A hybrid energy storage system power coordination control method

Abstract

The application relates to the technical field of electric power energy storage control systems, in particular to a hybrid energy storage system power coordination control method, which generates a dynamic power limiting value by online identification of the equivalent series internal resistance of a super capacitor group, calculates a state of charge change rate in real time to determine a nonlinear power smoothing coefficient, and performs first-order low-pass filtering smoothing processing and real-time deviation closed-loop correction on the initial power distribution result based on the dynamic power limiting value and the power smoothing coefficient, so that power coordination control is realized. The application solves the technical problems of existing technologies, such as static control parameters, unstable state transition, lack of perception and adaptation to the internal resistance change of the super capacitor group, and the like.

Description

Technical Field

[0001] This invention relates to the field of power energy storage control system technology, and more specifically, to a power coordination control method for a hybrid energy storage system. Background Technology

[0002] When renewable energy is integrated into the grid on a large scale, power system power fluctuations become severe, and the demand for frequency regulation and peak shaving increases. A single energy storage technology cannot simultaneously meet the dual demands of high power density and high energy density. Supercapacitors offer high power density and fast response speed, but low energy density; lithium batteries offer high energy density, but limited power density. Hybrid energy storage systems achieve complementary advantages between power-type and energy-type energy storage through the coordinated configuration of supercapacitors and lithium batteries. However, power coordination and allocation are the core issues in the operation and control of hybrid energy storage systems. Existing technologies employ the following strategies to address this problem:

[0003] 1. Fixed Ratio Allocation: Power regulation commands are allocated to the supercapacitor bank and lithium battery bank according to a preset fixed ratio. This method is simple to implement, but it cannot adapt to dynamic changes in power commands, nor can it adjust the allocation ratio according to the real-time status of the energy storage units. This results in the supercapacitor bank's rapid response capability not being fully utilized, and the lithium battery bank being unable to withstand power surges exceeding its tolerance capacity.

[0004] 2. Mode switching based on the SOC range of the supercapacitor bank: When the SOC is in the middle range, the supercapacitor bank provides the main power; when the SOC is close to the upper or lower limit, the power is switched to the lithium battery bank.

[0005] However, the above-mentioned processing methods all use static control parameters (such as power smoothing filter coefficient and power limiting value) in the operation and control of hybrid energy storage systems. They lack multi-dimensional perception and adaptive adjustment of the supercapacitor bank's operating status. Furthermore, when the supercapacitor's SOC approaches the critical value or priority switching occurs, the power distribution will change abruptly. There is a lack of buffer and transition mechanisms, which affects the efficient and stable operation of the hybrid energy storage system. Summary of the Invention

[0006] The purpose of this application is to provide a power coordination control method for a hybrid energy storage system, which solves the technical problems existing in the prior art, such as static control parameters, unstable state transitions, and lack of perception and adaptation to changes in the internal resistance of supercapacitor banks.

[0007] To solve the above-mentioned technical problems, the solution adopted in this application is as follows:

[0008] A power coordination control method for a hybrid energy storage system includes the following steps:

[0009] S1: Receive the power regulation command issued by the power grid and determine the validity of the power regulation command. At the same time, monitor the status of the hybrid energy storage system. If the power regulation command is valid and the status of the hybrid energy storage system is normal, then execute step S2; otherwise, suspend the power coordination control process and issue an alarm signal.

[0010] S2: Based on the port voltage and current of the supercapacitor bank, the equivalent series internal resistance of the supercapacitor bank is identified online.

[0011] S3: Based on the current current and the equivalent series internal resistance identified in S2, calculate the instantaneous heating power inside the supercapacitor bank, and derive the maximum allowable continuous charging and discharging power under the current operating conditions as the dynamic power limit value based on the thermal balance equation of the supercapacitor bank.

[0012] S4: Calculate the rate of change of state of charge of the supercapacitor bank, and determine the power smoothing coefficient of the supercapacitor bank based on the rate of change of state of charge and according to the preset nonlinear mapping relationship.

[0013] S5: Based on the power adjustment command, dynamic power limit value, and state range of the supercapacitor bank, perform initial power allocation to obtain the initial power target value of the supercapacitor bank and the initial power target value of the lithium battery bank.

[0014] S6: Based on the initial power target value and the power smoothing coefficient, the initial power target values ​​of the supercapacitor bank and the lithium battery bank are smoothed by first-order low-pass filtering to obtain the smoothed target power.

[0015] S7: The energy storage converter performs a charge-discharge operation based on the smoothed target power control, and corrects the smoothed target power based on the real-time state variables to obtain the corrected power target value. The energy storage converter then performs a second charge-discharge operation based on the corrected power target value. This power coordination control is completed, and the process returns to S1 to enter the next execution cycle.

[0016] Preferably, the specific implementation method of S1 includes the following steps:

[0017] S11: Obtain the power regulation command issued by the power grid dispatching system, and determine the validity of the power regulation command, specifically:

[0018] Determine whether the power adjustment command is within the rated adjustment power range;

[0019] Determine whether the difference between the power regulation command and the actual power at the power plant's grid connection point is greater than the preset power dead zone threshold;

[0020] If all the above judgment results are yes, then execute S12; otherwise, exit the power coordination control process.

[0021] S12: Collect the status variables and communication status of the hybrid energy storage system, and perform the following judgment:

[0022] Whether the health status of the lithium battery pack and the supercapacitor pack in the state variables meet the preset operating conditions;

[0023] Does the communication status of the hybrid energy storage system meet the preset operating conditions?

[0024] If all the above judgment results are yes, then execute S2; otherwise, exit the current power coordination control process.

