CN106877432B - Hybrid energy storage system for stabilizing wind power fluctuation - Google Patents
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Abstract
The invention discloses a hybrid energy storage system for stabilizing wind power fluctuation, which solves the problems of complex structure of an energy storage system and optimization of the working state of the energy storage system in the prior art. The device comprises a super capacitor and a storage battery which are connected in series, and also comprises a hysteresis comparison controller, wherein the hysteresis comparison controller is respectively connected with the super capacitor and the storage battery; the hysteresis comparison controller is provided with a first threshold, a second threshold, a third threshold and a fourth threshold which are from small to large and correspond to the residual electric quantity of the super capacitor, so that frequent actions and charging and discharging of the storage battery are effectively avoided, the service life is prolonged, the charge state fluctuation of the super capacitor is reduced, the overall economy of the hybrid energy storage system is improved, and the working state of the energy storage system is optimized. The invention is suitable for links of research and development design, operation control, electric energy metering, cost management and the like of a wind power generation system, has the characteristics of simple structure, good stability, environmental protection and reproducibility, and has higher production and research values.
Description
Technical Field
The invention relates to a wind power generation energy storage system, in particular to a hybrid energy storage system for stabilizing wind power fluctuation.
Background
With the gradual depletion of traditional energy sources, the power generation technology of renewable new energy sources such as wind power generation gradually draws attention of people. Because the wind energy has the characteristics of intermittence and randomness, the output power of the wind power system is in a fluctuating unstable state. When the wind power output power is directly merged into the power grid, negative influences are brought to the stability of the power system, the power grid frequency, the power quality, the power generation plan, the dispatching and the like. Therefore, the adoption of an Energy Storage System (ESS) to stabilize the output power fluctuation problem of the wind power plant has important practical significance. The characteristics of different energy storage devices are different from the applicable occasions, and the single energy storage technology is difficult to meet the stabilizing requirement of wind power generation multi-time scale power. Relevant researches find that a Hybrid Energy Storage System (HESS) is formed by combining energy storage systems with small capacity, high power ratio, long cycle life, large capacity and high energy ratio, and the fluctuation of different time characteristics in power fluctuation is compensated through a proper control strategy, so that a better control effect relative to a single energy storage device can be obtained.
The invention discloses a Chinese patent publication No. CN 201410391305.X, wherein the publication date is 11/19/2014, the name of the invention creation is 'a hybrid energy storage stabilizing wind power fluctuation system and a coordination control method thereof', the application discloses a hybrid energy storage stabilizing wind power fluctuation system and a coordination control method thereof, and the composition is as follows: collecting fan output power PgThe output power of the fan is processed by adopting a moving average algorithm to obtain the expected power P of wind power outputdesireAnd the difference value of the two is used as the energy storage compensation power delta P. The delta P is compared with the working voltage U of the super capacitoressAnd as the input of the wind storage coordination controller, analyzing and judging to start a fan regulation and control system or start an energy storage coordination control layer to carry out power stabilization. When the energy storage coordination control layer is used for power stabilization, the low-pass filter and the fuzzy controller optimize compensation power distribution to realize the internal coordination of the energy storage coordination control layerAnd (5) adjusting and controlling. The disadvantages of the application are: the system comprises a coordination controller, a control fan, a low-pass filter, a fuzzy controller A, a fuzzy controller B, a storage battery, a super capacitor and other technical characteristics, and has a complex structure, and the fuzzy controller and the filter have obvious transmission errors caused by roll-off; on the other hand, in order to make the super capacitor work in a specified charge state, the storage battery needs to compensate the power output of the super capacitor by frequently switching charge and discharge actions, so that the charge state of the super capacitor is easy to oscillate back and forth near a charge and discharge threshold value, and the service life of the super capacitor and the service life of the storage battery are shortened.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the wind power generation energy storage system solves the problem of complex structure and optimizes the working state of the energy storage system.
In order to solve the technical problem, the invention provides a hybrid energy storage system for stabilizing wind power fluctuation, which comprises a super capacitor and a storage battery, wherein the super capacitor is connected with the storage battery in a cascade manner; the hybrid energy storage system also comprises a hysteresis comparison controller, and the hysteresis comparison controller is respectively connected with the super capacitor and the storage battery;
the hysteresis comparison controller is provided with a first threshold, a second threshold, a third threshold and a fourth threshold which are from small to large and correspond to the residual electric quantity of the super capacitor;
the hysteresis comparison controller is used for controlling the storage battery to absorb electric energy from the super capacitor when the residual electric quantity exceeds a fourth threshold value;
the hysteresis comparison controller is also used for controlling the storage battery to stop absorbing the electric energy when the residual electric quantity is reduced to a third threshold value;
the hysteresis comparison controller is also used for controlling the storage battery to charge the super capacitor when the residual electric quantity is smaller than a first threshold value;
the hysteresis comparison controller is also used for controlling the storage battery to stop charging when the residual capacity is increased to a second threshold value.
