Reconfigurable energy storage auxiliary thermal power generating unit frequency modulation system and control method

Abstract

The invention provides a reconfigurable energy storage auxiliary thermal power generating unit frequency modulation system and a control method, the system comprises a reconfigurable energy storage system, a thermal power plant control system and a scheduling mechanism, and the reconfigurable energy storage system is in communication connection with the scheduling mechanism through the thermal power plant control system; the reconfigurable energy storage system comprises a reconfigurable battery network, a power conversion device and a coordination control module. One end of the reconfigurable battery network is connected with a power grid through the power conversion equipment, the other end of the reconfigurable battery network is in communication connection with the coordination control module, and the coordination control module is connected with the dispatching mechanism through the thermal power plant control system; according to the reconfigurable energy storage auxiliary thermal power generating unit frequency modulation system and the control method, the connection mode of all assemblies in an energy storage system can be optimized, balance among all battery packs can be improved, the SOC of the energy storage system and the SOC of all the battery packs can be kept at about 50% for a long time, and the response capacity of the energy storage system to AGC continuous up-regulation or continuous down-regulation instructions is improved.

Description

Technical Field

[0001] The present invention relates to the field of energy storage of new energy power systems, and in particular to a reconfigurable energy storage-assisted frequency regulation system for thermal power units and a control method thereof. Background Art

[0002] Generator sets use Automatic Generation Control (AGC) to respond to dispatching instructions and participate in grid frequency regulation, which is an important support for ensuring safe, economical and stable operation of the power grid. The large-scale grid connection of new energy sources has reduced the stability of the power system frequency, resulting in a surge in frequency regulation demand. As the main frequency regulation power source, thermal power units have large inertia and delay. When responding to AGC instructions, they have problems such as slow response speed, large equipment wear and large regulation deviation. At the same time, frequent regulation will shorten the life of the unit equipment and increase operating costs. The electrochemical energy storage system has fast and bidirectional power regulation capabilities. The use of electrochemical energy storage to assist unit frequency regulation can correct the deviation between the power generation and demand of thermal power units, improve the system frequency regulation performance, and improve the power quality of the grid.

[0003] During the energy storage-assisted frequency regulation process, the SOC of the energy storage unit needs to be maintained at around 50%, that is, it is in a chargeable and dischargeable state, which helps to cope with the continuous increase or decrease of the AGC command. In practical applications, because the traditional battery energy storage system is connected in a fixed series-parallel manner, the differences in battery cells will cause the performance of the entire energy storage system to depend on the battery cell with the worst performance, resulting in differences in the actual capacity of each energy storage unit, and SOC deviations are prone to occur. As a result, the SOC of some energy storage units during the regulation process is prone to exceed the upper limit of charging or the lower limit of discharging, making the energy storage system unable to fully exert its frequency regulation capabilities. Therefore, it is of great significance to study how to avoid the impact of battery cell differences on the entire energy storage system, and thereby improve the frequency regulation capability of the energy storage system.

[0004] Patent CN112865152A mentions a method for energy storage-unit combined frequency regulation control to maintain battery SOC, the method comprising: step S1, real-time reading of the state of the thermal power unit, AGC instruction and energy storage system state; step S2, when the AGC instruction is detected to be updated, judging whether the operating states of the thermal power unit and the energy storage system are normal according to their respective operating information; if normal, recording the size of the AGC instruction, the size of the unit load, the size of the energy storage system output, and reading the information of the thermal power unit; if abnormal, the energy storage system stops running; step S3, if the absolute value of the AGC instruction-unit load>Pm ax, starting from the detection of the AGC instruction change, the dead zone Pd is immediately generated based on the current combined output of the thermal power unit and the energy storage system, and maintained for U1 second, and then increased or decreased at the rate of PvMW / min until it is equal to the AGC instruction, and the theoretical instruction is obtained; if the absolute value of the AGC instruction minus the unit load is ≤Pmax, starting from the detection of the AGC instruction change, the theoretical instruction is equal to the AGC instruction; step S4, the theoretical instruction of step S3 is added to the frequency modulation instruction and subtracted from the actual load of the unit, and the difference after subtraction is delegated to the energy storage system as the energy storage instruction; step S5, the energy storage system performs charging or discharging operations according to the energy storage instruction of step S4. It can solve the problem of low AGC frequency modulation performance index of thermal power units and improve the comprehensive frequency modulation index; but it still cannot avoid the differences between different battery cells, and the frequency modulation method of the energy storage system is relatively complicated. Summary of the invention