[0025] Preferably, the specific implementation method of S2 includes the following steps:

[0026] S2.1: Acquire the port voltage of the supercapacitor bank and current ;

[0027] S2.2: Based on port voltage and current A first-order RC equivalent circuit model is established, and the differential equation of the first-order RC equivalent circuit model is:

[0028] ;

[0029] This is the equivalent series internal resistance of the supercapacitor bank. This is the equivalent capacitance of the supercapacitor bank. For continuous time variables;

[0030] Discretizing the differential equations and using a first-order backward difference approximation yields the difference equations for a first-order RC equivalent circuit model:

[0031] ;

[0032] The current sampling time is dimensionless. This refers to the previous sampling time. This is the port voltage collected at the current sampling moment; This represents the port voltage at the previous sampling time. This is the port current sampled at the current sampling moment. This represents the port current at the previous sampling time. , , The parameters to be identified;

[0033] S2.3: Based on the difference equation in S2.2, the recursive least squares method is used to identify the parameters to be identified online. , , ;

[0034] S2.4: Based on the relationship between the parameters to be identified and the circuit physical parameters in S2.2, the parameters obtained from online identification... Obtain the equivalent series internal resistance of the supercapacitor bank :

[0035] .

[0036] Preferably, the specific implementation method of S3 includes the following steps:

[0037] S3.1: Calculate the instantaneous heat generation power inside the supercapacitor bank :

[0038] S3.2: Set a safe temperature rise rate limit When the state of charge value of the supercapacitor bank When the temperature is within the preset warning range, the safe temperature rise rate limit will be reduced by a preset ratio. The reduced safe temperature rise rate limit is obtained. ;

[0039] S3.3: Based on the thermal balance equation of the supercapacitor bank, its maximum allowable continuous charge and discharge current is derived in reverse. ;

[0040] S3.4: Based on the maximum continuous charge / discharge current and the current port voltage of the supercapacitor bank Calculate the maximum permissible continuous charge and discharge power and compare it with the rated power of the supercapacitor bank, taking the smaller value as the dynamic power limit. .

[0041] Preferably, the heat balance equation in S3.3 is:

[0042] ;

[0043] Maximum continuous charge and discharge current for: ;

[0044] This refers to the average specific heat capacity of the supercapacitor bank. For the quality of the supercapacitor bank; The rate of temperature rise; This is for the heat dissipation power of the supercapacitor bank;

[0045] The reverse derivation process is as follows:

[0046] Under maximum continuous power conditions, the heat dissipation power and the heat generation power are balanced, i.e. Maximum continuous charge and discharge current :

[0047] ;

[0048] Solving the above equation yields the maximum continuous charge-discharge current. .

[0049] Preferably, the specific implementation method of S4 includes the following steps:

[0050] S4.1: Calculate the first derivative of the state of charge value of the supercapacitor bank as the rate of change of state of charge;

[0051] S4.2: Determine the power smoothing coefficient of the supercapacitor bank according to the absolute value of the rate of change of state of charge and a preset nonlinear mapping relationship. ;

[0052] S4.3: Based on the health status of the supercapacitor bank Preset upper limit for power smoothing coefficient The correction is performed to obtain the corrected power smoothing coefficient. : ;

[0053] S4.4: When the state of charge value of the supercapacitor bank enters the preset warning range, the preset lower limit of the power smoothing coefficient is adjusted to the preset boundary smoothing coefficient value. : .

[0054] Preferably, the specific implementation method of S4.2 includes the following steps:

[0055] Based on the rate of change of state of charge, the current power surge intensity of the supercapacitor bank is divided into three stages: low-surge zone, high-surge zone, and transition zone.

[0056] When the rate of change of state of charge is less than or equal to the first threshold, it is a low-impact zone;

[0057] When the rate of change of state of charge is greater than or equal to the second threshold, it is a high-impact zone;

[0058] When the rate of change of state of charge is less than or equal to the second threshold and greater than or equal to the first threshold, it is the transition zone;

[0059] The first threshold represents the boundary between the low-impact zone and the transition zone; the second threshold represents the boundary between the high-impact zone and the transition zone.

[0060] When the rate of change of state of charge is less than or equal to the first threshold, the power smoothing coefficient takes the preset upper limit value.

[0061] When the rate of change of state of charge is greater than or equal to the second threshold, the power smoothing coefficient decreases to a preset lower limit as the rate of change of state of charge increases, that is:

[0062] ;

[0063] The second threshold, Set an upper limit for the power smoothing coefficient; A lower limit value is preset for the power smoothing coefficient; The attenuation coefficient; It is a natural exponential function; This is the final power smoothing coefficient;

[0064] When the rate of change of state of charge is less than or equal to the second threshold and greater than or equal to the first threshold, the power smoothing coefficient is calculated by linear interpolation. The specific calculation method is as follows:

[0065] ;

[0066] This is the first threshold.

[0067] Preferably, the specific implementation method of S5 includes the following steps:

[0068] S51: Determine the charging / discharging direction based on the sign of the power adjustment command;

[0069] S52: Determine the state range of the supercapacitor bank based on its real-time state of charge value.

[0070] S53: Calculate the initial power target value of the supercapacitor bank based on the charging / discharging direction and the state range of the supercapacitor bank. ;

[0071] S54: According to the power adjustment command Calculate the initial power target value of the lithium battery pack based on the initial power target value of the supercapacitor pack. :

[0072] .

[0073] Preferably, the specific implementation method of S6 includes the following steps:

[0074] S61: Initial power target value for the supercapacitor bank A first-order low-pass filter is performed to smooth the power of the supercapacitor bank, yielding the smoothed target power. ;

[0075] S62: Initial power target value for the lithium battery pack A first-order low-pass filter is performed for smoothing to obtain the smoothed target power of the lithium battery pack. ;

[0076] S63: Calculate the sum of the smoothed target power of the supercapacitor bank and the lithium battery bank, and verify its consistency with the power regulation command. Specifically:

[0077] ;

[0078] like Then power compensation will be performed:

[0079] like hour, , ;

[0080] like When the target power is still insufficient, prioritize increasing the supercapacitor bank to smooth it out; if that is still insufficient, increase the lithium battery bank to smooth it out.

[0081] in To smooth out tolerances.

