CN115395545A - A method for lithium iron phosphate batteries to participate in power grid frequency regulation considering the parameters of the environmental correction model - Google Patents

Abstract

The present invention provides a method for participating in power grid frequency regulation by taking into account environment correction model parameters. The method is applied to a power grid system using batteries as energy storage, and includes the following steps: S101. Establishing the rated capacity of the battery considering the energy storage, charging SOC model of the energy storage battery for discharge efficiency; S102. Establish the operating state model of the energy storage battery; S103. Correct the rated capacity and charge-discharge efficiency of the energy storage battery by considering the environmental factors of the tropical island; S104. Correct the SOC state of the battery; S105. Consider the SOC state correction of the energy storage battery to control the energy storage frequency of the grid. The present invention can improve the accuracy of the model parameters in the power system modeling process, and consider the energy storage battery on this basis SOC state correction controls the frequency of grid energy storage, thereby improving the accuracy and efficiency of frequency control, and has high practical engineering application value.

Description

A method for lithium iron phosphate batteries to participate in power grid frequency regulation considering the parameters of the environmental correction model

technical field

The invention relates to the technical field of power grid frequency control, in particular to a method for a lithium iron phosphate battery to participate in power grid frequency regulation in consideration of environment correction model parameters.

Background technique

Large-scale energy storage technology is the key technology to realize the popularization and application of renewable energy. Since the power generated by wind power, photovoltaic and other new energy sources has volatility and poor adjustability, the configuration of energy storage devices can effectively adjust the energy balance of the power supply and demand side. Overcoming the intermittency and instability of renewable energy, improving the operating efficiency of power equipment, and ensuring the safe and reliable operation of the system are key supporting technologies for smart grids and new energy systems. The physical model of lithium iron phosphate (LiFePO4, LFP) battery occupies an important place in energy storage fields such as micro-grid systems containing renewable energy, electric vehicles, and communication base stations because of its excellent charge-discharge performance, good safety, and cycle life. important position. When the LiFePO4 energy storage system participates in grid frequency control, the existing control methods mainly adopt constant droop coefficient control. Constant droop control does not consider the battery SOC state, which is prone to overcharge and overdischarge problems of the battery. In addition, my country has a very wide geographical range, and the climate in different regions varies greatly, which will have a significant impact on the electrical performance of the battery, especially the high temperature, high humidity and high salt environment of tropical islands. The energy storage model in power system operation control is always based on conventional model data, and the generation of control schemes is based on imprecise simulation data and models, which lead to differences between the control effect of the control strategy and the real state of the actual power grid. Traditional mechanism model analysis and optimal control methods are difficult to meet the requirements of new power system monitoring analysis, operation optimization and stability control.

Contents of the invention

In view of this, the object of the present invention is to provide a method for the lithium iron phosphate battery to participate in power grid frequency regulation considering the parameters of the environment correction model, so as to overcome or at least partially solve the above-mentioned problems in the prior art.

In order to achieve the above-mentioned purpose of the invention, the present invention provides a method for participating in power grid frequency regulation of a lithium iron phosphate battery considering environment correction model parameters. The method is applied to a power grid system using batteries as energy storage. The method includes the following steps:

S101. Establishing an energy storage battery SOC (state of charge) model considering the rated capacity and charge-discharge efficiency of the energy storage battery;

S102. Establishing an operating state model of the energy storage battery;

S103. Correcting the rated capacity and charging and discharging efficiency of the energy storage battery in consideration of tropical island environmental factors;

S104. Correcting the SOC state of the energy storage battery in consideration of tropical island environmental factors;

S105. Considering the SOC state correction of the energy storage battery, the frequency of the grid energy storage is controlled.

Further, the SOC model of the energy storage battery is as follows:

Where SOC is the state of charge of the energy storage battery, SOC ₀ is the initial charge level of the energy storage battery, C _N is the rated capacity of the battery, P _b is the charging and discharging power, and η is the charging and discharging efficiency of the battery. , η=η _c , where η _c is the charging efficiency of the energy storage battery; when the energy storage is discharging, η=1/η _d , and η _d is the discharge efficiency of the battery.

Further, establishing the operating state model of the energy storage battery specifically includes: dividing the operating state of the energy storage battery into a normal operating state and an alert state, and the alert state includes a high alert state and a low alert state. When the energy storage battery SOC is in a normal state When the power is charged and discharged; when the energy storage battery is in a high alert state, it can only be discharged; when the energy storage battery is in a low alert state, it can only be charged.

Further, the tropical island environmental factors include temperature, humidity, and salinity.

