CN116316749A - Optical storage micro-grid control strategy based on flywheel and retired power battery - Google Patents

Optical storage micro-grid control strategy based on flywheel and retired power battery Download PDF

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Publication number
CN116316749A
CN116316749A CN202310107931.0A CN202310107931A CN116316749A CN 116316749 A CN116316749 A CN 116316749A CN 202310107931 A CN202310107931 A CN 202310107931A CN 116316749 A CN116316749 A CN 116316749A
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China
Prior art keywords
retired
output
photovoltaic array
power
battery system
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Inventor
张永密
朱昌煜
张凯
刘钰磊
谢磊
丁明进
朱祥
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Huadian Inner Mongolia Energy Co ltd
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Huadian Inner Mongolia Energy Co ltd
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Priority to CN202310107931.0A priority Critical patent/CN116316749A/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/007—Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources
    • H02J3/0075—Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources for providing alternative feeding paths between load and source according to economic or energy efficiency considerations, e.g. economic dispatch
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • H02J3/30—Arrangements for balancing of the load in a network by storage of energy using dynamo-electric machines coupled to flywheels
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0047—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with monitoring or indicating devices or circuits
    • H02J7/0048—Detection of remaining charge capacity or state of charge [SOC]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The invention discloses an optical storage micro-grid control strategy based on a flywheel and a retired power battery, which comprises the following steps: judging whether the state of charge (SOC_F) of the flywheel system is in a safety range, if so, automatically balancing the power of the flywheel system in real time, otherwise, adopting a corresponding strategy based on a system power balance formula and a mode that the SOC_F exceeds the safety range, and ensuring that the SOC_F of the flywheel system is maintained in the safety range. The invention solves the problem of large grid-connected fluctuation of the photovoltaic power station in the prior art.

Description

Optical storage micro-grid control strategy based on flywheel and retired power battery
Technical Field
The invention relates to an optical storage micro-grid control strategy based on a flywheel and a retired power battery, and belongs to the technical field of hybrid energy storage capacity configuration of a power grid system.
Background
As the market of electric vehicles has exploded, the continuous increase of the electric vehicle's keeping amount brings about the problem of disposing the retired power batteries, how to dispose the retired power batteries becomes a pain point to be solved in the industry,
the retired power battery has a charge-discharge rate which is only half of that of a new battery or even lower (0.5C or 0.33C) due to the reduction of charge-discharge performance, and can not meet the use requirement of the electric automobile, but can still continue to play a role in electric energy storage. However, due to the limitation of low charge-discharge rate, the battery can only be used as an energy application scene such as peak clipping and valley filling in a long time scale (2-4 hours), and for a power application scene of high-rate charge-discharge in a short time scale (seconds-minutes) or with impact load, which needs to be charged and discharged frequently, the battery can generate heat and aggravate the service life of the battery due to the increase of internal resistance and the frequent and rapid charge-discharge, or the battery OCV (open circuit voltage) "jumps" due to the high-power charge-discharge, so that the energy storage converter is stopped due to direct current under-voltage. For an off-grid 'photo-storage' micro-grid system, an electrochemical energy storage system with higher charge-discharge multiplying power is generally configured because part of the micro-grid system needs to work on a voltage source (V-F source) energy storage system to stabilize micro-grid voltage and frequency fluctuation caused by power difference between a photovoltaic array output and a current source (P-Q source) energy storage system and a load and large-scale fluctuation of instantaneous power caused by impact load.
Although the application requirement of the V-F source energy storage system can be met, in the off-grid type light storage micro-grid, the output force and the load of the photovoltaic array are randomly fluctuated, the energy storage Energy Management System (EMS) is usually used for adjusting the output force of the photovoltaic array, the output force and the load of the P-Q source energy storage system for a few seconds, the energy storage system working in the V-F source mode can frequently participate in power adjustment, the working condition is quite similar to electric auxiliary frequency modulation, the working condition is even worse in part of application scenes, the attenuation of the electrochemical energy storage system is aggravated, the operation cost and the battery replacement cost of the energy storage system are increased intangibly, and when the electrochemical energy storage system is applied in high-cold and high-altitude areas, the air conditioner power consumption is usually higher to keep proper working temperature, and the operation cost is increased.
Disclosure of Invention
The invention aims to provide an optical storage micro-grid control strategy based on a flywheel and a retired power battery, and solves the problems of large grid-connected fluctuation and low utilization rate of the retired power battery of a photovoltaic power station in the prior art.