[0082] Preferably, the specific implementation method of S7 includes the following steps:

[0083] S7.1: Energy storage converter receives smoothed target power from supercapacitor bank Smoothing target power of lithium battery pack And control the execution of charging and discharging operations;

[0084] S7.2: Collect real-time state parameters of the hybrid energy storage system, including: real-time state of charge values ​​of the supercapacitor bank. Real-time state of charge of lithium battery pack Actual power at the power station's grid connection point ;

[0085] S7.3: Calculate power regulation command Actual power at the power station's grid connection point Power regulation deviation :

[0086] ;

[0087] S7.4: Adjust according to power deviation Smoothing target power of supercapacitor bank Smoothing target power of lithium battery pack After making corrections, the corrected power target value of the supercapacitor bank is obtained. and the target power value of the lithium battery pack ;

[0088] S7.5: When the real-time state of charge value of the supercapacitor bank When the system enters the preset warning range, perform the following operations:

[0089] Reduce the power change rate of the supercapacitor bank, i.e., trigger the power smoothing coefficient adjustment in step S4.4;

[0090] S7.6: The revised power target value of the supercapacitor bank and the target power value of the lithium battery pack The control is sent to the energy storage converter to execute the secondary charging and discharging operation. The power coordination control is completed and returns to S1 to enter the next execution cycle.

[0091] The technical solution of this application has at least the following advantages and beneficial effects:

[0092] 1. This invention provides a power coordination control method for a hybrid energy storage system. First, it filters valid commands and confirms the safety status of the hybrid energy storage system through command validity judgment and system status monitoring, preparing for subsequent power coordination control. Then, it uses the recursive least squares method to identify the equivalent series internal resistance of the supercapacitor bank online and obtains its ohmic loss characteristics in real time. Next, it derives the dynamic power limit value in reverse based on the identified internal resistance and the thermal balance equation, making thermal safety constraints a prerequisite safety condition for power allocation. Simultaneously, it calculates the rate of change of state of charge and provides a nonlinear mapping to determine the dynamic smoothing coefficient, achieving an adaptive balance between response speed and smoothness. Based on this, it replaces the rated power of the hybrid energy storage system with the dynamic power limit value, performs initial power allocation according to the supercapacitor priority principle, and smooths the initial allocation results to suppress power switching shocks. Finally, it corrects and adjusts power deviations by real-time acquisition of grid connection point power, thus realizing an execution-feedback-correction power coordination control process. In this invention, a dynamic power limit value is generated based on the equivalent series internal resistance identification result and the thermal balance equation, and a dynamic smoothing coefficient is generated based on the nonlinear mapping of the rate of change of state of charge. The two together constitute time-varying control parameters. Unlike traditional static control parameters, the power coordination control of the hybrid energy storage system is performed through time-varying control parameters, so that the power adjustment command response process is smooth and without abrupt changes. After the initial power allocation is executed, the power deviation is corrected and compensated again according to the state of the hybrid energy storage system. This solves the technical problems of static control parameters, unstable state transition, and lack of perception and adaptation to changes in the internal resistance of supercapacitor banks in the prior art. Attached Figure Description

[0093] Figure 1 This is a flowchart of a power coordination control method for a hybrid energy storage system according to the present invention. Detailed Implementation

[0094] 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.

[0095] See Figure 1 This invention provides a power coordination control method for a hybrid energy storage system, comprising the following steps:

[0096] S1: Receive the power regulation command issued by the power grid and determine the validity of the power regulation command. At the same time, monitor the status of the hybrid energy storage system. If the power regulation command is valid and the status of the hybrid energy storage system is normal, then execute step S2; otherwise, suspend the power coordination control process and issue an alarm signal.

[0097] S2: Based on the port voltage and current of the supercapacitor bank, the equivalent series internal resistance of the supercapacitor bank is identified online.

[0098] S3: Based on the current current and the equivalent series internal resistance identified in S2, calculate the instantaneous heating power inside the supercapacitor bank, and derive the maximum allowable continuous charging and discharging power under the current operating conditions as the dynamic power limit value based on the thermal balance equation of the supercapacitor bank.

[0099] S4: Calculate the rate of change of state of charge of the supercapacitor bank. Based on the rate of change of state of charge, determine the power smoothing coefficient of the supercapacitor bank according to a preset nonlinear mapping relationship. The specific implementation includes the following steps:

[0100] S5: Based on the power adjustment command, dynamic power limit value, and state range of the supercapacitor bank, perform initial power allocation to obtain the initial power target value of the supercapacitor bank and the initial power target value of the lithium battery bank.

[0101] S6: Based on the initial power target value and the power smoothing coefficient, the initial power target values ​​of the supercapacitor bank and the lithium battery bank are smoothed by first-order low-pass filtering to obtain the smoothed target power.

[0102] S7: The energy storage converter performs a charge-discharge operation based on the smoothed target power control, and corrects the smoothed target power based on the real-time state variables to obtain the corrected power target value. The energy storage converter then performs a second charge-discharge operation based on the corrected power target value. This power coordination control is completed, and the process returns to S1 to enter the next execution cycle.

[0103] In this embodiment, in step S1, the power regulation command issued by the power grid is received and its validity is determined. At the same time, the status of the hybrid energy storage system is monitored. If the power regulation command is valid and the hybrid energy storage system is in a normal state, the specific implementation method of step S2 includes the following steps:

[0104] S11: Obtain the power regulation command issued by the power grid dispatching system, and determine the validity of the power regulation command, specifically:

[0105] Determine whether the power adjustment command is within the rated adjustment power range;

[0106] Determine whether the difference between the power regulation command and the actual power at the power plant's grid connection point is greater than the preset power dead zone threshold;

[0107] If all the above judgment results are yes, then execute S12; otherwise, exit the power coordination control process.

[0108] Specifically, the power adjustment command is denoted as The absolute value of the power adjustment command Compare this to the rated regulating power of the hybrid energy storage system, where the rated regulating power is denoted as... The rated adjustable power is determined by the rated power on the nameplate of the supercapacitor bank. With the brand name of the lithium battery pack, the rated power The superposition determines that:

[0109] ;

[0110] like If the command is deemed to meet the rated regulating power range limit, it is considered to be invalid; otherwise, it is considered an invalid command.

[0111] Collect actual power at the power station's grid connection point Calculate the absolute value of the difference between the power regulation command and the actual power at the grid connection point, i.e.:

[0112] ;

[0113] Will With preset power dead zone threshold If a comparison is made, If the power dead zone threshold limit is met, the instruction is deemed invalid.