Further, when considering the correction of temperature to the rated capacity of the energy storage battery in the environmental factors of tropical islands, the rated capacity of the energy storage battery is corrected by the temperature correlation coefficient, and the correction expression is as follows:

C _t2 ＝C _t1 [1+α×(t ₂ -t ₁ )]

Among them, C _t1 is the capacity of the energy storage battery at a temperature of t1°C, C _t2 is the capacity of the energy storage battery at a temperature of t2°C, and α is the temperature correlation coefficient of the capacity of the energy storage battery with temperature.

Further, when considering the correction of temperature to the charge and discharge efficiency of the energy storage battery in the environmental factors of tropical islands, the charge and discharge efficiency of the energy storage battery is corrected by the Coulomb coefficient, and the correction expression is as follows:

η _E ＝K _E η _e

Among them, η _E is the equivalent charge-discharge efficiency after considering the temperature, K _E is the Coulomb correlation coefficient considering the temperature, and η _e is the equivalent charge-discharge coefficient without considering the temperature.

Further, when considering the temperature in the tropical island environment to correct the SOC of the energy storage battery, the correction expression is as follows:

Wherein, SOC(T) is the state of charge of the energy storage battery at temperature T, SOC ₀ (T) is the initial charge level of the energy storage battery at temperature T, and η(T) is the charge and discharge efficiency of the battery at temperature T, C _N (T) is the rated capacity of the energy storage battery at temperature T.

Furthermore, consider the SOC state correction of the energy storage battery to control the energy storage frequency of the grid, specifically including: when the energy storage system participates in the grid regulation stage, collect the temperature of the energy storage system in real time, and continuously correct the SOC state. When the system generates power When the power increases, the energy storage system charges. If the SOC<0.1, the energy storage system charges at the maximum charging power to reduce the unbalanced power of the system; when the SOC>0.9, stop charging, and the energy storage system real-time according to the corrected SOC state Correct the droop coefficient of energy storage charging and discharging to realize real-time mapping with the actual scene working conditions. The droop coefficient is as follows:

Among them, m represents the exponential change rate, Kmax is the maximum droop coefficient, K _{b_d} is the droop coefficient when the energy storage battery is discharged, and K _{b_c} is the droop coefficient when the energy storage battery is charged.

Compared with prior art, the beneficial effect of the present invention is:

The method provided by the present invention considers tropical island environmental factors when energy storage batteries participate in power grid frequency control, and proposes a real-time correction method for model parameters based on tropical island environmental factors, which is more suitable for actual battery operating conditions and improves power system modeling. The accuracy of the model parameters in the process, and on this basis, the SOC state correction of the energy storage battery is considered to control the energy storage frequency of the grid, thereby improving the accuracy and efficiency of frequency control, which has high practical engineering application value.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings that need to be used in the description of the embodiments. Obviously, the drawings in the following description are only preferred embodiments of the present invention. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

Fig. 1 is a schematic diagram of the overall flow of a method for a lithium iron phosphate battery to participate in power grid frequency regulation considering environment correction model parameters provided by an embodiment of the present invention.

Fig. 2 is a schematic diagram of an SOC model of an energy storage battery provided by an embodiment of the present invention.

Fig. 3 is a schematic diagram of an SOC-based energy storage droop control strategy provided by an embodiment of the present invention.

Detailed ways

The principles and features of the present invention will be described below in conjunction with the accompanying drawings, and the enumerated embodiments are only used to explain the present invention, and are not intended to limit the scope of the present invention.

Referring to FIG. 1 , this embodiment provides a method for participating in power grid frequency regulation by a lithium iron phosphate battery considering environment correction model parameters. The method is applied to a power grid system using batteries as energy storage. The method includes the following steps:

S101. Establish an SOC (state of charge) model of the energy storage battery considering the rated capacity and charging and discharging efficiency of the energy storage battery.

S102. Establish an operating state model of the energy storage battery.

S103. Correcting the rated capacity and charge-discharge efficiency of the energy storage battery in consideration of tropical island environment factors.

S104. Correcting the SOC state of the energy storage battery in consideration of tropical island environment factors.

S105. Considering the SOC state correction of the energy storage battery, the frequency of the grid energy storage is controlled.