[0005] In view of this, the present invention aims to propose a reconfigurable energy storage-assisted thermal power unit frequency regulation system and control method, so as to solve the problem in the prior art that the traditional battery energy storage system adopts a fixed series-parallel connection mode, which makes the differences in battery cells have a greater impact on the frequency regulation capability of the energy storage system, thereby reducing the flexibility and stability of the frequency regulation of the energy storage system; thereby optimizing the connection mode of each component in the energy storage system, improving the balance between energy storage units or battery groups, so that the SOC of the energy storage system and the SOC of each battery group are maintained at about 50% for a long time, and improving the response capability of the energy storage system to the continuous increase or decrease command of the AGC; avoiding the influence of the differences in battery cells on the frequency regulation of the energy storage system, improving the flexibility of the system frequency regulation, simplifying the complexity of the system frequency regulation, and improving the stability and safety of the system frequency regulation, thereby greatly improving the system frequency regulation capability.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] The present invention relates to a reconfigurable energy storage-assisted thermal power unit frequency regulation system and a control method. The reconfigurable energy storage-assisted thermal power unit frequency regulation system comprises a reconfigurable energy storage system, a thermal power plant control system and a dispatching mechanism. The reconfigurable energy storage system is communicatively connected to the dispatching mechanism via the thermal power plant control system; the reconfigurable energy storage system comprises a reconfigurable battery network, a power conversion device and a coordination control module; one end of the reconfigurable battery network is connected to the power grid via the power conversion device, and the other end of the reconfigurable battery network is communicatively connected to the coordination control module, and the coordination control module is connected to the dispatching mechanism via the thermal power plant control system.

[0008] Furthermore, the control system of the thermal power plant includes a thermal power unit, a distributed control system DCS and a remote control terminal RTU; one end of the thermal power unit is connected to the power grid, and the other end of the thermal power unit is communicated with the distributed control system DCS, the distributed control system DCS is communicated with the remote control terminal RTU and the coordination control module respectively, and the remote control terminal RTU is communicated with the dispatching organization and the coordination control module respectively.

[0009] Furthermore, the dispatching mechanism includes an automatic generation control AGC, and the automatic generation control AGC is connected to the remote control terminal RTU in a two-way communication manner.

[0010] Furthermore, the reconfigurable battery network includes a battery pack, a control switch, and a bypass switch. One end of each battery pack is connected to one end of the bypass switch through the control switch, and the other end of each battery pack is connected to the other end of the bypass switch.

[0011] Furthermore, the number of battery packs, control switches, and bypass switches is n, where n is a positive integer.

[0012] A reconfigurable energy storage assisted thermal power unit frequency regulation control method, the method is applied to a reconfigurable energy storage assisted thermal power unit frequency regulation system, the method comprises the following steps:

[0013] Step 1: The distributed control system DCS in the thermal power plant control system collects the AGC command data issued by the automatic generation control AGC and the unit operating power data of the thermal power unit;

[0014] Step 2: The remote control terminal RTU in the thermal power plant control system generates the total target power of energy storage according to the time period to which the AGC command data belongs and the SOC state of the reconfigurable battery network in the reconfigurable energy storage system;

[0015] Step 3: The reconfigurable energy storage system decomposes the total target power of energy storage into the target power of each reconfigurable battery network based on the SOC balancing algorithm;

[0016] Step 4: The reconfigurable battery network controls the time slice of the battery pack accessing the reconfigurable battery network according to the reconstruction strategy to achieve charge and discharge control and SOC balance.

[0017] Further, step two includes:

[0018] Step S21: After receiving the AGC instruction issued by the automatic generation control AGC, the reconfigurable energy storage system compares the AGC instruction data of the current period with the AGC instruction data of the previous period to determine whether the absolute difference exceeds the response dead zone? If yes, the currently received AGC instruction data is a new instruction and enters the response period; execute step S22; if no, return to step 1;

[0019] Step S22: After entering the response period, the reconfigurable energy storage system outputs a certain energy storage output according to the range of the AGC command data to jump out of the response action dead zone, and maintains it for a preset time t, and enters the ramp-up period;

[0020] Step S23: After entering the ramp period, the adjustment rate is calculated; and it is determined whether the combined power in the AGC instruction data is less than 50% of the rated power of the energy storage. If yes, the difference response is adopted. After the unit has completed the ramp, it enters the stable period and executes step S24; if no, the step response is adopted. After the unit has completed the ramp, it enters the stable period and executes step S24;

[0021] Step S24: During the stable period, the reconfigurable energy storage system continuously adjusts the unit output of the thermal power unit; calculates the total target power of the energy storage; and enters the non-assessment period.

[0022] Step S25: During the non-assessment period, determine whether the SOC of the reconfigurable battery network in the reconfigurable energy storage system is higher than a preset value. If yes, the reconfigurable energy storage system discharges at a preset discharge power; if no, the reconfigurable energy storage system charges at a preset charging power.

[0023] Further, step three includes:

[0024] Step S31: After obtaining the maximum charge current and the maximum discharge current of each reconfigurable battery network according to the operating status of each reconfigurable battery network, the total charging power limit value P of the reconfigurable energy storage system is calculated by the first formula and the second formula respectively. c-lmt , the total discharge power limit of the reconfigurable energy storage system P d-lmt ;

[0025] Step S32: estimating the SOC of each battery pack in each reconfigurable battery network, thereby obtaining the SOC of each reconfigurable battery network;

[0026] Step S33: During charging, according to the target charging power P of the reconfigurable energy storage system c-agc Power allocation is performed based on the relationship between the sum of charging power limits of each reconfigurable battery network;

[0027] Step S34: During discharge, according to the target discharge power P of the reconfigurable energy storage system d-agc Power allocation is performed based on the relationship between the sum of the discharge power limits of each reconfigurable battery network;

[0028] Step S35: Each reconfigurable battery network places each battery pack into the reconfigurable battery network in different time slices according to the reconstruction strategy, so as to realize charge and discharge power control and SOC balance adjustment of each battery pack.

