CN109524974B - Power grid primary frequency modulation control method and system based on battery energy storage power supply - Google Patents
Power grid primary frequency modulation control method and system based on battery energy storage power supply Download PDFInfo
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- H—ELECTRICITY
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- H—ELECTRICITY
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract
The invention discloses a power grid primary frequency modulation control method and a system thereof based on a battery energy storage power supply, wherein the method comprises the steps of monitoring the power grid frequency in real time, calculating the absolute value of the power grid frequency deviation in real time based on the rated value of the power grid frequency, and determining the output model of the energy storage power supply based on the power grid frequency deviation change rate if the absolute value of the power grid frequency deviation is greater than or equal to the preset power grid frequency stability threshold value; and finally, finishing frequency modulation when the absolute value of the power grid frequency deviation is stabilized at the steady-state frequency deviation value. According to the invention, the corresponding output model of the energy storage power supply is designed according to the disturbance type, the primary frequency modulation effect is improved, the capacity configuration of the energy storage power supply is reduced, and the service life of the energy storage power supply is prolonged.
Description
Technical Field
The invention belongs to the field of power grid control, and particularly relates to a power grid primary frequency modulation control method and a power grid primary frequency modulation control system based on a battery energy storage power supply.
Background
In the primary frequency modulation of the power grid, the output of each unit is changed according to the static characteristic of the frequency of each unit, so that the frequency difference adjustment is realized, and the method is generally used for adjusting the second-level load fluctuation. When the frequency of the power grid changes, the rotation energy stored in the system load changes to prevent the change of the system frequency, in addition, the rotation speed of all generator sets in the system also changes, the speed regulators of the generator sets act to adjust the power of the prime motor, and the condition that the power of the prime motor and the load power are unbalanced is improved. However, the generator has the capability of participating in primary frequency modulation only when the generator has enough rotating reserve capacity, and when the frequency deviation exceeds the preset dead zone of the unit, the unit with the primary frequency modulation capability can participate in primary frequency modulation of the power grid and is put into a primary frequency modulation state, so that the power grid frequency is adjusted in a difference mode.
The battery energy storage power supply can realize alternation of up regulation and down regulation without limitation, has high efficiency, can quickly and accurately track load change due to output change of the battery energy storage power supply, and has small margin of response power reserve, so that the battery energy storage power supply is taken as novel and high-quality movable energy storage equipment and is widely concerned with second-level charge and discharge capacity, thousands of cycle life, wide temperature adaptability and environment-friendly characteristic. However, the energy storage power supply participates in frequency modulation, and the control strategy is difficult. When the energy storage power supply participates in primary frequency modulation of a power grid, the existing control modes comprise virtual inertia and virtual droop, the control strategy in the existing primary frequency modulation process is generally a single frequency modulation mode, the characteristics of the two frequency modulation models and the advantages of the two frequency modulation models in different frequency modulation stages are rarely considered, so that the single frequency modulation mode is difficult to meet the actual requirement, and the frequency modulation effect needs to be further improved; CN201711074813.5 discloses a "control method for a battery energy storage power source to participate in primary frequency modulation of a power grid", which is a method for integrating two frequency modulation modes at the same time, but this method mainly has two problems, because the frequency deviation in the inertial response stage is continuously increased, the maximum frequency deviation value cannot be actually obtained in the inertial response stage, and the designed power grid in this scheme can bear the empirical value of the maximum frequency deviation, but there is an error with the actual maximum frequency deviation value, and this error will cause that the optimal frequency modulation effect cannot be achieved; secondly, the characteristics of the frequency deviation caused by different disturbance types of the power grid are different, for example, if the disturbances are continuous disturbances with small fluctuation, the duration of the inertia response phase and the droop response phase in the frequency modulation process of the disturbances is very short, the two phases of the disturbances do not have an obvious limit or change rapidly, the two phases are difficult to be accurately controlled according to the frequency modulation mode of the method in practice, and meanwhile, the service life problem of the energy storage power supply is not considered.