[0114] The preset power dead zone threshold is generally taken as the rated regulating power of the hybrid energy storage system. 1% to 3%.

[0115] S12: Collect the status variables and communication status of the hybrid energy storage system, and perform the following judgment:

[0116] Whether the health status of the lithium battery pack and the supercapacitor pack in the state variables meet the preset operating conditions;

[0117] Does the communication status of the hybrid energy storage system meet the preset operating conditions?

[0118] If all the above judgment results are yes, then execute S2; otherwise, exit the current power coordination control process.

[0119] State quantities include: real-time state of charge values ​​of the supercapacitor bank. Real-time state of charge of lithium battery pack Health status of supercapacitor banks Health status of lithium battery pack ;

[0120] The communication status of the hybrid energy storage system includes the communication status between the supercapacitor battery management system, the lithium battery battery management system, the energy storage converter, and the energy management system.

[0121] Specifically, the health status of the collected supercapacitor banks Health status of lithium battery pack Perform threshold comparisons. For example, the preset operating conditions for lithium battery packs are... ,in This is the minimum battery capacity threshold that allows the lithium battery pack to operate, usually set to 70% of the lithium battery pack's capacity. The specific value can be changed according to the actual situation.

[0122] If the health status of the lithium battery pack If the capacity falls below the minimum battery capacity threshold, it indicates that the lithium battery pack has suffered severe capacity degradation or excessive internal resistance growth, and can no longer be charged and discharged at high rates.

[0123] Among them, the real-time state of charge value of the supercapacitor bank The calculation is based on a fusion of the ampere-hour integration method and the open-circuit voltage method by the supercapacitor battery management system.

[0124] Real-time state of charge of lithium battery pack Calculated by the lithium battery pack battery management system based on the extended Kalman filter algorithm;

[0125] Health status of supercapacitor bank Based on a comprehensive evaluation using the internal resistance growth method and the capacity decay method, it reflects the ratio of the current maximum usable battery capacity of the supercapacitor bank to the initial battery capacity.

[0126] Health status of lithium battery pack Based on a comprehensive evaluation of the number of charge-discharge cycles, changes in internal resistance, and battery capacity decay, this reflects the ratio of the current maximum usable battery capacity of the lithium battery pack to the initial battery capacity.

[0127] The communication status detection specifically includes:

[0128] CAN bus communication status between the supercapacitor bank's battery management system and energy management system: Detecting whether the heartbeat message cycle has timed out;

[0129] CAN bus communication status between the lithium battery pack battery management system and the energy management system: Detecting whether the heartbeat message cycle has timed out;

[0130] The communication status between the energy storage converter and the energy management system is monitored, and the response confirmation signal of the energy storage converter to the control commands issued by the energy management system is detected.

[0131] Data interaction status between various functional modules within energy management: Detect the data update flag in the shared memory area.

[0132] If any communication link is abnormal / If the power is zeroed, the energy management system sends a power zeroing command to the energy storage converter, setting the power target values ​​of the supercapacitor bank and lithium battery bank to zero. At the same time, it sends an alarm signal to the grid dispatch system. The alarm signal includes an anomaly type code and an anomaly subsystem identifier. Power coordination control will continue only after the operation and maintenance personnel intervene / the anomaly is eliminated.

[0133] In this step, the calculation and acquisition of each parameter are common processing methods in existing energy storage systems and are existing technologies. As described above, those skilled in the art can understand this, so the detailed calculation process of each parameter will not be elaborated here.

[0134] In this invention, the energy storage hybrid system comprises a power-type energy storage unit and an energy-type energy storage unit. The power-type energy storage unit is a supercapacitor bank, and the energy-type energy storage unit is a lithium battery bank.

[0135] The power grid dispatching system is located on the grid side and issues power regulation commands to the energy storage power station through a standard communication protocol. The energy storage power station is located on the power station side and is internally configured with an energy management system, an energy storage converter, a supercapacitor bank and its battery management system, and a lithium battery bank and its battery management system. The energy management system establishes communication connections with each battery management system and the energy storage converter to realize status acquisition and power control. The supercapacitor bank and the lithium battery bank are connected in parallel and exchange power with the grid through the energy storage converter to form a hybrid energy storage system.

[0136] In this embodiment, in step S2, the equivalent series resistance of the supercapacitor bank is identified online based on the port voltage and current of the supercapacitor bank. The specific implementation method includes the following steps:

[0137] S2.1: Acquire the port voltage of the supercapacitor bank and current ;

[0138] Specifically, port voltage and current Data is collected via an energy storage converter at a preset sampling period, which is set to be the same as the power coordination control period.

[0139] Port voltage The terminal voltage between the positive and negative terminals of the supercapacitor bank, measured in volts; the port current. This is the main circuit current flowing through the supercapacitor bank. The charging direction is positive, and the discharging direction is negative. The unit is amperes.

[0140] After data collection is completed, the energy storage converter transmits the collected data to the energy management system via a communication link.

[0141] S2.2: Based on port voltage and current A first-order RC equivalent circuit model is established, and the differential equation of the first-order RC equivalent circuit model is:

[0142] ;

[0143] in, This is the equivalent series internal resistance of the supercapacitor bank, expressed in ohms. This is the equivalent capacitance of the supercapacitor bank, measured in farads. It is a continuous time variable, with the unit being seconds;

[0144] The differential equations are then discretized, and a first-order backward difference approximation is used to obtain the difference equations for the first-order RC equivalent circuit model:

[0145] ;

[0146] in, The current sampling time is dimensionless. The previous sampling time is dimensionless; The port voltage collected at the current sampling moment is in volts. The port voltage at the previous sampling time is expressed in volts. This is the port current sampled at the current sampling moment. The port current at the previous sampling time is expressed in amperes.