[0029] Further, in step S31, the first formula is:

[0030]

[0031] Among them, P ci-lmt is the charging power limit of the i-th battery network; P c1-lmt is the charging power limit of the first battery network; P c2-lmt is the charging power limit of the second battery network; P cn-lmt is the charging power limit of the nth battery network.

[0032] Further, in step S31, the second formula is:

[0033]

[0034] Among them, P di-lmt is the discharge power limit of the ith battery network; P d1-lmt is the discharge power limit of the first battery network; P d2-lmt is the discharge power limit of the second battery network; P dn-lmt is the discharge power limit of the nth battery network.

[0035] Compared with the prior art, the reconfigurable energy storage-assisted thermal power unit frequency regulation system and control method described in the present invention have the following beneficial effects:

[0036] By setting up the system and method, it is possible to optimize the connection mode of each component in the energy storage system, improve the balance between energy storage units / battery groups, keep the SOC of the energy storage system and the SOC of each battery group at about 50% for a long time, and improve the response capability of the energy storage system to the continuous upward or downward adjustment instructions of the AGC; avoid the influence of the differences of battery cells on the frequency regulation of the energy storage system, improve the flexibility of the system frequency regulation, simplify the complexity of the system frequency regulation, improve the stability and safety of the system frequency regulation, and thus greatly improve the frequency regulation capability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings, which constitute part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention. In the accompanying drawings:

[0038] Figure 1 It is a schematic diagram of the overall structure of the reconfigurable energy storage assisted thermal power unit frequency regulation system;

[0039] Figure 2 It is a schematic diagram of the principle of the reconfigurable energy storage system assisting the AGC frequency regulation of the thermal power unit;

[0040] Figure 3 It is a flowchart diagram of a control method for AGC frequency regulation strategy of a thermal power unit assisted by a reconfigurable energy storage system;

[0041] Figure 4 It is a flowchart diagram of the upper-level strategy of AGC frequency regulation of thermal power units assisted by the reconfigurable energy storage system.

[0042] Explanation of the accompanying drawings: 1. Reconfigurable energy storage system; 11. Reconfigurable battery network; 12. Power conversion equipment; 13. Coordination control module; 2. Thermal power plant control system; 21. Thermal power unit; 22. Distributed control system DCS; 23. Remote control terminal RTU; 3. Dispatching agency. DETAILED DESCRIPTION

[0043] The inventive concepts of the present disclosure will be described below using terms commonly used by those skilled in the art to convey the essence of their work to other persons skilled in the art. However, these inventive concepts can be embodied in many different forms and should not be considered limited to the embodiments described herein.

[0044] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0045] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0046] In order to solve the problem in the prior art that the differences of battery cells have a great impact on the frequency regulation capability of the energy storage system due to the fixed series-parallel connection in the traditional battery energy storage system, thereby reducing the flexibility and stability of the frequency regulation of the energy storage system; this embodiment proposes a reconfigurable energy storage auxiliary thermal power unit frequency regulation system and a control method, the reconfigurable energy storage auxiliary thermal power unit frequency regulation system includes a reconfigurable energy storage system 1, a thermal power plant control system 2 and a dispatching mechanism 3, and the reconfigurable energy storage system 1 is connected to the dispatching mechanism 3 through the thermal power plant control system 2. The reconfigurable energy storage system 1 includes a reconfigurable battery network 11, a power conversion device 12 and a coordination control module 13; one end of the reconfigurable battery network 11 is connected to the power grid through the power conversion device 12, and the other end of the reconfigurable battery network 11 is connected to the coordination control module 13, and the coordination control module 13 is connected to the dispatching mechanism 3 through the thermal power plant control system 2, and is used to realize the frequency regulation of the thermal power plant unit under the control of the dispatching mechanism 3.

[0047] Through the coordinated setting of the reconfigurable energy storage system 1, the thermal power plant control system 2 and the dispatching mechanism 3, it is possible to optimize the connection mode of the components in the energy storage system, improve the balance between the energy storage units / battery groups, keep the SOC of the energy storage system and the SOC of each battery group at about 50% for a long time, and improve the response capability of the energy storage system to the continuous upward or downward adjustment instructions of the AGC.

[0048] The thermal power plant control system 2 includes a thermal power unit 21, a distributed control system DCS22 and a remote control terminal RTU23. One end of the thermal power unit 21 is connected to the power grid, and the other end of the thermal power unit 21 is connected to the distributed control system DCS22 for communication. The distributed control system DCS22 is connected to the remote control terminal RTU23 and the coordination control module 13 for communication, and the remote control terminal RTU23 is connected to the dispatching mechanism 3 and the coordination control module 13 for communication. Among them, the remote control terminal RTU23 is connected to the dispatching mechanism 3 and the distributed control system DCS22 for bidirectional communication.

