to participate in the coordinated control of the grid's third-line defense, providing the grid with fast and efficient frequency regulation performance and ensuring grid safety and stability. Specific steps are as follows: Figure 1 As shown:

[0038] Step A: Based on the frequency response thresholds of energy storage and the traditional third line of defense to the power system, establish a frequency response model for energy storage to participate in the frequency adjustment of the traditional third line of defense, and control the active power charging and discharging state of energy storage.

[0039] When the frequency deviation does not reach the threshold for the third line of defense to take action:

[0040] ;

[0041] At this time, energy storage does not need to participate in frequency adjustment, and the active power of the energy storage system during charging and discharging is:

[0042] ;

[0043] in, This refers to the charging and discharging power of energy storage.

[0044] When the frequency deviation reaches the threshold for the third line of defense to take action:

[0045] ;

[0046] At this point, energy storage and the third line of defense jointly participate in frequency adjustment. The relationship between the active power of the energy storage system during charging and discharging and the operating power of the third line of defense is as follows:

[0047] ;

[0048] in, The active power provided for the third line of defense; This refers to changes in the system's active power load.

[0049] In step B, it is necessary to consider the frequency deviation and the state of charge of the energy storage power station under different scenarios, so as to formulate energy storage charging and discharging control strategies under different power system operating conditions. Based on the energy storage droop response coefficient set under different frequency thresholds and state of charge, the energy storage's response capability to frequency signals can be improved.

[0050] Frequency deviation includes multiple segmented thresholds: small frequency deviation threshold Δ f low Mid-frequency deviation threshold Δ f mid Large frequency deviation threshold Δ f high , and Δ fdead <Δ f low <Δ f mid <Δ f high Please refer to Figure 2 The main information for energy storage power stations is the state of charge of the batteries. It is constrained by the maximum and minimum charge / discharge capacity, where the frequency deviation of multiple segmented thresholds is calculated based on the third line of defense action dead zone threshold; the charge / discharge power of the energy storage is set according to the frequency difference of each scenario, and the charge / discharge power and capacity limitations of the energy storage are taken into account. Please refer to [reference needed]. Figure 3 The relationship between its energy storage charging and discharging power and frequency deviation is shown below:

[0051] ;

[0052] in, K low , K mid , K high These represent the energy storage at small frequency deviation Δ f low , mid-frequency deviation Δ f mid Large frequency deviation Δ f high The droop coefficient at different stages.

[0053] Furthermore, due to the inherent charging and discharging characteristics and capacity limitations of energy storage, it cannot provide a large amount of active power for extended periods. Therefore, the charging and discharging power of energy storage is constrained by its own capacity and state of charge (SOC). Please refer to [link / reference needed]. Figure 3 :

[0054] ;

[0055] ;

[0056] ;

[0057] In the above formula, the droop coefficient K yes K low , K mid , K high The set, SOC t and SOC t-1 They are t Time and t- SOC of energy storage at 1 momentP B,t for t The active power of energy storage during charging and discharging. E B It refers to the energy storage capacity. SOC min and SOC max These are the minimum and maximum SOC (State of Charge) thresholds allowed for energy storage.

[0058] In step C, model predictive control is used to further optimize the output of energy storage, with the optimization objective being the combined effect of frequency deviation pairwise optimization and the optimized value versus the actual output value. Then, a feedback correction mechanism is used to correct the output error of energy storage, thereby improving the frequency stability of the power grid.

[0059] The implementation method of using model predictive control to correct energy storage output is as follows: set an overall frequency adjustment optimization target, re-optimize the energy storage output in each optimization time, and substitute the output error between the optimized value and the actual output into the next optimization process to perform feedback correction on the energy storage output, thereby reducing the optimization error between the optimized value and the actual output value.

[0060] Based on the adjustable charging and discharging power characteristics of energy storage, model predictive control is used to optimize the charging and discharging power of energy storage. To ensure the frequency security of the power system, the rolling optimization model aims to minimize the system frequency deviation and the energy storage output error. The objective function is shown below:

[0061] ;

[0062] in, The objective function is... To optimize the time domain; and for Weighting coefficients at each time point; For the first Energy storage and output at all times; for The actual output of energy storage at any given moment.