The hybrid energy storage system is provided with a limit management module, and the limit management module is respectively connected with the super capacitor and the storage battery;
the limit management module is provided with a lower limit threshold and an upper limit threshold corresponding to the sum of the residual electric quantity of the super capacitor and the storage battery;
the limit management module is used for locking the super capacitor to discharge the output power grid when the sum of the residual electric quantity is smaller than a lower limit threshold value, and controlling the super capacitor to charge through a wind power generation network outside the hybrid energy storage system;
and the limit management module is also used for locking the charging of the super capacitor when the sum of the residual electric quantity is greater than an upper limit threshold value, and controlling the super capacitor to discharge.
The limit management module is provided with N charge-discharge thresholds between the lower limit threshold and the upper limit threshold, wherein N is a positive integer; and the limit management module is also used for controlling the charging intensity and the discharging intensity of the super capacitor according to the interval determined by the charging and discharging threshold corresponding to the sum of the residual electric quantity.
N is 2 and is set as a lower limit charge-discharge threshold value and an upper limit charge-discharge threshold value;
the limit management module is further used for controlling the discharge intensity of the super capacitor to be A times of the rated discharge intensity when the sum of the residual electric quantity is larger than the lower limit threshold and smaller than the lower limit charge-discharge threshold, wherein A is a rational number larger than 0 and smaller than 1, and the charge intensity is controlled to be the rated charge intensity;
the limit management module is further used for controlling the discharge intensity of the super capacitor to be rated discharge intensity and controlling the charge intensity to be rated charge intensity when the sum of the residual electric quantity is greater than a lower limit charge-discharge threshold and smaller than an upper limit charge-discharge threshold;
the limit management module is further used for controlling the charging intensity of the super capacitor to be B times of the rated charging intensity when the sum of the residual electric quantity is larger than an upper limit charging and discharging threshold value and smaller than the upper limit threshold value, wherein B is a rational number larger than 0 and smaller than 1, and the discharging intensity is controlled to be the rated discharging intensity.
The limit management module is provided with a rated capacity unit, a current residual capacity unit, an addition unit and a phase reversal unit;
the rated capacity unit is respectively connected with the super capacitor and the storage battery and is used for obtaining the sum of the rated capacities of the super capacitor and the storage battery;
the current residual capacity unit is respectively connected with the super capacitor and the storage battery and is used for obtaining the sum of the current residual capacities of the super capacitor and the storage battery;
the reverse unit is connected with the current residual capacity unit and is used for obtaining the opposite number of the sum of the current residual capacity;
and the addition unit is used for connecting the rated capacity unit with the inversion unit and obtaining the difference value between the sum of the rated capacities and the sum of the current residual capacities as the sum of the residual capacities.
The sum of the residual electric quantity is represented by a charge state parameter, and the charge state parameter is a rational number in a closed interval [0, 1 ].
The limit management module is provided with a rated capacity unit, a current residual capacity unit, a ratio unit, an addition unit and a phase reversal unit;
the rated capacity unit is respectively connected with the super capacitor and the storage battery and is used for obtaining the sum of the rated capacities of the super capacitor and the storage battery;
the current residual capacity unit is respectively connected with the super capacitor and the storage battery and is used for obtaining the sum of the current residual capacities of the super capacitor and the storage battery;
the reverse unit is connected with the current residual capacity unit and is used for obtaining the opposite number of the sum of the current residual capacity;
the addition unit is used for connecting the rated capacity unit with the inversion unit and obtaining the difference value between the sum of the rated capacities and the sum of the current residual capacity;
the ratio unit connects the adding unit with the rated capacity unit, and is used for obtaining a ratio of a difference value between the sum of the rated capacities and the sum of the current remaining capacities to the sum of the rated capacities, and taking the ratio as the state of charge parameter.
The storage battery charges the super capacitor or absorbs electric energy at rated power.