[0049] Through the energy storage system, the thermal power plant control system 2, and the dispatching mechanism 3; the dispatching mechanism 3 can receive the data information uploaded in the thermal power plant control system 2, and the dispatching mechanism 3 can also issue frequency modulation instructions to the remote control terminal RTU23 in the thermal power plant control system 2 after processing the received information. The remote control terminal RTU23 can issue instructions to the distributed control system DCS22, and the remote control terminal RTU23 can also receive the unit output data uploaded by the distributed control system DCS22, and receive the energy storage output data uploaded by the coordination control module 13. The distributed control system DCS22 can control the operation of the thermal power unit 21 according to the instructions issued by the remote control terminal RTU23, and the distributed control system DCS22 can also forward the instructions issued by the remote control terminal RTU23 and the unit output data to the coordination control module 13. The coordination control module 13 can control the reconfigurable battery network 11 through the power conversion device 12 according to the received instructions to realize the charging and discharging regulation between the power grid; the coordination control module 13 can also upload the energy storage output data to the remote control terminal RTU23.

[0050] The dispatching mechanism 3 includes an automatic generation control AGC, which is bidirectionally connected to the remote control terminal RTU23. The automatic generation control AGC can send frequency modulation instructions to the remote control terminal RTU23, and the automatic generation control AGC can also receive the combined output data uploaded by the remote control terminal RTU23; wherein the combined output data is the total output data obtained by adding the unit output data and the energy storage output data.

[0051] The reconfigurable battery network 11 includes a battery pack, a control switch, and a bypass switch. One end of each battery pack is connected to one end of the bypass switch through the control switch, and the other end of each battery pack is connected to the other end of the bypass switch. There are n battery packs, control switches, and bypass switches, and n is a positive integer.

[0052] Based on the setting of series and parallel connection between battery groups by control switches and bypass switches, the battery groups corresponding to the control switches are connected / removed from the reconfigurable battery network 11 by closing and opening the control switches and bypass switches, thereby realizing the overall reconstruction of the battery network. It is beneficial to avoid the influence of the differences of battery cells on the frequency regulation of the energy storage system, improve the flexibility of the system frequency regulation, simplify the complexity of the system frequency regulation, improve the stability and safety of the system frequency regulation, and thus greatly improve the system frequency regulation capability. In addition, the reconfigurable energy storage system 1 can simultaneously monitor the instructions and unit output data issued by the automatic generation control AGC; and can generate the total target power of energy storage in the reconfigurable energy storage system 1 according to the time period of the AGC instruction and the difference between the current time period and the previous time period of the AGC instruction. The reconfigurable energy storage system 1 can also decompose the total target power into the target power of each reconfigurable battery network 11 in combination with the SOC state and operation state of each reconfigurable battery network 11. In addition, the reconfigurable battery network 11 runs a reconstruction strategy according to the target power and the SOC state of each battery pack, and puts each battery pack into the reconfigurable battery network 11 in a different time slice to achieve charge and discharge power control and SOC balance of each battery pack.

[0053] The process of the reconfigurable energy storage system assisting the thermal power unit 21 in frequency regulation is as follows: after the distributed control system DCS22 (Distributed Control System) in the thermal power unit 21 receives the AGC frequency regulation instruction issued by the dispatching organization 3, it controls the thermal power unit 21 to respond, and at the same time sends the instruction to the coordination control module 13 in the reconfigurable energy storage system 1; the coordination control module 13 of the reconfigurable energy storage system 1 obtains the real-time output of the thermal power unit 21 through communication; by judging the deviation between the AGC instruction and the unit output, the reconfigurable energy storage system 1 supplements the power of the thermal power unit 21 and outputs power to the plant power unit; the thermal power output data and the energy storage output data are merged by the RTU (Remote Terminal Unit) and uploaded to the power grid dispatch, realizing a common response to the AGC frequency regulation instruction.

[0054] In the electrochemical energy storage assisted frequency regulation project, considering factors such as cost and economic operation, the energy storage is generally configured at 3% of the rated power of the thermal power unit 21, and the charge and discharge rate is set at 2C or 1C, that is, the battery can be fully charged and discharged within half an hour / one hour at the rated power. In the process of energy storage assisted regulation, it is necessary to generate a control strategy based on any one or more factors of the power target and energy storage power level.

[0055] The control strategy of the present invention is divided into an upper strategy and a lower strategy. The upper strategy is a power target strategy that responds to AGC instructions; the lower strategy is a power decomposition strategy within the energy storage system. The control strategy is included in a reconfigurable energy storage-assisted thermal power unit frequency regulation control method.

[0056] Specifically, a reconfigurable energy storage-assisted thermal power unit frequency regulation control method is applied to a reconfigurable energy storage-assisted thermal power unit frequency regulation system; the method comprises the following steps:

[0057] Step 1: The distributed control system DCS22 in the thermal power plant control system 2 respectively collects the AGC instruction data issued by the automatic generation control AGC and the unit operating power data of the thermal power unit 21;

[0058] Step 2: The remote control terminal RTU23 in the thermal power plant control system 2 generates the total target power of energy storage according to the time period to which the AGC command data belongs and the SOC state of the reconfigurable battery network 11 in the reconfigurable energy storage system 1;

[0059] Step 3: The reconfigurable energy storage system 1 decomposes the total target power of energy storage into target powers of each reconfigurable battery network 11 based on the SOC balancing algorithm;

[0060] Step 4: The reconfigurable battery network 11 controls the time slice of the battery group accessing the reconfigurable battery network 11 according to the reconstruction strategy to achieve charge and discharge control and SOC balance.