Referring to Figure 2, the SOC of the energy storage battery refers to the ratio of the remaining power of the battery to the rated power at a certain discharge rate. In step S101, the SOC model of the energy storage battery is as follows:

Where SOC is the state of charge of the energy storage battery, SOC ₀ is the initial charge level of the energy storage battery, C _N is the rated capacity of the battery, P _b is the charging and discharging power, and η is the charging and discharging efficiency of the battery. , η=η _c , where η _c is the charging efficiency of the energy storage battery; when the energy storage is discharging, η=1/η _d , and η _d is the discharge efficiency of the battery.

In this embodiment, the operating state of the energy storage battery is divided into a normal operating state and an alert state. The alert state includes a high alert state and a low alert state. lifespan. Therefore, this embodiment assumes that when the SOC of the energy storage battery is in a normal state, power charging and discharging can be performed; when the energy storage battery is in a high alert state, it can only be discharged; when the energy storage battery is in a low alert state, it can only be charged to avoid Energy storage batteries affect battery life due to overcharging and discharging.

In steps S103 and S104, the tropical island environmental factors include at least temperature, humidity, and salinity. In this embodiment, by comprehensively considering the images of various special environmental factors of tropical islands on the rated capacity and charge-discharge efficiency of the energy storage battery, the SOC The model is corrected so that the SOC value calculated by the method is more in line with the actual operating conditions of the energy storage battery in the tropical island environment, thereby improving the accuracy of the model parameters in the power system modeling process.

As a preferred example, this embodiment takes the lithium iron phosphate battery as the research object, based on the test result data of the actual manufacturer, when considering the correction of the temperature to the rated capacity of the energy storage battery in the tropical island environment factors, the temperature correlation coefficient Correct the rated capacity of the energy storage battery, and the modified expression is as follows:

C _t2 ＝C _t1 [1+α×(t ₂ -t ₁ )]

Among them, C _t1 is the energy storage battery capacity at temperature t1°C, C _t2 is the energy storage battery capacity at temperature t2°C, α is the temperature correlation coefficient of energy storage battery capacity with temperature, and α is different at different temperatures.

When considering the temperature correction of the charge and discharge efficiency of the energy storage battery in the environmental factors of tropical islands, the charge and discharge efficiency of the energy storage battery is corrected by the Coulomb coefficient, and the correction expression is as follows:

η _E ＝K _E η _e

Among them, η _E is the equivalent charge-discharge efficiency after considering the temperature, K _E is the Coulomb correlation coefficient considering the temperature, and η _e is the equivalent charge-discharge coefficient without considering the temperature.

When considering the temperature in the tropical island environment to correct the SOC of the energy storage battery, the correction expression is as follows:

Wherein, SOC(T) is the state of charge of the energy storage battery at temperature T, SOC ₀ (T) is the initial charge level of the energy storage battery at temperature T, and η(T) is the charge and discharge efficiency of the battery at temperature T, C _N (T) is the rated capacity of the energy storage battery at temperature T. In the actual operation process, the SOC that considers the environmental factors of tropical islands and the SOC that does not consider the environmental factors of tropical islands will be significantly different in extreme environments, which will also affect the difference in the time when the battery reaches the high alert position and the low alert position when participating in grid regulation. As a result, it is difficult for the energy storage system to accurately execute the control instructions. The method provided in this embodiment can effectively estimate the SOC of the energy storage battery in extreme weather conditions, so as to ensure that the battery can better participate in power grid regulation in practical applications.

When the energy storage system is applied to the frequency regulation of the power grid, the constant droop coefficient control is usually used, but this may cause overcharging and overdischarging, so the SOC state needs to be taken into account in the energy storage frequency regulation strategy. Referring to Fig. 3, in this embodiment, the SOC state correction of the energy storage battery is considered to control the energy storage frequency of the grid, which specifically includes: when the energy storage system participates in the grid regulation stage, the temperature of the energy storage system is collected in real time, and the SOC state is continuously monitored. Correction, when the power generated by the system increases, the energy storage system charges, as shown in the charging curve in Figure 3. If SOC<0.1, the energy storage system will charge with the maximum charging power to reduce the unbalanced power of the system; when SOC>0.9, stop charging, and the energy storage system will correct the droop coefficient of energy storage charge and discharge in real time according to the corrected SOC state to realize For real-time mapping with actual scene conditions, the droop coefficient is as follows:

Among them, m represents the exponential change rate, Kmax is the maximum droop coefficient, K _{b_d} is the droop coefficient when the energy storage battery is discharged, and K _{b_c} is the droop coefficient when the energy storage battery is charged.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (8)

1. A method for participating in power grid frequency modulation by a lithium iron phosphate battery considering environment correction model parameters is applied to a power grid system with the battery as an energy storage, and comprises the following steps:

s101, establishing an energy storage battery SOC (state of charge) model considering the rated capacity and the charge-discharge efficiency of the energy storage battery;

s102, establishing an energy storage battery running state model;

s103, correcting the rated capacity and the charge-discharge efficiency of the energy storage battery by considering tropical island environmental factors;

s104, correcting the SOC state of the energy storage battery by considering tropical island environment factors;

and S105, controlling the energy storage frequency of the power grid by considering the SOC state correction of the energy storage battery.