In order to achieve the above object, the present invention adopts the following technical scheme:
an optical storage micro-grid control strategy based on a flywheel and a retired power battery comprises the following steps:
judging whether the state of charge (SOC_F) of the flywheel system is in a safety range, if so, automatically balancing the power of the flywheel system in real time, otherwise, executing the next operation;
establishing a system power balance formula:
P FW = P PV +P B -P L
P PV the output of the photovoltaic array, W,
P L load demand, W,
P FW real-time power, W,
P B -retired power battery system output, W;
based on a system power balance formula and the way that the SOC_F exceeds the safety range, the following strategy is adopted to ensure that the SOC_F of the flywheel system is maintained in the safety range:
1) When the SOC_F reaches the lower limit of the safety range, the common output force of the photovoltaic array and the retired power battery system is larger than the load demand;
2) When the SOC_F reaches the upper limit of the safety range, the combined output force of the photovoltaic array and the retired power battery system is smaller than the load demand.
Further, the safety range of the flywheel system SOC_F is 10 percent-90 percent.
Further, the method further comprises confirming the output state of the retired power battery system in the system power balance formula based on the relation between the output of the photovoltaic array and the load demand:
the output of the photovoltaic array is larger than the load demand, the EMS controls the retired battery system to charge, and the power balance formula of the system is as follows:
P FW =（P PV - P BAT_C ）-P L
P B =- P BAT_C
P BAT_C -retired power battery system charging power, W;
the output of the photovoltaic array is smaller than the load demand, the EMS controls the retired battery system to discharge, and the power balance formula of the system is as follows:
P FW =P BAT_DC + P PV - P L
P B =P BAT_DC
P BAT_DC -retired power battery system discharge power, W;
the output of the photovoltaic array is equal to the load demand, and the EMS controls the output P of the retired battery system B Until 0.
Further, when soc_f >90%, the following operations are performed to ensure that the combined output of the photovoltaic array and the retired power battery system is less than the load demand:
when the output force of the photovoltaic array is larger than the load demand and the common output force of the photovoltaic array and the retired power battery system is larger than the load demand, the following operations are sequentially executed: reducing the output of the photovoltaic array and increasing the charging power of the retired battery system until the output of the photovoltaic array is again smaller than the sum of the load demand and the charging power of the retired battery system;
when the output force of the photovoltaic array is smaller than the load demand and the common output force of the photovoltaic array and the retired power battery system is larger than the load demand, the following operations are sequentially executed: reducing the output of the photovoltaic array and the discharge power of the retired battery system until the output of the photovoltaic array is again smaller than the sum of the load demand and the charge power of the retired battery system;
when the photovoltaic array output is equal to the load demand and the retired power battery system is discharging, then the following operations are performed: and reducing the output of the photovoltaic array, controlling the discharge power of the retired battery system to be 0, and controlling the retired battery system to be charged until the sum of the output of the photovoltaic array and the output of the retired battery system is smaller than the load demand.
Further, when soc_f is less than 10%, the following operations are performed to ensure that the combined output of the photovoltaic array and the retired power battery system is greater than the load demand:
when the output force of the photovoltaic array is larger than the load demand and the common output force of the photovoltaic array and the retired power battery system is smaller than the load demand, the following operations are sequentially executed: increasing the output of the photovoltaic array, reducing the charging power of the retired battery system, cutting off non-important loads and starting the diesel engine until the output of the photovoltaic array is larger than the sum of the load demand and the charging power of the retired battery system;
when the output force of the photovoltaic array is smaller than the load demand and the common output force of the photovoltaic array and the retired power battery system is smaller than the load demand, the following operations are sequentially executed: increasing the output of the photovoltaic array, increasing the discharge power of the retired battery system, cutting off non-important loads and starting the diesel engine until the load demand is smaller than the sum of the output of the photovoltaic array and the discharge power of the retired battery system;
when the photovoltaic array output is equal to the load demand and the retired power battery system is charging, then the following operations are performed: the output of the photovoltaic array is increased, the charging power of the retired battery system is controlled to be 0, and the retired battery system is controlled to be changed into discharge until the combined output of the photovoltaic array and the retired power battery system is greater than the load demand.