[0061] By setting the frequency control method, it is possible to realize balanced adjustment of the battery groups in the reconfigurable battery network 11 under the frequency control of the automatic generation control AGC according to the real-time situation of the thermal power unit 21, thereby improving the adjustment flexibility between the battery groups, so that the SOC of the energy storage system and the SOC of each battery group are maintained at about 50% for a long time, and improving the responsiveness of the energy storage system to the continuous upward or downward adjustment instructions of the AGC; and avoiding the influence of the differences of battery cells on the frequency regulation of the energy storage system, thereby improving the flexibility of the system frequency regulation, simplifying the complexity of the system frequency regulation, and improving the stability and safety of the system frequency regulation, thereby greatly improving the system frequency regulation capability.

[0062] Step 2 is a strategy for calculating the total target power of energy storage in the reconfigurable energy storage system 1, i.e., an upper-level strategy. Specifically, step 2 includes:

[0063] Step S21: After receiving the AGC instruction issued by the automatic generation control AGC, the reconfigurable energy storage system 1 compares the AGC instruction data of the current period with the AGC instruction data of the previous period to determine whether the absolute difference exceeds the response dead zone? If yes, the currently received AGC instruction data is a new instruction and enters the response period; execute step S22; if no, return to step 1;

[0064] Step S22: After entering the response period, the reconfigurable energy storage system 1 outputs a certain energy storage output according to the range of the AGC command data to jump out of the response action dead zone, and maintains the preset time t to ensure that the dispatching mechanism 3 can collect the data of the response dead zone issued and enter the ramp-up period;

[0065] Step S23: After entering the ramp period, calculate the adjustment rate. And judge whether the combined power in the AGC instruction data is less than 50% of the rated power of the energy storage. If yes, respond according to the difference. After the unit completes the ramp, it enters the stable period and executes step S24. If no, respond according to the stepping response. After the unit completes the ramp, it enters the stable period and executes step S24.

[0066] Step S24: During the stable period, the reconfigurable energy storage system 1 continuously adjusts the unit output of the thermal power unit 21; calculates the combined output data, i.e., the total target power of the energy storage. And ensures that the combined output data can be maintained within the target dead zone value range with the minimum error; and enters the non-assessment period; wherein the combined output data is the sum of the energy storage output data and the unit output data of the thermal power unit 21.

[0067] Step S25: During the non-assessment period, no new instructions are issued, and the reconfigurable energy storage system 1 does not need to participate in the frequency modulation process. It is determined whether the SOC of the reconfigurable battery network 11 in the reconfigurable energy storage system 1 is higher than the preset value. If yes, the reconfigurable energy storage system 1 discharges at the preset discharge power; if no, the reconfigurable energy storage system 1 charges at the preset charging power.

[0068] In step S22, the value of t is set as required. In this embodiment, the value range of t is 3s-4s. In step S24, the value range of the duration of the stable period is 30s-40s. In addition, in steps S22-S25, if a new instruction is received, the current frequency modulation step is interrupted and the process returns to step S22.

[0069] By setting the upper-level strategy in step 2, the speed at which the reconfigurable energy storage system 1 responds to the AGC command issued by the automatic generation control AGC can be effectively improved, the flexibility and accuracy of the system's response to the AGC command can be improved, and the speed and accuracy of the balanced adjustment of the battery pack within the system can be improved.

[0070] Step S21 includes:

[0071] Step S211: After receiving the AGC instruction issued by the automatic generation control AGC, the reconfigurable energy storage system 1 compares the AGC instruction data of the current period with the AGC instruction data of the previous period to determine whether the absolute difference exceeds the response dead zone? If yes, the currently received AGC instruction data is a new instruction, and step S212 is executed; if no, return to step 1; wherein the value of the response dead zone is 0.5% of the rated power of the energy stored in the reconfigurable energy storage system 1. The absolute difference refers to the absolute value of the difference between the combined power in the AGC instruction data of the current period and the combined power in the AGC instruction data of the previous period.

[0072] Step S212: Determine whether the reconfigurable energy storage system 1 allows charging and discharging. If yes, enter the response period and execute step S22; if no, return to step 1.

[0073] By comparing the AGC command data in different time periods, it is possible to effectively prevent the phenomenon of mistaking issued commands as new commands and performing repetitive work, thereby effectively improving the accuracy of the system's response to AGC commands.

[0074] Step S23 includes:

[0075] Step S231: After entering the ramp period, calculate the adjustment rate. And determine whether the combined power in the AGC instruction data is less than 50% of the rated power of the energy storage. If yes, execute step S232; if no, execute step S233;

[0076] Step S232: respond according to the difference, energy storage output data = combined power in AGC command data - unit output data; execute step S234;

[0077] Step S233: Determine whether 50% of the rated power of the energy storage is less than the combined power in the AGC instruction data and less than 100% of the rated power of the energy storage. If yes, divide the formation into m parts and step one part per second; if no, the combined power in the AGC instruction data exceeds the rated power of the energy storage; the energy storage output remains at a value that jumps out of the response dead zone, and executes step S234;

[0078] Step S234: The thermal power unit 21 completes ramping and enters a stable period.

