CN113972668B - Wind-storage-combination-based electromagnetic transient control method for power system - Google Patents
Wind-storage-combination-based electromagnetic transient control method for power system Download PDFInfo
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Abstract
The invention discloses an electromagnetic transient control method of an electric power system based on wind power storage combination, which belongs to the technical field of electric power system control and solves the problem that the stable operation of the system is influenced due to the impact of fluctuation and uncertainty of wind power output on a power grid when wind power is connected, and the method balances the voltages at two ends of a super capacitor, so that the super capacitor connected in series is ensured to work in the same state, the damage risk of the super capacitor is reduced, the response time of the super capacitor is shortened, and the super capacitor is enabled to regulate the frequency more rapidly and effectively; and then, transient control is carried out by utilizing the super capacitor, absorption or compensation is carried out when the wind power output power is suddenly changed, the impact of wind power grid connection on voltage is reduced, and the running stability and economy of the power grid are improved.
Description
Technical Field
The invention belongs to the technical field of power system control, and relates to an electromagnetic transient control method of a power system based on wind-energy storage combination.
Background
Along with the continuous progress of global economy and science and technology, the demand of traditional energy sources such as coal and petroleum is larger and larger, energy crisis is gradually caused, and the fossil fuels can generate carbon monoxide, carbon dioxide and other gases in the combustion process, so that the balance of ecological environment is damaged to a certain extent, and the electric energy source is taken as a secondary energy source with strong cleanliness, has wider application field and becomes an indispensable important component in national production and life. The safe and stable power energy supply is a guarantee force for continuous and stable development in various fields such as global economy, industry, culture and the like, and the large consumption of fossil energy causes serious ecological damage problems, serious environmental problems such as greenhouse effect, atmospheric pollution and the like, and the human society faces a huge threat. The world nations have established urgent development targets for low-carbon green development, and are actively developing and utilizing renewable energy sources. The consumption of fossil fuels such as coal, petroleum and the like is huge in China as the largest developing country in the world at present, and heavy pressure is brought to the ecological environment, so that clean renewable energy sources are urgently needed to be developed. Wind energy is used as a pollution-free renewable energy source and becomes one of important available energy sources under the great background of the global energy Internet. In the development of renewable energy sources in the world today, wind power generation is the most mature technology, and the most renewable energy source power generation form has large-scale development and commercial development conditions.
The wind power generation capacity of China exceeds the United states in 6 months of 2012, the first of the spring world is reached by the end of 2014, the accumulated wind power installation capacity of China reaches 11.46GW, and wind power generation becomes an important energy source for promoting energy diversity and realizing sustainable development. The wide use of wind energy brings innovations to human life style in the future. However, wind power resources belong to uncontrollable natural energy, and as the wind power generation proportion is continuously improved, certain impact is caused to a power grid when wind power is connected due to fluctuation and uncertainty of wind power output, and stable operation of the system is affected. The literature (Li Junhui, etc. of northeast university) with the publication date of 2017, namely 5 months, modeling and operation control of a wind-storage combined grid-connected power generation system, aims at random fluctuation of grid-connected wind power generation, a large-scale battery energy storage system is configured in a wind power plant, a permanent magnet synchronous wind turbine generator set with a simple structure and good control performance is adopted, and a wind-storage combined grid-connected power generation system model is constructed and operation control of the wind-storage combined grid-connected power generation system model is realized. However, the energy storage device in the document is a battery, and no mention is made of how to adopt a super capacitor as the energy storage device of the wind power storage combined grid-connected system, when the wind power output power is suddenly changed, the super capacitor is utilized to absorb or compensate the power suddenly changed, so that the wind power grid-connected power is smoothly output, and the electromagnetic transient stability of wind power grid-connected is increased.
Disclosure of Invention
The invention aims to design an electromagnetic transient control method of an electric power system based on wind power storage combination so as to solve the problem that the fluctuation and uncertainty of wind power output impact the power grid when wind power is connected, and the stable operation of the system is affected.