Compared with the prior art, the hybrid energy storage system has the advantages that the hybrid energy storage system is only composed of the super capacitor, the storage battery and the hysteresis comparison controller, and the super capacitor is used as a primary energy storage device to directly compensate fluctuation of wind power generation; the storage battery is a secondary energy storage device and is connected with the super capacitor in series for energy exchange, the defect of low energy density of the super capacitor is compensated, the rated capacity required by the super capacitor is reduced, and the storage battery and the super capacitor are connected in series to enable the structure of the super capacitor to be simple. The hysteresis comparison controller controls the working state of the storage battery by using the residual capacity of the super capacitor: the threshold corresponding to the residual electric quantity of the 4 super capacitors is set, so that frequent actions and charging and discharging of the storage battery near the threshold are avoided, the service life is prolonged, the charge state fluctuation of the super capacitors is reduced, the overall economy of the hybrid energy storage system is improved, and the working state of the energy storage system is optimized.
Drawings
FIG. 1 is a schematic diagram of the system architecture of the present invention;
FIG. 2 is a threshold setting diagram for the restriction management module;
FIG. 3 is a plot of the hysteresis comparison controller;
FIG. 4 is a schematic diagram of a target power curve for a hybrid energy storage system;
FIG. 5 is a schematic diagram of the charge and discharge states of a battery without the addition of a hysteresis comparison controller;
fig. 6 is a schematic diagram of the charge and discharge state of a battery incorporating a hysteresis comparison controller.
Detailed Description
The present invention is described in further detail below with reference to the attached drawings and specific examples so that those skilled in the art can better understand the present invention and can implement the present invention, but the examples are not intended to limit the present invention.
Example 1:
in the embodiment, a wind generating set with the rated power of 10MW is arranged, and the hybrid energy storage system disclosed by the invention is used for compensating power fluctuation. The hybrid energy storage system comprises a super capacitor, a storage battery, a hysteresis comparison controller and a limit management module, and is shown in the attached figure 1. The super capacitor and the storage battery are connected in series (cascade), the hysteresis comparison controller is respectively connected with the super capacitor and the storage battery, and the restriction management module is respectively connected with the super capacitor and the storage battery; the hybrid energy storage system is merged into a power grid according to kirchhoff current law (KCL law), and a target power curve of the hybrid energy storage system needing compensation is shown in the attached figure 4. The initial state of charge of the hybrid energy storage system is set to be 50% so as to exert the optimal performance of the hybrid energy storage system.
In order to ensure that the storage battery is in an optimized working state, the storage battery is set to be charged and discharged only at rated power in the embodiment; the hysteresis comparison controller controls the working state of the storage battery by using the residual charge (state of charge, denoted as SOCsc) of the super capacitor. The SOCsc represents the ratio of the current residual capacity of the super capacitor to the rated capacity of the super capacitor, and the value range of the SOCsc is 0-1. When the SOCsc is 0, it indicates that the super capacitor is completely discharged, and when the SOCsc is 1, it indicates that the super capacitor is completely filled.
Setting a first threshold value D _ on, a second threshold value D _ off, a third threshold value C _ off and a fourth threshold value C _ on from small to large, wherein the first threshold value D _ on, the second threshold value D _ off, the third threshold value C _ off and the fourth threshold value C _ on correspond to the residual capacity of the super capacitor, and a hysteresis curve is shown in figure 3, wherein the abscissa represents the SOCsc value of the super capacitor, and the ordinate P represents the SOCsc value of the super capacitorbaRepresenting the output power of the battery.
1) When the SOCsc is between D _ off and C _ off, the super capacitor can normally compensate the target power at the moment, and the super capacitor is set to be in a normal working state, and the hysteresis comparison controller and the storage battery do not need to operate.
2) When the SOCsc gradually increases and the value of the SOCsc exceeds C _ on, the storage battery absorbs electric energy from the super capacitor at rated power so as to enhance the discharge of the super capacitor and improve the condition of excessive electric quantity. And at the moment, the electric quantity of the super capacitor is gradually reduced due to the action of the storage battery, the super capacitor is restored to a normal working state, and when the SOCsc is set to be reduced to C _ off, the storage battery is controlled to stop absorbing the electric energy in order to prevent the charging and discharging state of the storage battery from being frequently changed due to the frequent fluctuation of the SOCsc near C _ on.
3) And the electric quantity of the SOCsc is gradually reduced, and when the value of the electric quantity of the SOCsc is lower than D _ on, the storage battery provides energy for the super capacitor by rated power so as to enhance the charging of the super capacitor and improve the condition that the electric quantity of the super capacitor is too low. At this time, the electric quantity of the super capacitor is gradually increased due to the action of the storage battery, the super capacitor is restored to a normal working state, and in order to prevent the charging and discharging state of the storage battery from being frequently changed due to the frequent fluctuation of the SOCsc near D _ on, the storage battery is controlled to stop charging when the SOCsc is set to be increased to D _ off.