[0063] To ensure the output accuracy of energy storage, the actual active power of the energy storage in the current system is used as the initial value for the new round of rolling optimization, forming a closed-loop control. The calculation formula is as follows:

[0064] ;

[0065] In the above formula, for Time-corrected energy storage rolling optimized charge and discharge power For the first Energy storage and output at all times.

[0066] This application proposes an energy storage frequency regulation control strategy, including frequency response threshold setting, model predictive control rolling optimization, and error correction; frequency response strategies are formulated for different scenarios based on frequency deviation and energy storage operating status; the energy storage system further optimizes its charging and discharging power using model predictive control according to different corresponding strategies, so as to control the energy storage system to charge or discharge, thereby changing the frequency of the power grid, so that the power grid frequency always fluctuates smoothly within a safe range, so as to ensure the safe and stable operation of the power grid.

[0067] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A coordinated control method for energy storage participating in frequency correction control and traditional third-line defense, characterized in that, Includes the following steps: Step 1: Establish a frequency response model for energy storage to participate in the frequency adjustment of the traditional third line of defense, and control the active power charging and discharging state of energy storage, as shown in equations (1) and (2): At that time, ; At that time, ; In the above formula, Δ f For frequency deviation, Δ f dead The action threshold for the third line of defense. P B The active power used to charge and discharge the energy storage system. P 3rd The active power provided for the third line of defense, Δ P load This refers to changes in the system's active power load. Step 2: Based on the frequency deviation and the state of charge (SOC) of the energy storage power station described in Step 1, formulate an energy storage charging and discharging control strategy. Step 3: Optimize the output of energy storage using model predictive control, and correct the output error of energy storage using feedback correction circuit to improve the frequency stability of the power grid. The frequency deviation Δ mentioned in step 2 f This includes multiple segmented thresholds, specifically: small frequency deviation threshold Δ f low Mid-frequency deviation threshold Δ f mid Large frequency deviation threshold Δ f high , and Δ f dead <Δ f low <Δ f mid <Δ f high ; The charging and discharging power of the energy storage is set according to the different frequency deviations mentioned above, as shown in the following formula (3): ； In the above formula, K low , K mid , K high They are respectively energy storage Δ f low Δ f mid Δ f high The droop coefficient at that time; The relationship between the above droop coefficient and the active power of the energy storage system is as follows: (4)-(6): ； ； ； In equations (4)-(6) above, the droop coefficient K yes K low , K mid , K high The set, SOC t and SOC t-1 They are t Time and t- SOC of energy storage at 1 moment P B,t for t The active power of energy storage during charging and discharging. E B For energy storage capacity, SOC min and SOC max These are the minimum and maximum SOC (State of Charge) thresholds allowed for energy storage.

2. The coordinated control method for energy storage participating in frequency correction control and the traditional third line of defense as described in claim 1, characterized in that: Step 3 specifically involves: Set an overall frequency adjustment optimization target, recalculate the energy storage output in each optimization period, and carry the optimization error between the two optimizations into the next optimization process to provide feedback correction for the energy storage output; Based on the adjustable charging and discharging power characteristics of energy storage, model predictive control is used to optimize the charging and discharging power of energy storage. In order to ensure the frequency security of the power system, the rolling optimization model aims to minimize the system frequency deviation and the energy storage output error. The objective function is shown in the following equation (7): ； In the above formula, The objective function is... To optimize the time domain; and for Weighting coefficients at each time point; For the first Energy storage and output at all times; for Actual output of stored energy at any given moment; To ensure the output accuracy of energy storage, the actual active power of energy storage in the current system is used as the initial value for the new round of rolling optimization, as shown in the following formula (8): ； In the above formula, for Time-corrected energy storage rolling optimized charge and discharge power For the first Energy storage and output at all times.

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