[0147] , , The parameter to be identified is dimensionless, and its relationship with the circuit physical parameters of the supercapacitor bank is as follows:

[0148] ;

[0149] ;

[0150] ;

[0151] S2.3: Based on the difference equation in S2.2, the recursive least squares method is used to identify the parameters to be identified online. , , ;

[0152] Specifically, define a data vector: ; It is a 3-dimensional column vector;

[0153] Define the parameter vector: ; 3D column vector;

[0154] The iterative formula for the recursive least squares method is:

[0155] Gain Update ; It is a 3-dimensional gain vector, dimensionless; Estimate the covariance matrix of the parameters at the previous sampling time;

[0156] Parameter update ; The parameter estimate at the current sampling time; This is the parameter estimate from the previous sampling time.

[0157] Covariance Update ;

[0158] in, This is the forgetting factor, typically ranging from 0.95 to 0.99, which can be selected based on the actual scenario to reduce the weight of historical data. Estimate the covariance matrix for the parameters; It is the gain vector; It is a third-order identity matrix with 1s on the main diagonal and 0s on the secondary diagonal, and is dimensionless.

[0159] S2.4: Based on the relationship between the parameters to be identified and the circuit physical parameters in S2.2, the parameters obtained from online identification... Obtain the equivalent series internal resistance of the supercapacitor bank :

[0160] ;

[0161] Simultaneously utilize To perform verification, that is:

[0162] ;

[0163] Specifically, equivalent series internal resistance It is a time-varying parameter that reflects the ohmic loss characteristics of the supercapacitor bank under the current operating conditions, including the current temperature, aging state, and state of charge.

[0164] In this step, S3, based on the current current and the equivalent series internal resistance identified in S2, the instantaneous heat generation power inside the supercapacitor bank is calculated. Based on the thermal balance equation of the supercapacitor bank, the maximum allowable continuous charge and discharge power under the current operating conditions is derived as the dynamic power limit value. Its specific implementation includes the following steps:

[0165] S3.1: Calculate the instantaneous heat generation power inside the supercapacitor bank :

[0166] ;

[0167] Specifically, the instantaneous heat generation power inside the supercapacitor bank Characterizes the ohmic loss heat generation rate of the supercapacitor bank under current operating conditions;

[0168] S3.2: Set a safe temperature rise rate limit When the state of charge value of the supercapacitor bank When the temperature is within the preset warning range, the safe temperature rise rate limit will be reduced by a preset ratio. ;

[0169] Specifically, safe temperature rise rate limit The value is determined based on the thermal characteristic parameters of the supercapacitor bank and the temperature resistance rating of the insulation material, and is usually taken in the range of 0.5K / min to 2K / min.

[0170] The above-mentioned preset warning interval is set as follows: or ,Right now:

[0171] ;

[0172] The reduced safe temperature rise rate limit, This is the state of charge correction factor, i.e., the preset ratio, with a value range of 0.5-0.7.

[0173] S3.3: Based on the thermal balance equation of the supercapacitor bank, its maximum allowable continuous charge and discharge current is derived in reverse. ;

[0174] The heat balance equation is:

[0175] ;

[0176] Maximum continuous charge and discharge current for: ;

[0177] in, This is the average specific heat capacity of the supercapacitor bank, expressed in joules per kilogram Kelvin. The mass of the supercapacitor bank is expressed in kilograms. The rate of temperature rise is expressed in Kelvin per second. This is for the heat dissipation power of the supercapacitor bank;

[0178] Specifically, the reverse derivation process is as follows:

[0179] Under maximum continuous power conditions, assuming that heat dissipation power and heat generation power are balanced, i.e. Maximum continuous charge and discharge current :

[0180] ;

[0181] Solving the above equation yields the maximum continuous charge-discharge current. .

[0182] S3.4: Based on the maximum continuous charge / discharge current and the current port voltage of the supercapacitor bank Calculate the maximum permissible continuous charge and discharge power and compare it with the rated power of the supercapacitor bank, taking the smaller value as the dynamic power limit. ;

[0183] Specifically, dynamic power limiting value The unit is watt;

[0184] The maximum allowable continuous charge and discharge power is calculated using a power limiting function calibrated based on the thermal balance equation and experimental data. The specific form of the power limiting function is obtained by fitting experimental data, and can be achieved using a lookup table method or a polynomial fitting method.

[0185] For example, by using the table lookup method, a system can be established. , , A three-dimensional lookup table is used to obtain the dynamic power limit value through linear interpolation.

[0186] In this invention, the parameters obtained by detection and calculation are also subjected to outlier processing, including outlier removal and correction. Outlier processing is a conventional data processing method, so this invention will not elaborate on this part.

[0187] In this embodiment, in step S4, the rate of change of the state of charge of the supercapacitor bank is calculated. Based on the rate of change of the state of charge, the power smoothing coefficient of the supercapacitor bank is determined according to a preset nonlinear mapping relationship. The specific implementation includes the following steps:

[0188] S4.1: Calculate the first derivative of the state of charge value of the supercapacitor bank as the rate of change of state of charge;

[0189] The specific calculation method is as follows:

[0190] ;

[0191] in, This is the rate of change of state of charge, measured in seconds. The current state of charge of the supercapacitor bank at the current sampling time is dimensionless. This represents the real-time state of charge (SOC) value of the supercapacitor bank at the previous sampling time. It is dimensionless and ranges from 0% to 100%. The sampling period is expressed in seconds.

[0192] The larger the absolute value of the rate of change of state of charge, the stronger the power impact of the current power regulation command on the supercapacitor bank, requiring stronger smoothing and suppression; conversely, the smaller the value, the lower the impact intensity, allowing for a faster response speed.

[0193] S4.2: Determine the power smoothing coefficient of the supercapacitor bank according to the absolute value of the rate of change of state of charge and a preset nonlinear mapping relationship. ;

[0194] Specifically, based on the rate of change of state of charge, the current power surge intensity of the supercapacitor bank is divided into three stages: low surge zone, high surge zone, and transition zone.

[0195] When the rate of change of state of charge is less than or equal to the first threshold, it is a low-impact zone;

[0196] When the rate of change of state of charge is greater than or equal to the second threshold, it is a high-impact zone;

[0197] When the rate of change of state of charge is less than or equal to the second threshold and greater than or equal to the first threshold, it is the transition zone;

[0198] The first threshold, measured in units of seconds, represents the boundary between the low-impact zone and the transition zone, and has a value of 0.01 / s.