Disclosure of Invention
The invention aims to provide a power grid primary frequency modulation control method and a power grid primary frequency modulation control system based on a battery energy storage power supply. Herein, the battery energy storage power supply is simply referred to as an energy storage power supply.
A power grid primary frequency modulation control method based on a battery energy storage power supply comprises the following steps:
s1: monitoring the power grid frequency in real time, calculating the absolute value of the power grid frequency deviation in real time compared with the rated value of the power grid frequency, and judging whether the absolute value of the power grid frequency deviation is greater than or equal to a preset power grid frequency stability threshold value or not;
if the frequency is greater than or equal to the preset power grid frequency stability threshold, performing frequency modulation processing, and executing step S2; otherwise, repeating step S1;
the time from the first monitoring that the absolute value of the power grid frequency deviation is greater than or equal to the power grid frequency stability threshold value to the monitoring that the power grid frequency deviation is equal to the steady-state frequency deviation value is a primary frequency modulation period;
s2: calculating the change rate of the power grid frequency deviation at the current moment, and calculating the output of the energy storage power supply based on the power grid frequency deviation, the change rate of the power grid frequency deviation and a preset disturbance threshold;
adjusting the output of an energy storage power supply in real time in the primary frequency modulation period based on the real-time calculated power grid frequency deviation and the frequency deviation change rate, wherein when the power grid frequency deviation value at the current moment is greater than 0, the energy storage power supply is charged, and when the power grid frequency deviation value is less than 0, the energy storage power supply is discharged;
when the absolute value of the change rate of the power grid frequency deviation is greater than or equal to a preset disturbance threshold value, the output force of the energy storage power supply is defined as △ PstepThe calculation formula is as follows:
in the formula, ME、KERespectively representing a virtual inertia coefficient and a virtual unit adjustment coefficient of the energy storage battery; a is1、a2Distribution ratio coefficients, f, representing the virtual inertia mode and the virtual droop mode, respectivelyi、fi-1、f0Respectively representing the power grid frequency at the current moment, the power grid frequency at the previous sampling moment and the rated value of the power grid frequency, wherein delta t represents the time difference of the adjacent power grid frequency sampling moments;
when the absolute value of the change rate of the power grid frequency deviation is smaller than a preset disturbance threshold value, the output force of the energy storage power supply is defined as △ PcontinueCalculatingThe formula is as follows:
ΔPcontinue＝KE·(fi-f0)。
the invention classifies the types of the disturbances, sets different output models for the disturbances of different types, and better adapts to the requirements of various disturbances, such as step load disturbance mainly based on frequency modulation, and continuous disturbance also considers the continuity of the energy storage power supply on the basis of frequency modulation, thereby prolonging the service life of the energy storage power supply, reducing the capacity configuration of the energy storage power supply, reducing the cost of the energy storage power supply and smoothing the output of the energy storage power supply.
Further preferably, the distribution ratio a of the virtual inertia mode and the virtual droop mode in step S21、a2The acquisition modes of (1) are as follows:
the current time power grid frequency is lower than the power grid frequency rated value, the current time power grid frequency deviation change rate is less than 0, and the distribution proportion system a1、a2The calculation formula of (a) is as follows:
the grid frequency at the current moment is higher than the grid frequency rated value, the grid frequency deviation change rate at the current moment is greater than 0, and the distribution proportion system a1、a2Comprises the following steps:
the current time power grid frequency is lower than the power grid frequency rated value and the current time power grid frequency deviation change rate is larger than 0 or the current time power grid frequency is higher than the power grid frequency rated value and the current time power grid frequency deviation change rate is smaller than 0, and the distribution proportion system a1、 a2The calculation formula of (a) is as follows:
in the formula, △ fmaxIndicating the maximum frequency deviation value in the current primary chirp period, △ flowIs a preset grid frequency stability threshold.