The invention solves the technical problems through the following technical scheme:
an electromagnetic transient control method of an electric power system based on wind-storage combination comprises the following steps:
s1, detecting voltages at two ends of each super capacitor in sequence, and judging difference values of voltages of adjacent super capacitorsSum ofWhether zero is set, if so, performing step S2; if the voltage is not zero, a switch in the voltage equalizing control circuit is closed, and after the voltage equalizing control is carried out on the super capacitor by the incorporated regulating capacitor, the sum of the difference values of the voltages of the adjacent super capacitors is judged again +.>Whether the voltage is zero or not until the voltages at the two ends of each super capacitor are equal;
s2, detecting the system frequency and judging whether the absolute value |delta f| of the system frequency deviation is larger than a set threshold value, and ending if the absolute value |delta f| is not larger than the set threshold value; if the power is larger than the set threshold value, the charging and discharging power P is used for adjusting the frequency of the super capacitor a,t Performing frequency modulation, and detecting the system frequency again after the frequency modulation until the system is free of disturbance;
the calculation formula of the charge and discharge power during the super capacitor frequency modulation is as follows:wherein K is c Is the sagging control coefficient of the super capacitor, +.>The charging and discharging power of the super capacitor in the normal working state is represented, and Δf represents the system frequency deviation.
According to the method, voltages at two ends of the super capacitor are balanced, and the super capacitors connected in series are guaranteed to work in the same state, so that the damage risk of the super capacitor is reduced, the response time of the super capacitor is shortened, and the super capacitor can regulate the frequency more rapidly and effectively; and then, transient control is carried out by utilizing the super capacitor, absorption or compensation is carried out when the wind power output power is suddenly changed, the impact of wind power grid connection on voltage is reduced, and the running stability and economy of the power grid are improved.
As a further improvement of the technical scheme of the invention, the voltage equalizing control circuit comprises n voltage equalizing control circuits which are sequentially connected with each otherSuper capacitor C connected in series 1 、C 2 ……C n Where n is a positive even number, n/2 switches S 1 ……S n/2 N/2 regulating capacitors C' 1 ……C' n/2 The method comprises the steps of carrying out a first treatment on the surface of the Switch S n/2 And regulating the capacitance C' n/2 After being connected in series, the capacitor C is connected in parallel with the capacitor C in series n-1 、C n Two ends.
As a further improvement of the technical scheme of the invention, the calculation formula of the difference value of the adjacent super capacitor voltages is as follows:
wherein,representing super capacitor C n And super capacitor C n-1 A voltage difference between them;Representing super capacitor C n Voltage at two ends>Representing super capacitor C n-1 The voltage across it.
As a further improvement of the technical scheme of the invention, the super capacitor C n The calculation formula of the voltage at two ends is as follows:
wherein U is m,t Representing wind power plant output voltage; t represents time; alpha n ,β n ,γ n A conversion coefficient representing the equivalent resistance; n represents the serial number of the super capacitor; n represents the total number of supercapacitors (N e N),representation superrepresentationThe per unit value of the equivalent resistance of the branch connected with the stage capacitor;Representing the per unit value of the capacitance value of the super capacitor.
As a further improvement of the technical scheme of the invention, after the regulating capacitor is incorporated to carry out voltage equalizing control on the super capacitor, the super capacitor C n The calculation formula of the voltage at two ends is as follows:
wherein,representing the equalizing control gain coefficient;Representing super capacitor C n The voltage at two ends when the voltage equalizing control is not performed at the time (t-1);Representing super capacitor C n-1 The voltage values at both ends at the time (t-1); ζ represents a consistency coefficient of the pressure equalizing control;Representing adjacent tracking coefficients for the equalization control.
As a further improvement of the technical scheme of the present invention, the calculation formula of the system frequency deviation Δf is as follows:
wherein f t Representing the power system frequency measured at time t; f (f) k Representing the frequency obtained at the kth sampling; k represents the number of measurement samples; k represents the total number of measurement samples; f (f) t-1 The power system frequency measured at time (t-1) is shown.