[0079] By setting the difference response and step response together, it can ensure that the system can respond quickly when faced with changes, shorten the response time, and improve the overall frequency modulation efficiency. In addition, the combination of the two is conducive to enhancing system stability and preventing the system from losing control due to too fast or too slow response. It is also conducive to combining fine adjustment with gradual adjustment, which helps to improve the accuracy of system adjustment.

[0080] Step S25 includes:

[0081] Step S251: During the non-assessment period, no new instructions are issued, and the reconfigurable energy storage system 1 does not need to participate in frequency modulation processing. Determine whether the SOC of the reconfigurable battery network 11 in the reconfigurable energy storage system 1 is higher than the preset value. If yes, execute step S252; if no, execute step S253;

[0082] Step S252: the reconfigurable energy storage system 1 adopts a discharge strategy based on its internal SOC state and performs discharge processing at a preset discharge power;

[0083] Step S253: the reconfigurable energy storage system 1 adopts a charging strategy based on its internal SOC state and performs charging at a preset charging power.

[0084] In step S252, when responding to the AGC power reduction instruction, the discharge strategy adopted is as follows. Specifically, step S252 includes:

[0085] Step S2521: Determine whether 0% of the rated power of the energy storage is less than the internal SOC state of the reconfigurable energy storage system 1 and less than 10% of the rated power of the energy storage? If yes, discharging is prohibited; the reconfigurable energy storage system 1 does not respond to the AGC instruction; if no, execute step S2522;

[0086] Step S2522: Determine whether 10% of the rated power of the energy storage is less than the internal SOC state of the reconfigurable energy storage system 1 and less than 30% of the rated power of the energy storage? If yes, passive discharge; the reconfigurable energy storage system 1 focuses on meeting the indicators of the response period and the stable period, and reduces the adjustment during the climbing period; if no, execute step S2523;

[0087] Step S2523: Determine whether 30% of the rated power of the energy storage is less than the internal SOC state of the reconfigurable energy storage system 1 and less than 70% of the rated power of the energy storage. If yes, discharge evenly; during the ramp period, increase the energy storage output (i.e., discharge power); if no, discharge actively; perform discharge processing normally.

[0088] In addition, when responding to the AGC power increase instruction in step S253, the charging strategy adopted is as follows. Specifically, step S253 includes:

[0089] Step S2531: Determine whether 90% of the rated power of the energy storage is less than the internal SOC state of the reconfigurable energy storage system 1 and less than 100% of the rated power of the energy storage? If yes, charging is prohibited; the reconfigurable energy storage system 1 does not respond to the AGC instruction; if no, execute step S2532;

[0090] Step S2532: Determine whether 70% of the rated power of the energy storage is less than the internal SOC state of the reconfigurable energy storage system 1 and less than 90% of the rated power of the energy storage? If yes, passive charging is performed; the reconfigurable energy storage system 1 focuses on meeting the indicators of the response period and the stable period, and reduces the adjustment during the climbing period; if no, execute step S2533;

[0091] Step S2533: Determine whether 30% of the rated power of the energy storage is less than the internal SOC state of the reconfigurable energy storage system 1 and less than 70% of the rated power of the energy storage. If yes, balance charging is performed; during the ramp period, the energy storage output (i.e., charging power) value is increased; if no, active charging is performed; and the charging process is performed normally.

[0092] By setting a non-assessment period, the reconfigurable battery network 11 in the reconfigurable energy storage system 1 can be charged and discharged in a timely manner without participating in the frequency regulation process, so as to improve the performance of each battery group in the reconfigurable battery network 11 and ensure that each battery group is in a good state, so as to prepare for the subsequent frequency regulation of the thermal power unit 21.

[0093] Step three is the power decomposition strategy within the reconfigurable energy storage system 1, i.e., the lower-level strategy. The lower-level strategy is formed by splitting the power according to each reconfigurable battery network 11 after the upper-level strategy calculates the total target power of the energy storage. Specifically, step three includes:

[0094] Step S31: After obtaining the maximum charge current and the maximum discharge current of each reconfigurable battery network 11 according to the operating status of each reconfigurable battery network 11, the total charging power limit value P of the reconfigurable energy storage system 1 is calculated by the first formula and the second formula respectively. c-lmt , Reconfigurable Energy Storage System 1 Total Discharge Power Limit P d-lmt ;

[0095] Step S32: estimating the SOC of each battery pack in each reconfigurable battery network 11, thereby obtaining the SOC of each reconfigurable battery network 11;

[0096] Step S33: During charging, according to the target charging power P of the reconfigurable energy storage system 1 c-agc The power allocation is performed based on the relationship between the sum of the charging power limits of each reconfigurable battery network 11;

[0097] Step S34: During discharge, according to the target discharge power P of the reconfigurable energy storage system 1 d-agc The power allocation is performed based on the relationship between the sum of the discharge power limits of each reconfigurable battery network 11;

[0098] Step S35: Each reconfigurable battery network 11 places each battery pack into the reconfigurable battery network 11 in different time slices according to the reconstruction strategy, so as to realize charge and discharge power control and SOC balance adjustment of each battery pack.

[0099] Preferably, in step S31, the first formula is:

[0100]

[0101] Among them, P ci-lmt is the charging power limit of the i-th battery network; P c1-lmt is the charging power limit of the first battery network; P c2-lmt is the charging power limit of the second battery network; P cn-lmt is the charging power limit of the nth battery network.