Both overcharge and overdischarge can cause significant damage to the hybrid energy storage system. In order to protect the hybrid energy storage system, the hybrid energy storage system can be limited to discharge when the energy storage electric quantity is less, and the hybrid energy storage system does not discharge when the electric quantity reaches the lower limit; and when the stored energy electric quantity is large, the charging power is limited, and the charging is not carried out when the electric quantity reaches the upper limit, and the protection parameter SOC for preventing overcharge and over-discharge is set. The SOC represents the ratio of the current residual capacity of the hybrid energy storage system (the super capacitor and the storage battery) to the rated capacity of the hybrid energy storage system, and the value range of the SOC is 0-1. When the SOC is 0, the hybrid energy storage system is completely discharged, and when the SOC is 1, the hybrid energy storage system is completely full. As shown in fig. 2, a lower limit threshold SOC corresponding to the sum of the remaining capacities of the super capacitor and the secondary battery is set in the limit management moduleminAnd upper threshold SOCmax. Limiting management module to be smaller than SOC when SOC is smaller than SOCminAnd the super capacitor is locked to discharge the output power grid, and the super capacitor is controlled to be charged through a wind power generation network outside the hybrid energy storage system. The limit management module is larger than the SOC at the SOCmaxAnd the charging of the super capacitor is locked, and the super capacitor is controlled to discharge.
In order to further optimize the charge and discharge management of the hybrid energy storage system, the management module is limited to be in SOCminAnd SOCmax2 charge-discharge threshold values are arranged between the two, and the charge-discharge threshold value is set as a lower limit charge-discharge threshold value SOClowAnd an upper limit charge-discharge threshold SOCupAs shown in fig. 2.
1) The limit management module is larger than the SOC at the SOCminAnd is less than SOClowAnd meanwhile, controlling the discharge intensity of the super capacitor to be 0.5 times of the rated discharge intensity, and simultaneously controlling the charge intensity to be the rated charge intensity.
2) The limit management module is larger than the SOC at the SOClowAnd is less than SOCupAnd when the charging and discharging threshold is limited, controlling the discharging intensity of the super capacitor to be the rated discharging intensity and controlling the charging intensity to be the rated charging intensity.
3) The limit management module is larger than the SOC at the SOCupAnd is less than SOCmaxAnd meanwhile, controlling the charging intensity of the super capacitor to be 0.5 times of the rated charging intensity, and simultaneously controlling the discharging intensity to be the rated discharging intensity.
In order to obtain the value of the SOC, the limit management module is provided with a rated capacity unit, a current residual capacity unit, a ratio unit, an addition unit and an inversion unit. The rated capacity unit is respectively connected with the super capacitor and the storage battery to obtain the sum of the rated capacities of the super capacitor and the storage battery; the current residual capacity unit is respectively connected with the super capacitor and the storage battery to obtain the sum of the current residual capacities of the super capacitor and the storage battery; the reverse phase unit is connected with the current residual capacity unit to obtain the opposite number of the sum of the current residual capacity; the addition unit connects the rated capacity unit with the inversion unit to obtain the difference between the sum of the rated capacity and the sum of the current residual capacity; the ratio unit connects the addition unit with the rated capacity unit, obtains the ratio of the difference value of the sum of the rated capacities and the sum of the current remaining capacities to the sum of the rated capacities, and takes the ratio as the value of the SOC.
The hysteresis comparison controller is arranged in the embodiment to ensure that the storage battery is in an optimized working state; referring to fig. 5, in order to clearly show the charge and discharge state of the storage battery when the hysteresis comparison controller is turned off, the frequent charge and discharge state interval of the storage battery in fig. 5 is partially enlarged. In order to enable the super capacitor to work in a specified charge state, the storage battery needs to compensate the power output of the super capacitor by frequently switching charge and discharge actions, so that the charge state of the super capacitor is easy to oscillate back and forth near a charge and discharge threshold value, and the cycle service life of the super capacitor and the cycle service life of the storage battery are extremely unfavorable. Fig. 6 shows the charging and discharging states of the storage battery when the hysteresis comparison controller is opened, and the comparison shows that the charging and discharging conversion times of the storage battery are obviously reduced and the charge state fluctuation of the super capacitor is also obviously reduced after the hysteresis comparison controller of the storage battery is added, so that the long-term use of the energy storage device is facilitated.