[0199] The second threshold value is 0.1 / s;

[0200] When the rate of change of state of charge is less than or equal to the first threshold, the power smoothing coefficient takes a preset upper limit value, and the preset upper limit value of the power smoothing coefficient is in the range of 0.8~0.95;

[0201] When the rate of change of state of charge is greater than or equal to the second threshold, the power smoothing coefficient decreases to a preset lower limit as the rate of change of state of charge increases, that is:

[0202] ;

[0203] in, The second threshold, An upper limit value is preset for the power smoothing coefficient. It is dimensionless and ranges from 0.8 to 0.95. A lower limit value is preset for the power smoothing coefficient. It is dimensionless and ranges from 0.2 to 0.4. The attenuation coefficient is dimensionless and ranges from 10 to 50. It is a natural exponential function; This is the final power smoothing coefficient;

[0204] When the rate of change of state of charge is less than or equal to the second threshold and greater than or equal to the first threshold, the power smoothing coefficient is calculated by linear interpolation, and the specific calculation formula is as follows:

[0205] ;

[0206] in, This is the first threshold.

[0207] S4.3: Based on the health status of the supercapacitor bank Preset upper limit for power smoothing coefficient The correction is performed to obtain the corrected power smoothing coefficient. ;

[0208] Specifically, ;

[0209] The preset upper limit of the power smoothing coefficient is adjusted according to the health status of the supercapacitor bank, so that the power surge force can be reduced and the aging process can be slowed down when the supercapacitor bank with a high degree of aging responds to the power regulation command.

[0210] S4.4: When the state of charge value of the supercapacitor bank enters the preset warning range, the preset lower limit of the power smoothing coefficient is adjusted to the preset boundary smoothing coefficient value. ;

[0211] Specifically, the preset warning interval is usually set to or ,in This is the threshold for the prohibited discharge zone, with a maximum value of 20%. This is the threshold for the prohibited charging zone, with a minimum value of 80%.

[0212] Among them, the preset boundary smoothing coefficient value The value is typically between 0.1 and 0.3, which is less than the value under normal operating conditions. This is to achieve a smoother transition in the rate of power change and prevent the supercapacitor bank from exceeding the state of charge limit and entering the prohibited range.

[0213] More specifically, the adjusted power smoothing coefficient is: ;

[0214] The specific values ​​of the above parameters are all exemplary explanations and are not limited by this invention. In actual situations, their values ​​can be selected according to actual needs and application scenarios.

[0215] In this embodiment, in S5, initial power allocation is performed based on the power adjustment command, dynamic power limit value, and state range of the supercapacitor bank to obtain the initial power target value of the supercapacitor bank and the initial power target value of the lithium battery bank.

[0216] S51: Determine the charging / discharging direction based on the sign of the power adjustment command;

[0217] Specifically: if power adjustment command If it is a discharge command, it is determined to be a power adjustment command. This was determined to be a charging command;

[0218] S52: Determine the state range of the supercapacitor bank based on its real-time state of charge value.

[0219] For example, This is a prohibited discharge zone;

[0220] S53: Calculate the initial power target value of the supercapacitor bank based on the charging / discharging direction and the state range of the supercapacitor bank. ;

[0221] Specifically, when a discharge command is issued and the operating range is safe, the supercapacitor bank shall bear all the discharge power first, provided it does not exceed the dynamic power limit.

[0222] when hour, ;

[0223] when hour, ;

[0224] When a charging command is issued and the system is within a safe operating range, the supercapacitor bank will preferentially bear all charging power, provided that the power does not exceed the absolute value of the dynamic power limit. Specifically:

[0225] when hour, ;

[0226] when hour, ;

[0227] When the battery is in a prohibited discharge zone and a discharge command is issued, all discharge power is supplied by the lithium battery pack, and the initial power target value of the supercapacitor pack is set to zero. ;

[0228] When in a prohibited charging zone and a charging command is issued, all charging power is supplied by the lithium battery pack, and the initial power target value of the supercapacitor pack is set to zero. ;

[0229] When the supercapacitor bank is in a prohibited discharge zone but the power regulation command is a charging command, or in a prohibited charging zone but the power regulation command is a discharging command, the supercapacitor bank shall bear the power in the corresponding direction according to the rules of the safe operating zone.

[0230] S54: Calculate the initial power target value of the lithium battery pack based on the power adjustment command and the initial power target value of the supercapacitor pack. :

[0231] ;

[0232] In this embodiment, in step S6, based on the initial power target value and the power smoothing coefficient, the initial power target values ​​of the supercapacitor bank and the lithium battery bank are subjected to first-order low-pass filtering smoothing processing to obtain the smoothed target power. The specific implementation method includes the following steps:

[0233] S61: Initial power target value for the supercapacitor bank A first-order low-pass filter is performed to smooth the power of the supercapacitor bank, yielding the smoothed target power. ;

[0234] S62: Initial power target value for the lithium battery pack A first-order low-pass filter is performed for smoothing to obtain the smoothed target power of the lithium battery pack. ;

[0235] S63: Calculate the sum of the smoothed target power of the supercapacitor bank and the lithium battery bank, and verify its consistency with the power regulation command. Specifically:

[0236] ;

[0237] like Then power compensation will be performed:

[0238] like hour, , ;

[0239] like When the target power is still insufficient, prioritize increasing the supercapacitor bank to smooth it out; if that is still insufficient, increase the lithium battery bank to smooth it out.

[0240] in To smooth out tolerances, a value is typically taken. times .