Further preferably, the coefficient K in step S2EThe calculation formula of (a) is as follows:
in the formula (I), the compound is shown in the specification,
expressing virtual unit regulating coefficient K when energy storage power supply dischargesE，
Virtual unit adjustment coefficient K for representing charging of energy storage power supplyE，KmaxRepresenting the maximum value of the virtual unit regulating coefficient of the energy storage power supply; SOC (i) represents the state of charge of the energy storage power supply at time i; SOCinitialRepresenting an initial state of charge of the energy storage power source; SOCmaxAnd SOCminRespectively representing the maximum charge state and the minimum charge state of the energy storage power supply, wherein n is a sensitivity coefficient.
Further preferably, the sensitivity coefficient is calculated when the energy storage power supply reaches the maximum state of charge and the minimum state of charge, and the sensitivity of the virtual unit adjustment coefficient to the SOC is zero, and the calculation formula is as follows:
SOCmaxAnd SOCminThe value of (c) is determined by the self-characteristics of the energy storage cell and is substantially constant. At SOCmaxAnd SOCminUnder the condition that the value of (A) is known, let KndisAnd KnchIs 0, the value of n is solved and is not zero, thus determining the value of n.
Further, the method can be used for preparing a novel materialPreferably, the initial state of charge SOC of the energy storage power sourceinitialIs 0.5. Maximum state of charge SOCmaxAnd minimum state of charge SOCminThe value of (b) is determined by the characteristics of the energy storage battery itself and is a constant value.
Further preferably, the grid frequency deviation change rate in step S2 is calculated as follows:
wherein △ O (i) represents the change speed of the grid frequency deviation, i.e., the frequency deviation change rate, fi-1Representing the grid frequency collected at the previous sampling instant.
Further preferably, when the absolute value of the change rate of the power grid frequency deviation is greater than or equal to a preset disturbance threshold, the load disturbance at the current moment is step disturbance; and when the absolute value of the change rate of the power grid frequency deviation is smaller than a preset disturbance threshold value, the load disturbance at the current moment is continuous disturbance.
On the other hand, the invention also provides a primary frequency modulation system of the energy storage power supply based on the method, which comprises a monitoring module, a data processing module and a power output module which are sequentially in communication connection;
the monitoring module is used for monitoring the frequency of the power grid in real time;
the data processing module is used for calculating an absolute value of the power grid frequency deviation in real time based on the monitored power grid frequency and judging whether the absolute value of the power grid frequency deviation is greater than or equal to a preset power grid frequency stability threshold value or not;
the data processing module is used for calculating the change rate of the power grid frequency deviation at the current moment and judging the absolute value of the change rate of the power grid frequency deviation and a preset disturbance threshold value;
the power output module is used for calculating the output of the energy storage power supply.
Advantageous effects
1. The invention classifies the types of the disturbances, sets different output models for the disturbances of different types, and better adapts to the requirements of various disturbances, such as step type load disturbance mainly based on frequency modulation, and continuous disturbance also considers the continuity of the energy storage power supply on the basis of the frequency modulation.
2. The step type load disturbance of the invention is that the absolute value of the change rate of the frequency deviation of the power grid is greater than or equal to the preset disturbance threshold, so that the step type load disturbance can cause larger frequency deviation, and at the moment, because the larger frequency deviation exists, the step type load disturbance needs to be subjected to rapid frequency modulation for the main purpose. The primary frequency modulation process is mainly divided into an inertia response stage and a primary frequency modulation stage, the frequency characteristic shown in the inertia response stage is an inertia response characteristic, and the frequency characteristic shown in the primary frequency modulation stage is a droop response characteristic, so that the virtual inertia and virtual droop modes are synthesized to simultaneously perform frequency modulation aiming at step-type load disturbance. In the inertial response stage, mainly using inertial response to carry out frequency modulation, and using droop response as an auxiliary; in the droop response stage, frequency modulation is mainly carried out by utilizing droop response, the inertia response is assisted, and the virtual inertia mode and the virtual droop mode are actually distributed according to a proportion system a1、a2Is controlled by the value of a1And a2The rate of change of the value of (c) is adapted to the rate of change of the frequency deviation ratio and the rate of change of the frequency deviation value. In the inertial response phase, when the absolute value of the frequency deviation change rate is reduced, a1Will be reduced accordingly, a2The value of (c) will increase accordingly; in the sag phase, a becomes smaller as the absolute value of the frequency deviation becomes smaller2Will increase accordingly, a1The value of (c) will decrease accordingly. Compared with patent CN201711074813.5, the model proposed by the patent has computability and operability, and a1And a2The method and the device have better value adaptability, and can solve the problem of error caused by the fact that the maximum frequency deviation cannot be accurately obtained in the existing scheme, thereby bringing better frequency modulation effect, reducing the capacity configuration of the energy storage power supply and bringing better economic benefit.