In the embodiment, the super capacitor and the storage battery are connected in series, so that the structure of the hybrid energy storage system becomes simple; the energy density of the storage battery is high, but the charging and discharging state cannot be frequently changed due to the influence of the service life of the storage battery; the super capacitor is used as a power type energy storage device and has the advantages of high power density, long cycle life and high response speed. The advantages of the two are combined, frequent charging and discharging of the storage battery can be effectively avoided, the service life of the storage battery is prolonged, and the overall economy of the energy storage system is improved. The economic benefits obtained by the embodiment are as follows:
converting the energy released by the energy storage system into electricity selling income, converting the energy which does not meet the expected output part into punishment cost, and simultaneously considering the inherent cost of the energy storage equipment, establishing a model with the maximum comprehensive net income of the three parts as an optimization target:
1) and (6) selling electricity revenue.
Compared with a wind power system without the hybrid energy storage system, when the output power of the fan is larger than the grid-connected power, the hybrid energy storage system can store a part of energy and release the energy when the energy of the fan is insufficient. The energy released by the part of stored energy is the total generated energy of the wind power plant increased after the hybrid energy storage system is installed, and is converted into electricity selling income, and the calculation formula is as follows: f. of1＝ne·∑Ehess，Ehess> 0, wherein f1Selling electricity for the system to obtain revenue; ehessEnergy released for storing neIs the electricity selling coefficient.
2) And penalizing the cost.
The penalty cost means that after compensation of the hybrid energy storage system, the output power of the system still does not reach the expected output, the part of the unsatisfied energy is called penalty energy, the corresponding economic cost is called penalty cost, and the penalty is set for the condition that the output power does not reach the expected output. The penalty energy includes two parts:
firstly, when the energy of the hybrid energy storage system reaches the maximum limit value, redundant wind power cannot be stored in the hybrid energy storage system continuously, and the wind power needs to be stored in the hybrid energy storage systemAbandoning wind, wherein a part of energy is lost; and secondly, when the energy of the hybrid energy storage system reaches the minimum limit value, the missing wind power cannot be compensated by the hybrid energy storage system, the expected output cannot be met, and at the moment, a part of energy is lost. The penalty cost calculation formula is as follows: f. of2＝nl·∑ElossIn the formula, f2Penalizing costs for the system; elossEnergy released for storing nlIs a penalty cost coefficient.
3) The inherent cost.
The inherent cost is mainly the installation cost of the energy storage system, and is related to the capacity of the hybrid energy storage system. In order to embody the rationality, the inherent cost is converted into the average cost in the time scale, and the specific expression is as follows: f. of3＝kba(nb,pPrba+nb,wWrba)+ksc(ns,pPrsc+ns,wWrsc) In the formula, f3Calculating an intrinsic cost for the system on a time scale; pr (Pr) ofba、Wrba、PrscAnd WrscRated power and rated capacity of the storage battery and the super capacitor respectively; n isb,p、nb,w、ns,pAnd ns,wThe power unit price and the capacity unit price of the storage battery and the super capacitor are respectively; k is a radical ofbaAnd kscRespectively representing the depreciation factors of the storage battery and the super capacitor.
To sum up, the hybrid energy storage system optimization model objective function calculates the net gain in the time scale for the system, i.e., F1-f2-f3And establishing an optimal configuration model taking the power, the capacity and the state of charge of the energy storage device as constraint conditions.
And power balance constraint: in order to enable the total output power of the system to meet grid-connection requirements, the output power of the hybrid energy storage system should be equal to the difference between the grid-connection power and the wind power.
Power constraint and capacity constraint: in order to ensure that the storage battery and the super capacitor operate normally, the output power and energy of the storage battery and the super capacitor do not exceed rated values.
And (3) state of charge constraint: the state of charge of both the battery and the supercapacitor should be within reasonably limited ranges, and overcharging and overdischarging can reduce the service life of the stored energy.
In summary, the constraints can be expressed asSubscript ba is a parameter corresponding to a storage battery, subscript sc is a parameter corresponding to a super capacitor, subscript grid represents a grid-connected parameter, subscript grid represents a wind power parameter, P represents power, W represents energy, and SOC represents a state of charge.