As a further improvement of the technical scheme of the invention, the calculation formula of the charge and discharge power of the super capacitor in the normal working state is as follows:
wherein,representing the per unit value of the wind power output voltage;Representing the per unit value of the charge and discharge power of the super capacitor in a general state;And the per unit value of the voltages at the two ends of the super capacitor is represented.
As a further improvement of the technical scheme of the invention, the calculation formula of the sagging control coefficient of the super capacitor is as follows:
wherein eta c,t Represents the charging efficiency of the super capacitor, eta f,t The discharge efficiency of the super capacitor is represented, and kappa represents the discharge power factor of the super capacitor; epsilon represents the super capacitor charging power factor.
As a further improvement of the technical scheme of the invention, the voltage at two ends of the super capacitor is changed from the lowest voltage in the charging processRising to maximum voltage +.>The super capacitor charging efficiency eta c,t The calculation formula of (2) is as follows:
wherein W is c,t Representing that the super capacitor energy storage device is charged with electric energy under ideal conditions; epsilon represents the charging power factor of the super capacitor; w (W) r,t Indicating the actual charged energy of the super capacitor energy storage.
As a further improvement of the technical scheme of the invention, the voltage at two ends of the super capacitor is controlled by the voltage during dischargingReduced to a minimum voltage +.>The discharge efficiency eta of the super capacitor f,t The calculation formula of (2) is as follows:
wherein W is f,t The electric energy emitted by the super capacitor under ideal conditions is represented; kappa represents the discharge power factor of the supercapacitor; w (W) r ' ,t Indicating the actual energy discharged by the super capacitor.
The invention has the advantages that:
according to the method, voltages at two ends of the super capacitor are balanced, and the super capacitors connected in series are guaranteed to work in the same state, so that the damage risk of the super capacitor is reduced, the response time of the super capacitor is shortened, and the super capacitor can regulate the frequency more rapidly and effectively; and then, transient control is carried out by utilizing the super capacitor, absorption or compensation is carried out when the wind power output power is suddenly changed, the impact of wind power grid connection on voltage is reduced, and the running stability and economy of the power grid are improved.
Drawings
FIG. 1 is a flow chart of an electromagnetic transient control method of a power system based on wind-energy storage combination;
fig. 2 is a voltage equalizing control circuit diagram of the electromagnetic transient control method of the power system based on wind-storage combination.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The technical scheme of the invention is further described below with reference to the attached drawings and specific embodiments:
example 1
As shown in fig. 1, the invention mainly performs electromagnetic transient control on a wind power grid-connected power system based on a super capacitor, and the control process comprises two steps:
step 1, performing voltage equalizing control on the super capacitor: when a plurality of super capacitors are connected in series, the problem of uneven voltage often occurs, and the equal voltage at two ends is a necessary condition that the super capacitors work in the same state, so that voltage equalizing control is performed on the super capacitors.
In order to meet the power requirement of an electric power system, in a high-proportion wind power access system, when the fluctuation of wind power output is large, voltage regulation is performed in a mode of adopting a plurality of super capacitors in series, the problem of uneven capacitor voltage easily occurs in a series circuit, and only if the voltages at two ends of the super capacitors are equal, the super capacitors which are connected in series can work in the same state, so that voltage equalizing control is performed on the super capacitors.
When the model is built, the per unit value is adopted for part of elements:
step 1.1, establishing a super capacitor voltage model
In order to perform voltage equalizing control, a super capacitor voltage model is established:
wherein:representing super capacitor C n The voltage across the terminals; u (U) m,t Representing wind power plant output voltage; t represents time; alpha n ,β n ,γ n A conversion coefficient representing the equivalent resistance; n represents the serial number of the super capacitor;n represents the total number of super-capacitors (n.epsilon.N).