3. The continuous load disturbance of the invention is small continuous disturbance of the power grid frequency, and the frequency deviation is small. In view of the situation, the invention takes the economic output of the energy storage power supply as a primary target and the frequency modulation effect as a secondary target, so that the aim is that of the energy storage power supplyThe SOC is kept in a proper range, when the SOC value of the energy storage power supply is larger, the energy storage power supply mainly discharges, and if the SOC value is smaller than or equal to the SOC valueminThe energy storage power supply forbids discharging; when the SOC value of the energy storage power supply is smaller, the energy storage power supply is mainly charged, and if the SOC value is more than or equal to the SOC valuemaxAnd the energy storage power supply prohibits charging. The present invention determines K based on the above principlesEThe output model of the energy storage power supply aiming at continuous disturbance is further determined, the energy storage power supply meets the requirement of frequency modulation, meanwhile, the economy of the energy storage power supply is also considered, the charge state of the energy storage power supply is maintained near the reference value, and therefore the service life of the energy storage power supply is prolonged. The simulation result of the invention also shows that the SOC of the energy storage power supply is basically maintained between 0.4 and 0.6.
4. According to the method, the maximum frequency deviation value can be obviously reduced aiming at the type of the step disturbance through simulation verification, so that the capacity configuration of the energy storage power supply is reduced, the cost of the energy storage power supply is reduced, and meanwhile, the output of the energy storage power supply can be gentle through simulation verification.
Drawings
FIG. 1 is a flow chart of a power grid primary frequency modulation control method based on a battery energy storage power supply provided by the invention;
FIG. 2 shows the distribution ratio coefficient a of the virtual inertia mode and the virtual droop mode when the grid frequency deviation change rate provided by the invention is less than 01、a2A schematic diagram of variation with frequency deviation;
FIG. 3 shows the distribution ratio coefficient a of the virtual inertia mode and the virtual droop mode when the grid frequency deviation change rate is greater than 01、a2A schematic diagram of variation with frequency deviation;
FIG. 4 shows the virtual unit adjustment coefficient K in the frequency modulation processEWherein (a) is a virtual regulation unit coefficient in discharge
The variation curve along with the SOC (b) is a graph of a virtual regulation unit coefficient in charging
A variation curve with SOC;
FIG. 5 is a SOC curve for the energy storage power supply provided by the present invention;
FIG. 6 is a graph comparing the variation trend of the frequency deviation under the step disturbance with other prior methods or under the condition of no energy storage;
fig. 7 is a schematic diagram of the energy storage power supply of the present invention.
Detailed Description
The present invention will be further described with reference to the following examples.
The invention aims to provide a power grid primary frequency modulation control method based on a battery energy storage power supply, which mainly comprises two parts, namely a load disturbance type identification model and an energy storage power supply output model, namely, the load disturbance type is determined by using the load disturbance type identification model; secondly, determining an output model of the energy storage power supply according to the load disturbance type identification result; and finally, finishing frequency modulation when the power grid frequency deviation value is stabilized to be close to the steady-state frequency deviation value. The specific process is as follows:
s1: monitoring the grid frequency f in real timeiAnd based on the nominal value f of the grid frequency0Calculating absolute value | △ f of grid frequency deviation in real timeiAnd judging the absolute value of the grid frequency deviation | △ fiWhether | is greater than or equal to preset grid frequency stability threshold △ flow；
If the grid frequency is greater than or equal to the preset grid frequency stability threshold value △ flowIf yes, performing frequency modulation processing, and executing step S2; otherwise, step S1 is repeated.