In order to compare the difference between the single energy storage mode and the embodiment mode, the two modes are analyzed and calculated by using the same original data, and the final calculation result is shown in the following table:
from the data in the table, it can be seen that, under the condition that the wind power generation system needs the energy storage device to compensate the same power, the yield of the single energy storage mode adopting the super capacitor is 28673 yuan, and the required configuration rated power and rated capacity are 2.059MW and 1.9393MWh respectively. And the yield of the hybrid energy storage system formed by the embodiment is 29859 yuan, and the yield is increased by about 4% compared with that of a single energy storage mode. The rated power and the capacity of the storage battery to be configured are respectively 1MW and 1.3358 MWh; the rated power and the capacity of the super capacitor are 1.9106MW and 0.9334MWh respectively. The storage battery of the embodiment well makes up the defect of low energy density of the super capacitor, greatly reduces the rated capacity required by the super capacitor, reduces the capacity cost and increases the total income of the wind power generation system.
According to the embodiment, the lower limit threshold and the upper limit threshold are arranged in the limit management module, and the hybrid energy storage system is prevented from being overcharged and overdischarged.
In this embodiment, two charge and discharge thresholds are set in the limit management module: the upper limit charge-discharge threshold and the lower limit charge-discharge threshold optimize charge-discharge management of the hybrid energy storage system, and the service life of the hybrid energy storage system is prolonged.
In the present embodiment, a plurality of data acquisition units and operation units are provided in the restriction management module, so that the SOC value can be quickly and easily obtained.
The storage battery of the embodiment is charged and discharged under rated power so as to exert the optimal performance.
Example 2:
in the embodiment, a wind generating set with the rated power of 10MW is arranged, and the hybrid energy storage system disclosed by the invention is used for compensating power fluctuation. The hybrid energy storage system comprises a super capacitor, a storage battery, a hysteresis comparison controller and a limit management module, and is shown in the attached figure 1. The super capacitor and the storage battery are connected in series (cascade), the hysteresis comparison controller is respectively connected with the super capacitor and the storage battery, and the restriction management module is respectively connected with the super capacitor and the storage battery; the hybrid energy storage system is merged into a power grid according to kirchhoff current law (KCL law), and a target power curve of the hybrid energy storage system needing compensation is shown in the attached figure 4. The initial state of charge of the hybrid energy storage system is set to be 50% so as to exert the optimal performance of the hybrid energy storage system.
In order to ensure that the storage battery is in an optimized working state, the storage battery is set to be charged and discharged only at rated power in the embodiment; the hysteresis comparison controller controls the working state of the storage battery by using the residual charge (state of charge, denoted as SOCsc) of the super capacitor. The SOCsc represents the ratio of the current residual capacity of the super capacitor to the rated capacity of the super capacitor, and the value range of the SOCsc is 0-1. When the SOCsc is 0, it indicates that the super capacitor is completely discharged, and when the SOCsc is 1, it indicates that the super capacitor is completely filled.
Setting a first threshold value D _ on, a second threshold value D _ off, a third threshold value C _ off and a fourth threshold value C _ on from small to large, wherein the first threshold value D _ on, the second threshold value D _ off, the third threshold value C _ off and the fourth threshold value C _ on correspond to the residual capacity of the super capacitor, and a hysteresis curve is shown in figure 3, wherein the abscissa represents the SOCsc value of the super capacitor, and the ordinate P represents the SOCsc value of the super capacitorbaRepresenting the output power of the battery.
1) When the SOCsc is between D _ off and C _ off, the super capacitor can normally compensate the target power at the moment, and the super capacitor is set to be in a normal working state, and the hysteresis comparison controller and the storage battery do not need to operate.
2) When the SOCsc gradually increases and the value of the SOCsc exceeds C _ on, the storage battery absorbs electric energy from the super capacitor at rated power so as to enhance the discharge of the super capacitor and improve the condition of excessive electric quantity. And at the moment, the electric quantity of the super capacitor is gradually reduced due to the action of the storage battery, the super capacitor is restored to a normal working state, and when the SOCsc is set to be reduced to C _ off, the storage battery is controlled to stop absorbing the electric energy in order to prevent the charging and discharging state of the storage battery from being frequently changed due to the frequent fluctuation of the SOCsc near C _ on.
3) And the electric quantity of the SOCsc is gradually reduced, and when the value of the electric quantity of the SOCsc is lower than D _ on, the storage battery provides energy for the super capacitor by rated power so as to enhance the charging of the super capacitor and improve the condition that the electric quantity of the super capacitor is too low. At this time, the electric quantity of the super capacitor is gradually increased due to the action of the storage battery, the super capacitor is restored to a normal working state, and in order to prevent the charging and discharging state of the storage battery from being frequently changed due to the frequent fluctuation of the SOCsc near D _ on, the storage battery is controlled to stop charging when the SOCsc is set to be increased to D _ off.