Step 1.2, super capacitor voltage equalizing calculation
To regulate the voltage across the super-capacitor, a voltage-equalizing control circuit may be used, as shown in fig. 2, which includes n super-capacitors C serially connected in sequence 1 、C 2 ……C n Where n is a positive even number, n/2 switches S 1 ……S n/2 N/2 regulating capacitors C' 1 ……C' n/2 The method comprises the steps of carrying out a first treatment on the surface of the Switch S n/2 And regulating the capacitance C' n/2 After being connected in series, the capacitor C is connected in parallel with the capacitor C in series n-1 、C n Two ends.
According to the wind power grid-connected output voltage, the voltage at two ends of the voltage equalizing control circuit can be determined, and every two adjacent super capacitors are connected with one regulating capacitor in parallel.
In order to realize the aim of voltage equalizing control of the super capacitor, the difference value of the voltages of the adjacent super capacitors needs to be judged:
wherein:representing super capacitor C n And super capacitor C n-1 A voltage difference between them;Respectively represent super-capacitor C n And super capacitor C n-1 The voltage across the terminals at the time of measurement.
When the voltage difference of the adjacent super-capacitor is not zero, a switch S in the voltage-sharing control circuit acts, the regulating capacitor starts to act, and the voltage-sharing control circuit acts on the super-capacitor C n The voltage at two ends of the voltage-equalizing control is as follows:
wherein:representing the equalizing control gain coefficient;Representing super capacitor C n The voltage at two ends when the voltage equalizing control is not performed at the time (t-1);Representing super capacitor C n-1 The voltage values at both ends at the time (t-1); ζ represents a consistency coefficient of the pressure equalizing control;Representing adjacent tracking coefficients for the equalization control.
Before the voltage-sharing control of each round plays a role, the gain coefficient of the voltage-sharing control is changed according to the control cycle times, after the voltage-sharing control circuit plays a role, the voltage difference value of all adjacent super capacitors is judged again, if the voltage difference value is not zero, the adjustment of the gain coefficient of the voltage-sharing control is continued, and the voltage-sharing control is carried out on the super capacitors until the voltages at the two ends of each super capacitor are equal.
And 2, adjusting the frequency of the power grid by using the super capacitor, when the wind power output is suddenly changed, adjusting by using the super capacitor, setting a frequency modulation dead zone, and when the frequency deviation is not in the dead zone range, operating the super capacitor to adjust the frequency of the system until the system is free from disturbance.
After the step 1, the voltages at the two ends of the super capacitor are equal and can work in the same state, so that the super capacitor can be used for adjusting the frequency of the power grid, the frequency modulation dead zone is set to be |Deltaf| or less than or equal to 0.03 during frequency modulation, the system can be approximately judged to be free of disturbance at the moment, if the frequency deviation of the system does not meet the condition, the phenomenon that the wind power output has abrupt change is indicated, and the super capacitor still needs to be used for adjusting.
Step 2.1, system frequency calculation
In order to adjust the system frequency, the system frequency needs to be calculated:
wherein: f (f) t Representing the power system frequency measured at time t; f (f) k Representing the frequency obtained at the kth sampling; k represents the number of measurement samples; k represents the total number of measurement samples; f (f) t-1 Representing the power system frequency measured at time (t-1); Δf represents the system frequency deviation.
Step 2.2, establishing a super capacitor charge-discharge model
In order to control by utilizing the super capacitor, a super capacitor charge and discharge power model needs to be established:
wherein:and the charging and discharging power of the super capacitor in the normal working state is shown.
In the charging process, the voltage at two ends of the super capacitor is from the lowest voltageRising to maximum voltage +.>The charging efficiency model can be built from this process:
wherein: w (W) c,t Representing that the super capacitor energy storage device is charged with electric energy under ideal conditions; epsilon represents the charging power factor of the super capacitor; w (W) r,t Representing the electric energy actually charged by the super capacitor energy storage; η (eta) c,t Indicating the charging efficiency of the super capacitor.