Further, the aforementioned strategy for starting the diesel engine is:
starting a diesel engine to establish a V-F source and establishing a voltage reference standard of a micro-grid;
the photovoltaic array, the retired battery energy storage system and the flywheel energy storage system are integrated into a micro-grid in a P-Q source mode;
charging the retired power battery system and the flywheel system through EMS control, so that the SOC of the retired power battery system reaches 100%, and the SOC of the flywheel energy storage system reaches 90%;
based on the adjusted relation between the output of the photovoltaic array and the load demand, if the output of the photovoltaic array is still smaller than the load demand, the diesel engine automatically adjusts the output to balance the power fluctuation of the micro-grid, otherwise, the diesel engine exits.
The invention has the beneficial effects that:
1. the flywheel system is utilized to replace the electrochemical energy storage system, so that the accelerated decay of the service life of the battery under the working condition that the power of the electrochemical energy storage system frequently fluctuates, and the reinvestment and maintenance cost caused by the repeated replacement of the battery in the whole life cycle can be effectively solved, and meanwhile, the cost caused by the recovery of the electrochemical battery in the later stage and the influence on the environment possibly caused can be greatly reduced.
2. The relation between the photovoltaic array and the load demand is considered, and on the premise of fully ensuring the consumption of photovoltaic energy, an energy management and control strategy of the EMS on the retired power battery system and an automatic real-time power balance strategy of the flywheel system are formulated. On the basis, in order to ensure stable operation of the optical storage micro-grid, a flywheel system SOC control strategy is provided under the premise of considering maximum consumption of photovoltaic energy. Finally, an operation control strategy for starting and pushing out the diesel engine is provided
Drawings
Fig. 1 is a flywheel + retired power cell optical storage micro-grid system of the present invention.
FIG. 2 is a flow chart of the system operational strategy of the present invention;
fig. 3 is a schematic diagram of the diesel engine operating strategy of the present invention.
Description of the embodiments
The following detailed description of the technical solutions of the present invention is made by the accompanying drawings and specific embodiments, and it should be understood that the specific features of the embodiments and embodiments of the present application are detailed descriptions of the technical solutions of the present application, and not limiting the technical solutions of the present application, and the technical features of the embodiments and embodiments of the present application may be combined with each other without conflict.
The embodiment of the invention relates to an optical storage micro-grid system based on a flywheel and a retired power battery, as shown in fig. 1, which comprises an energy storage Energy Management System (EMS), a photovoltaic array, a photovoltaic inverter, an energy storage converter (PCS), a flywheel array, a retired power battery system, a diesel generator and a local load, wherein the flywheel array comprises a flywheel management system FMS and at least one flywheel unit, and the retired power battery system comprises a battery management system BMS and at least one retired power battery unit.
The retired power battery system works in a P-Q source mode, receives power scheduling of the EMS and is used for primarily matching the power difference between the output of the photovoltaic array and the load, and because the adjusting process has time delay, the power of the whole micro-grid system is adjusted to be in differential adjustment. The flywheel is used for a V-F source energy storage system, the real-time power matching of the micro-grid system is automatically completed, the real-time balance and the indifferent adjustment of the micro-grid power are realized, so that fluctuation of voltage and frequency of the micro-grid caused by power difference among output of a photovoltaic array, output of a retired power battery system and load demand is stabilized, and the voltage and frequency of the micro-grid are stabilized; meanwhile, the management of the output of the photovoltaic array, the output and the load of the retired power battery system is realized by reasonably setting the energy management strategy of the EMS, a diesel engine is not required to be started to establish a power grid and balance power fluctuation, and the diesel engine is only restarted under the condition that the electric quantity of the energy storage system is close to the lower limit, so that the starting frequency of a diesel generator can be greatly reduced, and the oil consumption cost and the abrasion of the diesel engine are reduced.
1. Energy management and control strategy of retired power battery system and automatic real-time power balance strategy of flywheel system
The EMS collects the output of the photovoltaic array, the charge state and the real-time load of the retired power battery system, and performs primary adjustment (differential adjustment) of the power of the micro-grid system. Two situations are distinguished:
1) The photovoltaic array output is larger than the load demand, and in order to absorb the photovoltaic array output as much as possible, the EMS dispatches the retired power battery system to work in a charging state under the condition that the charging state (SOC_B) of the retired power battery system does not reach 100%;
2) The output force of the photovoltaic array is smaller than the load demand, and the EMS schedules the retired power battery system to work in a discharging state under the condition that the charge state (SOC_B) of the retired power battery system exceeds 20 percent (in order to prolong the service life of the retired battery, the lower limit of the SOC is not set to 0 percent in general);
3) The output of the photovoltaic array is equal to the load demand, and the EMS controls the output P of the retired battery system B Until 0.