From the first monitoring of the absolute value of the grid frequency deviation | △ fi| is greater than or equal to grid frequency stability threshold △ flowThe time until the grid frequency deviation is detected to be equal to the steady-state frequency deviation value at another moment is a primary frequency modulation period, wherein the steady-state frequency deviation value is less than or equal to the grid frequency stability threshold △ flowThe absolute value of the grid frequency deviation | △ f is monitored for the first timei| is greater than or equal to grid frequency stability threshold △flowIt means that a primary frequency modulation process phase is entered, in which the network frequency f is still monitored in real timeiAnd identifying the absolute value of the grid frequency deviation | △ fiI is less than grid frequency stability threshold △ flowIf not, executing S2 to regulate and control the output of the energy storage power source. The monitoring process of the invention realizes real-time monitoring and adjustment according to the sampling of the preset frequency. It should be understood that the present invention does not consider the situation that after the step disturbance occurs, the frequency is reversely changed by the disturbance of a new phase when the regulation is in the droop phase.
S2: calculating the frequency deviation and the frequency deviation change rate of the power grid at the current moment, and calculating the output of the energy storage power supply based on the frequency deviation and the frequency deviation change rate of the power grid and a preset disturbance threshold;
the grid frequency deviation change rate is calculated as follows:
wherein △ O (i) represents the change speed of the grid frequency deviation, i.e., the frequency deviation change rate, fi-1Representing the grid frequency collected at the previous moment.
The absolute value | △ O (i) | of the grid frequency deviation change rate is greater than or equal to a preset disturbance threshold value △ OthThe output of the energy storage power supply is defined as △ PstepThe calculation formula is as follows:
in the formula, ME、KERespectively representing a virtual inertia coefficient and a virtual unit adjustment coefficient of the energy storage battery, wherein the values of the virtual inertia coefficient and the virtual unit adjustment coefficient are values obtained according to simulation conditions, and are empirical values, such as the virtual unit adjustment coefficient is 3.45 or 3.8 in the embodiment; a is1、a2Distribution ratio coefficients, f, representing the virtual inertia mode and the virtual droop mode, respectivelyi、fi-1、f0Respectively representing the grid frequency at the present moment, the grid frequency at the previous sampling moment and the rated value of the grid frequency, and delta t representsAnd time difference of adjacent grid frequency sampling moments.
It should be understood that the current grid frequency is lower than the grid frequency rated value, rarely, the current grid frequency is higher than the grid frequency rated value, which are considered in the present invention, but the primary frequency modulation process mainly comprises a virtual inertia phase and a virtual droop phase no matter whether the current grid frequency is higher or lower than the grid frequency rated value. For example, when the current grid frequency is lower than the grid frequency rated value, the frequency characteristic exhibited by the inertia response stage is the inertia response characteristic, and the frequency characteristic is characterized in that the absolute value of the frequency deviation rate is gradually reduced from the maximum value to 0, and the absolute value of the frequency deviation is gradually increased to the maximum frequency deviation value (the maximum frequency deviation value indicates that the maximum frequency deviation absolute value is maximum). The frequency characteristic presented in the primary frequency modulation stage is a droop response characteristic, and the frequency characteristic is characterized in that the frequency deviation change rate is greater than 0 and the absolute value is smaller, and the frequency deviation absolute value is gradually reduced from the maximum frequency deviation to the steady-state frequency deviation value. Therefore, the distribution ratio coefficient a with respect to the virtual inertia mode and the virtual droop mode1、a2The calculation formula of (a) is as follows:
distribution proportion system a when the current time power grid frequency is lower than the power grid frequency rated value and the current time power grid frequency deviation change rate is less than 01、a2Comprises the following steps:
the grid frequency at the current moment is higher than the grid frequency rated value, the grid frequency deviation change rate at the current moment is greater than 0, and the distribution proportion system a1、a2Comprises the following steps:
the above all indicate that the virtual inertia phase is in the moment, and the distribution ratio coefficient a of the virtual inertia mode is in the moment1Distribution ratio coefficient a larger than virtual droop mode2And the absolute value of the rate of change with frequency deviationDistribution ratio coefficient a of virtual inertia mode when it becomes smaller1With a consequent reduction in the distribution ratio coefficient a of the virtual droop mode2And then decreases greatly. As shown in fig. 2, the grid frequency at the present time is lower than the grid frequency rating and the grid frequency deviation change rate at the present time is less than 0.