In the discharging process, the voltage at two ends of the super capacitor is equal to the slave voltageReduced to a minimum voltage +.>Establishing a super capacitor discharge efficiency model:
wherein: w (W) f,t The electric energy emitted by the super capacitor under ideal conditions is represented; kappa represents the discharge power factor of the supercapacitor; w'. r,t The actual electric energy emitted by the super capacitor is represented; η (eta) f,t Indicating the discharge efficiency of the super capacitor.
Judging according to the system frequency deviation measured in the formula (4), setting a frequency modulation dead zone at |delta f| which is less than or equal to 0.03, and when the frequency deviation does not meet the requirement, starting frequency modulation work by the super capacitor, wherein the frequency modulation power of the super capacitor is calculated in the following manner:
in which P is a,t Representing the charge and discharge power of the super capacitor during frequency modulation; k (K) c Is the sagging control coefficient of the super capacitor. When the absolute value of the system frequency deviation is delta f>0.03, the super capacitor is charged and discharged, the system frequency is adjusted, and when deltaf is in different intervals, the sagging coefficient is calculated as follows:
when delta f is more than 0.03Hz, the wind power generation power suddenly increases, the super capacitor is charged, and the sagging coefficient takes a negative value; when Deltaf < -0.03Hz, the wind power generation power is suddenly reduced, the super capacitor discharges, and the sagging coefficient takes a positive value.
And (3) returning to the step (2.1) again after the super capacitor is adjusted to measure the system frequency until the system is free from disturbance.
Application instance computing
The example calculation was performed in a scenario where the wind speed was constant at 10 m/s. Has a wind power plant with 30 wind power units, and rated output voltage of the wind power plant is U m,t =28.8 kv; rated wind speed of the wind turbine generator is 10m/s, and reference value of output voltage of a given wind power plant is U m =10kv; each super capacitor value is C n Equivalent resistance conversion coefficient α of supercapacitor=27.5f n 、β n 、γ n 0.5, 1 respectively; a consistency coefficient ζ=0.34; adjacent tracking coefficientsSuper capacitor charging power factor epsilon=50.32; super capacitor discharge power factor κ= -7.05; the reference value of the equivalent resistance of a given super capacitor connecting branch is R N =0.1 kΩ; given a reference capacitance of C for the super capacitor N =1.0f; the reference charge-discharge power of the given super capacitor is +.>Rated operating frequency f=50hz of the system, and the system operates at the rated frequency, given a reference value of the voltage across the supercapacitorSetting the number of super capacitors to be N=15, (N epsilon N), and suddenly reducing the output power of the system by 100MW at 15 s.
The equivalent resistances of the circuits connected with the known super capacitor are respectively as follows:
| R 1 ＝272.25kΩ | R 9 ＝88.92kΩ |
| R 2 ＝260.95kΩ | R 10 ＝88.74kΩ |
| R 3 ＝258.05kΩ | R 11 ＝87.02kΩ |
| R 4 ＝136.14kΩ | R 12 ＝84.57kΩ |
| R 5 ＝135.72kΩ | R 13 ＝52.25kΩ |
| R 6 ＝124.43kΩ | R 14 ＝43.08kΩ |
| R 7 ＝123.70kΩ | R 15 ＝42.72kΩ |
| R 8 ＝123.76kΩ |
step a, performing voltage balance control
The problem of uneven capacitor voltage easily occurs in the series circuit, and only if the voltages at two ends of the super capacitor are equal, the super capacitor connected in series can work in the same state, so that voltage equalizing control is performed on the super capacitor at first.