The flywheel system automatically performs real-time power balance (no difference adjustment), and is also divided into two cases:
1) When the common output force of the photovoltaic array and the retired power battery system in the micro-grid is smaller than the load demand, the flywheel system automatically discharges and balances the power in real time within the allowable SOC range.
2) When the common output force of the photovoltaic array and the retired power battery system in the micro-grid is larger than the load demand, the flywheel system automatically charges and balances the power in real time in an allowable SOC range.
3) When the combined output of the photovoltaic array and the retired power battery system in the micro-grid is equal to the load demand, the output of the flywheel system is 0.
In conclusion, the flywheel system can automatically charge and discharge within the allowable SOC range, and the micro-grid power is balanced in real time.
If the SOC of the flywheel system exceeds the allowable range, the SOC control strategy of the flywheel system is required to be executed so as to ensure that the flywheel system can have the capability of balancing micro-electric power in real time and ensure the stable operation of the micro-grid.
2. Flywheel system state of charge SOC_F control strategy
State 1: the state of charge soc_f of the flywheel system reaches 90% and the flywheel system is in a state of charge.
In order to maximally absorb the output of the photovoltaic array and ensure that the flywheel system can have the capability of adjusting the power up and down at any time, it is generally required to ensure that the soc_f works within a certain range, which is set to 10-90% in this embodiment.
In this state, if the flywheel system is not controlled at this time, the flywheel system will be continuously charged, and the state of charge soc_f of the flywheel system may reach 100% and cannot absorb active power any more, so that the micro-grid may eventually be overclocking and collapse. To ensure that soc_f operates within a certain range, the following actions are taken:
1.1 If the photovoltaic array output is greater than the load demand at this time
The retired power battery system is in the charging process, and the power balance formula of the system is as follows:
P FW = P PV +P B -P L = P PV -（P L + P BAT_C ) Wherein P is B = - P BAT_C （1）
P B -retired power battery system output, W;
P BAT_C -retired power battery system charging power, W;
P PV -photovoltaic array output, W;
P L load demand, W;
P FW real-time power of flywheel system, W.
1.1.1 Photovoltaic array output less than the sum of load demand and retired battery system charge power
At this time, the EMS does not adjust the output of the photovoltaic array, the load size and the output of the retired battery system, and according to the system power balance formula (1), the flywheel system automatically discharges and releases power, so that soc_f is not higher than 90%.
1.1.2 Photovoltaic array output greater than the sum of load demand and retired battery system charge power
To prevent the flywheel system from continuing to charge, according to the system power balance equation (1), the following methods may be adopted: and the output of the photovoltaic array is reduced, and the charging power of the retired battery system is increased, so that the output of the photovoltaic array is again smaller than the sum of the load demand and the charging power of the retired battery system. When soc_b=100%, the requirement of the flywheel can no longer be maintained by increasing the charging power of the retired battery system in order to protect the retired battery system.
1.1.3 Photovoltaic array output is equal to the sum of load demand and retired battery system charging power
The flywheel system will maintain the current SOC unchanged, neither charging nor discharging.
1.2 If the photovoltaic array output is less than the load demand at this time
The retired power battery system is in a discharging process, and the power balance formula of the system is as follows:
P FW = P PV +P B -P L =P BAT_DC + P PV - P L wherein P is B = P BAT_DC （2）
P B -retired power battery system output, W;
P BAT_DC -retired power battery system discharge power, W;
P PV -photovoltaic array output, W;
P L load demand, W;
P FW real-time power of flywheel system, W.
1.2.1 Load demand is greater than the sum of the output of the photovoltaic array and the discharge power of the retired battery system
At this time, the EMS does not adjust the output of the photovoltaic array, the load size and the output of the retired battery system, and according to the system power balance formula (2), the flywheel system automatically discharges and releases power, so that soc_f is not higher than 90%.