[0102] In step S31, the second formula is:

[0103]

[0104] Among them, P di-lmt is the discharge power limit of the ith battery network; P d1-lmt is the discharge power limit of the first battery network; P d2-lmt is the discharge power limit of the second battery network; P dn-lmt is the discharge power limit of the nth battery network.

[0105] By setting the lower-level strategy in step three, the power in the reconfigurable energy storage system 1 can be effectively decomposed to achieve the balance of different battery groups in the reconfigurable energy storage system 1, reduce the impact of battery group differences on the reconfigurable energy storage system 1, and improve the flexibility and accuracy of the frequency regulation system of the reconfigurable energy storage-assisted thermal power unit.

[0106] Step S33 includes:

[0107] Step S331: During charging, determine whether the target charging power P of the energy storage system 1 can be reconfigured. c-agc ≥ the sum of the charging power limits of each reconfigurable battery network 11? Yes, go to step S332; No, go to step S333;

[0108] Step S332: Each reconfigurable battery network 11 is allocated according to the upper limit power, that is, P c-agc =P c-lmt ;

[0109] Step S333: Target charging power P of reconfigurable energy storage system 1 c-agc<The sum of the charging power limits of each reconfigurable battery network 11; when charging, each reconfigurable battery network 11 is allocated according to the SOC. Among them, the charging power of different reconfigurable battery networks 11 is inversely proportional to the mth power of their corresponding SOC, that is, the lower the SOC corresponding to the different reconfigurable battery networks 11, the greater the allocated charging power; the higher the SOC corresponding to the different reconfigurable battery networks 11, the smaller the allocated charging power. Specifically, the relationship between the charging power of different reconfigurable battery networks 11 and their corresponding SOC is as follows:

[0110]

[0111] Among them, P c1 is the charging power of the first reconfigurable battery network 11; is the mth power of the SOC of the first reconfigurable battery network 11. Combined with the constraint condition P ci ≤P ci-lmt ; It can be concluded that P ci The optimal solution of .

[0112] Step S34 includes:

[0113] Step S341: During discharge, determine whether the target discharge power P of the energy storage system 1 can be reconfigured. d-agc ≥ the sum of the discharge power limits of each reconfigurable battery network 11? Yes, go to step S342; No, go to step S343;

[0114] Step S342: Each reconfigurable battery network 11 is allocated according to the upper limit power, that is, P d-agc =P d-lmt ;

[0115] Step S343: Target discharge power P of the reconfigurable energy storage system 1 d-agc <The sum of the discharge power limits of each reconfigurable battery network 11; when discharging, each reconfigurable battery network 11 is allocated according to the SOC. Among them, the discharge power of different reconfigurable battery networks 11 is proportional to the mth power of their corresponding SOC, that is, the lower the SOC corresponding to the different reconfigurable battery networks 11, the smaller the allocated discharge power; the higher the SOC corresponding to the different reconfigurable battery networks 11, the greater the allocated discharge power. Specifically, the relationship between the discharge power of different reconfigurable battery networks 11 and their corresponding SOC is as follows:

[0116]

[0117] Among them, P d1 is the discharge power of the first reconfigurable battery network 11; is the mth power of the SOC of the first reconfigurable battery network 11. Combined with the constraint condition P di ≤P di-lmt ; It can be concluded that P di The optimal solution of .

[0118] By distributing the power of each battery pack in the reconfigurable energy storage system 1 during the charging and discharging processes, it is beneficial to improve the efficiency of the frequency modulation system regulation, and can also improve the stability of the frequency modulation system regulation, enhance the accuracy of the frequency modulation system regulation, make the energy storage system SOC and the SOC of each battery pack remain at about 50% for a long time, and improve the response capability of the energy storage system to the AGC continuous increase or continuous decrease command.

[0119] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A reconfigurable energy storage assisted thermal power unit frequency regulation system, characterized in that: The invention comprises a reconfigurable energy storage system (1), a thermal power plant control system (2) and a dispatching mechanism (3); the reconfigurable energy storage system (1) is connected to the dispatching mechanism (3) through the thermal power plant control system (2); the reconfigurable energy storage system (1) comprises a reconfigurable battery network (11), a power conversion device (12) and a coordination control module (13); one end of the reconfigurable battery network (11) is connected to the power grid through the power conversion device (12), and the other end of the reconfigurable battery network (11) is connected to the coordination control module (13) through the thermal power plant control system (2); and the coordination control module (13) is connected to the dispatching mechanism (3) through the thermal power plant control system (2).

2. A reconfigurable energy storage assisted thermal power unit frequency modulation system according to claim 1, characterized in that: The thermal power plant control system (2) comprises a thermal power unit (21), a distributed control system DCS (22) and a remote control terminal RTU (23); one end of the thermal power unit (21) is connected to the power grid, and the other end of the thermal power unit (21) is connected to the distributed control system DCS (22) for communication; the distributed control system DCS (22) is connected to the remote control terminal RTU (23) and the coordination control module (13) for communication; and the remote control terminal RTU (23) is connected to the dispatching mechanism (3) and the coordination control module (13) for communication.