Similarly, the power grid frequency at the current moment is lower than the power grid frequency rated value and the power grid frequency deviation change rate at the current moment is greater than 0, or the power grid frequency at the current moment is higher than the power grid frequency rated value and the power grid frequency deviation change rate at the current moment is less than 0, and the distribution proportion system a1、a2Comprises the following steps:
in the formula, △ fmaxAnd representing the maximum frequency deviation value in the current primary frequency modulation period. At this time, the distribution ratio coefficient a of the virtual inertia mode is shown in the virtual droop stage1Distribution ratio coefficient a smaller than that of the virtual droop mode2. As shown in fig. 3, the grid frequency at the present time is lower than the grid frequency rating and the grid frequency deviation change rate at the present time is greater than 0.
The absolute value | △ O (i) of the grid frequency deviation change rate is less than a preset disturbance threshold value △ OthThe output of the energy storage power supply is defined as △ PcontinueThe calculation formula is as follows:
ΔPcontinue＝KE·(fi-f0)
in the formula, KEAnd expressing the virtual unit adjusting coefficient, wherein the calculation formula is as follows:
in the formula (I), the compound is shown in the specification,
expressing virtual unit regulating coefficient K when energy storage power supply dischargesE，
Virtual unit adjustment coefficient K for representing charging of energy storage power supplyE. Wherein, the sensitivity coefficient n is calculated according to the condition that the sensitivity of the virtual unit adjusting coefficient to the SOC is zero. It should be noted that the virtual unit adjustment coefficient K in the continuous disturbanceEAnd virtual unit regulating coefficient K in step disturbanceEValues are different, and the values are taken as empirical values during step disturbance; during continuous disturbance, the SOC of the energy storage power supply is kept in a proper range, when the SOC value of the energy storage power supply is larger, the energy storage power supply mainly discharges, and if the SOC value is smaller than or equal to the SOC valueminThe energy storage power supply forbids discharging; when the SOC value of the energy storage power supply is smaller, the energy storage power supply is mainly charged, and if the SOC value is more than or equal to the SOC valuemaxAnd the energy storage power supply prohibits charging. This criterion designs the above-mentioned virtual unit adjustment coefficient KEAs shown in (a) and (b) of fig. 4, it was also verified through simulation that the virtual adjustment unit coefficient K is thus setEThe above object is achieved, and it can be seen from the figure that when n takes different values, the curve changes slightly differently so that the SOC value is greater than or equal to the SOC valuemaxThe energy storage power supply is forbidden to charge, and the SOC value is less than or equal to the SOC valueminThe energy storage power supply is forbidden to discharge, so the sensitivity coefficient n of the invention is the current SOCmaxAnd SOCminThe sensitivity corresponding to charging and discharging is calculated as zero. The purpose is to keep the SOC of the energy storage power supply in a suitable range. In this embodiment, the SOC is setmaxAnd SOCminThe values are respectively 0.8 and 0.2, an SOC curve graph shown in fig. 5 is obtained through simulation, and it can be known from the graph that the SOC of the energy storage power supply is basically maintained between 0.4 and 0.6. In addition, as shown in fig. 6 and 7, the present invention verifies through simulation that the maximum frequency deviation value can be significantly reduced for the type of step disturbance by using the method, thereby reducing the capacity configuration of the energy storage power supply and reducing the cost of the energy storage power supply, and simultaneously verifies through simulation that the output of the energy storage power supply can be smoothed by using the method.