1.2.2 Load demand is less than the sum of photovoltaic array output and retired battery system discharge power
To prevent the flywheel system from continuing to charge, according to the system power balance equation (2), the following methods may be adopted: and the output of the photovoltaic array is reduced, and the discharge power of the retired battery system is reduced, so that the load demand is larger than the sum of the output of the photovoltaic array and the discharge power of the retired battery system. In order to prolong the service life of the retired battery, the lower limit of the soc_b of the retired power battery system is not set to 0%, and the lower limit of the soc_b of the retired power battery system is selected to be 20% in this embodiment, so that when soc_b is less than or equal to 20%, the discharging power of the retired power battery system cannot be reduced to maintain the requirement of the flywheel.
1.2.3 Load demand is equal to the sum of the output of the photovoltaic array and the discharge power of the retired battery system
The flywheel system output is 0, neither charging nor discharging.
1.3 If the photovoltaic array output is equal to the load demand at this time
1.3.1 If the retired power battery system is discharging at the moment
According to the system power balance formula (2), it is known that if not controlled, the flywheel system will continue to charge, so that soc_f exceeds 90%. To prevent the flywheel system from continuing to charge, according to the system power balance equation (2), the following methods may be adopted: the output of the photovoltaic array is reduced, the discharge power of the retired battery system is controlled to be 0, and the retired battery system is controlled to be charged, so that the load demand is larger than or equal to the sum of the output of the photovoltaic array and the output (charge or discharge) of the retired battery system again. 1.3.2 If the retired power battery system is charging at the moment
According to the system power balance formula (1), the flywheel system automatically discharges and releases power, so that the SOC_F is not higher than 90%.
1.3.3 If the output of the retired power battery system is 0 at the moment
The flywheel system output is 0, neither charging nor discharging.
State 2: the flywheel system state of charge soc_f drops to 10% and the flywheel system is in a discharged state.
If the flywheel system is not controlled at this time, the flywheel system will continue to discharge, and soc_f may drop to 0% and active power cannot be released, which eventually results in the micro-grid being underfrequency and crashed.
In order to avoid damage to the retired power battery system caused by overdischarge and ensure the capability of the flywheel system to adjust power up and down at any time, the following operation strategies are set according to different situations:
2.1 If the photovoltaic array output is greater than the load demand at this time
In the charging process of the retired power battery system, the power balance formula of the system is as follows:
P FW =P PV -（P L + P BAT_C ） （1）
P BAT_C retired power batterySystem charging power, W;
P PV -photovoltaic array output, W;
P L -load demand, W;
P FW real-time power of flywheel system, W.
2.1.1 Photovoltaic array output greater than the sum of load demand and retired battery system charge power
At this time, the EMS does not adjust the output of the photovoltaic array, the load size and the output of the retired battery system, so that the flywheel system can be automatically charged to absorb the redundant output of the photovoltaic array, and thus the soc_f is always not lower than 10%.
2.1.2 Photovoltaic array output less than the sum of load demand and retired battery system charge power
To prevent the flywheel system from continuing to discharge, according to the system power balance equation (1), the following modes may be adopted: and (3) increasing the output of the photovoltaic array, cutting off non-important loads and increasing the discharge power of the retired battery system, so that the output of the photovoltaic array is larger than the sum of the load demand and the charge power of the retired battery system again. In order to prolong the service life of the retired battery, the lower limit of the soc_b of the retired power battery system is not set to 0%, and the lower limit of the soc_b of the retired power battery system is selected to be 20% in this embodiment, so that when soc_b is less than or equal to 20%, the discharging power of the retired power battery system cannot be increased to maintain the requirement of the flywheel.
If the output of the photovoltaic array is still smaller than the sum of the load demand and the charging power of the retired battery system after all the modes are adopted, adopting a diesel engine working strategy:
and starting the diesel engine to operate as a V-F source (voltage source) of the micro-grid, at the moment, presynchronizing according to the voltage phase and frequency of the micro-grid established by the diesel engine by controlling the output currents of the flywheel system and the photovoltaic array, and after presynchronizing, merging the flywheel system and the photovoltaic array into the micro-grid to operate in a P-Q source mode, and then charging the retired power battery system and the flywheel system by EMS control.