2. The method for participating in grid frequency modulation by taking into account environment correction model parameters according to claim 1, wherein the energy storage battery SOC model is as follows:

wherein SOC is the state of charge, SOC, of the energy storage battery ₀ Is the initial charge level of the energy storage cell, C _N Is the rated capacity, P, of the battery _b Eta is the charge-discharge efficiency of the battery, and eta = eta is the energy storage charge _c Wherein eta _c Charging efficiency for the energy storage battery; when the stored energy is discharged, eta = 1/eta _d ，η _d The cell discharge efficiency.

3. The method for participating in power grid frequency modulation by taking into account environmental correction model parameters according to claim 1, wherein the establishing of the energy storage battery operating state model specifically comprises: dividing the running state of the energy storage battery into a normal running state and an alert state, wherein the alert state comprises a high alert state and a low alert state, and when the SOC of the energy storage battery is in the normal state, power charging and discharging can be carried out; when the energy storage battery is in a high-alert state, only discharge can be carried out; the energy storage battery can only be charged when in a low alert state.

4. The method for participating in frequency modulation of a power grid by lithium iron phosphate batteries considering environment correction model parameters as claimed in claim 1, wherein the tropical island environmental factors comprise temperature, humidity and salinity.

5. The method for participating in grid frequency modulation by lithium iron phosphate battery considering environmental correction model parameters as claimed in claim 4, wherein when the rated capacity of the energy storage battery is corrected by temperature in consideration of tropical sea island environmental factors, the rated capacity of the energy storage battery is corrected by temperature correlation coefficient, and the correction expression is as follows:

C _t2 ＝C _t1 [1+α×(t ₂ -t ₁ )]

wherein, C _t1 Is the capacity, C, of the energy storage battery at the temperature t1 DEG C _t2 The capacity of the energy storage battery at the temperature of t2 ℃, and alpha is the capacity of the energy storage batteryTemperature dependence coefficient as a function of temperature.

6. The method for participating in frequency modulation of a power grid by lithium iron phosphate batteries in consideration of environmental correction model parameters, according to claim 4, is characterized in that when the correction of the charging and discharging efficiency of the energy storage batteries by temperature in tropical sea island environmental factors is considered, the charging and discharging efficiency of the energy storage batteries is corrected by coulomb coefficients, and the correction expression is as follows:

η _E ＝K _E η _e

wherein eta is _E To take into account the equivalent charge-discharge efficiency after temperature, K _E To take account of the coulomb correlation coefficient of temperature, η _e The equivalent charge-discharge coefficient of temperature is not considered.

7. The method for participating in frequency modulation of a power grid by lithium iron phosphate battery considering environment correction model parameters as claimed in claim 1, wherein when the SOC of the energy storage battery is corrected by considering the temperature in tropical sea island environment factors, the correction expression is as follows:

wherein SOC (T) is the state of charge (SOC) of the energy storage battery at the temperature T ₀ (T) is the initial charge level of the energy storage battery at the temperature T, eta (T) is the charge-discharge efficiency of the battery at the temperature T, C _N And (T) is the rated capacity of the energy storage battery at the temperature T.

8. The method for participating in grid frequency modulation by considering the environmental correction model parameters according to claim 7, wherein the step of controlling the grid energy storage frequency by considering the SOC state correction of the energy storage battery specifically comprises: in the stage that the energy storage system participates in power grid regulation, the temperature of the energy storage system is collected in real time, the SOC state is continuously corrected, when the power generation power of the system is increased, the energy storage system is charged, and if the SOC is smaller than 0.1, the energy storage system is charged with the maximum charging power, so that the unbalanced power of the system is reduced; when the SOC is more than 0.9, stopping charging, and correcting the energy storage charging and discharging droop coefficient in real time by the energy storage system according to the corrected SOC state to realize real-time mapping with the actual scene working condition, wherein the droop coefficient is as follows:

where m represents the exponential rate of change, kmax is the maximum sag factor, K _{b_d} Is the sag coefficient, K, of the energy storage cell during discharge _{b_c} The sag factor when charging the energy storage battery.

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