Calculating the voltage across the supercapacitor at 15 s:
the method comprises the following steps:
referring to the super capacitor voltage equalizing control circuit in fig. 2, to achieve the goal of super capacitor voltage equalizing control, the difference between adjacent super capacitor voltages needs to be determined:
when (when)When the voltage equalizing control circuit works, the switch S in the voltage equalizing control circuit acts, the regulating capacitor starts to act, and the voltage equalizing control circuit works on the super capacitor C n The voltage at two ends of the voltage-equalizing control is as follows:
before the voltage-sharing control of each round plays a role, the gain coefficient of the voltage-sharing control is changed according to the control cycle times, after the voltage-sharing control circuit plays a role, the voltage difference value of the adjacent super capacitor is judged again, if the voltage difference value is not zero, the adjustment of the gain coefficient of the voltage-sharing control is continued until the voltage-sharing control is obtainedAt the moment, the voltages at the two ends of each super capacitor are equal +.>
Step b, controlling the frequency of the power system
After the step a, the voltages at the two ends of the super capacitor are equal and can work in the same state, so that the super capacitor can be used for adjusting the frequency of the power grid, the frequency modulation dead zone is set to be |Deltaf| or less than or equal to 0.03 during frequency modulation, the system can be approximately judged to be free of disturbance at the moment, if the frequency deviation of the system does not meet the condition, the phenomenon that the wind power output has abrupt change is indicated, and the super capacitor still needs to be used for adjusting.
In order to adjust the system frequency, the system frequency needs to be calculated first, the sampling times are 4 times when the system frequency is measured, and the system frequencies obtained by four times of sampling are known as follows: f (f) 1 ＝49.19Hz f 2 ＝50.25Hz f 3 ＝49.45Hz f 4 =50.91 Hz to calculate the frequency of the power system after sudden change of wind power output:
calculating the absolute value of the system frequency deviation after the wind power output is suddenly changed:
|Δf|＝|f t -f t-1 |＝0.05
because Deltaf < -0.03, the system frequency deviation does not meet the condition of no disturbance, the super capacitor should be utilized to carry out frequency modulation, and at the moment, if the super capacitor works, the super capacitor is discharged, and the calculation can be carried out according to a super capacitor discharging model:
the super capacitor carries out frequency modulation P according to the discharging mode a,t After the supercapacitor work was completed, the system frequency was measured again and the absolute value of the frequency deviation was calculated:
|Δf|＝|f t -f t-1 |＝0.02
at this time, the absolute value of the system frequency deviation is smaller than 0.03, and the system frequency deviation is in the frequency modulation dead zone, so that the system can be judged to be free of disturbance, the operation is stable, and the control method is effective.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (5)
1. The electromagnetic transient control method of the power system based on the wind-storage combination is characterized by comprising the following steps of:
s1, detecting voltages at two ends of each super capacitor in sequence, and judging the sum of differences of voltages of adjacent super capacitorsWhether zero is set, if so, performing step S2; if the voltage is not zero, a switch in the voltage equalizing control circuit is closed, and after the voltage equalizing control is carried out on the super capacitor by the incorporated regulating capacitor, the sum of the difference values of the voltages of the adjacent super capacitors is judged again +.>Whether the voltage is zero or not until the voltages at the two ends of each super capacitor are equal;
the voltage equalizing control circuit comprises n super capacitors C which are sequentially connected in series 1 、C 2 ……C n Where n is a positive even number, n/2 switches S 1 ……S n/2 N/2 regulating capacitors C' 1 ……C' n/2 The method comprises the steps of carrying out a first treatment on the surface of the Switch S n/2 And regulating the capacitance C' n/2 After being connected in series, the capacitor C is connected in parallel with the capacitor C in series n-1 、C n Both ends;
the calculation formula of the difference value of the adjacent super capacitor voltages is as follows:
wherein,representing super capacitor C n And super capacitor C n-1 A voltage difference between them;Representing super capacitor C n Voltage at two ends>Representing super capacitor C n-1 The voltage across the terminals;
the super capacitor C n The calculation formula of the voltage at two ends is as follows:
wherein U is m,t Representing wind power plant output voltage; t represents time; alpha n ,β n ,γ n A conversion coefficient representing the equivalent resistance; n represents the serial number of the super capacitor; n represents the total number of supercapacitors (N e N),representing the per unit value of the equivalent resistance of the branch connected with the super capacitor;Representing the per unit value of the capacitance value of the super capacitor;
after the super capacitor is subjected to voltage equalizing control by incorporating the regulating capacitor, the super capacitor C n The calculation formula of the voltage at two ends is as follows:
wherein,representing the equalizing control gain coefficient;Representing super capacitor C n The voltage at two ends when the voltage equalizing control is not performed at the time (t-1);Representing super capacitor C n-1 The voltage values at both ends at the time (t-1); ζ represents a consistency coefficient of the pressure equalizing control;Indicating pressure equalizing controlAdjacent tracking coefficients of (a);
s2, detecting the system frequency and judging whether the absolute value |delta f| of the system frequency deviation is larger than a set threshold value, and ending if the absolute value |delta f| is not larger than the set threshold value; if the power is larger than the set threshold value, the charging and discharging power P is used for adjusting the frequency of the super capacitor a,t Performing frequency modulation, and detecting the system frequency again after the frequency modulation until the system is free of disturbance;
the calculation formula of the charge and discharge power during the super capacitor frequency modulation is as follows:wherein K is c Is the sagging control coefficient of the super capacitor, +.>The charging and discharging power of the super capacitor in the normal working state is represented, and Δf represents the system frequency deviation;
the calculation formula of the charge and discharge power of the super capacitor in the normal working state is as follows:
wherein,representing the per unit value of the wind power output voltage;Representing the per unit value of the charge and discharge power of the super capacitor in a general state;and the per unit value of the voltages at the two ends of the super capacitor is represented.
2. The electromagnetic transient control method of the power system based on wind power and energy storage combination according to claim 1, wherein the calculation formula of the system frequency deviation deltaf is as follows:
wherein f t Representing the power system frequency measured at time t; f (f) k Representing the frequency obtained at the kth sampling; k represents the number of measurement samples; k represents the total number of measurement samples; f (f) t-1 The power system frequency measured at time (t-1) is shown.
3. The electromagnetic transient control method of the power system based on wind-storage combination according to claim 1, wherein the calculation formula of the sagging control coefficient of the super capacitor is as follows:
wherein eta c,t Represents the charging efficiency of the super capacitor, eta f,t The discharge efficiency of the super capacitor is represented, and kappa represents the discharge power factor of the super capacitor; epsilon represents the super capacitor charging power factor.
4. The method for electromagnetic transient control of a wind-powered electricity generation system based on wind-powered electricity generation and storage combination according to claim 3, wherein the voltage across the super capacitor is reduced from the lowest voltage during the charging processRising to maximum voltage +.>The super capacitor charging efficiency eta c,t The calculation formula of (2) is as follows:
wherein W is c,t Representing that the super capacitor energy storage device is charged with electric energy under ideal conditions; epsilon represents the charging power factor of the super capacitor; w (W) r,t Indicating the actual charged energy of the super capacitor energy storage.
5. The wind-storage-combination-based electromagnetic transient control method for the power system according to claim 3, wherein in the discharging process, voltages at two ends of the super capacitor are controlled from voltagesReduced to a minimum voltage +.>The discharge efficiency eta of the super capacitor f,t The calculation formula of (2) is as follows:
wherein W is f,t Indicating the ideal of super capacitorThe electric energy emitted under the condition; kappa represents the discharge power factor of the supercapacitor;
W r ' ,t indicating the actual energy discharged by the super capacitor.
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| CN109888904A (en) * | 2019-03-15 | 2019-06-14 | 中南大学 | A kind of asynchronous compensation pressure-equalizing device and control method of vehicle-mounted super capacitor |
| CN110611320A (en) * | 2019-07-22 | 2019-12-24 | 华北电力大学（保定） | Double-fed wind turbine generator inertia and primary frequency modulation method based on super capacitor energy storage control |
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