When the SOC_B reaches 100%, the SOC_F reaches 90%, and in order to avoid the increase of fuel cost caused by frequent start and stop of the diesel engine, the relation between the output of the photovoltaic array and the load demand needs to be considered when the diesel engine works and exits:
a) If the output force of the photovoltaic array is smaller than or equal to the load demand, the diesel engine automatically adjusts the output force to balance the power rate fluctuation of the micro-grid, and the frequency of the micro-grid is maintained in a normal operation range;
b) If the output of the photovoltaic array is larger than the load demand, the diesel engine is required to be stopped, meanwhile, the working mode of the flywheel system is adjusted from a P-Q source to a V-F source, so that the voltage source of the whole micro-grid is established, and meanwhile, the photovoltaic array and the retired battery energy storage system are integrated into the micro-grid to operate in a P-Q source mode.
2.1.3 Photovoltaic array output is equal to the sum of load demand and retired battery system charging power
The flywheel system will maintain the current SOC unchanged, neither charging nor discharging.
2.2 If the photovoltaic array output is less than the load demand at this time
In the charging process of the retired power battery system, the power balance formula of the system is as follows:
P FW =P BAT_DC + P PV - P L （2）
P BAT_DC -retired power battery system discharge power, W;
P PV -photovoltaic array output, W;
P L -load demand, W;
P FW real-time power of flywheel system, W.
2.2.1 Load demand is less than the sum of photovoltaic array output and retired battery system discharge power
At this time, the EMS does not adjust the output of the photovoltaic array, the load size and the output of the retired battery system, and the output of the photovoltaic array and the discharge power of the retired power battery system are redundant, so that the flywheel system can be automatically charged, and the soc_f is always not lower than 10%.
2.2.2 Load demand is greater than the sum of the output of the photovoltaic array and the discharge power of the retired battery system
To prevent the flywheel system from continuing to discharge, according to the system power balance equation (2), the following methods may be adopted: and (3) increasing the output of the photovoltaic array, cutting off non-important loads and increasing the charging power of the retired battery system, so that the load demand is smaller than the sum of the output of the photovoltaic array and the discharging power of the retired battery system. When soc_b=100%, the requirement of the flywheel can no longer be maintained by increasing the charging power of the retired battery system in order to protect the retired battery system.
If the load demand is still larger than the sum of the output of the photovoltaic array and the discharge power of the retired battery system after all the modes are adopted, a diesel engine working strategy is adopted.
2.2.3 Load demand is equal to the sum of the output of the photovoltaic array and the discharge power of the retired battery system
The flywheel system output is 0, neither charging nor discharging.
2.3 If the photovoltaic array output is equal to the load demand at this time
2.3.1 If the retired power battery system is charging at the moment
According to the system power balance formula (1), it is known that if not controlled, the flywheel system will continue to discharge, so that soc_f is lower than 10%. To prevent the flywheel system from continuing to discharge, according to the system power balance equation (1), the following modes may be adopted: the output of the photovoltaic array is increased, the charging power of the retired battery system is controlled to be 0, and the retired battery system is controlled to be changed into discharge, so that the load demand is smaller than or equal to the sum of the output of the photovoltaic array and the output (charging or discharging) of the retired battery system again.
2.3.2 If the retired power battery system is discharging at the moment
According to the system power balance formula (2), the flywheel system automatically charges and absorbs power, so that the SOC_F is not lower than 90%.
2.3.3 If the output of the retired power battery system is 0 at the moment
The flywheel system output is 0, neither charging nor discharging.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and variations could be made by those skilled in the art without departing from the technical principles of the present invention, and such modifications and variations should also be regarded as being within the scope of the invention.

Claims (6)

1. An optical storage micro-grid control strategy based on a flywheel and a retired power battery is characterized by comprising the following steps:
judging whether the state of charge (SOC_F) of the flywheel system is in a safety range, if so, automatically balancing the power of the flywheel system in real time, otherwise, executing the next operation;
establishing a system power balance formula:
P FW = P PV +P B -P L
P PV the output of the photovoltaic array, W,
P L load demand, W,
P FW real-time power, W,
P B -retired power battery system output, W;
based on a system power balance formula and the way that the SOC_F exceeds the safety range, the following strategy is adopted to ensure that the SOC_F of the flywheel system is maintained in the safety range:
1) When the SOC_F reaches the lower limit of the safety range, the common output force of the photovoltaic array and the retired power battery system is larger than the load demand;
2) When the SOC_F reaches the upper limit of the safety range, the combined output force of the photovoltaic array and the retired power battery system is smaller than the load demand.
2. The optical storage micro-grid control strategy based on flywheel and retired power battery according to claim 1, wherein the flywheel system soc_f safety range is 10% +.ltoreq.soc_f+.ltoreq.90%.