[0241] In this embodiment, in S7, the energy storage converter performs a first charge-discharge operation based on the smoothed target power control, and corrects the smoothed target power based on real-time state variables to obtain a corrected power target value. The energy storage converter then performs a second charge-discharge operation based on the corrected power target value. After this power coordination control is completed, the process returns to S1 to enter the next execution cycle. The specific implementation steps include:

[0242] S7.1: Energy storage converter receives smoothed target power from supercapacitor bank Smoothing target power of lithium battery pack And control the execution of charging and discharging operations;

[0243] S7.2: Collect real-time state parameters of the hybrid energy storage system, including: real-time state of charge values ​​of the supercapacitor bank. Real-time state of charge of lithium battery pack Actual power at the power station's grid connection point ;

[0244] S7.3: Calculate power regulation command Actual power at the power station's grid connection point Power regulation deviation :

[0245] ;

[0246] S7.4: Adjust according to power deviation Smoothing target power of supercapacitor bank Smoothing target power of lithium battery pack After making corrections, the corrected power target value of the supercapacitor bank is obtained. and the target power value of the lithium battery pack ;

[0247] For example: when When this occurs, it indicates that the actual discharge power is insufficient or the actual charging power is excessive. Priority should be given to increasing the discharge power of the supercapacitor bank, while the amount of increase is subject to the following constraints:

[0248] Dynamic power limiting constraint: The corrected power target value of the supercapacitor bank shall not exceed the dynamic power limiting value calculated in step S3;

[0249] State of charge safety range constraint: The corrected power target value of the supercapacitor bank shall not cause its state of charge to enter the prohibited discharge range.

[0250] If the supercapacitor bank is already at the upper limit of the dynamic power limit / discharge prohibition range and cannot continue to increase the discharge power, then increase the discharge power of the lithium battery bank.

[0251] S7.5: When the real-time state of charge value of the supercapacitor bank When the system enters the preset warning range, perform the following operations:

[0252] Reduce the power change rate of the supercapacitor bank, i.e., trigger the power smoothing coefficient adjustment in step S4.4;

[0253] S7.6: The revised power target value of the supercapacitor bank and the target power value of the lithium battery pack The control is sent to the energy storage converter to execute the secondary charging and discharging operation. The power coordination control is completed and returns to S1 to enter the next execution cycle.

[0254] The secondary charge-discharge operation is as follows: based on the execution result of the primary charge-discharge operation, the actual power at the power station's grid connection point is collected, the power adjustment deviation between the power adjustment command and the actual power at the power station's grid connection point is calculated, the smoothing target power is corrected in a closed loop according to the power adjustment deviation to obtain the corrected power target value, and the charge-discharge operation is executed again according to the corrected power target value.

[0255] The various embodiments of the present invention have now been described in detail. To avoid obscuring the concept of the invention, some details known in the art have not been described. Those skilled in the art will fully understand how to implement the technical solutions of this invention based on the above description, and the scope of the invention is defined by the appended claims.

Claims

1. A power coordination control method for a hybrid energy storage system, characterized in that, Includes the following steps: S1: Receive the power regulation command issued by the power grid and determine the validity of the power regulation command. At the same time, monitor the status of the hybrid energy storage system. If the power regulation command is valid and the status of the hybrid energy storage system is normal, then execute step S2; otherwise, suspend the power coordination control process and issue an alarm signal. S2: Based on the port voltage and current of the supercapacitor bank, the equivalent series internal resistance of the supercapacitor bank is identified online. S3: Based on the current current and the equivalent series internal resistance identified in S2, calculate the instantaneous heating power inside the supercapacitor bank, and derive the maximum allowable continuous charging and discharging power under the current operating conditions as the dynamic power limit value based on the thermal balance equation of the supercapacitor bank. S4: Calculate the rate of change of state of charge of the supercapacitor bank, and determine the power smoothing coefficient of the supercapacitor bank based on the rate of change of state of charge and according to the preset nonlinear mapping relationship. S5: Based on the power adjustment command, dynamic power limit value, and state range of the supercapacitor bank, perform initial power allocation to obtain the initial power target value of the supercapacitor bank and the initial power target value of the lithium battery bank. S6: Based on the initial power target value and the power smoothing coefficient, the initial power target values ​​of the supercapacitor bank and the lithium battery bank are smoothed by first-order low-pass filtering to obtain the smoothed target power. S7: The energy storage converter performs a charge-discharge operation based on the smoothed target power control, and corrects the smoothed target power based on the real-time state variables to obtain the corrected power target value. The energy storage converter then performs a second charge-discharge operation based on the corrected power target value. This power coordination control is completed, and the process returns to S1 to enter the next execution cycle.

2. The power coordination control method for a hybrid energy storage system according to claim 1, characterized in that, The specific implementation method of S1 includes the following steps: S11: Obtain the power regulation command issued by the power grid dispatching system, and determine the validity of the power regulation command, specifically: Determine whether the power adjustment command is within the rated adjustment power range; Determine whether the difference between the power regulation command and the actual power at the power plant's grid connection point is greater than the preset power dead zone threshold; If all the above judgment results are yes, then execute S12; otherwise, exit the power coordination control process. S12: Collect the status variables and communication status of the hybrid energy storage system, and perform the following judgment: Whether the health status of the lithium battery pack and the supercapacitor pack in the state variables meet the preset operating conditions; Does the communication status of the hybrid energy storage system meet the preset operating conditions? If all the above judgment results are yes, then execute S2; otherwise, exit the current power coordination control process.

3. The power coordination control method for a hybrid energy storage system according to claim 2, characterized in that, The specific implementation method of S2 includes the following steps: S2.1: Acquire the port voltage of the supercapacitor bank and current ; S2.2: Based on port voltage and current A first-order RC equivalent circuit model is established, and the differential equation of the first-order RC equivalent circuit model is: ； This is the equivalent series internal resistance of the supercapacitor bank. This is the equivalent capacitance of the supercapacitor bank. It is a continuous-time variable; Discretizing the differential equations and using a first-order backward difference approximation yields the difference equations for a first-order RC equivalent circuit model: ； The current sampling time is dimensionless. This refers to the previous sampling time. This is the port voltage collected at the current sampling moment; This represents the port voltage at the previous sampling time. This is the port current sampled at the current sampling moment. This represents the port current at the previous sampling time. , , The parameters to be identified; S2.3: Based on the difference equation in S2.2, the recursive least squares method is used to identify the parameters to be identified online. , , ; S2.4: Based on the relationship between the parameters to be identified and the circuit physical parameters in S2.2, the parameters obtained from online identification... Obtain the equivalent series internal resistance of the supercapacitor bank : 。 4. The power coordination control method for a hybrid energy storage system according to claim 3, characterized in that, The specific implementation method of S3 includes the following steps: S3.1: Calculate the instantaneous heat generation power inside the supercapacitor bank : S3.2: Set a safe temperature rise rate limit When the state of charge value of the supercapacitor bank When the temperature is within the preset warning range, the safe temperature rise rate limit will be reduced by a preset ratio. The reduced safe temperature rise rate limit is obtained. ; S3.3: Based on the thermal balance equation of the supercapacitor bank, its maximum allowable continuous charge and discharge current is derived in reverse. ; S3.4: Based on the maximum continuous charge / discharge current and the current port voltage of the supercapacitor bank Calculate the maximum permissible continuous charge and discharge power and compare it with the rated power of the supercapacitor bank, taking the smaller value as the dynamic power limit. .