Both overcharge and overdischarge can cause significant damage to the hybrid energy storage system. In order to protect the hybrid energy storage system, the hybrid energy storage system can be limited to discharge when the energy storage electric quantity is less, and the hybrid energy storage system does not discharge when the electric quantity reaches the lower limit; and when the stored energy electric quantity is large, the charging power is limited, and when the electric quantity reaches the upper limit, the charging is not carried out, and a protection parameter BASC for preventing overcharge and over-discharge is set. The BASC represents the remaining capacity of the hybrid energy storage system (sum of the remaining capacities of the super capacitor and the storage battery). A lower limit threshold BASC corresponding to the sum of the remaining capacities of the super capacitor and the storage battery is set in the limit management moduleminAnd an upper threshold BASCmax. The limit management module is smaller than the BASC at the BASCminAnd the super capacitor is locked to discharge the output power grid, and the super capacitor is controlled to be charged through a wind power generation network outside the hybrid energy storage system. The limit management module is greater than the BASC at the BASCmaxAnd the charging of the super capacitor is locked, and the super capacitor is controlled to discharge.
In order to further optimize the charge and discharge management of the hybrid energy storage system, the limit management module is in the BASCminAnd BASCmaxThere are 2 charge-discharge thresholds between, and the charge-discharge threshold is set as the lower limit charge-discharge threshold BASClowAnd an upper limit charge-discharge threshold BASCup。
1) The limit management module is greater than the BASC at the BASCminAnd is less than BASClowThe discharge intensity of the super capacitor is controlled to be 0.618 times of the rated discharge intensity, and the charge intensity is controlled to be the rated charge intensity.
2) The limit management module is greater than the BASC at the BASClowAnd is less than BASCupAnd when the charging and discharging threshold is limited, controlling the discharging intensity of the super capacitor to be the rated discharging intensity and controlling the charging intensity to be the rated charging intensity.
3) The limit management module is greater than the BASC at the BASCupAnd is less than BASCmaxThe charging intensity of the super capacitor is controlled to be 0.618 times of the rated charging intensity, and the discharging intensity is controlled to be the rated discharging intensity.
In order to obtain the value of the BASC, the limit management module is provided with a rated capacity unit, a current residual capacity unit, an adding unit and an inverting unit. The rated capacity unit is respectively connected with the super capacitor and the storage battery to obtain the sum of the rated capacities of the super capacitor and the storage battery; the current residual capacity unit is respectively connected with the super capacitor and the storage battery to obtain the sum of the current residual capacities of the super capacitor and the storage battery; the reverse phase unit is connected with the current residual capacity unit to obtain the opposite number of the sum of the current residual capacity; the addition unit connects the rated capacity unit and the inversion unit, and obtains the difference value between the sum of the rated capacities and the sum of the current residual capacity as the value of the BASC.
The invention provides a wind power generation energy storage system which solves the problem of complex structure and optimizes the working state of the energy storage system, thereby effectively avoiding frequent charging and discharging of a storage battery, prolonging the service life, reducing the charge state fluctuation of a super capacitor, improving the overall economy of a hybrid energy storage system and optimizing the working state of the energy storage system. The invention is suitable for links of research and development design, operation control, electric energy metering, cost management and the like of a wind power generation system, has the characteristics of simple structure, good stability, environmental protection and reproducibility, and has higher production and research values.
The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.
Claims (6)
1. A hybrid energy storage system for stabilizing wind power fluctuation comprises a super capacitor and a storage battery, and is characterized in that the super capacitor is connected with the storage battery in a cascade manner; the hybrid energy storage system also comprises a hysteresis comparison controller, and the hysteresis comparison controller is respectively connected with the super capacitor and the storage battery;
the hysteresis comparison controller is provided with a first threshold, a second threshold, a third threshold and a fourth threshold which are from small to large and correspond to the residual electric quantity of the super capacitor;
the hysteresis comparison controller is used for controlling the storage battery to absorb electric energy from the super capacitor when the residual electric quantity exceeds a fourth threshold value;
the hysteresis comparison controller is also used for controlling the storage battery to stop absorbing the electric energy when the residual electric quantity is reduced to a third threshold value;
the hysteresis comparison controller is also used for controlling the storage battery to charge the super capacitor when the residual electric quantity is smaller than a first threshold value;
the hysteresis comparison controller is also used for controlling the storage battery to stop charging when the residual capacity is increased to a second threshold value;
the hybrid energy storage system is provided with a limit management module, and the limit management module is respectively connected with the super capacitor and the storage battery;
the limit management module is provided with a lower limit threshold and an upper limit threshold corresponding to the sum of the residual electric quantity of the super capacitor and the storage battery;
the limit management module is used for locking the super capacitor to discharge the output power grid when the sum of the residual electric quantity is smaller than a lower limit threshold value, and controlling the super capacitor to charge through a wind power generation network outside the hybrid energy storage system;
the limit management module is also used for locking the charging of the super capacitor when the sum of the residual electric quantity is greater than an upper limit threshold value and controlling the super capacitor to discharge;
the limit management module is provided with N charge-discharge thresholds between the lower limit threshold and the upper limit threshold, wherein N is a positive integer; and the limit management module is also used for controlling the charging intensity and the discharging intensity of the super capacitor according to the interval determined by the charging and discharging threshold corresponding to the sum of the residual electric quantity.