3. The optical storage micro-grid control strategy based on flywheel and retired power battery according to claim 2, further comprising confirming the retired power battery system output status in the system power balance formula based on the relation between the output of the photovoltaic array and the load demand:
the output of the photovoltaic array is larger than the load demand, the EMS controls the retired battery system to charge, and the power balance formula of the system is as follows:
P FW =（P PV - P BAT_C ）-P L
P B =- P BAT_C
P BAT_C -retired power battery system charging power, W;
the output of the photovoltaic array is smaller than the load demand, the EMS controls the retired battery system to discharge, and the power balance formula of the system is as follows:
P FW =P BAT_DC + P PV - P L
P B =P BAT_DC
P BAT_DC -retired power battery system discharge power, W;
the output of the photovoltaic array is equal to the load demand, and the EMS controls the output P of the retired battery system B Until 0.
4. A "flywheel + retired power cell" based optical storage micro grid control strategy according to claim 3, characterized in that when soc_f >90%, the following is performed to ensure that the combined output of the photovoltaic array and retired power cell system is less than the load demand:
when the output force of the photovoltaic array is larger than the load demand and the common output force of the photovoltaic array and the retired power battery system is larger than the load demand, the following operations are sequentially executed: reducing the output of the photovoltaic array and increasing the charging power of the retired battery system until the output of the photovoltaic array is again smaller than the sum of the load demand and the charging power of the retired battery system;
when the output force of the photovoltaic array is smaller than the load demand and the common output force of the photovoltaic array and the retired power battery system is larger than the load demand, the following operations are sequentially executed: reducing the output of the photovoltaic array and the discharge power of the retired battery system until the output of the photovoltaic array is again smaller than the sum of the load demand and the charge power of the retired battery system;
when the photovoltaic array output is equal to the load demand and the retired power battery system is discharging, then the following operations are performed: and reducing the output of the photovoltaic array, controlling the discharge power of the retired battery system to be 0, and controlling the retired battery system to be charged until the sum of the output of the photovoltaic array and the output of the retired battery system is smaller than the load demand.
5. A control strategy for an optical storage micro-grid based on "flywheel + retired power battery" according to claim 3, characterized in that when soc_f < 10%, the following operations are performed to ensure that the combined output of the photovoltaic array and retired power battery system is greater than the load demand:
when the output force of the photovoltaic array is larger than the load demand and the common output force of the photovoltaic array and the retired power battery system is smaller than the load demand, the following operations are sequentially executed: increasing the output of the photovoltaic array, reducing the charging power of the retired battery system, cutting off non-important loads and starting the diesel engine until the output of the photovoltaic array is larger than the sum of the load demand and the charging power of the retired battery system;
when the output force of the photovoltaic array is smaller than the load demand and the common output force of the photovoltaic array and the retired power battery system is smaller than the load demand, the following operations are sequentially executed: increasing the output of the photovoltaic array, increasing the discharge power of the retired battery system, cutting off non-important loads and starting the diesel engine until the load demand is smaller than the sum of the output of the photovoltaic array and the discharge power of the retired battery system;
when the photovoltaic array output is equal to the load demand and the retired power battery system is charging, then the following operations are performed: the output of the photovoltaic array is increased, the charging power of the retired battery system is controlled to be 0, and the retired battery system is controlled to be changed into discharge until the combined output of the photovoltaic array and the retired power battery system is greater than the load demand.
6. The optical storage micro grid control strategy based on flywheel and retired power battery according to claim 5, wherein the strategy for starting the diesel engine is:
starting a diesel engine to establish a V-F source and establishing a voltage reference standard of a micro-grid;
the photovoltaic array, the retired battery energy storage system and the flywheel energy storage system are integrated into a micro-grid in a P-Q source mode;
charging the retired power battery system and the flywheel system through EMS control, so that the SOC of the retired power battery system reaches 100%, and the SOC of the flywheel energy storage system reaches 90%;
based on the adjusted relation between the output of the photovoltaic array and the load demand, if the output of the photovoltaic array is still smaller than the load demand, the diesel engine automatically adjusts the output to balance the power fluctuation of the micro-grid, otherwise, the diesel engine exits.
CN202310107931.0A 2023-02-01 2023-02-01 Optical storage micro-grid control strategy based on flywheel and retired power battery Pending CN116316749A (en)

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