KmaxRepresenting the maximum value of the virtual unit regulating coefficient of the energy storage power supply; SOC (i) represents the state of charge of the energy storage power supply at time i; SOCinitialIndicates the initial state of charge, SOC in this embodiment, of the energy storage power sourceinitialThe value is 0.5; SOCmaxAnd SOCminThe maximum state of charge and the minimum state of charge of the energy storage power supply are respectively represented, and in this embodiment, the values are 0.8 and 0.2, respectively.
Based on the method, the primary frequency modulation system of the energy storage power supply comprises a monitoring module, a data processing module and a power output module which are sequentially in communication connection;
the monitoring module is used for monitoring the frequency of the power grid in real time; the data processing module is used for calculating an absolute value of the power grid frequency deviation in real time based on the monitored power grid frequency and judging whether the absolute value of the power grid frequency deviation is greater than or equal to a preset power grid frequency stability threshold value or not; the data processing module is used for calculating the change rate of the power grid frequency deviation at the current moment and judging the size of the change rate of the power grid frequency deviation and a preset disturbance threshold value; the power output module is used for calculating the output of the energy storage power supply.
Wherein it is understood that the energy storage power supply is incorporated into the grid, by means of which the grid frequency is regulated.
It should be emphasized that the examples described herein are illustrative and not restrictive, and thus the invention is not to be limited to the examples described herein, but rather to other embodiments that may be devised by those skilled in the art based on the teachings herein, and that various modifications, alterations, and substitutions are possible without departing from the spirit and scope of the present invention.
Claims (7)
1. A power grid primary frequency modulation control method based on a battery energy storage power supply is characterized in that: the method comprises the following steps:
s1: monitoring the power grid frequency in real time, calculating the absolute value of the power grid frequency deviation in real time compared with the rated value of the power grid frequency, and judging whether the absolute value of the power grid frequency deviation is greater than or equal to a preset power grid frequency stability threshold value or not;
if the frequency is greater than or equal to the preset power grid frequency stability threshold, performing frequency modulation processing, and executing step S2; otherwise, repeating step S1;
the time from the first monitoring that the absolute value of the power grid frequency deviation is greater than or equal to the power grid frequency stability threshold value to the monitoring that the absolute value of the power grid frequency deviation is equal to the steady-state frequency deviation value is a primary frequency modulation period;
s2: calculating the change rate of the power grid frequency deviation at the current moment, and calculating the output of the energy storage power supply based on the power grid frequency deviation, the change rate of the power grid frequency deviation and a preset disturbance threshold;
adjusting the output of an energy storage power supply in real time in the primary frequency modulation period based on the real-time calculated power grid frequency deviation and the frequency deviation change rate, wherein when the power grid frequency deviation value at the current moment is greater than 0, the energy storage power supply is charged, and when the power grid frequency deviation value is less than 0, the energy storage power supply is discharged;
when the absolute value of the change rate of the power grid frequency deviation is greater than or equal to a preset disturbance threshold value, the output force of the energy storage power supply is defined as △ PstepThe calculation formula is as follows:
in the formula, ME、KERespectively representing a virtual inertia coefficient and a virtual unit adjustment coefficient of the energy storage battery; a is1、a2Distribution ratio coefficients, f, representing the virtual inertia mode and the virtual droop mode, respectivelyi、fi-1、f0Respectively representing the power grid frequency at the current moment, the power grid frequency at the previous sampling moment and the rated value of the power grid frequency, wherein delta t represents the time difference of the adjacent power grid frequency sampling moments;
when the absolute value of the change rate of the power grid frequency deviation is smaller than a preset disturbance threshold value, the output force of the energy storage power supply is defined as △ PcontinueThe calculation formula is as follows:
ΔPcontinue＝KE·(fi-f0)
wherein, the distribution ratio of the virtual inertia mode and the virtual droop mode is a1、a2The acquisition mode is as follows:
the grid frequency at the present moment is lower than the rated value of the grid frequency and the grid at the present momentFrequency deviation change rate less than 0, distribution ratio a1、a2The calculation formula of (a) is as follows:
the grid frequency at the current moment is higher than the grid frequency rated value, the grid frequency deviation change rate at the current moment is greater than 0, and the distribution proportion system a1、a2Comprises the following steps:
the current-time power grid frequency is lower than the power grid frequency rated value and the current-time power grid frequency deviation change rate is less than 0 or the current-time power grid frequency is higher than the power grid frequency rated value and the current-time power grid frequency deviation change rate is greater than 0, and the distribution proportion system a1、a2The calculation formula of (a) is as follows:
in the formula,. DELTA.fiRepresenting the grid frequency deviation at the present moment, △ fmaxIndicating the maximum frequency deviation value in the current primary chirp period, △ flowIs a preset grid frequency stability threshold.