3. A reconfigurable energy storage assisted thermal power unit frequency modulation system according to claim 2, characterized in that: The dispatching mechanism (3) comprises an automatic generation control AGC, and the automatic generation control AGC is connected to a remote control terminal RTU (23) in a two-way communication manner.

4. A reconfigurable energy storage-assisted thermal power unit frequency modulation system according to claim 1, characterized in that: The reconfigurable battery network (11) comprises a battery pack, a control switch and a bypass switch, wherein one end of each battery pack is connected to one end of the bypass switch via the control switch, and the other end of each battery pack is connected to the other end of the bypass switch.

5. A reconfigurable energy storage-assisted thermal power unit frequency modulation system according to claim 4, characterized in that: The battery pack, the control switch and the bypass switch are all provided in n numbers, where n is a positive integer.

6. A frequency regulation control method for a reconfigurable energy storage-assisted thermal power unit, characterized in that: The method is applied to a reconfigurable energy storage-assisted thermal power unit frequency regulation system according to any one of claims 1 to 5, and the method comprises the following steps: Step 1: The distributed control system DCS (22) in the thermal power plant control system (2) respectively collects AGC instruction data issued by the automatic generation control AGC and unit operating power data of the thermal power unit (21); Step 2: The remote control terminal RTU (23) in the thermal power plant control system (2) generates a total target power of energy storage according to the time period to which the AGC command data belongs and the SOC state of the reconfigurable battery network (11) in the reconfigurable energy storage system (1); Step 3: The reconfigurable energy storage system (1) decomposes the total target power of the energy storage into the target power of each reconfigurable battery network (11) based on the SOC balancing algorithm; Step 4: The reconfigurable battery network (11) controls the time slice of the battery group connected to the reconfigurable battery network (11) according to the reconstruction strategy to achieve charge and discharge control and SOC balance.

7. A frequency regulation control method for a reconfigurable energy storage-assisted thermal power unit according to claim 6, characterized in that: The second step comprises: Step S21: After receiving the AGC instruction issued by the automatic generation control AGC, the reconfigurable energy storage system (1) compares the AGC instruction data of the current period with the AGC instruction data of the previous period to determine whether the absolute difference exceeds the response dead zone. If yes, the currently received AGC instruction data is a new instruction and enters the response period; execute step S22; if no, return to step 1; Step S22: After entering the response period, the reconfigurable energy storage system (1) outputs a certain energy storage output according to the range of the AGC command data to jump out of the response action dead zone, and maintains it for a preset time t, and enters the ramp-up period; Step S23: After entering the ramp period, the adjustment rate is calculated; and it is determined whether the combined power in the AGC instruction data is less than 50% of the rated power of the energy storage. If yes, the difference response is adopted. After the unit has completed the ramp, it enters the stable period and executes step S24; if no, the step response is adopted. After the unit has completed the ramp, it enters the stable period and executes step S24; Step S24: During the stable period, the reconfigurable energy storage system (1) continuously adjusts the unit output of the thermal power unit (21); calculates the total target power of energy storage; and enters the non-assessment period; Step S25: During the non-assessment period, determine whether the SOC of the reconfigurable battery network (11) in the reconfigurable energy storage system (1) is higher than a preset value. If so, the reconfigurable energy storage system (1) discharges at a preset discharge power; if not, the reconfigurable energy storage system (1) charges at a preset charging power.

8. A frequency regulation control method for a reconfigurable energy storage-assisted thermal power unit according to claim 6, characterized in that: The step three comprises: Step S31: After obtaining the maximum chargeable current and the maximum dischargeable current of each reconfigurable battery network (11) according to the operating status of each reconfigurable battery network (11), the total charging power limit value P of the reconfigurable energy storage system (1) is calculated by the first formula and the second formula respectively. c-lmt , Reconfigurable Energy Storage System (1) Total Discharge Power Limit P d-lmt ; Step S32: estimating the SOC of each battery pack in each reconfigurable battery network (11), thereby obtaining the SOC of each reconfigurable battery network (11); Step S33: During charging, according to the target charging power P of the reconfigurable energy storage system (1), c-agc The power allocation is performed based on the relationship between the sum of the charging power limits of each reconfigurable battery network (11); Step S34: During discharge, according to the target discharge power P of the reconfigurable energy storage system (1), d-agc The power allocation is performed based on the relationship between the sum of the discharge power limits of each reconfigurable battery network (11); Step S35: Each reconfigurable battery network (11) places each battery pack into the reconfigurable battery network (11) in different time slices according to the reconstruction strategy, so as to realize charge and discharge power control and SOC balance adjustment of each battery pack.

9. A frequency regulation control method for a reconfigurable energy storage-assisted thermal power unit according to claim 8, characterized in that: In step S31, the first formula is: Among them, P ci-lmt is the charging power limit of the i-th battery network; P c1-lmt is the charging power limit of the first battery network; P c2-lmt is the charging power limit of the second battery network; P cn-lmt is the charging power limit of the nth battery network.

10. A frequency regulation control method for a reconfigurable energy storage-assisted thermal power unit according to claim 8, characterized in that: In step S31, the second formula is: Among them, P di-lmt is the discharge power limit of the ith battery network; P d1-lmt is the discharge power limit of the first battery network; P d2-lmt is the discharge power limit of the second battery network; P dn-lmt is the discharge power limit of the nth battery network.

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