2. The hybrid energy storage system for stabilizing wind power fluctuation according to claim 1, wherein N is 2 and is set as a lower limit charge-discharge threshold value and an upper limit charge-discharge threshold value;
the limit management module is further used for controlling the discharge intensity of the super capacitor to be A times of the rated discharge intensity when the sum of the residual electric quantity is larger than the lower limit threshold and smaller than the lower limit charge-discharge threshold, wherein A is a rational number larger than 0 and smaller than 1, and the charge intensity is controlled to be the rated charge intensity;
the limit management module is further used for controlling the discharge intensity of the super capacitor to be rated discharge intensity and controlling the charge intensity to be rated charge intensity when the sum of the residual electric quantity is greater than a lower limit charge-discharge threshold and smaller than an upper limit charge-discharge threshold;
the limit management module is further used for controlling the charging intensity of the super capacitor to be B times of the rated charging intensity when the sum of the residual electric quantity is larger than an upper limit charging and discharging threshold value and smaller than the upper limit threshold value, wherein B is a rational number larger than 0 and smaller than 1, and the discharging intensity is controlled to be the rated discharging intensity.
3. The hybrid energy storage system for stabilizing wind power fluctuation according to claim 2, wherein the limit management module is provided with a rated capacity unit, a current remaining capacity unit, an addition unit and a phase reversal unit;
the rated capacity unit is respectively connected with the super capacitor and the storage battery and is used for obtaining the sum of the rated capacities of the super capacitor and the storage battery;
the current residual capacity unit is respectively connected with the super capacitor and the storage battery and is used for obtaining the sum of the current residual capacities of the super capacitor and the storage battery;
the reverse unit is connected with the current residual capacity unit and is used for obtaining the opposite number of the sum of the current residual capacity;
and the addition unit is used for connecting the rated capacity unit with the inversion unit and obtaining the difference value between the sum of the rated capacities and the sum of the current residual capacities as the sum of the residual capacities.
4. The hybrid energy storage system for stabilizing wind power fluctuation according to claim 2, wherein the sum of the residual electric quantities is represented by a state of charge parameter, and the state of charge parameter is a rational number in a closed interval [0, 1 ].
5. The hybrid energy storage system for stabilizing wind power fluctuation according to claim 4, wherein the limit management module is provided with a rated capacity unit, a current remaining capacity unit, a ratio unit, an addition unit and a phase reversal unit;
the rated capacity unit is respectively connected with the super capacitor and the storage battery and is used for obtaining the sum of the rated capacities of the super capacitor and the storage battery;
the current residual capacity unit is respectively connected with the super capacitor and the storage battery and is used for obtaining the sum of the current residual capacities of the super capacitor and the storage battery;
the reverse unit is connected with the current residual capacity unit and is used for obtaining the opposite number of the sum of the current residual capacity;
the addition unit is used for connecting the rated capacity unit with the inversion unit and obtaining the difference value between the sum of the rated capacities and the sum of the current residual capacity;
the ratio unit connects the adding unit with the rated capacity unit, and is used for obtaining a ratio of a difference value between the sum of the rated capacities and the sum of the current remaining capacities to the sum of the rated capacities, and taking the ratio as the state of charge parameter.
6. The hybrid energy storage system for stabilizing wind power fluctuation according to any one of claims 1 to 5, wherein the storage battery charges the supercapacitor at rated power or absorbs electric energy.
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| CN109995030B (en) * | 2019-04-28 | 2020-06-30 | 湖南大学 | Energy storage device SOC lower limit value optimal setting method considering offline risk |
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