2. The method of claim 1, wherein: coefficient K in step S2EThe calculation formula of (a) is as follows:
in the formula (I), the compound is shown in the specification,
expressing virtual unit regulating coefficient K when energy storage power supply dischargesE，
Virtual unit adjustment coefficient K for representing charging of energy storage power supplyE，KmaxRepresenting the maximum value of the virtual unit regulating coefficient of the energy storage power supply; SOC (i) represents the state of charge of the energy storage power supply at time i; SOCinitialRepresenting an initial state of charge of the energy storage power source; SOCmaxAnd SOCminRespectively representing the maximum charge state and the minimum charge state of the energy storage power supply, wherein n is a sensitivity coefficient.
3. The method of claim 2, wherein: the sensitivity coefficient is calculated when the energy storage power supply reaches the maximum charge state and the minimum charge state, the sensitivity of the virtual unit adjustment coefficient to the SOC is zero, and the calculation formula is as follows:
wherein, Kndis、KnchAnd the sensitivity of the virtual unit adjustment coefficient to the SOC is respectively expressed when the energy storage power supply is discharged and charged.
4. The method of claim 2, wherein: initial state of charge (SOC) of energy storage power supplyinitialIs 0.5.
5. The method of claim 1, wherein: the grid frequency deviation change rate in step S2 is calculated as follows:
wherein △ O (i) represents the change speed of the grid frequency deviation, i.e., the frequency deviation change rate, fi-1Representing the grid frequency collected at the previous sampling instant.
6. The method of claim 1, wherein: when the absolute value of the change rate of the power grid frequency deviation is greater than or equal to a preset disturbance threshold value, the load disturbance at the current moment is step disturbance; and when the absolute value of the change rate of the power grid frequency deviation is smaller than a preset disturbance threshold value, the load disturbance at the current moment is continuous disturbance.
7. A primary frequency modulation system of an energy storage power supply based on the method of any one of claims 1-6, characterized by: the device comprises a monitoring module, a data processing module and a power output module which are sequentially in communication connection;
the monitoring module is used for monitoring the frequency of the power grid in real time;
the data processing module is used for calculating an absolute value of the power grid frequency deviation in real time based on the monitored power grid frequency and judging whether the absolute value of the power grid frequency deviation is greater than or equal to a preset power grid frequency stability threshold value or not;
the data processing module is used for calculating the change rate of the power grid frequency deviation at the current moment and judging the absolute value of the change rate of the power grid frequency deviation and a preset disturbance threshold value;
the power output module is used for calculating the output of the energy storage power supply.
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| CN110445198B (en) * | 2019-08-27 | 2023-02-03 | 国网河南省电力公司电力科学研究院 | Power grid primary frequency modulation control method and system based on energy storage battery |
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| CN110783935B (en) * | 2019-11-13 | 2021-04-16 | 国网江苏省电力有限公司扬州供电分公司 | Method for limiting battery energy storage response frequency modulation signal under charge state |
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