5. The power coordination control method for a hybrid energy storage system according to claim 4, characterized in that, The heat balance equation in S3.3 is as follows: ； Maximum continuous charge and discharge current for: ; This refers to the average specific heat capacity of the supercapacitor bank. For the quality of the supercapacitor bank; The rate of temperature rise; This is for the heat dissipation power of the supercapacitor bank; The reverse derivation process is as follows: Under maximum continuous power conditions, the heat dissipation power and the heat generation power are balanced, i.e. Maximum continuous charge and discharge current : ； Solving the above equation yields the maximum continuous charge-discharge current. .

6. The power coordination control method for a hybrid energy storage system according to claim 5, characterized in that, The specific implementation method of S4 includes the following steps: S4.1: Calculate the first derivative of the state of charge value of the supercapacitor bank as the rate of change of state of charge; S4.2: Determine the power smoothing coefficient of the supercapacitor bank according to the absolute value of the rate of change of state of charge and a preset nonlinear mapping relationship. ; S4.3: Based on the health status of the supercapacitor bank Preset upper limit for power smoothing coefficient The correction is performed to obtain the corrected power smoothing coefficient. : ; S4.4: When the state of charge value of the supercapacitor bank enters the preset warning range, the preset lower limit of the power smoothing coefficient is adjusted to the preset boundary smoothing coefficient value. : .

7. The power coordination control method for a hybrid energy storage system according to claim 6, characterized in that, The specific implementation method of S4.2 includes the following steps: Based on the rate of change of state of charge, the current power surge intensity of the supercapacitor bank is divided into three stages: low-surge zone, high-surge zone, and transition zone. When the rate of change of state of charge is less than or equal to the first threshold, it is a low-impact zone; When the rate of change of state of charge is greater than or equal to the second threshold, it is a high-impact zone; When the rate of change of state of charge is less than or equal to the second threshold and greater than or equal to the first threshold, it is the transition zone; The first threshold represents the boundary between the low-impact zone and the transition zone; the second threshold represents the boundary between the high-impact zone and the transition zone. When the rate of change of state of charge is less than or equal to the first threshold, the power smoothing coefficient takes the preset upper limit value. When the rate of change of state of charge is greater than or equal to the second threshold, the power smoothing coefficient decreases to a preset lower limit as the rate of change of state of charge increases, that is: ； The second threshold, Set an upper limit for the power smoothing coefficient; A lower limit value is preset for the power smoothing coefficient; The attenuation coefficient; It is a natural exponential function; This is the final power smoothing coefficient; When the rate of change of state of charge is less than or equal to the second threshold and greater than or equal to the first threshold, the power smoothing coefficient is calculated by linear interpolation. The specific calculation method is as follows: ； This is the first threshold.

8. The power coordination control method for a hybrid energy storage system according to claim 7, characterized in that, The specific implementation method of S5 includes the following steps: S51: Determine the charging / discharging direction based on the sign of the power adjustment command; S52: Determine the state range of the supercapacitor bank based on its real-time state of charge value. S53: Calculate the initial power target value of the supercapacitor bank based on the charging / discharging direction and the state range of the supercapacitor bank. ; S54: According to the power adjustment command Calculate the initial power target value of the lithium battery pack based on the initial power target value of the supercapacitor pack. : 。 9. The power coordination control method for a hybrid energy storage system according to claim 8, characterized in that, The specific implementation method of S6 includes the following steps: S61: Initial power target value for the supercapacitor bank A first-order low-pass filter is performed to smooth the power of the supercapacitor bank, yielding the smoothed target power. ; S62: Initial power target value for the lithium battery pack A first-order low-pass filter is performed for smoothing to obtain the smoothed target power of the lithium battery pack. ; S63: Calculate the sum of the smoothed target power of the supercapacitor bank and the lithium battery bank, and verify its consistency with the power regulation command. Specifically: ； like Then power compensation will be performed: like hour, , ; like When the target power is still insufficient, prioritize increasing the supercapacitor bank to smooth it out; if that is still insufficient, increase the lithium battery bank to smooth it out. in To smooth out tolerances.

10. The power coordination control method for a hybrid energy storage system according to claim 9, characterized in that, The specific implementation method of S7 includes the following steps: S7.1: Energy storage converter receives smoothed target power from supercapacitor bank Smoothing target power of lithium battery pack And control the execution of charging and discharging operations; S7.2: Collect real-time state parameters of the hybrid energy storage system, including: real-time state of charge values ​​of the supercapacitor bank. Real-time state of charge of lithium battery packs Actual power at the power station's grid connection point ; S7.3: Calculate power regulation command Actual power at the power station's grid connection point Power regulation deviation : ； S7.4: Adjust according to power deviation Smoothing target power of supercapacitor bank Smoothing target power of lithium battery pack After making corrections, the corrected power target value of the supercapacitor bank is obtained. and the target power value of the lithium battery pack ; S7.5: When the real-time state of charge value of the supercapacitor bank When the system enters the preset warning range, perform the following operations: Reduce the power change rate of the supercapacitor bank, i.e., trigger the power smoothing coefficient adjustment in step S4.4; S7.6: The revised power target value of the supercapacitor bank and the target power value of the lithium battery pack The control is sent to the energy storage converter to perform the secondary charging and discharging operation. The power coordination control is completed and returns to S1 to enter the next execution cycle.

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